Steel Castings

Steel Castings are produced by pouring molten steel of the desired composition into a mold of the appropriate configuration and allowing the steel to solidify. Steel castings produced in any of several types of molds and forged steel of equivalent chemical composition respond similarly to heat treatment, have the same weldability and have similar physical and mechanical properties. However, steel castings do not show the effects of directionality on mechanical properties that are typical for forged steels.

For the deoxidation (i.e. control of oxygen content) of carbon steels and low alloy steels, aluminum, titanium and zirconium are used. Of these, aluminum is used more often due to its effectiveness and low cost. Unless otherwise specified, the normal sulfur limit for carbon and low alloy steels is 0.06% and the normal phosphorus limit is 0.05%.

Carbon steel castings can be classified into three broad groups according to their carbon content:
- Low carbon steel castings: 0.20% C or less
- Medium carbon steel castings: 0.20 to 0.50% C
- High carbon steel castings 0.50% C or more

Low-Carbon Cast Steels
Low-carbon cast steels are those with a carbon content of less than 0.20%. Most of the tonnage produced in the lowcarbon classification contains between 0.16 and 0.19% C, with 0.50 to 0.80% Mn, 0.05% P (max), 0.06% S (max), and 0.35 to 0.70% Si.

Medium-Carbon Cast Steels
The medium-carbon grades of cast steel contain 0.20 to 0.50% C and represent the bulk of steel casting production. In addition to carbon, they contain 0.50 to 1.50% Mn, 0.05% P (max), 0.06% S (max), and 0.35 to 0.80% Si.

High-Carbon Cast Steels
Steel castings containing more than 0.50% C are classified as high carbon steels. This grade also contains 0.50% to 1.50% Mn, 0.05% P (max), 0.05% S (max) and 0.35% to 0.70% Si. High carbon cast steels are usually fully annealed. The microstructure of high carbon steels is controlled by the heat treatment. Carbon also has a significant influence.