Development and Application of Refractory Materials for Molten Aluminum Applications

Abstract

Two new refractory materials have been developed for use in molten aluminum contact applications that exhibit improved corrosion and wear resistance leading to improved thermal management through reduced heat losses caused by refractory thinning and wastage. The development of these materials was based on an understanding of the corrosion and wear mechanisms associated with currently used aluminum contact refractories through physical, chemical, and mechanical characterization and analysis performed by Oak Ridge National Laboratory (ORNL) and the University of Missouri, Rolla Rolla (UMR), along with their industrial partners, under the ITP Materials project ''Multifunctional Metallic and Refractory Materials for Energy Efficient Handling of Molten Metals.'' Spent castable refractories obtained from a natural gas-fired reverberatory aluminum alloy melting furnace were analyzed, leading to identification of several refractory degradation mechanisms and strategies to produce improved materials. The newly developed materials have been validated through an R&D industrial trial.

Effects of Different Barium Compounds on the Corrosion Resistance of Andalusite-Based Low-Cement Castables in Contact with Molten Al-Alloy

“…Therefore, these two factors have contributed to the reduction of the corrosion resistance of sample A (which has no additives). [44] Table IV shows that the amount of porosity in this sample after heat treatment at 1373 K (1100°C) is low compared with the other samples. Also, this table shows that the addition of barium-containing compounds to andalusite LCC refractory does not increase the water required or the porosity after heat treatment (except for samples containing BaO).…”

Effects of Different Calcium Compounds on the Corrosion Resistance of Andalusite-Based Low-Cement Castables in Contact with Molten Al-Alloy

“…Andalusite contains low quantities of fluxes (Na 2 O, K 2 O, CaO, and MgO) and remains unaltered with no change in density and shape after firing up to 1473 K (1200°C). [41] Andalusite has been reported to be resistant to contact with molten aluminum [42] because of the high purity and density of andalusite aggregates. Figures 4 and 5 show that anorthite is not formed from wollastonite after heat treatment at 1373 K (1100°C).…”

Improving Corrosion Resistance of Aluminosilicate Refractories towards Molten Al-Mg Alloy Using Non-Wetting Additives: A Short Review

“…It has been observed that the penetration of the molten Al alloys is highest at the bellyband. For instance, at the onset of corrosion in aluminosilicate refractories, the SiO 2 is reduced by molten Al to Si, which is accompanied by a negative volume change [ 59 ], by as much as 26% volume reduction [ 60 ]. Therefore, this volume contraction may generate cracks that allow further metal penetration into the refractory [ 39 ], and the amount of Al alloy diffusing into the unreacted refractory controls the rate of corrosion [ 49 ].…”

“…The corrosion of aluminosilicate refractories initiates the decomposition of 3Al 2 O 3 ·2SiO 2 to Al 2 O 3 and SiO 2 . Then, the SiO 2 is reduced by Al metal to form the primary corundum (α-Al 2 O 3 ) and releases the free Si to molten Al [ 60 ]. When the molten Al-Mg alloy comes into contact with the refractory, MgO, MgAl 2 O 4 (spinel), and MgSiO 3 are formed.…”