I'm interested in low carbon steel for oil and gas line-pipe. Some steel made after 1950 has higher cobalt content (0.015-0.040%) than pre-1945 steel (
According to West Yorkshire Steel, the following are the main elements in steel:
1-Aluminium (Al)
2-Boron (B)
3-Carbon (C)
4-Cobalt (Co). Cobalt can be used up to 10% content in some high-speed steels. It becomes radioactive when exposed to nuclear radiation therefore for radioactive applications it must not be present in the steel.