鋳鉄の黒鉛球状化に及ぼすチタンの影響および石灰窒素添加の効果

抄録

  In order to examine the influence of titanium on the spheroidization of graphite in cast iron, the detrimental critical content of titanium was determined by the addition of 0∼1.5% of titanium to molten metal with 3.51% carbon and 2.70% silicon. 2% of CaCN₂ was added to decrease any unfavorable effect of titanium on the graphite spheroidization before Mg treatment. The effects of cooling rate on the graphite spheroidization and on the matrix were also discussed.
 The results obtained were as follows:
  1) The detrimental critical content of titanium on the graphite spheroidization was about 0.20%, but it increased to about 0.43% by addition of 2% of CaCN₂.
  2) The increase of insoluble nitrogen in HCl was negligible even when CaCN₂ was added. This was due to the formation of TiN which floated on the surface of molten metal.
  3) The number of graphite nodules in cast iron increased with the addition of CaCN₂.
  4) The existence of TiN was not detrimental for graphite spheroidization and the formation of TiC was also not detrimental up to 0.24% titanium.
  5) TiN and TiC were randomly distributed in the matrix, but the gravity segregation was partially found.
  6) The increase of cooling rate of molten metal decreases the unfavourable effect of titanium and the size of titanium compounds.