Microstructure and properties of air cooled high silicon medium carbon low alloy steel

The microstructures and mechanical properties of the high silicon medium carbon low alloy steels subjected to air cooling and tempering after air cooled were investigated.After austenized at 860 ℃ for 0.5 h,the testing steels were air cooled to ambient temperature,subsequently some of the samples were further tempered at 250 ℃ and 400 ℃ for 1h respectively.The experimental results show that the microstructure of testing steels subjected to air cooling is a mixed microstructures comprised of bainite/martensite plus retained austenite,and the hardness of testing steels is 41 HRC.While after tempered at 250 ℃,although the microstructure of testing steels is changed slightly,the hardness is increased to 49 HRC,the toughness is distinctly increased from 44 to 66 J/cm2,however the tensile strength,the yield strength and the elongation are markedly decreased.The further increase of tempering temperature has not large effect on mechanical properties.