LUDERS DEFORMATION IN WELD SEAMS

The article considers the process of elastic-plastic transition in welded samples from low-carbon steel. Two methods of manualarc welding with a consumable electrode are used: traditional fixed arc and pulse welding with controlled heat input. It is shown that both methods are identical with respect to the obtained structural characteristics and mechanical properties. In both cases, a stretched elastic-plastic transition is observed by the nucleation and propagation of the Luders bands. However, depending on the welding method, it is realized in different scenarios. When using traditional welding with a stationary arc in a loaded sample, the Luders band nucleus is formed in the weld metal first in the form of diffuse deformation localization regions that fill the seam and transfer it to a plastically deformed state. Movable fronts of the band are finally formed in the heat-affected zones and pass into the base metal. The velocities of fronts and their morphology are identical to those of fronts in similar objects of similar steel. In the case of pulsed arc welding, the nucleation of the Luders bands occurs at a distance from the weld seam at the clamps of the loading device. Up to the heat-affected zones, the morphology and the velocity of the fronts correspond to the data for the parent metal. At the fusion boundary, the front stops and forms the nucleus of a new band that sprouts into the weld metal. This new band first transforms the weld metal into a deformed state, and then creates a movable front in the opposite heat-affected zone. The velocities of the fronts in the deposited and base metals differ by an order of magnitude. The welded seam determines the process of nucleation of the Luders band. The explanation of different scenarios of elastic-plastic transition is offered depending on the welding method. When using the traditional method of welding with a stationary arc in heat affected zones, the local long-range stresses are much higher than in the base metal, so here, as a relaxation process, the band originates. In the case of pulsed arc welding, these stresses are higher in the base metal, where the Luders bands originate. The obtained data can be used to justify the parameters of the heat-and-power equipment test.

1. Gladkov E.A., Kuznetsov P.S., Brodyagin V.N., Kopoteva E.N., Sholokhov M.A., Aleshin N.P. Pulse control technologies for droplet transfer during MIG / MAG welding. Svarka i diagnostika. 2014, no. 3, pp. 43–47. (In Russ.).

2. Knyaz’kov V.L., Knyaz’kov A.F. Povyshenie effektivnosti ruchnoi dugovoi svarki truboprovodov [Improving the efficiency of manual arc welding of pipelines]. Kemerovo: izd. KuzGTU, 2008, 104 p. (In Russ.).

3. Rezinskikh V.F., Zlepko V.F. Shtromberg Yu.Yu. The main requirements for the control of metal heat power equipment. Thermal Engineering. 1999, vol. 46, no. 5, pp. 8–20.

4. Klyuev V.V. Degradatsiya diagnostiki bezopasnosti [Degradation of safety diagnostics]. Moscow: ID ”Spektr”, 2012, 128 p. (In Russ.).

5. Cottrell A.H. Dislocations and plastic flow in crystals. Oxford: Oxford University Press, 1953, 260 p.

6. Mazière M., Luisb C., Maraisa A., Foresta S., Gaspérini M. Experimental and numerical analysis of the Lüders phenomenon in simple shear. International Journal of Solids and Structures. 2017, vol.  106-107, pp. 305–314.

7. Plekhov O.A., Naimark O.B., Saintier N., Palin-Luc T. Elastic-plastic transition in iron: Structural and thermodynamic features. Technical Physics. 2009, vol. 54, no. 8, pp. 1141–1146.

8. Beardsmore D.W., Quinta da Fonseca J., Romero J., English C.A., Ortner S.R., Sharples J., Sherry A.H., Wilkes M.A. Study of Luders phenomena in reactor pressure vessel steels. Materials Science and Engineering. 2013, A588, pp. 151–166.

9. Sorokin V.G., Gevras’ev M.A., Paleev V.S., Gevras’eva I.V., Paleva  S.Ya. Stali i splavy. Marochnik: Spravochnoe izdanie [Steels and alloys. Grade guide: Reference book]. Sorokin V.G., Gevras’ev  M.A. eds. Moscow: Intermet Inzhiniring, 2001, 608 p. (In Russ.).

10. Smirnov A.N., Kozlov E.V., Ozhiganov E.A., Ababkov N.V., Knyaz’kov V.L. Influence of deformation degree of welded joints of carbon steels on structuralphase state and fields of internal stresses. Svarka i diagnostika. 2016, no. 3, pp. 25–28. (In Russ.).

11. Gadalov V.N., Zakharov I.S., Kryukov V.A., Baturin L.V. Metallografiya s atlasami mikrostruktur metallov, splavov, pokrytii i svarnykh soedinenii [Metallography with atlases of microstructures of metals, alloys, coatings and welded joints]. Kursk: izd. Kurskogo gosudarstvennogo tekhnicheskogo universiteta, 2004, 479 p. (In Russ.).

12. Gorbatenko V.V., Danilov V.I., Zuev L.B. Plastic flow instability: Chernov–Lüders bands and the Portevin–Le Chatelier effect. Technical Physics. 2017, vol. 62, no. 3, pp. 395–400.

13. Livshits L.S., Khakimov A.N. Metallovedenie svarki i termicheskaya obrabotka svarnykh soedinenii [Metal science of welding and heat treatment of welded joints]. Moscow: Mashinostroenie, 1989, 336 p. (In Russ.).

14. Trefilov V.I., Moiseev V.F., Pechkovskii E.P. Deformatsionnoe uprochnenie i razrushenie polikristallicheskikh metallov [Strain hardening and fracture of polycrystalline metals]. Kiev: Naukova dumka, 1989, 256 p. (In Russ.).

15. Freudental A.M., Geiringer H. The mathematical theory of inelastic continuum. Elasticity and plasticity. Encyclopedia of Physics. Vol.  3. Berlin: Springer, 1958, pp. 229–443.

16. Zuev L.B. Autowave mechanics of plastic flow of solids. Phys. of Wave Phenom. 2012, vol. 20, pp. 166–173.

17. Ploskov N.A., Danilov V.I., Zuev L.B., Zavodchikov A.S., Bolotina  I.O., Orlova D.V. Evolution of strain localization autowaves in a zirconium alloy and evaluation of plasticity margin in a rolling area. Journal of applied mechanics and technical physics. 2012, vol. 53, no. 4, pp. 611–615.

18. Murav’ev T.V., Zuev L.B. Acoustic emission during the development of a Lüders band in a low-carbon steel. Technical Physics. 2008, vol. 53, no. 8, pp. 1094–1098.

19. Popova N., Nikonenko E., Koneva N., Kozlov E., Smirnov A., Ozhiganov E., Structure and phase composition on deformed heat-affected zone on the weld ST3. In: AIP Conference Proceedings, 13 Ser. “Prospects of Fundamental Sciences Development, PFSD-2016: Proceedings of XIII International Conference of Students and Young Scientists”. 2016, pp. 030006.

20. Popova N.A., Nikonenko E.N., Ivanov Yu.F., Gromov V.E., Budovskikh E.A., Raikov S.N., Kapralov E.V., Vashuk E.S. Structure and properties of wear-resistant weld deposit formed on martensitic steel using the electric-arc method. Advanced Materials Research. 2014, vol. 1013, pp. 194–199.