Welding high-nickel alloys is a challenge for most fabricators. Here’s how one company tamed the beast.

by: Mike Sammons, product manager, Miller Electric Mfg. Co.

Major Tool & Machine smashed its rejection rate goal. By incorporating 48 Miller Electric Mfg. Co. power sources into its operation, Major Tool beat its 3% goal with a rejection rate of 1.8%. In May, that rate dropped further, to less than 1%. Incorporating welding equipment that uses the latest inverter technology not only helped improve quality, but it also enabled the company to accomplish jobs never before possible.

“We X-ray anywhere from 3,000 to 4,000 welds in a year. Quality is our top priority, and we need to make sure that the X-rays confirm weld quality,” says Matt Vislay, fabrication manager. “Our rejection rate was creeping up because of the age of the equipment. We noticed quite a bit of variation when going from one power source to another. This variation in performance was making it more difficult for our operators to maintain consistency.”

Major Tool & Machine, located in Indianapolis, demands quality and consistency as it fabricates, machines and assembles tooling, fixtures, component parts and assemblies for aerospace, defense, power generation and other industries. The company has more than 60 welders certified to a number of commercial, military and aerospace codes.

Metals welded include carbon steel, high-strength low-alloy steel (HSLA), heat-treatable low-alloy steel (HTLA), chrome-molybdenum steel, stainless steel (ferritic, austentitic, martensitic and precipitation hardened), high-nickel alloys, cobalt alloys and aluminum.

Established in 1946, Major Tool & Machine’s scope “ranges from components less than one cubic foot to 21x65x16 ft. We also have the ability to turnkey a project — supplying material, welding preparation, performing the fabrication work and the finished machining,” says Joel Manship, sales director.

“We’re known for being able to weld many diverse materials, but especially for the fabrication of high-nickel alloys. We’re one of the largest users of 617 Inconel in the country.”

Welding high-nickel parts often involves TIG welding the root pass and MIG welding the fill and finishing passes.

“Lack of flexibility was an issue with our old machines,” Vislay says. “We had machines that were designated for MIG and pulsed MIG, and we had machines that were designated for TIG and pulsed TIG. But we didn’t have any machines that could do both. It got to be very hectic when we had to pull two machines around the shop in order to complete a job.”

After evaluating products for their multiple process capabilities and state-of-the-art arc control capabilities, MTM chose 37 Phoenix 456P CC/CV power sources paired with 60M programmable feeders and 11 Dynasty 300 DX power sources (an AC/DC TIG inverters).

“The Phoenix is a perfect system for DC TIG, MIG and pulsed MIG welding, where some competitive machines are only good for pulsed MIG,” Vislay says. “It gives us the ability to use one machine instead of using two machines half of the time. It really comes down to doing smart business because we cut inventory in half.”

Mike Trosen, welding engineer, comments, “We really wanted the Dynasty to lend the flexibility with its AC capabilities for welding aluminum, its built-in pulsing controls and ability to store four welding programs. I’ve never seen that on a TIG machine prior to this. We also have some dedicated TIG applications and we didn’t want to tie up a Phoenix for those.”

Acquiring the Dynasty paid off immediately because it allowed Major Tool to tackle a tough job that its 10-year-old Syncrowave TIG welders couldn’t: welding 6061-T6 aluminum mountain bike frames for a major American bicycle manufacturer.

The tubes on the frames have wall thicknesses ranging from 0.060 to 0.125 in. The specification for the frame requires a 1/8 in. space between weld bead ripples controlled to within 0.040 in. Naturally, sharp stress risers, roll-overs (a cold lap where the bead flows out of the joint and lays on the base metal) and cracking are not permitted.

“What we’re able to do with the Dynasty is not only control AC balance, but AC frequency,” Trosen says. “Our guys are able to tune the Dynasty to their welding technique a lot easier than they could with our older machines.”

Using a 3/32 in. dia., 1.5% lanthenated tungsten ground to point, welding operators set the Dynasty’s frequency to 200 Hz, set the balance control at 70% penetration and manually pulse the welding arc with their foot pedal.

“The Dynasty technology gives them the control to maintain a balance between the bead width and penetration, and it permits using a pointed tungsten,” states Trosen. “It was impossible to make a bead that met the cosmetic requirements using conventional TIG technology.”

Conventional AC TIG welders have a fixed output of 60 Hz, but the output frequency on the Dynasty has a range of 20-250 Hz. Increasing frequency produces a tighter, more focused arc cone. This creates deeper penetration, narrows the weld bead and lets operators direct the arc precisely at the joint.

The Dynasty also provides extended balance control, allowing the operator to fine tune the duration of the EN portion of the cycle from 50 to 90%, where conventional TIG machines are limited to 68%. Greater amounts of EN create a deeper, narrower weld bead, better joint penetration and a smaller etched zone. This helps when appearance, such as a minimal etched zone, is important.

“The frame has a lot of tight curves and sharp angles. It’s a challenge to replicate your weld bead profile from joint to joint, but the Dynasty makes it a lot easier for me to make a good bead,” says Rick Weaver, one of eight welding operators fabricating bike frames. “The Dynasty has a more focused arc so I don’t have to fight the puddle. It solves puddle control problems.”

Even though he has six years of TIG welding experience, Weaver, like the other frame welders, went through training before welding on production frames.

“By welding test frames, operators can develop a technique that works for them,” Trosen says. “A lot of the technique is power source-dependent. Very few people pass on the first try and it usually takes two or three test frames before they develop a good technique.”

In addition to advanced AC welding capabilities, inverters like the Dynasty also produce a very stable DC output, especially at low amperages.

“High nickel metals like 617 Inconel are especially susceptible to crater cracking,” Vislay says. “More so if the operator cannot control the welding arc precisely at lower amperages. One thing we’ve found out about the Dynasty, as well as the Phoenix, is that their DC TIG arcs taper down so smoothly that crater cracking has been eliminated.”

One Inconel component benefiting from this level of control is the turbine hot-gas casing support ring produced for a major aerospace company. This weldment consists of 10 forged ring segments that need to be joined. After preparing the surface, the segments are set in a fixture, and the back side is purged with argon and the segments are welded. Each weld joint is X-rayed 100% to confirm weld quality.

When switching between components for the turbine hot gas casing, welder Doug Hobbs doesn’t need to reset his welding parameters. Instead, he presses one of the memory buttons and the machine automatically recalls his preferred welding parameters for that job.

Just as the machine’s advanced inverter capabilities help with AC and DC TIG welding projects, the Phoenix’s DC TIG and pulsed MIG capabilities provide Major Tool & Machine with capabilities they didn’t have before. This includes equally good DC TIG and MIG arcs, and when paired with the 60M feeder, advanced pulsed MIG capabilities.

“Everyone realizes that we needed new equipment to improve our capabilities. With our old equipment, the operators noticed quite a bit of variation when going from one machine to the next,” says Trosen. “With the new Phoenix units, the welders can set their parameters and expect the same performance as the machine 10 ft. away.”

Vislay attributes the reduction in weld rejection rates to the quality and consistency of the Phoenix’s welding output.

“We’ve only had the Phoenix units for a few months and we’ve already seen a drop-off in rejection rates,” he says. “As we further refine our welding programs and explore more of the 60M feeder’s capabilities — like SharpArc and its programmable memory — we look forward to continued declines in the rejection rate.”

Reprinted with permission from CANADIAN MACHINERY & METALWORKING, November 1999, Volume 93, Issue 9 Copyright 1999 by MacLean Hunter Publishing LTD. All rights reserved. For reorders call Repring Services at 1.800.217.7874. Printed in the USA