Changes in the Structure and Microhardness of Permanent Joints of Load-Bearing Structures Made of Titanium Alloy VT23 by Electron Beam Welding

The study of the influence of capillary-condensed moisture, the process of weld pool formation and crystallization on the formation of specific defects in electron beam welding of titanium alloys is a pressing task. A review of the literature shows that the problem of formation of macropores reaching 0.1 mm was investigated by many researchers, but the advent of modern x-ray machines allowed detecting a particular defect along the fusion line, the so-called dark stripes, during in-process control of permanent joints created by electron beam welding. The results of welding the alloy VT23 using an electronic beam welding machine 30E300 are presented in the article. An analysis of the results of the radiographic control, a study of macro- and microstructure and measurements of microhardness of the cross section of the weld joint in the areas of strengthening and the weld root are performed. A conclusion about the type of the defect is made, a theory describing the effect of capillary condensation in the form of titanium hydride on the occurrence of the defect is put forward, and the reason for the difference in microhardness in the areas of strengthening and the weld root is established.

References

[1] Gurevich S.M., Zamkov V.N., Blashchuk V.E. Metallurgiya i tekhnologiya svarki titana i ego splavov [Metallurgy and welding technology of titanium and its alloys]. Kiev, Naukova Dumka publ., 1986. 240 p.

[2] Murav’yev V.I., Bakhmatov P.V., Dolotov B.I. Obespecheniye nadеzhnosti konstruktsiy iz titanovykh splavov [Ensuring the reliability of structures made of titanium alloys]. Moscow, Ekom publ., 2009. 752 p.

[3] Murav’yеv V.I., Bakhmatov P.V., Debelyak A.A. Definition of an opportunity to calculate residual deformations on thermal fields at welding thin plates end-to-end. Scholarly Notes of Komsomolsk-na-Amure State Technical University, 2010, no. 4 1(4), pp. 68–80 (in Russ.).

[4] Kolachev B.A., Elagin V.I., Livanov V.A. Metallovedeniye i termicheskaya obrabotka tsvetnykh metallov i splavov [Metal science and heat treatment of non-ferrous metals and alloys]. Moscow MISIS publ., 2005. 432 p.

[5] Papusha A.G., Andreyev A.N. Analysis of defects in weld connections implemented by electron-beam welding. Aktual’nyye problemy aviatsii i kosmonavtiki, 2017, vol. 1, no. 13, pp. 424–426 (in Russ.).

[6] Novokreshchenov V.V., Rodyakina R.V. Kinetics of particle interactions in penetration channel at electron-beam welding. Svarochnoye proizvodstvo, 2012, no. 12, pp. 18–22 (in Russ.).

[7] Shevelev A.D., Zamkov V.N., Gurevich S.M. Features of electron beam welding of VT6 alloy of large thickness. Aktual’nyye problemy svarki tsvetnykh metallov. Sbornik dokladov 1-y Vsesoyuznoy konferentsii [Actual problems of welding of non-ferrous metals. Collection of reports of the 1st all-union conference]. Kiev, Naukova Dumka publ., 1980, pp. 306–310.

[8] Shevelev A.D., Zamkov V.N., Lokshin V.E. Single-pass electron-beam welding of titanium sheets of large thickness in the lower position. Avtomaticheskaya svarka, 1980, no. 4, pp. 69–70 (in Russ.).

[9] Fishgoit A.F., Kolachev B.A., Mamaev A.A., Shtemler Y.M. Diffusion of hydrogen during and after electron beam welding titanium alloys. Welding International, 1993, no. 3, pp. 230–233, doi: 10.1080/09507119309548380

[10] Shtampovka, svarka, payka i termoobrabotka titana i ego splavov v aviastroyenii [Stamping, welding, brazing and heat treatment of titanium and its alloys in aircraft industry]. Ed. Bratukhin A.G. Moscow, Mashinostroyeniye publ., 1997. 600 p.

[11] Murav’yev V.I., Sharobarin V.G., Bogatov Yu.D. Quality assessment of welded frames of alloy VT20. Aviatsionnaya promyshlennost’, 1986, no. 5, pp. 75–77 (in Russ.).

[12] Dolotov B.I. Svarka pogruzhennym vol’framovym elektrodom [Tungsten Electrode Welding]. Moscow, Mashinostroyeniye publ., 2004. 208 p.

[13] Gorynin I.V., Chechulin B.B. Titan v mashinostroyenii [Titanium in mechanical engineering]. Moscow, Mashinostroyeniye publ., 1990. 400 p.

[14] Dolotov B.I., Murav’yev V.I., Mar’in B.N., Ivanov Yu.L., Makarov K.A. Mixing metal in the bath during welding with a submerged tungsten electrode. Svarochnoye proizvodstvo, 1998, no. 2, pp. 15–16 (in Russ.).

[15] Murav’ev V.I., Bakhmatov P.V., Pletnev N.O., Develyak A.A. Influence on the stress state on the structure and properities of welded steel and alloy structures. Steel in Translation, 2016, no. 4, pp. 256–259, doi: 10.3103/S0967091216040070

[16] Sansonnets L., Haidar J. Lowke J. Prediction of properties of free burning arcs including effects of ambipolar diffusion. Journal of Physics D: Applied Physics, 2000, vol. 33, pp. 148–157, doi: 10.1088/0022-3727/33/2/309

[17] Redchits V.V., Frolov V.A., Lukin V.I., Kazakov V.A. Poristost’ pri svarke tsvetnykh metallov [Porosity when welding non-ferrous metals]. Moscow, Tekhnologiya mashinostroyeniya publ., 2002. 448 p.