Research On The Mechanism Of Ultrafine Iron Powder Prepared By Low Temperature Reduction

With the rapid development of the progress of the society and economy,people’s demand for quality of life is gradually improving,so it puts forward higher requirements on living environment.For nearly 10 years,the competition in the steel market has become more and more fierce,the disadvantages of blast furnace ironmaking and its pollution situation is more and more serious,which lead to countries have been seeking and test new ironmaking process,to promote the non-blast furnace technology has been put on the topic,for non-blast furnace ironmaking technology research and unprecedented active.This paper mainly studied the low temperature reduction micro of preparing nano-sized iron oxide to superfine iron powder process,this method is compared with the blast furnace,which removes the huge blast furnace and the serious pollution coking plant,not only reduce a lot of manpower and material resources,save the resources,energy,but also for the environment-friendly.The purity of ultrafine iron powder prepared by direct hydrogen reduction is high,its morphology is good,its application range is wide,in the social from all walks of life will have very good use.Firstly,the kinetics and thermodynamics of reduction of micro-nano iron oxide by hydrogen at low temperature was studied,and the feasibility of low temperature reduction reaction was analyzed.Secondly,using high energy ball mill to mill the iron oxide powder,changing the ball milling process to obtain micro-nano iron oxide powder with different particle size;Respectively under different conditions of reduction temperature,reduction time for hydrogen reduction.Finally,the particle size of iron oxide powder and reduced iron powder after ball milling was measured by laser particle size analyzer.Using scanning electron microscopy（SEM）of reduced iron powder on the microstructure observation and powder morphology analysis;By nitrogen oxygen analyzer data to compute the reduction rate of ferric oxide.The reduction mechanism and reduction characteristics of the low temperature reduction reaction and the preparation of the ultrafine iron powder under different process conditions were analyzed.The reaction of low temperature reduction of micro-nano iron oxide on the kinetics of the characteristics of the layered structure,that is,according to the model of the non-reaction core,the sequence structure of Fe₂O₃ | Fe3O4 | FexO | Fe.And the reaction is carried out step by step in thermodynamics,the first is the formation of lower oxide,and the last is iron.Through thermodynamic calculation: the reduction temperature is 300 ℃,the low temperature reduction reaction can be conducted,but the reaction is carried out slowly.The high energy ball milling method is very effective for the uniform refinement of iron oxide powder,and the iron oxide powder with different particle size can be obtained by changing the different milling processes.In this experiment,after 30 h of milling can make the iron oxide powder particle size from the original 50 μm refined to 1 μm below;At the same time,the particle size distribution of the iron oxide powder particles becomes narrow and the particle size of the iron oxide powder tends to be uniform.The higher the reduction temperature,the greater the reduction rate of iron oxide powder;Along with the reduction of the extension of time,the reduction rate of iron oxide powder is also increasing.The hydrogen flow rate in the experiment had little effect on the reduction reaction,but for the experiment to proceed and stability should be maintained at positive pressure.With the decrease of the ferric oxide powder granularity,the reduction reaction is carried out more quickly,the particle size of the reduced iron powder is slightly smaller than that of the iron oxide powder.Get the optimum process conditions of ferric oxide powder at low temperature reduction,reduction temperature is 700 ℃,the reduction time for 60 min,ferric oxide powder particle size is 0.8μm,hydrogen flow rate is 1 L/min.Under the optimum conditions,the reduction reaction is easy and thorough,and the obtained reduced iron powder is good and has high value.