DIRECT ANNEALING FURNACE FOR FERRITIC STAINLESS STEEL

A new process route has been envisaged and implemented in manufacturing ferritic stainless steel coils that may be annealed before subsequent cold rolling directly at the exit of the hot strip mill by holding at high temperature the coil downloaded at about 800 °C from the down-coiler. The process exploits the sensible heat of the coil at the exit from the hot strip mill, instead of cooling it down to room temperature and then re-heating it again in the conventional, batch type, bell furnace, with great advantages in energy and handling costs. 
The pit furnace is rapidly loaded with several tens of coils by a fully automated handling equipment, to be treated by controlling initial temperature, soaking and cooling.  The heat treatment lasts a few hours consuming a very limited amount of fuel, before the pit furnace can be cleared and made ready for the next batch operation.


Main features:

• Capacity of each cell: n. 5 coils up to 30 t.
• Design temperature: 900°C.
• Coil transfer equipment (horizontal or vertical axis) from hot rolling mill exit section to loading area.
• Automatic coil charging crane (loader). The loader will be also used to discharge the furnace and then to transfer annealed coils in the final storage area.
• Automatic furnace cover lifting devices.
• Annealing system, provided with some cells internally lined by refractory.
• Combustion system, with gas piping and combustion air piping for burners feeding, sub-system for air pre-heating and exhaust gas ducts and chimney.
• Furnace control and regulation system.
• Furnace electrical power feeding, electrical feeding for control and regulation system and electrical feeding for supervision system.