Intergranular Corrosion Behavior of Low C, N-17%Cr Stainless Steel

Abstract

Intergranular corrosion at weld zone of 17% Cr steel was investigated. Commercially produced 17% Crsteel (SUS 430) contains usually about 0.06-0.08% C+N and is fairly resistant to intergranular corrosion at weld zone inactual services where the environment is not severe. On the other hand, 17% Cr steel containing 0.01-0.06% C+N, is quite susceptible to intergranular corrosion at weld zone in mild corrosion environments such as tap water. The experimental results indicate that this can be attributed to the decrease of martensite at weld zone. The martensite (austenite at high temperature) acts as the absorber of C and N, and prevents the deposition of Cr-carbide or Cr-nitride at grain boundaries on welding. Therefore, 17% Cr steel containing martensite at weld zone is more resistant to intergranular corrosion than 17% Cr steel, the structure of which is fully ferritic at weld zone. The amounts of Ti necessary to prevent intergranular corrosion at weld zone was also determined. Electrocbemical measurements gave results that agreed with the immersion test.