Characterization of LC/HC-FeMn alloys and their melting mechanism in the molten iron

Abstract

Low density high strength steel has become an important lightweight structural material for future civilian and military vehicles due to its combination of less weight and high strength and toughness. However, due to extremely high amount of Mn content (∼25%), the fast melting of ferromanganese in molten steel is extremely important. Two grades of commercial FeMn alloy were used in this study: LC-FeMn and HC-FeMn, respectively. Compared with LC-FeMn, HC-FeMn contains more MnO and MnS inclusions. The density of HC-FeMn (6550 kg/m3) are lower than LC-FeMn (7110 kg/m3). The liquidus temperature of HC-FeMn (1389 °C) are higher than LC-FeMn (1219 °C). After being inserted into the molten iron for 6 s, an initial size of 4 mm HC-FeMn melted to be 3.1 mm, while the same size of LC-FeMn became 0.45 mm. The adding the cold ferromanganese alloy to the molten iron resulted in the formation of a solid shell on the surface. The solid shell thickness of the cold alloy reaches its maximum value after 1 s in the molten pool, 2.09 mm for LC-FeMn and 1.86 mm for HC-FeMn respectively. The solid shell was expected to melt completely within about 3 s.