loud bang when welding? too hot?

[brendan h]

i was welding 2 peices of 3-4mm steel angle together to form an X shape. they are roughly 250mm long.

i tacked the ends of the work but they where a bit small.

anyway i started in the middle and got about an inch of weld down and then i herd this loud bang. could this be one of tacks braking due to heat? i was putting about 100amps into the work.

 

[Hitch]

Yep, most likely.
If you welded one side, as the weld cools it shrinks. Trying to pull the opposite side apart.

If you hear a tack break its normally a good idea to stop and investigate.