Odd metal or welding issue?

[Shug]

I was welding together some thick (4mm?) metal that had been galvanised. I took a flap disc on grinder to take it down to bare metal before I went near it with the welder. When I came to weld the metal, it didn't sound like normal steel welding. Less bacon frying and more a loud humming. And the welding light was a rather lumenous green colour rather than the blue I normally see. Ended up with a lot of soot around the weld. Could this be I never cleaned the zinc off fully (tho it looked fine to me) or could it have been some particular kind of steel? Was using Coogar 5. Weld was strong enough. Gave it a good few whacks and hung considerable weight of it (i.e. me!) and it held fine.

 

[gavuk]

Sounds like galv to me ,

 

[backpurge]

Agree it is probably galv, just cleaning the surface isn't sufficient, you really need to dig down into the steel to get all the galv out. Switching to a gas with a higher CO2 content can help due to the increased heat created

 

[Bsmith]

it didn't sound like normal steel welding. Less bacon frying and more a loud humming.

Would increase the WFS until you get a more crackling sound. Maybe using a grinding disc rather than flap disc will 'cut' the galv off the plate better..

 

[outofthefire]

Even though youve ground back to what looks like bare steel theres still galv within it due to the hot dipping process opens the molecular pore structure and the galv is embedded all through. I'd avoid it like the plague the fumes can make you really ill.

 

[Hitch]

Sounds like you didnt get all the galv off. There is a very visible colour difference when its gone.

Sometimes when welding galv thats not cleaned fully, you get a lot more spatter, often a bit will stick to the contact tip and impede the wire feed, giving the same symptom of not enough wire.

 

[Shug]

I did have to keep chipping bits of weld off the shroud. Being paranoid about the fumes, I was welding at a bit more of a distance than normal!
Bracket I made isn't good enough so have to do another. Was just scrap bits lying around I used so think I'll go get some plain ol mild steel instead.