For the prediction of deformation behavior of casting, elasto-plastic analysis coupled with heat transfer analysis has been carried out by a multi-purpose finite element code.
  Al-4.5 % Cu alloy is used as the target material, which is assumed to be an elastic and perfect plastic material. A simulation model is 2-dimensional cylinder with dimensions 3 cm in radius and height, respectively. In the calculation, temperature dependency of physical properties (specific heat and thermal conductivity) and mechanical properties (linear expansion coefficient, Young's modulus and yield stress) are taken into account, and the volume ratio of solidification shrinkage is set to be 7 %.
  While plastic deformation is dominant before solidification, elastic deformation becomes greater than plastic one after solidification. The contribution of plastic deformation to total change in size of a casting during and after solidification is shown to be smaller than that of elastic deformation. If the deformation of mold is known, therefore, deformation behavior of the casting can be predicted by elastic thermal stress analysis. The error of casting diameter by elastic thermal analysis compared to elasto-plastic analysis is less than 11 %.

View full abstract

  The spongy cast metal can be produced by a new process, that is, pressure casting with the infiltration of molten metal into pores of sintered particles, followed by dissolving the particles in a solvent. The spongy cast stainless steel (Fe-18 % Cr-8 % Ni) with the porosity between 50 and 55 % was obtained by making use of MgO or CaO particles.
  Liquid phase sintering of particles with a small amount of B₂O₃ as a sintering additive was performed at 1638 K (MgO) and 1748 K(CaO) for 3.6 ks in the air. B₂O₃ did not reduce the solubility of the particle in a solvent.
  The critical preheating temperatures of sintered particles required for the pressure casting at 1873 K were 1523 K for sintered MgO with the packing density of 50 % and 1373 K for sintered CaO with that of 55 % . Since sintered particles preheated in a ceramic-wool case were used, it was possible to avoid sticking of casting to the mold in consequence of relatively low preheating temperature (∼393 K).
  MgO particles in the composite was possible to dissolve in HN0₃, and CaO particles dissolved in HN0₃, NH₄Cl and chelating agent. It is the most practical way to use CaO particles and HN0₃ as a solvent to produce the spongy cast stainless steels.

View full abstract

  The waste and which discharged from a foundry with treated green sand contains a lot of active bentonite having a ability as binder. Accordingly if we can recovery and reuse this active bentonite efficently, we can attempt to cut down natural resources, and to decrease the industrial waste. For the purpose of it we tried to separate active bentonite from the mixed bentonite (not heating bentonite + heating bentonite) by elutriation.
  As a result, we could separate active bentonite from the mixed bentonite making use of its nature that conducts of montmorillonite particles vary in water.
  Next, we gathered the upper side of the heating bentonite in the way of elutriation to examine its charactristics as a binder of green sand mold.
  As a result, the bentnite heated at 480°C showed the peak of compressive strength.
  Also, the characteristics of bentonite in recovering from wasted sand in the foundry (recovery bentonite), was good condition for us.

View full abstract

  Temperature, pressure and time are parameters in the solid-state bonding of ceramics to metal. The factorial effect of these parameters in the bonding of alumina to low-carbon steel with insert metal is experimentally investigated in relation to the bonding strength. Bonding strength can be expressed in a function of pressure and thickness of insert metal plate as
    y = 118.4 - 19.12(x_A - 2.0) - 5.65 { (x_A - 2.0)² - 0.75} + 0.938(x_B - 12.25)
        - 0.117 {(x_B - 12.25)² - 30.01} - 1.16(x_A - 2.0)(x_B -12.25) at 1173K
    y; bonding strength (MPa), x_A; thickness of Cu plate (mm), x_B; pressure (MPa)
  In the brazing of alumina to low-carbon steel with Al-11.7 wt % Si braze, bonding strength can be expressed as a function of temperature as
    y = 20973 - 89.75(x_C - 273) + 0.127(x_C - 273)² - 0.00006(x_C - 273)³
x_C ; temperature (K)

View full abstract

  To investigate the formation of oxide layer on the surface of cast iron, seven kinds of pellets, containing 10 to 50 wt % Si and having the various ratios of electrolytic iron, metallic silicon, ferro-silicon (41.7 wt %) and Fe₃Si, were prepared by mixing and pressing, and heated in air for 10 to 300min. The oxide layer and sintered metallic grains were observed and analyzed with EPMA and XRD. The exothermic reaction was observed on all specimens except for the specimen of ferro-silicon alone. On four specimens, containing silicon less than 20 wt % of which temperature rose above 1250°C, the oxide layer were thick, and on the other specimens, containing 20.9 and 50 wt % Si with the temperature going up about 1200°C, the oxide layer were thin. The difference in the composition of initial melts formed in specimens at high temperature could account for these results.

View full abstract

  In the laser surface modification, it is important to estimate the size of melted zone and the cooling rate in a given irradiation condition.
  In this work, the thermal conduction analysis is applied to estimate the surface modification of alloy by using a finite element method (FEM) program, MARC.
  The absorptivity of energy on the surface of specimen is studied by comparing the melt width given by calculation with that given by experiment. The absorptivity of energy is estimated to be 13 %.
  The analysis with this absorptivity is applied to cases where the scanning rate of the beam is changed and cases where the laser beam power is changed. It is shown that analysis gives proper size of melted zone and the cooling rate.
  This thermal conduction analysis is shown useful to estimate the surface modification conditions by a laser.

View full abstract

  In these days, solidification simulation has come to be applied in order to set up faster and proper casting plan. However, there are still few cases where such simulation was applied to spheroidal graphite iron castings, and it is not easy to foresee the occurence of shrinkage cavities, because solidification process is complicated, involving expansion in addition to shrinkage.
  As to fundamental castings, we measured actual temperature change of molten iron as well as mold in the course of solidification, which we repeatedly compared with temperature analysis obtained by simulation, and the propriety of solidification analysis basic date was examined. Further, with respect to the various plans for test castings, we tried to foresee the occurence of shrinkage cavities by two or three dimentional simulation. As a result, accurate data could be obtained on material properties, initial and boundary conditions required for solidification analysis related to the subject iron.
  The result of temperature analysis by simulation based on such data was appoximate to the actual change of casting temperature. Also, it was recognized that the shrinkage cavities were predictable from solidification analysis contour.

View full abstract