Effect of Post-weld Heat Treatment on CTOD Properties of Welded Joint of S420ML High Strength Steel
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摘要: 采用断裂韧性测试和宏观断口分析等方法，研究了焊后热处理对高强钢S420ML焊接接头焊缝、粗晶区、回火区和部分相变区分界线的断裂韧性CTOD的影响。结果表明， 80 mm厚S420ML焊接钢板，无论是否经过焊后热处理，其断裂韧性CTOD性能均能满足相关标准要求，同时580℃×4 h焊后热处理能够显著提升断裂韧性CTOD特征值；特征值为δm的试样，裂纹扩展面以纤维区为主，特征值为δu的试样，裂纹扩展面初始阶段包含部分脆断区，随后由于载荷释放，裂纹扩展停止，材料及时止裂。在后续加载时重新获得裂纹扩展抗力，断口的剩余部分仍呈现纤维断裂的特征。Abstract: Fracture toughness test and scanning electron microscopy(SEM) were adopted to investigate the effects of post-weld heat treatment(PWHT) on the joint weld, coarsened grain zone, and CTOD properties of line between subcritical HAZ and intercritical HAZ of welded joint of S420 ML high-strength steel for offshore engineering.Resultsshowed that the CTOD properties of 80 mm thick S420 ML welded steel plate could satisfy the requirements of relevant standards whether the plate went through post-weld heat treatment or not, and that the CTOD properties of welded plates were significantly improved after PWHT at 580℃ for 4 hours. The crack propagation surface of specimen with characteristic value of δm were mainly characterized by fiber zone, and for the specimen with characteristic value of δu, the initial stage of the crack propagation surface had some brittle fracture regions, then due to the release of load, the crack propagation stopped, and the cracking stopped in time. The crack propagation resistance was regained during subsequent loading, so that the remaining part of the fracture still presented the characteristic of fiber fracture.
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Keywords:
- high-strength steel /
- CTOD /
- post-weld heat treatment /
- macrofractography
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