Abstract
In a series of the study on the nonmetallic inclusions, especially sand marks in steel, some consideration herein is made towards the origin of sand marks referring to the results of experiment which have been reported in the second to the fourth report on this subject. (Tetsu-to-Hagané 47 (1961) 11, p. 1588; 48 (1962) 7, p. 850; 47 (1961) 7, p. 907)
The main causes which presumably induce occurrence of sand marks are made clear as. follows;
(1) Erosion of refractory materials for steel ingot-making in contact with molten steel;
(2) Change of molecular species constituting nonmetallic inclusions, and decrease of fluidity of molten steel under different conditions of deoxidation or austenite-grain refining;
(3) Oxidation of molten steel by open air; and (4) oxidation of aluminium, for instance, as deocidizer and as austenite-grain refiner, that might occur together with oxidation of molten steel by air.
