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Krivtsun I.,The Eo Paton Electrical Welding Institute | Reisgen U.,RWTH Aachen | Semenov O.,The Eo Paton Electrical Welding Institute | Zabirov A.,RWTH Aachen
Journal of Laser Applications | Year: 2016

The efficiency of the welding process in terms of weld penetration and weld width is greatly determined by the heat, mass, and charge transfer phenomena in the weld pool. These phenomena, in turn, depend on the thermal and electromagnetic interaction of the heat source used with the metal being welded. The most adequate models of the welding processes should consider the interaction of the phenomena in the heat source, on the base metal surface and inside its volume by a self-consistent way. This paper is devoted to the development of a self-consistent model of weld pool dynamics in tungsten inert gas (TIG), laser and hybrid (laser + TIG) spot welding without a keyhole formation. The proposed model allows simulation of processes taking place in the weld pool and on its surface. The model takes into account free surface deformation, influence of plasma shear stress, thermocapillary Marangoni effect, and Lorentz forces on the weld pool, as well as of the processes in the arc plasma including laser-arc interaction. For this purpose, the model of the weld pool is combined with a model of arc plasma column where the interaction processes between Gaussian beam radiation emitted by a continuous-wave CO2 laser and the argon arc plasma are described. The equations of the model proposed are solved numerically by means of finite element method. The simulation results are compared with real welding experiments performed with steel S-235JR. A good accordance between simulation and experimental results is observed. © 2016 Laser Institute of America.


Sokolsky V.E.,Taras Shevchenko National University | Roik A.S.,Taras Shevchenko National University | Davidenko A.V.,Taras Shevchenko National University | Kazimirov V.P.,Taras Shevchenko National University | And 3 more authors.
Journal of Mining and Metallurgy, Section B: Metallurgy | Year: 2012

The ceramic flux for submerged arc-surfacing with main component composition MgO (10.0 wt. %)-Al 2O 3 (25.0 wt. %)-SiO 2 (40.0 wt. %)-CaF 2 (25.0 wt. %) was prepared in a disk dryer-granulator using a sodium/potassium silicate solution as a binder. X-ray powder diffraction (XRPD) collected at r.t. identified α-phase of quartz, Al 2O 2, MgO and CaF 2 of the initial components in the samples taken after granulation and subsequent annealing at 600 °C. In contrast to the low temperature annealing, anorthite (CaAl 2Si 2O 8) is the main phase in the composition of the samples remelted at 1500 °C and quenched subsequently. Chemical analysis performed by means of scanning electron microscopy with energy-dispersive X-ray spectroscopy analysis (SEM/EDX) detects that the grains of the remelted samples possess the same Ca: Al: Si elemental ratio as anorthite. High temperature X-ray diffraction (HTXRD) was used to examine structural transformation in the solid at 600 °C < T < 1200 °C and stages of thermal evolution of ceramic flux were determined. The ceramic flux melts completely at the temperature above 1350 °C. The intensity pattern of the flux melt was obtained by X-ray diffraction of scattered X-rays at 1450 °C. After calculating the structure factor (SF), the radial distribution function (RDF) was evaluated and used to calculate the structural basicity of the flux melt.


Kartavykh A.V.,National University of Science and Technology "MISIS" | Asnis E.A.,The Eo Paton Electrical Welding Institute | Piskun N.V.,The Eo Paton Electrical Welding Institute | Statkevich I.I.,The Eo Paton Electrical Welding Institute | Gorshenkov M.V.,National University of Science and Technology "MISIS"
Journal of Alloys and Compounds | Year: 2015

Advanced Ti-44Al-5Nb-3Cr-1.5Zr (at.%) structural alloy was previously synthesized by the electron beam semi-continuous casting technique. The rod-shaped blanks of raw alloy with irregular coarse microstructure have been directionally upward re-solidified by the vertical induction float zone (FZ) technique in argon flow. FZ processing led to specific duplex microstructure creation consisting of (γ + α2) lamellar colonies and γ grains with minor intergranular fraction of B2 phase. The grain size, interlamellar spacing and ordered axial alignment of lamellae along the applied thermal gradient were controlled by FZ conditions. Structure, phase and elemental composition were analyzed with XRD, SEM, EBSD and hot gas extraction techniques. Mechanical properties were comparatively examined by uniaxial compression testing at ambient temperature. It was shown that (1) fine submicron interlamellar spacing; (2) ordered lamellae alignment; (3) relative volumetric ratio of (γ + α2)/γ/B2 structural-phase constituents and (4) dissolved oxygen content are the key parameters for controlling the compressive properties of FZ-alloy. Both yield strength, and ultimate compressive strength enhance drastically as a result of the FZ processing, being in correlation with the duplex microstructure development and refining of the material from oxygen. © 2015 Elsevier B.V. All rights reserved.

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