添加MgO、Mg(OH)2、MgCO3微粉对镁钙材料性能的影响

Effect of MgO,Mg(OH)2,and MgCO 3 micro-powder additions on properties of MgO-CaO refractories

为了提高镁钙材料的抗水化性和常温强度,以合成镁钙砂颗粒(5~3、3~1、≤1 mm),合成镁钙砂细粉(≤0.074 mm)和MgO、Mg(OH)2、Mg CO33种高纯镁质微粉(d50分别为1.825、1.665和3.981μm)为原料,配制了由合成镁钙砂细粉和其中一种镁质微粉组成的w(镁质微粉)分别为0、4%、7%、10%和13%的粉料试样,以及由合成镁钙砂颗粒料、合成镁钙砂细粉和其中一种镁质微粉组成的w(镁质微粉)分别为0、1.2%、2.1%、3.0%和3.9%的全料试样。经混练,200 MPa压力成型,1600℃保温3 h煅烧后,检测粉料试样的体积密度、显气孔率、水化质量增大率,检测全料试样的常温耐压强度和常温抗折强度,并分析了粉料试样的物相(XRD)和显微结构(SEM)。结果表明:添加Mg O微粉或适量Mg(OH)2微粉可以促进镁钙材料的烧结致密化,从而改善材料的抗水化性能和常温强度。而添加MgCO3微粉导致烧后试样致密度降低,导致其抗水化性和常温强度劣化。

This study aims at improving the hydration resistance and cold strength of MgO-CaO refractories.Synthetic MgO-CaO clinker particles(5-3,3-1,and≤1 mm),synthetic MgO-CaO clinker fine powder(≤0.074 mm)and three kinds of high purity micropowders(MgO of d 50=1.825μm,Mg(OH)2 of d 50=1.665μm,and MgCO 3 of d 50=3.981μm,respectively)were used as the starting materials to prepare powder specimens and full-formulation specimens.The powder specimens were prepared with synthetic MgO-CaO clinker powder and one kind of the micropowders(0,4%,7%,10%,and 13%,by mass,respectively);and the full-formulation specimens were prepared using the synthetic MgO-CaO clinker particles,synthetic MgO-CaO clinker powder and one kind of the micropowders(0,1.2%,2.1%,3.0%,and 3.9%,by mass,respectively).After mixing and pressing at 200 MPa,the specimens were fired at 1600℃for 3 h.The bulk density,the apparent porosity,and the mass increase rate after hydration of the powder specimens as well as the cold crushing strength and the cold modulus of the rupture of the full-formulation specimens were tested.The phase composition and the microstructure of the powder specimens were also analyzed by XRD and SEM.The results show that adding MgO micropowder or an appropriate amount of Mg(OH)2 micropowder can promote the sintering densification of MgO-CaO refractories thus improving their hydration resistance and cold strength;however,adding MgCO 3 micropowder reduces the density of the fired specimens resulting in the deterioration of their hydration resistance and cold strength.