Research and Development > JFE TECHNICAL REPORT > No.15 Special Issue on “Steel Bar and Wire Rod” > Examination of Surface Hardening Process for Dual Phase Steel and Improvement of Gear Properties

No.15 Special Issue on “Steel Bar and Wire Rod”

Examination of Surface Hardening Process for Dual Phase Steel and Improvement of Gear Properties

FUKUOKA Kazuaki      TOMITA Kunikazu      SHIRAGA Tetsuo

Abstract

The dual phase steel was developed for improvement of fatigue strength and decrease in heat treatment distortion. The chemical compositions, formation of microstructure, carburizing properties, and influence of ferrite area fraction on heat-treatment distortion was discussed. Additionally, improvement of fatigue strength with optimizing of surface hardening process was examined. As a result, pitting fatigue strength was improved by 29% compared with conventional one. The breakdown is; change in steel 9%, change in heat treatment condition (vacuum atmosphere and nitrogen added) 12%, and addition of double shot peening 7%.

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