On the Microscopic Structure and Chemical or Crystalline Composition of Nonmetallic Inclusions in Steel

Abstract

The remarkably large streak seams occurred under particular operational conditions or experiments were observed to study precisely the mutual relations among their microscopic structures, chemical compositions, crystalline structures with an X-ray diffraction and polarizing microscope and by measurement of microhardness and etching grade. Most of these inclusions were artificially composed in order to identify the compositions of inclusions and to research the process of such occurrence.
(i) The physical and chemical characters of α-alumina, SiO₂, MnO, MnO-FeO, sulphide, comparatively simple silicate and aluminate were sufficiently ascertained.
(ii) Microhardness test on inclusions was easily carried out in general case and recognized to be effective for the determination of various inclusions.
(iii) Grades of etching caused by reagents on each crystalline compositions of inclusions were different respectively, but often difficult to be decided quantitatively.(iv) According to these experiments, chemical or crystalline compositions of streak seams can be nearly detected by their microscopic structure and microhardness.
(v)α-alumina inclusions were sometimes produced from the mullite in chamotte, when the deoxidation product which contained a high percentage of MnO reacted with the refractory chamotte.