1018 is classified as a standard low carbon steel grade, making it one of the most widely utilized metals in global manufacturing. This versatile material serves as a foundational benchmark for many industrial processes due to its balanced properties. This grade is a staple in engineering, often chosen when a moderate strength material that is easy to machine and weld is required.
The Chemical Definition of 1018 Steel
The designation 1018 follows the standard system developed by the American Iron and Steel Institute (AISI) and the Society of Automotive Engineers (SAE). The “10xx” series identifies it as a non-resulfurized basic carbon steel, meaning the primary alloying elements are iron and carbon. The final two digits, “18,” indicate the carbon content, representing an average of 0.18% carbon by weight.
This carbon percentage, typically ranging from 0.15% to 0.20%, formally classifies 1018 as a low carbon, or mild, steel. Steels below 0.30% carbon are considered low carbon, distinguishing them from medium (0.30% to 0.60%) and high carbon steels (above 0.60%). The low carbon content ensures a microstructure that is predominantly ferrite, which is soft and ductile.
The composition also includes a carefully controlled range of manganese, usually between 0.60% and 0.90%. Manganese acts as a deoxidizer during steel production and significantly improves the steel’s hot working properties and strength. Trace amounts of phosphorus and sulfur are also present, typically kept below 0.040% and 0.050% respectively.
Practical Performance Characteristics
The chemical makeup of 1018 steel translates into a distinct set of mechanical properties. In its cold-drawn condition, a common commercial form, the material exhibits a typical minimum yield strength of around 370 megapascals (MPa). The ultimate tensile strength, the maximum stress the material can endure before fracture, generally starts at 440 MPa.
These moderate strength values provide sufficient load-bearing capability for non-structural and general-purpose applications. The material’s hardness is relatively low, often measuring around 126 on the Brinell scale or 71 on the Rockwell B scale. This softness is directly linked to its excellent ductility, allowing the steel to undergo significant plastic deformation without fracturing.
Ductility is quantified by its elongation at break, which is typically in the range of 15% to 20%. This high elongation allows the steel to be readily bent, stretched, and formed. 1018 is often regarded as the benchmark for free-machining low carbon steels, with a machinability rating of about 70% compared to 1212 steel. It cuts cleanly, producing small, manageable chips, which is an advantage for high-volume machining operations.
Typical Uses and Processing
The combination of moderate strength and exceptional workability makes 1018 steel a workhorse across numerous industrial sectors. It is frequently selected for components requiring extensive machining or cold forming, but not the extreme strength of a heat-treated alloy steel. Common applications include shafts, pins, axles, gears, and fasteners like bolts and studs, where dimensional accuracy and a clean surface finish are necessary.
The steel is highly suitable for cold working processes, such as cold drawing or cold rolling. Cold drawing refines the grain structure, improving the surface finish, enhancing dimensional tolerance, and slightly increasing yield strength through work hardening. This processing is why cold-drawn 1018 is preferred for precision machine parts.
The material’s superb weldability is due to its low carbon content, which minimizes the risk of cracking or hardening in the heat-affected zone. It can be easily joined using virtually all conventional welding techniques, including Shielded Metal Arc Welding (SMAW), Gas Metal Arc Welding (GMAW or MIG), and Gas Tungsten Arc Welding (GTAW or TIG).