The permeability of shell molds is a key property for investment casting technologies because it affects casting defects like non-fill and de-wax cracking. Currently, the permeability measurement method for investment casting shell molds is not specified in Japanese Industrial Standard (JIS). Permeability is presently measured by two common methods : Ping pong ball method and Pipe method. Because the mold cracks during the preparation of shell mold samples, there is room for improving these methods.

  In JIS, permeability measurement for ceramics materials is specified in JIS R 2115 (2008). Thus, in this study, we investigated a method to prepare shell mold samples and a method to measure investment casting shell molds based on JIS R 2115 (2008). Moreover, the influence of stucco size and firing temperature on the permeability value were reviewed. The results showed that the permeability value is affected by the sintering extent and crack number or its size.

  Precision casting is one of the most important processes for the production of aero engine and turbo-charger parts. The IHI Group has been developing and improving the manufacturing process for the last three decades according to demands for higher mechanical properties, higher quality, and lower production costs of casting parts. However, in recent years, new and higher-level demands for casting parts are seen accompanying the need to reduce environmental load, save energy, and reduce weight. In this article, three process development topics in IHI Group are introduced. With respect to the turbo-charger, new processes for achieving defect-free and low cost production processes for aluminum compressor impellers produced with plaster mold castings are needed. We therefore developed the Low-pressure and Vacuum casting process for the mass production of compressor impellers. Furthermore, as for aero engine parts produced with ceramics mold castings, we developed new low-cost alloys for the single crystal casting blade, and a new mold system for titanium alloy castings. The new alloy for single crystal castings showed equivalent creep properties to commercial alloys with lower rare earth elements contents. Material cost is significantly decreased, and it is expected to be applicable to new blade materials. The new molding system for titanium alloys castings prevent alpha case formation during solidification. This reduces post-processing costs and keeps mechanical properties higher.

  In these developments, IHI Group has contributed to the recent technology progress of precision castings, and we will make further contributions to the advancement of the casting industry in Japan.