The article presents the results of comprehensive experimental studies aimed at investigating the relationship between base metal and welding parameters (chemical composition of welded pipes and welding consumables, welding mode), the structure of received weld metal, its basic mechanical properties (strength, ductility and impact strength), and the parameters of static and cyclic cracking strength, used within the force criterion of fracture mechanics. For this purpose, standard and special metal tests have been carried out as well as a study of metal structure after heat treatment over a wide range of cooling rates. The established correlations were confirmed by testing the ring type welded pipe joints and tanks’ steel structures, welded using the most common Transneft technologies. Based on the results obtained, a model has been developed for refining the operability of welded joints according to the initial data of various levels. In particular, the influence of the cooling rate and main parameters of the welded joint metal structure on the change in its basic mechanical properties has been established. In addition, empirical expressions linking a set of mechanical properties (impact strength, relative elongation and proof/ultimate ratio), combined into a complex performance factor, to the metal cracking strength parameters used within the force criterion of fracture mechanics. In order to obtain the greatest practical outcome from the implementation of the developed model, it is proposed to introduce differentiated reduction factors when carrying out strength and durability calculations in accordance with current normative documentation, depending on the level of available data on the welded joint.
References
1. Idrisov R.Kh., Idrisova K.R., Kormakova D.S., Analysis of accident rate of main pipelines in Russia (In Russ.), Transport i khranenie nefteproduktov i uglevodorodnogo syr'ya, 2019, no. 2, pp. 44–46.
2. Aladinskiy V.V., Mel'nikova A.V., Formation of requirements for the geometry and properties of welded joints of pipes, ensuring the reliability of pipelines (In Russ.), Nauka i tekhnika v gazovoy promyshlennosti, 2009, no. 4 (40), pp. 43–48.
3. Golikov N.I., Ammosov A.P., Prochnost' svarnykh soedineniy rezervuarov i truboprovodov, ekspluatiruyushchikhsya v usloviyakh Severa (Strength of welded joints of tanks and pipelines operating in the North), Yakutsk: Publ. of North-Eastern Federal University, 2012, 232 p.
4. Makarov E.L., Yakushin B.F., Teoriya svarivaemosti staley i splavov (Theory of weldability of steels and alloys), Moscow: Publ. of Bauman University, 2014, 487 p.
5. Savkin A.N., Andronik A.V., Koraddi R., Determination of the coefficients of the crack growth rate equation upon cyclic load (In Russ.), Zavodskaya laboratoriya. Diagnostika materialov, 2016, V. 82, no. 1, pp. 57–63.
6. Mamontov V.A., Kuzhakhmetov T.A., Iksanov R.U., Doan Van Tin', Diagram building of fatigue destruction of ship shaft models (In Russ.), Vestnik AGTU, 2008, no. 5 (46), pp. 44–49.
7. Stress intensity factors. Handbook: edited by Murakami Y., The Society of Materials Science, Japan & Elsevier Science Ltd., 1987.
8. Terent'ev V.F., Ustalost' metallicheskikh materialov (Fatigue of metallic materials), Moscow: Nauka Publ., 2003, 254 p.
9. Zorin A.E., Analysis of structural and thermal processes in welding (to optimize the technology of cutting circular welded joints of pipelines) (In Russ.), Neft', gaz i biznes, 2011, no. 6, pp. 67–70.
10. Zorin A.E., The design of the sample for mechanical testing of pipe metal (In Russ.), Territoriya NEFTEGAZ, 2015, no. 3, pp. 124–128.
11. Zorin A.E., Nauchno-metodicheskoe obespechenie sistemy podderzhaniya rabotosposobnosti dlitel'no ekspluatiruemykh gazoprovodov (Scientific and methodological support of the system for maintaining the operability of long-term operated gas pipelines): thesis of doctor of technical science, Moscow, 2016.
12. Bel'chenko G.I., Gubenko S.I., Osnovy metallografii i plasticheskoy deformatsii stali (Fundamentals of metallography and plastic deformation of steel), Kiev: Vishcha shkola Publ., 1987, 240 p.
13. Bidulya P., Steel foundry practice, 1968, 319 p.
14. Geller Yu., Tool steels, 1978, 659 p.
15. Okerblom N.O., Demyantsevich V.P., Baykova I.P., Proektirovanie tekhnologii izgotovleniya svarnykh konstruktsiy (Designing a technology for manufacturing welded structures), Lenigrad: Sudprom GIZ Publ., 1963, 602 p.
16. Svarka v mashinostroenii (Welding in mechanical engineering): edited by Ol'shanskiy N.A., Moscow: Mashinostroenie Publ., 1978, V. 1, 504 p.
