Welding slag

Hi All,

I'm trying to weld up a gate for my brother, I have cleaned the paint off the steel back to bare metal on both pieces that are to be joined together. I weld them together it seems as though I'm getting a good bead going but once I chip off the slag I have a crack through my weld a crack that just seems to be all slag as well. I clean it and try to weld it the same and once again I have a crack of slag in the join.

Just wondering if anyone could please tell me what might be causing...

Source: http://www.woodworkforums.com/f160/welding-slag-127753/

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