The use of tubular elements in the chemical industry is widely used. The special properties of materials and their reaction to the welding thermal cycle is quite complex. This is especially true of titanium alloys, which when heated are sensitive to environmental influences, require special welding techniques and undergo residual welding deformations.
The welded joints of tubular elements made of titanium alloy brand PT-7m, which undergo transverse deformations due to welding, are studied. It is necessary to ensure high-quality sealed welds.
Analysis of the literature has shown that to obtain a guaranteed penetration it is necessary to increase the power of the arc discharge or perform multi-pass welding. This will provide larger cross sections of welded parts and should provide the specified strength characteristics. However, this technology, in turn, leads to an increase in residual deformation in the vicinity of the welded joint due to the intensive increase in the coefficient of linear expansion when heating the material. Also, the special thermophysical properties of titanium alloy such as increasing the affinity for gases when heated, increasing the grain size lead to a decrease in strength properties.
In the presented work it is proposed to use a mechanical angular deformer with an indicator head and a reference base for the study of transverse residual deformations. Peculiarities of measuring sockets and methods of their preparation are revealed. A calculation scheme for determining the amount of deformation has been developed, which has been tested on flat welded specimens and transferred to tubular elements. The sequence of deformation measurement process is described and the peculiarities of their formation on flat samples and tubular sections are studied.
The constructive decision of a welded joint of pipes which provides use of a compensation ring is offered. This approach allows to provide reliable protection of the root of the seam and its optimal formation with minimal residual deformation. At the same time it is possible to reach the reproducible form of a dagger of similar penetration in one pass. The result is a welded joint of the lock type, which is sealed and has a free formation of the seam root with high-quality protection by the gas atmosphere. The use of pulsed arc welding with a non-fusible electrode in an argon environment with filler wire allows to minimize the thermal impact on the base metal.
Statistical processing of experimental data on the parameters of the welding mode and their influence on the residual transverse welding deformations is carried out. To obtain an unambiguous statistically reliable answer about the valid law of distribution of experimental data of the results of strain measurement, the balancing procedure and the development of an analytical approximation distribution model are involved. It is shown that the measured values of the residual transverse deformation of the welded assembly are correctly described by the Laplace distribution, which predicts (probability not worse than 90 %) a decrease in the average value of the deformation value by 1.3 times.
[1] Yu. Molkov, et al., “Experimental determination of critical strain energy density of ductile materials”, Ukrainian Journal of Mechanical Engineering and Materials Science, vol. 5, no. 1, pp. 39–44, 2019. https://doi.org/10.23939/ujmems2019.01.039
[2] Z. A. Duriagina, et al., Splavy z osoblyvymy vlastyvostiamy [Alloys with special properties]. Lviv, Ukraine: Lviv Polytechnic National University Publ., 2007. [in Ukrainian].
[3] S. V. Hajduk, and C. B. Bielikov, Naukovi osnovy proektuvannia lyvarnykh zharomitsnykh nikelevykh splaviv z neobkhidnym kompleksom sluzhbovykh vlastyvostei [Scientific bases of designing of foundry heat-resistant nickel alloys with a necessary complex of service properties]. Zaporizhzhia, Ukraine: Zaporizhzhia Polytechnic National University Publ., 2017. [in Ukrainian].
[4] S. T. Kishkin, Liteinyie zharoprochnyie splavy na nikielievoi osnovie [Nickel-based heat-resistant foundry alloys]. Moscow, Russia: Mashinostroenie Publ., 1987. [in Russian].
[5] R.M. Nazarkin, et al., “Strukturno-fazovyie kharaktieristiki splava ZhS32-VI, poluchienoho mietodami napravlennoi kristallizatsyi, hranulnoi mietallurhii i sieliektivnoho laziernoho splavlenіia” [“Structural and phase characteristics of the ZhS32-VI alloy obtained by methods of directed crystallization, granular metallurgy and selective laser fusion”], Trudy VIAM [Proceedings of VIAM], vol. 50, no. 2, pp. 11–17, 2017. [in Russian]. https://doi.org/10.18577/2307-6046-2017-0-2-2-2
[6] A.V. Zavodov, et al., “Mikrostruktura i fazovyi sostav zharoprochnoho splava ZhS32 poslie sieliektivnoho laziernoho splavlieniia, vakuumnoi tiermicheskoi obrabotki i horiacheho izostaticheskoho pressovaniia” [“Microstructure and phase composition of ZhS32 superalloy after selective laser melting, vacuum heat treatment and hot isostatic pressing”]. Pisma o matierialakh [Letters on Materials], vol. 7 (2), pp. 111–116, 2017. [in Russian]. https://doi.org/10.22226/2410-3535-2017-2-111-116
[7] N. Ye. Kalinina, et al. “Mekhanichieskiie i korrozionnyie svoistva mnohokomponientnykh splavov, modifitsyrovannykh dispersnymi kompozitsyiami” [“Mechanical and corrosion properties of multicomponent alloys, modified by disperse compositions”], Stroitielstvo, matierialoviedieniie, mashynostroieniie [Construction, materials science, mechanical engineering], vol. 104., pp. 146–150, 2018. [in Russian].
[8] N. A. Lysenko, V. V. Klochykhin, and V. V. Naumyk, “Struktura i svoistva pustotelykh otlivok lopatok turbiny iz nikielievykh splavov poslie horiachieho izostatichieskoho prossovaniia [“Structure and properties of hollow castings of turbine blades from nickel alloys after hot isostatic pressing”], Aviatsyonno-kosmycheskaia tekhnika i tekhnolohiia [Aerospace engineering and technology], no. 10 (127), pp. 19–27, 2015. [in Russian].
[9] A. H. Andriienko, S. V. Gayduk, and V. V. Kononov, “Mekhanichieskiie svoistva i tiekhnolohichieskiie osobiennosti poluchieniia detalei HTU s napravliennoi (mono) strukturoi iz zharoprochnoho korrozionnostoikoho nikielievoho splava” [“Mechanical properties and technological procedure features in manufacture of gas turbine parts with directed (mono) crystallization made of corrosion-resistant nickel-base superalloy”], Novi materialy i tekhnolohii v metalurhii ta mashynobuduvanni [New materials and technologies in metallurgy and mechanical engineering], no. 2, pp. 81–86, 2012. [in Russian].
[10] Elvatech. Advanced XRF equipment and solutions, 2019. [Online]. Available: https://elvatech.com/. Accessed on: December 30, 2019.
[11] L. G. Akselrud, Yu. N. Grin, and P. Yu. Zavalij, “CSD-universal program package for single crystal or powder structure data treatment”, in Collected Abstracts of 12th European Crystallographic Meeting, Moscow, Russia, August 20–29, 1989, p. 155.
[12] Available Software for Powder Diffraction Indexing including a Literature Search List, 2019. [Online]. Available: http://www.ccp14.ac.uk/solution/indexing/. Accessed on: December 30, 2019.
[13] J. Rodriguez-Carvajal, “Recent developments of the program FULLPROF, in Ccommission on Powder Diffraction (IUCr)”, Newsletter, vol. 26, pp. 12–19, 2001.
[14] Materialy metalevi. Vyznachennia tverdosti za Vikersom [Metallic materials. Determination of Vickers hardness], DSTU ISO 6507-1:2007, 2010. [in Ukrainian].
[15] V. V. Аzhazha, et al., “Rol teplofizicheskikh uslovii v protsessie formirovaniia struktury pri napravliennoi krystallizatsyi zharoprochnykh splavov na nikielievoi osnovie” [“Role of thermal and physical conditions during shaping structure at a directional crystallization of heat resisting alloys on nickel base”], Voprosy atomnoi nauki i tekhniki [Issues of nuclear science and technology], no. 6, pp. 128–135, 2004. [in Russian].
[16] E. N. Kablov, E. E. Hierasimov, and A. V. Dubrovskii, “Tekhnolohichieskiie aspekty upravleniia strukturoi zharoprochnykh splavov pri napravliennoi kristallizatsyi” [“Technological aspects of control of structure of heat-resistant alloys at the directed crystallization”], Lytieinoie proizvodstvo [Foundry production], no. 4, pp. 11–25, 1994. [in Russian].
[17] V. V. Аzhazha, et al., “Pierspiektivnyie napravlieniia v sovershenstvovanii struktury monokristallichieskykh lopatok hazoturbinnykh dvihatieliei” [“Promising directions in improving the structure of single-crystal blades of gas turbine engines”], Matierialoviedieniie [Materials science], no. 11, pp. 8–19, 2006. [in Russian].