The properties of after-recycling slag in the recycling process of the particle reinforced metal matrix composite materials
Jacek Jackowski, Magdalena Suchora, Paweł Szymański
Quarterly No. 4, 2009 pages 342-346
DOI:
keywords: particle-reinforced composites, recycling, production technology
abstract The most reasonable recycling of the metal composite materials manufactured with casting methods consists in separation of the components. The suspended composite materials may be indeed remelted and the suspension recasted again, nevertheless, this would be rather a particular case of recycling. In case of fine and contaminated suspension wastes of the composite materials and the materials with saturated reinforcement, the recycling process consists in separation of the components. The process of separation of the suspension components of the composite material under recycling requires the use of an additional liquid phase of the recycling system, that is called a medium. It is a melted salt mixture that intercepts the particles of the reinforcing phase of the suspension under the recycling process. The process of interchange of the suspensions (i.e. the transfer of the reinforcing particles from the matrix to the medium) requires mixing of the system in order to emulsify it. The after-recycling slag formed this way is a suspension of the reinforcing phase particles in the liquid medium. Its properties, particularly the densi-ty, are decisive for its behaviour after the process termination and, in consequence, for possible separation of the components of the system composed of the recovered composite matrix and the after-recycling slag. The experiments have been performed in a furnace-mixer, with the use of a charge composed of the composite material batch (F3S.20S), mainly in the form of chips and varying amount of the salt mixture (the medium). In result of such an approach the after-recycling slag samples have been obtained, of differentiated contents of the phase particles that reinforce the composite material. The pictures show the examples of the solidified after-recycling systems found in the crucible sections upon the process termination. The observations of the slag behaviour during the recycling process, together with the analysis of the contents of the reinforced particles derived from the slag samples, enabled formulating the relationship shown in the diagram. The diagram explains the reason of the phenomenon of slag “disappearance” during the process. It is due to the change (growth) of slag density caused by the increase in the reinforcing particles contents. This gives rise to disadvantageous consequences, resulting in more difficult coagulation of the recycled system emulsion drops (the drops of the composite matrix/ the drops of after-recycling slag), their slower sedimentation after the process termination, and more difficult separation of the after-recycling system components, i.e. the recovered composite matrix and after-recycling slag.