Plain Carbon Steels

Also known as plain carbon steels or unalloyed machine-building steels, manufacturing steels are unalloyed steels with a carbon content ranging from approximately 0.20% to 0.60%. Due to their high carbon content, they are also referred to as carbon steels. The hardenability of manufacturing steels increases in parallel with their carbon content, while their toughness is inversely proportional to the carbon amount. For applications requiring higher hardenability, low-alloy steels are preferred.

Manufacturing steels are commonly used in machine components that do not require high strength. They are widely applied in shafts, pins, gears, gear components, bolts, and axles. Additionally, they are utilized in vehicle, engine, machine, and equipment manufacturing, as well as in hooks and mold sets. The machine manufacturing industry, in particular, favors these steels.

Depending on the carbon content, they exhibit moderate mechanical properties. In applications where high strength is required or for thick sections, manufacturing steels are replaced by low-alloy or alloy steels. Their machinability and weldability are lower than those of low-carbon steels. However, they are well-suited for surface hardening. Low-carbon manufacturing steels (<0.25% C) are typically subjected to carburizing, while higher-carbon manufacturing steels can undergo flame or induction hardening.

Examples of plain carbon steels grades include SAE 1030, 1040, 1050, and 1060, along with equivalent grades such as C30, C40, C50, and C60. Since many parts made from manufacturing steels undergo machining processes, sulfur-added variants are in high demand. These sulfur-alloyed steels are designated as C30R, C40R, C50R, and C60R. The sulfur content is typically standardized in the range of 0.020%–0.035%.