To form a reforming layer to a desired depth from the surface of a steel material and to simply perform this formation at a low cost.
A rotating tool T rotating at high speed is brought into contact with the surface of the steel material W and then, the contact part of the steel material W with the rotating tool T is softened with frictional heat and this softened part is stirred with a probe 2 to reform the steel material W. Since this rotating tool T is composed of a heat-resistant cemented carbide mainly composed of a tungsten carbide, wear hardly occurs, even in the temperature zone of 1,000C where the steel material W is softened. The depth of the reforming layer 3 can be made a desired depth by changing the length of the probe 2 projectingly arranged on the rotating tool T. Further, when performing this treatment in a state the rotating tool T is inclined to the back part in the advancing direction, since a fluid f2 vertically stirring the softened steel material, is generated with the inclined probe 2, stirring with the fluid is more effectively performed.
UEDA YASUSHI
Torii Kazuhisa
Takayoshi Tagawa
Higashio Masahiro
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