A study on the microstructure characteristics of SiMnCr system high strength steel

The microstructure characteristics of SiMnCr system high strength steel have been investigated by using optical microscope,scaning (SEM) and transmission(TEM) electron microscope under the different process conditions, such as forging followed,tempering,quenching and isothermalizing.The CCT diagram and the mechanical properties of the steel have been tested.The experiment shows that a composite structure consisting of the dominant lath martensite,a little part of bainite and retained austernite under forging,metabainite structure under the isothermalizing and the lath martensite structure with a little films of retained austernite under quenching are observed. No cementite precipitation occurs under tempering at as high as 300℃.