Properties and Alloys of Ferrous Metals, Tin, and Copper

Ferrous Metals Classification

Based on Carbon Content

• Irons (0.01% to 0.03% C): White, difficult to obtain, with few industrial applications.
• Steels (0.03% to 1.76% C): Iron-carbon alloys that may contain other elements.
• Cast Irons (1.76% to 6.67% C): Iron-carbon alloys that may have other elements.
• Graphites (more than 6.67% C): Very fragile with no industrial applications.

Types of Cast Iron

Regular Cast Iron

• White Cast Iron: Very hard and brittle, used to make malleable iron.
• Gray Cast Iron: Used in malleable castings.
• Mottled Cast Iron: An intermediate between white and gray cast iron.

Alloyed Cast Iron

Contains iron, carbon, and other elements to improve its chemical properties.

Special Cast Iron

• Whiteheart Malleable Iron: A piece is molded in white cast iron. It is then introduced into an oven with iron ore at 1000°C and cooled slowly to room temperature.
• Blackheart Malleable Iron: A piece is molded in white cast iron, covered with sand, placed in an oven at 900°C, and then slowly cooled to room temperature.
• Pearlitic Malleable Iron: Similar to blackheart malleable iron.
• Ductile (Nodular) Iron: Created by adding cerium and magnesium to gray cast iron, which is then poured into a mold and allowed to cool to room temperature.

Tin: Extraction and Alloys

Obtaining Tin

1. The ore, cassiterite, is ground in mills.
2. It is placed into a vat with water and stirred. Through decanting, the heavier ore settles at the bottom and is separated from the gangue (impurities).
3. The ore is introduced into a furnace where tin sulfides are oxidized and transformed into oxides.
4. The oxide ore is introduced into a reverberatory furnace where reduction occurs. The tin is deposited on the bottom and scum forms at the top.
5. To achieve 99% purity, the tin must undergo electrolysis.

Tin Alloys

• Bronze: A copper-tin alloy.
• Soft Solders: Tin-lead alloys.

Copper: Extraction and Alloys

Obtaining Copper

Dry Method (Pyrometallurgy)

Used when copper ore concentration exceeds 10%.

1. Copper ore is introduced into a shredder and then a grinder to be pulverized.
2. To separate the ore and gangue, the mineral powder is placed in a water tank and agitated. The heavier ore sinks to the bottom while the gangue floats.
3. The concentrated ore is taken to an oven where it is oxidized. This process oxidizes the iron, but not the copper.
4. Everything is then introduced into a reverberatory furnace where it melts.
5. A flux is added, which reacts with iron oxide and sulfur to form slag.
6. The resulting copper has a purity of about 40% (raw copper).

Wet Method (Hydrometallurgy)

Used when copper ore concentration is below 10%.

The ore is crushed and treated with sulfuric acid. The copper is then extracted through the process of electrolysis.

Copper Alloys

• Bronze (Copper-Tin)
  • Regular Bronze: Copper and tin (e.g., for bells).
  • Special Bronze: Copper, tin, and other elements (e.g., for electrical wires).
• Brass (Copper-Zinc)
  • Regular Brass: Copper and zinc (e.g., for screws).
  • Special Brass: Copper, zinc, and other elements (e.g., for taps).
• Aluminum Bronze: Copper-aluminum alloy (e.g., for pipes).
• Nickel Silver: Copper-nickel-zinc alloy (e.g., for costume jewelry).
• Cupronickel: Copper-nickel alloy (e.g., for coins).