The abnormal corrosion of hot iron ladles was investigated.The performance,the composition and the structure of bricks for hot iron ladles were analyzed.The results show that(1)compared with the alumina-silicon carbid...The abnormal corrosion of hot iron ladles was investigated.The performance,the composition and the structure of bricks for hot iron ladles were analyzed.The results show that(1)compared with the alumina-silicon carbide-carbon bricks for the ladle bottom,those for the ladle wall have more pyrophyllite and the Al2O3 content of 36.32 mass%;their bulk density,apparent porosity and cold compressive strength are lower than the requirement of industry standard;they have poor anti-oxidation performance and are oxidized to form a porous layer during service,which loosens the brick lining structure thus leading to fracture,local wear and structural damage of bricks;(2)without preheating,steel scraps are not completely melted,resulting in slag or steel attachment at the mouth or the bottom of ladles thus increasing damage of ladles;(3)and the residual bricks react with the attached slag to form low melting point phases affecting their hot properties.The refractories for the lining of hot iron ladles must be improved in combination with process changes,not entirely by raw materials replacement to reduce costs.展开更多
Three lightweight Al_(2)O_(3)-MgO castables were fabricated with tabular alumina or microporous corundum as the aggregates,reactiveα-Al_(2)O_(3)micropowder,tabular alumina powder,and fused magnesia powder as the matr...Three lightweight Al_(2)O_(3)-MgO castables were fabricated with tabular alumina or microporous corundum as the aggregates,reactiveα-Al_(2)O_(3)micropowder,tabular alumina powder,and fused magnesia powder as the matrix,calcium aluminate cement as the binder,and MgO ultrafine powder(d50=5.4μm)and Al(OH)3 ultrafine powder(d50=8.2μm)as additives.The influence of aggregates and ultrafine powders on the properties,including pore size distribution,heat conductivity,thermal shock resistance,and slag resistance of lightweight refractory castables was investigated.The results show that the incorporation of microporous corundum reduces the bulk density of Al_(2)O_(3)-MgO castables,and MgO and Al(OH)3 ultrafine powders further increases the proportion of micropores in castables,which is beneficial to reducing the heat conductivity,and improving the thermal shock resistance and slag resistance of castables.Additionally,MgO ultrafine powder and Al(OH)3 ultrafine powder increase the fluidity and the strength of castables.展开更多
Coatings on the surface of Mg alloys are inevitably damaged during their practical applications,and corrosion can easily initiate from the damaged areas to accelerate the failure of Mg parts.A dual self-healing coatin...Coatings on the surface of Mg alloys are inevitably damaged during their practical applications,and corrosion can easily initiate from the damaged areas to accelerate the failure of Mg parts.A dual self-healing coating has already been developed to solve this problem in our previous work.Considering the practical application of this coating,it is necessary to investigate its service behavior in atmospheric environment.Thus,the corrosion behavior of AM60 Mg substrate with and without the self-healing coating was compared in Shenyang industrial atmospheric environment.The results show that the enrichment of sediments and rainwater on the scratch areas can accelerate the corrosion of the exposed Mg substrate.The inhibitors can be released from the damaged coating to inhibit corrosion.The dual self-healing coating shows better inhibition ability to narrow scratches due to the higher inhibitor concentration and less resumption.Also,the coating with wide scratches displays enough inhibition ability as well.The dual self-healing coating is a good alternative for Mg alloy parts in the practical applications.展开更多
The fatigue behavior of 30 WGP1600 non-oriented electrical steel, which is generally used in the motors for electrical vehicles, was investigated. The detailed microstructure and dislocation configurations of the fati...The fatigue behavior of 30 WGP1600 non-oriented electrical steel, which is generally used in the motors for electrical vehicles, was investigated. The detailed microstructure and dislocation configurations of the fatigue specimens were examined by OM, SEM, and TEM. The test results showed that fatigue cracks were commonly initiated from the surface grain boundaries, crystals plane, and inclusions. The rapid fatigue crack propagation was characterized by transgranular cleavage fracture, while most transient fracture exhibited ductile tearing characteristics. After cyclic deformation of the non-oriented electrical steels, various dislocation structures, such as short and thick lines, veins, persistent slip bands, cells, and labyrinth, were observed.展开更多
The microstructure evolution and its effects on the mechanical performance of 2000 MPa bridge cable steel wires were investigated by transmission electron microscope(TEM),electron backscatter diffraction(EBSD),X-ray d...The microstructure evolution and its effects on the mechanical performance of 2000 MPa bridge cable steel wires were investigated by transmission electron microscope(TEM),electron backscatter diffraction(EBSD),X-ray diffractometer(XRD)and mechanical tests.Experimental results reveal that,with the increasing strain from 0 to 1.42,a fiber structure and a<110>fiber texture aligned with the wire axis are gradually developed accompanied by cementite decomposition and the formation of sub-grains;the tensile strength increases linearly from 1510 to 2025 MPa,and the reduction of the area is stable with a slight decline from 44%to 36%.After annealing at 450℃for different times,pronounced changes in the microstructure occur.Cementite lamella fragment into coarser globules corresponding to a remarkable spheroidization process,while ferrite domains recover and recrystallize,and this process is associated to modifications in the mechanical properties.Furthermore,based on the observations on dislocation lines crossing through cementite lamellae,a possible mechanism of cementite decomposition is discussed.展开更多
To reduce the burning loss and the spalling and to improve energy efficiency,the mullite composite lining plates were used to replace cast steel or alloy lining in rotary coke tanks for coke dry quenching equipment.Th...To reduce the burning loss and the spalling and to improve energy efficiency,the mullite composite lining plates were used to replace cast steel or alloy lining in rotary coke tanks for coke dry quenching equipment.The results show that:the dense mullite composite lining plate in the cone part has the density of 2.20 g·cm^(-3) and the wear test,s volume loss of 4.08 cm^(3),and the light weight mullite composite lining plate in the straight cylinder part has the density of 1.95 g·cm^(-3) and the wear test,s volume loss of 17.6 cm^(3).After using,there is no shrinkage gap,no burn loss or holes in the plates,indicating good sealing of the mullite composite lining plates.The lining plate for the cone part has low burning loss,without spalling for more than half a year.The outer surface temperature of coke tanks adopting the cast steel or the alloy lining is 480 to 570℃,while that of the ones adopting mullite composite lining plates is 120 to 170℃,showing a largely improved insulating property.Adopting mullite composite lining plates on the basis of the current coke tank cage,the lining plates can be timely treated and wholly replaced,improving the service life and reducing the maintenance workload.展开更多
The characteristic of near-surface microstructure and its effects on the torsion performance of cold-drawn pearlitic steel wires for bridge cables were investigated by focused ion beam-scanning electron microscope,tra...The characteristic of near-surface microstructure and its effects on the torsion performance of cold-drawn pearlitic steel wires for bridge cables were investigated by focused ion beam-scanning electron microscope,transmission electron microscopy and differential scanning calorimetry.The samples with similar tensile strength before and after hot-dip galvanizing process are,respectively,characterized as delaminated and non-delaminated in torsion test which indicates that the tensile strength is independent of the toughness value(i e,reduction area and torsion ability).It is interesting to find that there exists submicron granular ferrite on near-surface of the wires,which can be attributed to dislocation rearrangement and sub-grains rotation during cold drawing and hot-dip galvanizing process.And their distribution can suggest homogeneousness of deformation degree to a certain extent:the closer to the surface of their distribution,the more homogeneous deformation of the wires.There is a close relationship between the thermal stability of the cementite layer and distribution of granular ferrite:differential scanning calorimetry(DSC)analysis shows that the sample is accompanied by submicron granular ferrite which is located closer to the surface has higher thermal stability under galvanizing temperature(450°C).A new mechanism of the torsion delamination of pearlitic steel wires is discussed in terms of the thermal stability of the cementite layer and distribution of granular ferrite.展开更多
At present,blast furnace ironmaking is still the main process for producing molten iron,and sinters are the main raw material for blast furnace ironmaking.A sinter with good metallurgical performance can not only ensu...At present,blast furnace ironmaking is still the main process for producing molten iron,and sinters are the main raw material for blast furnace ironmaking.A sinter with good metallurgical performance can not only ensure smooth operation of the blast furnace but also reduce the blast furnace fuel ratio and increase the molten iron production.Structure is the most important factor affecting the metallurgical properties of the sinter.Thus,the research progress of sinter pore and mineral phase structures was reviewed and the mechanism by which they influence sinter properties was expounded.Multiscale characterization methods for the sinter and their advantages and disadvantages were introduced,and the future research direction of sinter was discussed.展开更多
Hydrogen-enriched blast furnace ironmaking has become an essential route to reduce CO_(2)emissions in the ironmaking process.However,hydrogen-enriched reduction produces large amounts of H_(2)O,which places new demand...Hydrogen-enriched blast furnace ironmaking has become an essential route to reduce CO_(2)emissions in the ironmaking process.However,hydrogen-enriched reduction produces large amounts of H_(2)O,which places new demands on coke quality in a blast furnace.In a hydrogen-rich blast furnace,the presence of H_(2)O promotes the solution loss reaction.This result improves the reactivity of coke,which is 20%-30%higher in a pure H_(2)O atmosphere than in a pure CO_(2)atmosphere.The activation energy range is 110-300 kJ/mol between coke and CO_(2)and 80-170 kJ/mol between coke and H_(2)O.CO_(2)and H_(2)O are shown to have different effects on coke degradation mechanisms.This review provides a comprehensive overview of the effect of H_(2)O on the structure and properties of coke.By exploring the interactions between H_(2)O and coke,several unresolved issues in the field requiring further research were identified.This review aims to provide valuable insights into coke behavior in hydrogen-rich environments and promote the further development of hydrogen-rich blast furnace ironmaking processes.展开更多
The optimization of continuous casting production planning(CCPP)in the steel industry was studied.The essence of CCPP is the productive capability balance of back-end facilities over the planning time period.The facil...The optimization of continuous casting production planning(CCPP)in the steel industry was studied.The essence of CCPP is the productive capability balance of back-end facilities over the planning time period.The facilities with the demands of productive capability are called the flows.On the basis of charge plans,the task of CCPP is to produce cast plans according to the rules of cast design in order to meet the flows.Firstly,a multi-objective model was established with considering the demands of flows,the capability requirements of liquid steel refini ng devices,and the rules of cast design.Secondly,the model was decomposed into a master problem(set partitioning problem model)and a series of subproblem(pricing problem model)by using Dantzig-Wolfe decomposition strategy.Finally,a column generation-based optimization algorithm(CGBOA)was presented.The experimental results on practical production data from Baosteel demonstrate that the proposed algorithm is effective and feasible.Moreover,a new decision support system based on CGBOA has been successfully established and applied to No.2 Steelmaking Plant at Baosteel.展开更多
Medium Mn steel was metal inert gas(MIG)welded with NiCrMo-3 and 307 Si filler wires.The effect of filler wires on the microstructure and mechanical properties of joint was investigated,and the carbide precipitates we...Medium Mn steel was metal inert gas(MIG)welded with NiCrMo-3 and 307 Si filler wires.The effect of filler wires on the microstructure and mechanical properties of joint was investigated,and the carbide precipitates were contrastively discussed.The results revealed that the microstructure of weld metal,heat-affected zone and base metal are austenite.Obvious grain coarsening occurred in the heat-affected zone(HAZ),and the maximum grain size grew up to 160μm.In HAZ,C and Cr segregated at grain boundaries,the carbides was identified as Cr7 C3.The dispersive(Nb,Mo)C phase was also found in weld metal with NiCrMo-3 filler wire.All the welded joints failed in HAZ during tensile tests.The tensile strength of welded joint with NiCrMo-3 filler wire was 675 MPa,which is much higher than that with307 Si filler wire.In comparison to base metal,higher microhardness and lower impact toughness were obtained in HAZ for these two welded joints,which was attributed to the precipitation of Cr7 C3 phase and grain coarsening.The impact toughness around the fusion line is the worst for these two welded joints.展开更多
In order to investigate the high-temperature fatigue and fatigue-creep behavior of 15CrNbTi ferritic stainless steel at 800°C,fatigue tests without holding time in laboratory air and with 10 s holding time induce...In order to investigate the high-temperature fatigue and fatigue-creep behavior of 15CrNbTi ferritic stainless steel at 800°C,fatigue tests without holding time in laboratory air and with 10 s holding time induced at maximum cyclic stress under argon atmosphere were conducted on an electrohydraulic servo fatigue testing machine.In addition,the morphologies of fatigue fracture surfaces were observed,and the precipitates and dislocation substructures were characterized.The experimental results show that the fatigue limit of 15CrNbTi ferritic stainless steel is 30 MPa at 800°C.The fatigue life of the experimental steel obviously decreases if holding time of 10 s is introduced at maximum cyclic stress.Under two test conditions,the fatigue cracks transgranularly initiate at the free surface of fatigue specimens and then propagate in a transgranular mode.It is dem on strated that three kinds of precipitates inclu ding(Nb,Ti)C phase,Fe2Nb phase and Fe3Nb3C phase can be observed in 15CrNbTi ferritic stainless steel,and the Fe2Nb and Fe3Nb3C phases are mainly precipitated during the fatigue tests.In the fatigue deformation area,both dislocation tangles and dislocation arrays are observed.Furthermore,the sub-grains which form during the cycling deformation with holding time of 10 s are also found.Moreover,the formation of sub-grains leads to the deterioration of the fatigue life of 15CrNbTi steel.展开更多
Charge planning is one of batching problems for steelmaking and continuous casting production,and its optimization will be conducive to subsequent cast planning.Charge planning problem in the twin strands continuous c...Charge planning is one of batching problems for steelmaking and continuous casting production,and its optimization will be conducive to subsequent cast planning.Charge planning problem in the twin strands continuous casting production was studied,where casting width of the odd strand might be different from that of the even strand.Considering the different widths in the twin strands,the resulting counterweights and the constraints of steelmaking and continuous casting,a multiobjective optimization model was established to minimize the number of charges,the number of scale pairs,the surplus and the upgrading costs of steel grades.Furthermore,a hybrid optimization algorithm combined with heuristic and mutation-based estimation of distribution algorithm was proposed to solve the model.Experiments were conducted on several groups of test data collected from practical production orders of Baosteel.The computational results demonstrate that the proposed algorithm can generate better solutions than the manual method.The proposed model and algorithm proved to be effective and practical.展开更多
Characteristic of iron ore is the essential factor of granulating.Three ores,namely specularite,magnetite concentrate and limonite,were selected as adhesion powder to investigate granulating behavior and evolution pro...Characteristic of iron ore is the essential factor of granulating.Three ores,namely specularite,magnetite concentrate and limonite,were selected as adhesion powder to investigate granulating behavior and evolution process of agglomeration.Experiments and modeling were performed to represent granulating behavior on the basis of selectivity,ballability and adhesion rate.The mass fraction of water and particles size of adhesion and nucleation were set at(11±1)%,0-1 mm and 3-5 mm,respectively.Experimental results show that selectivity and ballability promote the evolution of granulation.The water absorption rate of specularite and the ballability of limonite are better.The coupling effects exist in two ores mixing and present positive effect when the proportion of magnetite concentrate is greater than that of specularite or specularite and limonite blend.During three ores mixing,the coupling effect presents a complex superposition state.A characterization model of adhesion rate of mixing granulation was established by random forest algorithms.Its output is adhesion rate,and its inputs include water absorption rate,balling index and mixing proportion.The model parameters are 957 trees and four branches,and the training and prediction errors of the model are 2.3%and 3.7%,respectively.Modeling indicates that the random forest model can be used to represent coupling effects of mixing granulation.展开更多
The hydrogen-induced delayed cracking(HIDC)behaviors of two types of 1500 MPa grade hot stamping steels(HSSs)have been investigated by the method of slow strain rate tensile test and hydrogen permeation,where one is m...The hydrogen-induced delayed cracking(HIDC)behaviors of two types of 1500 MPa grade hot stamping steels(HSSs)have been investigated by the method of slow strain rate tensile test and hydrogen permeation,where one is manufactured by compact strip production(CSP)process which is a revolution to the traditional HSS and the other by the traditional cold rolling process.The results show that the performance of HSS produced by CSP is superior to that of the traditional HSS,due to lower hydrogen embrittlement index,lower hydrogen diffusion coefficient and lower hydrogen content.It has been found that HIDC behavior is closely associated with inclusions.The inclusions of HSS produced by CSP are mainly spherical Al-Ca-O and CaS,while the inclusions in the traditional HSS are TiN+AI2O3+MnS with sharp edges and corners.Based on these results,the influence of composition,shape and distribution of inclusions in HSS on HIDC and the mechanism of HIDC from the perspective of inclusions were analyzed and discussed.展开更多
Correction to:J.Iron Steel Res.Int.(2019)26:1199-1208 https://d0i.0rg/l 0.1007/S42243-019-00312-z The original version of this article unfortunately contained a mistake.Table 6 was incorrect.The corrected table is giv...Correction to:J.Iron Steel Res.Int.(2019)26:1199-1208 https://d0i.0rg/l 0.1007/S42243-019-00312-z The original version of this article unfortunately contained a mistake.Table 6 was incorrect.The corrected table is given below.The line 11 of page 1205 is revised as“The diffusion coefficient of hydrogen in CSPS is 2.76×10^(-7)cm^(2)/s,which is lower than that of CRS”.展开更多
文摘The abnormal corrosion of hot iron ladles was investigated.The performance,the composition and the structure of bricks for hot iron ladles were analyzed.The results show that(1)compared with the alumina-silicon carbide-carbon bricks for the ladle bottom,those for the ladle wall have more pyrophyllite and the Al2O3 content of 36.32 mass%;their bulk density,apparent porosity and cold compressive strength are lower than the requirement of industry standard;they have poor anti-oxidation performance and are oxidized to form a porous layer during service,which loosens the brick lining structure thus leading to fracture,local wear and structural damage of bricks;(2)without preheating,steel scraps are not completely melted,resulting in slag or steel attachment at the mouth or the bottom of ladles thus increasing damage of ladles;(3)and the residual bricks react with the attached slag to form low melting point phases affecting their hot properties.The refractories for the lining of hot iron ladles must be improved in combination with process changes,not entirely by raw materials replacement to reduce costs.
基金the National Natural Science Foundation of China(grant no.51774218 and 51374162)for providing financial support for this work.
文摘Three lightweight Al_(2)O_(3)-MgO castables were fabricated with tabular alumina or microporous corundum as the aggregates,reactiveα-Al_(2)O_(3)micropowder,tabular alumina powder,and fused magnesia powder as the matrix,calcium aluminate cement as the binder,and MgO ultrafine powder(d50=5.4μm)and Al(OH)3 ultrafine powder(d50=8.2μm)as additives.The influence of aggregates and ultrafine powders on the properties,including pore size distribution,heat conductivity,thermal shock resistance,and slag resistance of lightweight refractory castables was investigated.The results show that the incorporation of microporous corundum reduces the bulk density of Al_(2)O_(3)-MgO castables,and MgO and Al(OH)3 ultrafine powders further increases the proportion of micropores in castables,which is beneficial to reducing the heat conductivity,and improving the thermal shock resistance and slag resistance of castables.Additionally,MgO ultrafine powder and Al(OH)3 ultrafine powder increase the fluidity and the strength of castables.
基金This work was supported by the National Natural Science Foundation of China(No.51671199)the National Key Research and Development Program of China(No.2016 YFB0301105).
文摘Coatings on the surface of Mg alloys are inevitably damaged during their practical applications,and corrosion can easily initiate from the damaged areas to accelerate the failure of Mg parts.A dual self-healing coating has already been developed to solve this problem in our previous work.Considering the practical application of this coating,it is necessary to investigate its service behavior in atmospheric environment.Thus,the corrosion behavior of AM60 Mg substrate with and without the self-healing coating was compared in Shenyang industrial atmospheric environment.The results show that the enrichment of sediments and rainwater on the scratch areas can accelerate the corrosion of the exposed Mg substrate.The inhibitors can be released from the damaged coating to inhibit corrosion.The dual self-healing coating shows better inhibition ability to narrow scratches due to the higher inhibitor concentration and less resumption.Also,the coating with wide scratches displays enough inhibition ability as well.The dual self-healing coating is a good alternative for Mg alloy parts in the practical applications.
基金Funded by the High Technology Research and Development Program of China(2011AA11A238)
文摘The fatigue behavior of 30 WGP1600 non-oriented electrical steel, which is generally used in the motors for electrical vehicles, was investigated. The detailed microstructure and dislocation configurations of the fatigue specimens were examined by OM, SEM, and TEM. The test results showed that fatigue cracks were commonly initiated from the surface grain boundaries, crystals plane, and inclusions. The rapid fatigue crack propagation was characterized by transgranular cleavage fracture, while most transient fracture exhibited ductile tearing characteristics. After cyclic deformation of the non-oriented electrical steels, various dislocation structures, such as short and thick lines, veins, persistent slip bands, cells, and labyrinth, were observed.
基金Funded by the National Key R&D Program of China(No.2017YFB0304801)
文摘The microstructure evolution and its effects on the mechanical performance of 2000 MPa bridge cable steel wires were investigated by transmission electron microscope(TEM),electron backscatter diffraction(EBSD),X-ray diffractometer(XRD)and mechanical tests.Experimental results reveal that,with the increasing strain from 0 to 1.42,a fiber structure and a<110>fiber texture aligned with the wire axis are gradually developed accompanied by cementite decomposition and the formation of sub-grains;the tensile strength increases linearly from 1510 to 2025 MPa,and the reduction of the area is stable with a slight decline from 44%to 36%.After annealing at 450℃for different times,pronounced changes in the microstructure occur.Cementite lamella fragment into coarser globules corresponding to a remarkable spheroidization process,while ferrite domains recover and recrystallize,and this process is associated to modifications in the mechanical properties.Furthermore,based on the observations on dislocation lines crossing through cementite lamellae,a possible mechanism of cementite decomposition is discussed.
文摘To reduce the burning loss and the spalling and to improve energy efficiency,the mullite composite lining plates were used to replace cast steel or alloy lining in rotary coke tanks for coke dry quenching equipment.The results show that:the dense mullite composite lining plate in the cone part has the density of 2.20 g·cm^(-3) and the wear test,s volume loss of 4.08 cm^(3),and the light weight mullite composite lining plate in the straight cylinder part has the density of 1.95 g·cm^(-3) and the wear test,s volume loss of 17.6 cm^(3).After using,there is no shrinkage gap,no burn loss or holes in the plates,indicating good sealing of the mullite composite lining plates.The lining plate for the cone part has low burning loss,without spalling for more than half a year.The outer surface temperature of coke tanks adopting the cast steel or the alloy lining is 480 to 570℃,while that of the ones adopting mullite composite lining plates is 120 to 170℃,showing a largely improved insulating property.Adopting mullite composite lining plates on the basis of the current coke tank cage,the lining plates can be timely treated and wholly replaced,improving the service life and reducing the maintenance workload.
基金Funded by the National Key R&D Program of China(No.2017YFB0304801)。
文摘The characteristic of near-surface microstructure and its effects on the torsion performance of cold-drawn pearlitic steel wires for bridge cables were investigated by focused ion beam-scanning electron microscope,transmission electron microscopy and differential scanning calorimetry.The samples with similar tensile strength before and after hot-dip galvanizing process are,respectively,characterized as delaminated and non-delaminated in torsion test which indicates that the tensile strength is independent of the toughness value(i e,reduction area and torsion ability).It is interesting to find that there exists submicron granular ferrite on near-surface of the wires,which can be attributed to dislocation rearrangement and sub-grains rotation during cold drawing and hot-dip galvanizing process.And their distribution can suggest homogeneousness of deformation degree to a certain extent:the closer to the surface of their distribution,the more homogeneous deformation of the wires.There is a close relationship between the thermal stability of the cementite layer and distribution of granular ferrite:differential scanning calorimetry(DSC)analysis shows that the sample is accompanied by submicron granular ferrite which is located closer to the surface has higher thermal stability under galvanizing temperature(450°C).A new mechanism of the torsion delamination of pearlitic steel wires is discussed in terms of the thermal stability of the cementite layer and distribution of granular ferrite.
基金The authors acknowledge the financial support from the National Natural Science Foundation of China(51474164,U1760101 and 51704216).
文摘At present,blast furnace ironmaking is still the main process for producing molten iron,and sinters are the main raw material for blast furnace ironmaking.A sinter with good metallurgical performance can not only ensure smooth operation of the blast furnace but also reduce the blast furnace fuel ratio and increase the molten iron production.Structure is the most important factor affecting the metallurgical properties of the sinter.Thus,the research progress of sinter pore and mineral phase structures was reviewed and the mechanism by which they influence sinter properties was expounded.Multiscale characterization methods for the sinter and their advantages and disadvantages were introduced,and the future research direction of sinter was discussed.
基金financially supported by the Young Elite Scientist Sponsorship Program by CAST(No.YESS20210090)the National Natural Science Foundation of China(No.51974019),Beijing Natural Science Foundation(J210017)China Baowu Low Carbon Metallurgy Innovation Foundation(Nos.BWLCF202119 and BWLCF 202117)。
文摘Hydrogen-enriched blast furnace ironmaking has become an essential route to reduce CO_(2)emissions in the ironmaking process.However,hydrogen-enriched reduction produces large amounts of H_(2)O,which places new demands on coke quality in a blast furnace.In a hydrogen-rich blast furnace,the presence of H_(2)O promotes the solution loss reaction.This result improves the reactivity of coke,which is 20%-30%higher in a pure H_(2)O atmosphere than in a pure CO_(2)atmosphere.The activation energy range is 110-300 kJ/mol between coke and CO_(2)and 80-170 kJ/mol between coke and H_(2)O.CO_(2)and H_(2)O are shown to have different effects on coke degradation mechanisms.This review provides a comprehensive overview of the effect of H_(2)O on the structure and properties of coke.By exploring the interactions between H_(2)O and coke,several unresolved issues in the field requiring further research were identified.This review aims to provide valuable insights into coke behavior in hydrogen-rich environments and promote the further development of hydrogen-rich blast furnace ironmaking processes.
文摘The optimization of continuous casting production planning(CCPP)in the steel industry was studied.The essence of CCPP is the productive capability balance of back-end facilities over the planning time period.The facilities with the demands of productive capability are called the flows.On the basis of charge plans,the task of CCPP is to produce cast plans according to the rules of cast design in order to meet the flows.Firstly,a multi-objective model was established with considering the demands of flows,the capability requirements of liquid steel refini ng devices,and the rules of cast design.Secondly,the model was decomposed into a master problem(set partitioning problem model)and a series of subproblem(pricing problem model)by using Dantzig-Wolfe decomposition strategy.Finally,a column generation-based optimization algorithm(CGBOA)was presented.The experimental results on practical production data from Baosteel demonstrate that the proposed algorithm is effective and feasible.Moreover,a new decision support system based on CGBOA has been successfully established and applied to No.2 Steelmaking Plant at Baosteel.
基金supported financially by the National Key Research and Development Program(No.2016YFB0701401)the Fundamental Research Funds for the Central Universities(No.DUT18LAB01)。
文摘Medium Mn steel was metal inert gas(MIG)welded with NiCrMo-3 and 307 Si filler wires.The effect of filler wires on the microstructure and mechanical properties of joint was investigated,and the carbide precipitates were contrastively discussed.The results revealed that the microstructure of weld metal,heat-affected zone and base metal are austenite.Obvious grain coarsening occurred in the heat-affected zone(HAZ),and the maximum grain size grew up to 160μm.In HAZ,C and Cr segregated at grain boundaries,the carbides was identified as Cr7 C3.The dispersive(Nb,Mo)C phase was also found in weld metal with NiCrMo-3 filler wire.All the welded joints failed in HAZ during tensile tests.The tensile strength of welded joint with NiCrMo-3 filler wire was 675 MPa,which is much higher than that with307 Si filler wire.In comparison to base metal,higher microhardness and lower impact toughness were obtained in HAZ for these two welded joints,which was attributed to the precipitation of Cr7 C3 phase and grain coarsening.The impact toughness around the fusion line is the worst for these two welded joints.
基金National Natural Science Foundation of China(Nos.51134010 and U1660205).
文摘In order to investigate the high-temperature fatigue and fatigue-creep behavior of 15CrNbTi ferritic stainless steel at 800°C,fatigue tests without holding time in laboratory air and with 10 s holding time induced at maximum cyclic stress under argon atmosphere were conducted on an electrohydraulic servo fatigue testing machine.In addition,the morphologies of fatigue fracture surfaces were observed,and the precipitates and dislocation substructures were characterized.The experimental results show that the fatigue limit of 15CrNbTi ferritic stainless steel is 30 MPa at 800°C.The fatigue life of the experimental steel obviously decreases if holding time of 10 s is introduced at maximum cyclic stress.Under two test conditions,the fatigue cracks transgranularly initiate at the free surface of fatigue specimens and then propagate in a transgranular mode.It is dem on strated that three kinds of precipitates inclu ding(Nb,Ti)C phase,Fe2Nb phase and Fe3Nb3C phase can be observed in 15CrNbTi ferritic stainless steel,and the Fe2Nb and Fe3Nb3C phases are mainly precipitated during the fatigue tests.In the fatigue deformation area,both dislocation tangles and dislocation arrays are observed.Furthermore,the sub-grains which form during the cycling deformation with holding time of 10 s are also found.Moreover,the formation of sub-grains leads to the deterioration of the fatigue life of 15CrNbTi steel.
基金This work was supported by the National Key Research and Development Program of China(No.2017YFB0304100).
文摘Charge planning is one of batching problems for steelmaking and continuous casting production,and its optimization will be conducive to subsequent cast planning.Charge planning problem in the twin strands continuous casting production was studied,where casting width of the odd strand might be different from that of the even strand.Considering the different widths in the twin strands,the resulting counterweights and the constraints of steelmaking and continuous casting,a multiobjective optimization model was established to minimize the number of charges,the number of scale pairs,the surplus and the upgrading costs of steel grades.Furthermore,a hybrid optimization algorithm combined with heuristic and mutation-based estimation of distribution algorithm was proposed to solve the model.Experiments were conducted on several groups of test data collected from practical production orders of Baosteel.The computational results demonstrate that the proposed algorithm can generate better solutions than the manual method.The proposed model and algorithm proved to be effective and practical.
基金This work was financially supported by the National Natural Science Foundation of China(No.51674042)Hunan Province 2011 Collaborative Innovation Center of Clean Energy and Smart Grid.
文摘Characteristic of iron ore is the essential factor of granulating.Three ores,namely specularite,magnetite concentrate and limonite,were selected as adhesion powder to investigate granulating behavior and evolution process of agglomeration.Experiments and modeling were performed to represent granulating behavior on the basis of selectivity,ballability and adhesion rate.The mass fraction of water and particles size of adhesion and nucleation were set at(11±1)%,0-1 mm and 3-5 mm,respectively.Experimental results show that selectivity and ballability promote the evolution of granulation.The water absorption rate of specularite and the ballability of limonite are better.The coupling effects exist in two ores mixing and present positive effect when the proportion of magnetite concentrate is greater than that of specularite or specularite and limonite blend.During three ores mixing,the coupling effect presents a complex superposition state.A characterization model of adhesion rate of mixing granulation was established by random forest algorithms.Its output is adhesion rate,and its inputs include water absorption rate,balling index and mixing proportion.The model parameters are 957 trees and four branches,and the training and prediction errors of the model are 2.3%and 3.7%,respectively.Modeling indicates that the random forest model can be used to represent coupling effects of mixing granulation.
基金The authors would like to express sincere gratitude to Dr.Na Luo for her insightful comments and helpful assistance to the revision of this manuscript.This work was supported by National Natural Science Foundation of China(No.51871172).
文摘The hydrogen-induced delayed cracking(HIDC)behaviors of two types of 1500 MPa grade hot stamping steels(HSSs)have been investigated by the method of slow strain rate tensile test and hydrogen permeation,where one is manufactured by compact strip production(CSP)process which is a revolution to the traditional HSS and the other by the traditional cold rolling process.The results show that the performance of HSS produced by CSP is superior to that of the traditional HSS,due to lower hydrogen embrittlement index,lower hydrogen diffusion coefficient and lower hydrogen content.It has been found that HIDC behavior is closely associated with inclusions.The inclusions of HSS produced by CSP are mainly spherical Al-Ca-O and CaS,while the inclusions in the traditional HSS are TiN+AI2O3+MnS with sharp edges and corners.Based on these results,the influence of composition,shape and distribution of inclusions in HSS on HIDC and the mechanism of HIDC from the perspective of inclusions were analyzed and discussed.
文摘Correction to:J.Iron Steel Res.Int.(2019)26:1199-1208 https://d0i.0rg/l 0.1007/S42243-019-00312-z The original version of this article unfortunately contained a mistake.Table 6 was incorrect.The corrected table is given below.The line 11 of page 1205 is revised as“The diffusion coefficient of hydrogen in CSPS is 2.76×10^(-7)cm^(2)/s,which is lower than that of CRS”.
