Swedish white p'g iron was first used as the sample. It was melted in the nitrogen atomosphere at every temperature up to 1, 450°C, and the graphite content of the melt was observed. From numerous experimental results, the author introduced the following theory for explaining the variation of graphite content with respect to the melting temperature.
The reduction of oxides in the sample which hinder the graphitization by its carbon, will promote the graphitization. The carbonmonoxide thus evolved by the reduction will also directly promote the graphitization and by expelling such gases as N
2 or H
2 which hinder the graphitization from the melt, will indircctly promote it.
Some experiments were made to confirm this theory. The author carried out also the same experiment with samples of Swedish white iron adding each element. He found that a marked increase of graphite content of the melt at a temperature range of 1, 400-1, 450°C, occured only in both the samples of Swedish white iron with and without addition of silicon.
In the case of the samples containing each element which forms a stable carbide or makes pearlite stable, the variation of graphite content with respect to the temperature is in a considerably less extent.
Each sample containing 1%Cr, 4%W and 4%Mr, showed a critical melting temperature of about 1, 200°C, below which the melt became completely white but above which it became completely gray. The author c nfirmed these phenomena to be due to the chilling effect of oxygen.
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