SU1581394A1 - Method of producing thin strips - Google Patents

Abstract

The invention relates to sheet-rolling production and can be used in the preparation of a rolled stock for cold rolling mills of sheet and tin. The purpose of the invention is to improve the quality of cold-rolled strips by reducing edge waviness and flattening of mechanical properties. According to the method of production of thin strips, during hot rolling in the middle section of the cross-section of the rolled, equal to 0.6-0.8 of the width of the latter, create warpiness with an amplitude-wavelength ratio of 0.005-0.05. In the process of straightening the buckling with stretching, the degree of deformation is determined depending on the ratio of the amplitude of the created boxiness to the wavelength and the ratio of the roll-up thickness to the diameter of the rollers of the flexural-stretching machine. The cold-rolled strip obtained from the treated in this way has a higher density. 1 il. 1 tab.

Description

The invention relates to sheet-rolling production and can be used in the preparation of a rolled steel for cold rolling mills and sheet metal.

The purpose of the invention is to improve the quality of cold-rolled strips by reducing their edge waviness by aligning the mechanical properties of the rolled strip across the width.

The drawing shows sections of the strip by a plane passing through the axis of rolling and perpendicular to the plane of rolling

The strips rolled on the broadband mill have an uneven distribution of yield strength across their width. For example, when producing a rolled stock for a tin shop of steel 08 kp at the Karaganda Metallurgical Combine, the yield strength of the metal at the edges of hot rolled strips is lower than the yield strength of the metal in the middle part of the width of the strip. Straightening bands in a bending and stretching machine (IRM) does not eliminate the non-uniformity of the yield strength in thickness, and with an initial wavy tackle after straightening

Sl

oo

with

Ј 4b

In the process of cold rolling, the edges of the strip, which have a lower yield strength, are deformed to a greater degree (due to a smaller deflection of the rolls and a smaller amount of flattening).

The essence of the invention is as follows.

With hot rolling in the middle section of the cross section of the strip, equal to 0.6-0.8 of its width, they create a non-flatness — warping with parameters 0.005 4 a / L Ј0.05. After this, the rolled strip is straightened, the degree of deformations according to the following dependence

. gp, / tt / j h h

t WA) m + (H / d) n3-100%,

where a a

g

(i)

magnitude of the non-flat amplitude, MMj wavelength of the non-flatness, mm;

the degree of deformation during straightening the bending with stretching,%:

m is the exponent depending on the nature of the warping of the rolled strip, (t Ј 2.0);

H - thickness of the rolled, mm; d - diameter of the correct roller

bending and stretching machine, mm; p. is an exponent depending on the thickness of the rolled strip (1.45 p. 1.6) o

After straightening, the roll is etched and cold rolled is performed.

During the straightening process of the IRM rolled stock, the flatness defect (warping) is eliminated. At the same time, the flat sections at the strip edges are deformed to a greater degree than the horny sections, which leads to their greater hardening. Since the yield strength of the metal on the edges before straightening the strips is lower than in the middle part of the strip along its width, after deformation of the strips in the IRM, the mechanical properties are equalized in their width. This allows subsequent cold rolling to produce stripes that do not have flatness defects such as wave along edges due to non-uniformity of mechanical widths.

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five

0

five

d

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The need to create warpiness in a certain section of the strip width is associated with the nature of variation of the yield strength across the width of the strips produced from low carbon steels of type 08 kp. The studies carried out at the Karaganda Metallurgical Combine (KMK) showed that a change in the yield strength (6T) occurs in a section equal to 150-200 mm from the edges of the stripes. The rest of the strips along their width 6T practically do not change. For hot-rolled strips 1000 mm wide, the section with a constant value equal to 1000-2 200 600, which will be 0.6 of its width. With a strip width of 2000 mm, the ratio of the section with a constant 6T to the total width is c: 0.8. Creating a warpiness on a greater than 0.8 strip width is practically impracticable and impractical from the point of view of ensuring uniformity of mechanical properties. If the size of the jagged portion of the strip is less than 0.6 of its width, then straightening will deform a portion with a large yield point. which negatively reflects the flatness of the cold rolled strip.

To create warping with the specified parameters of 0.005 4 a / L 0.005, you can use roll water bending systems, axial roll shifting, grinding profiling and.

A rolling roughness with a / L 0.005 is not sufficient to align the mechanical properties across the width. When creating a roughness with an a / A ratio of 0.05, irreparable defects occur when the strips are rolled on the coilers after hot rolling, the edges of the strips are deformed due to the variation of the coils in the roll. with the average values of the recommended interval a / L 0.025, It should be noted that obtaining warpiness with such parameters is technically the easiest to reach.

When choosing a grade factor n, depending on the thickness of the rolled stock, one should be guided by the following considerations. Smaller values, up to a value of 45, are taken when editing relatively thin strips (e.g., 8-3 mm) on an IRM. This is due to the fact that

As a rule, sons have a greater degree of flatness, for which elimination requires a greater degree of deformation in the IRM (with a decrease in n, the degree of deformation increases) 0 At values of n: 1.45, the mechanical properties of the rolled strip can change significantly, which will affect the quality of cold-rolled strips and tin, drive, for example, to an increase in hardness. Maximum values close to, b, it is advisable to assign when editing thicker strips (for example - 6 mm). The use of even larger values of n does not provide the necessary modes of deformation of the rolled stock in the IWW and may lead to a decrease in its flatness.)

The exponent m depends on the nature of the roughness of the rolled stock (see drawing). With a smooth waveform (pos. 1), the length of the strip in the cross section shown in the drawing is longer and, accordingly, a greater degree of deformation is required during the straightening process than with a waveform with sharper tops (pos. 2). As the observation has shown, the non-planarity wave has a smooth shape with the ratio a / L, close to 0.005, and the shape with sharp tops, the wave with a / A, close to 0.05. Therefore, smaller values of the exponent m, up to, 5, it is advisable to use at lower values of a / A o close to 2.0, can be recommended for a / A values then When ka 0.050 1.5 m due to the increase of degree of deformation may occur in the higher band residual stress magnitudes Use m 2 reduces the efficiency of the process changes and deteriorates quality mistimed

EXAMPLE In the production of a rolled stock for sheet metal at the Karaganda Metallurgical Combine, by bending the bending of the hot rolling mill rolls, 1,700 received stripes with a / A tacking parameters equal to 0.005J 0.025 and 0.05 “Then, in IRM roller type, installed in the line of the continuous pickling unit (NTA-2), they were corrected, the degree of deformation was determined in accordance with the dependence (l) f, then rolled up was etched, and cold rolling was performed. The results of the experiments are presented in the table, from

0

It follows that the implementation of the method for producing thin strips in accordance with the invention (examples 2, 3 and 4) provides improved quality indicators for cold-rolled strips in comparison with the known method (example 1). In this case, the minimum and maximum levels of deformation during dressing lead to a slight decrease in the volume of production of grade II with increased edge waviness, and the maximum effect is achieved with average values of the parameters of dependence (I):, 5; m 1.7; , 025, which corresponds to the degree of deformation, 76%. A decrease in the flatness of the bands is also observed when using IRM rollers with diameters different from those indicated in the table.

The implementation of the invention improves the quality of cold-rolled strips due to the reduction of their edge 5 waviness.

Claims (1)

Invention Formula Method for the production of thin strips D, predominantly of low carbon steels, including hot rolling, straightening, torsional bending with stretching, etching and subsequent cold rolling, characterized by so that, in order to improve the quality of cold rolled strips by reducing edge waviness and flattening of the mechanical properties, during hot rolling in the middle section The 0 cross section of the rolled section with a width of 0.6–0.8 width creates warpiness with parameters 0.005 Ј a / A / 0.05, and straightening is carried out with the degree of deformation determined by 5 according to Ј (t- a / A) m + (H / d) - 100, where Ј is the degree of deformation when the right side is rolled by bending with stretching,%; a is the amplitude of the compactness, mm; A is the wavelength of the created warping, mm; m is an exponent depending on the nature of the warping of the rolled stock (1.5, 0); H - thickness of the rolled, mm; five d is the diameter of the correct roller of the bending and stretching machine, mm; - exponent, depending on the thickness of the rolled stock (1.45, 4p L, 6). The results of the comparative testing of the known for the proposed methods for the production of thin strips (tin) on the NShS 1400 of rolled-in sizes 2, A 910 mm from steel 08 kp, obtained by ShSNG 1700 and then edited by IRM on NTL-2 (KMK) Note. LBT - the value of the difference in mechanical properties across the width of the strip; 4bt; - the ratio of d6T to the magnitude of the difference in mechanical properties & wide for bands rolled by a known method.