Heating to a suitable temperature, holding long enough to reduce residual stresses, and then cooling slowly enough to minimize the development of new residual stresses. It relieves the stresses that occur as a result of the spring forming operation. It also returns the material to the strength levels prior to the forming operation and can actually increase the strength to levels greater than origi-nally supplied [3].
The normalizing of steel is carried out by heating ap-proximately 100°F (38°C) above the upper critical tem-perature (Ac3 or Acm) followed by cooling in air to room temperature Normalizing is often considered from both a thermal and a micro structural standpoint. In the thermal sense, normalizing is austenitizing followed by a relatively slow cooling.