It is generally known that the precipitation hardening of Cu-Be alloy containing beryllium about 2% is due to such precipitating transformation as the formation of G. P. zone, intermediate γ'-phase and stabilized precipitate β'-phase from the supersaturated matrix-α at aging temprature about 340°C after quenching from 800°C.
  As it is considered that the grain boundary crack of Cu-Be alloy castings (20C alloy) is mainly due to the internal strain of crystal of the alloy during aging, the author carried out a study on the relationship between the crack and the strain of the alloy during aging in the case of both graphite and sand mold castings, by dilatation test, microstructure observation and X-ray diffraction analysis.
  From the result it was cleared on 20C alloy that the contraction of sand mold castings with coarse grain is larger than that of graphite mold castings with refined grain having no crack.
  This contraction during aging is due to the formation of intermediate γ'-phase which lattice constant is smaller than that of matrix α- or stabilized β'-phase. As the precipitation of stabilized β'-phase increases comparatively much in the case of the alloy with refined grain during aging, the contraction causing by the formation of intermediate γ'-phase during aging is canceled. This is the reason why the strain is small at the stage of age hardening and consequently no crack occurres in the case of the alloy with refined grain.

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  There were many investigations on the effects of the several elements on the spheroidal graphite formation in cast iron, but only a few investigation which concerned to when and how these elements affect the harmful influence to the spheroidal graphite formation, were reported. In order to clarify these points mentioned above, the following experiments were carried out.
  The base metal, composed of electrolytic iron, electrode graphite and 99% lead was melted in a high frequency induction furnace, and then was cast into an iron mould.
  The chemical composition of the alloys are shown in Table 1.
50 grams of each alloy was melted in a fused silica crucible by a siliconit resistance furnace, and Fe-Ti (42.18%) alloy was added to each alloy except the alloy number 2 and 3. At 1,350°C, each alloy was treated with Fe-Si-Mg (18.9%) alloy and furnace-cooled while the cooling curve was plotted. At the predetermined various temperature, the specimen was quenched into ice water, then the graphite nodule size and number in these specimens were measured microscopically.
  The experimental results were as follows.
  (1) The spheroidal graphite separates successively from the melt during the eutectic solidification period.
  (2) In alloy containing titanium, the vermicular graphite and the quasi-spheroidal graphite separate at the austenite grain boundary and at the same portion attached to the spherulite respectively.
  (3) In alloy containing lead, the granular graphite and the thread-like graphite precipitate at the austenite grain boundary after the eutectic solidification.
  (4) The detrimental effect on the graphite spheroidization in iron containing both titanium and lead is greater than that in iron contaning one species alone.
  (5) Lead accelerates the fading of magnesium, but titanium keeps the effect of magnesium.
  (6) The harmful elements in the spheroidal graphite cast iron are classified into the following three groups based on their detrimentation mechanism, i. e. sulphur group, titanium group and lead group.

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  It is said that nearly ninety per cent of the cause of failure of construction and machines which exposed under repeating stress is occupied by the failure due to fatigue. So the necessity to investigate the fatigue strength of materials as a standard for machine designing comes into an importance. It is also important, however, to clear other properties of the material.
  Nowadays in the region of iron castings, it is required strongly that to make clear fatigue properties of spheroidal graphite cast iron for proper application. P-S-N diagrams of spheroidal graphite cast irons were investigated in connection with other mechanical properties.
  The results of fatigue test with other mechanical test are shown in following table :
[Written in non-displayable characters.].
Moreover two kinds of P-S-N diagrams were obtained for ferritic spheroidal graphite cast irons, i. e. sample No.1 and No.2, by testing each ten specimens.

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  When molten metal is poured into a mold, the solidified layer forming on the interface between the molten metal and the mold, raises the gas pressure inside the mold during gas is generated in the mold. Such high pressure gas may breaks the solidified layer and penetrates into molten metal. Consequently small quantity of gas remainder which fails to float up to the surface results in the occurrence of blow hole or pin hole in castings.
  One of the objects of our experiment is to review the behavior of gas generated within various types of mold, particularly within self-hardening mold using dicalcium silicate and sodium silicate as its principal hardening agents.
  The test results are as follows:
  Gas generation, to a large extent, is influenced by the remainder of inactive sodium silicate. In other words, the more inactive sodium silicate remains, the more gas is generated. In addition to this, sand grain expansion and elevated pressure following temperature rise maylower the permeabitity, thus resulting in the elevation of gas pressure in mold. As sodium silicate mold is in fluid state at elevated temperature, striking lowering of permeability is observed.
  Test results are summerized below:
  1) In the case of using sodium silicate equal in molecular ratio and density, the less is sodium silicate added, the less are generated gas volume and gas pressure, with the greater permeability.
  2) In use of sodium silicate of higher molecular ratio and lower density lessens both gas volume and gas pressume. These cause to improve the permeability.
  3) The more C₂S is added, the less are the volume and gas pressure. This causes to obtain better peameability during pouring.
  4) As a result of our study on generated gas, it is concluded that this type of self-hardening mold has less deleterious effect on molten metal than CO₂ mold.

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  Blackheart malleable cast iron has the disadvantage that needs a long annealing time at high temperature.
  To shorten the annealing time various additions of alloy elements have been studied so as to promote graphitization of white cast iron.
  The authors have developed the titanium-silicon alloy, the chemical composition of which has 20.48%Ti, 66.0%Si, 9.4%Fe, 3.28%Al and 0.23%C.
  Commercial white iron used for the experiments was made by melting Kamaishi foundry pig iron for spheroidal graphite cast iron.
  It was cast into step-type sand mold and the addition of the alloy to the molten iron was made just before casting.
  The specimens were annealed by the three kinds of heat treatment cycle, which were 950°C×5h., 950°C×5h. →800-700°C×5h. and 450°C×2h. →950°C×5h. →800-700°C×5h., respectively.
  The results thus obtained were:
  (1) The increase of alloy addition promoted more mottle in cast iron structure.
  (2) The form of graphite nodule was changed from aggregated to broken snowflaky by the increase of alloy addition.
  (3) Graphite nodule number were increased remarkably by adding of alloy.
  (4) The pre-annealing treatment increased graphite nodule number and showed a ferritization tendency.

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