Some Characteristics of the Electrode Melting Phenomena in Narrow-Gap Mig-Arc Welding (Rept II)

Effect of Chemical Composition of Shielding Gas

Abstract

Effect of chemical composition of shielding gas on the relationship between groove width and wire melting rate has been studied in GMA welding (shielding gas composition; 100 % CO₂, 70 % CO₂ + 30 % Ar, 20 % CO₂+80 % Ar, 100 % Ar).
In DCSP, it was found that wire melting rate increased with increasing groove width, and wire melting rate became a constant. For instance, as shielding gas composition was 20 % CO₂+80 % Ar and groove shape was square, wire melting rate increased as groove width increased up to about 27 mm (=boundary groove width). And over that width, wire melting rate became a constant. The value of boundary groove width became narrower as CO₂ gas content was increased in shielding gas and welding current became higher. But in the case of using 100 % Ar shielding gas, any precise relationship between groove width and wire melting rate was not found.
In DCRP, characteristics of arc and wire melting rate were not affected by groove width in all cases of various shielding gas composition.