400℃时效对304不锈钢晶间敏化行为的影响

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The 400 ℃ aged 304 stainless steels were characterized for their degree of sensitization （DOS） by double - loop （DL） electrochemical potentiokinetic reactivation （EPR） method. Then the chromium depletion zones of these tested specimens were observed by metallographic microscope. The results showed that the degree of sensitization of solution 304 after solution treatment did not increase under 400℃- 10 h aging, while the degree of sensitization of 650 ℃ sensitized 304 increased obviously under the same 400 ℃ x 10 h aging. Thus solution treatment is very important for 304 stainless steel. Hot working process should be controlled strictly to prevent increasing of DOS and occurring of intergranular corrosion, espe- cially for those which have not carried on solution treatment.采用双环电化学动电位再活化法（EPR）对400℃时效处理后的304不锈钢试样进行晶间腐蚀试验，并采用金相法观察试验后试样贫铬区的形态特征。研究结果表明，固溶态304不锈钢在400℃时效10h条件下，敏化度未见增大，晶间腐蚀敏感性并未加大；650℃敏化后304不锈钢在400℃时效10h条件下，随着时效时间的延长，敏化度则显著增大，晶间腐蚀敏感性也随之加大。敏化态304不锈钢即使在低温条件下，其晶间腐蚀敏感性也会随着时效时间的延长而逐步增大，因此，304不锈钢的固溶处理是十分重要的，对于未经固溶处理的304不锈钢需要严格控制热加工工艺参数，杜绝敏化度的进一步增大，以避免腐蚀事故的发生。