HIGH SPEED TOOL STEEL MATERIAL FOR COLD FORGING, HIGH SPEED TOOL STEEL HOLLOW PRODUCT AND ITS MANUFACTURING METHOD

摘要

PROBLEM TO BE SOLVED: To provide a high speed tool steel hollow product which is extremely smooth on the outer face, can shorten a polishing time after following heat treatment, does not cause a hazardous fracture of a coarse eutectic carbide at least on the outer face, and can improve reliability of the hollow product after undergoing the heat treatment and the polishing process and its manufacturing method, and to provide a high speed tool steel material for cold forging capable of manufacturing this high speed tool steel hollow product.;SOLUTION: The material is pressed and worked by using the high speed tool steel cylindrical material in which material hardness is less than 102 HRB, the coarse eutectic carbide having more than 25 μm of a major axis does not exist inside part and the coarse eutectic carbide and a coarse eutectic carbide piece having more than 15 μm of the major axis are not exposed on the surface, and by using dies having the inner diameter at a forming part which differs from the diameter of the material in less than 0.5 mm. The worked hollow product has less than 1 μm of surface roughness, and in which more than 15 μm of the coarse eutectic carbide and the coarse eutectic carbide piece are not exposed on the outer peripheral face.;COPYRIGHT: (C)2002,JPO