Metal Classification, Extraction, and Processing Methods

Classification of Metals

Metals are categorized based on their composition and density:

• Ferrous: Metals or alloys that contain iron.
• Non-ferrous: Pure metals that do not contain iron.

Density Classification

• Ultralight: Density less than 2 g/cm³.
• Light: Density between 2 and 5 g/cm³.
• Heavy: Density superior to 5 g/cm³.

The Metal Extraction Process

1. Obtaining minerals from mines and pits.
2. Separation of the mineral into ore and gangue.
3. Obtaining the pure metal from the mineral.
4. Final treatment.

Mining Operations

Mining is an industrial activity that consists of extracting elements, compounds, and minerals of economic interest from the Earth. There are two types of mines:

• Open-air mines
• Underground mines

Siderurgy and Iron Production

Siderurgy is the industry dedicated to obtaining iron. The raw materials used are iron ores, limestone, and coke coal.

The Blast Furnace Process

1. Raw materials are placed into the top of the blast furnace, and hot air is introduced into the lower part.
2. As materials descend, a chemical reaction occurs.
3. Waste materials (slag) stay at the top, floating on the molten metal.
4. The molten iron is known as pig iron.
5. To become steel, it must be melted and reprocessed to reduce the carbon content to the correct amount.

Electrolysis

Electrolysis is a process primarily used to obtain or purify non-ferrous metals. Purification or refining consists of eliminating impurities left in the metal after extraction. This process is commonly used for copper.

Ferrous Products

Obtained after operations in the blast furnace and steelworks:

• Soft iron: A brittle material with poor mechanical properties.
• Cast iron: Less ductile than steel but harder. Carbon makes the metal harder yet more fragile; it can be melted and molded easily.
• Steel: Varies based on carbon content and alloying elements. Examples include mild steel, hard steel (less ductile), stainless steel (with chrome and nickel to prevent oxidation), and special steels for tools like knives or drills.

Non-Ferrous Metals

• Copper: The first metal used by humans as it is found in nature.
• Aluminum: The most abundant metal in the Earth's crust; difficult to obtain due to stable chemical bonds.
• Tin: A silvery-white, ductile, and malleable metal.
• Zinc: Used in alloys; highly resistant to corrosion and oxidation, though it has poor mechanical properties.
• Lead: A dense, highly malleable, and very soft metal.
• Titanium: Low density with good corrosion resistance.
• Tungsten: High density and a very high melting point.
• Nickel: Resistant to corrosion; used to create alloys.

Metalworking Methods

Different methods are used for shaping and developing products:

1. Casting
2. Plastic deformation: Includes rolling, forging, and extrusion.
3. Machining: Includes drilling, turning, and milling.

Hand Tools

Common tools include rulers, hammers, bench clamps, files, screwdrivers, and saws.