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| STUDY ON SECONDARY HARDENING MECHANISM OF Cr8Mo2SiV STEEL |
| CHI Hongxiao 1,2, MA Dangshen 2, WANG Chang 2, CHEN Zhaizhi 2, YONG Qilong 1,2 |
1. Faculty of Materials Science and Engineering, Kunming University of Science and Technology, Kunming 650093
2. Institute for Structural Materials, Central Iron and Steel Research Institute, Beijing 100081 |
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Cite this article:
CHI Hongxiao MA Dangshen WANG Chang CHEN Zhaizhi YONG Qilong. STUDY ON SECONDARY HARDENING MECHANISM OF Cr8Mo2SiV STEEL. Acta Metall Sin, 2010, 46(10): 1181-1185.
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Abstract Cr8–type cold work die steels, such as Cr8Mo2SiV steel have been widely used in recent years due to high strength and high toughness, These steels have obvious secondary hardening effect. It has been widely reported that the secondary hardening mechanism of these die steels resulted from the combination of retained austenite and carbide precipitation. However, less attention has been paid on the secondary hardening of Cr8Mo2SiV steel. In order to investigate the secondary hardening mechanism of Cr8Mo2SiV steel, the hardness, retained austenite and precipitation of Cr8Mo2SiV steel were investigated in this paper by SEM, EDS, TEM and XRD analysis. Experimental results indicate that the secondary hardening peak of Cr8Mo2SiV steel which was quenched at 1030 ℃ appears at 520 ℃. Deep cryogenic treatment observably reduces the content of retained austenite, and thus increases the tempering hardness before secondary hardening peak and the secondary hardening peak shifted to low temperature by about 20 ℃. The tempered hardness of Cr8Mo2SiV steel decreased linearly wth the increase of soaking time when tempering at 520 ℃. The secondary hardening mechanism of Cr8Mo2SiV steel is the combination of the transformation of retained austenite and the earlstage of Mo2C precipitation, and the role of transformation of retained austenite is more obvious. The early tage of Mo2C–carbide precipitation is likely to be G.P. zone which ormed y [Mo–C] segregation group. As the tempering time extended, Mo2C precipitated, and it ws dispersive and uniformly distributed.
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Received: 13 July 2010
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| Fund: Supported by National Key Technologies R&D Program of China (No.2007BAE510B04) |
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