| 摘要 |
PROBLEM TO BE SOLVED: To provide a multi-stage forward extrusion method capable of preventing generation of internal cracks during the extrusion, and reducing the manufacturing cost. SOLUTION: The forward extrusion is performed by using a material having the similar quenching property evaluated in terms of manganese equivalent Mneq, and the die angleαof an extrusion die forming a preset area where any chevron crack (internal crack of a center) is hardly generated for each stage of the extrusion, and the reduction rate of area Rd at the extrusion. By performing the extrusion using the die angleαof the extrusion die forming the preset area where such a chevron crack is hardly generated, and the reduction rate of area Rd at the extrusion, the forward extrusion free from any internal crack can be performed even when simplifying or eliminating the heat treatment for the softening in advance, or even without using a material to be worked having a special metal composition. COPYRIGHT: (C)2007,JPO&INPIT
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