To study the effect of ausforming on hardenability in steel 09MnNb used for L485QS sour service pipeline

different ausforming processes were performed and the subsequent hardenabilitis and microstructures were tested. It revels that three types of microstructures could be gained when ausforming at temperature from 850°C to 1 100 °C and under deformation degree e from 0.2 to 0. 8. In the transformation of microstructures

it was a leading role of the deformatiorm temperature that acicular ferrite

thin-strip bainite and thick-lath bainite were mainly obtained respectively when the temperatures at 900°C . and below

from 950 °C to 1000 °C and at 1050 °C or higher. Increasing deformation degrees could promote transformation of acicular ferrite in unrecrystallization zone and thin-strip bainite in partial recrystallization respectively

but in fully recrystallization zone make the lath bainite either coarsed or refined. When ausforming used of steel 09MnNb at temperatures from 950 °C to 1000°C and under deformation degree of ε ≥0.4 or above

the microstructure consisted fully of thin-strip bainite could be obtained so as a higher and more stable hardenabilities could be achieved

which may be beneficial to the properties control when tempered in following.