The causes of damage to the circulating tube of the RH vacuum furnace are complex and diverse, mainly including material factors, operating factors and environmental factors. The following is a specific analysis of these causes and corresponding solutions:
1. Analysis of the causes of damage
Material reasons
Refractory characteristics: The refractory materials used in the circulation tube, such as magnesia-chrome bricks, have a large apparent porosity, and the slag can easily penetrate into the matrix, forming a high-melting-point composite spinel phase to make the slag sticky, but it cannot form a whole to prevent the slag from continuing to penetrate.
The influence of thermal stress: The temperature fluctuates greatly when the RH furnace is working, and there is a difference in the expansion coefficient between the penetration layer and the original brick layer, which leads to thermal stress, and then forms cracks parallel to the heating surface, accelerating the spalling of the material.
Quality difference: The quality of refractory materials directly affects their corrosion resistance and service life. Refractory materials with unstable quality are more susceptible to erosion by molten steel and slag.
Operational factors
Intermittent production: The RH furnace adopts an intermittent production method, and the interval time between furnaces is long, which leads to large temperature fluctuations in the furnace, exacerbating the thermal and structural spalling of the refractory materials.
Mechanical failure: If the top gun fails, the baking cannot be done effectively, causing the temperature in the furnace to fluctuate further, accelerating the damage of the refractory.
Improper operation: If there are defects in the assembly process of the immersion tube, the brick support plate is missing, or the pouring process of the castable is improper, the immersion tube brick will sink or the circulating tube brick will float, affecting the stability of the refractory.
Environmental factors
Erosion of molten steel and slag: The carbon in the molten steel and the reducing atmosphere formed by the discharged gas phase reaction products, as well as the components such as Fe2O3, SiO2 and CaO in the slag, will cause erosion of the refractory.
Temperature fluctuation: The temperature of the RH furnace is as high as about 1600℃ when it is working, and the temperature drops sharply when it is on standby. This drastic temperature change causes thermal stress inside the refractory, thereby accelerating damage.
2. Solution
Optimize material selection
Select high-quality refractory materials, such as MgO-Cr2O3 refractory bricks with high Cr2O3 content, to improve the erosion resistance and service life of the refractory materials.
Regularly test the performance of refractory materials to ensure that the material quality meets the requirements.
Improve the operation process
Rationally allocate production, improve the use efficiency of RH furnace, shorten the interval time, and reduce the impact of temperature fluctuations on refractory materials.
Take measures to bake the lower top gun during the interval to keep the temperature in the furnace stable.
Strengthen equipment maintenance to ensure the normal operation of key equipment such as the top gun to avoid production interruption caused by mechanical failure.
Strengthen construction management
Strictly control the masonry and pouring process of refractory materials to ensure that the construction quality meets the standards.
Leave a reasonable expansion gap between the circulation pipe and the immersion pipe to slow down the local spalling caused by the expansion and extrusion of magnesia-chrome bricks.
Regularly spray and repair the circulation pipe and immersion pipe to slow down the development speed of the groove.
Strengthen monitoring and maintenance
Establish a refractory material usage monitoring system to monitor the damage of refractory materials in real time.
Regularly conduct an overall inspection and evaluation of the RH furnace to promptly discover and deal with potential problems.
Through the implementation of the above measures, the damage rate of the circulation pipe of the RH vacuum furnace can be effectively reduced, its service life can be extended, and production efficiency and economic benefits can be improved.
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