采用脉冲超窄间隙焊（UNGW）工艺对20 mm厚1Cr18Ni9Ti不锈钢板进行焊接，研究了该脉冲UNGW接头的显微组织、力学性能及耐腐蚀性能。结果表明：脉冲UNGW接头打底焊缝区的组织为奥氏体等轴晶+板条状δ铁素体，填充和盖面焊缝组织为奥氏体柱状晶+板条状和网状δ铁素体；部分熔合区组织为奥氏体+蠕虫状δ铁素体，而不完全混合区组织为奥氏体+δ铁素体，且其组织形态较为杂乱；热影响区组织为奥氏体+条带状δ铁素体。脉冲UNGW接头的塑性和韧性优于直流UNGW接头的，但强度低于直流UNGW接头的。脉冲UNGW接头熔合区+热影响区、焊缝区、完整接头及母材在NaCl溶液中的耐腐蚀性能依次增强；脉冲UNGW接头在硝酸溶液中的耐晶间腐蚀性能比未敏化处理母材的与直流UNGW接头的差，但明显优于敏化处理母材的。

The pulsed ultra-narrow-gap welding (UNGW) was applied to 1Cr18Ni9Ti austenitic stainless steel plate with 20 mm thickness. The microstructure, mechanical properties and corrosion resistance of the pulsed UNGW joint were analyzed. The results show that the microstructures of backing weld zone in pulsed UNGW joint were austenitic equiaxed grain+lath δ-ferrite; the microstructures of filling bead and cover pass weld zone were columnar austenite+lath and cellular δ-ferrite. The microstructures of partially melted zone were austenite + vermicular δ-ferrite; the microstructures of imperfect mixing zone were austenite+δ-ferrite, and their shape was disorderly. The microstructures of heat affected zone were austenite+striped δ-ferrite. The ductility and toughness of the pulsed UNGW joint were better than those of the direct-current UNGW joint, but the strength was lower than that of the direct-current UNGW joint. The corrosion resistance of fusion zone+heat affected zone, weld zone, whole joint and base metal of the pulsed UNGW joint increased in turn in NaCl solution. The intergranular corrosion resistance of the pulsed UNGW joint in nitric acid solution was worse than that of the base metal without sensitizing and the direct-current UNGW joint, but was better than that of the sensitized base metal.