The effects of thermo-mechanical control process on microstructures and mechanical properties of a commercial pipeline steel

The thermo-mechanical control process (TMCP) was investigated for its effect on microstructures and mechanical properties of a commercial pipeline steel. Regression equations describing the relationship between processing parameters and mechanical properties were obtained through analyses of the experimental results: yield strength (YS)=0.508Ts−0.231Tf−0.334Tc+1.905Vc+323.6, EL (elongation)=−0.002Ts−0.064Tf−0.086Tc+0.325Vc+121.8, where Ts, Tf and Tc are the start rolling, final rolling and final cooling temperature (°C), respectively, and Vc is the cooling rate (°C s−1). The processing parameters of TMCP for obtaining better mechanical properties were given, i.e. Ts is approximately 1100 °C, Tf 890 °C, Tc 520 °C and Vc 30 °C s−1. It was found that the acicular ferrite dominated microstructure obtained by the optimized TMCP has optimum mechanical properties, and the microstructural characteristics of acicular ferrite play important roles in enhancement of both strength and toughness of pipeline steels.