Effect of prior austenitisation temperature on creep rupture in Grade 22 steel

Abstract

ABSTRACT The uniaxial tensile creep resistance at 600°C for Grade 22 bainitic steel was measured as function of prior normalisation heat treatment which was carried out in the range 900–1100°C. A decrease in creep rate is favoured by larger prior austenite grain size, but creep ductility is substantially reduced. Of particular interest is the significant difference in creep performance for the 900°C and 1000°C heat treatment conditions. Although the prior austenite grain size is only marginally different for the two conditions, the creep rupture time is substantially longer for the 1000°C condition. Dilatometry tests, which simulate the normalisation thermal cycles, indicate differences in phase dissolution during normalisation and hence it is proposed that variations in solute distribution account for the differences in creep behaviour.