Optimization of Spheroidizing Annealing Conditions in SM45C Steel

SM45C강의 구상화 어닐링조건 최적화 연구

  • Jeong, Woo Chang (School of Mechanical and Automotive Engineering, Catholic University of Daegu)
  • 정우창 (대구가톨릭대학교 기계자동차공학부)
  • Received : 2006.04.26
  • Accepted : 2006.05.18
  • Published : 2006.05.30

Abstract

The effects of eight types of spheroidizing annealing conditions including annealing temperature, annealing time, cooling rate, and gas atmosphere in the annealing furnace on the microstructure were determined in SM45C steel which has been widely used for automotive parts. The well-developed spheroidized structure and minimum hardness were obtained when the steel was heat-treated 6 hours at $740^{\circ}C$, cooled to $710^{\circ}C$ at a cooling rate of $24^{\circ}C/h$, and then kept for 7 hours at the $710^{\circ}C$ followed by air cooling. In order to increase the productivity and to save the manufacturing cost, it is desirable to apply a faster cooling rate in the spheroidizing annealing. It was found that air cooling was the fastest cooling rate applicable to the SM45C steel. The steel heat treated in air showed the decarburized layer of about $110{\mu}m$ in thickness at the surface of the specimen, resulting in serious problems in the quality of the quenched product.

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