Gas Metal Arc Welding (GMAW) Advancements in the welding of Hot Galvanized Steel

Over the past few decades the automotive structures industry has been facing tough scrutiny from many sources. They have to build a car that satisfies established safety criteria, endurance demands, and while doing both must become lighter for greater fuel efficiency. Aluminum would seem the logical choice but adds cost to the vehicle. Fortunately steel technology has also advanced giving us weight advantages by making lighter gauge steels designed to toughen during work hardening or heat treatment. Unfortunately, the development of any corrosion has a negative impact on these light gauge steels affecting the durability and corrosion resistance, therefore the application of a zinc coating ensures the components always maintain their integrity.

Welding Hot Dipped Galvanized Steel (HDGS) has always been a challenge. Zinc is considered to be a contaminant given its tendency to create both internal and/or external porosity. Using current industry standard GMAW travel speeds for uncoated steel the resulting level of porosity attained would be considered a defect under any automotive standard. In many cases we can achieve very good quality welds if we reduce the travel speeds.

Omniweld is the Welding Engineering division of Air Liquide Canada. In the summer of 2012 Omniweld was requested to assist a large Automotive Tier 1 company in the development and implementation of a competitive wire feed process. Omniweld and Air Liquide Canada felt the project was important enough to the industry and took responsibility for the project. The resulting project involved the testing and development of travel speed, pulse and shielding gas mixtures. We intend to present our testing process from hypotheses to the conclusion of Project 8 which defined a travel speed, gas mix, and pulse program resulting in reduced porosity levels in the welding of HDGS.