Hiiliterästen

Hiiliterästen is the Finnish term for carbon steels, a broad family of steels in which carbon is the main alloying element. Compared with alloy steels, carbon steels contain little or no alloying elements, aside from small amounts of manganese, silicon, and other elements that occur naturally in steelmaking. The carbon content of carbon steels ranges roughly from 0.05% to about 2.0% by weight; cast iron typically has higher carbon content.

Carbon steels are commonly classified by carbon content: low-carbon (mild) steels with about 0.05–0.25% C; medium-carbon steels about 0.25–0.6% C; high-carbon steels roughly 0.6–1.0% C. Higher carbon content generally increases strength and hardness but reduces weldability and ductility, whereas low-carbon steels are more formable.

Heat treatment—annealing, normalization, quenching and tempering—allows adjustment of hardness, strength, and toughness. Typically, higher carbon steels are harder after quenching and tempering, but may be more brittle. Weldability decreases as carbon content increases.

Manufacture involves standard steelmaking processes (such as basic oxygen furnace or electric arc furnace) and subsequent rolling, forging, and finishing. Common applications include structural components, automotive parts, pipes, machinery housings, and tools; higher carbon grades are used for blades and wear parts, while very low-carbon grades are favored for sheet metal and painted structures.

Corrosion resistance is limited in carbon steels; they are usually protected by coatings or alloyed with chromium or other elements in stainless steels. Standards for carbon steels vary by country, with international and regional classifications guiding chemical composition and mechanical properties.