To obtain a silicon steel sheet for motors having an excellent blanking property and high-frequency characteristics.
This process consists of a first stage of subjecting a low-carbon steel sheet to a siliconizing treatment by heating the steel sheet in a non- oxidizing gaseous atmosphere of 900 to 1000°C and blowing a non-oxidizing gas of high temperature containing SiCl1 to the steel sheet surface, a second stage of subjecting the inside of the steel sheet to a diffusion treatment by heating Si subjected to the siliconizing treatment on the surface of the steel sheet in the non-oxidizing gaseous atmosphere not contg. SiCl1 at 900 to 1000°C and a third stage of cooling the steel sheet subjected to the diffusion treatment in the non-oxidizing gaseous atmosphere. The Si concentration of the surface layer part is regulated to 5 to 6.5 wt.% and the Si concentration in the central part of the sheet thickness to <3%. When the thickness of the steel sheet is defined as (t) and the thickness of the surface layer part until the Si concentration decrease to 5% from the surface as (d), the thickness ratio R of the thickness (d) in the surface layer part to the sheet thickness (t) is specified to 0.01 to 0.25.
MAEMURA AKIHIKO
KATSUMA TAKASHI
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