RU2535840C1 - Production of silicon-free dynamo steel sheets - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention relates to metallurgy and can be used for production of isotropic electric steel 0.2-1.8 mm thick sheets. Proposed method comprises feed of hot-rolled etched strip to six-stand continuous mill, reduction at stands and cold rolling. Steel sheet higher flatness is ensured by reduction at stands is set in compliance with the following accumulated relative reductions: 1^st stand - to 43%; 2^nd stand - 45-54%; 3^rd stand - 56-66%; 4^th stand - 68-74%; 5^th stand - 76-78% and 6^th stand - at least 80%.

EFFECT: higher flatness of steel sheet.

1 dwg, 1 tbl, 1 ex

Description

The invention relates to rolling production and can be used to obtain a silicon-free sheet dynamo (isotropic electrical) steel with a thickness of 0.2-1.8 mm

A known method for the production of sheet steel, including refueling a hot-rolled pickled strip from steel grade 08YUR 2.0 mm thick and its cold rolling in four passes to a final thickness of 0.38 mm with a total relative compression of 81%, distributed over the passages [1].

There is also known a method of manufacturing sheet steel 2.0 mm thick, comprising rolling a hot-rolled pickled strip from 08kp steel on a continuous four-stand mill with the distribution and installation of the total relative compression over the stands (passes) according to the following scheme: 35.5% → 54.5% → 68.4% → 70% [2].

A disadvantage of the known methods [1, 2] is that when rolling a hot-rolled tackle from silicon-free dynamo steel, cold-rolled strips have a large non-flatness.

The closest analogue to the present invention is a method for the production of dynamite-free dynamite sheet steel, which is used for hot rolling of strips, etching, dressing in a continuous four-stand mill, distribution and installation of crimping in stands and subsequent cold rolling with a total relative deformation of 75-80% and regulated intercell tension [3].

The disadvantage of this method is that as a result of cold rolling, the silicon-free sheet dynamo steel has a large non-flatness. This ultimately leads to a decrease in yield.

The technical problem solved by the invention is to increase the flatness of the silicon-free dynamo steel sheet.

To solve the technical problem in the known method for the production of dynamite-free sheet steel, including hot-rolled etched strip dressing in a continuous mill, distribution and installation of crimps in the stands and subsequent cold rolling, according to the invention, the compressions in the stands are set in accordance with the following values of the accumulated relative reductions: up to 43 %; 45-54%; 56-66%; 68-74%; 76-78%; not less than 80%.

The figure shows the experimental dependence of the rolling force on the total relative compression during cold rolling of silicon-free sheet dynamo steel. Compression was changed in increments of 1%.

The invention consists in the following. As experimental studies have shown, in the range of total relative reductions of 40 ÷ 80%, there are anomalous zones with a width of ≈2%, indicated on the figure by positions 1-5 located in the vicinity: 1-44%, 2-55%, 3-67%, 4 -75%, 5-79% ("affected points"). In these anomalous zones, due to the accumulated energy of the deformation of the metal and adiabatic heating of the metal, the character of the formation of the texture and fine structure of the steel changes. In this case, a dislocation structure is formed from elongated cells with clear lateral boundaries, and in the areas between the anomalous zones, a full-fledged cellular structure with equiaxed cells is formed. As a result, in anomalous zones 1-5 (figure), an abrupt change in the mechanical properties of the steel strip takes place, which is accompanied by fluctuations in the rolling force, a local change in the hoods, process instability, and, as a result, flatness of the strip at the exit from the deformation zone. Rolling with accumulated values of relative reduction up to 43%; 45-54%; 56-66%; 68-74%; 76-78%; not less than 80% allows to exclude getting into the zones of abnormal compression (see figure), to avoid fluctuations in rolling forces, strip hoods and violations of their flatness. This increases the stability of the rolling process and the flatness of the cold rolled sheet steel.

With the accumulated total relative deformation of 43%, more than 45%, more than 56%, more than 68% or more than 76%, an abnormal change in the mechanical properties of steel in the deformation zone, instability of the hoods along the strip width and an increase in non-flatness occur. With the accumulated total relative deformation of less than 54%, less than 66%, less than 74%, less than 78%, or less than 80%, the absolute compression in the stand also falls into the zone of anomalous values. This leads to instability of the mechanical properties of the rolled steel and an increase in the non-flatness of the strips.

Method implementation examples

As a rolling stock for the production of silicon-free dynamo sheet steel with a thickness of H ₆ = 0.5 mm, a hot-rolled etched strip with a thickness of H ₀ = 3.1 mm is used, having the following chemical composition, wt.%:

C Mn Al S P Cr Ni Fe + impurities 0.05 0.4 0.35 0.014 0.08 0.2 0.3 Rest

Hereinafter, H corresponds to the thickness of the strip at the exit of the stand, the number of which is indicated by a lower index.

The front end of the strip is sequentially set in the work rolls of a continuous 6-stand cold rolling mill quarto 1400 and fixed on a coiler. Using hydraulic push mechanisms, a predetermined mode of relative compressions in the stands is established:

.Crate 1 $${\epsilon }_{\mathrm{one}}=\frac{H_0-H_{\mathrm{one}}}{H_0}\cdot \mathrm{one\; hundred}\%=\frac{\mathrm{3,1}-2.0}{\mathrm{3,1}}\cdot \mathrm{one\; hundred}=35.5\%$$

.

.Crate 2. $${\epsilon }_2=\frac{H_0-H_2}{H_0}\cdot \mathrm{one\; hundred}\%=\frac{\mathrm{3,1}-\mathrm{1,5}}{\mathrm{3,1}}\cdot \mathrm{one\; hundred}=51.6\%$$

.

.Crate 3. $${\epsilon }_3=\frac{H_0-H_3}{H_0}\cdot \mathrm{one\; hundred}\%=\frac{\mathrm{3,1}-\mathrm{1,1}}{\mathrm{3,1}}\cdot \mathrm{one\; hundred}=64.5\%$$

.

Crate 4. $${\epsilon }_{\mathrm{four}}=\frac{H_0-H_{\mathrm{four}}}{H_0}\cdot \mathrm{one\; hundred}\%=\frac{\mathrm{3,1}-0.85}{\mathrm{3,1}}\cdot \mathrm{one\; hundred}=72.5\%$$

Crate 5. $${\epsilon }_5=\frac{H_0-H_5}{H_0}\cdot \mathrm{one\; hundred}\%=\frac{\mathrm{3,1}-0.7}{\mathrm{3,1}}\cdot \mathrm{one\; hundred}=77.4\%$$

Crate 6. $${\epsilon }_6=\frac{H_0-H_6}{H_0}\cdot \mathrm{one\; hundred}\%=\frac{\mathrm{3,1}-0.5}{\mathrm{3,1}}\cdot \mathrm{one\; hundred}=83.9\%$$

A lubricating-cooling technological agent (5% emulsion of mineral oil in water) is supplied to the rolls and strip and cold rolling of a strip of thickness H ₆ = 0.5 mm with interstand tension is carried out. Due to the fact that the total relative reductions in each of the stands do not fall into the “affected points” 1; 2; 3; 4 and 5 (figure), the rolling process proceeds stably, the non-flatness of the cold-rolled strips is minimal and does not exceed S = 1.0 mm per meter length.

Implementation options for the production of dynamite-free dynamo steel sheet are presented in the table.

Table No. p / p The total accumulated compression at the exit from the stand,% S, mm / m one 2 3 four 5 6 one. 18,4 44.0 55.1 67.2 75.1 79.2 10.3 2. 25.8 45.0 56.0 68.0 76.0 80.0 2.0 3. 35.5 51.6 64.5 72.5 77.4 83.9 1,0 four. 43.0 54.0 66.0 74.0 78.0 95.4 1.8 5. 44.0 55.1 67.0 75.3 79.1 96.3 8.8

As follows from the data given in the table, when implementing the proposed method (options No. 2-4), an increase in the stability of the rolling process is achieved, due to which the non-flatness of the cold-rolled strips is minimal: S = 1 ÷ 2 mm / m. In cases of transcendental values of the declared parameters (options No. 1 and No. 5), when the total relative compression falls into the “affected” zones indicated by positions 1-5 in the figure, due to the violation of the stability of the rolling process, the non-flatness of the silicon-free sheet dynamo steel increases to S = 8.8 ÷ 10.3 mm. The same non-flatness values were obtained when implementing the known method [3].

The technical and economic advantages of the proposed method consist in the fact that the use of the proposed ranges of the total relative reductions during continuous cold rolling eliminates the modes in which an unfavorable structure and texture of the metal is formed, and the rolling process becomes unstable. Due to this, an increase in the flatness of cold-rolled silicon-free sheet dynamo steel with a thickness of 0.2-1.8 mm is achieved. Using the proposed method provides an increase in the profitability of the production of this type of metal products by 10-12%.

Literary sources

1. Patent of the Russian Federation No. 2340414, IPC В21В 1/28, 2008

2. Patent of the Russian Federation No. 23235241, IPC В21В 1/28, 2008

3. Patent of the Russian Federation No. 2271255, IPC В21В 1/28, 2006

Claims (1)

A method for the production of silicon-free sheet isotropic electrical steel with a thickness of 0.2-1.8 mm, comprising cold rolling of a hot-rolled pickled strip in a continuous six-stand mill, in which a predetermined crimping mode is set in the stands, characterized in that the crimping mode is set in the stands with the total relative reduction in the first stand - up to 43%, in the second stand - 45-54%, in the third stand - 56-66%, in the fourth stand - 68-74%, in the fifth stand - 76-78 and in the sixth stand - not less 80%