Bubbles in weld

Dirtbag · Tue Feb 04, 2014 8:17 pm

just finished a Swag Offroad project. Had to assemble a Press Brake. All the welds went smoothly until I got to the press arbor welds to the brake base. The arbor is 3/8" angle, as is the base. I ground the millscale off the edge of the angle prior to welding, then proceeded to tack it in 6 spots. Swag recommends that the welds be kept short and alternated from side to side to avoid deformation. There's 19" of weld on each side. I welded about 1.5" off each tack, alternating sides. So far, so good. When I went in for the next set of 1.5" beads (continuing the same sequence), I noticed that the weld puddle looked like it was boiling and the resulting weld was as holy as swiss cheese. I thought the gas was getting blown away, but that was not the case. The metal was clean and contamination free. What would cause this sudden change in the quality of the weld if nothing else changed? The machine is a MillerMatic 220. I was on #4 (don't know the amperage, it's just a rotary switch with numbers between 1 and 6) I'm using .30 wire @ a setting of 60. (which also doesn't relate to IPM on the wire speed. Sorry) Any ideas what would make a weld "boil"?

Superiorwelding · Tue Feb 04, 2014 8:45 pm

Dirtbag,
Two things come to mind if it is not your gas cylinder empty. Is your nozzle clean of weld berry's? Is the fiberglass coming free inside your nozzle? A clogged nozzle will not let enough gas through for adequate coverage. If the fiberglass fibers are coming free inside your nozzle it will give you porosity. These are two possibilities.

AKweldshop · Tue Feb 04, 2014 10:20 pm

you got some pics???
might help us diagnose the cause.

John~

noddybrian · Wed Feb 05, 2014 2:58 pm

Sounds stupid - but just run a test weld on something else to confirm it's the machine not the material - but it's pretty well always lack of gas cover that causes this as per the previous replies - try to get used to setting gas flow " by ear" - don't rely on what a pressure gauge says - the only valid measurement is at the nozzle & as I've posted before - the cheap easily bought flow meter pictured below is the only effective way to know what flow is present where it counts.

: peashooter-large.jpg (47.89 KiB) Viewed 1549 times

MinnesotaDave · Wed Feb 05, 2014 4:05 pm

noddybrian wrote:Sounds stupid - but just run a test weld on something else to confirm it's the machine not the material - but it's pretty well always lack of gas cover that causes this as per the previous replies - try to get used to setting gas flow " by ear" - don't rely on what a pressure gauge says - the only valid measurement is at the nozzle & as I've posted before - the cheap easily bought flow meter pictured below is the only effective way to know what flow is present where it counts.

Yep +1

Superiorwelding · Sat Feb 08, 2014 11:55 am

Dirtbag,
Did you find out what was causing your problem?

Dirtbag · Sun Feb 09, 2014 11:15 pm

Hello all:
Just got back to this forum, to see what sort of insight has percolated. I should have offered a photo or two, but was remiss. Noddybrian, the suggestion to weld something similar is just what I have done this afternoon, albeit the material was not as robust. No bubbles. I'm buying some steel for another project tomorrow, and should be able to duplicate the conditions with the bubbly welds.
I did hear the gas hissing as I was working (I generally check that because no gas produces a REALLY crappy weld, as I have proven in the past) but will invest in a flow meter, with the added benefit that I can calibrate the gauge on my regulator.
I'll check the gas orifices for obstruction (beebees, etc) I had the nozzle off but didn't look closely at the holes the gas comes out of. There wasn't much spatter in there, but it wouldn't take much.
I'll follow all the suggestions and see if this thing has a bottom.

Superiorwelding · Mon Feb 10, 2014 12:13 am

Thanks for getting back with us. Let us know what you ultimately come up with. Also if it happens again or if you still have access to the original weld, get some pics up.

AKmud · Mon Feb 10, 2014 1:32 pm

I've run in to that before as well. The weld will look just fine until I stop then a bubble will develop and rise as the puddle cools. It doesn't happen all the time and I can't intentionally duplicate it. I usually just knock it down and tack over the top of it.

ZfrkS62 · Mon Feb 10, 2014 11:11 pm

AKmud wrote:I've run in to that before as well. The weld will look just fine until I stop then a bubble will develop and rise as the puddle cools. It doesn't happen all the time and I can't intentionally duplicate it. I usually just knock it down and tack over the top of it.

Do they tend to rise up out of the puddle randomly like a stalagmite in a cave (the one that comes up out of the ground)? And when you grind it off, it's hollow underneath? I get those little bat rastards on occasion too and it drives me nuts. Would also like some insight on this as I was going to roll it into my other thread.

AKmud · Mon Feb 10, 2014 11:21 pm

ZfrkS62 wrote:
AKmud wrote:I've run in to that before as well. The weld will look just fine until I stop then a bubble will develop and rise as the puddle cools. It doesn't happen all the time and I can't intentionally duplicate it. I usually just knock it down and tack over the top of it.
Do they tend to rise up out of the puddle randomly like a stalagmite in a cave (the one that comes up out of the ground)? And when you grind it off, it's hollow underneath? I get those little bat rastards on occasion too and it drives me nuts. Would also like some insight on this as I was going to roll it into my other thread.

Exactly! Really hacks me off sometimes.