Stress Relaxation of 20Cr1Mo1V1 Steel for Cylinder Bolt after Working for 3×10⁵ h at High Temperature

Stress relaxation curves of 20Cr1Mo1V1 steels for cylinder bolt after working for 3×105 h at 540 ℃ and 9.8 MPa were measured by equal-strength loop method under different initial tighten strains. The stress relaxation values of this steel at 540 ℃ for 1×104, 3×104 , 1×105 h were given through extrapolation method. The results show that cylinder bolts made by 20Cr1Mo1V1 steel after working for 3×105 h were tight enough under the initial pressure of 319.51 MPa to guarantee no-leak in an overhaul period basically.