Effect of high-temperature reduction pretreatment on internal quality of 42CrMo casting billet

Comparative analysis was conducted to illustrate the effect of high-temperature reduction pretreatment on the internal quality of 42CrMo casting billet. Analysis of macrostructure clarifies that reduction pretreatment could reduce the size of central cavities and equiaxed crystals and improve the segregation degree and porosity on statistics. Lath bainite matrix and granular structure on segregation bands mainly dominate the microstructure of original billet, while pro-eutectoid ferrite and its accompanying troostite are added due to the application of reduction pretreatment. Additionally, C, Mn, and Mo are suggested to be enriched in segregation bands where pores and inclusions tend to be generated. By clarifying the microstructure evolution during cooling process, physical compression and multiplication of prior austenite grain boundaries caused by recrystallization are regarded as the main reasons in improving the internal quality of 42CrMo billet.