TWI Industrial Member Report Summary 46/1977
By M Amin and P V C Watkins
Using square wave pulsed current and a transistorised power supply, the range in operating parameters (amplitude and duration) can be determined for any given wire feed speed and pulse repeat frequency. At any given pulse duration and arc length, the background current can be varied over a limited range with corresponding changes in pulse current amplitude.
For 1.2mm diameter mild steel wire in bead-on-plate runs in argon/5%CO2 it is found, for a 2:1 change in pulse frequency (25 and 50Hz) and in wire feed speed (2 and 4m/min), that the viable range of pulse current level is roughly unchanged. However, the requisite pulse duration varies substantially as the droplet volume (directly as the feed speed and inversely with frequency). Also a given pulse condition is valid for a range of wire feed speeds if the repeat frequency is varied directly with feed rate.
Such relations lead to the concept of 'synergic' pulse operation where the preferred pulse frequency, amplitude, duration and background current are together directly linked to the wire feed rate, such that the pulse parameters are automatically adjusted with change in feed speed. This greatly simplifies the welding procedure whereby, without causing major changes in arc length, the wire feed speed can be freely changed over wide ranges even with a constant current supply, without necessitating any other adjustments to the power supply.