JPS60131917A - Manufacture of silicon steel sheet - Google Patents

Abstract

PURPOSE:To manufacture efficiently silicon steel sheets having favorable magnetic characteristics by hot rolling silicon steel blanks and cold rolling the resulting two steel strips in an overlapped state after reducing the surface roughness of the contacting surfaces of the strips. CONSTITUTION:Silicon steel blanks contg. <=40wt% Si are hot rolled, and the resulting steel strips are cold rolled once to provide the final thickness. The steel strips may be cold rolled twice or more while carrying out process annealing between the cold rolling stages. In at least one of the cold rolling stages, the two steel strips are cold rolled in an overlapped state, and the average surface roughness Ra of at least the contacting surfaces of the strips is reduced to <=0.8mum by smoothening before the cold rolling. By the smoothening, silicon steel sheets having favorable characteristics can be obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing silicon steel sheets used as core materials for transformers, electric motors, and the like.

As is well known, silicon steel sheets can be broadly divided into grain-oriented silicon steel sheets and non-oriented silicon steel sheets, and they are used depending on the purpose. When manufacturing grain-oriented silicon steel sheets, it is necessary to align the crystal orientation of the material steel strip in one or two directions during the manufacturing process, and even when manufacturing non-oriented silicon steel sheets, it is necessary to coarsen the crystal grains. Generally speaking, silicon steel sheets require a complicated process of hot rolling a silicon steel slab, followed by repeated annealing and cold rolling, and finally surface treatment. Manufactured through. In addition, the demands for improving the performance of silicon steel sheets by reducing their core loss and increasing their magnetic flux density are becoming more and more severe year by year. As a result, the manufacturing process of silicon steel sheets has become even more complicated, and an increase in manufacturing costs due to the complication of such a process has become a problem.

The present invention has been made in view of the above-mentioned conventional circumstances, and is capable of meeting the demands for improving the performance of silicon steel sheets, and of efficiently manufacturing silicon steel sheets and reducing manufacturing costs. The purpose of the present invention is to provide a method for manufacturing silicon steel sheets that can be manufactured using the following methods.

By the way, in the production of composite metal plates, a method has been used in the past in which two metal plates are piled up and hot rolled. For example, Japanese Patent Publication No. 51-19819 describes a method of hot rolling plywood of dissimilar metals. Teishi, and even Tokukai Sho 5
Publication No. 7-121804 describes a method for manufacturing ultra-thin steel sheets by applying similar means to cold rolling of steel sheets and improving the manufacturing efficiency. However, when such a method is applied to the production of silicon steel sheets, magnetic properties that meet the requirements cannot be obtained, so there have been no examples of applying the above-mentioned method to the cold rolling of silicon steel sheets.

Therefore, the present inventors applied the above-mentioned method to the production of a silicon steel plate, and if satisfactory magnetic properties were obtained, the present invention would improve the production efficiency of the silicon steel plate and improve the magnetic properties. Based on the premise that the above objective can be achieved, we investigated the reason why sufficient magnetic properties could not be obtained by the above-mentioned method, and the following findings were obtained.

In other words, the surface roughness (Ra) of a steel plate before cold rolling is usually at least about 1 μm, but when the steel plate is lap-rolled, the surface of the steel plate that does not come into contact with the rolling rolls, that is, the two copper strips, The surface roughness of the mating surfaces is 1.5 to 2 μm
Therefore, when a rolled steel sheet with such a large surface roughness is subsequently annealed, the surface oxidation layer becomes thick, and as a result, good magnetism cannot be obtained.

Based on the above findings, the present inventors found that good magnetic properties can be obtained by increasing the smoothness of the steel plate surface before lap rolling and reducing the surface roughness of the mating surface of the steel plates after lap rolling. He came up with an invention.

That is, the method for manufacturing a silicon steel sheet of the present invention has a manufacturing method of 4.0% (
Manufacture of a silicon steel plate by hot rolling a silicon steel material containing Si (weight%, same hereinafter) or less, and obtaining the final thickness by one cold rolling or two or more cold rollings with intermediate annealing in between. In the method, cold rolling is performed at least once in the cold rolling process by overlapping two raw material steel strips, and the average ( It is characterized by smoothing Ra) to 0.8 μm or less in advance.

Next, this invention will be explained in more detail.

In this invention, a silicon steel material containing 8i of 40 or less is used. If Si is contained in excess of 4.0 inches, plate cracking will occur during cold rolling, making cold rolling impossible.
The Sr content is limited to 4.0% or less.

1. In grain-oriented silicon steel materials, MnS is used as an inhibitor to selectively develop secondary recrystallization in the Goss orientation.
A required amount of lai or two or more components selected from MnSe, AJl'N, Sb, BN, etc. is contained.

On the other hand, regarding non-oriented silicon steel sheets, in addition to Si, AA”P
Mn is 2. (It is possible to include more than 1 F.

First, a silicon steel slab having the above-mentioned composition is heated, for example, from 1100 to 1
After heating to a required temperature of 400° C., hot rolling is performed to obtain a hot rolled steel strip having a required thickness, for example, 1.0 to 3.5 inches thick.

The hot-rolled steel strip is then annealed and annealed an additional number of times, e.g. 2
The final product with the target thickness is obtained by repeating cold rolling and annealing.

In the present invention, at least one cold rolling process out of the required number of times, for example, two cold rolling processes, is performed on the above-mentioned hot rolled steel strips by overlapping two raw steel strips. Cold rolling, that is, lap rolling, in which two raw steel strips are overlapped, can be performed using a well-known reverse mill or tandem mill, and the reduction rate and reduction distribution during rolling are determined according to the target product thickness. and the characteristics of the rolling mill. Further, during rolling, it is desirable to place two raw material steel strips in a superposed state in advance. 1st
The figure shows an example of a line in which two raw steel strips are overlapped in advance before rolling. A pair of raw steel strips 2 drawn out from a pair of hot-rolled coils 1 are continuously annealed by passing through a two-stage continuous annealing furnace 3, and a roll disposed on the exit side of the two-stage continuous annealing furnace 3. 4. They are passed through a roll 5, overlapped with each other, and wound up in that state to form a coil 6. By overlapping the raw steel strips in advance to form the coil 6, the two copper strips are overlapped with their widthwise edges aligned in advance and subjected to the rolling process. This makes it possible to improve the efficiency of rolling and prevent rolling. Furthermore, in the present invention, when performing the above-mentioned lap rolling, the average roughness (Ra) of at least the mating surface side surface of the raw copper strip before the lap rolling is set to 0.8 μm or less and smoothed in advance.

This means that the surface average roughness (Ra) of the mating surface side of the raw steel strip is 0.
．． This is because if it exceeds 8 μm, the surface roughness of the mating side after over-rolling becomes excessive, which causes deterioration of the magnetic properties of the product. In order to support this, FIG. 1 shows the results of measuring iron loss for products obtained by overlapping rolling of raw steel strips with various surface roughnesses.

Figure 2 shows that when finishing a hot-rolled plate of grain-oriented silicon steel material containing 3.2% 8i to a plate thickness of 0.23mm by two cold rollings, the second cold rolling was performed on two steel strips. This figure shows the final product obtained by superimposing the above, followed by decarburization annealing and box annealing. As shown in the figure, when the surface roughness of the raw steel strip exceeds 08 μm, the iron loss also increases.
When exceeding Q w/Al, the iron loss increases rapidly as the roughness increases. The surface roughness of the raw steel strip to be lap-rolled is previously smoothed to 0.8 μm or less by the following method. Normally, when cold rolling silicon steel material, in order to remove oxides from the surface of the material steel strip before pressing,
Pickling is performed using flowing acid or hydrochloric acid. However, this pickling treatment of the raw steel strip significantly increases the surface roughness of the raw steel strip. Therefore, as a final measure to smooth the surface of the raw copper strip after pickling, or as a treatment in place of pickling, chemical polishing or mechanical polishing is performed, or the raw steel strip is passed between skin pass rolls. Smooth the surface of the raw steel strip. Furthermore, when cold rolling is performed separately before lap rolling, the surface roughness of the rolls used for cold rolling is reduced, or intermediate annealing is performed in an inert gas atmosphere to minimize surface oxidation. It is desirable to minimize the number of scratches from the hearth roll.

Finally, the steel plate that has been cold-rolled to the target thickness is subjected to decarburization annealing and box annealing in the case of grain-oriented silicon steel plates, and is further coated to produce the final product. Also,
Non-oriented silicon steel undergoes recrystallization annealing and coating treatment to produce the final product.

Next, examples of this invention will be described.

Example 1゜CO, 040%, Si 3.25%, Mn 0
．． 060'%.

A 2 to 3 m thick hot rolled steel strip containing 0.020% Se and 0.025% SbO was first cold rolled to 060fi.
After finishing to a thick finish, intermediate annealing was performed at 1000° C. for 3 minutes in a continuous annealing furnace. Thereafter, second cold rolling was performed by lap rolling using a reverse mill to obtain a silicon steel plate with a thickness of 0.23 wm. 5 at 800℃ for the silicon steel plate
Decarburization annealing is performed for 1 minute in a wet hydrogen atmosphere, and the surface of the steel plate is M
After applying gO, box annealing was performed at 1200° C. for 5 hours in a hydrogen stream. In particular, in this Example 1, the above-mentioned intermediate annealing was performed in a reducing H2 atmosphere, and the surface roughness Ra of the raw steel strip before lap rolling was set to 0.2611 m.

Comparative Example 1゜Similar to the above-mentioned Example 1 except that intermediate annealing was performed using N,
The surface roughness R of the raw steel strip before lap rolling is carried out in an atmosphere.
a was set to 105 μm.

Example 2 CO, 002%, Si 3. lOS, Mn
0.21%.

AA! After annealing a 1.8 fi thick hot rolled steel strip containing 0.58% at 900°C for 5 minutes, the surface oxide was removed by pickling with 10% H2SO4, and then the surface oxide was removed with 10% HF.
+ Surface roughness reduced to 0.46μ by chemical polishing in H2O2 bath
m, and then during cold rolling, lap rolling was performed using a tandem mill to obtain a non-oriented silicon steel plate with a thickness of Q, 35t+on. 920 for steel plates after cold rolling
Recrystallization annealing for 5 minutes at 0.degree. C. was carried out in dry hydrogen, and the product was coated.

Comparative Example 2 The same material as in Example 2 was subjected to the same treatment to remove surface oxides, and then the material steel plate was wound into a coil shape and rolled. The surface average roughness Ra of the raw steel sheet before lap rolling was 3.5 μm. Thereafter, a non-oriented silicon steel plate was obtained in the same manner as in Example 2.

The magnetic properties of the silicon steel sheets obtained in each of the above Examples and Comparative Examples were investigated. The results are shown in Tables 1 and 2.

As can be seen from Table 1, Table 2, and Table 1, Example 1 in which this invention was implemented
Compared to Comparative Example 1, the iron loss is smaller and the magnetic flux density B10
The value was large, and good results were obtained. Similarly, as shown in Table 2, in Example 2 in which the present invention was implemented, the iron loss was significantly smaller than in Comparative Example 2.

As described above, according to the method for manufacturing a silicon steel sheet of the present invention,
Two raw material steel strips after hot rolling are stacked and cold rolled, and the average roughness (Ra) of the surface of at least the mating surface side of the raw material steel strips before the stacking and cold rolling is determined in advance. 0
, 8 μm or less, it is possible to efficiently manufacture a silicon steel sheet having good magnetic properties.

[Brief Description of the Drawings] Fig. 1 is a schematic diagram showing an example of a line in which two raw steel strips are overlapped in advance before cold rolling in order to carry out the present invention, and Fig. 2 is a Various surface roughness Ra (μm
Fig. 3 is a diagram showing the iron loss W+7750 (wAg) of the product obtained by superimposing and cold-rolling the raw steel strips of 1.) and illustrating the results in relation to the surface roughness. DESCRIPTION OF SYMBOLS 1...Hot rolled coil, 2...Material steel strip, 3...2-stage continuous m blunt furnace, 4...Ronil, 5...Roll, 6...
·coil.

Claims (1)

[Claims] A silicon steel material containing 4.0% by weight or less of Si is hot rolled, and the final plate thickness is reduced by one cold rolling or two or more cold rollings with intermediate annealing in between. In the method for producing a silicon steel sheet, at least one cold rolling step is performed in the cold rolling process by overlapping two raw material steel strips, and at least the mating surface of the raw material steel strips before the overlapping cold rolling. A method for manufacturing a silicon steel sheet, characterized in that the average (Ra') of the side surface is smoothed in advance to 0.8 μm or less.