SU1503902A1 - Method of reversable rolling of low-ductility steels and alloys ingots - Google Patents

Abstract

FIELD OF THE INVENTION The invention relates to rolling production, in particular, to the production of low-plastic steels and alloys in reverse mills. The purpose of the invention is to improve the quality of rolled products by leveling the plasticity resource along the length of the roll. The ingots are rolled in each aisle, except the last, with a reduction that decreases in the direction opposite to the direction of movement of the ingot. The amount of reduction is 25-100%. According to the length of the roll, the reduction is changed according to the exponential law. 3 dw., 2 tabl.

Description

FIELD OF THE INVENTION The invention relates to rolling production, in particular, to the production of low-plastic steels and alloys in reverse mills.

The aim of the invention is to improve the quality of rolled metal by leveling the plasticity resource along the length of the roll.

FIG. 1 shows an ingot before and after the first pass; in fig. 2 - peal before and after the second pass; in fig. 3 - roll before and after the last pass.

The method is carried out as follows.

. The heated ingot 1 of low-ductile steel is fed to the rolls 2 of the reversing stand, between which a gap 3 is installed, which constitutes the minimum value for this passage. When rolling, the gap between the rolls is continuously increased (i.e., the reduction is reduced), bringing it up to the maximum value of the gap 4 used in this passage. As a result, after the first pass, roll 5 is obtained, in which the end nearest to the rolls is deformed no less than 25% less than the one farthest from the rolls. After that, the gap between the rolls is reduced to the minimum value (gap 6) corresponding to the second pass, and roll 7 is rolled in the second pass, again gradually increasing the solution of the rolls 8 and receiving roll 9, in which the end nearest to the rolls is deformed by no less than 25% less than the farthest from the rolls. Similarly, rolling is carried out in all passes, except the last, where the wedge-shaped 11th roll

:

Yu

. 150

10 gyr rolls in rollers with a constant gap 11, to obtain finished rolled products with a constant cross section 12.

According to the proposed method, the amount of reduction during a single pass is determined experimentally and is 25% in the event that the ratio of the height of the roll H to the diameter of the rolls D is greater than or equal to 0.65, the time of one pass is less than or equal to 2.0 s. As the strip height decreases and the rolling time increases in a single pass, a decrease in the reduction in one pass increases and can reach 100% if the tail part of the roll is not crimped.

The use of reductions in each pass, which decrease in the direction opposite to the direction of movement of the roll, results in areas of kata 5 having a large formation gap during the rolling reversibility, being subjected to a larger work hardening, as a result of which the rolling length is constant throughout the rolling cycle. use of plasticity and, consequently, the possibility of defect-free deformation.

The degree of weakening depends on the pause time according to the exponential law; therefore, along the length of the roll in each pass, the reduction should be changed also according to the exponential law.

Example. On the blooming 950 of ingots 590 590 2000 steel 12Х18Н10Т organize the production of blooms 300x300. Rolling is carried out in three ways: conventional reversing rolling without changing the reduction during the passage, according to the prototype, increasing the reduction during the passage, according to the proposed method, reducing the compression during the passage.

Only ingots from surface defects come into rolling. After rolling, the defects formed during rolling are removed from the surface of the blooms and the area affected by the surface of the blooms (%) corresponding to each of the three methods is determined; sobs rolling.

In the case of conventional reversing rolling, flaws and cracks are struck on average 20% of the surface area of blooms; when rolling bp proto

0

five

0

five

0

five

0

five

0

five

type - 30%; when using the proposed method - 2%.

In tab. 1 shows the current sizes of roll, on the base mode of reductions.

Geometric factors of the deformation zone for this mode

zhatiy: - (the ratio of the height of the roll

the diameter of the wapcocks) and (relative reduction) vary in the intervals of 0.64-0.36 and 23, respectively, A-7.3% (Table 1, columns 5 and 6). An analysis of the length of interdeformational pauses shows that for the middle of the roll, their length increases almost monotonically from passage to passage. Some deviation from the monotonous increase of the pauses after the 2nd and 6th passes is explained by the need to make canals of the bar (Table 1, column 8). In contrast to pauses for the middle of a roll, the length of interdeformation pauses for the ends of a roll is substantially uneven and ranges from 0.5 to 4-5 s already in the first passes, and by the end of the reduction mode the difference in the duration of adjacent interdeformation pauses is 9 s. (Table 1, columns 7 and 9). This leads to the fact that with constant roll breakdowns, the accumulation of the degree of utilization of the plasticity of the metal on the lateral faces of the roll for the front and rear ends of the roll is different in a number of passes by 40% or more (Table 1, columns 11 and 13) . At the same time, the maximum value of the degree of utilization of plasticity for the middle of a roll is 0.36 (Table 1, column 12), significantly less than the maximum values of the degree of use of the plasticity margin of metal volumes located at the ends of the roll. The rolling force along the aisles does not exceed the allowable (Table 1, column 10) and varies along the aisles quite smoothly. The availability of reserves for rolling forces for the considered reduction mode is explained by the fact that during rolling special low-ductile steels and alloys, the amount of reductions is limited not by the conditions of ensuring the strength of the mill equipment, but by preventing

exhaustion of stock plasticity of the metal.

aisle At the same time, the degree of utilization of the plasticity of the metal for the ends of the roll is almost the same as the values of this indicator for the middle of the roll (Table 1, column 12). The use presented in the table. 2 compression modes significantly reduce the time of passage S (Table 1, column-10 of the surface area of the breakages, crumbs 5 and 8) were determined by the required flaws. In the considered value of the change in crimping along the length of the case, the flaws affected only the roll (Table 2, column 2). With 2% bloom surface area. Thus, if the magnitude of the change is magnifiable, the use of the predicted tee exceeded the absolute compression of the method 15 allows for a significantly higher table. 2 presents data compression mode.

For the implementation of the rolling method

H by known values - and average

kata passage, this change was assumed to be 100%, which meant the lack of compression of the rear end for the pact of the passage under consideration. Next, the relative change in roll reduction along the length of the stock (Table 2, column 5) was determined, which was 25–100% for different passes. As a result of the adjustment of reductions, the current size of the roll through the aisles when using the exponential reduction of reductions in the direction opposite to the direction of movement of the roll, looked like it is presented in columns 5-8 of the table. 2. This mode of crimping allows for equalization of the values of the degree of utilization of the metal ductility stock for the various zones of roll in each

20

to increase the quality of products when rolling steels and alloys.

Claims (1)

Invention Formula A method of reverse rolling ingots from mapoplastic steels and alloys, including rolling a roll in several passes with a change in the amount of reduction during the passage, characterized in that, in order to improve the quality of rolling by leveling the ductility resource along the length of the roll, during rolling 30 in each pass, the reduction is reduced along the length of the roll by the exponential law by 25-100% of the amount of reduction at the moment of the metal being caught by the rollers.  The maximum possible reduction rate is 100%. Phi1.1 Editor T. Parfenova Compiled by V. Vkselman Tehred M. Morgental Proofreader N. Borisova Order 5181/11 Circulation 459 VNIIPI State Committee for Inventions and Discoveries at the State Committee on Science and Technology of the USSR 113035, Moscow, Zh-35, Raushsk nab. 4/5 fng. Z Subscription