Stress relaxation behaviour of hot deformed austenite in high strength micro-alloyed pipeline steel

Abstract

The objective of the present study is to investigate the static restoration of CMn(V-Nb-Ti) pipeline steel utilising comparative study of the stress relaxation and micro-alloying precipitates behaviour. The hot compression tests in temperature range of 850°C to 1,000°C, strains of 0.04, 0.1, 0.25, 0.4 and strain rates of 0.1 and 0.5 s−1 have been carried out and the hot flow stress of austenite has been evaluated by stress relaxation technique at annealing time intervals of 0.05 to 1000 s. The results indicate that at the specific deformation temperature of 850°C, the strain induced precipitation starts with the beginning of annealing time which retards recrystallisation. At higher temperatures than 900°C and strains more than 0.25 and 0.4, first recrystallisation occurs and then the plateau appears. The electron backscattering diffraction (EBSD) image also confirms the partial recrystallisation in a sample quenched at the end of the plateau.