Effect of parameters of quenching at 890 〜930 ℃ for 25 ~45 min and tempering at 570 ~610 ℃ for 50 〜 80 min on structure and mechanical properties of 245 mm x 12 mm tube of steel 25MnV (% : 0. 25 〜0. 30C

1. 50 ~ 1. 80Mn

0. 06 ~0. 15V) has been studied by measured CCT curves and orthogonal test of heat treatment. Results show that with austenizing at 910 °C for 35 min

water quenching

and tempering at 590 ℃ for 65 min

the comprehensive mechanical properties of casing tube are optimum i. e. yield strength 878 ~906 MPa

tensile strength 923 ~ 963 MPa and elongation 16. 6% ~ 17. 4% to meet the standard requirement.