Effect of Propylene Addition to Conventional Shielding Gases on GMAW Applied to Top and Angle Joints

Abstract

The objective of this work was to evaluate the addition of 1.3% C₃H₆ to pure CO₂ and 0.6% C₃H₆ to the mixture of Ar+25%CO₂ in the welding of carbon steel using the Gas Metal Arc Welding (GMAW) applied to V-groove and T-angle joints. The welds were made using SAE 1020 steel sheets, ER70S-6 weld wire of 1.2 mm, contact tube to workpiece distance (CTWD) of 12 mm, welding speed of 300 mm/min and shielding gas flow of 15 l/min. The wire feed speed (V_alim) used were 4 m/min and 5 m/min with the voltage defined based on the electrical signals generated. The qualitative analysis did not indicate alterations of the weld beads caused by the addition of C₃H₆. The evaluation of the electrical signals showed that the addition of C₃H₆ affected the stability of the process only for Ar+25%CO₂. The results show that addition of C₃H₆ was beneficial to CO₂, reducing the slag and spatter rate, generating a small increase in deposition rate, and increasing the values of effective throat and root penetration. On the other hand, the addition of C₃H₆ to Ar+25%CO₂ was not advantageous, resulting in higher amounts of slag and spatter, and reduction of deposition rate and root penetration. The addition of C₃H₆ was more effective at V_alim of 5 m/min, providing an improvement in the process operational behavior for CO₂, and a reduction in the stability index values for Ar+25%CO₂. The addition of C₃H₆ did not result in changes in both the fusion zone (ZF) microstructure and hardness values. It was possible to conclude that the addition of C₃H₆ was beneficial for CO₂, resulting in improved process stability and higher productivity, but did not present advantages for Ar+25%CO₂, reducing the efficiency and stability of the process.

Key-words: GMAW; Stability of process; Shielding gases; Propylene effect; Operational behavior