Engineering Application Research On Welding X70 Spiral Sub-merged Welding Pipe

The quantity of pipeline construction has been increasing rapidly as people's need for energy expands. Being featured for economic, safe and continuous, the method of transporting oil and gas through pipeline has gained more and more attention and preference from people as one of the most economic and safe way. As the need for energy expands, hundreds of cross-country oil and gas pipeline will be constructed around the world. The vast market of petroleum industry has promoted the development of pipeline steel at great extent. The scale of oil and gas exploitation in the coming ten years will exceed that of the last fifty years. The 7540km oil pipeline and 14570km gas pipeline to be constructed has revealed the second booming period of pipeline industry in our country, where gas pipeline will be placed in the center.X70 is estimated to become the major pipeline steel in oil and gas pipeline construction. The production of X70 pipeline steel has matured in foreign countries while the production of such steel in our country is still at the starting stage. Therefore, this thesis analyzes the property and application of domestic X70 in order to ensure the safe application and accelerate the domestic production of X70 pipeline steel as well as to promote the competitive ability of domestic X70 pipeline steel in China and foreign countries.The workmanship of pipeline steel welding is mainly divided into three types, which are ERW, SSAW and LSAW. Because SSAW is simple in production process and requires low investment for equipment and low operation cost, its advantage of low cost is distinctive. However, the distribution of residual stress in SSAW pipe is uneven with high apex value, and furthermore, the residual stress in SSAW pipes from different producers differs apparently.This thesis tests and analyzes the X70 plate produced by Shanghai Baoshan Steel Corporation and Wuhan Steel Corporation comparatively, makes comparative analysis for the mechanical property and residual stress of X70 pipe and evaluates the spiral welding seam of the X70 pipe from the two corporations.