The Weld Clad Overlay process is not used for general-purpose parts jointing, let’s get that fact straight from the get-go. Like the term implies, overlay welding is intended to add layer “cladding.” Essentially, with a workpiece mounted on a turntable, a stationary arc welding torch deposits a protecting layer, which entirely coats a lesser material base. This metallurgically bonded plating then acts as a corrosion-inhibiting barrier. Less actual welding and more protective parts shielding, the process coating is designed to protect pipes, industry fittings, flanges, and valves from material-adverse environments.

Welding Dissimilar Alloys

Let’s put material fusing techniques out of mind, just for now at least. What’s taking place here is quite different. Rather than bonding two separate but material-similar metal faces together, this welding procedure binds dissimilar metals. Just for the purposes of this example, the imagined part resolves as a large pipe. It’s maybe a metre in diameter, and it’s made of a cost-effective alloy. The lower cost steel will work well as a material base in a hundred-kilometre pipeline. Only, there’s a problem. The pipe metal will oxidize. To the rescue, a machine-operated Weld OverLay (WOL) rig starts to apply a coating of Inconel or stainless steel. Bonded to the base metal, while the pipe section rotates on the equipment turntable, the new surface skin applies as an anti-corrosion envelope.

Weld Clad Overlay Benefits

It’s not exactly difficult to pick out the advantages. A whole pipeline could be built out of Hastelloy, out of tungsten and molybdenum pipe sections, but imagine the exorbitant costs as each solid superalloy section extended a terrain-crossing pipeline. Instead of making an entire pipeline out of those superior but expensive alloys, they’re laid down as a metal-bonded substrate. That fused coating protects pipelines. Ultimately, it’s almost as if the entire line were actually made out of that protective surface cladding, as established by the weld overlay equipment. Again, the process is not restricted to pipeline applications. Valves or fittings, vessel shells or flanges, the rust-resistant plating forms as that remarkably tough surface overlay.

During the process, if a base alloy is rust prone, it’s hoisted onto a turntable and rotated until the stationary welding torch has done its job. Taken off the rig, the cladding is ready to perform like a superalloy. To all intents and purposes, it is an oxidation resilient workpiece. Only, the underlying parent metal is actually a regular alloy, so those normally expensive surface properties don’t exact superalloy costs. That’s clearly a compelling process feature, one that makes Automated Weld Clad Overlay technology an attractive industry option.

Tandem-mag welding (also known as twin-wire welding) uses two different wires to flash-create weld joints. Also of note, Tandem-Mag technology is an active gas technique. Instead of a MIG (Metal Inert Gas) shield, a MAG (Metal Active Gas) shield cloud mixes argon, carbon dioxide and oxygen into a steel-specific welding gas. Back to the “tandem” label, why is the welding torch utilizing a doubled-up wire feed system?

Approaching Double-Wire Welding

As automated rigs speed up, probably because of the need for high-productivity manufacturing environments, contemporary GMAW technology is struggling to keep up. A single wire system can just about manage, but that ability is about to hit a wall. To leapfrog that barrier, Tandem-Mag welding delivers a speedier edge. Now, with this tech firmly in place at the end of an automated machine’s arm, the necessary spot welds can be applied in a fraction of a time it once took to do the job. It’s just basic arithmetic, the knowledge that all of these swiftly applied welds equals a faster production run. In many industrial sectors, especially automobile assembly work, such production-accelerated work speeds are indispensable.

Breaking Down Tandem Welding Technology

Basically, the process gets as much weld material onto the joint surfaces in as possible. And it happens fast. That feature benefits robot-operated manufacturing lines. The speedier weld deposition uses a two-wire feed system and a dedicated weld gun type. Additionally, inside the welding equipment, high-powered power sources employ advanced inverter circuits and waveform control tech to manage the weld deposit rate of the twin wire lines. Ultimately, although the two different weld wires work independently, and they’re insulated from one another, they’re pulsed so that they don’t create magnetic interactions.

Employs Metal Active Welding Shielding

If there are two lines of wire and pulse-controlled electrical currents running through the gear, why has the shield gas changed? To be sure, an inert gas is favoured in other applications, but Tandem-MAG Welding gear is mostly used to join carbon steel parts. Engineers, knowing carbon is the alloying element here, opt for an active gas. They call upon carbon dioxide and argon, plus a little oxygen, as the active components. It’s this active gas that works with the alloy steel to encourage arc stability, splatter control and metal transference. Again, the automotive sector has the most to gain, for automated welding robots have access to this purpose-provided cloud of carbon-heavy shield gas.

This is probably one of the finest examples of the old “right tool for the right job” adage. Not only do the dual wires and pulsed power supplies maximize weld joint integrity over a reduced time frame, but the active shield gas also provides a deliberate, environment-specific edge, with the carbon adding control to the steel whetted welding surfaces.