I can't say (In order to fix this can I just reheat to weld temp and give it a smack to re-weld?)what I would do is make sure you flux real good.I have not done this in a open heat, it's all ways closed oven. When I do this it is under perisher. Clamp, two stainless steel plates, A x B X C ? two to four bolts SS. then heat soak. Copper and like metals are way diffrent than steel. and when combind the melt temp changes.