Effect of chemical composition of welding consumable on slag formation and corrosion resistance

Abstract

In the automotive industry, it is essential to reduce the weight of the car body to improve fuel efficiency and reduce CO2 gas emissions. As such, the application of advanced high-strength steels is rapidly increasing. However, in the case of gas metal arc (GMA) welding of advanced high-strength steels (AHSS), slag particles are observed to form on the weld surface resulting in poor corrosion resistance. The presence of slag particles on the weld also affects mechanical performance. This paper focuses on the degradation of corrosion resistance due to these slag particles. Current methods to decrease slag islands are costly as they attempt (1) to better protect the weld pool by decreasing the content of oxygen-containing ingredients or increasing argon in the shielding gas and (2) to mechanically clean the weld surface using processes such as shot blasting after gas metal arc welding (GMAW). In this study, the amount of slag was reduced by adjusting the chemical composition of welding consumables. Silicon was decreased to minimize silica/silicate formation, and sulfur was adjusted to affect the surface tension balance of the molten pool. Slag particles were observed to flow along the welding direction to solidify into a large particle in the weld crater that could be removed easily. In a separate consumable, Si and Mn contents were adjusted to form Mn3O4 and SiO2 slag. The use of these two welding consumables reduced the amount of slags, which improved the corrosion resistance. It is not the intent of this paper to compare the performance of these two experimental consumables, however.