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Ways to improve the performance of aluminum-carbon refractories

wallpapers Industry 2020-12-30
Carbon-bonded alumina-graphite composite refractories (abbreviated as aluminum-carbon refractories) have excellent thermal shock resistance and corrosion resistance.
Performance characteristics and performance improvement of aluminum-carbon refractories
Therefore, it is widely used in continuous casting processes with harsh operating conditions. For example, the shroud, immersion nozzle and stopper are all aluminum-carbon refractory materials, but the fatal disadvantage of aluminum-carbon refractories is that they are easily oxidized in high-temperature oxidizing atmospheres, resulting in The refractory has failed.
Solutions to the above shortcomings
(1) At present, the commonly used method is to add antioxidants to the materials or to coat the products with anti-oxidation coatings to prevent the oxidation of refractory materials during high-temperature use.
(2) Composite ceramic bonding is based on carbon bonding so that after the combined carbon is oxidized, the presence of the ceramic bonding phase will not cause the material to fail immediately.
When casting high-speed cutting steel with high oxygen content, the aluminum-carbon refractory compounded with AlN is used on the head of the stopper rod or the bowl of the immersion nozzle, which can significantly improve the resistance of the refractory to molten steel.
Metal introduction produces ceramic bonding phase to improve performance
Due to the presence of a high melting point carbon phase and lower heat treatment temperature in alumina-graphite refractories, it is difficult for the material to introduce the second ceramic bonding phase by sintering. The better way is to introduce metal in situ. The reaction temperature is low, and it is easy for the material to produce a second binding phase.
At present, the more practical ones are metal silicon, metal aluminum, metal magnesium and their alloys. After the introduction of metal silicon into the alumina-graphite composite refractory, SiC, Si3N4, SiO2, etc. will be generated during the heat treatment process, although they can improve the strength of the refractory, Antioxidant and other advantages.
However, silicon-containing substances will reduce the corrosion resistance of refractory materials, especially when casting steels with higher Mn content. Magnesium metal is a very active metal. It has a very high ability to deprive oxygen and has strong volatility. It is easy to form MgO-containing compounds during heat treatment. For example, spinel is formed in aluminum-carbon refractories. The performance impact is small.
The introduction of metallic aluminum into alumina graphite refractory materials will produce AlN, Al4C3 and other ceramic bonding phases after heat treatment, both of which are high melting point compounds, especially the oxidation products of metallic aluminum AlN and Al4C3-alumina will not affect the refractory. The erosion resistance of the material affects it.

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