Valurauta

Valurauta, meaning cast iron in Finnish, refers to iron alloys that contain a higher carbon content than typical steel, usually about 2.5 to 4 percent, often with silicon. It is produced by melting iron with alloying elements and then pouring the molten metal into molds, where it solidifies into components or objects. The relatively high carbon content makes valurauta harder to forge but easy to cast, and it often contains graphite which influences its properties.

There are several subtypes of valurauta, differentiated by graphite structure. Gray cast iron contains graphite flakes, which gives good damping and machinability but relatively lower tensile strength and increased brittleness. Ductile (nodular) cast iron features spheroidal graphite, providing higher ductility and impact resistance. White cast iron is hard and brittle due to cementite, while malleable cast iron is produced by heat treating white iron to form irregular graphite clusters and improved ductility. These microstructures lead to a range of mechanical behaviors that suit different applications.

Common applications include automotive and industrial components, pipes, and machinery housings. A widely known use is cast iron cookware, where the material’s heat retention and even heating are valued; seasoning creates a protective, nonstick-like surface over time. Cast iron is also used for stoves, pipes, and heavy machine parts.

Care and handling emphasize rust resistance and longevity. Cast iron tends to corrode if left wet, so it is typically dried and oiled after use, and kept in a dry environment. It is relatively heavy and can be brittle under sharp impact, but its durability in terms of wear resistance and heat retention remains a defining feature.