JPH0649902B2 - Iron loss improvement method for grain-oriented silicon steel sheet - Google Patents

Description

The present invention relates to a method for improving iron loss of grain-oriented silicon steel sheets,
In particular, the present invention intends to improve the efficiency of electrical equipment such as a transformer using the steel sheet as an iron core.

To reduce the iron loss of grain-oriented silicon steel sheets, metallurgical methods such as bringing the secondary recrystallization structure of the steel sheet closer to the (110) [001] orientation and increasing the Si content have been mainly adopted. It was However, with these methods, for example, it is difficult to reduce the iron loss W _17/50 at 1.7 Tesla and 50 Hz to 1.00 W / kg or less for a steel plate having a thickness of 0.30 mm, and the iron loss reduction has its own limit.

As another method, there is a method of reducing the steel plate thickness, and at present, a 0.20 mm-thick steel plate is also manufactured and used. However, even if the steel plate thickness is reduced, for example, for a steel plate having a thickness of _0.23 mm, W _17/50 is limited to about 0.90 W / kg.

(Prior Art) Various methods for improving iron loss have been proposed in addition to metallurgical methods.

As a main method other than the metallurgical method, there is a method of irradiating a laser beam disclosed in Japanese Patent Publication No. 57-2252. By using this method, iron loss can be significantly reduced as compared with the conventional method, but there are problems in terms of high cost, workability, and safety.

(Problems to be Solved by the Invention) By the way, the inventors previously developed a method of radiating a plasma flame on a steel sheet as a means for solving these problems, and disclosed it in Japanese Patent Application No. 60-236271.

The present invention was developed after pushing the above-mentioned iron loss reduction technology by plasma flame radiation one step further, and an object thereof is to propose a method capable of stably obtaining a good iron loss reduction effect. .

That is, the present invention is one of tensile stress σ _T (kg / mm ² ) and bending stress σ _R (kg / mm ² ) in the rolling direction of finish-annealed grain-oriented silicon steel sheet, or a combination thereof. While applying stress, when radiating a plasma flame linearly in a direction intersecting the rolling direction of the steel plate, the relative velocity between the radiation nozzle of the plasma flame and the steel plate is S (mm / s), and the current density of the plasma flame is I ( A / mm ² ), the following relational expression Is a method for improving iron loss of grain-oriented silicon steel sheet, characterized in that plasma flame is radiated under the condition satisfying the above condition.

Here, the relative speed S refers to the following equation S = v ₁ −V ₂ cos θ v ₁ : moving speed of the radial nozzle v ₂ : moving speed of the steel plate θ: moving direction of the radial nozzle in a direction transverse to the rolling direction of the steel plate. It is the velocity expressed by the angle formed by the moving direction of the steel sheet. That is, when only one of the radiant nozzle and the steel plate moves, the speed becomes the relative speed S, and when the radiant nozzle and the steel plate move in the same direction, S = v ₁ −v ₂ , the opposite direction. When moving to S, S = v ₁ + v ₂ .

Hereinafter, the present invention will be described based on the experimental results.

A bending stress is applied to a steel sheet having a thickness of 0.23 mm and 0.30 mm, which has been finish-annealed, by rolling it on a roll with a radius of 60 mm to 6000 mm so that the rolling direction of the steel sheet is aligned with the circumferential direction of the roll. with added ^{_{σ R (kg / mm 2)}} , while applying a tensile stress sigma _T rolling direction ^{0~30kg / mm 2 (kg / mm} 2) of the steel sheet, at right angles the direction of the plasma flame to the rolling direction of the steel sheet The radiation was emitted at a radiation interval of 7.5 mm.

At this time, when the roll radius is small, the tension is lowered, and when the tension is high, the roll diameter is increased to select the roll diameter and the tension within a range in which the steel sheet is not plastically deformed.
Further, an experiment in which only tensile stress was applied on a plane was also conducted. Bending stress σ _R due to roll is Given in. Where E is Young's modulus of steel sheet (kg / mm ² ), t
Is the plate thickness of the steel plate (mm), and R is the roll radius (mm).

The plasma flame was emitted from a nozzle having a nozzle hole diameter of 0.05 to 2.0 mm, and the gas used was Ar. The output current of the plasma flame can be increased as the nozzle hole diameter increases, but it was changed in the range of 1A to 300A. The relative speed S between the nozzle and the steel plate was changed within the range of 1 mm / s to 4000 mm / s. Experiments were carried out by changing the ratio S / I of the relative velocity S and the plasma current density I (A / mm ² ) in the range of 0.001 to 100 by changing these values. Here, the current density is a value obtained by dividing the output current by the nozzle hole cross-sectional area.

The iron loss W _17/50 of the steel plate before and after plasma flame radiation was measured by a single plate porcelain measuring device, and the effect of plasma flame radiation was investigated.

The obtained results are shown in FIG. Iron loss is 0.02 W / in the figure.
When the weight is improved by more than kg, on the other hand, the X mark shows the case where the iron loss remains unchanged or deteriorates.

As is clear from the figure, the iron loss reduction effect by plasma flame radiation is the sum of S / I and tensile or bending stress σ _R + σ _T
S / I and σ _R + σ _T depend on It has been found that there is a particularly excellent plasma flame radiation effect when the range is satisfied.

(Operation) The grain-oriented silicon steel sheet used for plasma flame radiation according to the present invention can be used regardless of the presence or absence of a steel sheet surface coating as long as it is finish annealed. That is, usually, the steel sheet after finish annealing is covered with a film containing forsterite formed as a main component during finish annealing. However, the presence or absence of this film and further the phosphate etc. applied on the forsterite film It can be used with or without overcoating. The radiation of the plasma flame is preferably in the direction substantially perpendicular to the rolling direction of the steel sheet, but it may be staggered within 45 ° with respect to the direction perpendicular to the rolling direction. In the case of linear radiation, the distance between the lines is preferably in the range of 2 mm to 30 mm, and if it deviates from this range, the effect may be small or the characteristics may deteriorate. When applying stress, it is necessary to take care so that bending stress, tensile stress, and the sum thereof do not exceed the yield point of the steel sheet. If the yield point is exceeded, the characteristics will be significantly deteriorated.

An inert gas such as Ar is generally used to generate the plasma flame, but other gas may be used. The nozzle hole diameter of the plasma flame radiating nozzle is preferably 2 mm or less, and the plasma current and the relative speed between the nozzle and the steel plate are appropriately selected from the range satisfying the above relational expression in consideration of the life of the nozzle and the like. .

The reason why the iron loss is reduced by the radiation of the plasma flame is presumed to be that the portion where the plasma is radiated becomes magnetically hard and the magnetic domains are subdivided.

(Example) Example 1 A 0.23 mm-thickness annealed grain-oriented silicon steel sheet was used as the radius.
It is put on a 100 mm roll and 5 kg / in the rolling direction of the steel plate.
While applying a tensile stress of mm ² , the current density I shown in Table 1
Further, under the condition of the relative velocity S between the nozzle and the steel sheet, linear plasma irradiation was performed in a direction perpendicular to the rolling direction of the steel sheet.

The total stress calculated using the Young's modulus of the steel plate is about 21
It was kg / mm ² . The nozzle diameter of the plasma torch is 0.15
mm, voltage was 30V. Ar gas was used as the gas.

Table 1 also shows the results of examining the iron loss characteristics before and after plasma flame irradiation.

As is clear from the table, particularly good reduction in low loss was achieved when plasma flame radiation was performed under conditions satisfying the above-mentioned relational expression.

Example 2 A 0.23 mm-thick finish-annealed grain-oriented silicon steel plate was used as a radius
It was stuck on a roll of 200 mm, and a plasma flame was radiated to this steel plate linearly in the direction perpendicular to the rolling direction of the steel plate. At this time, the bending stress on the surface of the steel sheet was 8 kg / mm ² . A similar plasma flame was radiated without bending a steel sheet of the same kind and with or without applying a tensile stress of 8 kg / mm ² .

The nozzle diameter of the plasma torch was 0.1 mm and the gas used was Ar + H ₂ . The relative speed S between the nozzle and the steel plate and the current density I are as shown in Table 2. The radiation interval is 8 mm.

Table 2 also shows the results of measuring the magnetic characteristics before and after radiation with a single-plate magnetic testing device.

As shown in the table, when the radiation conditions according to the present invention are satisfied (Sample Nos. 2 and 6), a particularly excellent iron loss reducing effect is obtained.

(Effect of the Invention) Thus, according to the present invention, the iron loss of the grain-oriented silicon steel sheet can be remarkably reduced, and the energy loss of the iron core in the transformer or the like can be remarkably reduced.

[Brief description of drawings]

FIG. 1 shows the S / I reduction effect of iron loss due to plasma flame radiation.
It is the figure shown by the relationship of σ _R + σ _T.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Atsuto Honda Atsushi Kawasaki-cho, Chiba-shi, Chiba Kawasaki Steel Co., Ltd.

Claims (1)

[Claims] 1. A tensile stress σ _T (kg / mm ² ) and a bending stress σ in the rolling direction of a grain-finished grain-oriented silicon steel sheet.
Relative velocity between the radiation nozzle of the plasma flame and the steel plate when linearly radiating the plasma flame in the direction intersecting the rolling direction of the steel plate while applying either one of _R (kg / mm ² ) or a combined stress thereof. Is S (mm / s) and the current density of the plasma flame is I (A / mm ² ), the following relational expression A method for improving iron loss of grain-oriented silicon steel sheet, characterized in that a plasma flame is radiated under a condition satisfying the conditions.