JPH036327A - Manufacture of low iron loss grain oriented silicon steel sheet - Google Patents

Abstract

PURPOSE:To permit the low iron loss which exceeds a limit in the past in the silicon steel sheet by mechanically imparting strains to a micro area constituted of tertiary recrystallization grains obtd. by subjecting a grain oriented silicon steel sheet to cold rolling and heating treatment under specified conditions and subdividing the magnetic domain width in the steel sheet. CONSTITUTION:Grain oriented silicon steel blank sheet contg. 2 to 8wt.% silicon is cold-rolled at >=50% draft into <=150mum sheet thickness. The stock is heated at >=1.5 deg.C/sec temp. rising rate in a nonoxidizing or evacuated atmosphere, is held to about 1000 to 1400 deg.C for >=3hr and is thereafter cooled. Micro strains having a wire shape or the like are imparted to a micro area of the obtd. silicon steel sheet constituted of tertiary recrystallization grains by mechanical means to subdivide the magnetic domain width in the steel sheet. The distance between the wire-shaped micro strains is preferably regulated to about 1 to 20mm, the angle between the micro strains and the rolling direction to >=30 deg. and the width of the micro strains to about 10 to 300mum.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for manufacturing a grain-oriented silicon steel sheet, and particularly to a method for manufacturing a grain-oriented silicon steel sheet with low iron loss.

[Conventional technology]

Grain-oriented silicon steel sheets are usually made by secondary recrystallization of silicon steel containing around 3% Si, with (110) planes on the steel plate surface and (110) planes in the rolling direction.
It is a developed material with a so-called Goss orientation having a [001] axis, and is known as a material with low core loss because the axis of easy magnetization ([001] axis) is in the rolling direction. As a method of highly aligning the (001) axis in the rolling direction in order to further reduce iron loss, for example, as in Japanese Patent Publication No. 40-15644, it is necessary to specify the inhibitor in the steel plate components and the cold rolling and annealing conditions. has been adopted.

It is also known that the iron loss of the above-mentioned grain-oriented silicon steel sheet can be further reduced by reducing the magnetic domain width within the steel sheet, and one proposed method is to mechanically apply micro-strain to the surface of the steel sheet. (Special Publication No. 58-5968)
. However, even with this method, the iron loss Wl 7150 at a magnetic flux density of 1.7T and a frequency of 50Hz is 0.83W/
The limit was around kg.

By the way, as a new method for manufacturing silicon steel sheets, Si is
A grain-oriented silicon steel sheet having 8% silicon is cold-rolled under the conditions of a plate thickness of 150 μm or less and a reduction rate of 50% or more, and then a heat treatment process in a non-oxidizing atmosphere or reduced pressure atmosphere that increases the temperature at a rate of 1.5°C/second or more. Heat from room temperature at a speed of about 1000 to 140
After being maintained at 0° C. for 3 hours or more, it is cooled. This results in
A manufacturing process for producing grain-oriented silicon steel sheets with low core loss and consisting of tertiary recrystallized grains has been proposed (Japanese Patent Application No. 62-327).
No. 0).

[Problem to be solved by the invention]

However, with the conventional technology mentioned in 1, even grain-oriented silicon steel sheets that utilize tertiary recrystallization, which can achieve the lowest iron loss, can achieve W]7150.
=0.58W/kg was the limit.

An object of the present invention is to obtain a grain-oriented silicon steel sheet with particularly low core loss by improving the method for manufacturing grain-oriented silicon steel sheet.

[A step that solves problems]

As a result of repeated research to achieve the above object, the inventors found that by applying cold rolling and high-temperature heat treatment to a commercially available grain-oriented silicon steel sheet as a starting material, a grain-oriented structure consisting of tertiary recrystallized grains was obtained. It was confirmed that it is extremely effective to combine the process of obtaining a silicon steel plate with the process of applying mechanical microstrain to the surface of the steel plate.

Specifically, a grain-oriented silicon steel sheet material containing 2 to 8% silicon is cold rolled under the conditions of a plate thickness of 150 μrn or less and a rolling reduction of 50% or more, and then a heat treatment process in a non-oxidizing atmosphere or a reduced pressure atmosphere. It is heated from room temperature at a temperature increase rate of 1.5°C/sec or more, maintained at about 1000 to 1400°C for 3 hours or more, and then cooled. This allows (001
') Average axis deviation angle 2.5° or less, magnetic field strength 800
A series of manufacturing processes to produce a 1M grain-oriented silicon steel plate with a magnetic flux density Bs > 1.957 in A/m and consisting of tertiary recrystallized grains, and a mechanical method to create a 1M grain-oriented silicon steel plate with ta mechanical means. The above object is achieved by combining the steps of applying linear strain with 2 Qim and dividing the magnetic domain width in the steel sheet.

[Effect]

The reason why the magnetic properties are significantly improved is considered to be as follows. Conventionally, an insulating coating is applied to a grain-oriented silicon steel sheet made of tertiary recrystallized grains after heat treatment, and tension is applied by the difference in expansion between the steel sheet and the coating, thereby reducing the magnetic domain width in the steel sheet and reducing iron loss. Ta. However, there was a limit to the tension that the coating could provide, and there was also a limit to the improvement in iron loss.

However, in addition to the above-mentioned method, the method of the present invention can further reduce the magnetic domain width by applying micro-strain to the steel sheet, making it possible to lower core loss beyond the conventional limit. Further, in the conventional method of imparting micro-strain to a grain-oriented silicon steel sheet made of secondary recrystallized grains, the reduction in iron loss was about 10% on average. By the way, the effect of reducing iron loss by applying minute strain is closely related to the magnetic flux density B8 of the steel plate, and as shown in Fig. 3, 88>1.9.
It was known that a particularly remarkable effect is seen at 4T or higher. However, with the production method using secondary recrystallization, Be
It is difficult to consistently obtain >1.94T, and therefore, on average, the iron loss reduction rate due to strain application was improved by about 10%.

In the present invention, the manufacturing method uses tertiary recrystallization, and B
e>1.957 can be consistently obtained. Therefore, as shown in Table 2 below, a high reduction rate of about 20% was achieved. As a result, W17150=0.4
i is a grain-oriented silicon steel sheet with extremely low core loss of 6W/kg.
η is rejected.

In addition, in the conventional grain-oriented silicon steel sheet made of secondary recrystallized grains, the grain size was on average about 3 mm, so the iron loss reduction effect did not occur when the linear strain spacing was 15 m1 or less. However, in the grain-oriented silicon steel sheet made of tertiary recrystallized grains used in the present invention, the grain size is as large as 15 fins on average, so even if the linear strain interval is 2011, it has the effect of reducing the magnetic domain width.

〔Example〕

The silicon content in the raw material silicon steel strip used in the present invention is 2 to 2.
A substance regulated within a range of 8% is used. 2% silicon
Since the silicon steel strip containing the above does not undergo γ transformation, it is possible to enlarge the crystal grains by high-temperature annealing or to cause secondary and tertiary recrystallization to form a preferable length structure. If the silicon content is less than 2%, the above-mentioned features will not be exhibited, and if the silicon content exceeds 8%, the saturation magnetic flux density will be 1.7'F or less, making it unsuitable as a magnetic +A material. Not only is this suitable, but it becomes extremely mechanically fragile.

Particularly, those having a silicon content of 2.5 to 4.0% are suitable because they have excellent mechanical properties such as rolling properties and have a saturation magnetic flux density of 1.89 T or more.

For example, Mn, A! ,S,Se,Sn,S
b. MnS, MnSe', MnSb, AIN, etc. can be added in a total amount of up to 0.5% as necessary.

In addition, as unavoidable mixed elements, for example, NlXCu, M
It may also contain small amounts of OXW, CO1Cr, etc.

Further, the content of unavoidable impurities such as C, N, and 0 is preferably limited depending on the final target quality of the steel sheet.

As the grain-oriented silicon steel plate used in the present invention, a commercially available grain-oriented silicon steel plate can be used, and the plate thickness is 150 μm.
m or less. It is sufficient if the rolling reduction rate at this time is 50% or more, and the purpose of rolling is to create crystal strain (111) (1
12) To obtain an ultrathin body with orientation.

Heat treatment after cold rolling is performed in an inert gas atmosphere, 112 gas atmosphere, a mixed gas atmosphere of inert gas and H2 gas, or a reduced pressure atmosphere of these gases or air reduced pressure to prevent oxidation of the steel plate during heat treatment. It takes place in an atmosphere.

The heat treatment temperature is 1000 to 1400°C, the heat treatment time is 3 hours or more, preferably 7 to 24 hours, and the heat treatment temperature increase rate is 1.5°C/S or more, preferably 3°C/S or more.

It is preferable to form linear minute strains at intervals of 1 to 20 WI11 by pressing the steel plate after these heat treatments.

The linear minute strain of 1 g can be achieved by placing a ball on the surface of a steel plate and drawing the ball by rotating it while applying a load. However, the method for bypassing minute strain is not limited to the above method, and it is preferable to apply linear strain with a width of 10 to 300 μm to C that leaves a scratch.

If the width is less than 10 μm, the surface of the steel plate may be damaged, and if it is wider than 300 μm, the strain area may become large and may not be effective.

Next, the present invention will be explained using specific examples.

The material is grain-oriented silicon steel plate (308105
) was used. The properties of this silicon steel plate are shown in Table 1. This silicon steel plate was immersed in a mixed solution of concentrated sulfuric acid and fluoric acid (3 sulfuric acid: 1 part fluoric acid) for 30 minutes, washed with water, further pickled with a 10% nitric acid aqueous solution, rinsed with water, and coated on the surface of the steel plate. Remove any insulating coating or oxide coating.

Table 1 Next, the material was cold rolled to 100 μm at a reduction rate of 67%, and then heated to 1200°C at a heating rate of 3°C/s under a vacuum of 2×10=Torr. The temperature was maintained for l1 to grow tertiary recrystallized grains. Thereafter, a coating solution containing phosphate and colloidal silica as main components was applied to the surface of the 1121 plate and baked at 800°C.A ball with a diameter of 3 m was placed on the surface of the steel plate thus obtained. Place, load 15
It was rotated while applying 0 g to apply linear strain at 151 intervals.

FIG. 1 does not show the relationship between the angle θ between the direction of the line of linear strain and the rolling direction of the steel plate and the reduction rate of iron loss (w17150). θ
It was confirmed that the iron loss did not decrease at θ>20°, but decreased by 15% or more when θ>30°, and by 20% or more when θ>45°. In other words, the optimal angle θ is 30° or more, more preferably 45° or more.

Next, the load applied to the ball with the diameter of 3 is 100.200.3
00 g, and the interval of linear strain at that time was also varied from 1 to 30 am. FIG. 2 shows the relationship between the linear strain interval and the iron loss reduction rate. In the figure, curve A is when a load of 100 g is applied, curve B is when a load of 200 g is applied, and curve C is when a load of 300 g is applied. Although the optimum range differs depending on the load, a reduction in iron loss is observed when the spacing is 1 as or more, and there is almost no lino effect when the spacing is 20vII or more, and the optimum range is from 1 to 20IIm.

Table 2 shows that a ball with a diameter of 31II is placed on a steel plate made of tertiary recrystallized grains and coated with an insulating coating and baked, and a load of 30
The graph shows the changes in iron loss before and after applying strain when rotating with 0g applied and applying strain at 2 (ln) in a direction 90° to the rolling direction. Figure 3 also shows the change in iron loss before and after applying strain. Loss W
Although a relationship of 17/50 reduction rate was shown, the iron loss was reduced by about 20% by applying linear strain, and Wl 7150 = 0.4
We were able to obtain an unprecedentedly low iron loss of 6W/kg.

Table 2 [Effects of the Invention] According to the present invention, a grain-oriented silicon steel sheet with extremely low iron m can be obtained.

[Brief explanation of drawings]

Figure 1 shows the angle between the rolling direction and linear strain and the iron loss Wl 7
150 reduction rate relationship diagram, Figure 2 shows linear strain interval and iron loss W
17/50 Low frequency ratio diagram, Figure 3: Magnetic flux density B8
It is a relationship diagram between the iron loss Wl 7150 reduction rate and iron loss Wl 7150 reduction rate.

Claims (3)

[Claims] (1) A grain-oriented silicon steel sheet material containing 2 to 8% by weight of silicon is cold rolled to a thickness of 150 μm or less at a reduction rate of 50% or more, and then a heat treatment process in a non-oxidizing atmosphere or a reduced pressure atmosphere, Microscopic regions of grain-oriented silicon steel sheet made of tertiary recrystallized grains obtained by heating from room temperature at a temperature increase rate of 1.5 ° C / sec or more, holding at about 1000 to 1400 ° C for more than 3 hours, and then cooling. A method for manufacturing a grain-oriented silicon steel sheet with low iron loss, characterized by applying strain by mechanical means and subdividing the magnetic domain width of the steel sheet. (2) In claim (1), the linear microstrain is set at intervals of 1 to 2
A method for manufacturing a low iron loss grain-oriented silicon steel sheet, characterized in that the iron loss is applied to a grain-oriented silicon steel sheet with a thickness of 0 mm. (3) In claim (2), the angle between the linear microstrain and the rolling direction is 30° or more, and the width of the linear microstrain is 10 to 300°.
A method for producing a grain-oriented silicon steel plate with a low core loss characterized by a thickness of μm.