Tetsuya Akiyama1 and Toshio Terasaki1
1Department of Materials, Kyushu Institute of Technology, Kitakyushu
The phenomena of the sensitization of a base metal and the method to predict the time when the degree of sensitization of the base metal exceeds a critical value were investigated by comparing the degree of sensitization of the base metal and that of the welded heat affected zone (HAZ).
To compare these sensitizations, mathematical analysis and experimental tests were carried out. The materials used in this experiment were type 304 stainless steel plates having 10 and 30% plastic strains. To determine the degree of sensitization, the EPR test was used.
From the mathematical analysis, the following results were obtained. In the case where the materials had a plastic strain of above 3%, the degree of sensitization of the base metal became larger than that of the heat affected zone.
From the experimental tests, the following results were obtained. The degree of sensitization of the base metal became larger than that of the heat affected zone. However, in the case where the hardness of the base metal became smaller to a level of the HAZ with the prolonged time for the low temperature sensitization, this phenomenon disappeared.
For the materials having 10 or 30% plastic strain, we were able to predict the time needed for the degree of sensitization of the base metal to exceed the critical value.
base metal low temperature sensitization, plastic strain, life prediction
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