Carbon steelA low- to medium-carbon alloy with good machinability, weldability, and hot or cold workability, AISI 1040 is ideal for a wide range of construction and engineering applications. With more manganese, AISI 1039 offers higher hardenabilty than the similar AISI 1025.
Carbon steel is used for simple structural application such as cold headed bolts. It is often used in the case hardened condition. Carbon steel also use for mold ,die, gear, machine part .