Noise from aluminum structure when welding?

[Trboatworks]

So I am running the last welds in a structure which is getting pretty tight/locked up.

I lay on with the torch and I’m getting creaking and pinging and thinking crap- I’m cracking welds.

Well I carry on and start thinking this isn’t the case probably after all- some of the pings are a goodly distance from when I’m working and they don’t sound quite right for weld cracking.
More creaks than those pings one hears when a tack weld lets go.

So what’s up?

My best theory is the copes in finished welds pulled damn tight by welding creak as they shift when the geometry changes with the heat .
But… who knows.

Anyone have this happen?
It’s a bit disconcerting to think I am getting a bunch of weld cracks.
The structure quieted down as I got towards fully welded up.

 

[DDoug]

So I am running the last welds in a structure which is getting pretty tight/locked up.

I lay on with the torch and I’m getting creaking and pinging and thinking crap- I’m cracking welds.

Well I carry on and start thinking this isn’t the case probably after all- some of the pings are a goodly distance from when I’m working and they don’t sound quite right for weld cracking.
More creaks than those pings one hears when a tack weld lets go.

So what’s up?

My best theory is the copes in finished welds pulled damn tight by welding creak as they shift when the geometry changes with the heat .
But… who knows.

Anyone have this happen?
It’s a bit disconcerting to think I am getting a bunch of weld cracks.
The structure quieted down as I got towards fully welded up.

Start wearing earplugs when in your shop.....

 

[Trboatworks]

Start wearing earplugs when in your shop.....

Ha- yeah I got ya.

Welding at 150hz- plugs all the damn time.
It is noisy..

You welding much anodized pipe Doug?

 

[gustafson]

Is the ground far from the weld? The reason they got rid of aluminum wiring in houses is it moves when current flows through and wiggles out of the outlets, or so I am told.

 

[DDoug]

Ha- yeah I got ya.

Welding at 150hz- plugs all the damn time.
It is noisy..

You welding much anodized pipe Doug?

Nope, why would that matter at all ?
I weld aluminum.

Maybe the anodizing is affecting what few brain cells you have left ?

 

[Trboatworks]

Nope, why would that matter at all ?
I weld aluminum.

Maybe the anodizing is affecting what few brain cells you have left ?

Who said I had any left..

Grab a stick of BD polished anodized pipe and give it a try sometime.
Lots of little details getting decent welds in the stuff- I am cautious as my work has to hold in pretty rough service.

 

[sfriedberg]

Dunno if this is your situation, but it's very common for structures thin enough to "oil can" to flip between stable configurations under thermal expansion/contraction. Happens all the time to baking sheets (and the interior panels of my 50-year-old oven). The typical sound is often a "twang", not as drawn out as a "creak" and not as sharp as a weld-cracking "ping".
Another possibility is what you suggested, where parts with a one-side fillet weld are rubbing a bit as one part expands slightly and flexes the joint.

 

[Trboatworks]

Dunno if this is your situation, but it's very common for structures thin enough to "oil can" to flip between stable configurations under thermal expansion/contraction. Happens all the time to baking sheets (and the interior panels of my 50-year-old oven). The typical sound is often a "twang", not as drawn out as a "creak" and not as sharp as a weld-cracking "ping".
Another possibility is what you suggested, where parts with a one-side fillet weld are rubbing a bit as one part expands slightly and flexes the joint.

Gotcha.

I am used to the high pitch ping when a tack weld lets go as pipe moves when welded.

This is the first time I had any noise from fully welded joints.

It seems improbable that a micro crack is opening up but I want to be sure so I am not sending this out with crack’s already present.

I had crushed some test fit ups and no problems- pipe goes flat and no letting lose at weld or cracks.

The structure is tight where I was welding- locked up and enough heat to do fillet welds of 3/8” to SCH 40 pipe.
Something has to move a bit- I guess it’s just the copes squirreling around inside the welds as heat come on and moves the pipe.

 

[climb-101]

the part moving/flexing and rubbing a little on the jig or hold downs?

 

[BT Fabrication]

Is the ground far from the weld? The reason they got rid of aluminum wiring in houses is it moves when current flows through and wiggles out of the outlets, or so I am told.

the heating of the wire while in use allows the conductor to expand and contract in the bolt down lug etc. even more expansion on smaller wire as it takes less for it to heat up. larger wire like ACSR that feeds most houses is all still aluminum as its only 18/ meter here for 3 conductor compared to almost $60/ meter for single strand of the same gauge wire to feed 200A to a house.

 

[BT Fabrication]

So I am running the last welds in a structure which is getting pretty tight/locked up.

I lay on with the torch and I’m getting creaking and pinging and thinking crap- I’m cracking welds.

Well I carry on and start thinking this isn’t the case probably after all- some of the pings are a goodly distance from when I’m working and they don’t sound quite right for weld cracking.
More creaks than those pings one hears when a tack weld lets go.

So what’s up?

My best theory is the copes in finished welds pulled damn tight by welding creak as they shift when the geometry changes with the heat .
But… who knows.

Anyone have this happen?
It’s a bit disconcerting to think I am getting a bunch of weld cracks.
The structure quieted down as I got towards fully welded up.

the noise is just the aluminum expanding and contracting and moving at the connections not yet fully welded. 100F will change the aluminum alot for the dimensions over even 6 ft, easily enough to make a tube bow 1/4" per 6 ft