View Full Version : Mig Welding

Trent Flemming
03-18-2010, 10:27 PM
Hey Gang,

I just got a Millermatic 211 welder and purchased some 3/4 square tubing. It seems to be coated in some light oil. Should I the clean tubing before welding?



Gary Click
03-18-2010, 10:43 PM
I don't typically, I either use Flux-Core or CO2 with solid wire and get good results with slightly dirty and lightly rusted steel.

Eric DeSilva
03-18-2010, 11:07 PM
I've got the same 211. You are going to have fun with that thing, trust me. I use Argon w/solid wire. Most of what I've been welding has been in the 14 ga to 1/4" thickness range, a lot of 14 ga 2"x2" square tubing and 1"x1" angle. I used to clean the metal really well, but have been getting lazy and I still get strong welds.

I suppose part of it comes down to how pretty you want the weld to look and how strong you need the weld to be. I'm assuming if you are doing something really heavy wall, crap on the outside of the steel might limit the penetration. It certainly doesn't make for pretty welds (then again, it is MIG). But I haven't been building hang gliders or airplanes or race cars or art for the Hirshorn, so I haven't worried that much.

I mentioned this in another welding-related thread, but if you doing garage fabrication and are looking for a saw, think about the Evolution Rage series. Sears carriers 'em, but they are mail order only. They have a 7.5" TCT cold cut carbide chopsaw for about $250 that works really well--a heckuva lot better than any abrasive saw I've ever used. Goes through my 2" square tubing like butter. Clean cuts, no black dust, no heat, no shrinkage of the blade as it gets used, no blade deflection. Just nice clean cuts.

Rob Ballard
03-18-2010, 11:13 PM
Using a Miller 180 w/ Flux-Core is very forgiving with slightly dirty mild steel, however, you get better penetration with lower heat if you take the time to clean with degreaser and a wire wheel on a hand held grinder.

Robert Snowden
03-19-2010, 12:08 AM
The gas you need for hard wire or fluxcore is 75/25 mix if you clean the steel you will get better welds.Mig can and does produce good weld's that look good as the user learn's more about the process.

Tom Veatch
03-19-2010, 5:47 AM
The gas you need for hard wire or fluxcore is 75/25 mix ....

Gas with fluxcore????

Chuck Saunders
03-19-2010, 8:05 AM
Oil is no problem, rust is some problem, paint can be quite a problem. Sheilding gases run from
CO2 - cheapest but more spatter
75%Argon/25%CO2 - Cheaper but cleaner
88%Ar/12%CO2 - beats Argon in price
Argon - kinda pricey for most steel welding, good for Aluminum
Helium - for Aluminum

ER70s-3 wire good for CLEAN steel
ER70s-6 wire good for dirtier (rusty) steel, better for general use

Flux core doesn't need a shielding gas and I don't care for it, but outdoors in wind it keeps you from needing a stick welder too.

I just upgraded to a Miller 212 and I have been very happy

Wood is hard to weld even with butternut dowel rod

Matt Meiser
03-19-2010, 8:39 AM
I find if I don't clean it off I get more splatter and smoke so I usually clean it off. The crud on new steel cleans off real easy with a flap disc on an angle grinder too. Buy one of the $17 angle grinders from HF and dedicate it to a flap disc (plus one for a one for a grinding wheel :)) I have 2 of the cheap ones plus a good DeWalt (the $90 one, not the $50 one which is no better than the HF's for 1/3 the price.) The only thing I really need the DeWalt's power for is a big knotted wire cup. But I use flap discs the most.

I've only used the 75/25 gas and ER70s-6 wire. I've got flux core wire that came with my machine but have never tried it. The only thing I welded outside that had to be done outside I did when it wasn't windy. Sometimes if its not windy and nice out I'll weld out there. I try to do any grinding outside if the weather is good enough.

Rod Sheridan
03-19-2010, 9:23 AM
[QUOTE=Chuck Saunders;

Wood is hard to weld even with butternut dowel rod[/QUOTE]


Everyone knows you use Weldwood for that.:D

Regards, Rod.

Cary Falk
03-19-2010, 9:58 AM
I clean my metal off before. Most of my stuff will get painted afterwards and it is easier to clean it off before. I always assumed clean metal welds better. Also If I don't clean it off before, it just ends up getting on everything else it touches. I have a Hobart 187(since everyone else is giving out that info).

Mac McQuinn
03-19-2010, 10:04 AM
I always clean the impurities off whether it's oil or rust. I'm surprised no one has mentioned this although get yourself a good quality welder's respirator for under your hood protection. Welding is no different than woodworking, cover up!;)


Scott T Smith
03-19-2010, 12:18 PM
Trent, lots of great feedback thus far from the usual suspects!

To summarize, if you pre-clean your metal (rust, oil, paint, etc) you will end up with a cleaner appearing weld (as well as a stronger one). I typically will wipe off oil with MEK first, wire brush if needed and then re-clean. In some instances, if I'm doing a lot of steel I will clean it with good old soap and hot water, and let it dry for a while (or overnight) before welding. If I'm in a hurry, I'll blow it off with compressed air and it I'm welding cast iron I'll pre-heat it to get rid of the residue.

Cleaning is not always necessary, but it IS better. Oil can cause voids in your weld when it cooks off (creating porosity), not to mention that you're not breathing the vapors from burning oil, paint, etc. Don't forget to try to clean inside the tubing, since this oil too can creep up into your weld.

Hard wire and gas allows you to have a more attractive weld as well, with significantly less spatter to clean up.

Trent Flemming
03-19-2010, 11:46 PM
Sawmill Creek members are the best. Thanks for all the great responses. I am loving my welder and I'm using the 75%Argon/25%CO2 with ER70s-6 wire. I did go ahead and clean the metal today before welding. I was using the Autoset function on the welder, but I think some of the beads were standing a bit proud. I will have to play with it more.

Thanks again,