Evaluation on Decrease of Elastic Limit on Quenched Medium Carbon Steel

Carbon steel with a medium or high carbon content can realizes high hardness, and is widely used for bearing parts, which are the main mechanical elements, because of its high strength and wear resistance. The authors investigated changes in the tensile strength and elastic limit of medium carbon steel by tempering. As the result, the tensile strength and elastic limit of the as-quenched steel were lower than those of the tempered. In this study, to reveal the mechanism of the decrease in the elastic limit of quenched medium carbon steel was studied. Relaxation test and electron backscattering diffraction analysis were performed for characterization of inhomogeneous strains. The stress of 80% Young's modulus was taken as the elastic limit, and the specimen was held for 15 minutes at the stroke when the stress was reached elastic limit. The kernel average misorientation values were decreased after the relaxation test, suggesting that the relaxation test reduced the non-uniform strain in the crystal grains.