What issues should be paid attention to when baking and sintering the lining of medium frequency induction annealing furnace?

The grilling and sintering of the furnace lining vary according to different conditions such as the refractory materials used in the furnace and the furnace capacity of the medium frequency induction annealing furnace. The following is an example of the magnesia-aluminum spinel material used in our company's medium frequency induction annealing furnace.

After the furnace lining is knotted, it can be oven-baked and sintered. The purpose is to fully eliminate the moisture in the furnace lining and finally sinter it at high temperature to form a dense ceramic surface with high-temperature strength. When oven and sintering, the following matters must be paid attention to:

(1) The cooling water system, tilting system, control loop and instrumentation of the medium frequency induction annealing furnace must be carefully inspected before drying.

(2) A certain amount of charge should be added to the oven, about 70% of the height of the furnace, to maintain the uniformity of temperature rise and fall.

(3) The oven should use low power and slowly heat up. The cooling water should be turned on while powering on. The initial heating rate of the oven is 100°C/h, and it will rise evenly until 800~900°C. Depending on the size of the oven, Heating rates vary.

(4) When the temperature of the furnace lining reaches above 1000°C, switch to 50% power supply to slowly heat up the crucible mold and the charge and melt them slowly to reduce the erosion effect.

(5) Try to use clean and rust-free returned materials as the furnace material to reduce slag. Large pieces of material should be installed around the crucible wall, and small pieces should be added at the center of the furnace bottom.

(6) Keep the molten steel temperature about 50°C higher than the working temperature for 1 to 2 hours so that the furnace lining is evenly sintered. The entire melting time of the first furnace is 2 to 3 times the normal melting time.

(7) The molten steel in the first furnace is fully melted, so that the furnace mouth is also sintered satisfactorily. The entire crucible has a uniform and dense sintering layer from top to bottom.

(8) After melting the first furnace of the intermediate frequency induction annealing furnace, the sintering layer of the crucible is still very thin. It should be continuously melted for 2 to 3 furnaces before the sintering process can be completed. If the sintering temperature is too low and the holding time is not enough, the furnace lining will crack as it cools.

(9) The oven must be baked in accordance with the oven system. It is best to use a voltage regulator to deliver power in stages. If there is no voltage regulator, intermittent power delivery can also be used.

The requirements for oven and sintering are low-temperature slow-burning and high-temperature full-furnace sintering. The first furnace charge should be clean, rust-free, contain few impurities, and preferably have low carbon content.

For a sintered furnace lining, the sintered layer is required to account for 30% of the total thickness of the lining. The minimum thickness of the sintered layer should be 10~15mm. The sintered layer is too thin and cannot withstand the mechanical impact during feeding and the erosion of molten steel; if the sintered layer is too thick, It may break through. However, it should be noted that an excessively thick sintered layer will only appear after long-term operation. The transition layer accounts for about 30%-40%, and the loose layer that acts as a buffer accounts for 20%-30%.