Implementing pulsed GMAW

Understand how it works and its associated filler metals

For many manufacturers, a switch from CV GMAW to pulsed GMAW with solid or metal-cored wire can deliver lower heat input, reduced spatter and cleanup, greater productivity, and decreased training time.

For manufacturers looking to make improvements in their welding operations — whether it’s reducing spatter and cleanup, decreasing the time spent on rework, or fixing bead profile issues — pulsed gas metal arc welding (GMAW) can deliver results. It offers the opportunity to introduce benefits that help save time and money and increase productivity.

To ensure success in implementing the process, it’s important to understand how pulsed GMAW works and how to determine what filler metal is the best choice for a specific application.

Pulsed GMAW: How It Works and the Benefits

The pulsed spray transfer mode is a modified spray transfer process. The welding power source rapidly switches the welding output between a high peak current and low background current. The peak current pinches off a spray transfer droplet and propels it toward the weldment, which helps create proper fusion. The background current maintains the arc but is too low for metal transfer to occur.

Because the weld pool gets to cool slightly during the background cycle, it allows for welding in all positions on thin or thick metals.

With pulsed GMAW, operators can run faster wire speeds while keeping a clean arc and bead profile. This reduces spatter, along with the time and money for cleanup.

The ability to run faster wire feed speeds also increases travel speeds — one of the main drivers of heat input. When travel speed increases, heat input decreases, allowing pulsed GMAW to reduce distortion and burn-through.

And because pulsed GMAW is generally an easy process to learn and use, it can help operations train new welders faster. Pulsed GMAW systems are designed with synergic control to help ensure that welders of all skill levels are using the right parameters for the job.

These features help decrease the time and money spent on non-value-added activities — those activities that don’t directly contribute to throughput in a welding operation. These include grinding, cleaning spatter, and completing rework. Minimizing these activities helps operations improve productivity and reduce costs.

When to Consider Pulsed Welding

Because of the benefits of the process, many industries — from automotive to heavy equipment manufacturing and general fabrication — have made the move to pulsed GMAW.

Because of the benefits of the process, many industries — from automotive to heavy equipment manufacturing and general fabrication — have made the move to pulsed GMAW. Its growing use is also helped in part by the fact that many industrial welding systems now have pulsing capabilities.

Operations that are now using CV GMAW with solid wire or metal-cored wire are good candidates for conversion to pulsed GMAW. This is especially true if the operation frequently deals with these common challenges:

  • Excessive time and money spent on rework or spatter removal
  • Trouble finding skilled welders or a lot of time spent training new welders
  • Frequent distortion or burn-through in parts caused by high heat input
  • Problems with poor fit-up that result in larger gaps to fill

Pulsed GMAW is typically very productive in the flat and horizontal positions.

Applications that aren’t as suited to pulsed GMAW include those in which larger wire diameters (over 1/16 in.) are used. In those applications, operations are likely looking for very high deposition rates and probably aren’t concerned with reducing heat input, or they are welding thicker materials that require high heat input for proper weld penetration and quality.

Because welding equipment must have the capability for pulsed GMAW, a switch to this process may also involve an investment in new equipment. Operations may also need different shielding gases with a switch to pulsed GMAW, since the process uses a gas with higher argon content.

Filler Metals for Pulsed GMAW

Pulsed GMAW can be used on mild steel alloys and aluminum, and the process can be used with solid wires or metal-cored wires. Flux-cored wire is not recommended for the process.

Most of the pulsed GMAW applications that can be used with solid wire can also be completed with metal-cored wire. Both filler metals will provide similar reductions in heat input, spatter, and cleanup time. Metal-cored wire can potentially provide greater productivity benefits than solid wire in some pulsed applications.

• Solid wire

Solid wire is often the first choice many manufacturing operations make when they switch from CV MIG to pulsed GMAW. Common choices for the process are 0.035-, 0.045-, and 0.052-in.-diameter wires bearing either the American Welding Society (AWS) ER70S-3 or ER70S-6 classification.

• Metal-cored wire

In general, metal-cored wire can run faster than solid wire, delivering higher deposition rates, faster travel speeds, and lower heat input. Metal-cored wire also provides good gap-filling potential if an operation has issues with fit-up. Common metal-cored wires have an AWS E70C-6M classification.

It is important to note that using metal-cored wire with pulsed GMAW can result in reduced contact tip life. Solid wire is copper-coated, providing a more consistent current-carrying surface. Metal-cored wire isn’t as conductive from a surface standpoint, which can result in more mechanical wear.

The proper technique for solid wire and metal-cored wire in pulsed GMAW applications is similar. It’s recommended to use a 10- to 15-degree push angle with the welding gun, and the operator doesn’t typically need to use a lot of torch manipulation.

Choosing Between Solid and Metal-cored Wire

When choosing between solid and metal-cored wire, manufacturers should keep in mind that solid wire is typically better-suited for performing a lot of short welds with frequent stops and starts, while metal-cored wire is a good option that delivers productivity benefits for completing longer welds.

The condition of the base metal is also an important factor to consider. If the base material often has mill scale, dirt, or other impurities on its surface, the formulation of metal-cored wires has the ability to burn through the mill scale or surface rust better than solid wire. The tubular metal-cored wires are filled with metallic powders and small amounts of arc stabilizers that can produce quality welds even in poor material conditions.

Metal-cored wire might not be suitable for welding very thin material.

Advantages of Pulsed GMAW

While pulsed GMAW is typically an easy process to learn and use, it’s crucial that welders understand and are comfortable with the process before implementing it in production. A knowledgeable welding distributor or welding equipment manufacturer can offer assistance in evaluating and implementing a welding process change. For many manufacturers, a switch from CV GMAW to pulsed GMAW with solid or metal-cored wire can deliver lower heat input, reduced spatter and cleanup, greater productivity, and decreased training time. With these common benefits, it’s easy to see why more manufacturers continue to make the move to pulsed GMAW.

Caleb Haven is director, throughput matters, at Hobart Brothers, 101 Trade Square E., Troy, Ohio 45373, 888-489-9353, caleb.haven@hobartbrothers.com, hobartbrothers.com.