亜共晶鋳鉄の凝固過程に及ぼす接種の影響

抄録

  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.