Since I'm new to MIG welding this is probably a very obvious question. My brother was doing some mig welding on 1/4 plate. at a 90 degree angle to eachother "Fillet" weld I believe. Anyway when you look at his welds they look a lot like "Sponge" coral with lots of holes etc.
I think he wasn't shielding the weld properly, you? Also when welding in a corner what is the proper technique (Back to front, or front to back?) (Angle 45 degrees?)
That sponge effect is called porosity, and yes, it is typically from lack of shielding gas. Was your brother using gas shielded MIG process or flux core MIG process welding?
A weld that is full of porosity will not hold under any kind of stress. The best bet is to gring the entire weld out until there is no more evidence of the holes. This will mean grinding the weld completely out and also grinding down into the base metal.
What type of welding machine are you using? Is it set up for gas shielded MIG welding? Or is it a flux core machine that is only set up to run flux core electrode wire?
James Walsh Jr. Jigsaw Custom Fabricating
We are using a MILLERMATIC 175 with a I believe ARGON gas.
For MIG welding mild steel you should be using a 75/25 Argon/CO2 mix. Pure argon really is only used for TIG welding. If you're running pure argon, that may cause the problems as well.
Check the obvious things first on your rig. Make sure you have gas in the bottle. Make sure the gas lines from the machine to the regulator are tightened securely. Make sure your regulator is tightened into the gas bottle. Check your gas hoses to make sure there is no splits or leaks. Make sure the gas hose from the regulator to the machine has no blockages. Make sure your gas diffuser in side the gun nozzle is not blocked or obstructed. Press the trigger on your MIG gun and it should hiss at you indicating that you have gas flowing. Your regulator should also have a flow meter that indicates gas is flowing to the machine.
The less obvious things might be a bad gas solenoid in the machine. That would be a last resort however.
My .02 James Walsh Jr. Jigsaw Custom Fabricating
Any idea what pressure I should be looking for? By the way the gas is the
75/25 split you indicated. THANKS
This is probably not what you mean, but just in case -- when you ask about proper technique, back to front or front to back -- are you pushing or dragging the welding gun? For MIG, you should be moving in the direction the nozzle is pointing (pushing), rather than dragging back.
Okay, I've now exhausted the extent of my MIG expertise!
Andrew
I'm asking about the technique becuase I have always pulled the gun, starting the furthest from my and working closer. My brother starts close and works away from him. I thought it made more send to pull the gun away from what was being welded instead of trying to weld "over the top" of the newest bead. GUESS I'm wrong. Anyone else?
with stick (SMAW) and with Flux core (FCAW) you always drag or pull , you want the slag to stay behind and float to the top of the bead. you do not want slag to get in front of the weld pool, slag will be enbedded in the wled bead. with MIG (GMAW) you CAN push or pull since there is no slag to worry about. by pulling the gun you will have deeper penetration, taller weld bead. when pushing the gun you will have less penetration, wider bad. comon among sheet metal, body shop, or thin material welding to spread the heat better rather than burning through.
what is pushing or pulling a gun ? in this example you are right handed. point the mig gun perpendicular to the work table. lay the gun toward the right side , start moving your hand to the right .... you are dragging the gun , just like you would grag a piece of chain. drag or pull technique ......the same thing
stop the gun in the same tilted to the right position , and now start pushing is , just like if it would push a piece of ball bearing fornt of it. this is push technique, use with MIG (GMAW) and TIG (GTAW)
secondly , in your original post you stated your brothers weld looks like a sponge, a few reason why this would happend using wire feed. lack of shielding gas, or strong draft blowing away shielding gas, DIRTY metal (grease , rust paint ...... wrong metal , ( cast iron or something with high iron content, example rebar.
good luck
The regulator on the gas bottle has two gages. One is bottle pressure, in pounds per square inch, and the other is gas flow, in cubic feet per hour. The gage for bottle pressure should be around 2000 psi when the bottle is full. This reading will decrease as you use the gas and the bottle becomes emptier. The other gage shows how much gas is flowing out of the gun and onto the weld, and is controlled by the regulator knob. You should adjust the regulator to set the flow to about 25 cubic feet per hour.
INFORMATION GREATLY APPRECIATED
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