Normalizing

• Normalizing process is a heat treatment process for making material softer but does not produce the uniform material properties as produced with an annealing process.
• The most common reason for the normalizing process is to adjust mechanical properties to suit the service conditions.
• The other purpose of the normalizing is:
  1. To relieve the internal stresses,
  2. To refine the grain structure, and
  3. To improve the machinability.
• Normalizing involves heating steel to above 50°C above the upper critical temperature, (for hypo-eutectoid steel) and to 50°C above the lower critical temperature (for hyper eutectoid steel).
• Holding at this temperature for a shorter time to prevent grain growth and finally, cooling in air.
• The time allowed should be sufficient so that the temperature is equalized throughout the section.
• The structure produced by normalizing is similar to that of annealing. But air cooling is faster than furnace cooling. Thus the normalized steels possess fine grains than annealed steels.
• The normalized structure of low-alloy steel consists of sorbite (fine pearlite) and fine ferrite.
• The increased rate of cooling in normalizing results high hardness and low ductility than annealed steel –> machinability will be easy.
• Normalizing is usually performed after forging or casting, to put steel in the best condition for machining or hardening.