mig welders

Is flux core wire adequate for quality body work or should
full on gas be used to shield the weld from contaminants / oxygen etc?
i don't want my repairs to rust out at the welds down the road sometime...

thanks in advance guys...

You need gas shielding for sure.

To weld sheet metal you need to run .023 wire and use shielding gas generally 75 carbon dioxide/25 argon. Having a welder with a infinite dial as opposed to discrete settings is also nice.

flux core wire produces a lot of spatter, might be OK for floor patching but not for outer panel work

[quote=rowin4]flux core wire produces a lot of spatter, might be OK for floor patching but not for outer panel work [/What Rowin Saidquote]

I don't recommend flux core wire for bodywork. It will work, but the thicker wire will want to burn through, and it is a mess to cleanup with the flux cover and spatter.
The small 0.023" wire and 75/25 Argon/CO2 works very good for sheetmetal.

http://www.lincolnelectric.com/en-us/sup...rc-welding.aspx

The problem with flux core for bodywork is that you want to put a patch on completely with tacks - no continuous beads. So the flux core will leave a flux coating on each bead which would have to be thoroughly cleaned before you could put one next to it. It would take forever to put on even a small patch !!

.023 is ok for for tacks but for plug welding I prefer .030 (personal preference)

You definitely want to use the argon/co2 mix.

Look into the wire - apparently there is a wire that yields a softer bead, making grinding much easier and therefore generating less heat. I haven't found it yet but haven't looked that hard either!

I agree with most of your statement, however my personal preference is .035 wire, and just Argon gas, as far as grinding the welds, I find a 36 grit Zirconia flap wheel the best, but change often for a true flat cut

The problem with flap wheels is they'll ride over the bead and take metal off the panel on either side. A solid grinding disk will only remove metal where you touch it. Again, personal preference.

And I would never run straight argon on a mig, argon is for tig. Keep in mind that straight CO2 gives the best penetration BUT a lot of spatter. A mix of CO2/argon reduces penetration but virtually eliminates spatter. So it only stands to reason that straight argon will have the least penetration but no less spatter. Also, argon on a mig is only recommended to be used on sheet metal, so if you use your welder for multipurposes including thicker metals, you don't want argon. The mixes I've used are "Mig gas - Gold" and "Auto weld".

seems straight argon is ok with the silicon bronze wire that is the easy grind stuff
and that wire looks tempting except it seems pretty expensive.

if i were looking for a welder for sheetmetal then i'd look for a mid size mig, miller, hobart or lincoln with the capability to run shielding gas.
something like a miller 175/180/211

cut up some spare metal and go to town welding it back together, figure out how to get a nice spot weld and really figure out how the machine works.

I have a miller 180 and use .035 for normal welding and .023 for body stuff all with 75/25. If you cant get enough penetration with 75/25 then you are using the wrong type of welding system. I also have a buzz box Lincoln stick welder, for heavy stuff and really enjoy laying down stick welds more than migging. I feel like stick welding is more rewarding, in a artistic/skill sense!

I agree. My Miller 252 is not happy running at the lower range.

Silicon bronze is fine for lap joints but no good for butt joints. It does not penetrate the parent metal like a steel wire does, so on a butt joint the only material left after grinding the joint is the weaker filler material.

Gas for sure, argon/co2, 75/25.

My Miller 252 with .035 wire does not like to do the low range butt welds on sheet metal, but lap welds work out OK. I use the same wire I weld everything else with.

For weld clean up, I use a 3/16" cutoff wheel on a die grinder to take the high spots off. Since I mostly lap weld, I also flange the sheet metal and leave the step down a little and weld in the low section between the step and the new metal. A lot less grinding. I don't hang many quarters, so the lap joint is not an issue. Gene

Argon runs hotter than 75/25 gas

I use to be of the "old school" when it came to grinding welds, using a hard solid wheel, but flap discs have evolved quite a bit in the last decade or so, there's angled discs, flat discs, even discs just for doing 90 degree joints, "see thru" flap discs so you can see exactly what your grinding under the disc as it's cutting, "cool run" flap discs, etc, etc, the down side is price, most are $10-$20 each and don't last long, so most stick with the $3-$4 hard grinding wheels/disc, once you use a proper flap wheel for cutting down and finishing a weld, you'll never use a black hard disc ever again, the only time I find myself needing a hard disc is to cut down a grotesque weld one of the new guys welding at the shop may have done, just so I don't waste a good flap wheel....but to each his/her own, as we learn and like different styles/techniques, but it's always good to hear/see others experiences

Mike

I use these Neiko flap disks from Amazon, 20 for $25
http://www.amazon.com/gp/product/B008DJGWPC?keywords=60%20grit%20flap%20disc&qid=1457480552&ref_=sr_1_2&refinements=p_72%3A1248921011&s=industrial&sr=1-2

They are pretty good for the low price.