Welding Tips and Tricks

Greetings all. Just wanted to throw this out there. I just changed jobs and the shop I'm working in now MIGs almost everything. I'm pretty good at MIG if I do say so myself but I've never had much practice on welding pipe or anything related (couplings, small vessels, small tubing ect ect) with MIG. I've done a lot of structural welding with MIG and my welds look great and are solid but I am definitely having a hard time getting air tight welds on any pipe related welding. If its a beveled joint I don't have any problems really but when I try to weld a coupling or a piece of pipe thats sticking through a hole in some plate, at least 50% of the time I get a leak when we do the dye penetrant testing. Very frustrating to say the least. Wondering if any of the good folks on the forums here have any suggestions? My own assessment of the problem seems to be that you need to be very careful to not step outside your puddle in the slightest as you advance forward if you want it to seal air tight, but you also don't want to go too slow and let filler pile up reducing penetration. Just a theory I have... your thoughts? Oh and I should mention, this is short circuit transfer. Most common problem is on #3000 couplings welding through a piece of 1/8" - 1/4" thick plate. All parts are sand blasted, 100% clean or mill scale and rust and I'm meticulous about keeping my welding machine in tip top shape. Ground is good and clean. Correct gas. . Tried everything I can think of with only limited success avoiding leaks. ANY advice or tips you guys could offer would be very much appreciated! Thank you in advance.

-James

Background: Welder for 4+ years and fitter for about 2. Graduate of Tulsa Welding School. Experienced mostly in small part fabrication (items under about 200 lbs). Some experience with larger items. A few 15 ton platforms for an oil rig and some large structural items for acid hauling trailers. Also a fair amount of blow down stack welding for oil refineries. Both long and round seams. A small amount of vessel fitting (basically was told I couldn't do it... so then I did 3 of them with 0 markups from QC much to the chagrin of my lead man who has never build 1 without mark ups). Trained in stick, mig, tig and fluxcore and decent at all 4 though my tig is probably a bit rusty these days. Lastly, experienced enough to know, that I don't know it all. Your wisdom is always appreciated by this welder.

James,
Few questions first. What was your parameters, what gas exactly is "correct"? You mentioned jumping ahead so I assume you are jumping ahead while welding. With that I would have to guess you are not going back over your missed spot well enough. One thing you didn't mention is where are the leaks showing themselves? I have a hard time believing your leaks are mid weld rather they are probably at your start stops. If this is the case I suggest trying this and see where it takes you. If you are welding around a pipe grind your start/stop down a bit and always weld over your previous weld at least 1". This should help your leaking issue.
-Jonathan

Jonathan, as far as weld parameters go, I'm not sure exactly what you're asking for but the weld is a fillet weld somewhere around 3/16" in size. It could actually pass if it was only 1/8" but usually we add just a tiny bit to the size. The gas I'm using is just run of the mill 75ar/25co2 and what I'm welding is just ordinary carbon steel plate. I believe its cold rolled steel. The couplings are also just ordinary carbon steel. Using ER70S-6 wire (.035). Running approximately 200-230 ipm and as far as voltage I've tuned it by ear and eye because the volt meter on my machine at work is WAY out of calibration. Lastly, the majority of the leaks ARE popping up mid weld but not always. The leaks are always at the toes of the weld. Hope these details help. Gotta get back to work. Thanks!

Ok if the leaks are at the toes of the weld I would have to say it is either you are not hitting the joint correctly or you are not hot enough. Are you doing a whip, kinda like mig like tig?

One thing that can be considered is if it is sand blasted you would have impregnated the steel with impurities and this could also become a factor. I once made two fuel tanks that the customer wanted sandblasted on the inside (which turned out to be a mistake by the way) and I had to go back and sand off the surface where the welds were to go, otherwise I had a nasty weld. This will also depend in what the blast media is.

The parameters I was looking for is what you offered, Volts, amps etc. Keep us posted.
-Jonathan

Jonathan, as far as I know our blasting sand is some sort of granular metal product but I'm not certain. I do whip my weld a little, much in the same way as Jody does in his mig videos but as I said before I'm trying to be very careful and not step outside the leading edge of the puddle. I will try running it hotter and see if that's the solution. Its pretty thin plate but I guess as long and I'm not blowing holes in it, its not too hot lol. Thanks for the tips. I'll keep you posted on how it turns out.

-James

James
Can you get us a picture I your welds, specifically one that has a leak and a pic of a weld with die check?
-Jonathan

JRowe wrote:Jonathan, as far as I know our blasting sand is some sort of granular metal product but I'm not certain. I do whip my weld a little, much in the same way as Jody does in his mig videos but as I said before I'm trying to be very careful and not step outside the leading edge of the puddle. I will try running it hotter and see if that's the solution. Its pretty thin plate but I guess as long and I'm not blowing holes in it, its not too hot lol. Thanks for the tips. I'll keep you posted on how it turns out.

-James

A quick pass with a flap-wheel on a grinder in the weld zone may help. An agressive blast media will leave residue that may be interfering with the fusion. This has to be a lack-of-fusion issue to leak at the toes. Increasing the heat should help, as well, but expect to move a bit faster (increasing the amps in MIG means increasing the wire speed or decreasing the voltage, and I can't recommend decreasing the voltage at the wire speeds you posted... I suspect you may have to up the voltage a bit, too.)

When I "whip" a MIG weld, my goal is to move the arc abrupty to the very edge of the puddle, but whipping is not required if you have the heat "just right"... once it's dialed in, I find it easier to just advance at a smooth steady pace. But, then again, welders are like "snowflakes"... No two of us do it exactly the same.

Steve S

Hi guys. I'm new to the forum, joining only today.
Not sure if my issue would be classified "leaky" but here it is nonetheless:
I bought a new Miller MIG welder model 252 with a Spoolmatic gun.
Welding aluminum, each time I make a bead and pull up from the weld, I see a crater with a pin hole in the middle. This happens every time no matter what I do. I'm at a loss to determine why this is happening. Even attempting to fill in the crater still produces the same result. What am I doing wrong?

RPat wrote:Hi guys. I'm new to the forum, joining only today.
Not sure if my issue would be classified "leaky" but here it is nonetheless:
I bought a new Miller MIG welder model 252 with a Spoolmatic gun.
Welding aluminum, each time I make a bead and pull up from the weld, I see a crater with a pin hole in the middle. This happens every time no matter what I do. I'm at a loss to determine why this is happening. Even attempting to fill in the crater still produces the same result. What am I doing wrong?

I'm assuming you mean at the end of the weld only - one way to stop that is use a run-off tab and stop there instead.

Run-on and run-off tabs are how I use a spool gun for aluminum when edges are involved (I prefer tig though so hardly ever do it).

Good luck