Investigation on a postmortem resin-bonded Al-Si-Al2O3 sliding gate with functional gradient feature

A resin-bonded Al-Si-Al2O3 sliding gate was designed on the basis of sintered alumina containing both Al and Si fine powders, and the sliding gate achieved good application results in the practical process of steel pouring. Moreover, the postmortem sliding gate was characterized and analysed by X-ray diffraction, scanning electron microscope, and energy dispersive X-ray spectroscopy. The results show that the postmortem sliding gate presents a functional gradient feature with a reinforcement zone-transition zone-plastic zone phase distribution, in which the phases in the reinforcement zone from 0 mm to 5 mm are Al2O3, Al4O4C, SiC, and Al4C3; i.e., the Al, Si, and carbon in the composite totally converted into non-oxide phases. Further, phases in the transition zone from 5 mm to 10 mm are Al2O3, SiC, and Al4C3, whereas phases in the plastic zone from 10 mm to 15 mm are Al2O3, SiC, Al4C3, Al and Si. The formation mechanism of the grade distribution of phases in the postmortem sliding gate is described as follows. During operation, Al and Si reacted with C so that Al4C3 and SiC formed in situ; then, Al4C3 further reacted with Al2O3, whereby Al4O4C was formed as the reinforcement phase at the 0-5-mm zone with a high temperature. As the temperature decreased from the hot face to interior, a part of the free Al and Si remained in the form of plastic phases.