| 摘要 |
<p>PURPOSE:To economically manufacture a parts having high strength and high precision by heating a medium or high carbon steel blank, austenizing, plastic- working, reheating at just above the austenizing temp. after once cooling, quenching and tempering it. CONSTITUTION:The blank composed of the medium or high carbon steel is heated and austenized. This blank is subjected to plastic working at least in the warm temp. zone and precisely formed to a desired shape of the parts having matrix structure accomulating plastic strain. Successively, this worked blank is cooled to the pearlite transformation temp. or lower to precipitate carbide. Thereafter, this blank is preheated to the austenizing temp. or lower to remove the residual working strain and also, adjusted to the structure being apt to be austenized. This preheating is desirable to execute at 550-720 deg.C for 5sec-3min. Successively, the preheated blank is immediately cooled after rapidly heating to just above the austenizing temp. By this method, the contour quenching to only the surface along the contour of the blank is executed and further, the tempering treatment is executed to improve the toughness.</p> |
