Equipment and tools for rolling. Equipment for rolling mills What tools are needed for rolling

Rolling tool are rolls, with the help of which ingots and other blanks are processed. Rolls are:

smooth for rolling sheets, strips;

stepped for rolling strip steel;

brook for obtaining long products.

The profile of the notch on the side surface of the roll is called brook... The stream of the upper and lower rolls together form caliber.

Several calibers are placed on each pair of rolls, the shape of which depends on the rolled profile. Complex rolled profiles are obtained by successive passes of metal through a series of gauges. For rails, the number of gauges is 9, for beams from 9 to 13, for wire - from 15 to 19.

Depending on the rolling stage, a distinction is made between crimping calibers ( reducing the section of the workpiece), rough(approximating the section of the workpiece to a given profile) and finishing or finishing(giving a given profile).

Equipment on which the metal is rolled is called a rolling mill. Rolling mill operating principle next: the milling rolls are mounted in bearings located in the frame posts. The set of rolls together with the bed is called the working stand. The work rolls receive rotation from the motor through a gearbox that transmits the rotational motion through a gear stand and spindles.

The rolling mill also includes auxiliary machines and mechanisms that perform auxiliary operations for cutting, finishing, and transporting the rolled metal.

§ 3. Classification of rolling mills

Mills are classified according to 3 main criteria:

by appointment;

by the number and arrangement of rolls in the working stands;

3. according to the number and location of the working stands.

By appointment mills are divided into 2 main types:

mills for the production of semi-finished products;

mills for the production of finished products.

To the first type relate crimping and billet stans. Crimping mills - blooming and slabbing with a roll diameter of 800 - 1400 mm - designed for rolling ingots into large billets (blooms and slabs), which are supplied as an intermediate product for subsequent rolling into smaller billets or to obtain a finished product. Blank mills with roll diameters of 450 - 750 mm are intended for rolling blooms into smaller blanks (from 50 50 mm to 150 150 mm), which are the starting material for further rolling on section mills.

To the second type of staves include:

1.Rail and girder with rolls with a diameter of 750 - 900 mm for rolling

railway rails, I-beams, channels, angles

large sizes;

2. large-section with rolls with a diameter of 500 - 750 mm for rolling large-section steel (square and round from 80 to 150 mm), beams and channels 120 - 140 mm;

3. medium-section with rolls with a diameter of 350 - 500 mm for rolling medium-sized steel (square and round 40 - 80 mm), beams and channels up to 120 mm in height;

4.Small-section with rolls with a diameter of 250 - 350 mm for rolling small sections (square and round 8 - 40 mm), corner sections 20 20 to 50 50 mm;

5. wire mills with rolls with a diameter of 250 - 300 mm for rolling wire (rod) with a diameter of 5 - 9 mm;

6. strip (strip) mills with rolls 300 - 400 mm in diameter for rolling strips 65 - 500 mm wide and 1.5 - 10 mm thick;

7. plate mills for rolling sheets with a thickness of 4 - 60 mm;

8. hot and cold rolled sheets for sheets 0.2 - 4 mm thick and 500 - 2500 mm wide;

9. universal mills for rolling universal strips with a width of 200 - 1500 mm;

10. pipe mills for the production of seamless and welded pipes;

11.Mills for special purposes - wheel and tire rolling, ball rolling, etc.

As can be seen from the above classification, the main characteristic of section mills is the diameter of the work or gear rolls. If the mill has several stands, then the characteristic of the entire mill is the diameter of the rolls of the finishing stand. For example, a wire mill 250 means that the diameter of the work rolls or gear rolls of the finishing stand is 250 mm.

According to the number and arrangement of rolls in the working stands of the mill distinguish:

duo-mills - (two-roll) with two rolls in each stand located horizontally one above the other in a vertical plane.

Duo mills can have a constant direction of rotation of the rolls (non-reversible) and variable (reversible). In the latter case, the rolls periodically change the direction of rotation and the ingot or strip passes between the rolls back and forth several times; both rolls are usually driven. Reversible duo-mills are more widespread: blooming, slabbing, thick-leaf, etc.

Trio-mills, in which three rolls are located horizontally one above the other in the same vertical plane. The strip is rolled first between the lower and middle rolls, and then, with a special device (lifting and swinging tables), it rises to the split level of the middle and upper rolls and, during the return stroke, is rolled between the middle and upper rolls. The trio-mills roll section metal and sheets. Sheet trio-mills have an average non-driven roll of a slightly smaller diameter than the upper and lower ones, and on section rolls - all rolls of the same diameter.

Quarto-mills have four rolls, vertically located one above the other, two rolls of smaller diameter (middle) are working, and large (upper and lower) are supporting. The backup rolls take up the rolling pressure and reduce the deflection of the work rolls. Quarto stands are reversible and irreversible. They are designed for rolling sheets and strips.

multi-roll mills are six-roll, twelve-roll, dvadtsatalkovy, etc. These mills have two working rolls of small diameter, and the rest - supporting. Due to the small deflection of the work rolls, these mills are used for cold rolling of thin strips and narrow strips in coils.

universal mills with vertical and horizontal rolls in one working stand. On these mills, the metal is crimped in width and height. Universal mills are used for rolling strips called universal steel.

By the number and location of working stands rolling mills share on single-cell and multi-cell... The simplest type is a single stand mill. These include blooming mills, slabbing mills, heavy-plate duo- and trio-mills, universal mills.

Multi-stand mills have two or more working stands. The arrangement of the stands can be: linear, sequential and continuous... In these mills, each working stand or group of 2 - 4 stands has a roll drive line.

Linear mills with the arrangement of working stands in one line are rail and structural mills and large section mills.

The most common type of modern multi-stand mills are continuous mills, in which the number of working stands is equal to the required number of passes; rolling is carried out according to the principle - one pass in each stand. The stands are arranged sequentially one after the other so that the strip is simultaneously in two or more stands. The rolling speed in each working stand increases as the section of the rolled strip decreases, which is achieved by changing the number of rolls revolutions with an individual drive of the rolls of each working stand, or by changing the gear ratio and the number of rolls revolutions and the diameter of the work rolls with a group drive.

Continuous mills are used as billet, bar, wire, strip (strip), sheet for cold and hot rolling. The rolling speed on these mills reaches 30 - 35 m / sec and more, due to which continuous mills have high productivity.

The rolling tool is rolls, which, depending on the rolled profile, can be smooth(Fig. 4, a) - for rolling sheets, strips, etc., stepped- for rolling strip steel, brook(Fig. 4, b) - to obtain long products.

Rice. 4. Rolling tools and equipment: a - smooth roll; b - stream roll; в - open and closed calibers; d - diagram of the rolling mill

By the brook called a cut on the side surface of the roll, and the combination of two grooves of a pair of rolls forms caliber... Gauges distinguish between open and closed (Fig. 4, c). Have open calibers the parting line of the rolls is within the caliber, and at closed- outside its limits. Several calibers are usually placed on each pair of grooved rolls. The development of a system of sequential calibers required to obtain a particular profile is called calibration... The greater the difference in the sizes of the cross-sections of the original workpiece and the final product and the more complex the profile of the latter, the more gauges are required to obtain it. So, to obtain rails, a system of 9 calibers is used, beams - from 9-13, to obtain wire - from 15-19.

The rolls consist of a barrel 1 (the working part of the roll), necks 2 (pins) and clubs 3. The necks of the rolls rotate in bearings installed in the frame racks. The bed has mechanisms for changing the distance between the rolls and the relative position of their axes.

The set of rolls together with the bed is called working stand 4 (Fig. 4, d). The rolls receive rotation from the motor 8 through the reduction gear 7, which transmits the rotational motion through the gear stand 6 and the spindles 5. The set of the drive, the gear stand, one or more working stands forms rolling mill.

By the method of cross-rolling, for example, gear wheels and chain sprockets are obtained on special machines with toothed rolls.

Cross-helical (oblique) rolling is widely used in the production of seamless pipes from a solid billet (Fig. 5, b). Rolls 1 rotate in one direction, and their axes are located at a certain angle, so the workpiece 2 during processing not only rotates (vy), but also moves along its axis (vx). To obtain the correct shape and smooth surface of the pipe hole (sleeve), a mandrel 3 is installed in the hole formation zone. The sleeves obtained at the piercing mill are rolled out on pipe rolling mills. The helical rolling method is also used for the production of balls, axles and other products using specially calibrated rolls. The hot rolled steel is heated to a temperature above the 68K line (see Fig. 5); copper, aluminum and their alloys are also hot rolled. From a hot-rolled billet (sheet with a thickness of 1.25 mm), thin products (up to 0.1 mm and less), strips for springs, sheets, foil, etc. are obtained by cold rolling.

Rolling mills are distinguished by purpose, the number of rolls in a stand, the number of stands and their arrangement.

By designation, rolling mills are divided into blooming (blooming and slabbing), billet, section, sheet and special mills. First, the ingot is rolled on a crimping mill, then on a billet mill and, finally, on a bar, sheet or special mill.

By the number and arrangement of rolls in working stands, mills are classified into duo-mills, trio-mills, quarto-mills, multi-roll and universal mills.

Rice. 5.

Stan duo has two rolls (Fig. 5, a), which have either a constant direction of rotation (irreversible stuns), or the direction of rotation, which can be changed and thus pass the processed metal in both directions (reversible mills).

Quarto mill(Fig. 5, b) has two working and two backup rolls located one above the other. The work rolls are driven. Multi-roll mills: 12-rolls (Fig. 5, c) and 20-rolls also have only 2 work rolls, and all the others have support rolls. The work rolls are driven through intermediate backup rolls. The use of back-up rolls allows the use of small-diameter work rolls, which increases the stretch and reduces the metal pressure on the rolls.

Universal mills have not only horizontal, but also vertical rolls (Fig. 5, d).

By arrangement of working stands distinguish between countries single-stand and multi-stand with a linear or sequential arrangement of stands. Have linear mills stands are located in one or several lines (Fig. 6, a); in each line the rolls are interconnected and rotate at the same speed. Sequential arrangement of stands in continuous mills(Fig. 6, b) can significantly increase the productivity of rolling.

Rice. 6.

The drive of the working stands of continuous mills can be group - from one engine, or individual - each stand has its own engine. In both cases, the rolling speed in each subsequent stand is higher than the speed in the previous one. In continuous mills, the metal moves in a straight line and is deformed simultaneously in several stands.

By appointment rolling mills are divided into semi-finished product mills and mills for the production of finished rolled products... The first group includes blooming and billet mills. Mills for finished products are characterized by the type of products they produce: rail and steel sections, sheet, pipe-rolling, wire and special types of rolled products.

Crimping mills (blooming and slabbing) designed for rolling ingots (up to 60 tons) into large billets (blooms and slabs). Bloom- billet of square cross-section with dimensions from 450 to 150 mm, after blooming it is rolled on section mills. Slab has a rectangular section with a thickness of 65-300 mm and a width of 600-1600 mm and is a blank for a sheet. Blank mills are intended for obtaining a semi-product of a smaller section from blooms, slabs or ingots of a small mass.

The cross-sectional shape of the rolled strip is called a profile. The set of shapes and sizes of profiles obtained by rolling is called assortment. In the USSR, almost the entire range of rolled products is manufactured in accordance with GOST (State All-Union Standard). In GOSTs for the assortment of rolled products, the cross-sectional area, dimensions, weight of 1 m of the profile length and permissible deviations from the nominal dimensions are given. The assortment of rolled profiles is divided into four main groups: long products, sheets, pipes and special types of rolled products.

Sections are divided into simple geometric shapes (square, circle, hexagon, rectangle) and shaped (channel, rail, angle and T-profiles, etc.). Round and square steel is rolled, respectively, with a diameter or side of a square of 5-250 mm; hexagonal - with an inscribed circle diameter of 6-100 mm; strip - 10-200 mm wide and 4-60 mm thick.

Non-ferrous metals and their alloys are rolled mainly into simple profiles - round, square, rectangular.

Sheets made of steel and non-ferrous metals are used in various industries. In this regard, sheet steel, for example, is divided into automotive, transformer, roofing sheet, etc. The production of sheet steel with tin, zinc, aluminum and plastic coatings is expanding. In addition, sheet steel is divided into plate steel (4-160 mm thick) and thin plate (less than 4 mm thick). Sheets less than 0.2 mm thick are called foil.

Pipes are divided into seamless and welded. Seamless pipes are rolled with a diameter of 30-650 mm with a wall thickness of 2-160 mm from carbon and alloy steels, and welded pipes with a diameter of 5-2500 mm with a wall thickness of 0.5-16 mm from carbon and low-alloy steels.

Special types of rolled products include wheels, rings, balls, periodic profiles with periodically changing shape and cross-sectional area along the axis of the workpiece

Rolling tools and equipment

Rice. 2. Rolling tool:

a - smooth roll; b - stream roll; в - caliber; d - the arrangement of the rolls in a four-roll stand, d - the same, in a 12-roll stand.

Rolling tools are rolls, which, depending on the profile being rolled, can be smooth (Fig. 2, a), used for rolling sheets, strips, etc., stepped, for example, for rolling strip steel, and grooved (Fig. 2, b) to obtain long products. A groove is called a cut on the side surface of the roll, and the combination of two grooves forms a caliber (Fig. 2, c). Each pair of grooved rolls usually forms several calibers.

The rolls consist of a working part - barrel 1, necks 2 and clubs 3. The necks of the rolls rotate in bearings, which at one of the rolls can be moved by a special pressure mechanism to change the distance between the rolls and regulate the relative position of their axes. A set of rolls with a bed is called a working stand; the latter, together with a spindle for driving the rolls, a gear, a stand for transferring rotation from one to two shafts, a gearbox, couplings and an electric motor, form the working line of the mill.

By the number and arrangement of rolls, the working stands can be two-roll; four-roll (Fig. 2, d), which have two working rolls and two support rolls; multi-roll (Fig. 2, e), which also have two worker rolls, and the rest are support rolls. The use of back-up rolls allows the use of small-diameter work rolls, which increases the stretch and reduces the deformation force.

Rolling mills can be single-stand (with one working stand) and multi-stand.

The most advanced multi-stand mills are continuous, in which the working stands are arranged sequentially one after the other. The rolled strip passes through each stand only once, that is, the number of working stands of these mills is equal to the required number of strip passes. The distance between the stands is usually less than the length of the rolled strip, therefore, it is rolled simultaneously in several stands. On continuous mills, high productivity is achieved with the complete elimination of manual labor. The maximum rolling speed on modern continuous mills is 50-60 m / s.

By designation, rolling mills are subdivided into mills for the production of semi-finished products and mills for the production of finished products. The first group includes crimping mills for rolling ingots into a semi-finished product of a large section (blooming mills, which give a billet for long products, and slabs, giving a billet for sheet metal) and billet mills for obtaining a semi-product of a smaller section.

Mills for the production of finished rolled products include bar, sheet, pipe and special. The size of blooming, slabbing, billet and section mills is characterized by the diameter of the roll barrel (for example: blooming 1500; section 350); the size of the sheet mills is the length of the barrel (for example: mill 3600), and the size of the pipe mills is the outer diameter of the rolled pipes.

ROLLED PRODUCTS

The cross-sectional shape of the rolled strip is called profile. The set of shapes and sizes of profiles obtained by rolling is called assortment . In the DSTU for the range of rolled products, the cross-sectional area, dimensions, weight of 1 m of the profile length and permissible deviations from the nominal dimensions are given. The range of rolled profiles is divided into four main groups : long products, sheet, pipes and special types of rolled products.

Long products are divided into profiles simple geometric shape (square, circle, hexagon, rectangle) and shaped(channel, rail, angle and T-profiles and round and square steel are rolled, respectively, with a diameter or side of a square of 5-250 mm; hexagonal - with an inscribed circle diameter of 6-100 mm; strip - 200 mm wide and 4-60 mm thick. Non-ferrous metals and their alloys are rolled mainly into simple profiles - round, square, rectangular .Sheet steel is divided by purpose into automotive, transformer, roofing sheet, etc. According to the type of coating, sheet steel is divided into coated with zinc, aluminum, plastic coating, etc. In addition, sheet steel is divided into thick sheet with a thickness of 4-160 mm) and thin sheet (less than 4 mm thick), with a thickness of less than 0.2 mm is called foil. Pipes are divided into seamless and welded. Seamless pipes are rolled with a diameter of 30-650 mm with a wall thickness of 2-160 mm from carbon and alloy steels, and welded pipes with a diameter of up to 2500 mm with a wall thickness of 0.5-16 mm from carbon and low-alloy steels. Special types of rolled products include wheels, balls, periodic profiles with a periodically changing shape and cross-sectional area along the axis of the workpiece. .

Rolling tools are rolls, which, depending on the profile being rolled, can be smooth, used for rolling sheets, strips, etc., stepped, for rolling strip steel, and strand, for obtaining long products. A groove is called a cut on the side surface of the roll, and the combination of two grooves forms a caliber . Each pair of grooved rolls usually forms several calibers. A set of rolls with a bed is called a working stand; the latter, together with a spindle for driving the rolls, a gearbox, couplings and an electric motor, form the working line of the mill. The working stands by the number and arrangement of rolls can be two-high four-high, which have 2 worker rolls and two support rolls; multi-roll , which also have two worker rolls, and the rest are support rolls. The rolling mills can be single-stand (with one working stand) and multi-stand. The most advanced multi-stand mills are continuous, in which the working stands are arranged sequentially one after the other. The strip to be rolled passes through each stand only once, i.e. the number of working stands of these mills is equal to the required number of strip passes. The maximum rolling speed on continuous mills is 50-60 m / s. By appointment rolling mills are subdivided into mills for the production of semi-finished products and mills for the production of finished products. The first group includes swaging mills for rolling ingots into a semi-finished product of a large section (blooming mills that give a billet for long products, and slabs that give a billet for sheet metal) and billets for producing a semi-product of a smaller section. , pipe and special. The size of blooming, slabbing, billet and section mills is characterized by the diameter of the roll barrel (for example: blooming 1500; section 350); the size of the sheet mills is the length of the barrel (for example: mill 3600), and the size of the pipe mills is the outer diameter of the rolled pipes.

7.1. Types of rolling mills

The complex of machines and mechanisms for producing products by rolling and processing them in a stream is called a rolling mill.

It follows from this definition that in addition to the main operation - plastic shaping of the roll, a number of others are also performed on the mill.

In the theory of the organization of production, the individual operations necessary for the implementation of the technological process are subdivided into the main accompanying and auxiliary ones. In accordance with this, a distinction is made between main, accompanying and auxiliary equipment.

With regard to rolling, the main ones include operations for the implementation of plastic deformation of the metal, i.e. rolling itself, and, accordingly, the main equipment includes a rolling stand, an electric drive and transmission devices.

Related operations include operations in the course of which the physical state and / or dimensions of the roll can change, but without changing the shape and cross-sectional area. These are heating, cooling, cutting to length, straightening, stripping of rolled products, etc. And, accordingly, equipment: heating devices, refrigerators, straightening machines, cutting, finishing, etc.

Ancillary operations include operations in which neither the shape, nor the dimensions, nor the physical state of the rolled metal changes. These are operations and the corresponding equipment for the longitudinal and transverse movement of the rolls (roller tables, schleppers, lifting mechanisms), their tilting and branding, coiling into coils and rolls, strapping of rolled stock, transfer of rolls, etc. In everyday life, however, accompanying and auxiliary operations and equipment is usually referred to as auxiliary.

The line on which the main equipment is located is called the main (working) line of the rolling mill (Figure 7.1). Its main elements are: a working stand with rolls (1), spindles with couplings (2), a gear stand (3), a main clutch (4), a gearbox (6), a main (motor) clutch (7) and a motor (5) ...

Rolls (Figure 7.2) consist of a barrel (1) with a diameter d and a length l, two bearing journals (2) and shanks (3). The dimensions and number of rolls in the stand determine the type of stand and rolling mill. Section mills are characterized by the nominal diameter of the roll barrel (for example, a 280 mill), and sheet mills, by its length (for example, a 3600 mill). If a section mill consists of several stands with different roll diameters, the type of mill is usually determined by the rolls of the finishing stand.

Rolling mills are classified according to the following criteria: by mode of operation, by purpose, by the number and arrangement of rolls in the stand, by the number and arrangement of stands.

By mode Rolling mills are divided into non-reversible (the frequency and direction of rotation of the rolls are constant) and reversible (rolling is carried out in the forward and reverse directions by changing the direction of rotation of the rolls). The second group includes blooming mills, slabs, billet and plate mills.

By appointment mills are subdivided into semi-product mills and finished steel mills. The first include blooming, slabbing, blank mills. The second include:

Rail and steel mills (rolls diameter 750-900 mm);

Large-section mills (500-700 mm);

Medium section mills (350-500 mm);

Light section mills (250-330 mm);

Wire mills (150-280 mm);

Strip mills (300-400 mm);

Plate mills (roll barrel length up to 5500 mm);

Hot strip mills (up to 2500 mm);

Wide-strip cold rolling mills (up to 2800 mm);

Universal strip mills (up to 2000 mm);

Tube mills of various types;

Other mills (tire-wheel, axial rolling, ball rolling, etc.)

By the number and arrangement of rolls in the cage there are:

Two-roll (duo) stands (see fig. 1.1). They are widely used in reversible and non-reversible modes.

Three-roll (trio) stands, section (7.3 a) and sheet (Fig. 7.3 b). Used for rolling billets, grades and sheets.

Double double roll stands (double duo). They are rarely used, mainly for rolling small grades of alloy steels (Figure 7.4).

Four-roll stands (quarto). They are used mainly in sheet production (Figure 7.5). Work rolls (2) are of smaller diameter, support rolls (1) are larger in order to increase the rigidity of the system.

Six-roll stands (Figure 7.6) are rarely used. Rolls arrangement is in one vertical axial plane. Drive rolls are working.

Multi-roll stands - 12 and 20-roll. They are used for rolling the thinnest strips (up to 2 microns) in coils (fig. 7.7.- 7.8). Working roll diameter up to 50 mm. Back-up rolls are driven.

Universal stands - for sheet rolling, apart from horizontal ones, they are equipped with two vertical driven rolls; for rolling wide-flange beams, idle vertical rolls are placed in the same vertical plane with horizontal ones (Figure 7.9).

By the number and arrangement of stands rolling mills are subdivided into single and multi-stand. Single-stand - blooming mills, slabbing mills, sheet rolling mills, crimping and billet mills, etc. (Figure 7.10).

Multi-stand mills are of linear type, continuous, semi-continuous and with a sequential arrangement of stands.

Linear mills (Figure 7.11) are used for rolling billets, small-, medium- and large-section sections. The disadvantages of such mills are high costs of manual labor, low rolling speeds and productivity. Partially these disadvantages can be avoided by placing the stands in several lines (fig. 7.12.).

More advanced are continuous mills with stands located one after another (Figure 7.13). Such mills work according to the principle: "in each stand - one pass". The roll can be simultaneously in several stands. Therefore, it is necessary to observe the rule of so-called second volumes, i.e. the same amount of metal must pass through each stand per unit of time:, where V and F- the speed and cross-sectional area of ​​the rolling stock in the stands, respectively. If this condition is violated, stretching of the roll or a loop may occur between the stands. Therefore, predominantly simple profiles are rolled in continuous mode.

The principle of continuous rolling is used on continuous billet mills, medium and small-section, wire, strip mills, broad-strip mills for hot and cold sheet rolling, etc.

For rolling more complex profiles, semi-continuous mills and mills with a sequential arrangement of stands are used. Semi-continuous mills are used for rolling small grades. They combine a continuous roughing and a linear finishing group of stands (Figure 7.14).

In mills with a sequential arrangement of stands (Figure 7.15), the roughing group can be continuous, and subsequent stands are located one after another at a distance exceeding the length of the roll. To shorten the overall length of the mill, the stands are arranged in several parallel lines. In these stands there is no need to comply with the rule of second volumes. These mills are mainly used for rolling medium and large grades.

A variety of such mills is a staggered mill (Figure 7.16)

7.2 Basic and auxiliary equipment for rolling mills.

The working stand consists of two stands, rolls with bearings, mechanisms for setting and fixing the position of rolls in the vertical and horizontal planes, roll reinforcement, devices for lubricating and cooling rolls.

Beds of open or closed types (Figure 7.17) are cast from steel grade 30 ... 35L of I-section or rectangular cross-section.

Closed-type beds in the form of a one-piece frame can withstand large rolling forces, but are less convenient in operation: rolls are difficult to handle, their diameter is limited by the width of the window.

Rolling rolls - the main deforming tool - operate in harsh conditions: sharp heat changes, high pressures, abrasive friction, etc. Therefore, they must be not only high-strength, but also heat- and wear-resistant.

According to the material, rolls are subdivided into steel (cast, forged) and cast iron. Steel rolls have a sufficiently high strength and ductility, so they are used in stands that experience high rolling forces. Cast iron rolls are less durable but more wear resistant than steel rolls. Therefore, they are more often used in pre-finishing and finishing stands.

The rolls are made of carbon, low-alloyed and alloyed steels (Art. 50 ... 55, 50 ... 60KhN, 9KhF, etc.), alloyed and unalloyed cast irons (SSHKhN-60, LPKhN-60, etc.). Letters C, L denote graded and sheet rolls; Ш, П - cast iron with spheroidal or lamellar graphite; X, H - alloyed with chromium and nickel, respectively; 60 - hardness, Shore units.

When loading into a stand and during operation, the position of the rolls must be adjusted. For this, the roll setting mechanisms are used.

These include a pushing device, a balancing device and a device for adjusting the position of the rolls in the axial direction.

The pressing device is used to adjust the position of the rolls in the vertical plane. It consists of a nut (phosphor bronze), fixed in the upper cross member of the bed, and a pressure screw (forged steel 40 ... 45 XN).

Pressure screw drive - manual on mills with small displacement of the upper roll (50-100 mm), electromechanical - on mills with frequent and large