Welding Tips and Tricks

The tubing has a rough, pitted surface finish after sanding off pickle coat. It is not rust, more like dry galling when it was pulled through the die or just bad materials? Welds nice. There is no mill or manufacture markings- only script
TM-AMS 6336 OM AMS-T- 6736B. MIL-T-6736 4130 SMLS COND N 0.625 X .035 80544
Love to hear from the more knowledgeable on this...yes I am OCD about tiny details.
This is going into aircraft build #2. I have close up pix of the tube and a welded part. Question is there a way to test it? Tensile, other destructive test? Just not happy with surface finish..and not knowing where it was made. Came from race city steel. I know Asian steel is around....just hope I don't have any of it. Need to make sure it's safe. No reply from them yet on what mill it's from. Any help appreciated .
Just worried tubing may not be safe.

I don't have the answer to your question, but is cleaning up the surface not an option to remove those imperfections?

No idea. But here's my two cents if a customer brought it to me to weld:

If it's for an aircraft and the soundness of the material is in any doubt, and the origin is unknown, I would refuse to weld it.

Spartan wrote:No idea. But here's my two cents if a customer brought it to me to weld:

If it's for an aircraft and the soundness of the material is in any doubt, and the origin is unknown, I would refuse to weld it.

This, I'm going to assume you had a reasonable amount of experience with 4130 BEFORE you decided to build an aircraft so if your experience is telling you something isn't quite right and you'll fall out of the sky if it isn't I just wouldn't risk it.

As far as testing, short of paying a lab likely a lot of money to perform tests on specially welded coupons, if I had a lot of the steel I'd weld a couple test pieces in ways I could apply a lot of force to and generally do whatever it took to bend it until it breaks or can't be bent any further. Preferably I'd do it along side a couple control pieces with steel I trusted more and welds I felt confident in.

A couple questions here, is it a certified airplane or an Experimental Amateur Built aircraft?

If it is a certified airplane, you should have material certs with the tubing ( you don’t always get them). Are you an A&P, or is another Person with an A&P going to sign off the work? If someone else is signing off the work, coordinate with him, and follow his guidance.

If it is a homebuilt, it’s up to the builder to determine the quality of the material. My suggestion would be do what he wants, cash deal, no paperwork toeing you to the project.

For a certified airplane, the A&P holds all the liability. For a homebuilt, the builder holds all the liability.


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