Alum Shiji ��-sialon Composite Low-carbon Aluminum Carbon Slide Material,

The low carbon Al₂O₃—β-Sialon fired slide plate material and the unfired Al/Si containing Al₂O₃—β-Sialon slide plate material belonged to bauxite-basedβ-Sialon bonded low carbon slide plate materials are researched and developed in order to solve present main problems of commercial available Al₂O₃-C slide materials and satisfy clean steel ladles. The relationship among compositions, microstructures and properties of both of slide plate materials is studied in detail. Furthermore, industrial trials have been operated on-site of con-casting.In this paper, the relationship between thermo-mechanical properties and microstructures of the low carbon Al₂O₃-β-Sialon slide plate materials is investigated. The bauxite basedβ-Sialon content in the slide plate material is 10%, and the carbon content is only 3～6%, far below carbon content (7～12%) in conventional Al₂O₃-C slide plate material. Investigations show that the thermo-mechanical properties of low carbon Al₂O₃-β-Sialon slide plate materials are excellent. Furthermore, the hot strength data under middle and high temperatures are higher. For example, HMOR at 1400℃is 30MPa or so, 15% higher than conventional Al₂O₃-C slide plate material. Though with the low content of carbon, the residual strength remains 49% warer-cooled once whenΔT=1200℃, which is a little higher than commercial available Al₂O₃-C slide material (47.3%).Why the low carbon Al₂O₃-β-Sialon slide plate material possesses excellent thermodynamic properties and hot mechanical behavior? The hypostasis is that local oxidation occurs on the surface of bauxite-basedβ-Sialon when sintering at high temperatures buried in carbon. SiO₂ separates out and react with corundum, so mullite crystals form and linkβ-Sialon and corundum closely, which strengths the structure of matrix. Thermodynamics analysis shows that the oxidation reaction ofβ-Sialon buried in carbon can be controlled, namely,β-Sialon reacts with CO gas and form mullite and SiO₂ under 1409℃, whileβ-Sialon appears stable above 1409℃. Therefore, by adopting reasonable sintering curve, the oxidation degree ofβ-Sialon can be controlled, even more microstructures of slide plate materials. The new theory provides basis for optimized design of microstructure of the low carbon Al₂O₃-β-Sialon slide plate materials.In this paper, the relationship between thermo-mechanical properties and microstructures of unfired Al/Si containing Al₂O₃-β-Sialon slide plate materials is investigated. It is made by adopting 8% bauxite basedβ-Sialon, and the carbon content in the slide plate is as low as 3～5%. Comparing with Al/Si metal containing unfired Al₂O₃-C slide plate material, the hot strength vs temperature curve presents similar trend, it rises rapidly starting from 600℃and the HMOR is more than 40MPa at 1200℃, 2.5 times as MOR at room temperature. Later the strength still increases slowly to 45MPa at 1400℃. The residual strength maintains 72.3% cooled once by wind whenΔT=1200℃, which means improved thermal shock resistance. Excellent thermo-mechanical properties of unfired Al/Si containing Al₂O₃-β-Sialon slide plate materials are attributed to in-situ synthesized reaction, such as carbonizing or nitriding etc. Under reduction atmosphere when the materials are buried in Al or Si powder, non-oxide resultants form to strengthen the micro-connection among crystalline grains, and the binding system gives priority to non-oxide phase other than the previous carbon.The oxidation behavior and mechanism of the two low carbon slide plate materials have been studied and discussed. For both burned and unburned low carbon slide plate refractory materials, in comparison with the Al₂O₃-C slide plate materials without bauxite basedβ-Sialon, the oxidation resistance of the bauxite-basedβ-Sialon combined low carbon slide plate materials is improved remarkably. The main reason is that a lot of mullite crystals form after oxidation. The mullite crystals fill in the interstices of corundum skeleton structure, resulting in a denser structure to prevent oxygen from permeation to the inner part.Both of low carbon slide plate materials have separately been used in the con-casting processes of steel works. In 90t and 160t ladles, the service life of the low carbon Al₂O₃-β-Sialon fired slide plate material is similar as commercial Al₂O₃-C slide plate material or Al₂O₃-ZrO₂-C slide plate material, but galling and cracks on the plates are less. For the unfired Al/Si containing Al₂O₃—β-Sialon slide plate material, the service life is 4 heats and there is no galling on the plates at all. Only a few fine cracks appear on the surface. The two kinds of low carbon slide plate materials can meet the needs of con-casting processes of clean steel due to lower carbon content.