What are the techniques of the hood annealing furnace

Hood annealing furnace generally USES hydrogen or hydrogen nitrogen mixed gas as protective gas, but hydrogen has better thermal conductivity than hydrogen nitrogen, and hydrogen has stronger decarbonization capacity than hydrogen nitrogen. The carbon residue content on the surface of strip steel treated by hood annealing furnace using hydrogen as protective gas is less, and the mechanical characteristics are more uniform.

The main process equipment of hood annealing furnace includes annealing furnace table with supply pipe and drain pipe, inner cover, heating cover, cooling cover and valve station, etc. At the beginning of annealing, the steel coils that need to be annealed should be stacked on the annealing furnace table first, and the inner hood should be lifted, and the cold state sealing test should be carried out on the furnace table, inner hood system and hydrogen inlet valve. After the test is successful, nitrogen purge should be carried out, and the heating hood should be lifted, and then the heating hood should be ignited. When nitrogen purge meets the conditions, hydrogen purge is used to replace nitrogen in the inner cover. The heating starts and the temperature is controlled according to the heating curve selected for different materials until the coil core temperature meets the requirements of the process.

In the cowl annealing process, the cooling begins with the heating hood still on the top of the furnace. Air is first blown into the heating hood and then removed. Then the cooling hood is hoisted and the surrounding air cooling inner hood is pumped through the fan above the cooling hood. When the circulation atmosphere in the inner cover reaches the set temperature, the fan of the cooling cover should stop running. After a period of time, the spray cooling will start. When the coil core temperature reaches the set value, the cooling is finished and the cooling cover is removed. Nitrogen purge is then carried out to replace the hydrogen in the inner hood, remove the inner hood, and then lift off the steel coil. This process is completed.