Developers of a new commercial hybrid technology say it could double the speed of some of the most common industrial welding systems, even while it produces deeper welds and reduces splatter and heat distortion. Developed by former researchers from Ukraine's Paton Welding Institute, the technology is called Super-MIG and marries two welding technologies: plasma arc and metal inert gas, generally known as MIG, a variant of gas metal arc welding.

Super-MIG was designed to work with such available MIG welding systems as Lincoln, Miller, Panasonic, OCT, and ESAB. "If you already have a standard robotic welding cell, for approximately $50,000 you could add the system and run most operations nearly twice as fast," according to Ray Davis, sales and marketing manager of Welding Solutions Inc., the technology's North American sales agent.

This hybrid welding robot combines a conventional metal inert gas head with a plasma arc welder.

Super-MIG speeds welding because plasma and MIG share the load. MIG is often called "short circuit welding" because the weld wire and the workpiece carry opposite charges. When they touch, the weld wire expels metal from the workpiece. This carves a crater, which fills with molten metal and melted weld wire that cool to form the weld.

"A single weld wire has a lot of functions," Davis said. "We take away half that work by using plasma." Plasma is exceptionally good at making deep cuts into metal. Super-MIG aims its plasma ahead of the MIG welder. Like a plow, the plasma slices through the workpiece, creating a deep crater and a pool of molten metal before the MIG head gets there.

The MIG head then slices into the workpiece through the bottom of this "keyhole," penetrating three to four times deeper than MIG alone. "We've been successful welding 12-13 millimeters into steel," Davis said. "Standard MIG can do that, but you have to really slow the process down."

According to Davis, the process is very good for heavy structural welds, the types used in beams, heavy truck suspensions and frames, tube-to-tube welding, boilers, and heavy axle components.

Super-MIG has also produced true overlapping welds. They bond two or three pieces of flat steel plate to one another by welding together their centers. "Other systems say they can do it, but they'll put a slot or hole or some sort of joint preparation in the part and weld through that. We go right through the center without it. The only other systems that can do this are lasers," Davis said.

Lasers, however, cost upward of $1 million for starter systems, and require highly skilled operators and expensive consumables like optics. Super-MIG, Davis said, is for companies that may not need or cannot afford a laser, but want to run at faster speeds.

To introduce a new type of composite based on nanocrystalline metal cladding over a plastic core, DuPont Co. is partnering with Toronto-based Integran Technologies Inc. Potential uses range from under-hood and powertrain automotive parts to sporting goods.

According to Integran's president, Gino Palumbo, the composite combines the best properties of polymers and metals. Polymers are lightweight and easy to mold into intricate shapes that can consolidate a complex metal assembly into a single component. However, all but the most advanced and expensive polymers are prone to break down under abrasion and high temperatures. Metals, on the other hand, can be strong, hard, and heat-resistant, but also heavy and relatively hard to form into complex shapes.

MetaFuse composites combine the formability and light weight of plastics with the hardness and thermal conductivity of their nanocrystalline metal coating.

The new MetaFuse hybrids are billed as combining the strengths of metals and plastics while minimizing their weaknesses. Engineers can mold plastics into intricate, lightweight shapes. Coating them with nanocrystalline metals makes them much harder. It also boosts thermal conductivity, enabling MetaFuse parts to transport heat away from the plastic core and to extend their heat range.

Certainly, many companies have coated plastics with metal before. According to Palumbo, what makes MetaFuse different is the nanoscale nature of the coatings. Metals are made up of tiny crystalline grains. They deform (bend or break) when forces collide at weak points where the crystals are not aligned. These dislocations then move through the metal like a ripple running along the length of a carpet.

"You can push a ripple along a carpet more easily than lifting the entire carpet and moving it," Palumbo said.

The smaller size of nanocrystals gives dislocations less room to move. "The strength goes up by a factor of five," he said. Hardness also increases. According to Palumbo, the nanometals deliver these properties without the usual sacrifice of ductility. As a result, a thin nanometal coating can provide a surprising boost in properties.

Integran's first use of the technology came when it was a research group within the Canadian utility company Hydro Ottawa. It needed to resurface the interior of the water tubes running through its nuclear reactor without pulling them out.

"Using a conventional sleeve would have affected flow," Palumbo said. "Our nanocoating let us do the repair with one-quarter to one-fifth the amount of material. Those tubes have been in service for 15 years without a problem."

Palumbo expects his collaboration with DuPont to lead to many more applications in the near future. One of the most promising is automotive injector rails, which deliver pressurized fuel to the fuel injector. Affordable polymers cannot take the heat, and gasoline tends to permeate through them. MetaFuse's metal cladding dissipates heat before it weakens the polymer core and also prevents permeation.

Metal also could harden glass-filled nylon, making it competitive in powertrain components as well as in wheel hubs and door handles subject to stone chip damage and abrasion. DuPont and Integran are also working on sporting goods, such as bicycles and ski equipment, and on other consumer products.

The process itself doesn't use nanoparticles, obviating the potential health questions they raise. Instead, Integran deposits the coating from a solution at rates of 0.004 inch an hour. That sounds slow, but many applications require only 0.001 inch of coating (although others may use 0.03-0.04 inch or more). Still, as Palumbo notes, he can coat thousands of components in a single batch run.

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