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A self-consisted mathematical model is presented, describing nonstationary processes of energy, momentum, mass and charge transfer in plasma column and anode boundary layer of an electric arc burning in atmospheric pressure inert gas at pulsed modulation of current. A numerical study of distributed and integrated characteristics of 2 mm long argon arc was performed in the case of current modulation by rectangular pulses at 10 kHz frequency and different values of the duty cycle (0.3; 0.5; 0.7) under the condition that the average current value remains unchanged and equal to 140 A. Calculated time dependencies of plasma temperature, velocity and current density in the arc column centre, as well as axial values of plasma temperature and pressure near the anode surface, anode current density and heat flux into the anode are given for the selected values of duty cycle. Radial distributions of averaged over the current modulation period heat flux, introduced by the arc into the anode, pressure and force of friction of arc plasma flow on its surface were calculated, which are the determinant ones for simulation of thermal and hydrodynamic processes in the metal being welded in TIG welding with high-frequency pulsed current (HFPC) modulation. Results of simulation of nonstationary arc characteristics are compared with the respective results for a direct current (DC) arc, at current equal to average value of modulated current. Analysis of the obtained results leads to the conclusion that in the case of HFPC TIG welding at 10 kHz frequency decrease of duty cycle (increase of pulse current) at constant value of average current leads to greater force impact of such an arc on weld pool metal and to increase of its penetrability, respectively. 20 Ref., 2 Tabl., 6 Fig. [ABSTRACT FROM AUTHOR]

A review of studies, devoted to the processes of nonconsumable electrode inert-gas welding with welding current modulation was performed. The second part of the review is devoted to analysis of the works, dealing with the features of metal penetration (aluminium alloys, stainless steel, high-temperature nickel-chromium alloys) and weld formation in TIG welding with modulated current. [ABSTRACT FROM AUTHOR]

Works devoted to the processes of inert-gas nonconsumable electrode welding with current modulation were reviewed. In the first part of the review attention is focused on studies, dealing with the features of running of thermal, gas-dynamic and electromagnetic processes in non-stationary arcs with refractory cathode at different modes of arc current modulation. [ABSTRACT FROM AUTHOR]

The experience of the E.O. Paton Electric Welding Institute in creating a metal-cored wire for helium arc TIG welding of copper and its alloys was described. The deposited metal of the wire contains not more than 0.35 wt. % of alloying additives and is characterized by a high electrical and heat conductivity. Examples of the effective use of the developed wire in welding rotors of electric machines and in repair of gas-oxygen copper chambers are given. [ABSTRACT FROM AUTHOR]

The paper considers an approach for selection of filler material in TIG welding of titanium alloy VT22. It is shown that weld metal obtained using pilot flux-cored wire PPT-22 is a representative of transient class of titanium alloys, to which VT22 alloy is referred to (coefficient of β-stabilizing of such metal equals 1). This wire can be used for argon-arc welding of high-strength titanium alloys VT22. Mechanical properties of such welded joints after heat treatment reach the level of base metal indices. Application of PPT-22 wire in restoration argon-arc surfacing of VT22 alloy parts provides their high service characteristics. 15 Ref., 4 Tabl., 5 Fig. [ABSTRACT FROM AUTHOR]

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