The production of 20.5- and 24.9-mm-thick X80 steel plates, for large diameter gas line pipe application, was tested at Azovtal Iron & Steel Works in Mariupol, Ukraine. The designed steel chemistry and the selected thermomechanical rolling conditions resulted in mechanical properties that met the requirements of X80 steel pipe. The designed grade was evaluated for microstructure, notch toughness, brittle fracture resistance on DWTT at +20 to -80°C, and weldability by using thermal cycle simulation. Large diameter pipe of 1220-mm-diameter by 20.5-mm-wall and 1420-mm-diameter by 24.9-mm-wall were manufactured at Khartsyzk Pipe Works. The significant effect of pipe manufacturing process has been established that manifested itself in the increase strength properties of base metal in pipe made from X80 steel plates produced by TMCP.