Applications of Two X70M Linepipe-purposed Steels with Different Chemical Compositions to Manufacture of HFW Pipes

Elaborated here in the paper are the applications of two X70M linepipe-purposed steels with different chemical compositions（i.e.，Steel A and Steel B） to manufacture of HFW pipes.And analyzed are the changes of the properties of the two steels as occurring during the manufacturing process of the HFW pipes，involving chemical composition，impact toughness，DWTT property，butting property，and weld pipe integrity，etc.The application results show that after being turned out as pipes，changes of yield strength and tensile strength of Steel A is just a little，while quality stability thereof is obvious.As for Steel B，its yield strength is decreased obviously after pipeforming，whereas its tensile strength almost remains the original，and thus cost-effectiveness of pipe-making with Steel B is comparatively advantageous.Speaking of strength，toughness and weldability，both steels are up to the requirements as for HFW pipe manufacturing process.