PARTIAL HARDENING METHOD FOR ANNULAR STEEL PARTS

摘要

PURPOSE:To obtain partially hadened hardness differing in the inside and outside circumferential surfaces respectively by partioning the inside and outside circumferential spaces of heated annular steel parts by means of partioning members and injecting pessurized cooling liquid from the inside and outside respectively. CONSTITUTION:A hardening device 20 provided with a rotary supporting base (partioning member) 22 and a cover member (partioning member) 26 contacting with both end surfaces of an annular steel part 10 is prepared. A part 10 heated to a prescribed hardening temp. is set in the device 20, and both are partitioned to a space 30 on a bore side and a space 40 on an outside circumferential side by means of the members 22, 26. Pressurized cooling liquid is injected from the bore side and the ouside diameter side respectively toward the entire width of the part 10. The rate of the injection is made larger on one side and smaller on the other. Thus the required partially hardened hardeness differing in the inside and outside circumferential surfaces respectively is obtained by the simple hardening stage.