On the Reactions between Non-metallic Inclusion and Matrix Metal in a Rimmed Steel

Abstract

Steel ingots are generally subjected to various heat treatments during processing to final products.
For example, those are annealed for a long time in a soaking pit prior to rolling. In this period, there is a possibility that some reactions between non-metallic inclusions and matrix around them can occur.
The reactions during annealing of ingot and slab of a rimmed steel were studied here by examining the changes in composition of inclusions and matrix by means of the electron probe microanalyser. Results obtained are as follows. 1) When the ingot was annealed at the soaking temperature for a long time, compositions of inclusions changed probably to attain the equilibrium with matrix at the temperature. The magnitude of such changes varied with the position in ingot, hence it was supposed to depend on the rates of solidification at each position. Some reactions may take place between inclusion and matrix and between components of inclusion such as oxide and sulfide. 2) In the case of slab under similar treatment, inclusions changed their shapes to spherical readily at above 1300°, and the compositions changed largely at 1100°C resulting in an increase of manganese concentration.