Effect of Heating Temperature on the Growth of Austenite Grain of Titanium Microalloyed Steel

The Ti microalloyed steel was heated in an electric furnace up to the temperature ranging from 850℃ to 1 250℃ and heldfor 30 min.The behavior of austenite grain growth and the solid solution of Ti were investigated by observing the microstructure of austenite grain and the distribution of precipitates.The results indicate that the tested steel has two austenite grain coarsening temperatures,i.e.,1 050℃and 1 250℃,corresponding to the solution temperature of two types of Ti precipitates,however,they are lower than the values expected from solid solution product equation.It is found that the activate energy of grain growth decreases from 265.6 kJ/mol to 239.8 kJ/mol with the dissolving of TiC precipitates by analyzing two stages of the austenite grain growth process.