Normalizing is a defined as softening process in which iron base alloys are heated 40 to 50°C above the upper-critical limit for both hypo and hyper eutectoid steels and held there for a specified period and followed by cooling in still air up to room temperature. Fig 1 shows the heating temperature ranges for normalizing process of both hypo and hyper carbon steel. Fig. 2 shows the structure obtained after normalizing of medium carbon steel.
Objectives of Normalizing
1. To soften metals
2. Refine grain structure
3. Improve machinability after forging and rolling
4. improve grain size
5. Improve structure of weld
6. Prepare steel for sub heat treatment