Upcoming weld test: D17.1 4130 tube.

[mjc79]

Hi all,
I have a new certification test coming up, and would greatly appreciate any pointers anyone might have. Here are the particulars:

D17.1 Aerospace code, class A weld.
4130 tube, 0.375" OD. 0.035" wall
Test will be in the 6G position.
Argon purge? (the production parts may not be readily adaptable to purging, but I don't think the test is "passable" without purging.)

Have any of you taken a test like this?

There are a few things that I am concerned about. A couple are simply things that I will have to figure out: positioning/indexing/travel speed/filler addition, and all that jazz. Another challenge is that I think my eyesight has changed (and not for the better) since I last look a weld test (I am rapidly closing in on my "mid forties"...probably need glasses before I can succeed at this.) While my eyesight is an issue, I suspect I would still find this joint difficult to see even with good vision: the tube ends fit up perfectly, and it is really hard to see the exact location of the seam while welding.

However, my real question has to do with surface oxides. I have had a terrible time with oxides forming when doing non-code welding on similar geometries made of 4130. In a nutshell, I start out with a nice clean weld joint, and it welds nicely at the beginning. The trouble starts when I am about halfway-to three quarters around the tube, from oxides that have been forming on the other side of the tube from where I started welding. By the time I am getting close to finishing up the weld, the oxides are so troublesome that I cannot get a good weld profile (nasty undercut at the toes, mainly. I struggle to get a smooth final crater fill at the end, too.) Now, this happens even though I strive to brush the oxides off with a small stainless wire brush (a hand brush, not a powered one) whenever I stop and before I re-start.

Any pointers on the oxide issue, or the test in general? Thanks much!

-MJC

[Ltbadd]

I understand what your facing, I have done 6G tests but never on tube and especially that small of diameter.

I am curious to know how this test (6G) was selected to qualify for the production part, was it a engineer or customer requirement?

As far as seeing, either use reading glasses or a cheater lens in the hood, make sure all protective covers are clean or replace them.
Position yourself when welding so light sources don't enter the hood from behind, use LED task lighting to illuminate the weld joint/area.

[mjc79]

I understand what your facing, I have done 6G tests but never on tube and especially that small of diameter.

I am curious to know how this test (6G) was selected to qualify for the production part, was it a engineer or customer requirement?

As far as seeing, either use reading glasses or a cheater lens in the hood, make sure all protective covers are clean or replace them.
Position yourself when welding so light sources don't enter the hood from behind, use LED task lighting to illuminate the weld joint/area.

Thanks for the input and pointers!

The truth is that, for the job that motivates this test, it wouldn't strictly need to be taken in the 6G position. However, my superiors want to take the opportunity to "cover as much ground" as possible with this test. I am on board with is too, because it would look nice in my list of certifications! If it does end up being too difficult/time consuming, we could "wimp out" and go to 1G if we had to. This is for control rods on WWII aircraft.

[mjc79]

Anyone have any thoughts on the surface oxide issue is described? Thanks!

[ryanjones2150]

If it’s happening every time you’re about half way around, maybe you’re hand is getting fatigued and your arc length is suffering because if it. Try welding 1/4, let it cool a bit and pick up again. All things considered correct, meaning cleaning and prep is correct, I can’t think of any other reason.

What cup are you using? What filler metal? How much argon?

[mjc79]

If it’s happening every time you’re about half way around, maybe you’re hand is getting fatigued and your arc length is suffering because if it. Try welding 1/4, let it cool a bit and pick up again. All things considered correct, meaning cleaning and prep is correct, I can’t think of any other reason.

What cup are you using? What filler metal? How much argon?

I have actually run into trouble of this kind on other weldments involving thin 4130. The back side of the joint always oxidizes, and the last portion to be welded usually has picked up enough oxides to impede welding. Makes me wonder if I have been missing simple/obvious about welding thin steel.

The current setup is:
Special cup (with gas lens)
ER70s-2 filler (.045")
20 CFH argon flow.

Thanks!

[chrismac]

Are you working to an approved weld procedure, what gap you got in it, is it going for destructive testing, small pipe like that is not good to do, but if your working to an approved weld procedure just stick the the set parameters and see how it goes, purging will change how it welds, it seems to have quite a cooling effect on the weld.

Interested to here how you get on.

Chris

[Ltbadd]

Anyone have any thoughts on the surface oxide issue is described? Thanks!

When the metal gets that hot the oxides are par for the course, and the tube being so small and thin...I'd want to use .035" filler, the thicker the filler the more heat needed thus adding to the problem. Before completing the last half wire brush it

[tarry99]

Make sure you clean the tube with a little sand paper if ya can both outside and inside and then wipe it down with acetone in both locations......ya can't be too clean...

[ryanjones2150]

I’m assuming you’re removing the mill scale on the inside of the pipe as well?

[mjc79]

Thanks for the replies!

This test is on a slight modification of an existing, qualified procedure. The main motivation to do this now is qualify me: the welder who had originally qualified for this left the company years ago. The original was on .25" OD tube with .028" walls. This was not purged.

At this point in time, I have yet to "officially" try this test. Thus far, I have been just trying out the joint on scrap material to see what the challenges will be. The official "approved material" for the test will be here on Monday. My preliminary tries have actually been on plain steel tube (1020 I think?) rather than the 4130 the test calls for. I have been running into the "oxide issue" on the 1020 tube, but what really concerns me is that, if memory serves, I have had the same issue, but worse, on 4130 tube of these dimensions in the past.

In previous welding on this type of material, I had overlooked cleaning the inside of the tubes, but I am doing that now. Certainly seems to help, but the largest issue, it seems to me, is external.

I am thinking that changing to ER70S-6 (from the "-2) will help. I actually ran a little bit out of the MIG welder, and tried it a practice joint. The weld "behaved" much more nicely on the discolored "backside."

Another thing is that I am just getting it too hot overall. I think it will improve when I "tighten" everything up: (dial in amperage, reduce arc length, figure out travel speed better, etc.)

I will report back when there is anything new. Thanks!

[ryanjones2150]

That’s some pretty small stuff if I read that right, 1/4” OD tubing? Something that small would be easy to overheat. Dress that tungsten down to a polished needle and maybe even give pulse tig a try. I’ve never used it on tubing, but I’ve used it on plenty of the thin stainless outside corners and it definitely helps reduce heat input. Of course with chromoly you want it to get good and hot so it all cools slowly to prevent cracking, but with that small stuff, that’ll happen anyway. Get some pictures of the weld problem areas if you can. I’d also like to see this small stuff setup. Good luck!