Study On Preparation And Properties Of Alumina-Zirconia-Carbon Refractories Using Carbothermic Reducted Zirconia Products

Alumina-Zirconia-Carbon materials are widely used as the refractories in the continuous casting processes of the steel industry.To decrease the carbon contents of the steel-casting refractoris as being required to improve steel quality,electric-melting zirconia is widely used as substitute during preparation,which makes the production cost of the refractories excessively high.The carbothermic reduction phase behaviors of zircon effected by given additives were study in the dissertation and the resultant reduction zirconia products have been testifid as proper ingredients in the preperation of Alumina-Zirconia-Carbon refractories.The carbothermic reduction phase behaviors and micromorphology under different conditions were studied,which were mainly controled by different temperatures,and various kinds of additives with different amounts.The study showed that both CaCO₃,Y₂O₃ and MgO can promote the carbothermal reduction process of zircon and reduce the reaction temperature;the role of CaCO₃ is more superior.The stability of zirconia can also be enhanced progressively by MgO,CaCO₃and Y₂O₃;the zirconia would mainly exist in form of t-ZrO₂ when the content of Y₂O₃reached over 80%;CaCO₃ additives could make the zirconia exist as the mixed form of m-ZrO₂ and t-ZrO₂,which is partially stable;besides,the role of MgO in this part is comparatively weak.Preparaion of CaSZ and YSZ powder according to the optimum conditions.Add CaSZ and YSZ powder in the preparation of Al₂O₃-CaSZ-C and Al₂O₃-YSZ-C refractories respectively by using different mass ratios?0wt%?5wt%?10wt%?15wt%and 20wt%?.The study showed that as the adding amount of CaSZ powder inceasing,the flexural strength,thermal shock resistance and the anti-corrosion performance of slag would also been improved.The flexural strength of prepared sample was 10.90Mpa and the strength rentention ratio was 82.51%when adding the optimal dozage?10wt%?of CaSZ powder.As the adding amount of YSZ powder increasing,the flexural strength of Al₂O₃-YSZ-C refractories has no significant change trend,while the thermal shock resistance and anti-corrosion performance has been improved.The flexural strength of prepared sample was 8.7 Mpa and the strength rentention ratio was 81.70%when adding the optimal dozage?10wt%?of YSZ powder.Besides,the bending performance of Al₂O₃-CaSZ-C refractories was better than Al₂O₃-YSZ-C refractories,and the thermal shock resistance and anti-corrosion performance of both refractoris was fairly similar.The Al₂O₃-MgSZ-C refractories were prepared being added in various amounts?5wt%?10wt%?15wt%?20wt%,respectively?of the MgO-ZrSiO₄-C mixed powder with optimum mixed ratios.The study showed that,as the adding amount of MgO-ZrSiO4-C powder increasing,the flexural strength of Al₂O₃-MgSZ-C refractories has not changed a lot,while the thermal shock resistance and anti-corrosion performance has been improved.The flexural resistance and anti-corrosion performance of Al₂O₃-MgSZ-C refractories is better than both Al₂O₃-CaSZ-C and Al₂O₃-YSZ-C refractories,while the thermal shock resistance is comparatively poor.At the optimization dosage?20wt%?of MgO-ZrSiO₄-C powder,the flexural strength of the prepared sample was 38.96Mpa,strength retention rate was 14.97%.