JP2991908B2 - Method for producing non-oriented electrical steel sheet having excellent magnetic flux density - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a non-oriented electrical steel sheet used for a rotating machine for home appliances or industrial use or a small transformer such as an EI core.

[0002]

2. Description of the Related Art From the viewpoint of global environmental problems and effective utilization of fossil energy resources, improvement of the efficiency of electric equipment, which is a component consuming energy, is an important issue today. For this reason, there is a strong demand for non-oriented electrical steel sheets, which are often used in electrical equipment, to reduce the iron loss and to improve the magnetic flux density effective for the copper loss.

As a means for improving the magnetic properties, a method for controlling the finish rolling temperature in hot rolling is known, for example, from Japanese Patent Application Laid-Open No. 2-73919. However, the desired hot rolled sheet texture could not be obtained only by controlling the temperature of the hot rolling. Further, after finish rolling of hot rolling is completed, rolling or plastic strain is further introduced on a run-out table, as disclosed in JP-A-60-258414 and JP-A-3-53.
No. 022 is known. Although this method is a new method, it was impossible because of a large capital investment industrially.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for manufacturing a non-oriented electrical steel sheet having an excellent magnetic flux density by an industrially easy method for solving the above-mentioned problems.

[0005]

In order to achieve the above object, the present invention provides: C ≦ 0.01% by weight, Si + Al ≦ 5%, Mn ≦
1.5%, P ≦ 0.2%, S ≦ 0.01%, N ≦ 0.0
When hot rolling a slab consisting of iron and unavoidable impurities, the slab is heated at 950 to 1250 ° C., then the final stand of the finishing tandem rolling mill is reduced to 3 to 17%, and then water is injected. And roll it up,
A method for producing a non-oriented electrical steel sheet having excellent magnetic flux density characterized by performing descaling, cold rolling, and annealing, and adding skin pass rolling at a cold rolling reduction of 2 to 15% after annealing. And a method for producing a non-oriented electrical steel sheet having an excellent magnetic flux density.

The present invention is based on the discovery of the following three points. That is, first, increasing the surface layer grain size of the hot-rolled sheet improves the magnetic flux density of the final product. Second, the rolling reduction of the final stand in the finish rolling in hot rolling governs the crystal grain size of the surface layer of the hot rolled sheet. Third, it is effective that the reduction ratio of the final rolling final stand is 3 to 17%.

Hereinafter, the reasons for limitation of the present invention will be described in detail. If the amount of C is large, the mixed phase of ferrite and austenite increases during hot rolling, which is harmful to crystal grain growth. Naturally, it is preferable to increase the amounts of Si and Al to reduce iron loss. However, if the amounts are too large, a brittleness problem occurs in the cold rolling and the punching process.
The Al content is 5% or less. Mn is effective for obtaining hardness, but is not more than 1.5% because of the problem of addition cost. P increases the strength of the steel sheet and prevents drooping and burrs at the time of punching, but 0.2%
The following is assumed. Since S forms sulfides and deteriorates iron loss, the content of S is set to 0.01% or less. If the N content is too large, blister defects called blisters occur.
% Or less. It should be noted that known Cu, Cr, B, Sn, S
Even if an element that improves the texture such as b is added, the effect of the present invention is not impaired, but the addition amount is preferably 0.2% or less from the viewpoint of cost.

A slab is produced by continuously casting molten steel containing the above elements, and slab heating is performed.
250 ° C. The reason for this is that if the temperature exceeds 1250 ° C., solid solution of sulfides and nitrides occurs, and fine precipitates are generated during hot rolling, so that the purpose of the present invention cannot be achieved by suppressing crystal grain growth. On the other hand, when the temperature is lower than 950 ° C., the load applied to the hot-rolled roll increases, which is a problem in operation.

After the rough rolling, a finishing tandem rolling is performed. The number of finishing stands is usually 3 to 8, but the rolling reduction at the final stand is important. Heretofore, a reduction ratio of 20 to 40% has been commonly used. But,
The present inventors have found that the structure of the hot-rolled sheet is improved by reducing the pressure. 3 reduction of final stand
By limiting to ~ 17%, an excellent magnetic flux density can be obtained. The reason for the limitation is that if it is less than 3%, the rolling reduction is too small, and if it exceeds 18%, the rolling distortion is too large and the magnetic flux density does not improve. This is because of the so-called skin pass effect in cold rolling. It will be a similar phenomenon. In addition, it is more effective if the light pressure reduction is adopted in the stand just before the final stand, but the effect cost is small. In other words, the rolling distribution for each finishing stand is lighter in the rear stage and heavier in the front stage or the middle stage, which is also the idea of the present invention. The thickness of the hot rolled sheet is usually 1 to 5
mm and the finishing temperature is usually 750 to 1100 ° C. Also, the winding temperature is not particularly regulated,
Normally, 500 to 800 ° C. is desirable.

The hot-rolled sheet is pickled without annealing and cold-rolled. The finished thickness after cold rolling is usually 0.2 to 1.5 mm. The recrystallization annealing after the cold rolling is performed in the usual range of 600 to 900 ° C. In addition, in addition to this step, the final cold rolling is performed at a generally known 2 to 15%, and then the grains are grown at the time of strain relief annealing by a customer, so-called semi-process non-oriented electrical steel sheets. Process can also be adopted. Next, examples will be described.

[0011]

EXAMPLE 1 0.004% C, 0.15% S by weight
i, 0.11% Mn, 0.08% P, 0.004% S,
A slab containing 0.003% Al, 0.003% N and substantially the remainder Fe was cast, and the test was carried out by changing the conditions of hot rolling after heating at 1020 ° C as shown in Table 1 below. did. The thickness of the finishing inlet was 35 mm, the finishing was rolled on 6 stands, the winding temperature was 650 ° C., and the thickness of the hot rolled sheet was 2.8 mm. Next, after pickling, it was cold-rolled to 0.5 mm, degreased, and soaked at 800 ° C. for 10 seconds to measure magnetic properties. Magnetic properties Epstein sample (30mm width x 300
mm length) in the rolling direction and the direction perpendicular to the rolling direction.
The measurement was performed according to SC 2550, and Table 1 was obtained.

[0012]

[Table 1]

[0013] As shown in Table 1, the sample Nos. ~ Has a level characteristics where the magnetic flux density B ₅₀ was not obtained more conventional 1.79T.

[0014]

Example 2 0.004% C, 0.15% S by weight ratio
i, 0.11% Mn, 0.08% P, 0.004% S,
A slab containing 0.003% Al, 0.003% N and substantially the remainder Fe was cast, and the test was carried out by changing the conditions of hot rolling after heating at 1020 ° C as shown in Table 1 below. did. The thickness of the finishing inlet was 30 mm, the finishing was rolled on 6 stands, the winding temperature was 650 ° C., and the thickness of the hot rolled sheet was 1.4 mm. Next, after pickling, it was cold-rolled to 0.526 mm, degreased, soaked at 750 ° C. × 10 seconds, and then skin-passed to 0.5 mm to obtain a magnetic property Epstein sample (30 mm width × 300 mm length). ) Was cut out in the rolling direction and a direction perpendicular thereto, and then magnetic annealing was performed at 750 ° C. for 2 hours, and then the magnetic properties were measured. JIS C 255
The measurement was carried out according to 0 and Table 2 was obtained.

[0015]

[Table 2]

[0016]

Example 3 0.002% C, 1.85% S by weight
i, 0.06% Mn, 0.11% P, 0.001% S,
A slab containing 0.262% Al, 0.001% N and the balance substantially consisting of Fe was cast, and the test was conducted by changing the conditions of hot rolling after heating at 1230 ° C as shown in Table 2 below. did. The plate thickness at the finishing entrance was 35 mm, and the finishing was rolled at six stands. Winding temperature 610 ° C, hot rolled sheet thickness 2.1mm
And Next, after pickling, it was cold-rolled to 0.5 mm, degreased, and soaked at 760 ° C. for 30 seconds to measure magnetic properties. Magnetic properties Epstein sample (30mm width x 300
mm length) in the rolling direction and the direction perpendicular to the rolling direction.
The measurement was performed according to SC 2550, and Table 3 was obtained.

[0017]

[Table 3]

[0018]

As described above, according to the present invention, a non-oriented electrical steel sheet having an extremely excellent magnetic flux density can be manufactured by controlling the rolling reduction in a specific rolling mill for hot rolling.

────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Yoshiyuki Masuda 1st Fuji Town, Hirohata-ku, Himeji City, Hyogo Prefecture Nippon Steel Corporation Hirohata Works (72) Inventor Takashi Sadamasa Fujimachi, Hirohata-ku, Himeji City, Hyogo Prefecture No. 1 Nippon Steel Corporation Hirohata Works (56) References JP-A-2-73919 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) C21D 8/12 C22C 38/00 303 C22C 38/06 H01F 1/16

Claims (2)

(57) [Claims] 1. C ≦ 0.01% by weight%, Si + Al ≦
5%, Mn ≦ 1.5%, P ≦ 0.2%, S ≦ 0.01
%, N ≦ 0.004%, and when the slab composed of iron and unavoidable impurities is hot-rolled,
The slab is heated at 0 ° C., and thereafter, the rolling reduction of the final stand of the finishing tandem rolling mill is set to 3 to 17%, and then water is wound and wound, followed by descaling, cold rolling and annealing. A method for manufacturing non-oriented electrical steel sheets having excellent magnetic flux density. 2. The method for producing a non-oriented electrical steel sheet having an excellent magnetic flux density according to claim 1, wherein skin pass rolling is added at a cold rolling reduction of 2 to 15% after annealing.