Classification of Porosity in Die Castings. Porosity in casting aluminum alloys directly affects the reliability and quality of products which incorporating die cast metals into their design. Die Casting Manufacturing companies rely on advanced technologies and methodologies to minimize porosity so as to avoid additional overhead.
The types of porosity in die castings vary in terms of their characteristics. The three basic classifications however are continuous, blind and totally enclosed, which are manifested in four general types namely micro, micro/macro, funnel and macro.
The first instance of continuous porosity in metal castings is the presence of leak path from a particular enclosed section towards another. The Micro Manifestation shows a slow single-point leak.
The second instance of continuous porosity is the presence of collective defects which are interconnected in many areas. The Micro/Macro Manifestation of such characteristic is multiple leak points at a slow rate.
The third instance of continuous porosity is the presence of externally visible defects with micro-sectional defects. The Funnel Manifestation is a slow single-point leak.
The fourth instance of continuous porosity is the gross visible defects in the surface of metal castings, shows extreme leaking in the Macro level.
The first circumstance is the absence of visible defects on the surface of die cast metals while micro manifestation displays a weeping of contaminants towards the surface. A wet or darkened region is also visible. On the other hand, the said casting holds pressure.
The second circumstance is the absence of visible imperfections on the surface. There are however darkened parts of the casting surface. The Micro/Macro Manifestations include gushing of machining fluid towards the surface. The castings on this instance still hold pressure.
The third circumstance is the visible die cast porosity and pitting on the surface. The Funnel Manifestation includes discoloration of the surface and weeping of machining liquids.
The fourth circumstance of blind porosity is the display of visible porosity holes on the surface of the metals and the roughness of the said surface. The Macro Manifestation includes surface discoloration and the presence of contaminants.
Totally Enclosed Porosity
Defects and impurities are not visible on the surface which is often caused by material shrinkage or gas accumulation. Shrink porosity is characterized by irregular shape and rough surface. Gas porosity is displays a smooth and regular shaped castings.
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