RU2354465C1 - Cold rolling method for carbon strip steel and related mill - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention is intended for improving rolling quality and reducing rolling redistribution cost during cold rolling of carbon strip steel. The method includes serial metal reduction in cuts to the given thickness. When 200…300 mm wide and B=8…11 mm thick strips are rolled, metal is reduced to the value (0.75…0.85) H in the first cut and to the final value 0.8…2.0 mm in the second cut. At the same time, the strip rounds three rolls. The cold rolling mill contains recoiler, feed roll, pendulum stand with crank-operated mechanism and two drag rolls, and a reel. In addition, the mill includes intermediate roll and four-roll stand with Y-like arrangement of rolls and two driven rolls being located in common vertical plane. The total coverage angle of strip rolled by three rolls is within 500°…560°.

EFFECT: increased flatness of rolling, wide range of rolling and unchanged industrial costs.

2 cl, 1 dwg, 1 ex

Description

The invention relates to the processing of metals by pressure and can be used in the rolling of carbon strip steel (tape).

The technology of cold rolling of such steel consists in sequentially compressing the hot-rolled strip billets in the stands of the cold rolling mill. The features of this technology and the design of the mills used are described in sufficient detail, for example, in the book of P. I. Polukhin and others. “Rolling mills”, M., “Metallurgy”, 1982, pp. 491-518. The design of the mill used is determined by the assortment and the desired properties of the obtained strip rolling, and the latter, in turn, largely depend on the compression regimes used (for example, on their total value).

A known method of cold rolling strips of heat-resistant and corrosion-resistant steels, in which rolling to a total degree of deformation of 57% is carried out at the same peripheral speed of the rolls, and with the specified deformation of more than 57% - with a mismatch of peripheral speeds (see ac CCCP No. 1093368, Cl B21B 1/22, published in BI No. 19, 1984).

However, this method requires a relatively large number of passes, which increases the cost of redistributing the rental.

The closest analogue to the claimed method is a method of cold rolling by AS USSR No. 1546183, class B21v 1/22, publ. in BI No. 8, 1990

This method consists in sequentially compressing the metal through the passages to a predetermined thickness and is characterized in that the degree of total relative deformation is determined from the mathematical expression.

The known method also requires an increased number of passes and an increase in the cost of redistributing the rental.

A known mill for cold rolling of thin strips, which has tension rollers installed on both sides of the working stand, and the corresponding CAP (automatic control system), which monitors the weld and other operations (see Japanese application No. 62-54512, class . B21B 37/00, publ. 10.03.87 g.). This mill is single-standed, which significantly narrows its technological capabilities.

The closest analogue to the claimed mill is a cold rolling mill, described in the book by Y. S. Finkelshtein "Handbook of rolling and pipe production", M., Metallurgy, 1975, p. 183 and Fig. 2.

This carbon strip steel rolling mill comprises an uncoiler defining rolls, a pendulum stand with a crank mechanism and two idle work rolls, and a coiler.

The disadvantage of this design of the mill is the possibility of the appearance of longitudinal thickness variation (transverse undulation) on the finished strip steel, which affects its consumer properties. Indeed, with an unsatisfactory setting of the mill (mismatch of the longitudinal speed of the strip with the frequency of contact of the work rolls and metal) periodically alternating thickened and thinned sections may appear on the surface of the strip, which will not be fixed later.

The technical task of the present invention is to improve the quality of the obtained strip hire (tape), which improves its consumer properties, as well as reducing the cost of redistribution of such hire.

To solve this problem, in the proposed method of cold rolling, which consists in sequentially compressing metal to a predetermined thickness in passes, when rolling strips 200 ... 300 mm wide with an initial thickness of H = 8 ... 11 mm, compression is performed in the first pass by a value of (0.75 ... 0.85) N, and in the second pass - to a final thickness of 0.8 ... 2.0 mm with partial bending around a strip of three rolls; The mill proposed for the implementation of this method comprises an uncoiler, defining rolls, a pendulum stand with a crank mechanism and two working single rolls, and a winder, further comprises an intermediate roller and a four-roll stand with a Y-shaped arrangement of rolls and with two drive rolls lying in a common vertical plane , with a total coverage angle of the rolled strip of three rolls within 500 ° ... 560 °.

The parameters of the method and device obtained as a result of the processing of experimental data and are empirical.

The essence of the claimed technical solutions lies in the additional tensile-compression deformation of the strip obtained in the pendulum stand using a four-roll stand. At the same time, firstly, the technological capabilities of the process are expanded, which reduces the cost of redistribution (almost constant costs when expanding the assortment of cold-rolled strip), and secondly, the quality of rolled products increases (its flatness improves) due to additional roll deformation.

The proposed cold rolling mill is schematically shown in the drawing (arrow is the direction of movement of the strip).

The mill contains an unwinder 2, defining rolls 3, a pendulum stand 4 with a crank mechanism and with two working single rolls 5, an intermediate roller 6, a four-roll stand 7 with a Y-shaped arrangement of rolls 8, 9 and 10 and with two drive rolls 9 and 10, lying in a common vertical plane, the winder 11. The amount of compression between the rollers 9 and 10 is adjusted using the pressure device 12, which changes the roll gap.

The device operates as follows.

Rolled strip billet 1 with an initial thickness N from the unwinder 2 with the help of master rolls 3 enters the pendulum stand 4 of the mill, where the metal is crimped by the amount of (0.75 ... 0.85) N by working idler rolls 5, making a reciprocating movement in vertical the plane about the yy axis. Then a strip of thickness H goes around the intermediate roller 6 and enters a four-roll stand 7, where it goes around three rolls 8 and 9. The compression of the strip is carried out when it passes between the drive rolls 9 and 10 lying in a common axial (vertical) plane, and the amount of this compression is regulated using a pressure device 12 that changes the roll gap. The total angle of bending around the strip of rolls 8, 9 - 500 ° ... 560 °.

From stand 7, a strip of thickness h = 0.8 ... 2.0 mm enters the winder 11 of the mill, where it is wound into a roll.

An experimental verification of the proposed method and the mill was carried out at a pilot plant of Magnitogorsk State Technical University (MSTU). For this purpose, when rolling strips with a thickness of 0.8 ... 2.0 mm (tapes) and a width of 200 ... 300 mm from a hot-rolled billet with a thickness of H = 8 ... 11 mm from various carbon steels, the reductions in both stands of the mill were varied, as well as the angle coverage of the rolled strip of rolls of the four-roll stand. The results of the experiments were evaluated by the quality of the obtained hire.

The best results (high-quality tape yield with a minimum longitudinal thickness difference of up to 99.3 ... 99.8%) were obtained using the proposed method on the proposed mill. Deviations from the recommended parameters worsened the achieved indicators.

Thus, a decrease in the size of the compression in the first pass (less than 0.75 N) led to the need to increase the compression in the second pass, which led to accelerated wear of the rolls of the four-roll stand. With reductions in the first pass of more than 0.85 N, a longitudinal thickness difference in excess of the permissible value appeared on part of the strips, which was not eliminated in the second pass. With a total angle of coverage of the rolled strip of rolls in this passage less than 500 °, slippage of the bands in the rolls with the appearance of longitudinal marks and scratches was observed, and with a coverage angle of more than 560 ° the drive power of the four-roll stand was insufficient (especially for final thicknesses of 0.8 ... 1 , 2 mm), which led to its overload with known negative consequences.

The mill selected as the closest analogue (see above) was not tested in the experiments, since in fact it is the proposed mill, but without a four-roll mill (i.e., with the need for too large reductions in the first pass, the lack of which is described above) .

The known method (the closest analogue) was also not tested due to its obvious shortcomings (increased number of passes and an increase in the cost of redistribution in connection with this).

Thus, an experimental verification confirmed the acceptability of the technical solutions found to achieve the goal and their advantage over known objects.

According to technical and economic studies conducted at MSTU, the use of the invention for producing cold-rolled strips of 0.8 ... 2.0 × 200 ... 300 mm will increase their quality while reducing production costs by at least 1.5 times.

Concrete example

The cold rolling mill of strip steel with a thickness of 0.8 ... 2.0 mm and a width of 200 ... 300 mm from a workpiece with a thickness of H = 8 ... 11 mm has the form shown in the drawing.

To obtain strips with h = 1.4 mm from a workpiece with H = 9.5 mm in the first pass, the compression value is: 0.8 N = 0.8 · 9.5 = 7.6 mm, i.e. a 4-roll stand includes a strip of thickness H ₁ = 9.5-1.6 = 1.9 mm, which is crimped to a thickness of 1.4 with a total angle of coverage of the strip of three rolls equal to 530 °.

Claims (2)

1. A method for cold rolling strips of carbon steel with a width of 200 ... 300 mm and an initial thickness of H = 8 ... 11 mm, including sequentially compressing metal rolls to a predetermined thickness by passes, characterized in that the strip is crimped in the first pass by (0, 75 ... 0.85) N, and in the second pass - to a final thickness of 0.8 ... 2.0 mm with partial bending around a strip of three rolls. 2. A cold strip rolling mill made of carbon strip steel, comprising an uncoiler, drive rolls, a pendulum stand with a crank mechanism and two idle rolls, a winder, characterized in that it comprises an intermediate roller and a four-roll stand with a Y-shaped roll arrangement and with two drive rolls located in a common vertical plane, configured to cover a strip of three rolls with a total angle of coverage within 500 ... 560 °.