焊后热处理对12Cr1MoV钢焊缝组织和性能影响

Effect of Postweld Heat Treatment on Microstructure and Property of Weld Seam of 12Cr1MoV Steel

采用D856-10焊条对12Cr1MoV钢进行焊接,通过金相观察、冲击试验和扫描电镜分析,研究了焊后直接空冷及焊后不同回火保温时间对12Cr1MoV钢焊缝显微组织、冲击韧性和断口形貌的影响。结果表明:焊后空冷条件下,焊缝主要为粗大的片状马氏体,脆性较高,缺口冲击韧性最低,为18 J,断面出现大面积的扩展区,且呈放射花样,断口韧窝较浅,表现为典型的解理断裂。焊后随着回火保温时间的延长,焊缝逐渐转变为细小的板条状回火马氏体及粒状回火索氏体,焊缝缺口冲击韧性明显改善,同时焊缝断面出现部分纤维区和剪切唇。当焊后热处理条件为750℃×6 h时,焊缝主要为分布均匀的粒状回火索氏体,韧性较高,为45 J,断面的断裂韧窝数量较多,表现为准解理断裂。

Taking D856-10 welding rod to weld 12Cr1MoV steel, the effects of air cooling and preservation time of post-weld heat treatment（PWHT） on the microstructure, impact toughness and fracture morphology of welding seam of12Cr1MoV steel were investigated by optical microscopy（OM）, impact test and SEM. The results show that under the condition of air cooling after welding, the weld seam is mainly thick plate martensite, the brittleness is higher and notched impact toughness is the lowest（18J）. The cross section generates large extension area, which is in radiation pattern, and the dimple fractures are shallower, which show the typical cleavage fracture. With the extension of tempering time of heat preservation after welding, the welding seam transforms into a small plate strips of tempered martensite and granular tempered sorbite gradually, and the notched impact toughness improves obviously. There are part of fiber zone and shear lips in welding seam cross section. When heat treatment after welding conditions reach 750 ℃ ×6 h, the welding seam is mainly uniform distribution of granular tempered sorbite, the toughness is high（ 45 J）, and there are a large number of fracture toughness nest section, showing cleavage fracture.