The Impact Of CA₂ Lightweight Raw Materials On Properties Of Corundum Castables

Due to the high strength,high volume stability and excellent slag erosion resistance corundum castable has been widely used in high temperature industries.Nowadays,iron and steel industry faced the challenge of overcapacity.And the major cause of heat loss was heat dissipation of industrial kilns.Reducing the thermal conductivity of furnace lining which can improve the poor thermal shock resistance of corundum castables is an important route to decrease the heat dissipation of the furnace.Recently,it was reported that pores were introduced into materials by adding lightweight aggregates.A new type of calcium dialuminate?CA₂?lightweight raw material with high purity and apparent porosity was used in this work.Aggregates,matrix and additives are important components of corundum castbles,therefore phase composition,microstructure bulk density,apparent porosity,strength and other properties were analyzed in this work to explore the effects of addition and particle size of calcium dialuminate light aggregate.Beyond that the dosage of reactive alumina and nano-TiO₂ were also investigated.?1?With the addition of calcium dialuminate lightweight raw materials,the strength of the samples decreased.But the pores which was introduced by the raw materials could alleviate the thermal stress and prevente the propagation of the crack at high temperatures,therefore the thermal shock resistance of samples were improved.When the particle size of calcium dialuminate lightweight raw materials was large,unreacted calcium dialuminate still left in the samples after calcining at high temperature.As the decrease of the particle size of CA₂ lightweight raw materials,the size of flake calcium hexaluminate?CA₆?in the samples became smaller.Sample with addition of 3-5mm CA₂ lightweight raw material had the lowest bulk density and the highest apparent porosity which means the most effective one for introducing porosity.Based on grey correlation analysis,properties of samples were relative to the addition of CA₂ lightweight raw material.?2?Apart from aggregates,matrix is also an important compponent of the castables,so the influence of the addition of reactive alumina on the properties of corundum castables content CA₂ lightweight raw materials were investigated.Results showed that flowability of slurries was improved with the increasing amount of reactive alumina.When the content of reactive alumina was 6wt%,the permanent line change?PLC?,bulk density and apparent porosity of the samples were improved,and it was considered as the optimum content.By using grey system theory,it was found that properties of the samples calcined at 1550?were correlative to the addition of reactive alumina.?3?Additives are usually added to the castables to regulate its properties.With the addition of nano-TiO₂,formation of CA₆ was promoted.With the increase of nano-TiO₂content,the grain growth trend was changed and the flake CA₆ was thicker.The addition of 0.5wt%nano-TiO₂ can improve the strength of samples calcined at a certain temperature,which also optimize PLC of samples.