| Taking the panel steel of household appliances as the research object,there are problems of"unqualified phosphorus content,poor cleanliness of molten steel and surface quality defects caused by inclusions"for the panel steel of Chenggang smelting household appliances.The dephosphorization thermodynamic model,theoretical calculation,physical simulation,numerical simulation and industrial test methods are used to study the key technologies such as pre-dephosphorization of molten iron,converter steelmaking,LF and RH refining,and tundish flow field,which are vanadium-containing high-phosphorus molten iron.Smelting high clean household appliance panel steel lays the theoretical and experimental basis.The main contents of this paper are as follows:Firstly,the phosphorus distribution ratio and phosphorus capacity of eight-element V2O5 and TiO2 pre-dephosphorization slag system were studied by molecular ion coexistence theory.The influence of slag composition and temperature change on dephosphorization leaching ability of pre-dephosphorization slag was obtained.And dephosphorization mechanism is clear.The optimum pre-dephosphorization slag composition of vanadium-containing high-phosphorus molten iron was determined as follows:CaO/SiO2=3.0,FeO=25.0～30.0%,MgO=4.0～6.0%.After optimization of slag composition,the dephosphorization rate of vanadium-containing high-phosphorus iron water is 67.05～77.97%,and the end point is w[P]=0.039～0.058%.Compared with the optimized pre-phase,the dephosphorization rate is increased by 16.08%,and the end point w[P]Reduced by 0.03%to provide low-phosphorus semi-steel for the converter steelmaking process.Secondly,based on the structure of the oxygen furnace gun head of the converter steelmaking,the supersonic oxygen gun jet is studied.The parameters of the optimal oxygen gun head were determined as follows:Mach number 2.02,nozzle hole angle 14.0°,5-hole nozzle hole,throat diameter 41.3 mm,outlet diameter 54.1 mm,design flow rate 28000-33000 Nm3/h.The optimized oxygen lance structure can reduce the average[O]content,carbon oxide product and final slag w（FeO）of the converter end point by 147.7ppm,0.0002,7.48%,respectively,which improves the cleanliness and smelting effect of the initial molten steel.Thirdly,through the study of the mixing time and flow field distribution of the LF ladle bottom blowing arrangement,it is determined that the optimal bottom blowing arrangement of the ladle is 0.50R and the double hole angle is 60°.The optimized bottom blowing arrangement can promote the floating of ≥3μm inclusions and improve the removal effect.The removal rate is 71.58～78.64%,which is twice the original bottom blowing arrangement,which provides good quality molten steel for RH refining.Fourthly,the influence of the gas argon flow rate,the immersion tube insertion depth on the RH refining mixing time and the circulation flow rate was studied by physical simulation method,and the optimal RH refining process parameters were determined.The flow rate of argon blowing after the decarburization stage and decarburization was 120 Nm3/h and 110 Nm3/h,respectively,and the insertion depth of the immersion tube was 600 mm.Using the optimized RH refining process parameters,the T.O and[N]contents of the RH end point steel can be reduced by 2.2 ppm and 2.4 ppmm,respectively,and the proportion of large particle inclusions is reduced.Finally,based on the numerical simulation study of the flow field and RTD curve of different combinations of retaining wall,dam and flow stabilizer,the optimal tundish structure is determined as scheme 5,namely "double retaining wall+double retaining dam+steady flow"（height 390mm）".The new tundish structure can reduce the T.O content of the molten steel in the continuous casting process by 4.3-5.8ppm,the proportion of inclusions>3μm by 11.68%,and the number of inclusions by 0.27/cm2,indicating a new tundish structure.The research results show that the new tundish structure is beneficial to the floating and removal of inclusions,which further improves the cleanliness of molten steel.Through the research and optimization of the above key technologies,the qualification rate of household panel steel is increased to 95.77%,and the surface quality defect of cold rolled surface due to inclusions is only 4.6/10,000 tons,which improves the surface quality of cold rolled home appliance panel steel.It is indicated that the pre-dephosphorization and cleanliness key control technology of vanadium-containing high-phosphorus hot metal is feasible and effective for improving the component qualification rate and the cleanliness of molten steel.The research has formed a stable vanadium-containing high-phosphorus hot metal smelting high-clean household appliance panel steel.Production process and key technology integration. |
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