To investigate the evolutionary behavior of the MnO–SiO_(2)–Al_(2)O_(3)–MgO inclusions during heat treatment,water quenched samples were isothermally held at 1100°C for 120 min in Ar and air atmosphere,and the...To investigate the evolutionary behavior of the MnO–SiO_(2)–Al_(2)O_(3)–MgO inclusions during heat treatment,water quenched samples were isothermally held at 1100°C for 120 min in Ar and air atmosphere,and the obtaining samples were analyzed by X-ray diffraction,scanning electron microscopy and energy dispersive spectrometer.It showed that 3MnO·Al_(2)O_(3)·3SiO_(2)and MnO·SiO_(2)were detected in the 5 wt.%MgO system after isothermal holding in Ar atmosphere,while MgO·Al_(2)O_(3),MnO·SiO_(2)and Mn7O8·SiO4 were detected in air atmosphere.The evolutionary behavior of the 10,15 and 20 wt.%MgO systems after isothermal holding in different atmosphere were consistent.Oxygen affected the solid phase transformation of the low MgO content systems.The calculation results of FactSage 8.1 showed that MgO·Al_(2)O_(3)was formed in the 5 wt.%MgO system with air atmosphere.The solid phase transformation was accompanied by grain coarsening during the isothermal holding process.The differences in the solid phase transformation in different atmosphere of the 5 wt.%MgO system indicated that it was a gas-phase transport grain coarsening mechanism.The enrichment of Al element in the liquid phase region at the grain edges,the homogeneous distribution of Mg element and the disappearance of the liquid phase within the crystal revealed that other MgO content systems were liquid–solid transport grain coarsening mechanism.展开更多
Thermodynamics and kinetics of dissociation and precipitation of MnS inclusions,as well as the effect of reoxidation in liquid steel on MgO·Al_(2)O_(3)inclusions in AISI M35 steel during electroslag remelting(ESR...Thermodynamics and kinetics of dissociation and precipitation of MnS inclusions,as well as the effect of reoxidation in liquid steel on MgO·Al_(2)O_(3)inclusions in AISI M35 steel during electroslag remelting(ESR)process were investigated.The inclusions found in the consumable electrode were MnS,MgO·Al_(2)O_(3)and MnS adhering to MgO·Al_(2)O_(3).MnS inclusions were nearly spherical and ellipse in morphology,and most of them were less than 2μm in size.MgO·Al_(2)O_(3)inclusions were polygonal and nearly spherical and most about 1-4μm in size.The inclusions in ESR ingot observed by scanning electron microscopy-energy-dispersive X-ray spectrometer were polygonal and nearly spherical MgO·Al_(2)O_(3).MnS inclusions in the consumable electrode were completely dissociated before the liquid film dripping into molten slag pool.The controlling step of MnS inclusions dissociation was the mass transfer of[Mn]in the liquid steel.During the solidification process,the thermodynamic driving force could not meet MnS inclusions precipitation before the solid fraction exceeds 0.996,and the kinetics condition is too poor for the growth of MnS inclusions in the steel when the solid fraction is larger than 0.996.MgO·Al_(2)O_(3)inclusions in ESR ingot originated from the remained MgO·Al_(2)O_(3)inclusions in consumable electrode and the fresh ones formed by the reaction between dissolved magnesium,oxygen and aluminum in liquid steel.展开更多
Submerged entry nozzle(SEN)clogging during continuous casting of Ti-stabilized ultra-pure ferritic stainless(Ti-UPFS)steels was systematically investigated via cross-sectional analysis and acid dissolution treatment.T...Submerged entry nozzle(SEN)clogging during continuous casting of Ti-stabilized ultra-pure ferritic stainless(Ti-UPFS)steels was systematically investigated via cross-sectional analysis and acid dissolution treatment.The SEN deposit profile was characterized as occurring in three major layers:(1)an eroded refractory layer;(2)an initial adhesive layer comprised an Al_(2)O_(3)-ZrO_(2) composite sub-layer and a dense Al_(2)O_(3)-based deposit sub-layer;and(3)a porous multiphase deposit layer mainly consisting of MgO·Al_(2)O_(3),CaO-Al_(2)O_(3),and CaO-TiOx.The MgO·Al_(2)O_(3)-rich inclusions did not adhere directly to the eroded refractory but were entrapped during the deposit growth.Results of inclusion characterization in the tundish revealed that the MgO·Al2O3-rich particles present in the tundish served as the primary source of clogging deposits.Furthermore,a novel cavity-induced adhesion model by circular approximation was established to explain the effects of complex inclusion characteristics and refractory material type on adhesion force.A high number of small MgO·Al_(2)O_(3) inclusions were expected to accelerate the buildup of clogging deposits.Improving the modification of MgO·Al_(2)O_(3)-rich inclusions in the size range of 2-4μm by Ca treatment was crucial to minimizing the risk of SEN clogging during the continuous casting of Ti-UPFS steels.展开更多
基金supported by the National Natural Science Foundation of China(Nos.52274341 and 51974210).
文摘To investigate the evolutionary behavior of the MnO–SiO_(2)–Al_(2)O_(3)–MgO inclusions during heat treatment,water quenched samples were isothermally held at 1100°C for 120 min in Ar and air atmosphere,and the obtaining samples were analyzed by X-ray diffraction,scanning electron microscopy and energy dispersive spectrometer.It showed that 3MnO·Al_(2)O_(3)·3SiO_(2)and MnO·SiO_(2)were detected in the 5 wt.%MgO system after isothermal holding in Ar atmosphere,while MgO·Al_(2)O_(3),MnO·SiO_(2)and Mn7O8·SiO4 were detected in air atmosphere.The evolutionary behavior of the 10,15 and 20 wt.%MgO systems after isothermal holding in different atmosphere were consistent.Oxygen affected the solid phase transformation of the low MgO content systems.The calculation results of FactSage 8.1 showed that MgO·Al_(2)O_(3)was formed in the 5 wt.%MgO system with air atmosphere.The solid phase transformation was accompanied by grain coarsening during the isothermal holding process.The differences in the solid phase transformation in different atmosphere of the 5 wt.%MgO system indicated that it was a gas-phase transport grain coarsening mechanism.The enrichment of Al element in the liquid phase region at the grain edges,the homogeneous distribution of Mg element and the disappearance of the liquid phase within the crystal revealed that other MgO content systems were liquid–solid transport grain coarsening mechanism.
基金The financial support by the National Natural Science Foundation of China(Grant No.52104339)the Hubei Provincial Key Laboratory for New Processes of Ironmaking and Steelmaking(Grant No.KF-20-3)are greatly acknowledged.
文摘Thermodynamics and kinetics of dissociation and precipitation of MnS inclusions,as well as the effect of reoxidation in liquid steel on MgO·Al_(2)O_(3)inclusions in AISI M35 steel during electroslag remelting(ESR)process were investigated.The inclusions found in the consumable electrode were MnS,MgO·Al_(2)O_(3)and MnS adhering to MgO·Al_(2)O_(3).MnS inclusions were nearly spherical and ellipse in morphology,and most of them were less than 2μm in size.MgO·Al_(2)O_(3)inclusions were polygonal and nearly spherical and most about 1-4μm in size.The inclusions in ESR ingot observed by scanning electron microscopy-energy-dispersive X-ray spectrometer were polygonal and nearly spherical MgO·Al_(2)O_(3).MnS inclusions in the consumable electrode were completely dissociated before the liquid film dripping into molten slag pool.The controlling step of MnS inclusions dissociation was the mass transfer of[Mn]in the liquid steel.During the solidification process,the thermodynamic driving force could not meet MnS inclusions precipitation before the solid fraction exceeds 0.996,and the kinetics condition is too poor for the growth of MnS inclusions in the steel when the solid fraction is larger than 0.996.MgO·Al_(2)O_(3)inclusions in ESR ingot originated from the remained MgO·Al_(2)O_(3)inclusions in consumable electrode and the fresh ones formed by the reaction between dissolved magnesium,oxygen and aluminum in liquid steel.
基金This work was financially supported by the National Natural Science Foundation of China(No.51574026).
文摘Submerged entry nozzle(SEN)clogging during continuous casting of Ti-stabilized ultra-pure ferritic stainless(Ti-UPFS)steels was systematically investigated via cross-sectional analysis and acid dissolution treatment.The SEN deposit profile was characterized as occurring in three major layers:(1)an eroded refractory layer;(2)an initial adhesive layer comprised an Al_(2)O_(3)-ZrO_(2) composite sub-layer and a dense Al_(2)O_(3)-based deposit sub-layer;and(3)a porous multiphase deposit layer mainly consisting of MgO·Al_(2)O_(3),CaO-Al_(2)O_(3),and CaO-TiOx.The MgO·Al_(2)O_(3)-rich inclusions did not adhere directly to the eroded refractory but were entrapped during the deposit growth.Results of inclusion characterization in the tundish revealed that the MgO·Al2O3-rich particles present in the tundish served as the primary source of clogging deposits.Furthermore,a novel cavity-induced adhesion model by circular approximation was established to explain the effects of complex inclusion characteristics and refractory material type on adhesion force.A high number of small MgO·Al_(2)O_(3) inclusions were expected to accelerate the buildup of clogging deposits.Improving the modification of MgO·Al_(2)O_(3)-rich inclusions in the size range of 2-4μm by Ca treatment was crucial to minimizing the risk of SEN clogging during the continuous casting of Ti-UPFS steels.
