Change of X-Ray Elastic Constants of Carbon Steel Caused by Quenching and Effect of Its Change on X-Ray Stress Measurement
Yoshihisa SAKAIDA and Kosuke TANAKA
Abstract:X-ray elastic constants, EX and ƒËX, were measured before and after quenching using three kinds of carbon steel, S45C, S48C and S55C, defined by the Japanese industrial standard. The microstructures, mechanical elastic constants and hardness of these materials were also measured. Change of X-ray elastic constants caused by quenching corresponded to the microstructure change due to martensitic transformation, and depended on the mechanical elastic constant change. Amount of change in X-ray Young's modulus after quenching was different by the used material. The ratio of X-ray to mechanical Young's modulus, EX/EM, after quenching lowered in comparison with that before quenching, regardless of carbon content. Finally, using the measured X-ray elastic constants before and after quenching, compressive residual stresses on the hardened layer of S48C gear induced by induction hardening were measured by X-ray stress measurement. As a result, X-ray Young's modulus, EX, and stress constant, K, of S48C after quenching showed about 22% and 18% lowering to that before quenching, respectively. And then, the maximum deviation of compressive residual stress was about 86MPa in comparison with the result ignored considerations of microstructure change. It is concluded that estimation of stress constant considering microstructure change by quenching are necessary when the residual stresses of quenched carbon steel are measured by X-ray stress measurement. Key Words:X-ray stress measurement, Carbon steel, Quenching, X-ray elastic constant, Stress constant, Residual stress