Search

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]