Heat Treatment

Heat Treatment

1. Hardening

   • fast cooling
   • heated to over 723
   • cooled in water, oil or brine
   • must contain more than 5% carbon to harden steel

2. case hardening

   • used to harden mild steel
   • level of carbon in the outer skin is increased
   • improves surface hardness
   • engine shafts

3. normalised

   • steel is cooled slowly
   • normalise the crystal structure
   • cooled in still air

4. annealing

   • hold the component at the specific temp for a period of time
   • soft, ductile and stress free state
   • cooled slowly to ensure formation
   • recycrystallisation can be achieved