JP2691837B2 - Method for manufacturing high magnetic flux density grain-oriented electrical steel sheet with good workability - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

FIELD OF THE INVENTION The present invention relates to a grain-oriented electrical steel sheet having no glass coating (forsterite coating), particularly a high magnetic flux density and an ultra-low iron loss orientation which is remarkably excellent in machinability such as cutting property and punching property. The present invention relates to a method for manufacturing an electromagnetic steel sheet.

[0002]

2. Description of the Related Art Grain-oriented electrical steel sheets are generally used as a soft magnetic material, mainly as an iron core of transformers and other electric equipment, and are required to have good magnetic excitation characteristics and iron loss characteristics. It In order to obtain good magnetic properties, it is important that the <001> axis, which is the axis of easy magnetization, is highly aligned in the rolling direction. Further, the plate thickness, the grain size, the specific resistance, the coating, etc. have a great influence on the magnetic properties, and are important.

[0003] Regarding the crystal orientation, AlN, MnS
The method has been greatly improved by a method characterized by final cold rolling under high pressure, using as an inhibitor, and now magnetic flux density has been manufactured to a value close to the theoretical value. on the other hand,
When used in the consumer of grain-oriented electrical steel sheets, what is important along with magnetic properties is workability due to the coating. Usually, the surface of a grain-oriented electrical steel sheet is treated by a two-layer coating of a glass coating and an insulating coating formed at the time of final finish annealing. The glass film is a reaction product of MgO which is an annealing separator and SiO ₂ which is formed during decarburization annealing and is forsterite (Mg ₂
SiO ₄ ) is the main film. This ceramic coating is hard and has strong wear resistance, and exerts a markedly adverse effect on the durability of tools such as slits, cutting and punching when processing electromagnetic steel sheets. For example, when punching a grain-oriented electrical steel sheet having a glass coating, die wear occurs,
By punching a few thousand times, the return of the sheet becomes large when punching, and the return is such that a problem occurs during use. Therefore, it is necessary to re-polish the mold and replace it with a new one. This results in a reduction in the work efficiency of the core processing by the customer and an increase in cost.
Further, although it has an effect of improving iron loss due to the film tension with respect to the magnetic characteristics of the electromagnetic steel sheet itself, there is a problem that the magnetic flux density decreases due to the non-magnetic material due to an increase in the film thickness depending on the formation state. For this reason, in the case of a material such as a steel plate having a large thickness, for which the effect of improving iron loss due to film tension cannot be expected, or in a case where the magnetic domain is subdivided by other means and the iron loss can be improved, the above problem is rather reduced. A grain-oriented electrical steel sheet having no glass coating is desired.

In particular, in recent years, as a magnetic domain subdivision technique, a technique developed by optical, mechanical and chemical means has been developed so that iron loss can be improved without the tension of the glass coating. It has also been found that the grain-oriented electrical steel sheet which does not have the advantage is free from adverse effects such as the internal oxide layer of the glass coating that causes the pinning phenomenon of wall movement during magnetization. Therefore, the development of a high magnetic flux density grain-oriented electrical steel sheet having no glass coating is important for consumers when considering various usage conditions, and needs are increasing.

At present, amorphous alloys are being used as a soft magnetic material in place of grain-oriented electrical steel sheets, but the magnetic flux density is low, the space factor is low, and the workability is poor.
We are facing various difficulties in practical application. Therefore, in order to develop a grain-oriented electrical steel sheet that can counter an amorphous alloy in iron loss characteristics, it has become important to develop a material having no glass coating.

As a method for producing a grain-oriented electrical steel sheet having no glass coating, there is one disclosed in, for example, JP-A-53-22113. This is because the thickness of the oxide film is reduced to 3 μm or less in decarburization annealing, and fine alumina containing 5 to 40% of hydrated silicate mineral powder is used as an annealing separating agent, which is applied to a steel plate and finish-annealed. Become.
According to this, it is said that a glass film that is easy to peel off is formed by thinning the oxide film and further by incorporating a hydrous silicate mineral, and that having a metallic luster is obtained. As a method for suppressing the formation of a glass film by an annealing separator, as disclosed in JP-A-56-65983, annealing is performed by adding 20 parts by weight of an additive for removing impurities of aluminum hydroxide and 10 parts by weight of a suppressing substance. The separating agent is applied to the steel sheet, and
There is a method of forming a thin glass film having a thickness of 5 μm or less. Further, in JP-A-59-96278, Al ₂ O ₃ having a weak reaction with SiO ₂ in an oxide layer formed by decarburization annealing,
Mg whose activity was reduced by firing at a high temperature of 1300 ° C or higher
An annealing separator composed of O and O has been proposed. According to this, formation of forsterite is suppressed.

All of these prior arts are conventional orientations.
The magnetic flux density called the ent core is B ₈Value of 1.88T or less
A low-grade grain-oriented electrical steel sheet with a low bottom and therefore a high iron loss value
It is a technology based on the ultra low iron loss as in the present invention.
Stable grain oriented electrical steel sheets that meet the requirements for realization
The technology to gain is not yet developed.

[0008]

SUMMARY OF THE INVENTION The present invention provides an industrially inexpensive high magnetic flux density ultra-low iron loss grain-oriented electrical steel sheet having extremely excellent punching properties, slitting properties, cutting properties, etc. and having almost no glass coating. It is an object of the present invention to provide a manufacturing method.

The gist of the present invention is as follows. (1) Si: 1.0 to 7.0% by weight, acid-soluble A
1: Hot-rolling, cold-rolling, primary recrystallization annealing, applying an annealing separator, and then applying high temperature to a steel ingot or slab containing 0.010 to 0.070% and the balance being Fe and impurities In a method of manufacturing a grain-oriented electrical steel sheet by performing finish annealing, at any time after the temperature reaches 800 ° C. during the temperature rising process during finish annealing, F, Cl, Br, I,
A method for producing a high magnetic flux density grain-oriented electrical steel sheet having good workability, which comprises introducing a gas having one or more of S and Se as constituent elements together with an annealing atmosphere.

(2) The high magnetic flux density grain-oriented electrical steel sheet having good workability according to the above item 1 , wherein the gas concentration in the atmosphere as described in the above item is 50 ppm or more and 5000 ppm or less directly above the steel sheet. Production method. Hereinafter, the present invention will be described in detail. The present invention provides high-temperature finish annealing conditions for producing a grain-oriented electrical steel sheet having no coating while maintaining a high degree of orientational recrystallization grain orientation integration.

It has been conventionally known that there is a correlation between the quality of film formation and the quality of secondary recrystallization, and it was expected that not forming a film would affect the increase in magnetic flux density. The present invention has been made on the basis of a series of experimental results for clarifying this effect and obtaining a coating-free high magnetic flux density material.
Regarding the components of the material of the present invention, Si is required to be 1.0% in order to obtain iron loss characteristics. The upper limit is limited to 7.0% from the viewpoint of workability. Further, Al is limited to a range of 0.010 to 0.070% as a range capable of forming a good inhibitor.

Normally, the coating of grain-oriented electrical steel sheet is decarburized and annealed.
SiO formed on the surface of steel sheet _TwoScale and high temperature
Made of MgO applied to prevent seizure during finish annealing
It is generated by reacting with the annealing separator. So this reaction is blocked
The surface of the decarburized annealed plate is pickled to prevent
When crystal annealing was performed, no film was formed.
However, at the same time, secondary recrystallization became extremely poor.
Was. This means that the presence of a coating is important for secondary recrystallization.
It means that it plays a role.

Therefore, in order to know the influence of the timing of film formation on the secondary recrystallization, the following experiment was conducted. A normal decarburizing plate is coated with a normal annealing separator, put in a finishing annealing furnace, and the temperature rise rate is 15 ° C / Hr.
It was annealed to a temperature of 200 ° C. with H ₂ 50% and N ₂ 50%. The steel sheet was pickled to remove oxides on the surface, rapidly heated to the temperature at which the annealing was interrupted, and then annealed to 1200 ° C. FIG. 1 shows the state of secondary recrystallization and film formation of the material obtained at this time. 800-90 from now on
It was found that the secondary recrystallization becomes good if a normal film is formed up to 0 ° C.

Based on this finding, a method of forming a coating film during finish annealing and removing the coating film from the stage where secondary recrystallization is not affected was considered. The method of interrupting the finish annealing and pickling the steel sheet as in the previous experiment is extremely unproductive. Therefore, we tried vapor-phase etching using a gas that corrodes the steel sheet. Below, HC
An example using 1 gas will be described. It was found that when the product plate having a coating film was annealed in an atmosphere containing HCl gas, the interface between the base metal and the coating film was corroded and the coating film was peeled off.

Therefore, during the finish annealing, the H
An attempt to introduce Cl gas resulted in 800-90
By introducing the gas from 0 ° C., it was possible to obtain a steel sheet which did not form a coating film and also had good secondary recrystallization.
The optimum conditions obtained from a series of experimental results based on the above findings will be shown below, and the constituent features of the present invention will be described.

At any time after reaching 800 ° C. during the temperature rising process during finish annealing, F, Cl, Br, I, S,
The atmospheric concentration of a gas (etching gas) containing one or more of Se as constituent elements is set to 50 just above the steel plate.
The reason for defining ~ 5000 ppm is as follows.
That is, when the amount of etching gas was less than 50 ppm, sufficient compound formation was not obtained between the coating and the base metal so that the coating could be completely peeled off, so the lower limit was set to 50 ppm, while if it exceeded 5000 ppm, the steel plate surface Not only becomes extremely rough, but also the produced compound bites into the steel plate and cannot be removed, and the gas components diffuse and penetrate into the steel plate, deteriorating the magnetic properties, so the upper limit is 5000 pp.
m. Incidentally, when a gas containing P is used, P forms Fe ₃ P inside the steel sheet and deteriorates the magnetic characteristics.

Next, regarding the timing of introducing the etching gas in the finish annealing step, this is determined from the viewpoint of preventing deterioration of the inhibitor necessary for secondary recrystallization. Secondary recrystallization is usually fast, starting at 850 ° C and at the latest 1
Finish at 050 ° C. At this time, it is necessary that a certain portion or more of the steel sheet be covered with the coating. The reason is that if there is no film at this time, the effect of preventing the inhibitor decomposition rate from unnecessarily increasing due to the reaction between the atmospheric gas and the inhibitor in the base iron (that is, the sealing effect) cannot be obtained, and the magnetic properties Is deteriorated.

By the way, the film formation starts at 800 ° C. during the temperature rise and at 900 ° C. at the latest. Therefore, it is necessary to introduce the etching gas after 800 ° C. The reason for this is
It is as follows. Introducing the etching gas at 800 ° C or higher during the temperature rise forms a film at least once,
After that, it will be peeled off. As a result, a high magnetic flux density can be obtained. This is because the film was peeled off without disturbing the sealing effect of the inhibitor by introducing the etching gas from 800 ° C. That is, it takes a certain time from the introduction of the etching gas to the peeling of the coating film, and the limit temperature considering this period is 800 ° C. The gas may be introduced at any time thereafter, but it is necessary to ensure that the time is sufficient to complete the reaction. For example, HC should be adjusted to 500 ppm on the steel plate surface.
When the 1 gas was introduced, the introduction of the gas was started from 900 ° C. during the temperature rising, and the temperature was changed from 1200 ° C.
It took time.

The main object of the present invention is to remove the surface coating made of forsterite or the like while sufficiently securing the strength of the inhibitor required for secondary recrystallization during finish annealing. In the secondary recrystallization process of the grain-oriented electrical steel sheet, the inhibitor suppresses the growth of crystal grains until just before the secondary recrystallization, and decreases the strength as the secondary recrystallization progresses. The forsterite coating plays an important role in controlling such changes in inhibitor strength.

Particularly, in the case of grain-oriented electrical steel sheet using AlN as an inhibitor, which is said to be effective for achieving high B ₈ , the sealing effect of the coating is utilized to prevent excessive nitridation or denitration. Make sure that the progress of nitriding does not go too far. As a result, the inhibitor can be used until secondary recrystallization.
Keep it right.

In the case of the method for producing an electromagnetic steel sheet for which no coating is formed as in the present invention, it is difficult to sufficiently obtain the inhibitor control effect by the coating. Therefore, in the present invention, when securing an inhibitor necessary for secondary recrystallization, a film is formed as usual, and the film is destroyed when it is no longer necessary, or the film is peeled from the steel sheet. In the present invention, in addition to the gas having Cl as a constituent element used in the above example, F, Br, I,
A gas containing S and Se as constituent elements is contained. These gases react with Fe at the interface between the coating and the base iron to form a compound. These compounds form a layer between the coating and the base iron to extremely deteriorate the adhesion of the coating, or vaporize by high temperature annealing to separate the coating from the base iron. As a result, a base steel can be obtained as a steel sheet having no coating in a state where secondary recrystallization is normally completed.

[0022]

[0023]

【Example】

[Example 1] Si: 3.25% by weight, C: 0.08 by weight
2%, Mn: 0.61%, S: 0.022%, Al:
A steel slab containing 0.021% and N: 0.009% and the balance substantially consisting of Fe is heated at 1380 ° C., then hot-rolled, and hot-rolled sheet annealed at 1130 ° C. and pickled. Then, it was cold-rolled to a plate thickness of 0.220 mm. This steel sheet was decarburized and annealed in a humid atmosphere at 830 ° C. and C: 11 ppm
After that, 6 g / m ^{2 of the} annealing separator shown in Table 1 was applied to the front and back surfaces of the steel sheet, respectively, and finish annealing was performed. The finish annealing was performed by heating from room temperature to 1200 ° C. at a temperature rising rate of 20 ° C./hr, and then holding at 1200 ° C. for 20 hours. The annealing atmosphere is N ₂ : 50% + H ₂ : 50%, 1200 during the temperature rise.
H ₂ : 100% during holding at ℃. At this time, the etching gas was introduced into the annealing furnace under the conditions shown in Table 1.

As can be seen from Table 1, when the gas is introduced at a low temperature of less than 800 ° C., the secondary recrystallization becomes unstable and the magnetic properties deteriorate. It is considered that this is because the inhibitor was removed before the secondary recrystallization was started. If the etching gas concentration in the atmosphere is low, the film remains formed. On the contrary, the formed film was good with very few defects. If the amount of introduced gas was too large, the properties of the steel sheet surface were poor, and it was extremely easy to rust. Rust could be removed by light pickling, but the surface of the steel sheet was severely uneven, and the gas components were diffused into the steel, and the magnetic properties were considerably degraded.

[0025]

[Table 1]

[0026]

[0027]

[0028]

[0029]

According to the present invention, it is possible to obtain a grain-oriented electrical steel sheet having good magnetic properties and having no glass coating.

[Brief description of the drawings]

FIG. 1 is a diagram showing a relationship between a finish annealing temperature and a magnetic flux density (B ₈ ).

Claims (2)

(57) [Claims] 1. A steel ingot or slab containing Si: 1.0 to 7.0%, acid-soluble Al: 0.010 to 0.070% by weight, and the balance being Fe and impurities, is hot-rolled. In the method for producing a grain-oriented electrical steel sheet by performing high-temperature finish annealing after applying cold-rolling, primary recrystallization annealing, and applying an annealing separator, 800 ° C. in the temperature rising process during finish annealing.
F, Cl, B at any time after reaching
A method for producing a high magnetic flux density grain-oriented electrical steel sheet having good workability, which comprises introducing a gas having one or more of r, I, S, and Se as constituent elements together with an annealing atmosphere. 2. The atmosphere of gas according to claim 1.
The method for producing a high magnetic flux density grain-oriented electrical steel sheet with good workability according to claim 1, wherein the medium concentration is 50 ppm or more and 5000 ppm or less directly above the steel sheet.