Abstract

In the modern copper industry, it is important to achieve continuous operation to increase the productivity and reduce the environmental problems. Launder is one of the essential components to rapidly transfer molten matte and copper in different processes. In most of the copper-making plants, castable alumina-silicate refractories have been used for the launder materials. However, these refractories cannot meet the requirements of the continuous operation as the molten matte and copper metal can react with the refractory causing serious damage. Development of new launder materials with good resistances and environmental friendly is urgent for the copper industry.

SiC has some unique properties like high hardness, toughness, chemical and thermal stability and, in particularly, low wettability to matte and copper metal. SiC-based ceramics have been proposed to be the alternative material for the launders and it can also be potentially used as lining for refining furnace and ladel. However, SiC is hard to be sintered directly and suitable bonding phase is required to make strong and cheaper refractories. In the present study, SiC-based refractories will be prepared by various methods with different bonding phases. These refractories will be evaluated with molten matte and copper respectively.  

The Si3N4 bonded SiC materials can be prepared by carbothermal reduction of silica under controlled conditions. Reaction temperature, time and partial pressure of N2 have been tested to achieve an optimum condition. The silicates bonded SiC can also be prepared starting from accurately controlled oxygen partial pressure, temperature and time to form a required layer of SiO2 on the surface. The pre-oxidised SiC powders were then mixed with Al2O3 and heated under controlled temperature and time. The silicate formed acts as the bonding phase to join the SiC particles. Static corrosion resistance tests were carried out to test the resistances of the new materials to molten matte and copper. The sample to be tested was placed in an Al2O3 crucible with matte or Cu. The sample was heated to high temperatures for a required period in Ar gas flow. After reaction the material was quenched into water for electron probe X-ray microanalysis (EPMA). The depth of the penetration, phases present and their compositions can be accurately measured by EPMA.      

The careful analyses of the microstructures clear reveal the reaction mechanisms of the SiC-based materials with matte and copper. The performances of these materials show the possibility to be used as the launder material or linings for ladle and refining furnace in copper industrial.