Process Research And Production Practice Of 120t Converter Duplex Technology For High-silicon Hot Metal Steelmaking

Faced with blast wandering of the furnace in the early production of Southern Xinjiang Bayi Iron and Steel Baicheng Limited Company and the smelting problem caused by the high silicon content in hot metal,a new technology of steelmaking which is called converter duplex process method has been developed in order to remove the silicon in an efficient way.This new technology provides a theoretical basis for the smelting process of the high silicon hot metal and combined with the process characteristics and development status,developing the operation and researches for desilication furnace,and has some important significance relating to optimize the process of duplex desilication,which benefits to smooth production and balances the ratio of iron and steel.This paper combining the production condition of melting high silicon hot metal in the steel plant of Bagang Nanjiang Company,discusses characteristics of desilication duplex method,which relate to raw material into the furnace system,slagging system,oxygen supplying system and so on.At the same time,desilication dynamics and thermodynamics condition of converter duplex method have been analyzed.This paper introduces typical technical parameter and production effect of converter duplex method by four steel and iron factories both in and abroad.And it describes the successful result,which is caused by the melting process of converter duplex method.The melting process of converter duplex method can control the quality of liquid steel well,improve converter production efficiency,and have significant effect on decreasing the cost of production process.The main conclusions are summarized as follows:(1)The injection of the raw material within the desilicification furnace requires an increasing input of the scrap steel when the initial silicon content rises in the hot metal.When the silicon content is between 4.0 and 5.0,the maximum input quantity of the scrap steel is 25 t,and the ratio of scrap steel and hot metal id 1:2.6.For the slag formation system,the content of the lime is required as follows:CaO?85%,SiO2?3.5%,S?0.04%,and the ignition loss should be limited within 7%.Moreover,the basicity of the slag should be limited between 0.6-0.8,and the multi-batch of inputs of the slag charge is required.For the oxygen supply system,if the oxygen flow is too big,the desilication time will be shorter and the silicon content in the final stage is high;however,if the oxygen flow is too small,the slag melting within the furnace will be affected as well as a weaker stirring capability,which will result in a drop in the desilication rate.When the silicon content is 1.2%?5.0%,the oxygen supply should be required between 21800m3/h?26000m3/h,and the "low-high-low" smelt pattern should be adopted in the desilication gun height.When it comes to the end of the smelting process,the terminal goal of the silicon content should be guaranteed to be less than 1.0%,the carbon content should be controlled between 2.0%-3.0%and the final slag should be limited within 15%.(2)In the decarburization furnace,the basicity of slag should be controlled between 2.8-3.0 when the less slag smelting pattern is adopted;the drop way of the gun is from high to low combined with "constant voltage changing gun" in the gun height control mode.The position of the blowing gun is charged between 1.9-2.1 m at the beginning of the blowing,and the position of the gun drops to 1.6 m after 2-3 minutes of blowing.The dropping of the gun will be gradually adjusted according to the slag condition within the furnace and the position of the gun should be dropped to 1.3 m the same as catch carbon 60 seconds before the end of the smelting process.The weight percentage of the carbon content should be guaranteed between 0.08%-0.16%while the temperature should be controlled within 1670-1720 ?.(3)The weaker bellowing of argon is required in the tapping process,and all the way argon blowing is adopted during the later process,aiming at the acquisition of the uniform hot metal content and the temperature.In a word,desilication through converter duplex process for steelmaking has many advantages such as shorter time converter blowing,low slag basicity,low temperature within the furnace as well as high desilication rate.The quality of the hot metal has been well controlled by adopting the duplex process for steelmaking,which in turn increases production efficiency of the converter and plays a great impact on the reduction of the production cost.