1.1 Continuous mill 2500 of the Magnitogorsk Iron and Steel Works

The workshop was put into operation in 1968. The mill equipment is located in seven bays (Figure 1).

Figure 1. Main diagram technological equipment Mill 2500 of the Magnitogorsk Iron and Steel Works:

I - hot-rolled coil warehouse span, II - NTA span, III - mill span, IV - bell furnace span; 1 - hot-rolled coil transfer conveyor, 2 - overhead cranes, 3 - continuous pickling units, 4 - cross-cutting unit for hot-rolled coils, 5 - mill working line, 6 - skin tempering mill, 7 - skin tempering mill 1700, 8 and 9 - longitudinal units and cross cutting, 10 - bell furnaces.

The mill is designed for cold rolling of strips with a cross section of (0.6-2.5) x (1250-2350) mm h? 30-roll internal diameter 800 mm, external? 1950 mm from steels 08Yu, 08kp, 08ps (GOST 9045-80), steels 08 - 25 of all degrees of deoxidation with chemical composition according to GOST 1050-74 and St0 - St3 boiling, semi-calm and calm (GOST 380-71).

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Use of systems and means of automation of technological facilities at the OJSC MMK enterprise

Production at MMK begins with an ore processing plant (ore processing) and a sinter plant (producing sinter by finely agglomerating ore material, which is necessary for smelting cast iron). Next comes coke production...

Complex of mechanical equipment for sintering production

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Application of technology for vacuum drying of the surface of cold-rolled strip to remove cutting fluids in the conditions of mill 2500 LPC-5 of OJSC MMK

I - annealing department, II - mill bay, III - machine room, IV - finished product warehouse; 1 - overhead cranes, 2 - annealing furnaces, 3 - tilters, 4 - electrolytic cleaning unit, 5 - unwinder, 6 - mill line, 7 - winder, 8 - cutting unit...

Development of a technological process for the production of sheets using the cold rolling method

The mill, put into operation in 1956, is located in eight bays (Fig. 1) with a total width of 195 m and a length of 456 m. I - annealing department, II - mill bay, III - machine room, IV - finished product warehouse; 1 - overhead cranes, 2 - annealing furnaces, 3 - tilters...

Table 2 Characteristics of the NM 2500-230 pump when operating on water Q H 3 N 300 250 0.28 820 500 248 0.4 850 700 246 0.51 900 900 244 0.61 1000 1100 240 0.7 1050 1300 2 38 0.77 1100 1500 235 0.81 1200 1700 230 0...

Calculation and regulation of operating modes of a centrifugal pump

Table 4- The characteristics of the pump NPV 2500-80 when working on water Q h h N 300 80 0.22 300 500 80 0.35 320 700 78 0.48 350 900 78 0.52 380 1100 77 0.65 400 1300 75 0, 7 430 1500 72 0.75 450 1700 68 0...

Adjustment of strip thickness and tension in the mill entry zone

To measure the strip tension in each inter-stand space, a single-roller tension meter is installed on the cold rolling mill 2500, which uses a magnetically anisotropic pressure sensor DM-5806 designed by VNIIAChermet...

System of extraction, preparation and enrichment of raw materials for ferrous and non-ferrous metallurgy

In addition to commercial products obtained from the processing of non-ferrous metal ores, non-ferrous metallurgy enterprises produce numerous wastes and intermediate products metallurgical production. These include slag, dust, gases...

Cold rolling mills

The first stage of the cold rolling shop was put into operation in 1963, the mill equipment is located in 12 bays (Figure 2). Figure 2...

Cold rolling mills

Of the mills considered, the most suitable is the Continuous Mill 2030. The continuous five-stand cold rolling mill 2030 is designed for rolling strips with a thickness of 0.35-2.0 mm in an endless mode and 0.35-3...

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Shops of the metallurgical plant named after. Ilyich

All metallurgical plants are divided into: those with a full (or complete) production cycle and plants with an incomplete metallurgical cycle. MMK im. Ilyich - a plant with a complete metallurgical cycle...

Introduction

The bulk of the steel produced passes through rolling shops and only a small amount through foundries and forging shops. Therefore, much attention is paid to the development of rolling production.

The course “Technological lines and complexes of metallurgical shops” is a special discipline that develops students’ professional knowledge in the field of theory and technology of continuous metallurgical lines and units.

As a result of execution course work The following sections must be completed:

Develop and describe technological processes as a whole for sections (units) and for individual operations with elaboration of issues of technology continuity;

Make a choice according to the given productivity and cross-sectional dimensions of the rolled sheets of the cold sheet rolling mill from existing designs;

Calculate the distribution of reductions along the passes in the rolling mill stands;

Perform calculations of rolling forces in each stand of the rolling mill and the power of electric drives;

Determine the annual productivity of the mill;

Automate the technological modes of compression.

In the course of course work, the knowledge gained from studying the TLKMC course is consolidated and expanded, skills appear in the selection of production equipment, calculations of technological modes of reduction and power parameters of rolling, and the use of electronic computers in calculations.

Cold rolling mills

By cold rolling, tapes, sheets and strips of the smallest thickness and width up to 4600...5000 mm are obtained.

The main parameters of broadband mills are the barrel length of the working stand (in continuous mills of the last stand).

For the production of cold-rolled steel sheets, reversible single-stand and sequential multi-stand mills are used.

According to the task, the most suitable are 3 camps:

Continuous mill 2500 of Magnitogorsk Iron and Steel Works

The workshop was put into operation in 1968. The mill equipment is located in seven bays (Figure 1).

Figure 1. Diagram of the main technological equipment of mill 2500 of the Magnitogorsk Iron and Steel Works:

The mill is designed for cold rolling of strips with a cross section of (0.6-2.5) x (1250-2350) mm h? 30-roll internal diameter 800 mm, external? 1950 mm from steels 08Yu, 08kp, 08ps (GOST 9045-80), steels 08 - 25 of all degrees of deoxidation with chemical composition in accordance with GOST 1050-74 and St0 - St3 boiling, semi-calm and calm (GOST 380-71).

Continuous mill 1700 of the Mariupol Metallurgical Plant named after. Ilyich

The first stage of the cold rolling shop was put into operation in 1963, the mill equipment is located in 12 bays (Figure 2).

Figure 2. Layout of the main technological equipment of the cold rolling mill 1700 of the Mariupol Metallurgical Plant named after. Ilyich:

I - warehouse for hot-rolled coils, II - mill bay, III - machine room, IV - gas bell furnace bay, V - finished product warehouse; 1, 3, 8, 10, 12, 13, 19, 20, 22, 24, 26, 28 - overhead cranes, 2 - cross-cutting unit, 4 - transfer conveyors with tilters, c5 - packing units for sheet bundles, 6 - shears , 7 - continuous pickling units (CTA), 9 - combined cutting unit, 11 - guillotine shears, 14 - conveyor for feeding rolls to the mill, 15 - unwinder, 16 - working line of the mills, 17 - winder, 18 - outfeed conveyor, 21 - single-stall bell-type furnaces, 23 - baling tables, 25 - scales, 27 - tempering units, 29 - skin-passing cage, 30 - slitting unit, 31 - roll packaging units, 32 - double-stack bell-type furnaces, 33 - baling press

The mill is designed for cold rolling of strips with a cross-section of (0.4-2.0) x (700-1500) mm in rolls from carbon steels of ordinary quality (boiling, calm, semi-quiet): St1, St2, St3, St4, St5; carbon high-quality structural: 08kp, 08ps, 10kp, 10ps, 10, 15kp, 15ps, 15, 20kp, 20ps, 20, 25, 30, 35, 40, 45; ageless 08Yu, 08Fkp; electrical steel.

Boiling and mild steels are supplied in accordance with GOST: 16523-70, 9045-70, 3560-73, 17715-72, 14918-69, 19851-74 and technical specifications with a chemical composition in accordance with GOST 380-71 and 1050-74. Electrical steel is supplied in accordance with GOST 210142-75. [2]

Introduction........................................................ ........................... 3

1 Short review composite rolling rolls.

Characteristics of mill 2500. Mill assortment.................................... 4

1.1 Brief overview and analysis of the designs of composite rolling rolls. 4

1.2 Characteristics of hot rolling mill 2500.................................................... 8

1.3 Mill assortment by steel grades and strip sizes.................................... 9

2 Research and development of the banded design

back-up roll of hot rolling mill 2500.............................................. 10

2.1 Selection of tension, shape, thickness of the bandage and calculation

load-bearing capacity of the connection................................................... .... 10

2.2 Calculation of stresses in a banded support roll.................................. 16

2.3 Calculation for the frequency of use of the axis of a composite support roll 30

2.4 Determination of cyclic endurance in section 1-1.................................. 33

2.5 Determination of cyclic endurance in section 2-2.................................. 36

2.6 Determination of the slip and deflection zone

composite and solid support roll................................................................. 37

2.7 Determining the deflection of a solid support roll.................................................... 37

2.8 Determination of deflection and slip zone for

composite support roll................................................................... ............. 39

2.9 Development of measures to prevent fretting -

corrosion on sedimentary surfaces and increase in the surface of the roll46

2.10 Study of the influence of coatings of mating coatings

on the bearing capacity of the axle-bandage connection.

Selection of material and coating technology.................................................... 48

2.11 Selection of axle and tire material and methods of their heat treatment. 52

4 Economic justification for the project.................................................... 57

4.1 Calculation of the production program.................................................... 57

4.2 Calculation of capital cost estimates.................................................... 58

4.3 Labor organization and wages.............................. 59

4.4 Calculation of contributions for social needs.................................... 63

4.5 Calculation of product costs.................................................... 64

4.6 Calculation of main technical and economic indicators........... 65

Conclusion................................................. ........................ 68

List of sources used......................................................... 70

Introduction

The purpose of this thesis is to develop the design of composite support rolls, ensuring their reliability during operation, increasing their durability and reducing cost.

Rolls are the main element of the rolling stand, with the help of which the rolled strip is compressed. The requirements for rolling rolls are varied and relate not only to their operation, but also to the manufacturing process. The rolling roll operates under the simultaneous influence of rolling force, torque, temperature in the deformation zone, etc. Therefore, one of the main requirements is high wear resistance and thermal fatigue strength, which determines low and uniform wear of the rolls.

One of the ways to increase the durability of rolling rolls and reduce their metal consumption is to use composite rolls. The use of tires made of high-strength materials and the possibility of replacing worn tires when using the axle repeatedly will give a great economic effect.

Currently, in the 5.6 finishing stands of the 2500 mill of OJSC MMK, support rolls of 1600x2500 mm are used, which are made of forged steel 9HF. In this work it is proposed to use composite rolls with a bandage made of cast steel 150ХНМ or 35Х5НМФ. It is proposed to use used solid forged rolls as axles. Experience in operating rolls made of similar materials shows that their wear resistance is 2-2.5 times higher than forged ones. The connection of the tire to the axle is carried out by a fit with guaranteed interference. In order to increase the transmitted torque, it is proposed to apply a metal coating to the seating surface of the axle, which significantly increases the coefficient of friction, the area of actual contact between the axle and the tire, and its thermal conductivity.

1 Brief overview of composite mill rolls. Characteristics of mill 2500. Mill assortment.

1.1 Brief overview and analysis of composite mill roll designs

The main advantages of composite rolls:

The ability to produce a bandage and axle from materials with different mechanical and thermophysical properties;

Possibility of replacing a worn bandage when using the roll axis repeatedly;

Heat treatment of the axle tire can be carried out separately, which makes it possible to increase hardenability, obtain uniform hardness throughout the entire thickness of the tire and reduce the residual stress gradient, which is very high in a solid roll of large mass.

The production of banded support rolls for sheet metal mills was mastered back in the 70s of the last century. The band and the axle are connected, as a rule, by a thermal method with a guaranteed fit; tires are made forged or cast, axles are forged; decommissioned rolls are usually used for their production. The hole in the bandage is most often cylindrical, seat the axis can be cylindrical, barrel-shaped or similar in shape to reduce stress concentration at the ends of the bandage after assembly.

According to the method of fastening the tires, composite rolls can be divided into the following groups:

Using a fit with guaranteed interference;

Application of various mechanical methods bandage fastenings;

Use of light alloys and adhesive joints.

Many works of domestic and foreign scientists are devoted to improving designs, production and assembly methods, and increasing the technological characteristics of composite rolls. Much attention is paid to work to ensure a reliable connection of the tire to the axle.

For example, in the work it is proposed to use a composite rolling roll containing a tension band and placed on an axis with channels made in a spiral on the surface in contact with the band and a shoulder. The work proposes the use of rolls with a composite band made of sintered tungsten carbide. In a number of works recent years Welded bandages made of high-alloy alloys are increasingly being proposed for use. In many cases, when simplifying the roll manufacturing technology and increasing the wear resistance of its surface, the cost increases significantly due to the use of a large number of alloying elements. Therefore, in order to increase the service life of rolls, many authors devote their work to improving the design of composite rolling rolls.

The work proposes composite rolls containing a bearing profiled axis and a band with a profiled inner surface, fitted with an interference fit with the possibility of free movement of its sections of smaller diameter in a heated state along the bearing axis through sections with a larger diameter along the length. Moreover, the generatrices of the surfaces of the barrel of the axle and the tire are made profiled in the form of a smooth curve according to certain dependencies (Figure 1,2). The disadvantages of such rolls include the complexity of their manufacture, the inability to control the required curvature of the profile of the seating surfaces, and in this case, the service life of the roll is also limited, caused by the small number of possible regrinding of the band, due to the occurrence of tensile stresses in the middle part from heating and thermal expansion of the bearing axis in process of rolling stand operation (Figure 2). But the main disadvantage can still be considered the complexity of the curves describing the profiles of the mating surfaces, which complicates the turning process, and the accuracy required when

their production is practically impossible with the technologies existing at machine-building plants.

Figure 1 – Composite rolling roll

Figure 2 – Composite rolling roll

In the work, under the conditions of the MMK OJSC mill 2500, it is proposed to use a composite support roll, made in accordance with the diagram in Figure 3. The disadvantage of such a roll is the presence of a transition section of the axis from the shoulder to the conical part, which is a concentrator for increasing stress, which can lead to breakage of the axis when increased loads and deflection, as well as limiting its service life. In addition, this design is low-tech in production.

Figure 3 – Composite rolling roll

The objective of the proposed manufacture of a composite support roll is the simplest technical solution, which will increase the service life by ensuring constant tension along the entire length of the mating surfaces.

It is proposed to make the seat of the bandage and the axle cylindrical, from the point of view of simplicity and manufacturability. On the edges of the axle, make unloading chamfers - bevels, to reduce stress concentration. To increase the load-bearing capacity of the connection and the performance of the roll, the main attention should be focused on choosing the optimal tension value, developing measures that significantly increase the coefficient of friction on the mating surfaces and the thermal conductivity of the axle-tire contact.

When performing strength calculations, it is necessary to choose a technique that allows taking into account the influence of rolling forces on the stress-strain state of the bandage.

1.2 Characteristics of hot rolling mill 2500

The 2500 wide strip hot rolling mill consists of a loading section, a heating furnace section, roughing and finishing groups with an intermediate roller table between them and a winding line.

The loading area consists of a slab warehouse and a loading roller table, 3 lifting tables with pushers.

The heating furnace section consists of 6 methodical heating furnaces, a roller table in front of the furnaces with pushers, and a furnace roller table after the furnaces.

The roughing group consists of stands:

Reversible duo cage;

Quarto expansion cage;

Reversible universal quarto cage;

Universal quarto stand.

The finishing group includes flying shears, a finishing descaler (duo stand), 7 quarto stands. Devices for accelerated strip cooling (inter-stand cooling) are installed between the stands.

The intermediate roller conveyor ensures the removal and separation of deficiencies (it is planned to equip the roller conveyor with encopanel-type heat shields).

The coiling line includes an outlet roller conveyor with 30 strip cooling sections (upper and lower showering), four winders, and trolleys with lifting and rotating tables.

1.3 Mill assortment by steel grades and strip sizes

The wide strip mill 2500 is designed for hot rolling of strips of the following steels:

Carbon steel of ordinary quality in accordance with GOST 16523-89, 14637-89 steel grades in accordance with GOST 380-71 and current specifications;

Steel weldable for shipbuilding according to GOST 5521-86;

High-quality structural carbon steel in accordance with GOST 1577-81, 4041-71, 16523-89, 9045-93 and current specifications;

Alloy steel grade 65G according to GOST 14959-70;

Low alloy steel according to GOST 19281-89;

Steel 7ХНМ according to TU 14-1-387-84;

Carbon and low-alloy steel for export according to TP, STP based on foreign standards.

Limit strip sizes:

Thickness 1.8×10 mm;

Width 1000×2350 mm;

Roll weight up to 25 tons.

2 Research and development of the design of the banded back-up roll of the 2500 hot rolling mill

2.1 Selection of tension, shape, thickness of the bandage and calculation of the load-bearing capacity of the connection

The back-up roll 5 and 6 stands of hot rolling mill 2500 of OJSC MMK, in accordance with Figure 4, has the following main dimensions:

Barrel length l=2500 mm;

Maximum outer diameter of the barrel d=1600 mm;

Minimum outer diameter d=1480 mm;

The diameter of the necks at the junction with the barrel is 1100 mm;

The seat of the bandage is cylindrical. At a distance of 100 mm from each edge of the axis, it is proposed to make unloading chamfers 10 mm high to reduce the stress concentrations of the bandage after assembly. This is explained by the fact that the bandage is connected to the axle by a thermal method, and when forming the connection, the edges of the bandage cool faster than its middle part, which leads to the appearance of stress concentration and provides an additional opportunity for the development of fretting corrosion and fatigue cracks in the future

Often, to prevent the bandage from slipping in the axial direction, a shoulder is made on the axis, and a groove is made on the bandage, or the seating surfaces are shaped like a cone. In this case, such devices are not used, since it can be assumed that if the mating surfaces are long enough, axial displacement will not occur, and the strength of the connection will also be ensured by guaranteed interference and a possible increase in the coefficient of friction on the surfaces due to the application of a metal coating or abrasive powder to them .

Also, this design is much simpler and cheaper to manufacture.

Analysis of factors influencing the choice of landing diameter shows that the region of optimal values of the ratio of landing and outer diameters fluctuates in the range d/d 2 =0.5...0.8.

If we talk about the choice of connection tension, then you may encounter disagreements. In practice, the optimal interference is usually taken to be 0.8-1% of the landing diameter: D=(0.008?0.01)d. Some authors advise increasing it to 1.3%, and some, on the contrary, reducing it to 0.5%

For calculations, we will select three different values of interference: D 1 =0.8 mm; D 2 =1.15 mm; D 3 =1.3 mm.

Also, to compare and select optimal connection criteria, we will perform calculations for different friction coefficients and bandage thicknesses.

	d landing 1 =1150 mm
	d landing2 =1300 mm

As mentioned above, the value of the friction coefficient can be changed by applying some kind of coating to the mating surfaces.

The greatest thickness of the bandage (d fit = 1150 mm) is determined by its passage through the necks of the rolling roll during assembly.

D fit > 1300 mm is not taken into account, since when the minimum outer diameter is reached (d 2 = 1480 mm), the bandage will become too thin.

Let's calculate some parameters of the load-bearing capacity of the connection under given conditions.

Maximum axial force that a connection can withstand:

where K is the pressure on the landing surface, MPa;

F=pdl – seating surface area, mm 2; (d and l are the diameter and length of the seating surface, respectively, mm)

f – coefficient of friction between mating surfaces.

The pressure K on the seating surfaces depends on the interference and the wall thickness of the female and male parts.

According to Lame's formula:

where D/d is the relative diametrical interference;

q - coefficient.

where E 1 = E 2 = 2.1x10 5 N/mm 2 – elastic modulus of the axle and bandage;

m 1 =m 2 =0.3 – Poisson’s ratios for steel axle and tire

C 1 , C 2 – coefficients characterizing thin-walledness;

where d 1 and d 2 are the internal diameter of the axis and the outer diameter of the tire, respectively.

For this case, there is no hole in the axis - d 1 = 0, and we take the average diameter of the roll as the diameter d 2:

Then C 1 =1 (d 1 =0).

Maximum torque transmitted by the connection:
The compressive stress in the axis is maximum on the inner surface:

On the inner surface of the bandage the maximum tensile stresses are:

The calculation results are summarized in Table 1.

Conclusions: As you can see, the pressure K, and, consequently, load bearing capacity connections is proportional to the tension and inversely proportional to the coefficients C 1 and C 2, characterizing the thinness of the wall.

The difference in landing diameters is only 150 mm, but with the same interference fits, the difference in contact pressure is almost twice as large for a smaller diameter.

It should be noted that the compressive stress in the axis is also lower in the case of a thinner bandage, but the tensile stresses in the bandage remain practically unchanged with a change in its thickness.

Table 1 - Characteristics of rolling rolls 5,6 stands of mill 2000 and their load-bearing capacity at various values of diameters, interference, friction coefficients in the connection

Metal pressure on rolls, t

Rolling moment, tm

Outer diameter of bandage, mm

d2=1600 (1480) dav=1540

Mating length, mm

Diameter of mating surfaces, mm

d=1150 (C2=3.52)

d=1300 (C2=5.96)

Mounting surface area sq.mm

Preload, mm

Contact pressure, MPa

Roll axis stress, MPa

Tension in the bandage, MPa

Friction coefficient f

Maximum axial force Ros, t

Maximum torque Mkr, tm

Figure 4 - Composite rolling roll

With increasing friction coefficients, the load-bearing capacity of the connection also increases significantly, both in the case of d=1150 mm and with d=1300 mm, but in the case of d=1150 mm it is more maximum.

It is important that for all conditions the connection ensures transmission of torque with a good margin of safety

M pr<М кр

Moreover, the safety factor increases as the contact pressure in the connection increases, caused by interference.

In general, we can say that in both cases a good load-bearing capacity of the connection and fairly low stresses in the roll parts are ensured, but a bandage with an internal diameter d = 1150 mm is more preferable, due to a significant increase in the same load-bearing capacity.

2.2 Calculation of stresses in a banded support roll

The stresses in the composite back-up roll of the 2500 mill are determined for the same basic technical data specified in paragraph 2.1. It is required to determine the contact stresses on the seating surface of the bandage and the axle.

Let's denote the bandage area by S 2 , and the shaft area by S. Let's denote the radius of the mating surface after assembly by R, and the outer radius of the bandage by R 2 .

A force P is applied on the outer contour of the bandage C2, equal in magnitude to the metal pressure on the rollers P0. Taking P=P 0, we have a system of forces that are in equilibrium. The seating surface forms contour C.

The calculation scheme is presented in Figure 5.

Figure 5 – Calculation scheme for determining contact stresses in the roll

When solving a problem, it is convenient to determine stress in polar coordinates. Our task is to determine:

s r – radial stresses

s q - tangential (circumferential) stresses

t r q - tangential stresses.

Calculations of stress components are usually quite cumbersome in general form and in calculations. Using the method of N.I. Muskhelishvili, in relation to the problem posed and carrying out a solution similar to that given in the work, the stresses on the seating surface of the bandage are determined in the form of formulas convenient for numerical implementation. The final expressions are:

where P=P 0 – specific load per unit length of the bandage from an external force;

R – radius of the contact surface;

h and g are series summed up in closed form, reflecting the peculiarity of the solution in the zones of points of application of concentrated forces P and allowing to improve the convergence of the series;

q - angular coordinate of points of contour C;

Constant Muskhelishvili;

m=0.3 - Poisson's ratio;

a is the angle measured from the x-axis to the point of application of force P;

n=R 2 /R – coefficient characterizing the thickness of the bandage.

The last terms in formulas (9) and (10) represent stress components that depend on interference. Then the radial and tangential stresses in the composite roll are determined from two components, from the stresses caused by interference and normal load:

sr =srp +srD (12)

sq =sqp+sqD (13)

Normal tension stresses are determined by the formula:

where K – contact pressure from interference (see Table 1), MPa;

n=R 2 /R – relative thickness of the bandage.

Stress s q D is calculated using the following formula:

where d is half the interference value;

E – elastic modulus of the first kind.

As is known, there are no tangential stresses on surfaces due to tension.

Then the voltages s rp , s q p and t r q can be represented as:

The values of s rp, s q p and t r q were calculated on a computer for various values of n, some of which are given in Table 2.

The stress values are presented in the form of dimensionless coefficients C p, C q, C t, which should be multiplied by the value P/(R 2 x10 3), where P is the external load per unit length of the bandage, N/mm; R 2 – outer radius of the bandage.

To determine the stress components, it is necessary to know only n (the relative thickness of the bandage) and q (the polar angular coordinate of the point at which the stresses are determined).

In accordance with Figure 5, under the given conditions that the main vector and the main moment of force P are equal to zero, the stress diagrams on the contact are symmetrical relative to the y-axis, that is, it is sufficient to determine the stresses in 2 of the 4 quarters, for example, in I and IV (from 3p/2 to p/2 rad).

The nature of the stress distribution along the axle – bandage contact is presented in Figures 6, 7, 8.

Table 2 – Stress components and radial, tangential, tangential stresses on the seating surface of the bandage from the influence of a force P = 1200 kg/mm of stands 5.6 of mill 2500

N=1.34 (d=1150 mm)

n=1.19 (d=1300 mm)

Figure 6

Figure 7

Figure 8

Analysis of the data obtained made it possible to identify the following patterns: s rp takes the smallest values along the line of action of the concentrated force P together with its direct application q = 270°. At certain values of the angle q "295° for n=1.34 and q"188° for n=1.19 the values of s rp change sign. Compressive stresses turn into tensile stresses, tending to break the solidity of the connection. Consequently, the s rp diagrams can have a certain physical interpretation: the contact points at which the stress signs change determine the areas of the joint opening zone in the absence of contact pressure from tension due to the elastic deformation of the bandage.

The thinner the bandage, the greater the maximum increase in s rp at q=270° and the greater the stress gradient in the region q=260–280°.

The thicker the bandage, the greater the tensile stress, but their gradient is insignificant, that is, the thinner the bandage, the greater the compression force on the axis.

The diagrams of tangential stresses in the zone of action of force P show that s qр are tensile, and their maximum value is practically independent of the thickness of the bandage. The stress gradient increases with decreasing bandage thickness, and the width of the zone decreases. On most of the contact surface of the axle and the bandage, the stresses are compressive with a smaller gradient for n=1.34.

The diagrams of tangential stresses t r q in Figure 9 change sign at points at q»215° and on most of the contact surfaces they are tensile, but small for both cases, and, therefore, not too significant.

Table 3 presents the values of s r D and s q D for various values of D and n.

Table 3 – The magnitude of contact pressure and tangential stress from interference.

Based on the data in Tables 2 and 3, we will construct diagrams for s rp s r D and the resulting s r in accordance with Figure 9. Tangential stresses from tension are different in sign for the contact stresses of the axle and bandage, therefore, consideration of the total diagrams on these surfaces must be done separately (Figure 10, eleven).

The analysis of stresses at the axle-tire contact of a composite roll shows that for any load pattern, the total diagram of the contact pressure differs significantly from the diagram of the pressure caused by interference. Contact pressures are distributed evenly around the circumference and have a high gradient in zones of disturbance from metal pressure forces on the roll. In this case, the contact pressures from the interference constitute only a part of the total contact pressure (in accordance with Figure 9) over a significant part of the contact. On part of the contact surface, the total pressure is slightly less than the tension pressure.

MPR? [Mkr] = R? f? R (19)

where Mpr is the rolling moment;

Figure 9

Figure 10 – Diagrams s q р, s q D, s q on the contact surface of the axis of the support roll of the mill 2500 at P = 1200 kg/mm; n=1.19; n=1.34 and D=0.8; 1.15; 1.3

Figure 11 – Diagrams s q р, s q D, s q on the contact surface of the support roll bandage of mill 2500 at Р=1200kg/mm; n=1.19; n=1.34 and D=0.8; 1.15; 1.3

a significant part of the contact. On part of the contact surface, the total pressure is slightly less than the tension pressure.

Calculation of the roll for the possibility of turning the bandage on the axis due to the action of torque is carried out according to the formula:

MPR? [Mkr] = R? f? R (19)

where Mpr is the rolling moment;

[Mkr] – torque that the connection can transmit with interference;

P – contact pressure in the connection;

f – coefficient of static friction on the seating surfaces of the connection;

R – radius of the landing surface.

The permissible torque is directly proportional to the contact pressure; therefore, when calculating a composite roll for the possibility of turning the band, it is necessary to take into account the distribution features and the magnitude of the contact pressure in the rolls.

The total contact pressure in a composite roll is determined by the formula:

P=sr =srp +srD

By integrating s r in a circle, we can determine the maximum torque that a composite roll can transmit, taking into account the action of external forces P:

Calculations made using this formula showed that the increase in the maximum torque that a composite roll can transmit without turning the band, taking into account the influence of external forces P, is approximately 20-25%.

The transmitted torque is proportional to the friction coefficient f. The deformation of the roll under load also depends on the value of the friction coefficient. Obviously, to prevent deformation and microdisplacements at the points of contact, it is possible to increase the friction coefficient and create the required specific pressure at the contact. Changing the contact pressure can be achieved by changing the amount of tension and changing the thickness of the bandage. As can be seen from Figures 6, 7, 8, a decrease in the thickness of the bandage leads to an increase in stress gradients at the places where the load is applied. And an increase in interference, in turn, leads to an increase in the stresses themselves, which already at a value of D = 1.15 for d 2 = 1150 mm and D = 1.3 for d 2 = 1300 mm exceed the permissible values for steel 150ХНМ, equal to 200 MPa (Table 1), from which it is proposed to make a bandage.

Therefore, it becomes obvious to increase the coefficient of friction on the seating surfaces. The optimal choice of values for the tension and friction coefficient will avoid surface wear, which will facilitate the repeated use of the axle.

2.3 Calculation for the frequency of use of the axis of a composite support roll

The axles of banded support rolls are made from decommissioned, already used rolls. Therefore, the calculation for the frequency of use of the axle is based on the fatigue strength of its material - 9HF steel.

The calculations took into account the number of loading cycles, the fatigue characteristics of the axle material, as well as the values of 3 types of stresses:

1 – compressive, caused by the fit of the bandage on the axis with tension;

2 – bending, caused by metal pressure on the rolls;

3 – tangents caused by torsion.

The calculation was carried out for the most dangerous sections 1-1 and 2-2 (Figure 12) with different values of the fit interference.

The back-up roll 1600x2500 is transshipped in 5 and 6 stands every 150 thousand tons of rolled products. When sanding, remove from the surface

Figure 12 – Schematic representation of the sections for which the roll axis was calculated for fatigue strength.

1-1 – cross section of the middle of the roll barrel

2-2 – section, at the point of transition from the roll barrel to the neck.

barrels are produced with a diameter of at least 3 mm. The total removal is 120 mm (? max = 1600 mm, ? min = 1080 mm), that is, the roll can be installed at least 40 times, for example, 20 in each stand

The main technological characteristics of the 5th and 6th stands of the finishing group of the 2500 hot rolling mill of OJSC MMK are given in Table 4.

Table 4 – Main characteristics of stands 5, 6

In the calculations we take the average rolling diameter of the support roll d av = 1540 mm.

The metal pressure on the rolls is constant, therefore, the maximum bending stresses s bend max are equal to s bend min taken with the opposite sign. The compression stresses s сж (Table 1), depending on the magnitude of the interference, are also constant.

Calculations were made for three different interference values D=0.8; 1.15; 1.3.

Thus, cyclic loading in all cages, combining the action of constant and variable loads, is asymmetrical in nature.

The number of loading cycles in each cage is:

where V i is the rolling speed in each stand, m/s;

d av – average rolling diameter of the support roll barrel, m;

t is the operating time of the roll in each stand per installation, h;

K – number of installations.

The calculation results are summarized in Table 5.

Table 5 – Number of operating hours and loading cycles in each cage

The total number of loading cycles of the support roll when using the axis once is: N=SN i =5.14x10 6 .

2.4 Determination of cyclic endurance in section 1-1

Maximum bending stress:

where P = 3000 tf – metal pressure on the rolls;

a = 3.27 m – distance between the axes of the pressure screws;

W bend = pd 2 axes /32 – moment of resistance of the section during bending;

L barrel =2.5 m – length of the support roll barrel.

The maximum compressive stresses s compress are found according to formula (7). Therefore, we have:

Where j s is the coefficient of sensitivity of the metal to cycle asymmetry;

s 0 =(1.4…1.6) s -1 - fatigue limit for the pulsating cycle.

The maximum stress caused by torsion t maxi in each stand depends on the maximum torque M cr i = 217 tm:

Equivalent stress, taking into account all types of stresses acting on the composite roll:

The calculation results are summarized in Table 6.

Table 6 – Stress values in the roll for various values of landing diameters and interferences

Bore diameter, m

s bend, MPa

Preload, mm


s eq, MPa

The corresponding number of cycles that the sample can withstand before failure is:

The axle material is 9HF steel, with the following fatigue characteristics:

s -1 =317 MPa – endurance limit;

N 0 =10 6 – base number of cycles;

R=tga=(0.276s -1 -0.8)=7.95 kg/mm 2 – slope of the fatigue curve

To assess the durability margin and service life of a part when calculating for limited durability, the n additional duty criterion is used. – permissible durability margin:

where n additional =1.5 – permissible safety factor.

Multiplicity of axle use with full use of the strength properties of the material:

The calculation results are summarized in Table 7.

Table 7 - Influence of the bore diameter and axle tension on its multiplicity

Bore diameter, m
Preload, mm

T axis ratio

Based on the calculations, the following conclusions can be drawn: with increasing tension, the frequency of use of the axis of the composite support roll is reduced due to an increase in constant compressive stresses caused by the hot fit of the band on the axis with interference. In the case of a thinner band (d=1.13 m), there is an increase in the frequency of use of the axle by more than 3 times at the same tension values, since d=1.13 m is characterized by lower axle compression stresses. If we turn to the stress distribution diagrams for different thicknesses of the bandage (Figure 6, 7, 8, 9, 10, 11), then we should note a less favorable picture for a thinner bandage. It should also be taken into account that the calculations took into account not just the maximum permissible loads on the roll, but their peak values. If we take into account that for steel 150ХНМ, from which it is proposed to make the bandage, the tensile stresses in the bandage exceed the permissible ones in the cases of d=1.15 m at D=1.15 mm and d=1.3 m at D=1.3 mm (Table .1), then the option with d=1.15 m, D=0.8 can be considered optimal. The axis multiplicity in this case is 2.45 times. But, taking into account that the actual loads are somewhat less than the calculated ones, and also that it is proposed to apply a metal coating to the mating surfaces, which increases the load-bearing capacity of the connection without significantly changing its stress state, the frequency of use of the axis will naturally increase.

2.5 Determination of cyclic endurance in section 2-2

The axis of the support composite roll in section 2-2 experiences bending and tangential stresses. Under such loading, the stresses change in a symmetrical cycle:

There is no danger of fatigue failure of the axle in this section.

2.6 Determination of the slip and deflection zone of a composite and solid support roll

It is a known fact that during work, as a result of the action of applied loads, both the working and support rolls begin to bend. The phenomenon of deflection can cause deterioration in the quality of the rolled strip, runout of the rolls, which, in turn, can lead to rapid failure of bearing units and the appearance of fretting corrosion.

The temperature difference between the band and the axle during the rolling process, in the case of a composite roll, can lead to rotation of the band relative to the axis, that is, the appearance of a slip zone.

Below are calculations of the possible size of the slip zone taking into account the existing loads and determining the deflection of a composite and solid support roll in order to compare their values.

2.7 Determination of deflection of a solid support roll

The metal pressure on the rolls during rolling is transmitted through the work rolls to the support rolls. The nature of the pressure distribution along the barrel of the support rolls depends on the width of the roll, the rigidity and length of the barrel of the working and support rolls, as well as on their profile.

If we assume that the metal pressure on the rolls is transmitted uniformly by the work roll to the support roll, then the deflection of the support rolls can be calculated as the bending of a beam freely lying on two supports, taking into account the action of transverse forces.

Overall support roll deflection:

f o.v. =f o.n. =f 1 +f 2 (32)

where f 1 – deflection due to bending moments;

f 2 - deflection arrow from the action of transverse forces.

In its turn

where P is the metal pressure on the roll;

E – modulus of elasticity of the roll metal;

G – shear modulus of the roll metal;

D 0 – diameter of the support roll;

d 0 – diameter of the support roll neck;

L – length of the support roll barrel;

a 1 – distance between the axes of the support roller bearings;

c – distance from the edge of the barrel to the axis of the support roller bearing.

Table 8 - Data for calculating the deflection of a solid support roll

Name	Designation	Meaning
Metal pressure on the roll, N
Modulus of elasticity of the roll metal, N/mm 2
Roll metal shear modulus, N/m 2
Support roller diameter, mm
Support roll neck diameter, mm
Support roller neck length, mm
Continuation of table 8
Distance between bearing axes, mm
Distance from the edge of the barrel to the bearings, mm
Deflection due to bending moments, mm
Deflection due to shear forces, mm

Then the total deflection of the support roll is:

f=0.30622+0.16769=0.47391 mm

2.8 Determination of deflection and slip zone for a composite support roll

Basic data for the calculation are given in Table 9.

Table 9 – data for calculating the rigidity of a composite support roll

Index	Designation	Meaning
Bandage radius, m
Axle radius, m
Modulus of elasticity of the first kind, N/m 2
Modulus of elasticity of the second kind, N/m 2
Coefficient taking into account the uneven distribution of shear stresses

Coefficient taking into account the design of the edges of the bandage
Coefficient depending on the cross section of the axis
Coefficient depending on the cross section of the bandage
Continuation of table 9
Poisson's ratio
Preference between the band and the roll axis, m
Influence coefficient of the axle parts protruding along the edges of the tire
Friction coefficient
Torque, Nm
Support roll barrel length, m
Impact force on the roll, N
Roll neck radius, m
Roll neck length, m
Neck coefficient

Cross-sectional area of the bandage and axle:

Moments of inertia of the bandage and axle:

Constant coefficient:

Contact pressure P H =32.32x10 6 N/m 2 (see Table 1).

Bending moment per unit length arising due to friction forces:

m = 4mP HR 2 = 12822960 Nm (39)

Calculation of the length of the area where the bandage slips relative to the axis during bending:

Let us determine the deflection of the composite support roll using the methodology given in the work. The design diagram is shown in Figure 13.

Figure 13 – Diagram of the acting forces in the axial section of the banded roll

Bending moment acting on the roll in section:

Shearing force acting on the roll in section:

Q 0 =q 0 (l 0 -l) = 10.23x10 6 N (45)

Determination of deflection at [x=0]:

Angle of rotation at [x=0]:

Intensity of the interaction force between the axle and the bandage:

Determination of deflections for the bandage and axle in the slipping area:

Angles of rotation of the bandage and axle:

Bending moment on the bandage and axle:

Shearing force acting on the band and axle:

Shift of the band relative to the axis at the edge of the roll barrel:

Roll neck deflection:

Full deflection of the banded roll:

y=y x +y w = 0.000622 m = 0.622 mm(65)

As can be seen from the calculation results, the deflections of composite and solid rolls under load are almost the same. The deflection of a composite roll is slightly greater than the deflection of a solid one (y solid = 0.474 mm, y composite = 0.622 mm). This suggests that the rigidity of the composite roll is lower, as a result of which the band can slide relative to the axis. Calculations, in turn, showed that the slip zone is small and amounts to only 0.045 m. The size of the slip zone and the rigidity of the roll as a whole are affected by the circumferential tensile stresses in the sleeve s t (in accordance with Figure 13).

Experiments carried out to study the rigidity of composite rolling rolls made it possible to see that the highest tensile stresses s t are located on the inner contour of the bandage in the area of its contact with the shaft; this indicates an increase in contact pressures from landing when the roll bends. It has been established that a decrease in the relative interference reduces the stress s t. Consequently, by reducing the tension of the press connection, it is possible to eliminate the destruction of the bandage, however, this leads to a loss of shaft rigidity, weakens the press connection, expands the area of the bandage slipping and promotes fretting corrosion of the seating surface. Since the minimum interference value (D=0.8 mm) was chosen for the calculations, to improve the adhesion of the shaft to the bandage, it is necessary to increase the friction coefficient on the seating surface, for example, by applying a metal coating.

2.9 Development of measures to prevent fretting - corrosion on sedimentary surfaces and increasing the surface of the roll

Fretting – corrosion – damage to a metal surface as a result of contact friction in which separated particles and surface layers interact with components environment(most often with oxygen).

It is known that with the slightest loads on contacting surfaces, noticeable damage to the surface layers from fretting can occur. This fully applies to composite rolling rolls assembled using an interference fit, in which contact pressures reach significant values and there are slip zones adjacent to the ends of the band. At the junction points, with alternating displacements of the seating surfaces of the axle and the tire, scuffs are formed, the number of which increases almost proportionally to the tension. Subsequently, they become stress concentrators, which causes accelerated fatigue failure of the axis located at some distance from the end of the bandage along the seating surface. As a rule, in roll designs where fretting corrosion is pronounced, destruction occurs here, and not along the neck. In order to reduce the influence of this process at the ends of the axle, destructive chamfers are made in order to increase the reliability of the axle by removing stress concentrators, which become zero at the mating edge (Figure 14).

Figure 14 – Bevels on the edge of the axis of the banded roll

However, without special types of processing of the seating surfaces, it is not possible to avoid axle failures for this reason. In this case, soft galvanic coatings are most effective. Their use significantly increases the area of actual mating contact. In this case, strong bonds arise in the contact of the mating parts (metal bonding), due to which the metal surfaces of the mating parts are protected from scuffing and mechanical damage. At the same time, the likelihood of the formation of residual deflection sharply decreases, and the prerequisites for repeated use of the axle with replaceable tires increase.

2.10 Study of the influence of mating coatings on the load-bearing capacity of the axle-tire connection. Selection of material and coating technology.

The load-bearing capacity of an interference fit connection is directly proportional to the coefficient of friction on the seating surface, which is included in the basic calculation formulas for determining the highest torques and axial force. The friction coefficient depends on many factors: the pressure on the contact surfaces, the size and profile of microroughnesses, the material and condition of the mating surfaces, as well as the assembly method. It should be noted that for large diameters (d=500 - 1000 mm) of seating surfaces and, accordingly, interferences (up to 0.001 d), which are characteristic of the design of composite rolls, there are no experimental data on the magnitude of friction coefficients. Usually, when calculating composite rolls, the assembly of which is carried out by heating the band to 300-400°C, the friction coefficient is taken equal to f = 0.14. Such caution and the choice of a very low friction coefficient are fully justified. The fact is that at large values of interference (up to 1 - 1.3 mm), the influence of the initial surface roughness and the oxide films formed on it when the bandage is heated, increasing the friction coefficient, may be very insignificant.

A number of works indicate that the load-bearing capacity of tension joints can be significantly increased by applying galvanic coatings to one of the seating surfaces. The thickness of the coatings is usually 0.01 - 0.02 mm. On average, the use of coatings increases friction coefficients by one and a half to four times for all assembly methods.

The increase in the strength of connections with galvanic coatings is explained by the appearance of metallic bonds in the contact zone and an increase in the actual contact area. It was revealed that soft galvanic coatings, even in the region of low pressures, are subject to plastic deformation and will fill the depressions in the microprofile of the covered part without causing plastic deformation. The increase in the strength of the joints is caused by the fact that at the initial moment of displacement of the parts, a simultaneous cutting of a large number of microvolumes of the coating with irregularities of the covered part occurs. The most favorable effect on the load-bearing capacity of cylindrical joints with interference is exerted by soft (anodic) coatings (zinc, cadmium, etc.). They help not only increase the strength of the joints, but also the fatigue resistance of the shafts. Application of zinc coating increases the endurance limit of shafts during circular bending by 20%.

When coatings are applied, the tension in the joint increases. Typically, the increment in interference is taken equal to twice the thickness of the coating, regardless of its type. It should be noted that with large interferences and large diameters of the connection, the influence of the coating thickness is not so significant.

An analysis of the results of works that examine the effect of coatings on the load-bearing capacity of interference joints gives reason to believe that a coating made of sufficiently ductile metals is most suitable for composite rolls. Applying such coatings to the seating surface of the axle allows you to increase the friction coefficient by at least 2 times. When choosing a coating method and technology, we will be guided by the following considerations.

There are various methods of applying metal coatings to prevent corrosion, high temperature, reduce wear, etc. Almost all coating methods (hot, electrolytic, spraying, chemical deposition, etc.) require surface preparation, usually including degreasing, etching , chemical and electrochemical polishing. These operations are harmful to operating personnel and, despite careful wastewater treatment, pollute the environment.

Using the above methods to coat the axle of a composite mill roll about 5 meters long presents significant technical difficulties. It should be noted that in works that provide data on the effect of coatings on the coefficient of friction, coatings were applied electrolytically or hot to small samples or models of rolling rolls. The use of such methods for large-sized rolls will require the creation of special departments or workshops. It seems appropriate to use friction coating methods. One of the simplest and most effective is the method of applying a coating with a rotating metal brush (VMShch, friction cladding). In this case, simultaneously with the application of the coating, surface plastic deformation (SPD) occurs, which will help increase the fatigue strength of the roll axis.

A diagram of one of the options for applying a coating with a rotating metal brush is shown in Figure 14.

The coating material (MP) is pressed against the pile of the VMSh and is heated in the contact zone with it to a high temperature. Particles of the coating metal are attached to the ends of the fibers and transferred to the surface to be treated. The surface of the workpiece is strengthened due to intense plastic deformation by flexible elastic elements. At the same time, plastic deformation of the coating metal particles located at the ends of the fibers occurs and they adhere to the surface of the product. Removal of oxide films, exposure of clean surfaces with joint plastic deformation of the surface layers and particles of the coating material ensures their strong adhesion to the base.

Figure 14 – Scheme of coating application by friction cladding (FP)

1- blank of coating material (MP)

2- tool with flexible elastic elements (VMSh)

3- workpiece (axis of the composite roll)

The coating that is applied to the seating surface of the axis of the rolling roll must have the following properties: significantly increase the coefficient of friction, be sufficiently plastic and fill the cavities of the microprofile, and have good thermal conductivity. Aluminum can meet these requirements. It is well applied to a steel surface using a VMSh and forms a coating of sufficient thickness. However, the answer to the main question - about the value of the friction coefficient in a connection with an interference fit, one of the mating surfaces of which is coated with aluminum - is missing in the technical literature. Cylindrical joints made of steel - aluminum materials, assembled using an interference fit, are also not known, since pure aluminum is not used as a structural material due to its low strength characteristics. However, there is data on friction coefficients during plastic deformation of metals (Table 10).

Table 10 - Coefficients of dry friction of various metals on steel grade EKh-12 with hardness HB-650

			Brass L-59	Aluminum
Average friction coefficient

As follows from Table 10, aluminum under conditions of plastic deformation has a maximum coefficient of friction in contact with the rest of the surface. In addition, aluminum has very high thermal conductivity. These factors were the reason for choosing aluminum as the coating material for the male surface of the roll axis.

2.11 Selection of axle and tire material and methods of heat treatment

When choosing the material for composite rolls, the thermomechanical conditions of their service should be taken into account. Rolls are subjected to significant static and impact loads, as well as thermal effects. Under such harsh operating conditions, it is very difficult to select a material that simultaneously provides high strength and wear resistance.

There are different requirements for the roll barrel and its core. The core must have sufficient viscosity and strength, and be able to resist bending, torque and impact loads well. The surface of the barrel must have sufficient hardness, wear resistance, and heat resistance.

The roll axis is made of 9ХФ steel, the roll band is 150ХНМ, based on the experience of using this steel in the manufacture of composite roll bands at OJSC MMK. It is proposed to use a more alloyed steel as the bandage material - 35Х5НМФ, which has higher wear resistance in comparison with 150ХНМ. Data on the wear resistance of roll materials under hot rolling conditions are presented in Table 11.

Table 11 - Mechanical properties and wear resistance of roll materials.

steel grade	Approximate chemical composition	Mechanical properties			Relative wear resistance
steel grade	Approximate chemical composition	Hardness	s V, kg/cm 2	s t, kg/cm 2	Relative wear resistance
	0.08-0.9%C, 0.15-0.3%V, 0.15-0.35%Si, 0.3-0.6Mn, 0.4-0.6%Cr, S, P?0.03%
	0.5-0.6%C, Ni?1.5%, S, P?0.03%
	1.4-1.6%C, 0.8-1.2%Ni, 0.5-0.8%Mn, 0.25-0.5%Si, 0.9-1.25%Cr, S, P?0.04%
	0.3-0.4%C, 5%Cr, Ni?1.5%, Mn?1.5%, Y?1.5%, S, P?0.04

It follows from the table that steels 60ХН and 9ХН, which are used mainly for vertical and horizontal rolls of the roughing group, have the lowest relative wear resistance, which is confirmed by the experience of their operation. But these steels, according to their characteristics, are quite suitable for the manufacture of axes of composite rolls. For the manufacture of cast bandages, it seems advisable to use steel 150ХНМ 35Х5НМФ.

35Х5НМФ has a higher cost compared to 150ХНМ, but, having significant strength and wear resistance, it justifies itself during operation, since, providing increased resistance to wear and chipping, it retains the good surface structure of the roll barrel longer.

To give the tires and axles the necessary performance properties, they are first separately heat treated. Then the bandage, heated to a certain temperature, ensuring sufficiently free fitting onto the profiled axle, is formed into a press fit (during cooling, the axle is enclosed).

These technological operations lead to the formation of significant residual stresses in the bandage from heat treatment. There are known cases where, due to the high level of these stresses, the bandages were destroyed even before use: during storage or transportation.

According to operating conditions, axles are not subject to high hardness requirements (230?280HB), while for tires the requirements are more stringent (55?88HSD). In this regard, a milder heat treatment is used for the axles compared to tires, which does not lead to the occurrence of significant residual stresses. In addition, tensile stresses from fit, which are dangerous from the point of view of brittle strength, arise only in the bandage, as a result of which a fracture can occur along the roll barrel.

As experience in the heat treatment of these steels in the manufacture of bandages shows, the most effective treatment is triple normalization at temperatures of 1050°C, 850°C and 900°C, followed by tempering, which provides the most favorable combination of plastic and strength characteristics.

Triple normalization results in the preservation of the heritage cast structure and promotes distribution of properties that provide increased resistance to wear and chipping.

The roll axis is made from a waste roll. After grinding to the required dimensions, an aluminum coating approximately 20-25 microns thick is applied to the seating surface of the axle using the friction method. The final treatment of the seating surface before coating is clean grinding.

Thermal assembly significantly (on average 1.2-1.5 times) increases the load-bearing capacity of interference joints. This is explained by the fact that during assembly under pressure the micro-irregularities are crushed, while during thermal assembly they close into each other, which increases the coefficient of friction and adhesion strength. In this case, the coating particles penetrate both the surface of the axle and the tire, and mutual diffusion of atoms of the coating and the base metal occurs, which makes the connection almost monolithic.

Therefore, in the connection it is possible to reduce the interference required to transmit a given torque, with a corresponding reduction in stresses in the axle and bandage.

If the bandage is heated sufficiently high, it is possible to obtain zero interference or provide a gap when assembling the connection. The recommended temperature for heating the bandage before assembling the roll is 380°C-400°C.

The following methods for replacing worn bandages are possible:

Mechanical - along the generatrix of the bandage along its entire thickness, two slots are made on a planing or milling machine, as a result of which the bandage is divided into two halves, which are easily dismantled. The slots are located diametrically opposite to one another.
Heating of the bandage in an inductor with industrial frequency currents (IFC) - the bandage is heated to 400°C-450°C. this temperature is achieved in three or four inductor transitions within 15-20 minutes. When the bandage is heated across its cross-section to the specified temperature, it falls off the seating surface.
Dismantling the bandage using an explosion - this technology was used at MMK back in the 50s of the last century. In 1953, the 1450 hot rolling mill was completely converted to composite back-up rolls. Worn tires are removed from the axle by the explosion of small charges placed in drilled holes. This technology is possible in the conditions of Magnitogorsk.

4 Economic justification for the project

OJSC MMK is the largest metallurgical plant in our country. Its main task is to fully satisfy the market needs for high-quality products. Shop LPC-4 is part of MMK, which is a joint-stock company. The development of the plant does not stand still: metal processing methods are being improved, new ideas are being implemented, and modern equipment is being purchased.

The modernization of mill 2500 LPC-4 of OJSC MMK is carried out by replacing solid rolls with banded ones. The cost of one banded roll is 1.8 million rubles, while the annual consumption of rolls is 10 pcs. The cost of banded rolls is 60% of the cost of solid ones, and due to the use of more wear-resistant material for the band, the annual consumption of rolls will decrease by 1.6 times and amount to 6 pcs. in year.

4.1 Calculation of the production program

Drawing up a production program begins with calculating the balance of equipment operating time in the planned period.

The actual operating time of the equipment is calculated using the formula:

T f =T nom *S*T s *(1-T t.pr /100%)(66)

where C=2 – number of equipment operation shifts,

Т с =12 – duration of one shift,

Т t.pr – percentage of current downtime in relation to the nominal time (8.10%),

T nom – nominal operating time of the equipment, calculated by the formula:

T nom =T cal -T rp -T p.pr -T in (67)

where T cal = 365 days. – calendar fund of equipment operating time,

T rp = 18.8 days. – regime downtime;

T p.pr = 12 - number of days the equipment is undergoing scheduled maintenance,

T in – the total number of holidays and weekends in a year.

T in =0, since the work schedule is continuous.

The annual production volume is calculated as:

Qyear=P av *T f (68)

Where P av = 136.06 t/hour – average hourly productivity.

Actual operating time of the equipment and annual production volume:

T no =365-18.8-12-0=334.2 (days)

T t.pr =0.081*334.2=27.7 (days) or 650 (hours)

T f =334.2*2*12*(1-8.1/100)=7371 (h)

Q year =136.06*5033=1002870 t

The calculated data are shown in Table 12.

Table 12 - Equipment operating time balance

4.2 Calculation of capital cost estimates

The costs of modernizing mill 2500 are calculated using the formula:

K z = C about + M + D ± O-L(69)

where M is the cost of installing equipment,

D – costs of equipment dismantling,

О – residual value of dismantled equipment

L – liquidation value (at the price of scrap metal), calculated as:

L=m*C l(70)

where m is the mass of the dismantled equipment,

Ts l – price of 1 ton of scrap metal,

C ob – cost of purchased equipment.

Then the cost of purchasing rolls will be:

With rev =6*(1800000*0.6)=6480000 rub.

The costs of dismantling old and installing new rolls are zero, since changing rolls is the current work in the workshop: M=D=0 rub.

Solid rolls are being replaced, which are already worn out, and accordingly their residual value is O = 0 rub.

Worn-out solid rolls are recycled and therefore have no salvage value (L = 0).

Thus, capital costs for modernization:

To z =6480000+0+0+0-0=6480000 rub.

4.3 Organization of labor and wages

The calculation of the wage fund is shown in Table 13.

Table 13 - Calculation of the wage fund

Indicator name	Worker's name
	Master (senior)	Brigadier	Crane operator	Roller	Post operator
Relation to production
Job grade or salary
Tariff schedule
Tariff rate, rub./hour.
Remuneration system
Schedule
Continuation of table 13
Number of employees including replacement
Planned fulfillment of production standards
Working time fund, person/hour
Work on holidays
Processing according to schedule, person/hour.
Night work, person/hour
Work in the evening
Basic salary, rub./month (? line 10.1? 10.8)
Payment according to tariff (page 4*page 9)
Piecework earnings
Production bonus
Additional pay for working on holidays
Additional payment for overtime according to schedule
Extra pay for night work
Extra pay for working in the evening
Additional payment according to the regional coefficient
Additional salary
Total wages per worker (line 10+line 11)
Total wages of all workers

Explanations for Table 13:

Calculation of working time fund (clause 9):

tmonths=365*With shifts*tshifts/(12*b) (71)

where C shifts =2 – number of shifts per day,

t shifts = 12 hours – duration of one shift,

b=4 – number of teams,

t months =365*2*12/(12*4)=182.5 person*hour

Working hours on holidays:

tetc=n pr * From shifts *tshifts/(12*b) (72)

t pr =11*2*12/12*4=5.5 person*hour

Scheduled processing time:

T month =t gr -(2004/12),

t gr =? t month -t pr.

T month =182.5-2004/12=15.5 person*hour,

t gr =15.5-5.5=10 person*hour.

Calculation of operating hours at night and evening:

t night =1/3* t month,

t evening =1/3* t month,

t night =1/3*182.5=60.83 person*hour,

t evening =1/3*182.5=60.83 person*hour.

Calculation of wages according to the tariff (clause 10.1):

Salary tar = t hour * t month,

t hour – hourly tariff rate.

For the 7th category: salary tar = 24.78 * 182.5 = 4522.35 rubles;

For the 6th category: salary tar = 21.71 * 182.5 = 3962.07 rub.

For the 5th category: salary tar = 18.87 * 182.5 = 3443.78 rub.;

Calculation of piecework earnings (clause 10.2):

ZP sd = ZP tar *[(N exp -100)/100], where

N exp - planned fulfillment of production standards, %.

For both workers: ?ZP sd =0, since the production rate is 100% and there is no break-in.

Calculation of production bonus (clause 10.3):

Salary premium =(Salary tar. + ?Salary sd)*Bonus/100%,

The production bonus established for this area is 40%.

For 7th grade: premium salary. =(4522.35+0)*40%/100%=1808.94 rub.;

For 6th grade: premium salary. =(3962.07+0)*40%/100%=1584.83 rub.

For 5th grade: premium salary. =(3443.78+0)*40%/100%=1377.51 rub.;

Calculation of additional payment for work on holidays with a production rate of 100%:

Salary pr = t hour *(100/100)* t pr.

For the 7th category: ?ZP pr =24.78*5.5=136.29 rub.,

For the 6th category: ?ZP pr =21.71*5.5=119.41 rub.

For the 5th category: ?ZP pr =18.87*5.5=103.78 rub.,

Calculation of additional payment for overtime according to schedule (37.5%):

Salary gr = t hour *(37.5/100)* t gr

For the 7th category: ?ZP gr =24.78*10*0.375=92.93 rub.,

For the 6th category: ?ZP gr =21.71*10*0.375=81.41 rub.

For the 7th category: ?ZP gr =18.87*10*0.375=70.76 rub.,

Calculation of additional payment for night work (40%):

Salary night = t hour *(40/100)* t night

For the 7th category: ?Salary night =24.78*0.4*60.83=602.95 rub.,

For the 6th category: ?Salary night =21.71*0.4*60.83=528.25 rub.

For the 5th category: ?Salary night =18.87*0.4*60.83=459.14 rub.,

Calculation of additional payment for work in the evening (20%):

Salary per hour = t hour *(20/100)* t per hour

For the 7th category: ?Salary evening =24.78*0.2*60.83=301.47 rub.,

For the 6th category: ?Salary evening =21.71*0.2*60.83=264.12 rub.

For the 5th category: ?Salary evening =18.87*0.2*60.83=229.57 rub.,

The regional coefficient for the Ural region is 15%.

Salary r = 0.15*(Panel tar +? Salary sd +? Salary pr +? Salary gr +? Salary night +? Salary evening + Salary prem.).

For the 7th category: ?ZP p =0.15*(4522.35+0+1808.94+136.29+92.93+

602.95+301.47)=1502.32 rub.,

For the 6th category: ?ZP p =0.15*(3962.07+0+1584.83+119.41+

81.41+528.25+264.12)=966.01 rub.

For the 5th category: ?ZP p =0.15*(3443.78+0+1377.51+103.78+70.76+

459.14+229.57)=852.68 rub.,

Calculation of additional wages (clause 11):

When the duration of the next vacation is 30 days, the coefficient of dependence of additional wages on the main one is 17.5%.

For the 7th category: additional salary = 0.175 * 8584.67 = 1502.32 rubles,

For the 6th category: additional salary = 0.175 * 7406.10 = 1296.07 rubles.

For the 5th category: additional salary = 0.175 * 6537.22 = 1144.01 rub.

4.4 Calculation of contributions for social needs

Annual wage fund:

Payroll year =Snumber*Salary month *12 (73)

where S number is the payroll number,

Salary month – monthly salary of one employee.

Payroll year =(80695.92+69617.36+30724.92+34808.68+30724.92)*12=2958861.6 rub

Table 14 - Calculation of contributions to extra-budgetary funds

Total payroll with deductions: 2958861.6 +1053354.7=34012216.33 rub.

4.5 Calculation of product costs

Table 15 - Cost calculation for 1 ton of finished products

Name of cost item	Price, rub./unit	deviation
Name of cost item	Price, rub./unit

1.semi-finished products, t
Ends and trimmings into the mixture Substandard ends and trimmings Scale
By rental Marriage 1st limit For metal
Total minus waste and scrap
1.electricity
2.technological fuel
3. waste heat
4. industrial water
5. compressed air


8. auxiliary materials
9. main salary PR
10. additional salary PR
11.contributions for social needs
12.depreciation
13. replacement equipment incl. rolls
14.transport costs
Total costs for redistribution
15. losses from marriage
16. pickling costs
17. heat treatment costs
Total production cost

Calculations for table 15:

1. Basic salary of production workers:

Salary main = Salary main *12*Snumber/ Qyear (74)

Salary main = (8584.67*8+7406.10*12+6537.22*8)*12/187946=3.46 rub.

2. Additional pay for production workers:

Salary extra = Salary extra *12*Snumber/ Qyear (75)

Additional salary =(1502.32*8+1296.07*12+1144.01*8)*12/187946=0.61 rub.

3. Deductions from the wage fund:

Deductions from the wage fund were calculated in the previous chapter in table. 3 and amount to 2958861.6 rubles. for the entire annual production volume, then per 1 ton they will be: 2958861.6 /186946 = 4.07 rubles.

In the design version, all costing items will remain unchanged, except for the costs of replacement equipment (rolls).

4.6 Calculation of main technical and economic indicators

Profit from product sales:

Pr=(C-S/s)*Qyear (76)

where C is the average wholesale price excluding VAT for 1t of finished products.

Ts=4460 rubles, then with VAT Ts=5262.8 rubles.

in the basic version:

Pr=(4460-4052.85)*1002870=408318520 rub.,

in the design version:

Pr / =(4460-4026.89)*1002870=434353026 rub.

Table 16 - Calculation of net profit

The name of indicators	Amount, rub.	Deviations
The name of indicators		Deviations
Revenue from sales of products, total (Price including VAT*Qyear)
incl. VAT (line 1*0.1525)
Revenue from sales of products net of VAT (line 1-line 2)
Cost of production (С/с*Qyear)
Administrative expenses
Business expenses
Gross profit (pages 2-3-4-5)
Proceeds from the sale of fixed assets and other property
Interest receivable
Income from government securities
Income from participation in other organizations
Other non-operating income
Payments for the use of natural resources
Expenses for the sale of fixed assets and other property
Other operating expenses
Percentage to be paid
Property tax

Other non-operating expenses
Profit of the reporting year (? line 6? 11 –? line 12? 18)
Taxable income (line 19-8-9-10)
Income tax (line 20*0.24)
Net profit (page 19-page 21)

Pch=326888666-307102442=19786224 rub.

Product profitability:

Rp=(Pr/S/s)*100% (77)

in the basic version:

Рп=(4460-4052.85)/4052.85*100%=10%,

in the design version:

Rp / =(4460-4026.89)/4026.89*100%=10.75%.

PNP=Pch/I (78)

where I is the total volume of investment.

The total volume of investments is equal to the amount of capital costs (I=Kz=6,480,000 rub.)

PNP=326888666/6480000=50.44.

Payback period:

Current=I/?Ir (79)

Current=6480000/19786224=0.32 g or 4 months.

Conclusion

It is proposed to replace the use of solid forged back-up rolls in stands 5 and 6 of mill 2500 (LPTs-4) of MMK OJSC with composite rolls.

Based on the review, analysis of designs and operating experience of banded rolls, the optimal design of a composite roll was selected in terms of ease of production and lower cost.

It is proposed to use steel 150ХНМ or 35Х5НМФ as the bandage material, the wear resistance of which is 2-3 times higher than 9ХФ steel, from which solid forged rolls are made. It is proposed to manufacture the bandages cast with triple normalization. To make axles, use waste rolls.

Calculations of the stress-strain state and load-bearing capacity were made for various values of landing diameters (? 1150 mm and ? 1300 mm), minimum, average and maximum values of interference (D = 0.8; 1.15; 1.3) and friction coefficient ( f=0.14;0.3;0.4). It has been established that in the case of ?1150 mm, the stress distribution pattern in the roll is more favorable than for ?1300 mm, and the load-bearing capacity is 1.5-2 times higher. But as the interference increases, the tensile stresses in the joint also increase, exceeding those allowed for steel 150ХНМ. Therefore, it becomes advisable to use a minimum tension of D = 0.8 mm, which ensures transmission of torque with a sufficient margin even with a minimum friction coefficient of f = 0.14.

To increase the load-bearing capacity of such a connection without increasing the stress value, it is proposed to increase the coefficient of friction on the mating surfaces by applying a metal coating. Aluminum was chosen as the coating material based on its cost and thermophysical properties. As the experience of using such a coating on the mating surfaces of the axle and tire under the operating conditions of composite rolls at the mill 2000 (LPS-10) of OJSC MMK shows, aluminum increases the coefficient of friction to values f = 0.3-0.4. In addition, the coating increases the area of actual contact between the axle and the bandage and its thermal conductivity.

The maximum possible deflection, determined by calculation, is 0.62 mm, the slip zone is 45 mm.

The connection of the bandage to the axle is carried out thermally, by heating the bandage to 350°-400°C.

Based on the calculations, the selected design of a composite roll with cylindrical seating surfaces of the axle and tire, without the use of any additional fixing devices (collars, cones, keys), was considered optimal.

To prevent fretting corrosion and relieve the concentration of residual stresses at the ends of the bandage, bevels are made at the edges of the axis, so that in the areas adjacent to the ends of the bandage the interference is zero.

The cost of a composite roll is 60% of the cost of a new solid forged roll (1.8 million rubles). With the transition to composite rolls, their consumption will be reduced from 10 to 6 pcs per year. The expected economic effect will be about 20 million rubles.

List of sources used

Useful Maud. 35606 RF, MPK V21V 27/02. Composite rolling roll /Morozov A.A., Takhautdinov R.S., Belevsky L.S. and others (RF) - No. 2003128756/20; application 09/30/2003; publ. 01/27/2004. Bull. No. 3.
Roll with a bandage made of sintered tungsten carbide metal. Kimura Hiroyuki. Japanese patent. 7B 21B 2700. JP 3291143 B2 8155507A, 11/29/94.
Useful Maud. 25857 RF, MPK V21V 27/02. Rolling roll /Veter V.V., Belkin G.A., Samoilov V.I. (RF) - No. 2002112624/20; application 05/13/2002; publ. 10/27/2002. Bull. No. 30.
Pat. 2173228 RF, IPC V21V 27/03. Rolling roll /Veter V.V., Belkin G.A. (RF) - No. 99126744/02; application 12/22/99; publ. 10.09.01//
Pat. 2991648 RF, IPC V21V 27/03. Composite rolling roll /Poletskov P.P., Firkovich A.Yu., Tishin S.V. and others (RF) - No. 2001114313/02; application 05/24/2001; publ. 10/27/2002. Bull. No. 30.
Useful Maud. 12991 RF, MPK V21V 27/02. Composite roll /Poletskov P.P., Firkovich A.Yu., Antipenko A.I. and others (RF) - No. 99118942/20; application 01.09.99; publ. 03/20/2000. Bull. No. 8.
Pat. 2210445 RF, MPK V21V 27/03. Composite roll /Poletskov P.P., Firkovich A.Yu., Antipenko A.I. and others (RF) - No. 2000132306/02; application 12/21/2000; publ. 08/20/2003. Bull. No. 23.
Grechishchev E.S., Ilyashchenko A.A. Interference connections: Calculations, design, manufacturing - M.: Mashinostroenie, 1981 - 247 pp., ill.
Orlov P.I. Fundamentals of design: Reference and methodological manual. In 2 books. Book 2. Ed. P.N. Uchaeva. – 3rd ed., corrected. – M.: Mechanical Engineering, 1988. – 544 p., ill.

10 Narodetsky M.Z. To the choice of landing rings of rolling bearings. “Engineering collection” Institute of Mechanics of the USSR Academy of Sciences, vol. 3, no. 2, 1947, p. 15-26

11 Kolbasin G.F. Study of the performance of composite rolling rolls with replaceable tires: Dis.: ..Ph.D. – Magnitogorsk, 1974. – 176 p.

12 Timoshenko S.P. Strength of materials, h. P.M. – L., Gostekhteorizdat, 1933.

13 Balatsky L.T. Fatigue of shafts in joints. – Kyiv: Technology, 1972, - 180 p.

14 Polukhin P.I., Nikolaev V.A., Polukhin V.P. etc. Strength of rolling rolls. – Alma-Ata: Science, 1984. – 295 p.

15 Hot rolling of strips on the 2500 mill. Technological instruction TI - 101-P-Gl.4 - 71-97

16 Calculation of the multiplicity of use of the axis of a composite roll / Firkovich A.Yu., Poletskov P.P., Solganin V.M. – Sat. center. lab. OJSC MMK: issue. 4. Magnitogorsk 2000. – 242 p.

17 Sokolov L.D., Grebenik V.M., Tylkin M.A. Research of rolling equipment, Metallurgy, 1964.

18 Sorokin V.G. Brand of steels and alloys, Mechanical Engineering, 1989.

19 Firsov V.T., Morozov B.A., Sofronov V.I. and others. Study of the performance of press joints of the shaft-bushing type under conditions of static and cyclic alternating loading // Bulletin of Mechanical Engineering, - 1982. No. 11. - With. 29-33.

20 Safyan M.M. Rolling of broadband steel. Publishing house "Metallurgy", 1969, p. 460.

21 Tselikov A.I., Smirnov V.V. Rolling mills, Metallurgizdat, 1958.

22 Firsov V.T., Sofronov V.I., Morozov B.A. Experimental study of rigidity and residual deflection of banded support rolls // Strength and reliability of metallurgical machines: Proceedings of VNIMETMASH. Sat. No. 61. – M., 1979. – p. 37-43

23 Bobrovnikov G.A. Durability of plantings carried out using cold. – M.: Mashinostroenie, 1971. – 95 p.

24 Belevsky L.S. Plastic deformation of the surface layer and formation of a coating when applied with a flexible tool. – Magnitogorsk: Lyceum RAS, 1996. – 231 p.

25 Chertavskikh A.K. Friction and lubrication in metal forming. – M.: Matallurgizdat, 1949

26 Vorontsov N.M., Zhadan V.T., Shneerov B.Ya. etc. Operation of rolls in crimping and section rolling mills. – M.: Metallurgy, 1973. – 288 p.

27 Pokrovsky A.M., Peshkovtsev V.G., Zemskov A.A. Assessment of crack resistance of banded rolling rolls // Bulletin of Mashinostroeniya, 2003. No. 9 – p. 44-48.

28 Kovalev V.V. Financial analysis: Methods and procedures. – M.: Finance and Statistics, 2002. – 560 p.: ill.

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Introduction

One of the trends in the sheet metal industry is the expansion of temper mills for finishing hot-rolled steel. Hot-rolled thin strips, rolled on continuous broadband mills, are tempered on mills installed in pickling lines or cross-cutting units. Tempering of hot-rolled metal, carried out with nominal reductions of 1 - 1.5%, makes it possible to reduce the variation in thickness, waviness and warpage of the strips, and improve the quality of their surface.

Hot-rolled and cold-rolled annealed sheet steel intended for cold stamping and deep drawing is usually tempered at temperatures below 80°C. During storage of sheet metal, deformation aging develops in it, which leads to intermittent deformation and the appearance of slip lines and parts stamped from thin metal. To prevent this negative phenomenon, in some cases temper training of cold-rolled steel intended for deep drawing is used. Using this method, to prevent aging, sheet steel is tempered at 150 - 200 C o. Tempering in the specified temperature range is carried out during cooling, after annealing

The properties of steel processed by heat tempering remain practically unchanged if the temperature of the metal does not exceed the dynamic aging temperature. The tensile diagram of samples made of sheet steel, tempered at a temperature of 100 - 200 C o, has a monotonous “no tooth” and yield plateaus. By preventing metal aging and through warm tempering, calm steel can be replaced with boiling or semi-boiling steel.

The advantage of the process of thermal tempering and rolling of hot-rolled sheets of low-carbon steels is a significant reduction in the cooling time of the coils in the warehouse after hot rolling. In addition, the resistance of low-carbon steels at temperatures of warm tempering is significantly lower than 20 - 30 °C due to this, the energy-power parameters of the processes of tempering and subsequent melting of strips are reduced. (1. from 12)

1. General part

1.1 Technological process in manufacturing plant - 4 of OJSC MMK, brief analysis of the main technological equipment

The launch date of LPC - 4 is considered to be December 27, 1960, it was on this day that the state commission signed the act of acceptance of the hot rolling mill "2500" into operation. The workshop produces hot-rolled steel sheet as a commercial product, measuring 1.8-10.0 mm thick, 1000-2350 mm wide, the weight of the rolls reaches up to 25 tons. The mill produces 7 million tons of hot-rolled sheet per year.

Slabs enter the workshop in open cars from the oxygen-convector shop, which are then unloaded by overhead cranes equipped with magnetic grippers to the slab warehouse.

The supply of slabs to the furnaces is carried out via a transport and finishing line directly to the loading roller table at the furnaces, as well as using loading devices. Laying of slabs on trolleys is carried out by overhead cranes equipped with tong grips. The maximum weight of a stack of slabs is 130 tons.

A stack of slabs is transported by a crane to a lifting and lowering table, transferred to the table, and then the slabs are pushed one by one onto the loading roller table.

The slabs are transported by roller conveyors depending on their length and loaded into the furnaces in one, two rows or in a run-up fashion. The position of the slabs relative to the axis of the furnace before they are placed in the furnace is determined by means of photo sensors on the roller table near the furnace.

The heating temperature of the slabs is 1200-1250° depending on the steel grade. Heated to the rolling temperature, the slabs are ejected one by one from the furnaces and smoothly, without impact, placed on the receiving roller table using a slab receiver.

Next, the slabs released from the furnace are transported by a receiving roller table to the rough descaling machine, where the slab scale is removed, and then transported by the roller table to the roughing group of stands. In the roughing group, the slab is sequentially rolled in an expansion stand and in three universal stands. Descaling in the roughing group is carried out using high-pressure water using water descaling units. Depending on the cross-section of the strips being rolled, the thickness of the rolled material after the roughing group is 26-50 mm.

After rolling in the roughing group, the rolled stock is transported by an intermediate roller table to the finishing group of stands. The final rolling of the strips to a given thickness is carried out in the finishing group stands, where the strip is simultaneously in all 11 stands.

In the inter-stand spaces of the finishing group of stands there are also laminar-type inter-stand strip cooling units. The installation looks like a pipeline in which nozzles are located. It is through them that the installation cools the strip of liquid at the required temperature.

After the front end of the strip leaves the last finishing stand, the strip is directed at filling speed along the outfeed roller conveyor to one of the winders for winding into a roll.

Three coilers are installed behind the finishing stands. In the fourth and fifth, thin strips with a thickness of 1.2 - 4 mm are wound into a roll, in the sixth - thicker strips from 2 to 16 mm. Before the strip enters the winder, the pneumatic rulers are set apart and adjusted by the screw installation mechanism to a solution that is 10-20 mm less than the sum of the nominal width of the strip and two strokes of the pneumatic ruler. After the strip is captured by the rollers, pneumatic cylinders bring the rulers together, which center the strip with constant force throughout the entire winding process. After winding is completed, the rulers return to their original position.

In front of each winder, laminar-type strip cooling systems are located on the outlet roller table. The strip is cooled from above and below. After the strip is captured by the winder, thin strips are usually wound under tension without the participation of forming rollers, while thick strips are wound under constant pressure from the forming rollers. After winding the strip into a roll, the winder drum stops in a position that prevents the rear end of the strip from sagging on the roll.

Further, after the roll is released as a result of compression of the winder drum, the rolls are transferred by a stripper trolley to the contactor and the roll is placed in a vertical position on the transfer trolley. The trolley transports the roll to the conveyor.

Coil conveyors move the coil from the respective groups of coilers to a turntable mounted some distance in front of the thick strip coilers. During transportation, the rolls are tied, weighed and labeled. Next, the rolls are transported by overhead cranes equipped with clamps to the finished product warehouse. They are then loaded onto railcars and sent to customers or to cold rolling mills for further processing. Also on the workshop territory there are three cross-cutting units, which cut finished products into dimensional sheets.

The main technological equipment of the furnace department includes: methodical heating furnaces, a slab receiver, a device for stripping slabs, a loading roller table, a weighing roller table.

The methodical furnace is designed accordingly for heating the slab. A methodical furnace consists of a working space (hearth), where fuel is burned and metal is heated, and a number of systems: heating, transportation of workpieces, cooling of furnace elements, thermal management and others. The working space of the furnace is divided into zones: methodical zone, welding zone, simmering zone.

Figure 1. Layout of manufacturing plant - 4: Ґ° - slab warehouse; Ґ± - furnace compartment; ҐІ - machine room; Ґі - warehouse of finished products; Ґµ - electrical machine room; Ґ¶ - roll warehouse; Ґ· - rolling department. 1 - furnace roller conveyor; 2 - slab pusher; 3 - receiving roller conveyor; 4-roughing group of stands; 5 - scale breaker; 6 - finishing group of stands; 7 - flying drum shears; 8 - winders; 9 - roll conveyor; 10 - heating furnaces.

All zones, except the methodological one, are equipped with burners in which fuel (natural gas) is burned. The workpieces are heated gradually (methodically), moving first through an unheated methodical zone (preheating zone), where the temperature is relatively low, then through welding (heating) zones with high temperatures, where rapid heating of the metal occurs, and the simmering zone, in which simmering - equalization of temperatures across the cross section of the workpiece.

The slab receiver is designed to position the slab on the loading roller table and move the slab from the loading roller table to the furnace; it is powered by an electric motor controlled by a frequency converter. The working stroke of the machine is calculated based on the width of the slab and the space available in the furnace. The slab receiver consists of a frame on which a trolley with rods for removing slabs from the furnace is mounted. The frame, in turn, is fixed to the hinged support using a hinge. The trolley is mounted on a frame with the ability to move along grooves made on the frame by means of rollers and is interconnected with a drive for its movement, made in the form of an articulated four-link, one link of which is a hydraulic cylinder. The frame is made in the form of a two-arm swinging lever, one end of which is connected to the slab lifting mechanism and is also a four-link articulated link with a hydraulic cylinder.

The device for cleaning slabs is designed to clean the upper surface of the slab from scale, dirt, debris and foreign objects with a roller brush before loading the slabs into the furnaces. The device for stripping slabs consists of a working part with gas cutting heads, an idle roller table, a frame and a driving mechanism. To expand the gas cutting heads in the vertical direction, pneumatic cylinders mounted on calipers are used. In the horizontal direction, the gas cutting heads move together with the calipers.

The loading roller conveyor is designed for transporting slabs coming from an existing slab warehouse. It consists of a frame, forged steel rollers, plates, an individual drive for each roller section which consists of a gear motor.

The weighing roller conveyor weighs the slab on it using weight sensors installed under the frames of the weighing roller conveyor. It consists of a frame, rollers, plates, a weighing system and recognition of the position of the slab. (2. with 115)

1.2 Design, operation and technical specifications receiving roller conveyor for heating furnaces

The receiving roller table for heating furnaces is located in the furnace department of the hot rolling mill “2500” of LPC-4 OJSC MMK and is intended for receiving heated slabs from the furnace and transporting them to the working roller table in front of the roughing group of stands. The receiving roller table at the furnaces consists of one two-roller, fourteen three-roller and three four-roller sections. Each section consists of a frame and rollers. Frames welded from sheet metal. The rollers are made of forgings. The roller supports are radial spherical double-row roller bearings installed in the cushions. The pillows are installed in frames. The rollers are driven into rotation by a drive through a gear coupling. The drive consists of a motor gearbox and a sub-motor plate. The sub-motor plates are welded from sheet metal. The rollers are rotated by a gear motor. The motor-gearbox is made in a single housing, due to which the electric motor shaft is the first shaft of a two-stage gearbox.

Table 1. Technical characteristics of the receiving roller table at the furnace.

	Characteristic	Quantities
	Dimensions of transported metal

		1000…2350 mm

	The largest mass of transported slab
	The highest temperature of the transported slab

	Roller barrel diameter
	Roller barrel length
	Roller pitch	850,1050,1100,1300,1350,1500 mm
	Roller peripheral speed
	Roller rotation frequency	84.9 rpm
	Geared motor G82A ARC225M4
	Motor power
	Gear ratio

Figure 2. Receiving roller table at heating furnaces. 1 - gear motor, 2 - gear coupling, 3 - roller assembly, 4 - roller bearing, 5 - roller table section frame, 6 - sub-motor plate.

Figure 3. Kinematic diagram of the drive of the receiving roller table for heating furnaces. 1 - motor - gearbox, 2 - gear coupling, 3 - roller, 4 - roller bearing.

1.3 Analysis of existing designs of roller tables for rolling mills

Roller conveyors are designed to transport metal to a rolling mill, transfer metal into rolls, receive it from rolls and move it to shears, saws, levelers and other machines. According to their purpose, roller conveyors are divided into working and transport. Workers are roller tables located directly at the working stand of the mill and used to roll metal into rolls and receive it from the rolls. Transport is the name given to all other roller tables installed in front of and behind the working stand and connecting individual machines and devices of the mill.

Roller conveyors are available with group and individual drives and idle rollers.

Figure 3. Roller conveyor with individual drive: a - from a flange electric motor, b - from an electric motor through a gear coupling. 1 - roller, 2 - tapered roller bearings, 3 - cardan shaft, 4 - electric motor, 5 - electric motor plate.

With individual drive, each roller of a given section of the roller table is driven by a separate electric motor. Such rollers are widely used in high-speed transport roller tables for moving rolls, the length of which after rolling is significant, and also as the first rollers of working roller tables of crimping mills.

With a group drive, all the rollers of one roller conveyor section, consisting of 4 - 10 rollers or more, are driven from one electric motor through bevel gears and a transmission shaft. Roller conveyors with a group drive are used for low transportation speeds over a relatively short distance. (3. p. 347)

Figure 4. Roller table with a group drive: 1 - roller frame, 2 - roller, 3 - bearing housing, 4 - bevel gears, 5 - transmission shaft, 6 - cylindrical gear, 7 - clutch, 8 - electric motor, 9 - rolling bearings, 10 - roller, 11 - roller bearings, 12 - cast covers, 13 - cast traverses.

The rollers of each section are driven by one electric motor through a clutch, two pairs of cylindrical gears, as well as bevel gears mounted on the transmission shaft and the ends of the roller journals. On the drive side, the rollers are mounted on tapered roller bearings housed in a housing. On the other hand, they, like the transmission shaft, are mounted on rolling bearings (2. p115)

1.4 Rules technical operation roller conveyors

When accepting a shift, you must check the following:

Check if all rollers rotate; is there any runout in the rollers in the bearings; whether the inter-roller plates are shifted and whether they are in contact with the rollers; serviceability of fastening of guide rulers; serviceability of roller cooling systems; supply of thick lubricant to the friction units upon activation of the feeders; oil level in gearboxes according to oil indicators; add oil if necessary; supply of thick and liquid lubricant to the roller bearings, transmission shaft, and gearbox shaft. If necessary, adjust the amount of lubricant supplied to the friction units using feeder pistons, as well as clean the oil channels and trays from dirt; through the inspection hatches in the gearbox covers, check the reliability of the fastening of the gears on the shafts, as well as the radial and axial clearances of the shafts in the bearings.

During the shift, service personnel are required to monitor:

Operate the equipment and remove pieces of metal (scrap), scale or other foreign objects from the roller conveyors; Do not hold heated slabs or rolls on rollers motionless. If the rolled metal is delayed on the roller table for some reason, then while waiting it should be moved along the roller table by “swinging” in order to avoid warping of the rollers and unacceptable heating of the bearings; when laying slabs on the roller conveyor, avoid hitting the rollers; Reverse the rollers smoothly; ensure that the rollers are cooled with water where this is provided; if necessary, stop the mill and eliminate any malfunctions; Are there any oil leaks from the gearboxes?

Inspections and repairs of receiving and transport roller tables should be carried out once a month. Also check:

Condition and amount of wear of roller barrels, bearing seats; Replace rollers with wear on the barrel diameter of more than 20 mm; restore weakened bearing seats on the roller neck, transmission shafts, gear unit shafts, gear housings and roller conveyor frames to the drawing dimensions or restore parts; the level of the flooring plates should be below the top edge of the rollers by no more than 1/3 of the radius of the roller barrel on the metal entry side; the gap between the rollers and the floor slabs, the minimum permissible value of which is 10 mm; the condition of the roller table frames, gearbox housings and connecting traverses, if cracks and chips are detected on them that impair the strength and tightness, as well as if they are deformed, carry out appropriate repairs or replace them; state gears, bearings, shafts, couplings, bolted and keyed connections. If necessary, carry out repairs or replace them. (5. p. 24)

2. Special part

2.1 Selection of initial data and power circuit for calculating the drive power of the receiving roller conveyor for LPTs-4 furnaces

The weight of one slab moving along the roller table is Q = 18t = 180kN;

Roller weight G p = 3.97 t = 39.7 kN;

Roller barrel diameter d = 450mm = 0.45m;

Friction diameter in bearings d p = 190 mm = 0.19 m;

Slab speed along the roller conveyor V = 2m/s;

The number of rollers in a roller conveyor section driven by one electric drive. dv. n = 1;

The state of the metal transported along the roller conveyor is a hot slab;

Step between rollers t = 1.1;

Figure 5. Power circuit for calculation

2.2 Calculation of the power of the electric motor drive of the roller conveyor section of heating furnaces LPC - 4

Moment due to friction losses in bearings when moving metal along a roller conveyor:

where: m p - friction coefficient in roller bearings m p = 0.005 - 0.008

Q m - slab weight per 4 rollers of one section;

Q ----------- 10m

Q m ---------- t

Moment from possible slipping of rollers on metal:

where: M beech - coefficient of friction of the roller when slipping, for hot metal M beech = 0.3

Static drive torque

M st = 0.025 + 0.731 = 0.756 kNm

Dynamic moment for transporting metal:

where: m p - roller mass, (t)

m m - metal mass, (t)

D ip - diameter of inertia of the rotating roller, (m)

Angular acceleration of the roller,

where: i is the acceleration of translational metal moving along the rollers, for hot metal i = 3.0

Total roller conveyor drive torque:

Drive power of the roller table section:

where: w r o l - angular speed of the rollers, (s -1)

Efficiency of the roller conveyor drive.

because In the project, the electric motor is mounted in a single housing with a gearbox, then we select a motor - gearbox G82A ARC225 M4 with a power of N = 22 kW and a rotation speed of n = 1450 rpm.

2.3 Kinematic calculation of the drive of the roller conveyor section of heating furnaces LPC - 4

Let us determine the gear ratio of the roller table section drive for heating furnaces:

where: sch dv - angular speed of the engine, s -1

We accept φ = 8.8 s -1 (see paragraph 2.2)

Let us determine the torque on the drive shaft of the roller conveyor section of heating furnaces:

Let us determine the torque on the output shaft of the drive section of the roller table of the heating furnaces:

2.4 Calculation of the strength of the main parts and assemblies of the roller conveyor section

2.4.1 Test calculation for the durability of the roller supports of the roller conveyor section

Let us determine the distributing load acting on the roller:

Let us determine the reactions of the roller supports in the vertical plane:

Check: ?F y = 0; Y a - G p + Y b - g m = 0

21532, 76 - 34640 + 21532, 76 -8425,53 = 0

Let us determine the reaction of the roller to bending and torsion:

We outline rolling bearings, double rows with spherical rollers

No. 3538 d = 190, D = 340 mm, C = 1000000 N, C o = 805000 N

where: v - coefficient of rotation of the inner ring, v = 1.2

K t - at a temperature of 125 o C, K T = 1.45

Let's determine the design durability, million rpm:

Let us determine the estimated bearing life, hour:

where: n engine - engine speed, rpm.

Conclusion: the durability of the receiving roller conveyor drive bearing is ensured.

2.4.2 Test calculation of the rollers of the roller conveyor section for strength

Let us carry out calculations for the dangerous section of the roller in the roller conveyor section. The dangerous section of the roller is its center; it is there that the greatest loads and deformations due to bending and torsion are observed. The torque in this section is 19483.85 Nm. Roller material: steel 45, heat treatment - improved. With a roller diameter of 200 mm

Fatigue limit for symmetrical bending cycle:

Fatigue limit for a symmetrical cycle of tangential stresses:

Let us determine the safety factor:

at d = 200mm, b x h = 45 x 25 mm, t 1 = 15 mm.

Let us determine the moment of resistance to bending using the formula:

Let us determine the safety factor for normal stresses:

Let us determine the resulting safety factor of the roller:

Conclusion: S = 5.06 > [S] = 2.5 The strength of the roller is ensured.

2.4.3 Calculation of the strength of the roller key connection

The keys are prismatic with rounded ends. Dimensions of length of keys and grooves according to GOST 23360 - 78

Key material - steel 45 normalized.

Let us determine the bearing stress and the strength condition of the keyed connection:

Allowable bearing stress with a steel hub [ = 100 -120 MPa

d = 120mm, b x h = 28 x 16mm, t 1 = 10.0 mm

The strength of the keyed connection is ensured.

3. Organization of production

3.1 Organization of repair service in LPC - 4

The repair service of the workshop includes specialists responsible for the condition of all equipment in the workshop, including specialists from leading engineers to repairmen. All mechanical repair service personnel in any workshop are divided into sections of the workshop. The functions of the duty personnel include checking the serviceability of pipelines and fittings, checking and tightening fasteners, checking the serviceability of thick and liquid lubrication systems, checking for oil leaks from crankcases or systems.

Figure 7. Scheme of the repair service of MSC LLC LPC-4.

The master is obliged:

Ensure that the site fulfills production targets in a timely manner in terms of volume of production (work, services), quality, specified nomenclature (assortment), increasing labor productivity, reducing the labor intensity of products based on rational loading of equipment and the use of its technical capabilities, increasing the shift ratio of equipment, economical use of raw materials, materials, fuel, energy and cost reduction. Prepares production in a timely manner, ensures the placement of workers and teams, monitors compliance with technological processes, promptly identifies and eliminates the causes of their violation. Participates in the development of new and improvement of existing technological processes and production modes, as well as production schedules. Checks the quality of products or work performed, takes measures to prevent defects and improve the quality of products (works, services).

Takes part in the acceptance of completed work on the reconstruction of the site, repair of technological equipment, mechanization and automation of production processes and handmade. Organizes the introduction of advanced methods and techniques of labor, as well as forms of its organization, certification and rationalization of jobs. Ensures that workers meet production standards, correct use production areas, equipment, office equipment (equipment and tools), uniform (rhythmic) work of the site. Carries out the formation of teams (their quantitative, professional and qualification composition), develops and implements measures for the rational maintenance of teams, and coordinates their activities.

Establishes and promptly delivers production tasks to teams and individual workers (not members of teams) in accordance with approved production plans and schedules, standard indicators for the use of equipment, raw materials, supplies, tools, fuel, energy. Provides production instruction to workers, carries out measures to comply with labor protection rules, safety regulations and industrial sanitation, technical operation of equipment and tools, as well as monitoring their compliance.

Promotes the introduction of progressive forms of labor organization, makes proposals for the revision of production standards and prices, as well as for the assignment of working categories to workers in accordance with the Unified Tariff and Qualification Directory of Works and Professions, takes part in the tariffication of work and the assignment of qualification categories to site workers. Analyzes the results of production activities, controls the expenditure of the wage fund, established area, ensures the correctness and timeliness of preparation of primary documents for recording working hours, output, wages, and downtime. Promotes the dissemination of best practices, the development of initiative, and the introduction of innovation proposals and inventions. Ensures timely review of labor cost standards in the prescribed manner, implementation of technically sound standards and standardized tasks, correct and effective application of wages and bonus systems.

Takes part in the implementation of work to identify production reserves in terms of quantity, quality and range of products, in the development of measures to create favorable conditions labor, improving the organizational and technical culture of production, rational use of working time and production equipment. Monitors workers' compliance with occupational health and safety rules, production and labor discipline, internal labor regulations, promotes the creation of an atmosphere of mutual assistance and strictness in the team, and develops among workers a sense of responsibility and interest in the timely and high-quality completion of production tasks. Prepares proposals to encourage workers or apply material sanctions, to impose disciplinary sanctions against violators of production and labor discipline. Organizes work to improve the qualifications and professional skills of workers and foremen, train them in second and related professions, and conducts educational work in the team.

The foreman is obliged to: Organize work to timely provide workers with the necessary semi-finished products and materials. Places workers in their places. Controls the quality of manufactured products, compliance with the technological process, the interconnection of operations, and the correctness of keeping records of workers' output. Takes measures to eliminate equipment and worker downtime. If necessary, replaces workers. Eliminates the reasons causing a decrease in product quality. Ensures the fulfillment of the main planned tasks of the team, conveyor, flow (section). Monitors the timely and high-quality correction of product defects. Instructs workers on safety precautions and rules of technical operation of equipment. Conducts inventory of work in progress at the beginning and end of the shift. The foreman at the main production sites has the right to: Receive from the enterprise employees the information necessary to carry out his activities. Submit proposals on issues related to their activities for consideration by their immediate management.

A mechanic-repairman is obliged to:

Disassembly, repair, assembly and testing of complex components and mechanisms.

Repair, installation, dismantling, testing, regulation, adjustment of complex equipment, units and machines and delivery after repair.

Metalworking of parts and assemblies according to 7-10 qualifications.

Manufacturing of complex devices for repair and installation.

Preparation of defect reports for repairs. Carrying out rigging work using lifting and transport mechanisms and special devices.

A repairman has the right to give instructions and tasks to subordinate employees on a range of issues included in his functional responsibilities. The repairman has the right to control the implementation of production tasks and the timely execution of individual assignments by employees subordinate to him. The repairman has the right to request and receive necessary materials and documents related to his activities and the activities of his subordinate employees. The repairman has the right to interact with other services of the enterprise on production and other issues included in his functional responsibilities. The repairman has the right to get acquainted with the draft decisions of the enterprise management concerning the activities of the unit. The repairman has the right to submit proposals for improvement of work related to those provided for herein for consideration by the manager. Job description responsibilities.

The repairman has the right to submit proposals for consideration by the manager on rewarding distinguished employees and imposing penalties on violators of production and labor discipline.

The repairman has the right to report to the manager about all identified violations and shortcomings in connection with the work performed.

The repairman is responsible for violating the rules and regulations governing the operation of the enterprise.

When transferring to another job or being released from a position, the repairman is responsible for the proper and timely delivery of work to the person taking up the current position, and in the absence of one, to the person replacing him or directly to his supervisor.

The repairman is responsible for compliance with current instructions, orders and regulations for maintaining trade secrets and confidential information.

The repairman is responsible for compliance with internal regulations, safety and fire safety rules.

3.2 Technology for repairs of metallurgical equipment. Documentation for repairs

All repairs of metallurgical equipment are divided into two types: current and capital.

Current repairs - repairs performed to ensure or restore the functionality of a product and the organization of repair facilities and equipment maintenance are based on a system of scheduled preventive maintenance (PPR).

Overhaul - complete disassembly of equipment and components, detailed inspection, washing, wiping, replacement and restoration of parts, checking for technological accuracy of processing, restoration of power, performance according to standards and specifications.

Maintenance is a set of operations to maintain the functionality of equipment when used for its intended purpose, during storage and transportation. In progress Maintenance periodically repeating operations - inspections, washing, accuracy checks, etc. - are regulated and carried out according to a pre-developed schedule.

Depending on the nature and volume of work performed when equipment is stopped for routine repairs, and on the duration of such stops, current repairs are divided into the first (T 1), second (T 2), third (T 3) and fourth (T 4) current repairs . Moreover, for the same type of equipment, the scope of work of each previous (in order) type of repair is included in the scope of the subsequent one.

Major repairs are carried out to eliminate malfunctions and completely or nearly completely restore the life of the equipment with the replacement or restoration of any of its parts, including basic ones. The overhaul work also includes work on modernizing equipment and introducing new equipment, carried out according to pre-developed and approved projects.

Major repairs of equipment are considered to be carried out at an established frequency of at least one year, during which they usually completely disassemble the unit, replace or restore all worn parts, assembly units and other structural elements, repair basic parts and foundations, assemble, calibrate, adjust and test the equipment idle and under load.

Normal operation of rolling equipment is regulated by technical operation rules developed and approved for all types of mechanical equipment of metallurgical plants.

To carry out equipment repairs at metallurgical plants, annual and monthly maintenance and repair schedules are drawn up. Annual schedules are compiled by the chief mechanic's management department for all production workshops based on plans for repairs of main technological equipment in the planned year.

For objects that are being prepared for major repairs, engineering and technical workers of the mechanical services of rolling shops draw up a list of defects six to seven months before the start of repairs. The list of defects contains a list of components and main structural elements of the facility, indicating the repair work performed on them. It also indicates the machines, structural units and parts to be replaced, materials and spare parts necessary for repair.

To carry out routine repairs, a repair list, operational schedule, and standard estimate are drawn up. Repair lists are compiled by the engineering and technical personnel of the mechanical service of the workshop. The repair list contains a list of mechanisms, repair work performed on them and replacement parts and assemblies; the number of assemblies and parts to be manufactured or restored, repaired, the volume of repair work and the required labor are indicated.

Repair sheets are handed over to repair departments no later than 5 - 7 days before the start of repairs. Acceptance of equipment after repair is carried out by the personnel of the production workshop and is documented in a report drawn up after testing the equipment. (2. from 202)

3.3 Measures to improve the reliability and durability of parts and assemblies of metallurgical equipment

Reliability is the property of an object to perform specified functions under certain operating conditions. There are ideal, basic and operational reliability.

Durability is the property of an object to remain operational until a limit state occurs with an established system of maintenance and repairs. Durability is characterized by resource and service life.

An effective means of restoring worn roller conveyors and increasing their wear resistance is automatic electric surfacing under a layer of flux. Conventional surfacing carbon wire allows you to reliably restore the dimensions of the rolls. However, an incomparably more important task is to increase the durability of the rolls by surfacing a wear-resistant layer.

Electric welding is a type of arc welding. Just as in welding, an electric arc burns between the product and the wire, to which current is supplied, melting the metal of the product and the wire.

Using automatic surfacing, a layer of metal of varying thickness (1-40 mm) can be applied to the surface of products of various shapes, forming one piece with the product. Due to the continuity of the process and the possibility of using high-power welding current, automatic surfacing is 5-10 times more productive than manual surfacing.

To strengthen and increase the wear resistance of roller tables, the method of rolling a barrel with rollers is also used. The most advanced way to obtain high hardness of the working surface of cold rolling mills is hardening with high and industrial frequency currents.

With induction heating, roll warping is reduced and it is possible to obtain the required thickness of the hardened layer. After hardening, the rolls are subjected to grinding, during which they are calibrated. (10. p. 234)

3.4 Lubricating the roller conveyor drive

The reliability of rolling equipment largely depends on the rational choice of lubricants, lubrication methods and modes, and quality control of the lubricant during operation.

The main function of lubricants is to reduce frictional resistance and increase wear resistance and rubbing surfaces of parts. In addition, they remove heat from friction units and protect lubricated surfaces from corrosion and rust. The following types of lubricants are used to lubricate metallurgical equipment: liquid (mineral oils), plastic (greases), solid lubricants and lubricating coatings.

The friction units of the receiving roller table at furnaces operate under difficult conditions caused by heavy loads, elevated temperatures, watering and contamination by abrasive particles from the environment.

Mineral oils are used in those friction units where liquid or semi-liquid friction can be provided, where forced heat removal or washing of rubbing surfaces is necessary.

Greases are used in open and unsealed friction units; in friction units where frequent replacement of lubricant is difficult or undesirable.

Lubrication methods are distinguished according to the principle of supplying lubricants to the contact surfaces at the source of deformation and the friction unit. When lubricating with liquid mineral oils, individual lubrication methods, oil bath lubrication and pressure lubrication are used.

An individual lubrication method is used to lubricate individual parts and friction units when connection to centralized systems is difficult or special requirements are imposed on them.

Immersion lubrication is mainly used in gearboxes when the heat generated in the gears is completely removed into the surrounding space through the crankcase wall or cover.

Pressure lubrication is the most effective method of lubrication. It is used in critical mechanisms and machines and is carried out using circulation systems lubricants

When lubrication with plate materials, individual, embedded, and centralized lubrication methods are distinguished. At in an individual way Lubricant is supplied periodically using hand-held syringes through grease nipples installed in the lubrication holes. The embedded method involves filling the friction unit with lubricant during assembly or repair. The centralized method is used when there are a large number of friction units located far from the pumping station. (2. p227)

Table 2. Map of lubrication of the receiving roller table at the furnaces

Figure 6. Lubrication map of the receiving roller table section: 1 - roller bearing, 2 - gear coupling

4. Labor protection

4.1 Safety and fire protection measures in the manufacturing plant - 4 of OJSC MMK

On the territory of sheet rolling shop No. 4, safety measures include Special attention. In the workshop there are such harmful industrial hazards as: noise, dust, high temperatures, mobile transport, rotating mechanisms.

Dust in the workshop air is one of the factors in the production environment that determines the working conditions of workers. The causes of dust can be different: lack of sealing and aspiration of dust emission sources, the use of manual operations for transportation, loading and unloading of dry highly dispersed materials. Dust emissions into the air are also formed from cleaning equipment, air ducts, floors and gas lines manually, with brushes, brooms or blowing with compressed air.

Dust of larger fractions is formed between the rolls and the rolled metal, which is then carried away by the hot air and slowly settles on the equipment and structure of the workshop. The dust size of 5 - 10 microns, which is formed from the evaporation of scale, is approximately 20%. This dust spreads throughout the workshop. Dust containing iron oxides affects the respiratory system. Penetrating deep into the respiratory tract, this dust can lead to the development of a specific disease - siderosis. Part of the dust, entering the respiratory system, lingers on the nasal mucosa, and then gradually enters the oral cavity and digestive organs.

The main measures to combat dust are: the introduction of rational technological processes and equipment improvements, the use of effective sealing and aspiration of all dust-emitting sources, moistening the dust with water or steam; installation of special dust-collecting ventilation from places of dust formation with air purification before releasing it into the atmosphere through a filter system, regular removal of dust from workplaces with special vacuum cleaners, use of personal protective equipment (respirators, goggles, special clothing, etc.).

To suppress dust during rolling, the most effective way is hydrodust removal, in which it is possible to settle up to 70 - 80% of the dust. Dust is deposited using nozzles.

Pneumatic dust collection can significantly reduce or completely eliminate dust emissions. At the same time, highly dispersed dust is not spread throughout the workshop, which usually happens when sweeping or cleaning equipment with brushes. In addition, the use of pneumatic cleaning increases labor productivity by 25 - 30% and makes it easy to remove dust from walls, ceilings, metal structures, air ducts, equipment, hard-to-reach places that are rarely cleared of dust using other methods and are sources of dust emissions.

An important factor in improving working conditions in rolling production is the reduction of production noise. Increasing the production intensity of rolling speeds significantly increases production noise in rolling shops. Industrial noise of varying intensity and spectrum, affecting workers for a long time, leads to a decrease in hearing acuity, and sometimes to occupational deafness in workers.

To reduce noise at the source of its formation, it is necessary, if possible, to replace impact interactions of parts with non-impact ones, reciprocating movements with rotational ones, and replacing metal parts with parts made of plastic or other silent materials. Units that create strong noise due to vortex formation or exhaust of air or gas, fans, pneumatic tools and machines must be equipped with special mufflers.

Mobile transport is also a huge danger for workers in the workshop. A huge number of trolleys move around the workshop territory, transporting finished products to warehouses, and electric locomotives that bring scrap metal or coils to and from the workshop every day. Overhead cranes, which have large lifting devices, move in the bays of the workshop. When moving around the workshop, you need to take these dangerous factors into account. Without following safety precautions, workers can be seriously injured. That is why there are special paths and bridges along which you need to move so as not to get hit by moving vehicles. Special helmets are required on the territory of the plant.

When working in places with elevated temperatures, people become dehydrated, sweat profusely, and blood pressure rises.

That is why special equipment is provided on the territory of the plant. clothes, in the workshops there are coolers with salt water. (7. p58)

The furnace department of LPC - 4 belongs to fire safety category G. This category includes areas where non-combustible substances and materials are used in a hot, incandescent or molten state, the processing of which is accompanied by the release of radiant heat, sparks and flames, and (or) flammable gases, liquids and solids that are burned or disposed of as fuel. Ferrous metallurgy enterprises use the most effective and appropriate fire extinguishing agents. The most common and cheapest means of extinguishing a fire is water, without which not a single metallurgical process can operate.

Water has a high heat capacity and therefore has a great cooling effect. The cooling effect of water is explained by the high heat of vaporization. In this case, a large amount of heat is removed from the burning substance. Steam, in turn, reduces the oxygen content in the air, exhibiting insulating properties. It is known that some materials (cotton, textiles, soot and others, especially smoldering substances) are poorly wetted, so extinguishing them with water is ineffective. The fire extinguishing effectiveness of water is increased by introducing surfactants and thickeners into it.

Water steam is widely used in enterprises to extinguish fires in oil cellars. To extinguish a fire with water vapor where a fire has occurred, it is necessary to create a steam concentration of 35%. For this purpose, oil cellars are equipped with stationary dry pipes connected to a steam main. Dry pipes are laid in the lower part of the room, since the steam coming out of them will begin to fill primarily the upper volume of the oil cellar.

Carbon dioxide widely used to extinguish fires in enterprises. It is a colorless and odorless gas. At a pressure of 6 MPa, it turns into a liquid state, in which it is stored in cylinders of carbon dioxide fire extinguishers. When leaving the fire extinguisher, turning into a gaseous state, carbon dioxide enormously increases its volume and cools to -50 o C, cooling the burning substance and isolating it from air access. Carbon dioxide is used in fire extinguishers and stationary installations for extinguishing fires electrical installations energized. Also in the territories of ferrous metallurgy enterprises there are fire shields, which must have a fire bucket, a fire extinguisher, and a box of sand. (11. from 297)

4.2 Environmental protection in the conditions of LPC - 4

To purify polluted air, devices of various designs are used, using various methods of purification from harmful substances.

The main parameters of gas cleaning devices and cleaning systems are efficiency and hydraulic resistance. Efficiency determines the concentration of harmful impurities at the outlet of the apparatus, and hydraulic resistance determines the energy consumption for passing the purified gases through the apparatus. The higher the efficiency and the lower the hydraulic resistance, the better.

Dust collectors, for cleaning exhaust gases from dust, there is a wide selection of devices that can be divided into two large groups: dry and wet (scrubbers) - irrigated with water. Cyclones, the most widely used in the practice of bullet catching are cyclones different types: single, battery.

Filters. In dust collection technology, filters are widely used, which provide high efficiency in collecting small particles. The cleaning process involves passing the air to be purified through a porous partition or layer of porous material. Based on the type of filter material, filters are divided into fabric fibrous and granular.

For fabric filters, the filter partition is a fabric (cotton, wool, lavsan, nylon glass, metal) with a regular weave structure of threads (twill, linen, etc.). (8. p44)

Fiber filters are a layer of thin and ultra-fine fibers with an irregular, chaotic structure.

Cleaning of drains

Industrial water is also used for cooling and washing equipment. At the 2500 mill, water is used to cool and wet the strip during the rolling process.

During hot rolling, coolants are subject to contamination by: tiny mechanical particles (impurities) released from the oxidized layer of metal, sludge after pickling and metal wear products; free (non-emulsified) oils released from the emulsion as a result of separation; oils entering the emulsion system of the mill as a result of leaks from the mechanical and hydraulic equipment of the mill; oils washed off from hot-rolled strips pre-oiled before rolling.

Table 3. Analysis of waste coolant effluents from the 2500 mill.

The duration of the coolant (emulsion) cycle depends on the capacity of the emulsion system and the quality of cleaning.

Spent coolant (emulsion) is a special type of wastewater that is very dangerous for water bodies, as it contains a large amount of persistently emulsified petroleum products. Spent coolant contains 10 - 30 g/l of emulsified oils and a large amount of free oils. The total amount of ether-soluble substances in emulsion wastewater is 20 - 30 g/l.

Treatment of emulsion wastewater must necessarily include reagent treatment to destroy the emulsifier and emulsified oils. Sulfuric and hydrochloric acids and spent pickling solution are used as demulsifiers.

Treatment facilities are designed to remove free oils, mechanical impurities and oxidation products from the cooling circulating emulsion.

The facilities of LPC - 4 of OJSC MMK provide for 2-stage purification by sedimentation and flotation, and include the following elements:

6 horizontal settling tanks equipped with scraper conveyors, 2 radial-type flotators, a pumping station containing a pump for supplying flotation, pumps for supplying coolant to the 2500 mill, 2 receivers for settled and purified coolant, reagent facilities.

Figure 7. Wastewater treatment under the conditions of LPC-4: 1 - horizontal settling tank; 2 - receiving chamber of “dirty” emulsion; 3 - pressure tank; 4 - flotator; 5 - receiving chamber of “pure” emulsion; 6 - pump 12D-9; 7 - pump 200D-60; 8 - pump 12NDS-60; 9 - automatic filter of the "SACK" system; 10 - tank of foam product from flotators; 11 - tank of foam product from settling tanks; 12 - pump RZ-30; 13 - ejector

The spent coolant from the 2500 mill is supplied through a distribution manifold to the receiving part of a horizontal settling tank, designed to collect and remove the lightest oil fractions and coarse mechanical particles (impurities). Then the coolant through the distribution partition enters the settling chamber, where finer-grained mechanical impurities are deposited to the bottom. The settled coolant is collected in a tray and supplied through a pipeline to an intermediate receiver, then to a flotation unit for post-treatment. The settled coolant is supplied by pumps to a pressure tank, in which the compressed air is dissolved in the emulsion. Next, the mixture enters the water distribution mechanism and is evenly distributed over the entire cross-section of the flotator for the final purification of oil products. The purified coolant is discharged into a tray and enters the purified emulsion tank, and from it it is pumped to the cold rolling shop for reuse. The oil products separated in the settling tank and flotator are taken to their regeneration site. (8. p. 97)

...

Pickling area. Etching section Study of the influence of mating coatings on the load-bearing capacity of the axle-tire connection. Selection of material and coating technology

1.1 Continuous mill 2500 of the Magnitogorsk Iron and Steel Works

Introduction

Cold rolling mills

Continuous mill 2500 of Magnitogorsk Iron and Steel Works

Continuous mill 1700 of the Mariupol Metallurgical Plant named after. Ilyich

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