Studying On Carbonization Regularity Of Ultra-low Carbon Steel By Low Carbon Raw Materials

Recently, ultra-low carbon steel (C<50ppm) has achieved rapid development, itscomposition features are: low carbon content, microalloyed, purity. Its production processis complex and strict manufacturing technology. Due to the smelting and castingtechnology conditions, the production of ultra-low carbon steel faced severe challenges inmany aspects. Some raw materials containing carbon are used from the end of RH tocasting slab what may impact the carbon content of liquid steel. The carbonization of ultra-low carbon steel is one of the problem to be solved in metallurgical industry.In this paper, the carbonization of ultra-low carbon steel from the end of RH to castingslab by some low carbon raw materials was study through the production of MA seriesautomobile plate in a steel mill. The following conclusions can be obtained：(1) Free carbon in carbon-containing ladle brick, tundish coatings, tundish coveringflux and submerged nozzle may cause liquid steel carbureting. In order to reduce theincrease of carbon in liquid steel, free carbon in this raw materials should be cut down.(2) The carbonization of the fist ladle in every cast is serious, because tundishcovering is used too much for the fist ladle.(3) Tundish covering is drawn into liquid by the liquid level fluctuation andtemperature fluctuations at the beginning of each ladle.(4) Rich carbon layer of mold powder is the main cause of carbonization in mold.Rich carbon layer may be drawn into meniscus of liquid steel in mold under unsteady stateoperation.