Contamination from filler rod

[J_K]

I've just finished repairing an alloy wheel crack (It's for off road use by me) and a recurring problem I have reared it's head again.

Sometimes when I dip the rod, it instantly goes like there is contamination in the weld.
Black crap running over the surface of the molten material and the molten material almost stays in a ball and doesn't want to join the pool.
I've had this happen before but it's pretty random. I've tried cleaning the rods with Scotchbrite then Acetone before welding. And sandpaper before acetone etc etc. But it doesn't always do it.

I'm using a gas lens and went from 4lpm up to 10lpm to see if it was the rod melting outside the gas but that doesn't seem to be the issue..

Can anyone give me any ideas how I can stop this happening?

 

[chevy2]

Thats common with alloy wheels,
Try a bit more ac balance on cleaning and weld small areas then stainless brush it between welding again.

 

[Jim_gsxr1000]

Bit more cleaning to penatration, an unfortunat problem that occurs with wheels

 

[pedrobedro]

Melt your wheel before you add any rod to boil the impurities out of the parent metal. You can see it turn shiny as it clears up a bit.

 

[J_K]

Tried all of the above.
And talking to the guy I got the wheels off, he tried fixing the crack with chemical metal.

Dumbarse..
That may explain where the random bits of crap are coming from...

 

[chevy2]

Stating the obvious but you know that pretty much all of that cr*p will have to be ground out, shame as it's making the job twice as hard now.

 

[langy]

Tried all of the above.
And talking to the guy I got the wheels off, he tried fixing the crack with chemical metal.

Dumbarse..
That may explain where the random bits of crap are coming from...

Wow I wouldn't want to buy anything off him in a hurry

 

[J_K]

Stating the obvious but you know that pretty much all of that cr*p will have to be ground out, shame as it's making the job twice as hard now.

Yes. I do know that.
And it took me nearly 3 hours to weld the bloody thing with all the extra grinding out and cleaning needed.

 

[hotrodder]

From this...

I've had this happen before but it's pretty random

I'm wondering if you could be be touching the arc with the filler wire or the wire's melting before it gets to the weldpool (angles of attack are one of the usual suspects)? Doing so can vaporise some wire and make a mess similar to a touch down but without the blob of ally stuck to the tungsten

If the mess is coming from the casting (inclusions/numpties playing with chemical metal etc) the black crud comes from the weldpool not the filler...

 

[J_K]

You could be onto something there.
I was using 2mm filler but 150amps and angle could've been a bit iffy.
I've got another one to do that hasn't been chemical metalled.