Rolling is a metal forming process the part is passed through rolling pair. the rolling is classified based on the temperature of metal. The temperature of metal above re-crystallization temperature is called hot roll and the metal of below re-crystallization temperature is called cold rolled process.
Types of rolling process:
Based on temperature
- Hot rolling
- Cold rolling
Based on method of rolling occur
- Flat strip rolling
- Shape rolling
- Thread and gear rolling
- Tube rolling
- Ring rolling
- Skew rolling
Hot roll method:
Hot rolling is a effective way to reduce grain size and improve strength & Ductility. The above re-crystallization temperature of material, the metal working process obtained, and then the grain deformed and recrystallize. This is maintaining an equaled micro-structure and work hardening prevented in the metal.
The staring materials are usually large piece like as semi-finished casting products such as blooms, billets and slabs. It may be come from continuous casting operation, the part directly fed into rolling mill within proper temperature and monitored to make sure it above re-crystallization temperature.
During the rolling process the cast ingot coarse structure is converted into fine grained structure.
The rolled parts are improved in mechanical properties such as ductility, toughness, strength and shock resistance. Hot rolling is mostly used in to produce sheet metal or simple cross section, such as rail tracks.
cold rolled process:
The cold rolling performed in below re-crystallization temperature of metal (room temperature). Which is improve the surface finish hold tighter tolerance and increased strength via strain hardening (up to 20%). The cold rolled products such as sheets bars strips and rods. This is usually smaller than the same product as hot rolled. Because of small size of cold rolling product usually more strength compared to hot rolled part. Which cold rolling cannot be reducing the work piece thickness as much as hot rolling in single process.