Ok ive heard of the root weld and top weld on manis and what not with a tig. But im working on welding a cage in my car its all mild steel and im using a mig. Before i screw anything up i figured id ask heres whats going on.

Im working on the plates to mount the tubing to, and since the sheet metal is thin i need to use really low heat. And in some spots the welds weren't looking so great LOL so in one spot i went over with the heat turned up a notch to pretty much flatten out the weld make things look better.

Now is that a bad thing, will it weaken the weld or is this an alright thing to do. I did like a 2 inch section and stopped figured i would wait and ask to see what you guys say.

 

Over 100 view and no info come on guys LOL

 

yes you can weld over welds

 

Cool thats pretty much all i needed LOL thanks

 

post a pic...

if it was BAD the first time then it probly not better the 2nd... if it looks bad then you wont have penetration

short circut mig is miss used ALLOT of time and you pipe and plate can just break apart

 

very true

 

 

I figured out what i was doing wrong had a real shitty ground on the first plate, had thought it was just from working with such thin metal. Next three plate turned out perfect just the first one is kind of shitty. Think i should grind out the old weld and then redo it??

Heres a pic look on the left side how its raised up and not flat thats what im talking about.

 

yes

 

Cool yea i have no prob doing it over just thought it was me at first but once i moved on to other spots and realized things working 10x better i figured out something was up on the first plate.

 

i'd run more heat, and carry your heat in the thicker plate. watch your puddle and make sure that it penetrates into the body of the vehicle. keep your gun pointed more at the plate, but make sure it is melting into your sheetmetal. that should help you from burning holes in the thin stuff, with more penetration.

 

when you redo it..

tack weld the 4 corners and the mid point of each side to avoid distortion =D

 

Yea i was trying to do that but i get into areas where i dont have the room to have the gun at a good angle. Thats why i was kind of thinking going over the top with a hotter pass.

 

cool, with mig it might be hard to run over an old pass and assure penetration, usually you just get a larger bead on top of your old bead. if you're going to try to run over your old bead, definately run more current and try not to have your wire speed that high. then you might be able to get into your original weld. but you'll have to change your settings again when you continue to weld just a single bead for the rest of your joint.

 

if it's bad it must be ground out and re-welded to assure it breaks down into the material. not simply passed over hotter.
if you are multi-pass welding to gain weld size you need to follow correct proceedure for placement and electrode angle.
beware of re-welding when welding stainless. many of the more common cheaper gases used on stainless are NOT for multi-pass welding.



incorrect electrode angles and insuffessient weld size / breakdown.

keep your electrode angle in correct placement and angle. keep your travel angle correct and SLOW DOWN. your weld is not fully breaking down into the plate.