Nodularization of Graphite in Cast Iron by the Addition of Ce, Y, La, Ti and Zr

Abstract

The present investigation is concerned with nodularization of graphite by the addition of elements such as Ce, Y, La, Ti and Zr, all of which have the distinctive feature to absorb a very large amount of hydrogen at room temperature and to liberate it when the temperature is raised.
The results in the present work are summarized as follows:
(1) The degree of nodularization depended mainly on absorbed hydrogen contents in Ce, Y, La, Ti and Zr.
(2) When Ce, Y and La containing a large amount of hydrogen are immersed into molten metal, fine bubbles of hydrogen about 10 μ in size are evolved.
(3) The addition of so-called sub versive elements like Ti and Zr which have absorbed a large amount of hydrogen also leads to the formation of nodular graphite.
(4) The nodularization of graphite by the addition of Ce, Y, La, Ti or Zr may be due mainly to the precipitation of carbon atoms into the bubbles of hydrogen, whereas these elements themselves have no nodularizing effect or rather have denodularizing effect.
The results in the present work were compared with those by other investigators and it was clarified that these could be explained most reasonably based upon the gas-bubble theory among current hypotheses for graphite nodularization.