Productive Technology, Microstructure and Properties of High Grade X70MS Acid Resistant Spiral Submerged Arc Welded Pipe

The high grade X70MS acid resistance of hot-rolled plate was producted by using the technologies of low carbon, low manganese, microalloying design and clean smelting. Through optimizing welding parameters, using acid resistance welding materials, controlling welding heat input and residual stress in pipe forming, the high grade X70MS acid resistant spiral submerged arc welded pipe was developed, and the mechanical properties, HIC resistance and SSCC resistance of the pipe were studied. The results show that the yield strength of the base metal of the pipe body was 515-525 MPa, tensile strength was 615-620 MPa, the tensile strength of the weld seam was 655-685 MPa, the hardness of the base metal and weld seam were less than 250 HV10. At 0 ℃ , the impact energies of the base metal and weld seam were more than 296 J and 120 J, respectively. The pipe had excellent HIC resistance and SSCC resistance and the mechanical properties and corrosion resistance of the pipe up to and and far higher than the standard requirements of API SPEC 5L(44th edition).