Identification of dominant factors determining droplet temperature in gas metal arc welding

In this study, to identify dominant factors of droplet temperature in a gas metal arc welding, the effects polarity on droplet temperature were investigated. In particular, the droplet temperature, the wire heat input and the wire melting rate with electrode positive (EP) polarity and electrode negative (EN) polarity using 100% Ar gas and 100% CO2 gas were measured. As a result, the droplet temperature with EP polarity was higher than EN polarity’s one using 100% Ar gas within the range of 130A to 230A. This result showed the reverse tendency compared with the case of 100% CO2. Moreover, the wire heat input and the wire melting rate with EN polarity were larger than EP polarity’s ones regardless of the shielding gas type. The simplified calculation suggested that this was because the ion current ratio was about 80% or more. Besides, especially with EP polarity, the wire melting rate using 100% CO2 was larger than 100% Ar’s one. It was suggested that this was because the wire melting rate was made a difference by the wire preheating effect depend on the droplet frequency determined by the specific heat of the shielding gas. These results identified the dominant factors of droplet temperature as the welding current, the ion current ratio and the specific heat of the shielding gas.