In actual production, the annealing process of a bell-type annealing furnace typically includes the following 12 steps:
- Loading the furnace – Use an overhead crane to place a batch of coils onto an available furnace base.
- Placing the inner cover – The crane lifts an inner cover and lowers it onto the loaded base. Steps (1) and (2) take approximately 25 minutes in total.
- Cold sealing – Check whether the inner cover is properly sealed. (~15 minutes)
- Pre-purging – Nitrogen is introduced to force out the oxygen inside the cover. (~30 minutes)
- Placing the heating cover – Use the crane to lift a heating hood and place it over the inner cover. (~8 minutes)
- Heating – Heating of the steel coils begins. The heating duration is determined by process requirements and varies based on coil specifications.
- Removing the heating cover – Once heating is completed, the crane removes the heating hood. (~8 minutes)
- Placing the cooling cover – A cooling hood is placed over the inner cover. (~8 minutes)
- Cooling – Cooling begins. Cooling time is also determined by process requirements.
- Post-purging – Nitrogen is used again to flush the coils. (~30 minutes)
- Removing the cooling cover – The crane removes the cooling hood. (~8 minutes)
- Unloading – The crane first removes the inner cover, then lifts out the coils one by one. (~25 minutes)
Among these 12 steps, except for the heating and cooling durations which depend on process settings, the other operation times are mostly fixed.