Welding thin tubing with a HF 125 flux core welder

I mostly got my welder to do some body repair (rust) on an old Land Cruiser. I was given similar advice for welding sheet metal from my welding teacher as Brino gives. Short welds and then move to a different spot so it can cool. Basically a series of long tack welds.
He said he has also used a wet sponge to help the area around the weld cool faster. Not on the weld, but a few inches away where it won't contaminate the weld bead, or cause too rapid of cooling which can weaken the weld.

Aluminum also works as a good heat sink. Where I've had sheet laying on an aluminum plate, and then pass onto an area not in contact with the aluminum the difference is immediately apparent. Easy on sheet or flat parts, not so much with tubing, but maybe if you were able to make a collar that closed tight around the tubing that might help?


A less caustic way to remove the zinc coating than muriatic acid is soaking in white vinegar. It takes longer, perhaps overnight but it is safer to handle. The vinegar you buy in the cleaning aisle is more concentrated than the kind sold for cooking. You can buy industrial white vinegar as strong as 30%, cooking vinegar is usually around 5%, the % being how much acetic acid is in the solution.
 
On this practice tubing I have been using the wire wheel on my grinder. Takes less that a minute to remove the galvanizing to get the metal bright and shiny.
 
Wire wheel works great for zinc. It takes a pretty good dose to get metal fume fever.

When you start working with exhaust tubing, you'll probably be dealing with stainless or aluminized tube. Both weld like a dream compared to galvy.

You'll definitely have to face your header flanges on the mill when you're done to get them flat. Until you get experience, you won't know which joints will want to warp from the heat or pull from the shrinking weld. Headers are what I consider "fine work" where minutia and nuance are what will get the result.

I bought a 240v/50Hz overseas version of that same HF machine a few years ago when I realized buying the blue fortune cookie welder was cheaper than buying a new exhaust to pass vehicle inspection. I barely made that repair happen for lack of heat control. I was either burning through or spattering the arc out most of the time. The little bamboo box welder was about as useful as a car battery, a pair of jumper cables, and a wire coat hanger when it came to burning metal together, but it could do thicker work easier than thin with a passable amount of integrity. I was interested in the DCEN straight polarity modifications that you've done, seems like a big help, but now that I'm back in the states with my big welders I don't think I'll ever get around to it.

I understand working within constraints, especially budget. Welders aren't cheap from the dealer, but craigslist seems to be a great place for welding equipment. If that's out of the question, I get it. I'm not saying fabricating a header is an impossible task with what you have, it'll just take effort, patience, and lots of extra grinding discs. Let us know how it goes, I'd like to see the project!
 
Local muffler shop had a huge scrap pile of exhaust tubing. Got a couple of pieces for free and can take as much as I want in the future. Should have my Lincoln nr211mp wire on Monday and have also ordered a magnifying lens for my helmet that I should get by Tuesday. More practice next week.
 
Between splitting more firewood this morning I took a break and did some practice welding on the exhaust tubing that I picked up last week. This is using the HF wire. Much easier to weld than the conduit. Did not get good penetration on the min setting on my welder. Switched over to the max setting with the wire speed at 3. Very easy to do tack welds. I was also able to run some beads without blowing thru. I think that I am getting this down. Still lots of practice ahead of me before I try to weld headers for my midget.

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A little while after this the UPS truck arrived with my Lincoln wire and the flux core nozzle. I bought this from Home Depot and it was shipped directly from Lincoln. Lincoln sent me the correct nozzle but the wrong wire. I got mild steel mig wire. Not flux core. Lincoln is sending the correct wire and told me to keep the mig wire. They didn't want it back. Cost more for the return shipping than their cost on the wire. Should have the correct wire in a couple of days.
 
mickri said:
Lincoln sent me the correct nozzle but the wrong wire. I got mild steel mig wire. Not flux core. Lincoln is sending the correct wire and told me to keep the mig wire.
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That will make a possible future gas conversion even easier/quicker/cheaper!
-brino
 
With that HF welder leave it set to max and just adjust the wire feed until its welding nicely.....
 
As far as the HF unit being not up to the task. Well every time I hear people say things like that I wonder how they ever managed to do these things before all this equipment. or how they manage to do this stuff in third world countries. Flux core is pretty lame, but it's what you have. We tend to forget that we can do things like this, it is just going to be not as pretty or take longer or have a longer learning curve (exceptions apply)
I would continue to raid the exhaust scrap pile. Also the amount of wire stick out can have some effect of the puddle due to the wire being heated by the current running through it.
 
Funny how just the other day I had to weld up something similar thickness and decided to go for it rather than go to OA. What I did was tack weld it together with 3-4 tacks then fill in with basically tacks, never trying to run a bead. Having a good helmet with an auto lense is key. That way i can overlap the tacks to make them into what looks like a solid weld for me. FYI my mig is a Lincoln 175T running .030 flux wire.
 
Got the nr211mp wire today. I finished repairing my patio deck today. Needed to get it done before the rains arrive tomorrow. Will do more practice on the exhaust tubing tomorrow and also more welding on my 1966 midget.
 
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