WELDING BODY PANELS WITH FLUX CORE
You’ve probably hear that you shouldn’t flux core weld automotive sheet metal body panels. We tried and have a different opinion…
So your new project car has rust. That means you’re planning to cut the rusty body panels out and replace them with fresh sheet metal. If you’ve been to your local hardware store like Harbor Freight you’ve probably also seen the price difference between a flux core welder verses a MIG/TIG welder. Not only is there a BIGGER price difference but, MIG/TIG will also require shielding gas. This means you’ll need to factor in the price of around $300 for a gas tank and another $90 to get it filled with the proper gas. If that sounds overwhelming, we completely understand. The solution… turn back to the flux core welder.
Flux Core Welding Sheet Metal uses gas-less flux core wire which means you don’t need gas. The wire contains “Flux” which will burn while you weld.
The flux acts as a protective gas that stops the weld from becoming contaminated. Tons of folks will tell you not to flux core weld thin sheet metal and here’s a list of their responses:
Its ugly… The weld initially looks bad because of the slag from flux core welding.
Spatter… Tiny beads of metal also get left behind after flux core welding which can create more grinding work.
Porosity… You’ll get tiny holes or pockets of contamination in your weld.
Blow out… This is when your sheet metal literally blows out the sheet metal into a hole.
But we’ve found that with a bit of practice you can overcome anything. A bit of fine tuning your voltage or wire speed/amperage welder settings and some grinding works wonders.
Tuning the AMPS and VOLTS settings on our Eastwood MP140i Elite Welder
So now you’re thinking which welder should you buy? You can go with Flux Core only or you could spend a little more and get a multi-process welder. Multi-process welders can do Flux, MIG, TIG, and/or Stick. This lets you start with Flux and add gas for MIG or TIG later.
Eastwood.com also makes a low cost Flux Core welder that can MIG weld with a future purchase of a gas regulator, hose, MIG wire, and a gas tank. It’s the Eastwood MIG 90 Flux Core Welder. It also comes with a 2lb spool of 0.030” Flux core wire included. We have the Eastwood MP140i which can do Flux, MIG, TIG or Stick welding. You can also compare different welder brands here.
Once you settle on your welder, flux core welding thin sheet metal can be pretty easy.
Load the wire into the welder, feed it into the torch feeder, and lock it in.
Feed the flux core wire through the torch.
Cut the end and leave about 1/4 inch of wire stick out.
I’d also recommend getting a flux core nozzle which will allow you to see the wire as it makes contact with the sheet metal a little easier through your welding helmet. Being that there’s no active shielding gas, you don’t need the cup shape nozzle.
Setting up a welder with flux core 0.030 diameter wire through a welding torch with a flux core nozzle
Also make sure you have all your other personal protection equipment such as flammable wear, appropriate welding gloves, welding mask, welding blanket, proper respirator, and a fire extinguisher.
Miscellaneous protective welding gear
FLUX CORE WELDING STEPS
Next get your sheet metal setup. Make sure the sheet metal is the weldable kind and get it a clean with a wire wheel or sander. I’d also recommend practicing with a butt joint on some spare thin sheet metal as that will be the most common weld you’ll be doing on your project car.
Practice with no backing of a welding table or any other metal behind the two pieces where the metal meets. This will help you practice without a heat sink. Next set your voltage and wire speed to the recommended value based on your Flux Core Wire diameter and the thickness of your sheet metal. Usually the reference table inside your welder is a good place to start. Make sure your parts are clean, attach the ground cable to another part of your clean sheet metal.
Butt welding 18 gauge sheet metal panel to BMW e30 firewall.
Now place your welding gun with the flux stick out hovering ever so slightly in the middle of your butt joint and pull the trigger for a second or two. Hopefully you don’t blow out the metal. If you do, lower your voltage and wire speed. Then try again.
Flux Core Stitch Welding a small circular sheet metal patch.
What you’ll find with sheet metal automotive welding is you’ll have to tack weld or pull the trigger for a second or so to get a single small weld laid down. Then stop and lay another tack right next to your previous tack. Its also recommended to jump around and tack weld in different places to prevent warping.
You’ll notice that high heat placed in a single area will create severe warping on thiner sheet metal. If you still have trouble, let a little more of your wire stick out and weld again. Sometimes we find that a little longer stick out with higher settings will lay a tack without blowing through the metal.
