Submerged arc welding is nearly a fully automated process.

“The operator isn't handling the equipment, but pushing a button. It can be done robotically, but people generally don't because most submerged arc welding is done in a straight line, whereas robots are better for complex shapes,” Mike Flagg, manager of the applications engineering department for the Lincoln Electric Company (www.lincolnelectic.com), said.

Some companies automate the process with a set of rollers, or they might place the arc and welding head on a beam that moves along the seam.

Putting robotics on submerged arc welding applications is challenging, Chuck Boyer, marketing coordinator for Wolf Robotics Inc. (www.wolfrobotics.com), acknowledged, but he said, his company does that for some applications.

“You're very limited as to what you can automate because of the flux — you have to be operating in flat and horizontal positions so the flux stays where it needs to stay,” Boyer said. Wolf Robotics has integrated the robotic process successfully with submerged arc welding equipment from several manufacturers, including Miller Electric, ESAB and Lincoln Electric.

The submerged arc welding process can provide higher deposition rates and faster travel speeds, and the process is known to produce a very smooth bead with good penetration and excellent fusion. And as with other welding processes, it lends itself to creative applications.

One application that Wolf Robotics worked on was to develop a system that puts a bead on large pipes and tubes used in sewer lines.

“The customer had all different sizes of tubes, and wanted a large bead on the end of each tube so that, when they shove the tubes together, it would lock the tubes in place,” Boyer said. The previous method of joining the pipes — cementing the ends together — gave Wolf Robotics' customer no way to hold them in place.

“A bead all the way around the end of each pipe locks the pipes together, and is working out well. This turned out to be a perfect application,” Boyer said.

The advantages of robotic submerged arc welding include less operator involvement in the actual welding process, the elimination of constant operator supervision because the robot can be programmed to control the welding process and to make the necessary adjustments as the weld is made.

Wolf Robotics uses technology it calls “Smartac” to search the seam and to ensure an accurate weld path. That is especially important in multi-pass applications. The Smartac system includes a flux recovery vacuum system that is designed to reduce consumables by recycling the flux.

In addition to the technology that helps to reduce the need for labor, robotic systems can be built with multiple weld stations to increase productivity and arc-on time.

Submerged arc welding equipment used to be available either as DC or AC units, which limited their versatility and application, but new machines are being equipped as both, Lincoln Electric's Flagg said.

“The old AC welding machines were only single phase, but the new ones are all 3 phase, which saves energy, and since it only draws a third of the amps, you can use copper wiring and installation costs are less than old machines,” Flagg said. An example of how far the technology has come is Lincoln Electric's Power Wave AC/DC 1000, made specifically for AC/DC submerged arc welding. It is designed as part of a modular welding system for single-arc or multiple-arc applications, and is targeted at submerged arc customers that need higher productivity, lower operating costs, greater production flexibility and high quality.

The machine is rated at 1,000 amps for AC or DC.

Each welding arc can be driven by a single machine or by a number of machines in parallel. For example, two machines can be used to produce as much as 2,000 amps at 100 percent duty cycle. At the same time, each Power Wave 1000 achieves 95 percent power with 86 percent efficiency for lower operating costs.

The Power Wave AC/DC 1000 produces a variable AC output, as well as straight DC+ or DC- output, and does not require changes to its hardware configuration to change the cycles. The changes are driven by advanced software, and are designed to permit complex welding performance in multi-arc applications similar to the high quality welding that is done in pipe mills and that is required for pressure vessel applications or structural steel fabrication.