Manifolds made of cast iron are joined by melt welding, which however has the risks of causing partially chilled structures. In this study, lap joint friction stir welding of high silicon spheroidal graphite cast iron (high Si-FCD) and austenitic stainless steel (SUS) was investigated. In this process, the rotating stir rod is pushed into the lapped plates of SUS and high Si-FCD. The results showed that friction stir welding of high Si-FCD and SUS is possible regardless of the Si content, and that the area affected by heat spreads with increasing Si content. Microstructures of very fine ferrite were obtained at the high Si-FCD side by friction stir welding. In addition, joints free from chilled structure could be obtained by providing appropriate heat.

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  This study aimed to clarify the fatigue characteristics of spheroidal vanadium carbide cast iron (SCI-VCrNi) and the fatigue fracture mechanism of cast iron with spheroidal vanadium carbide (VC) dispersed in the stainless matrix microstructure. SCI-VCrNi is not only a high hardness and high toughness material but also has excellent abrasion resistance because of the high hardness (approximately 2300HV) VC dispersed in its matrix.
  First, a plane bending test was conducted to clarify fatigue strength, and the results confirmed that the fatigue limit σ_w to be 358MPa for SCI-VCrNi. Based on these results, a fractographic study was carried out to make clear the fatigue mechanism of SCI-VCrNi. As for SCI-VCrNi, typical fatigue fracture by macro-observation has not been observed due to the large bumps on fracture surface. SEM observation showed the fatigue fracture surface to have typical fatigue striations. In addition, numerous fracture cracks of VC were observed, as well as secondary cracks at the interface between VC and the matrix. These results suggest that the binding strength of VC and the matrix is strong, and crack progress is delayed by VC fracture.

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  Casting using frozen molds made by only of sand and water is an appealing casting process, as it does not produce industrial waste. However, the thermal conductivity mechanism of frozen molds is not yet well understood. For this reason, this mechanism was investigated by measuring temperature changes in the mold due to the pouring of CAC902 bronze in this study, and the following findings were obtaind.
  High temperature vapor generated just after pouring at the interface between the casting and mold, after which this vapor moves to the outside of the mold passing the vacancy in the mold. The generated vapor cools the casting, and the increasing water content in the mold, because increases the cooling speed of the casting. In contrast, the permeability of the mold decreased with increasing water content, because water fills in to the mold cavity. As a result, the apparent thermal conductivity decreases.

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