A36 is a low carbon steel. Low carbon steels are classified by having less than 0.3% carbon by weight. This allows A36 steel to be easily machined, welded, and formed, making it extremely useful as a general-purpose steel. The low carbon also prevents heat treatment from having much of an effect on A36 steel.

The American Society for Testing Materials (ASTM) issued the A36 steel specification in 1960. It is considered a low carbon steel (those classified with 0.04% to 0.30% carbon content) and also contains such alloying elements as manganese, phosphorus, sulfur, silicon, and copper.