The hot ductility of 150 mm x 150 mm casting billet of 10B15 cold heading steel (% : 0. 17C
0. 16Si
0. 46Mn
0. 017P
0. 025S
0.000 2Ti
0.000 8A1
0.001 4B) with strain rate 0.000 5 -0. 001 s
-1
at 700 1 000 ℃ has been studied by using Gleeble-1500 thermal simulator. Results show that the casting billet of 10B15 cold heading steel has hot brittleness at 850 ~ 900 °C ; the dynamic recrystallization is promoted by decreasing strain rate led to increase of hot ductility ; the nitrides of B
Ti and Al precipitate at grain boundary to take pin pinning effect on grain boundary to hinder slide of boundary and occurrence of dynamic recrystallization led to decrease of the hot ductility of steel.