The surface temperature of the billet exiting the caster is around 800-900°C and the core temperature is around 1100-1300°C. This becomes a hindrance in the plants where they practice Hot Charging of billets in the rolling mill. The billets lose about 50-100°C of their surface temperature and around 100-200°C of their core temperature during the travel from the caster to the rolling mill. At these temperature, the rolling of billets lead to serious problems like:
- 1. Breaking of the rolls of the roughing mill
- 2. Miss Roll of the billet
- 3. Inferior quality of the finished product
- 4. Rejection of finished material
To overcome these issues, the end-user needs to improvise and look for solution such as :-
- 1. Increasing the size of the motor and switchgear so that the motor does not trip; but this still does not solve the problem as the resultant material is of inferior quality and has lots of rejection.
- 2. Provide continuous heating, by Induction heaters, to raise the billet surface temperature to 1050°C; but this increases the overall cost of production and the CAPEX cost.
To overcome the above problems, ENCON provides a tunnel furnace which uses a liquid or gaseous fuel to raise the surface temperature of the billets from 800°C to 1050°C. The design of the burners is such that the resultant flame is short and highly luminous to ensure maximum heat transfer through radiation and convection. Moreover, the burner flame length can be adjusted according to the size of the billets.
The benefits of this approach are as follows:
- 1. Properly Soaked billets
- 2. Reduction in the cost of electricity for rolling by up to 8%
- 3. The Running of a tunnel furnace is 15-30% cheaper than the induction heater, depending on the fuel being used
- 4. The cost of the Tunnel furnace is 1/3rd the cost of an induction heater
We can also provide regenerative burners to increase system efficiency.