Effect of Watering and Non-Watering Cooling Rates on the Mechanical Properties of an Aluminum Smelter’s Potshell

Abstract

The cooling time of a shutdown aluminum reduction pot depends on the cooling method. Free-convection cooling (non-watering) takes about five to nine days depending on the surrounding environment while watering the pot shortens the cooling time to less than one day. Application of watering cooling rates on the pot from a high temperature can have consequences on the final mechanical property of the potshell. Facilitating a design of a cooling system which optimizes the cooling rate of a shutdown pot without deteriorating the desired mechanical properties of the potshell is required.

This study focuses on the effect of different cooling rates on the micro structure and mechanical properties of the potshell material. To this effect, samples of potshell material from a shutdown pot were collected and ASTM standard specimens for mechanical and micro structural examinations were machined. Specimens were heated up to a maximum temperature of 500°C and then cooled at various rates ranging from that of free convection cooling to water quenching cooling. Tensile and micro-hardness tests were carried out to examine the effect of these cooling rates on the mechanical properties of the material. Micro structural analysis was carried out to study the micro structural response of the material to the various cooling techniques. The variation of the thermal and thermo gravimetric properties of the potshell material with temperature has also been measured according to ASTM E1461 Test Method.