Ok, everyone knows that you cannot solder aluminum. Solder is a lead/tin based alloy used to attach copper to copper, as well as gold, tin, and probably a few other metals. Solder does not stick to aluminum, so what do I mean by aluminum soldering? Well, I have found two readily available products that will attach aluminum to aluminum using aluminum alloy rods and a propane torch, much like sweat soldering copper pipes. Note, that the HTS-2000 website uses the term "Aluminum Brazing", so this is probably a more appropriate term than "soldering".
The results that I have gotten experimenting with these products are very promising, so here's what I have found. The first product is HTS-2000 from a company called New Technology Products. Someone on the rotary list brought this to our attention a year or so ago, so I ordered the one pound starter package for about $65. When I got it I followed the instructions, and I was able to attach a couple of pieces of scrap 2024T3 angles to each other without too much trouble. I was pretty impressed, because all I needed was a propane torch.
My work was not perfect, but I was pretty sure that with a little practice, I would be able to use this stuff to fab an intake manifold somewhere down the road. In fact, last year, when I screwed-up my forward top skins with a dreaded figure 8, I was able to use the HTS-2000 to fab a patch that I'm pretty sure will do the job.
Sometime after my first experience with the HTS-2000, I found Alumiweld Rods at Harbor Freight. I didn't expect a lot, but the cost was only $13, so I bought a tube. There's only 8 rods in a tube, but that's plenty to experiment with. The instructions inside their tube, which I didn't read until now, lists their website as AlumiWeld.com. Their website lists the price as $30 for a one pound starter kit, so this seems to be half the price of the HTS-2000.
Anyway, fast forward to July 12, 2008. My engine mount should be done soon, so I thought I would practice a little with the HTS-2000 brazing rods on different types of aluminum. My previous experience with 2024T3 was positive, so I thought I would try some 6061 angle. I found some 3/4" aluminum angle at the aviation department of Home Depot that looked like 6061, so I thought I would give it a try.
I cut off two 3" pieces, clamped them in my vice, and tried to weld them together with the HTS-2000 using my propane torch. No matter how much heat I applied the stuff just would not attach itself to the HD 6061. I figured this HD 6061 just could not be brazed, which was a disappointment, but who knows what it really was, anyhow. To be sure that I knew what I was doing, I decided to play with some 2024T3, again. I clamped two small strips of .025 2024T3 in my vice. Again, I could not get the HTS-2000 to stick to the aluminum. So, I gave the HF AlumiWeld a try, with the same results! What gives?
Frustrated, I shut down the fans, and closed up the shop. Nothing like 100° weather in central Texas to make you want to quit when things do not go right. What am I going to do, now. My experience with trying to learn to arc weld did not go too well at all. No way can I rely on learning to Tig weld in order to fab my aluminum parts for the engine build. Things do not look good.
Later that night, I thought, surely, I must be doing something wrong, so I went to the New Technology Products website, and reviewed their instructions again. This stuff only requires 700° to melt. Why couldn't I get it to flow? Let's see, aluminum pieces clamped in a steel vice. Maybe I could not get the parts hot enough to melt the rods because the vice was sinking all of the heat. So, I made a couple of wooden vice jaws to replace the metal jaws--problem solved.
Below are some pictures of a few pieces that I have brazed. I do not have any pictures while I was actually doing the brazing, because it was too hard to take pictures with a rod in one hand, and a propane torch in the other. Just go to the website to have a look at how the professionals do the job. Below is just my experience with the brazing rods on a few test pieces.
So, what have we learned? First, it is possible to "weld" aluminum (or braze it), without having to buy a TIG welder and learning how to use it. With a little practice, even a software guy can do this. Second, both the HTS-2000 and the AlumiWeld Rods seem to do the job.