View Full Version : Is there a way to determine an alloy?

05-20-2011, 05:30 PM
With steel and aluminum how do you determine what alloy you're dealing with? With ALuminum i see about 20-30 different alloys (1000 | 1100 | 1145 | 1235 | 2007 | 2011 | 2017 | 2024 | 3003 | 6013 | 6020 | 6060 | 6061ETC..)

Is there a rule of thumb to determine what you're working with in a given situation? If i come across a random piece on the ground can i deterime which it is or at least get sort of close?

05-20-2011, 07:15 PM
Metallurgical analysis in a lab. Or try a large salvage yard - some have instruments that will identify alloys.

05-21-2011, 06:45 AM
Lab diagnosis is about the only way unless you see some numbers marked on the alloy itself. If one has a hardness tester you could go that route, but that will give the hardness and not the alloy itself. If you work with it day in and day out, you can kind of guess what alloy it is by the way it machines. If it is "gummy" it will be a soft alloy. If it machines nice without loading up any endmills or drill bits, it will be a harder alloy. Also if you have a smaller piece, the harder alloys will have a "ring" to them whereas the softer alloys will have a dull sound. When it comes to visual identification, it's pretty much a wash there. With barstock, you can take an educated "guess" by how it rings but you can also get dead soft material in barstock or "billets" that are used in a lot of extrusions. These will usually be 4" in diameter or larger. Square stock, or at least what I work with, tend to be in the harder ranges. Sheet stock can be anything from dead soft to hard. If you knoew where it came from and the product they made, would help to identify it somewhat.

So other than thoroughly confusing you, I have no answer :lol_hitti

05-21-2011, 07:59 AM
Appreciate that Kev, I figured it would be hard if next to impossible to identify by eyeballing,but i thought i'd take a shot.

05-25-2011, 10:14 PM
I believe you can use a Rockwell Hardness Tester. They make portable ones I have used on aluminum curtain wall systems to determine the alloy.

05-25-2011, 10:18 PM
There are also common alloys for certain shapes: sheet, bars, plates, etc. I believe the aluminum association manual groups the products in the various alloys they are produced in.

05-26-2011, 11:34 PM
well, a easy and more common test for steels is the spark test.. that will only help you determine low/med/high carbon steels and Iron...

Theres a flame test to determine between Aluminum and Magnesium.. chip a peice off and light it.. if it fires up, its magnesium..

as for different alloys of the same "grade" of aluminum, you'd have to contact a lab..

Theres the magnet test for stainless steels.. and believe it or not a rust test..

They arent going to tell you EXACTLY what alloy you are encountering, just the major alloy type.

05-27-2011, 09:44 AM
Just how close are you trying to get in your answer of "What alloy is that piece of metal?"

There are several ways of getting some information about what type of metal you are dealing with, such as weight/density, hardness, spark test, etc. Sometimes that is enough.

But if you really-really-really want/need to know what exact alloy a piece of metal is, then the answer is a lab doing a test on it. Simple and non-destructive way to test what alloy a piece of metal is made of is to use an X-ray fluorescence analyzer.

05-27-2011, 10:08 AM
Agreed, you can't tell many alloys apart by eye, especially aluminum.

05-31-2011, 02:33 PM
If you've been machining for a LONG time, you can start to tell some alloys apart, but not with 100% accuracy.

There are two ways to tell... one is the outside appearance and surface finish (certain alloys often come with certain patterns/finishes), and the other is how the material machines, and how it sounds when tapped.

There's no real way to explain this, but after you've had enough metal pass through your hands, you can start to pick up differences.

05-31-2011, 02:49 PM
With iron alloys, you can get a pretty good idea from the colour of grinder sparks. Al .. i just take to the recycle centre. They've got a gun there that tells you within seconds what you've got.