Thermite Reactions during Extrusion of Aluminum

摘要

The present work relates to a newly discovered phenomenon on die bearings during extrusion of aluminum that may have a major impact on quality parameters during extrusion. The hypothesis is that the phenomenon is caused by a thermite reaction. This is a reaction that takes place between the iron oxide layer on the bearing surface in the extrusion die and the aluminum that is extruded over it. The reaction is very exothermic and releases a huge amount of energy where the local temperatures may exceed 2000°C (3632°F), well above the melting temperature of the die steel at 1536°C (2796.8°F) for iron (Fe), and far above the melting temperature of aluminum (660°C, or 1220°F). If such a violent reaction takes place, it would be expected to cause severe damage to the surrounding materials. The present work focuses on documenting that a micro-scale thermite reaction does take place during extrusion of aluminum, as well as documenting this reaction's effects. It is shown to have a significant impact on factors such as profile surface quality and extrusion die wear.