Study on Silicon Induced Phase Transformation in Bainite Ductile Iron by Monified Step Quenching

A low bainite ductile iron with different Si content was used to study silicon induced bainitic transformation by a modified step quenching process.The microstructures and mechanical properties were examined by means of SEM,hardness and impact tests.The mechanism of effect of silicon content on bainitic phase transformation was discussed.The results show that silicon content higher than 3.3 wt% can induce distinctly phase transformation of low bainite in the process of modified step quenching(isothermal temperature 230℃).The microstructure is fined and mechanical properties are improved for the bainite ductile iron treated by the modified step quenching.