On the subject of hard soldering brasses, I remember learning the hard way (on an inconsequential piece) that yes indeed if you overheat the pieces, you will not be able to separate them. I have a cousin and now deceased uncle who ran a radiator repair business for 40+ years, and my brother and I would go on weekends and play around tearing down old radiators, and just for practice repair a few basket cases. The Tank/header is where I learned. Teh idea is to hold a blowgun in one hand and heat the solder along a few inches of the joint, then blow it out. A few cycles of this, and the tank would be easy to separate from the header. Incidentally, this is the first step in the old Rod and Repair you could get done in a shop. Well, after getting it too hot, not realizing it, I had essentially welded the tank to the header. So it can be done with Oxy/Fuel heat. As an aside to modern materials, the "solder" used by many HVAC guys is no longer fluxed. It has become more like welding. The melting point is closer to copper, and when you get the temp right, it flows like water, and wicks up into the joint about as good as any 50/50 I have used. And it is very dificult, if not impossible to sweat apart. Most don't even try. I don't. I helped a friend do a swap out on a 5 ton unit (got the old one for the shop) and I did all the connections. He calls it "welding", and I believe that may be more accurate than "hard soldering" or "brazing" like it used to be called. I did my A/C here years ago, but used Ultra-flux and real silver solder. Love that stuff. But the cost is up there pretty good now. I have some sil-phos rod I will be using on the 5 ton when I install it in a few weeks. I'm not sure it is self fluxing. I have always used flux with it, but I may get some of what my friend uses. I do like the way it performs. Sorry for the topic drift.