Originally Posted by charlie56
I have used other aluminum welding rods (from Home Depot) with a propane torch to weld up antenna parts with good results. Granted the parts are not structural in nature but the welds have held for years. The real tuff part is getting the temperature right. The aluminum doesn't glow red like steel and if you get it a few degrees too hot, its a pool of goo.
Not saying it doesn't work at all -- but it's not "welding" -- there is no fusion of the parent metal. It's really a way of soldering aluminum. If you think of it that way, as soldering, then any situation in which you would be comfortable with a soldered joint in steel or copper-based metal, should be OK with the aluminum stuff as well, provided you do a really good job of cleaning the joint and scraping it with the rod as you proceed.
If you want an actual **weld**, this isn't for you. In that case, you want TIG or the specialized rods and fluxes for torch welding aluminum, such as Tinmantech sells. TIG or torch weld will give you a joint that is as strong as the original parts.
Re melting parts, the problem is, in fact, that a h/w store propane torch isn't hot enough! It takes too long to bring the joint up to temperature, and by that time the heat is diffusing away from the joint into the parent metal, so you wind up having to heat a large section of the parts to near melting. If you use oxy/propane or oxy/acetylene, as you would to braze or weld steel, then the job is over before the heat migrates away, so much less danger of melting the parts. Practice on some scrap first, before you try to fix that expensive billet bit, though!