Tackling precision stainless steel TIG welding as a team

August 16, 2019 2:47 pm

Three New Hampshire welders tackle protype work, in-house training

THE WELDER JULY/AUGUST 2019

TIG welders are a different breed. To be successful, you must possess patience, precision, muscle memory, creativity, and a knowledge of the base material. And if you have those characteristics, they must then be carefully honed with time under the hood. A lot of it.

But in some environments, one more trait is paramount to success: trust.

Brian Thessen’s, Tom Hammer’s, and Ernest Coolong’s diverse work experiences and skill sets have come in handy in a job that requires out-of-the-box thinking, a high level of skill, and a depth of experience to help troubleshoot never-before-fabricated components.

The three highest-ranking welders at Axenics, a contract manufacturer of components for medical devices, semiconductors, and the alternative energy industry, with locations in Middleton, Mass., and Nashua, N.H., have developed a bond built on mutual respect and experience, which has led to trust.

Why is that important? The components the three welders work on are one of a kind and highly scrutinized. They must collaborate with one another to develop a plan of attack. They must also train other welders in-house on the art of gas tungsten arc welding to ensure those welders are ready and able to step in at any time.

Their diverse backgrounds and work experiences have come in handy in a job that requires out-of-the-box thinking, a high level of skill, and a depth of experience to help troubleshoot never-before-fabricated components.

Meet the TIG Team

Brian Thessen, Tom Hammer, and Ernest Coolong are responsible for the brunt of the specialized TIG work at Axenics. They are all college-educated and have deep and varied work experiences that come in handy when navigating difficult-to-weld parts and materials.

Before joining Axenics four years ago, Thessen spent the previous 25 years as a sheet metal fabricator and pressure vessel welder, a pipe welder, and an adjunct welding instructor at Keene Community Education Center in Keene, N.H.

“I had been doing the same job for quite a few years and was just ready for a change, and that’s when I saw an Axenics application. I have the most experience in stainless steel TIG, even prior to Axenics, and that’s primarily what the company does so it was a perfect match for me,” Thessen said.

Tom Hammer has been welding for nearly 20 years. Before joining Axenics nine years ago, he spent time building wasterwater recycling machines and performing vacuum furnace heat treating, brazing, and welding of aircraft parts.

“The economy dropped pretty low and I was in between jobs. I found an ad for Axenics on Craigslist. I came in and felt it was a great fit for me. I liked that the company did all sorts of prototype parts, so I was able to jump right in working with customers on their prototypes,” Hammer explained.

Coolong has been with Axenics for about a year, making the move after experiencing a bit of an economic downturn. His background includes working at a machine shop that built hydrogen fuel cells out of mostly stainless steel that ranged from thin gauge all the way up to 5⁄8 in. thick. Before that he was a commercial pipe welder.

“I took a tour of the facility and found it was organized and clean, and I liked that. They had a good workforce and a good culture, so I decided to make the move,” Coolong said.

The jobs that come through require TIG work that is anything but ordinary. Some of the more challenging welds are within the parameters of a strand of human hair.

Part of the work culture that each of the three enjoy is the collaboration that occurs with each new project and prototype. This is when their unique backgrounds and skill sets come in handy.

It makes sense. Many of the parts they work on are brand new, Hammer explained. There’s no instruction manual, but welds must conform to certain specifications.

“Sometimes we get told that we need to conform to a certain specification, and then we have to figure out how to get everything to that specification while conforming to the demands of the part configuration and base material. We do that extremely well. It takes us a little bit, but we figure out ways around working with the metal and being able to conform to specifications,” Hammer said.

The end result must be correct. If anything goes wrong, they must start over given how small some of the components are.

“It’s not easy to fix something where your tolerances are a couple of times bigger than a human hair. The end result is to get it right, and sometimes it takes all three of us working together to make one piece,” Thessen said.

That constant collaboration has established a bond between the three men, which is understandable given they are in the shop with one another more than they are home with their families. Hammer describes them as a family away from home.

Sometimes it can be tough for other co-workers to break into that bond.

“The three of us have had, at times, what seems like a simple conversation and the fourth or fifth person involved finally has to walk away because they don’t understand what we’re saying. We have a language between the three of us that is specific to welding,” Thessen said.

Facing Stainless Steel Head-on

A majority of the time, Thessen, Hammer, and Coolong weld on stainless steel. While not necessarily considered an exotic metal, stainless does have its nuances.

The whole purpose of making things out of stainless steel is to provide desirable corrosion resistance properties. But if you’re not careful, those properties can be undone.

“The welding process, if done incorrectly, will corrode the stainless. You can’t just weld on stainless and expect it to remain stainless. You have to weld stainless in an exact manner and in a precise way for it to remain stainless when you’re done. Specific prep work and specific postcleaning is required too,” Thessen explained.

“When you’re welding you have to account for the fact that it’s going to distort; it’s going to pull a lot in the direction that you’re welding. With tube, it’s not that big of a deal because it tends to even itself out when you travel around, but it will shrink. You have to account for that shrinkage, especially where we deal with 0.03 tolerances. We have to be really careful with how much heat we put into our welds,” Hammer said.

Dialing in the right pressure based on the different tube diameters can be a challenge. They must purge the inside of a tube during autonomous welding, and the amount of back pressure they have determines the bead profile. Too much pressure will yield a bead that is puffy or convex, but not enough back pressure produces a concave or sunken-in weld. They don’t want either.

They must weld stainless in an exact manner and in a precise way for it to remain stainless. That includes performing specific prep work and postcleaning.

Education, experience, and trust are vital in the work that Thessen, Hammer, and Coolong do because it’s not your ordinary TIG work. Some of the more challenging welds are 0.005 in., or within the parameters of a strand of human hair, Thessen explained.

“These are some of the smallest applications that can be achieved by a human, and they can be achieved only by a seasoned journeyman,” Thessen said.

One of the biggest challenges with TIG welding, he added, is maintaining uniform root and cover passes to achieve the required tolerances.

Depending on the application, they perform autogenous weldments, without the use of a filler metal; homogeneous welds, where like metals are joined together by the same type of filler metal; and heterogeneous welds, where the filler metal is different than the metals being fused. Every weld must then undergo nondestructive testing (NDT) and sometimes destructive testing in-house. For example, Axenics has performed both nondestructive and destructive testing on the welds it has executed on three-pass heat exchanger hydrogen fuel cells.

Some customers require a randomly selected destructive test on the welds as well. Cutting, bending, or flattening the weld occurs in order to ensure it comes apart in the correct manner. If a weld does not become destroyed in its intended way, that means it was not welded accurately.

In-house quality control is another way to keep manufacturing lean, saving potential time and money. Depending on the purity level required for a weld, both TIG and orbital welding can be performed in a Class 100 clean room. Tools are color-coded so they are used only on the same type of metal.

“There’s literally no room for error,” Thessen emphasized. “These welds have to be flawless.”

Training TIG Welders From Within

With all that in mind, it makes sense that the company doesn’t let just anyone do the TIG welding.

“You don’t have the luxury of just throwing somebody into the mix with TIG welding. It is so refined from the starting point; it’s not something you can pick up and do without a journeyman there to help you troubleshoot,” Thessen said.

The company takes an incremental training approach, giving competent, young welders increasingly difficult challenges in an effort to bring them up to speed and gauge their potential for further skill development. Because Thessen, Coolong, and Hammer are college-educated and on equal footing with one another, collectively they are responsible for implementing the incremental training practices.

“We’ll take people and teach them the basics of TIG welding so that when we have a surplus of work they can help out on the lower-end portion of the work, and that frees us up to do the higher-quality work. If we see a prospect or talent, then we can hone into the next level. We spend time evaluating, and when we have someone who does well, we bring them along even more,” Thessen said.

Specifically, they are looking for candidates who have good hand/eye dexterity, can work diligently, and can pay attention to detail. The evaluation process starts simple and gets progressively tougher.

First, they give TIG welding students a torch to disassemble and reassemble. Failure to put a torch back together in the correct order could create a bad weld with corrosivity or other defects. They then give welders pieces of tungsten and guide them through the sharpening process.

Next, they teach the fundamentals of electricity and alternating current versus direct current.

Welders must then perform tack welds on scrap metal. Mistakes are expected to happen at this stage.

“Once they can perform simple tasks without any mathematics involved to my liking, I will give them the most basic assembly just to tack,” Thessen said.

Mathematics then come into the equation: 90-degree take outs, shrinkage take outs, and different diameters are introduced one at a time. As each hurdle is crossed, Thessen exposes them to the next tier.

Once the welders become skilled in tacking, they will then attempt an actual weld on pieces of scrap. Only when they have mastered welding the scrap do the students get the opportunity to weld on simple parts.

Advice

For all of the aspiring TIG welders out there, the journey can be filled with a variety of welding experiences, but it all begins with the basics. Coolong said it starts by spending as much time as possible under the hood and listening to the more experienced welders.

“Listen to your elders. Yes, you may have book smarts, but don’t go out and tell these guys how much you know. They don’t care how smart you are. They want to see you working and learning on the job. You can get a lot out of these older guys if you just listen and learn,” Coolong said.

Thessen’s advice is similar.

“Practice, practice, practice, and do it even on your own time, especially in the beginning. I can’t tell you how many hours I’ve spent, and not only was I not getting paid, but I was paying. All of us together have paid a few thousand dollars to earn degrees. I spent a ton of time on my own learning how to be a pipe welder after my workday was done. That’s my big thing. Practice, even on your own time.”

Editor Amanda Carlson can be reached at [email protected].

Corey Stulce is an associate with Savoir Faire Marketing/Communications. He can be reached at [email protected], 978-490-3195. Photos courtesy of Nick Brown Photography, Milford, N.H.

 

Which Inspections Must the Welds Pass?

Just how highly scrutinized are Thessen, Hammer, and Coolong’s welds?

Here are some of the tests their welds must pass.

Visual inspections often are combined with hydrostatic testing or helium leak

testing. During a visual inspection, the welders are looking for potential defects and discontinuities, such as corrosion, fissures, banding distortions, porosity inclusions, inadequate joint penetration, incomplete fusion, arc strikes, undercut, overlap, underfill, surface flaws, or inconsistencies in the metal.

Hydrostatic leak testing utilizes liquid pressure to identify leaks. In the case of DOT cylinders, a component is filled with water or another liquid that has a dye added to it. Once the liquid hits a pressure that is higher than the working pressure for the cell, it is held for a predetermined amount of time. The cylinder is then checked for potential leak points.

Dye penetration inspection is used to locate tiny surface cracks and porosity. The component being tested is cleaned of possible contaminants, then dried. Often a thin, red dye penetrant is applied to the component. Then the dye is wiped away. A developing powder is then sprayed on the component, which will expose any flaws once applied. Depending on the type of penetrant used, a visual inspection will occur under white light, or an inspection can occur under ultraviolet black light.

The helium leak testing process involves pulling a vacuum on a weldment. Helium is then sprayed in tiny amounts on areas where there could be potential leaks. A helium leak detector, also known as a mass spectrometer leak detector (MSLD), then “pulls” the helium into the welds. The MSLD sounds an alarm if a leak is present in the weld.

Pressure tests also can be performed by pressurizing welds with helium and using a sniffer probe that is connected to the MSLD around potential leak areas. The sniffer probe pulls the helium through the leak and into the MSLD to sound an alarm.

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