The NC Whisper forges are good for making horseshoes or general blacksmithing, the problem with these forges for forge welding is the atmosphere is to oxidizing and the flame blast right on your work causing massive amounts of scale and the are real bad about hot and cold spots another thing is the top temp is very marginal for forge welding, if you are new to it you will have nothing but headaches of failed welds and lost materials. I know I use a Whisper Momma everyday in my farrier business.
Like IG said more info of what you built would be most helpful and if I was you I would build one of IG's welding forges and you will probably save $200 over buying a Whisper. I know I paid $400 for my Whisper Momma back in 1999 and the last welding forge I built I have about $200 into it.