RU2264876C1 - Method for coiling cold rolled steel strip - Google Patents

Abstract

FIELD: rolled stock production, namely processes for cold rolling of strips in continuous rolling mills.

SUBSTANCE: method comprises steps of creation of predetermined strip tension changed during coiling process. At coiling strip of steel with thickness h = 0.6 - 2.0 mm and with carbon content up to 0.25 mass % maximum value of specific tension τ for first 140 - 160 m of coiled strip length is set equal to (t + 50)n/mm² where t - specific strip tension with uniformly lowered tension along said length of strip till its value t in end portion ,

n/mm² for h₁ = 0.6 -1.2 mm and t = 40.1/h₂  ^0,25 n/mm² for h₂ = 1.3 - 2.0 mm. Then coiling process is going on at τ = const.

EFFECT: enhanced efficiency of mill, less loss of yield of suitable quality rolled sheets.

1 cl, 1 ex

Description

The present invention relates to rolling production and can be used in the manufacture of cold rolled strip steel.

Such steel is usually produced on continuous cold rolling mills by sequentially crimping the strip in rolls, followed by winding it into a roll on a drum type winder. The technology of cold rolling and some features of winding strips into rolls are described, for example, in the book by S. P. Efimenko and V. P. Slednev “Roller of sheet rolling mills”, M .: Metallurgy, 1980, pp. 230-241. The basic requirements for a cold-rolled strip wound into a roll: the roll must be removed from the reel drum without leaving the inner turns beyond the plane of the end face of the roll, and the density of its winding should ensure that there is no “fluffing” (that is, an increase in the radial distance between the individual turns of the roll) during transportation .

There is a known method of winding a metal strip into a roll, in which the radius of curvature of the rolled strip changes during winding using special forming rollers, which improves the quality of winding (see Japanese Pat. Pat. No. 3524, class B 65 N, publ. 31.01.72 g .). The disadvantage of this method is the need for additional equipment with a complex electrical circuit for its control, as well as the uncertainty of the magnitude of the strip tension during winding, which can lead to the above-mentioned defects of the coil winding.

The closest analogue to the claimed object is a method of winding into a roll of cold rolled steel, described in A.S. USSR No. 3332883, cl. At 21 C, publ. 10/02/72

This method includes creating a predetermined tension of the strip and is characterized in that the first five turns are wound on the reel drum with a tension exceeding the technological one by 2-2.5 times, followed by a gradual reduction in tension to the technological one by 50-100 revolutions of the reel drum.

The disadvantage of this winding technology is the possibility of the appearance of rolled defects such as kinks and scratches (especially on wide and thin strips up to 2 mm thick), as well as the impossibility of defect-free rolling at higher speeds.

Indeed, as shown by an experimental verification (see below) of the known and proposed methods, too much tension on a small number of first turns of the roll, firstly, leads to the appearance of the above defects, the number of which increases with increasing speed of rolling (and winding); secondly, after removing the roll from the drum, the winder leads (on a thin strip) to the exit of several internal turns from the plane of the end face of the roll.

All this forces to reduce the rolling speed of a wide and thin strip, and also reduces the yield due to the need to remove part of the strip with defects.

The technical task of the invention is to increase the productivity of cold rolling mills and increase the yield of sheet metal.

н/мм² для h₁=0,6...1,2 мм и t=40,1/h₂ ^0,25 н/мм² для h₂=1,3...2,0 мм, продолжая дальнейшую смотку при τ=const.To solve this problem, in the method of winding into a roll of cold rolled strip steel, including the creation of a given strip tension, changing during the winding, when winding steel with a thickness h = 0.6 ... 2.0 mm with a carbon content of up to 0.25 wt.% the maximum value of the specific tension τ at the first 140 ... 160 m of the length of the reeling strip is taken to be t + 50 n / mm ² with a uniform decrease in tension at the specified length to a value of t at its end, where

n / mm ² for h ₁ = 0.6 ... 1.2 mm and t = 40.1 / h ₂ ^0.25 n / mm ² for h ₂ = 1.3 ... 2.0 mm, continuing further winding at τ = const.

The above mathematical dependences were obtained during the processing of experimental data and are empirical. By specific tension is meant the tension of the strip per unit area of its cross section.

The essence of the proposed technical solution is to create from the internal turns of the formed roll of a rigid frame, on which the subsequent turns of the roll are wound. After removing the coiled roll from the reel drum, these internal compressed turns of the strip tend to increase their diameter, which leads to compaction of the coil of the whole roll. Such a tightly wound roll, firstly, does not have a lateral displacement of the turns, which allows the roll to be installed unhindered, for example, on the drum of the unwinder of a temper mill, and secondly, there is no mutual longitudinal (along the roll forming) slipping of its individual turns, which prevents the appearance of metal defects such as kinks and scratches (scratches).

The proposed method is implemented during cold rolling by changing the rotation speed of the reel drum, which is determined by the current load of the reel motor. The winding is carried out first with increased tension, gradually reducing it to a value at which the subsequent winding continues.

Experimental verification of the proposed method was carried out on a two-stand reversible cold rolling mill of OJSC "Magnitogorsk Iron and Steel Works".

For this purpose, when rolling strip steel with a thickness of 0.6 ... 2.0 mm and a width of 1000 ... 1650 mm with a carbon content of up to 0.25 wt.%, Various types of winding were tested with varying specific tension values. The best results (mill productivity up to 80 ... 100 t / h and yield up to 99.5%) were obtained when implementing the proposed technical solution. Deviations of actual values of t from the calculated values were within -5.6 and + 5.5%.

The best results were obtained with a constant τ = 30 ... 40 n / mm ² and on strips with a width of 1300 ... 1650 mm. Deterioration of the results was also observed with a decrease and increase in the optimal length (140 ... 160 m) of the front end of the strip, wound up with increased tension, as well as with t values, smaller and larger recommended values, and at the same t for all thicknesses. In this case, a decrease in t worsens the winding, and an increase injures the surface of the metal.

Control rolling with the winding of strips according to the known method, taken as the closest analogue (see above), made it possible to achieve a mill productivity of not more than 70-80 t / h with a yield within 97.6%.

Thus, experimental verification has confirmed the acceptability of the technical solution found to achieve the goal and its advantages over a known object.

Technical and economic studies carried out in the Central laboratory of the plant showed that the use of the proposed method for winding the specified parameters into a cold rolled strip steel strip allows to increase the productivity of cold rolling mills by at least 20%, and increase the yield of sheet metal by approximately 1.9 abs .%.

Concrete example

Strip steel with a carbon content [C] = 0.18 wt.% 1 mm thick is wound after cold rolling into a roll.

н/мм², а на длине переднего конца полосы до 150 м-τ=t+50=87,7 н/мм².The value of the specific tension after winding the first 150 m of the strip is taken constant and equal

n / mm ² , and on the length of the front end of the strip to 150 m-τ = t + 50 = 87.7 n / mm ² .

Steel of the same grade but with a thickness of 1.7 mm is rolled up at t = 40.1 / h ₂ ^0.25 = 40.1 / 1.7 ^0.25 ≅35.1 n / mm ² and τ = t + 50 = 35.1 + 50 = 85.1 n / mm ² .

Claims (1)

The method of winding into a roll of cold rolled strip steel, including the creation of a given strip tension, changing during the winding process, characterized in that when winding steel with a thickness h = 0.6 ... 2.0 mm with a carbon content of up to 0.25 wt.% Maximum the specific tension value τ at the first 140 ... 160 m of the length of the reeling strip is taken to be t + 50 N / mm ² , where t is the specific tension of the strip, with a uniform decrease in tension on the specified length to a value of t at its end, where t = 37 , 7 /

N / mm ² for h ₁ = 0.6 ... 1.2 mm and t = 40.1 / h ₂ ^0.25 N / mm ² for h ₂ = 1.3 ... 2.0 mm, continuing further winding at τ = const.