JP2679932B2 - Method for manufacturing ultra low iron loss unidirectional silicon steel sheet - 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 unidirectional silicon steel sheet mainly used as an iron core of a transformer or other electric equipment. In particular, it is intended to improve iron loss characteristics by effectively finishing the surface.

[0002]

2. Description of the Related Art Oriented silicon steel sheets are used as magnetic iron cores in many electric appliances. Unidirectional silicon steel sheet
It is a steel sheet containing 0.8 to 4.8% of Si and having the crystal grains of the product highly integrated in the {110} <001> orientation. The magnetic properties are required to have a high magnetic flux density (represented by a B ₈ value) and low iron loss (represented by a W _17/50 value). In particular, recently, there has been an increasing demand for reduction of power loss from the viewpoint of energy saving. In response to this demand, a technique for subdividing magnetic domains has been developed as a means for reducing the iron loss of a unidirectional silicon steel sheet.

In the case of a laminated iron core, a method of subdividing magnetic domains to reduce iron loss by irradiating a steel plate after finish annealing with a laser beam to give a local minute strain is disclosed, for example, in Japanese Patent Laid-Open No. 58-26505. It is disclosed in the publication. Further, in the case of a wound core, a method in which the magnetic domain refining effect is not lost even if strain relief annealing is performed after processing the core is also disclosed in, for example, Japanese Patent Application Laid-Open No. 62-8617. Iron loss has been greatly reduced by subdividing magnetic domains by these technical means.

However, by observing the movement of these magnetic domains, it is found that some magnetic domains do not move. Therefore, in order to further reduce the iron loss value of the unidirectional silicon steel sheet, it is necessary to combine the magnetic domain refinement with the magnetic domain subdivision. It was found that it is important to eliminate the pinning effect from the glass film on the surface of the steel plate that hinders movement.

For that purpose, it is effective not to form a glass film on the surface of the steel sheet which hinders the movement of magnetic domains. As a means, a method which does not form a glass coating film by using a coarse high pure alumina as an annealing separator material, for example, U. S. Patent 3,785,882. However, with this method, it is not possible to eliminate the inclusions just below the surface, and the improvement in iron loss is W _15/60 at most 2.
Only%.

Further, in order to improve iron loss, it is effective to increase the orientational integration degree of the material, and as a method therefor, Taguchi / Sakakura (Japanese Patent Publication No. 40-15644), Komatsu et al. (Japanese Patent Publication No. 62-45285). Japanese Patent Laid-Open Publication) discloses a method using Al nitride as an inhibitor. However, U. to annealing separator material alumina
S. When the method of Patent 3,785,882 is applied to these methods using Al nitride as an inhibitor, secondary recrystallization becomes unstable, and improvement of iron loss cannot be achieved.

On the other hand, as a method of controlling inclusions just under the surface and achieving a mirror-finished surface, a method of performing chemical polishing or electrolytic polishing after finish annealing is disclosed in, for example, Japanese Patent Laid-Open No. 64-64-
No. 83620. However, chemical polishing, electrolytic polishing, and other methods can process small sample materials at the laboratory level, but for industrial scale processing, chemical concentration control, temperature control, and provision of pollution equipment are required. There is a big problem in terms of such things, and it has not yet been put to practical use.

[0008]

DISCLOSURE OF THE INVENTION The present invention is directed to a method which does not form a glass film (for example, US Pat.
3), 785, 882), the above-mentioned problem (1)
Instability in secondary recrystallization of high magnetic flux density materials such as Taguchi and Sakakura (Japanese Patent Publication No. 40-15644) and Komatsu (Japanese Patent Publication No. 62-45285) that use Al nitrides as inhibitors And (2) a method for improving iron loss by solving the presence of inclusions under the surface.

[0009]

[Means for Solving the Problems] The present inventors first of all solve the problem (1) A of Taguchi / Sakakura (Japanese Patent Publication No. 40-15644), Komatsu et al. (Japanese Patent Publication No. 62-45285), etc.
The cause of the unstable secondary recrystallization of the high magnetic flux density material using the nitride of 1 as an inhibitor was investigated. As a result, it was found that the rapid weakening of the inhibitor during finish annealing was the cause of the unstable secondary recrystallization when the glass film was not formed.

This is because solid solution nitrogen in steel easily escapes from the system without a glass film. Then, various means for suppressing this denitrification were studied, and it was found that it is effective to add Sn, Sb, etc. to the steel to concentrate these elements on the surface before secondary recrystallization ( Japanese Patent Application 4-1
16453).

After that, further investigation was made and it was newly found that the addition of Pb to the steel is effective in stabilizing the secondary recrystallization. Further, as a result of research on the problem (2) of inclusions just below the surface, it was found that the oxide layer formed by decarburization annealing has a great influence on the inclusions. As a result of various studies on the method of eliminating the inclusions, it was found that it is very effective to remove the oxide layer of the plate after decarburization, and the iron loss is remarkably improved.

The present invention will be described in detail below. By weight,
Si: 3.3%, Mn: 0.14%, C: 0.05%,
S: 0.007%, acid-soluble Al: 0.028%, N:
0.008%, Pb: 0-0.1% silicon steel slab 1
After heating at 150 ° C., it was hot rolled to a plate thickness of 2.0 mm. This hot-rolled sheet was annealed at 1100 ° C for 2 minutes, and then the final sheet thickness was 0.2.
Cold rolled to 3 mm. This cold-rolled sheet was annealed at 850 ° C. for 70 seconds in a wet gas for decarburization to carry out primary recrystallization.

Then, the amount of nitrogen was increased to 0.02% by ammonia nitriding to strengthen the inhibitor, and then the surface oxide layer was removed by pickling. After the annealing separator material containing alumina as a main component was applied electrostatically to the samples were subjected to finish annealing. Finish annealing is N ₂ : 25% -up to 1200 ° C.
H ₂ was performed at a temperature rising rate of 10 ° C./hr in an atmosphere gas of 75% and switched to H ₂ : 100% at 1200 ° C. and purified annealing was performed for 20 hours.

1 and 2 show the magnetic properties and the secondary recrystallized structure of the products of these samples after the tension coating treatment and the magnetic domain refinement treatment by laser irradiation. From FIG. 1 and FIG. 2, it can be seen that the secondary recrystallization was stabilized in the sample in which Pb: 0.001% or more was added. This is due to the inhibitor (Al
It is considered that this is because deterioration of N, (Al, Si) N, etc. is suppressed. It is also considered that this is because Pb becomes a barrier of denitrification by concentrating on the surface.

Next, an embodiment will be described. In order to increase the magnetic flux density of a steel sheet, a manufacturing method using AlN and MnS as main inhibitors by Taguchi, Sakakura et al.
No. 15644) or by Komatsu et al. (Al, S
i) A production method using N as a main inhibitor (for example, Japanese Patent Publication No. 62-45285) may be applied. In this case, Pb was added to thicken the surface before secondary recrystallization,
It is essential to suppress denitrification from the interface and stabilize the Al nitride inhibitor.

The amount of Pb added is 0.001% in order to thicken the surface during finish annealing and suppress denitrification.
Above, preferably 0.005% or more needs to be added. In terms of magnetic flux density, the upper limit is 0.005%
Although almost the same value was obtained up to 0.1%,
If added in excess of 0.05%, the shape (hot rolled edge portion) deteriorates, so it is desirable to set it to 0.05% or less.

Annealing separation when stacking decarburized annealing plates
As the material, a material that does not react with silica on the surface of the steel sheet or a material that does not easily react may be used. (1) Al ₂ O ₃ ,
SiO ₂ , ZrO ₂ , BaO, CaO, SrO, Mg ₂
Use a powder of a substance such as SiO _{4 in a} state where hydrated water is not brought in by a method such as electrostatic coating, or (2) A
l ₂ O ₃ , SiO ₂ , ZrO ₂ , BaO, CaO, Sr
Using a plate on the surface of which a substance such as O or Mg ₂ SiO ₄ is present, or (3) Al ₂ O ₃ , SiO ₂ , ZrO ₂ , BaO, CaO having an average particle size of 0.5 to 10 μm ,
An effective method is to remove the hydrated water by applying a powder of a substance such as SrO or Mg ₂ SiO _{4 in} the form of a water slurry and then drying it.

When applied as a water slurry, the particle size is 1
If it is 0 μm or more, coarse alumina will bite into the steel sheet, and if it is 0.5 μm or less, it will be active and will easily seize on the steel sheet. The product after finish annealing is subjected to tension coating treatment and magnetic domain refinement treatment such as laser irradiation.

[0019]

【Example】

Example 1 Si: 3.3% by weight, Mn: 0.12%, C: 0.0
5%, S: 0.007%, acid-soluble Al: 0.026
%, N: 0.008%, Pb: 0.01%, a silicon steel slab was heated at 1150 ° C., and then hot rolled to a plate thickness of 1.8 mm. The hot rolled sheet was annealed at 1100 ° C. for 2 minutes and then cold rolled to a final sheet thickness of 0.2 mm. This cold-rolled sheet was annealed at 850 ° C. for 70 seconds in a wet gas for decarburization to carry out primary recrystallization. Then, by annealing at 750 ° C. in an ammonia atmosphere, the amount of nitrogen was increased to 0.02% to strengthen the inhibitor.

After removing the oxide layer on the surface by pickling, the plate is partially coated with (1) alumina having an average particle size of 1 μm in a water slurry, and (2) magnesia in a water slurry state. Was applied, laminated, and finish-annealed. The finish annealing was performed up to 1200 ° C. in an atmosphere gas of N ₂ : 100% at a temperature rising rate of 10 ° C./hr, and the annealing was switched to H ₂ : 100% at 1200 ° C. for 20 hours for purification annealing.
After subjecting these samples to a tension coating treatment, the samples were subjected to laser irradiation to refine magnetic domains. Table 1 shows the magnetic properties of the obtained products.

[0021]

[Table 1]

It can be seen that when the alumina is applied, the iron loss value is about 10% lower (good) than when the magnesia is applied in the form of a water slurry.

Example 2 By weight, Si: 3.2%, Mn: 0.08%, C: 0.
08%, S: 0.025%, acid-soluble Al: 0.025
%, N: 0.009%, Pb: 0.008% of a silicon steel slab was heated at 1320 ° C. and then hot-rolled to a plate thickness of 2.3 mm. This hot-rolled sheet was annealed at 1050 ° C. for 2 minutes and then 0.2
Cold rolled to a thickness of 0 mm.

This cold-rolled sheet also serves as decarburizer in wet gas.
It was annealed at 0 ° C. for 90 seconds for primary recrystallization. Part (A) of this steel sheet is pickled to remove the oxide layer on the surface, and part (B) is directly coated with alumina having an average particle size of 1.0 μm in a water slurry and dried, followed by finish annealing. did.

The finish annealing is Ar: 10 up to 1200 ° C.
In a 0% atmosphere gas at a heating rate of 15 ° C./hr,
Purification annealing was performed at 200 ° C. for 20 hours by switching to H ₂ : 100%. After subjecting these samples to a tension coating treatment, the samples were subjected to laser irradiation to refine magnetic domains. Table 2 shows the magnetic properties of the obtained products.

[0026]

[Table 2]

It can be seen that iron loss is further improved (lowered) by removing the oxide layer formed by decarburization annealing.

Example 3 After the pickling of the decarburized plate of Example 2, a part of (A) a steel plate with forsterite (Mg ₂ SiO ₄ ) on the surface was inserted, and (B) an average particle size of 3 μm. Electrostatic coating of silica, (C)
Zirconia having an average particle size of 3.3 μm was electrostatically applied, and (D) strontium oxide having an average particle size of 3.0 μm was electrostatically applied and laminated. After that, finish annealing was performed to achieve secondary recrystallization and surface mirror finishing. After subjecting these samples to tension coating, laser irradiation was performed to subdivide the magnetic domains. Table 3 shows the magnetic properties of the obtained products.

[0029]

[Table 3]

[0030]

According to the present invention, during finish annealing, (1) smoothing of irregularities on the surface of a steel sheet, which is a factor of deteriorating iron loss characteristics, and (2) crystal orientation control by secondary recrystallization for improving magnetic flux density. Can be simultaneously achieved, so that a unidirectional silicon steel sheet having good magnetic properties can be manufactured at low cost.

[Brief description of the drawings]

FIG. 1 is a table showing the relationship between the amount of Pb added and the magnetic properties (B ₈ ) of products.

2 (a), (b) and (c) are schematic views of a macrostructure after finish annealing (length 160 mm × width 60 mm).

FIG. 3 is a table showing the effect of Pb addition in steel on the change of the inhibitor (indicated by the amount of nitrogen) during finish annealing.

Claims (5)

(57) [Claims] 1. By weight: Si: 0.8 to 4.8%, acid soluble Al: 0.012 to 0.05%, N ≤ 0.01%, balance, substantially from Fe and unavoidable impurities. Become silicon heat
After the steel strip is annealed or not annealed, it is cold rolled once or twice or more with intermediate annealing to obtain a final sheet thickness, and then decarburization annealed and nitrogen-enhanced, and then the steel sheet. By using a substance that does not react with silica or is difficult to react as an annealing separator between plates when stacking
In the method for producing a mirror-oriented silicon steel sheet having a mirror-finished surface after finish annealing, Pb is 0.0 by weight as an element in the steel.
A method for producing an ultra-low iron loss unidirectional silicon steel sheet, characterized by stabilizing secondary recrystallization by adding at least 01%. 2. The method according to claim 1 , wherein after the decarburization annealing, the oxide layer formed by the decarburization annealing is removed. 3. An annealing separator, Al ₂ O ₃ , SiO
₂ , ZrO ₂ , BaO, CaO, SrO, Mg ₂ SiO
Claim is characterized by using ₄ one or a powder composed of two or more in a state of not bring hydration water 1 or
3. The method according to 2 . 4. An annealing separator, Al ₂ O ₃ , SiO
₂ , ZrO ₂ , BaO, CaO, SrO, Mg ₂ SiO
The method according to claim 1 or 2 , wherein a plate having on its surface a substance consisting of one or more of ₄ is used. 5. As an annealing separator, Al ₂ O ₃ , SiO ₂ , ZrO ₂ , BaO having an average particle size of 0.5 to 10 μm ,
The method according to claim 1 or 2 , wherein a powder of one or more of CaO, SrO, and Mg ₂ SiO ₄ is made into a slurry and applied to the steel sheet.