JPH0772300B2 - Method for manufacturing low iron loss grain oriented silicon steel sheet - Google Patents

Description

TECHNICAL FIELD The present invention relates to a manufacturing method for significantly reducing the iron loss of grain-oriented silicon steel sheets used in transformers and the like.

The iron loss of grain-oriented silicon steel sheet is a thermal energy loss generated by the steel sheet used for the iron core of transformers, etc., and there is a demand for reduction of iron loss of grain-oriented silicon steel sheet due to the recent energy situation. It is increasing.

By the way, in order to reduce iron loss, the crystal orientation of the steel sheet should be (11
0) Various attempts have been made to make the steel sheet highly aligned by the <001> orientation, increase the Si content to increase the electrical resistance of the steel sheet, reduce impurities, and in recent years, reduce the thickness of the steel sheet.

However, iron loss reduction by these metallurgical methods has almost reached the limit.

(Prior Art) Various methods for improving iron loss have been proposed in addition to metallurgical methods. Among these, the one currently industrialized is the iron loss reduction method by pulse laser irradiation disclosed in Japanese Patent Publication No. 57-2252. By using this method, the iron loss can be greatly reduced compared with the conventional method, but it is inevitable that the initial cost and the running cost increase due to the expensive equipment and the short life of the laser excitation lamp. In addition, the laser used is often not visible light, so safety measures are essential.

Further, Japanese Patent Laid-Open Nos. 59-33802 and 59-92506 disclose a method of irradiating continuous laser. However, in addition to the same drawbacks as pulsed laser E, there is little iron loss reduction effect and There is a drawback that the effect is not constant because the laser light absorptance fluctuates inevitably.

(Problems to be Solved by the Invention) A new low iron loss grain oriented silicon steel sheet which does not have the above-mentioned drawbacks and can significantly reduce iron loss by means advantageous in terms of productivity, workability, safety and cost It is an object of the present invention to provide a method of manufacturing

(Means for Solving Problems) As a result of intensive experiments to solve the above problems, the inventors have found that significant iron loss is caused by radiating a plasma flame to the surface of the finish-annealed grain-oriented silicon steel sheet. The inventors have newly found that the reduction effect can be obtained and have completed the present invention.

In other words, this invention applies to finish-annealed grain-oriented silicon steel sheets 2.
A method for manufacturing an iron loss grain oriented silicon steel sheet, which comprises radiating a plasma flame emitted from a nozzle hole having a diameter of 0 mm or less.

The present invention will be specifically described below based on the experimental results.

Nozzle hole 0.05 mmφ ~ 2.5 m in 0.23 mm thick steel plate that has been finish annealed
A plasma flame was emitted from a torch with mφ.

The plasma was generated by flowing argon or a mixed gas of argon and hydrogen with a voltage applied between a cathode containing tungsten as a main component and an anode.

Larger output current can flow with larger nozzle hole diameter, but 1A ~
I changed it in the range of 300A.

The radiation of the plasma flame radiates in a continuous line in a direction almost perpendicular to the rolling method of the steel sheet, and the radiation interval in the rolling direction is 6.35 mm. The relative velocity between the plasma flame and the steel plate, which determines the plasma radiation residence time, was varied between 1 mm / sec and 400 cm / sec.

As a result of experimenting under these wide range of experimental conditions, the nozzle hole diameter is
It was newly found that iron loss is improved by appropriately selecting the output current, the relative velocity of the plasma flame and the steel plate at each nozzle hole diameter except when it is larger than 2.0 mmφ. The results of these experiments are shown in FIG. The figure shows the iron loss difference ΔW _17/50 (flux density 1.7T, 50Hz) before and after plasma flame radiation, but a large reduction in iron loss was observed when the nozzle hole diameter was 2.0mmφ or less.

The direction of radiation of the plasma flame was the most perpendicular to the rolling direction, but the iron loss reduction effect was recognized even if the direction was up to 45 ⁰ .

Further, the effect of reducing iron loss was recognized not only in a continuous linear shape but also in a discontinuous linear or curved shape. It is desirable that the radiating parts are local, and if they are linear, the radiating distance in the rolling direction is preferably 2 to 30 mm.

(Operation) It is presumed that the reason why the iron loss decreases due to the plasma flame radiation is that the part where the plasma flame is radiated becomes magnetically hard and the magnetic domains are subdivided by it.

The steel plate used for plasma flame radiation of this invention is MnS, MnSe, A
l Hot rolled steel sheet containing N and Sb as inhibitors is cold-rolled once or twice with intermediate annealing to obtain the final thickness, then decarburized and then annealed and separated with MgO as the main component. After that, it is a steel sheet that has been finish annealed at a high temperature of about 1200 ° C, and that has undergone secondary recrystallization.

Normally, the finish-annealed steel sheet is covered with the forsterite coating formed during the finishing annealing, but the flame radiant radiation is in the absence of forsterite even from above the forsterite, and the phosphate to be overcoated on the ordinary forsterite. It may be performed from the top of the main coating.

Further, recoating may be performed after plasma irradiation.

The plasma flame may be either non-transfer type or transfer type, but the non-transfer type is easier to radiate. The voltage and the current for generating the plasma flame are not particularly limited, but it is necessary to determine in consideration of stable generation of the plasma flame and the life of the nozzle. The gas for generating plasma is preferably an inert or non-oxidizing gas such as Ar, N ₂ or H ₂ and a mixed gas thereof, but an oxidizing gas or a mixture thereof may be used.
Further, plasma irradiation may be performed under reduced pressure.

At the time of plasma irradiation, tension may be applied to the steel sheet, or the steel sheet may be bent and emitted.

(Example) A 0.23 and 0.30 mm thick grain oriented silicon steel sheet was finally annealed.
A plasma flame was emitted by a torch with nozzle hole diameters of 1 mmφ and 2.5 mmφ. Argon gas was used as the gas. The output current was 7A for the 0.1mmφ nozzle and 50A for the 2.5mmφ nozzle. The direction of radiation is perpendicular to the rolling direction and radiates in a continuous linear manner with a spacing of 6 mm in the rolling direction.

Table 1 shows the results of measurement of the characteristics before and after radiation with a single-plate magnetic test device. B _IO values nozzle hole diameter of 0.1 mm? (Magnetic field 1000A / m
A large improvement in iron loss was observed even for materials with relatively low magnetic flux density.

(Effect of the Invention) According to the present invention, it is possible to significantly reduce the iron loss of grain-oriented silicon steel sheet by plasma flame radiation.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the nozzle hole diameter and the iron loss reduction height ΔW of plasma flame.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Atsuto Honda, 1 Kawasaki-cho, Chiba-shi, Chiba Kawasaki Steel Co., Ltd. Technical Research Division (56) References JP-A-60-89523 (JP, A)

Claims (1)

[Claims] 1. A method for producing a low iron loss grain-oriented silicon steel sheet, which comprises radiating a plasma flame emitted from a nozzle hole having a diameter of 2.0 mm or less to a grain-finished grain-oriented silicon steel sheet.