JPS62167822A - Production of grain oriented silicon steel sheet of extremely low iron loss - Google Patents

Abstract

PURPOSE:To obtain an extremely low iron loss by combining three things; the reduction of the sheet thickness of a product, the formation of a forsterite film on the surface of a steel sheet to an adequate thickness and the reduction of the crystal grain size of the product. CONSTITUTION:A grain oriented silicon steel stock contg., by weight %, 2-4 Si, 0.01-0.035>=1 kinds of Se and S as an inhibitor, and 0.01-0.08>=1 kinds among Sb, As, Bi, and Sn is used. Such steel stock is subjected to hot rolling then to one pass or >=2 passes of cold rolling including intermediate annealing to a final sheet thickness of 0.15-0.25mm thickness. The steel sheet is then subjected to decarburization annealing and after a separating agent for annealing is coated thereon, the steel sheet is subjected to the final annealing to effect secondary recrystallization and to form the forsterite film at 1-4g/m<2> per face on the surface of the steel sheet. The steel sheet is held for 0.1-15min at 900-1,050 deg.C and the secondary recrystallization is completed at 800-900 deg.C prior to the final annealing to maintain the average crystal grain size after the secondary recrystallization at 1-6mm.

Description

Detailed Description of the Invention The present invention provides a method for producing a unidirectional silicon steel plate having an extremely low core loss and having an easy axis of magnetization <ioo> in the rolling direction of the steel plate and (110) parallel to the plate surface. It is related to.

Unidirectional silicon steel sheets are soft magnetic materials that are mainly used in the cores of electrical equipment such as transformers.In recent years, there has been a strong demand for higher performance, smaller size, and lower noise in electrical equipment.
Furthermore, there is a need for electric iron plates with even better electromagnetic properties from the standpoint of energy conservation.

The electromagnetic properties of steel sheets are generally evaluated based on both iron loss properties and magnetization properties. Increasing the magnetization characteristics (represented by the magnetic flux density Bgo when a magnetic field of 1000/m is applied) is particularly effective in increasing the design magnetic flux density and downsizing the device. On the other hand, iron loss characteristics (represented by iron tMW+t/s per 1 kg when magnetized to 17 kG with 5011z)
Increasing the energy consumption is effective in reducing the amount of heat energy lost when used as electrical equipment and saving power consumption. Increasing the directionality of the product, that is, aligning the <100> axes of the product grains to a high degree in the rolling direction, can improve not only the magnetization properties but also the iron loss properties, and in recent years a great deal of research has been done in this area in particular. overlapped,
Products with a BIG of 1.90T or more have even been manufactured.

Now, as is well known, iron loss can be broadly divided into two parts: hysteresis loss and eddy current loss.As for the physical factors that affect these losses, first of all, in addition to the crystal orientation mentioned above, hysteresis loss The purity of the material and internal distortion. In addition, the eddy current loss includes the electric abrasive resistance of the steel plate (for example, the amount of Si, the plate thickness, the size of the magnetic domain, and the crystal grain size), and the tension exerted on the steel plate. In normal grain-oriented silicon steel, eddy current loss accounts for more than 3/4 of the total iron loss, so lowering eddy current loss from the history is more effective in reducing total iron loss. For this reason, various attempts have been made to reduce the eddy current loss. One method is to increase Sil, but if it is increased to nearly 4.0%, cold rollability is significantly impaired, and there is a 1@ boundary, which is not very practical. A known method for applying tension to a steel plate is to utilize the difference in thermal expansion coefficient between the base film or top coating and the base steel, but this method also has a limit to the tension that can be applied industrially from the coating. However, due to constraints such as the uniformity, adhesion, and appearance of the film, it is not possible to expect much reduction in iron loss. Recently, a method has been proposed in which the surface of a product plate is scratched in a direction perpendicular to the rolling direction to refine the magnetic domains and thereby reduce eddy current loss. However, this method may not always be fully effective depending on the shape, average grain size, thickness, etc. of the product plate.Furthermore, if a product plate with scratches is subjected to strain relief annealing, the iron loss may be reduced. It is not very practical because it has the fatal flaw that it returns to its original state.

An object of the present invention is to provide a method for manufacturing a unidirectional silicon steel sheet with extremely low core loss, which eliminates and improves the above-mentioned drawbacks of conventional unidirectional silicon steel sheets, and the scope of the invention is as set forth in the claims. The above object can be achieved by providing a method for manufacturing a unidirectional silicon steel sheet.

Next, the present invention will be explained in detail.

The present inventors have developed three methods: reducing the thickness of the product, controlling the thickness of the forsterite film formed on the surface of the steel sheet within an appropriate range, and refining the crystal grain size of the product. The present invention was completed based on the new finding that extremely low iron loss can be obtained by combining the two.

In other words, is the product of the present invention WI? 150 is 0.90W/k
It is an ultra-low iron loss unidirectional silicon steel sheet with a core loss of 1.5 g or less, and the steel sheet to be bent has a product thickness of 0.15 to 0.25 mm, and the amount of forsterite film formed on the surface of the product is 1. 〜4B7m'', and the average grain size of the product is 1〜4B7m''.
By simultaneously satisfying the three important factors, the above-mentioned unidirectional silicon steel sheet with ultra-low core loss can be obtained.

By the way, it is generally known that the eddy current loss decreases when the thickness of a grain-oriented silicon steel sheet product is reduced by a method such as chemical polishing or mechanical polishing. However, conversely, the hysteresis loss increases as the plate thickness decreases.

The increase in hysteresis loss is slow when the plate thickness is relatively thick, but increases rapidly as the thickness becomes thinner, and the plate thickness of the product with the lowest total iron loss is between 0.15 and 0.25 mm. do. However, simply reducing the plate thickness will not meet the objective of the present invention. Products with a weight of less than 0.90 W/kg cannot be obtained. In particular, when producing a thin product using the normal manufacturing method in which a forsterite film is formed on the surface of the resulting steel sheet by repeating cold rolling and annealing and finally adding high-temperature annealing, the directionality may be slightly impaired. ,0.
It was even more difficult to obtain ultra-low iron loss of 90 W/kg or less.

Regarding the relationship between particle size and iron loss, it is known that the iron loss generally decreases as the particle size of the product becomes smaller. For example, M
, F. Littnan (J, static pl, Phys.

According to 1967, 38.1104), the lowest value of iron loss is around the particle size of 0.5 am, and the lowest value of iron loss when the product plate thickness is 0.1+n is 0.45W/7 at 1,76°! b, W+7/S. It is shown that it is approximately 0.96 W/kg when converted to .

However, even if the particle size is reduced further, the directionality will be impaired, so conventional techniques have been used to achieve the objectives of the present invention.
7. . It was impossible to manufacture a material with a low core loss of 0.90 W/kg or less.

Regarding the relationship between the amount of forsterite film formed on the steel plate surface and iron loss, there was not a very clear correlation in conventional products with a product plate thickness of 0.27 m or more.

However, when the product board thickness is as thin as 0.15 to 0.25n+, it is important to control this amount to an appropriate amount depending on the board thickness, and the amount is in the range of 1 to 4 g/a+" per side. The reason for the deterioration of iron loss due to an excessively thick forsterite film when the product board is thin is not only due to an increase in the weight of the forsterite film relative to the total weight, but also due to an increase in the thickness of 4 g/m. This is because if the amount exceeds 1, the smoothness of the interface between the film and the base metal is impaired, and the influence of strain remaining near the interface becomes particularly large, degrading the iron loss. Note that the reason why the lower limit of the amount of forsterite is set at 1 g/m 2 is to maintain the insulation properties of the surface, and it is necessary to regulate the lower limit to 1 g/m 2 in order to obtain a high-quality top coating.

Three factors are involved in controlling the amount of forsterite on the product surface: the atmosphere during decarburization annealing, the amount and nature of MgO applied as a separating agent, and the box annealing atmosphere. The atmosphere during decarburization annealing is usually hydrogen or a mixed gas of hydrogen and nitrogen, but it is necessary to properly control the mixture ratio and the dew point of the atmosphere to prevent excessive overoxidation. . Also, among the properties of MgO, the amount of hydration of MgO, which affects the amount of oxidation in steel sheets, is particularly important, and in order to reduce the amount of forsterite to 4 g/m" or less, it is necessary to use one with the lowest possible amount of hydration. can be,
For example, in a hydration test at 20° C. for 30 minutes, it is desirable to use a material with a hydration amount of 5% or less.

The amount of forsterite on the product surface is most easily controlled by the amount of surface oxidation after decarburization annealing, the amount of applied MgO, and the amount of hydration.
x It is necessary to make the annealing atmosphere as low in oxidation as possible to prevent additional oxidation during annealing.

In this way, the inventors have determined that the product board thickness is 0.15 to 0.2.
At the same time as thinning the steel sheet to 5 m, the weight of the forsterite film on the surface of the steel sheet was controlled to 1 to 4 g/m'' per side, and as described below, the average grain size was controlled to be in the range of 1 to 6 ms. ..0.90W/k
We have achieved stable production on an industrial scale of grain-oriented silicon steel sheets with a low core loss of less than 100 g.

Figure 1 explains this, and shows the product thickness and core loss Wl'l/S of grain-oriented silicon steel sheets containing 3 and 10% Si with various average secondary grain sizes. This shows the relationship between All products have a forsterite film on the surface of 2 to 3 g/m" per side, and the magnetic flux density B1° is 1.89 to 1.93.
It was 7. Although the plate thickness that shows the lowest value varies somewhat depending on the average grain size of the product, it is WI? /S. It is clear that the steel exhibits a low iron loss of 0.90 W/kg or less.

FIG. 2 shows the relationship between the amount of forsterite on the surface of grain-oriented silicon steel sheets containing 3.02% Si and iron loss for products with different thicknesses. It can be seen that when the product thickness is thin, it is necessary to set the forsterite basis weight to 1 to 4 g/m'' per side in order to obtain a low-iron ingredient.

Next, the method and conditions for manufacturing the ultra-low core loss grain-oriented silicon steel sheet of the present invention will be explained.

First of all, the grain-oriented silicon steel material as a constituent element suppresses the growth of undesirable crystal grains in the final high-temperature annealing process and improves the Goss orientation.
In order to enable the next recrystallization, a fine precipitated dispersed phase called an inhibitor, such as MnS, MnSe, A
It contains IN, BN, VN, and grain boundary segregation type elements such as Sb, As, Bi, and Sn. By using a silicon steel material containing the necessary amount of one or more selected from these and controlling the thickness and secondary grain size of the product within the range of the present invention, w+
, /so of 0.90 W/kg or less can be produced.

The present inventors prepared 50 kg vacuum melted steel ingots with various inhibitor compositions (Si 2.90-3.35%, GO, 0
30-0.048%, MnO, 045-0.080%
0.15~0.25m by cold rolling 2 same process using )
A product with a thickness of m was produced, and the final cold rolling reduction was varied within the range of 55 to 85% in order to investigate the process conditions for obtaining a product satisfying the properties specified in the present invention. The stability of properties was compared by changing the temperature increase rate during annealing and changing 10 different process conditions for materials with the same composition.

As a result, it was found that at least one of Se and S was contained in an amount of 0.010 to 0.035% as an inhibitor;
It has been found that the combined inclusion of 0.010 to 0.080% of one or both of Bi, As, and Sn is particularly effective in stably obtaining products with low iron loss. I found out.

Some of the experimental data obtained are shown in Table 1.

Table 1 shows the lowest and average values of iron loss obtained for each inhibitor composition and W+,
/S. This is a summary of the pass rate of those who satisfy 0.90W/kg or less.

The pass rate here refers to a plate thickness that satisfies the grain size of 1 to 611 and is therefore essential for this invention steel plate.

Satisfying the three requirements of particle size and forsterite film amount,
Furthermore, this invention aims to achieve -1, 7. . is 0.90
This is the ratio of products with a low core loss value of W/kg or less to all products (for each inhibitor used).

As is clear from the table, MnS-based and MnSe-based inhibitors are optimal in order to satisfy the three requirements of this invention and obtain a low core loss of Lt/sa≦0.90W/kg. . However, such MnS-based and MnSe
A7 for the system! Contains a small amount of N, or Mn
Even when only Se is used as an inhibitor, although the pass rate is low, a product is obtained that satisfies the above three requirements and exhibits predetermined iron loss characteristics.

A method of manufacturing a grain-oriented silicon steel sheet having excellent magnetic properties by coexisting with Se, S; IcSb + ASI I3i + Sn, etc. is already known in Japanese Patent Publication No. 50-29496 and Japanese Patent Publication No. 54-32412. . However, these are all for products with a plate thickness of 0.30 mm to 0.35 m, and the iron loss level of the product is also between 11 and 7. . is 1. It showed a manufacturing method for products with OW/kg or more. In this case Se
? For Sft, it is often 0.005 to 0.1% each alone or as the sum of both, and Sb
, As+Old, Sn, etc., a wide range of content of 0.015 to 0.40% of one or more of these is allowed.

In contrast, in the present invention, the thickness of the finished product is 0.15 to 0.25.
1 layer, the basis weight of forsterite film is 1 to 4 per side.
g/m" and furthermore, by setting the average particle size to 1 to 6 fl, it is possible to satisfy Lt/s of 0.90 W/kg or less. To achieve this, the range of ingredients of these inhibitors must be further adjusted than in conventional methods. must be regulated within a narrow range.

However, it is not always possible to obtain the desired characteristic values based on the ingredients and content of the inhibitor alone, and various considerations must be made regarding the manufacturing conditions of the silicon steel sheet. The present inventors tried various methods and found the effective method described below.

That is, the method is a secondary recrystallization nucleation treatment performed after decarburization annealing. All conventional methods attempted to refine the secondary grains by making the primary recrystallized grains finer and increasing the number of Goss-oriented crystal grains, but this method 0.1-15mi at 900-1050℃
The goal is to increase the Goss grains in the surface layer to a size that easily functions as secondary recrystallization nuclei, that is, to a size that is at least twice the average crystal grain size by applying a short-time heat treatment of n. Then, when performing the final box annealing after applying such nucleation treatment, by holding the box at a temperature in the range of 800 to 900°C for one hour or more to complete the secondary recrystallization, The average secondary particle size can be adjusted to 1 to 6, which is the condition of the present invention, without damaging the magnetic flux density of the product. In this case, the nucleation temperature is regulated to 900 to 1050°C because the optimum nucleation temperature varies somewhat depending on the type of inhibitor and the final cold rolling reduction. but,
If the upper limit of 1050° C. is set at Ueda, grains with unfavorable crystal orientation will also become coarse and the orientation of the product will be impaired, and this is the same reason why the upper limit of the holding time is set at 15 min.

Next, the reason for limiting the component composition and processing conditions in the present invention will be explained.

The silicon steel material to which the present invention is applied can be produced by any known method, but it contains Si as a component.
is required to be contained in an amount of 2.0 to 4.0%. Si
The lower limit of the amount was set because if it goes down, the low iron loss material that is the object of the present invention cannot be changed, and the upper limit is set because the cold rollability will be poor.Other components are not particularly regulated, but as mentioned above. In addition to nitrides, sulfides, and selenides known as inhibitors, grain boundary segregation type elements are also included as necessary.

And the iron loss of the product is -, ma/,. In order to stably satisfy 0.90 W/kg or less, the total amount of any one or both of S and Se is 0.010 to 0.035%, and further sb.

It is advantageous that any one or a combination of two or more of As, Bi, and Sn is contained in an amount of 0.010 to 0.080%.

A material having the above components, that is, a slab or an ingot, is hot-rolled according to a known method (in the case of an ingot, a blooming step is added) to form a hot-rolled plate having a thickness of 1.5 to 3.0 fl. During hot rolling, the slab is heated to a sufficiently high temperature, for example, 1300° C. or higher, in order to obtain a preferable dispersion of MnSe, Mns, and other nitrides contained as inhibitors. The thickness of the hot-rolled sheet is not necessarily constant depending on the type and composition of the inhibitor, but it is preferably 2.0 to 3.0 m for the normally adopted two-time cold rolling method, and the one-time cold rolling method is preferred. In this case, it is preferable to make it as thin as 1.5 to 2.0 Tsuru.

The hot rolled sheet is then cold rolled one or more times and optionally 850
Intermediate annealing is performed for 0.5 to 15 minutes at a temperature range of ~1150°C to obtain a cold rolled plate having a final product thickness of 0.15 to 0.25+n.

The cold-rolled sheet with a product thickness of 0.15-0.25 m is then subjected to decarburization annealing in wet hydrogen at 780-880°C for 0.5-15 min to reduce the carbon content of the steel sheet to 0.005%. It is decarburized below. After the subsequent decarburization annealing, 900 to 105
It is preferable to apply nucleation treatment heating at 0° C. for 0.5 to 15 minutes in order to make the secondary particle size of the product fine and obtain a low iron loss material. Here, the decarburization annealing atmosphere is a 0-order MgO atmosphere in which the oxygen potential of the atmosphere must be controlled to avoid overoxidation, as the amount of oxidation after decarburization annealing affects the amount of forsterite in the product, as mentioned above. After applying a separating agent, it is subjected to secondary recrystallization and high-temperature box annealing for purification. Purification annealing is usually carried out in hydrogen at a temperature of 1100°C or higher for 1 hour or more, but before that, as a treatment to improve directionality, in order to complete secondary recrystallization at a temperature range of 800 to 900°C, during this period to a temperature of 5
It is effective to maintain the temperature for a period of time or more or to remove heat at 15° C./Hr or less during this period in order to enhance the effects of the present invention.

Thereafter, a coating for insulation and tension addition is applied as necessary to produce a product, and the product thus obtained has a fine secondary particle size and a significantly low core loss.

Next, the present invention will be explained with reference to examples.

SIL CO, 042%, Si 3.28%, Mn
O,068%, Se0.022%, Sb
O,035%, Sn 0.020%, AsO
,010%, balance Fe 1340 silicon steel slab
After heating at 311° C., hot rolling was performed to obtain a hot rolled sheet having a thickness of 2.2 me. Next, after heating at 950°C for 5w+in, primary cold rolling was performed at 75% to give an intermediate thickness of 0.55m, and intermediate annealing was performed again at 950°C for 5min, followed by secondary cold rolling at a rolling reduction of 64%. A cold-rolled plate with a thickness of 0.20 m5 was used. Then in wet hydrogen at 800℃ for 5 minutes
When performing decarburization annealing, the temperature increase rate from 450 to 750°C was 70°C/lll1n and 150°C/min.

The test was carried out under four conditions: 300°C/ll1in and 600°C/win. In addition, some samples were heated to 950°C after decarburization.
+ 5 min of secondary recrystallization nucleation treatment was added. Next, after applying MgO as a separating agent, the temperature was heated at 860°C in Ar.
, followed by secondary recrystallization annealing for 24 hours in hydrogen.
Purification annealing was performed at 200° C. for 5 hours to obtain a final product.

The magnetic properties and average secondary particle size of the product thus obtained are
It was as shown in the table.

Table 2 150 None 5.2
0.88 1.92300 None
3.8 0.86 1.92300
Yes 3.2 0.8
4 1.92600 None
3.5 0.84 1.92600
3.0 0.83 1.91

[Brief explanation of drawings]

Figure 1 shows the product board thickness (- and iron loss 1,7.. (W/'g)
Figure 2 shows the relationship between the average secondary particle size (me) of the product as a variable, and Figure 2 shows the weight Wk (g/m'') per side of forsterite formed on the product surface and the iron tjmW+t/s.
. FIG. 3 is a diagram showing changes in the relationship (W/kg) depending on product board thickness. Figure 1 0.14 0. fe) 0.220,26 0.30 Rice thickness (mm) 246f3 Forsterite tl (y/m2 Procedure Amendment Written by the Commissioner of the Patent Office on October 23, 1986) 1) Mr. Akio, of the case Indication Patent Application No. 202691 of 1985 2, Name of invention Method for manufacturing unidirectional silicon steel sheet with extremely low iron loss 3, Relationship with the amended case Patent applicant (125) Kawasaki Steel Corporation 4, Attorney Person 5, Subject of amendment Full text (corrected) statement 1, Title of the invention Method 2 for manufacturing unidirectional silicon steel plate with extremely low iron loss, Claim 1, 5i Contains 2 to 4%, and At least one of Sn and S as an inhibitor 0.010 to 0
．． 035% and at least one selected from Sn + As, ■ and Sn 0.010 to 0.080
A unidirectional silicon steel material containing
．． After the final thickness of the steel plate is 15 to 0.25 mm, decarburization annealing is performed, and an annealing separator is applied, followed by final annealing, and with secondary recrystallization, 1 to 4 g per side is applied to the surface of the steel plate.
In a method for producing a grain-oriented silicon steel sheet in which a forsterite film of m2 is formed, prior to final annealing, the temperature range is maintained at 900 to 1050°C for 0.1 to 15 minutes, and then the temperature range is maintained at 800 to 900°C for 2 minutes. A method for producing a unidirectional silicon copper plate with extremely low iron loss, characterized in that the average crystal grain size after secondary recrystallization is in the range of 1 to 6 mm by completing secondary recrystallization. 3. Detailed Description of the Invention (Field of Industrial Application) The present invention is directed to a steel plate having an easy axis of magnetization <100> in the rolling direction and parallel to the plate surface (1101), which has an extremely low iron loss. Unidirectional silicon steel sheet is a soft magnetic material that is mainly used in the cores of electrical equipment such as transformers. , and there is a strong demand for low noise.
Furthermore, there is a need for electric iron plates with even better electromagnetic properties from the standpoint of energy conservation. (Prior Art) The electromagnetic properties of steel sheets are generally evaluated based on both iron loss properties and magnetization properties. Increasing the magnetization characteristics (represented by the magnetic flux density BIG when a magnetic field of 100 OA/m is applied) is particularly effective in increasing the design magnetic flux density and downsizing the device. On the other hand, iron loss characteristics (50) Iron loss per Lkg when magnetized to 17kG at 1z WM77S. ) is effective in reducing the amount of heat energy lost when used as electrical equipment and saving power consumption. Increasing the directionality of the product, that is, aligning the <100> axes of the product grains to a high degree in the rolling direction, can improve not only the magnetization properties but also the iron loss properties, and in recent years a great deal of research has been done in this area in particular. stacked, B
,. Products with a value of 1.907 or higher have even been manufactured. Now, as is well known, iron loss can be broadly divided into two parts: hysteresis loss and eddy current loss.As for the physical factors that affect these losses, first of all, in addition to the crystal orientation mentioned above, hysteresis loss The purity of the material and internal distortion. In addition, the eddy current loss includes the electrical resistance of the steel plate (for example, the amount of Si), the plate thickness, the size of the magnetic domain, and the crystal grain size), and the tension exerted on the steel plate. In ordinary grain-oriented silicon steel, the eddy current loss accounts for 374 or more of the total iron loss, so lowering the eddy current loss than the hysteresis loss is more effective in lowering the total iron loss. For this reason, various attempts have been made to reduce the eddy current loss. One method is to increase the amount of Si, but increasing it to nearly 4.0% significantly impairs cold rollability, so there is a limit and it cannot be said to be very practical. A known method for applying tension to a steel plate is to utilize the difference in thermal expansion coefficient between the base film or top coating and the base steel, but this method also has a limit to the tension that can be applied industrially from the coating. However, due to constraints such as the uniformity, adhesion, and appearance of the film, it is not possible to expect much reduction in iron loss. Recently, a method has been proposed in which the surface of a product plate is scratched in a direction perpendicular to the rolling direction to refine the magnetic domains and thereby reduce eddy current loss. However, this method does not depend on the shape of the product plate, the average
The effect may not always be fully demonstrated depending on the grain size, plate thickness, etc. Furthermore, if strain relief annealing is applied to a scratched product plate, the reduced iron loss will return to its original level, which is a fatal problem. It is not very practical due to its flaws. (Problems to be Solved by the Invention) The present invention advantageously solves the problems of the prior art described above, and has the advantage of being able to stably produce a grain-oriented silicon steel sheet with extremely low core loss. The purpose is to propose a new manufacturing method. (Means for Solving the Problems) As a result of intensive research to solve the above problems, the inventors have reduced the thickness of the product sheet and reduced the thickness of the forsterite film formed on the surface of the steel sheet. We have obtained new knowledge that extremely low iron loss can be obtained by combining the following three steps: controlling the iron to an appropriate range and making the crystal grain size of the product fine. In other words, for unidirectional silicon steel sheets, the product thickness is 0.1
5 to 0.25 mm, and the amount of forsterite film formed on the surface of the product to be 1 to 4 g/m2 per side, and three factors to make the average crystal grain size of the product 1 to 6 l. By simultaneously satisfying 1, /,. It was found that a unidirectional silicon steel sheet having the following excellent core loss characteristics of 0.90 W/ could be stably obtained. The present invention is based on the above findings. That is, the present invention contains 2 to 4% Si, and 0.0% of at least one of Sn and S as an inhibitor.
10-0.035%, Sn, As, Bi and S
At least one selected from n 0.010
A unidirectional silicon steel material containing ~0.080% was hot-rolled and then cold-rolled once or twice or more with intermediate annealing to give a final plate thickness of 0.15 to 0.25 m. Afterwards, decarburization annealing is performed, and an annealing separator is applied, followed by final annealing to form a forsterite film of 1 to 4 g/m'' per side on the surface of the steel sheet along with secondary recrystallization. In the manufacturing method of silicon steel sheet, 0.1 to 15 m is heated within a temperature range of 900 to 1050°C prior to final annealing.
In this method, the average crystal grain size after the secondary recrystallization is made to be in the range of 1 to 6 by holding it in the temperature range of 800 to 900°C and completing the secondary recrystallization. This is a method for manufacturing unidirectional silicon steel sheets that are easy to grind. The present invention will be specifically explained below. First, the background to the elucidation of the present invention will be explained. Generally, it is known that eddy current loss decreases when the product thickness of grain-oriented silicon steel sheet is thinned using methods such as chemical polishing or mechanical polishing.However, conversely, hysteresis loss decreases as the sheet thickness decreases. The increase in mechanical strength is slow when the plate thickness is relatively thick, but increases rapidly as the plate thickness becomes thinner, and the plate thickness of the product with the lowest total steel structure is 0.15 to 0. 25+
exists between u. However, simply reducing the plate thickness is not the objective of the present invention.77. Products with a weight of less than 0.90 W/kg cannot be obtained. In particular, when making thin products using the normal manufacturing method that has a forsterite film on the surface of the resulting steel sheet by repeating cold rolling and annealing and finally adding high-temperature annealing, the directionality may be slightly distorted. ,0.
It was even more difficult to obtain ultra-low iron loss of 90 W/kg or less. Regarding the relationship between particle size and iron loss, it is known that as the particle size of the product becomes smaller, the iron loss suddenly decreases. For example, M
, F. Littnan (J, ^pp1. Phys.
. 1967, 38.1104), the lowest value of iron loss is around the grain size of 0.5 Tsuru, and the lowest value of iron loss when the product plate thickness is 0.1 mm is 0.45 W/7 at WI5/6°! In b,
WIT/S. It is shown that it is approximately 0.96 W/kg when converted to . However, even if the particle size is reduced further, the directionality will be impaired, so with the conventional technology, the objective of the present invention is
It was impossible to manufacture a material with low iron loss of less than 115° 0.9 (V/kg). Regarding the relationship between the amount of forsterite film formed on the steel plate surface and iron loss, the product plate thickness was 0.27 mm. There was not a very clear correlation in the above conventional products. However, when the product plate thickness is as thin as 0.15 to 0.25 mm, it is important to control this amount to an appropriate amount according to the plate thickness. We found that the amount is in the range of 1 to 4 g/m'' per side.When the product board is thin, the deterioration of the iron member due to an excessively thick forsterite film is due to the amount of forsterite relative to the total weight. This is not only due to the increase in the weight of the stellite coating, but also because if the weight exceeds 4 g/m2, the smoothness of the interface between the coating and the base steel deteriorates, and the influence of strain remaining near the interface becomes particularly large, degrading iron loss. In addition, the lower limit of the amount of forsterite is l
The reason for this is to maintain the insulation properties of the surface, and the lower limit must be regulated to 1 g/mt in order to obtain a high quality top coat. Control the amount of forsterite on the product surface. Three factors are related to the method: the atmosphere during decarburization annealing, the amount and nature of MgO applied as a separating agent, and the box annealing atmosphere.The atmosphere during decarburization annealing is usually hydrogen or a mixed gas of hydrogen and nitrogen. However, it is necessary to properly control the mixing ratio and atmospheric dew point at this time to prevent excessive overoxidation.Also, among the properties of MgO, MgO's water content, which affects the amount of oxidation of the steel sheet, is necessary. The amount of hydration is particularly important, and in order to keep the amount of forsterite below 4g/m2, it is necessary to use one with the lowest possible hydration amount.
For example, in a hydration test at 20° C. for 30 minutes, it is desirable to use a material with a hydration amount of 5% or less. Orsterite+-i on the product surface is most easily controlled by the amount of surface oxidation after decarburization annealing, the amount of applied Mg0O, and the amount of hydration.
The atmosphere for 3ox annealing must be as low in oxidation as possible to prevent additional oxidation during annealing. In this way, the inventors have determined that the product board thickness is 0.615 to 0.2.
By thinning the steel plate to 5m and at the same time controlling the weight of the forsterite film on the surface of the steel plate to 1 to 4 g/m'' per side, and controlling the average grain size to a range of 1 to 61m, as described below. WI?/!i.0.9
We have achieved stable production on an industrial scale of grain-oriented silicon steel sheets with a low core loss of 0 W/kg or less. Figure 1 explains this and shows the product thickness and iron IMLyzs of grain-oriented silicon steel sheets containing 3 and 10% Si with various average secondary grain sizes. This shows the relationship between All products have a forsterite film of 2 to 3 g per side and 7 m'' on the surface, and the magnetic flux density B1° is 1.89 to 1.93.
It was 7. Although the plate thickness that shows the lowest value varies somewhat depending on the average grain size of the product, it is 1.5mm when the average grain size is in the range of 1 to 6. /,. It is clear that the steel exhibits a low iron loss of 0.90 W/kg or less. FIG. 2 shows the relationship between the amount of forsterite on the surface of grain-oriented silicon steel sheets containing 3.02% SS and iron loss for products with different thicknesses. It can be seen that when the product thickness is thin, it is necessary to set the forsterite basis weight to 1 to 4 g/m" per side in order to obtain a low iron loss material. Next, the ultra-low iron loss oriented silicon according to the present invention The specific manufacturing conditions of the steel plate will be explained. First, the grain-oriented silicon steel material as a constituent element suppresses the growth of unfavorable crystal grains in the final high-temperature annealing process and improves the Goss orientation.
In order to enable the next recrystallization, a fine precipitated dispersed phase called an inhibitor, such as MnS, MnSe+^lN, is added.
, ON, VN and Sb, which is known as a grain boundary segregation type element.
, As, Bi, Sn, etc. By using a silicon steel material containing the required amount of one or more selected from these, and controlling the thickness and secondary grain size of the product within the range of the present invention, W1150 can be produced.
It is possible to produce grain-oriented silicon steel with ultra-low core loss of 0.90 W/kg or less. The present inventors investigated vacuum melted steel ingots (St 2.90-3.35%, CO, 03) with various inhibitor compositions.
0-0.048%, Mn 0.045-0.080%)
0.15-0.25tm by cold rolling process using
To produce a thick product, the final cold rolling reduction was varied within the range of 55 to 85% in order to investigate the process conditions for obtaining a product satisfying the characteristics specified in the present invention, and further decarburization annealing was performed. The stability of properties was compared by changing ten different process conditions for materials with the same composition in combination with changes in the heating rate. As a result, it was found that at least one of Se and S was contained in an amount of 0.010 to 0.035% as an inhibitor;
It has been found that the combined inclusion of 0.010-0.080% of one or both of Bi, As and Sn is particularly effective in stably obtaining products with low iron loss. I found out. Some of the experimental data obtained are shown in Table 1. Table 1 shows the lowest and average values of iron loss obtained for each inhibitor composition and Wl? for several process conditions.
/S. This is a summary of the pass rate of those who satisfy 0.90W/kg or less. The pass rate here refers to the plate thickness that satisfies the grain size of 1 to 6 fins and is therefore essential for the steel plate of this invention. Satisfying the three requirements of particle size and forsterite film amount,
What is the goal of this invention? /SO is 0.90
This is the ratio of products with a low core loss value of W/kg or less to all products (for each inhibitor used). As is clear from the table, in order to satisfy the three requirements of this invention and obtain a low iron loss of "I'l/S6≦0.90W/kg, MnS-based and MnS-based inhibitors are required.
The e system is optimal. However, such MnS-based and Mn
A7 for Se series! Even when a small amount of N-based material is added or only MnSe is used as an inhibitor, although the pass rate is low, a product that satisfies the above three requirements and exhibits the specified iron loss characteristics is obtained. . Regarding the method of producing grain-oriented silicon steel sheets having excellent magnetic properties by coexisting Se and S with sb, 8s, Bi, Sn, etc., Japanese Patent Publication No. 50-29496 and Japanese Patent Publication No. 1984-
No. 32412 is already known. However, these are all for products with a plate thickness of 0.30 to 0.35 Tsuru, and the iron loss level of the products is also 0.30 to 0.35 Tsuru. It showed a manufacturing method for products with a weight of 1 kg or more. In this case, in most cases, the content of Se and Sl is 0.005 to 0.1% each alone or as the sum of both, and Sb, As,
Regarding Bi+Sn, etc., a wide range of content of one or more of these components was allowed, from o, ois to 0.40%. In contrast, in the present invention, the thickness of the finished product is 0.15 to 0.25.
Ryu, the basis weight of forsterite film is 1 to 4 per side.
g/m", and furthermore, by setting the average particle size to 1 to 61 m, W+y/S is 0.90 W/kg or less. To achieve this, the range of ingredients of these inhibitors must be further adjusted than in conventional methods. It must be regulated within a narrow range.However, it is not always possible to obtain the desired characteristic values only by the ingredients and content of the inhibitor, and various considerations must be made regarding the manufacturing conditions of silicon steel sheets.The present inventor As a result of trying various methods, they found the effective method described below. That is, the method is a secondary recrystallization nucleation treatment performed after decarburization annealing. All conventional methods This method attempted to refine the secondary grains by making the grains finer and increasing the number of Goss-oriented crystal grains.
The goal is to increase the Goss grains in the surface layer to a size that easily functions as secondary recrystallization nuclei, that is, to a size that is at least twice the average crystal grain size by applying a short-time heat treatment of n. Then, when performing the final box annealing after applying such nucleation treatment, by holding the box at a temperature in the range of 800 to 900°C for one hour or more to complete the secondary recrystallization, The average secondary particle size can be adjusted to 1 to 6 grains, which is the condition of the present invention, without impairing the magnetic flux density of the product. In this case, the nucleation temperature is regulated to 900 to 1050°C because the optimum nucleation temperature varies somewhat depending on the type of inhibitor and the final cold rolling reduction. but,
If the upper limit of 1050° C. is maintained, grains with an unfavorable crystal orientation will become coarse and the orientation of the product will be impaired. This is the same reason why the upper limit of the holding time is set at 15 min. (Function) Next, the reason for limiting the component composition and processing conditions in the present invention will be explained. The silicon steel material to which the present invention is applied can be produced by any known method, but it contains Si as a component.
is required to be contained in an amount of 2.0 to 4.0%. Si
The lower limit of the amount was set because if it exceeded this, it would be impossible to obtain the low core loss material that is the object of the present invention, and the upper limit was set because cold rollability would deteriorate. Other components are not particularly restricted, but as described above, in addition to the nitrides, sulfides, and selenides known as inhibitors, grain boundary segregation type elements may be added as necessary. And the iron loss of the product is -1.7. In order to stably satisfy 0.90 W/kg or less, the total amount of any one or both of S and Se is 0.010 to 0.035%, and further sb. It is advantageous that any one or a combination of two or more of ^s, Bi, and Sn is contained in an amount of 0.010 to o, oso%. A material having the above components, that is, a slab or an ingot, is hot-rolled according to a known method (in the case of an ingot, a blooming step is added) to form a hot-rolled plate having a thickness of 1.5 to 3.0 mm. During hot rolling, the slab is heated to a sufficiently high temperature, for example, 1300° C. or higher, to obtain a preferable dispersion of MnSe, MnS%, and other nitrides contained as inhibitors. Although the thickness of the hot-rolled sheet is not necessarily constant depending on the type and composition of the inhibitor, it is preferably 2.0 to 3.0 l for the two-time cold rolling method that is usually adopted, and If adopted, it is preferable to use a thin fin of 1.5 to 2.0 fins. The hot rolled sheet is then cold rolled one or more times and optionally 850
Intermediate annealing is performed for 0.5 to 15 minutes at a temperature range of ~1150°C to obtain a cold rolled sheet having a final product thickness of 0.15 to 0.25 mm. The cold-rolled sheet with a product thickness of 0.15-0.25 mm is then heated at 780-880°C for 0.5-15 min for 15 min.
The steel sheet is subjected to decarburization annealing to reduce the carbon content of the steel sheet to 0.005% or less. After the subsequent decarburization annealing, 900 to 10
It is preferable to apply nucleation treatment heating at 50° C. for 0.5 to 15 minutes in order to make the secondary particle size of the product fine and obtain a low iron loss material. Here, in the decarburization annealing atmosphere, as mentioned above, the amount of oxidation after decarburization annealing affects the amount of forsterite in the product, so it is necessary to control the oxygen potential of the atmosphere to avoid overoxidation. After applying a separating agent such as MgO, the material is subjected to secondary recrystallization and high-temperature box annealing for purification. Purification annealing is usually carried out in hydrogen at a temperature of 1100°C or higher for 1 hour or more, but before that, as a treatment to improve directionality, in order to complete secondary recrystallization at a temperature range of 800 to 900°C, during this period It is effective to maintain the temperature for 5 hours or more or to remove the heat at 15° C./Ilr or less during this time in order to enhance the effects of the present invention. Thereafter, a coating for insulation and tension addition is applied as necessary to produce a product, and the product thus obtained has a fine secondary particle size and a significantly low iron loss. (Example) Souse Oku-shi CO, 042%, Si 3.28%, Mn 0.068
%, Se0.022%, SbO,035%, S
A silicon steel slab consisting of 0.020% n, 010% As O, and the balance Fe was heated at 1340° C. for 3 hours and then hot rolled to obtain a hot rolled plate with a thickness of 2.2 mm. Then 950℃+
After heating for 5 minutes, primary cold rolling was carried out at 75%.
After performing intermediate annealing at 950° C. for 5 minutes to obtain an intermediate thickness of 55 sn, a cold-rolled sheet having a thickness of 0.20 sn was obtained by secondary cold rolling at a rolling reduction of 64%. Then 8 in wet hydrogen
Decarburization annealing was performed at 00°C for 5 minutes. After the decarburization annealing, a secondary recrystallization nucleation treatment was performed at 950°C for 5 minutes. Next, after applying MgO as a separating agent, secondary recrystallization annealing was performed at 860° C. for 24 hours in-line, followed by purification annealing at 1200° C. for 5 hours in hydrogen to obtain a final product. The magnetic properties and average secondary particle size of the product plate thus obtained were as shown in Table 2. For comparison, the same table also includes the results of investigation on product boards obtained by the conventional method without performing the secondary recrystallization nucleation treatment as described above. No Table 2 7.6 0.91 1.91
Comparative individuality 4.0 0.86 1.92
Compatibility example 4, brief explanation of drawings Figure 1 shows product plate thickness (am) and iron FNW+ ty5o
(W/kg) using the product's average secondary particle size (w) as a variable. (
FIG. 3 is a diagram showing changes in the relationship (W/kg) depending on the product board thickness.

Claims (1)

[Claims] 1. Contains 2 to 4% of Si, and contains Sn as an inhibitor.
, S 0.010-0.035%
and 0.010 to 0.080% of at least one selected from Sn, As, Bi and Sn, hot rolled and then once or twice with intermediate annealing in between. After cold rolling, the thickness is 0.15~0.
．． After the final thickness of the steel sheet is 25 mm, decarburization annealing is performed, and an annealing separator is applied, and final annealing is performed to produce secondary recrystallization and forsterite of 1 to 4 g/m^2 per side on the surface of the steel sheet. In the method for producing a grain-oriented silicon steel sheet in which a film is formed, prior to final annealing, the temperature is held within a temperature range of 900 to 1050°C for 0.1 to 15 minutes, and then secondary recrystallization is performed in a temperature range of 800 to 900°C. A method for producing a unidirectional silicon steel sheet with extremely low iron loss, characterized in that by completing the process, the average grain size after secondary recrystallization is in the range of 1 to 6 mm.