Abstract: The effects of the direct rolling of cast billet， large pass deformation and intermediate billet heating on microstructure evolution of austenite in low-carbon steel were studied in direct rolling experiment of wedge-shaped cast billet and hot rolling experiment of large pass deformation with intermediate billet heating， and were also compared with austenite evolution in the conventional hot rolling process. The results show that grain size of the austenite decreases gradually with increasing the reduction rate. Compared with the reheating rolling process， the austenite grains after the direct rolling process are coarser in the reduction rate of 48%， 53.6% and 66.7%， while the deformed microstructure becomes finer and more homogeneous when the reduction rate is 72.3%. In comparison with the conventional hot rolling process， the large pass deformation promotes austenite recrystallization in the rough rolling stage， while the intermediate billet heating process improves the uniformity of grain size in the austenite.

Key words: endless strip production (ESP) process; cast billet; austenite; deformation amount; intermediate billet heating