Influence of C, Cr and Mo Elements on Microstructure and Properties of X70 Pipeline Steel

Chemical composition of X70 pipeline steel was adjusted, and the effects of C, Cr, Mo elements on the microstructure, mechanical properties and wear resistance of the pipeline steel were studied. The results show that the microstructures of the tested steels with different composition were composed of acicular ferrite, quasi-polygonal ferrite and granular bainite, and the mechanical properties all met the requirements of API SREC 5L specifications for X70 pipeline steel. Increasing the content of C or Cr element appropriately increased the tensile strength and wear resistance of the tested steel. Mo element had little effect on the tensile strength of the tested steel, and the wear resistance of the tested steel first decreased and then increased when the mass fraction of Mo increased from 0 to 0.22%.