In Situ Observation of Collision Between Exogenous and Endogenous Inclusions on Steel Melts for Active Steel Filtration

Abstract

Investigations at the high-temperature confocal laser scanning microscope (HT-CLSM) allow observing the interaction of non-metallic particles in terms of potential filter material with endogenous particles of molten steel in the high-temperature range. The respective particle velocities are determined from the particle movements and conclusions are drawn about the attractive forces of the particles. The interactions of exogenous Al2O3 particles, MgO and MgAl2O4 spinel particles, and CA6 calcium aluminate particles with endogenous constituents of molten steel X15CrNiSi25-20 are analyzed in the present work. Accompanying experiments were performed in a heating microscope on the interaction between steel and MgO and steel and CA6. Scanning electron microscopy SEM/EDX/EBSD studies reveal not only the interactions of the non-metallic inclusions with each other, but also reactions of the molten steel with the exogenous particles that affect the agglomeration behavior. While exogenous and endogenous Al2O3 particles exhibit high attractive forces and almost no react with the molten steel, a liquid reaction layer forms around the magnesia particles, which leads to a reduction of the attractive forces. After dissolution of the reaction layer, the attractive forces increase. Spinel particles are surrounded by a strong meniscus in the observed steel melt. Endogenous particles moving toward the spinel do not adhere to the particle. Reactions were also observed when CA6 particles came into contact with molten steel. In this process, the calcium aluminate is depleted of calcium. Only loose connections of the exogenous Ca-depleted CA6 with endogenous Al2O3 particles have been detected.