铬矿对镁质浇注料性能的影响

Influence of chrome ore on properties of magnesia based castables

在以8～5mm(18%,质量分数,下同)、5～3mm(18%)、3～1mm(22%)的97高纯镁砂和≤1mm(12%)的97电熔镁砂为骨料,≤0.088mm(20%)的97电熔镁砂,SiO2微粉(2%),α-Al2O3微粉(5%),亚白刚玉粉(3%)为基质细粉,六偏磷酸钠等为复合分散剂的镁质浇注料基础配方中,分别用5%、8%、15%的铬矿砂(0.833～0.178mm和≤0.088mm的混合料)等量替代≤0.088mm的电熔镁砂制成不同铬矿含量的镁质浇注料试样。分别测试样经110℃24h、1100℃3h和1550℃3h处理后的线变化率、显气孔率和抗折强度,并利用SEM和EDX分析1550℃3h处理后试样的显微结构。结果表明:(1)镁质浇注料中加入适量的铬矿,有利于提高方镁石晶粒间的直接结合强度,使材料抗折强度提高,显气孔率下降;适量微裂纹的产生有利于浇注料抗热震性的提高。铬矿的适宜加入量为5%～8%。(2)SEM和EDX分析表明,试样经1550℃3h处理后,铬矿和镁砂呈相互扩散,并脱溶出二次尖晶石,增强了晶粒间的直接结合程度,从而有效地提高了镁质浇注料的力学性能。

Magnesia based castables with different chrome ore additions was prepared using 97 high purity magnesite （8-5 mm：18%,5 -3 mm：18% and 3 -1 mm：22%） and 97 fused magnesite （≤1 mm：12%） as aggregate, 97 fused magnesite （ ≤0.088 mm ：20%） ,2% silica fume,5% ultrafine α-Al2O3 ,and 3% sub-white corundum powder as matrix powder,sodium hexametaphosphate and other materials as comp6site dispersant, using 5% ,8% and 15% chrome ore （the mixture of O. 833 -0.178 mm and ≤0.088 mm） to replace the same quan- tity of ≤0.088 mm fused magnesite. The linear change rate,apparent porosity and modulus of rupture of specimens after being treated at 110℃ for 24 h,1 100 ℃ for 3 h and 1 550 ℃ for 3 h were measured,and the microstructure of specimens fired at 1550 ℃ for 3 h was analyzed by SEM and EDX. The results show that： （1）Adding the appropriate chrome ore （5% -8%） in magnesia based castables is beneficial to improving the direct bonding strength of periclase grains,increasing the modulus of rupture and decreasing the appar- ent porosity,and is also beneficial to enhancing the thermal shock resistance by forming the appropriate mi- crocrack. （2）The results of SEM and EDX analysis show chrome ore and magnesite diffuse mutually and separate out secondary spinel in the specimen fired at 1 550 ℃ for 3 h,which strengthens the direct bonding strength of grains and enhances effectively the mechanical properties of magnesia based castables.