Materials: Metals

Metals

• Metals are naturally occurring materials mined from the ground as ore.
• Approximately 25% of the Earth's crust comprises metal ores.
• Bauxite is the most common ore, followed by iron.
• Raw metal extraction involves crushing, smelting, heating, and adding chemicals, requiring substantial electrical energy.
• Recycling metals helps in resource conservation and reduces import dependence.

Raw Metal and Ore

• Copper is extracted from Chalcopyrite.
• Aluminum is extracted from Bauxite.
• Tin is extracted from Cassiterite.
• Zinc is extracted from Zinc blende.

Classification of Metals

Non-Ferrous Metals

• Aluminum
  • Properties: Lightweight, ductile, malleable, corrosion resistant, electrical and thermal conductor; can be MIG and TIG welded.
  • Uses: Drinks cans, aircraft bodies, bike frames, window frames, packaging, baking foil.
  • Melting Temperature: $660 °C$
• Copper
  • Properties: Ductile, malleable, tough, corrosion resistant, good electrical and thermal conductor; can be soldered and brazed.
  • Uses: Electrical wire, printed electrical circuits, water pipes, hot water tanks, central heating pipes
  • Melting Temperature: $1,083 °C$
• Zinc
  • Properties: Low melting point, good corrosion resistance.
  • Uses: Galvanizing steel as a protective coating for dustbins, buckets, farm gates; intricate die castings.
  • Melting Temperature: $420 °C$
• Silver
  • Properties: Malleable, ductile, corrosion resistant; can be soldered.
  • Uses: Jewelry, cutlery, plating other materials.
  • Melting Temperature: $962 °C$
• Gold
  • Properties: Malleable, ductile, corrosion resistant; can be soldered.
  • Uses: Jewelry, electronic components, connectors, switch components.
  • Melting Temperature: $1,063 °C$
• Titanium
  • Properties: Hard, similar strength to steels but more lightweight, high resistance to corrosion.
  • Uses: Joint replacements, tooth implants, spectacle frames, aircraft, spacecraft, golf clubs, bicycles, ship hulls.
  • Melting Temperature: $1,668 °C$
• Tin
  • Properties: Ductile, malleable, low melting point, corrosion resistant.
  • Uses: Soft solder, coatings for food cans; rarely used in pure form.
  • Melting Temperature: $232 °C$

Ferrous Metals

• Low Carbon Steel
  • Properties: Ductile, high tensile strength, tough, malleable, poor resistance to corrosion; 0.15-0.30% carbon content.
  • Uses: Nuts, bolts, washers, screws, car bodies, outer panels for white goods.
  • Melting Temperature: $1,427 °C$
• Medium Carbon Steel
  • Properties: Harder than low carbon steel but less ductile, malleable, and tough; 0.30-0.70% carbon content.
  • Uses: Springs, gardening tools (trowels, forks).
• Cast Iron
  • Properties: Hard outer skin but brittle core, good under compression; 3.5% carbon content.
  • Uses: Disc brakes, machine parts, engine blocks; sheet furniture, for example, decorative bollards, bins, and lighting.
  • Melting Temperature: $1,149 °C$

Ferrous Alloys

• Stainless Steel
  • Properties: Tough, hard, corrosion resistant; 18% chrome, 8% nickel.
  • Uses: Sinks, kitchenware, cutlery.
  • Melting Temperature: $1,510 °C$
• High-Speed Steel (HSS)
  • Properties: Hard, tough, high level of resistance to frictional heat; 18% tungsten, 4% chromium, 1% vanadium, 0.5-0.8% carbon.
  • Uses: Tool blades, drill bits, milling cutters, router bits.
• Die Steel (Tool Steel)
  • Properties: Hard, tough.
  • Uses: Blanking punches and dies, extruder dies, fine press tools.

Non-Ferrous Alloys

• Bronze
  • Properties: Tough, corrosion resistant; can be cast; 90% copper, 10% tin.
  • Uses: Statues, coins, bearings.
  • Melting Temperature: $850-1000 °C$
• Brass
  • Properties: Corrosion resistant, good electrical and thermal conductor, low melting point, casts well; 65% copper, 35% zinc.
  • Uses: Boat fittings, door furniture, cast valves and taps, ornaments.
  • Melting Temperature: $930 °C$
• Duralumin
  • Properties: Equivalent strength properties to low carbon steel but more lightweight, ductile, becomes harder as it is worked; 4% copper, 1% magnesium and manganese.
  • Uses: Aircraft parts, vehicle parts.
• Pewter
  • Properties: Malleable, low melting point, casts well; 85-99% tin, with the remainder consisting of copper and antimony.
  • Uses: Tankards, flasks, goblets, photo frames, decorative items, candlesticks, sports trophies.
  • Melting Temperature: $170-230 °C$

Stock Forms

Generally, more complex or material-rich stock forms are more expensive.

• Sheet: Large flat sections of metal, less than 1 mm up to approximately 3 mm thick.
• Plate: Generally thicker than 3 mm and narrower than sheet metals.
• Bar: Solid form, flat bar, square bar, round bar, or hexagonal bar.
• Tube: Hollow in cross-section; can be square, rectangular (box section), round, or hexagonal.
• Structural: Angular shapes such as H beams, L beams (angle), I beams, tee bar, and channel.