M42 high speed steel （HSS）, a high grade alloy, was produced using the spray forming technology. Optical metallography （OM）,X-ray diffraction （XRD） and scanning electron microscope （SEM） were used to investiga...M42 high speed steel （HSS）, a high grade alloy, was produced using the spray forming technology. Optical metallography （OM）,X-ray diffraction （XRD） and scanning electron microscope （SEM） were used to investigate the microstructures of the as-sprayed M42 HSS and the as-atomized powders. It is found that as-sprayed M42 HSS is composed of martensite, retained austenite and carbides. The grain size, as well as the morphology, size and distribution of the carbides have been greatly improved compared with those of the as-cast M42 steel （ a traditional process）. The size of the powder obtained at a high cold speed was ranged from 50 μm to 100μm in diameter. Its representative microstructures include dendrite, dendritic fragments, a mixture of dendrites, equiaxed grains and dendritic fragments,and equiaxed grains. The rapid solidification in the spray forming is a key factor to cause the refinement of the M42 HSS.展开更多
A 3D coupling mathematical simulation program of the fluid flow, thermal transfer and solidification was developed based on the slab continuous casting process. Some characteristics such as fluid flow, solidification ...A 3D coupling mathematical simulation program of the fluid flow, thermal transfer and solidification was developed based on the slab continuous casting process. Some characteristics such as fluid flow, solidification and temperature distribution near the submerged entry nozzle （SEN） and the corner of the mold were simulated and analyzed. The result of the calculation indicates that the flow of molten metal forms two big cycling zones in the mold after it flows out of the SEN, and the temperature at the center of the two zones is relatively low. Moreover, there is a small narrow cycling zone near the narrow side of the mold due to casting. The velocity of the surface flow, the turbulent kinetic energy and the F value might reveal the relationship between the fluctuation of meniscus and the quality of the slab to some degree.展开更多
A 1：1 water model of a twin-roll strip caster was set up based on the Froude number（Fr） and Reynolds number （Re） similarity criteria. Fluctuation and the mixing effect in the molten pool of twin-roll strip castin...A 1：1 water model of a twin-roll strip caster was set up based on the Froude number（Fr） and Reynolds number （Re） similarity criteria. Fluctuation and the mixing effect in the molten pool of twin-roll strip casting process were analyzed through hydraulic simulation. The height of the fluctuation of the liquid pool surface and the residence time were measured by DJ800 multifunctional monitor under different process conditions. The results show that the casting velocity, the insertion depth and the pool level have a great effect on the fluctuation.展开更多
Targeting the single tuyere and double tuyere methods of argon blowing for Baosteel＇ s 300 t ladle furnace, the 3D continuity equation, the N-S equation and the turbulent k-ε double-equation were used to model the f...Targeting the single tuyere and double tuyere methods of argon blowing for Baosteel＇ s 300 t ladle furnace, the 3D continuity equation, the N-S equation and the turbulent k-ε double-equation were used to model the form of the molten steel flow and the dead areas under six different argon blowing conditions. The different flow field forms and the degree of mixing under different argon blowing methods were compared. The results demonstrate that when large ladles are operated via different methods of argon blowing, the spray from the centre of a single tuyere forms a symmetrical vortex, while when a double tuyere sprays, there is basically no clear vortex. In regards to the amount of argon blowing that will produce the best blend of molten steel, the amount of dead area reduction will not be clearly noticeable if there is an excessive argon blowing amount.展开更多
Using the equation of continuity and the double equation of Navier-Stokes and k-ε, numerical modeling on a single outlet continuous casting tundish has been carried out during the process of non-thermal flow coupling...Using the equation of continuity and the double equation of Navier-Stokes and k-ε, numerical modeling on a single outlet continuous casting tundish has been carried out during the process of non-thermal flow coupling. The flow field distribution inside the tundish was calculated and the viscosity response time was calculated with the mass transfer equation based on the flow field distribution. The flow characteristics of the molten steel inside the tundish were analyzed, with the results of the numerical modeling compared to the hydraulic modeling. The results showed that the Resident Time Distribution （RTD） curves in the latter anatomosed comparatively better. This certified the validity established by the mathematical model. Numerical modeling was carried out on both large and small tundishes during the processes of thermal flow coupling and also thermal non-flow coupling. The results showed that in regards to large tundishes with relatively simple flow processes, using numerical modeling for thermal flow coupling is necessary.展开更多
The microstructure of high vanadium and cobalt high speed steel （high-V/Co HSS ） and the morphology of its carbides were analyzed by optical microscope （OM）,scanning electron microscope （SEM） ,electron probe mic...The microstructure of high vanadium and cobalt high speed steel （high-V/Co HSS ） and the morphology of its carbides were analyzed by optical microscope （OM）,scanning electron microscope （SEM） ,electron probe microanalysis （EPMA）, X-ray power diffraction （XRD）, atomic force microscopy （AFM） and single phase erosion （SPE）. The results suggest that the as-sprayed high-V/Co HSS has fine equiaxed grains （about 20 μm in size）, which were homogeneously distributed. The carbides have two classical morphologies- one is fine particles （ about 2 μm in size） distributed along the grain boundaries and the other is needle-like one, distributed on the grain boundaries. There are MC carbides, M2C carbides,M6C carbides and Cr2WC2 carbides in the as-sprayed high-V/Co HSS samples,however,in the as-cast high-V/ Co HSS ,there are MC carbides and CrzWC2 carbides only. The SPE results show that there are two types of MC carbides in the as-sprayed HSS ：the sphere one and the particle-like one. The former is about 2 ixm in size and the latter is less than 1 μm, dispersed inside the grains,quite different from the MC carbides in the as-cast HSS. According to the AFM results, the skeleton-like M6C carbides of the as-sprayed high-V/Co HSS are embedded in the matrix along the grain boundaries. It is found that there are sharp membrane pieces on the carbides. Some small bamboo-shoot-like MC carbides grow from the matrix and are dispersed inside the grain. Those larger MC carbides are spherical particles embedded at the grain boundary junctions.展开更多
文摘M42 high speed steel （HSS）, a high grade alloy, was produced using the spray forming technology. Optical metallography （OM）,X-ray diffraction （XRD） and scanning electron microscope （SEM） were used to investigate the microstructures of the as-sprayed M42 HSS and the as-atomized powders. It is found that as-sprayed M42 HSS is composed of martensite, retained austenite and carbides. The grain size, as well as the morphology, size and distribution of the carbides have been greatly improved compared with those of the as-cast M42 steel （ a traditional process）. The size of the powder obtained at a high cold speed was ranged from 50 μm to 100μm in diameter. Its representative microstructures include dendrite, dendritic fragments, a mixture of dendrites, equiaxed grains and dendritic fragments,and equiaxed grains. The rapid solidification in the spray forming is a key factor to cause the refinement of the M42 HSS.
文摘A 3D coupling mathematical simulation program of the fluid flow, thermal transfer and solidification was developed based on the slab continuous casting process. Some characteristics such as fluid flow, solidification and temperature distribution near the submerged entry nozzle （SEN） and the corner of the mold were simulated and analyzed. The result of the calculation indicates that the flow of molten metal forms two big cycling zones in the mold after it flows out of the SEN, and the temperature at the center of the two zones is relatively low. Moreover, there is a small narrow cycling zone near the narrow side of the mold due to casting. The velocity of the surface flow, the turbulent kinetic energy and the F value might reveal the relationship between the fluctuation of meniscus and the quality of the slab to some degree.
文摘A 1：1 water model of a twin-roll strip caster was set up based on the Froude number（Fr） and Reynolds number （Re） similarity criteria. Fluctuation and the mixing effect in the molten pool of twin-roll strip casting process were analyzed through hydraulic simulation. The height of the fluctuation of the liquid pool surface and the residence time were measured by DJ800 multifunctional monitor under different process conditions. The results show that the casting velocity, the insertion depth and the pool level have a great effect on the fluctuation.
文摘Targeting the single tuyere and double tuyere methods of argon blowing for Baosteel＇ s 300 t ladle furnace, the 3D continuity equation, the N-S equation and the turbulent k-ε double-equation were used to model the form of the molten steel flow and the dead areas under six different argon blowing conditions. The different flow field forms and the degree of mixing under different argon blowing methods were compared. The results demonstrate that when large ladles are operated via different methods of argon blowing, the spray from the centre of a single tuyere forms a symmetrical vortex, while when a double tuyere sprays, there is basically no clear vortex. In regards to the amount of argon blowing that will produce the best blend of molten steel, the amount of dead area reduction will not be clearly noticeable if there is an excessive argon blowing amount.
文摘Using the equation of continuity and the double equation of Navier-Stokes and k-ε, numerical modeling on a single outlet continuous casting tundish has been carried out during the process of non-thermal flow coupling. The flow field distribution inside the tundish was calculated and the viscosity response time was calculated with the mass transfer equation based on the flow field distribution. The flow characteristics of the molten steel inside the tundish were analyzed, with the results of the numerical modeling compared to the hydraulic modeling. The results showed that the Resident Time Distribution （RTD） curves in the latter anatomosed comparatively better. This certified the validity established by the mathematical model. Numerical modeling was carried out on both large and small tundishes during the processes of thermal flow coupling and also thermal non-flow coupling. The results showed that in regards to large tundishes with relatively simple flow processes, using numerical modeling for thermal flow coupling is necessary.
基金Spray forming,an advanced processing technique,isa key project of Baoshan Iron & Steel Co.,Ltd. (No.BG010102)
文摘The microstructure of high vanadium and cobalt high speed steel （high-V/Co HSS ） and the morphology of its carbides were analyzed by optical microscope （OM）,scanning electron microscope （SEM） ,electron probe microanalysis （EPMA）, X-ray power diffraction （XRD）, atomic force microscopy （AFM） and single phase erosion （SPE）. The results suggest that the as-sprayed high-V/Co HSS has fine equiaxed grains （about 20 μm in size）, which were homogeneously distributed. The carbides have two classical morphologies- one is fine particles （ about 2 μm in size） distributed along the grain boundaries and the other is needle-like one, distributed on the grain boundaries. There are MC carbides, M2C carbides,M6C carbides and Cr2WC2 carbides in the as-sprayed high-V/Co HSS samples,however,in the as-cast high-V/ Co HSS ,there are MC carbides and CrzWC2 carbides only. The SPE results show that there are two types of MC carbides in the as-sprayed HSS ：the sphere one and the particle-like one. The former is about 2 ixm in size and the latter is less than 1 μm, dispersed inside the grains,quite different from the MC carbides in the as-cast HSS. According to the AFM results, the skeleton-like M6C carbides of the as-sprayed high-V/Co HSS are embedded in the matrix along the grain boundaries. It is found that there are sharp membrane pieces on the carbides. Some small bamboo-shoot-like MC carbides grow from the matrix and are dispersed inside the grain. Those larger MC carbides are spherical particles embedded at the grain boundary junctions.
