PSI - Issue 30

A.A. Antonov et al. / Procedia Structural Integrity 30 (2020) 6–10 A.A. Antonov et al. / Structural Integrity Procedia 00 (2020) 000–000

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5

Table 2. Tensile test results. No. S 0 mm 2 L 0 , mm

Rp 0,2 MPa

Rm MPa

A %

1 2 3

79,011 75,28 74,20

50,00 50,00 50,00

514,53 543,25 512,11

604,50 612,224 598,86

25,65 22,61 21,20

4. Conclusion A typical change in hardness values in the HAZ of the root weld and each fill pass is associated with the specifics of the formation of multi-pass welds and the peculiarities of thermal deformation processes in the HAZ metal with repeated local exposure to the welding source. Therefore, a significant softening of the HAZ metal occurred as a result of exceeding the preheating temperature and multi-pass welding with the hot passage, which, in turn, contributed to a significant decrease in the cooling rate of the HAZ metal and the shift of structural transformations to the ferrite-pearlite region. The RWS distributions show that the values of circular and axial residual stresses reach approximately 300 and  600 MPa, respectively, on the outer side of the pipe wall at a distance of 10 mm from the fusion line. Towards the fusion line, their values decrease and tend to zero. When approaching the fusion line, the values of axial and circular RWS values increase and reach 375 MPa and -100 MPa, respectively, on the inner side of the pipe wall at a distance of 5 mm from the fusion line. Destructive and non-destructive direct methods were used to determine the mechanical properties of the metal on standard samples of the welded joint and the HAZ of the pipeline. Tensile strength, yield strength, and relative elongation are determined. The mechanical properties of the pipeline metal are calculated in terms of hardness. It has been established that the mechanical properties and structure of the welded joint of the pipeline metal correspond to the regulatory documents, certificates, and technical specifications for pipelines. The analysis of results shows that there is a tendency towards hardening of the HAZ during welding with multilayer welds and ductility reduction. Acknowledgements This research has been supported by The Ministry of Science and Education of the Russian Federation (Project III.28.1.1). References Ammosov G.S., Yakovlev U.A., Kornilova Z.G., 2017. Prognoz dlitelyinoi prochnosti svarnih soedineniy stikov trub lukera PPMN VSTO -1 cherez r. Lena [The Forecast of Long-Term Strength of Welded Joints of Pipes of a Siphon of the Underwater Crossing of the Oil Pipeline ESPO (VSTO)-1 across the Lena River]. Nauka i obrazovanie 1(85), 81-87. (In Russian) Andrijashin V.A., Kostjuchenko A.A., Komarov A.I., Vorob'ev V.V., 2006. Korrozionnoe razrushenie poverhnostej magistral'nyh trub nefteprovoda posle dlitel'noj jekspluatacii [Corrosive destruction of surfaces of main oil pipes after long-term operation]. Zashhita metallov [Protection of metals], 42(1), 52-56. (In Russian) Golikov N.I., Ammosov A.P., 2012. Prochnost' svarnyh soedinenij rezervuarov i truboprovodov, jekspluatirujushhihsja v uslovijah Severa [Strength of welded joints of tanks and pipelines operating in the North], Publ. House of SVFU, Yakutsk, pp. 232. (In Russian) Lebedev M.P., Bykov A.N., Ammosov A.P., Permjakov P.P., Ammosova O.A., Ivanov Dzh.S., 2012. Ocenka deformacii truby PPMN VSTO cherez r. Lena i vozmozhnosti ee razryva [Evaluation of the pipe deformation of the underwater crossing of ESPO PS across the river Lena and the possibilities of its break]. Materials of All-Russian Research and Practice Conference “Svarka i bezopasnost'” [Welding and safety] 1, Yakutsk: Ofset, 49-61. (In Russian) Makarov Je.L., 1981. Holodnye treshhiny pri svarke legirovannyh stalej [Cold cracks when welding alloy steel]. Mashinostroenie, Moscow, pp. 247. (In Russian) Seyffarth P., Meyer B., Scharff A., 1992. Grober Atlas Schweiss-ZTU-Schaubilder. Dt. Verf. Fur Schweisstechnic, DVS Verlag., Dusseldorf, pp. 175. Sitenkov V.T., Perevozchenko V.I., 2004. Raschet skorosti korrozii truboprovodov, transportirujushhih neftegazovuju smes' [Calculation of the corrosion rate of pipelines transporting oil and gas mixture]. Oil Industry, 11, 104-107. (In Russian) Teplinskij Ju.A., Birillo I.N., Voronin V.N., Alennikov S.G., 2007. Rassledovanie prichin snizhenija jekspluatacionnoj nadezhnosti truboprovodov. Analiz prichin avarij [Investigation of the reasons of reducing the operation reliability of pipelines. Analysis of the causes of accidents]. Bezopasnost' Truda v Promyshlennosti [Labor Safety in Industry], 2, 22-24. (In Russian)