열처리공학회지 (Journal of the Korean Society for Heat Treatment)
- 제21권2호
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- Pages.69-78
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- 2008
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- 1225-1070(pISSN)
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- 2508-4046(eISSN)
구상흑연주철의 열처리에 따른 미세조직 및 경도 변화
Change in Hardness and Microstructure with Quenching and Tempering of Ductile Cast Iron
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정우창
(대구가톨릭대학교 기계자동차공학부)
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Jeong, Woo Chang
(School of Mechanical and Automotive Engineering, Catholic University of Daegu)
- 투고 : 2008.02.01
- 심사 : 2008.02.28
- 발행 : 2008.03.31
초록
Differences in hardness and microstructure between surface and area at 0.3 mm below the surface after quenching and tempering of ductile cast iron for rear planet carrier of automotive transmission have been investigated. Microstructure of ductile cast iron consisted of ferrite, pearlite, and nodular graphite. The amount of pearlite increased with going down to the half-thickness area. It was found that Cr and Mo segregated to the pearlite and the pearlite transformed to the harder martensite during quenching. The martensite was more resistant to the decomposition to ferrite and cementite during tempering because of segregation of Cr and Mo, resulting in the harder tempered martensite. Consequently, the hardness of the surface with less amount of pearlite, corresponding to the harder martensite in the quenched and tempered microstructure, was lower than that of the area at 0.3 mm below the surface.