The followings are the results of experiments on various degrees of temperature with which steelcore inserted cast iron is made. The casting temperature was set at 1350°C, 1400°C and 1450°C. The results are : —
  1. The higher the casting temperature, the greater the fuse-stick ratio.
  2. The same tendency can be applied to the adhesion strength. When the difference of pouring temperature gives noticeable effect on the adhesion strength especially in case of the pouring temperature is relatively low.
  3. In case of cores which surpass the limit of fuse stick ratio, the depth of chill becomes smaller when the casting temperature is higher.

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  The authors made some experiments to clarify the effect of moisture on molten cast iron, and secured the followings :
  1. When the air of various moisture contents were blown over cast iron at 1000°C, moisture increased the iron oxide films on the metal before melting down, so that molten cast iron was oxidized.
In consequence, the molten cast iron increased the chill tendency, total oxides and SiO₂ contents.
  2. When the air was blown into molten cast iron at 1400°C, moisture did not oxidized it remarkably.
  3. As the result of oxidation of the melt by moisture in the air before melting down, the formation of shrinkage cavity which is one of the characteristics of defects of oxidized melt is caused.
  4. Moisture in the air blasted through high temperature coke shows no remarkable change when it is compared before and after the air blasting.
  5. In cupola, a lot of moisture larger than being hitherto supposed is observed.
  The authors think that this is due to the moisture of coke and lining materials of cupola which are added to the moisture in air blast.
  The results of experiment, mentiond above, lead us to the conclusion that the moisture in the air blasted into cupola increases oxidation of the metal before melting down and, consequently, brings about bad effects on molten cast iron such as chill tendency and shrinkage cavity occurrence.

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  In order to make clear the effect of vacuum melting on cast iron melt, iron-carbon alloys of hypo- and hyper-eutectic compositions were melted at several constant temperatures for different durations under vacuum.
  The effects of vacuum melting on the natures of the melt such as gas contents, chemical compositions, features of cooling curve during solidification, microstructures after solidification etc. were studied. Results obtained were as follows :
  1) Some decreases in carbon and sulphur contents and increases in silicon and phosphorus were observed by vacuum melting. Oxygen and nitrogen contents decreased as low as about 5 p. p. m. in relatively short time, but the further decrease could not be detected by the present gas analysis equipment.
  2) The most common microstructure of the vacuum melted samples was that with nne eutectic graphites in pearlitic and ferritic matrix and carbide network in the boundary of eutectic cells. Special microstructures such as with nodular graphite or ledeburitic one with acicular carbide were often observed in samples vacuum melted at elevated temperature for long time.
  3) The microstructure of vacuum melted samples varied differently depending upon the melting temperature, carbon content of the melt and or the degree of evacuation.
  4) From the cooling-curve data, the degrees of supercooling in austenite-graphite and austenite-carbide eutectic solidification were discussed.

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  There were many investgations on magnesium-treated cast irons, but the arguments were in their solidification processes. In the present paper, the investgations were carried out on the solidification processes of the magnesium-treated Fe-C and Fe-C-Si alloys with different degrees of carbon saturation were discussed. Cast irons having carbon saturation degrees of 0.47∼1.12 were made from the electrolytic iron, the electrode graphite and ferrosilicon containing 75% of Si. Magnesium alloys added were Ni-Cu-Mg, Fe-Si-Mg and Cu-Mg alloys composed from pure metals. 40 grs. of each iron was melted in a Tammann tube in a silit furnace and was treated with magnesium alloy and furnace-cooled while the cooling curve was plotting. At any point of the cooling curve, the specimen was quenched into water and the microstructure was observed. The specimen quenched at each step of cooling showed the structure developed to the time which would show the process of the solidification.
    From the experiments mentioned above, the following evidences were observed.
  1) There are four types on the formation of nodular graphite in magnesium-treated cast iron ;
    I. The separation from the melt as primary graphite.
    II. The separation from the melt on the dendrites of the primary austeinite and is enclosed in the followed austenite.
    III. The separation from the spheroidal austenite which is supersaturated with carbon.
    IV. The separation from the supercooled primary austenite dendrite.
  2) The I-process takes place in hyper-eutectic cast iron at the pro-eutectic temperature, the II-process in the hyper-eutectic and slightly hypo-eutectic cast iron below the eutectic temperature, the III-process in slightly hypo-eutectic cast iron under the eutectic temperature after the II-prccess, and the IV-process in the hypo-eutectic cast iron with low degrees of carbon saturation at the end of the solidification process.
  3) Inoculation of silicon promotes the I and II-processes, accordingly the increase of nodular numbers by inoculation is more remarkable in the iron with higher carbon saturation degree. For slightly hypo-eutectic cast iron, the inoculation of silicon promotes the II-process and reduces III-process, and the rapid cooling promotes the III-process and reduces the II-process on the contrary.
  4) The III-process may be replaced with the ledeburite formation when the silicon content is low, and with the formation of quasiflake graphite when magnesium is added insufficiently. Conequently, the spherodization degree of graphite may be lowest in the slightly hypo-eutectic cast iron, and the degree may be improved by inoculation of silicon.
  5) The process of ferrite and pearlite formation in the magnesium-treated cast iron is not so different as that of the flake graphite one, but the austenite around quasi-flake graphite is easier to form ferrite than that around nodular graphite, and for normal flake graphite cast iron, ferrite is hardest to be formed.

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  Good effects can be observed in melting some sorts of Ti containing pig iron by cupola.
  1) In case of melting the pig iron containing more than 0.17 per cent Ti, net work and eutectic structures of graphite appears.
  2) Dendritic austenite is seen in the microstructure and, ferrite and pearlite are appeared in its matrix.
  3) Although carbon and silicon contents are high, the mechanical properties such as tensile and bending strength are much greater than those of ordinally cast iron.
  4) The appearance of such a net work mentioned above differs by the melting time. Such structure can not be obtained in the first melt, even the pig contains Ti. However, it is obtained gradually with the elapse of melting time of cupola.
  5) The cooling curve obtained by thermal analysis shows that super cooling is occurred when Ti content is high. It is supposed that most of Ti exists in the form of TiC in molten iron.

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