The process of solidification and graphite formation at a given slow rate of cooling was investigated on the commercial hypo-eutectic, inoculated cast irons by calcium-silicon and not inoculated ones. The cooling curves were determined and samples quenched at various stages during solidification were examined microscopically. The results obtained are as follows.
  (1) Addition of calcium-silicon showed a slight tendency to form the more uniform distribution of primary anstnite particles.
  (2) On the cooling curves, inoculated irons show the less degree of undercoolinga nd more rapid recalescence than uninoculated irons. That is to say, inoculation increase the rate of occurence and growth of eutectic cells.
  (3) Solicenters centers of eutectic cells are initiated in narrow parts between primary austenite particles. In the corresponding parts of inoculated irons quenched from the temperature approximately 40°C higher than entectic arrest, a few mesh graphite-austenite eutectic spots, which were apparently considered to be formed by short time during quench, were recognized.
  (4) Number of eutectic cells are increased by inoculation. The occurence of eutectic cells are confined in the early stage of eutectic reaction. The dominating reaction in middle and later stage of eutectic reaction is the growth of eutectic cells previously appeared.
  (5) Inoculation by calcium-silicon changes the mode of development of eutectic cell and graphite remarkably. In inoculated irons quenched from early and middle stages of eutectic reaction, graphite flakes of random orientation were recognized along the central ribs of willow-leaf type anstenite. In the corresponding specimens of uninoculated irons, the willow-leaf anstenites were very few and mossy graphite or fine undercooled graphite were recognized.
  (6) Specimens cooled to room temperature in furnace showed uniform distribution of flaky graphite (type A) in inoculated irons and undercooled graphite (type D and E) in uninoculated irons.
  (7) The microscopic examination under plane-polarized light showed that calcium-silicon inoculation decreased the optical anisotropy of sulphide in clusions and changed the elongated type of manganese sulphide to fine compact type. Furthermore, microscopic examination of sulphur prints showed that degree of sulphide segregation to the boundary of eutectic cell was decreased by inoculation. These phenomena were attibuted to decrease of ferrous sulphite and some oxide in sulphide inclusions by inoculation from the consideration on the several diagrams of MnS-FeS etc.

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  As to the Influence of the melting condition —superheating and inoculation with ferro-silicon— on the graphitization and the casting structure of white cast iron, the present work has been performed for a malleable iron for the purpose of confirmation of the results obtained in the previous work. The present work which gave results similar to those reported previously showed that the rate of first stage graphitization became greater with less amounts of iron oxide and nitrogen, and that the casting structure became finer with more amount of silica. Effects of the superheating and the inoculation on the annealability and the structure are illustrated. The melting at the temperature between 1400 and 1450°C has a tendency to increase the amounts of iron oxide and silica. The inoculation with ferro-silicon decreases the amounts of iron oxide, silica and nitrogen.

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  Through metallographic examination and measurements of expansion-time curves, the S-curves of 0.5%Mo-1.4%Cu cast irons containing about 0.2% or 0.5% of chrominium, vanadium, tungsten and 0.01% of boron were determained.
  Chromium was revealed as the most effective element, which accelates the pearlite reaction yet retains bainite formation. By the addition of Vanadium, the S-curve showing the begining and ending of the transformation moved to the left in pearlite, but moved to the right in lower bainite range, and fine bainitic structure was formed. Tungsten showed a tendency to retard the transformation in the ranges of both pearlite and bainite. Boron addition showed hawever, almost no effect for the rate of isothermal transformation. When iron containing carbide forming elements was austenized at high temperature, the isothermal pearlite reaction was retarded slightly, and also the bainite reaction remarkably restrained.

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    In the preceding report, we clarified that the high phophorus brake shoes, containing 0.7% of phosphorus had a superior characteristic as the brake shoe castings for railway cars. To improve the wear resistance of the brake shoes, lately we investigated the high phosphorus brake shoes added Alloying Elements of Cu-Cr, and came to the following conclusion.
  (1) The wear of the so-called “Cu-Cr-P brake shoes” is less than that of “0.7%P brake shoes”.
  (2) The variation of Cu-Cr content has not so remarkable effect on the wear resistance of brake shoes in the experiments, but generally for the more Cr content the less wear of brake shoes is observed.
  (3) Slightly higher wear of tire is observed when the tire is combined with “Cu-Cr-P brake shoes” than the wear of tire combined with the high P brake shoes, yet the wear of tire combined with Cu-Cr-P brake shoes is considerablly less than the wear of tire combined with the low P brake shoes. Practically, the wear of tire combined with Cu-Cr-P brake shoes can be neglected.
  (4) The hardness of brake shoes increases by adding reagent and in this case the pearlite in the matrix is strengthened by adding Cu-Cr. However, any abnormal wear of tire has not been caused.

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  The generation of residual stress in bronze castings was investigated in the same methods as reported previously. The results obtained are as follow;
  1. Approximate for cooling curves of cast bars is obtained and the temperature differences in the cast frameworks composed of a center bar and two outer ones, which have different cross sectional areas, are estimated. The observed temperature differences are smaller than the estimated values by 10∼20%.
  2. The stress in the center bar, teh cross sectional area of which is larger than those of the outer ones, changes from compression to tension casting is cooled.
  3. The temperature at which teh stress in the center bar changes from compression to tension and the residual stress begins to grow shift from 650°∼600°C to 500°C as the ratio of the crosssectional areas decresses from 3.82 to1. This shift of temperature is attributed to the shift of temperature difference curves to the same direction.
  4. As the stress relaxation by plastic deformation occures at higher temperature, the compressive stress in the center bar during the cooling is less than 0.15∼0.25kg/mm², but below about 600°C the plastic deformation hardly occurs and thus the stress grows as the temperature difference decreases.

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  When an alloy solidifies, the equilibrium composition of the originating solid phase differs in general from the composition of the liquid phase. Thus, segregation may take place, and the composition of the solid phase formed at different instant differs from the bulk compositons.
  In the case of the β to α phase transformation of Nickel Aluminium Bronze cast, as well as in the solidification of solid solution, the composition of the coexisting β and α-phase must change continuously. This change requires diffusion, which at best remains incomplete in the α-phase, because the diffusion rate in α-phase are comparatively low. The resulting non-equilibrium eutectoid remains in the alloy containing 9 to 10 pct Aluminium and 5 pct each of nickel and iron.
  Theoretical analysis has been also made for the degree of segregation, which depends on factors of nucleation rate of α-phase and cooling rate. It has been shown that under slow cooling conditions significant segregation is expected if the nucleation rate of α-phase is low.

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