The wetting behavior between liquid aluminium and substrates made from industrial Al2O3 and SiC based ceramic foam filters （CFF） was investigated. The same CFF filters were also tested in plant scale filtration expe...The wetting behavior between liquid aluminium and substrates made from industrial Al2O3 and SiC based ceramic foam filters （CFF） was investigated. The same CFF filters were also tested in plant scale filtration experiments. The wetting experiment results show that the SiC based filter material is better wetted by liquid aluminium than the Al2O3 based filter material. This indicates that the improved wetting of aluminium on a filter material is an advantage for molten metal to infiltrate the filter during priming. Also, better wetting of Al-filter might increase the removal efficiency of inclusions during filtration due to better contact between filter and metal. Non-wetted inclusions are easier to be removed.展开更多
Ti-stabilized 321 stainless steel was prepared using an electric arc furnace, argon oxygen decarburization (AOD) furnace, ladle furnace (LF), and continuous casting processes. In addition, the effect of refining proce...Ti-stabilized 321 stainless steel was prepared using an electric arc furnace, argon oxygen decarburization (AOD) furnace, ladle furnace (LF), and continuous casting processes. In addition, the effect of refining process and utilization of different slags on the evolution of inclusions, titanium yield, and oxygen content was systematically investigated by experimental and thermodynamic analysis. The results reveal that the total oxygen content (TO) and inclusion density decreased during the refining process. The spherical CaO–SiO2–Al2O3–MgO inclusions existed in the 321 stainless steel after the AOD process. Moreover, prior to the Ti addition, the spherical CaO–Al2O3–MgO–SiO2 inclusions were observed during LF refining pro-cess. However, Ti addition resulted in multilayer CaO–Al2O3–MgO–TiOx inclusions. Two different samples were prepared by conventional CaO–Al2O3-based slag (Heat-1) and -TiO2-rich CaO–Al2O3-based slag (Heat-2). The statistical analysis revealed that the density of inclusions and the -TiOx content in CaO–Al2O3–MgO–TiOx inclusions found in Heat-2 sample are much lower than those in the Heat-1 sample. Furthermore, the TO content and Ti yield during the LF refining process were controlled by using -TiO2-rich calcium aluminate synthetic slag. These results were consistent with the ion–molecule coexist-ence theory and FactSage?7.2 software calculations. When -TiO2-rich CaO–Al2O3-based slag was used, the -TiO2 activity of the slag increased, and the equilibrium oxygen content significantly decreased from the AOD to LF processes. Therefore, the higher -TiO2 activity of slag and lower equilibrium oxygen content suppressed the undesirable reactions between Ti and O.展开更多
The formation of Al2O3 inclusions in liquid iron has been investigated in a resistance heated tube furnace to obtain deoxidation and reoxidation related data. The formation of inclusions during the early stages of deo...The formation of Al2O3 inclusions in liquid iron has been investigated in a resistance heated tube furnace to obtain deoxidation and reoxidation related data. The formation of inclusions during the early stages of deoxidation was simulated by bringing a piece of AI in contact for a short time with liquid Fe containing different dissolved oxygen levels. Reoxidation was studied by exposing AI containing Fe melts to a CO/CO2 atmosphere, Through modeling, an estimate of the local and time-dependent growth conditions for the inclusions can be made and linked to the inclusion characteristics.展开更多
The latest publications regarding the development of technology to control inclusion compositions focusing on MgO?Al2O3 spinel inclusions were summarized in this review article. The problems caused by spinel inclusion...The latest publications regarding the development of technology to control inclusion compositions focusing on MgO?Al2O3 spinel inclusions were summarized in this review article. The problems caused by spinel inclusions, which affect practice as well as products were shown. The formation mechanism of MgO?Al2O3 spinel inclusions is secondly explained thermodynamically from the view points of chemistries of molten steels and slag compositions. Furthermore, crystallization behaviour of spinel was introduced. Countermeasures conducted in practices and laboratories were shown along with some problems still left that should be solved in the future.展开更多
The effect of pre-melting refining slag containing different contents of Ce2O3 on the absorption and modification of Al2O3 inclusion in an Al-killed steel was investigated through the slag/steel reaction experiment at...The effect of pre-melting refining slag containing different contents of Ce2O3 on the absorption and modification of Al2O3 inclusion in an Al-killed steel was investigated through the slag/steel reaction experiment at 1600 oC.It was found that the replacement of 10 wt.% Al2O3 with Ce2O3 for 50 wt.%CaO-33 wt.%Al2O3-7 wt.%MgO-10 wt.%SiO2 refining slag promoted the slag absorption ability of alumina inclusion,which made the total oxygen content determined by infrared absorption method decrease from 100 to 25 ppm in 15 min.The Mg-Al-Ce-O type inclusion was also detected in the as-solidified samples by scanning electron microscopy（SEM）.Thermodynamic analysis indicated that the Ce2O3.Al2O3 type inclusions would be formed with the cerium content in the range of 6.9 ppb to 3.6 ppm when the content of aluminum was 0.01 wt.%.展开更多
A phase diagram was drawn through thermodynamic calculation to understand the equilibrium conditions of 2MgO · SiO2 , MgO · Al2O3 , 3Al2O3 · 2SIO2, and 2MgO·2Al2O3 · 5SiO2 formation in Mg-AI-S...A phase diagram was drawn through thermodynamic calculation to understand the equilibrium conditions of 2MgO · SiO2 , MgO · Al2O3 , 3Al2O3 · 2SIO2, and 2MgO·2Al2O3 · 5SiO2 formation in Mg-AI-Si-O system of 430 stainless steel melts at 1873 K. Further, the thermodynamic formation and transformation conditions of MgO · Al2O3 inclusion were discussed. The following results are obtained when ws, =0.26% and wo = 1.0 × 10^-5 in molten steel. The uniphase cordierite inclusion is difficult to exist stably; MgO· At203 inclusion cannot he formed in case of wAl being less than 1× 10^- 6 ; 3Al2O3 · 2SiO2 would change to MgO· Al2O3 and 2MgO · SiO2 in turn with increasing the Mg content when wAl is above 1.7× 10^- 6 ; with the formation of MgO · Al2O3 inclusion, A1 content increases with increasing Mg content when wMg is over 1. 7 × 10^- 9. For equilibrium condition and calculated steel composition, 2MgO·SiO2 inclusion would be formed ultimately and MgO · Al2O3 is almost inexistent.展开更多
Titanium alloyed steel has been widely used as automobile sheet steels, thick plate steels, and also stainless steels to improve the mechanical and chemical properties of many grade steels. Since Ti has strong affinit...Titanium alloyed steel has been widely used as automobile sheet steels, thick plate steels, and also stainless steels to improve the mechanical and chemical properties of many grade steels. Since Ti has strong affinity with oxygen, Ti is normally alloyed after Al deoxidation to keep the high yield of Ti. Therefore, Al-Ti deoxidation is one of the common and important secondary refining processes. Although the chemical stability diagram for this system has been reported by many researchers, these diagrams are inconsistent significantly each other. In the present study, the stability region of Al2TiO5 oxide was measured by equilibrating Fe-Al-Ti alloy and Al2TiO5 pellet in Al2O3 crucible at 1873 K. However, inclusions in metal after equilibration were Ti-containing Al2O3 or Al-containing TiOx. The precise phase diagrams and related thermodynamic data for the Al2O3-TiOx-FeO system should be determined.展开更多
Because CaSi core wire was not fed in external refining process for 26CrMo4S/2 steel making, it was found that the molar ratio of calcium versus alumina was very low and subsequently resulted in generation of much mor...Because CaSi core wire was not fed in external refining process for 26CrMo4S/2 steel making, it was found that the molar ratio of calcium versus alumina was very low and subsequently resulted in generation of much more non-metallic inclusions. Hence, it was reasonable to sugguest feeding appropriate amount of Ca core wire. Before the performance, the thermodynamic calculation had been carried out to obtain the theoretical amount of Ca wire to be fed. According to the practical data from steel plant and the thermodynamic data, it was calculated that only when 5 2/34.97 10 [%Al]T-≥×4 2/31.38 10 [%Al] [%Ca]T T-×≥≥in molten steel the Al2O3 inclusions could be properly modified.展开更多
基金the Research Council of Norway (RCN) funded BIP Project No. 179947/I40 and BIA Project No. 219940/O30the partners: Alcoa Norway ANS, SAPA Heat Transfer AB, Hydro Aluminium AS, SINTEF MK Trondheim, and NTNUFunding by the industrial partners and RCN
文摘The wetting behavior between liquid aluminium and substrates made from industrial Al2O3 and SiC based ceramic foam filters （CFF） was investigated. The same CFF filters were also tested in plant scale filtration experiments. The wetting experiment results show that the SiC based filter material is better wetted by liquid aluminium than the Al2O3 based filter material. This indicates that the improved wetting of aluminium on a filter material is an advantage for molten metal to infiltrate the filter during priming. Also, better wetting of Al-filter might increase the removal efficiency of inclusions during filtration due to better contact between filter and metal. Non-wetted inclusions are easier to be removed.
基金The authors gratcfully acknowledge the sup-port of the National Natural Science Foundation of China(Grant No.51374020)the State Key Laboratory of Advanced Metallurgy at theUniversity of Science and Technology Beijing(USTB)the JiuquanIron and Steel Group Corporation.
文摘Ti-stabilized 321 stainless steel was prepared using an electric arc furnace, argon oxygen decarburization (AOD) furnace, ladle furnace (LF), and continuous casting processes. In addition, the effect of refining process and utilization of different slags on the evolution of inclusions, titanium yield, and oxygen content was systematically investigated by experimental and thermodynamic analysis. The results reveal that the total oxygen content (TO) and inclusion density decreased during the refining process. The spherical CaO–SiO2–Al2O3–MgO inclusions existed in the 321 stainless steel after the AOD process. Moreover, prior to the Ti addition, the spherical CaO–Al2O3–MgO–SiO2 inclusions were observed during LF refining pro-cess. However, Ti addition resulted in multilayer CaO–Al2O3–MgO–TiOx inclusions. Two different samples were prepared by conventional CaO–Al2O3-based slag (Heat-1) and -TiO2-rich CaO–Al2O3-based slag (Heat-2). The statistical analysis revealed that the density of inclusions and the -TiOx content in CaO–Al2O3–MgO–TiOx inclusions found in Heat-2 sample are much lower than those in the Heat-1 sample. Furthermore, the TO content and Ti yield during the LF refining process were controlled by using -TiO2-rich calcium aluminate synthetic slag. These results were consistent with the ion–molecule coexist-ence theory and FactSage?7.2 software calculations. When -TiO2-rich CaO–Al2O3-based slag was used, the -TiO2 activity of the slag increased, and the equilibrium oxygen content significantly decreased from the AOD to LF processes. Therefore, the higher -TiO2 activity of slag and lower equilibrium oxygen content suppressed the undesirable reactions between Ti and O.
文摘The formation of Al2O3 inclusions in liquid iron has been investigated in a resistance heated tube furnace to obtain deoxidation and reoxidation related data. The formation of inclusions during the early stages of deoxidation was simulated by bringing a piece of AI in contact for a short time with liquid Fe containing different dissolved oxygen levels. Reoxidation was studied by exposing AI containing Fe melts to a CO/CO2 atmosphere, Through modeling, an estimate of the local and time-dependent growth conditions for the inclusions can be made and linked to the inclusion characteristics.
文摘The latest publications regarding the development of technology to control inclusion compositions focusing on MgO?Al2O3 spinel inclusions were summarized in this review article. The problems caused by spinel inclusions, which affect practice as well as products were shown. The formation mechanism of MgO?Al2O3 spinel inclusions is secondly explained thermodynamically from the view points of chemistries of molten steels and slag compositions. Furthermore, crystallization behaviour of spinel was introduced. Countermeasures conducted in practices and laboratories were shown along with some problems still left that should be solved in the future.
基金Project supported by the National Natural Science Foundation of China (50734008)
文摘The effect of pre-melting refining slag containing different contents of Ce2O3 on the absorption and modification of Al2O3 inclusion in an Al-killed steel was investigated through the slag/steel reaction experiment at 1600 oC.It was found that the replacement of 10 wt.% Al2O3 with Ce2O3 for 50 wt.%CaO-33 wt.%Al2O3-7 wt.%MgO-10 wt.%SiO2 refining slag promoted the slag absorption ability of alumina inclusion,which made the total oxygen content determined by infrared absorption method decrease from 100 to 25 ppm in 15 min.The Mg-Al-Ce-O type inclusion was also detected in the as-solidified samples by scanning electron microscopy（SEM）.Thermodynamic analysis indicated that the Ce2O3.Al2O3 type inclusions would be formed with the cerium content in the range of 6.9 ppb to 3.6 ppm when the content of aluminum was 0.01 wt.%.
基金Item Sponsored by National Natural Science Foundation of China (50704010)
文摘A phase diagram was drawn through thermodynamic calculation to understand the equilibrium conditions of 2MgO · SiO2 , MgO · Al2O3 , 3Al2O3 · 2SIO2, and 2MgO·2Al2O3 · 5SiO2 formation in Mg-AI-Si-O system of 430 stainless steel melts at 1873 K. Further, the thermodynamic formation and transformation conditions of MgO · Al2O3 inclusion were discussed. The following results are obtained when ws, =0.26% and wo = 1.0 × 10^-5 in molten steel. The uniphase cordierite inclusion is difficult to exist stably; MgO· At203 inclusion cannot he formed in case of wAl being less than 1× 10^- 6 ; 3Al2O3 · 2SiO2 would change to MgO· Al2O3 and 2MgO · SiO2 in turn with increasing the Mg content when wAl is above 1.7× 10^- 6 ; with the formation of MgO · Al2O3 inclusion, A1 content increases with increasing Mg content when wMg is over 1. 7 × 10^- 9. For equilibrium condition and calculated steel composition, 2MgO·SiO2 inclusion would be formed ultimately and MgO · Al2O3 is almost inexistent.
文摘Titanium alloyed steel has been widely used as automobile sheet steels, thick plate steels, and also stainless steels to improve the mechanical and chemical properties of many grade steels. Since Ti has strong affinity with oxygen, Ti is normally alloyed after Al deoxidation to keep the high yield of Ti. Therefore, Al-Ti deoxidation is one of the common and important secondary refining processes. Although the chemical stability diagram for this system has been reported by many researchers, these diagrams are inconsistent significantly each other. In the present study, the stability region of Al2TiO5 oxide was measured by equilibrating Fe-Al-Ti alloy and Al2TiO5 pellet in Al2O3 crucible at 1873 K. However, inclusions in metal after equilibration were Ti-containing Al2O3 or Al-containing TiOx. The precise phase diagrams and related thermodynamic data for the Al2O3-TiOx-FeO system should be determined.
基金Item Sponsored by the National Natural Science Foundation of China(51074009,51072022,50874013)National Science and Technology Support Plan of China(2011BAB03B02,2013BAC14B07)
文摘Because CaSi core wire was not fed in external refining process for 26CrMo4S/2 steel making, it was found that the molar ratio of calcium versus alumina was very low and subsequently resulted in generation of much more non-metallic inclusions. Hence, it was reasonable to sugguest feeding appropriate amount of Ca core wire. Before the performance, the thermodynamic calculation had been carried out to obtain the theoretical amount of Ca wire to be fed. According to the practical data from steel plant and the thermodynamic data, it was calculated that only when 5 2/34.97 10 [%Al]T-≥×4 2/31.38 10 [%Al] [%Ca]T T-×≥≥in molten steel the Al2O3 inclusions could be properly modified.
