Formation, evolution and remove behavior of manganese-containing inclusions in medium/high manganese steels

Abstract

The effect of manganese content, aluminium content, top slag and stirring on manganese-containing inclusions characteristics was investigated by laboratory thermal experiments and precipitation thermodynamics calculation. The results indicated that the types of manganese-containing inclusions in manganese steel were mainly single MnS, MnS–Al2O3, MnS–TiN and MnS–Al2O3–TiN complex inclusions. The morphology of manganese-containing inclusions was transformed from spherical and ellipsoidal to polyhedral as result of manganese content increased, which is attributed to large solidus-liquidus phase difference of high manganese steel, promoting the formation of type III MnS. It is also found that the manganese-containing inclusions shows irregular morphology with clear angularities after addition of aluminium, which was determined by both formation of flaky AlN and type III MnS with polygonal caused by increased of activity coefficient of S and the surface tension of molten steel. Furthermore, the manganese-containing inclusions in manganese steel is considered MnS–MnO type with top salg, in which patchy or multipoint shape MnS is embedded on the surface of oxide. The force field analysis in induction stirring demonstrated that the inclusion particles are removed by top slag and refractory adsorption under the action of strong electromagnetic force and buoyancy. This work provides an improved understanding for the controlling and removing of manganese-containing inclusions in high quality medium/high manganese steel.

Keywords

• Manganese-containing inclusions
• Manganese content
• Addition of aluminium
• Top slag
• Inclusion removal