Using two ladles of different sizes carried out experiments on the flow of water from pouring devices equipped with a quick tilt-center up-down mechanism. Experimental formulas for the flow rates at the start of pouring and end of the pouring and that for the pouring volume were proposed. Using these formulas, it is possible to estimate the inclined angular velocity and the up-down strokes of the tilt-center by substituting the diminishing pattern for the flow rate change, pouring time and pouring volume in formulas.

View full abstract

  The cooling rate, mechanical Strength and DAS (Dendrite Arm Spacing) were investigated for aluminum plate castings (AC4B) with square column and round-column that have the same shaped core, and for plate castings. The results showed that when the core size decreased, thereby increasing the volume to surface area ratio (V/S), the cooling rate also decreased The mechanical strength decreased with increasing V/S, but DAS iricreased with increasing V/S. The solidification time of AC4B square column castings and plate castings was proportional to the nth power of the modulus (V/S) : t_f = A (V/S)ⁿ, where n = 1.6 for the square column castings, and n = 1.4 for the plate castings. The following relationships (in-line logarithms) were found for mechanical Tensile strength σ_B = K_l(V/S)^-n Brinell hardness, HB = K₂(V/S)^-n, and DAS, D_S = B(V/S)ⁿ

View full abstract

  Availability of the computer simulation based on the nucleation and growth models have been examined by comparing the results of simulation with those obtained by chill test of the Fe-C-Ni-Si-Cr multicomponent cast iron using a wedge-shape mold. A linear growth model for ledeburite combined with the radial growth model for gray eutectic was introduced and the prediction showed a satisfactory agreement with the observed distribution of chill fraction and chill depth. The graphitizing ability of silicon was comparable with the anti-graphitizing effect of chromium on relatively slow cooling, while faster cooling enhanced the graphitizing ability of silicon. It was demonstrated from the results of simulation that silicon equivalent of chromium, given by SE^∗ = (%Si) - (2/3) (%Cr) as a chilling index, showed a good correlation with logarithmic chill depth and logarithmic critical cooling rate for chill formation.

View full abstract

  Much has been discussed over the extraordinary high reflected point at the center of spheroidal graphite in ductile iron under optical microscopes. The calculated images of radial oriented model and the observed images were compared to understand the strange contrast. The following physical effects on high reflectivity have been discussed; (1) optical anisotropy of graphite, (2) surface roughness and surface gradient against optical axis, (3) existence of foreign particles at the center of the structure. At the each intersection, the optically calculated images of spheroidal graphite shows good agreements with the observations. The effect of surface roughness and surface gradient is much smaller than that of optical anisotropy. And the reported foreign particles are expected to show lower reflectivity than the observations. The optical anisotropy of spheroidal graphite can be the main reason for the high reflected point.

View full abstract

  The burn-on of iron castings has posed as one of the main casting defects for a long time. However, no solution has yet been clarified for this intricate phenomenon (namely chemical penetration).
  In this paper, we discuss how the burn-on (chemical penetration) occurs from the standpoint of wettability using the sessile drop method. In the case of sand mold ferrous castings, the apparent contact angle between the sand grains and melt decreases with the formation of FeO at the interface ; chemical penetration then occurs. There are two ways of preventing the chemical penetration, namely preventing the formation of FeO by atmosphere control and using basic refractory materials such as MgO for the sand mold, which reacts with FeO to form high melting temperature slag.
  The reason why chemical penetration defects occur more frequently in steel castings more than in gray iron castings is not only due to the difference in their melting points but also due to the ease of formation of FeO because of the low C and Si contents in the steel casting melt.

View full abstract

  The behaviour of mold flow with different cross sections of gate is studied through visual observation. The melt fills smoothly into the metal mold from the bottom of the mold at a large cross sectional area of gate. In the case of cross sectional area of gate below 15mm², the fluid jets straightforward to the upper side of the mold and then returns back to lower region in the mold. The difference of alloy composition has no marke effect on filling behaviour. It is observed that filling behaviour is much influenced by the gate cross sectional area. When gate is as thin as 1 mm, mold filling is not carried out normally. The filling depends on melt velocity at the gate. Gate flow tends to change from smooth jet to wavy one at a lower Z number and Reynolds number as compared with the case of water. Clogging with solidified metal occurs during solidification at the gate when cross sectional area is small, which reduces the volume of filled metal. Behaviour of melt filling into the metal mold can be correlated with heat absorption at the gate.

View full abstract