Abstract
As a part of the studies on the mechanism of eutectic solidification which exerts great effect on various properties of gray cast irons, the effects of carbon, silicon, manganese and sulfur on the eutectic cell number were investigated by mean of counting cells revealed clearly with the “intermittent immersion technique” which authors had found to be suitable as a method of revealing eutectic cells by the Stead's reagent.
The results obtained were as follows:
1. The effect of carbon and silicon on the cell number varied intricately with the amount of Si or C co-existing in cast iron, then the cell number varied with the variation of carbon equivalent (C.E%=C%+1⁄(3)Si%): The cell number increased slightly with increasing from 3.5% to 3.9%C.E., became to the maximum at about 3.9%C.E., and then decreased slightly with increasing from 3.9% to 4.3%C.E.
2. The cell number in cast irons contained 3.2%C, 2.2%Si, 0.01∼1.0% Mn, and 0.01∼0.5%S varied intricately with the amount of manganese and sulfur as showen in the preivous literatures. Then the relation amoung the cell number in these cast irons and the amount of dissolved manganese and sulfur in solution were considered. These dissolved manganese and sulfur were determined by the curve of equilibrium concentration of manganese and sulfur crystallization of mangansulfide at 1,100°C.
These results are as follows:
(1) The dissolved manganese and sulfur increases a cell number, respectivelly. The effect of sulfur on increase of the cell number is remarkably greater than the effect of manganese on it.
(2) When the amount of dissolved sulfur is below 0.03%, the cell number varies in comparatively narrower range depending on the respective effect of dissolved manganese and sulfur on the cell number.
(3) When the amount of dissolved sulfur is over 0.03%, the cell number increases proportionally with increasing the amount of dissolved sulfur.
(4) Only in the case of cast iron containing over 0.03% disolved sulfur, the cell number of the cast iron present of mangansulflide can increase slightly, regardless the amount of mangansulfide in it.
3. In cast irons of the same amount of each dissolved manganese and sulfur, the carbon content increasing from 3.2% to 3.6% decreases the cell number when the amount of dissolved sulfur is <0.05%. On the other hand, it does not vary the cell number when the amount of dissolved sulfur is >0.05%.
