The present study addresses the incorporation of fine particles into liquids via the creation of ... more The present study addresses the incorporation of fine particles into liquids via the creation of a large-scale swirling vortex on the liquid free surface using a rotary impeller positioned along the axis of a cylindrical vessel. Four types of particles are used in the experiments to investigate the incorporation efficiency of the particles into a water bath under different impeller rotation speeds. Additionally, the vortex characteristics are investigated numerically. The results reveal that two factors, namely the particle wettability and turbulent oscillations at the bottom part of vortex surface, play dominant roles in determining the particle incorporation behavior. Hydrophobic particles are incapable of being incorporated into the water bath under any of the conditions examined in the present study. Partly wettable particles are entrained into the water bath, with the efficiency increasing with the impeller rotation speed and particle size. This is because an increase in the impeller rotation speed causes vortex deformation, whereby its bottom part approaches the impeller blades where the turbulent surface oscillations reach maximum amplitudes. Another possible mechanism of particle incorporation is the effect of capillary increases of liquid into the spaces between particles, which accumulate on the bottom surface of the vortex.
The present study addresses the incorporation of fine particles into liquids via the creation of ... more The present study addresses the incorporation of fine particles into liquids via the creation of a large-scale swirling vortex on the liquid free surface using a rotary impeller positioned along the axis of a cylindrical vessel. Four types of particles are used in the experiments to investigate the incorporation efficiency of the particles into a water bath under different impeller rotation speeds. Additionally, the vortex characteristics are investigated numerically. The results reveal that two factors, namely the particle wettability and turbulent oscillations at the bottom part of vortex surface, play dominant roles in determining the particle incorporation behavior. Hydrophobic particles are incapable of being incorporated into the water bath under any of the conditions examined in the present study. Partly wettable particles are entrained into the water bath, with the efficiency increasing with the impeller rotation speed and particle size. This is because an increase in the im...
Acoustic cavitation occurs in ultrasonic treatment causing various phenomena such as chemical syn... more Acoustic cavitation occurs in ultrasonic treatment causing various phenomena such as chemical synthesis, chemical decomposition, and emulsification. Nonlinear oscillations of cavitation bubbles are assumed to be responsible for these phenomena, and the neighboring bubbles may interact each other. In the present study, we numerically investigated the dynamic behavior of cavitation bubbles in multi-bubble systems. The results reveal that the oscillation amplitude of a cavitation bubble surrounded by other bubbles in a multi-bubble system becomes larger compared with that in the single-bubble case. It is found that this is caused by an acoustic wake effect, which reduces the pressure near a bubble surrounded by other bubbles and increases the time delay between the bubble contraction/expansion cycles and sound pressure oscillations. A new parameter, called "cover ratio" is introduced to quantitatively evaluate the variation in the bubble oscillation amplitude, the time delay, and the maximum bubble radius.
The present work investigated melt flow pattern and temperature distribution in the sump of alumi... more The present work investigated melt flow pattern and temperature distribution in the sump of aluminum billets produced in a hot-top equipped direct chilling (DC) caster conventionally and with ultrasonic irradiation. The main emphasis was placed on clarifying the effects of acoustic streaming and hot-top unit type. Acoustic streaming characteristics were investigated first by using the earlier developed numerical model and water model experiments. Then, the acoustic streaming model was applied to develop a numerical code capable of simulating unsteady flow phenomena in the sump during the DC casting process. The results revealed that the introduction of ultrasonic vibrations into the melt in the hot-top unit had little or no effect on the temperature distribution and sump profile, but had a considerable effect on the melt flow pattern in the sump. Our results showed that ultrasound irradiation makes the flow velocity faster and produces a lot of relatively small eddies in the sump bu...
The main purpose of the present study is to evaluate mass transfer in an aluminum melting furnace... more The main purpose of the present study is to evaluate mass transfer in an aluminum melting furnace stirred mechanically during flux treatment through water model experiment. Instead of the flux particles, model perlite particles were utilized, and the mass transfer between the pre-coated model particles and water bath was evaluated. Numerical simulation was also carried out to understand the flow pattern and mass transfer mechanisms. The fast impeller rotation speed enhanced the mass transfer. Besides, counter clockwise (CCW) rotation of impeller yielded larger mass transfer as compared to that of the clockwise impeller rotation (CW). The area of higher kinetic energy expanded with increase of impeller rotation speed, and the turbulent energy for the case of CCW rotation was higher compared to the CW case. The mechanism of the mass transfer enhancement under the CCW rotation conditions can be understood in terms of the turbulent energy at the free surface. The averaged downward flow was insufficient to cause the particle entrainment. On the other hand, the turbulent fluctuations were strong enough to cause the particle entrainment.
Although the effect of ultrasonic vibrations on the structure of solidifying metals has been know... more Although the effect of ultrasonic vibrations on the structure of solidifying metals has been known for long time, the practical application of ultrasound to casting technology still remains a big challenge. Ultrasonic casting exploits cavitation in molten metal to disperse particles of grain refiners or to break dendrites during solidification. Therefore, care must be taken to control the passage of melt through the cavitation zone. There is still, however, a lack of data in this area. The present study consisted of two parts. In the first one, intensity and spectral characteristics of cavitation noise generated during radiation of high-intense ultrasonic vibrations into water and molten aluminum alloys were investigated by using a high temperature cavitometer. Based on these data, a measure for evaluating the cavitation intensity was established and verified for relatively low and high vibration amplitudes. The second part presents results on the application of ultrasonic vibrations to a DC caster to refine the primary silicon grains of a model Al-17Si-0.01P alloy during the casting of 178-mm billets. High amplitude ultrasonic vibrations were radiated into a specially designed hot-top unit of a DC caster to allow a better control of the melt flow through the cavitation zone as compared, for example, to ultrasonic treatment in launder. It was shown that refinement effect of ultrasonic vibrations and structure uniformity can be significantly improved by optimizing the amplitudes of horn tip vibration and horn position in the unit.
The present study focuses on the behavior of dust particles in a high temperature gas atmosphere ... more The present study focuses on the behavior of dust particles in a high temperature gas atmosphere exposed to powerful standing sound waves. Six resonance frequencies within the range of 0-1 000 Hz were chosen for the experiments because they provide high values of sound pressure in the working space. The particles (0.1ϳ80 mm) were produced by evaporating a sample of Zn at temperature about 1 173 K under Ar atmosphere, cooling the Zn vapor and transferring the formed particles to a sonoprocessing chamber for sound exposure. The particle samples were taken at the upper place of the chamber, and the samples were analyzed for size distribution and number density in the gas phase. Application of sound waves is found to result in enlargement of particles (acoustic agglomeration), and reduction of their number density and concentration in the gas. The experiments showed that the particle agglomeration is enhanced as the sound pressure amplitude increases, while the effect of sound frequency played a smaller role in the particle behavior. In the frequency range tested, the most evident agglomeration effect was obtained at frequencies of 210 and 991 Hz at which a 50 % increase in particle size and 60 % decrease of particle number density in exhaust gas can be achieved in comparison to the corresponding values without sound application. The experimental results are discussed on the basis of the orthokinetic mechanism in relation to the acoustically forced oscillation and collision between the differently sized particles.
IOP Conference Series: Materials Science and Engineering, 2018
Induction heating of non-metallic molten fluid has been investigated, mainly performed on melt gl... more Induction heating of non-metallic molten fluid has been investigated, mainly performed on melt glass stirring. Because silicate glass has relatively high viscosity and low electric conductivity for induction stirring, their experiments require very high temperature above 1500 o C, and are difficult for observation and measurements. In this report, observation and simulation of heat generation and flow in molten salt are presented. And flow states of molten vanadium oxide glass is observed, both of them have low melting points. It is intended to investigate them from both experimental and theoretical directions, as a fundamental research. It is demonstrated that molten NaCl-KCl possessed the low impedance value in frequency range of hundred kHz to 1MHz, preferable for giving rise to induction current generation. Circulating flow of the fluids from the container wall to the center was observed. Temperature measurement in the melt was also conducted at various positions with respect to the coil configuration. The flow velocity and temperature distribution were analyzed by numerical simulation, and compared with the measurements, taking account of the transparent nature of the molten salts. They are shown to explain the experimental results, mostly. Molten vanadium oxide glass having the similar physical properties exhibited the similar flow characteristics.
The technique of mechanical alloying (MA) was used to coat the metal substrate with other metals.... more The technique of mechanical alloying (MA) was used to coat the metal substrate with other metals. The Al-Ti and Al-Ni binary systems were investigated, at that, all the elements were used both as substrates and as coating powders. Thickness and quality of coating depending on the MA treatment parameters, such as intensity and duration of milling, amount of loaded powder, were investigated. As-synthesized coatings showed structures with high apparent density and free of porosity. However, the surface morphology of the MA-coatings was very rough. Annealing treatment led to the leveling of surface microstructure and formation of different aluminide phases in the coatings. MA allows to produce thick coatings for a relatively short time with good adherence.
In this work, we proposed a novel mechanical alloying method to deposit Ni x-Ti x intermetallic c... more In this work, we proposed a novel mechanical alloying method to deposit Ni x-Ti x intermetallic coating on various metallic substrates using laser treatment. Three different substrates (Al-based alloy, Ti-based alloy, and hypoeutectoid steel) were used, and 50-70 µm thick Ni x Ti x coating was deposited during the process. For mechanical alloying, we used a self-constructed vibratory ball mill (single chamber) and for laser treatment, we used a "TrumpfTruDisk 1000" machine equipped with a four-dimensional control system "Servokon" designed specifically for experimental studies. Different laser beam intensities were used for laser operation. The cross-sectional microstructures of coatings were studied using a scanning electron microscope equipped with a Bruker energy-dispersive X-ray Spectrometer (EDS). Additional investigation of a cross-sectional area of one of the Ni x Ti x-coated samples was performed with field emission high-performance SEM and focused ion beam (FIB). Phase compositions of the obtained coatings, before and after laser treatment, were analyzed using X-Ray diffraction method. After the deposition process, the micro-hardness of the coatings was measured using a Vickers hardness tester. The structure and morphology of the obtained coatings were investigated.
Journal of Iron and Steel Research, International, 2010
ABSTRACT The results of numerical simulation of the mosaic embedding iron ore sintering (MEBIOS) ... more ABSTRACT The results of numerical simulation of the mosaic embedding iron ore sintering (MEBIOS) process according to the model presented in the first part of the study are introduced. The main objective of the second part is the elucidation of key factors influencing the process efficiency, particularly the sintering completeness, velocity of the heat wave propagation and maximum temperature achievable in the pellet during the wave propagation. Numerical results reveal that the mass fraction of coal, diameter of coal particles and air inlet velocity are of prime importance in determining efficiency of the MEBIOS sintering process.
In recent years, a large number of studies have been published on the use of high intensity ultra... more In recent years, a large number of studies have been published on the use of high intensity ultrasonics in various high temperature technologies. This paper provides an overview of the recent achievements and ongoing works on the application of high intensity sound waves to pyrometallurgy and its related areas. The published results have strongly suggested that ultrasonics has the potential to play a more significant role in such areas as the dedusting of high-temperature exhaust gas, improvement of fuel-combustion efficiency, control of air-pollutant emissions, improvement of the quality of ingots, production of metal powders and ascast composite materials. At higher temperatures, special attractiveness of sound waves is associated with the fact that the waves can propagate through gas, liquids, and solids, and thus supply the acoustic energy from a cooled sonic generator to materials being processed under high temperature conditions. This provides a unique tool, for example, for controlling the rates of interfacial phenomena that is unachievable by any other methods under high temperatures. Industrial competitiveness of the ultrasonic-based technologies is reinforced by the relatively low cost of power-generating equipment and ultrasonic transducers. However, further research efforts are called for to develop new heat-resistant waveguide materials and to integrate the ultrasonic installations with existing industrial facilities in high temperature technologies.
Design of bed structure is a promising approach to maintain/increase the productivity of sinter u... more Design of bed structure is a promising approach to maintain/increase the productivity of sinter under the condition of increasing use of iron ores having high combined water content. In this paper, a new process image, MEBIOS, is illustrated and further "in situ" observation of the change in the void structure of the sintering bed by using X-ray CTS and a numerical simulation have been conducted in order to preliminary evaluate the possibility of this proposal. X-ray CTS observation suggests that the existence of pellets of 15 mm in size does not significantly affect the formation of macroscopic void network in the sintering bed and not lead to inhomogeneous sintering. A series of the laboratory-scale of sinter pot experiment was also carried out to obtain parameters for the simulation. The gas flow near the pellet surface and the differences in the temperature profiles among the pellet center and surface were simulated by using the numerical model although further studies are necessary, e.g., on the considering ways of structural changes of void in the sintering bed, reduction and oxidation reactions and a mesh generation method properly representing the contraction of bed height.
The perfect mixing time, t~, of the water bath, during gas injection through bottom (vertical and... more The perfect mixing time, t~, of the water bath, during gas injection through bottom (vertical and iclined) and side nozzles has been measuredby using electrical conductivity technique. Effects of gas flow rate, bath depth, nozzle angle and location have been examined. The measurements indicate that under the condition of a shallow bath (H/D =0.31) and large gas flow rate (specific powere> I O-' W/kg) influences of the nozzle angle and nozzle location on the mixing time are significant, On the other hand, effects of those parameters on t~are negligible in a deep bath (HID=1 ,25). Change in the tracer concentration with time was predicted by numerical modelling. A satisfactory agreement between the computed and experimental results can be obtained by parameter fitting for the average plume rise velocity and effective viscosity in the mathematical model. It is presumedthat turbulent mass transfer of the tracer is dominant in the deep bath, whi]e the convection of liquid is more effective in the homogenization in the sha]low bath. KEYWORDS: perfect mixing time; cold model; side and inclined injection; numerical modelling; turbulent mass transfer; convection. 1.
Heat transfer between gas bubble and liquid bath has been studied by using cold models. The risin... more Heat transfer between gas bubble and liquid bath has been studied by using cold models. The rising bubble diameter, velocity and the heat efficiency were measuredto explain the mechanism of the heat exchange for various gas-liquid systems. Preheated gas (N,, He, Ar-He mixture) was injected into the bath of volatile (water) or non-volatile (ethylene glycol, methyl carbitol and ethylene glycol-glycerin mixture) Iiquid, It is shown that liquid surface tension, gas density and gas temperature are of great importance in determining the bubble diameter. The heat efficiency increases as the bath depth increases and the gas flow rate decreases. The heat exchange is found to be controlled by the heat transfer within the gas bubble. A model describing time variations in the average temperature and the vapor content inside the bubble has been developed. The computedand measuredresults reveal that the heat transfer is enhanced with thermai conductivity of gas in the case of gas injection into non-volatile liquid. However, whengas is injected into volatile liquid, the heat efficiency must be considered with accounting for the heat transfer and the vaporization proceeding concurrently.
Engineering, Nagoya The mixing time of a water bath stirred by gas injecton through a rotary lanc... more Engineering, Nagoya The mixing time of a water bath stirred by gas injecton through a rotary lance was measured by an electrical conductivity method. Effects of the gas flow rate, the rotation speed and the bath depth. on the mixing time were examined. Measurement of torque produced during the lance rotation was also carried out. It is found that the effect of the gas flow rate on the mixing time becomessignificant in the deep bath, H, under the low rotation speed. R. In the present experiments, the conditions are H/D>0.625 and R 0.33 s~1 , where D is the vessel diameter. On the other hand, the effect of the lance rotation is appreciable when the bath is shallow. Thetorque increases with increasing the rotation speed, whereasthe bath depth has no effect on the torque. The results are explained in terms of specific powers of the injected gas and the rotary lance. The effects of operati ng variables on the mixi ng time are examinedquantitatively from the mu Itiple regression anal ysis.
The present study addresses the incorporation of fine particles into liquids via the creation of ... more The present study addresses the incorporation of fine particles into liquids via the creation of a large-scale swirling vortex on the liquid free surface using a rotary impeller positioned along the axis of a cylindrical vessel. Four types of particles are used in the experiments to investigate the incorporation efficiency of the particles into a water bath under different impeller rotation speeds. Additionally, the vortex characteristics are investigated numerically. The results reveal that two factors, namely the particle wettability and turbulent oscillations at the bottom part of vortex surface, play dominant roles in determining the particle incorporation behavior. Hydrophobic particles are incapable of being incorporated into the water bath under any of the conditions examined in the present study. Partly wettable particles are entrained into the water bath, with the efficiency increasing with the impeller rotation speed and particle size. This is because an increase in the impeller rotation speed causes vortex deformation, whereby its bottom part approaches the impeller blades where the turbulent surface oscillations reach maximum amplitudes. Another possible mechanism of particle incorporation is the effect of capillary increases of liquid into the spaces between particles, which accumulate on the bottom surface of the vortex.
The present study addresses the incorporation of fine particles into liquids via the creation of ... more The present study addresses the incorporation of fine particles into liquids via the creation of a large-scale swirling vortex on the liquid free surface using a rotary impeller positioned along the axis of a cylindrical vessel. Four types of particles are used in the experiments to investigate the incorporation efficiency of the particles into a water bath under different impeller rotation speeds. Additionally, the vortex characteristics are investigated numerically. The results reveal that two factors, namely the particle wettability and turbulent oscillations at the bottom part of vortex surface, play dominant roles in determining the particle incorporation behavior. Hydrophobic particles are incapable of being incorporated into the water bath under any of the conditions examined in the present study. Partly wettable particles are entrained into the water bath, with the efficiency increasing with the impeller rotation speed and particle size. This is because an increase in the im...
Acoustic cavitation occurs in ultrasonic treatment causing various phenomena such as chemical syn... more Acoustic cavitation occurs in ultrasonic treatment causing various phenomena such as chemical synthesis, chemical decomposition, and emulsification. Nonlinear oscillations of cavitation bubbles are assumed to be responsible for these phenomena, and the neighboring bubbles may interact each other. In the present study, we numerically investigated the dynamic behavior of cavitation bubbles in multi-bubble systems. The results reveal that the oscillation amplitude of a cavitation bubble surrounded by other bubbles in a multi-bubble system becomes larger compared with that in the single-bubble case. It is found that this is caused by an acoustic wake effect, which reduces the pressure near a bubble surrounded by other bubbles and increases the time delay between the bubble contraction/expansion cycles and sound pressure oscillations. A new parameter, called "cover ratio" is introduced to quantitatively evaluate the variation in the bubble oscillation amplitude, the time delay, and the maximum bubble radius.
The present work investigated melt flow pattern and temperature distribution in the sump of alumi... more The present work investigated melt flow pattern and temperature distribution in the sump of aluminum billets produced in a hot-top equipped direct chilling (DC) caster conventionally and with ultrasonic irradiation. The main emphasis was placed on clarifying the effects of acoustic streaming and hot-top unit type. Acoustic streaming characteristics were investigated first by using the earlier developed numerical model and water model experiments. Then, the acoustic streaming model was applied to develop a numerical code capable of simulating unsteady flow phenomena in the sump during the DC casting process. The results revealed that the introduction of ultrasonic vibrations into the melt in the hot-top unit had little or no effect on the temperature distribution and sump profile, but had a considerable effect on the melt flow pattern in the sump. Our results showed that ultrasound irradiation makes the flow velocity faster and produces a lot of relatively small eddies in the sump bu...
The main purpose of the present study is to evaluate mass transfer in an aluminum melting furnace... more The main purpose of the present study is to evaluate mass transfer in an aluminum melting furnace stirred mechanically during flux treatment through water model experiment. Instead of the flux particles, model perlite particles were utilized, and the mass transfer between the pre-coated model particles and water bath was evaluated. Numerical simulation was also carried out to understand the flow pattern and mass transfer mechanisms. The fast impeller rotation speed enhanced the mass transfer. Besides, counter clockwise (CCW) rotation of impeller yielded larger mass transfer as compared to that of the clockwise impeller rotation (CW). The area of higher kinetic energy expanded with increase of impeller rotation speed, and the turbulent energy for the case of CCW rotation was higher compared to the CW case. The mechanism of the mass transfer enhancement under the CCW rotation conditions can be understood in terms of the turbulent energy at the free surface. The averaged downward flow was insufficient to cause the particle entrainment. On the other hand, the turbulent fluctuations were strong enough to cause the particle entrainment.
Although the effect of ultrasonic vibrations on the structure of solidifying metals has been know... more Although the effect of ultrasonic vibrations on the structure of solidifying metals has been known for long time, the practical application of ultrasound to casting technology still remains a big challenge. Ultrasonic casting exploits cavitation in molten metal to disperse particles of grain refiners or to break dendrites during solidification. Therefore, care must be taken to control the passage of melt through the cavitation zone. There is still, however, a lack of data in this area. The present study consisted of two parts. In the first one, intensity and spectral characteristics of cavitation noise generated during radiation of high-intense ultrasonic vibrations into water and molten aluminum alloys were investigated by using a high temperature cavitometer. Based on these data, a measure for evaluating the cavitation intensity was established and verified for relatively low and high vibration amplitudes. The second part presents results on the application of ultrasonic vibrations to a DC caster to refine the primary silicon grains of a model Al-17Si-0.01P alloy during the casting of 178-mm billets. High amplitude ultrasonic vibrations were radiated into a specially designed hot-top unit of a DC caster to allow a better control of the melt flow through the cavitation zone as compared, for example, to ultrasonic treatment in launder. It was shown that refinement effect of ultrasonic vibrations and structure uniformity can be significantly improved by optimizing the amplitudes of horn tip vibration and horn position in the unit.
The present study focuses on the behavior of dust particles in a high temperature gas atmosphere ... more The present study focuses on the behavior of dust particles in a high temperature gas atmosphere exposed to powerful standing sound waves. Six resonance frequencies within the range of 0-1 000 Hz were chosen for the experiments because they provide high values of sound pressure in the working space. The particles (0.1ϳ80 mm) were produced by evaporating a sample of Zn at temperature about 1 173 K under Ar atmosphere, cooling the Zn vapor and transferring the formed particles to a sonoprocessing chamber for sound exposure. The particle samples were taken at the upper place of the chamber, and the samples were analyzed for size distribution and number density in the gas phase. Application of sound waves is found to result in enlargement of particles (acoustic agglomeration), and reduction of their number density and concentration in the gas. The experiments showed that the particle agglomeration is enhanced as the sound pressure amplitude increases, while the effect of sound frequency played a smaller role in the particle behavior. In the frequency range tested, the most evident agglomeration effect was obtained at frequencies of 210 and 991 Hz at which a 50 % increase in particle size and 60 % decrease of particle number density in exhaust gas can be achieved in comparison to the corresponding values without sound application. The experimental results are discussed on the basis of the orthokinetic mechanism in relation to the acoustically forced oscillation and collision between the differently sized particles.
IOP Conference Series: Materials Science and Engineering, 2018
Induction heating of non-metallic molten fluid has been investigated, mainly performed on melt gl... more Induction heating of non-metallic molten fluid has been investigated, mainly performed on melt glass stirring. Because silicate glass has relatively high viscosity and low electric conductivity for induction stirring, their experiments require very high temperature above 1500 o C, and are difficult for observation and measurements. In this report, observation and simulation of heat generation and flow in molten salt are presented. And flow states of molten vanadium oxide glass is observed, both of them have low melting points. It is intended to investigate them from both experimental and theoretical directions, as a fundamental research. It is demonstrated that molten NaCl-KCl possessed the low impedance value in frequency range of hundred kHz to 1MHz, preferable for giving rise to induction current generation. Circulating flow of the fluids from the container wall to the center was observed. Temperature measurement in the melt was also conducted at various positions with respect to the coil configuration. The flow velocity and temperature distribution were analyzed by numerical simulation, and compared with the measurements, taking account of the transparent nature of the molten salts. They are shown to explain the experimental results, mostly. Molten vanadium oxide glass having the similar physical properties exhibited the similar flow characteristics.
The technique of mechanical alloying (MA) was used to coat the metal substrate with other metals.... more The technique of mechanical alloying (MA) was used to coat the metal substrate with other metals. The Al-Ti and Al-Ni binary systems were investigated, at that, all the elements were used both as substrates and as coating powders. Thickness and quality of coating depending on the MA treatment parameters, such as intensity and duration of milling, amount of loaded powder, were investigated. As-synthesized coatings showed structures with high apparent density and free of porosity. However, the surface morphology of the MA-coatings was very rough. Annealing treatment led to the leveling of surface microstructure and formation of different aluminide phases in the coatings. MA allows to produce thick coatings for a relatively short time with good adherence.
In this work, we proposed a novel mechanical alloying method to deposit Ni x-Ti x intermetallic c... more In this work, we proposed a novel mechanical alloying method to deposit Ni x-Ti x intermetallic coating on various metallic substrates using laser treatment. Three different substrates (Al-based alloy, Ti-based alloy, and hypoeutectoid steel) were used, and 50-70 µm thick Ni x Ti x coating was deposited during the process. For mechanical alloying, we used a self-constructed vibratory ball mill (single chamber) and for laser treatment, we used a "TrumpfTruDisk 1000" machine equipped with a four-dimensional control system "Servokon" designed specifically for experimental studies. Different laser beam intensities were used for laser operation. The cross-sectional microstructures of coatings were studied using a scanning electron microscope equipped with a Bruker energy-dispersive X-ray Spectrometer (EDS). Additional investigation of a cross-sectional area of one of the Ni x Ti x-coated samples was performed with field emission high-performance SEM and focused ion beam (FIB). Phase compositions of the obtained coatings, before and after laser treatment, were analyzed using X-Ray diffraction method. After the deposition process, the micro-hardness of the coatings was measured using a Vickers hardness tester. The structure and morphology of the obtained coatings were investigated.
Journal of Iron and Steel Research, International, 2010
ABSTRACT The results of numerical simulation of the mosaic embedding iron ore sintering (MEBIOS) ... more ABSTRACT The results of numerical simulation of the mosaic embedding iron ore sintering (MEBIOS) process according to the model presented in the first part of the study are introduced. The main objective of the second part is the elucidation of key factors influencing the process efficiency, particularly the sintering completeness, velocity of the heat wave propagation and maximum temperature achievable in the pellet during the wave propagation. Numerical results reveal that the mass fraction of coal, diameter of coal particles and air inlet velocity are of prime importance in determining efficiency of the MEBIOS sintering process.
In recent years, a large number of studies have been published on the use of high intensity ultra... more In recent years, a large number of studies have been published on the use of high intensity ultrasonics in various high temperature technologies. This paper provides an overview of the recent achievements and ongoing works on the application of high intensity sound waves to pyrometallurgy and its related areas. The published results have strongly suggested that ultrasonics has the potential to play a more significant role in such areas as the dedusting of high-temperature exhaust gas, improvement of fuel-combustion efficiency, control of air-pollutant emissions, improvement of the quality of ingots, production of metal powders and ascast composite materials. At higher temperatures, special attractiveness of sound waves is associated with the fact that the waves can propagate through gas, liquids, and solids, and thus supply the acoustic energy from a cooled sonic generator to materials being processed under high temperature conditions. This provides a unique tool, for example, for controlling the rates of interfacial phenomena that is unachievable by any other methods under high temperatures. Industrial competitiveness of the ultrasonic-based technologies is reinforced by the relatively low cost of power-generating equipment and ultrasonic transducers. However, further research efforts are called for to develop new heat-resistant waveguide materials and to integrate the ultrasonic installations with existing industrial facilities in high temperature technologies.
Design of bed structure is a promising approach to maintain/increase the productivity of sinter u... more Design of bed structure is a promising approach to maintain/increase the productivity of sinter under the condition of increasing use of iron ores having high combined water content. In this paper, a new process image, MEBIOS, is illustrated and further "in situ" observation of the change in the void structure of the sintering bed by using X-ray CTS and a numerical simulation have been conducted in order to preliminary evaluate the possibility of this proposal. X-ray CTS observation suggests that the existence of pellets of 15 mm in size does not significantly affect the formation of macroscopic void network in the sintering bed and not lead to inhomogeneous sintering. A series of the laboratory-scale of sinter pot experiment was also carried out to obtain parameters for the simulation. The gas flow near the pellet surface and the differences in the temperature profiles among the pellet center and surface were simulated by using the numerical model although further studies are necessary, e.g., on the considering ways of structural changes of void in the sintering bed, reduction and oxidation reactions and a mesh generation method properly representing the contraction of bed height.
The perfect mixing time, t~, of the water bath, during gas injection through bottom (vertical and... more The perfect mixing time, t~, of the water bath, during gas injection through bottom (vertical and iclined) and side nozzles has been measuredby using electrical conductivity technique. Effects of gas flow rate, bath depth, nozzle angle and location have been examined. The measurements indicate that under the condition of a shallow bath (H/D =0.31) and large gas flow rate (specific powere> I O-' W/kg) influences of the nozzle angle and nozzle location on the mixing time are significant, On the other hand, effects of those parameters on t~are negligible in a deep bath (HID=1 ,25). Change in the tracer concentration with time was predicted by numerical modelling. A satisfactory agreement between the computed and experimental results can be obtained by parameter fitting for the average plume rise velocity and effective viscosity in the mathematical model. It is presumedthat turbulent mass transfer of the tracer is dominant in the deep bath, whi]e the convection of liquid is more effective in the homogenization in the sha]low bath. KEYWORDS: perfect mixing time; cold model; side and inclined injection; numerical modelling; turbulent mass transfer; convection. 1.
Heat transfer between gas bubble and liquid bath has been studied by using cold models. The risin... more Heat transfer between gas bubble and liquid bath has been studied by using cold models. The rising bubble diameter, velocity and the heat efficiency were measuredto explain the mechanism of the heat exchange for various gas-liquid systems. Preheated gas (N,, He, Ar-He mixture) was injected into the bath of volatile (water) or non-volatile (ethylene glycol, methyl carbitol and ethylene glycol-glycerin mixture) Iiquid, It is shown that liquid surface tension, gas density and gas temperature are of great importance in determining the bubble diameter. The heat efficiency increases as the bath depth increases and the gas flow rate decreases. The heat exchange is found to be controlled by the heat transfer within the gas bubble. A model describing time variations in the average temperature and the vapor content inside the bubble has been developed. The computedand measuredresults reveal that the heat transfer is enhanced with thermai conductivity of gas in the case of gas injection into non-volatile liquid. However, whengas is injected into volatile liquid, the heat efficiency must be considered with accounting for the heat transfer and the vaporization proceeding concurrently.
Engineering, Nagoya The mixing time of a water bath stirred by gas injecton through a rotary lanc... more Engineering, Nagoya The mixing time of a water bath stirred by gas injecton through a rotary lance was measured by an electrical conductivity method. Effects of the gas flow rate, the rotation speed and the bath depth. on the mixing time were examined. Measurement of torque produced during the lance rotation was also carried out. It is found that the effect of the gas flow rate on the mixing time becomessignificant in the deep bath, H, under the low rotation speed. R. In the present experiments, the conditions are H/D>0.625 and R 0.33 s~1 , where D is the vessel diameter. On the other hand, the effect of the lance rotation is appreciable when the bath is shallow. Thetorque increases with increasing the rotation speed, whereasthe bath depth has no effect on the torque. The results are explained in terms of specific powers of the injected gas and the rotary lance. The effects of operati ng variables on the mixi ng time are examinedquantitatively from the mu Itiple regression anal ysis.
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