Abstract

Refractories are widely used in all high temperature processes and provide resistance to the thermal stress, physical wear and chemical corrosions. Development of the advanced refractory is always a great challenge to the researchers as the tests of refractories in the lab is difficult to truly reflect the operating conditions of the industrial furnaces. It is practically difficult to directly test the new materials in the furnace as the replacement of the refractories will need to stop the operation, which will cause significant productivity losses. It is necessary to develop a reliable technique to perform the corrosion test of the refractory with simulated operating conditions, which includes temperature, oxygen partial pressure, flowing melts and reaction time. An accurate simulation of the refractory corroded in the melt will provide the first hand information for the further development of refractory materials, such as the corrosion mechanism and wearing rate.

In the present study, a new dynamic corrosion test apparatus was developed to simulate the corrosions in the furnace. A vertical tube furnace is employed as well as a gas-tight chamber enclosed at the top of the furnace. The crucible holding melt sample is suspended using alumina tube with Pt wires, and located in the hot-zone of the reaction tube. The refractory sample prepared is suspended by an electric stirrer through an alumina tube, and the rotation speed of the refractory sample can be adjusted by a computer connected to the stirrer. The platforms holding the melt and refractory can move by independent motors. The atmosphere in the furnace and chamber can be controlled by inert gas or gas mixtures. After certain reaction time at a given temperature, the refractory sample can be rapidly raise to the cold end of the furnace and the crucible with melt can be directly dropped into ice water. This way the reactions between the refractory and the melt are stopped and the microstructure and compositions of the phases present are freezed. The retained microstructures and compositions of the refractory and melt can provide accurate information at high temperature. The quenched refractory sample and melt are sectioned, mounted, polished and carbon coated for electron probe X-ray microanalysis (EPMA). The depth of the penetration, phases present and their compositions can be accurately measured by EPMA.      

Examples have been given to demonstrate the advantage of the present apparatus with features of accurately controlled atmosphere, temperature, reaction time, rotation speed followed by quenching both refractory and melt. The magnesia-chrome refractory and the synthetic MgO-Al2O3 spinel material have been tested with copper smelting slag and melted Cu2O respectively.