Metal
Overview
Metal refers to materials that, in solid state, have a characteristic luster, conduct electricity and heat well, and can be hammered or drawn into thin sheets or fine wires. In the periodic table, they are classified as transition metals, alkali metals, alkaline earth metals, etc., with representative examples including iron, copper, aluminum, gold, and silver. Metals are historically significant as a criterion for dividing stages of human civilization (Bronze Age, Iron Age) and form the foundation of modern industry and technology.
Main Content
1. General Properties of Metals
Metals are composed of metallic bonds between atoms, resulting in the presence of free electrons. These free electrons impart electrical and thermal conductivity, and cause malleability and ductility as atomic layers can slide under external force while maintaining bonds. Additionally, metals generally have high density, high melting and boiling points, and a luster that reflects light.
2. Classification of Metals
- Ferrous Metals: Metals with iron (Fe) as the main component. Includes steel and cast iron; they are magnetic and have high strength, widely used in construction, automobiles, shipbuilding, etc.
- Non-Ferrous Metals: Metals other than iron. Includes aluminum (Al), copper (Cu), zinc (Zn), lead (Pb), nickel (Ni), titanium (Ti), etc., each utilized for special properties such as light weight, electrical conductivity, and corrosion resistance.
- Precious Metals: Chemically stable and rare metals such as gold (Au), silver (Ag), and platinum (Pt). Used in jewelry, currency, electronic components, etc.
- Rare Earth Metals: Scandium (Sc), yttrium (Y), and lanthanide series elements. Essential for high-tech industries (magnets, batteries, lasers).
3. Production and Processing of Metals
Most metals are extracted from ores. Through smelting, pure metals are obtained from ores in oxide or sulfide form, and then processed into various shapes via alloying, casting, forging, rolling, drawing, etc. For example, iron ore reacts with coke in a blast furnace to produce pig iron, which is then purified in a converter or electric furnace to become steel.
4. Uses of Major Metals
- Iron and Steel: Core materials for infrastructure such as building structures, bridges, automobiles, ships, railways, and pipelines.
- Aluminum: Used in aircraft, automotive parts, packaging (cans), construction materials, and electrical wires. Lightweight and corrosion-resistant.
- Copper: Used in electrical wires, electric motors, plumbing, heat exchangers, and coins. Has the second highest electrical conductivity after silver.
- Gold and Silver: Used in electronic circuit contacts, semiconductor bonding wires, jewelry, and investment assets.
- Titanium: Used in artificial joints, aircraft engines, military equipment, and watch cases. Known for high strength-to-weight ratio and biocompatibility.
5. Physical and Chemical Properties of Metals
- Electrical Conductivity: Silver > Copper > Gold > Aluminum.
- Thermal Conductivity: Silver > Copper > Gold > Aluminum.
- Density: Osmium (22.59 g/cm³) is the highest, lithium (0.534 g/cm³) the lowest.
- Melting Point: Tungsten (3422°C) is the highest, mercury (-38.83°C) the lowest.
- Corrosion Resistance: Gold and platinum do not corrode in almost any environment; aluminum is protected by a surface oxide layer.
6. Metals and Human Civilization
The discovery and use of metals changed human history. The Bronze Age, beginning around 4000 BCE in West Asia, saw bronze (an alloy of copper and tin) used for tools and weapons, enhancing agriculture and warfare. Subsequently, the Iron Age around 1200 BCE brought iron tools and weapons, enabling population growth and empire expansion. The Industrial Revolution was driven by mass production technologies for iron and steel (Bessemer process, open hearth process).
Latest Trends
As of 2024-2025, the metal industry is characterized by sustainability and high-tech convergence. First, green hydrogen steelmaking technology is approaching commercialization, with 'hydrogen reduction steelmaking' that drastically reduces carbon dioxide emissions from traditional blast furnace processes being tested in Europe and South Korea. Second, surging demand for electric vehicle batteries has made the mining and recycling of battery metals such as lithium, nickel, cobalt, and manganese crucial. In particular, the 'urban mining' business of recovering metals from spent batteries is expanding. Third, smart smelters utilizing artificial intelligence (AI) and the Internet of Things (IoT) are emerging, enhancing production efficiency and safety. Fourth, demand for high-performance metals such as titanium, superalloys, and tungsten is increasing in space exploration and defense industries, and 3D printing (additive manufacturing) is increasingly used to directly produce complex-shaped metal parts. Finally, strengthened ESG management has made eco-friendly mining technologies and improved metal recycling rates a challenge across industries.
Related Topics
- [[Alloy]]
- [[Ironmaking]]
- [[Periodic Table]]
- [[Electrical Conductor]]
- [[Resource Recycling]]
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