Research on Microstructure Performance of New Type Large-diameter Forged B3 Steel Ball
Taking φ125 mm forging ball as reference,the mechanical properties and microstructure of B3 steel newly used for forging steel balls were researched.The results show that the overal hardness of B3 ball is between 56.0-59.5 HRC,the impact toughness is between 23.00-29.90 J/cm2.The surface microstructure of B3 ball is mainly acicular martensite.There are much troostite and bainite in the heart besides the martensite.The reasons for the phenomenon are the Mn and Cr contents which are not uniform in the heart of B3 steel ball,and the quenching temperature is lower,the cooling rate of heart of forging ball is slow,the supercooled austenite easily transforms into fine flake troostite,while higher carbon content decreases the martensite transition temperature,which can accelerate the tendency of forging heart transforming into bainite and troostite.
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