Distortion and Residual Stress Behavior of Super-High Frequency Induction Hardened Carbon Steel Bar with Small Diameter
Daisuke SUZUKI, Koji YATSUSHIRO, Seiji SHIMIZU, Yoshio SUGITA, Motoki SAITO and Katsuhiko KUBOTA
Abstract:To reduce distortion due to quenching for small diameter round bar of carbon steel, an induction hardening instrument with a super-high frequency generator of 2MHz was developed. Quenching for specimen (6mm in diameter) was examined under various conditions of voltage and specimen transfer speed. Quenched specimen was evaluated by measuring hardness distribution, residual stress and distortion. As a result, the condition of 230V`20.6mm/s brought about the good result: the depth of hardened zone was 0.4mm and the hardness near the surface was 600HV. As for the well-quenched specimens, the maximum compressive residual stress in the longitudinal direction reached -400`-600MPa at surface, and decreased slightly from surface to center. However, at hoop direction, compressive residual stress was close to 0MPa. This anisotropy was due to large thermal stress compared with the present induction hardening and conventional one. The specimen that had deeper hardened zone had large distortion equivalent full quenching, and the specimens that had thinner hardened zone had small distortion as same as annealing or non-heat-treatment specimens. Key Words:Induction hardening, Quench, Residual stress, Distortion, Half-value breadth