The invention discloses a
carburizing and
quenching heat treatment method which is applied to gas
carburizing and
quenching production normally required by common low-
carbon steel and low-carbon alloysteel workpieces. The
carburizing and
quenching heat treatment method specifically comprises the following steps of S1, firstly, putting the workpieces into a carburizing furnace, and strong carburizing section treatment and
diffusion section treatment are performed on the workpieces in the carburizing furnace, wherein the carburizing temperature of the strong carburizing section treatment is 915DEG C-925 DEG C, the
carbon potential of the strong carburizing section treatment is 1.1%-1.2%, the carburization temperature of the
diffusion section treatment is 905 DEG C-915 DEG C, the
carbon potential of the
diffusion section treatment is 0.8%-0.9%, and the carburizing heat preservation
time ratio of the strong carburizing section treatment to the diffusion section treatment is 11: 9; S2, performing cooling and quenching along with the carburizing furnace; S3, performing quenching
oil cooling; and S4, performing
tempering. By means of the method, the
hardness and the hardened layer depthof the low-
carbon alloy steel workpieces are guaranteed, meanwhile, it is guaranteed that the refined metallographic structure meets the
national standard, and the carburizing and quenching quality is stably improved.