Study on the Microstructure and Properties of Air Cooled Bainite Cast Steels with Low-Alloy and Medium Carbon

A new kind of air cooled bainite cast steel(medium carbon air cooled bainite cast steel) was obtained by adding ferro-manganese iron,ferro-silicon iron,chromic iron and ferromolybdenum,a few rare earths in the raw A3 steel,cast through medium frequency induction furnace.designed consisting of low alloy medium carbon by element alloying in the paper.In the subject,we study the effect of the alloys on the microstructure and mechanical property of low alloy systematically and synthetically.using 16 diffirent heat treatment method to find the relation between heat treatment and microstructure.Microstructure and mechanical property of heat-treated,and treated in different heat treating processes experimental steel were were performed by OM,SEM,hardness tester and impact machine.Microstructure changes of Granular bainite and chemical constitution of carbide precipitated when tempered were performed by TEM.The influences of microstructure on strength-toughness as well as wear resistance of the steel under low stress conditions were investigated,through the study,the following conclusions were obtained: Medium Carbon air cooled bainite cast steel is bainite,martensiteadn little retained austenite mixed microsture.and keeping 2 hours time in 980℃ austenitizing temperature then air cooled,and keeping 1 hours time in 880℃ austenitizing then cooled in normal temperature temperature and keeping 2 hours time in 250℃ anealing,the hardness is 49.7 HRC,the impact toughnes is 52.53J/cm2.