Research And Analyses On The Control Of Nozzle Blockage Of 38CrMoAl Steel

38CrMoAl steel is a kind of advanced nitriding steels.Because of its high hardness,excellent wear resistance and corrosion resistance,it is mainly used for the mechanical fabrication,aviation and space,weapon,etc.Due to the advantages of continuous casting relative to the yield and efficiency of die casting,in recent years,the domestic special steel plant has started to produce 38 CrMoAl steel with continuous casting process.Therefore,it is urgent to solve the problem of how to satisfy the stable production of high-alumina steel.In this thesis,the author used the basic principles of thermodynamics to calculate production conditions of the major inclusions in high aluminum steel,and study the reaction between the slag and steel.Based on thermodynamics calculation,the experiment was done in the MoSi₂ resistance furnace.The thesis is aimed at exploring the absorption conditions in LF refining slag with different proportions.By means of this model,scientific basis for optimizing the flow field of molten steel in the mold and the design of submerged nozzle is established.The following conclusions are derived:?1?Through the different calcium treatment processes of shuikou nodules were analyzed and found,because of the high concentration of 38 crmoal steel aluminum,calcium content in the steel can not meet the Al₂O₃ inclusions in steel degeneration of low melting point 12CaO·7Al2O3,with calcium process will generate high melting point of CaO·6Al₂O₃,easily on the inner wall of the nozzle attachment,accumulation,reduce molten steel and liquid fuel nozzle nodulation.?2?The thermodynamics calculation shows that under the smelting temperature,w?Al?=1.0%,in steel will generate priority Al₂O₃ inclusions,but in the liquid steel and slag system and refractory material of MgO style contact process,the part of the MgO style may react with steel chinalco,produces a certain amount of magnesium spinel.In 38 CrMoAl steel refining process,high aluminum content easy to restore steel refining slag of silica,resulting in alumina,fuel nozzle nodulation.?3?The melting speed by melting point Factsage software calculation and experiment,the ratio of low melting point of the molten slag:CaO=70%⁷5%,SiO₂=1%³%,Al₂O₃=6%⁸%,MgO=4%⁸%,refining slag melt temperature range1396?¹426?,hemisphere points in 1421?¹442?temperature range,complete melting temperature range of 1436?¹456?.?4?By refining the results analysis,comparison level of various factors on the number of inclusions in steel,average size,particle size and other factors,and incorporating the effect of refining slag melting and the desulfurization performance,ingredients are:CaO=70%,SiO₂=1%,Al₂O₃=6%,MgO=6%,CaF₂=5%of the refining slag refining effect is best. ?5?Using Fluent software to simulate the state and operation parameters of different water nodules and operation parameters,the results show that the flow field of molten steel in the crystallizer is optimal at 110 mm.Side hole nodular rate had the greatest influence on the flow field of molten steel in mould,with nodular degree increasing,the internal flow field in mold for inclusion floatation,mould liquid level prone to spiral,and induce slag phenomenon;The influence of the middle nodules on the flow field of the crystallizer is not obvious.