The twin-body plasma arc has the decoupling control ability of heat transfer and mass transfer,which is beneficial to shape and property control in wire arc additive manufacturing.In this paper,with the wire feeding s...The twin-body plasma arc has the decoupling control ability of heat transfer and mass transfer,which is beneficial to shape and property control in wire arc additive manufacturing.In this paper,with the wire feeding speed as a characteristic quantity,the wire melting control ability of twin-body plasma arc was studied by adjusting the current separation ratio(under the condition of a constant total current),the wire current/main current and the position of the wire in the arc axial direction.The results showed that under the premise that the total current remains unchanged(100 A),as the current separation ratio increased,the middle and minimum melting amounts increased approximately synchronously under the effect of anode effect power,the first melting mass range remained constant;the maximum melting amount increased twice as fast as the middle melting amount under the effect of the wire feeding speed,and the second melting mass range was expanded.When the wire current increased,the anode effect power and the plasma arc power were both factors causing the increase in the wire melting amount;however,when the main current increased,the plasma arc power was the only factor causing the increase in the wire melting amount.The average wire melting increment caused by the anode effect power was approximately 2.7 times that caused by the plasma arc power.The minimum melting amount was not affected by the wire-torch distance under any current separation ratio tested.When the current separation ratio increased and reached a threshold,the middle melting amount remained constant with increasing wire-torch distance.When the current separation ratio continued to increase and reached the next threshold,the maximum melting amount remained constant with the increasing wire-torch distance.The effect of the wire-torch distance on the wire melting amount reduced with the increase in the current separation ratio.Through this study,the decoupling mechanism and ability of this innovative arc heat source is more clearly.展开更多
Boron is an important industrial raw material often sourced from minerals containing different compounds that cocrystallize,which makes it difficult to separate the mineral phases through conventional beneficiation.Th...Boron is an important industrial raw material often sourced from minerals containing different compounds that cocrystallize,which makes it difficult to separate the mineral phases through conventional beneficiation.This study proposed a new treatment called flash reduction-melting separation(FRMS)for boron-bearing iron concentrates.In this method,the concentrates were first flash-reduced at the temperature under which the particles melt,and the slag and the reduced iron phases disengaged at the particle scale.Good reduc-tion and melting effects were achieved above 1550℃.The B_(2)O_(3) content in the separated slag was over 18wt%,and the B content in the iron was less than 0.03wt%.The proposed FRMS method was tested to investigate the effects of factors such as ore particle size and tem-perature on the reduction and melting steps with and without pre-reducing the raw concentrate.The mineral phase transformation and morphology evolution in the ore particles during FRMS were also comprehensively analyzed.展开更多
Phosphorus removal from oolitic high-phosphorus hematite using direct reduction followed by melting sep aration was investigated. At the direct reduction stage, highly volatile wood char was prepared by carbonizing ju...Phosphorus removal from oolitic high-phosphorus hematite using direct reduction followed by melting sep aration was investigated. At the direct reduction stage, highly volatile wood char was prepared by carbonizing jujube wood at 673 K for 2 h and was used as reducing agent. The results of the direct reduction tests show that at a tem- perature of 1373 K, a char mixing ratio of 0.8, and a reduction time of 10-25 min, the briquettes reached a metal- lization degree of 80% -84% and a residual carbon content of 0.13 -1.98 mass%. Phosphorus remained in the gangue as calcium phosphate after reduction. The results of the melting separation tests show that residual carbon in reduced briquette negatively affects the phosphorus content （W[p]） in hot metal. When the reduced briquettes ob- tained under the aforementioned conditions were used for melting separation, hot metal suitable for basic oxygen steelmaking （w[p]〈0.4 mass%） could not be obtained from metallic briquettes with a residual carbon content more than 1.0 mass~. In contrast, it could be obtained from metallic briquettes with residual carbon content less than 0.35 mass% by mixing with 2%-4% Na2CO3.展开更多
The phosphorus migration mechanism during melting separation of non-carbon-reduced high phosphorus iron ore was investigated.Firstly,the equilibrium compositions of hydrogen-reduced high phosphorus iron ore at differe...The phosphorus migration mechanism during melting separation of non-carbon-reduced high phosphorus iron ore was investigated.Firstly,the equilibrium compositions of hydrogen-reduced high phosphorus iron ore at different temperatures were simulated by the use of equilibrium composition module of HSC Chemistry software.Then,thermodynamic calculation was verified by the real heat treatment of simulated hydrogen-reduced high phosphorus iron ore with several pure reagents including self-made pure fluorapatite.The iron particles in the simulated samples gathered and grew up during heat treatment.Meanwhile,the hypoeutectic structure of Fe-P with grid shape of high phosphorus phase and circular shape of low phosphorus phase emerged within those iron particles.With the penetration of phosphorus from the periphery into the iron particles,the grid structure became denser and denser.It proves that the elemenlal phosphorus can be reduced from the gangue phase by metallic iron without solid carbon at high temperatures.展开更多
Herein, a multi-index analysis of the nickel content of an alloy, output rate of the alloy, nickel recovery rate, and iron recovery rate during the melting of laterite metallized pellets was performed. The thermodynam...Herein, a multi-index analysis of the nickel content of an alloy, output rate of the alloy, nickel recovery rate, and iron recovery rate during the melting of laterite metallized pellets was performed. The thermodynamic reduction behavior of oxides such as NiO, FeO, Fe_3 O_4, and Cr_2 O_3 was studied using the FactSage software, which revealed that SiO_2 is not conducive to the reduction of iron oxides, whereas the addition of basic oxides such as CaO and MgO is beneficial for the reduction of iron oxides. On the basis of a comprehensive analysis to achieve greater nickel recovery and lower iron recovery rates, the optimum experimental parameters in the orthogonal experiment were A3 B1 C3(t = 30 min, C/O = 0.4, R = 1.2); the indicators wNi, φalloy, ηNi, and ηFe had values of 15.0 wt%, 12.1%, 44.9%, and 96.4%, respectively. In single-factor experiments, increasing basicity(R) substantially improved the separation effect in the low-basicity range 0.5 ≤ R ≤ 0.8 but not in the high-basicity range 0.8 ≤ R ≤ 1.2. Similar results were obtained for the effect of the C/O ratio. Moreover, the recovery rate of nickel increased with increasing recovery rate of iron.展开更多
In order to recycle the phosphorus from P-bearing steelmaking slag, the influences of magnetic field inten- sities, slag particle sizes and slag compositions were investigated by magnetic separation experiments. SiO2,...In order to recycle the phosphorus from P-bearing steelmaking slag, the influences of magnetic field inten- sities, slag particle sizes and slag compositions were investigated by magnetic separation experiments. SiO2, A1203 and TiO2 melting modification of converter slag was made respectively and phosphorus-rich phase was extracted by magnetic separation. The results show that MgO, MnO, Na2 0 and CaF2 have little effect on the phosphorus recovery, whereas the addition of SiO2, Al2 03, and TiO2 has great effect on phosphorus enrichment in slag and magnetic separation. With adding the reagent of SiO2 Al2 03 and TiO2, recycled non-magnetic substances are increased obviously and P2 05 content in nowmagnetic substances and phosphorus recovery rate are also increased. The phosphorus recovery rates of modified slag No. 8 （SiO2 modification）, slag No. 10 （AI2 03 modification） and slag No. 11 （TiO2 modification） are 84.75 %, 82.16 % and 74.46 %, respectively. Then, most of phosphorus was recycled.展开更多
A novel process for boron enrichment and extraction from ludwigite based on iron nugget technology was proposed. The key steps of this novel process, which include boron and iron separation, crystallization of boron-r...A novel process for boron enrichment and extraction from ludwigite based on iron nugget technology was proposed. The key steps of this novel process, which include boron and iron separation, crystallization of boron-rich slag, and elucidation of the boron extraction be- havior of boron-rich slag by acid leaching, were performed at the laboratory. The results indicated that 95.7% of the total boron could be en- riched into the slag phase, thereby forming a boron-rich slag during the iron and slag melting separation process. Suanite and kotoite were observed to be the boron-containing crystalline phases, and the boron extraction properties of the boron-rich slag depended on the amounts and grain sizes of these minerals. When the boron-rich slag was slowly cooled to 1100℃, the slag crystallized well and the efficiency of ex- traction of boron （EEB） of the slag was the highest observed in the present study. The boron extraction property of the slow-cooled bo- ron-rich slag obtained in this study was much better than that of szaibelyite ore under the conditions of 80% of theoretical sulfuric acid amount, leaching time of 30 min, leaching temperature of 40℃ ,and liquid-to-solid ratio of 8 mL/g.展开更多
The effects of Na_2CO_3 on the reduction and melting separation behavior of ludwigite/coal composite pellet, the desulfurization ratio and the property of the separated boron-rich slag were investigated at laboratory ...The effects of Na_2CO_3 on the reduction and melting separation behavior of ludwigite/coal composite pellet, the desulfurization ratio and the property of the separated boron-rich slag were investigated at laboratory scale in the present work. Na_2CO_3 could improve the reduction rate of the composite pellet to some extent. The melting separation of the composite pellet became increasingly difficult with the increase of Na_2CO_3 in the pellet due to the sharply increasing of the melting point of slag. The sulfur content of the iron nugget gradually decreased from 0.27% to 0.084%（mass fraction） with the Na_2CO_3 content in the pellet increasing from 0 to 6%. The efficiency of extraction of boron（EEB） of the slow cooled boron-rich slag decreased from 86.46% to 59.52% synchronously. Na_2CO_3 had obviously negative effect on melting separation of the composite pellet and boron extraction of the boron-rich slag.展开更多
基金Supported by Youth Program of National Natural Science Foundation of China(Grant No.51905008)Beijing Postdoctoral Research Foundation of China(Grant No.2021-zz-064)+2 种基金Shandong Provincial Major Science and Technology Innovation Project of China(Grant No.2020JMRH0504)Jinan Innovation Team Project of China(Grant No.2021GXRC066)Quancheng Scholars Construction Project of China(Grant No.D03032).
文摘The twin-body plasma arc has the decoupling control ability of heat transfer and mass transfer,which is beneficial to shape and property control in wire arc additive manufacturing.In this paper,with the wire feeding speed as a characteristic quantity,the wire melting control ability of twin-body plasma arc was studied by adjusting the current separation ratio(under the condition of a constant total current),the wire current/main current and the position of the wire in the arc axial direction.The results showed that under the premise that the total current remains unchanged(100 A),as the current separation ratio increased,the middle and minimum melting amounts increased approximately synchronously under the effect of anode effect power,the first melting mass range remained constant;the maximum melting amount increased twice as fast as the middle melting amount under the effect of the wire feeding speed,and the second melting mass range was expanded.When the wire current increased,the anode effect power and the plasma arc power were both factors causing the increase in the wire melting amount;however,when the main current increased,the plasma arc power was the only factor causing the increase in the wire melting amount.The average wire melting increment caused by the anode effect power was approximately 2.7 times that caused by the plasma arc power.The minimum melting amount was not affected by the wire-torch distance under any current separation ratio tested.When the current separation ratio increased and reached a threshold,the middle melting amount remained constant with increasing wire-torch distance.When the current separation ratio continued to increase and reached the next threshold,the maximum melting amount remained constant with the increasing wire-torch distance.The effect of the wire-torch distance on the wire melting amount reduced with the increase in the current separation ratio.Through this study,the decoupling mechanism and ability of this innovative arc heat source is more clearly.
基金supported by the Science and Technology Special Plan Project from China Minmetals Group (No.2020ZXA01)the International Exchange and Growth Program for Young Teachers (No.QNXM20220061)the National Key Research and Development Program of China (No.2022YFC2906100).
文摘Boron is an important industrial raw material often sourced from minerals containing different compounds that cocrystallize,which makes it difficult to separate the mineral phases through conventional beneficiation.This study proposed a new treatment called flash reduction-melting separation(FRMS)for boron-bearing iron concentrates.In this method,the concentrates were first flash-reduced at the temperature under which the particles melt,and the slag and the reduced iron phases disengaged at the particle scale.Good reduc-tion and melting effects were achieved above 1550℃.The B_(2)O_(3) content in the separated slag was over 18wt%,and the B content in the iron was less than 0.03wt%.The proposed FRMS method was tested to investigate the effects of factors such as ore particle size and tem-perature on the reduction and melting steps with and without pre-reducing the raw concentrate.The mineral phase transformation and morphology evolution in the ore particles during FRMS were also comprehensively analyzed.
基金Item Sponsored by National Natural Science Foundation of China(51144010)
文摘Phosphorus removal from oolitic high-phosphorus hematite using direct reduction followed by melting sep aration was investigated. At the direct reduction stage, highly volatile wood char was prepared by carbonizing jujube wood at 673 K for 2 h and was used as reducing agent. The results of the direct reduction tests show that at a tem- perature of 1373 K, a char mixing ratio of 0.8, and a reduction time of 10-25 min, the briquettes reached a metal- lization degree of 80% -84% and a residual carbon content of 0.13 -1.98 mass%. Phosphorus remained in the gangue as calcium phosphate after reduction. The results of the melting separation tests show that residual carbon in reduced briquette negatively affects the phosphorus content （W[p]） in hot metal. When the reduced briquettes ob- tained under the aforementioned conditions were used for melting separation, hot metal suitable for basic oxygen steelmaking （w[p]〈0.4 mass%） could not be obtained from metallic briquettes with a residual carbon content more than 1.0 mass~. In contrast, it could be obtained from metallic briquettes with residual carbon content less than 0.35 mass% by mixing with 2%-4% Na2CO3.
基金the China Postdoctoral Science Foundation(2017M610768)the Open Projects of State Key Laboratory of Advanced Metallurgy(No.41617013)the National Key Research and Development Plan of China(2016YFB0601304).
文摘The phosphorus migration mechanism during melting separation of non-carbon-reduced high phosphorus iron ore was investigated.Firstly,the equilibrium compositions of hydrogen-reduced high phosphorus iron ore at different temperatures were simulated by the use of equilibrium composition module of HSC Chemistry software.Then,thermodynamic calculation was verified by the real heat treatment of simulated hydrogen-reduced high phosphorus iron ore with several pure reagents including self-made pure fluorapatite.The iron particles in the simulated samples gathered and grew up during heat treatment.Meanwhile,the hypoeutectic structure of Fe-P with grid shape of high phosphorus phase and circular shape of low phosphorus phase emerged within those iron particles.With the penetration of phosphorus from the periphery into the iron particles,the grid structure became denser and denser.It proves that the elemenlal phosphorus can be reduced from the gangue phase by metallic iron without solid carbon at high temperatures.
基金financially supported by the National Natural Science Foundation of China (Nos. 51474024, 51674021, and 51574021)
文摘Herein, a multi-index analysis of the nickel content of an alloy, output rate of the alloy, nickel recovery rate, and iron recovery rate during the melting of laterite metallized pellets was performed. The thermodynamic reduction behavior of oxides such as NiO, FeO, Fe_3 O_4, and Cr_2 O_3 was studied using the FactSage software, which revealed that SiO_2 is not conducive to the reduction of iron oxides, whereas the addition of basic oxides such as CaO and MgO is beneficial for the reduction of iron oxides. On the basis of a comprehensive analysis to achieve greater nickel recovery and lower iron recovery rates, the optimum experimental parameters in the orthogonal experiment were A3 B1 C3(t = 30 min, C/O = 0.4, R = 1.2); the indicators wNi, φalloy, ηNi, and ηFe had values of 15.0 wt%, 12.1%, 44.9%, and 96.4%, respectively. In single-factor experiments, increasing basicity(R) substantially improved the separation effect in the low-basicity range 0.5 ≤ R ≤ 0.8 but not in the high-basicity range 0.8 ≤ R ≤ 1.2. Similar results were obtained for the effect of the C/O ratio. Moreover, the recovery rate of nickel increased with increasing recovery rate of iron.
文摘In order to recycle the phosphorus from P-bearing steelmaking slag, the influences of magnetic field inten- sities, slag particle sizes and slag compositions were investigated by magnetic separation experiments. SiO2, A1203 and TiO2 melting modification of converter slag was made respectively and phosphorus-rich phase was extracted by magnetic separation. The results show that MgO, MnO, Na2 0 and CaF2 have little effect on the phosphorus recovery, whereas the addition of SiO2, Al2 03, and TiO2 has great effect on phosphorus enrichment in slag and magnetic separation. With adding the reagent of SiO2 Al2 03 and TiO2, recycled non-magnetic substances are increased obviously and P2 05 content in nowmagnetic substances and phosphorus recovery rate are also increased. The phosphorus recovery rates of modified slag No. 8 （SiO2 modification）, slag No. 10 （AI2 03 modification） and slag No. 11 （TiO2 modification） are 84.75 %, 82.16 % and 74.46 %, respectively. Then, most of phosphorus was recycled.
基金financially supported by the National Natural Science Foundation of China (No. 51274033)
文摘A novel process for boron enrichment and extraction from ludwigite based on iron nugget technology was proposed. The key steps of this novel process, which include boron and iron separation, crystallization of boron-rich slag, and elucidation of the boron extraction be- havior of boron-rich slag by acid leaching, were performed at the laboratory. The results indicated that 95.7% of the total boron could be en- riched into the slag phase, thereby forming a boron-rich slag during the iron and slag melting separation process. Suanite and kotoite were observed to be the boron-containing crystalline phases, and the boron extraction properties of the boron-rich slag depended on the amounts and grain sizes of these minerals. When the boron-rich slag was slowly cooled to 1100℃, the slag crystallized well and the efficiency of ex- traction of boron （EEB） of the slag was the highest observed in the present study. The boron extraction property of the slow-cooled bo- ron-rich slag obtained in this study was much better than that of szaibelyite ore under the conditions of 80% of theoretical sulfuric acid amount, leaching time of 30 min, leaching temperature of 40℃ ,and liquid-to-solid ratio of 8 mL/g.
基金Project(51274033) supported by the National Natural Science Foundation of China
文摘The effects of Na_2CO_3 on the reduction and melting separation behavior of ludwigite/coal composite pellet, the desulfurization ratio and the property of the separated boron-rich slag were investigated at laboratory scale in the present work. Na_2CO_3 could improve the reduction rate of the composite pellet to some extent. The melting separation of the composite pellet became increasingly difficult with the increase of Na_2CO_3 in the pellet due to the sharply increasing of the melting point of slag. The sulfur content of the iron nugget gradually decreased from 0.27% to 0.084%（mass fraction） with the Na_2CO_3 content in the pellet increasing from 0 to 6%. The efficiency of extraction of boron（EEB） of the slow cooled boron-rich slag decreased from 86.46% to 59.52% synchronously. Na_2CO_3 had obviously negative effect on melting separation of the composite pellet and boron extraction of the boron-rich slag.
