High chromium cast iron has a very poor machinability due to its high carbide content. Fe-2.4 mass % C-15 mass % Cr-1 mass % Mo-P-S alloys containing 0 to 0.2 mass % Pb and 0 to 0.4 mass % S were made by casting. The machinability of rodlike these alloys was examined by use of a lathe. Granular MnS was found to be distributed between primary γ dendrites and neighboring chromium carbide (M₇C₃) in iron containing sulphur. Since MnS became the starting point of rupture of chips and it had the effect which divided chips into small pieces in turning, they diminished in size and the machinability of iron containing sulphur improved. Addition of lead to iron was effective to improve the machinability. The wear of cutting tools decreased largely in turning by addition of lead and sulphur to high chromium cast iron. Since the high chromium as cast iron containing lead and sulphur had austenite matrix, the cutting surface of the cast iron was hardened by machining.

抄録全体を表示

  The use of filters offers a means of cost-effective production by reducing inclusions in castings. The wide application of ceramic foam filter is based on its structure that allows a high filtration efficiency. In this study, the relation between inclusions removal and flow behavior has been studied experimentally and analytically. In the model experiment, aluminum alloy containing alumina particles was poured into the mold with ceramic foam filter inserted vertically or horizontally. And, the distribution of inclusions in the filter was discussed based on the measurement of the sample and the volume flow ratio by the simulation analysis. As the result, at high flow rate where inclusions removal by gravity separation is not dominant, it was possible to estimate the distribution of inclusions by simulation analysis. However, estimation was difficult at low flow rates. It was also found possible to remove inclusions of about 90 % by the reasonable selection of the setting pattern and pore size of the filter and flow rate.

抄録全体を表示

  The melting process of aluminum 1.5 mol % copper alloy was numerically simulated using a phase-field model with thin interface limit parameters. After isothermal dendritic solidification at 865 K, the system temperature was raised to 915 K, 920 K or 923 K and the melting process was examined. The melting rate was large at the initial stage and gradually decreased as circular liquid regions were formed by the aggregation of small liquid droplets. It was due to the negative curvature of solid/liquid interfaces that raised the equilibrium liquidus temperature and decreased the driving force for melting. When the system temperature was high, circular liquid regions were easily connected to each other and continuous melting proceeded. For qualitative analysis, one-dimensional analysis was also carried out. The melting behavior at different system temperatures showed similar tendency and solid fraction continuously decreased with time. The solid and liquid solute concentrations at the interface were slightly higher than equilibrium concentrations because of the kinetic effect.

抄録全体を表示

  New austempered ductile cast iron precipitated ferrite around the spheroidal graphite was produced by heat treatment. The process involved austempering at 653 K after furnace cooling to 998 K from an austenitizing temperature of 1173 K (α-ADI). In this process, the ferrite thickness around the graphite was about 25 μm, and the matrix was a bainite structure. The tensile strength and 0.2 % proof strength of α-ADI were about 30 % lower than that of the conventional ADI. However, the elongation and Charpy impact strength of α-ADI were increased remarkably. The brittle-ductile transient temperature was about 210 K for both ADI and α-ADI.

抄録全体を表示

  The effects of the temperature of metal mold and the coat thickness on the solidification time of aluminum alloy castings in gravity die casting were investigated theoretically and experimentally. Plate aluminum alloy casting was cast by the gravity die casting. The experimental data showed that the solidification times of the casting increased as the thickness of coat and the temperature of the metal mold increased. One-dimensional analysis of the solidification of the casting with heat resistance of the coat and that at the interface between the casting and the coat was carried out. It was found that the effects of the interfacial heat resistance on the solidification time of the casting was large and that the temperature change at the casting surface was not significant.

抄録全体を表示

  This research has been carried out on the assumption that the driving force of graphite alteraion in molten iron is the specific density difference between flake and spheroidal graphite iron melt controlled by the melt treatment of the Modified Inmold process. Alterative control of some kind of graphite structure was investigated by choosing the combination and content of treating alloys set in both reaction chambers. Remarkable alteration of graphite structure from spheroidal upward to flake downward in casting specimen was realized by these selections.

抄録全体を表示