hot and cold working process

Hot and Cold working Processes:
The metal working processes are derived into hot working and cold working processes. The division is on the basis of the amount of heating applied to the metal before applying the mechanical force. Those processes working above the re-crystallization temperature are hot working processes where as the below or termed as cold working processes.
Under the action of heat and force when the atom reach a certain high energy level the new crystal start forming , which is termed as re- crystallization. Re-crystallization destroys the old grain structure deform by the mechanical working and entirely new crystal which are strain free and form.
Re-crystallization temperature is defined as the approximate minimum temperature at which complete re-crystallization of a cold work metal occurs with in a specified time.
Hot working processes.
Hot working of metals takes place above re-crystallization by hot working processes the metal are given desired shape by subjecting then two forces which cause then to undergo plastic deformation at the temperature above the re-crystallization range.
Different hot working processes are as follows:
1: Forging
• Hammer or smith forging
• Drop forging
• Upset forging
• Press forging
• Roll forging
• Swaging
2: pipe welding
• Butt welding of heated strips
• Butt welding of electrical resistance
• Lap welding
• Hammer welding
3: Rolling
4: Piercing
5: Spinning
6: Extruding
7: Drawing or Cupping
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