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76th PMXG Welding Shops are forging strong bonds

  • Published
  • By Kimberly Woodruff
  • Staff Writer
TINKER AIR FORCE BASE, Okla. --  If you walk into the welding shop in Bldg. 3001 expecting to see a light show, you'll leave greatly disappointed.

However, if you can look past the lack of a spark and see the vital work being done, you'll leave with a new appreciation for the welders.

Unlike the welding with bright sparks flying everywhere, the shops of the 76th Propulsion Maintenance Group use primarily manual gas tungsten arc welding (GTAW) or Heliarc welding, now called tungsten inert gas, or TIG for short.

"We do aerospace welding," said Lester Walker, a member of the 548th Propulsion Maintenance Squadron and an observing official with the welding shop. "So if we have sparks, then we have a problem."

Welding supervisor Kelly Wright said many of the component repair operations are on critical areas of the parts that have an effect on the oil supply or the fuel combustion functions on the engine.

The 76th PMXG works on many components of the TF33, F110-100/129, F118, F101 and F108 engines. The 548th PMXS shops work primarily on the F110-100/129 front frame, TF33 intermediate compressor and diffuser cases, F101 fan frame and the combustion assemblies for the TF33 and F108 engines. 

The metals used at Tinker include titanium, stainless steel, aluminum, magnesium, inconel and cobalt.  "If someone came in and had not worked for the government, they probably have never welded these materials before," said Mr. Walker.

Mr. Wright said when the welding shop receives a new batch of welding rods it is sent for testing at Tinker. The 76th MXDTAA-Analytical Chemistry Lab test each sample submitted to make sure it is the correct alloy as labeled.

"We don't want to weld with the wrong alloy," he said. "That could be catastrophic to the aircraft. We are the best in the world at what we do."

Tinker has 40 welders working in the 76th PMXG and the 548th PMXS shops. Before any of them start welding aircraft components, they must first be certified, which can be accomplished right here on base. In fact, Tinker is the only Air Force facility where welders can receive both their certification and training, according to Mr. Walker.

He said Air Force members, both active duty members and reservists, come here for additional hands-on training after they finish technical school.

Certification is required every three years. Mr. Walker is the lead observing official and weld certification training leader in the 76th PMXG, responsible for overseeing the training and re-certification of all welders in 76th PMXG. OC-ALC/OBTP's certified welding inspectors, or CWIs make the final call to determine if a welder's certification samples meet all required standards through metallurgy testing before the welder can be certified to weld on production components.  The TIG welding certification is one of the toughest a welder can achieve.

TIG welding is a manual welding process that requires the use of both hands to weld. One hand is used for holding the TIG torch that produces the arc and the other hand is to add the filler metal to the weld joint. Because two hands are required to weld, TIG welding is the most difficult of the processes to learn, but is the most versatile when it comes to different metals. 

TIG welding is mostly used for critical weld joints, welding metals other than common steel, and where precise, small welds are needed.

For even more precise welds, the shop has 10 automated welding machines. Tinker does the only automated welding in the Air Force, according to Mr. Wright. The automated gas tungsten arc welding is performed on computer-controlled machines that can hold tolerances within one thousandth of an inch and repeatability not obtainable by manual welding. The automated machines are still operated by a person, but the machine can be programmed to do a particular weld over again many times.

"We can run the same part for years after programming it in, and it will make the same weld over and over -- it's highly repeatable." said Mr.Wright.

"We do all our own programming, making us unique since we do both the welding and the programming at Tinker," said Mr. Deral Hunter, automated welder.

The 548th PMXS recently installed a new Liburdi Laws 5000 automated welding machine. This machine has upgraded software and HD video system that give us the ability to perform welds that will be blind to the operator, said Jason Mercer, automated welding work leader.

The new machine will also absorb some of the workload of the existing Liburdi Laws 5000, which according to the manufacturer "has more hours of run time than any machine they have manufactured," said Mr. Wright. 

The 548th also uses other welding and brazing technology such as automated gas tungsten arc welding and induction brazing for component repairs.

The induction brazing process uses electromagnetic induction to create heat in an object. This heat, which is created without anything physically touching the component, can be applied rapidly and is very repeatable and controllable.

"We use induction heating for high temperature brazing of gold/nickel alloy for oil system tubes for many of the engines we repair," said Mr. Wright.  "We also use induction heating for local stress relief after welding for components that cannot be put in a furnace for a heat treat cycle."  

Darren Raines, a braze welder with the 548th PMXS, explained that Tinker is the only base that uses the induction brazing machine. Brazing and de-brazing is accomplished using an induction coil that applies consistent heat up to 2,700 degrees around the complete circumference of the joint assemble to be brazed or de-brazed.

The 548th PMXS produces joints of high strength that will withstand the high temperatures of the turbine section of the engine using a gold/nickel alloy that bonds at 1,800 degrees.

"The gold/nickel braze joint is the strongest braze joint you can make," aid Mr. Raines. "The advantage of the induction brazing process is that it takes just seconds to reach that temperature."

"Everyone in our welding organization knows that we must perform our task to the highest standards because a failure of one of our welds or braze joints could mean the catastrophic loss of life or of the aircraft," said Mr. Wright.