We studied Relative Härte, Reife Grad and stress released heat treatment and wear resisting property of vanadium high grade cast iron and found that these are superior to those of plain high grade cast iron. On the stress released heattreatment at 500-600°C, for 6 hour, vanadium cast iron keeps of better mechanical properties compared to those of plain cast iron.
  Vanadium cast iron is more resist to abnormal abrasion causion caused by increase of friction velocity.

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  Spheroidizing agents such as magnesium and cerium are added in the stmosphere in general making processes of graphite cast iron. These metals, however, show much melting losses since they are oxidizable, and their effects on the spheroidizing are unstable. If these metals are added in the reduced prresure, their lossed may be lowered. Since a shrinkage cavity is said to have a concern in gasses included in the melt, if the shrinkage is reduced by degassing the melt, the large feeders of spheroidal graphite cast iron as hitherto will no more be necessary. Though cerium is a valuable metal, it is esaier to treat than magnesium, so, if the over all yield of added cerium is improved by reduced pressure addition, cerium will stand a chance to be used in the spheroidal graphite cast iron industry again.
  Pig iron was melted in the 50 kg or 100 kg induction furnace in atmosphere, desulphurized, composition adjusted with ferro-manganese and ferro-silicon, set in the vacum apparatus, statically degassed with reduced pressure of 7 mm Hg, during which added with metalic cerium or cerium-mishmetal, and poured into the test bars and shrinkage test castings.
  Results are concluded as follows:
  1. Optimum amount of additives in the reduced pressure are 0.20 to 0.25 per cent with metalic cerium and 0.25 0.30 per cent with mishmetal. Excessive addition does not improve the strength because it disfigures the spheroidal graphite is collapsed and the free cementite appears in matrix.
  2. Since the optimum amount of additives in the atmosphere are 0.34 to 0.40 per cent with metalic cerium and 0.40 to 0.45 per cent with mishmetal, additions in the reduced pressure make savings of about 40 per cent with both additives.
  3. The time of reduced pressure degassing before adding the spheroidizing agents has very little influence on the strength, however, as it has a good effect on the solidification shrinkage, it should be as long as possible in so far as the temperature falling permits.
  4. There is an optimum range of degassing time after adding the spheroidal agents, and excessive time of degassing lowers the strength sharply due to the evaporation of cerium. However, the solidification shrinkage reduces rapidly with increased degassing time after adding the agents, so that the optimum degassing time should be selected by compromising the both effects.

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  The phosphorus segregation in eutectic cell in gray cast iron was investigated with microhard ness tester and X-ray microanalyzer, and on the basis of the results, the thenomena ocurred in revealing eutectic cell by the Stead's reagent were considered. Moreover the revealing methods of eutectic cell by the Stead's reagent in cast iron inoculated with ferro-silicon and calcium- silicide were investigated.
  The results obtained were as follow :
  1. There is a variety of microhardness values both in the inside and the boundary of a eutectic cell.
  2. There is microsegregation of phosphorus both in the inside and the boundary of a eutectic cell.
  3. It is considered that the intermittent immersion method is more suitable than the continuous immersion method for the revealing the eutectic cell.
  4. Cellnumbers in inoculated cast iron can be counted rathes easily by increasing the first continuous immersion time in the inter-mittent immersion and increasing magnification.

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  This study has been performed to seek the optimum casting plan for the green sand mould of the thin sectional ring castings, about 100mm int. dia., 4∼7.5mm thickness (tapered) and 50mm height. Sixteen flasks of test castings (two castings in each flask) were made varying the seven factors which were expected to have influences on the soundness of castings, and the defects, hardnesses and their flucuations were measured. Data were analyzed by using the L¹⁶ (2)¹⁶ type of orthogonal arrangement of experimental designs.
  Factors and levels selected were as follows:
            Factors                        Levels
    Arrangement of casting      Cope, Drag
    Directin of Gates               Rectangular, Tangential to the Castings
    Sectional Area of Gates     100mm², 40mm²
    Pouring Method                Use, No Use of the Stopper
    Vent of Mould                  Applied, Not Applied
    Moisture Content of Sand  4%, 6%
    Pouring Temperature         1,400°C, 1,350°C
  Moulds were made by a moulding machine with jolt, squeese and stripper, jolting being applied ten times each. Moulding sands were composed of 90 parts of old sand, including 5 per cent bentonite, and 10 parts of new silica sand. 1 per cent bentonite and 0.3 per cent starch were added to them.
  Iron used had a tensile strength of about 25 kg/mm² and was melted in a water-cooled cupola. Tapping temperature was about 1,500°C.
  Pin holes and sand scab inclusions appeared in the test castings. Their number and size were measured on the internal surface of the ring machined by 0.8mm. Rock well C hardnesses were obtained at 16 points on the both ends and the middle section of the ring. Means and standard deviations of hardness on each surface were calculated, stress being put on the data about the thinner section end.
  Analysis of the data by means of the experimental design showed that the pouring temperature gave the strongest influence to the soundness of castings, and the effects of the direction of gates and the arrangement of castings came second.
  Poring temperature effected the pin holes and the hardnesses at the thinner section end and the middle section. Pin holes and hardnesses increased with low temperature pouring. The end sections were chilled in some cases. The direction of gates had a concern in the fluctuation of the hardnesses of thinner section end, gates directed tangential to the castings made the fluctuation smaller. Whether the castings are put in the drag or cope gave contrary results by the interaction with other factors, however, putting in the drag showed rather better results.
  The stopper had more or less concern in the sand inclusions defects, that is, a rapid pouring by the use of the stopper caused many sand inclusions. But as the contribution rate of error was large in the analysis of the data for the sand inclusions, it was considered there were effects of factors which were not included in the data of this experiment, for example a strength of moulding sand.
  Effects of other factors, that is, the sectional area of gate, the vent of mould and the moisture of moulding sand were little recognized.

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  A Ce-misch metal was used as an adding reagent of the rare earth metal, and the yield of rare earth, the porosity of cast steel and the desulphrization effect of rare earth were investiged in a range of 0 to 0.3% addition.
  The results obtained may be summarized as follows :
  1. The influence of predeoxidation by Al on yield of rare earth was not recognized.
  The yield of rare earth in case of ladle addition was higher than that of before-tapping addition.
  2. The porosity decreased in proportion to the content of rare earth, but Al was found to be more effective that the rare earth for the prevention of porosity
  3. When the sulphur content of steel scrap used was about 0.02%, the desulphurization effect due to the rare earth was not observed.

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