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Investigation in the changes in metalic materials as a result of heating
thesisposted on 2022-03-28, 16:34 authored by Steven Wang
Steel and aluminium are two of the most commonly used metals, ans are used in many industries. As the manufacturing processes involved with these metals often involve high temperatures, it is important to understand the consequences of exposing the metals to these temperatures. Steel welding and aluminium extruding are manufacturing processes which involve the heating of the metal. Steel welding involves high temperatures in order to fuse two pieces of metal together, however these high temperatures cause the properties and microstructure of the metal in a localised area to change. On the other hand, aluminium extrusion requires the metal to be preheated before the process to reduce the forces required to shape the metal. As undesirable properties occur as a result of the elevated temperatures during steel welding, heat treatments may be applied to optimise the final properties and microstructure. During the aluminium extrusion process imperfections may occur, causing the final product to be flawed, this was the case at Capral with an extrusion of cladding causing the part to be rejected by the architect. AS a result an investigation on the cause of the imperfection was launched. In order to investigate the properties of both the welded steel joints and aluminium extrusion, specimens were created, cut, hot mounted, polished and chemical etched, so that the Vickers hardness test and microscopy analysis could be performed. The findings of this report suggest that annealing is the most appropriate heat treatment to optimise the properties of the welded steel joints. Further research should be conducted into the annealing conditions in order to optimise the properties and microstructure of the welded steel. Through testing it was found that the properties and microstructure of the aluminium extrusion were not the cause of the imperfection, however through further testing of the profile of the extrusion, it was found that the flow rate in the extrusion die caused the imperfections. As a result it is suggested that modifications be made on the design of the extrusion die to remove the imperfection.