JPH08269560A - Production of grain-oriented silicon steel sheet without glass film and excellent in iron loss - Google Patents

Abstract

PURPOSE: To produce a grain-oriented silicon steel sheet having no glass film and excellent in iron loss by applying a separation agent at annealing, composed of chlorine-compound-containing MgO, to the surface layer part, having a known grain-oriented silicon steel composition with respectively specified Si and C contents, under specific conditions. CONSTITUTION: A separation agent at annealing, prepared by adding chlorine compound (CaCl2 ) to MgO so that chlorine content becomes 0.05-0.5 pts.wt. based on 100 pts.wt. of MgO, is applied by 1-20% per side to the surface layer part consisting of <=2.0wt.% Si, 0.030-0.10wt.% C, and the balance usually known grain oriented silicon steel components. Then, annealing is executed. By this method, the grain oriented silicon steel sheet having a composition consisting of 2.5-4.5wt.% Si, 0.030-0.10wt.% C, and the balance usually known grain oriented silicon steel components, which has no glass film and is excellent in iron loss, can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a grain-oriented electrical steel sheet which does not have a glass coating (forsterite coating), is excellent in cutting property and punching property, and has high magnetic flux density and low iron loss.

[0002]

2. Description of the Related Art Unidirectional electrical steel sheets are used as iron core materials for electrical equipment such as transformers, and must have good magnetic excitation characteristics and iron loss characteristics. Moreover, in recent years, the market demand for low iron loss materials with particularly low energy loss has been increasing. On the other hand, what is important for consumers of grain-oriented electrical steel sheets is workability as well as magnetic properties and coating properties. The grain-oriented electrical steel sheet is usually surface-treated with a glass coating and an insulating coating formed during final finish annealing.

The glass film is a film whose main component is forsterite (Mg ₂ SiO ₄ ), which is a reaction product of the annealing separator MgO and the oxide film SiO ₂ formed during decarburization.
This glass coating is hard and has strong wear resistance, and has a significant effect on the durability of tools such as slit cutting and punching when processing electromagnetic steel sheets. For example, when punching a grain-oriented electrical steel sheet having a glass coating, the die wears, and the punched sheet is largely returned by punching several thousand times, which causes a problem in use. For this reason, it is necessary to re-polish the mold and replace it with a new one.

This results in a reduction in the work efficiency of the customer at the time of machining the iron core and an increase in cost. Similarly, with respect to slitting property and cutting property, the adverse effect of the glass coating is a problem. Regarding the magnetic properties of grain-oriented electrical steel sheets, this glass coating has an effect of improving iron loss due to the effect of the coating tension, and in the case of a material having a high magnetic flux density, this effect is remarkable, and an effect of improving iron loss of nearly 20% is obtained. To be However, depending on the state of its formation, the increase in the coating thickness and the presence of the internal coating layer have a negative effect on the magnetic flux density reduction and the iron loss improving effect during the magnetic domain refining treatment.

In particular, in recent years, techniques for optical domain, mechanical, and chemical means have been developed as a magnetic domain subdivision technique, and further, a technique for increasing the tension of the insulating coating has been developed. Therefore, iron loss can be improved without the tension of the glass coating. I got it. For this reason, the grain-oriented electrical steel sheet without a glass coating has the advantage that there is no domain wall movement pinning phenomenon during high magnetic flux density and magnetization, and there is a need for development of products with high magnetic flux density and no glass coating. It is rising.

[0006] As a method for producing a grain-oriented electrical steel sheet having no glass coating, for example, there is one disclosed in JP-A-53-22113. In this case, fine particles of alumina containing 5 to 40% of hydrous silicate mineral powder are used as an annealing separating agent with a thickness of an oxide film of 3 μm or less in decarburizing annealing. This is applied to a steel plate and finish annealing is performed. According to this, it is said that an oxide film is thinned, and a glass film that is easily peeled off is formed by blending a hydrated salt mineral, and a glass having a metallic luster is obtained.

Further, as a method for suppressing the formation of a glass film by an annealing separator, in JP-A-56-65983, 20 parts by weight of an additive for removing impurities and 10 parts by weight of an inhibiting substance are mixed in aluminum hydroxide, and the annealing separation is carried out. There is a method of applying the agent to a steel plate to form a thin glass film of 0.5 μm or less. Further, in JP-A-59-96278, Al ₂ O, which has a weak reactivity with SiO ₂ in an oxide layer formed by decarburization annealing.
₃ and M whose activity was decreased by firing at a high temperature of 1300 ° C or higher
There is an annealing separator consisting of gO. According to this, formation of forsterite is suppressed.

Although all of these prior arts are methods for producing a grain-oriented electrical steel sheet having no glass coating, they are industrially inexpensive and do not have a uniform glass coating, and have high magnetic flux density and low iron loss. It is difficult to manufacture a high-grade grain-oriented electrical steel sheet having characteristics.

[0009]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for industrially inexpensively producing a grain-oriented electrical steel sheet having a high magnetic flux density and not having a glass coating. Further, by applying a magnetic domain control technique and a high-tension insulating film to this, a grain-oriented electrical steel sheet having an extremely low iron loss is obtained. Further, it is an object to obtain a product having excellent workability such as punching, cutting and slitting at the same time by suppressing glass film formation.

[0010]

As a result of various studies to solve the above problems, the inventors of the present invention can suppress the formation of forsterite by reducing the amount of surface layer Si of the material before decarburization annealing. , It has been clarified that a high magnetic flux density grain-oriented electrical steel sheet without a glass coating can be manufactured at low cost by adding a relatively small amount of chlorine compounds.

The gist of the present invention is, in terms of weight ratio,
Si: 2.5-4.5%, C: 0.030-0.10
%, The balance is usually 2.0% or less, C: 0.
030 to 0.10%, with the balance being 1% or more and 20% or less on one side of the surface layer portion which is usually composed of a well-known unidirectional electrical steel component,
Further, an annealing separator containing 0.05 to 0.5 parts by weight of a chlorine compound as a chlorine component is applied to 100 parts by weight of MgO as an annealing separator, which is excellent in iron loss without a glass film. It is in the method of manufacturing grain-oriented electrical steel.

[0012]

The present invention will be described in detail below. The present invention, in the method for producing a grain-oriented electrical steel sheet with excellent iron loss, by reducing the amount of surface layer Si of the material before decarburization annealing, suppress the formation of forsterite, by adding a relatively small amount of chlorine compounds It is characterized by obtaining a high-grade grain-oriented electrical steel sheet that is industrially inexpensive, does not have a uniform glass coating, and has high magnetic flux density and low iron loss characteristics.

The final cold-rolled material is decarburized and annealed in a continuous line. By this decarburization annealing, C in the steel is removed and primary recrystallization is performed, and in the conventional 3% Si steel, an oxide film containing SiO ₂ as a main component is simultaneously formed on the surface of the steel sheet. However, since the low Si layer exists near the surface of the steel sheet, the oxide film is hardly formed. Decarburization annealing is 80
The atmosphere is 0 to 875 ° C., and the atmosphere is N ₂ + H ₂ in which the dew point is controlled.

Then, if necessary, a nitriding treatment is performed in the same line or in another line after the latter half of the decarburization annealing or after the completion of the decarburizing annealing. The nitriding amount at this time is 150 ppm or more, preferably 150 to 300 ppm. After this, an annealing separator is applied, dried, wound, and finish annealed. The finish annealing is performed with N ₂ at the time of temperature rise being 30% or more. This stabilizes (Al, Si) N, and good secondary recrystallization is obtained.

The high magnetic flux density material which does not have the finish-annealed glass coating is subjected to shape correction and strain relief annealing, and the insulation coating material coating and heat flattening are performed at 800 to 900 ° C. in a continuous line.

Next, the reasons for limitation of the construction technique in the present invention will be described. The inner layer Si has a specific resistance of 2.5% or more in order to increase the specific resistance and improve the iron loss. On the other hand, if the Si content is too large, bendability of the hot rolled sheet and workability such as cracking during cold rolling are deteriorated, so the upper limit was made 4.5% or less. The surface layer Si is 2.0% or less, preferably 1.0% or less in order to suppress the formation of forsterite that is effective in preventing glass film formation.

On the other hand, regarding the elements described below, the amounts of the same components were set in the flab and the surface layer. C has a lower limit of 0.030% so that the γ phase is appropriately generated and fine dispersion of the precipitate is good, and is set higher unless decarburization is difficult, and its upper limit is 0.10%. Furthermore, the following components are impurities used as a precipitation dispersed phase for secondary recrystallization, and must be contained in appropriate amounts for effective action.

That is, Mn: 0.02 to 0.50%,
S: 0.001-0.05%, acid-soluble Al: 0.00
5 to 0.10%, N: 0.003 to 0.015%, S
b: 0.01 to 0.20%, Se: 0.01 to 0.10.
By properly combining two or more of the above-mentioned%, secondary recrystallization having a high degree of Goss-oriented grain accumulation can be obtained. Other C
At least one of u and Sn may be added so as to be 1.0% or less for the purpose of strengthening the inhibitor.

Here, the surface layer portion comprising the above components is 1% or more on one side in order to stably suppress the oxide film forming reaction after the decarburization annealing step, and if the surface layer low Si portion is too much, iron loss is deteriorated. Cast a slab of 20% or less.

Next, this cast slab is hot-rolled, and then, if necessary, annealed at 950 to 1200 ° C. for 30 seconds to 30 minutes, and then once or in the middle so that the final cold rolling reduction becomes 80% or more. Cold rolled twice or more including annealing, thickness 0.50
The final plate thickness should be less than mm. After that, decarburization annealing is performed in a wet hydrogen atmosphere, and then nitriding treatment is performed if necessary.

Furthermore, as an annealing separator, 0.05 to 0.5 parts by weight of a chlorine compound as a chlorine component is added to 100 parts by weight of MgO, and an annealing separator is applied. Here, if the chlorine content is less than 0.05 part by weight, the oxide film is not uniformly removed. On the other hand, from the industrial point of view of manufacturing at low cost,
Normally, since the annealing separator application equipment for the production of grain-oriented electrical steel sheet with a glass coating is shared, in order to facilitate the work of changing the annealing separator to switch the product type with or without the glass coating,
The upper limit of chlorine content was set to 0.05 parts by weight.

That is, when an annealing separator containing an excessive chlorine content is used, quality troubles are likely to occur in the production of grain-oriented electrical steel sheets that require glass film formation. Have an adverse effect. As described above, the present invention specifies the optimum additive conditions (type, amount) for making the glass coating of the grain-oriented electrical steel sheet having a low Si layer on the surface layer glassless on the surface layer to improve magnetic properties and workability. It is a technology that has been established at a low cost without adverse effects.

Next, finish annealing is performed at 1100 ° C. or higher for secondary recrystallization and purification to produce a low iron loss unidirectional electrical steel sheet having a high magnetic flux density. The effect of the present invention is further enhanced by using a glass film forming technique such as the addition of an oxide formation inhibitor to the conventionally known annealing separator.

[0024]

【Example】

Example 1 Continuous steel ingots A, B, C, D were obtained by forming a static magnetic field in the entire width of the slab perpendicular to the casting direction and supplying molten steel containing the steel components shown in Table 1 with this as a boundary. It was Steel ingot E was prepared by a usual method of supplying molten steel having a single component. Next, these steel ingots are heated and hot-rolled into hot-rolled sheets having a thickness of 2.3 mm, and further hot-rolled sheet annealing is performed at 1050 ° C. for 5 minutes,
Cold rolled to a product thickness of 0.30 mm. Next, these cold-rolled sheets were decarburized and annealed in an atmosphere of wet hydrogen and nitrogen.

Then, an annealing separator containing CaCl ₂ containing 0.1 part by weight of chlorine was applied to 100 parts by weight of MgO, and then high temperature annealing was performed at 1200 ° C. for 10 hours in a hydrogen gas atmosphere.

As shown in Table 2, the product sheets obtained as a result of the invention materials A, B, and C have no glass coating and have a metallic luster as compared with the comparative materials D and E, and have an excellent low iron loss. Got the characteristics.

[Table 1]

[0027]

[Table 2]

Example 2 In the casting stage, after solidifying the portion corresponding to the surface layer or the inner layer, the remaining portion was solidified with different component materials, and a multi-layer steel ingot F containing the steel components shown in Table 3 was obtained. G, H and I were obtained.
Steel ingot J was prepared by a usual method of supplying molten steel having a single component. Next, these steel ingots were heated and hot-rolled to form a hot-rolled sheet having a thickness of 2.0 mm, further subjected to hot-rolled sheet annealing at 1050 ° C. for 5 minutes, and then cold-rolled to a product thickness of 0.23 mm.

Next, these cold rolled sheets were decarburized and annealed in an atmosphere of wet hydrogen and nitrogen. Then, perform nitriding treatment at 750 ° C. for 30 seconds in a hydrogen / nitrogen atmosphere containing 1% of ammonia,
The amount of nitrogen in the steel sheet was 200 ppm. Next, MgO100
NaCl containing 0.3 parts by weight of chlorine based on parts by weight
After applying the annealing separator with the addition of
High temperature annealing was performed in a hydrogen gas atmosphere for an hour.

As shown in Table 4, the product sheets obtained as a result of the invention materials F, G, and H have no glass coating and have a metallic luster and excellent low iron loss as compared with the comparative materials I and J. Got the characteristics.

[Table 3]

[0031]

[Table 4]

Example 3 Hot-rolled sheets K, L, M, N, and O having a three-layer structure of two steel components and having a thickness of 2.3 mm shown in Table 5 were manufactured by a rolling press-bonding method. Steel ingot P
Was prepared by a conventional method of supplying molten steel having a single component.
Next, these steel ingots were heated and hot-rolled to form a hot-rolled sheet having a thickness of 2.3 mm, further subjected to hot-rolled sheet annealing at 1050 ° C. for 5 minutes, and then cold-rolled to a product thickness of 0.30 mm. Next, these cold-rolled sheets were decarburized and annealed in a wet hydrogen and nitriding atmosphere.

Then, an annealing separator containing BaCl ₂ containing 0.06 parts by weight of chlorine was applied to 100 parts by weight of MgO, and then high temperature annealing was performed at 1200 ° C. for 10 hours in a hydrogen gas atmosphere. The resulting product plate is
As shown in Table 6, the materials K, L, M and N of the present invention had no glass coating and had metallic luster and excellent low iron loss characteristics as compared with the comparative materials O and P.

[0034]

[Table 5]

[0035]

[Table 6]

[0036]

EFFECTS OF THE INVENTION According to the present invention, by reducing the amount of Si in the surface layer portion of the material before decarburization annealing, a relatively small amount of chlorine compound is added so that a glass coating (forsterite coating) is not uniformly formed. It has excellent cuttability and punchability,
Moreover, it is possible to inexpensively manufacture a unidirectional electrical steel sheet having a high magnetic flux density and a low iron loss.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the amount of Si in the surface layer of a multilayer material before decarburization annealing and the amount of glass coating on a product plate.

Claims (4)

[Claims] 1. A material before cold rolling which comprises, by weight ratio, Si: 2.5 to 4.5%, C: 0.030 to 0.10%, and the balance consisting of generally known unidirectional electrical steel components. In this case, Si: 2.0% or less, C: 0.03
0 to 0.10%, with the balance being 1% to 20% on one surface of a surface layer portion which is usually a well-known unidirectional electrical steel component, and a chlorine compound is used as an annealing separator with respect to 100 parts by weight of MgO. A method for producing a grain-oriented electrical steel sheet having no glass coating and having excellent iron loss, characterized by applying an annealing separator added in an amount of 0.05 to 0.5 part by weight. 2. By weight ratio, Si: 2.5 to 4.5%, C: 0.030 to 0.10%, Mn: 0.02 to 0.50%, S: 0.001 to 0. 05%, acid-soluble Al: 0.005 to 0.10%, N: 0.001 to 0.015%, balance: Si: 2.0% or less when producing a pre-cold-rolling material consisting essentially of Fe , C: 0.030-0.10
%, Mn: 0.02-0.50%, S: 0.001-
0.05%, acid-soluble Al: 0.005-0.10%,
N: 0.001 to 0.015%, the balance having a surface layer portion substantially consisting of 1% or more and 20% or less on one side, and a chlorine compound as a chlorine content of 0 to 100 parts by weight of MgO as an annealing separator. A method for producing a grain-oriented electrical steel sheet having no glass coating and having excellent iron loss, characterized by applying an annealing separator added in an amount of 0.05 to 0.5 part by weight. 3. By weight ratio, Si: 2.5-4.5%, C: 0.030-0.10%, Mn: 0.02-0.50%, Acid-soluble Al: 0.005- 0.10%, N: 0.001 to 0.015%, Sb: 0.01
.About.0.20% and S, Se: 0.01 to 0.10%, and at the time of producing a pre-cold-rolling material consisting essentially of Fe, Si: 2.0% or less, C : 0.
030-0.10%, Mn: 0.02-0.50%, acid-soluble Al: 0.005-0.10%, N: 0.001
To 0.015%, Sb: 0.01 to 0.20% and S, Se: 0.01 to 0.10%, and the balance is a surface layer portion consisting essentially of Fe 1% on one side. that's all,
The content of the chlorine compound is 20% or less, and the chlorine content is 0.05 to 0.
A method for producing a grain-oriented electrical steel sheet having an excellent iron loss without a glass coating, which comprises applying an annealing separator added in an amount of 5 parts by weight. 4. The grain-oriented unidirectional electrical steel sheet having no glass coating according to claim 1 or 2 or 3, characterized in that the amount of Si in the surface layer is less than 0.1% by weight. Manufacturing method.