Plate-shaped sintered corundum is a high-end refractory material that has been rapidly promoted in the domestic refractory industry in the past 30 years, especially in the field of high-performance refractory products such as carbon-free refractory materials for molten steel refining ladles, functional refractory materials, and high-throughput iron trough castables. It partially replaces the traditional white corundum, sub-white corundum and brown corundum. In recent years, as domestic enterprises have optimized the production process of tabular sintered alumina, greatly increased production capacity and continuously reduced production costs, the technical and economic advantages of tabular sintered corundum have been further improved, and sub-white corundum and brown corundum no longer exist in terms of price. In the refractory raw material market, the reserved share of brown fused alumina in some special scenarios will be further replaced.
Production Process
The common production process of tabular sintered corundum is industrial alumina powder-grinding-adding water to form balls-drying-high-temperature firing in shaft kiln-crushing and crushing-packaging. The firing equipment is a high-temperature shaft kiln, using clean energy natural gas as fuel, and firing at 1900~1950°C in the shaft kiln to transform the transition phase such as γ-Al2O3 of industrial alumina powder into the most stable α-Al2O3 phase. Using the firing process of rapid firing and rapid cooling, the grain size of plate-shaped sintered corundum is generally within 30-150 μm. Due to rapid cooling, there are a large number of micropores in the plate-shaped sintered corundum, and most of the pores are nano-scale. , due to the existence of these closed micropores, the plate-shaped sintered corundum has excellent thermal shock resistance.
Brown corundum is produced by electric melting method. Three raw materials of high alumina bauxite clinker, carbon material and iron filings are used and mixed into the electric arc furnace. piece. The mineral composition is dominated by α-Al2O3 phase. The central part of the crystal shape is diamond-shaped, thick-plate-shaped and grains with cracks. There are many titanium oxide, silicon oxide, and calcium oxide melt crystals in the periphery, which are long-plate-shaped and most Coarse grains are skeletal lamellae. Since the impurities have not been completely removed, brown corundum also contains secondary crystal phases such as calcium hexaaluminate, calcium plagioclase, spinel, and rutile, as well as glass phases, iron alloys, and solid solutions. The hue of brown corundum depends largely on the titanium oxide remaining in the product.