Bell annealing furnaces generally use hydrogen or hydrogen-nitrogen mixed gas as the protective gas, but hydrogen has better thermal conductivity than hydrogen-nitrogen, and high-standard hydrogen has a stronger decarburization ability than hydrogen-nitrogen. The cover-type using hydrogen as the protective gas The carbon slag content on the surface of the strip steel processed by the annealing furnace is less, and the mechanical properties are more uniform. Therefore, the use of full hydrogen as a protective gas has been commonly used in some metallurgical industries. So what is the annealing process of such a bell annealing furnace? How does it complete the annealing treatment of the workpiece?
The main process equipment of the full-hydrogen bell annealing furnace includes the annealing furnace stand with supply pipeline and discharge pipeline, inner cover, heating cover, cooling cover, valve station and so on. At the beginning of annealing, the steel coils to be annealed should be stacked on the annealing furnace table, the inner cover should be hoisted, and the cold sealing test of the furnace platform and the inner cover system and the hydrogen inlet valve should be carried out. After the test is successful, a cold sealing test is required. Nitrogen purge, while hoisting the heating mantle, and then the heating mantle ignites. When the nitrogen purge meets the conditions, it is necessary to replace the nitrogen in the inner cover with hydrogen purge. The heating starts and the heating curve is selected according to different materials for temperature control until the temperature of the steel coil core meets the requirements of the process.
In the process of the all-hydrogen bell annealing furnace, the cooling should start from the heating mantle still above the furnace table. First, air is blown into the heating mantle, and then the heating mantle is removed. Then the cooling cover is hoisted, and the air from the surrounding environment is sucked by the fan on the cooling cover to cool the inner cover. When the circulating atmosphere inside the inner cover reaches the set temperature, the cooling cover fan should stop running. After a period of time, spray cooling starts. When the temperature of the steel coil core reaches the set value, the cooling ends, and the cooling cover is removed. Then, a nitrogen purge is performed to replace the hydrogen in the inner cover, remove the inner cover, and then lift off the steel coil. This process is completed.
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