On the Relation between Sand Marks and Top- and Bottom-Teeming Procedures

Studies on the nonmetallic inclusions, e specially sand marks in steel. IV

Abstract

With the chromium-molybdenum steel No. 21 containing vanadium acting as the austenite grain refiner, which had been treated with calcium-silicide as deoxidizer, the authors examined top- and bottom-teeming procedures for ingot making, which had some effects on the occurrence of the sand marks.
Experimental results are as follows:
1. The occurrence tendency of the sand marks is a little more remarkable in the bottomteeming than in the top-teeming.
2. Sand marks of the complicated and the amorphous types are found in the examined steel. The rate of the occurrence of the complicated type sand marks are more remarkable than that of the amorphous type sand marks.
3. No difference are found between top- and bottom-teeming procedures in the type of the sand marks and in the nonmetallic inclusions which constitute them.
4. Oxide inclusions in the examined steel mainly consist of MnO and Si0₂ and, in general, the bottom-teemed ingot has a little more oxide inclusions than top-teemed one. In the topteemed ingot, oxide inclusions are rich in the top part of the ingot, while relatively poor in the middle and the bottom parts of it in quantity. In the bottom-teemed ingot, on the other hand, they are rich in the top and the bottom parts, but relatively poor in the middle part.
5. There is a correlation between the occurrence tendency of the sand marks and the quantities of oxide inclusions. Namely, forged or rolled steel containing many oxide inclusions has a greater possibility of the occurrence of the sand marks in comparison with forged or rolled steel which has less oxide inclusions.