Metal treatment – Process of modifying or maintaining internal physical... – Magnetic materials
Patent
1997-08-18
1998-09-08
Sheehan, John
Metal treatment
Process of modifying or maintaining internal physical...
Magnetic materials
148120, 148113, 148122, H01F 1147
Patent
active
058039880
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method for manufacturing an non-oriented electrical steel sheet which is used as steel cores for electrical machines such as electric motors, electric generators, small transformers and the like. More specifically, the present invention relates to a method for manufacturing an non-oriented electrical steel sheet showing a superior adherence of the insulating coated layer.
2. Description of the Prior Art
The non-oriented electrical steel sheet is used as a steel core for electrical machines such as electric motors, electric generators, transformers and the like. This steel core is generally manufactured by press-punching electrical steel sheets and by stacking them.
In the case where the steel core is manufactured by stacking, each sheet is coated with an insulating layer so as to insulate each sheet, thereby reducing the eddy currents.
Generally, the iron loss of the non-oriented electrical steel sheet consists of eddy current loss and hysteresis loss, and this iron loss can be measured in the unit of watts.
The major factors which influence the eddy current are the electric insulation property of the insulating coated layer, the thickness of the steel sheets, and their composition.
Particularly, in the case where an energy saving is required, or where it is used as a core of high frequency products, it is absolutely necessary to reduce eddy current.
Meanwhile, the insulating coated layer which is coated on the surface of the electrical steel sheet is classified into an organic coating material, an inorganic coating material and an organic-inorganic composite coating material. If the thickness of the insulating layer is increased, the insulating current value is lowered.
If iron loss, particularly eddy current loss, is to be decreased, the insulating layer should be firmly adhered on the surface of the steel sheet. The reason for this is that if the insulating layer is peeled during a punching or during a heat treatment, then the insulating strength is lowered, and the magnetic properties may be aggravated. Further, the peeled pieces may cause disorders in the relevant apparatus, and the environment is contaminated.
Typical methods for improving the adherence of the coated insulating layer of non-oriented electrical steel sheets are disclosed in U.S. Pat. No. 3,853,971 and Japanese Patent Application Laid-open No. Sho-60-38069. In these methods, the composition of the insulating coated layer is controlled, thereby improving the adherence of the insulating coated layer.
However, in these conventional methods, there are limits in improving the adherence strength of the insulating layer.
SUMMARY OF THE INVENTION
The present inventors carried out research and experiments on the method of improving the adherence strength of the insulating layer, and came to propose the present invention based on the results of the research and experiments.
Therefore it is an object of the present invention to provide a method for improving the adherence strength of a non-oriented electrical steel sheet, in which the annealing conditions of a cold rolled steel sheet are properly controlled so as to form a dense surface oxide layer, thereby improving the adherence strength of the insulating layer.
In achieving the above object, the method for manufacturing a non-oriented electrical steel sheet having a superior adherence of an insulating coated layer according to the present invention includes the steps of: less of Si, 1.5% or less of Mn, 0.15% or less of P, 0.015% or less of S, 1.0% or less of Al, one or more elements selected from a group (consisting of 0.03-0.30% of Sn, 0.03-0.3% of Sb, 0.03-1.0% of Ni and 0.03-0.50% of Cu), a balance of Fe and other unavoidable impurities; the hot rolled steel sheet; a temperature of 750.degree.-850.degree. C. for 30 seconds to 5 minutes under a humid atmosphere having a dew point of 25.degree.-65.degree. C.; cold rolled steel sheet at a temperature of 800.degree.-1070.degree. C. for 10 seconds to 3 m
REFERENCES:
patent: 3853971 (1974-12-01), Kato et al.
patent: 3930906 (1976-01-01), Irie et al.
patent: 4326899 (1982-04-01), Henricks
Japanese Abstract No. 60-38069, Feb. 27, 1985, 1 p., (English language).
Japanese Abstract No. 60-152628, Aug. 10, 1985. 1 p., (English language).
Japanese Abstract No. 61-231120, Oct. 15, 1986, 1 p., (English language).
Japanese Abstract No. 3-223423, Oct. 2, 1991, 1 p., (English language).
Bae Byung Keun
Chang Sam Kyu
Lee Wun Gul
Woo Jong Soo
Pohang Iron & Steel Co. Ltd.
Sheehan John
LandOfFree
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