Effect of austenisation temperature on phase transformation in low carbon microalloyed pipeline steel

A detailed investigation was carried out on the effect of austenisation temperature on the phase transformation in X65 microalloyed pipeline steel during continuous cooling at a rate of 200 degrees C min(-1) by means of high resolution dilatometric measurement and microstructure observation. The results showed that with austenisation temperature increasing in the range of 850-1000 degrees C, phase transformation temperature range shifts to lower temperatures and the formation of acicular ferrite phase is promoted. Furthermore, the increase in austenisation temperature results in refined grains after continuous cooling to room temperature, associating with the appearance of acicular ferrite structure in steel. The present investigation is helpful to optimise the parameters of rolling or heat treatment technology in industrial production of X65 steel.