Evaluation of Mechanical Properties and Microstructure of X70 Pipeline Steel with Strain-Based Design

The microstructure and mechanical properties of X70 pipeline steel with a ferrite/martensite dual-phase produced by thermo-mechanical controlled processing were investigated tensile tests, Charpy V-notched (CVN) impact drop-weight tear guided-bend scanning electron microscopy transmission combined thermodynamic simulation analysis. All the met strength, ductility, toughness deformability requirements grade strain-based design. shear fracture area absorbed energy CVN at ?10 °C >97% >205 J in base metal (BM), weld (WM) heat affected zone (HAZ) low transition temperature, indicating adequate resistance to propagating fracture. WM was mainly intragranular acicular ferrite that can guarantee high over matching welded joint. Because being exposed successive inputs, plus martensite/bainite BM heated between Ac1 Ts forming HAZ. However, 345 HAZ obtained, which indicated excellent would not be seriously deteriorated during welding thermal cycles reasonable addition Ti Nb.