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Vol.46, No.12, 800 ~ 809, 2008
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| Title |
| Study on the Anisotropic Size Change by Austenitizing and Tempering Heat Treatment of STD11 Tool Steel Using Dilatometry |
| 홍기정 Ki Jung Hong , 강원국 Won Guk Kang , 송진화 Jin Hwa Song , 정인상 In Sang Chung , 이기안 Kee Ahn Lee |
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| Abstract |
| Heat treatment is an important step for tool manufacture, but unavoidably generates dimensional distortion. This study investigated the continuous dimensional change and the anisotropic behavior of STD11 tool steel during austenitizing and tempering heat treatment especially using quenching dilatometer. Dilatometric results represented that the dimensional change along longitudinal direction was larger than that along transverse direction. Anisotropic phase transformation strain was produced in forged STD11 tool steel during heat treatment. Anisotropic dimensional change increased with increasing austenitizing temperature. After tempering, anisotropic distortion was partially reduced. FactSage thermodynamic equilibrium phase simulation and microstructural observation (FE-SEM, TEM) showed that large (7~80 μm) elongated M7C3 carbides could be formed along rolling direction. The resolution of elongated carbides during austenitizing was found to be related with the change of martensite transformation temperature after heat treatment. Anisotropic size change of STD11 tool steel was mainly attributed to large elongated carbides produced during rolling process. Using dilatometric and metallographic examination, the possible mechanism of the anisotropic size change was also discussed. |
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| Key Words |
| anisotropy, STD11, tool steel, quenching dilatometer, austenitizing and tempering |
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