JP3169427B2 - Method for producing bidirectional silicon steel sheet with excellent magnetic properties - 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 bidirectional silicon steel sheet having excellent magnetic properties.

[0002]

2. Description of the Related Art An iron-based material has a feature that the energy state of electrons carrying magnetism differs depending on the direction with respect to the crystal axis, and the material is easily magnetized in the direction of the Miller index <100> axis. Utilizing this crystal magnetic anisotropy, a unidirectional magnetic steel sheet used for a magnetic core of a transformer or the like has a Miller index of ｛11.
Only crystal grains expressed as 0｝ <001> (called Goss orientation) were selectively grown, and the magnetic permeability in one direction in the plane of the steel sheet was dramatically improved.

[0003] This grain-oriented electrical steel sheet ({110} <00
1)) in two orthogonal directions in the plane of the steel sheet.
Biaxially oriented electrical steel sheet with oriented axis (mirror index of $ 10
0 <001>) is a more ideal soft magnetic material. However, since the industrial process is complicated, sufficient magnetic properties cannot be obtained, so that the bidirectional magnetic steel sheet has not been widely used as a core material.

[0004] Conventional methods for producing a bidirectional magnetic steel sheet are roughly classified into the following three methods. 1) A method using a directional ingot made of columnar grains. In this method, as disclosed in JP-B-33-7509 or JP-B-33-7952, an ingot in which columnar grains are developed while maintaining a temperature gradient is produced, and the direction of extension of the columnar grains is constant. In this method, cold rolling is performed in a direction that satisfies the angular relationship, and recrystallization is performed. The point of this method is that, as described in JP-B-33-7953, if the deviation from the {100} <001> orientation of the material is within a certain allowable range, the material is again {100} <001> after cold rolling and recrystallization. Orientation of the crystal grains.

2) A method using surface energy. This method is described in JP-B-36-8554 and JP-B-37-7.
As disclosed in Japanese Patent Publication No. 110 or Japanese Patent Publication No. 38-16212, the atmosphere of the heat treatment is controlled when cold rolling and recrystallizing a thin material, so that only the crystal grains having {100} planes on the surface of the plate. Is recrystallized.

3) A method of cold-rolling cloth. In this method, as disclosed in Japanese Patent Publication No. 35-2657, after a silicon steel material is cold-rolled in one direction, further cold-rolled in a direction crossing the cold-rolled material, a short-time annealing and 900 ~ 1300 ° C
This is a method of performing high-temperature annealing of. The principle of this method is that a cold rolled cloth develops a texture that becomes a base on which {100} <001> oriented grains are easily grown, and a secondary recrystallization using an inhibitor of grain growth such as AlN causes a {100} orientation. ｝
<001> Orientation grains are developed.

[0007]

As described above, as described above,
Although the bidirectional electrical steel sheet is an ideal magnetic material in which two of the three easy axes are oriented in the plane of the steel sheet, it has hardly been used industrially to date. This is because, although it is extremely difficult to industrially perform the manufacturing method devised up to the present, the degree of integration of the crystal orientation as expected cannot be obtained.

For example, in the method 1) using a directional ingot, in order to sufficiently develop columnar grains, it is necessary to cool the bottom surface while heating the side surface of the mold and to give a temperature gradient to the molten steel. Mass production as a process has been extremely difficult.

In the method 2) using surface energy, it is industrially difficult to strictly control the atmosphere of the heat treatment so that only {100} oriented grains grow, and in principle, The <100> axis orientation in the plane of the plate cannot be aligned.

In the method 3) using the cross cold rolling, a considerably high crystal orientation can be obtained and a considerably high magnetic permeability can be expected in two directions in the plane of the sheet. However, this method is an improved patent of Japanese Patent Publication No. 35-2567. According to the examples of JP-B-38-8213, the magnetic flux density with respect to an exciting force of 800 A / m is 1.92.
5T is the highest, and it cannot be said that a sufficiently high degree of integration was obtained.

[0011]

[Means for Solving the Problems] For a cross-rolled material,
It was mentioned earlier that a bi-directional electrical steel sheet having a considerably high degree of crystal orientation can be obtained by developing secondary recrystallization using an inhibitor of grain growth. The present inventors have invented a method for obtaining a bidirectional electrical steel sheet which can be sufficiently put to practical use by improving the method using the cross cold rolling.

That is, in terms of weight ratio, Si: 1.8 to 6.7.
%, C: 0.1% or less, acid-soluble Al: 0.010-0.
050%, N: 0.0010 to 0.0120%, C:
Cold rolling is performed on a silicon steel sheet containing 0.15% or less, the balance being Fe and unavoidable impurities, at a rolling reduction of 40 to 80%, and further, 30 to 70% cold rolling is performed in a direction perpendicular to the cold rolling. . Next, annealing for primary recrystallization at an average temperature rising rate of 200 ° C. to 800 ° C. of 10 ° C./min or more is performed, followed by secondary recrystallization and final annealing for purification. It has been found that a bidirectional silicon steel sheet extremely well integrated in the {100} <001> direction can be obtained by the above steps.

Hereinafter, the present invention will be described in detail. Regarding the component, Si is added to increase the electrical resistance of the material and improve the soft magnetic properties in an alternating magnetic field, but the lower limit is 1.8% in order to suppress the destruction of the crystal structure due to α-γ transformation during final annealing. Set to. If Si exceeds 4.8%, cracks occur and cold rolling becomes difficult, but since rolling can be performed by warm rolling, the upper limit is 6.7%, which is effective for improving soft magnetic properties.

The lower limit of the content of acid-soluble Al is set to 0.010% in order to secure an inhibitor of grain growth for performing secondary recrystallization in final annealing. If the amount is too large, the secondary recrystallization becomes unstable, so the upper limit is set to 0.050%.

N is effective as AlN to strengthen the inhibitor, so the lower limit was made 0.0010%. If the content exceeds 0.0120%, a defect called a blister occurs in the steel sheet.
%.

[0016] In addition, MnS, Cu ₂ S, MnSe, Nb (C, N),
One or more selected from Sn, Sb and the like can be included in a known range. The silicon steel slab composed of the above components is heated and hot rolled.

Thereafter, the hot-rolled sheet may be annealed to eliminate the rolled structure, but it is more preferable to perform annealing at a temperature of 900 ° C. or more which is sufficient to eliminate the hot-rolled structure.

Next, cold rolling is performed in the hot rolling direction at a rolling reduction of 30 to 70% at a rolling reduction, and 40
Perform ~ 80% cold rolling. This condition is in Japanese Patent Publication No. 35-265.
The conditions are the same as those disclosed in Japanese Patent Publication No.

This steel sheet is subjected to a short annealing for the purpose of primary recrystallization. The temperature range is not particularly limited, but is preferably 700 ° C. or higher in order to completely perform the primary recrystallization. An oxidizing atmosphere can also be used for the purpose of removing the C component that deteriorates the magnetism of the silicon steel sheet by this annealing.

In the annealing for the purpose of the primary recrystallization, the present inventors controlled the average heating rate from 200 ° C. to 800 ° C. to 10 ° C./min or more, thereby reducing
It has been found that a bidirectional silicon steel sheet having a high degree of integration in the 0 ° <001> direction can be manufactured.

Then, final annealing is performed for the purpose of secondary recrystallization and purification. The temperature range of these annealings is not particularly limited, but is 900 ppm in order to completely develop and purify secondary recrystallization.
High-temperature annealing at a temperature of at least ℃ is desirable.

Further, in order to stabilize the secondary recrystallization, the steel sheet may be nitrided after the completion of the primary recrystallization but before the start of the secondary recrystallization. This nitriding method involves mixing a nitriding gas such as N ₂ or NH ₃ into the atmosphere of the final annealing,
A method of adding a nitriding substance such as ferromanganese nitride to the annealing separator at the time of final annealing, a method of treating in an atmosphere containing a nitriding gas such as NH ₃ after the soaking process of primary recrystallization annealing, etc. Either is fine.

By the above process, a bidirectional silicon steel sheet having a high accumulation of <100> axes in two directions perpendicular to each other in the plane of the sheet can be obtained. That is, according to the present invention, it is possible to obtain a bidirectional silicon steel sheet having a high degree of orientation integration by utilizing secondary recrystallization.

[0024]

【Example】

(Example 1) Si: 3.1% by weight ratio, C: 0.055
%, Al: 0.028%, N: 0.0075%, and the balance of Fe and inevitable impurities was 11%.
It was heated to 00 ° C. and hot rolled to a thickness of 1.8 mm. After the hot-rolled sheet is annealed at 1100 ° C. for 2 minutes, the steel sheet is cold-rolled in the same direction as hot-rolling to a thickness of 1.0 mm, and cold-rolled to a thickness of 0.5 mm perpendicular to the cold-rolling direction. Rolled.

The cold rolled sheet was annealed in wet hydrogen at 850 ° C. × 5 minutes for both decarburization and primary recrystallization. In the process of raising the temperature of this annealing, the temperature rising rate from 200 ° C. to 800 ° C. was linearly increased by 5 ° C./min, 8 ° C./min, 12 ° C./mi.
n, 100 ° C./min, and 800 ° C./min, respectively.

Next, after applying an annealing separator mainly composed of MgO, annealing was performed at 1200 ° C. for 20 hours. The atmosphere at the time of this annealing was N ₂ : 25 when the temperature was raised to 1200 ° C.
%, H ₂ : 75%, H ₂ : 100 when soaking at 1200 ° C.
%Met.

The exciting force of the bidirectional silicon steel sheet obtained by the above process in the hot rolling direction and in the direction perpendicular thereto is 800 A / m.
Table 1 shows the results of the magnetic flux density at.

[0028]

[Table 1]

(Example 2) Si: 3.0% by weight,
C: 0.047%, Al: 0.024%, N: 0.00
A silicon steel slab containing 75%, the balance being Fe and unavoidable impurities, was heated to 1250 ° C. and hot-rolled to a thickness of 1.6 mm. This hot-rolled sheet is annealed at 1000 ° C. for 1 minute, cold-rolled to a thickness of 0.8 mm in the same direction as the hot-rolled sheet, and cold-rolled to a thickness of 0.35 mm in a direction perpendicular to the cold-rolling direction. Rolled.

Further, decarburization at 820 ° C. for 4 minutes in wet hydrogen and annealing for primary recrystallization were performed. During the annealing process, the temperature was raised to 500 ° C for 0 min and 1 min, respectively.
, 10 min, and 100 min, and the average heating rate was changed. 1200 ° C heating rate other than retention time
/ Min.

Next, at 800 ° C. in an atmosphere containing NH _3.
For 30 seconds, and after applying an annealing separator mainly composed of MgO, annealing was performed at 1200 ° C. for 20 hours.
The atmosphere during this annealing is as follows: N ₂ : 10% when the temperature is raised to 1200 ° C., H ₂ : 90%, and H when the temperature is uniform at 1200 ° C.
₂ : 100%. Table 2 shows the measured values of the magnetic flux densities of the 0.35 mm thick silicon steel sheet thus obtained in the hot rolling direction and the perpendicular direction. It can be seen that the magnetic properties are improved under the temperature rising conditions in the range of the present invention.

[0032]

[Table 2]

[0033]

According to the present invention, it is possible to obtain a bidirectional silicon steel sheet having excellent magnetization characteristics particularly in a medium magnetic field.

──────────────────────────────────────────────────続 き Continued on the front page (58) Fields surveyed (Int. Cl. ⁷ , DB name) C21D 8/12 C21D 9/46 501 C22C 38/00-38/60

Claims (1)

(57) [Claims] 1. Si: 1.8 to 6.7% by weight, acid-soluble Al: 0.010 to 0.050%, N: 0.0120% or less by weight, silicon consisting of the balance Fe and inevitable impurities The steel sheet is cold-rolled at a rolling reduction of 40 to 80%, and further cold-rolled at a rolling reduction of 30 to 70% in a direction perpendicular to the cold rolling.
Average temperature rise rate from 00 ° C to 800 ° C is 10 ° C / min
A method for producing a bidirectional silicon steel sheet having excellent magnetic properties, comprising: performing annealing for primary recrystallization as described above, and then performing final annealing for secondary recrystallization and purification.