文献类型：期刊文献

英文题名：Cracks and precipitate phases in 321 stainless steel weld of flue gas pipe

作者：Guan, K.S.[1]; Xu, X.D.[2]; Zhang, Y.Y.[2]; Wang, Z.W.[1]

机构：[1]E China Univ Sci & Technol, Res Inst Proc Equipment, Shanghai 200237, Peoples R China;[2]China Petrochem Corp, Jinan Branch, Jinan 250061, Peoples R China

年份：2005

卷号：12

期号：4

起止页码：623

外文期刊名：ENGINEERING FAILURE ANALYSIS

收录：;EI(收录号：2005199086629);WOS:【SCI-EXPANDED(收录号:WOS:000229818000012)】；

语种：英文

外文关键词：austenite stainless steels; precipitates; sigma-phase; cracks; welds

摘要：The present work studies the AISI304 weld cracking mechanism of AISI321 austenite stainless steel of flue gas pipe, which served up to 60,000 h at 650-700 degrees C. The performance and microstructure of failed material were characterized by impact test, optical microscopy, scanning electron microscopy (SEM) equipped with energy dispersive spectroscopy (EDS), X-ray diffraction (XRD). The results show that cracks ware caused by embrittlement of weld metal and thermal stress. Needle like a-phase precipitation during service is primarily responsible for significant degradation in mechanical properties and microstructures of weld metal. Needle type a-phase is a severe stress-raiser and plays a role as crack initiator at the interface with matrix. In addition, maximum equivalent stress is about 175 MPa in the elbow which is near to the yield stress of the steel. It is highly possible that a crack will be initiated under above stress condition and will propagate faster along embrittled sigma-phase. Several approaches should be employed to control sigma-phase precipitation in weld. These approaches include: decreasing content of ferrite and M23C6 carbide in weld and selecting Nb added weld wire during welding. (c) 2004 Published by Elsevier Ltd.