Welding Digest

For construction contractors and steel erectors searching for ways to offset project slowdowns and labor challenges, paying attention to the following four tips on welding operations can help improve efficiency and performance on the jobsite.

Tip 1: Consider the Welding Process

Shielded metal arc welding (SMAW) is useful for many field applications, including handrail and stair installation as well as erection of open web steel joists, but switching to a self-shielded flux cored welding wire for projects requiring larger multipass welds offers several benefits.

• Higher deposition rates. Commonly used 1/8-in. 7018 SMAW electrodes typically yield deposition rates of 3 lb/hour or less. In contrast, a comparable all-position flux cored welding wire can double or even triple this production.
• Greater deposition efficiency. Deposition efficiency refers to the percentage of the electrode that actually makes it into the final weld. After every weld, the remaining electrode stub usually ends up on the ground or in the waste bucket, adding to consumable costs. Switching to a flux cored welding wire can deliver efficiency gains of 10% or more due to the increased ability to feed and deposit molten metal into the weld joint. Also, welders can start and stop at any time without consumable waste.

Tip 2: Choose the Right Welding Wire for the Job

When it comes to structural welding with a self-shielded flux cored welding wire, many contractors use what is known as a T-8 welding wire. T-8 is shorthand for E71T-8, the classification listed in AWS A5.20, Specification for Carbon Steel Electrodes for Flux Cored Arc Welding. T-8 welding wires are versatile and suitable for welding in all positions. They provide good impact toughness at low service temperatures and can be used for multipass welds of unlimited thickness. These welding wires operate using direct current electrode negative (DCEN) polarity.

While the appeal of using a single welding wire for an entire project is understandable, consider switching to a T-6 welding wire, which is classified as E70T-6 in AWS A5.20. Although its use is limited to the flat and horizontal positions, T-6 welding wires typically yield higher deposition rates than T-8 wires, improved operating characteristics, and ease of use at very high amperages. They also provide good penetration and typically produce good low-temperature impact toughness. Unlike T-8 welding wires, T-6 welding wires are designed for welding using direct current electrode positive (DCEP) polarity.

Many producers of T-8 and T-6 welding wires perform filler metal testing in accordance with the requirements of AWS D1.8, Structural Welding Code — Seismic Supplement, Annex A. These welding wires are informally known as seismic wires. By performing testing in accordance with AWS D1.8, Annex A, users of seismic self-shielded flux cored welding wires gain insight into the performance of the welding wire at different heat inputs.

T-11 (classified as E70T-11) welding wires, a popular choice for structural field welding prior to the introduction of T-6 and T-8 welding wires, don’t offer the same level of toughness as the seismic wires, which limits their ability to be used in these applications. They also have pass limitations per many fabrication codes. For this reason, they are generally not used for material thicknesses or weld sizes greater than ½ in. Still, they are a popular choice for ancillary connections on thinner material. They are also available in a much wider range of diameters and offer improved ease of use compared to T-8 welding wires.

Tip 3: Understand and Address Voltage Drop

A common hurdle with wire welding processes on the jobsite is the voltage drop that occurs in weld cables. Voltage drop takes place due to resistance in the current path, which is usually caused by the distance, configuration, and condition of the weld circuit through which the current must travel.

To minimize voltage drop, watch out for excessive lead lengths, leads that are in poor condition, improper cable gauge for the application, and any impedance to the current flow in the connections. Even small changes in voltage can cause a welding power source to significantly adjust amperage when using constant voltage (CV) wire welding processes. Another way to prevent voltage drop is to invest in technology that automatically adjusts for it. For example, cable length compensation (CLC™) technology on certain Miller Electric Mfg. LLC power sources automatically corrects the voltage by sensing then adjusting for the voltage drop.

Regardless of how problematic voltage drop may be or if a compensating technology is used, make sure weld leads are in good shape and fit for service. Be sure to regularly inspect and maintain welding cables. They should be taken out of service as necessary to avoid safety hazards.

Tip 4: Choose Solutions That Improve Jobsite Safety

A safer jobsite is more productive and profitable. Many equipment and technology choices play a role in jobsite safety. These options range from quieter engine drives to versatile helmets that provide coverage for both welding and grinding.

Look for welding solutions that help keep workers safer, more comfortable, and productive. This includes reducing operator fatigue and the risk of slip, trip, and fall injuries on the jobsite. For example, ArcReach® technology lets operators adjust parameters right where they’re working using the wire feeder or SMAW/gas tungsten arc welding (GTAW) remote, eliminating the need to walk back to the power source every time changes are needed.

This article was written by Aaron Moore, CWI (product manager) and Matt Goelzer, CWI (technical product specialist), both of Miller Electric Mfg. LLC, Appleton, Wis., for the American Welding Society.