Internal Code: MAS516
The demand for natural gas has been ever increasing over the recent years due to the need for clean energy with reduced Carbon dioxide emissions (Ishikawa 2011). Major sources of gases are located in remote locations and therefore line pipe steels have been used for their transportation (Koo, Luton et al. 2004). Moreover, about 15% of the world estimated crude oil is in the North Pole, but the refineries are
located mainly in Western Europe and North America (Shin, Hwang et al. 2007). This is due to the worldwide industrialization which has caused the natural depletion of resources from convenient locations and it has moved to active oil drilling in extremely cold places and harsh environment conditions (Shin, Woo et al. 2009). Therefore the study of line pipes is an important factor. According BlueScope Steel, which is an Australian company, high pressure of transportation, minimizing pipe production cost and reducing the weld costs are the major factors driving the development of new grades in line pipes(David Langley 2010). The increasing demand for natural gas will influence its
transportation from the strategic and economic frame of reference (Hans-Georg Hillenbrand 2004). In response to the increasing demand for this efficiency, the steel pipe industry has brought numerous ways to develop its properties (D. Belato Rosado 2013). To obtain the transportation efficiency, superior comprehensive pipes are to be obtained through innovation and optimization of chemical composition,
microstructure design, and related production process (Wang, Shan et al. 2009). Long distance pipes are a safe and economical means to transport gas (Hans-Georg Hillenbrand 2004) as well as large diameter pipe (Koo, Luton et al. 2004). Combining the above-mentioned factors, the development and demand of high strength and high toughness line pipes increased, for which we should increase the working
pressure , reduce the quantity of steel used and the welding cost (Ishikawa 2011). The production of these pipes depends upon the grade set by the American Petroleum Institute (API) and the processes vary from one grade to the other. But mostly longitudinal welded pipes are used owing to its safety and cost (Dr. Ing 2001). The API has set a number of specifications which when satisfied forms a grade of the pipe. These grades are based on strength, toughness, fracture arrest capacity, Charpy energy etc. The primary step of pipe production is rolling of the pipe (Dr. Ing 2001). For API X60 grade, the pipe was hot rolled and normalized, but for the X70, hot rolling was replaced with thermo mechanical rolling and the micro alloying with Niobium (Nb) and Vanadium (V) along with reduction of Carbon content. When this process is combined with accelerated cooling, grade X80 is formed. Further changes in micro alloying formed higher grades of pipe like X100 and X120 (Dr. Ing 2001). The variants of Thermo Mechanical Control Process (TMCP) is used to achieve high strength and toughness (J Bauer 2000).
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