To promote the chromium-free smelting of ultra-low carbon steel and high value-added utilization of spent refractories,MgAlON composites were in-situ synthesized by the carbothermal reduction nitriding method with spent slide bricks,spent MgO-C bricks and Al2O3 micropowder as raw materials through pre-ssureless sintering at 1 600 ℃ for 3 h.The effects of the spent slide brick additions(0,22.22％,44.44％and 66.66％,by mass)on the phase composition,morphology and properties of the specimens were in-vestigated.The molten steel corrosion resistance of some specimens was investigated as well.The results show that:the principal crystalline phase of all the specimens is MgAlON.With the spent slide brick addi-tion increasing,Al2O3 in the specimens disappears,the amount of β-SiAlON and ZrN gradually increases,the internal porosity of the material decreases first and then increases,and the bulk density and bending strength increase first and then decrease;meanwhile,the fracture mode of the specimens changes from transgranular fracture to transgranular fracture with a small amount of intergranular fracture,and finally to cleavage fracture.When the spent slide brick addition is 44.44％,the specimen has the best comprehen-sive performance with the bending strength of 140.1 MPa,corrosion depth of 76 μm after corrosion in mol-ten ultra-low carbon steel at 1 600 ℃ for 2 h and the utilization rate of the spent bricks of 55.56 mass％.
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