RU2287383C2 - Strip cold rolling process - Google Patents

Abstract

FIELD: plastic working of metals, namely by rolling, possibly for making thin steel sheets.

SUBSTANCE: process for cold rolling of strip comprises steps of successive reduction of strip in stands of continuous rolling mill with tension between stands. According to invention in five-stand rolling mill tension of strip before third stand is set in such a way that it exceeds strip tension after said stand by 1.01 - 1.56 times. Tension of strip before fourth stand exceeds by 1.01 - 1.85 times tension after said stand. Tension after second stand exceeds by 1.01 - 1.04 times tension before said stand.

EFFECT: lowered vibration degree of rolling and backup rolls at rolling process.

1 ex

Description

The invention relates to the processing of metals by pressure, in particular to rolling, and can be used in the rolling of sheet steel.

A known method of cold rolling strips, including sequential compression of the hot-rolled billet in the stands of a continuous mill with tension between the stands (RU 2014916, IPC 21 1/28, publ. 30.06.94,).

A disadvantage of the known solution is the presence of transverse stripes on the surface of the cold-rolled sheet, which reduces the quality of the rental.

The closest is the method of cold rolling strips, including sequential compression of the strip in the stands of a continuous mill with tension between the stands (SU 1044347, IPC B 21 V 1/26, publ. 09/30/83).

A disadvantage of the known technical solution is the presence of transverse stripes on the surface of the cold-rolled sheet, which reduces the quality of the rental.

The objective of the invention is to improve the quality of hire.

The technical result is a reduction in the number of transverse strips on the surface of the cold-rolled metal by reducing the vibration of the backup and work rolls during the rolling process.

The technical result is achieved in that in the method of cold rolling strips, including sequential compression of the strip in the stands of a continuous mill with tension between the stands, characterized in that for a five-stand mill, the strip tension in front of the third stand is assigned 1.01-1.56 times the tension after this stand, and the tension of the strip in front of the fourth stand is assigned 1.01-1.85 times the tension of the strip after this stand. The tension of the strip before and after the second stand is assigned the same, or the tension after the second stand is assigned 1.01-1.40 times more than before this stand.

Recently, high-speed rolling modes lead to more intensive use of equipment. An increase in the rolling speed leads to the manifestation of dynamic effects, in particular to high-frequency oscillations. The consequence of the occurrence of vibrations is a decrease in the rolling speed, as well as a decrease in the quality of the surface of the product due to the appearance of transverse strips (transverse to the rolling direction) on the strip and the strip breaking.

There may be several reasons for the occurrence of vibrations. One of them is the presence of gaps between the pillows of the work rolls and the bed and in the bearings of the pillows of the work rolls. The presence of gaps during rolling leads to a displacement of the work rolls in the direction of rolling. This shift leads to an increase in the gap between the rolls. At the same time, as a result of the contact of the working and backup rolls, a force acts on the working rolls, striving to return them to their original state. The magnitude of these forces depends on the coefficient of friction, which at a certain rolling speed leads to the appearance of longitudinal vibrations, which in turn cause vertical vibrations of the rolls. This process leads to the occurrence of vibration in the cold rolling mill having a self-oscillating character.

Studies have shown that for a five-stand mill, fluctuations are mainly observed in the third and fourth stands, where the strip is already thin and the reductions are still high. It was established that an increase in tension in front of the third stand is 1.01-1.56 times greater than after this stand, and in front of the fourth stand 1.01-1.85 more than after this stand leads to a decrease in the advance zone in the deformation zone , longitudinal vibrations are reduced, which, in turn, leads to a decrease in vertical oscillations in the roll system and a decrease in the number of imprints of the transverse stripes at the rental. A decrease in the ratio of tension before and after the third and fourth stands below the regulated ratio does not lead to a decrease in the number of transverse strips, and an increase can cause a break in the rolled metal. The tension after the second stand is less than 1.01, than in front of this stand does not lead to a decrease in the imprints of the transverse strip at the rental, and the increase in tension after the second stand is more than 1.40 than before this stand leads to the break of the strip.

An example implementation of the method. Continuous rolling of low-carbon steel 08PS with a size of 2.5 × 1200 mm is carried out on a five-stand cold rolling mill with successive compression along the stands up to 0.5 mm. During the rolling process, the following specific tension of the strip in the inter-stand spaces is maintained, kg · s / mm ² :

Crates one - 2 - 3 - four - 5 Specific tension fourteen 16 fourteen 10

Thus, the tension of the strip in front of the third stand is maintained 1.14 times higher than the tension after the stand, and the tension of the strip in front of the fourth stand is 1.4 times higher than the tension after the stand. The tension of the strip after the second stand is maintained 1.14 times more than before this stand.

The use of the recommended ratio of the magnitude of the tension of the strip led to a decrease in the number of imprints of the transverse strips at the finished rental and a decrease in the number of defects.

The technical and economic advantage of the proposed technical solution is to reduce the transverse imprints on the surface of the finished product, to improve the quality of the products while increasing the productivity of the mill and reducing the rolling forces while maintaining the amount of compression.

Claims (1)

A method of cold rolling strips, including sequential compression of the strip in the stands of a continuous mill with tension between the stands, characterized in that for a five-stand mill, the tension of the strip in front of the third stand is assigned 1.01-1.56 times the tension after this stand, and the strip tension in front of the fourth stand - 1.01-1.85 times the tension of the strip after this stand, while the tension after the second stand is set to 1.01-1.40 more than in front of this stand.