Austenite Grain Growth Behavior in Nb-Ti Microalloyed Steel

Nb and Ti are the most common microalloying elements in pipeline steel.The effects of the microalloying elements Nb and Ti in Nb-Ti microalloyed steel and the reheating schedule on the austenite grain growth were investigated using heat treatment and vacuum carburizing treatment.The results show that during reheating process,the austenite grain size in tested steel increases with an increase in the reheating temperature.In normal niobium-containing steel,titanium content should be controlled in a certain range(approximately 0.010%-0.015%),to obtain small reheated austenite grain.Moreover,with the same titanium content,the austenite grain of the steel with high niobium content grows obviously,and the steel with high niobium content has a different optimum titanium content range from that of the steel with normal titanium content.