JP2953978B2 - Thick grain-oriented electrical steel sheet having no glass coating with excellent insulating coating properties and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a (grassless) thick grain-oriented electrical steel sheet having no glass coating (forsterite or spinel coating). The present invention relates to a thick grain-oriented electrical steel sheet having no glass coating and a method for producing the same.

[0002]

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

[0003] The directionality of the crystal has been greatly improved by the method characterized by the final cold rolling reduction under high pressure using AlN as an inhibitor. At present, it is possible to produce a magnetic flux density close to the theoretical value. ing. On the other hand, when the grain-oriented electrical steel sheet is used by a consumer, the film properties and workability are important together with the magnetic properties. Normally, the grain-oriented electrical steel sheet is surface-treated by a glass coating and an insulating coating formed at the time of final finish annealing. The glass film is made of MgO as an annealing separator and SiO _{2 as} an oxide formed during decarburizing annealing.
And a spinel-based compound of Al ₂ O ₃ , SiO ₂ , MgO or the like, which is mainly composed of forsterite (Mg ₂ SiO ₄ ) and is formed by decomposition of AlN used as an inhibitor.

[0004] This glass coating is hard and has high wear resistance, and has a significant effect on the wear resistance of tools at the time of slitting, cutting, punching, etc. in the processing of a transformer core.
For example, when performing a punching process on a grain-oriented electrical steel sheet having a glass coating, a die is worn, and the return of a sheet punched out by punching several thousand times becomes large enough to cause a problem in use. For this reason, it is necessary to re-polish the mold or replace it with a new one, which leads to a reduction in work efficiency and an increase in cost at the time of iron core processing at the customer. Similarly, the adverse effect of the glass coating is also a problem on the slitting property, the cutting property and the like.

[0005] With respect to the magnetic properties of the grain-oriented electrical steel sheet, iron loss is improved by the film tension of the glass coating, and this effect is remarkable in the case of a material having a high magnetic flux density.
An iron loss improving effect of about 20% can be obtained as compared with a case without a coating. However, the state of formation, particularly the increase in the thickness of the coating and the presence of the internal oxide layer, have a negative effect on the reduction of the magnetic flux density and the effect of improving iron loss at the time of magnetic domain refining. But,
On the other hand, the glass coating plays an important role in the adhesion of the insulating coating to the steel sheet surface as a whole due to its structure that develops finely and densely in the forming process.

In the grain-oriented electrical steel sheet having no glass coating, the adhesion of the insulating coating is disadvantageous because there is no anchor effect by the glass coating. In particular, in the case of a thick material, the adhesion of the insulating film cannot be sufficiently obtained, and not only the frame peeling at the time of slitting, cutting, and punching, but also peeling due to bending or strain relief annealing or in extreme cases In some cases, the steel sheet may fall off from the steel plate surface during baking of the insulating film in the production line. Therefore, it is important to develop a technique for improving the adhesion of an insulating film in the production of a grain-oriented electrical steel sheet having no glass film.

As a method for producing a grain-oriented electrical steel sheet having no glass coating, JP-A-64-62417 discloses a method.
Decarburization annealing at a temperature of 800 to 850 ° C. in an atmosphere of PH ₂ O
/ PH ₂ is set to 0.25 to 0.55, and annealing separation is performed by mixing 2 to 40 parts by weight of one or more alkali metal or alkaline earth metal chlorides with respect to 100 parts by weight of magnesia. A method for producing a grain-oriented electrical steel sheet having a metallic luster characterized by applying an agent and performing finish annealing is described. As a result, chloride in the annealing separating agent decomposes SiO _{2 in} the oxide and does not lead to the formation of a glass film, so that a remarkable improvement in punching property is obtained.

Further, in recent years, Japanese Patent Application Laid-Open No. 6-173019 discloses a method for obtaining a unidirectional magnetic steel sheet having excellent magnetic properties and a large thickness and a small glass coating. In this method, the slab is heated at a low temperature of less than 1280 ° C., and then continuously subjected to cold rolling at a rolling reduction of 60 to 79% without performing hot rolling and hot-rolled sheet annealing, and then decarburizing annealing and applying an annealing separating agent. In a method for producing a thick unidirectional electromagnetic steel sheet having a thickness of 0.4 to 1.0 mm, which is subjected to finish annealing and applying an insulating coating agent, the hot rolling end temperature is set to 800 to 1100 ° C. and the final three passes of hot rolling are accumulated. The rolling reduction is set to 40% or more, the temperature of the steel sheet between the cold rolling passes is set to 250 ° C. or less, and the average particle size of the primary recrystallized grains from the decarburizing annealing to the start of the final finish annealing is 18
３０30 μm, a nitriding treatment was performed after hot rolling and before the start of final annealing, and Li, K, Na, Ba, Ca, Mg, Zn,
One or two or more selected from chlorides, nitrates, sulfides, and sulfates of Fe, Zr, Sr, Sn and Al
An object of the present invention is to provide a method for producing a grain-oriented electrical steel sheet having excellent magnetic properties and a small glass coating with a small thickness by applying 0 parts by weight of an annealing separator.

All of these prior arts relate to a so-called glassless grain-oriented electrical steel sheet which does not have a glass coating and does not have a thick glass coating or has little glass coating. A remarkable improvement in workability such as cutability has been obtained. However, in the treatment of the insulating film in these conventional techniques, sufficient workability and adhesion of the insulating film cannot be obtained depending on the surface condition, and it is still a sufficient technique in consideration of the overall film performance of the product. Not really.

[0010]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for manufacturing a glassless grain-oriented electrical steel sheet having a large thickness by forming a glass film on the surface of the steel sheet in comparison with a conventional glassless material manufacturing technique. Another object of the present invention is to provide a product which is more reliably prevented and which has excellent workability and adhesion and a method for producing the same.

[0011]

In order to obtain the product of the present invention, C is used as a steel component as a starting material in a weight ratio of C;
0.075%, Si; 2.5-4.5%, acid-soluble Al;
0.010-0.040%, N: 0.0030-0.0
130%, S ≦ 0.0140%, Mn: 0.05-0.
Using an electromagnetic steel slab containing 45%, the balance being Fe and unavoidable impurities, this slab is heated to a temperature of less than 1280 ° C., hot-rolled, and subjected to one or two or more cold-rolling steps with intermediate annealing. After the final plate thickness, then decarburizing annealing,
After performing a nitriding treatment and applying an annealing separating agent, a high-temperature finish annealing is performed, and a manufacturing method including heat flattening and application and baking of an insulating film is performed.

That is, in the present invention, the slab heating step does not dissolve the inhibitor element, for example, Al, N, Mn, S, etc. in the steel, and after the decarburizing annealing, the material is subjected to a nitriding treatment in a strong reducing atmosphere. By doing so, an inhibitor containing (Al, Si) N as a main component was formed, and a slurry containing a halogen compound as an annealing separator in a range of 2,000 to 200,000 ppm as a total amount of halogen elements per 100 parts by weight of MgO. Is applied as final finish annealing, and the average temperature rise rate at 800 to 1100 ° C is 12 ° C /
After the final annealing at Hr or less, the basic step is to bake the insulating coating agent while maintaining the tension at a certain level or less after developing glass-less and good secondary recrystallization in the final annealing process.

[0013] In the production of the glassless, thick, grain-oriented electrical steel sheet of the present invention having excellent adhesion by such components and processes, the surface treatment in the process of applying an annealing separator, finishing annealing and applying an insulating film. The method is unique. The final cold rolled material is first decarburized and annealed in a continuous line. By this decarburization annealing, C in the steel is removed and primary recrystallization is performed, and at the same time, an oxide film mainly composed of SiO ₂ is formed on the surface of the steel sheet. This decarburization annealing is 800-875 ° C
In is performed by controlling the P H ₂ O / P H ₂ in N ₂ + H ₂ atmosphere.

Next, a nitriding treatment is performed in the latter half of the decarburizing annealing, after the end of the decarburizing annealing, or in another line. At this time, the nitriding amount is set at 150 to 300 ppm. After this,
An annealed separating agent is applied, dried and wound on a coil.
At this time, as an annealing separating agent which is the first feature of the present invention, H, Li, Na, K, Mg, Ca,
Sr, Ba, Ti, Zr, V, Ta, Cr, Mo, W,
Mn, Fe, Co, Ni, Cu, Zn, Ag, Cd, A
One or more halogen compounds selected from the group consisting of 1, Sn, Pb, Sb, Bi, and B are added and used in a total amount of 2,000 to 200,000 ppm of halogen elements.

The final finish annealing which is the second feature of the present invention, which is performed subsequently, is important in the process of the present invention in order to more reliably obtain glasslessness. That is, nitriding treatment is performed after decarburizing annealing as in the present invention, and (Al, Si)
In the case of forming an inhibitor mainly composed of N and obtaining a steel sheet having glassless and good secondary recrystallization by using an annealing separator and finish annealing conditions, the atmosphere at the time of annealing and the heating at elevated temperature Speed is important. In the present invention, as a countermeasure against this, the final finish annealing is performed at a temperature rise of 80%.
Finish annealing is performed at an average temperature rise rate of 12 ° C./Hr or less at 0 to 1100 ° C.

As in the present invention, MnS is used as an inhibitor.
Is formed almost without using (Al, Si) N, and Al is formed later.
In the process of changing to N, the secondary recrystallization initiation temperature is higher than that of a normal grain-oriented electrical steel sheet, and is 1100 ° C.
Before and after. Therefore, it is necessary to keep the inhibitor stable up to the secondary recrystallization start region while performing the glassless reaction and the oxidation suppression. This is because the conditions of the temperature raising process greatly affect the absorption of nitrogen from the atmospheric gas and the decomposition of the inhibitor due to the denitrification in the glassless process. For this reason, unless a special finish annealing cycle is used as in the present invention, a steel plate having a uniform glassless state and good secondary recrystallization cannot be obtained. The final annealing conditions are as follows: the time required for uniform decomposition of the glass coating.
As a condition of 0 to 1100 ° C., in an N ₂ + H ₂ atmosphere, the average heating rate is set to 12 ° C./Hr or less, and the temperature is gradually raised or a uniform temperature is maintained.

The thus treated glassless grain-oriented electrical steel sheet is subjected to an insulating coating treatment and a heat flattening treatment for both shape correction and distortion removal in a continuous line. At this time, the insulating film treatment, which is the third feature of the present invention, is important for obtaining good adhesion. In a thick glassless grain-oriented electrical steel sheet such as the material of the present invention, it is difficult to ensure good adhesion and workability of the insulating film by the conventional method of treating an insulating film.

That is, unless the components of the insulating film and the baking conditions are properly controlled, the adhesion and workability are extremely poor, and the insulating film falls off or foams from the steel sheet surface during the cooling process of the baking process. Further, even if the film formation is realized, in the core processing steps such as punching, cutting, bending and the like, peeling near the processed portion, which is usually called frame peeling, and propagation of film peeling due to processing impact occur.

As a countermeasure, the present inventors have studied an insulating film for a glassless grain-oriented electrical steel sheet, paying attention to the film tension control by the film component and the baking conditions. As a result, it has been found that the above-mentioned problems can be solved by controlling the heating conditions at the time of baking for an insulating film having a film tension of 0.4 kg / mm ² or less.

That is, in the conventional insulation coating treatment of a grain-oriented electrical steel sheet having a glass coating, the ratio of colloidal silica to phosphate is appropriately controlled in order to improve iron loss and magnetostriction characteristics.
Tension imparting insulating coatings have been treated. Instead, in the present invention, a low-tension coating agent having a novel composition is used, or in the case of a phosphate-colloidal silica-based coating, the insulating coating is heated under a constant heating condition with a component system in a region having a small tension effect. And the amount of adhesion.

The components of the insulating coating are: (a) 100 parts by weight of phosphoric acid and Al ₂ O ₃ , MgO, Zn
15 to 35 parts by weight of one or more of O, CaO and one or more of chromic acid, boric acid, and silicate compound
(B) 80 to 200 parts by weight of colloidal silica and 4 to 22 parts by weight of a chromium compound are used for 100 parts by weight of the first phosphate of Al, Mg, Zn, and Ca, and 800 to 200 parts by weight in a continuous line. It is baked at 900 ° C. The application conditions at this time are ² to 6 g / m ² in terms of the application amount after drying and baking of the insulating film, and the coating is processed so that the film tension is 0.4 kg / mm ² or less.

Next, the reasons for limiting the constituent elements in the present invention will be described. First, in the glassless grain-oriented electrical steel sheet of the present invention, the total amount of substances such as forsterite and spinel on the steel sheet surface is 0.45 g / m ² or less as MgO, SiO ₂ , and Al ₂ O ₃ . This is because these oxide substances cause deterioration of workability such as cutting and punching in the iron core processing step, and particularly, there is a large problem in the punching of the iron core for a rotating machine. If it exceeds 0.45 g / m ² ,
These are limited because good processability cannot be obtained. Further, in the product of the present invention, the surface tension generated by the insulating coating is 0.4 kg / mm ² or less. This is because when a very good glassless material is obtained as in the present invention, there is no anchor effect due to the root of the glass coating unlike the conventional grain-oriented electrical steel sheet. For this reason, the adhesion of the insulating film is poor, and the higher the film tension, the lower the adhesion. If the tension due to the insulating coating exceeds 0.4 kg / mm ² , the adhesion of the insulating coating to the steel sheet surface is reduced, and in extreme cases, the insulating coating falls off the steel sheet surface during cooling in the insulating coating application step.

[0023] The thickness of the steel plate is 0.35 mm or more.
The material of the present invention is characterized by providing a product with a glassless and low-tensile insulating coating. In grain-oriented electrical steel sheets, it is one of the important techniques in recent years to obtain a low iron loss material by utilizing the iron loss improvement effect by the film tension. For this reason,
When a low-tensile coating is applied as in the present invention, the application is limited when the plate thickness is large. If the plate thickness exceeds 0.35mm,
Since there is almost no effect of improving iron loss by tension, no problem occurs.

Next, the reasons for limiting the manufacturing method of the present invention will be described. First, the reasons for limiting the component composition of the material slab used as the starting material are as follows. C content thereof becomes unstable secondary recrystallization is less than 0.021%, 1.80Te flux density of the product even when the secondary recrystallization at B ₈
It will be as low as sla. On the other hand, if the content exceeds 0.075%, a long time is required for decarburization, which impairs productivity. S
The specific resistance of i changes depending on its content. 2.5%
If it is less than 30, good iron loss characteristics cannot be obtained. On the other hand, 4.5%
If the content is too large, cracks and breaks occur frequently during cold rolling, making stable cold rolling work difficult. One of the characteristics of the component system of the starting material of the present invention is that S is set to 0.0140% or less.

Conventionally known techniques, for example, JP-B-47-25
In the technology disclosed in Japanese Patent Publication No. 220, S is M
nS is an element that forms a precipitate necessary for causing secondary recrystallization to occur, and there is a content range in which S is most effective in the above-mentioned known technology, and MnS is contained in a slab heating step performed prior to hot rolling. It was defined as an amount capable of forming a solid solution. However, in a recent study, in a production process of a grain-oriented electrical steel sheet using (Al, Si) N as a precipitate necessary for secondary recrystallization, a slab containing a large amount of Si in a material is heated at a low temperature to perform slab heating. When hot rolling, S
Was found to promote poor secondary recrystallization. When the amount of Si in the material is 4.5% or less, if S is 0.014% or less, preferably 0.0070% or less, occurrence of secondary recrystallization failure does not occur at all.

In the present invention, (Al, Si) N is used as a precipitate required for secondary recrystallization. Therefore, the minimum A
To secure 1N, acid-soluble Al must be 0.010% or more and N must be 0.0030% or more. However, if the acid-soluble Al exceeds 0.040%, the Al
N becomes inappropriate and secondary recrystallization becomes unstable.
Limited to 10-0.040%. On the other hand, if the N content exceeds 0.0130%, cracks on the surface of the steel sheet called blisters occur, and the grain size of primary recrystallization cannot be adjusted, so that the content is limited to 0.0030 to 0.0130%. M
If n is less than 0.050%, secondary recrystallization becomes unstable.
However, although the higher B ₈ value becomes large, certain level of addition becomes disadvantageous in cost. For this reason, 0.05-0.
Limited to 45%.

Next, as an annealing separator, MgO is used.
One or more halogen compounds are added in a total amount of 2,000 to 200,000 ppm of the halogen element. As the halogen compound at this time, preferably, H, Li, Na, K, Mg, Ca, Sr, B
a, Ti, Zr, V, Ta, Cr, Mo, W, Mn, F
e, Co, Ni, Cu, Zn, Ag, Cd, Al, S
one or two selected from n, Pb, Sb, Bi, and B
Seeds or more are added.

These halogen compounds play an important role in controlling the formation and decomposition of the glass film during the temperature rise in the finish annealing. In particular, in the decomposition reaction of the glass film, the halogen compound etches Fe and film components in the glass film layer during the temperature rise in the final annealing, and removes the sulfur in the film layer.
It releases iO ₂ , spinel, etc. from the surface layer of the base iron, causing an absorption reaction of the coating components into the annealing separator.

If the total amount of halogen elements of the halogen compound is less than 2,000 ppm, it is difficult to obtain a product having no glass coating uniformly, and the amount of residual forsterite or spinel substance on the surface is increased, which is limited. On the other hand, if the total amount of halogen elements exceeds 200,000 ppm,
The constituent elements of the additive diffuse into the steel and have an adverse effect on the inhibitor.Excessive halogen elements cause excessive etching of the grain boundaries and the surface, resulting in poor surface conditions and adverse effects during subsequent purification. It is not preferable because it gives.

These additives first lower the melting point of the surface of MgO at around 800 ° C. in the temperature rising stage of the finish annealing, and form an MgO—SiO ₂ -based coating on the surface layer of the steel sheet at an early stage. This suppresses additional oxidation from the atmospheric gas into the steel. Thereafter, after 1000 ° C., which is the latter stage at the time of temperature rise, the Fe portion of the coating layer is etched by the halogen compound, and the glass coating layer is decomposed. Thereafter, when the film decomposition reaction proceeds at a higher temperature, the surface without the glass film is subjected to thermal etching at a high temperature, and a smooth steel plate surface is obtained.

Next, in the final finish annealing in the present invention, the average rate of temperature rise at 800 to 1100 ° C. is 12 ° C./Hr
Performed below. In the process of the present invention, the etching effect of the annealing separating agent is characterized in that the reaction proceeds effectively by slow heating in the finish annealing. With rapid heating exceeding this, it is difficult for the decomposition reaction of the glass coating during the heating process to occur uniformly,
Uniform glasslessness cannot be obtained. In addition, there is a limitation because the balance between the inhibitor inhibitory rate and the appropriate amount of the inhibitor at the time of grain growth or the like in the steel sheet at the time of temperature rise is broken, and good secondary recrystallization cannot be obtained.

When performing gradual heating at 800 to 1100 ° C., it is most preferable to maintain a uniform temperature at a constant temperature in this range in order to sufficiently cause a glassless reaction. The atmosphere gas at this time is not particularly limited, but is preferably an N ₂ + H ₂ atmosphere containing 25% of N ₂ .
% Or more is advantageous for keeping the inhibitor stable in the process using the material of the present invention as a starting material.

In the present invention, the processing conditions of the insulating film are adjusted by adjusting the components of the insulating film agent and the processing conditions so that the film tension becomes 0.4 kg / mm ² . The present inventors have studied the adhesiveness of the insulating coating of the glassless grain-oriented electrical steel sheet and found that the coating tension has a great effect on the adhesiveness of the insulating coating. 0.4kg tension
If it is / mm ² or more, the adhesion between the insulating film and the steel sheet decreases as the tension increases.

This is because there is no improvement in the adhesion due to the anchor effect with the ground iron by the glass coating unlike the conventional grain-oriented electrical steel sheet. When the tension is 0.4 kg / mm ² or more, there is no glass coating, so the tension of the insulating coating causes cracks at the interface between the coating and the ground iron during handling such as baking or coil transport, and the coating may fall off. The coating peels off due to the impact of cutting, punching, or the like in a later core processing step. In particular, in the case of a thick material such as the material of the present invention, when the interface of the insulating film is smooth, film peeling due to bending, impact, or the like is more likely to occur. Therefore, control of the interface state by film tension or the like is important.

Preferably, the insulating coating agent is (a) 100 parts by weight of phosphoric acid and Al ₂ O ₃ , MgO, Zn.
15 to 35 parts by weight of one or more of O, CaO and one or more of chromic acid, boric acid, and silicate compound
(B) A treatment solution consisting of 80 to 200 parts by weight of colloidal silica and 4 to 22 parts by weight of a chromium compound with respect to 100 parts by weight of a primary phosphate of Al, Mg, Zn, and Ca is dried and baked. 2-6g by weight after
/ M ² is important for tension control.

In the coating composition in (a), the ratio of phosphoric acid to oxides such as Al ₂ O ₃ , MgO, ZnO, CaO is important. This ratio is important for vitrification of the coating and control of free phosphoric acid. Al ₂ O ₃ , MgO, Zn
If the total amount of O, CaO, etc. is less than 15 parts by weight, the coating after baking tends to become sticky due to an increase in free phosphoric acid. On the other hand, if it exceeds 35 parts by weight, the oxides become excessive, and the vitrification of the coating becomes insufficient, causing roughness on the surface, deteriorating the space factor by powdering, or impairing the adhesion of the coating. Limited.

The chromic acid compound and the silicate compound react with phosphoric acid or oxide as a main component to prevent stickiness due to free phosphoric acid, improve the vitrification of the film, and form a glossy film. If the amount is less than 0.5 part by weight, these effects cannot be obtained. If the amount exceeds 10 parts by weight, the chromium compound or silicate becomes excessive, causing stickiness by itself or impairing the appearance of the coating, which is limited.

In the case of the composition in (b), Al, M
The ratio of primary phosphate of g, Zn, Ca, colloidal silica, and chromium compound is important for controlling film tension, film appearance and corrosion resistance. If the primary phosphate of Al, Mg, Zn, Ca is less than 80 parts by weight of colloidal silica, the coating tension becomes large, and a low-tension coating as in the present invention cannot be obtained, and good adhesion is obtained. I can't achieve it. 200
If the amount is more than 10 parts by weight, low tension and improvement in appearance of the coating can be sufficiently achieved, but cracks are generated in the coating due to insufficient binder, and corrosion resistance is deteriorated, so that it is limited.

Next, the coating amount of the coating agent in the treatment of the insulating coating is important for obtaining a good product appearance and workability. If the adhesion amount is less than 2 g / m ² , the sealing properties of the insulating coating agent will be insufficient, and oxidation of the steel sheet surface will occur depending on the atmospheric conditions at the time of baking, resulting in uneven color tone and impairing the workability due to the generation of oxides. On the other hand, if the thickness exceeds 6 g / m ² , the space factor is deteriorated due to an increase in the thickness of the insulating film, and the deterioration of the adhesion is reduced.

[0040]

【Example】

(Example 1) C: 0.054% by weight, Si: 3.2 by weight ratio
5%, Mn: 0.10%, acid-soluble Al: 0.030%,
S: A slab comprising 0.0070%, the balance being Fe and unavoidable impurities, heated to a temperature of 1250 ° C., hot-rolled to a thickness of 3.0 mm, annealed at 1130 ° C., pickled and cold-rolled, The cold rolled sheet was 0.5 mm thick. Then N ₂ 25% + H ₂ 7
After decarburizing annealing at 850 ° C. × 250 seconds in an atmosphere having a dew point of 65 ° C. and 5%, N ₂ 25% +
H ₂ 75% + NH ₃ in the steel N amount in a dry atmosphere 200pp
m was obtained as a starting material by performing a nitriding treatment.

As shown in Table 1, the steel sheet was coated with an annealing separator prepared by adding a halogen compound to MgO, and then, as a finish annealing condition, the temperature was raised under an atmosphere and heat cycle as shown in FIG. Heat treatment was performed.

Next, the steel sheet was made 1% H ₂ SO ₄ , 85
After performing the topical ring at 15 ° C. × 15 seconds, the insulating coating agent solution having the composition shown in Table 2 was dried to have a weight of 3.0 g / m 2.
^A baking process was performed so as to obtain ² . Table 3 shows the surface condition of the steel sheet, the cutability of the steel sheet after the insulating film treatment, the state of the edge portion after the cutting, and the result of the film adhesion in this test.

[0043]

[Table 1]

[0044]

[Table 2]

[0045]

[Table 3]

As a result of this test, when the annealing separator of the present invention was applied and a low-strength insulating film using the phosphoric acid-oxide type composition of the present invention as the insulating film agent was baked, any of them was baked. Extremely good workability such as cutability and adhesion,
A product with excellent adhesion was obtained. On the other hand, in the case where the annealing separator of the present invention and the insulating film of the comparative material are not applied, in any case,
The cutting properties and adhesion were poor, and especially when a high-tension type coating agent was baked as an insulating film, the adhesion was extremely poor. FIG. 2 shows a sample cutting test method, in which 1: sample, 2: cutting blade, 3: press.

Example 2 The same material as in Example 1 was used as a starting material, and a cold-rolled sheet having a thickness of 0.5 mm, which was similarly treated, was similarly decarburized and nitrided to obtain a starting material. Next, an annealing separating agent to which a halogen compound having a composition shown in Table 4 was added was applied, and the final annealing was performed by changing the heating conditions at the time of raising the temperature as shown in FIG. Then, as an insulating coating agent, 7
5% H ₃ PO ₄ 100 ml + MgO 15 g + ZnO
7 g + a CrO ₃ 3 g composed of the treatment agent was applied so as to 4.5 g / m ² in weight after drying, it was baked for 850 ° C. × 30 seconds. Table 5 shows the results of the insulating film characteristics and the adhesion properties.

[0048]

[Table 4]

[0049]

[Table 5]

As a result of the test, both the annealing separator of the present invention and the finish annealing resulted in good glasslessness, and in particular, the finish annealing maintained at 1000 ° C.
The result of (2) was a uniform and completely glassless condition. As a result, the workability such as the cutting property and the punching property was extremely excellent. On the other hand, in the case of FIG. 1 (3) in which the rate of temperature rise in the finish annealing is high, oxide residue which is seen as a slight glass coating layer is observed, resulting in considerably inferior workability such as cutability and punchability. Was.

[0051]

According to the present invention, in the production of a grain-oriented electrical steel sheet having a large thickness, it does not have a glass coating and has excellent adhesion of an insulating coating. It is possible to obtain a grain-oriented electrical steel sheet having extremely excellent workability such as

[Brief description of the drawings]

FIG. 1 is a table showing finish annealing conditions in Examples 1 and 2. (1) and (2) are based on the temperature raising condition of the present invention, and (3) is the finish annealing condition of the comparative example.

FIG. 2 is an explanatory diagram showing a cutting test method. 30mm × 20
Twenty samples of 0 mm were laminated and cut by applying a load to the cutting blade, and the cutting load at that time was recorded.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kizu Ishibashi 1-1, Tobata-cho, Tobata-ku, Kitakyushu Nippon Steel Corporation Inside Yawata Works (72) Inventor, Kimihiko Sugiyama 1st, Tobita-cho, Tobata-ku, Kitakyushu No. 1 Nippon Steel Corporation Yawata Works (56) References JP-A-5-263135 (JP, A) JP-A-6-17137 (JP, A) JP-A-5-311353 (JP, A) JP-A-5-320770 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) C22C 38/00 303 C21D 9/46 501 C23C 22/00

Claims (4)

(57) [Claims] 1. A steel sheet containing 2.5 to 4.5% of Si by weight, and the total amount of forsterite and spinel on the surface of the steel sheet is 0.45 g / MgO, SiO ₂ , Al ₂ O _3.
m ² or less, and the film tension brought to the steel sheet surface by the insulating film is 0.4 kg / mm ² or less, and the sheet thickness is 0.3
A thick grain-oriented electrical steel sheet having no glass coating and having an excellent insulating coating characteristic characterized by being 5 mm or more. 2. C: 0.021 to 0.075% by weight, Si: 2.5 to 4.5%, acid-soluble Al: 0.010 to 0.040%, N: 0.0030 to 0.2% by weight. 0.0130%, S ≦ 0.0140%, Mn: 0.05 to 0.45%, The remainder is hot-rolled with a silicon steel slab consisting of Fe and unavoidable impurities, and once or twice or more with intermediate annealing The steel sheet having a final sheet thickness of 0.35 mm or more is subjected to decarburizing annealing, nitriding annealing, applying an annealing separator, and finish annealing.
In a method of manufacturing a grain-oriented electrical steel sheet having no glass coating by applying an insulating coating agent and baking and heat flattening, MgO as an annealing separator,
A slurry in which one or more halogen compounds are blended in a total amount of 2,000 to 200,000 ppm of the halogen element amount is applied, and the final finish annealing is performed.
Average temperature rise rate at 800-1100 ° C during temperature rise 12 ° C /
After finish annealing at Hr or less, the coating tension is 0.4 kg / mm ²
A method for producing a thick grain-oriented electrical steel sheet having no glass coating having excellent insulating coating properties, comprising baking an insulating coating agent as follows . 3. The method according to claim 1, wherein the halogen compound added to the annealing separator is H, Li, Na, K, Mg, Ca, Sr, Ba, T
i, Zr, V, Ta, Cr, Mo, W, Mn, Fe, C
o, Ni, Cu, Zn, Ag, Cd, Al, Sn, P
3. The method for producing a thick grain-oriented electrical steel sheet having no glass coating having excellent insulating coating properties according to claim 1 or 2, wherein at least one selected from b, Sb, Bi, and B is selected. . 4. An insulating film treating agent comprising: (a) 100 parts by weight of phosphoric acid, Al ₂ O ₃ , MgO, Zn
15 to 35 parts by weight of one or more of O, CaO and one or more of chromic acid, boric acid, and silicate compound
(B) 100 to 100 parts by weight of primary phosphate of Al, Mg, Zn, and Ca, a processing solution consisting of 80 to 200 parts by weight of colloidal silica and 4 to 22 parts by weight of a chromium compound is dried and baked. 2-6g in weight
The method for producing a thick grain-oriented electrical steel sheet having no glass coating having excellent insulating coating properties according to claim 2 or 3, wherein the coating is applied in the range of / m ² .