4130 Chrome Moly Steel is a low alloy steel having molybdenum and chromium as strengthening agents. Carbon content is around 0.3% and due to this very low carbon content, the alloy is very useful for fusion welding. The alloy can be hardened using heat treatment. The alloy is best machined in the tempered and normalized condition. Even though the alloy can be machined when fully heat treated, when the alloy is hardened it becomes very difficult to work with. The alloy is best known for its weldability. 4130 Chrome Moly Steel has a density of 7.8g/cm3.