2.6 Heat and chemical treatment

• Normalising


  A heat treatment that results in metal that is tough with some ductility
• Annealing


  A heat treatment that makes a metal softer and easier to work
• Hardening


  A heat treatment that increases the hardness and strength of a metal due to a change in the arrangement of the atoms within it
• Quenching


  The rapid cooling of a hot metal by immersing it in a liquid, often oil or brine
• Tempering


  A heat treatment to remove some of the brittleness in a hardened steel, at the cost of some hardness
• Normalising


  Heating steel then allowing it to cool in air
• Annealing


  Heating a metal and allowing it to hold at a temperature where grain growth occurs
• Hardening steel


  Heating and quenching
• Quenched steel


  Normally tempered, which reduces some of the brittleness at the expense of some of the hardness
• Aluminium alloys


  • Can be precipitation hardened, where elements dissolved in the alloy can increase the strength