Effect of Austenitizing Treatment on Structure and Hardness of Bainite DuctileCast Iron

By continuous quenching process, the effect of austenitizing temperature and time on the structure and hardness of bainite ductile cast iron was studied. It was found that (l) low austenitizing temperature would result in scrap ferrite existing in matrix, which reduces the macro-hardness of bainite ductile cast iron; (2) high austenitizing temperature would make carbide decomposed, which also induces the macro-hardness of bainite cast iron, and (3) austenitizing time has little effect on the structure of bainite ductile cast iron, but as it increases, the macro-hardness of bainite ductile cast iron and micro-hardness of bainite increases. To the ductile cast iron, as a result,the suitable austenitizing temperature and time are recommended as 880℃ and 120 min respectively.