Thermal treatment method for improving low-temperature impact toughness of rods

The invention provides a thermal treatment method for improving the low-temperature impact toughness of rods and belongs to the technical field of thermal treatment machining. The thermal treatment method includes a quenching process, wherein the hot-rolling large rods or thermal treatment workpieces are put in a thermal treatment furnace at the temperature of 840 DEG C to 860 DEG C to be heated, and the temperature is kept for 60 min to 120 min; and then a water-cooling or oil quenching manner is adopted; and a tempering process, wherein the rods or workpieces obtained after moderate quenching treatment is conducted are put into a tempering furnace at the temperature of 610 DEG C to 640 DEG C, the temperature is kept for 60 min to 120 min, and the rods or workpieces are water-cooled to the room temperature after being taken out of the furnace. By the adoption of the thermal treatment method, to overcome the defect that oil quenching capacity is insufficient, the quenching degree of large bolts is increased effectively, the tensile strength ranges from 861 MPa to 944 MPa, the yield strength ranges from 727 MPa to 804 MPa, the percentage elongation after fracture reaches 19.5% to 21.8%, the percentage reduction of the area Z ranges from 59% to 64%, and -100 DEG C impact absorbing energy Akv ranges from 27 J to 50.1 J. The tensile strength of workblank workpieces is 943 MPa, the yield strength is 818 MPa, the percentage elongation after fracture reaches 18.3%, the percentage reduction of the area Z is 63%, and the -100 DEG C impact absorbing energy Akv is 33 J.