Refining Steel in the Tundish

Making the steel of continuous-cast ingots cleaner with respect to nonmetallic inclusions is one of the most important problems in ferrous metallurgy and is difficult to solve simply by means of a single out-of-furnace treatment. This article discusses steps being taken by the Magnitogorsk Metallurgical Combine to improve the refining of nonmetallic inclusions from steel, these measures involving the use of filtration diaphragms in the tundish. The diaphragms are designed so that an inert gas can be injected into a prescribed region of the tundish through a reinforcing layer located inside the concrete diaphragm. The gas forms a bubble screen on the path travelled by the nonmetallic inclusions, forcing them to rise to the surface. Test results showed the following: the quality of the steel is improved — the average rating for point segregation on metallographic sections was 1.58 with the use of a standard diaphragm and 1.36 with use of the diaphragm supplied with argon; the use of argon reduces the content of sulfides in steel cast through the experimental diaphragm by 14% and reduces the content of oxides by 17–19%.