Papers by Author: Arild Håkonsen

Abstract: Hycast TM RAM, hereafter called RAM, is a crucible fluxing technology for removal of alkaline elements (Na, Ca, and Li), as well as carbides, oxides and cryolite, from aluminium pot-room metal without the use of chlorine. AlF3 powder is injected into the liquid metal (below the metal surface) by the use of a specially designed rotor system and argon as a carrier gas. The fluxing system can be adapted to different crucible transport/tapping system, and is proven for crucible sizes from 2 to 9 tons. Since surface active elements like Sodium are removed before the metal enters into the furnace, the metal oxidation during pouring and furnace treatment is significantly reduced. Pretreatment will also reduce the carbide level in the metal, and by this improve the overall metal quality, and prevent clogging/deposits in furnaces, degassers, ceramic foam filters etc. This paper describes the principles of the RAM technology, effect on metal quality and documented operational benefits in a primary casthouse. Also environmental issues are discussed.

Abstract: A simplified numerical model for the solid state phase transformation from Al6(Mn,Fe) to α-Al(Mn,Fe)Si phase in 3xxx alloys has been constructed. In this model, the phase transformation is assumed to be initiated by the heterogeneous nucleation of α-Al(Mn,Fe)Si dispersoids at the interface between Al6(Mn,Fe) particle and matrix and the growth of the α- Al(Mn,Fe)Si phase into the Al6(Mn,Fe) particle is controlled by the diffusion of Si from the matrix. The model has been implemented into a numerical homogenization model. The simulation results show that the implementation of the phase transformation model improves much the prediction results of the homogenization model on the evolution of solid solution level of alloying elements and the volume fraction evolution of dispersoids in 3xxx alloys during homogenization.