Influence of tempering temperature on microstructure and properties of steel 30Cr3SiNiMoVA in thermomechanical processing

Microstructure resulted from thermomechanial processing for an ultrahigh strength microalloyed steel 30Cr3SiNiMoVA( 30Cr3)was characterized using optical and scanning electron microscopy in order to optimize parameters in the processing to obtain required properties. Tensile properties and work hardening behavior were analyzed for the steel tempered at different temperatures in the thermomechanial routes. The microstructure of the steel after spinning deformation and tempering at 400 ℃ exhibits a better combination of strength and toughness owing to its fine tempered ferrite matrix and precipitation of dispersed carbide. Plastic deformation results in high density dislocations in microalloyed steel 30Cr3 by the thermomechanial treatment,which improves the precipitation of carbides in the matrix to rise the tension strength,however,overgrowth of the carbides after the tempering at temperature higher than 400 ℃ decreases the tension property because of the vanishing of carbide dispersion-strengthening. The optimized tempering temperature of 400 ℃ is recommended for thermomechanically treated 30Cr3 steel based on the experiment.