Tools and equipment for rolling production. Rolling mill equipment
Rolling tool are rolls, which, depending on the rolled profile, can be smooth(Fig. 4, a) - for rolling sheets, strips, etc., stepped- for rolling strip steel, stream(Fig. 4, b) - to obtain long products.
Rice. 4. Rolling tools and equipment: a - smooth roll; b - stream roll; c - open and closed calibers; d - scheme of the rolling mill
Creek called a cutout on the side surface of the roll, and the combination of two streams of a pair of rolls forms caliber. Gauges are distinguished between open and closed (Fig. 4, c). At open calibers the parting line of the rolls is within the caliber, and closed- outside of it. On each pair of grooved rolls, several calibers are usually placed. The development of a system of successive calibers necessary to obtain a particular profile is called calibration. The greater the difference in the dimensions of the cross sections of the initial workpiece and the final product, and the more complex the profile of the latter, the large quantity calibers 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.
Rolls consist of barrel 1 ( working part roll), necks 2 (trunnions) and clubs 3. The necks of the rolls rotate in bearings mounted in the racks of the frame. The frame has mechanisms for changing the distance between the rolls and the relative position of their axes.
A set of rolls together with a bed is called working stand 4 (Fig. 4d). The rolls receive rotation from the engine 8 through the reduction gear 7, which transmits rotational motion through the gear stand 6 and spindles 5. The combination of the drive, the gear stand, one or more working stands forms rolling mill.
For example, gear wheels and chain sprockets are produced by the transverse rolling method 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 receive correct form and the smooth surface of the pipe hole (sleeve) in the hole formation zone, a mandrel 3 is installed. The sleeves obtained on 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. Steel for hot rolling 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 1.25 mm thick), 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 layout.
By purpose, rolling mills are divided into swaging (blooming and slabbing), billet, section, sheet and special. First, the ingot is rolled on a swaging mill, then on a billet mill, and finally on a sectional, sheet or special mill.
According to the number and arrangement of rolls in the working stands, the mills are classified into duo-mills, trio-mills, quarto-mills, multi-roll and universal.
Rice. 5.
Stan duo has two rolls (Fig. 5, a), which have either a constant direction of rotation (irreversible mills), or the direction of rotation, which can be changed and thus pass the processed metal in both directions (reversing mills).
Stan quarto(Fig. 5, b) has two working and two support rolls, located one above the other. The work rolls are driven. Multi-roll mills: 12-roller (Fig. 5, c) and 20-roller also have only 2 working rolls, and all the rest are support rolls. The work rolls are driven through intermediate support rolls. The use of back-up rolls allows the use of work rolls of small diameter, which increases the draft and reduces the pressure of the metal on the rolls.
Universal mills have not only horizontal, but also vertical rolls (Fig. 5, d).
According to the location of the working stands distinguish between countries single cage and multi-cell with linear or sequential arrangement of stands. At linear mills the stands are arranged 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) allows you to significantly increase the productivity of rolling.
Rice. 6.
The drive of 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 intermediate production mills and mills for the production of finished steel. The first group includes swaging and billet mills. Finished rolled mills are characterized by the type of products they produce: rail and beam, section, sheet, pipe, wire, and mills for special types of rolled products.
Crimping mills (bloomings and slabs) designed for rolling ingots (up to 60 tons) into large billets (blooms and slabs). Bloom- billet of square 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. Billet mills designed to obtain a semi-finished product of a smaller section from blooms, slabs or ingots of small mass.
Rolling is the process of plastic deformation of a material that is consistently entrained into the deformation zone by friction forces acting on the contact surface "a deformable workpiece - a moving tool".
During rolling, not the entire volume of the material is simultaneously subjected to plastic deformation, but only its part located in the deformation zone. This allows processing large masses of material with optimal energy consumption and equipment dimensions, processing at high speeds, and ensuring high accuracy of the resulting products with minimal tool wear.
Rolling is one of the most progressive methods for obtaining finished metal products and occupies a leading position among the existing methods of metal forming.
There are three main rolling methods that differ in the direction of processing or the nature of the deformation: longitudinal, transverse and transverse-longitudinal (helical). Each of these methods can be performed with heating of workpieces (hot) and without heating (cold rolling).
Longitudinal rolling is based on the deformation of metal by rolls arranged parallel in one plane and rotating in different directions; the metal rolling axis is perpendicular to the major axes of the rolls (Fig. 3.1a).
Cross rolling is the deformation of metal by two rolls rotating in the same direction; the rolling axis is parallel to the major axes of the rolls (Fig. 3.1b).
Rice. 3.1
Oblique rolling is the deformation of metal by two rolls located at a certain angle to each other and rotating in the same direction. In this case, the metal is set into the rolls along their major axes (Fig. 3.2). This arrangement of rolls gives the metal a rotational and translational motion.
Rice. 3.2
The last two rolling methods are intended for the manufacture of products in the form of bodies of revolution (pipes, balls, etc.).
The technological process of rolling pre-cleaned and heated steel includes the following operations:
1) cutting of rolled products into cut lengths;
2) cooling;
3) heat treatment;
4) editing;
5) finishing;
6) quality control.
The technological parameters of rolling include: the temperature of the deformable billet, partial (in one pass between the rolls) and total reduction of the billet, rolling speed (the speed of the billet exiting the rolls can reach up to 100 m/s), the diameter of the rolls and the coefficient of contact friction between the tool and the deformable blank. To characterize the deformation during rolling, absolute and relative indicators are used:
Absolute compression;
Relative compression;
Elongation coefficient, where:
h0 - billet height before deformation;
h1 - billet height after deformation;
L0 is the length of the workpiece before deformation;
L1 is the length of the workpiece after deformation.
The absolute and relative reduction of the workpiece in one pass is limited by the condition of metal capture by the rolling rolls, as well as by their strength. Therefore, depending on the rolling conditions, the relative reduction per pass usually does not exceed 0.35 - 0.45. In addition, certain limitations are imposed by the physical and mechanical properties of the deformed material, especially during cold rolling.
Rolls are usually the main deforming tool for rolling metal products; in rare cases, a flat wedge tool is also used. In the manufacture of pipes, mandrels (short, long, floating) are used, the purpose of which is to shape the inner surface of hollow products.
The roll consists of a working part, or a barrel, two supports, or necks, and a shank for transmitting torque to a rotating roll. Rolls are solid and compound, ribbed and without ribbed (with a smooth cylindrical or conical surface, for example, for rolling sheets or profiles). Rolls are a deforming tool that perceives high specific and total pressures and operates under difficult conditions (temperature, sliding friction). Rolls are made of cast iron, steel and hard alloys. Typically, the working surface of the rolls must have a high hardness, especially in cold rolling, which is characterized by high specific loads. Diameter working surface the roll, depending on the purpose of the rolling equipment, can lie in a wide range - from 1 mm to 1800 mm.
Small diameters are used in cold rolling of high-strength alloys. In this case, to ensure their normal operation, the so-called back-up rolls are used, which are installed in special multi-roll stands.
Rolling is carried out on special equipment, which is commonly called a rolling mill. It includes a complex of technological machines and devices. The main equipment of the rolling mill is designed to perform the main operation in the technological process - rolling, i.e. for the implementation of the rotation of the rolls and direct plastic deformation of the workpiece to give it the required shape, size and properties. This equipment is called the main line of the rolling mill. There are mills: single-roll, two-roll, multi-roll, linear, continuous, semi-continuous, blank, sheet, sectional, beam, special, etc.
In addition to plastic deformation, a variety of other operations are performed on the rolling mill, including both the preparation for rolling discussed above, and transportation, finishing and quality control of finished products.
Transport devices move workpieces along and across the mill, raise and lower, rotate around the horizontal and vertical axes. These include: roller tables, manipulators, tilters and rotary mechanisms, lifting and pumping tables, tippers, ingot carriers, etc. Equipment for finishing and control of rolled products includes: devices for cutting metal, machines for straightening rolled products, devices for heat treatment of rolled products, units for metal and polymer coatings, devices and devices for quality control of rolled products, machines for tying and bundling rolled products.
ROLLING 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 DSTU, the cross-sectional area, dimensions, weight of 1 m of the length of the profile and permissible deviations from the nominal dimensions are given for the range of rolled products. The assortment of rolled profiles is divided into four main groups : long products, sheets, pipes and special types of products.
Long products are divided into profiles simple geometric shape (square, circle, hexagon, rectangle) and shaped(channel, rail, corner and tee 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 - with a width of -200 mm and a thickness of 4-60 mm. Non-ferrous metals and their alloys are rolled mainly into simple profiles - round, square, rectangular.Sheet steel is divided according to its purpose into autotractor, transformer, roofing tin, etc. According to the type of coating, sheet steel is divided into zinc-coated, aluminum, plastic coated, etc. In addition, sheet steel is divided into thick sheets with a thickness of 4-160 mm) and thin sheets (less than 4 mm thick), with a thickness of less than 0.2 mm, 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 grooved, to obtain long products. A stream is called a cutout on the side surface of the roll, and the combination of two streams forms a caliber . Each pair of stream rolls usually forms several calibers. A set of rolling rolls with a bed is called a working stand; the latter, together with the spindle for driving the rolls, the gearbox, the couplings and the electric motor, form the working line of the mill. The working stands, according to the number and arrangement of the rolls, can be two-roll four-roll, which have 2 work rolls and two support rolls; multiroll , which also have two rolls of workers, and the rest - support. 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, i.e. the number of working stands of these mills is equal to the required number of strip passes. Max speed rolling on continuous mills is 50-60 m/s. By appointment Rolling mills are divided 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 with a large cross-section (blooming, producing a blank for long products, and slabs, producing a blank for sheet metal) and blanks for producing a semi-finished product with a smaller cross 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 mill 350); the size of sheet mills - the length of the barrel (for example: mill 3600), and the size of pipe mills - the outer diameter of the rolled pipes.
1.5. Rolling
Rolling is a method of working metals by pressure, which consists in compressing a workpiece between rotating rolls.
Rolling production is of great importance in the national economy, since about 90% of all steel produced and most of the non-ferrous metals are rolled.
Due to the continuity of the process, rolling is the most productive way of forming metals.
Depending on the location of the rolls and the workpiece, there are three main types of rolling: longitudinal, transverse and transverse helical.
During longitudinal rolling (Fig. 5, a), the billet is deformed between two rolls and moves perpendicular to the axes of the rolls. This is the most common rolling method.
During transverse rolling (Fig. 5, b), rolls rotating in one direction impart rotation to the workpiece, which, moving along the axis of the rolls, is deformed.
In transverse helical rolling (Fig. 5c), the axes of the rolls are located at an angle to each other and impart rotational and translational motion to the workpiece during deformation.
Tools and equipment for rolling
Rolls are the rolling tool. Depending on the rolled profile, they can be smooth (Fig. 6, a) and calibrated (strand) (Fig. 6, b).
The roll consists of a middle working part - barrel 1, which performs rolling, necks 2, which are installed in bearings and clubs 3, through which the roll is rotated.
Smooth rolls are used for rolling sheet steel and roasting ingots into a square billet (bloom) or rectangular billet (slab).
Calibrated rolls have cutouts on the working surface of the barrel. The profile formed by the cut surface and the generatrix of the roll is called a stream, and the figure formed by the combination of two streams of a pair of rolls is called a caliber. A set of rolls installed in a special frame is called a stand.
The combination of the roll rotation drive, one or more working stands, feed roller tables forms a rolling mill.
Rolling mills according to their purpose are divided into mills producing semi-finished products and mills for the production of finished products.
The former include swaging mills (bloomings and slabs) for rolling ingots into billets of large cross-section, which are subsequently used for rolling bars and sheets.
The second includes mills for rolling sheets, shaped profiles, rails, pipes, etc.
Rolling production
Rolled products are used in metal structures(bridges, buildings, reinforced concrete structures, railway tracks, machine beds, etc.) as blanks for the manufacture of parts by cutting in machine shops and blanks for subsequent forging and stamping.
The cross-sectional shape of a rolled product is called a profile. A collection of profiles of various sizes is called a range. The range of rolled products is divided into four main groups: long products, sheets, pipes and special types of rolled products.
Rolled products obtained by longitudinal rolling are divided into rolled products of a simple geometric shape - a square, a circle, a hexagon, a strip (Fig. 7, a); shaped steel general purpose- I-beam, channel, angle, tee, rail (Fig. 7.b) and special-purpose rolled products (Fig. 7, c).
Sheet metal, depending on the purpose, is divided into electrical, shipbuilding, boiler, automotive, tin for the canning industry. In addition, sheet steel is divided into thick sheets (4 ... 160 mm thick) and thin sheets (4 ... 0.2 mm thick). Depending on the production technology, sheet metal can be hot-rolled and cold-rolled.
Steel pipes are divided into seamless with a diameter of 30...650 mm and welded with a diameter of 10...1420 mm.
Special types of rolled products include wheels of railway cars, gears, ball bearings, periodic profiles, which are a workpiece, the shape and cross section of which periodically change along the axis.
A special kind of special types of rolled products are cold-formed profiles (Fig. 8), made on bending roller mills from a strip. The use of such profiles by increasing the rigidity of structures in construction and mechanical engineering instead of hot-rolled profiles allows saving up to 40% of metal.
1.6. Drawing
Drawing consists in pulling the workpiece through the tapering hole of the die. In this case, the cross-sectional area of the workpiece decreases and acquires the shape of the cross-section of the die hole.
Diagrams of the process of drawing a solid round or shaped profile are given in Fig. 9, a, and a round pipe on a mandrel - in Fig. 9, b.
A drawing tool - a die (matrix) is made of hardened steel, hard alloys, and diamond inserts are made for especially thin products. The drawing forces to a large extent affect the friction forces on the surface of the workpiece metal - matrix, which tend to be reduced by the use of lubricants (mineral oils, talc, graphite, soap).
The drawing process is usually carried out in several passes. In most cases, drawing is carried out without heating, i. in a cold state. During the drawing process, the metal is hardened. Therefore, before each subsequent pass, annealing (heating with slow cooling) is carried out to remove hardening.
By drawing from steel and non-ferrous metals, wire is obtained, which is widely used in engineering (cables, springs, electric wires, electrodes for welding, etc.), rods and profiles of complex cross-section, pipes with a diameter of 0.3 to 220 mm with a thickness walls from 0.05 to 6 mm.
1.7. Pressing
Pressing consists in extruding metal from a closed cavity through an opening corresponding to the section of the pressed profile.
The schematic diagram of pressing is shown in Fig.10. In the process of pressing, the pressed metal I is squeezed out through the matrix 2 from the container 3 during the movement of the punch 4.
Pressing can be carried out by the direct method, in which the finished product moves in the same direction as the punch (Fig. 10, a) and the reverse, in which the finished product moves towards the punch (Fig. 10, b). The method of direct pressing in practice is used much more often.
The initial workpiece during pressing is an ingot or rolled products.
Pressing produces products of various assortments from structural, stainless and other steels and from non-ferrous metals. This method produces bars of various sections with a diameter of 3 to 250 mm, pipes with a diameter of 20 ... 400 mm with a wall thickness of 1.5 ... 12 mm, hollow profiles of a complex section, etc.
During pressing, the metal is deformed under conditions of all-round compression, as a result of which it shows maximum ductility. Therefore, by pressing it is possible to process such metals, which, due to their low ductility, are impossible or difficult to subject to other types of pressure treatment.
The disadvantages of pressing include large metal waste, since all the metal cannot be squeezed out of the container and the press residue remains in it (up to 40% of the mass of the original billet). Due to high pressing forces and high temperatures, the pressing tool wears out quickly. To reduce wear, it is made of expensive high-alloy heat-resistant steels, special lubricants are used (for example, liquid glass).
The main equipment for pressing are vertical or horizontal hydraulic presses.
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.
From this definition it follows that in addition to the main operation - the plastic shaping of the roll, a number of others are also performed on the mill.
In the theory of organization of production, the individual operations necessary for the implementation technological process, subdivided into the main accompanying and auxiliary. In accordance with this, a distinction is made between the main, related and auxiliary equipment.
With regard to rolling, the main ones include operations for the implementation of plastic deformation of the metal, i.e. the actual rolling, and, accordingly, the main equipment includes the rolling stand, electric drive and transmission devices.
Related operations include operations during 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, cleaning of rolled products, etc. And, accordingly, equipment: heating devices, refrigerators, straightening machines, cutting, finishing, etc.
Auxiliary operations include operations in which neither the shape, nor the dimensions, nor the physical state of the rolled metal changes. These are operations and related equipment for the longitudinal and transverse movement of rolls (rollers, schleppers, lifting mechanisms), their tilting and stamping, winding into riots and rolls, tying rolled stock, transshipment of rolls, etc. In everyday life, however, related and auxiliary operations and equipment is usually referred to as ancillary.
The line on which the main equipment is located is called the main (working) line of the rolling mill (Fig. 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 an engine (5) .
The rolls (Fig. 7.2) consist of a barrel (1) with a diameter d and a length l, two support journals (2) and shanks (3). The dimensions and number of rolls in a stand determine the type of stand and rolling mill. Section mills are characterized by the nominal diameter of the roll barrel (for example, mill 280), and sheet mills - by its length (for example, mill 3600). 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 location of rolls in the stand, by the number and location of stands.
By regime 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 forward and reverse direction by changing the direction of rotation of the rolls). The second group includes blooming, slabing, billet and plate mills.
By appointment mills are divided into mills for the production of semi-finished products and mills for the production of finished products. The former include blooming, slabing, billet mills. The second include:
Rail and beam mills (roll diameter 750-900 mm);
Large section mills (500-700 mm);
Medium section mills (350-500 mm);
Small section mills (250-330 mm);
Wire mills (150-280 mm);
Strip mills (300-400 mm);
Thick plate mills (barrel length up to 5500 mm);
Broadband hot rolling mills (up to 2500 mm);
Broadband cold rolling mills (up to 2800 mm);
Universal strip mills (up to 2000 mm);
Pipe mills of various types;
Other mills (wheel shroud, axle rolling, ball rolling, etc.)
By the number and arrangement of rolls in the cage distinguish:
Two-roll (duo) stands (see Fig. 1.1). Widely used in reverse and non-reverse modes.
Three-roll (trio) stands, high-quality (7.3 a) and sheet (Fig. 7.3 b). Used for rolling blanks, grades and sheets.
Double two-roll stands (double duo). Rarely used, mainly for rolling small grades of alloy steels (Fig. 7.4).
Four-roll stands (quarto). They are mainly used in sheet production (Fig. 7.5). Work rolls (2) have a smaller diameter, support rolls (1) have a larger diameter to increase the rigidity of the system.
Six-roll stands (Fig. 7.6) are rarely used. Variant of roll arrangement – in one vertical axial plane. Drive rolls are working.
Multi-roll stands - 12 and 20 rolls. Used for rolling the thinnest strips (up to 2 microns) in rolls (Fig. 7.7. - 7.8). Working roll diameter up to 50 mm. The drive rolls are back-up rolls.
Universal stands - for rolling sheets, in addition to horizontal ones, they are equipped with two vertical drive rolls; for rolling wide-shelf beams, idle vertical rolls are placed in the same vertical plane with horizontal ones (Fig. 7.9).
By the number and location of cages rolling mills are divided into single and multi-stand. Single-stand - blooming, slabing, sheet-rolling, crimp-blank and other mills (Fig. 7.10).
Multi-stand mills - linear type, continuous, semi-continuous and with a consistent arrangement of stands.
Linear type mills (Fig. 7.11) are used for rolling blanks, small, medium and large section profiles. The disadvantage of such mills is high costs manual labor, low speeds rolling and performance. Partially, these shortcomings can be avoided by placing the stands in several lines (Fig. 7.12.).
More perfect are continuous mills with stands located one behind the other (Fig. 7.13). Such mills work according to the principle: "in each stand - one pass". The roll can be in several stands at the same time. Therefore, it is necessary to observe the rule of the so-called second volumes, i.e. the same amount of metal must pass through each stand per unit time: , where V and F are the speed and cross-sectional area of the roll along the stands, respectively. If this condition is violated, stretching of the roll or a loop may occur between the stands. Therefore, mainly simple profiles are rolled in continuous mode.
The principle of continuous rolling is used in continuous billet mills, medium- and small-section, wire, strip mills, wide-strip mills for hot and cold rolling of sheets, 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 continuous roughing and linear finishing groups of stands (Fig. 7.14).
For mills with a sequential arrangement of stands (Fig. 7.15), the roughing group can be continuous, and subsequent stands are located one after the other at a distance exceeding the length of the roll. To reduce the overall length of the mill, the stands are arranged in several parallel lines. In these stands, there is no need to follow the rule of second volumes. Such mills are mainly used for rolling medium and large grades.
A variation of such mills is a mill with a staggered arrangement of stands (Fig. 7.16)
7.2 Main and auxiliary equipment of rolling mills.
The working stand consists of two frames, rolls with bearings, mechanisms for setting and fixing the position of the rolls in the vertical and horizontal planes, roll fittings, devices for lubricating and cooling the rolls.
Beds of open or closed types (Fig. 7.17) are cast from steel grade 30 ... 35L with an I-beam or rectangular section.
Closed-type beds in the form of a solid frame withstand high rolling forces, but are less convenient in operation: it is difficult to transfer rolls, their diameter is limited by the width of the window.
Rolls - the main deforming tool - operate under harsh conditions: sudden 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, the rolls are divided 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.
Rolls are made of carbon, low-alloy and alloy steels (St. 50…55, 50…60KhN, 9KhF, etc.), alloyed and unalloyed cast irons (SShKhN-60, LPKhN-60, etc.). The letters C, L denote varietal and sheet rolls; Sh, P - cast iron with nodular or lamellar graphite; Х, Н – doped with chromium and nickel, respectively; 60 - hardness, Shore units.
When filling into the cage and during operation, the position of the rolls must be adjusted. For this, the mechanisms for installing rolls are used.
These include a pressing device, a balancing device and a device for adjusting the position of the rolls in the axial direction.
The pressure device is used to control 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 a small movement of the upper roll (50-100 mm), electromechanical - on mills with frequent and large