N.G. Goncharov, Cand. Sci. (Eng.), Lead Researcher G.V. Nesterov, Cand. Sci. (Eng.), Lead Researcher, NesterovGV@niitnn.transneft.ru A.A. Yushin, Cand. Sci. (Eng.), Laboratory Head OOO NII Transneft, Moscow, Russia
The key element in forming the reliability and safety of the trunk pipelines is the quality of making butt welded joints.
When welding under conditions of negative temperatures as a result of increasing the cooling rate of the weld pool, the metal loses its plastic and viscous properties and becomes prone to the formation of hot and cold cracks. When welding from the molten metal the output of gases and oxides is hampered that increases the content of hydrogen, oxygen, nitrogen of nonmetallic inclusions in the metal weld and can lead to the formation of poor penetration, pores, and hot cracks. The possibility of formation of the hot cracks is further enhanced with an increase in the rate of elastoplastic deformation in the critical temperature range, when the heated metal is already in the brittle state. After welding, the probability of cold cracks is high. To give the welded joints metal properties meeting the regulatory requirements, it is required to conduct additional technological activities that ensure optimal heat input to the metal during welding operations.
Selection of the optimum thermal cycle of welding determines the nature of the metallurgical processes running at the welded joint crystallization, mechanical properties of the weld metal and the weld zone, and the quality of the weld joint as a whole.
The complex of carried out researches made it possible to determine the most rational parameters of thermal welding cycles when performing work at low temperatures for pipes of steel of strength class K56 applied to the technology of manual arc welding and the combined technology with the welding of the root layer by STT method and filling and facing layers by the automatic welding with welding heads M-300S. The metal of welded joints had the satisfactory complex of the mechanical properties and resistance to the formation of cold cracks. This allowed to recommend the parameters of the thermal cycle when making butt welded joints from pipes of strength class K56 in the Arctic zone of the Russian Federation at temperatures up to –40 °C.
1. Kolesnikov O.I., Goncharov N.G. Welding of pipelines at low temperatures. Nauka i tekhnologii truboprovodnogo transporta nefti i nefteproduktov = Science and Technologies of Pipeline Transport of Oil and Oil Products. 2011. № 2. pp. 14–16. (In Russ.).
2. Goncharov N.G., Kolesnikov O.I., Bratus A.A. Increase in resistance of pipes welded joints against the formation of the cold cracks. Nauka i tekhnologii truboprovodnogo transporta nefti i nefteproduktov = Science and Technologies of Pipeline Transport of Oil and Oil Products. 2014. № 3. pp. 63–65. (In Russ.).
3. Poluzyan Zh.A., Mazel A.G. Welding of the trunk pipelines at air low temperatures. Construction of the trunk pipelines and construction of oil and gas fields. Trudy VNIIST = VNIIST Proceedings. 1974. Iss. 30. Pt. 1. pp. 262–331. (In Russ.).
4. Goncharov N.G., Kolesnikov O.I., Yushin A.A. A study of the impact of low ambient temperatures on weld technology and the properties of welded joints in trunk pipelines. Pipeline Science and Technology. 2017. Vol. 1. № 1. pp. 57–63.
5. Makarov E.L. Cold cracks at the welding of alloy steels. Moscow: Mashinostroyeniye, 1981. 246 p. (In Russ.).
6. Sleptsov O.I., Mikhaylov V.E., Petushkov V.G., Yakovlev G.P., Yakovleva S.P. Increase in strength of the welded structures for the North. Novosibirsk: Nauka. Sibirskoye otdeleniye, 1989. 223 p. (In Russ.).
7. Aleshin N.P., Chernyshov G.G. Welding. Cutting. Control: Reference book: in 2 volumes, Vol. 1. Moscow: Mashinostroyeniye, 2004. 624 p. (In Russ.).
8. AWS API-M:2017 Study Guide for API Standard 1104 Welding of Pipelines and Related Facilities. Available at: https://www.browntechnical.org/products/api-m-2017-study-guide-for-api-standard-1104-welding-of-pipelines-and-related-facilities.html (accessed: June 01, 2018).
9. PWE:2000 Practical Welding Engineer, AWS. Available at: https://weldperfect.com/products/pwe2000-practical-welding-engineer-aws (accessed: June 01, 2018).
10. GOST R 56403—2015. Trunk pipeline transport of oil and oil products. Steel welded pipes. Specification. Available at: https://standartgost.ru/g/GOST_R_56403-2015 (accessed: June 01, 2018). (In Russ.).
11. Felber S. Welding of the High Grade Pipeline-Steel X80 and Description of Different Pipeline-Projects. Welding in the World. 2008. Vol. 52. Iss. 5–6. pp. 19–41.
12. Younas M. Contrasting Welding Techniques Used on Pipelines and Refinery Piping: Uphill Versus Downhill. Pipeline & Gas Journal. 2012. Vol. 239. № 1.
