International fairs their role. International exhibitions and fairs: organization and features

The main tool for rolling are rolls, which, depending on the rolled profile, can be smooth (Fig. 3.20, a) , calibrated (stream) (Fig. 3.20, b) and special. Smooth rolls are used when rolling sheets, strips, etc. All types of long products are rolled on calibrated rolls. Special rolls are used in the production of special types of rolled products.

The rolls have a working part (barrel) 1, two necks 2 for installation in bearings and cruciform ends (clubs) 3 for connecting the roll to the drive (Fig. 3.20).

On the working (side) surface of the calibrated rolls there are grooves - streams. The set of streams of a pair of rolls is called a caliber . Each pair of rolls usually accommodates several calibers. Gauges can be open (Fig. 3.20, c) and closed (Fig. 3.20, d).

Rolls necks based on bearings installed in the frame. With the help of a special pressure mechanism, the distance between the rolls can be adjusted. A set of rolling rolls with a bed is called a working stand. The rolling mill consists of one or more working stands and a drive, including an electric motor and a transmission mechanism (Fig. 3.21).

Depending on the design and location of the rolls, the working stands of rolling mills are divided into six groups (Fig. 3.22): duo, trio, quarto, multi-roll, universal and special design.

Duo (two-roll) stands are reversible (rolling in both directions) and non-reversible (rolling in one direction). Trio stands (three-roll) are most often non-reversible. Rolling on such mills is carried out forward between the lower and middle rolls and backwards between the upper and middle ones. Quarto (four-roll) stands have four rolls located one above the other, of which two work rolls of a smaller diameter and two support rolls of a larger diameter. Due to the rigidity and relatively low deflection of the back-up rolls, these stands produce cold rolling of thin strips and narrow strips with a small thickness tolerance. Universal stands have horizontal and vertical rolls: the latter provide metal reduction in the transverse direction. Vertical swaths are located, as a rule, on the front side. Stands of special design include the stands of narrow-purpose rolling mills: wheel-rolling, bandage-rolling, ring-rolling, ball-rolling, rolling mills for rolling profiles of variable section.

According to the type of products produced, rolling mills are classified into the following main types: swaging, billet, rail and beam, section, wire, plate, pipe and special-purpose mills.

Crimping mills are designed for compression of steel ingots into large billets. Crimping mills include blooming mills that produce square profile blanks - blooms and slabs that produce rectangular rolled products - slabs.

Blanking mills are used for rolling blooms into billets, mainly of square section, which are subsequently used for rolling at bar mills.

Rail beam mills are used to obtain rails, large beams, channels and other profiles from blooms.

section mills, used for the manufacture of long products of simple and shaped profiles.

Wire mills designed for rolling wire with a diameter of 5 ... 10 mm.

sheet rolling mills, subdivided into thick and thin sheets. Thick plate mills roll a sheet with a thickness of more than 6 mm. The blanks are slabs.

Tube mills used for the production of seamless and welded pipes.

Special mills are intended for obtaining blanks of special and periodic profiles. Balls, ribbed tubes, wagon axles, gear wheels and many other products of complex configuration are rolled on special mills.

Tool for rolling are rolls.

Rolls (fig. 3.5) consist of a working part or a barrel 1 , support parts or necks 2 and connecting part 3 .

Rolling sheets and strips produced on rolls with a smooth barrel having a cylindrical, slightly convex or concave surface (3.5, but).

Section rolling produced in calibrated rolls, on the barrel of which cutouts are machined 4 (3.5, b). cutout made on one roll, called a stream.

The cutouts of two rolls and the gap between them form caliber.

Caliber can be open (13.5, b) or h covered(13.5, in).

Rolls are made of cast iron, cast and forged carbon and alloy steel and hard alloys. The number of rolls, the diameter and length of the barrel of the working roll are the main parameters rolling mill.

Rice. 13.5. Rolls: a - with a smooth barrel; b - stream with an open caliber; in - stream with a closed caliber; one - working part(barrel); 2 - supporting part (neck); 3 - connecting part; 4 - stream of the upper roll; 5 - stream of the lower roll; 6 - caliber.

Rolling is carried out in rolling mills. Rolling mill (Fig. 13. 6 ) consists of a working stand, connecting spindles, gear stand, couplings, gearbox, flywheel, engine.

Rice. 3.6. Rolling mill: 1 - working stand; 2 - connecting spindles; 3 - gear cage; 4, 7 - couplings; 5 - reducer; 6 - flywheel; 8 - engine; P is the rolling force.

Pressing.

Pressing- extrusion of metal from a closed cavity through a hole in the tool. Main methods:

1.straight;

2.reverse.

At direct pressing (3.7, but) billet metal 3 extruded by a punch 2 and press washer 5 through the matrix hole 4 . When obtaining a hollow profile by direct pressing (3.7, b) the metal is squeezed out through the gap formed by the hole in the matrix and the needle 6 .

At back pressing the press force is transmitted through the punch (13.7, in) to the matrix. The matrix moves relative to the walls of the container. The workpiece metal is extruded through the die hole, forming a product 7 . Similarly, the reverse pressing of the hollow profile is carried out.

Rice. 3.7. Pressing schemes: a - direct pressing of a solid profile; b - direct pressing of a hollow profile; c - reverse pressing of a solid profile; 1 - container; 2 - punch; 3 - blank; 4 - matrix; 5 - press washer; 6- needle; 7 - pressed product; P is the pressing force.

At direct pressing the direction of movement of the punch and the extruded metal are the same. Distinctive feature the direct pressing method is the movement of the workpiece metal relative to the walls of the container 1 . Due to friction against the walls of the container, the central layers of metal are ahead of the outer ones. This phenomenon is further enhanced when the outer layers are cooled by the walls of the container. At some stage of pressing, a funnel is formed in the center from the side of the punch (press washer), through which surface layers contaminated with oxides and grease are drawn into the central part of the product, forming the so-called press sink. The presence of a press weight in the product is unacceptable. Therefore, pressing at this stage is stopped, the good product is separated, and the metal remaining in the container (press residue) is sent for remelting.

At back pressing the direction of movement of the extruded metal and the punch are opposite. The relative movement of the metal of the workpiece and the walls of the container, therefore, the contact friction between the metal and the walls of the container is practically absent.

During reverse pressing, the metal flow is more uniform than during direct pressing, due to the reduction of friction losses, the force less pressing is reduced by 25 ... than with direct.

Products . By pressing you get:

1. bars diameter 3…250 mm,

2.wire diameter 1…6 mm,

3.pipe with a diameter of 20 ... 600 mm with a wall thickness of 1.0 ... 1.5 mm or more,

4.solid and hollow profiles.

Alloys . Pressing is subjected to zinc, tin, lead, aluminum and aluminum alloys, magnesium and magnesium alloys, copper and copper alloys, nickel and nickel alloys, carbon and alloy steels, titanium and titanium alloys.

Equipment. When pressing, specialized hydraulic horizontal and vertical presses are most widely used. Vertical presses with a nominal force of up to 30 MN are mainly used in the production of pipes, horizontal presses are made with a nominal force of up to 100 MN.

Tool. Press tools include: needle, matrix, container, press washer (in order of increasing operating temperature). The temperature of the workpiece on the contact surface with the tool during the pressing of light alloys reaches 500°C, copper and copper alloys - 900°C, steels, nickel and titanium - 1250°C.

For the manufacture of tools, heat-resistant die steels of the type 3X2V8, 4XVS, 5XVS, etc. . Hard alloy inserts are sometimes used to increase the durability of dies. The profile of the working part of the matrix has a great influence on the pressing force and durability of the dies. Usually, conical matrices are used with an angle of inclination that is optimal for the given conditions.

Pressing, as a rule, is carried out under hot deformation conditions.

The initial workpiece is usually a cylindrical ingot or a polyhedron obtained by continuous casting, less often a rolled workpiece is used.

Before pressing, the working parts of the tool are covered with process lubricant. Also apply cladding(coating) blanks with ductile metals.

Advantages of pressing:

1.Ability to receive solid and hollow profiles of complex section, which cannot be obtained by other methods.

2.Press changeover on a new profile is produced significantly faster than rolling, the dimensional accuracy of the profile during pressing is higher, the surface roughness is smaller.

3.Ability to receive thin-walled seamless pipes of large diameter with little variance.

4. Possibility of pressure treatment of metals and alloys with reduced plasticity(high-strength aluminum alloys, bronzes, heat-resistant steels and alloys, etc.).

5. Opportunity high degrees of deformation(92% in cross section and more), which provides high mechanical properties, including vibration strength and fatigue resistance.

Disadvantages of pressing:

1.Significant tool wear, dies and especially needles, due to high contact stresses and temperatures, especially when pressing nickel alloys, steels and heat-resistant steels and alloys

2.The high cost of the tool.

3.unevenness mechanical properties along the length of the pressed product due to the uneven flow of the metal.

4. Large process waste, especially when pressing pipes of large diameter. (with the direct method 12 ... 15%, with the reverse - 5 ... 6% of the mass of the workpiece).

Drawing.

Drawing- the process of pulling the workpiece through a gradually narrowing hole in the tool (die).

When drawing, the cross-sectional area decreases, acquiring a constant cross-section along the entire length. The application of a tensile force reduces ductility and limits the amount of deformation per pull.

Rice. 3.8. Drawing schemes:

a - drawing wire, rod, solid profile;

b - pipe drawing on a mandrel;

1 - blank; 2 - portage; 3 - mandrel; 4 - clip (bandage); P is the drag force.

Products . By drawing you get:

1.wire (13.8, but) with a diameter of 6 to 0.008 mm;

2.solid and hollow profiles;

3.pipes (13.8, b) with an outer diameter of 1 ... 360 mm and a wall thickness of 10 ... 0.1 mm, having sections that are accurate in size and low surface roughness.

The blank for drawing is obtained by rolling or pressing; the workpiece must have a sectional shape similar to the sectional shape of the finished product.

Raw materials for drawing :

1. wire -wire rod And pressed wire diameter 5…9 mm;

2. bars and profiles - varietal rental and pressed profiles diameter 5…150 mm;

3. pipes - welded pipes diameter 6…200 mm, seamless rolled with a diameter of 40 ... 200 mm and pressed diameter 20…400 mm.

Drawing is usually carried out under conditions cold deformation. Wire drawing from tungsten, molybdenum, nichrome and zinc produce in hot.

Particular attention is paid to increasing the plasticity of the original workpiece and reducing the drawing force. This is achieved by applying heat treatment (annealing) to remove hardening, high quality the surface of the workpiece, the use of high-performance lubricants, the optimal profile and low surface roughness of the working areas of the tool.

Equipment. Drawing mills:

1. intermittent type - chain;

2. continuous type - drum.

Tool. Carbide die and diamond (thin wire drawing).

Alloys .

Drawing advantages:

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

smooth for rolling sheets, tapes;

stepped for rolling strip steel;

stream to obtain long products.

The cut profile on the side surface of the roll is called creek. 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 passages of metal through a series of calibers. For rails, the number of gauges is 9; for beams, from 9 to 13; for wire, from 15 to 19.

Depending on the stage of rolling, there are crimping gauges ( reducing the cross section of the workpiece), draft(approximating the section of the workpiece to a given profile) and finishing or finishing(giving a given profile).

Equipment where metal is rolled is called a rolling mill. Working principle of rolling mill next: rolling rolls are mounted in bearings located in the racks of the frame. A set of rolls together with a bed is called a working stand. The work rolls are rotated by the engine through a gearbox, which transmits rotational motion through the gear cage 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 features:

by appointment;

according to the number and arrangement of rolls in the working stands;

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

By appointment mills are divided into 2 main types:

mills for the production of intermediate products;

mills for the production of finished products.

To the first type relate crimping and blank mills. Crimping mills - bloomings and slabs with a roll diameter of 800–1400 mm - designed for rolling ingots into large billets (blooms and slabs), which are fed as semi-finished products for subsequent rolling into smaller billets or to obtain a finished product. Billet mills with a roll diameter of 450–750 mm are designed for rolling blooms into billets of smaller sizes (from 50 50 mm to 150 150 mm), which are the starting material for further rolling on section mills.

To the second type of mills include:

1. rail and beam with rolls with a diameter of 750 - 900 mm for rolling

railway rails, I-beams, channels, angles

large sizes;

2. large sections with rolls 500–750 mm in diameter for rolling large sections steel (square and round from 80 to 150 mm), beams and channels 120–140 mm;

3. medium sections with rolls 350–500 mm in diameter for rolling medium section steel (square and round 40–80 mm), beams and channels up to 120 mm high;

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

5. wire mills with rolls 250–300 mm in diameter for rolling wire (wire rod) 5–9 mm in diameter;

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. thick plate mills for rolling sheets 4–60 mm thick;

8. thin sheets of hot and cold rolling for sheets 0.2–4 mm thick and 500–2500 mm wide;

9. universal mills for rolling universal strips 200–1500 mm wide;

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

11. special purpose mills - wheel and bandage 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 finishing stand rolls. For example, a wire mill of 250 means that the diameter of the work or pinion rolls of the finishing stand is 250 mm.

According to the number and location 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 (irreversible) and variable (reversible). In the latter case, the rolls periodically change the direction of rotation and the ingot or strip passes back and forth between the rolls several times; both rolls are usually driven. Reversible duo-mills have become more widespread: blooming, slabing, thick-plate, 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 oscillating tables) it rises to the level of the middle and upper rolls and, during the reverse course, is rolled between the middle and upper rolls. Sectional metal and sheets are rolled on trio-mills. Sheet trio mills have an average non-drive roll of a slightly smaller diameter than the upper and lower ones, and on high-quality 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 support rolls. The back-up rolls take up the rolling pressure and reduce the deflection of the work rolls. Quarto mills are reversible and non-reversible. They are designed for rolling sheets and strips.

multi-roll mills are six-roll, twelve-roll, twenty-roll, etc. These mills have two work rolls of small diameter, and the rest are support rolls. In view of the small deflection of the work rolls, these mills are used for cold rolling of thin strips and narrow strips in rolls.

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

According to the number and location of working stands rolling mills separate on the single-cell and multi-cell. The simplest type is a single-stand mill. These include blooming, slabing, thick plate duo- and trio-mills, universal mills.

Multi-stand mills have two or more working stands. The location of the cages 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 beam mills and heavy-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 - in each stand there is one pass. The stands are arranged sequentially one after the other so that the strip is simultaneously located 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 revolutions of the rolls with an individual drive of the rolls of each working stand, or by changing the gear ratio and the number of revolutions of the rolls and the diameter of the working rolls with a group drive.

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

Rolling mills are classified according to purpose, design, relative position of the main elements and other features.

The predominant classification of mills is by purpose, depending on the type of rolling profiles. These are swaging, billet, rail-and-beam, large-section, medium-section, small-section, pipe-rolling mills, cold rolling mills, bandage and wheel rolling mills and special-purpose mills.

The main value that determines the standard size of a section rolling mill is the diameter of the roll, and that of a sheet mill is the length of the roll barrel, the size of which determines the possible width of the rolled sheets. So, for a section mill 300, the diameter of the rolls is 300 mm, and for a sheet mill 2000, the length of the roll barrel is 2000 mm.

Two-roll non-reversible stands (duo) (Fig. 14.1.2, a) are widely used in continuous mills for rolling billets, wire, profiles and thin strips. In each stand of such mills, only one passage of metal in one direction is carried out. In two-roll reversible stands, the direction of rotation of the rolls periodically changes, and the rolled metal passes through the rolls back and forth several times. These stands are used in blooming, slabbing, plate mills, etc.

Rice. 14.1.2. Options for the arrangement of rolls in the working stand

Three-roll (trio) stands - always non-reversible, are used in sectional and sheet - Lauta trio - mills, which differ from sectional mills by a smaller diameter of the middle non-driven roll compared to the upper and lower ones. The metal in the trio mills moves in one direction between the lower and middle rolls, and in the opposite direction - between the middle and upper rolls.

Four-roll stands (quarto) (Fig. 14.1.2, b) are very widely used when rolling thick and thin strips, armor plates.

Six-roll stands are used for cold rolling of thin and narrow strips in coils with tight thickness tolerances.

Twelve- and twenty-roll stands (Fig. 14.1.2, c) have two work rolls, the rest are support rolls and are used for rolling thin and thin strips and tapes, especially from hard-to-deform metals.

Universal mills, in addition to horizontal rolls, also have vertical ones located on one or both sides of the horizontal rolls (Fig. 14.1.2, d).

The scheme of the rolling mill is shown in fig. 14.1.3, city

Rolling tools are rolls, which, depending on the rolled profile, can be smooth (Fig. 14.1.3, a), used for rolling sheets, strips, etc.; stepped, for example, for rolling strip steel and stream (Fig. 14.1.3, b) for producing long products. A stream is called a cutout on the side surface of a roll, and the combination of two streams of a pair of rolls forms caliber. Calibers distinguish between open and closed (Fig. 14.1.3, c). For open calibers, the parting line of the rolls is within the caliber, and for closed calibers, it is outside its limits. On each pair of grooved rolls, several calibers are usually placed.

The rolls consist of a barrel 1 (working part of the roll), necks 2 (trunnions) and clubs 3. The necks of the rolls rotate in bearings installed in the beds. The frame has pressure mechanisms for changing the distance between the rolls and regulating the relative position of their axes. A set of rolling rolls with beds is called working stand 4. Torque from electric motor 8 through the reduction gear 7 is transmitted to the gear cage 6 , from the gears of which with the help of spindles 5 and couplings rotation is transmitted to the rolls. Due to the presence of a gear stand, all rolls of the working stand are leading.