Study on Microstructure Evolution of Micro-alloyed Steel During Hot Delivery and Hot Charging
Hot delivery and hot charging of a Ti micro-alloyed steel slab at different delivery temperature were simulated in laboratory.The microstructure morphologies of specimens at room temperature in different thermal histories were observed by optical microscope(OM).The law and specialty of the microstructure evolution of the specimen was also analyzed.The results show that,a demarcation line of hot charging at different temperature is about 700℃,the austenite decomposition of specimen occurs below 700 ℃,the high temperature microstructure of the specimen is austenite and the size of the austenite grain is similar above 700 ℃.The size of austenite grain above 700 ℃ is coarser than that below 700 ℃.The microstructure of thermal treatment at room temperature is very different at different hot charging temperature.The re-austenitization becomes easier as the hot charging temperature increases;the phase transformation becomes more complicated as the hot charging temperature decreases.Hot charging at 700℃ is reasonable,and hot charging at 750 ℃ can also be implemented.