1978 Volume 47 Issue 3 Pages 147-153
Weld decay in SUS 304 is a well-known phenomenon. The cause is said to be M23C6 precipitated in HAZ during welding. Many investigations have been carried out concerning the precipitation behaviour of M23C6 in SUS 304. However, few investigations about one during thermal cycles have been conducted. Consequently, the precipitation behaviour of M23C6 in HAZ of SUS 304 is not yet made so clear as that during the isothermal heat treatment.
In this report, in order to make clear the precipitation behaviour of M23C6 in HAZ of SUS 304, the method called "additivity rule", predicting the phenomenon during thermal cycle from one during the isothermal heat treatment was applied and its validity was considered.
The results obtained in this report are as follows;
1) The deterioration of corrosion resistance of SUS 304 not only in weld decayed region but in the region located between that and the weld metal in HAZ is caused by the precipitation of M23C6.
2) The beginning time for the precipitation of M23C6 during thermal cycles can be calculated from the precipitation curves of M23C6 during the isothermal heat treatment by applying the "additivity rule".
3) The region where M23C6 precipitates in HAZ during welding can be also predicted by applying the "additivity rule".