Influence of precipitation behavior on mechanical properties and hydrogen induced cracking during tempering of hot-rolled API steel for tubing

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• 作者：Joonoh Moon^a ; ^{mjo99@kims.re.kr" class="auth_mail" title="E-mail the corresponding author} ; Jongmin Choi^b ; Seong-Kyung Han^b ; Sungyul Huh^b ; Seong-Ju Kim^b ; Chang-Hoon Lee^a ; Tae-Ho Lee^a
• 关键词：Precipitation ; Hydrogen Induced Cracking (HIC) ; Tempered martensite
• 刊名：Materials Science & Engineering A
• 出版年：2016
• 出版时间：15 January 2016
• 年：2016
• 卷：652
• 期：Complete
• 页码：120-126
• 全文大小：4188 K

文摘

Precipitation behavior and its effect on hydrogen embrittlement during tempering process of hot-rolled API steel designed with 0.4 wt% Cr and 0.25 wt% Mo were investigated. The base steel was normalized and then tempered at 650 °C for up to 60 min. The precipitation behavior of the examined steel was explored using transmission electron microscopy (TEM) analysis, and it was found that the precipitation sequence during tempering at 650 °C were as follows: MX+M₃C→MX→MX+M₇C₃+M₂₃C₆. The change of particle fraction was measured by electrolytic extraction technique. At the early stage of tempering, the particle fraction greatly decreased due to dissolution of M₃C particle, and increased after 10 min by the precipitation of M₇C₃ and M₂₃C₆ particles. The particle fraction showed a peak at 30 min tempering and decreased again due to the dissolution of M₇C₃ particle. Vickers hardness tests of base steel and tempered samples were carried out, and then the hardness was changed by accompanying with the change of particle fraction. The sensitivity of hydrogen embrittlement was evaluated through hydrogen induced cracking (HIC) tests, and the results clearly proved that HIC resistance of tempered samples was better than that of base steel due to the formation of tempered martensite, and then the HIC resistance changed depending on the precipitation behavior during tempering, i.e., the precipitation of coarse M₂₃C₆ and M₇C₃ particles deteriorated the HIC resistance.