目的 研究熔化极活性气体保护电弧（MAG）焊的保护气体成分对SUS304焊接接头耐晶间腐蚀性能及耐电化学点蚀性能的影响。方法 通过不锈钢硫酸-硫酸铁晶间腐蚀试验方法（GB/T 4334.2—2000）、不锈钢点蚀电位测量方法（GB/T 17899—1999），对97%Ar+3%O2和95%Ar+5%CO2两种保护气体下的SUS304 MAG焊接接头的耐腐蚀性能进行了研究。结果 97%Ar+3%O2保护气体下的SUS304 MAG焊试件焊缝处的平均腐蚀率为2.78 g/(m2?h)；95%Ar+5%CO2保护气体下的试件焊缝处的平均腐蚀率为2.50 g/(m2?h)。由SEM扫描结果可知，在焊接热影响区，敏化区以保护气体为95%Ar+5%CO2的试样晶界腐蚀更严重，而非敏化区（焊缝与敏化区之间）和焊缝区以保护气体为97%Ar+3%O2的试样腐蚀较严重。采用97%Ar+3%O2保护气体的MAG焊试样热影响区和焊缝的E?b100分别为0.208 V和0.144 V；采用95%Ar+5%CO2保护气体的试样热影响区和焊缝的E?b100分别为0.199 V和0.155 V。保护气体为95%Ar+5%CO2的MAG焊焊缝试样的耐点蚀能力略好，保护气体为97%Ar+3%O2的热影响区试样的耐点蚀能力略好。结论 两种保护气体下MAG焊的接头的耐点蚀性能相差不大，95%Ar+5%CO2保护气体下MAG焊的接头的耐腐蚀性更好。

The work aims to study the effects of shield gas composition for MAG welding on intergranular corrosion resistance and electrochemical pitting resistance of SUS304 welding joints. Corrosion resistance of SUS304 MAG welding joints was studied in 97%Ar+3%O2 and 95%Ar+5%CO2 welding gases were investigated in the method of sulfuric acid-ferric sulfate intergranular corrosion test for stainless steel (GB/T 4334.2—2000) and the method of pitting potential measurement for stainless steel (GB/T 17899—1999). Mean corrosion rate of welding seams on SUS304MAG welding test-piece in 97%Ar+3%O2 wielding gases was 2.78 g/(m2?h) while that in 95%Ar+5%CO2 was 2.50 g/(m2?h). After SEM scanning, MAG welding test-piece in sensitization zone in HAZ (heat affected zone) of 95%Ar+5%CO2 welding gases sustained worse grain boundary corrosion. However, the test-piece in un-sensitization zone in HAZ (between sensitization zone and seam) and weld zone of 97%Ar+3%O2 welding gases was corroded more seriously. E‘b100 pitting potential in welded HAZ and seam of 97%Ar+3%O2 welding gases was 0.208 V and 0.144 V, respectively; and that in welded HAZ and seam of 95%Ar+5%CO2 welding gases was 0.199 V and 0.155 V, respectively. The MAG welding seam test-piece in HAZ of 97%Ar+3%O2 welding gases exhibited better pitting corrosion resistance. The results shows that: in two different wielding gases, MAG welding joints show similar pitting resistance, and MAG welding joints in 95%Ar+5%CO2 wielding gases exhibit better corrosion resistance.