The effects of ferrite thickness around flake graphite on ductility and fracture toughness of gray cast iron were investigated. Gray cast iron with different ferrite thickness of 10μm, 15μm and 20μm, were produced at various furnace cooling velocities (0.071 K/s, 0.083 K/s, 0.250 K/s) from an austenitizing temperature of 1143 K.
  The ferrite around the graphite was effective for improving the ductility of gray cast iron. The Charpy impact strength increased with the ferrite thickness, which was most effective for suppressing the crack propagation on the fracture. In the bending test of a notched specimen, acoustic emission counts were observed for relatively high amplitudes without ferrite around the graphite. In the matrix containing ferrite layer around the graphite, the acoustic emission counts were less than that without ferrite. These resalts indicate that ferrite around graphite is effective for absorbing the energy of fractures.

抄録全体を表示

  Cast steel was locally hard-faced using inserted hard alloy powder layer containing several percent of spray alloy (BNi 3). The vertical cross-section of the inserted layer was examined regarding microstructure with EPMA and hardness with a Vickers hardness tester. The results obtained are as follows: Sound inserted layers of 3 mm in thickness were confirmed to be formed without any defects at the surface of cast steel. An intermediate layer with some lump shaped particles were formed at a region between the inserted layer and mother metal (cast steel). The lump shaped particles were identified to be Fe₃W₃C. The hardness of cast steel was about HV 300, while the inserted layer exhibited a hardness of HV 600 to 1400. The maximum hardness was obtained in the case of hard alloy powder containing 20 vol.% spray alloy. This was considered due to the formation of a hard martensitic structure at the bonding phase in the hard alloy powder. No effects of post heat treatment on the hardness distribution in the inserted layer were detected. The present method using the inserted hard alloy powder is therefore considered to be very effective for the locally hard facing of cast steel.

抄録全体を表示

  The modulus method was used to calculate solidification time ratio of iron castings of various shapes relative to that of an infinite plate. When compared with the results of numerical analysis, the modulus method gave excessively small values for shapes having internal (re-entrant) corners. Correction factors were proposed to give an effective area smaller than the actual area at an internal corner. Critical distance with regard to the end effect was also proposed. In most of the examples examined, the error of the modulus correction method was within ±20% of the numerical analysis.

抄録全体を表示

  Decarburized graphite in the matrix of cast iron was investigated to produce high-value-added cast iron. The aim was to develop new uses for cast irons. Graphite was eliminated at the surface by high temperature oxidation in air atmosphere, and the other useful materials were infiltrated into the resulting pores.
  The effects of holding time (3h-36h), holding temperature (1023K-1223K), and chemical composition (C; 3.27%-4.0%, Si;2.0%-4.0%) were investigated for each graphite morphology (flake graphite, compacted graphite, spheroidal graphite). It was found that the rate of formation of porosity (due to the decomposition of graphite) in cast iron follows the diffusion law. The rate of formation of porosity in flake graphite irons was faster than other types of graphite. Flake graphite is continuous in the matrix, but spheroidal graphite is independent The continuity of the graphite morphology was found to have a remarkable effect on the rate of formation of porosity.

抄録全体を表示

  Generally aluminum diecasting is superior in productivity compared to other casting processes, but inferior in strength due to casting defects. As a result of application of MMC ( ＝ Metal Matrix Composite) to all aluminum cylinder blocks, high quality diecasting which consists of directional solidification and melt laminar flow was developed. This technology makes it possible to re-design the base engine for high performance with the narrowest bore-to-bore distance in the world.

抄録全体を表示

  We wrestled to shorten development term of Aluminum road wheel. We applied 3-dimension data to product design, die design and die manufacturing in stead of the conventional 2-dimension drawing for shortening development term. We standardized die parts and improved modeling efficiency with 3-dimension design. We abolished electric discharge machining and applied high-speed excision machining for die manufacturing. Then we can shorten a development term of new project with 5 months to 2.5 months by this new system and accomplish cost reduction in 30 percents.

抄録全体を表示