Definition
When the working temperature is above the recrystallization temperature is called "Hot working Process".
When the working temperature is above the recrystallization temperature is called "Hot working Process".
The Grain refinement is due to braking up of grains into smaller crystals in hot working process. In this process deformation of metals occur above the recrystallization temperature.Most of the metals and alloys are working in high temperature and high recrystallization temperature. In hot working metal posses different characteristics.
The upper limit working temperature is based on the following factors.
1. Metal composition
2. Deformation Priority
3. The metal contains impurities
Selection of optimum temperature for hot working process depends on the following,
1. Metal Grain structure
2. Force and heat applied
3. Plastic deformation rate
4. The increase solute concentration in solid solution the temperature increases
5. Second phase particles decrease temperature
6. There should not be any strain hardening
7. Scaling of the surface is not priority in hot working temperature
8. Continuous reformation of the grains yielded
9. High amount of ductility of metal should optimum temperature
10. It increases ductility
Properties of Hot working Process
1. Surface finish is poor
2. cracks and blow holes welded
3. No need intermediate annealing
4. Contamination problems is more
5. Impurities are squeezed into fibres
6. Scaling and oxidation of the surface occurring at high teperature
7. No problem of development residual stresses
The Hot working Process as follows,
1. Rolling
2. Piercing
3. Drawing
4. Spinning
5. Extruding
6. Forging
Advantages of Hot working Process
1. Most of the metals can be worked at economical and rapid process
2. No strain hardening
3. Low power required to shape of the metal
4. Strength and hardness decreases while temperature high
5. Fiber structure can be obtained
Disadvantages of Hot working Process
1. Some metals can not be hot working process due to high brittleness and temperature
2. Surface finish is poor
3. Hot metal can not handle
4. Tool life reduces
5. Scaling of surface finish poor