Metallurgy Techniques

Processes

• Different metals require different metallurgy techniques, but all metals must be separated from ores before refinement and study take place. The metal content of ores varies. Copper ore has a low metal content; Iron ore has a higher metal content and occurs in varying grades. Refining metals after extraction strengthens or alters their composition for different uses. Once extracted and refined, metallurgists study metals under a microscope, a process known as metallography.

Smelting

• Smelting, the oldest and most common form of extractive metallurgy, produces metal from ore through heat. Smelting requires a chemical reducing agent to change the oxidation state of the metal. Common and base metals like iron use carbon-based reducing agents such as coke, or historically charcoal, which removes oxygen from the ore, leaving just the metal. Smelting requires varying heat levels to melt different ores, which is why early humans first developed metals with a low melting point, such as bronze, before the extraction of iron and other metals developed.

Powder Metallurgy

• Powder metallurgy extracts and refines metals from rocks crushed into fine powder. Used when smelting is impractical, powder metallurgy can also create special properties in metals. Cold-pressing the powder between steel dies at room temperature produces adhesion of the particles, while heating the compacted powder creates final cohesion. Used in the production of high melting-point materials, metals produced by powder metallurgy are characterized by fine porosity.

Solidifying and Plating

• Solidifying is a modern metallurgy technique by which crystallization, using large amounts of material to produce a metallic crystal, creates minute metallic grains. While expensive, solidification techniques produce materials used in high technology, such as turbine engine blades and solar cells. Plating, a more common metallurgic technique, adds a layer of metal on to another material, providing protection or better aesthetic qualities. Plating coats a metal with a think layer of material.