【摘 要】
：
In multi-pass welding process,various thermal cycle of both weld metal(WM)and heat affected zone(HAZ)will be subjected several times.This will make the initial microstructure occur an irreversible tra
【机 构】
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School of Material Science and Engineering,University of Science and Technology Beijing,Beijing,1000
论文部分内容阅读
In multi-pass welding process,various thermal cycle of both weld metal(WM)and heat affected zone(HAZ)will be subjected several times.This will make the initial microstructure occur an irreversible transformation.As the transformed microstructure become extremely complex,the mechanical properties,especially the low temperature toughness are very much fluctuant.In this research,the microstructure and low temperature toughness of WM obtained from a real multi-pass weld joint(up to 55 mm)by submerged arc welding have been elaborated.The results indicated that the necklace-type coarse martensite-austenite(M-A)constituent formed in interlayer heat affected zone(IHAZ)of WM and the impact energy of WM at-40℃was only 39 J.Furthermore,by conventional tempering with holding time of 30 min,the toughness of WM cant be effectively improved.However,by a new developed heat treatment process,the toughness of WM could be significantly improved,and it is believed to be caused by the composition of weld metal and the post-welding heat treatment process.It also shows that the decomposition of M-A constituent and formation of the retained austenite are the mechanism of the improvement of low temperature toughness.
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