Effect of melt cleanliness on the formation of porosity defects in automotive aluminium high pressure die castings

The effect of melt cleanliness on the formation of porosity defects in automotive aluminium high pressure die castings (TA Transmission Case) was investigated experimentally. The experiments were conducted under actual industrial production conditions at Nissan Casting Australia Pty Ltd. (NCAP). It was found that the probability of rejection due to excessive porosity present at critical locations in the castings (determined using a real-time X-ray radiographic method) increased as the number of inclusions in the melt (measured with LiMCA II) increased. The types of inclusion in the melt were identified as mainly amorphous oxides, oxide films and sludge particles.