The bell type annealing furnace generally uses hydrogen or hydrogen nitrogen mixture gas as shielding gas, but the thermal conductivity of hydrogen is better than that of hydrogen nitrogen The decarburization ability of 90% hydrogen is stronger than that of hydrogen and nitrogen. The carbon slag content on the surface of strip steel treated by bell type annealing furnace using hydrogen as shielding gas is less, and the mechanical characteristics are more uniform. Therefore, using hydrogen as shielding gas has been widely used in some metallurgical industries. So what is the annealing process of such a bell type annealing furnace? How does it complete the annealing of the workpiece?

The main process equipment of all hydrogen bell type annealing furnace includes annealing furnace platform with supply pipeline and discharge pipeline, inner hood, heating hood, cooling hood and valve station, etc. At the beginning of annealing, the steel coils to be annealed should be stacked on the annealing furnace platform, and the inner hood should be hoisted. The cold sealing test should be carried out on the furnace platform, inner hood system and hydrogen inlet valve. After the test is successful, nitrogen purging should be carried out. At the same time, the heating hood should be hoisted and ignited with the latter heating hood. When the condition of nitrogen purging is satisfied, the nitrogen in the inner hood should be replaced by hydrogen purging. The heating starts and the heating curve is selected according to different materials to control the temperature until the temperature of the coil core meets the process requirements.

In the process of all hydrogen bell type annealing furnace, the cooling should start from the heating hood which is still on the hearth. Firstly, air should be blown into the heating hood, and then the heating hood should be removed. Then the cooling hood is hoisted, and the air in the surrounding environment is pumped through the fan above the cooling hood to cool the inner hood. When the circulating atmosphere inside the inner hood reaches the set temperature, the fan of the cooling hood will stop running. After a period of time, the spray cooling will start. When the temperature of the coil core reaches the set value, the cooling is finished and the cooling cover is removed. Then, the nitrogen is purged, the hydrogen in the inner hood is replaced, the inner hood is removed, and the steel coil is hoisted away. This process is completed.