Abstract
It is one of the problems unsolved for a long time in steel making to make a sound ingot preventing the occurrence of sand marks which are a defect in forged or rolled steels.
First of all, the nature of sand marks, namely their type, their distribution and their constituent, should be known in order to solve the problem and then the “origin” of the sand marks would be really grasped in consequence.
The authors, therefore, studied the type and the constituent of sand marks in various kinds of forged or rolled steels by optical microscopy, etching test, electron-diffraction reflection method and chemical analysis. It was recognized that there was a close relation between the type of sand marks observed by optical microscopy and its constituents, and moreover between the conditions of austenite-grain refining as well as deoxidation and the type of sand marks.
