The effects of composition in active filler metals, brazing temperature and reaction layer on the shear strength of Al₂O₃-spheroidal graphite cast iron (FCD400) joints were studied using two types of active filler metals (type A and type B). The variation of microstructures of reaction products formed at the interface between Al₂O₃ and the active filler metals was investigated by scanning electron microscopy and auger electron microscopy. The Al₂O₃-FCD400 joints indicated the strong shear strength with the increasing brasing temperarures in the range of 1023∼1173K. The Al₂O₃-FCD400 joints showed shear strength to about 230∼240MPa, 243∼250MPa under the brazing condition at 1073∼1123K for 900s, 1123∼1173K for 900s respectively using two types of active filler metals (type A and type B). Increasing the thickness of the active filler metals from 0.05mm to 0.10mm resulted in decreasing shear strength of the joints by 15-30PMa. Two reaction layers Ti_3.3 (Cu, Al)_3.6 O_2.7 , Ti_4.7 (Cu, Al)_3.1 O_1.9 were formed in the interface between the active filler metals and Al₂O₃, depending on the composition in the active filler metals. The shear strength of Al₂O₃-FCD400 joints are attributed to the formation of these reaction layers.

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  The effects of the forced draft in the flask on the solidification time of casting by the evaporative pattern casting process were investigated experimentally. The plate casting of aluminum alloy was casted by using two different sizes of silica sand and steel shot as a mold with the forced draft in the flask. It was found that the flow rate of air in the flask and the effects of the forced draft on the solidification time of casting increased with increasing size of packing. When the mold was made of steel shot of 2.5mm in diameter, the solidification time of the casting decreased 20% by the forced draft in the flask.

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  The behaviors of alloying elements and their effects on hardenability were investigated for quenched and tempered Fe-2.1mass%C-5mass%Cr-5mass%Mo-5.5mass%V-0/5mass%W-0/10mass%Co alloys. EPMA analysis of the specimens quenched just after solidification reveals that each alloying element distributes almost uniformly in the primary γ from the center of the dendrite arm to the boundary with eutectic MC, but near M₂C, Cr increases and V decreases. During holding the specimen at 1323K for 1hr, MC particles preferentially precipitate at the central part of dendirite arms and M₆C particles dominate to precipitate near eutectic M₂C and MC. V distributed near eutectic MC precipitates as the secondary MC on the eutectic MC. By the precipitation of these secondary carbides, the V, Wand Mo content in the matrix decrease from 2.0% to 0.4%, 2.2% to 1.2% and 2.0% to 1.6%, respectively. The change in Cr content is small. The carbide formers still remained in γ should contribute to the martensite transformation and the secondary hardening by the tempering. CCT diagrams, determined by a deratometer, show that Co raises Ms temperature and the critical cooling rates for pearlite and bainite transformations (V_P and V_B). In tempering the quenched specimen at around 823K, so-called secondary hardening occurs. However, too long holding results in a decrease of hardness. Co enhances the secondary hardening and delays the softening. W also increases Ms temperature and V_B, though the effects are less than those of Co.

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  Friction welding of spheroidal graphite cast iron (FCD) and mild steel (S20C) were carried out under various rotation conditions. The friction pressure, the forge pressure and friction time were constant. The dimensions of the test pieces were 15mm in diameter and 70mm in length respectively. Micro and macroscopic observation, and scanning electron microscopic (SEM) observation were employed in order to clarify the characterization at the welding interface. The tensile strength of the joint was also investigated. In the FCD adjacent to the center of the welding interface, the deformation layer of spheroidal graphite (DLSG) was observed and the shape of the graphite in this DLSG was similar to the one of A or D-type flaky graphite. It is considered that DLSG was formed by the plastic deformation of the spheroidal graphite during friction welding. The tensile strength of the joint with DLSG was very low. There was a close relationship between the percentages of the area of the DLSG and tensile strengths of the joints. The appropriate welding condition reduced the amount of DLSG in the joints of FCD and S20C.

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  The burn-on of iron castings, namely chemical penetration, has posed as one of the main casting defects for a long time. However, no solution has yet been clarified for this intricate phenomena. In this paper, we discuss how the burn-on is affected with the SiO₂ content of sands from the standpoint of wettability using the sessile drop method. The apparent contact angle between the sand grains and melt decreases with the formation of FeO slag at the interface, and stop the advancing by the dissolution of SiO₂into the slag due to the increase in the melting temperature. The reason why chemical penetration defects can be prevented by the addition of coal dust into mold, is not only due to the decrease the FeO slag formation but also due to the ease of saturation of the slag with SiO₂ to increase the melting temperature.

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  Charpy-V notched specimens were prepared and the strain rate dependency of bending transition properties of ductile cast irons were investigated. Impact bending tests at loading velocities up to 10m/s (nominal strain rate for the specimens up to 10³/s) were performed with hydraulic impact loading machine. The experimental results demonstrate that the ductile-brittle transition curve rises to higher temperature side with the increase in the strain rate. This transition curve rises higher in the as cast material with higher pearlite content in the matrix, than those of ferritic material. The bending yield stress and the maximum stress were found to increase with increasing strain rate and deceasing temperature. The transition temperature and the behavior can not be simply estimated by strain rate-temperature parameter, R-value. Sstrain rate dependency on the brittle fracture behavior exists, and it seems to relate with the crack arrester effect of graphite nodule against brittle crack propagation.

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