Introduction of ordinary carbon structural steel

Carbon steel or plain-carbon steel, is a metal alloy. It is a combination of two elements, iron and carbon. Other elements are present in quantities too small to affect its properties. The only other elements allowed in plain-carbon steel are: manganese (1.65% max), silicon (0.60% max), and copper (0.60% max). Steel with a low carbon content has the same properties as iron, soft but easily formed. With more carbon the metal gains hardness and strength but becomes less ductile and more difficult to weld. Higher carbon content lowers steel's melting point and its temperature resistance in general.

Low alloy steels are a category of ferrous materials that exhibit mechanical properties superior to plain carbon steels, due to the addition of alloying elements such as nickel, chromium, and molybdenum.

Plain carbon structural steel has wider restrictions on carbon content, performance range, and phosphorus, sulfur, and other residual elements.

Plain carbon structural steels are divided into three categories: Group A steel (Class A steel) is a steel that guarantees mechanical properties; Class B steel (Class B steel) is a steel that guarantees chemical composition; Steel that guarantees mechanical properties and chemical composition.