The Effect Of Heat Treatment On Grain Size Heredity Of 30CrMoTi Steel

30CrMoTi steel is a low-alloy high-strength bolt steel,which widely used in construction,light industry,automotive and other fields.As a martensitic steel,the phenomenon of structural heredity is liable to occur in the heat treatment process,which will result in the decrease of toughness.In this paper,30CrMoTi steel was subjected to austenitizing treatment at different temperatures to determine the regularity of the grain growth of the steel.The effects of different deformation temperature,deformation degree and secondary quenching rate on the grain refinement and the change of microstructure of 30 CrMoTi steel was studied.The results show that the austenite grains grow rapidly after the heating temperature higher than 1150°C.With the increase of austenitizing temperature,the size of the lath martensite increase,and the directionality decrease simultaneously.After thermal deformation,the grain size become smaller.When the deformation degree at50%,the samples with original coarse grain can occur dynamic recrystallization when deformation temperature at 1000? or 1050?.After increasing the deformation degree to 70%,dynamic crystallization can occur at 950? or 1000?.With the increase of dynamic recrystallization,the size and distribution of lath martensite become uniform gradually.On the condition that austenite temperature at 1150?,the deformation temperature at 1050? and the deformation at 50%,the size of grains become coarsening and structural heredity phenomenon took place when reheated to 880? with heating rate at200?/min and 1000°C/min respectively.When austenitizing temperature at 1250? and the deformation temperature and deformation are the same as the former,phenomenon of structural heredity appear after reheated to 880? with heating rate at 1000?/min.In other heat treatment systems,austenite grains were refined after quenching at two different secondary quenching rate...