THE RELATION BETWEEN THE SAND MARKS AND THE NON-METALLIC INCLUSIONS OF BEARING STEEL

The study of non-metallic inclusions-III

Abstract

In the third report, the authors studied the relation between the sand marks of steel rods corresponding to the shrinkage head of an ingot and that of the ingot itself, and also the relation between the sand mark and non-metallic inclusions, which was extracted by chemically. The sand mark was examined microscopically.
The results were briefly summarized as follows:
(1) The number of sand marks, large and small, of steel rod, which was prepared from the shrinkage head of the ingot, is numerous, but the number of sand marks of a normal steel rod, which was rolled from the ingot itself, was small.
(2) Weight of chemically extracted non-metallic inclusions at where sand marks are gathered into a certain position of steel rods was larger than that of another position of the steel rod.
(3) Generally, the weight of the chemically extracted non-metallic inclusions at the center of steel rods was larger than that at the periphery of the same steel rod.
(4) By microscopic examination, mostly, the non-metallic inclusions existed in the sand marks.
(5) Segregation sand marks, which were caused by phosphorus and sulphur, were rarely found in the high-carbon low-chromium steel rod.