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The relationship of J factor and internal casting quality in high pressure die casting was investigated by leakage testing conducted after the machining process. The trial die, used for motorcycle engine applications, was a single closed-deck-type liner-less cylinder block with an expendable salt core. The J factor was calculated by using the VanRens equation with varied gate thickness, gate speed, plunger diameter, and casting pressure. To confirm casting quality by leakage testing, we conducted X-ray computerized tomography (XRC), micro-focus XRC, and thermal decomposition gas chromatographic determination analysis. In addition, XRC was used to calculate the total shrinkage volume. A strong correlation was found between the J factor and tightness against pressure leakage.

This paper describes a technique of manufacturing expendable salt cores developed to form undercut shaped aluminum closed deck cylinder block by high pressure die casting (HPDC) process. The salt cores are comprised of Potassium Chloride-Sodium Chloride-Sodium Carbonate-Potassium Carbonate system whose liquidus point is between 873 and 973K. The bending strength of the developed salt core was more than 30MPa. The manufacturing process of the salt cores was the HPDC similar to the process for metallic alloys. This process offered high dimensionality and productivity of the salt cores.