Application of CaCO₃ and SiO₂ Fluxes in MIG Welding and Their Effect on the Free-flight Metal Transfer

Abstract

The metal transfer mode in MIG/MAG welding directly influences the productivity, process stability and the weld bead shape. The present work evaluates the use of calcium carbonate and silicon dioxide as fluxes in A-MIG welding of AISI 304L austenitic stainless steel. The flux influence on operational aspects was evaluated with free flight metal transfer by free flight. Welds were carried out for currents between 160 and 250 A using Ar-2.5% CO2 shielding and a constant current power supply. Welding voltage and current signals were acquired and analyzed. Arc length was measured with projection system and was controlled by manually varying the wire feed rate. The results show that the fluxes actively affect the process. It was observed that calcium carbonate reduces the arc voltage and metal transfer frequency, delaying the transition between globular and spray modes. On the other hand, silica increases the arc voltage and do not significantly change metal transfer. Both fluxes also caused modifications in the geometric aspects of the weld bead width penetration and profile.

Key-words:
A-MIG welding; Active flux; Operational characteristics; Metal transfer; Transition current