Effect of thermo-mechanical control process on microstructures and mechanical properties of X60 pipeline steel

Effects of technological parameters of thermo-mechanical control process (TMCP) on microstructure and mechanical properties of X60 pipeline steel have been investigated. Regression equations describing the relationship between technological parameters and mechanical properties are obtained: sigma (s)=0.5075t(S)-0.2387t(f)-0.3242t(C)+ 1.9163 upsilon (C)+324.8287, delta (5)=-0.0017t(S)-0.0585t(f)-0.0976t(C)+ 0.3162 upsilon (C)+123.97, where t(S), t(f) and t(C) are the start rolling temperature, final rolling temperature and final colling temperature (degreesC), respectively, and vc cooling rate (degreesC /s). The parameters of TMCP for obtaining better mechanical properties are given. The experimental results show that the mixed microstructure mostly composed of acicular ferrite has the optimum strength and ductility