How to Overcome Feedability Issues in Steel to Aluminum

Feedability in GMAW Welding of Aluminum: Exploring the Issues and Solutions

QUESTION: I have recently moved from the gas metal arc welding of steel to welding aluminum with the same process. I find it very difficult to feed the aluminum wire through my feeding system. I am often experiencing equipment problems such as the fusion of the aluminum welding wire to my contact tip, which requires the breakdown of the feeding system and replacement of the contact tip. These problems are time-consuming and costly. Is there any way I can improve this situation? I am using ER4043 filler alloy of .035-inch diameter.

Feedability is probably the most common problem experienced when moving from GMAW welding of steel to GMAW welding of aluminum. Feedability, in this instance, can be described as the ability to consistently feed the spooled welding wire in GMAW welding, without interruption, during the welding process.

Feedability in Steel Vs Aluminum

Feedability is a far more significant issue with aluminum than steel. This is primarily due to the difference between the material’s mechanical properties. Steel welding wire is rigged, can be fed more easily over a greater distance, and can withstand far more mechanical abuse when compared to aluminum. Aluminum is softer, more susceptible to being deformed or shaved during the feeding operation, and consequently requires far more attention when selecting and setting up a feeding system for GMAW welding.

Exploring Feeding System and its Effect on Aluminum Welding Wire

Feedability problems can be increased when using the smaller diameter wires and the softer aluminum alloys such as the 1100 and 4043 over the harder alloys such as 5356. Feedability problems often express themselves as irregular wire feed or as burn-backs (the fusion of the welding wire to the inside of the contact tip). To prevent excessive problems with feedability of this nature, it is important to understand the entire feeding system and its effect on aluminum welding wire.
 
         
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Applying the Right Brake Pressure: Improved Stability

If we start with the spool end of the feeding system, we must first consider the brake settings. Brake setting tension is required to be backed off to a minimum. Only sufficient brake pressure to prevent the spool from free-wheeling is required when stopping welding, Any pressure over and above this will increase the potential for feeding problems and burn-backs. Electronic braking systems and electronic and mechanical combinations have been developed to provide more sensitivity within the braking system and are particularly useful for improved feeding of aluminum wire.

Non-abrasive Materials for Inet and Outlet Guide

Inlet and outlet guides, as well as liners, which are typically made from metallic material for steel welding, must be made from a non-metallic material such as Teflon or nylon to prevent abrasion and shaving of the aluminum wire. Drive rolls designed specifically for feeding aluminum should be used. These often have U-type contours with edges that are chamfered and not sharp. They should be smooth, and aligned, and provide correct drive roll pressure. Drive rolls that have sharp edges can shave the soft aluminum wire. These shavings can collect within the feeding system and cause burn-backs from blockages within the liner. Excessive drive roll pressure and/or drive roll misalignment can deform the aluminum wire and increase friction drag through the liner and contact tip.

High-Quality Contact Tip Utilization

Contact tip I.D. and quality are of great importance. You should only use contact tips which are made specifically for aluminum wire welding, with smooth internal bores and the absence of sharp burrs on the inlet and outlet ends of the tips which can easily shave the softer aluminum alloys. The contact tip bore diameter should be approximately 10% to 15% larger than the electrode diameter.

Consider High-Quality Welding Wire

The quality of the welding wire used for GMAW welding can influence the feedability characteristics. Such things as surface smoothness, wire diameter control, and final treatment of the wire during the spooling operation can assist or detract from the ability to easily deliver the wire through the feeding system. The consistent quality characteristics of the aluminum welding wire should be considered to minimize feedability problems.

Select the Most Suitable Feeding System

In terms of aluminum wire feeding, four recognized feeding systems are used: push feeders, pull feeders, push-pull feeders, and spool-on-gun feeding systems. For aluminum welding, the push and pull feeders have limitations dependent on the application and feeding distance. These systems are generally limited to a practical length of about 12 feet. 

• Push feeders

With the push feeders, the feeding distance limit is a result of the flexibility of the aluminum wire and its tendency to buckle and bend in the liner, and with the pull feeders from a rapid increase in friction drag in the liner, particularly if there are bends in the conduit. 

• Push-pull feeders 

Push-pull feeders were developed to overcome the wire feeding problems experienced by the other systems and are the most positive method of feeding aluminum welding wire. The push-pull systems can improve feedability in many applications and are often essential for more critical/specialized operations such as robotic and automated applications to ensure consistent feedability. 

• Spool-on-gun feeding systems 

The spool-on-gun feeding system is usually designed to use a 1-lb spool wire that is mounted in the gun. These spool guns are air-cooled and generally limited to smaller wire sizes and light-duty service. Because of their relatively low current rating, they are not perfectly suited to heavy-duty continuous production welding but they are often quite effective for tack welding and other light-duty applications.

Conclusion

The choice of the most suitable feeding system for each application is based on such factors as the type of welding (light or heavy duty), the electrode size and alloy (large or small diameter / hard or soft filler alloy), the need for a long flexible conduit, and the importance of minimizing electrode cost (larger diameter wire is generally lower priced than smaller diameter). The demands of welding applications vary extensively, and the cost of each feeding system also varies. The cost of downtime from feeding problems and replacement parts can also be significant. For these reasons, you should choose the feeding system that is best suited to your application and set it up to optimize its feeding capability.