Abstract: 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 pressureless 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 investigated.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 addition 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 comprehensive performance with the bending strength of 140.1 MPa,corrosion depth of 76 μm after corrosion in molten ultra-low carbon steel at 1 600 ℃ for 2 h and the utilization rate of the spent bricks of 55.56 mass%.

Key words: ultra-low carbon steel smelting, MgAlON composites, spent slide bricks, bending strength, molten steel corrosion resistance

摘要： 为了促进超低碳钢冶炼的无铬化进程和用后耐火材料的高附加值利用,以用后滑板砖、用后镁碳砖和Al₂O₃微粉为原料,通过碳热还原氮化法于1 600 ℃常压烧结3 h原位合成MgAlON复相材料。研究用后滑板砖添加量(质量分数分别为0、22.22%、44.44%、66.66%)对试样的物相组成、形貌和性能的影响,并考察了部分试样的抗钢液侵蚀性。结果表明:试样的主晶相皆为MgAlON;随用后滑板砖添加量的增大,试样中的Al₂O₃相消失,β-SiAlON和ZrN相逐渐增多,材料内部气孔先减少后增多,体积密度和抗弯强度先增加后降低;随用后滑板砖添加量的增大,试样的断裂方式从穿晶断裂转变为穿晶断裂伴随少量沿晶断裂,最后变为解理断裂;当用后滑板砖添加量为44.44%(w)时,试样的抗弯强度为140.1 MPa,在1 600 ℃超低碳钢液中侵蚀 2 h 后,侵蚀熔损深度为76 μm,废砖利用率达55.56%(w),综合性能最佳。

关键词: 超低碳钢冶炼, MgAlON复相材料, 用后滑板砖, 抗弯强度, 抗钢液侵蚀性