No abstract

Effect of spinel kinds on the properties of alumina—spinel castables was investigated. The results showed that the addition of various kinds of spinels has an effect on the physical and mechanical properties of these refractory castables. The reason is that the Al2O3‐rich spinel precipitated Al2O3 and MgO‐rich spinel solid solution and formed secondary spinel. In addition, stable spinel in castables during heat treatment process was found to be more effective for enhancing cold and hot strength.

Samples of interstitial free (IF) steel were heated in alumina-graphite crucibles with flux cover at 1600uC for 120 min in a medium frequency induction furnace. The carbon contents of IF steel samples taken from the molten steel at times 0, 5, 10, 20, 30, 45, 60, 90 and 120 min were examined and the refractories after heating were investigated by electron probe microanalysis (EPMA) with energy dispersive spectroscopy (EDS). The steel carbon content increased rapidly in the first 10 min, and then decreased because of the formation of a decarburising layer on the refractory. This layer separated the molten steel from the bulk refractory and stopped pickup of carbon. At the same time, decarburisation via oxygen through the flux and liquid layer started to reduce the carbon content in the molten steel.

No abstract

No abstract

In this paper corundum-mullite composites were prepared used tabular corundum as coarse clinker, ultra-fine tabular alumina, fused mullite powder, SiO 2 micro powder and white clay as host material, dextrin as binder. Under the condition of the same content of SiO 2 micro powder and white clay, the effect of SiO 2 micro powder addition on the sintering, mechanical strength, thermal shock resistance, phase composition and microstructure of the specimens treated at 1600 ºC for 3 h in an air atmosphere were studied by XRD and SEM analyses. The results indicate that the bulk density, mechanical strength decrease and there are apparent amount of porosities, thermal shock resistance increases with increasing the content of SiO 2 micro powder. This is because that the in-situ mullite content of sample after sintering increases with increasing the content of SiO 2 micro powder. At the same time. It is found that there are some needle-like secondary mullite in the sample after thermal shock recycling five times.

No abstract

The effect of polymorphism of Al2O3 on sintering and grain growth of magnesia aluminate spinel was studied. γ - Al2O3 and α - Al2O3 were mixed with MgO according to the stoichiometric MA ratio, respectively, and pressed into billets with a 20mm diameter and 15mm height, and then were sintered at temperature from 1250ºC to 1400ºC in air atmosphere. Bulk density, apparent porosity and grain size were measured. The results indicated that the grain size of MA with γ-Al2O3 is larger than the grain size of MA with α - Al2O3. This is because the activation energy of grain growth of magnesia aluminate spinel prepared by γ-Al2O3 is lower than that by α -Al2O3, the former is 159KJ/mol and the latter is 217KJ/mol