Reaction of Al<sub>2</sub>O<sub>3</sub>-SiO<sub>2</sub> Ceramics with Calcium Carbide

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  • Ａｌ２Ｏ３‐ＳｉＯ２系焼結体とカルシウムカーバイドとの反応
  • Al2O3 SiO2ケイ ショウケツタイ ト カルシウム カーバイド ト ノ

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Abstract

Severe wear of lining refractories in torpedo car occurs when injection of desulphurizing agent containing calcium carbide is done to desulphurize molten pig iron. To make clear the corrosion mechanism of the refractories, reactions between calcium carbide and Al2O3-SiO2 ceramics were studied. Three kinds of mullite and corundum disks were embeded in calcium carbide powder, and heated at 1200°-1400°C in a reducing atmosphere. Mullite ceramics formed a reacted zone, leaving metallic silicon particles in it. The thickness of the reacted zone is proportional to the square root of time. Thin boundary zone, which is mainly consisted of alumina, is formed between the reacted and the original ceramic zones. On the other hand, corundum ceramics did not form any reaction zone.<br>From these results, SiO2 component in the mullite ceramics is considered to be reduced by CaC2, forming metallic silicon, calcium oxide, and carbon monoxide or carbon. The reaction would proceed by the following steps:<br>(1) Transportation of CaC2 through the reacted zone and the boundary zone.<br>(2) Decomposition of mullite: 3Al2O3⋅2SiO2→3Al2O3+2SiO2<br>(3) Reduction of SiO2 by CaC2: 3SiO2+CaC2→3SiO(g)+CaO+2CO<br>(4) Transportation of SiO gas through the boundary zone<br>(5) Reduction of SiO by CaC2: 3SiO+CaC2→3Si+CaO+2CO<br>The rate of the reaction is considered to be controlled by transportation of CaC2 through reacted zone and boundary zone.

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