Rodolfo Morales - Academia.edu (original) (raw)
Papers by Rodolfo Morales
Fabrication Methods, 2016
AISTech - Iron and Steel Technology Conference Proceedings, Oct 19, 2009
Stability of metal-flux interface is affected mainly by the casting speed, mold width, steel and ... more Stability of metal-flux interface is affected mainly by the casting speed, mold width, steel and flux chemistries and nozzle-port geometry. Maintaining constant all other mold operating factors, port geometry plays the most important role to attain a stable interface. Fluid flow through the ports dictates the performance of a nozzle for casting all the spectrum of slab mold widths in a given caster. In this work, various port geometries were tested. The root of flux entrainment is the generation of velocity spikes which are difficult to identify even through the statistical analysis of turbulent fluid flow data of steel in the mold. Through physical modeling, theoretical considerations, dimensional analysis and mathematical simulations the generation of velocity spikes at the interface are identified in this work. On the other hand, a critical capillary number for flux entrainment onset is compared with capillary numbers calculated using the velocity spikes. Whenever the magnitudes of these capillary numbers exceed the critical one the flux entrainment existence will be predicted. Therefore, by the number of spikes per minute and their magnitude it is possible to assess the performance of a nozzle making possible the link between steel chemistry, flux chemistry, mold width and nozzle design.
Metallurgical and Materials Transactions B, 2021
There are many correlations for Nusselt numbers applied to calculate heat transfer between a flui... more There are many correlations for Nusselt numbers applied to calculate heat transfer between a fluid and a sphere. In all massive industrial processes of metal production, there is the need to calculate the melting times of metal additions during alloying operations. A multiphase mathematical model helps to assess the applicability of these correlations to actual industrial processes. This model simulates the heat transfer between solid particles and liquid steel under turbulence conditions during the tapping operation of steel with simultaneous argon bottom stirring. There are six recommendable correlations among the 16 most relevant available ones in the literature. These correlations apply to small Prandtl numbers (Pr = 0.01 to 0.2, i.e., metals) or medium magnitudes of Prandtl numbers (Pr = 1 to 10, air and water). Melting rates depend on the turbulence intensities and superheat of the metal. High superheats cause the hydrodynamic effects to have less influence on the melting time...
Journal of Materials Science and Engineering with Advanced Technology, Jul 15, 2017
Metallurgical and Materials Transactions B, 2012
ABSTRACT The performance characteristics of a tundish, such as the flotation of inclusions and sl... more ABSTRACT The performance characteristics of a tundish, such as the flotation of inclusions and slag entrainment, are largely influenced by the fluid-flow phenomena. Physical modeling in water is widely used to understand the fluid flows in a tundish and as a tool to improve, control, and design procedures for high-quality steel processing operations. These approaches were used to study the performance of fluid flow for a new design of ladle shroud. The new design for a dissipative ladle shroud (DLS) was studied, using a one-third scale, delta shaped, four-strand tundish. The results were compared with those achieved with the conventional ladle shroud. Different cases have been analyzed, including a conventional ladle shroud (LS) with a bare tundish and a tundish furnished with an impact pad. Similarly, the new design of the shroud (DLS) was studied under equivalent conditions. The physical experiments included the use of particle image velocimetry (PIV) and conductivity tracer techniques. The PIV measured the instantaneous velocities at the outlet of the DLS and the LS at different flow rates, showing the detailed jetting characteristics of water leaving the two types of ladle shroud. Residence time distribution (RTD) curves were also obtained for the different flow arrangements previously mentioned, and the dispersion of a colored dye tracer was observed at different intervals of time during tundish operation and analyzed using the video visualization technique.
Metallurgical and Materials Transactions B, 2016
The design of the ports of a casting nozzle has profound effects on the fluid flow patterns in sl... more The design of the ports of a casting nozzle has profound effects on the fluid flow patterns in slab molds. The influence of these outlets have also considerable effects on the turbulent flow and turbulence variables inside the nozzle itself. To understand the effects of nozzle design, three approaches were employed: a theoretical analysis based on the turbulent viscosity hypothesis, dimensional analysis (both analyses aided by computer fluid dynamics), and experiments using particle image velocimetry. The first approach yields a linear relation between calculated magnitudes of scalar fields of ε (dissipation rate of kinetic energy) and k2 (square of the turbulent kinetic energy), which is derived from the wall and the logarithmic-wall laws in the boundary layers. The smaller the slope of this linear relation is, the better the performance of a given nozzle is for maintaining the stability of the melt–flux interface. The second approach yields also a linear relation between flow rate of liquid metal and the cubic root of the dissipation rate of kinetic energy. In this case, the larger the slope of the linear relation is, the better the performance of a given nozzle is for maintaining the stability of the melt–flux interface. Finally, PIV measurements in a mold water model, together with equations for estimation of critical melt velocities for slag entrainment, were used to quantify the effects of nozzle design on the dynamics of the metal–slag interface. The three approaches agree in the characterization of turbulent flows in continuous casting molds using different nozzles.
JOM
The startup operations of continuous casting sequences of steel in a 4-strand tundish, using thre... more The startup operations of continuous casting sequences of steel in a 4-strand tundish, using three different turbulence inhibitors (TI), were investigated using a 1/3-scale water model in combination with numerical simulations through the volume of fluid model. The two-phase flow water–air is used to model the system, and the liquid steel–air and the liquid–gas interfaces are tracked by a donor–acceptor principle applied in the computational mesh. In the actual caster, one of the inhibitors releases the liquid steel with a sensible heat high enough to avoid freezing in the regions near the outer strands during the startup of the casting sequence. A second inhibitor improves the fluid flow control by yielding higher plug flow volume fractions. However, it promotes steel freezing in the outer strands. The analysis of the results lead to the design of the third TI with intermediate capability to control the steel flow, preventing steel freezing in the regions near the outer strands.
The process for recovering lead from battery residues used in several Mexican Plants include lead... more The process for recovering lead from battery residues used in several Mexican Plants include lead blast furnace and rotary furnaces. The formers are basically fed with recycled batteries together with the necessary additives to produce metallic lead. One of the by-products generated in the blast furnace is a dust mainly formed by lead sulfide. The rotary furnace is used to recover lead from lead batteries, dross from the refining-alloying process and the lead fines produced in the blast furnace. This paper describes thermodynamic analysis made to the rotary furnace process to understand the effect that each component of the system has upon the lead recovery. In order to enhance the process, the influence of iron chips composition and excess coke on slag viscosity is discussed. A computer optimization program has been developed to design the furnace charge based on material and energy balances, together with the thermodynamic equilibrium calculation.
ABSTRACT Gas-liquid flows inside the submerged entry nozzle (SEN) of a slab mold and their influe... more ABSTRACT Gas-liquid flows inside the submerged entry nozzle (SEN) of a slab mold and their influence on the flow field in the mold were studied using video recording, mathematical simulations and Digital Particle Image Velocimetry (DPIV) approaches. Coalescence-breakup phenomena of bubbles in liquid steel flowing through a slab mold were studied using a water model. At low gas loads (ratio of mass flow rates of gas and liquid in the submerged entry nozzle) bubble dynamics consist of coalescence-breakup and dragged processes from the SEN until close to the narrow wall. At high gas loads, bubbles are accumulated close to the narrow wall where they coalesce, break and ascend toward the bath surface forming bubble swarms or descend along the narrow wall by dragging forces exerted by liquid phase on the surfaces of the bubbles. These swarms consist of coalescing bubbles and agglomerating groups of bubbles. The presence of bubbles in the flow decreases the magnitudes of vorticity values in the flow field of mono-phase flows. Thus, to increase the casting speed, the injection of argon should be adjusted to an appropriate level to avoid an excess of liquid entrainment to the flux phase. Bubbly and annular flows in the SEN yield structurally-uncoupled and structurally coupled flows in the mold, respectively. High gas loads at high casting rates lead to increases of bubble population and bubbles sizes due to coalescence processes whose rate exceeds that of their breakup. The presence of gas bubbles or gas layers inside the SEN lead to periodical twisting of the liquid flow that induces biased flows through both ports yielding uneven flows in the mold. A multiphase mathematical model predicts acceptably well the flow dynamics of two-phase flows inside the SEN.
Metals
The current automation of steelmaking processes is capable of complete control through programmed... more The current automation of steelmaking processes is capable of complete control through programmed hardware. However, many metallurgical and operating factors, such as heat transfer control, require further studies under industrial conditions. In this context, computer simulation has become a powerful tool for reproducing the effects of industrial constraints on heat transfer. This work reports a computational model to simulate heat removal from billets’ strands in the continuous casting process. This model deals with the non-symmetric cooling conditions of a billet caster. These cooling conditions frequently occur due to plugged nozzles in the secondary cooling system (SCS). The model developed simulates the steel thermal behavior for casters with a non-symmetric distribution of the sprays in the SCS using different boundary conditions to show possible heat transfer variations. Finally, the results are compared with actual temperatures from different casters to demonstrate the predi...
Metals
Changes of unsteady multiphase fluid flow patterns of liquid steel during electric arc furnace-la... more Changes of unsteady multiphase fluid flow patterns of liquid steel during electric arc furnace-ladle tapping operations, with simultaneous argon bottom injection, are simulated using interfacial tracking computing techniques. The impinging steel jet interacts with the argon bubbling plume, suffering mutual bending effects, and imparting non-symmetric flows of liquid steel during the whole ladle filling time. At low bath levels, radial recirculating flows are generated and at high bath levels, these flows are substituted by vertical long flows generated by the permanent interaction between the impinging jet and the argon plume. Turbulence intensity increases as the bath level rises. Low bath levels are suitable for pre-melting and preheating ferroalloy particles. High bath levels of steel in the ladle, close to total ladle filling, are the most suitable conditions for thermal and chemical homogenizations. Argon gas forms an intermittent blanket over the air–liquid steel mix due to it...
ISIJ International
Effects of slag layer thickness on the fluid dynamics of liquid steel in gas-stirred ladles by bo... more Effects of slag layer thickness on the fluid dynamics of liquid steel in gas-stirred ladles by bottom injection of argon was studied through water modeling experiments and numerical simulations. Mixing times increase considerably with thicker slag layers and decrease of gas flow rates. The physical properties of the system have a smaller influence on mixing time. Slag Eye Opening (SEO) area is increased under thin slag layers, increase of gas flow rates, and denser and less viscous slags. The planes close to the metalslag interface, under the presence of thick slag layers for a given gas flow rate, are split in subregions of small velocities with different orientations making the lower fluid to come close to a stagnant condition. The presence of, either, thick or thin slag layers does not influence the axial velocity along the plume height for a fixed flow rate of gas. The SEO area follows a linear relationship with the square root of the densiometric Froude number based on the slag layer thickness.
Three-phase interactions (metal-slag-argon) in ladle stirring operations have strong effects on m... more Three-phase interactions (metal-slag-argon) in ladle stirring operations have strong effects on metal-slag mass transfer processes. Specifically, the thickness of the slag controls the fluid turbulence to an extent that once trespassing a critical thickness, increases of stirring strength have not further effects on the flow. To analyze these conditions, a physical model considering the three phases was built to study liquid turbulence in the proximities of the metal-slag interface. A velocity probe placed close to the interface permitted the continuous monitoring and statistical analyses of turbulence. The slag-eye opening was found to be strongly dependent on the stirring conditions, and the mixing times decreased with thin slag thicknesses. Slag entrainment was enhanced with thick slag layers, and high flow rates of the gas phase. A multiphase model was developed to simulate these results finding a good agreement between experimental and numerical results.
Fabrication Methods, 2016
AISTech - Iron and Steel Technology Conference Proceedings, Oct 19, 2009
Stability of metal-flux interface is affected mainly by the casting speed, mold width, steel and ... more Stability of metal-flux interface is affected mainly by the casting speed, mold width, steel and flux chemistries and nozzle-port geometry. Maintaining constant all other mold operating factors, port geometry plays the most important role to attain a stable interface. Fluid flow through the ports dictates the performance of a nozzle for casting all the spectrum of slab mold widths in a given caster. In this work, various port geometries were tested. The root of flux entrainment is the generation of velocity spikes which are difficult to identify even through the statistical analysis of turbulent fluid flow data of steel in the mold. Through physical modeling, theoretical considerations, dimensional analysis and mathematical simulations the generation of velocity spikes at the interface are identified in this work. On the other hand, a critical capillary number for flux entrainment onset is compared with capillary numbers calculated using the velocity spikes. Whenever the magnitudes of these capillary numbers exceed the critical one the flux entrainment existence will be predicted. Therefore, by the number of spikes per minute and their magnitude it is possible to assess the performance of a nozzle making possible the link between steel chemistry, flux chemistry, mold width and nozzle design.
Metallurgical and Materials Transactions B, 2021
There are many correlations for Nusselt numbers applied to calculate heat transfer between a flui... more There are many correlations for Nusselt numbers applied to calculate heat transfer between a fluid and a sphere. In all massive industrial processes of metal production, there is the need to calculate the melting times of metal additions during alloying operations. A multiphase mathematical model helps to assess the applicability of these correlations to actual industrial processes. This model simulates the heat transfer between solid particles and liquid steel under turbulence conditions during the tapping operation of steel with simultaneous argon bottom stirring. There are six recommendable correlations among the 16 most relevant available ones in the literature. These correlations apply to small Prandtl numbers (Pr = 0.01 to 0.2, i.e., metals) or medium magnitudes of Prandtl numbers (Pr = 1 to 10, air and water). Melting rates depend on the turbulence intensities and superheat of the metal. High superheats cause the hydrodynamic effects to have less influence on the melting time...
Journal of Materials Science and Engineering with Advanced Technology, Jul 15, 2017
Metallurgical and Materials Transactions B, 2012
ABSTRACT The performance characteristics of a tundish, such as the flotation of inclusions and sl... more ABSTRACT The performance characteristics of a tundish, such as the flotation of inclusions and slag entrainment, are largely influenced by the fluid-flow phenomena. Physical modeling in water is widely used to understand the fluid flows in a tundish and as a tool to improve, control, and design procedures for high-quality steel processing operations. These approaches were used to study the performance of fluid flow for a new design of ladle shroud. The new design for a dissipative ladle shroud (DLS) was studied, using a one-third scale, delta shaped, four-strand tundish. The results were compared with those achieved with the conventional ladle shroud. Different cases have been analyzed, including a conventional ladle shroud (LS) with a bare tundish and a tundish furnished with an impact pad. Similarly, the new design of the shroud (DLS) was studied under equivalent conditions. The physical experiments included the use of particle image velocimetry (PIV) and conductivity tracer techniques. The PIV measured the instantaneous velocities at the outlet of the DLS and the LS at different flow rates, showing the detailed jetting characteristics of water leaving the two types of ladle shroud. Residence time distribution (RTD) curves were also obtained for the different flow arrangements previously mentioned, and the dispersion of a colored dye tracer was observed at different intervals of time during tundish operation and analyzed using the video visualization technique.
Metallurgical and Materials Transactions B, 2016
The design of the ports of a casting nozzle has profound effects on the fluid flow patterns in sl... more The design of the ports of a casting nozzle has profound effects on the fluid flow patterns in slab molds. The influence of these outlets have also considerable effects on the turbulent flow and turbulence variables inside the nozzle itself. To understand the effects of nozzle design, three approaches were employed: a theoretical analysis based on the turbulent viscosity hypothesis, dimensional analysis (both analyses aided by computer fluid dynamics), and experiments using particle image velocimetry. The first approach yields a linear relation between calculated magnitudes of scalar fields of ε (dissipation rate of kinetic energy) and k2 (square of the turbulent kinetic energy), which is derived from the wall and the logarithmic-wall laws in the boundary layers. The smaller the slope of this linear relation is, the better the performance of a given nozzle is for maintaining the stability of the melt–flux interface. The second approach yields also a linear relation between flow rate of liquid metal and the cubic root of the dissipation rate of kinetic energy. In this case, the larger the slope of the linear relation is, the better the performance of a given nozzle is for maintaining the stability of the melt–flux interface. Finally, PIV measurements in a mold water model, together with equations for estimation of critical melt velocities for slag entrainment, were used to quantify the effects of nozzle design on the dynamics of the metal–slag interface. The three approaches agree in the characterization of turbulent flows in continuous casting molds using different nozzles.
JOM
The startup operations of continuous casting sequences of steel in a 4-strand tundish, using thre... more The startup operations of continuous casting sequences of steel in a 4-strand tundish, using three different turbulence inhibitors (TI), were investigated using a 1/3-scale water model in combination with numerical simulations through the volume of fluid model. The two-phase flow water–air is used to model the system, and the liquid steel–air and the liquid–gas interfaces are tracked by a donor–acceptor principle applied in the computational mesh. In the actual caster, one of the inhibitors releases the liquid steel with a sensible heat high enough to avoid freezing in the regions near the outer strands during the startup of the casting sequence. A second inhibitor improves the fluid flow control by yielding higher plug flow volume fractions. However, it promotes steel freezing in the outer strands. The analysis of the results lead to the design of the third TI with intermediate capability to control the steel flow, preventing steel freezing in the regions near the outer strands.
The process for recovering lead from battery residues used in several Mexican Plants include lead... more The process for recovering lead from battery residues used in several Mexican Plants include lead blast furnace and rotary furnaces. The formers are basically fed with recycled batteries together with the necessary additives to produce metallic lead. One of the by-products generated in the blast furnace is a dust mainly formed by lead sulfide. The rotary furnace is used to recover lead from lead batteries, dross from the refining-alloying process and the lead fines produced in the blast furnace. This paper describes thermodynamic analysis made to the rotary furnace process to understand the effect that each component of the system has upon the lead recovery. In order to enhance the process, the influence of iron chips composition and excess coke on slag viscosity is discussed. A computer optimization program has been developed to design the furnace charge based on material and energy balances, together with the thermodynamic equilibrium calculation.
ABSTRACT Gas-liquid flows inside the submerged entry nozzle (SEN) of a slab mold and their influe... more ABSTRACT Gas-liquid flows inside the submerged entry nozzle (SEN) of a slab mold and their influence on the flow field in the mold were studied using video recording, mathematical simulations and Digital Particle Image Velocimetry (DPIV) approaches. Coalescence-breakup phenomena of bubbles in liquid steel flowing through a slab mold were studied using a water model. At low gas loads (ratio of mass flow rates of gas and liquid in the submerged entry nozzle) bubble dynamics consist of coalescence-breakup and dragged processes from the SEN until close to the narrow wall. At high gas loads, bubbles are accumulated close to the narrow wall where they coalesce, break and ascend toward the bath surface forming bubble swarms or descend along the narrow wall by dragging forces exerted by liquid phase on the surfaces of the bubbles. These swarms consist of coalescing bubbles and agglomerating groups of bubbles. The presence of bubbles in the flow decreases the magnitudes of vorticity values in the flow field of mono-phase flows. Thus, to increase the casting speed, the injection of argon should be adjusted to an appropriate level to avoid an excess of liquid entrainment to the flux phase. Bubbly and annular flows in the SEN yield structurally-uncoupled and structurally coupled flows in the mold, respectively. High gas loads at high casting rates lead to increases of bubble population and bubbles sizes due to coalescence processes whose rate exceeds that of their breakup. The presence of gas bubbles or gas layers inside the SEN lead to periodical twisting of the liquid flow that induces biased flows through both ports yielding uneven flows in the mold. A multiphase mathematical model predicts acceptably well the flow dynamics of two-phase flows inside the SEN.
Metals
The current automation of steelmaking processes is capable of complete control through programmed... more The current automation of steelmaking processes is capable of complete control through programmed hardware. However, many metallurgical and operating factors, such as heat transfer control, require further studies under industrial conditions. In this context, computer simulation has become a powerful tool for reproducing the effects of industrial constraints on heat transfer. This work reports a computational model to simulate heat removal from billets’ strands in the continuous casting process. This model deals with the non-symmetric cooling conditions of a billet caster. These cooling conditions frequently occur due to plugged nozzles in the secondary cooling system (SCS). The model developed simulates the steel thermal behavior for casters with a non-symmetric distribution of the sprays in the SCS using different boundary conditions to show possible heat transfer variations. Finally, the results are compared with actual temperatures from different casters to demonstrate the predi...
Metals
Changes of unsteady multiphase fluid flow patterns of liquid steel during electric arc furnace-la... more Changes of unsteady multiphase fluid flow patterns of liquid steel during electric arc furnace-ladle tapping operations, with simultaneous argon bottom injection, are simulated using interfacial tracking computing techniques. The impinging steel jet interacts with the argon bubbling plume, suffering mutual bending effects, and imparting non-symmetric flows of liquid steel during the whole ladle filling time. At low bath levels, radial recirculating flows are generated and at high bath levels, these flows are substituted by vertical long flows generated by the permanent interaction between the impinging jet and the argon plume. Turbulence intensity increases as the bath level rises. Low bath levels are suitable for pre-melting and preheating ferroalloy particles. High bath levels of steel in the ladle, close to total ladle filling, are the most suitable conditions for thermal and chemical homogenizations. Argon gas forms an intermittent blanket over the air–liquid steel mix due to it...
ISIJ International
Effects of slag layer thickness on the fluid dynamics of liquid steel in gas-stirred ladles by bo... more Effects of slag layer thickness on the fluid dynamics of liquid steel in gas-stirred ladles by bottom injection of argon was studied through water modeling experiments and numerical simulations. Mixing times increase considerably with thicker slag layers and decrease of gas flow rates. The physical properties of the system have a smaller influence on mixing time. Slag Eye Opening (SEO) area is increased under thin slag layers, increase of gas flow rates, and denser and less viscous slags. The planes close to the metalslag interface, under the presence of thick slag layers for a given gas flow rate, are split in subregions of small velocities with different orientations making the lower fluid to come close to a stagnant condition. The presence of, either, thick or thin slag layers does not influence the axial velocity along the plume height for a fixed flow rate of gas. The SEO area follows a linear relationship with the square root of the densiometric Froude number based on the slag layer thickness.
Three-phase interactions (metal-slag-argon) in ladle stirring operations have strong effects on m... more Three-phase interactions (metal-slag-argon) in ladle stirring operations have strong effects on metal-slag mass transfer processes. Specifically, the thickness of the slag controls the fluid turbulence to an extent that once trespassing a critical thickness, increases of stirring strength have not further effects on the flow. To analyze these conditions, a physical model considering the three phases was built to study liquid turbulence in the proximities of the metal-slag interface. A velocity probe placed close to the interface permitted the continuous monitoring and statistical analyses of turbulence. The slag-eye opening was found to be strongly dependent on the stirring conditions, and the mixing times decreased with thin slag thicknesses. Slag entrainment was enhanced with thick slag layers, and high flow rates of the gas phase. A multiphase model was developed to simulate these results finding a good agreement between experimental and numerical results.