raudanvalmistuksen

Raudanvalmistus, also known as ironmaking, is the process of producing iron from its ore. This historical and ongoing industrial process has been fundamental to human civilization, enabling the creation of tools, weapons, and structures that have shaped societies. The primary raw material for ironmaking is iron ore, typically in the form of iron oxides like hematite or magnetite. These ores are usually found mixed with impurities such as silica and alumina.

The core of traditional ironmaking is the blast furnace. In this tall, refractory-lined vessel, iron ore is smelted with a fuel, most commonly coke, and a fluxing agent, usually limestone. The coke serves as both a fuel source, generating heat, and a reducing agent, chemically converting the iron oxides into metallic iron. The limestone reacts with impurities in the ore and coke to form a molten slag, which is less dense than iron and floats to the top, allowing for its separation.

The process within the blast furnace involves several stages as the materials descend. High temperatures at the bottom cause the iron to melt, forming liquid pig iron. This pig iron, containing a high percentage of carbon (typically 3.5-4.5%) and other impurities, is then tapped from the furnace. While pig iron can be used directly for some applications, it is often further refined into steel through processes like the Bessemer process or the basic oxygen furnace. Modern ironmaking continues to rely on blast furnaces, though advancements in technology aim to improve efficiency and reduce environmental impact.