Abstract
In the forth report, the authors studied the defects of the surface of ingot section, and examined whether these defects had connection with sand marks of the steel rod or not.
The results are briefly summarized as follows:
(1) Ingot defects are not changed by soaking, but analytical sands amount are changed.
(2) Generally, the part of chill crystals and columnar crystals of ingots have few defects, but free crystals on outside have many large defects, and there are many small defects in inner free crystals. These defects are the non-metallic inclusions. There are many cavities in the center of the ingot, of which length is long and diameter is small.
(3) The clearness of ingot is not always proportional to the number of sand marks of the steel rod.
(4) There are some large non-metallic inclusions in the free crystal on outside of ingots and these defects are elongated in the course of rolling and grow up as sand marks of the steel rod.
