This study describes the changes in the characteristics of wear amount and angle dependency according to the properties of impact particles. First, regarding dimension, for particle diameters 370 μm and 660 μm, the angle dependency of mild steel was found to be of the twin-peak type, and tended to increase in case of diameter 990 μm. With regard to hardness, while mild steel of standard steel grit showed the twin-peak characteristic, quench hardening steel grit tended to grow steadily.
  The unified assumption that factors such as particle-diameter and hardness affect cutting and deformation type erosive wear differently enables comprehension of these changes in erosive wear characteristics. Moreover, results of tests with polygonal steel grits in this study also well clarified the two wear-mechanisms above.

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  Aiming at manufacturing excellent iron castings which possess better toughness, wear resistance, solid lubricity, etc., than traditional iron castings, the semi-solid casting process has been studied extensively by using various methods. However few trials have been carried out on semi-solid casting systematically to develop a practical process. In the present study, fundamental estimation of the semi-solid casting process was done for the purpose of making about 50 kg iron castings, using mechanical rotation and cooling plate as a solid particles distributing/fining method. The mold filling ability of semi-solid slurry was investigated as well as the microstructure and mechanical properties of the cast material.
  Experimental results of mold filling using stepwise shaped mold confirmed that semi-solid iron fills smoothly into cavity with a thickness of 10 mm. It was also observed that 3 mm thickness cavity is filled completely when solid fraction is less than 0.05. The microstructure and mechanical properties of semi-solid iron casting are better than usual castings. Furthermore, simulation of flow and heat transfer was also attempted to predict the cooling process of metal slurry on the cooling plate. It was possible to quantitatively estimate the effects of the cooling plate.

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  Molten spheroidal graphite cast iron was melted as raw materials using steel can scrap (S.C.S), of which the Al cap portion was removed, and cast into several kinds of molds to examine spheroidal graphite cast iron characteristics (chilling tendency, nodule count, graphite spheroidization), mechanical properties (tensile strength, brinell hardness, elongation) and chemical composition. In this study, a standard sample was first melted, and then samples containing 10, 20, 30, 40, 50, 55, 60, 70% S.C.S. in raw materials were melted. Since it is known that the generation of chill is influenced by the critical nodule count for graphitization/stabilization (P.c. ), chilling tendency was investigated by P.c. rather than the total chill depth.
  In this experiment, Sn contents increased with increasing S.C.S. Cr, Ti, and Mn contents also increased, though slightly. The total chill depth increased when the compounding ratio of S.C.S. exceeded 50%. Although the percentage of graphite spheroidization did not change in the specimens, that of pearlite increased with increasing compounding ratio of S.C.S. P.c. increased in samples with 40% and 50% S.C.S., and decreased in samples with 60% and 70% S.C.S.. Moreover, the nodule count reached its maximum when the compounding ratio of S.C.S. was 50% at the same cooling rate (3.5 K/s). Therefore, 50% compounding ratio of S.C.S. is thought to be optimum from the viewpoint of spheroidal graphite nucleation.

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  Decomposition behavior of retained austenite (γ_R) due to heat treatment under critical temperature (A₁) of 17 mass%Cr cast iron containing 2 mass%Mo was investigated. Three kinds of specimens, of which treating conditions before heat treatment were as-cast, as-hardened from as-cast state and as-hardened from annealed state, were held at temperatures from 813 K to 923 K for 100 s to 1.2×10⁶s, and then volume fraction of retained austenite and hardness were measured.
  Regardless of the pre-treating conditions, the relationship between the decomposition ratio of retained austenite and logarithmic of holding time showed a sigmoidal curve, and decomposition accelerated as the temperature increased. The holding time also increased. The decomposition of retained austenite mainly causes transformation of pearlite or precipitation of carbides. The decomposition rate was smallest with heat-treatment from as cast state.
  Hardness increased with increasing decomposition ratio of retained austenite and reached maximum value obtained at 5 to 10%γ_R.

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  The type and alloy concentration of precipitated carbides in matrix were investigated using X-ray diffraction, SEM, TEM and EDS analyses in multi-component white cast iron with typical composition of Fe-2%C-5%Cr-5%V-5%Mo-5%W-5%Co (mass%). MC, M₂C and M₇C₃ carbides already exist in the as-cast state. M₆C and M₇C₃ carbides are precipitated during annealing, and carbides existing in the hardened-tempered state are MC, M₆C and M₇C₃ types. In the as-cast state, two types of crystal lattices were confirmed in the MC carbide, mostly face-centered cubic (FCC) and partly hexagonal. The MC carbides contain V by more than 65at%. M₂C carbide with hexagonal lattice contains 35at% of Cr and Mo, and 12at% of V and W. M₆C carbide with FCC lattice consists of 44at% of (Mo+W) and 45at% of Fe. M₇C₃ carbide has orthorhombic lattice, but shows different shapes ; string-shape in the as-cast and hardened-tempered states and oval in the as-annealed state. The M₇C₃ carbide is mainly formed from Cr and Fe.

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