Manufacturing method of austempered ductile cast iron with improved workability

摘要

The present invention provides a method for economically manufacturing osstemford spheroidal graphite iron containing cheap Cu and CaO and having excellent physical properties by a combination of heat treatment temperature profiles. The method of manufacturing austenford spheroidal graphite cast iron according to the present invention is an austenitizing heat treatment at about 900° C., followed by an austempering heat treatment at about 400° C. and an additional heat treatment at about 250° C. It is very efficient in terms of energy use of the overall heat treatment process. In addition, the osstemford spheroidal graphite cast iron produced by the manufacturing method according to the present invention has excellent tensile strength, elongation and hardness, and particularly has a high elongation and thus has improved workability.