Metals.

Introduction to Metals

Metals are technical materials obtained from minerals that are found naturally in rocks. These minerals must be extracted and processed before they can be used in manufacturing. Throughout history, metals have played a fundamental role in technological development, from the Bronze Age to modern engineering and aerospace industries.

Metals are characterised by their strength, durability, and ability to conduct heat and electricity. Their versatility allows them to be shaped into structures, tools, machines, electronic components, and transport systems. Because of these properties, metals are considered essential materials in industrial societies.

A metal is a material obtained from a mineral.
A mineral is a natural substance found in rocks that contains useful elements.
An alloy is a mixture of a metal with other elements to improve its properties.

Properties of Metals

The properties of metals determine their industrial applications. These properties can be classified as physical, mechanical, chemical, and ecological.

From a mechanical point of view, metals have high strength and resistance to forces such as tension, compression, and bending. They are generally ductile, meaning they can be stretched into wires, and malleable, meaning they can be hammered or rolled into thin sheets. Many metals also show toughness, which allows them to absorb energy without breaking easily.

Physically, metals are excellent conductors of electricity and heat. This makes them essential for electrical wiring, electronic circuits, and thermal systems. They also present fusibility, meaning they can be melted and reshaped, which is a key property in industrial production. Additionally, metals expand when heated and contract when cooled, a phenomenon known as thermal expansion.

Chemically, metals may react with oxygen and moisture, leading to oxidation and corrosion. For example, iron reacts with oxygen to form rust. This chemical behaviour must be considered when selecting materials for outdoor or humid environments.

From an ecological perspective, metals are not renewable resources, since mineral deposits are limited. However, one of their greatest advantages is that they are highly recyclable. Recycled metals maintain most of their original properties, reducing the need for new extraction.

Most metals are greyish colour, reddish colour, or yellowish.
Density. Metals are generally very dense, so they sink quickly in water.
Physical state. All metal are solids at room temperature except mercury and gallium.
Lustre. Metals reflect light to a greater or lesser degree.
Conductivity. Metals are good conductors of heat and electricity.
Ductility. most metals can be made into threads (wires) when they are stretched.
Malleability. Most metals can be made into sheets when they are compressed.
Toughness. Metals resist external forces such as bumps and knocks.

Extraction of Metals

Metals are obtained from minerals through mining activities. When minerals are located near the surface, surface mining is used. When they are deeper underground, underground mining techniques are required.

Once extracted, the mineral must be processed to separate the useful material, known as ore, from the unwanted waste material, called gangue. This separation involves both physical and chemical processes. The resulting purified material is then used to produce the desired metal.

Classification of Metals: Ferrous and Non-Ferrous

Metals are classified into two main groups according to their composition: ferrous metals and non-ferrous metals. The main difference between these two groups lies in the presence or absence of iron.

Ferrous Metals

Ferrous metals are those that contain iron as their principal component. They are widely used in industry due to their strength, durability, and relatively low cost.

One of the most important characteristics of ferrous metals is that they are usually magnetic and have high mechanical resistance. However, they tend to oxidise easily when exposed to oxygen and moisture, forming rust.

The most important ferrous metals are:

Iron, which is rarely used in its pure form.
Steel, an alloy of iron and carbon, which is the most widely used metal in construction and engineering.
Cast iron, which contains a higher percentage of carbon and is more brittle.
Stainless steel: contains Iron (Fe) → main component, Carbon (C) → small percentage, Chromium (Cr) → at least 10.5%, Sometimes Nickel (Ni), Molybdenum (Mo) or other elements. Prevents rust and protects against corrosion

Ferrous metals are commonly used in structures, machinery, tools, and construction materials.

A ferrous metal contains Iron.
It is difficult to assign common properties to ferrous metals, since they can have a wide variety of alloying elements that greatly change their characteristics.
Ferrous metals often have relatively high amounts of strength, especially when compared with copper, tin, and lead alloys.
Ferrous metals are also generally hard, and if they’re not alloyed with many other elements or coated,
can be subject to rust.
Most ferrous materials are magnetic, with the exception of stainless steel and some other grades because of chromium.

Alloys

An alloy is a mixture of two or more chemical elements where at least one of them is a metal.

Non-Ferrous Metals

Non-ferrous metals are those that do not contain iron, or contain it in very small quantities. They are generally more resistant to corrosion and are not magnetic. Many of them are lighter than ferrous metals and have excellent electrical and thermal conductivity.

Non-ferrous metals can be classified according to their density:

Light metals, such as aluminium, magnesium, and titanium.
Heavy metals, such as copper, zinc, tin, lead, brass, and bronze.

Copper
Tin
Aluminium
Bronze: copper+tin
Zinc
Galium
Brass: copper+zinc
Lead
Gold
Silver

Bronze is an alloy mainly composed of copper and tin. It usually contains approximately 88–95% copper and 5–12% tin. The addition of tin significantly improves the properties of copper by increasing its hardness and mechanical strength, making it more resistant to wear and corrosion. It also enhances its casting properties, allowing the metal to be easily shaped into moulds. While pure copper is soft and relatively flexible, when tin is added, the resulting material becomes much stronger, more durable, and more suitable for industrial and artistic applications. Bronze is commonly used to manufacture sculptures, church bells, boat propellers, bearings and decorative objects due to its resistance and durability.

Brass is an alloy mainly composed of copper and zinc, with copper representing about 55–90% of the composition and zinc about 10–45%. It is classified as a non-ferrous alloy because it does not contain iron. The addition of zinc improves copper’s properties by increasing its hardness and mechanical resistance, making it easier to machine and more resistant to corrosion. Furthermore, zinc gives brass its characteristic yellow-golden colour, which makes it attractive for decorative purposes. Pure copper is soft and reddish in colour, but when zinc is added, brass becomes stronger, more resistant and more versatile for industrial and decorative uses.

These metals are commonly used in electrical cables, aircraft manufacturing, electronics, packaging, and decorative elements.

Metallurgy and Steel Production

Metallurgy is the industrial process through which metals are extracted, refined, and transformed into useful products. A specific branch of metallurgy, called siderurgy, focuses exclusively on the production of iron and steel.

In steel production, the mineral is first crushed and washed. The ore is separated from the gangue and then mixed with coal and limestone. This mixture is introduced into a blast furnace, where it is heated to very high temperatures. The molten material obtained is then refined to reduce impurities and adjust its composition, resulting in steel.

Shaping and Forming Metals

After extraction and refinement, metals must be shaped into usable forms. This is achieved through various industrial processes.

Mechanical shaping techniques include rolling, extrusion, forging, bending, and wire drawing. These processes deform the metal without removing material. Casting is another important technique in which molten metal is poured into a mould and allowed to solidify. Powder metallurgy, which involves pressing and heating metal powder, is used to produce precise mechanical components.

Through these techniques, metals can be transformed into beams, sheets, wires, pipes, mechanical parts, and complex structures.

Metals in Technology

Metals are fundamental technical materials obtained from minerals. Their mechanical strength, conductivity, and versatility make them essential in modern industry. Although they are non-renewable resources, their recyclability contributes to sustainable technological development. Understanding their classification, extraction, and shaping processes is essential for selecting the appropriate metal for each application.

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