Forgings are often Normalized or Iso annealed to achieve consistent hardness in controlled hardness band and impart good Machinability. This need of Tempering arises primarily due to the uncontrolled cooling of forgings after trimming operation. The controlled cooling rate after trimming can give the similar results as normalizing barring few properties. The Microstructure obtained by controlled cooling is predominantly coarse grain and consists of pearlite plus ferrite matrix.  Coarse grain structure results in improved machinability. Controlled cooling process has potential of 20 Kg saving of oil per metric ton of net forging weight. The reduction in CO₂ emission is also possible to the tune of 250 Kg / metric ton of net forging weight. This needs specially designed tunnel to control cooling rate.

This paper will give details of properties achieved for different carburising grades of steel, refinement of steel specifications and process control required to replace normalizing / iso annealing by control cooling. The cycle & cooling rates established to achieve these results will also be discussed.

Key words : Controlled cooling, iso annealing, normalizing, forging, carburising grade steels.