To meet diverse customer demands, a growing number of manufacturers are now implementing the robotic welding of aluminum
parts via the gas metal arc welding (GMAW) process. Especially true for truck and trailer fabrication, the use of this lighter weight substrate offers several benefits, including:
— Meets Most Strength Needs
One-third the weight of steel – with a tensile strength up to 90 ksi – aluminum meets most strength needs for automotive, structural, container, aerospace, and even sporting equipment applications. The number of alloys available add to the material possibilities from extrusions to castings. This makes it ideal for automotive manufacturers looking to construct light weight vehicles for improved fuel economy, for example.
— Considerably Cheaper than Many Material Alternatives
Aluminum is considerably cheaper than many of its lightweighting material counterparts, such as carbon fiber which is 1,000% more expensive. While aluminum is still 20-30% more costly than steel, it is still very attractive to manufacturers looking to create long-term cost-savings with light weight products. Process cycle times are also the same as steel—both of which are much faster than composites such as carbon fiber.
— High Solidification Rate
Aluminum has a high solidification rate, allowing for faster weld speeds over steel, helping to optimize production throughput. It is also very workable like steel, and nonmagnetic for widespread potential use.
While plentiful in the earth, the use of aluminum has not always been widespread. In recent history, more affordable methods for the extraction and refinement of the element have made it more cost effective to attain and use. Moreover, when utilized with robotic automation and the right combination of consumables, aluminum is ideal for a variety of applications.
Do’s for Welding with Aluminum
However, users be aware! Aluminum is slightly more difficult to weld because of its high thermal conductivity and requires a much higher heat input, leaving less room for error. For this reason and others, it is important to use proven practices to achieve high-quality welds.
— Use Clean Material
As with any robotic welding process, it is important to make sure the aluminum is clean and free from any excessive oxides. While aluminum oxide does not become detrimental to welding quality like rust does to steel, it is always important to have the cleanest metal possible. A failure to do this may result in soot and porosity. To clean material, stainless steel brushes should be used and kept separate from other tools that would typically be used for welding with steel.
— Use Spray or Pulse Spray Arc Transfer
There are three basic types of transfer: Short Arc, Spray and Pulse Spray. Unlike the Short Arc method, Spray and Pulse Spray are well-suited for welding with aluminum. Spray arc transfer is ideal for high heat input on thicker materials, providing deeper penetration with low spatter for a smooth weld bead. Pulse Spray, on the other hand, is best used for lower heat input on out-of-position welding, creating less distortion and low-to-no spatter.
— Use U-Type Wire Feeder and Low Friction Liners
Aluminum weld wire is softer than steel and is prone to “bird nesting” or jamming, resulting in downtime and wire deformities that can cause “burnback”. For this reason, extra attention should be given to the feed system and the liners used. Using a U-Type wire feeder will help prevent weld defects, and low friction liners (i.e., made of PTFE) and those with a series of ball-bearing rollers can improve feeding issues. Note: these components should be inspected and changed, as necessary, to keep free of contaminants.
— Use Argon Shielding Gas
When welding with aluminum, the use of shield gas provides several things: 1) a plasma for commutation of the current, 2) protection for the weld pool from reacting with the surrounding air environment, and 3) cleaning action that partially removes the aluminum oxide from the base metal. Often more cost-effective and user-friendly than helium, argon shield gas can help achieve peak arc initiation and stability. Porosity is also reduced.
Other Considerations for Welding with Aluminum
Ignoring the unique properties of aluminum and its subsequent process considerations during the GMAW process could lead to multiple issues, such as porosity, weld cracking, incomplete penetration and incomplete fusion. To learn more about how to avoid these pitfalls, listen to our Aluminum Welding Processes
webinar. The use of different alloys will also be discussed, along with other helpful tips to achieve the perfect weld.
Josh Leath is a Product Manager