COARSENING OF SiO₂ PARTICLES IN COPPER AND MnS INCLUSIONS IN STEEL.

A model to simulate the diffusion-controlled coarsening and dissolution kinetics of particles within a metallic matrix is formulated. The change in size distribution of particles, average radius of particles, volume fraction, average distance between particles, surface area, and matrix composition are also calculated. Kinetics do not generally obey the Lifshitz-Slyozov-Wagner theory for diffusion controlled coarsening based upon concentration profiles around isolated spheres. Calculations are on silica particles in a copper matrix and manganese sulfide inclusions in iron, with emphasis on the latter, in order to predict behavior during homogenization or soaking treatments. The effect of manganese from 0. 1 to 1. 2 wt pct on the coarsening of sulfides in a high sulfur (0. 017 wt pct) and a low sulfur (0. 003 wt pct) steel was investigated. The model predicts that manganese strongly reduces the rate of coarsening, particularly for times of ten hours or less in the temperature range 1100 to 1400 degree C. The rate of dissolution is low at temperatures greater than the solvus for manganese sulfide inclusions in austenite.