Carbon and low alloy steel castings are used in parts for railroad cars, pumps and valves, heavy trucks, construction and mining equipment, and power generation equipment. Good applications utilize the performance of steel with the flexible geometry of a casting. Steel castings offer high mechanical properties over a wide range of operatingDifference Between Low, Medium & High Carbon Steel1. Low Carbon Steel. Low carbon steel is a carbon steel with a carbon content of less than 0.25% (or 0.29%). Due to its low strength, low hardness and softness, its also called mild steel. It includes most of the plain carbon steel and a part of high-quality carbon steel, mostly without heat treatment, used for engineering structural parts.