SU1382510A1 - Method of rolling round bar shapes and rods - Google Patents

Abstract

The invention relates to ferrous metallurgy, in particular to methods for the production of round rolled products and wire rod, and can be used on continuous small-section and wire mills. The purpose of the invention is to improve the accuracy of the geometrical dimensions of finished rolled products along its length and to increase the yield. A round bar at a portion of its rear end regulated by the length in the penultimate stand of the continuous mill is subjected to an additional reduction in length as compared with the compression to the rest of its length. After turning the roll on 90 ° before the last stand, the rear end has, as a result, a reduced njnpn-well, which makes it possible to compensate for the increased broadening of the rear end in the last stand and thereby reduce the width along the finished rolled products. (ABOUT

Description

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The invention relates to ferrous metallurgy, in particular to methods for the production of round rolled products and wire rod, and can be used on continuous small-section and wire mills.

The invention is an improvement in the geometrical dimensions of the rolled steel along its length and an increase in the output of one.

From the theory of rolling, the practice of exploitation of continuous small-section and wire) mills and the study of the accuracy of the size of rolled products, it follows that at a certain length of the rear end (the profile of the nirin goes beyond the positive tolerance of the standard. Moreover, the profile increases gradually from some constant level (with a slight variation), corresponding to the middle of the rolled metal, up to a maximum value corresponding to the width in the cross section of the rear end portion of the strip.

D. h of elimination (reduction) of the specified raspochirinpost of rolled products along the length, namely, to reduce the width of its rear end section, in accordance with the predetermined step.

The main part of the strip is rolled at constant inter-blade gaps in all the cells of the mill, i.e. The compression in each of the cranes is 1. The value is constant. When approaching the penultimate stand of the camp of the rear end portion of the strip (it was 1 ~ 1.0–7, the total length of the strip), along the entire length of which 1 O (on the finished file) H1irin differs significantly from the Piryrin middle part (or a special device) gradually decreases the interlayer gap to a value that provides an increase in the reduction rate to 5–8% of the reduction ratio in the middle part of the roll, i.e. in the process of rolling the end section of the strip constituting 1.0 to 7.5% of its length, the reduction rate in the penultimate stand increases to the indicated values, with the maximum degree of reduction corresponding to rolling the section of the strip with the greatest width. At the end of the rolling cycle cycle of the p-th strip, the mill roll returns to its original position, i.e. roll gap in the penultimate stand installed-. It is the same. Rolling of the rr-f of the 1st and the near-rolled bands is carried out analogously.

Improving the accuracy of the geometrical parameters of finished rolled products along its length and increasing the yield is ensured by the fact that when the proposed method is implemented, the reduction of the rear end portion of the strip in the penultimate mill stand, i.e. the width of finished rolled products is directly regulated, since in the last stand the reduction of the strip is carried out

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are in a direction perpendicular to the reduction in the pre-finishing stand (after turning).

On continuous, small-section and wire mills, the vertical diameter along the length of the strip varies slightly and completely fits into existing standards. This is due to the rather high rigidity of the stands and, above all, the finishing stand of the mill. Horizontal diameter

The finished profile due to a change in the width and width of the strip at the entrance to the finishing stand changes significantly and at a certain length the center of the rear end goes beyond the positive tolerance set by the standard. Overflowing rear ends are a marriage. The length of the overflowing rear end, depending on the distance between the cells, the size of the initial section and the length of the profile, the number of rolled threads and other factors, is different for different mills and amounts to 10-40 meters or 1.0- research data. 7.5% of the total rolling length of my strip. Therefore, an increase in the degree of reduction in the prestress stand at the length of the rear end, less than 1.0% of its total length, does not completely eliminate the razorshirnost rear end and reduces the yield of fit. Increasing the degree of reduction in the pre-cutting stand at the rear end, greater than 7.5% of the strip length, reduces the width of the finished profile on the middle part of the strip, which reduces the accuracy of the rolled metal. With an increase in the mass of the workpiece and a decrease in the diameter of the finished profile, this value decreases as the total length of the rolled product increases.

The increase in the degree of reduction in the prestressing stand with the passage of the rear end of the strip, as well as in determining the length of the additionally crimped rear end, depends on the number of rolled threads, the presence of loop guides, a calibration system, etc. The greatest raznosherinnost finished profile occurs when rolling in four strands on four-strand wire mills, not equipped with loopers in the finishing grooves of the stands, and the smallest raznorashirinnost finished profile - when rolling in one strand on single-strand and two-strand mills, equipped in finishing groups loop regulators or blocks of finishing stands.

Thus, if, when rolling in a single strand on a single-strand mill with loopers, increase the reduction rate in the final stand by less than 5% of the reduction ratio of the middle part of the strip, then the diversity of the width of the strip is not completely eliminated. If, when rolling on a four-thread mill not equipped with loop guides, to increase the reduction rate by more than 8% of the reduction ratio of the middle part, the width of the rear end is less than

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the middle part of the strip, i.e. the bandwidth is maintained. An increase in the degree of compression of the rear end of the rollout less than qm by 5% of the degree of compression of its middle part saves the wider rear end of the profile, and an increase in the degree of compression by more than 8% reduces the width of the rear end, which becomes less than the width of the middle parts, which reduces the accuracy of rolled products.

The ranges of change in the degree of reduction of the rear end of the strip in the pre-finishing stand and the length of the rear end, which requires a reduction in the clearance in the pre-finishing stand, are determined on the basis of a large amount of statistical studies of the accuracy of round steel produced at various continuous domestic mills.

The proposed method is tested on a continuous wire mill 250, the pre-stand of which is equipped with a control system for the cage push mechanism. The horizontal diameter at the rear ends significantly exceeds the corresponding diameter in the middle part of the strip and at a certain length exceeds the limits of the band tolerance specified in the relevant standards. The length of the rear ends that go beyond the tolerance limit when rolling a rod 8 mm in diameter from a billet with dimensions of 80 x 80 mm and weighing 500 kg is 18-22 m or 1.2-1.5% of the total length of the riot. To eliminate the misalignment of the rear end at a specified length in the mill's pre-cutting stand, the roll gap is smoothly reduced by 0.3 mm using the control device of the pressing device, which is 6.2% of the reduction rate of the middle part of the strip.

This ensures a decrease in the maximum mismatch along the length of the strip by 0.5-0.8 mm and a decrease in the spread of the horizontal diameter by 2.5-3.5 times.

which increases the yield of rolled products by 1.0-1.5%. For the implementation of the proposed method under the conditions of other mills, the length of the rear end of the strip having a greater width than its middle part and the variation of the width along the length of the rear end are determined experimentally using statistical methods. On the basis of the data obtained, the magnitude of the reduction in the roll gap in the pre-finishing stand and the length of the rear end, by which the gap should be reduced, are determined. To regulate the roll gap, it is possible to use the control system of the pressure mechanism of the stand.

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The proposed method improves the accuracy of the geometrical dimensions of finished rolled products along its length and increases the yield, in addition, the mill's productivity and grade of production increase and the scrap is reduced. The greatest effect in the implementation of the proposed method can be obtained on multi-line wire mills that are not equipped with loop guides in the finishing groups of the stands.

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Claims (1)

Invention Formula The method of rolling round varietal profiles and rods, including the deformation of the metal in the cages of continuous rolling mill and change the degree of reduction along the length of the roll, characterized in that, in order to increase the accuracy of the geometric dimensions of finished rolled products along its length and increase the yield of the suitable one, in the final finishing stand the deformation of the rear end of the roll a length of 1.0 to 7.5% of its total length is carried out with a gradual increase in the degree of reduction by up to 5-8% of the degree of reduction in the middle part of the roll.