Pipe fittings associated with the history of the development pipeline


Early pipeline has been using C, Mn, Si type of ordinary carbon steel, the focus on performance in the metallurgical, chemical composition no strict rules. Since the 1960s, with the oil and  di pipe  pressure and diameter increases, began to use high strength low alloy steels (HSLA), mainly supply hot-rolled and normalized condition. The chemical composition of these steels: C ≤ 0.2%, alloying elements ≤ 3 ~ 5%. With the further development pipeline, to the late 60s early 70s, the American Petroleum Institute and the API 5LX proposed standard API 5LS controlled rolled microalloyed X56, X60, X65 three steels. This steel is breaking the traditional concept of the steel, the carbon content of 0.1-0.14%, added in the steel ≤ 0.2% of Nb, V, Ti and other alloying elements, and by controlling the rolling process the mechanical properties of the steel has been significantly improved. To 1973 and 1985, API standards are added in succession X70 and X80 steel, and later developed the X100fittings , the carbon content is reduced below 0.01-0.04% carbon equivalent correspondingly dropped 0.35, appeared in the modern sense of the real Multiple micro-alloyed TMCP steels.
Our pipeline of applications and a late start, the past has been laid oil and gas pipelines, and most of the use Q235 16Mn steel. "Plan" period, China began to develop in accordance with API standard X60, X65 pipeline steel, and successfully used in conjunction with the imported steel pipe laying. 90s Baosteel, Wuhan Iron and have developed a high strength and high toughness X70 pipeline steel.