Sand mold bonded with dicalcium silicate and sodiun silicate has more advantages than other sand molds, but there is a disadvantage in that the mold bonded by them has the great tendency of sand burning on the surface of steel casting. The interrelationship between sintering point or refractoriness and sand burning have already been studied, so a study was conducted to clarify how the sintering point or refractoriness is influenced by the amount of commercial dicalcium silicate, sodium silicate or mol-ratio of sodium silicate added to silica sand. Dicalcium silicate ranged from 0 to 5.0% and sodium silicate ranged from 3.0 to 7.0% with mol-ratio of 2.7 and 3.2. As sand grain flineness influences the sintering point, sand grains of a unit mesh ranging from 35 to 150 mesh were used in the sintering test.
  The more the dicalcium silicate was added, the higher the sintering point became which later dropped. The highest sintering points were proved within the range from 0.5 to 0.8% dicalcium silicate. In the refracoriness test, there was roughly the same tendency. The more the sodium silicate was added, the higher the sintering point became which late dropped. The highest sintering points were proved within the range from 5.0 to 6.0% sodium silicate. The higher the mol-ratio of sodium silicate was, the higher the sintering point or refractoriness. The finer the grain size of sand, the higher was the sintering point. Hence, the burnig on the surface of sttel casting seems to be improved by using finer grains with addition of dicalcium silicate ranging from 0.5 to 0.8% and sodium silicate ranging from 5.0 to 6.0%.

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  Solid-state bonding using dynamic superplasticity is mainly dependent on extremely accelerated diffusion rates. Phenomenologically speaking, at the bonding interface, rotation, dispersion and/or recrystallization of grains is taking place, which might lead the flaky graphite to slide through the original interface. Based on these observations the authors have proposed a sort of crystal-structural pseudo-liquid model for dynamic superplasticity bonding.

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  The corrosion rate of Fe-Fe₃C alloys containing 0.18-4.8% carbon was measured in oxygen-free 0.01N H₂SO₄ solution at 20°C by linear polarization technique. Maximum corrosion was found to occur at about 3% carbon. This corresponds to the most favorable ratio of area of the cathode, Fe₃C against the anode, ferrite. The morphology of Fe₃C has a great influence in this respect, which was confirmed by the corrosion rate measurements of the three steels of hypo-eutectoid, eutectoid and hyper-eutectoid heat-treated in five different ways. The specimens tempered at 400°C and 600°C with very fine particles of carbide both strongly corroded as compared with the annealed or spheroidized specimens. The influence of the size and shape of Fe₃C upon the corrosion rate is much greater than its quantity.
  The cathodic Tafel constants β_c are considerably larger than the anodic Tafel constants β_a through the whole range of the carbon content tested; the corrosion of reaction Fe-Fe₃C alloys in oxygen-free diluted H₂SO₄ solution is, in general, controlled cathodically. A large corrosion rate for white cast irons is related with a high value of exchange current density for hydrogen.

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  The dispersion of metallic fume generated from molten 80%Cu-10%Sn-10%Pb alloy is effectively suppressed by the double layer covering on the molten metal surface with two kinds of mineral powder. The suppression efficiencies are about 90% for lead fume, 70% for copper and tin fume. The tensile strength value, elongation value and hardness value of the alloy obtained from the suppression-treated melt are 25.8-28.1kg/mm², 29.4-33.5% and 71.0-89.7 H_B respectively. That is, the quality of alloy is not affected by the surface covering treatment.

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  The value of surface tension of the molten ternary system of SiO₂-CaO-Al₂O₃ was 550-610dyne/cm in the temperature range of 1,350-1,450°C. Comparing the value obtained in this work with the data by Popel and Esin almost in the same slag composition, our data was a little higher. Surface tension of molten slags decreased by the addition of Na₂O. Though the temperature dependency was not so extensive, the surface tension of this system decreased gradually by raising the temperature. When Na₂SiF₆ was added into the slag, fluorine is considered to vaporize as SiF₄ from the surface of molten slag and most of them is lost. Therefore, the effect of Na₂SiF₆ addition on the surface tension of molten slags was similar to the effect of Na₂O added singly.

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  Because the size of the eutectic colony, and the shape and distribution of the eutectic carbide closely influence the properties of high chromium cast iron, it is necessary to express the eutectic structure quantitatively. Hypo·eutectic, eutectic and hyper-eutectic high chromium cast irons containing about 15 to 40%Cr were cast into 30φ×70mm exothermic molds on a watercooled copper chill plate, and solidified unidirectionally. The morphology of the eutectic structure could be expressed quantitatively by both the colony size and the carbide spacing, even when it showed some defferences in appearance according to the chemical compositions.
  The eutectic colony size (E_W) was given by the following equation as a function of the eutectic growth rate (R_E).
    E_E=A·R_E^-0.72 (A>0, E_W; μ. R_E; mm/min)
A, a constant depending on the chemical composition of the specimen, was smallest at 30%Cr, therefore the value E_E became smallest. The value of hypo-eutectic irons was much smaller than those of eutectic and hypereutectic irons when it was compared at around the same chromium level. The coarseness ofeutectic structure was determined by both the carbide spacing at the colony center (F??) and at thecolony boundary (F??). Each value, F?? and F?? increased in proportion to R_E^-1/2. The value F?? was little affected by the chemical composition of the specimen. On the other hand, the value F?? was affected greatly by the Cr and C content, and it was smallest at 30%Cr at the same eutectic ratio. Consequently the cutectic carbides existing in the eutectic colonies of 30%Cr irons were found to be most finely dispersed.

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