In order to prevent weld decay in SUS 304, several metheods have been recommended, namely, (1) to use extra low C steel, (2) to use stabilized steels containing Nb or Ti, (3) to limit the heat input in welding, (4) to post heat-treat to dissolve M
23C
6, and so on.
However, there have been few systematic investigations to determine the optimum condition in these methods, especially concerning (1) and (3). Consequently, only rough standards are given for the prevention methods even in present day.
In the previous report, authors have elucidated that the precipitation of M
23C
6 in HAZ of SUS 304 which causes weld decay can be predicted by applying the "additivity rule" which is translating rule from isothermal process to thermal cycle one.
In this report, this rule was applied to the intergranular corrosion in HAZ of SUS 304. Based on these results, it was quantitatively considered to elucidate the optimum condition concerning prevention method (1) and (3) for weld decay.
Experimental results obtained in this report are as follows;
1) The beginning time for intergranular corrosion occurred during thermal cycles can be calculated from TTS diagram by applying the "additivity rule."
2) The region where intergranular corrosion occurs in HAZ of SUS 304 during welding can be also predicted by applying the "additivity rule."
3) Based on these results, it was made clear that the limit of welding heat input and C content required to prevent weld decay can be predicted by calculation.
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