Peninsula Metal Fabrication uses sub-harmonic stress-relieving equipment to improve welds.

Peninsula Metal Fabrication in San Jose, Calif., was preparing a quote for new business when it realized that the request for proposal stipulated that vibratory stress relief was to be applied during the welding process. Peninsula did not have that capability. On occasion, the fabricator of large welded frames and chassis sent completed parts to be heat treated, but post-weld heat treating was not what the potential customer had in mind. Luckily, Peninsula had attended a recent trade show and knew what it needed.

Peninsula has prided itself on embracing advances in technology since it started business in 1973. The company uses a variety of manufacturing technologies, including robotic welding, because the capabilities the technologies support provide flexibility and adaptability — hallmarks of a competitive company.

To be eligible to respond with a quote to the latest new business that was available, Peninsula purchased a Pulse Puddle Arc Welding unit from Bonal Technologies Inc. (www.bonal.com).

Peninsula is a large frame manufacturer and uses stainless steel for the bulk of its work. Paul Eischens, weld manager of Peninsula, says the company tends to see a lot of distortion and issues with squareness, and hoped that the new machine would help with distortion control. "Once we had established the parameters, we found that not only did we get less distortion, we also got better penetration. Using the Pulse Puddle machine helped us to speed up production time and cut down on our setup time," Eischens says.

The Pulse Puddle machine creates a pulsating weld puddle as the metal is deposited. Pulsating the weld puddle creates a finer weld grain structure and a more homogeneous mix with fewer columnar structures. Fewer columnar structures improve the weld metal's mechanical properties by making metal more ductile while increasing its impact strength. The result is improved resistance to cracking.

Peninsula has been using the technology for six months now, and Jim Scocca, the plant manager for Peninsula, says it has made the company more competitive. "We have less straightening to do on the product since we implemented the (Bonal) systems," Scocca says, adding that using the technology has reduced labor input, and that Peninsula has purchased units for six weld benches. "We also know that the weld quality is better when we use it due to better weld penetration with less effort," he says.

Peninsula also is planning to retrofit its robotic welder with the Pulse Puddle technology, Scocca says.

The technology uses Bonal's Meta-Lax (metal relaxation) process that it developed and patented with the help of a grant from the U.S. Department of Energy's Inventions and Innovation Program. The sub-harmonic technology later was applied to arc welding. Instead of pulsing the current as some welding processes do, Bonal's technology uses a device to pulse the base metal as the weld metal is deposited. The energy is transferred from the base metal to the weld puddle.

The company says tests have shown standard welds on 1-in. thick, A36 steel test plates have a weld joint strength of 45,800 p.s.i .(310 multiple pulse width acquisition) using stick welding. By comparison, Bonal says a 1989 study performed by the U.S. Department of Energy shows weld joints on the same material with the same welding process have a strength of 86,000 p.s.i. (596 MPa) when its Pulse Puddle sub-harmonic technology was used during the welding process.