Weldable 13 percent Cr Steel Line Pipe

摘要

Low carbon martensitic stainless steels containing approximately 13 percent Cr have good toughness of weld heat affected zone (HAZ). Hence, they are called "Weldable 13 percent Cr steels". To develop the Weldable 13 percent Cr line pipes, the effects of alloying elements on mechanical properties and corrosion and SSC resistance in CO_2-(H_2S) environments were investigated. In addition to reducing C, reducing N and, adding some amounts of Ni also bring good HAZ toughness and field weldability of the steels. The steels also shows the better corrosion resistance compared with conventional 13 percent Cr steels having higher C content. 13Cr-6Ni-2Mo steel resists in light sour environment. NKK has newly developed the Weldable 13 percent Cr line pipes based on the results mentioned above. They are categorized to two types of the steel; 13 percent Cr-6 percent Ni-2 percent Mo for light sour 13 percent Cr-3 percent Ni for non-sour service and to three product types; seamless, laser welded and submerged arc welded pipe. The pipes have strength of X80 grade (YS>550MPa, TS>700MPa) and good low temperature toughness, regardless of the manufacturing process. Seam of the welded pipes (laser or submerged arc welded), which is heat treated in production route, also has the good toughness and the corrosion resistance as the same as the base metal. Girth welds have an enough toughness and corrosion resistance without post heat treatment.