The Study Of Preparation,structure And Properties Of Lightweight Spinel-based Refractory

The lightweight refractory has low conductivity in addition to the good mechanical properties and slag resistance,which can achieve the aim of saving energy consumption in comparison with dense refractory.However,the difficulty of fabricating lightweight aggregates with high close porosity restricts the application of lightweight refractory.In this study,lightweight spinel refractory was fabricated by carbothermal reduction of MgO,the oxygen diffusion rate controlled oxidation of Mg vapor and subsequent reaction between deposited MgO and Al₂O₃.The lightweight spinel refractory was characterized by SEM and XRD.Effects of flaky graphite particle size,carbon black content,firing temperature,holding time and aggregate on the microstructure and properties of lightweight spinel refractory were investigated.The slag resistance of lightweight corundum-spinel refractory was also investigated in comparison with that of dense corundum-spinel refractory.The conclusions were draw in the following:?1?With the increase of firing temperature and holding time,the apparent porosity,bulk density,compressive strength and refractoriness under load of specimens decreased,increased,decreased,increased and increased,respectively.The flaky graphite particle size affected packing density of green compacts and properties of fired samples.When the flaky graphite particle size was 42.44?m fired at 1550?for 4 h,the apparent porosity,bulk density,compressive strength and refractoriness under load were 27.4%,2.68 g/cm³,63.5 MPa,1641?,respectively.?2?With decrease of carbon black content,the pores from the carbon black oxidation decreased,which resulted in decreasing of the apparent porosity,bulk density and increasing of compressive strength and refractoriness under load of specimens.When the carbon black content and firing temperature were 3.8wt%and 1550?,the apparent porosity,bulk density,compressive strength and refractoriness under load were 28.4%,2.72 g/cm³,41.2 MPa,1655.3?,respectively.?3?The big pores and microcracks were caused by the small carbon black particle with high reactivity and resulted in the low compressive strength of specimens.When the carbon content was same,the strength of refractory using carbon black was lower than that of the refractory using flaky graphite.?4?The aggregate affected the bonding interface and properties of lightweight periclase-spinel,spinel-spinel and corundum-spinel refractory.The microcracks were formed in periclase aggregate/spinel matrix interface due to the high residual thermal stress.The aggregate/spinel matrix bonding interface of lightweight spinel-spinel and corundum-spinel resulted from diffusion sintering and reaction sintering.?5?Compared with lightweight periclase-spinel and spinel-spinel refractories,the lightweight corundum-spinel exhibited superior mechanical properties for the reaction sintering.?6?The lightweight corundum-spinel refractory had a comparable property of slag resistance to dense corundum-spinel refractory.The lightweight corundum-spinel refractory with high apparent porosity could effectively prevent slag penetration and corrosion for the compact and small pore size of surface.