Metals and Their Properties: notes

Ferrous and non-ferrous

• Ferrous metals: contain iron and are usually magnetic and rust. Examples: mild steel, high carbon steel, cast iron.
• Non-ferrous metals: contain no iron, are not magnetic and do not rust. Examples: aluminium, copper, lead, zinc, tin.
• Alloys: a mix of metals. Brass is copper and zinc. Bronze is copper and tin. Solder is tin and lead.

Common metals

• Mild steel: low carbon (about 0.15 to 0.3 percent), tough and easy to weld, used for general fabrication.
• High carbon steel: hard, used for chisels and files.
• Cast iron: hard but brittle, good for engine blocks and machine beds.
• Aluminium: light and corrosion resistant.
• Copper: a very good conductor of heat and electricity, used for wires and pipes.

Properties

• Hardness: resists scratching and denting.
• Toughness: resists breaking under a sudden blow.
• Ductility: can be drawn into wire.
• Malleability: can be hammered into shape.
• Elasticity: springs back after bending.
• Brittleness: snaps with little bending, like cast iron.

Identifying metals

• Spark test: hold a metal to a grinder. Mild steel gives long straight sparks; cast iron gives short red sparks.
• Stock forms: metals are sold as bar (round, square, flat), sheet, angle, tube and plate.