INFLUENCE OF THE CHEMICAL COMPOSITION OF CAST STEEL ON HOT-TEARING TENDENCY (III)

Abstract

In the preceding two reports under the same heading as this, (Tetsu-to-Hagané Vol. 40 (1954) p. 979, Vol. 43 (1957) p. 1293) the author described the influence of C, Si, Mn, P, S, Cu and Al on hot-tearing tendency of cast steel. In this last report he describes the influence of Ti, Sn, As, Sb, Bi, Pb, O, H and N, and finally gives a summary of the whole series.
The results are briefly summarized as follows:
(1) Titanium has little effect on hot-tearng tendency of low sulphur steel, but it has the effect of increasing resistance to hot-tearing of high sulphur steel. It will be more economical and effective to use titanium together with aluminium than to use titanium separately.
(2) Tin has a very bad effect on hot-tearing tendency of such steel that shows good resistance to hot-tearing before addition of tin. Addition of 0.1% tin is found to be clearly harmful.
(3) Arsenic has a similar effect as tin;
0.1% arsenic is found to be clearly harmful.
(4) Antinomy has an even more harmful effect than tin or arsenic.
(5) Bismuth too has a clearly bad effect on hot-tearing tendency of cast steel, though it is known that little or no bismuth is soluble in liquid iron.
(6) Lead is found to have no effect on hot-tearing tendency of cast steel, and this may come from the fact that lead is not soluble in liquid iron.
(7) Oxygen in steel has no direct effect upon hot-tearing tendency provided that oxygen content is not larger than usual value found in steel before deoxidation with silicon.
However, it is conceivable that oxygen gives harm indirectly to resistance of high sulphur steel to hot-tearing, because oxygen causes loss of silicon and aluminium which reduce the hot-tearing caused by sulphur.
(8) Bubbling water vapour through melt of steel is found to have little effect on hot-tearing tendency. This means that hydrogen too has little effect.
(9) Nitrogen in steel seems to have little effect on hot-tearing tendency.