Consideration on Accelerated Heat-treating Condition for Low Temperature Sensitization in Weld Metals of Austenitic Stainless Steels

Study on Low Temperature Sensitization in Weldments of Austenitic Stainless Steels and Its Improvement by Laser Surface Melting Treatment (Report 2)

Abstract

The sensitization behavior in the weld metals of Type 308 stainless steel was theoretically studied in order to determine the heat-treating condition to simulate low temperature sensitization (LTS). The theoretical parameter ΔS was introduced to evaluate the amount of chromium depleted zone adjacent to the grain boundaries. Calculation of ΔS has shown that the value of ΔS increased at first and then decreased from a certain time, which was corresponding to the deterioration of intergranular corrosion resistance and its healing in the weld metal of stainless steels during sensitizing heat-treatment. Moreover, the value of ΔS was found to agree fairly well with the degree of sensitization measured by EPR test. On the basis of the results of calculating ΔS, the sensitizing condition to simulate the low temperature sensitization was considered. The typical sensitizing condition was determined 773K × 30 ks, which is corresponding to the condition of 573K×1.26×10⁹s.