Full and process annealing
Two most common types of annealing treatments that are applied to commercial plain carbon steels are a) full annealing and b) process annealing. Fig 36.4 illustrates the full annealing and process annealing.
| Figure 36.4: |
Temperature ranges for annealing of plain carbon steels |
In full annealing hypo eutectoid and eutectoid steels are heated to a temperature  above the austenitic-ferrite boundary as shown in the figure. The steel is soaked and then cooled in the furnace. The hypereutectoid steels are heated above the austenitic region
Process annealing is used to relieve internal stresses induced due to cold working of metal. It is normally applied to hypo eutectoid steels by heating to a temperature in between  .
Normalising
Steel is heated to austenitic temperature and then cooled in air. Purpose is
- To refine grain structure
- To increase strength of steel
- To reduce segregation in castings or forgings
Temperature regions are shown in the figure 36.4 . In this lecture a very brief account of heat treatment procedure is discussed with the aim to understand steelmaking from the product-process integration point of view. Detailed discussions on heat treatment procedures can be found in any heat treatment book
References:
W.F.Smith: Principles of materials science and engineering
R.C.Sharma: Phase transformation in steel
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