I got a mig welder not to long ago and wasnt too impressed with the flux-cored wire welds (although I need more practice). I was told gas typicaly gives it a cleaner weld so I figured I would price it out. The shop wanted a bit more than I wanted to pay for the standard argon/co2 tanks. They said a cheaper option for me since I already have a 15# CO2 bottle was just to use straight CO2. So I picked up an adapter and regulator for it (after checking online I payed way too much for it dangit!!!).

My questions, as I have never welded with gas, is what do you set the pressure at? And does it need to change for different heat/metal thicknesses? Keeping in mind this is straight CO2 (not sure if it would be different for argon).

My first real project will be a sort of brush guard for my bumper. There is a picture of what I want to do in my gallery under my '99 f150 (the last couple pics in that gallerey). Thanks for any advice.

 

I believe on my welder I have the pressure set at right around 15 psi. I usually start with the pressure fairly low, run a couple of passes and make sure my gas flow is adequate enough. I typically use straight CO2 for all mild steel welding because of the availability of it for me. I do have a rented tank of straight Argon but it's only used for SS applications. Most places that sell welding supplies and gases will rent bottles and if I remember right mine is about $3 for 3 months not including the fill up. Hope this helps.

 

I didnt think of askign about renting... $3 seems kinda cheap (well actualy dirt cheap since I can probably scrounge that much up in the sofa cushions). For the tall tank here they wanted like $180ish if I remember. Another $120 for the reg, and how ever much the fill was. In all I think they quoted me around $330ish. I was like... ummm.... no. Not for the twice a year that I'll be using it. I only paid like $169 for the welder new (cheap ol' harbor frieghter).

I actually have a CO2 tank for my freshwater fish tank I inject gas into. Its a 15# bottle, not sure how long that will last.

So how do you know when you found the right pressure, whats the signs for it too low or too high?

 

The gas is simply to shield the weld from the atmosphere and prevent air bubbles. Practice a little with different settings. Run just enough to keep the bubbles/pinholes out of the weld. Any more is a waste. That bottle price isn't just WAAY out of line, but the regulator price is. You should be able to get a decent one for around $75. Just saw a really good one at the pawn shop the other day for $40. Hope this helps.

 

I know, its too late know though. He quoted me like $95 for a single guage and $120 for a dual guage. When I got home I searched online for the exact same model and I found one on i think it was weldingsupply.com for $60-some dollars! They were indicating that the 'list price' was $120. Maybe I can tell em that it leaks or somthing and take it back without having to pay the 15% restocking fee.

 

Check Ebay. I got my 20# CO2 tank for like $100 (used) to my door, with a good inspection. Regulator is an Argon jobber that I got free from my uncle (proffesional welder). They have used reg's on ebay as well for pretty cheap, and Northern carriers some descent reg's for like $70.


My opinion a new tank is a waste. . . Well, if you swap em out like most places do. Unless you specially request your tank to be sent out and returned, your just buying a tank to throw into circulation (like propane).

 

For the amount of welding you plan on doing I would suggest just getting the small tank. My regulater came with my welder but I did have to get another one for my TIG setup and I don't think it was more than $45. I imagine part of the cost that I got that day was the fact that I dropped near $1000 and they were wanting me to come back and get more.

 

Thanks for all the advice everyone. I probably didnt make it clear but I already have a 15# CO2 tank (got it for $65 from local welding shop - used). I already got the reg too and I am guessing its starting too get to late to return it. I'll probably start some practice welds with the new mig setup later this week. What I am welding is 2" 'hand rail' tubbing (2 3/8od) which I beleive is sched 40. My welder goes up to 85A and I need to buy new wire, all I got is flux-cored. So if anyone is still reading this post any suggestions on what heat would be good and what size wire for a noo-b? Thanks

 

2" schedule 40 has a 1/8" or 3/16" wall, I forget, so with your 65A welder turn it all the way up to "max" and adjust the wire feed rate to control the weld puddle appropriately. That's how I made my "now famous" superbumper - 1/4" plate, two passes, with a 120V mig welder (though I used flux core, I'm lazy and cheap).







Here is the whole story:
http://frederic.midimonkey.com/f350-superbumper.html

And there is nothing wrong with a smaller tank, as long as you know you're going to need to refill it more often. That's one of two reasons why I prefer flux-core, is refilling tanks is a pain in the *** if you don't live near a welding store. A lot of my welding is done in the evening (sometimes really late too!) and if I run out of gas I have to stop. The second reason is that *all* of my gas bottles are from a supplier in CT, and now that I live in NJ, no one will refill them, as the bottles "aren't theirs". I'm not driving 3 hours each way to CT to refill them, and I'm not buying into another set if bottles (co2/argon mix for Mig, Oxygen and Acetyene for my torch).

So, I've learned to deal with flux-core mig welding splatter and worked out various ways of reducing it.

Most welding supply places sell "welding spray" which you spray around your weld area and this helps prevent the little "mig *****" from sticking. If you breath in while spraying this stuff, you might notice it smells an awful lot like "Pam" cooking spray. So... I tried "Pam" and guess what - for 1/3 the price it works just as good.

What I do is cover the area to be welded with electrical tape, then spray over the area with PAM, then rip off the electrical tape. Zap my flux-core bead in, then grind and finish as I normally would. Pam (or welding spray) wipes off with a rag, or if you enjoy fumes you can spray it off with brake cleaner. The electrical tape doesn't stick well but just enough that you can spray over it then yank it off no problem. And, you can go around tubes and other oddly shaped joints no problem.

I've also used metal paint in place of the Pam cooking spray, without a primer. Just because it's lying around and I have probably 40 almost empty cans of different color rustoleum lying around. Same thing - tape over joint, spray, peel tape, then flux-core weld the joint together. Since all my projects require grinding, wirewheeling and so on to get a nice, finished surface for the final paint, I'm not worried about a little bit of different color rustoleum here and there.

Here are some flux-core welded schedule 40 tubing:



The left most sections of tube were just welded in this picture, using a 120V Lincoln SP130A, with flux-core wire. You can see the splatter isn't bad at all. Obviously some grinding to do but certainly not "awful". The right two tubes have been welded, and cleaned up, and you can see the beads are much nicer post-cleanup.

This is one of two exhaust manifolds for my twin-turbo 500cid stroker, made mostly out of schedule 40 "black pipe" which I got at Lowes or Home Depot. The header plate is 3/8" thick plate which I attacked with a hole saw, and yes, I know I have to shape the exhaust ports with a die grinder, and will do so to match the heads once I'm done porting them. The turbo flange is a chunk of 1/2" I cut using my oxy/acetylene cutting torch which I attached to a jerry-rigged pattern copier, and copied the turbo flange gaskets.

X-Y dolly-based pattern copier (partially completed, I can't find the finished picture):

 

When I was looking at my own post, I noticed none of the pictures came up. Seems the T1 to my little server farm is dead. Please be patient, I'm torturing my ISP at the moment!