Annealing process of bell annealing furnace

The bell annealing furnace generally uses hydrogen or hydrogen-nitrogen mixture gas as protective gas, but hydrogen has better heat conductivity than hydrogen-nitrogen, and 100% hydrogen has stronger decarbonization ability than hydrogen-nitrogen. The bell annealing furnace using hydrogen as protective gas has less carbon slag content and more uniform mechanical characteristics. Therefore, it is necessary to use hydrogen as protective gas in some metallurgical industries. It has been widely used. So what is the annealing process of such a bell annealing furnace? How does it complete the annealing of the workpiece?

The main process equipment of all-hydrogen bell annealing furnace includes annealing hearth, inner cover, heating cover, cooling cover and valve station with supply and discharge pipes, etc. At the beginning of annealing, the coils that need to be annealed should be stacked on the annealing hearth and hoisted with the inner cover. The hearth and the inner cover system and the hydrogen inlet valve should be tested for cold sealing. After the successful test, the nitrogen gas should be purged. At the same time, the heating cover should be hoisted and then ignited. When nitrogen purge meets the requirements, hydrogen purge is used to replace the nitrogen in the hood. 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 requirements of the process.

In the process of full hydrogen bell annealing furnace, the cooling begins with the heating cover which is still on the hearth. First, air is injected into the heating cover, and then the heating cover is removed. Then the cooling cover is hoisted, and the air cooling inner cover of the surrounding environment is sucked by the fan above the cooling cover. When the circulating atmosphere inside the hood reaches the set temperature, the fan of the cooling hood should stop running. After a period of time, the spray cooling begins. When the temperature of the coil core reaches the set value, the cooling is finished and the cooling cover is removed. Then nitrogen is purged, hydrogen is replaced in the inner cover, the inner cover is removed, and the coil is lifted. This process is completed.

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