MIG and thin sheet metal

Have you tried using .023 hard wire with shielding gas.The small hard wire penetrates much less than fluxcore without gas.

 

I'm running into the same issues as well on my trailer. Just replaced the lower 2" across the front panel yesterday, and had the same thing happen on the last pass! Thankfully the "re" patch is in a "won't show" area. I've been using .030 flux core, but will be going with Argon/ CO2 and .023 wire very shortly. Any other tips out there from more experienced welders...?

 

Do you have a wire speed control? On my Hobart mig, thin metal is best welded at power 1 with a fairly fast wire feed speed.

 

Low power, low wire speed. And using an air flanger, so you can overlap the panels makes the job a lot easier than butt welding the patches. Northern sells a good one for $63 - this is the one I have.

http://www.northerntool.com/webapp/...tDisplay?storeId=6970&productId=14322&R=14322

 

X2. I'll be trying the lowest power with a faster wire speed on my next patch made with flux core...

 

One thing I'll add. Someone mentioned making a pass. When doing sheet metal, you tack, spot to spot, w/ at least an inch between. You should be on the trigger no more than a second. Low heat and moderate wire speed. Work your way around the panel, filling in as you go. No beads here and its not pretty welding. Make it pretty when your done w/ a flap disc and body filler. The less heat means less warp means less body filler.:v6:

 

If you're able to reach the back side of what you're welding on you can use a piece of aluminum to absorb a lot of the heat and prevent the blow through.

I bought a few scrap pieces of 1-inch thick aluminum to do the trick. I've also used an old aluminum forged piston for corners and tight areas. Hold (or have a helper hold) the aluminum tight against the sheetmetal on the backside as you weld. You'll be suprised.

 

Take a look at this site...20 gauge welding wire
http://www.jwharris.com/images/twentygauge.pdf

 

I used .35 with a Lincoln 135 on the C setting and the speed turned about 3/4s to fill some extra screw holes in my body tub.

I used a 1/8 drill bit to make sure it was clean and stuck a piece of the same wire through the hole before welding around it. When I wsa trying to fill the holes before as soon as the wire arced it would blow pea size hole out.

 

Dan on the welders that we use at school we turn the heat down and the line speed UP. On a miller 175 usually set it about 2-3 heat and 50-60 line speed. Works great for tacking and welding the thinner stuff.