HSLA steels need extremely low levels of tramp elements like P,S,H and O t.During tapping the steel is deoxidized with aluminum and in the secondary metallurgy sulphur (【 10 ppm) and hydrogen (【 1 ppm) are extracted...HSLA steels need extremely low levels of tramp elements like P,S,H and O t.During tapping the steel is deoxidized with aluminum and in the secondary metallurgy sulphur (【 10 ppm) and hydrogen (【 1 ppm) are extracted.After tank degassing the steel is strongly Ca-treated by wire feeding to form CaS instead of MnS.Non-metallic inclusions in the steel and centre segregation with MnS are sinks for hydrogen which result in HIC (Hydrogen Induced Cracking).Therefore these steels ask for excellent oxide cleanness and S-contents of 【 10 ppm.Macro inclusions of 】 50 μm are harmful for the product.These large inclusions are seldom and difficult to be detected.Small inclusions of 【 15 μm do no harm to the product.The origin of non-metallic inclusions is,roughly spoken,one third each of de-oxidation-/reoxidation products,refractory and casting powder.Slag carry-over is mainly avoided by sensitive electronic devices.Slag covers and shrouding systems of the steel stream during the transfer of metal between ladle,tundish and mold are effective to avoid reoxidation.Systems to control the flow of steel in tundish and mold favor the floatation of inclusions and their even distribution in the strand.展开更多
Based on a current coherent jet,this study proposes a supersonic combustion(SC)coherent jet in which the main oxygen jet is surrounded by a supersonic fuel gas.The characteristics of the proposed coherent jet are anal...Based on a current coherent jet,this study proposes a supersonic combustion(SC)coherent jet in which the main oxygen jet is surrounded by a supersonic fuel gas.The characteristics of the proposed coherent jet are analyzed using experimental methods and numerical simulations in the high-temperature environment of electric arc furnace(EAF)steelmaking.The SC coherent jet achieved stable combustion in the EAF steelmaking environment.The simulated combustion temperature of the supersonic shrouding methane gas was 2930 K,slightly below the theoretical combustion temperature of methane–oxygen gas.The high speed and temperature of the supersonic flame effectively weakened the interaction between the main oxygen jet and the external ambient gas,inhibiting the radial expansion of the main oxygen jet and maintaining its high speed and low turbulence over a long distance.These features improved the impact capacity of the coherent jet and strengthened the stirring intensity in the EAF bath.展开更多
The O_(2)-CaO jet with shrouding combustion flame demonstrates some advantages in quick melting and effective slag foaming by delivering lime powder deeply into the molten bath.Combining the discrete particle model an...The O_(2)-CaO jet with shrouding combustion flame demonstrates some advantages in quick melting and effective slag foaming by delivering lime powder deeply into the molten bath.Combining the discrete particle model and the eddy dissipation concept model with the detailed chemical kinetic mechanisms(GRI-Mech 3.0),computational fluid dynamics models of the O_(2)-CaO jet with different shrouding fuel mediums injection were developed.Firstly,the results of the numerical simulation were validated by the measured data of cold test for O_(2)-CaO injection.Then,the interaction between the particles and the gas jet of the O_(2)-CaO jet and the effect of shrouding fuel medium species on the fluid flow characteristics of the O_(2)-CaO jet were analyzed.Results show that the CaO particles can be effectively heated by the shrouding high-temperature combustion flame and compared with the O_(2)-CaO jet without shrouding gas,the potential core length was increased about 2.5,3.3 and 4.3 times by the shrouding flame generated from CO,CH_(4) and C_(3)H_(8).And with shrouding CH_(4) and C_(3)H_(8) injection,the CaO particles can be clustered together in a long distance,which would be helpful to improve the utilization efficiency of CaO particles.展开更多
Fine bubbles will create when the inert gas is introduced to the high rapidsteel stream within the shroud nozzle between ladle and tundish. The collision and attachment amongthe bubbles and fine inclusions will promot...Fine bubbles will create when the inert gas is introduced to the high rapidsteel stream within the shroud nozzle between ladle and tundish. The collision and attachment amongthe bubbles and fine inclusions will promote the floatation efficiency of inclusions in the tundish.The behaviors of the bubbles, such as the dispersion in shroud, coalescence and floatation intundish, are studied. The results show that the maximum sizes of the bubbles in the water and steelflow within the shroud in the length of 1.2 m are 0.70-1.44 mm and 1.53-3.16 mm respectively whenthe flow rates are 0.006-0.016 m^3/s; the terminal velocities of fine bubbles in the water andmolten steel within the tundish are 0.02-0.2 and 0.05-0.6 m/s.展开更多
文摘HSLA steels need extremely low levels of tramp elements like P,S,H and O t.During tapping the steel is deoxidized with aluminum and in the secondary metallurgy sulphur (【 10 ppm) and hydrogen (【 1 ppm) are extracted.After tank degassing the steel is strongly Ca-treated by wire feeding to form CaS instead of MnS.Non-metallic inclusions in the steel and centre segregation with MnS are sinks for hydrogen which result in HIC (Hydrogen Induced Cracking).Therefore these steels ask for excellent oxide cleanness and S-contents of 【 10 ppm.Macro inclusions of 】 50 μm are harmful for the product.These large inclusions are seldom and difficult to be detected.Small inclusions of 【 15 μm do no harm to the product.The origin of non-metallic inclusions is,roughly spoken,one third each of de-oxidation-/reoxidation products,refractory and casting powder.Slag carry-over is mainly avoided by sensitive electronic devices.Slag covers and shrouding systems of the steel stream during the transfer of metal between ladle,tundish and mold are effective to avoid reoxidation.Systems to control the flow of steel in tundish and mold favor the floatation of inclusions and their even distribution in the strand.
基金financially supported by Fundamental Research Funds for the Central Universities (No. FRF-GF18-008B)
文摘Based on a current coherent jet,this study proposes a supersonic combustion(SC)coherent jet in which the main oxygen jet is surrounded by a supersonic fuel gas.The characteristics of the proposed coherent jet are analyzed using experimental methods and numerical simulations in the high-temperature environment of electric arc furnace(EAF)steelmaking.The SC coherent jet achieved stable combustion in the EAF steelmaking environment.The simulated combustion temperature of the supersonic shrouding methane gas was 2930 K,slightly below the theoretical combustion temperature of methane–oxygen gas.The high speed and temperature of the supersonic flame effectively weakened the interaction between the main oxygen jet and the external ambient gas,inhibiting the radial expansion of the main oxygen jet and maintaining its high speed and low turbulence over a long distance.These features improved the impact capacity of the coherent jet and strengthened the stirring intensity in the EAF bath.
基金the Fundamental Research Funds for the Central Universities(FRF-TP-19-031A1)the China Post Postdoctoral Science Foundation(2020T130053,2019M660459)the National Natural Science Foundation of China(No.51734003).
文摘The O_(2)-CaO jet with shrouding combustion flame demonstrates some advantages in quick melting and effective slag foaming by delivering lime powder deeply into the molten bath.Combining the discrete particle model and the eddy dissipation concept model with the detailed chemical kinetic mechanisms(GRI-Mech 3.0),computational fluid dynamics models of the O_(2)-CaO jet with different shrouding fuel mediums injection were developed.Firstly,the results of the numerical simulation were validated by the measured data of cold test for O_(2)-CaO injection.Then,the interaction between the particles and the gas jet of the O_(2)-CaO jet and the effect of shrouding fuel medium species on the fluid flow characteristics of the O_(2)-CaO jet were analyzed.Results show that the CaO particles can be effectively heated by the shrouding high-temperature combustion flame and compared with the O_(2)-CaO jet without shrouding gas,the potential core length was increased about 2.5,3.3 and 4.3 times by the shrouding flame generated from CO,CH_(4) and C_(3)H_(8).And with shrouding CH_(4) and C_(3)H_(8) injection,the CaO particles can be clustered together in a long distance,which would be helpful to improve the utilization efficiency of CaO particles.
基金The project is sponsored by the National Natural Science Foundation of China (No.50274007).
文摘Fine bubbles will create when the inert gas is introduced to the high rapidsteel stream within the shroud nozzle between ladle and tundish. The collision and attachment amongthe bubbles and fine inclusions will promote the floatation efficiency of inclusions in the tundish.The behaviors of the bubbles, such as the dispersion in shroud, coalescence and floatation intundish, are studied. The results show that the maximum sizes of the bubbles in the water and steelflow within the shroud in the length of 1.2 m are 0.70-1.44 mm and 1.53-3.16 mm respectively whenthe flow rates are 0.006-0.016 m^3/s; the terminal velocities of fine bubbles in the water andmolten steel within the tundish are 0.02-0.2 and 0.05-0.6 m/s.
