JP3480332B2 - Method for producing grain-oriented silicon steel sheet having excellent magnetic properties and coating 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 grain-oriented silicon steel sheet suitable for use as an iron core or the like of a transformer or other electric equipment, and particularly, in a cold rolling single-pass method not subjected to intermediate annealing, It is intended to greatly improve the magnetic properties and the properties of the forsterite coating by devising the three members of the hot rolled sheet annealing process, the cold rolling process and the decarburizing annealing process.

[0002]

2. Description of the Related Art Grained silicon steel sheets are mainly used as iron core materials for transformers and rotating equipment, and are required to have high magnetic flux density and small iron loss and magnetostriction as magnetic characteristics. In particular, in recent years, the need for grain-oriented silicon steel sheets having excellent magnetic properties has been increasing more and more from the viewpoint of energy saving and resource saving.

In order to obtain a grain-oriented silicon steel sheet having excellent magnetic properties, it is important to obtain a secondary recrystallized structure highly integrated in the {110} <001> orientation, the so-called Goss orientation. Such a grain-oriented silicon steel sheet is generally an inhibitor necessary for secondary recrystallization, for example, a silicon steel slab containing MnS, MnSe, AlN, etc. is heated and hot-rolled, and then annealed if necessary. One or two or more cold rollings with intermediate annealing sandwiched to obtain the final plate thickness, then decarburization annealing, then apply the annealing separator containing MgO as the main component to the final finish annealing. Manufactured by doing. And, on the surface of this grain-oriented silicon steel sheet, except for special cases, an insulating film mainly composed of forsterite (Mg ₂ SiO ₄ ) (hereinafter, simply “forsterite insulating film” or “forsterite film”). Is usually formed. This coating not only serves to electrically insulate the surface but also effectively improves iron loss and magnetostriction by imparting tensile stress to the steel sheet due to its low thermal expansion.

There are a wide variety of techniques for improving the magnetic properties of grain-oriented silicon steel sheets by devising the manufacturing method. One of them is hot-rolled sheet annealing or intermediate annealing conditions and cooling control technology at that time. For example, JP-A-58-55
According to Japanese Patent No. 530, when the final cold rolling reduction is 40 to 80%, C is added after the hot rolling process and before the cold rolling process.
A technique characterized by having a decarburization step of decarburizing 0.006 to 0.020% is disclosed in Japanese Patent Laid-Open No. 62-50528, in which hot rolling sheet annealing is performed when the final cold rolling reduction is 80% or more.
After decarburizing 50 to 250 ppm, a technique characterized by rapid cooling to room temperature is further disclosed in JP-B-62-50529, in which an intermediate annealing is performed to obtain a final cold rolling reduction of 80 to 95% and a plate thickness.
When manufacturing 0.10 ~ 0.23 mm product, after hot rolling,
A technique characterized by having a step of decarburizing C by 0.007 to 0.030% in the middle of the step before the final cold rolling is disclosed. In all of these methods, the surface layer decarburization of the steel sheet surface is performed during hot-rolled sheet annealing or intermediate annealing, and the Goss orientation ({11
0} <001> orientation) and promotes secondary recrystallization.

Further, in Japanese Patent Publication No. 63-5454, in the annealing before final cold rolling, the decarburization amount is controlled by annealing at 750 to 870 ° C. to control the carbon concentration near the surface layer of the plate thickness to 30.
The average grain size of the recrystallized grains near the surface of the plate thickness was reduced to 0 ppm or less and subsequently annealed at 880 to 1050 ° C.
A technique characterized by making it 17 μm or more is disclosed. This method is also a technique for promoting surface layer decarburization on the surface of the steel sheet and promoting the accumulation of Goss orientation.

However, the magnetic characteristics achieved by these methods have not been sufficient values. That is, the above-mentioned JP-A-58-55530 and JP-A-62-55
From the examples of 50528 and Japanese Examined Patent Publication No. 63-5454, B ₁₀ obtained by these techniques is 1.95 at most.
It can be seen that the value is as low as (T) (1.93 (T) at B ₈ ). Further, in the technique of Japanese Patent Publication No. 62-50529, although the magnetic flux density B ₈ has a high value near 1.95 (T),
This is a technique of the cold rolling twice method in which the intermediate annealing is indispensable, and there is a possibility that the manufacturing cost may increase. In any case, since these methods focus on only hot-rolled sheet annealing conditions or intermediate annealing conditions, it can be said that the studies were insufficient to obtain extremely excellent magnetic properties.

In addition, for example, in Japanese Examined Patent Publication No. 56-3892, in the cooling after annealing before the final cold rolling in the double cold rolling method, a cooling rate of 150 ° C./min or more between 600 and 300 ° C. is used. Techniques for cooling are disclosed. Further, in JP-A-58-157917, cooling after the intermediate annealing is performed.
While quenching up to 300 ℃, while gradually cooling in the temperature range from 300 to 150 ℃ for 8 to 30 seconds, fine carbides of 100 Å to 500 Å size are precipitated and recrystallized. A technique for increasing the (110) intensity and improving the magnetic properties is disclosed later. However, the magnetic properties obtained by these methods were not sufficient values. This is because it is not sufficient to study the cooling conditions alone in order to control the dispersion of carbides and nitrides. As a solution to the above problems, Japanese Patent Laid-Open No. 61-61
In Japanese Patent No. 149432, 1-30 during cooling of the intermediate annealing.
After introducing a working strain of% to the steel sheet, a method of performing final rolling at a temperature of 100 to 400 ° C. is disclosed. This technique was aimed at improving the structure by introducing dislocations by working to increase the amount of dissolved C. However, the magnetic flux density B ₁₀ obtained by this method was as low as 1.92 (T). In addition, since this technique is a cold rolling two-time method, intermediate annealing is indispensable, and there is a risk that the manufacturing cost will increase.

Therefore, a technique for improving these methods is disclosed in Japanese Patent Laid-Open No. 4-83828.
This technique uses 0.05% to 3.0% after stopping quenching of softening annealing (hot-rolled sheet annealing or intermediate annealing) before final cold rolling when AlN is used as the precipitation-dispersed phase and Sb is included as a material component.
This is a technique for improving the magnetic characteristics by imparting a small amount of strain. The technical idea of this method is that the carbide precipitation suppressing effect of Sb causes {111} <11 in the recrystallized texture.
2) It is intended to improve the magnetic flux density by increasing the strength. Although the magnetic flux density has been significantly improved by the development of this technique, there is a problem that the iron loss tends to vary because the secondary recrystallized grains have a strong tendency to coarsen. Further, when the final finish annealing is performed by batch type coil annealing due to the coarsening of the secondary recrystallized grains, the inclination angle (β of the orientation of the secondary recrystallized grains during the flattening annealing is proportional to the radius of curvature. However, there is also a problem that the magnetic flux density in the inner winding portion of the coil deteriorates by about 200 gauss (G) as compared with the outer winding portion. Further, when a product having a thin plate thickness, particularly 0.23 mm or less, is produced by the cold rolling once method without intermediate annealing, there remains a problem in that the magnetic properties are not stable.

In order to advantageously solve these problems, the inventors of the present invention previously described in Japanese Patent Laid-Open No. 188756/1995.
We have proposed a technique that uses a basic component system that uses AlN as the precipitation-dispersed phase to stably improve the magnetic properties by the cold rolling once method. This technique involves performing hot-rolled sheet annealing at a temperature of 1000 to 1200 ° C., and then performing rolling at a rolling reduction of 5% or more in a temperature range of 900 to 600 ° C. during the subsequent cooling process, and during the hot-rolled sheet annealing. Is a technology characterized by subjecting the surface layer to decarburization of 0.005 to 0.025%. With this technology, the magnetic flux density B ₈ is 1.96.
Although a value as high as (T) has been obtained, there have been cases where a forsterite coating having a sufficient quality with no defects and having excellent adhesion over the entire width and the entire length of the strip has been obtained. In addition, the magnetic properties are often deteriorated at the location where the quality deterioration of the forsterite insulating coating occurs, and from the viewpoint of obtaining a product excellent in both magnetic properties and coating properties in the entire coil width and full length, it is sufficient. Was not.

Further, in Japanese Examined Patent Publication No. 54-29182, in a process of annealing a hot-rolled sheet in a temperature range of 950 to 1200 ° C. and then rapidly cooling it, a strong cold rolling of 81 to 95% is performed to obtain a final sheet thickness. , During any one or more of the above cold rolling passes
A technique for keeping the temperature in the temperature range of 300 to 600 ° C. for 1 to 30 seconds is disclosed. However, it can be seen from the examples that with this technique, even if the magnetic flux density (B ₈ ) is high, only about 1.94 (T) is obtained. Therefore, it can be seen that a high magnetic flux density in which B ₈ exceeds 1.95 (T) cannot be obtained by the technique focusing only on the rapid cooling treatment after annealing the hot rolled sheet and the interpass aging treatment during cold rolling.

Further, Japanese Examined Patent Publication No. 59-48934 discloses a technique for defining the rate of temperature rise during annealing of hot-rolled sheet and the quenching start temperature after annealing. In a working example,
It can be seen that magnetic characteristics with a magnetic flux density B ₈ of 1.94 (T) were obtained by performing aging treatment at 200 ° C. between passes during cold rolling. However, even with this technology, B ₈ is 1.95.
It can be seen that a high magnetic flux density exceeding (T) has not been obtained.

In Japanese Patent Laid-Open No. 63-100127, a steel sheet is held in a temperature range of 50 to 300 ° C. for a period of 1 minute or more between the rapid cooling of hot-rolled sheet annealing and the first cold rolling. The technology of heat treatment and the technology of aging between passes in the first cold rolling are disclosed, and the magnetic flux density B ₈ is 1.95.
It can be seen that magnetic characteristics of about (T) are obtained. However, this is a technique of the cold rolling twice method in which the intermediate annealing is performed, and there is a possibility that the manufacturing cost may increase.

After all, in the conventional techniques, a basic composition system utilizing AlN as a precipitation-dispersed phase is used, and a stable high magnetic flux density (B ₈ exceeds 1.95 (T) is obtained by the cold rolling once method. ) And good film characteristics could not be obtained.

As is clear from the above description, although a technique which takes into consideration both the hot rolling sheet annealing condition and the cold rolling condition has been disclosed, it has a great influence on the film properties and the magnetic properties. Only the Japanese Patent Publication No. 7-42503 described below discloses the technology that defines the treatment conditions of hot-rolled sheet annealing and the cold rolling conditions in consideration of the decarburization annealing conditions that affect the temperature. This Japanese Patent Publication No. 7-42503 discloses a method of forming an excellent primary insulating coating by defining an atmosphere during annealing of a hot rolled sheet and an atmosphere of decarburizing annealing conditions. Precise on the base in the process
This is a method of forming an internal oxide layer rich in SiO ₂ . Therefore, it is different from the technique of securing a desiliconized layer to some extent on the surface layer of the steel sheet after annealing and pickling of the hot rolled sheet as in the present invention.

By the way, the forsterite coating formed on the surface of grain-oriented silicon steel sheet is formed by finish annealing, and the coating formation behavior is MnS, MnSe, AlN in the steel.
Since it affects the behavior of inhibitors such as, it also affects secondary recrystallization itself, which is an essential process for obtaining excellent magnetic properties. The formed forsterite coating also contributes to the improvement of the magnetic properties of the steel sheet by absorbing the inhibitor component, which becomes unnecessary after the secondary recrystallization is completed, into the coating to purify the steel. Therefore,
It is very important to control the forsterite film formation process to uniformly form a film in order to obtain a grain-oriented silicon steel sheet having excellent magnetic properties.

Further, as a matter of course, the formed forsterite coating has a uniform appearance and is free from defects, and in order to prevent peeling of the coating during shearing, punching, bending, etc., adhesion is improved. It is required to be excellent.

Thus, the forsterite insulating coating having a great influence on the product quality is generally formed by the following steps during the above-described manufacturing process of the grain-oriented silicon steel sheet. First, the final cold-rolled sheet for grain-oriented silicon steel sheet cold-rolled to a desired product sheet thickness is continuously annealed at a temperature of 700 to 900 ° C in wet hydrogen. By this annealing (decarburization annealing),
(1) The structure after cold rolling is recrystallized so that proper secondary recrystallization occurs in final finishing annealing, and (2) secondary recrystallization in final finishing annealing is performed completely, and
0.03% in steel to prevent aging deterioration of product magnetic properties
Carbon contained in about 0.12% is decarburized to 0.003% or less, and (3) the subscale containing SiO ₂ is generated on the surface of the steel sheet by the oxidation of Si in the steel.

After that, an annealing separator containing MgO as a main component is applied to the steel sheet, wound into a coil and subjected to a final finishing annealing that combines secondary recrystallization annealing and purification annealing in a reducing or non-oxidizing atmosphere. By performing at a temperature of up to 1200 ℃,
The forsterite insulating film is formed mainly by a solid-phase reaction represented by the following reaction formula. 2MgO
＋ SiO ₂ → Mg ₂ SiO ₄

This forsterite insulating coating has a thickness of 1 μm.
It is a ceramic film in which fine crystals before and after m are densely integrated. As described above, it was formed on the surface layer of the steel sheet by decarburization annealing.
Since the subscale containing SiO ₂ is generated on the steel sheet as one raw material, the type, amount, distribution, etc. of this subscale are involved in the nucleation and grain growth behavior of forsterite, and the coating film. It also affects the grain boundaries of the crystal grains and the strength of the grains themselves, and thus greatly affects the film quality after finish annealing.

Since the annealing separating agent mainly composed of MgO, which is the other raw material, is applied to the steel sheet as a slurry suspended in water, H ₂ which is physically adsorbed even after being dried is used.
In addition to possessing O ₂ , it is partially hydrated and converted to Mg (OH) ₂ . Therefore, during finishing annealing, a small amount of H ₂ O is continuously released up to around 800 ° C. The H ₂ O oxidizes the steel sheet surface during finish annealing. This oxidation also affects the behavior of forsterite as well as the behavior of the inhibitor, and if this additional oxidation is large, it becomes a factor that deteriorates the magnetic properties. The easiness of oxidation by H ₂ O released from this MgO is also greatly affected by the physical properties of the subscale formed by decarburization annealing. Also, as a matter of course, additives other than MgO 2 mixed in the annealing separator greatly influence the film formation and the secondary recrystallization process even if the amount added is small.

The physical properties of this subscale are as follows: especially in grain-oriented silicon steel sheets containing AlN as an inhibitor component.
It has a great influence on the denitrification behavior during finish annealing or the nitriding behavior from the annealing atmosphere, and thus also on the magnetic properties. As described above, controlling the physical properties of the subscale formed on the surface layer of the steel sheet during decarburization annealing is effective in order to form an excellent forsterite insulating coating uniformly at an appropriate temperature, and also to prevent secondary re-formation. It is a technology that is essential for the normal expression of crystals, and is one of the important items in the manufacturing technology for grain-oriented silicon steel sheets.

Regarding decarburization annealing of grain-oriented silicon steel sheets, a method of controlling the oxygen content of the steel sheet after decarburization annealing, as disclosed in, for example, JP-A-59-185725, As disclosed in Japanese Patent Publication No. 57-1575, the degree of oxidation of the atmosphere is set to 0.15 or more in the front region of decarburization annealing, and the degree of oxidation of the subsequent rear region is set to 0.75 or less and lower than that of the front region. Method, JP-A-2-240
No. 215 and Japanese Patent Publication No. 54-24686, 850-10 in a non-oxidizing atmosphere after decarburization annealing.
Method of heat treatment at 50 ° C, and Japanese Patent Publication No. 3-57167
As disclosed in Japanese Patent Publication No.
In the temperature range of 0 ° C. or lower, the oxidation degree is set to 0.008 or less and cooling is performed, or as disclosed in JP-A-6-336616, the ratio of water vapor partial pressure to hydrogen partial pressure in the soaking process is set to less than 0.70. And a method of making the ratio of the partial pressure of water vapor to the partial pressure of hydrogen in the temperature raising process lower than that in the soaking process, and further, as disclosed in JP-A-7-278668, the temperature raising rate and the annealing atmosphere. There are known methods for prescribing.

However, although the above-mentioned atmosphere control method at the time of decarburization annealing can be recognized to have a certain effect, it is not always sufficient, and the magnetic characteristics and the forsterite insulation in the width direction or the longitudinal direction of the strip are not necessarily sufficient. In some cases, the adhesion, thickness, or uniformity of the coating film may deteriorate, and there is still room for improvement in order to stably produce products with excellent quality and to further improve the yield. In particular, as mentioned above, when AlN is used as an inhibitor to manufacture grain-oriented silicon steel sheets with high magnetic flux density, secondary recrystallization becomes unstable and magnetic properties often tend to vary. It was

In short, in controlling the subscale produced by decarburization annealing, there have been few studies in which both the treatment conditions of hot-rolled sheet annealing and the cold rolling conditions are taken into consideration. In addition, in the technology for controlling the treatment conditions for hot-rolled sheet annealing, the cooling rate, decarburization amount, average grain size of recrystallized grains near the surface layer of the sheet thickness, etc. have been focused on in the past. There was no technology focusing on (Si layer removal).

[0025]

SUMMARY OF THE INVENTION The present invention advantageously solves the above problems by using a basic component system using AlN as a disperse phase for precipitation, and stably obtaining magnetic properties by the cold rolling once method. It is an object of the present invention to propose a method for producing a grain-oriented silicon steel sheet which can improve and obtain good coating properties over the entire width and length of the strip.

[0026]

[Means for Solving the Problems] Now, the inventors have found that AlN
Using the material of the basic component system that utilizes
A close examination was conducted on the treatment conditions of hot-rolled sheet annealing and cold rolling conditions, and it was newly found that the depth of the desiliconized layer before cold rolling, which had not been noticed in the past, had a great effect on the magnetic properties. It was Usually, the depth of the desiliconized layer greatly varies within the coil and between the coils, and the depth of the desiliconized layer is controlled within a certain range, and at least twice during cold rolling. The steel plate temperature immediately after the roll exit side is 150 ° C
It was found that the magnetic properties and the coating properties were dramatically improved when the rolling was performed at 350 ° C. or lower and the temperature rise temperature during decarburization annealing was 5 ° C./s or higher. The present invention is based on the above findings.

That is, the present invention contains C: 0.03-0.12 wt%, Si: 2.0-4.5 wt%, acid-soluble Al: 0.01-0.05 wt% and N: 0.004-0.012 wt%, and the balance Fe and Has inevitable impurity component composition
After hot-rolling the silicon steel slab and annealing the hot-rolled sheet, cold rolling with a reduction rate of 80-95% is performed, and then decarburization annealing is performed, and then the surface of the steel sheet is coated with MgO. After applying the annealing separating agent as the main component, in the method for producing the grain-oriented silicon steel sheet of the cold rolling once method consisting of a series of steps of performing secondary recrystallization annealing and purification annealing, after hot-rolled sheet annealing and When the sheet thickness before cold rolling is t _I (mm) and the sheet thickness after cold rolling is t _R (mm), hot-rolled sheet annealing is performed in the temperature range of 800 to 1200 ° C.
Oxidizing atmosphere and annealing temperature and subsequent pickling treatment
By changing the pickling time at 0.5, the region where the ratio of Si concentration to Si concentration in the central part of the plate thickness is 0.98 or less in the state before cold rolling is 0.5 × t _I / t from the surface in the thickness direction. _R μ
m or more and 8 × t _I / t _R μm or less, at least twice during cold rolling, the steel sheet temperature immediately after the rolling roll exit side is 150 ° C. or more and 350 ° C. or less, and A method for producing a grain-oriented silicon steel sheet having excellent magnetic characteristics and coating characteristics, which is characterized in that a temperature rising rate in a carbon annealing step is set to 5 ° C./s or more. In the present invention, it is more preferable to carry out skin pass rolling with a reduction of 20% or less after hot rolling and before hot-rolled sheet annealing.

[0028]

BEST MODE FOR CARRYING OUT THE INVENTION First of all, the present inventors investigated in detail the influence of the desiliconized layer profile formed in the sheet thickness direction after hot-rolled sheet annealing (before cold rolling) on the magnetic properties. The results of this experiment will be described below. [Experiment 1] C: 0.07 wt% (hereinafter referred to simply as "%"), Si: 3.2%, Mn: 0.076%, Al: 0.025%,
A silicon steel slab containing N: 0.0085%, Se: 0.020% and Sb: 0.025% is heated at 1430 ° C for 20 minutes and then hot rolled 2.
A hot rolled sheet having a thickness of 3 mm was used. Then, the hot-rolled sheet was annealed at 1100 ° C. in various atmospheres and annealing times, and the pickling time was changed variously to prepare samples with different desiliconized layer depths in the sheet thickness direction. . The formed desiliconized layer was investigated by EPMA mapping the Si distribution in the sample cross section. Then, it was cold rolled to a thickness of 0.26 mm. At this time, rolling was carried out at least twice such that the temperature of the steel sheet immediately after the exit side of the rolling roll was 250 ° C. This is disclosed in JP-B-54-29182 or JP-A-63-1001.
Unlike the technique of aging between passes during cold rolling as disclosed in Japanese Patent Publication No. 27, the rolling is such that the temperature immediately after the steel sheet is rolled into the roll reaches a predetermined temperature. . Therefore, the temperature between the passes may be as low as less than 50 ° C. After that, the temperature is raised at a heating rate of 10 ° C./s, and decarburization annealing is performed in wet hydrogen at 850 ° C. for 2 minutes (atmosphere P (H ₂ O) / P (H ₂ ) is 0.40 in the heating process, and is evened out. 0.45 in thermal process
And ), Then MgO: 100 parts by weight, TiO ₂ : 6
After applying an annealing separator with a weight ratio of 20 parts, hold it in a nitrogen atmosphere at 850 ° C for 20 hours, and then in a nitrogen: 25%, hydrogen: 75% atmosphere at a rate of 15 ° C / hr. After performing the secondary recrystallization annealing to raise the temperature to 1150 ° C., purification annealing was performed for 5 hours in a hydrogen atmosphere at 1200 ° C.

The appearance and bending adhesion of the forsterite coating film of each coil thus obtained were evaluated, and the magnetic properties (magnetic flux density B ₈ , iron loss W _17/50 ) were evaluated.
The effect of the depth of the desiliconized layer on magnetism is shown in FIG. 1, and the effect on the coating is shown in Table 1. Here, the desiliconized layer depth is defined as a region where the ratio of the Si concentration to the Si concentration in the central portion of the plate thickness is 0.98 or less in the steel sheet (the same applies hereinafter in this specification). The bending adhesion of the coating is measured by winding a test piece around a round bar having various diameters at 5 mm intervals and measuring the minimum diameter at which the coating does not peel.

[0030]

[Table 1]

From FIG. 1 and Table 1, it is understood that when the depth of the desiliconized layer before cold rolling is about 5 μm or more and 70 μm or less, the magnetic properties and the coating properties are remarkably improved.

Then, next, an experiment was conducted to examine the influence of the steel sheet temperature immediately after the rolling roll exit side during cold rolling. [Experiment 2] C: 0.07%, Si: 3.2%, Mn: 0.078%, A
l: 0.024%, N: 0.0082%, Se: 0.019% and Sb: 0.0
A silicon steel slab containing 25% was heated at 1430 ° C. for 20 minutes and then hot-rolled into a hot-rolled sheet having a thickness of 2.3 mm. Then 1100
After hot-rolled sheet annealing was performed at ℃ in an oxidizing atmosphere, pickling was performed by pickling to prepare a sample having a desiliconized layer depth of about 30 μm in the sheet thickness direction. The investigation of the desiliconized layer is based on EPMA mapping of the Si distribution of the cross-section sample as in Experiment 1. Then, it was cold rolled to a thickness of 0.26 mm. At this time, the steel plate temperature immediately after the rolling roll exit side is at least twice.
Rolling was carried out at 50 to 450 ° C, or rolling was carried out only once such that the temperature of the steel sheet immediately after the rolling roll exit side was 50 to 450 ° C. Such rolling is rolling in which the temperature of the steel sheet immediately after being rolled into the roll reaches a predetermined temperature, and the temperature between passes may be as low as less than 50 ° C. After that, the temperature is raised at a heating rate of 30 ° C./s and the temperature is raised to 85
Decarburization annealing was performed at 0 ° C for 2 minutes (atmosphere P (H ₂ O) / P (H
₂ ) was set to 0.40 during the heating process and 0.40 during the soaking process. ), Followed by MgO: 100 parts by weight, TiO _2: 8 parts by weight, Sr (OH) ₂ · 8H
₂ O: After applying 3 parts by weight of the annealing separator, hold it in a nitrogen atmosphere at 850 ° C. for 20 hours and then add nitrogen: 25
%, Hydrogen: After performing secondary recrystallization annealing in which the temperature was raised to 1150 ° C. at a rate of 15 ° C./hr in an atmosphere of 75%, purification annealing was performed in a hydrogen atmosphere at 1200 ° C. for 5 hours.

The appearance and bending adhesion of the thus obtained forsterite coating of each coil were evaluated, and the magnetic properties were evaluated. Fig. 2 shows the effect of the steel sheet temperature immediately after the rolling roll exit side during cold rolling on magnetism (magnetic flux density B ₈ ).
Table 2 shows the effects on the coating properties. The measurement of the bending adhesion of the coating is the same as in Experiment 1.

[0034]

[Table 2]

From FIG. 2 and Table 2, when the desiliconized layer depth before cold rolling was about 30 μm and the desiliconized layer depth in the above-mentioned Experiment 1 was within the range of good magnetism, cold rolling was performed. It can be seen that the magnetic properties and the coating properties are remarkably improved when the steel sheet temperature immediately after the rolling roll exit side is in the range of 150 ° C. to 350 ° C. for two or more rollings.

Next, an experiment was conducted to examine the effect of the hot-rolled sheet annealing temperature. [Experiment 3] C: 0.07%, Si: 3.2%, Mn: 0.072%, A
l: 0.025%, N: 0.0086%, Se: 0.018% and Sb: 0.0
A silicon steel slab containing 25% was heated at 1430 ° C. for 20 minutes and then hot-rolled into a hot-rolled sheet having a thickness of 2.3 mm. Then 700 ~
A hot rolled sheet was annealed at 1250 ° C. in various oxidizing atmospheres and annealing times, and then pickled to prepare a sample having a desiliconized layer depth of about 30 μm in the sheet thickness direction. The investigation of the formed desiliconized layer is the same as in Experiment 1. Then, it was cold rolled to a thickness of 0.26 mm. At this time, the steel plate temperature immediately after the rolling roll exit side is at least twice.
Rolling was performed so that the temperature reached 250 ° C. This is a rolling process in which the temperature immediately after the steel plate is bitten into a roll and rolled reaches a predetermined temperature. After that, the temperature is raised at a heating rate of 20 ° C / s, decarburization annealing is performed in wet hydrogen at 850 ° C for 2 minutes,
(Atmosphere P (H ₂ O) / P (H ₂ ) was set to 0.35 in the temperature rising process and 0.45 in the soaking process), then MgO: 100 parts by weight, TiO ₂ : 6 parts both parts, SnO ₂ : 5 parts by weight Part of the annealing separator is applied, followed by 20 hours of holding at 850 ° C in a nitrogen atmosphere,
11 at a rate of 15 ° C / hr in an atmosphere of nitrogen: 25%, hydrogen: 75%
After performing secondary recrystallization annealing to raise the temperature to 50 ℃, 1200 ℃
Purification annealing was performed for 5 hours in the hydrogen atmosphere.

The appearance and bending adhesion of the forsterite coating of each coil thus obtained were evaluated, and the magnetic properties were evaluated. The hot rolled sheet annealing temperature is magnetic (magnetic flux density B
Fig. 3 shows the effect on ₈ ) and Table 3 shows the effect on the coating properties. The measurement of the bending adhesion of the coating is the same as in Experiment 1.

[0038]

[Table 3]

Even when the desiliconized layer depth before cold rolling was about 35 μm and the desiliconized layer depth was within the range of good magnetism in Experiment 1 described above, the hot rolled sheet annealing temperature was 800 ° C. or more. It can be seen that the magnetic properties and the film properties are remarkably improved in the range of 1200 ° C or lower.

Therefore, next, an experiment was conducted to investigate the range of the optimum desiliconized layer depth before cold rolling when the plate thicknesses of the cold rolled plates were different. [Experiment 4] C: 0.07%, Si: 3.2%, Mn: 0.075%, A
l: 0.026%, N: 0.0088%, Se: 0.021% and Sb: 0.0
A silicon steel slab containing 25% was heated at 1430 ° C. for 20 minutes and then hot-rolled to obtain a hot-rolled sheet having a thickness of 2.0 mm. Then, hot rolled sheet annealing was performed at 1100 ° C. in various atmospheres and annealing times, and the pickling time thereafter was variously changed to prepare samples having different desiliconized layer depths in the sheet thickness direction. The formed desiliconized layer was investigated by EPMA mapping the Si distribution in the sample cross section. Then, cold rolling 0.19mm,
Finished 0.22mm and 0.34mm thick. At this time, rolling was carried out at least twice such that the temperature of the steel sheet immediately after the exit side of the rolling roll was 250 ° C. This is rolling in which the temperature immediately after the steel plate is bitten into a roll and rolled reaches a predetermined temperature. Then, the temperature was raised at a rate of 15 ° C./s, decarburization annealing was performed in wet hydrogen at 850 ° C. for 3 minutes, and the atmosphere (P (H ₂ O)
/ P (H ₂ ) was set to 0.50 during the temperature raising process and 0.50 during the soaking process. ), Then 100 parts by weight of MgO and 10 parts by weight of TiO ₂ are applied as an annealing separator, and then 850 in a nitrogen atmosphere.
After holding at ℃ for 20 hours, after performing secondary recrystallization annealing to increase the temperature to 1150 ℃ at a rate of 10 ℃ / hr in an atmosphere of nitrogen: 25%, hydrogen 75%, in a hydrogen atmosphere at 1200 ℃. Then, purification annealing was performed for 5 hours.

The appearance and bending adhesion of the thus obtained forsterite coating of each coil were evaluated, and the magnetic properties were evaluated. Desiliconization layer depth is magnetic (magnetic flux density B ₈ )
4, 5 and 6 show the effect on the film properties, and Tables 4, 5 and 6 show the effect on the film properties. The measurement of bending adhesion of the coating is the same as in Experiment 1.

[0042]

[Table 4]

[0043]

[Table 5]

[0044]

[Table 6]

From these results, it is understood that the range of the depth of the desiliconized layer before cold rolling, in which the magnetic properties and the film properties are remarkably improved, varies depending on the plate thickness after cold rolling. However, when the sheet thickness after annealing of the hot rolled sheet (before cold rolling) is t _I (mm) and the sheet thickness after cold rolling is t _R (mm), the desiliconized layer depth is 0.5 × t _I. It can be seen that the magnetic properties and the film characteristics are remarkably improved when the ratio is / t _R μm or more and 8 × t _I / t _R μm or less.

Next, an experiment was conducted to examine the influence of the heating rate during decarburization annealing. [Experiment 5] C: 0.068%, Si: 3.35%, Mn: 0.072%,
Al: 0.025%, N: 0.0086%, Se: 0.018% and Sb: 0.
A silicon steel slab containing 045% was heated at 1430 ° C. for 20 minutes and then hot rolled into a hot rolled 2.3 mm plate. Then, the hot-rolled sheet was annealed at 1125 ° C. in an oxidizing atmosphere and then pickled to prepare a sample having a desiliconized layer depth of about 20 μm in the sheet thickness direction. Then, it was cold-rolled to a thickness of 0.22 mm. At this time, rolling was carried out at least twice such that the temperature of the steel sheet immediately after the exit side of the rolling roll was 250 ° C. This is a rolling process in which the temperature immediately after the steel plate is bitten into a roll and rolled reaches a predetermined temperature. After that, 3 ℃ / s
Decarburization annealing is performed at 850 ° C for 2 minutes in wet hydrogen at various heating temperatures at various speeds, then an annealing separator containing MgO as the main component is applied, and then a nitrogen atmosphere is applied. Incubation at 850 ° C for 20 hours followed by nitrogen: 25%, hydrogen:
After performing secondary recrystallization annealing in which the temperature was raised to 1150 ° C. at a rate of 15 ° C./hr in a 75% atmosphere, purification annealing was performed in a hydrogen atmosphere at 1200 ° C. for 5 hours.

The appearance and bending adhesion of the thus obtained forsterite coating of each coil were evaluated, and the magnetic properties were evaluated. FIG. 7 shows the effect of the heating rate during decarburization annealing on magnetism (magnetic flux density B ₈ ), and Table 7 shows the effect on coating properties. The bending adhesion of the coating is the same evaluation method as in Experiment 1.

[0048]

[Table 7]

Even when the desiliconization layer depth before cold rolling was about 20 μm and the desiliconization layer depth was within the range of good magnetism in Experiment 1 described above, the rate of temperature rise during decarburization annealing was It can be seen that the magnetic properties and the film properties are remarkably improved at 5 ° C / s or more.

From the above experiments, regarding the magnetic properties and coating properties, the thickness of the steel sheet after hot-rolled sheet annealing and before cold rolling is t _I (mm), and the thickness after final cold rolling is t _R (mm). In the state before cold rolling, the region where the ratio of Si concentration to Si concentration in the central portion of the plate thickness is 0.98 or less is 0.5 × t _I / t _R μm or more in the thickness direction from the surface, 8 × t _I / t _R The hot-rolled sheet should be annealed at a temperature of 800 to 1200 ° C and the subsequent pickling treatment should be performed so that the thickness becomes equal to or less than μm. At the final cold rolling, the steel sheet immediately after the rolling roll exit side is at least twice. It was found that by performing rolling at a temperature of 150 ° C. or higher and 350 ° C. or lower, and by setting the rate of temperature rise in the decarburization annealing step to 5 ° C./s or higher, it is significantly improved.

According to the present invention, the depth of the desiliconized layer of the steel sheet surface layer is controlled by hot-rolled sheet annealing at 800 to 1200 ° C. and the subsequent pickling treatment, and the steel sheet immediately after the rolling roll exit side at the time of final cold rolling. The reason why the magnetic characteristics are improved by controlling the temperature has not been clarified yet, but the inventors consider the following. It has been conventionally considered that the Goss-oriented grains, which are secondary recrystallized grains, appear mainly from the side closer to the surface layer when considered in the plate thickness direction of the steel sheet. If a desiliconized layer with an appropriate depth is formed on the steel sheet surface and cold rolling is performed with the rolling temperature controlled to an appropriate range, deformation stress or shear stress on the steel sheet surface layer may be It seems to act favorably to promote the accumulation of orientation and stabilize the secondary recrystallization, and this is considered to contribute to the improvement of magnetic properties.

Further, the depth of the desiliconized layer before the cold rolling,
By controlling the cold rolling conditions, it is possible to control the depth of the desiliconized layer of the final cold rolled sheet after cold rolling and before primary recrystallization. The reason why good coating and magnetic properties can be obtained by controlling the depth of the desiliconization layer and by setting the heating rate during decarburization annealing to 5 ° C / s or more is still clear. Although it was not done, the inventors think as follows. If the desiliconized layer of the cold-rolled sheet is too small, the Si concentration near the surface is too high and the subscale formation proceeds excessively during the temperature rise process, resulting in a uniform oxide morphology at the initial stage of oxidation. This does not result in a favorable effect on the diffusion of oxygen into the steel during the thermal process. Conversely, when the desiliconized layer is too large, the Si concentration near the surface is too low, which results in a delay in subscale formation. In any of these cases, it is considered that good magnetic properties and coating properties cannot be obtained because good subscales are not formed. Also, by setting the heating rate to 5 ° C / s or more,
By promptly promoting the formation of subscales during the temperature rise process, the morphology and physical properties of the oxides formed during the initial stage of oxidation change, which affects the diffusion of oxygen into the steel during the subsequent soaking process. It is considered to contribute to obtaining good characteristics.

According to the present invention having the above constitutional requirements, the magnetic properties and the film properties are remarkably improved.

Next, the effect of skin pass rolling on the magnetic properties and coating properties was examined. [Experiment 6] C: 0.065%, Si: 3.4%, Mn: 0.071%,
Al: 0.026%, N: 0.0090%, Se: 0.019% and Sb: 0.
After heating the silicon steel slab containing 041% at 1430 ° C for 20 minutes,
Hot rolled, 2.2 mm, 2.3 mm, 2.4 mm, 2.6 mm, 2.7 mm, 2.
A hot-rolled sheet having each thickness of 8 mm was prepared. At this time, 2.3 ~
A 2.8 mm thick hot rolled sheet is skin-passed to a 2.2 mm thickness.
I chose The rolling reductions at this time are 2.3 mm, 2.4 mm, 2.6 mm,
2.7% and 2.8 mm hot-rolled sheets 4.3% and 8.
3%, 15.4%, 18.5% and 21.4%. Next, the hot-rolled sheet was annealed at 1100 ° C., and then pickled to make the desiliconized layer depth in the sheet thickness direction about 40 μm. Then, it was cold rolled to a thickness of 0.22 mm. At this time,
The steel plate temperature immediately after the rolling roll exit side is 250 at least twice.
Rolling was carried out so that the temperature became 0 ° C. This is a rolling process in which the temperature immediately after the steel plate is bitten into a roll and rolled reaches a predetermined temperature. Therefore, the temperature between the passes may be as low as less than 50 ° C. Then, the temperature was raised at a heating rate of 5 ° C./s, and decarburization annealing was performed in wet hydrogen at 850 ° C. for 20 hours (atmosphere P (H ₂ O) / P (H ₂ ) was raised to 0.45 in the heating process. , 0.40 in the soaking process.).

Then, TiO _{2 was} added to 100 parts by weight of MgO.
6 parts by weight of an annealing separator as a slurry was applied to each of the decarburized annealed plate coils and dried, followed by holding at 850 ° C. for 20 hours in a nitrogen atmosphere, followed by 25% nitrogen and 75% hydrogen. After performing secondary recrystallization annealing at a rate of 15 ° C./hr to 1150 ° C. in the atmosphere, purification annealing was performed in a hydrogen atmosphere at 1200 ° C. for 5 hours. After that, a coating containing magnesium phosphate and colloidal silica as main components was applied.

The magnetic properties (magnetic flux density B ₈ , iron loss W _17/50 ) of each product coil thus obtained, the bending adhesion of the coating, and the coating appearance were examined. At this time, the coating properties were good in all cases. The results of examining the effect of the skin pass reduction ratio on the magnetism are shown in FIG. 20% reduction rate
Under the following conditions, it can be seen that the magnetic characteristics are further improved as compared with the case where skin pass rolling is not performed. The surface layer structure of the steel sheet cross section after hot-rolled sheet annealing is shown in FIG. 9, and the surface layer grains after hot-rolled sheet annealing are coarsened by performing skin pass rolling. Therefore, the grain boundary area decreases relatively,
The proportion of intra-granular deformation zones generated in the subsequent cold rolling step will increase. Therefore, it is considered that as a result, the frequency of existence of Goss-oriented grains in the primary recrystallized texture was increased and the secondary recrystallized grains were refined to further improve the iron loss.

Next, the reasons for limiting the component composition of the present invention and the preferred ranges will be described. Regarding the component composition of the slab for silicon steel sheet which is the object of the present invention, C: 0.03 to 0.12
%, Si: 2.0 to 4.5%, acid-soluble Al: 0.01 to 0.05%, N:
It is necessary to contain 0.004 to 0.012%. In addition, if necessary, Mn: 0.02 to 0.20%, at least one selected from S and Se: 0.010 to 0.040%, Sb: 0.
01 to 0.20%, Cu: 0.01 to 0.20%, Mo: 0.01 to 0.10%, S
n: 0.02-0.30%, Ge: 0.02-0.30%, Ni: 0.01-0.50
%, P: 0.002-0.30%, Nb: 0.003-0.10%, V: 0.
003 to 0.10%, B: 0.0005 to 0.03% and Bi: 0.001 to 0.
Each component can be contained in the range of 10%.

C is an important component for improving the crystal structure by utilizing the α-γ transformation during hot rolling. If the content is less than 0.03%, a good primary recrystallization structure cannot be obtained, and if it exceeds 0.12%, decarburization becomes difficult and decarburization becomes poor and the magnetic properties deteriorate, so the content was limited to 0.03 to 0.12%.

Si is an important component for increasing the electric resistance of the product and reducing the eddy current loss. If the content is less than 2.0%, the crystal orientation is impaired by α-γ transformation during final finish annealing, and if it exceeds 4.5%, there is a problem in cold rolling.
Limited to 2.0-4.5%.

Acid soluble Al and N are needed to form the AlN inhibitor. For good secondary recrystallization, acid-soluble Al: 0.01 to 0.05% and N: 0.004 to 0.012% are required. If the amount exceeds this, Al
The inhibitory effect is lost due to the coarsening of N 2. Below this, the amount of AlN is insufficient and the effect of the inhibitor is not sufficient.

Mn, Se and S also function as inhibitors. If the amount of Mn is less than 0.02% or the amount of S and Se alone or in total is less than 0.010%, the inhibitor function becomes insufficient and the amount of Mn is 0.20. %, Or if S and Se alone or in total amount exceeds 0.040%, the temperature required for slab heating is too high to be practical, so Mn is 0.02 to
0.20%, S or Se alone or as a total amount of 0.010-
It is desirable to be in the range of 0.040%.

Further, in order to improve the magnetic flux density, Sb, C
It is possible to add u, Sn, Ge, Ni, P, Nb, V, B, Bi or the like alone or in combination. Sb content is 0.20%
If it exceeds 0.1%, the decarburizing property becomes poor, and if it is less than 0.01%, there is no effect. Therefore, the content is preferably 0.01 to 0.20%. Cu
If the content exceeds 0.20%, the pickling property deteriorates, and if it is less than 0.01%, there is no effect, so the content is 0.01 to 0.20%.
Is preferred. If the content of Sn and Ge exceeds 0.30%, a good primary recrystallization structure cannot be obtained, and if it is less than 0.02%, there is no effect. Therefore, the content of each is preferably 0.02 to 0.30%. Ni
When the content exceeds 0.50%, the hot strength decreases, and 0.01%
If it is less than the above range, no effect is obtained, so the content is preferably 0.01 to 0.50%.

When the content of P exceeds 0.30%, a good primary recrystallized structure cannot be obtained, and when it is less than 0.002, there is no effect. Therefore, the content of P is preferably 0.002 to 0.30%. When the content of Nb and V exceeds 0.10%, the decarburizing property deteriorates, and 0.003%
If it does not meet the requirements, the content is 0.00.
3 to 0.10% is preferable. If the content of B exceeds 0.03%, a good primary recrystallized structure cannot be obtained, and if it is less than 0.0005%, there is no effect. Therefore, the content is preferably 0.0005 to 0.03%. If the Bi content exceeds 0.10%, a good primary recrystallization structure cannot be obtained, and if it does not reach 0.001%, the effect is not obtained. Therefore, the Bi content is preferably 0.001 to 0.10%.

Further, Mo can be added to improve the surface properties. If the content exceeds 0.10%, the decarburizing property deteriorates, and if it does not reach 0.01%, there is no effect, so the Mo content is preferably 0.01 to 0.10%.

Next, the manufacturing conditions of the grain-oriented silicon steel sheet which is the object of the present invention will be described. Obtained slab by continuous casting method or ingot-casting method of molten steel prepared to have the above-mentioned composition by the conventional steelmaking method, 1100 to 1450
Slab heating is performed in the temperature range of ° C, and then hot rolling is performed.

Subsequently, according to the present invention, at 800 to 1200 ° C.
Atmospheric Oxidation and Oxidation in Hot Rolled Sheet Annealing in Temperature Range
Change the annealing temperature and pickling time in the subsequent pickling process
When the sheet thickness after hot-rolled sheet annealing (before cold rolling) is t _I (mm) and the sheet thickness after final cold rolling is t _R (mm), The Si concentration at the center of the plate thickness
The region where the Si concentration ratio is 0.98 or less is from the surface to the thickness direction.
0.5 × t _I / t _R μm or more and 8 × t _I / t _R μm or less. In addition, after hot rolling, before performing hot-rolled sheet annealing, the reduction ratio
Performing skin pass rolling of 20% or less is effective in further reducing iron loss.

Thereafter, the final cold rolling was carried out at a rolling reduction of 80 to 95%.
However, at that time, the steel sheet temperature immediately after the rolling roll exit side must be 150 ° C. or higher and 350 ° C. or lower at least twice. This rolling is Japanese Patent Publication No.
Unlike the technique of aging between passes during cold rolling as disclosed in Japanese Patent No. 9182 or Japanese Patent Laid-Open No. 63-100127, the temperature immediately after the steel sheet is bitten into a roll and rolled. The rolling is such that it reaches a predetermined temperature. Therefore, the temperature between the passes may be as low as less than 50 ° C.

Next, it is necessary to carry out decarburization annealing at a heating rate of 5 ° C./s or more. The decarburization-annealed steel sheet surface is coated with an annealing separator containing MgO as a main component in a slurry form and then dried. Here, the MgO used for the annealing separator has a hydration amount of 10% after hydration at 20 ° C for 60 minutes.
It is advisable to use one whose weight loss due to ignition at 00 ° C for 1 hour) is in the range of 1 to 4%. This is because when the hydration amount of MgO is less than 1%, the formation of forsterite film becomes insufficient and it becomes 4%.
If it exceeds, the amount of water brought into the coil layer becomes too large and the amount of additional oxidation of the steel sheet increases, so that a good forsterite coating may not be obtained. Further, it is preferable to use one having a citric acid activity (CAA40) of 30 seconds to 160 seconds at 30 ° C. If it is less than 30 seconds, the reactivity is too strong and forsterite is rapidly generated and easily peeled off.
This is because if it exceeds the second, the reactivity is too weak and the forsterite formation does not proceed.

The amount of the annealing separator applied is preferably in the range of 4 to 10 g / m ² per one side of the steel sheet. This is because if the coating amount is less than 4 g / m ^2, the production of forsterite becomes insufficient, and if it exceeds 10 g / m ² , the forsterite film is excessively produced and becomes thick, resulting in a decrease in space factor. is there. For the purpose of improving magnetic properties or coating properties, one or more compounds such as oxides and sulfides may be added to the annealing separator alone or in combination.

Next, secondary recrystallization / purification annealing (final finishing annealing) is performed, and then a phosphate-based insulating coating, preferably an insulating coating having tension is applied to obtain a product. Further, known domain refinement treatment may be performed after the final cold rolling, after the final finish annealing or after the insulating coating, which is effective for further reduction of iron loss.

[0071]

[Example] (Example 1) C: 0.068%, Si: 3.27%, M
n: 0.069%, Al: 0.025%, N: 0.0090%, Se: 0.020
%, Cu: 0.01% and Sb: 0.043%, a silicon steel slab heated at 1430 ° C for 30 minutes and hot-rolled to 2.0 mm.
It was a hot rolled sheet. Then, the hot-rolled sheet is annealed at 1100 ° C and then pickled to reduce the depth of the desiliconized layer in the sheet thickness direction to about 3
μm, about 15 μm, about 50 μm, and about 80 μm. The desiliconized layer formed is the Si of the sample cross section.
The distribution was examined by EPMA mapping. Then, it was cold rolled to a thickness of 0.22 mm. At this time, the steel plate temperature immediately after the rolling roll exit side is 50 to 450 only once.
Table 8 shows rolling at a temperature of 50 ° C and rolling at least twice such that the temperature of the steel sheet immediately after the exit side of the rolling roll is 50 to 450 ° C. After that, the temperature is raised at a heating rate of 12 ° C / s,
Decarburization annealing was performed at 850 ° C. for 2 minutes in wet hydrogen.

Next, an annealing separator containing MgO as a main component was applied as a slurry to each of the decarburized annealed plate coils and dried, followed by holding at 850 ° C. for 10 hours in a nitrogen atmosphere, followed by 25% nitrogen. After performing secondary crystal annealing at a rate of 10 ℃ / hr to 1150 ℃ in an atmosphere of 75% hydrogen, 12
Purification annealing was performed for 5 hours in a hydrogen atmosphere at 00 ° C. After that, a coating containing magnesium phosphate and colloidal silica as main components was applied.

[0073]

[Table 8]

The magnetic properties (magnetic flux density B ₈ , iron loss W _17/50 ) of each product coil thus obtained, the bending adhesion of the coating, and the coating appearance were examined. The bending adhesion of the coating is 5 mm
The test piece was wound around a round bar having various intervals and the minimum diameter at which the coating did not peel was measured. The results of these investigations are shown in Table 8. As is clear from Table 8,
All of the adaptations produced under the conditions according to the invention show good magnetic and coating properties.

(Example 2) C: 0.075%, Si: 3.4%,
Mn: 0.075%, Al: 0.026%, N: 0.0082%, Se: 0.02
A silicon steel slab containing 1%, Cu: 0.10% and Sb: 0.024% was heated at 1430 ° C for 30 minutes and then hot-rolled for 2.4 mm.
A thick hot rolled sheet was used. Then, skin pass rolling was performed to make the plate thickness 2.2 mm. Then, the hot-rolled sheet was annealed at 1150 ° C. and then pickled, so that the depth of the desiliconized layer in the sheet thickness direction became about 3 μm, about 15 μm, about 60 μm, and about 100 μm. Then, it was cold rolled to a thickness of 0.22 mm. At this time, rolling was carried out at least twice so that the temperature of the steel sheet immediately after the exit side of the rolling roll would be 300 ° C. This is a rolling process in which the temperature immediately after the steel plate is bitten into a roll and rolled reaches a predetermined temperature. Therefore, the temperature between the passes may be as low as less than 50 ° C. After that, the temperature is raised at a heating rate of 50 ° C / s, and 850 ° C in wet hydrogen,
Decarburization annealing was performed for 2 minutes.

Then, an annealing separator containing MgO as a main component was applied as a slurry to each of the decarburized annealed plate coils and dried, followed by holding at 850 ° C. for 25 hours in a nitrogen atmosphere, followed by 25% nitrogen. After performing secondary recrystallization annealing at a rate of 20 ℃ / hr to 1150 ℃ in an atmosphere of 75% hydrogen, 12
Purification annealing was performed for 5 hours in a hydrogen atmosphere at 00 ° C. After that, a coating containing magnesium phosphate and colloidal silica as main components was applied.

The magnetic properties (magnetic flux density B ₈ , iron loss W _17/50 ), the bending adhesion of the coating, and the coating appearance of each of the products thus obtained were examined. The evaluation of the bending adhesion of the coating is the same as in Example 1.

Table 9 shows the results of these investigations. As is apparent from this, all the conforming examples manufactured under the conditions according to the present invention show good magnetic properties and coating properties.

[0079]

[Table 9]

Example 3 Silicon steel slabs having various component compositions shown in Table 10 were prepared. These silicon steel slabs were heated at 1430 ° C for 30 minutes and then hot-rolled to 2.0 mm.
A thick hot rolled sheet was used. Then, the hot-rolled sheet was annealed at 1125 ° C. and then pickled to make the desiliconized layer depth in the sheet thickness direction about 3 μm, about 10 μm, about 50 μm, about 80 μm. Then, it was cold rolled to a thickness of 0.22 mm.
At this time, rolling was carried out at least twice such that the temperature of the steel sheet immediately after the exit side of the rolling roll was 250 ° C. This is a rolling process in which the temperature immediately after the steel plate is bitten into a roll and rolled reaches a predetermined temperature. Then, the temperature was raised at a heating rate of 15 ° C./s, and decarburization annealing was performed in wet hydrogen at 850 ° C. for 2 minutes.

Next, an annealing separator containing MgO as a main component was applied as a slurry to each of the decarburized annealed plate coils, dried, and then retained in a nitrogen atmosphere at 850 ° C. for 10 hours, followed by nitrogen 25%. After performing secondary recrystallization annealing in a 75% hydrogen atmosphere at a rate of 15 ° C / hr to 1150 ° C,
Purification annealing was performed for 5 hours in a hydrogen atmosphere at 1200 ° C. After that, a coating containing magnesium phosphate and colloidal silica as main components was applied.

[0082]

[Table 10]

For each product coil thus obtained,
The magnetic properties (flux density B ₈ , iron loss W _17/50 ), the bending adhesion of the coating, and the appearance of the coating were investigated. The evaluation of the bending adhesion of the coating is the same as in Example 1. Table 11 shows the results of these investigations. As is apparent from this, all the conforming examples manufactured under the conditions according to the present invention show good magnetic properties and coating properties.

[0084]

[Table 11]

[0085]

The method for producing a grain-oriented silicon steel sheet according to the present invention is a method for producing a grain-oriented silicon steel sheet having an AlN 3 -based inhibitor. Excellent film characteristics and magnetic characteristics can be obtained by the three parties' ideas of cold rolling and decarburization annealing.

[Brief description of drawings]

FIG. 1 is a diagram showing the effect of the desiliconized layer depth after annealing / pickling on a hot rolled sheet on magnetism (magnetic flux density B ₈ and _iron loss value W _17/50 ).

FIG. 2 is a diagram showing the effect of the steel sheet temperature immediately after the rolling roll exit side during cold rolling on magnetism (magnetic flux density B ₈ ).

FIG. 3 is a diagram showing an influence of a hot rolled sheet annealing temperature on magnetism (magnetic flux density B ₈ ).

FIG. 4 is a diagram showing the effect of the depth of the desiliconized layer after annealing / pickling on a hot rolled sheet on magnetism (magnetic flux density B ₈ ) in the case of a 0.19 mm thick product sheet.

FIG. 5 is a diagram showing the influence of the depth of the desiliconized layer after annealing / pickling on a hot rolled sheet on magnetism (magnetic flux density B ₈ ) in the case of a 0.22 mm thick product sheet.

FIG. 6 is a diagram showing the effect of the depth of the desiliconized layer after annealing and pickling on a hot rolled sheet on magnetism (magnetic flux density B ₈ ) in the case of a 0.34 mm thick product sheet.

FIG. 7: Temperature rising rate during decarburization annealing is magnetic (magnetic flux density B ₈ ).
It is a figure showing the influence on it.

FIG. 8 is a diagram showing the influence of the reduction ratio of skin pass rolling before hot-rolled sheet annealing on magnetism (magnetic flux density B ₈ and _iron loss value W _17/50 ).

FIG. 9 is a photograph showing a difference in grain size of a surface layer after hot-rolled sheet annealing with and without skin pass rolling.

─────────────────────────────────────────────────── --- Continuation of the front page (56) Reference JP-A-9-143637 (JP, A) JP-A-7-97631 (JP, A) JP-A-9-143562 (JP, A) JP-A-9- 194942 (JP, A) (58) Fields surveyed (Int.Cl. ⁷ , DB name) C21D 8/12 C22C 38/00 303 C22C 38/06 H01F 1/16

Claims (5)

(57) [Claims] 1. C: 0.03-0.12 wt%, Si: 2.0-4.5 wt%, acid-soluble Al: 0.01-0.05 wt% and N: 0.004-0.012 wt% , the balance Fe and unavoidable impurities. With component composition
After hot-rolling the silicon steel slab and annealing the hot-rolled sheet, cold rolling with a reduction rate of 80-95% is performed, and then decarburization annealing is performed, and then the surface of the steel sheet is coated with MgO. After applying the annealing separator as the main component, in the method for producing a grain-oriented silicon steel sheet of the cold rolling once method consisting of a series of steps of performing secondary recrystallization annealing and purification annealing, after hot-rolled sheet annealing and When the sheet thickness before cold rolling is t _I (mm) and the sheet thickness after cold rolling is t _R (mm), a temperature of 800 to 1200 ° C.
Oxidation and Annealing during Hot Rolled Sheet Annealing
Change the blunt temperature and pickling time in the subsequent pickling process
As a result, in the state before cold rolling, the region where the ratio of Si concentration to Si concentration in the central part of the plate thickness is 0.98 or less is 0.5 × t _I / t _R μm or more in the thickness direction from the surface, 8 × t _I / t _R μ
m or less, at least twice during cold rolling, the rolling at which the steel plate temperature immediately after the rolling roll exit side is 150 ° C. or higher and 350 ° C. or lower is performed, and the heating rate in the decarburization annealing process is 5 ° C. / s or more, a method for producing a grain-oriented silicon steel sheet having excellent magnetic properties and coating properties. 2. A silicon steel slab further comprising: Mn: 0.02-0.20wt%, One or two kinds of S and Se in total of 0.010 ~
The content of 0.040 wt% is included.
Of grain-oriented silicon steel sheet with excellent magnetic and coating properties
Production method. 3. A silicon steel slab further comprising: Sb: 0.01 to 0.20 wt%, Cu: 0.01 to 0.20 wt%, Sn: 0.02-0.30wt%, Ge: 0.02-0.30wt%, Ni: 0.01 to 0.50 wt%, P: 0.002-0.30 wt%, Nb: 0.003-0.10wt%, V: 0.003 to 0.10 wt%, B: 0.0005 to 0.03 wt% and Bi: 0.001-0.10wt% Characterized in that it contains any one or more of
The magnetic properties and coating properties according to claim 1 or 2
An excellent grain-oriented silicon steel sheet manufacturing method. 4. A silicon steel slab further comprising: Mo: 0.01 to 0.20 wt% The material according to claim 1, 2 or 3, characterized in that
Of grain-oriented silicon steel sheet with excellent magnetic and coating properties
Production method. 5. The magnetic property and coating according to claim 1, wherein after hot rolling, skin pass rolling with a rolling reduction of 20% or less is performed before hot-rolled sheet annealing. A method for producing a grain-oriented silicon steel sheet having excellent characteristics.