Abstract
Reoxidation is one of the main problem accompanying the aluminium alloy casting process. The oxide layer created on the melt surface during reoxidation is entrained into the bulk of liquid metal and “bifilms” are created. Bifilms have negative impact on cast quality and internal homogenity of final casting. Paper aim is to clarify the reoxidation phenomenon by visualization with the aid of ProCAST numerical simulation software. Experiemtnal work deals with the design of several types of gating systems (non pressurized and naturally pressurized) with vortex elements in order to determine how these elements affect the reoxidation processes. Achieved results clearly confirmed the positive effect of the naturally pressurized gating system with vortex elements. The evaluation focuses mainly on melt velocity and amount of oxides created in gating system and in mold cavity.
Highlights
The increasing demands on the aluminum alloys quality are related to the effort to eliminate as many casting defects as possible
Liquid metal reacts with the surrounding atmosphere and oxide layer of Al2O3 is formed on its surface
Reoxidation is considered to be the secondary oxidation that occurs from the beginning of the casting process until the moment when the mold cavity is filled, as well as the tertiary oxidation that occurs during solidification [2, 3]
Summary
The increasing demands on the aluminum alloys quality are related to the effort to eliminate as many casting defects as possible. The result of reoxidation processes are „bifilms“, which are formed and entrainment into the bulk of liquid metal by turbulence. Due to their small and compact dimensions, bifilms can pass through the entire gating system, they often cannot be removed even with the use of the filtration media. The amount of oxides and the melt flow velocity are among the most important parameters during the filling of the gating system, which affect the final quality of the casting. Experimental work deals with the design of several types of gating systems (non pressurized and naturally pressurized) with using vortex elements in order to determine how these elements affect the melt velocity and the amount of oxides in the casting by using numerical simulation
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