... /0.34 ≥910 ≥765 ≥12 232±0.75% 273±0.75% 325±0.75% 356±0.75% 406±0.75% 4.2,+15%,-04.8,+15%,-05.0 ... , +15%,-05.6, +15%,-01.5mm/M3-10.5 ≤0 ... ≥980 ≥835 ≥12 34Mn2V 0.30/0.37 ≥745 ≥530 ≥16 P≤0.020S≤0.020P+S≤0.030.Thermal treatment: quenching and tempering type 2 cylinder tube