I don't know the burning temp of propane.

All i know is you have to make sure your flame is small and blue - deep blue, nearly transparent. That means hot. Then as always you must heat your copper before soldering, and before heating it don't forget to put flux to prevent oxydation. You'll need a can of flux and a good deal of solder. You should try with 2 pieces of copper you can throw away first, just to get used to it.
You can finish the job in your oven, and remove excess solder with a dremel or a file.