Study on Behaviour of Carbides and Knife Line Attack Phenomenon in Stabilized Austenitic Stainless Steels (Report V)

Dissolution Phenomenon of Carbides During Weld Thermal Cycle

Abstract

In the previous report, theoretical considreation was carried out in regard to the dissolution phenomenon of Nb(C, N) in SUS 347 under the isothermal heat treatment, and it was made clear that good agreement was obtained between experimental results and theoretical values.
In this report, the thoretical equation on the dissolution phenomenon during the thermal cycles was derived. By comparing experimental results with theoretical values, this theoretical equation was discussed.
The dissolution phenomenon of TiC in HAZ of SUS 321 was also considered experimentally.
The results obtained in this report are as follows;
(1) Good agreement between experimental results and theoretical values was found in the dissolution phenomenon of Nb(C, N) in SUS 347 under heating, and heating and cooling thermal cycles.
(2) The theoretical equation under the thermal cycles was applicable to the dissolution phenomenon of Nb(C, N) in HAZ of SUS 347.
(3) Over about 50% of Nb(C, N) in stabilized SUS 347 had dissolved in the knife line attacked region of HAZ during welding.
(4) Over about 55% of TiC in stabilized SUS 321 had also dissolved in the knife line attacked region of HAZ during welding.