SU1585029A1 - Method of cold rolling of strips - Google Patents

Abstract

The invention relates to rolling production and can be used to obtain stiff on cold rolling mills. The purpose of the invention is to increase the yield of rolled metal by reducing the cracking of the edges of rolled strips during multi-pass rolling in the cages of a continuous mill. The method of cold rolling the strips involves the deformation of the workpiece in the rolls in several passes with a regulated ratio of the rolling forces between the stands of the continuous mill, which begin to change when D / H cf ≥1000, where D is the diameter of the rolls

H cf - the average thickness of the rolled strip, setting in each subsequent pass the rolling force is 1.05-1.25 times greater than the previous one. The method can be carried out on continuous cold rolling mills with four-roll sets of rolls. When rolling a sheet with a thickness of 0.40 mm, the yield is 99.5-99.8%. 1 tab.

Description

The invention relates to rolling production and can be used in the production of tin on cold rolling mills.

The purpose of the invention is to increase the yield of rolled metal by reducing the cracking of the edges of rolled strips during multi-pass rolling in the cages of a continuous mill.

During cold rolling, in particular of tin plate, the final thickness is 0.36-0.18 mm, in the line of modern mills with large diameter rolls, when the ratio is D / HCp (D is the roll diameter of thin rolls; H

the average strip thickness at the deformation zone becomes equal to or greater than 1000 to obtain the required thickness of the work rolls in the prestressed state along the barrels of the lower and upper rolls (bottom position), i.e. the amount of elastic flattening of the wapes is commensurate with the thickness of the strip. This leads to a thinning of the edges of the rolled strips, with a gradual delamination of the strips in the cells during rolling, the thinner edges are not compressed, cracks and fractures appear in them.

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due to uneven stretching across the width of the strips.

According to the proposed method, the ratio of rolling forces in adjacent passages is regulated so that in each subsequent pass the rolling force is set to 1.05-1.25 times greater than the previous one and this condition is maintained starting from the achievement of strip thickness at which D / Hcp YuOO.

Cold rolling a steel strip in several passes is accompanied by elastic flattening of the work rolls, the profiling of which is optimized by the criterion of flatness. In the case when the strip has a relatively large thickness of P / Hcr 1000, the elastic deformation of the rolls, as shown by experiments, affects the shape of the edges of the strip slightly and the thickness and flatness of the strip can be effectively controlled without taking into account the ratio of the rolling forces in adjacent aisles. But as soon as the value of the ratio D / HC approaches 1000 and the end sections of the rolls come into contact with each other and are elastically flattened, the effectiveness of the adjustment

NIA THICKNESS AND PLANE BAND

sharply reduced - the operation of the pressing devices only leads to a change in the magnitude of the elastic deformation of the roller system and does not affect the shape of the roll gap. This rolling mode is close to the rolling out limit and is characterized by an increase in edge thinning due to the broadening of the edge sections, which is accompanied by an increase in their strength, a decrease in the plasticity resource of the metal at the edges. When entering the next stand, the amount of stretching at the edges is less than in the middle part of the strip, which causes longitudinal tensile stresses in the edges, which cause them to crack.

In the case when D / Hcp 100Q, there is no thinning of the edges and their cracking, therefore there is no need to regulate the ratio of the rolling forces in adjacent aisles. If, at D / Hq ,, 100, the force in the subsequent stand exceeds the force of the previous one 1.05-1.25 times, as a result of the elastic flattening of the work rolls of the next stand, a roll gap will be formed,

uniform value of stretch, thinned edges and middle part of the strip. As a result, the longitudinal tensile stresses at the edges, leading to their cracking, will be eliminated.

It was established experimentally that if the ratio of the rolling force in the next cage to the force in the previous cage is less than 1.05, then this leads to a further broadening and edge thinning and the formation of cracks in them. In addition, with almost identical rolling forces in adjacent passages, the deformation of the metal after the second pass is insignificant. This requires an increase in the number of passes, which is irrational. With an increase in this ratio of more than 1.25, the nonuniformity of stretching of the edges and the middle part of the strip in the subsequent passage leads to an increase in tensile stresses along the edges, which cause the formation of cracks and fractures.

The optimal range of the rolling force ratio of 1.05-1.25 is determined experimentally for the cases of rolling tin with a final thickness of 0.36-0.18 mm from low carbon steels 08 kp, 08 ps, 10 ps, 08 o in work rolls with a diameter of 300-600 mm. Under these conditions, rolling of the strips was ensured without cracking the edges. Outside of the optimal range of the ratio of rolling forces behind the subsequent stand, the strip had a defect, a ripped edge, breaks in the bands “

Example. The method is carried out on a six-stand cold rolling mill 1400. A hot-rolled pickled strip of 08kp steel 2.4 mm thick is set into rolls of a 6-cell continuous cold rolling mill for tin with working rolls with a diameter of 600 mm. In the first four cells, the strip is compressed to a thickness of 0.70 mm. The absolute compression in the 5th stand is set to 0.20 mm, which corresponds to H cf 0.6. In this case, the ratio D / HCp 1000. The rolling force in the 5th stand is established by means of hydraulic cylinders of the pressing mechanism, equal to 9520 kN. The edges of the work rolls of the 5th stand are in contact (in the face). In the 6th stand, the absolute reduction is set to 0.17 mm. PL of this stand D / Hcp 1395. Rolling force

in the 6th stand with the help of the hydraulic clamping mechanism, it is set 1.15 times larger than in the 5th stand, i.e. equal to 10948 kN, and the whole strip is rolled to a final thickness of 0.36 mm without cracking the edges.

The table shows examples of the implementation of the proposed method within and outside the proposed range of the ratio of rolling forces in the finishing and finishing passes, as well as the prototype method.

As follows from the table, when implementing the proposed method, it is possible to reduce edge cracking when rolling tin from 0.36 (options 2-4) to 0.18 mm (options 7-9), when the D / HCp value is 1000. For exorbitant values ratios of stresses in adjacent aisles (variants 1, 5, 6, and 10) of the edges of the strips are affected by cracks that cause gusts, the rolling process is unstable. In the case of the implementation of the prototype method with a ratio of efforts in cages x 6 and 5 equal to two, cracks along the edges and strip breaks are also formed, as a result of which the rolling process is unstable. The implementation of the prototype method with an effort ratio of more than 2.4 turned out to be impossible due to the overload of the 6th stand of the mill.

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Increasing the yield (options 2-4) to 99.5-99.82 is caused by aligning the stretch across the width of the strips — the edges get the same stretch as the middle part of the strip, as a result the tendency of the stripe to gusts is reduced.

With extreme values of the regulated parameter in connection with the cracking of the edges of the bands, the yield decreased to 91 -, 5-92.3% (options 1, 5, 6, 10), and according to the prototype method it was 19.1%.

Invention formula

The method of cold rolling of strips, including the deformation of rolls between the rollers with a regulated ratio of rolling forces in adjacent passages, characterized in that, in order to increase the yield of suitable steel by reducing the cracking of the edges of the rolled strips during multipass rolling in continuous mill stands, / Hcp 1000, where D is the diameter of the rolls, and H SL is the average thickness of the rolled strip, the rolling force in each subsequent pass is set more than the previous one, 1.05-1.25 times.

Claims (1)

• 5 F-formula of the invention A method of cold rolling strips, including the deformation of the rolls between the rollers with a regulated ratio of the rolling force in adjacent passages, characterized in that, in order to increase the yield of rolled products by reducing cracking of the edges of the rolled strips during multi-pass rolling in the stands of a continuous mill, when the ratio D / H _t p? 1000, where D is the diameter of the rolls, and H _with p is the average thickness of the rolled strip, the rolling force in each subsequent pass is set to 1.05-1.25 times more than in the previous one. Option, £ Strip thickness before the 5th stand, mm The average thickness of the strip in the 5th maple _Wed , MM P The rolling force in the 5th stand, P _£ , kN The average crowd t strip D 6 ~ th stand, MM R The rolling force in 6-L glue is ty, Ρς, kV P * p; Strip quality and processability indicators one 0.70 0.60 1000 .9520 0.55 1090 9900 1,04 Cracks to the edges, gusts 2 0.70 0.60 1000 9520 0.46 1304 10,000 1.05 stripes Tropin to gusts of years 3 0, 70 0.60 1000 9520 0.43 1395 10948 1.15 No tears, no gusts four 0, 70 . 0.60 1000 9620 0.40 ' 1500 11900 1.25 No cracks 5 0.70 0.60 1000 9520 0.40 • 1,500 12090. 1.27 Edge cracks, gusts 6 0.52 0.42 1428 10130 0.25 24 00 10535 1, 04 STRIPES Edge cracks, gusts 7 0.52 0.42 1428 10130 0.25 2400 10637 1.05 stripes No cracks or gusts 8 0.52 0.42 1428 10130 0.24 2500 11650. 1.15 No cracks 9 0.52 0.42 1428 10130 0.23 2 609 12662 1.25 No cracks 10 0.52 0.42 1428 10130 0.23 2609 12764 1.26 Edge Cracks »Gusts 11 (prototype) 0.70 0.60 1000 9520 0.38 1579 19040 2.0 stripes Cracks, gusts, rolling