See Cast steel, under Steel.
Steel that has been produced by the pouring of molten iron into a mold. Cast steel components are common due to their relatively inexpensive production process. It is not recommended to weld on cast steel by a hobbyist. This is why forged steel Ranger beams from earlier models are sought after to be extended/plated.
A term originally applied to crucible steel and sometimes today used to describe tool steels. The term is misleading and is falling into misuse. It can also be applied to steel castings made by pouring molten steel into a mould but which are not subject to further forging or rolling.