The development of X120 line pipe steel hot rolled coil

In order to meet the increasing requirement for high grade linepipe steel to improve the transportation efficiency, the X120 hot rolled coil was developed and trial produced in Taiyuan Iron & Steel Company (TISCO) based on the experience obtained in the development of X80 for China's Second West East Gas Transportation Project. Multiple alloying elements were added to get the strength level of X120. The use of boron seemed indispensable to ensure low carbon equivalents. Properly designed TMCP with intensive cooling was to ensure the fine grain size and enough dislocation strengthening. Much attention was paid on the cooling rate and coiling temperature. The specification of the hot rolled coil is 1360mmX 9mmXL. Mechanical properties met requirements of the latest version of API Standards with yield strength of 926MPa, tensile strength of 1107MPa, and impact energy of 180J at -10 degrees C. The chemistry, rolling parameters and microstructure are introduced in this paper.