Abstract
Creep-rupture tests up to about 10, 000h., were carried out with the type 321 stainless steel in the two solution-treated conditions (1050°C W. Q. and 1200°C W. Q.) at 600, 650 and 700 .
Stresses and rupture times showed good straight-line relationship up to about 1000h., but beyond that point the line inclined downward. This tendency was more pronominent for 1050°C W. Q. specimens. Solution-treatment at 1200°C gave higher rupture strengths for the whole testing conditions. The difference of rupture strength between these two heat treatments was increased with higher temperature and longer time.
The shapes of creep curves showed marked difference too. 1200°C W. Q. specimens were fractured suddenly without any large creep. On the contrary, 1050°C W. Q. specimens revealed relatively large creep from the early stage and fractured after large elongation.
Microstructure of 1050°C W. Q. specimens fractured at about 2500h. or longer showed the prominent precipitation of σ-phase at grain boundries.
