Influence of Deformation on Phase Transformation and Precipitation of Steels for Oil Country Tubular Goods

This work presents different modeling approaches for the description of the microstructure evolution in a typical C-Mn micro-alloyed steel for pipes and tubes in the oil field industry. A comparison between the continuous-cooling-transformation (CCT) diagram of the material with no deformation and the DCCT diagram after single- and multiple-step deformation is presented. The experiments are performed on a high-speed deformation dilatometer. The start of austenite decomposition is simulated with the software JMatPro, whereas the bainite and martensite start temperature are additionally evaluated with empirical formulae available in the literature. The precipitation state of the micro-alloying elements is investigated by transmission and scanning electron microscopy and compared with calculated ones by using the software package MatCalc. Our simulation results are directly applicable to the optimization of microstructure and properties in the production of steels for oil country tubular goods.