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

Studies on the nonmetallic inclusions, especially sand marks in steel-III

Abstract

With the chromium-molybdenum steel No.21 containing aluminum acting as the deoxidizer and the austenite grain refiner, the authors examined into the top-and bottom-teeming procedures for ingot making, which had some effects on the occurrence tendency of the sand marks.
The results are as follows:
1. The occurrence tendency of the sand marks is a little more remarkable in the topteeming than in the bottom-teeming.
2. Sand marks of the complicated, the crystalline and the amorphous types are found in the examined steel. The rate of the occurrence of the sand marks is 60 to 70% for the complicated type, 26 to 30% for the crystalline type and 8 to 10% for the amorphous type.
3. No difference between top-and bottom-teeming procedures in the type of the sand marks and in the nonmetallic inclusions which constitute them has been found.
4. Oxide inclusions in the examined steel mainly consist of Al₂O₃ and, in general, the top-teemed ingot has a little more oxide inclusions than bottom-teemed one. In the topteemed ingot, oxide inclusions are rich in the top part of the ingot and relatively poor inthe middle and the bottom parts of it. In the bottom-teemed ingot, on the other hand, they are the richest in the bottom part and the next in the top parts in quantity, and 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 great possibility of the occurrence of the sand marks in comparison with forged or rolled steel which has less oxide inclusions.