Investigation on the Inclusions in the First Slab of Ultralow Carbon Steel

摘要

By the ways of optical microscope observation, scanning electron microscopy, the energy spectrum analysis and total oxygen content, the content change of inclusions in the first slab of ultra-low carbon Al-killed steel was investigated under the unsteady casting conditions. The result shows that the content of the inclusions in the first slab decreases progressively along the casting direction, occurs inflection point in 3m of the first slab, and then it appears to be leveling off. The content of the inclusions in 5m has fallen to its lowest level, approaching to the level of normal slabs. Microscopic inclusions are mainly aluminum deoxidizing products. The distribution of particle size under 15um is in the majority. The large inclusions over 50μm are relatively few; however, the content of the large inclusions is higher than that of normal slabs. Most of that are aluminum inclusions, which were formed by reacting between aluminum deoxidizing and slag. This was related to the entrapment of mould powder at the beginning of casting.