分别采用镍-铬-钼系和镍-钼系焊丝,在相同热输入条件下对一种新型超高强度钢进行了熔化极活性气体保护电弧焊(MAG焊),对比研究了两种接头的显微组织及力学性能;通过斜Y型坡口焊接裂纹试验评定了两种焊丝焊接接头的抗裂倾向.结果表明:镍-铬-钼系焊丝焊接接头焊缝组织主要为粗大的板条马氏体和少量贝氏体,镍-钼系焊丝焊接接头焊缝组织为细小的针状铁素体及少量的块状先共析铁素体;两种焊丝MAG焊都可以实现此钢的高强度连接,且镍-钼系焊丝焊接接头的韧性明显优于镍-铬-钼系焊丝焊接的,但焊接接头都在回火区出现了软化现象;镍-钼系焊丝焊接接头的抗开裂性能优于镍-铬-钼系焊丝的,两种焊丝斜Y型坡口焊接试样的冷裂纹断裂模式均以沿晶断裂为主,穿晶断裂为辅.
A new ultral-high strength steel was welded by metal active gas (MAG) welding with Ni-Cr-Mo and Ni-Mo welding wires, respectively, under the same heat input.The microstructures and mechanical properties of the two welded joints were compared and studied.The anti-crack sensitivity of two joints welded with the two welding wires was assessed by the Y-groove cracking test.The results show that weld microstructure of the welded joint with Ni-Cr-Mo welding wire mainly consisted of coarse lath martensite and small amount of bainite, while that with Ni-Mo welding wire as composed of fine acicular ferrite and small amount of block proeutectoid ferrite.The high strength joint of the steel can been obtain by the MAG welding with the two welding wires.But the toughness of the welded joint with Ni-Mo welding wire was better than that with Ni-Cr-Mo welding wire and the softening phenomenon in tempering zone was observed in both welded joints.The crack resistance of the welded joint with Ni-Mo welding wire was better than that with Ni-Cr-Mo welding wire, and the cold crack fracture patterns of Y-groove welded samples with the two welding wires were mainly intergranular fracture and little transgranular fracture.
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