The Study On Deep Decarburization By RH-KTB Processes

With the development of science and technology, the ultra-low carbon cold rolled steel sheets(with a carbon content of less than 30 10-6) have been thoroughly used in automobile and home electric appliance industries. It is well know that the carbon content of steel has significant effect on the deep punching properties of steel that is an important index for this steel grade. To meet uninterruptedly increasing in the demand for the cold rolled steel sheets and to meet the technological demand of continuous annealing, the production of ultra-low carbon steel is increasing.With the increased demand for ultra-low carbon steel, it becomes essential to establish an effective refining process. The conventional RH(Ruhrstahl-Heraeus) processes which has been applied to produce ultra-low carbon steel occurs many problems, such as high temperature of molten steel, long time of refining in RH, high rate of inferior product. The exploitation of RH-KTB(Ruhrstahl-Heraeus-Kawasaki top blowing) processes promote progress of RH.In the RH-KTB process developed to manufacture low and ultra-low carbon steel, oxygen gas is blown onto the molten steel surface through a top lance from the top of the vacuum vessel. RH-KTB which is enabled to increase the decarburization rate, as well as raise the temperature of molten steel and adjust the composition and others from simply degassing,WISCO is one of the internal main steel companies which produce ultra-low carbon with RH-KTB processes. But in practice, it is not easy to product steadily ultra-low carbon steel.By generally study decarburization reaction mechanism and the rate equation of the decarburization reaction, analysis effect of factors on the decarburization. These factors include initial composition of liquid steel, pressure in the chamber, circulation rate of the molten steel, lifting Ar gas flowrate, inner diameter of the snorkel and the other operating factors.We provide technics on producing ultra-low carbon steel utilizing RH-KTB to WISCO. The results of three times trial indicate that the carbon content of steel can be less than 15 10-6 after refining. Scheduled purpose is reached, which proves the technics is viable.