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Sheet metal identification numbers


Q. Could you please tell me exactly what the identification numbers on sheet metal mean? For instance, the 2024-T3...that I am seeing. Are these common identification numbers? Also, is there a difference between the identification numbers on sheet metal and other metals such as 18/8 stainless that would be used in a bowl or platter. I work for the USAF Reserves in Dover, DE. Just inquiring.

Thank you.

James Ferguson
Sheet Metal Mechanic - Aberdeen, Maryland, USA


A. Hi Jams. I can't say that such numbers always indicate the type of metal, but the two examples you provided do.

2024-T3 means aluminum of type 2024 with a T-3 temper. Aluminums in the 2xxx series are aluminum-copper alloys, and 2024 is one specific composition. T-3 means solution heat treated and cold worked.

18/8 stainless means stainless steel comprised of 18 percent chromium and 8 percent nickel.

There are numerous numbering systems for various metals, and unfortunately there are few easily discernible patterns. Good luck.

Ted Mooney, Teds signature
Ted Mooney, P.E. RET
Pine Beach, New Jersey


A. The numbers stamped on to the back of metals are there to help identify the type of metal and alloy that makes up that particular sheet of metal. For example the 2024 the 2000 series is aluminum the numbers that follow the 20 is the other metals that are present in that compound for example 24 is magnesium. Very rarely are you to find a metal that is 100% pure because, for one, they rarely exist in nature; and two, if they do they are too rare to be used for common sheet metal that me or you could afford. Secondly the T-? whatever the number 1,2,3 whatever it may be is the temper effect and mechanical properties of that metal. For common household or automotive applications these numbers don't mean a whole lot but when you get into aircraft or other high speed applications such things become very important.

Brian Z [last name deleted for privacy by Editor]
- Oceanside, California

March 29, 2012

Q. Hey I have some Q's about Metal Identification. Alright, do you know the metal and 10XX and 18% and 126 of each meal?
6061 T6

Adam Peters
- Salt lake City, Utah USA

March , 2012

A. Hi, Adam. Sorry, I don't even understand your question. But --

6061 T6 is a specific composition of a very common extruded aluminum with a T6 temper (solutionized and artificially aged).
7075 is a zinc-rich high strength, fairly expensive aluminum.
430 is a series 4xx (ferritic) stainless steel with chromium but no nickel; so is 409.
17-4PH is a martensitic precipitation-hardening stainless steel; so is 15-5PH.


Ted Mooney,
Teds signature
Ted Mooney, P.E. RET
Pine Beach, New Jersey

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