| 摘要 |
PURPOSE:To obtain abrasion resistance spheroidal graphite cast iron which secures high toughness and is provided with high abrasion resistance and fatigure strength by heating and holding only the surface part which requires abrasion resistance, of parts cast by ferrite type spheroidal graphite cast iron, and thereafter, air-cooling it, and subsequently, hardening the whole parts. CONSTITUTION:Only the surface part of parts cast by ferrite type spheroidal graphite cast iron whose pearlite area rate is <=30% is heated and held at 900- 1,000 deg.C for five seconds - five minutes. As a result, the base ground of said surface is converted to austenite. Subsequently, said surface which is heated and held is air-cooled, and the austenite is converted to pearlite. Thereafter, said whole parts are brought to hardening or austempering treatment, and the pearlite is transformed to a single structure of martensite (at the time of hardening) or bainite (at the time of austempering treatment) which does not contain ferrite. In this way, abrasion resistance and fatigue strength of the surface of said parts are improved. |
