1.Chemical composition C:1.00 ~ 1.10 (promised error: ± 0.01) Si:0.20 ~ 0.45 (promised error: ± 0.05) (Mn:0.15 ~ 0.40 to bias: 0.04) S ≤ 0.030 P ≤ 0.030 (Cr:3.75 ~ 4.50 to bias: ± 0.05) Ni: promise residual content ≤ 0.30 Cu: promise residual content ≤ 0.25 V:2.25 ~ 2.75 (promised error: ± 0.05) Mo:4.75 ~ 6.50 (promise: size deviation ≤ 6, ± 0.05; > 6, + 0.10) 2.Heat treatment process Specification: heat treatment quenching, 730 ~ 840 ℃ preheated, 1190 ~ 1210 ℃ (salt bath furnace) or 1200 ~ 1220 ℃ (box-type furnace) heating, oil cooling, 540 ~ 560 ℃ tempering 2 times, each time 2h. 3.Delivery status Hot rolling, forging, cold drawn steel bars in annealing state delivery, rolled, forged steel bar with annealing + other processing methods (skin, gently pull, grinding or polishing processing before delivery) Tungsten W:5.00 ~ 6.75 (promise: size deviation ≤ 10, ± 0.10; > 10, + 0.20)