Modeling of criteria on prevention of sensitization by delta-ferrite in austenitic stainless steel weld metal: Modeling of sensitization in austenitic stainless steel weld metal

The prevention of sensitization by delta-ferrite in austenitic stainless steel weld metal was investigated from a point of view of the required fraction of delta-ferrite to prevent in weld metal containing not low carbon. Intergranular corrosion test in copper-copper sulfate solution was conducted using the 20%Cr-11/14%Ni-0.045/0.075%C weld metal after sensitizing treatment at 650°C for 3h. The intergranular corrosion was prevented in the weld metal containing sufficiently high fraction of delta ferrite even in case of high carbon content such as 0.06%. A physical model was suggested to determine the delta-ferrite necessary for each carbon content in weld metal. This model was founded on the concept that sufficient fraction of delta ferrite exhausts those carbon atoms in austenitic phase due to consumption by rapid growth of chromium carbide in delta ferrite. It was confirmed the required fraction of delta ferrite to prevent the sensitization in each carbon content agrees with that of experimental results.