The damage of refractory materials used in RH refining furnaces: The furnace body of an RH furnace is generally divided from top to bottom into a hot bend pipe, upper tank (including alloy chute), middle tank (some RH furnaces do not have this), lower tank circulation pipes (rising and descending circulation pipes), and immersion pipes (rising and descending immersion pipes). The upper tank and the refractory lining of the top do not directly contact the molten steel and slag, so their service life is relatively long.

The middle tank comes into contact with part of the molten steel and slag during operation. In addition, when auxiliary materials are added into the RH furnace from the hopper, it will be subjected to huge mechanical stress and scouring, which will directly affect the high-temperature spalling and even damage of the lining material.

For the lower tank and lifting pipes (immersion pipes), their lining materials will undergo thermal spalling due to mechanical stress and scouring caused by molten steel and high-temperature gas flow. At this time, the outer wall is not only affected by rapid cooling and heating due to temperature changes but also corroded by slag. It can be seen that the lower tank and lifting pipes (immersion pipes) are the high-damage areas of the entire RH furnace, which determine the service life of the RH furnace.

Among the refractory materials used in the lower tank and lifting pipes (immersion pipes), due to the corrosion and infiltration of slag, an altered layer is formed inside the bricks. Then, cracks parallel to the working surface direction occur between the altered layer and the unaltered layer. The spalling caused by this can lead to early damage of the RH furnace. At the same time, the infiltration and corrosion of slag destroy the bonding between the particles of the lining, resulting in loose structure of the refractory material and easy loss of particles, thus causing damage. High-performance refractory materials with good resistance to slag corrosion and penetration, dense structure, and good thermal shock resistance should be selected for these key parts.

The normal working temperature of the RH refining furnace is generally between 1560~1650℃ (up to 1700℃), and the maximum vacuum degree can reach 10Pa. The vacuum pumping time for each heat should be less than 40 minutes. At present, the molten steel circulation flow rate of Baosteel's 300t RH refining furnace has been increased to 230-240t/min, which means higher application requirements for refractory materials.