SU1072931A1 - Method of hot rolling of strip steel - Google Patents

Abstract

1. A method of hot strip rolling, including pushing the strip between the passages, characterized in that, in order to increase the physicomechanical properties of the metal by intensifying the development of the central layers of the roll, it is pressed to a depth of 15-20% of the thickness of the strip in areas oriented along the rolling direction, alternating them with zones cold metal. (L y oo

Description

2. A method according to claim 1, characterized in that only the upper surface of the roll is pressed.

3. A method according to claim 1, characterized in that both surfaces of the roll are pressed, displacing the areas of the pressing of the upper surface relative to the areas of the pressing of the lower surface by an amount equal to half the distance between the axes of the pressing areas.

4. A method according to claim 1, characterized in that prior to each subsequent passage, the quenching zones are shifted relative to their position in front of the previous gauge by a high degree equal to half the distance between the axes of the quench zones.

5. A method according to claim 1, characterized in that in the roughing passages, rolling is carried out in rolls provided with annular protrusions, while having protrusions against the oppression zones.

one

The invention relates to the production of thick hot-rolled strips, mainly from continuously cast slabs in ferrous metallurgy, and can also be used in non-ferrous metallurgy.

In the production of thick hot-rolled strips, especially from continuous cast slabs, the urgent issue is intensive study of the deformation of the central layers of the sheet for destruction of the cast structure with liquidation sites having a high concentration of non-metallic inclusions. Due to this intensive study of the central layers of the roll increases the physicomechanical properties of the metal, especially strength and viscosity characteristics.

There is a known method of rolling rolling, in which intensive study of the central layers of the roll is achieved by variable compression across the width of the strip with rolls with a wavy profile followed by compression of the strip in smooth rolls 1.

The disadvantage of this method is the complexity of its implementation, especially in quarto cells, limiting the effect of metal processing by the possibility of installing a sufficient number of wafers with a wavy profile in alternation with the rollers with a smooth roll barrel.

There is a known rolling method with a strip between the passes, which is used to press the strip between the passages in order to obtain an increased level of mechanical properties. At the same time, due to a decrease in the plasticity of the surface layers of the metal, its central layers 2 are more intensively deformed.

However, such deformation is not effective enough to completely destroy the cast structure and eliminate segregation zones.

The purpose of the invention is to increase the physicomechanical properties of the metal by intensifying the study of the central layers of the roll.

This goal is achieved by the fact that, according to the method of hot rolling of strip steel, which includes podzhuzhivaniya roll between the aisles, podstuzhivanie produce to a depth of 15-20% of the thickness of the coil in areas oriented along the direction of rolling, alternating them with areas of non-povdelennogo metal-.

In this case, only the upper one is forced. surface roll.

Both surfaces of the roll are also reinforced, displacing the areas of the upper surface's cooling against the lower surface's areas of cooling by an amount. equal to half the distance between the OSs. 5 zones of imitation. In addition, before each subsequent passage, the pressure zones are shifted relative to their position before the previous passage by an amount equal to half the distance between the axes of the pressure zones.

In addition, in the roughing passages, rolling is carried out in rolls provided with annular protrusions, with protrusions against the quenching zones.

5 In FIG. 1 shows a diagram of the implementation of the method on the example of one of the passes; in fig. 2-5 illustrates the implementation of the method by the example of two passes and pressing in zones located along the rolling direction, the upper and lower surfaces.

0 metal; in fig. 6-9 - the same, using the example of pushing in zones only on the upper surface of the metal; in fig. 10 and 11 illustrate the implementation of the method using rolls with annular projections; in fig. 12 - podstuzhivaniya top surface of the roll, made in the form of point zones.

Moreover, in FIG. 2, 4, b, 8 and 10 cross-section shown at the time of entry into the deformation zone; in fig. 3, 5, 7, 9 and 11 - at the time of exit from the deformation zone.

The upper roller 1 and the lower roller 2 (Figs. 1, 3, 5, 7, 9 and 11) carry out the hot deformation of the metal 3. At the entrance to the deformation center in the immediate vicinity of it, a hot metal 4 is supplied to the hot metal (water or water emulsion). Cooler 4 is fed through zones located along the width of the stock at a distance S between the axes of the zones along the rolling direction. As a result, local reinforcement of sections 5 of the metal section to a depth (Go, the value of which is set in advance and ensured by the appropriate cooling intensity and its duration (selection, length t (Fig. 1)) is carried out.

The supply of the cooler to the metal is stopped immediately before entering the deformation zone, and the metal is deformed immediately, including calibrated rollers with annular projections 6 (Fig. 11).

The method of hot strip rolling of steel is mainly intended for use in the production of strip with a width of 5 mm thick on wide-strip and plate mills. At the same time, if the thickness of the initial preform HO is significant, for better development of the central metal layers, the thickening is performed from the upper and lower sides of the metal as shown in FIG. 2-5. In case of failure of such a design, calibrated rolls are used, as shown in FIG. 10 and 11. Otherwise, only one of the surfaces is pressed, for example, as shown in FIG. 6-9. In rare cases, according to the conditions of cracking in the cast metal or the low heat content of the original billet, it is realized in the dotted zones (Fig. 12, on thick plates, mills).

When implementing the method on a wide-strip hot rolling mill, at least in front of one of the roughing stands (more often the first), mainly in front of two roughing stands, and for the most part, in front of all the roughing stands, devices are installed to supply a cooler to the metal surface. As shown in FIG. 2–5 and 6–9, before each subsequent deformation, the axes of the suppression zones are shifted by about S / 2 (where S is the distance between the axes of the suppression zones) in the direction perpendicular to the rolling axis. The zones of pressing of the upper and lower surfaces of the metal are also offset relative to each other by approximately the value of S / 2 (Figs. 2, 4, 10). Under the constricted zones of the metal, the contact with the rollers, gives less heat to the rollers compared to the non-stressed zones, deforms and, accordingly, decreases in height. Ultimately, by the time the metal leaves the deformation zone, the difference in temperature between the tight and non-stressed areas

metal is significantly reduced, although it does occur.

As the metal passes through the previous and subsequent deformation sites, the difference in temperature between the stressed and unsupported zones is even more leveled due to the influx of heat from the central hot metal layers. However, the difference in temperature of the metal in the zones is completely

0 is not aligned, and from the point of view of better development of the central metal layers, it is necessary to change the areas of the cooling. Therefore, when implementing the method, the marked displacement of the pressure zones before each subsequent deformation is useful and necessary.

When implementing the method on a hot rolling plate mill, the device for pressing the metal surface is installed on both sides of the deformation zone so that (by analogy with the implementation already considered in Fig. 2 and 4, 6 and 8 on the broadband mill) the centers of the thickening zones with one and The other sides of the deformation zone are displaced relative to each other by a magnitude approximately equal to S / 2.

The device for boosting the rollout by zones, which implements the method, is made with regulation of the distance from the exit section of the cooler from the collector to the cooled surface. It is necessary for

0 passes the front end of the roll and the subsequent approach of the exit section of the cooler from the collector closer to the hot roll: over a distance of 100-150 mm. The latter, in turn, is necessary in order to maximally localize the zones of the collar and reduce the propagation of the collar to nearby metal areas.

Also, in all cases, the device for metal pressing in zones, realizing

0 method provides the supply of the cooler right up to the very entrance of the metal to the deformation zone (Fig. 1). The latter is also necessary in order to maximize localization of the areas of pressure and reduce the extent of pressure to nearby areas.

5 areas of metal.

When implementing the method, the depth of pressing is cg / is prescribed on the basis of the appropriate thickness of the rolled metal (6o f (Ho), G f (H,) (Figs. 2, 6 and 10 Figs. 4 and 8, respectively), increasing it

0 with an increase in Hi, but in any case do not exceed 15–20 ° / o thickness, since otherwise there will be a significant decrease in the temperature of the metal. This also limits the use of the method.

5 mainly in the production of strips with a thickness greater than 5 mm, during the rolling of which there is almost always an excess supply of heat in the initial billet.

Moreover, if, under rolling conditions, local cooling to a depth of 15–20% of thickness is undesirable, but at the same time required for better development of the central metal layers, a smaller depth of compression is established, and its efficiency is enhanced by using calibrated rolling rolls, combining the zone of reinforcement with the protrusions 6 of the roll (Fig. 11). In this case, on the next pass, calibrated rolls can also be applied according to the same principle, or rolls with a smooth barrel can be used. The latter is more preferable.

Otherwise, the process of hot strip rolling is carried out according to generally accepted modes.

The hot strip rolling method is carried out as follows.

A hot rectangular billet with a thickness of HD, obtained mainly by continuous casting, is fed first to roughing and then to finish rolling until the finished hot rolled strip is obtained. The workpiece, for example, has a temperature of 1200 ° C with a uniform distribution over the width and thickness. Immediately before entering the deformation zone of the first working stand, starting from the distance i from it (Fig. 1), to the workpiece (on the upper surface of the workpiece (Fig. 6) or on the top and bottom (Fig. 1, 2 and 6) ) from a height of 100–150 mm, from nozzles with a diameter of 5–8 mm installed in a row in the rolling direction, water is supplied or (even better), a mixture of water and air with a ratio of 0.04 mjcjx. / maojk 0.135. At the same time, a greater mass ratio of mgoj./mv. Corresponds to a greater intensity of cooling. As the workpiece moves into the cage at a speed of V, the metal surface and its subsurface layers are locally thickened to achieve the greatest depth of thinning (Tj by the time the metal enters the deformation zone.

The width of the workpiece is used by several rows of nozzles installed in this way along the rolling direction. Distance

5 between the rows, the nozzles are different depending on the rolling conditions, but B mainly takes S 75 mm, since at smaller values it is more difficult to locate the cooling.

The duration of the cooling is depending on the depth of the cold and the tT at the entrance to the deformation center, but generally T 2-3 sec, since otherwise it is more difficult to ensure the localization of the compression.

In the end, before entering the deformation zone in the section of the workpiece, we have compressed local areas (in Figs. 1, 2,

6 and 10 are darkened) with a surface temperature of 500-600 ° C, at a depth of 2.5-3.0 mm at a level of 700-800 ° C, at a depth of 5.0-6.0 mm at a level of 800-900 ° C, etc., with an increase to the level of 1200 ° C at a depth (J, .. equal to, for example, 10-15 mm. The metal layers near these areas, along the width and thickness of the workpiece, retain the initial temperature of 1200 ° C. With this temperature distribution section of the workpiece is in the deformation zone (Fig. 2, 6 and 10).

Undercut areas of the workpiece

Since the resistance of deformation in the deformation zone is significantly greater than the main metal mass, they actually begin to play the role of protrusions of calibrated rolls and are embedded in the main metal mass, intensively destroying its cast structure. An intensification on both surfaces (Figs. 1, 2, and 6) enhances this effect, all the more due to the displacement of the intensification zones above and below relative to each other by the S / 2 value.

0 The use of calibrated rolls with a groove depth of 6-10 mm (with the corresponding chamfers, eliminating the decline of metal), as shown in FIG. 11, further enhances the effect of the study of the central layers of the metal. However, the use of calibrated rolls is preferable for the initial thickness of the H gauge of 280-305 mm, when the development of the central layers of the roll is effective enough without the use of such rolls requires a significant boost of the roll. At the same time, if there is a two-roll stand on the mill, the use of calibrated rolls for the specified purpose can be justified for thicker slabs.

Example 1. On a plate mill of

240 mm thick continuous slabs produce strips 14 mm thick. Brand steel ZSP. Could be heated in a furnace to a temperature of 1280 ° C. Rough deformation is carried out in seven passes: 240-220-192-170-158-130-100-73 mm, finishing

deformation also in seven passes.

In the process of rough deformation immediately before the deformation zone of the first three passes, on both sides of the metal, the metal is pressed into zones, as shown in FIG. 2-5, to a depth of 10 mm, then the position is turned off. The distance between the pressure zones is set to S 100 mm. Soaking is carried out with an air / water mixture with a ratio of / tvd4 0.135 at a flow rate of 40 (4)

Q The nozzles are set at a distance of 100-130 mm from the surface of the metal. The duration of the cooling is assumed to be 1.5 s. Due to the better elaboration of the cast structure, the physicomechanical characteristics of the finished strips in the cold state increase by an average of 10-20 MPa; t 15-20 MPa; (G by 2-3%, impact strength at t -20 ° С at 3.0 x X 10 J / m.

Claims (5)

1. METHOD FOR HOT ROLLING OF STRIP STEEL, including reinforcing the roll between passes, characterized in that, in order to increase the physicomechanical properties of the metal by intensifying the development of the central layers of the rolling, the reinforcing is carried out to a depth of 15-2 ° / about the thickness of the roll in the zones, oriented along the rolling direction, alternating them with zones of unstressed metal. fiz-1 2. The method according to π. 1, characterized in that they reinforce only the upper surface of the roll. - 3. The method according to π. 1, characterized in that both surfaces of the roll are reinforced, while shifting the zones of reinforcement of the upper surface relative to the zones of reinforcement of the lower surface by an amount equal to half the distance between the axes of the zones of reinforcement. 4. The method according to π. 1, characterized in that before each subsequent passage the zones of reinforcement are displaced relative to their position before the previous passage by an amount equal to half the distance between the axes of the zones of reinforcement. 5. The method according to π. 1, characterized in that in rough passes, rolling is carried out in rolls provided with annular protrusions, while arranging protrusions against zones of undercrusting.