JPH0741860A - Production of grain-oriented silicon steel sheet - Google Patents

Abstract

PURPOSE:To produce a grain-oriented silicon steel sheet high in magnetic flux density, in the temp. raising stage in decarburizing annealing for a strip having a specified compsn. rolled into a final prduct thickness, by specifying the deheating amt. in the strip in a roll on the heated side. CONSTITUTION:A strip S having a compsn. contg., by weight, <=0.10% C, 2.5 to 7.0% Si and ordinary, inhibitor components, and the balance Fe with inevitable impurities and rolled into a final product thickness is heated electrically between two pairs of upper and lower rolls R1 and R2 in the temp. raising stage in decarburizing annealing. At this time, the strip S is cooled at a P point by the roll R2 on the heated side, the deheating amt. in the strip S at the outlet side roll R2 is regulated to <=200 deg.C, and the strip S is heated and is thereafter subjected to decarburizing and finish annealing. Thus, the grain- oriented silicon steel sheet having good magnetic properties is stably obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention has an S content of 2.5 to 7.0%.
The present invention relates to a method for producing a grain-oriented electrical steel sheet containing i and having a high magnetic flux density.

[0002]

2. Description of the Related Art Generally, the magnetic properties of a grain-oriented electrical steel sheet are evaluated by both the iron loss property and the excitation property. Increasing the excitation characteristics is effective for downsizing the porcelain that increases the design magnetic flux density. On the other hand, reducing the iron loss characteristics is effective in reducing the loss of heat energy when used as an electric device and saving the power consumption. further,
Aligning the <100> axes of the crystal grains of the product in the rolling direction can improve the magnetization characteristics and lower the iron loss characteristics.
In recent years, much research has been conducted especially in this respect, and various manufacturing techniques have been developed.

As a result, there are two typical manufacturing techniques for obtaining a high magnetic flux density in the typical industrially manufactured grain-oriented electrical steel sheet manufacturing techniques. As a first technique, Japanese Examined Patent Publication No. 40-15644 was disclosed. This makes AlN + MnS act as an inhibitor,
This is a manufacturing technique in which the rolling ratio in the final cold rolling step is a strong reduction exceeding 80%. By this method, the degree of integration of the (110) [001] orientation of the secondary recrystallized grains is high, and B ₈ is 1.
A grain-oriented electrical steel sheet having a high magnetic flux density of 870 (T) or higher is obtained. Furthermore, as a second technique, Japanese Patent Publication No.
MnS or MnSe + Sb disclosed in 13469.
A manufacturing technology has been developed in which the double cold-rolling process is used to function as an inhibitor.

As described above, many studies have been made on the production method of the grain-oriented electrical steel sheet,
The basic process has been largely defined. However, from the viewpoint of energy saving, the demand for high efficiency and miniaturization of electrical equipment is becoming more and more stringent, and in response to this, unidirectional electrical steel sheet with good magnetic properties is industrially stable and inexpensive. The technology for manufacturing is not yet completed. One of the keys to improving and stabilizing magnetic properties and improving productivity in the manufacturing process of unidirectional electrical steel sheets is
Decarburization annealing process is in control.

The inventors of the present invention have considered a method for treating the decarburization annealing step efficiently and by saving energy, and have changed the conventional heating method using gas energy from an efficient heating method using electric energy, particularly to a heating step. I have considered applying it.
Generally, there are an induction heating method and a direct current heating method for applying electric heating. Among these, efforts are being made to expand the application centered on the induction heating method.

The efficiency of the induction heating method is about 60%, but the efficiency of the direct current heating method is about 85%, which is desirable from the viewpoint of energy saving. Therefore, the present inventors have been working on applying a direct electric heating method, which is efficient even among electric heating. As a typical method for this, there is a method in which a strip is passed between two pairs of rolls to continuously heat by energizing. However, this method has a problem that the magnetic properties, particularly the magnetic flux density, are lower than those of the conventional gas heating method.

[0007]

DISCLOSURE OF THE INVENTION The present invention uses an efficient heating method using electric energy in the heating stage of the above decarburization annealing, which is industrially stable and has a good magnetic property. It is to provide a method for obtaining an electromagnetic steel sheet.

[0008]

The present invention provides C by weight:
Starting from a molten steel containing 0.10% or less, Si: 2.5 to 7.0% and a usual inhibitor component, and the balance Fe and unavoidable impurities as a starting material, a strip rolled to a final product thickness is removed. In the heating process of the charcoal annealing, an electric heating treatment is performed between the rolls, and subsequently, when performing decarburization annealing and final finishing annealing, the heat removal amount of the strip on the heated side roll is 200 ° C. or less,
It has been found that a grain-oriented electrical steel sheet having a high magnetic flux density can be obtained. In addition, it has been found that when the temperature rising rate of the strip when electricity is applied between the rolls is 80 ° C./s or more, a grain-oriented electrical steel sheet having a higher magnetic flux density can be obtained.

The present invention will be described in detail below. The unidirectional electrical steel sheet can be manufactured by sufficiently causing secondary recrystallization during the final annealing in the manufacturing process to obtain a so-called Goss texture. In order to obtain this Goss texture, growth coarsening of the primary recrystallized grains is suppressed, and only the recrystallized grains of the (110) <001> orientation are selectively grown in a certain temperature range.
That is, it is necessary to make a base material for secondary recrystallization.

However, in the heating using the conventional energizing roll method, the base material for secondary recrystallization is not sufficient, and there arises a problem that the magnetic characteristics, particularly the magnetic flux density is lowered. As a result of detailed investigation of this cause, according to the energizing roll method, strain was introduced into the steel sheet during heating, which acted as a driving force to change the primary recrystallization behavior and was aligned in the rolling direction (110) <001. It was found that the existence of primary recrystallized grains in the <> direction was reduced and the magnetic flux density was reduced. As a result of studying the location where strain is introduced into the steel sheet, it was found that the strip was rapidly cooled immediately after the strip was heated by the heat removal of the exit roll, and a minute strain remained in the steel sheet. Therefore, the influence of the heat removal amount on the magnetic characteristics was investigated. As a result, it was found that when the heat removal amount was 200 ° C. or less, the magnetic flux density did not deteriorate much.

FIG. 2 shows the relationship between the heat removal amount of the exit roll and the magnetic flux density. At this time, the temperature reached by the plate was 850 ° C., the roll diameter was 200 mm, and the temperature rising rate was 20 ° C./s. 20 heat removal
When the temperature is 0 ° C or higher, the magnetic flux density is significantly deteriorated, and when the temperature is 200 ° C or lower, the same level as the magnetic characteristics of conventional gas heating can be obtained. Here, in order to increase the magnetic flux density, in addition to suppressing the heat removal amount on the roll exit side to 200 ° C. or less, it is preferable to set the temperature rising rate of the strip when energizing between the rolls to 80 ° C./s or more. Magnetic characteristics are obtained.

FIG. 2 shows the relationship between the heat removal amount of the exit roll and the magnetic flux density when the heating rate is 200 ° C./s. The heat removal amount is 200
A large deterioration of the magnetic flux density is observed at temperatures above ℃, and a level above the conventional magnetic characteristics of gas heating is obtained at temperatures below 200 ℃. As an effect of improving the magnetic properties by the rapid heating, it is considered that the increase of the (110) plane in the primary recrystallization texture has a great influence on the subsequent secondary recrystallization.

[0013]

In the present invention, the reason why the steel composition and manufacturing conditions are limited as described above will be explained in detail. The reasons for limiting the steel composition are as follows. The upper limit of 0.10% for C is limited because if the amount exceeds C, the time required for decarburization becomes long, which is economically disadvantageous.

Si has a lower limit of 2.5 in order to improve iron loss.
%, But if it is too large, it easily cracks during cold rolling and processing becomes difficult, so the upper limit is made 7.0%. Furthermore, in order to manufacture the grain-oriented electrical steel sheet, it is preferable to add the following component elements as usual inhibitor components. When using MnS as an inhibitor, Mn and S are added. Mn is used to obtain an appropriate dispersed state of MnS.
0.02-0.15% is desirable. S is MnS, (Mn
-Fe) S is an element necessary for forming and is preferably 0.001 to 0.05% in order to obtain an appropriate dispersed state.

Further, when AlN is used as an inhibitor, acid-soluble Al and N are added. Acid soluble A
In order to obtain a proper dispersion state of Al and AlN, 0.01-0.
04% is desirable. N is also preferably 0.003 to 0.02% in order to obtain a proper dispersed state of AlN. Other, C
At least one of u, Sn, Sb, Cr and Bi may be added in an amount of 1.0% or less for the purpose of strengthening the inhibitor.

Next, the above molten steel is subjected to a conventional ingot casting method or continuous casting method, and hot rolling to obtain a strip having an intermediate thickness. At this time, the strip casting method can also be applied to the present invention. Furthermore, when a nitride is required as an inhibitor, it is necessary to deposit 950 to 120 because of precipitation of AlN or the like.
It is desirable to perform intermediate annealing for 30 seconds to 30 minutes at 0 ° C.

Next, a strip having a final product thickness is obtained by rolling once or twice or more including intermediate annealing. The final rolling reduction at this time requires a rolling reduction of 50% or more in order to obtain a product having a high degree of Goss accumulation. If the lower limit is 50%, the necessary Goss nucleus cannot be obtained below this range.

The strip thus rolled to the final product thickness is heated by the current-rolling method in the temperature rising process of decarburization annealing. At this time, it is necessary that the heat removal amount of the strip on the heated roll is 200 ° C. or less. The upper limit value of 200 ° C. is limited because the magnetic flux density deteriorates above this value. FIG. 1 shows a schematic diagram of one embodiment of the present invention. Two pairs of upper and lower rolls sandwiching the strip S are provided, and the strip S between the rolls R ₁ and R ₂ is energized to heat the strip S, and the roll R ₂ on the heated side cools at the point P. Is given. At this time, the heat removal amount of the strip on the exit roll R ₂ is set to 200
Must be within ℃. As a measure for this, there is a method of preheating the roll R ₂ with an induction heating device in order to minimize the temperature difference between the heated strip and the roll R ₂ .

Further, in order to reduce the heat removal of the plate as much as possible, a special metal, ceramic or the like is applied to the surface of the roll R ₂ .
There is a method in which the heat transfer coefficient of the roll is suppressed and the heat removal of the plate is reduced by applying a coating by thermal spraying or the like to about 100 to 300 μm. Furthermore, it is possible to combine the above two methods.

As a result, the heat removal amount of the strip on the output side roll R ₂ can be suppressed within 200 ° C., and a grain-oriented electrical steel sheet having a high magnetic flux density can be obtained. Note that it is desirable to carry out the above processing in the apparatus box B in a non-oxidizing atmosphere as much as possible, because of problems such as film formation. In addition, if the heat removal amount of the plate on the delivery side roll is set to 200 ° C. or less, there is also an effect that the plate shape becomes very good.

Further, if necessary, in order to enhance the productivity of decarburization annealing and to improve the magnetic characteristics, the heat removal amount on the roll outlet side is kept within 200 ° C. The heating rate of the strip is 80 ℃ / s
More than that. The lower limit value of 80 ° C./s of this temperature rising rate is limited because the improvement of the magnetic flux density cannot be expected as compared with the conventional gas heating below this.

After heating the strip as described above,
Decarburization annealing is performed in a wet hydrogen atmosphere. At this time, C must be reduced to 0.005% or less so as not to deteriorate the magnetic properties of the product. Here, when the slab heating temperature in hot rolling is low and only AlN is used as an inhibitor, nitriding treatment may be performed in an ammonia atmosphere.
Furthermore, by applying an annealing separator such as MgO and performing finish annealing at 1100 ° C. or higher for secondary recrystallization and purification, a grain-oriented electrical steel sheet having extremely low iron loss characteristics is manufactured. In order to further improve the iron loss of the obtained product, it is possible to subject the unidirectional electrical steel sheet to a treatment for subdividing magnetic domains.

[0023]

【Example】

[Example 1] A molten steel containing the composition shown in Table 1 was cast,
After heating the slab, hot rolling was performed to obtain a 2.2 mm hot rolled steel sheet. Next, it was annealed at 1100 ° C. for 5 minutes, further pickled, and then cold rolled to a thickness of 0.27 mm. Then, in the temperature rising process of decarburization annealing, the rolled steel sheet was heated under various conditions by a direct current roll heating device shown in the figure. At this time, various heat removals were performed by preheating the outlet roll with an induction heating device immediately after heating. Table 2 shows the amount of heat removed from the output side plate temperature at this time. At this time, the roll diameter was 200 mmφ and the plate passing speed was 20 mpm. The amount of heat removed from the plate when no preheating was performed was 300 ° C. For comparison, a conventional gas heating method is also shown (Example A, 20 ° C./s heating rate).

Subsequently, decarburization annealing was performed in wet hydrogen, nitriding treatment was performed in an ammonia atmosphere, MgO powder was applied, and then high temperature annealing was performed at 1200 ° C. for 10 hours in a hydrogen gas atmosphere. Table 2 shows the magnetic properties of the obtained products.
The magnetic property of the product is that the heat removal amount of the plate after reaching the maximum temperature is 2
A grain-oriented electrical steel sheet having a good magnetic property within a temperature range of 00 ° C. has been obtained.

[0025]

[Table 1]

[0026]

[Table 2]

Example 2 A molten steel containing the chemical composition shown in Table 3 was cast, heated to a slab, and hot-rolled to 2.3 mm.
The hot-rolled steel sheet of was obtained. This is annealed at 1100 ° C for 5 minutes, pickled, and then cold rolled to 0.22 mm.
Made thick. The rolled steel sheet was heated to 850 ° C. at a heating rate of 250 ° C./s with two pairs of direct current heating rolls.
At this time, the roll diameter was 200 mmφ and the sheet passing speed was 30 mpm. The exit roll is (A) normal carbon material,
(B) Two types were used, one having a Co-based metal surface-treated with 200 μm on the carbon surface. At this time, the heat removal amount of the output side plate was 300 ° C. in (A) and 50 ° C. in (B). Next, do not cool as it is.
It was heated at / s and decarburized and annealed in wet hydrogen.

After the MgO powder was applied to the above two types of decarburized annealed plates, high temperature annealing was performed at 1200 ° C. for 10 hours in a hydrogen gas atmosphere. Table 4 shows the magnetic properties of the obtained products. As for the magnetism of the product, it was possible to obtain satisfactory magnetism by the energizing roll method with a small heat removal amount.

[0029]

[Table 3]

[0030]

[Table 4]

[0031]

Industrial Applicability According to the present invention, a unidirectional electrical steel sheet having a high magnetic flux density can be manufactured by applying an electric heating method in the temperature rising process of decarburization annealing for energy saving, which is industrially possible. The contribution of is extremely large.

[Brief description of drawings]

FIG. 1 is a schematic view of an embodiment of an electric heating roll method according to the present invention.

FIG. 2 is a chart showing the relationship between the amount of heat drawn from a plate and the magnetic flux density in the exit roll.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tadao Kiriyama 1 Fuji-machi, Hirohata-ku, Himeji City Nippon Steel Co., Ltd. Hirohata Works

Claims (5)

[Claims] 1. C: 0.10% or less by weight, Si: 2.
5 to 7.0% as well as the usual inhibitor components,
The balance consists of Fe and unavoidable impurities, and the strip rolled to the final product thickness is subjected to an electric heating treatment between rolls in the temperature rising process of decarburization annealing, followed by heating during decarburization annealing and final finishing annealing. The method for producing a grain-oriented electrical steel sheet, wherein the heat removal amount of the strip on the rolled side is 200 ° C. or less. 2. The method according to claim 1, wherein the heat removal amount of the strip is 200 ° C. or less by subjecting the surface of the roll on the heated side to a surface treatment of metal, ceramic or the like. 3. The method according to claim 1, wherein the heat removal amount of the strip is 200 ° C. or less by subjecting the heated roll to preheat treatment by an induction heating device or the like. 4. The method according to claim 1, 2 or 3, wherein the rate of temperature rise of the strip when energized between the rolls is 80 ° C./s or more. 5. The unidirectional electrical steel sheet according to claim 1, 2 or 3 or 4 is subjected to a treatment for subdividing a magnetic domain,
A method for producing a grain-oriented electrical steel sheet, which is characterized by obtaining excellent magnetic properties.