View Full Version : Moving from Flux-core to gas MIG

01-19-2012, 02:29 AM
Article on tallbike.org (http://tallbike.org/blog/bikes/flux-to-gas)

I recently converted from flux core to gas-shielded MIG welding. The upgrade involved buying a gas bottle with an argon/CO2 mixture, and a flow regulator. My Clarke welder was a dual-purpose gas/no-gas unit that I've been using flux-core wire in.
The difference between flux and gas is INCREDIBLE.

This weld represents the best I can do with the flux-core wire. I made it just before I hooked the gas cylinder up. You'll notice that there's spatter that needs to be ground off, slag covers every weld and needs to be chipped/ground off, and the weld surface is pretty rough, so painting it would require further preparation to get a quality result.
http://tallbike.org/sites/default/files/styles/3-col/public/best-flux-core-weld.jpg (http://tallbike.org/sites/default/files/styles/10-col/public/best-flux-core-weld.jpg)

Now, here's my best weld with just a few minutes of practice after getting the gas bottle hooked up and the machine 'dialed in'.
the difference is striking! No spatter, no slag to chip, almost no cleanup at all and a brilliantly smooth 45 degree fillet!! Brush it a bit and call it DONE!
http://tallbike.org/sites/default/files/styles/3-col/public/best-mig-weld.jpg (http://tallbike.org/sites/default/files/styles/10-col/public/best-mig-weld.jpg)

Here's another flux core weld - this is pretty typical of the welds I was making before the gas. Not the best, but serviceable.
It's spattery, covered in slag, with an ugly weld surface.
These welds are strong enough, but they require a LOT of cleanup afterward.
The slag on this one has already been chipped off and wire brushed, but it could really use some attention with a drill-mounted wire wheel, and I'd probably even smooth it down with a flap disc before I'd feel comfortable painting over it.
http://tallbike.org/sites/default/files/styles/3-col/public/flux-to-mig-1.jpg (http://tallbike.org/sites/default/files/styles/10-col/public/flux-to-mig-1.jpg)

Cleaning flux core welds takes about 5-10 times longer than actually doing the welding, while almost none of this crap is required for the MIG welds! They have almost no spatter or slag at all, and a very smooth, finished-looking weld surface!

For a test with thicker material, I bent this piece (probably 3/16") into a ring and welded the ends together. I made a single weld on the inside with not great penetration, so I ground a V on the outside and connected them with two more welds - the first is called the 'root pass' and fills the bottom of the V, then I layed a wide, flat, filler weld over the top (shown) to complete the joint.
Besides brushing lightly with a wire brush after, there was NO cleanup required.
I'll use the ring as a tank retainer on a new welding cart I'm going to build another day.
http://tallbike.org/sites/default/files/styles/3-col/public/flux-to-mig-2.jpg (http://tallbike.org/sites/default/files/styles/10-col/public/flux-to-mig-2.jpg)

Here are some more practice welds with the gas. I wrote my initials, nice and clean with multiple passes to build up the letters. There's NO SLAG, so no chipping is required between layers!!
The weld above the letters isn't fantastic, but still looks better than most of my flux welds. This seems to be a very different process and I'm going to need more practice!
The other welds at the top look fantastic! They're much better than I could have ever done with flux! I have just 1 hour of using gas and I'm already a weld snob!!
There's a bit of brown smoke residue near the top welds, which I think is caused by either not enough shielding gas, or maybe some contaminants on the metal surface burning off.
http://tallbike.org/sites/default/files/styles/3-col/public/flux-to-mig-3.jpg (http://tallbike.org/sites/default/files/styles/10-col/public/flux-to-mig-3.jpg)

Here's a thick plumbing pipe at the top, connected to a thinner bit of bicycle tubing (seat tube, I think), then a little 17ga chromed tubing.
I could certainly do better with the thin stuff, but that top weld is GORGEOUS, even with a little bit of undercut at the bottom. There was a pretty large gap to fill 'cuz the plumbing pipe is a smaller diameter than the bike tube and my coping job was very basic.
http://tallbike.org/sites/default/files/styles/3-col/public/flux-to-mig-4.jpg (http://tallbike.org/sites/default/files/styles/10-col/public/flux-to-mig-4.jpg)

01-19-2012, 02:31 AM
That plumbing pipe at the bottom has a very thick wall, but that actually makes it easier to slow down and build up a nice weld without burning through the tube.
The chrome tubing is similar to what the solidarity bike is built of, and is a bit thinner than the bicycle tube. It came out OK, but I need more practice with that thin stuff.
http://tallbike.org/sites/default/files/styles/3-col/public/flux-to-mig-5.jpg (http://tallbike.org/sites/default/files/styles/10-col/public/flux-to-mig-5.jpg)

Compared to flux, the MIG has SO MUCH LESS smoke - practically none! You still have to be careful around zinc or chrome, and provide adequate ventilation in those cases. Welding with flux core would quickly fill the garage with haze - yuck! I think those days are over!

If you already have a wire feeder capable of gas, it's a pretty good investment. I paid about $340 for an 80cuft cylinder full of argon/co2, the flow-gauge regulator, and a 12.5lb spool of solid steel wire.
I think I may have spent $400 on the welder initially, so figure about $8-900 for everything if you get it all at once.

http://tallbike.org/sites/default/files/styles/3-col/public/DSC_0265.JPG (http://tallbike.org/sites/default/files/styles/10-col/public/DSC_0265.JPG)
My welder is a Clarke 125EN - similar to this one. It's no Miller or Lincoln I'm sure, but it's a good little unit for us garage hackers.

I hope you find this helpful! Comments/critiques about my (lack of) welding experience will be greatly appreciated! :D

01-19-2012, 02:31 PM
Thanks for taking the time to assemble this thread tree. I found it helpful, and temps me to upgrade. Looks like just the time savings alone is worth the extra money.

01-19-2012, 05:46 PM
Thanks for taking the time to assemble this thread tree. I found it helpful, and temps me to upgrade. Looks like just the time savings alone is worth the extra money.

Yeah, I think it's the best investment I've made so far. I wish I had upgraded earlier!

10lb solid-wire rolls are a bit cheaper than 10lb of flux wire, but when you compare a big roll of solid to the 2lb flux rolls I was buying previously, it's a no brainer - a 400% price difference per pound!
And to think of all the time I've thrown away chipping, brushing, grinding, re-welding, grinding some more... Just the trouble in cleaning up the welds is probably what has prevented me from ever painting my projects before. :P

Not to slag off on flux (get it? :laugh3:). Flux-core wire is a GREAT thing! Throw it in there, pull the trigger and you can start welding for half the initial price of a full gas unit! I may have never started welding if there wasn't this cheaper option, but daaaaammnnn those gas welds are sexy. Makes me wish I had the cash back when I started. :D

01-19-2012, 05:51 PM
Now you know why I'm looking at doing the conversion to mine!

01-25-2012, 01:37 AM
I've got some pics of the new argon bottle and regulator! I'm simply in love with this thing - it makes welding so much easier - obviously better penetration, no slag to chip, a smoother weld. I can't say enough good things about it. :D

It's an 80 cuft tank - they fill it to around 1900 psi.
The one problem I have is that the valve in my welder LEAKS - very slowly, but noticably, without pulling the trigger, there's a hissing sound at the nozzle. Remember to shut off the main valve when not working.
http://tallbike.org/sites/default/files/styles/3-col/public/IMG_20120124_211624.jpg (http://tallbike.org/sites/default/files/styles/10-col/public/IMG_20120124_211624.jpg)http://tallbike.org/sites/default/files/styles/3-col/public/IMG_20120124_211635.jpg (http://tallbike.org/sites/default/files/styles/10-col/public/IMG_20120124_211635.jpg)

I'm getting better with the process too - learning to keep the wire feed speed down and the power UP. MORE POWER!!
Some welds are better than others, but here's my best weld on the bottom bracket clamps.
http://tallbike.org/sites/default/files/styles/3-col/public/IMG_20120124_211607.jpg (http://tallbike.org/sites/default/files/styles/10-col/public/IMG_20120124_211607.jpg)
Again, the above has ONLY been lightly wire brushed!!

03-21-2012, 07:43 AM
When Mig welding, a good tip is to move your weld in a "U" or "E" pattern. This will help flatten the weld and ensure you are digging into both pieces. Moving left to right is called pulling the weld and moving right to left is called pushing the weld. Greater penetration is achieved by pulling the weld. Pushing will create a higher weld "Crown".

03-22-2012, 01:05 AM
the cleaner the metal the better the weld. And no just using a wire brush is not enough you need to completely remove all the rust and millscale dirt oil/grease and all other crud. Use a grinding wheel and sanding flap disk followed by a wipe down with asatone. DO NOT USE BRAKEKLEEN!!!!!!!! then chemical reaction caused by the heat of welding can make you sick or kill you

03-23-2012, 12:54 AM
the cleaner the metal the better the weld. ... Use a grinding wheel and sanding flap disk followed by a wipe down with asatone. DO NOT USE BRAKEKLEEN!!!!!!!!

Good advice. Clean weld, strong weld.
I'm guessing you saw a can of brakleen in one of my photos? I don't use that stuff for weld prep! I did a brake job not long ago and stuff never gets put back where it should... :P