[jumpinjackflash]

I know the other side was not shielded from atmosphere....just like the insides of all the tubes I have welded....there is push through. I know because I have scoped some of the tubes to look. Question is how much damage if any to the parent metal has taken place? These pieces{ .040" CrMo sheet} had to be welded on the inside edges where the radius of the parts meet. Just wondering if it weakens the parts any at the weld area. It will be glass beaded and epoxied. There is a .050" load spreader washer that was fused along the outer edge making a sandwich of 3 pieces and welded with filler the rest of the way around. I know this will be common on non purged welds...does it really weaken or damage the metal

[Poland308]

I think the bigger problem might be corrosion. That sugaring means the base metal no longer has the same properties.

[Braehill]

Jack,
Every time you weld something you're changing the parent metal in some way, whether it be it's grain structure, dilution with filler metal properties, heat input. So then the question is really, is there a way to build this without introducing these things to the part, and if I do introduce them , will they remain strong enough to do the job at hand.

You're going to get oxidation on the back side of anything you weld without shielding or outside of a purge chamber, that's a fact of life. There are ways to limit this, backer bars, flux, Argon dams, limit heat input. These things will just limit the oxidation, but not eliminate it.

You show a couple of parts, that from your past posts, I'm guessing, are going onto a home built aircraft. I don't think anybody here, just by looking at a picture, can tell you if you weakened a part beyond it's usable level by welding it. These things should be engineered into the design of the parts to account for the changes in the parent metal after it's been welded. This might be a need for post weld heat treating, stress relief or a number of other things. These aren't things that I'd trust to the opinion, though well meaning, of this group if I'm going to flying in this craft, but that's just me.

Len

[MosquitoMoto]

Ooh, this is an interesting one.

May I please introduce a question to augment the one at hand? (I'm going to anyhow, you just know it.)

I weld a lot of thin tube, often just carbon steel. Like the OP I see push through. I don't believe that there would be a way to weld this tube effectively without getting push through...the penetration would be so shallow.

Now, I've Googled this next question to no avail; rather than conventionally purging with argon, would it be possible to introduce a very low level vacuum to the inside of the tube so that argon from the torch is drawn through any tiny pre-weld gaps to effectively purge the inside of the tube right at/just ahead of the weld area?

I'm thinking that the problem might be that this technique would, at most, simply introduce a thin slice/jet of argon to the inside of the tube that might not actually serve as any sort of shielding...just thinking out loud.

Sorry...



Kym

[ex framie]

JJF,
If this is an aircraft structural piece I'd be worried.
Having said that the only way you will know if the properties are changed wold be to have it examined by a qualified metallurgist who has an electron microscope and a tensile measuring device.
Other tests would be drop your welded part into some salt water along with a non welded piece of parent metal and see which corrodes more over the time period its exposed.
What are you using for filler wire?
I have 30+ years working on aircraft and admiring a lot of aircraft quality welds on pipes, engine cradles etc, I dont remember seeing any push through on the pipes, a lot of which would have been machine welded.

Kym,
IMO that procedure would suck in more air than the argon, if it worked we'd be hearing about it somewhere on this forum and other welding sites etc.
Vacuum is a bugger of a thing to control and setup for something like this, probably easier to setup a small cabinet and purge/flood it with argon and weld in the cabinet.

[Poland308]

Welding on something that is under vacuum would theoretically work. But if your heating up the component enough to get full penetration you will run the risk of the puddle getting sucked in. Much like when a vacuum tank collapses but on a smaller scale.
I wonder if you truly need full pen on an application like this as I think of the etched photos Otto posted under another link. If this is for an air craft it might be worthy to have an engineer spec what is truly needed for this part.

[Coldman]

Sorry guys. Welding with any vacuum don't work. All that happens is your molten weld pool disappears. ask me how I know.

[MosquitoMoto]

Sorry guys. Welding with any vacuum don't work. All that happens is your molten weld pool disappears. ask me how I know.

Yeah, sorry for the thread jack. Newbie curiosity got the better of me.


Kym

[Otto Nobedder]

Sorry guys. Welding with any vacuum don't work. All that happens is your molten weld pool disappears. ask me how I know.

Yeah, sorry for the thread jack. Newbie curiosity got the better of me.


Kym

Actually, this is not uncommon when one "stick/MMA" welds on a vacuum vessel with perlite insulation... Run the vacuum pump for a few seconds, have someone kill it, and begin the weld. This sucks the perlite away from the weld zone, and a 6010 "fast freeze" rod can accomplish this without sucking through.

It does NOT work with TIG, though... ask me how I know....

Steve S

[dave powelson]

I know the other side was not shielded from atmosphere....just like the insides of all the tubes I have welded....there is push through. I know because I have scoped some of the tubes to look. Question is how much damage if any to the parent metal has taken place? These pieces{ .040" CrMo sheet} had to be welded on the inside edges where the radius of the parts meet. Just wondering if it weakens the parts any at the weld area. It will be glass beaded and epoxied. There is a .050" load spreader washer that was fused along the outer edge making a sandwich of 3 pieces and welded with filler the rest of the way around. I know this will be common on non purged welds...does it really weaken or damage the metal

"Question is how much damage if any to the parent metal has taken place?"
……..Okey Dokey---that melt thru is gross oxidation, etc. It ain't 4130 anymore, you burnt it up.
Are its mechanical properties the same as before??…..(that's really begging the question)
…..Will it pass a penetrant check?, even if you sand it down?

"I know this will be common on non purged welds...does it really weaken or damage the metal?"
----a hint of oxidation or scale is one thing, the sugaring on this example is another--no, it ain't common on
other flying crates.
……Weaken it?….that reinforcement washer only needed the teeniest bit of fillet weld. This melt thru is a stress riser
at the least.
…..Try working for really minimum heat input, try pulsing,etc. Solarflux and backing up will help if one's already
doing min. heat input--but won't do squat in this example of overheating.

Ditto what Braehill sez:
Every time you weld something you're changing the parent metal in some way, whether it be it's grain structure, dilution with filler metal properties, heat input. So then the question is really, is there a way to build this without introducing these things to the part, and if I do introduce them , will they remain strong enough to do the job at hand.

You're going to get oxidation on the back side of anything you weld without shielding or outside of a purge chamber, that's a fact of life. There are ways to limit this, backer bars, flux, Argon dams, limit heat input. These things will just limit the oxidation, but not eliminate it.

Since you haven't bothered to respond to this thread, the rest of us might as well be talking to ourselves.

[MosquitoMoto]

Hey, even if we are indeed just talking amongst ourselves I, for one, am learning.



Kym

[jumpinjackflash]

Didn't really expect to be chastised about not responding. Please accept my apology. Things aren't exactly as you have so keenly surmised to the state of this situation...IMHO. Pix will reveal washer weldments and culprit of inside tack. The brackets will be remade and after talking with a retired weld instructor has suggested some different methods of getting what I want done in a different sequence of activities. I was merely asking a question....
For anyone that wants to know...they are inter-plane strut braces and compression tube anchor points.

[Braehill]

Jack,
No need for apologies, the apology should come from the person chastising. We have a little carry over from another forum where that's the norm and they sometimes have trouble checking that at the door here.

Let us know how you make out with this new sequence.

Len

[Otto Nobedder]

Jack,
No need for apologies, the apology should come from the person chastising. We have a little carry over from another forum where that's the norm and they sometimes have trouble checking that at the door here.

Let us know how you make out with this new sequence.

Len

Well said.

Those from facebook and a few other chat forums that I'll leave unnamed are not accustomed to our pace, where a conversation may take weeks to evolve, with responses days apart. If you're after "instant gratification", this is not the place.

People seeking to massage their egos don't usually last long here, either.

Patience, in all things.

Steve S