Research On RH Key Technology Of Ultra-Low Carbon Steel Based On Coordinated Control Of Carbon,Oxygen And Temperature

With the development of the automobile industry,China has become the world’s first automobile producer and consumer.Ultra-low carbon(ULC)IF steel is the deep-drawn steel,which is the main material for complex stamping parts of automobiles.It requires not only high cleanliness,but also low carbon content in the steel.Smelting production process has a great impact on the quality of ULC steel,and the coordinated control of carbon,oxygen and temperature is the key to the production of high quality ULC steel.For the ULC steel production,this paper combined with the actual production of ULC steel,several key issues were expounded:RH rapid decarburization technology,carbon powder pre-deoxidation process under low carbon-high oxygen condition,double slag deoxidation process under high carbon-low oxygen condition,chemical up temperature process under low molten steel temperature condition and reasonable temperature control mode of ULC steel production.These researches provided a basis for the production of high quality ULC steel.In order to reduce the activity of oxygen content at the end of RH decarburization and the inclusions in molten steel under the condition of low carbon-high oxygen,a pre-doxidation process with carbon powder addition(CPA)was proposed.The main products of the pre-deoxidation process were CO and CO2,and the gas generated under vacuum conditions would be discharged in the vacuum chamber to reduce the oxygen concentration of the molten steel to achieve pollution-free deoxidation.The carbon addition controls in vacuum process were determined by industrial experiments.The reaction behaviors of carbon and oxygen in the pre-deoxidation process were analyzed.And the carbon-oxygen reaction model in RH was established.CPA process significantly reduced the activity oxygen at the end of decarburization,aluminum consumption and slab total oxygen.In order to make full use of the oxygen in slag,the double slag deoxidation(DSD)process was proposed.Through the thermodynamic calculation,laboratory tests and industrial experiments,the inclusion control and decarburization reaction for DSD process and conventional process were compared.The effect of slag content on the carbon and oxygen reaction behaviors with different(FeO)in slag during the decarburization reaction were analyzed.And the activity oxygen prediction model at the end RH decarburization was established.Under the coordinated control of carbon,oxygen and temperature,the chemical up temperature process was studied,the suitable aluminum oxidation heating-up temperature process control was determined.The factors affecting the temperature of the decarburization reaction process were analyzed,which provided a basis for reasonable temperature control model for ULC steel production.