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Bell annealing furnaces generally use hydrogen or hydrogen-nitrogen mixed gas as the protective gas. Hydrogen often has better thermal conductivity than hydrogen-nitrogen, and high-standard hydrogen has a stronger decarburization ability than hydrogen-nitrogen. Also, the surface of the strip steel treated by the bell type annealing furnace using hydrogen as the protective gas has less carbon slag content and more uniform mechanical properties. Therefore, the use of full hydrogen as a protective gas has been commonly used in some metallurgical industries. So what is the bell annealing furnace process? How does a hydrogen annealing furnace complete the annealing treatment of the workpiece?

Bell Annealing Furnace Process

The main process equipment of the bell type full-hydrogen 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 furnace table, inner cover system and hydrogen inlet valve should be tested for cold sealing. After the test is successful, a nitrogen purge is required, and the heating mantle is hoisted, and then the heating mantle is ignited. When the nitrogen purge meets the conditions, it is necessary to replace the nitrogen in the inner cover with hydrogen purge. When the heating starts, the heating curve should be selected according to different materials for temperature control until the temperature of the steel coil core meets the requirements of the process.

Annealing Treatment of the Workpiece by the Bell Annealing Furnace

In the working process of the bell type all-hydrogen annealing furnace, the cooling should start from the heating mantle still above the furnace table. Firstly, the 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 while, the 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 hoist the steel coil, so that a bell annealing furnace process is completed.

The metal hydraulic bell-type annealing furnace is one of the heat treatment equipment in the machinery industry. That is, the wires or metal parts are placed in different heating furnaces, slowly heated to a certain temperature, and maintained for a period of time. Then cool down them at an appropriate rate, usually is natural cooling, sometimes is controlled cooling. According to different energy sources, wire annealing furnace can be divided into electric annealing furnace, the second is gas energy annealing furnace and the third is petroleum energy LPG annealing furnace. Users can choose according to their own situations.