I'm new around here as well but I can tell you this board is VERY slow. Not much activity here.

I use to be a welder and I recall reading somewhere in my AWS books that welding alloys with chromium to alloys with nickel could result in cracking. And I seem to remember the cracking could develop after some aging. I sorry I don't remember the metallurgical explanation.

If you don't have access to technical books or get an answer from someone here, let me know and I'll try to dig it up for you.

Darvin

The minute you mention aircraft tube structures a red flag goes up to most people, liability issues. This is probably the reason for slow response times, additionally I believe everyone is busy. All I can do is suggest that many tests of the mechanical variety need to be performed along with data collection, I will add, this would be very expensive. You would be better off to look at coatings to gain your corrosion resistance, there are many. Hope this explains your situation for you.

Best regards, Brad M.

I would research this real carefully and devlop procedures carefully. Duplex SS can have high ferrite contents form in the HAZ if the welding procedure is off. This leads to poor toughness, essentially a brittle weld. Look beyond tensile strength - what about fatigue strength?

Yikes....... That's my first impression and Yikes a second time.

Aircraft component welding may be accomplished only with approved engineering documentation for the *Specific* component to be weld repaired.

The component vendor/manufacturer has all relevant data with regard to weld repairs of components, If they do not have it, it does not exist! To Deviate in any way from the requirements of a specific engineering document, (this includes fluxing when inert purge is called out) puts you, and you're A&P licensee at risk. However that point is secondary. If you're experimenting with joining of dissimilar metals, substituting parent materials for component parts or joining metals with filler wire chosen by whim on aircraft that fly, Stop Now! Lives are at risk. This entire conversation makes me nervous.

Experts choose materials and filler wires for a reason. Even if a material vendor suggests compatability of metals via some chart in a textbook or sales/ inventory catalog, they have not likely engineered your component or considered functional performance of the applications you intend. Nor will they stand behind you *when* something goes wrong!

Before you take further action I urge you to find an experienced A&P Mechanic to assist you in accessing the manufactures specifications for the components you wish to repair/fabricate. Remove ALL experimental components you have installed and replace with proper/certified parts. Than become conversant in, or better yet certified to the related welding specifications which apply to your work <Mil. Std. 1595a> for example.

To be blunt what is being discussed is the installation of Bogus Parts on aircraft and the FAA will not hesitate to levy fines or imprison offenders.

Your Questions are relevant and appropriate, if you had not asked; the result may have been catastrophic. However, in the end, your response is the most critical Issue!


With Gravity

Lawrence Bower
Maintenance instructor ~ Welding
Education Development
United Airlines

Yes this forum is a little slow, but if your job or business requires specific welding information, this is not a bad place to obtain this info.

I have to agree 100% with the previous post. Having spent about half of my welding carreer in the precision sheet metal and aircraft/aerospace industries, guessing can be hazardous to lives and property. Do not experiment when it comes to issues such as transportation of people, there are liability issues and the concerned parties are very concerned.

I would seek additional information from the manufacture of the craft regardless of the nature (i.e.: air, water, submersible, etc.) and from the material and consumable suppliers respectively.

Your question is not inappropriate and is valid for sure.

Airweld:
My intent was not to flame. Maybe I can say this another way and make it more understandable. It has been a blessing for me to work under the direction of and be exposed to some of the worlds leading eggheads (said with reverence), responsible for welding exotic metals in the both the military and civilian aerospace industry. From hang gliders to Blue Angels to jumbo jets, over the decades the folks who make and fix this stuff have collected uncounted libraries of data. Research and experimentation has been ongoing and well published.

Thinking outside the box is wonderful, but in the aviation world you will have to go WAY out there to find something that has not been tried and discarded by the experts. When they find a thing useful it gets published (because it must be if they use it) and becomes a standard practice. Proprietary materials are pretty scarce with only a few exceptional cast alloy pressure vessels notable.

If a substitution of parent material or filler alloy is possible it will be noted in the manufacturers spec. If the project is small or a homegrown kit, rather than spend the money playing the role of Jr. metallurgist, sending coupons to a costly lab, it will still be so much more simple and reliable to go to the fabricator or design engineer of that part and obtain the data from them. Somebody has already done the work.

Corrosion was for you a stated concern from the outset; this makes fluxing of 321 parent material or 347 filler problematic. Any residual flux left on the part will be a corrosion risk. In most cases if you have enough access to remove all traces of flux after completing the weld than you prolly could have purged it and gained the superior mechanical properties anyhow.

I can't apologize for emphatically encouraging you to find and follow documented guidelines. Doing so will add safety, integrity and peace of mind to every aspect of your projects. However, do know it is my desire to treat you as a craftsman with the same respect I treat our shared craft.



Lawrence

Blessed are the feet of those who bring good news!

How about that, our very own site host may be presenting the answer to the issue at hand. I am eager to dive into this one!

Read on!

MIAMI -- February 15, 2001 -- The result of years of research from welding experts around the world, the American Welding Society (AWS) has released the groundbreaking new standard, Specification for Fusion Welding for Aerospace Applications (AWS D17.1:2001). This new guide covers procedures never before addressed in previous documents. Included for the first time are authoritative procedures for weld repair of in-service flight hardware, as well as the design and repair of non-flight hardware.

Specification for Fusion Welding for Aerospace Applications includes detailed information on the welding of a variety of alloys, including nickel, aluminum and titanium-based alloys. The standard also includes the requirements for welding design, personnel and procedure qualification, and inspection and acceptance criteria.

Developed under the guidance of the AWS Committee of Welding in the Aircraft and Aerospace Industries, this ANSI-approved standard draws on the experience of experts in the field of aviation welding. Representatives from Boeing, GE Aircraft Engines, NASA and many other companies contributed to the development of this breakthrough in aerospace welding guidance.

The new Specification for Fusion Welding for Aerospace Applications is 104-pages long and lists for $112.00, $84.00 for AWS members. It can be ordered by calling Global Engineering Documents at (800)854-7179, or on the AWS website at www.aws.org.

As the author of the topic under discussion, it may be useful to explain why I ask the question. My business is welding on live airplanes, mostly 4130 tube frames. I do restorations of antiques (as old as 1920's), amateur built experimentals, and lots of Pipers, Champs, Taylorcrafts, Maules, Stearmans, etc. I have been flying and working on airplanes all my life and for the last 26 years, doing it in the state of Alaska. I replace miles of rusted 4130 tubing every year, and I don't mean light surface rust. And of course I replace it with the same 4130 tubing that rusted out in the first place. Does anyone else see where I'm going here? I think there is a better way and because nobody else has done it yet does not mean it 1; is not possible, 2;can't be done safely, or 3;is not "economical". Now as to the manufacturer and all his research, it ended 50 or 60 years ago, and I have a hard time even getting blueprints for these planes to know where the tubes are supposed to go after they're wrecked. I have to engineer the design and process myself and then get FAA approval to use it (on certificated airplanes, anyway). And what better place to go than here, where those who rub shoulders with the eggheads, may offer a suggestion or two, in the spirit of furthering the knowledge base of our chosen field. And I do appreciate all the commentary! And now, as far as who is qualified to weld on airplanes, it may surprise you to know that thousands of amateurs with a couple hours of practice have welded airframes together (lots of them of their own design) and structural failures are rare and the overall accident rate for experimental amateur-built is the same as certified planes (although it was expected to be at least double when first introduced). My 9 year-old son can weld on a certified airframe and I, as a FAA certified mechanic with an inspection authorization, can approve it as airworthy. And my authorization involves no welding certification other than the training I got when I went to A&P school. Add to that the fact that here in the far north the only way to get things done sometimes is improvisation. Something to think about the next time you go for a ride in a small tube-frame airplane, eh? The result of all this is called experience and that's what I'm looking for: someone with experience in welding duplex stainless. I'll even look in AWS D17.1:2001.
Thanks for all the suggestions, Scott.