Application of stereological procedures for quantitative assessment of dispersive oxide phase

Abstract

High requirements for the quality of steel concentrate on the appropriate microstructure of metal and its purity. Thus microscopic evaluation of structure is quite frequently introduced in quality control tests and it is as important as chemical analysis and mechanical tests. Hence, the importance of metallographic methods has become quite significant. Application of methods of quantitative metallography to evaluation of non-metallic inclusions content in steel helps to achieve this more correctly and objectively. Oxide inclusions in construction steel before and after calcium alloy treatment was subjected to examinations. Taking the non-metallic inclusions as a poly-dispersive arrangement of spheres an equation was used that expresses the relationship between the number of spheres per volume unit N V and mean diameter of the particles D. The number of particles in a volume unit N V was evaluated by classifing the diameters according to a geometrical progression with quotient C = 10 -0.075 . Relative volume V V and relative surface S V of oxide inclusions in steel before and after calcium treatment were calculated with the use of stereological relationships. On the basis of calculations it was found that generalised Saltykow's method proves to be very useful to assess stereological parameters of oxide inclusions. The treatment of construction steel with calcium alloys causes size reduction and increase in volume and relative surface of inclusions.