超级马氏体不锈钢焊丝MAG焊熔敷金属冲击性能优化

白鹤滩百万千瓦水电机组全部采用国产HS13/5L焊丝进行焊接，成功实现了中国高端装备制造的重大突破. HS13/5L焊丝为水轮机转轮同材质焊接材料，属于13Cr型超级马氏体不锈钢，然而其MAG焊熔敷金属的韧性低于母材，针对此问题，将现有的MAG平焊焊接工艺调整为立向上焊焊接工艺，以提高熔敷金属的冲击韧性.对比分析了平焊、立向上焊熔敷金属的微观组织和冲击性能. 结果表明，立向上焊位置回火热处理态熔敷金属的室温冲击吸收能量达到120 J以上，比平焊位置提高了约40%. 两种焊接位置下的熔敷金属微观组织的相组成无明显差异，焊态组织为淬火马氏体 + 残余奥氏体 + δ-Fe，回火热处理态组织为回火板条马氏体 + 逆变奥氏体 + δ-Fe.立向上焊熔敷金属中的氧化夹杂物密度比平焊位置降低了约22%.平焊和立向上焊熔敷金属冲击断口整体呈现出韧性断裂的特征，立向上焊位置熔敷金属的韧性优于平焊位置.

Impact performance optimization of supermartensitic stainless steel welding wire deposited metal by MAG welding

Baihetan 1 000 MW hydro unit is all welded with domestic HS13/5L welding wire, which has successfully achieved a major breakthrough in China's high-end equipment manufacturing. HS13/5L welding wire is the welding material identical with the hydraulic turbine runner, belonging to 13Cr supermartensitic stainless steel. However, the toughness of the deposited metal in metal active gas arc (MAG) welding is lower than that of the base metal. In view of this problem, the welding process is adjusted from flat to vertical-up welding position, to improve the impact toughness of MAG welding deposited metal. And the microstructure and impact properties of the deposited metal are compared and analyzed. The results show that the room temperature impact absorption energy of the as-tempered deposited metal in the vertical-up welding position reaches more than 120 J, which is about 40% higher than the flat welding position. There is no obvious difference in the phase composition of the deposited metal microstructure between the two welding positions, the as-welded microstructure is composed of quenched martensite, retained austenite and delta ferrite and the as-tempered microstructure is tempered lath martensite, reversed austenite and delta ferrite. The density of oxide inclusions in the vertical-up welding deposited metal is about 22% lower than the flat welding position. The impact fracture of the deposited metal shows the characteristics of ductile fracture for both welding composition as a whole, and the toughness of the deposited metal in the vertical-up welding position is better than that in the flat welding position.