JPH07188937A - Production of grain-oriented silicon steel sheet - Google Patents

Abstract

PURPOSE:To produce a grain-oriented silicon steel sheet excellent in film characteristics and magnetic characteristics by subjecting a silicon-contg. cold rolled steel sheet to decarburizing annealing, thereafter coating it with a separation agent for annealing consisting essentially of MgO in which characteristics are controlled and executing final finish annealing. CONSTITUTION:A silicon-contg. slab is subjected to hot rolling and is thereafter subjected to cold rolling for one time or for two times including process annealing to regulate its sheet thickness into a final one. Next, this cold rolled steel sheet is subjected to decarburizing annealing, is thereafter coated with a separation agent for annealing consisting essentially of MgO and is subjected to final finish annealing. In the method for producing the grain-oriented silicon steel sheet, as MgO in the separation agent for annealing, the one having 0.3 to 2.5mum average grain size and 10 to 22% coefficient of linear constraction by self-sintering at 1100 deg.C is used. Thus, a good forsterite film is formed, and excellent magnetic properties are imparted thereto.

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 grain-oriented electrical steel sheet, and by forming a particularly good forsterite insulating coating, it is intended to improve not only the coating characteristics but also the magnetic characteristics. It is a thing.

[0002]

2. Description of the Related Art In a unidirectional electrical steel sheet, an insulating coating formed on the surface has an extremely important meaning not only in terms of electrical insulation but also in magnetic characteristics and appearance. In forming such an insulating coating, a cold-rolled sheet cold-rolled to a desired final thickness is decarburized and annealed in a temperature range of 700 to 900 ° C in wet hydrogen, and the inner surface containing SiO ₂ is contained on the surface of the steel sheet. After the oxide layer is formed, an annealing separator containing magnesium (MgO) as a main component is applied, wound into a coil, and then subjected to high-temperature finish annealing to obtain a MgO-SiO ₂ based forsterite insulating film. The method of forming is common.

This forsterite insulating coating film is formed by causing MgO in the annealing separator to undergo a solid phase reaction with SiO ₂ existing on the surface of the steel sheet during high temperature finish annealing, and is caused by thermal stress on the steel sheet. By imparting tensile stress, it not only plays the role of reducing eddy current loss, but also determines the quality of the product appearance.

Therefore, it is extremely important to form a forsterite insulating coating having excellent coating characteristics on the surface of a grain-oriented electrical steel sheet, and many studies have been conducted so far. For example, regarding the activity of MgO, the particle size distribution, and the appropriate conditions for the particle morphology, see JP-A-55-583.
Various proposals have been made in JP-A No. 31, JP-A-50-11912 and JP-A-58-193373.

[0005]

[Means for Solving the Problems] In a manufacturing process of a grain-oriented electrical steel sheet, an annealing separator slurry containing MgO as a main component is applied to a steel sheet subjected to decarburization annealing after final cold rolling and dried. , Forsterite insulating coating is formed during coiling and finish annealing of the coil. Here, the form of forming the forsterite insulating coating is greatly affected by the coil interlayer atmosphere during finish annealing, and the flowability of this coil interlayer atmosphere gas is determined by the grain size of the annealing separator and the annealing separator after coating and drying. It depends on the coil winding tension. Further, MgO itself in the annealing separator undergoes self-sintering shrinkage during the final annealing to change the gas flowability between the coil interlayer atmospheres.

[0006] Conventionally, since no attention has been paid to the change in properties of MgO for an annealing separator during finish annealing, it was not always sufficient to form a forsterite insulating film having excellent film properties. . The present invention advantageously solves the above problems, and by controlling the characteristics of MgO used as the main component of the annealing separator, it is possible to form a good forsterite coating and obtain excellent magnetic characteristics. It is an object of the present invention to propose a method for manufacturing a grain-oriented electrical steel sheet capable of achieving the above.

[0007]

In the process of studying the correspondence between the forsterite formation reaction during finish annealing and the self-shrinkage change due to the sintering of MgO particles which is the main component of the annealing separator, It was found that the degree of self-sintering of MgO particles in the temperature range where the forsterite film formation reaction proceeds affects the film quality of the forsterite film. Therefore, the effect of the shrinkage rate of MgO by self-sintering and the average particle size of MgO on the film formation and magnetic properties was investigated, and by controlling the shrinkage rate and the average particle size within a predetermined range, We have found that the intended purpose can be achieved advantageously. The present invention is based on the above findings.

That is, according to the present invention, a silicon steel-containing slab is hot-rolled, and then cold-rolled once or twice including intermediate annealing to obtain a final plate thickness, and then decarburized and annealed, and then Mg.
When a unidirectional electrical steel sheet is manufactured by applying an annealing separator containing O as a main component and then performing final finishing annealing, the MgO in the annealing separator has an average particle size of 0.3 to 2.5 μm. Moreover, the method for producing a grain-oriented electrical steel sheet is characterized by using a material having a linear shrinkage rate of 10 to 22% by self-sintering at 1100 ° C.

[0009]

In the present invention, the reason why the average particle size of MgO and the linear shrinkage ratio are limited to the above ranges is as follows.
First, regarding the average particle size of MgO powder,
If it is less than 0.3 μm, the flowability of the atmospheric gas between the coil layers is deteriorated, so that the generation of forsterite is delayed and the appearance is apt to be deteriorated.On the other hand, if it exceeds 2.5 μm, the flowability of the atmospheric gas between the coil layers is too high. The average particle size is 0.3 because the dissociation and floating of SiO ₂ in the oxide layer formed during carbon annealing on the surface of the steel sheet easily progresses and the adhesiveness deteriorates.
Limited to the range of ~ 2.5 μm.

Next, if the linear shrinkage of the MgO powder at 1100 ° C. is less than 10%, the gas flowability between the coil layers is not sufficient and the forsterite formation reaction slows down. The adhesion of the coating deteriorates. On the other hand, if it exceeds 22%, the surface of the steel sheet is easily oxidized during finish annealing, which causes decomposition of the inhibitor and coarsening of the crystal grains of the forsterite coating. It was limited to the range of%. Since the surface pressure of the steel sheet coated with the annealing separator and dried is about 100 kg / cm ² , the MgO forming pressure is 100 kg / cm 2 when measuring the linear shrinkage ratio. ^{It was determined as 2} by calcination in a non-oxidizing gas and dimensional change before and after calcination. At this time, the retention process at the target temperature was not performed. In addition, in order to control the linear shrinkage ratio at 1100 ° C within the range of 10 to 22%, the MgO manufacturing process Mg
(OH) ₂ firing conditions, that is, the firing temperature pattern, steam pressure in the firing furnace, atmosphere, gas flow rate, etc. may be adjusted.

The composition of the silicon-containing steel which is the material of the present invention is not particularly limited, and any conventionally known one is suitable. For reference, the preferable composition range is as follows. C: 0.001 to 0.10% C is an element useful for not only the refinement of the structure during hot rolling and cold rolling but also the development of Goss orientation, and it is preferable to contain at least 0.001%. However, if the content exceeds 0.10%, decarburization becomes difficult and the Goss orientation is disturbed, so the upper limit is 0.10%.
% Is preferable.

Si: 2.5-4.5% Si increases the specific resistance of the steel sheet and contributes to the reduction of iron loss, but if the content exceeds 4.5%, the cold rolling property is impaired, while 2.5%
If not less than, not only the resistivity decreases, but also the random orientation of the crystal orientation due to α-γ transformation during the final annealing performed for secondary recrystallization and purification, sufficient iron loss improvement effect can be obtained. Since Si is not present, it is preferable to set Si to about 2.5 to 4.5%.

Mn: 0.02 to 0.12% Mn requires at least about 0.02% to prevent hot embrittlement, but if it is too much, the magnetic properties deteriorate, so the upper limit is made 0.12%. Is preferred.

As inhibitors, so-called MnS, Mn
There are Se type and AlN type. In the case of MnS, MnSe system At least one selected from S and Se: 0.005 to 0.
06% S and Se are both effective elements as inhibitors that control the secondary recrystallization of grain-oriented silicon steel sheets. From the viewpoint of restraint, at least 0.005% is required, but 0.
If it exceeds 06%, its effect is impaired. Therefore, it is preferable that the upper and lower limits are about 0.005% and 0.06%, respectively. In the case of AlN system Al: 0.005 to 0.10, N: 0.004 to 0.015% The range of Al and N is set to the above range for the same reason as in the case of MnS and MnSe systems. Note that the above Mn
S, MnSe type and AlN type can be used together. Furthermore, as the inhibitor component, the above-mentioned S, Se, Al
In addition, Cu, Sn, Sb, Mo, Te, Bi and the like also act advantageously, so that a small amount of each can be contained together. The preferred addition range of these components is Cu, Sn: 0.01 to 0.15, respectively.
%, Sb, Mo, Te, Bi: 0.005 to 0.1%, and each of these inhibitor components can be used alone or in combination.

The method of manufacturing the steel sheet is not particularly limited and may be carried out under conventionally known manufacturing conditions. That is, a silicon steel-containing slab is hot-rolled and then cold-rolled once or twice including intermediate annealing to obtain a final plate thickness, and then decarburized and annealed, and then an annealing separator is applied to the steel plate surface. After that, secondary recrystallization annealing and purification annealing may be performed.

[0016]

[Example] C: 0.07 wt%, Si: 3.25 wt%, Mn: 0.07 wt%
%, Se: 0.017 wt%, Al: 0.023 wt% and N: 0.0085 wt%
% Of the slab, the balance of which is substantially Fe, is hot-rolled, then cold-rolled twice including intermediate annealing to obtain a cold-rolled sheet with a final thickness of 0.23 mm, and then de-rolled. After charcoal annealing, various annealing separators containing MgO shown in Table 1 as a main component were applied, and then finish annealing was performed. The results of examining the coating characteristics and the iron loss value of the obtained product are shown in FIG.

[0017]

[Table 1]

As is apparent from FIG. 1, all of Nos. 1 to 5 obtained according to the present invention have uniform film formation,
Since the adhesion between the forsterite coating and the base iron is sufficient, a good iron loss value is obtained. On the other hand, in Comparative Examples Nos. 6 to 10 in which the average particle diameter and the linear shrinkage ratio deviate from the proper ranges, the coating properties are poor and the iron loss is also deteriorated.

[0019]

As described above, according to the present invention, finish annealing is performed by using MgO having an average particle size of 0.3 to 2.5 μm and a linear shrinkage rate of 10 to 22% by self-sintering at 1100 ° C. as an annealing separator. Gas distribution between the coil layers
Since the activity of MgO is optimized, a good forsterite coating can be formed, and a grain-oriented electrical steel sheet excellent not only in coating characteristics but also in magnetic characteristics can be obtained.

[Brief description of drawings]

FIG. 1 is a diagram showing coating characteristics and iron loss values when various MgO is used as an annealing separator.

Claims (1)

[Claims] 1. A silicon steel-containing slab is hot-rolled and then cold-rolled once or twice including intermediate annealing to obtain a final plate thickness, and then decarburized and annealed, and MgO is used as a main component. When the unidirectional electrical steel sheet is manufactured by applying the final annealing after applying the annealing separator, the average particle diameter of MgO in the annealing separator is 0.3 to 2.
A method for producing a grain-oriented electrical steel sheet, characterized in that a linear shrinkage rate of 5 µm and a self-sintering rate at 1100 ° C of 10 to 22% is used.