AISI 4130 is a low alloy steel containing molybdenum and chromium as strengthening agents. The carbon content is nominally 0.30% and with this relatively low carbon content, the alloy is excellent from the fusion weldability standpoint. The alloy can be hardened by heat treatment. With a lower carbon content range, AISI 4130 provides better weldability than that of other oil and gas steel grades such as AISI 4140.