Effect of thermo-mechanical control processing on microstructure and properties of high toughness X90 pipeline steel

Effect of the main TMCP parameters on mechanical properties and microstructure characteristics of X90 pipeline steel was investigated by a labroratory simulated TMPC with desired processing parameters, including reheating temperature, intermediate slab thickness and coiling temperature. Results show that the strength increases with the increment of reheating temperature at first, but dramatically reduces when the grain size gets coarse at reheating temperature of 1250℃. Thicker intermediate slab contributes to higher strength and toughness because of a homogenized microstructure with refined grains was brought out. Coiling temperature plays the most important role in controlling the steel property. A microstructure composed of proper combination of granular banite and lath banite of the steel with optimal matching of strength and toughness can be achieved when coiling at 320℃. An industrial production of X90 coil were carried out employing the parameters obtained through the investigation, high strength combined with great low temperature toughness has been achieved, which proves that TMCP technology in this study has a good practice effect. © All right reserved.