Need help identifying an alloy

[thackman]

I have a 12' piece of 4"x4" aluminum square tube with 1/4" thick walls. At least I assume that it's aluminum, silvery and very light weight. I doubt that it's magnesium but there's always a chance. It looks like an extrusion and it has a few tabs welded on it. I have a brand new mini mill and I'm planning on cutting this box beam up for practice material. Does anyone know of some simple tests that would help me determine how machineable it is? I don't want to start learning on some gummy AL that's going to destroy end mills on me. I'm not as concerned with identifying the exact type of AL alloy and temper, just in verifying that it is AL and if it's going to cut well. This is probably the best forum for this since the pros have special equipment that can identify exact alloy types and tend to not feed their machines unknown materials . From what I’ve read, mini-mill owners will attempt to cut any material that is vaguely solid if they can get it cheap enough.

Thanks,

[Stepper Monkey]

I'm sure there is an easier way, but sound and feel have a lot to do with it and that you just have to learn in time. Kind of like identifying steel alloys by thier sparks.
You can at least get an idea by seeing how it reacts to a sharp, relatively coarse file first.

Anybody out there have an easy trick?

[ataxy]

well magnesium will fizzle if you put vinegar on it or will burn bright if you light up a chip but be carefull as the light produce by burning magnesium can make you blind ,aluminium will in my opinion appear whiter then steel wich will appear more blue or dark grey while titanium will appear grey with a yellow-brown tint ill try to post an image of those material side by side later

the file trick will definitly give you a good idea

[in2steam]

Take a chisel to it, alum is nearly the same as wood as cutting speed goes, after that,( I would think its better to start with alum then steel as steel is alot less forgiving then alum, you will only gum up with alum if you take to much off). If you get a clean shaving with a sharp(can cut hair) wood chisel then take that shaving as already stated and put it some acid, it should turn black and fizzle also. I have never seen a mag extrustion, it could be pot metal, which tends be a little harder and brittle but still mild compared to steels.
Titanium will not dent/cut as easily as alum, so the above will be very apparent.

If its got something welded to it its more then likely alum, welding mag is harder IMHO.

I don't know anyone outside of a metalurglical lab that can identify exactly what alloy it is, even hardness testers are only so accurate.

The good old file test is the old stand by for me....

chris

[keebler303]

Some scrap metal places have little handheld guns that use a small arc to burn the metal and then analyzes the fumes to tell you what it is.

I would just start cutting it and see what happens. Go easy to start and you will quickly get an idea of how well it will machine.

Matt