TEMPERING PRECIPITATES OF STEEL 1.25Cr-0.5Mo AND THEIR EFFECTS ON ITS HYDROGEN ATTACK RESISTANCE
SU Tiejian; LUO Xinghong; FAN Cungan; LI Yiyi (Institute of Metal Research; The Chinese Academy of Sciences; Shenyang 110015)CHEN Xiao; GUO Aimin (Wuhan Iron and Steel Company; Wuhan 430080)Correspondent: SU Tiejian; Fax: 024-3891320; Tel. 024-3843531-55445)(Manuscript received 1997-04-30; in revised form 1997-07-08)
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SU Tiejian; LUO Xinghong; FAN Cungan; LI Yiyi (Institute of Metal Research; The Chinese Academy of Sciences; Shenyang 110015)CHEN Xiao; GUO Aimin (Wuhan Iron and Steel Company; Wuhan 430080)Correspondent: SU Tiejian; Fax: 024-3891320; Tel. 024-3843531-55445)(Manuscript received 1997-04-30; in revised form 1997-07-08). TEMPERING PRECIPITATES OF STEEL 1.25Cr-0.5Mo AND THEIR EFFECTS ON ITS HYDROGEN ATTACK RESISTANCE. Acta Metall Sin, 1998, 34(4): 393-399.
Abstract Studies were made on the tempering precipitates and their effects on hydrogen attack (HA) resistance of the medium-temperature HA-resistant Steel 1.25Cr-0.5Mo. It was shown by TEM of carbon extraction replicas that, with increasing tempering temperature, more carbides were precipitated and coarsened. When tempered at 520℃ and 620℃, almost only M3C was precipitated. When tempered at 670℃, M3C was the main precipitate with a small amount of M23C6. While tempered at 710℃, M23C6 was the main precipitate with a small amount of M3C. It was observed by SEM that,after charging hydrogen, samples tempered at 620℃ were seriously attacked by hydrogen, which resulted in great drop of strength and hardness.While no apparent HA phenomenon was observed for samples tempered at 520℃, 670℃ and710℃, but rupture strength of samples tempered at 520℃ was greatly decreased. It is related that large quantity of unstable M3C precipitated along grain boundaries, and the C-rich and Cr-poor regions for the sample tempered at 620℃ appeared, resulted in the HA degradation of the material.
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