沃斯田鐵系不銹鋼銲道經表面處理後殘留應力與應力腐蝕之研究

Effect of Different Surface Treatment on Residual Stress and Corrosion Behaviors of Austenitic Stainless Steel Welds

AISI 304不銹鋼為300沃斯田鐵系列之不銹鋼，經過銲接製程後所造成的高拉伸殘留應力皆會造成銲道的應力腐蝕，進而使不銹鋼抗腐蝕能力下降。本研究探討AISI 304不銹鋼經自動鎢極氣體保護銲平銲後，藉由研磨、珠擊及雷射衝擊強化等三種不同表面處理，並使用鉻靶殘留應力分析儀、電化學拋光技術及恆電位分析儀，探討表面處理對於AISI 304不銹鋼表面與次表面殘留應力分佈情形及應力腐蝕之影響。結果顯示，經過雷射衝擊強化後之銲道擁有最高壓縮殘留應力，且影響次表面殘留應力分佈亦為最深；腐蝕電流則隨著殘留壓縮應力的增加而下降。雷射衝擊強化為本研究中防止應力腐蝕最有效之方法。

In this study, it is designed to investigate the AISI 304 stainless steel after gas tungsten arc welding (GTAW) then go through in three different surface treatment to explore the relationship about the surface and sub-surface residual stress、 metallographic study and corrosion test. Three kinds of surface treatment conditions were grinding, shot peening and laser shock peening (LSP). The residual stress was measured by Cr target x-ray analyzer and corrosion test was measured by potentiostat. Result show that welding treated by LSP has largest compressive residual stress and the most deep affect zone in sub-surface, which also has the best corrosion resistance. Furthermore, we can find different surface treatment actually cause the microstructure refinement and homogeneity of microstructure distribution by Debye ring and profile analysis.