RU2164451C2 - Strip cold rolling process - Google Patents

Abstract

FIELD: metallurgy, namely rolled stock production, possibly cold rolling of thin strips of isotropic electrical steel. SUBSTANCE: process comprises steps of multipass reduction of hot rolled strip between rolls at supplying technological lubricant; reducing strip in last pass at deformation degree 15-25% with relation of thickness of rolled strip to roll diameter equal to (0.8-1.3) ×10³. EFFECT: enhanced quality of rolled strips of isotropic electrical steel due to creation of mostly favorable crystallographic texture of metal. 5 exp, 1 tbl

Description

 The invention relates to metallurgy, and more particularly, to rolling production, and can be used for cold rolling of thin strips of isotropic electrical (dynamo) steel.

 Cold-rolled isotropic electrical (dynamo) steel should combine high accuracy and flatness with specified magnetic properties with minimal specific losses. The quality indicators of dynamo steel are largely determined by the modes of its cold rolling.

 A known method of cold rolling strips of isotropic electrical steel on a continuous 4-stand mill quarto. The method includes crimping a hot-rolled strip in 4 passes in the rolls with the supply of technological lubricant to the deformation zone. The strip in the last, 4th passage is squeezed with a degree of deformation of 27.2% with a total degree of deformation of 75% [1].

 The disadvantages of this method are that the finished cold-rolled strip of dynamo steel has low electrical properties and is characterized by large specific losses. In addition, with an increase in the silicon content in dynamo steel of more than 0.8% to increase its electrical properties, the rolling out of the strips deteriorates, which is accompanied by an increase in their thickness variation and strip gusts in the mill.

 There is also known a method of cold rolling strips, including the compression of the strip for 5 passes on a continuous mill 2030 to a final thickness of 0.5-1.0 mm with a feed to the rolls and strip technological lubrication. Compression in the last, 5th pass is 2-7% [2].

 With this method of rolling in the cold-rolled strip, the optimal deformation texture is not formed. Therefore, strips of isotropic electrical steel are of low quality and are characterized by high specific losses.

The closest in their technical essence and the achieved results and the proposed invention is a method of cold rolling thin strips, including multi-pass compression of the hot rolled strip in the rolls with the supply of technological lubricant. According to this method, the rolling in the last pass is carried out with compression, determined from the expression
E = 0.4 - 0.429H _p - 0.0007σ + 0.1H _IS ,
where E is the relative compression in the last pass;
H _p - the thickness of the finished strip;
σ is the yield strength of the rolled material;
H _IS - the thickness of the tackle [3].

 The disadvantages of this method are that it does not improve the quality of strips of isotropic electrical steel. Dynamically rolled cold-rolled strips have unsatisfactory accuracy, flatness and high specific losses. An increase in the silicon content significantly worsens the rolling out of the cold-rolled strips.

 The technical problem solved by the invention is to improve the quality of strips of isotropic electrical steel.

The stated technical problem is solved in that in the known method of cold rolling strips of isotropic electrical steel, including multi-pass compression of the hot rolled strip in the rolls with the supply of technological lubricant, according to the proposal, the strip in the last pass is compressed with a degree of deformation of 15-25% with respect to the thickness of the rolled strip to the diameter of the rolls (0.8 - 1.3) · 10 ^-3 .

The invention consists in the following. The final formation of the quality of the strips during cold rolling occurs in the last pass. During compression in the last pass E = 15-25% and the ratio of the strip thickness to the diameter of the rolls k = (0.8 - 1.3) · 10 ^-3 , a deformation texture is formed in the strip with the predominant prevalence of the most favorable crystallographic orientation {200}, which ensures a significant reduction in specific losses. In addition, the dependence of the metal strain resistance on the degree of deformation of dynamo steel is extreme in nature with a minimum in the range of the degree of deformation of 15-25%. This improves the rolling out of the cold-rolled strips, especially with a high silicon content. The result is an increase in the quality of strips of isotropic electrical steel.

Method implementation examples
An etched hot rolled strip of dynamo steel grade 0402 with a cross section of 2.0 x 1020 mm, rolled up, is mounted on an uncoiler of a continuous 4-stand cold rolling mill 1400. The diameter of the work rolls of the 4th mill stand is D = 333.3 mm.

The front end of the rolled strip is set in the rolls of the mill, include the supply of technological lubricant, which is used as a 20% mixture of palm oil with water. The compression in the 4th stand is set equal to E = 20% and the strip is rolled to a final thickness of H = 0.35 with the ratio
H / D = 0.5 / 333.3 = 1.05 · 10 ^-3
With the specified compression E = 20% and the parameter of the deformation zone H / D = 1.05 · 10 ^-3 , the formation of the optimal structure and the best rolling out of the cold-rolled strip from dynamo steel are achieved. Due to this, the specific loss index P _{1.5 / 50} decreases to 1.1 W / kg, and the yield increases to 98%.

 Implementation options of the proposed method and indicators of their effectiveness are shown in the table.

 The table shows that when implementing the proposed method (options 2-4), an increase in the quality of cold-rolled strips of isotropic electrical steel is achieved. In cases of transcendental values of the declared parameters (options 1 and 5), the specific losses increase, the yield decreases, the rolling out of the strips deteriorates. Also, lower quality indicators are achieved when implementing the prototype method (option 6).

The technical and economic advantages of the proposed method consist in the fact that multi-pass cold rolling of isotropic electrical steel with process lubricant and compression in the last pass E = 15-25% with a ratio H / D = (0/8 - 1.3) · 10 ^-3 the most favorable crystallographic texture is formed, a decrease in the resistance of the metal to deformation is achieved, and the rolling out of the strips is improved. Due to this, improving the quality of the bands and as a result, increasing the yield.

 The prototype method is adopted as the base object. The application of the proposed method will increase the level of profitability of the production of cold-rolled strips from dynamo steel by 15-20%.

Sources of information
1. V.A. Vanchikov, N.G. Bochkov, B.V. Thresher. Fundamentals of the production of isotropic electrical steel. - M.: Metallurgy, 1985, p. 188-193.

 2. A.F. Pimenov, V.P. Polukhin, Yu.V. Lipukhin et al. High-precision rolling of thin sheets. - M.: Metallurgy, 1988, p. 102.

 3. Auth. St. USSR N 1667956, IPC B 21 B 1/28, publ. 1991 - prototype.

Claims (1)

A method of cold rolling strips of isotropic electrical steel, including multi-pass crimping of a hot-rolled strip in rolls with the supply of technological lubricant, characterized in that the strip in the last pass is crimped with a degree of deformation of 15 - 25% with respect to the thickness of the rolled strip to the diameter of the rolls (0.8 - 1.3) x 10 ^-3 .

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