What is Ring Rolling?
Ring rolling is a type of metal rolling in which the ring of smaller diameter is rolled into a precise ring of larger diameter with reduced cross section.
The initial ring preparation is done by forging process and then it is rolled in a ring rolling mill to get the final ring with required diameter and thickness.
As shown in the above image, the ring of smaller diameter is made from the forged steel (or metal) piece by punching operation.
Ring rolling process
In a ring rolling mill, the metal ring is rolled by using two or more rollers. One roller is driven by a mechanical power source and the other roller/s are idle.
The rollers are kept on either side of the cross section of a ring (see above image).
In industries, the edging rollers are generally used for rolling a forged ring. The edging rollers are used to ensure that the constant width of the metal ring is maintained during a forming process.
During the ring rolling process, the volume of the ring remains equal. So as the thickness of ring is reduced by the rollers, its volume is compensated by increasing its diameter.
In the above image, you can see that the thickness of the ring decreases as its diameter is increased.
Such ring rolling manufactured by using rollers is also known as the seamless ring rolling process.
By using a steel ring rolling process, the flat steel rings as well as grooved steel rings or rings with different cross sections can also be manufactured.
For grooved steel rings, the grooved rollers are used in place of flat rollers.
Ring rolling process produces a ring with high precision and less wastage of material.
There are two types of ring rolling process.
- Hot ring rolling process and
- Cold ring rolling process
Hot ring rolling process
Hot ring rolling is a type of metal rolling in which the ring of smaller diameter is heated above its recrystallization temperature and then it is rolled into a precise ring of larger diameter with reduced cross section.
The heat required for heating the ring is much higher in hot ring rolling process.
In hot ring rolling, the ring metal is soft as it is heated above its recrystallization temperature. Because of this, it can be reduced to a much thinner ring.
Also the main advantage of hot ring rolling is that the crystals are refined during the hot rolling operation of the ring which gives strength to the final rolled ring because of its heating above recrystallization temperature.
Cold ring rolling process
Cold ring rolling is a type of metal rolling in which the temperature of the smaller diameter ring is below its recrystallization temperature and it is rolled into a precise ring of larger diameter with reduced cross section.
In a cold ring rolling, the metal is hard. So the reduction in cross section of the ring is very less compared to hot ring rolling.
The rings manufactured by cold rolling may show high amounts of internal stresses.
Also as higher force is required to deform the non heated metal, a strong, bulky rolling mill is required to perform the cold ring rolling process.
Uses/Applications of ring rolling
The forged ring manufactured by the ring rolling process is used in following applications.
- Pressure vessels
- Ball bearing races, etc.