Investigation And Development Of Magnesia-zircon-chome Non-carbon Refractory Castables For Ladle Slag Line

Magnesia-zircon-chome castable is a new product of basic non-shape refractories, and an important application of MgO-ZrO₂-SiO₂-Cr₂O₃ system in the pure steel refinery.Magnesia-zircon clinkers were synthesized using light-burned magnesia and zircon as starting materials by wet grinding processes in this work. Influences of raw mix proportioning, sintering temperature, particle size of raw material on bulk density, apparent porosity, phase composition and microstructure of prereacted grain are deeply researched. The results show that magnesia-zircon compact clinkers can be synthesized and the densification of clinkers is effected deeply by the particle size of zircon. The smaller of zircon and light-burned magnesia particle, the more compact of clinkers. The suitable conditions are that when sintering at 1600℃, 85% of 20μm light-burned magnesia and 15% of 5μm zircon should be used, and when sintering at 1670¹700℃,90% of 20μm light-burned magnesia and 10% of 10μm zircon should be used.Magnesia-zircon-chome castables were prepared using prereacted grain as main materials on the base of the above researches. The slag resistance of magnesia-zircon-chome castables and magnesia-zircon castables was compared by static crucible test method. The influences of addition changing of zircon and chome oxide on the slag resistance were analyzed by SEM,EDS,XRD and so on. The experiment results show that the resistance of magnesia-zircon-chome castable to corrosion and penetration of slag are much higher than that of magnesia-zircon castable. The mechanism of improving the resistance to corrosion and penetration is that the castable's high temperature strength and slag resistance are improved because of the formation of MgCr2O4 spinels and higher melting point phase CaZrO3 in some range of matrix when the castable is used at 1700℃,by using industrial chome oxide micro-powders (d501.5μm) and zircon micro-powders in matrix of magnesia-zircon-chome castables.It is shown by the researches that the developmental castable's resistance to corrosion of slag decreases and to penetration of slag increases with the increment of zircon addition, and the maximum addition of zircon in matrix is 20%. Both the resistance to corrosion of slag and to penetration of slag are all improved with the increase of Cr₂O₃, and the castables have the property of best resistance to corrosion and to penetration of siag with the addition of 2-3% Cr₂O₃. The castables made using magnesia-zircon clinker with 10% zircon as aggregate and using fused magnesia, zircon, synthesized clinker, industrial chome as matrix have the property of high resistance to corrosion and to penetration of slag. The prepared castables are good materials for using in ladle slag line.