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崔壯宇,呂運寬,南勝義,韓允熙,朴明果 弘益大學校 1973 弘大論叢 Vol.5 No.-
Ordnance scrap materials such as tank body parts consisting of low carbon alloy steel (0.12% C, 0.8%, W, 0.5% Cr, 1.3% Ni, 0.3% Mo.) have great tougheess and low hardness. The maximum attainable hardness of any steel depends on carbon content. Therefore, the experiment thas been casried out to study a hardening process of this alloy in application for manufacturing the high speed rotary shearing tool or similar tools. The important results obtained from the study are summerized as follows: 1. Under the pack carburizing process at 925℃ for 10 hrs. we could take the case depth 2.5mm. By the quenching process the hardness of this alloy steel has increased up to HRC 64. 2. The case depth and carbon content could be increased by the carburizing time. When the process time took over 10hrs, the carbon content of the surface reached to that of the hypereudectoid steel (0.9 C). In this case, the structure of case surcture of case surface became a rough net work of brittle cementite. 3. The Quenching process must be done by two step quenching to control the rough austnite structure. The optimum quenching conditin was obtained with the first quenching temperature at 900℃ and the scend quenching temperatare at 770℃.