JP2735846B2 - Method for controlling surface roughness of cold rolled sheet during production of grain-oriented silicon steel sheet - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for controlling the surface roughness of a cold-rolled sheet during the production of a grain-oriented silicon steel sheet, and more particularly, to the method of controlling the sheet surface roughness on the front and back surfaces of the cold-rolled sheet. The difference is to be eliminated advantageously.

(Prior Art) Grain-oriented silicon steel sheets are mainly used as iron cores of transformers and other electric equipment, and are required to have excellent magnetic characteristics, particularly magnetization characteristics and iron loss characteristics.

By the way, the magnetic properties of grain-oriented silicon steel sheets are strongly affected not only by the material but also by the surface properties thereof. For example, JP-A-59-38326, JP-A-62-294131 and JP-A-6-294131.
As disclosed in Japanese Unexamined Patent Publication No. 2-267421, the smaller the surface roughness, the better the magnetic properties.

Therefore, in the cold rolling step, particularly in the final cold rolling, a so-called bright finish is performed to reduce the surface roughness of the steel sheet.

(Problems to be Solved by the Invention) However, the surface roughness of the rolled plate is not equal on both surfaces, and the surface (upper surface side) is rougher than the back surface (lower surface side) in terms of rolling characteristics. There is a tendency.

The main reason for this is that, in a normal cold rolling mill, there is a difference in lubrication between the upper and lower surfaces of the plate, and the lubrication condition is better on the upper surface than on the lower surface. It is considered that this occurs frequently.

An object of the present invention is to produce a directional silicon steel sheet capable of effectively eliminating the difference in sheet surface roughness between the front and back surfaces of a rolled sheet as described above, and having the same excellent sheet surface roughness on both the front and back surfaces. The purpose of the present invention is to propose a method of controlling the surface roughness of a cold-rolled sheet at the time.

(Means for Solving the Problems) That is, according to the present invention, the silicon-containing slab is hot-rolled, and finally cold-rolled twice including intermediate annealing to obtain the final sheet thickness, and then decarburized and primary recrystallized. In the method for producing a grain-oriented silicon steel sheet comprising annealing and then performing final finish annealing, the second cold rolling step is performed in a plurality of passes, and rolling is performed while reversing the front and back surfaces of the cold rolled sheet between each pass. This is a method for controlling the surface roughness of a cold-rolled sheet at the time of manufacturing a oriented silicon steel sheet.

Hereinafter, the experimental results on which the present invention is based will be described.

In FIG. 1, in the second cold rolling stage in the manufacturing process of the grain-oriented silicon steel sheet, the i-pass and (i + 1) -pass in the case where the rolling is performed by inverting the front and back surfaces of the steel for each pass. The results obtained by examining the front-back roughness ratio are shown in comparison with the results of the conventional normal rolling.

As is clear from the figure, when each pass reversal rolling is performed, the surface roughness ratio is extremely small as compared with the case of the conventional rolling in which the rolling is not performed.

(Operation) As the grain-oriented silicon steel sheet targeted in the present invention, any conventionally known component system can be used.

Also, the hot rolling condition and the cold rolling condition may be the same as before,
The point is that the second cold rolling is each pass reversal rolling. It should be noted that the first cold rolling may be performed in a plurality of passes and each pass reverse rolling may be performed.

Further, primary / recrystallization annealing and final finish annealing after cold rolling may be performed under ordinary conditions.

(Example) C: 0.040 wt%, Si: 3.27 wt%, Mn: 0.07 wt%, Se: 0.022 wt%
, The balance being composed of Fe and unavoidable impurities. The first cold-rolled silicon steel sheet (thickness: 3.5 mm) was subjected to the first cold rolling to 0.8 mm, and then 975 ° C for 3 minutes. The second cold rolling was performed with the intermediate annealing interposed therebetween to obtain a final cold-rolled sheet having a thickness of 0.35 mm.

Then, after decarburization and primary recrystallization annealing at 820 ° C for 3 minutes, an annealing separator mainly containing MgO was applied,
Final finish annealing was performed at 200 ° C. for 10 hours.

In the above process, the second cold rolling step was performed in three passes using a reverse rolling mill (work roll diameter: 125 mm). At this time, two passes of each pass reverse rolling according to the present invention and normal rolling were performed. Went on the street.

Table 1 shows the results of examining the surface roughness of the final cold-rolled sheet obtained in comparison with the case of following the conventional method.

As is clear from the table, by performing each pass reversal rolling according to the present invention, the surface roughness of the steel sheet is smaller than that of the conventional method on both the front and back surfaces, and the roughness ratio is also reduced. .

It was also investigated further obtained iron loss value of the product sheet, oriented silicon steel sheets obtained according to this invention, than conventional materials, was improved in W _15/60 as 0.04 W / kg.

(Effects of the Invention) Thus, according to the present invention, not only the surface roughness of the cold-rolled sheet but also the front-to-back surface roughness ratio during the production of a grain-oriented silicon steel sheet can be significantly reduced as compared with the conventional material. It can greatly contribute to the improvement of magnetic properties.

[Brief description of the drawings]

FIG. 1 is a graph comparing the front and back surface roughness ratios at the time of i-pass and (i + 1) -pass when the second cold rolling is performed according to the method of the present invention and the conventional method.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Kunio Kitamura 1st Kawasaki-cho, Chiba-shi, Chiba Kawasaki Steel Corporation Research and Development Headquarters

Claims (1)

(57) [Claims] (1) A silicon-containing steel slab is hot-rolled to a final thickness by two cold rollings including an intermediate annealing, followed by a decarburization / primary recrystallization annealing and a final finishing annealing. A method for producing a grain-oriented silicon steel sheet, comprising: performing a second cold rolling step in a plurality of passes, and rolling the sheet while reversing the front and back surfaces of the cold-rolled sheet between each pass. Of controlling the surface roughness of cold-rolled sheet at the time.