Korean Journal of Metals and Materials (대한금속재료학회지)

The Korean Institute of Metals and Materials (대한금속재료학회)
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Characterization and Transformation of 0.52%C steels for Wheel Bearing Units Produced by High Frequency Induction Hardening after Hot Forging

열간단조 후 고주파 유도경화에 의해 제조된 휠 베어링 유니트용 0.52%C강의 특성과 변태거동

  • Choi, Byung-Young (School of Advanced Materials Engineering and Research Institute of Advanced Materials Development, Chonbuk National University)
  • 최병영 (전북대학교 신소재공학부, 신소재개발연구소)
  • Received : 2010.09.27
  • Published : 2010.12.25
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Abstract

We fabricated flanged outer races for wheel bearing units using 0.52%C clean steels, and then characterized and studied the transformation behavior. The outer races produced by hot forging and high frequency induction hardening in this study were analyzed through microstructural characterization using OM, SEM, TEM, and X-ray diffractometer and their microhardness depth profiles of the raceway contacted by balls were measured using MVH tester. The surface hardened layers with a uniform hardness profile in the raceway consisting of very fine martensite with sub-micron sized retained austenite could be formed for very short time during high frequency induction hardening after hot forging. The very fine martensite may be transformed on rapid cooling, from the inhomogeneous austenite nucleated on rapid heating in small particles of pearlitic cementite fragmentated by hot forging. On the other hand the sub-micron sized retained austenite may be chemically stabilized due to their extremely small size, from the small austenite nucleated at the grain boundaries.

Keywords

Acknowledgement

Supported by : 통상산업부

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