Planar Flow Melt Spinning Process Research Articles

Effect of cavitation and spallation on ribbon morphology of Fe73.5Si13.5B9Cu1Nb3 alloy in planar flow melt spinning process

An experimental and analytical study concerns the effect of cavitation and spallation during the puddle solidification in planar flow melt spinning rapid solidification process. An instantaneous change in solidification temperature, dynamic variation in pressure distribution, density and motion of the liquid puddle leads to defect formation on ribbon surface. The initiation of nucleation and kinetic crystal growth at weak zone where pressure is relatively low may leads to inception of cavitation in the puddle province. The liquid puddle behaves like elastic membrane due imbalanced force between the liquid and entrapped air molecules caused to irregular contact on wheel substrate. Spallation of cavitate nuclei causes to grow equiaxed cellular shapes at boundary layer of the liquid puddle which leads formation of micro dimple on ribbon surface. The shear bands are affected to nucleus in the puddle due to dynamic fluctuation at the weak zones, which controls the solidification process of puddle.

Effect of offset of the crucible center with wheel center during planar-flow-melt-spinning process

Planar-flow-melt-spinning process (PFMS) produces amorphous ribbons for lamina of transformer core. However, the amorphous structure depend process parameters. The present work investigates the effect of offset of the crucible center to the wheel center, on puddle-formation and ribbon-thickness. Ribbon thickness is observed to increase to 13% and 10% respectively for an offset of 4 mm to wheel center in the clock-wise direction and in the anti-clockwise direction of rotation of the wheel. The preferable position of the crucible is its center being collinear with wheel center and the limiting offset of not>4 mm to the left of wheel center.

Influence of Angle of Inclination of the Crucible on Puddle Formation and Ribbon Thickness during Planar Flow Melt Spinning Process

Planar flow melt spinning process is widely used to manufacture amorphous ribbons for transformer core applications. The position of the crucible above cooling wheel for melt ejection in the realistic production conditions is crucial to producing the higher quality product. The quality of the product depends on the thickness and defect-free state of the ribbon. Puddle formation plays a significant role in the quality of the ribbon. As the experimental investigation is expensive and time consuming a numerical model is used to investigate the effect of clockwise and counter-clockwise inclination of the crucible on puddle formation and ribbon thickness. The thickness increases by 62.8 % and 111.5% with an augment in inclination angle from 0o to 5.4o in counter-clockwise and clockwise directions respectively. Limiting angle of inclination to avoid non-contact zone or cavity in the puddle at the nozzle wall is around 2o to 3o to obtain a higher quality ribbon. This limit can increase up to 3o to 4o for higher wheel speeds. The ideal position of the crucible is perpendicular to the wheel surface. Otherwise, the limiting angle of inclination to produce higher quality ribbon is, counter-clockwise with an optimum inclination of not more than 2 degrees.

Flow Dynamics in the Melt Puddle during Planar Flow Melt Spinning Process

Quality of amorphous ribbons obtained during planar flow melt spinning process depends highly on the dynamics of the melt puddle. The present study investigates the flow dynamics using pressure profiles, path lines and stream function. Pressure profiles help in predicting the melt blow-out. Transformation of planar flow melt spinning to free jet melt spinning can be observed using path lines in the puddle. Oscillations in the puddle can be traced by the stream function at the melt wheel contact. The analysis helps the experimentalists to carefully select the ejection pressure, wheel speed and nozzle-wheel gap to obtain a quality ribbon.

Flow CFD Analysis of 2D Transient Melt flow from crucible on to the rotating wheel in Planar Melt Spinning Process

Transient Flow numerical analysis in planar flow melt spinning process hasbeen carried out by several investigators considering uniform melt flow velocityexiting the nozzle slit on to the rotating wheel. The present numerical simulations studies the molten metal flow originating from the crucible, flowingthrough the nozzle slit, and making a 900 turn onto the rotating wheel. This renders the melt flow velocity exiting the nozzle slit to be non-uniform and parabolic in nature which is a more realistic representation of the actual flow. Inert gas present above the molten metal (Fe-B-Si)to prevent oxidation and push the melt out was simulated for pressures ranging from 2 to 6 psig. A Volume of Fluid (VOF) model has been developed in ANSYS Fluent to understand the effects of various process parameters influencing puddle length and amorphous strip formation such as:inert gas ejection pressure, nozzle contact angle θnozzle,and melt temperature. Conjugate heat transfer between the melt puddle and rotating wheel is investigatedas the wheel temperature does not remain constantduring an actual PFMS process. This causes the puddle length to increase and also a consequent decrease in the ribbon thickness which is in agreement with experimental data.

Numerical Simulation of Flow and Heat Transfer for Cooling Roller in Amorphous Spinning Process

Numerical simulation of cooling roller in planar flow melt spinning process was accomplished using CFD software, Get cooling water flow characteristics and the cooling roller wall temperature and pressure distribution with cooling roller rotation speed range 0-50r/s, The results show that: heat transfer coefficient h and Nusselt number between the cooling water and the inner wall surface of a copper roller creases with the increase of the cooling roller rotate speed, but the increase rate is relatively small; Effect of cooling roller rotate speed on inner wall pressure is large, cooling roller inner wall pressure increases with the rotation speed increase. This study provided a theoretical reference of amorphous cooling roller design and optimization.

Simulation for the Effect of Wetting Conditions of Melt Puddle on the Fe–Si–B Ribbon Alloy in the Planar-Flow Melt-Spinning Process

Simulation for the Effect of Wetting Conditions of Melt Puddle on the Fe–Si–B Ribbon Alloy in the Planar-Flow Melt-Spinning Process

Effect of Crucible Parameters on Planar Flow Melt Spinning Process

2D numerical simulation of planar flow melt spinning process was accomplished employing transient analysis of fully coupled fluid flow and heat transfer using CFD software—Ansys Fluent. Fe–B–Si alloy was chosen as the candidate alloy. In the PFMS process, the molten alloy flowed from a crucible through a nozzle slit onto a rotating copper wheel, where a puddle was formed and from which a continuous amorphous ribbon was spun. The objective of the investigation was to examine the melt flow through the crucible nozzle slit on the melt puddle formation and its stability over time as a function of: (a) the effect of gas ejection pressures taken between 0.1 and 0.35 kg/cm2; (b) the nozzle slit widths ranging from 0.3 to 0.5 mm; and (c) the amount of alloy used which was 0.5 kg. Herein, the dynamics of the development of the puddle immediately after melt ejection, the stability of puddle, the ribbon thickness, puddle oscillation and temperature distribution were examined. Simulations indicate that the puddle lengths and ribbon thickness were found to increase linearly with increase in gas ejection pressure; pinning of the liquid puddle at the nozzle edge was found for low gas ejection pressure which caused continuous air entrapment leading to defective amorphous strips. Heat transfer characteristics were also investigated.

Cooling wheel features and amorphous ribbon formation during planar flow melt spinning process

A numerical model incorporating actual production conditions of planar flow melt spinning process is presented. Knowledge of the process conditions at which an amorphous ribbon with uniform thickness can be obtained is important to reduce the manufacturing costs. Cooling wheel conditions play a significant role during rapid solidification of the melt. Hence a heat transfer analysis is performed to investigate the influence of cooling wheel temperature on ribbon formation. Nusselt's correlation is used for the first time for selecting a convective heat transfer coefficient between rotating wheel and surrounding air. This approach assists in predicting the conditions at which a continuous/broken/no ribbon formation is obtained during the process. The model could predict whether the ribbon to be obtained is amorphous or non-amorphous before the experiment is actually performed at a set of process conditions. Various internal and external conditions of the cooling wheel are tested, and they show little influence on the ribbon thickness up to 0.5s (10 rotations). Broken and nonamorphous ribbons are obtained for poor cooling conditions of the wheel with increase in time of cast from 0.5s to 1s (20 rotations). Amorphous ribbon with uniform thickness can be obtained for a wheel of 20mm wall thickness, when the inner and outer surfaces of the cooling wheel are maintained at a temperature of at least 300K.

Simulation of Initial Ribbon Formation during Planar Flow Melt Spinning Process

Planar flow melt spinning (PFMS) is a rapid solidification process to produce amorphous ribbons for transformer core applications. The present study deals with the development of 3dimensional time-dependent model, for the numerical simulation of ribbon formation during the PFMS process. Space between nozzle wall and the rotating wheel is considered as the computational domain. Volume of fluid technique is applied along with energy and momentum equations to simulate the two phase flow in the domain. Effect of ejection temperature of the melt is investigated during ribbon formation. Ribbon patterns like dimple and continuous are obtained for different ejection temperatures. Phenomenon of air entrainment which leads to dimple pattern is discussed. Vacuum conditions are suggested to avoid air entrainment.

Issues on Puddle Formation During Rapid Solidification of Fe–Si–B–Nb–Cu Alloy Using Planar Flow Melt Spinning Process

The present investigation deals with the processing of rapidly solidified 10–40 mm wide, 30–50 μm thick and 10–30 m long continuous amorphous ribbons of Fe–Si–B–Nb–Cu alloy using a planar flow melt spinning (PFMS) equipment. As the formation of quality amorphous ribbon depends on the melt puddle formed between the nozzle and the rotating copper wheel, the effect of different processing parameters such as nozzle wheel gap, ejection pressure etc. on the shape and stability of puddle has been studied using a high-speed imaging system and correlated with ribbon formation. Simultaneously, a two-dimensional numerical model has been developed to simulate the puddle formation during the PFMS process. The model is based on a computational fluid dynamics technique, called volume of fluid using transient heat transfer and fluid flow equations with the evolution of free boundaries. Different simulations have been performed to study the effect of process parameters on the puddle formation. The simulated results have been verified with the experimental observations considering same set of process parameters. It has been observed that the present simulations have produced exact replica of the experimental observations. Further parametric analysis as well as analysis of simulated result has been carried out to understand how the different process parameters affect the formation of quality amorphous ribbons during PFMS process.

Thermal Properties and Crystallization Behavior of <i>Co</i>67<i>Fe</i>4<i>Cr</i>7<i>Si</i>8<i>B</i>14 Amorphous Alloy

In order to investigate the crystallization behavior of the Co67Fe4Cr7Si8B14 amorphous metallic alloy, ribbons of this alloy were prepared by planar flow melt spinning process (PFMS). Differential scanning calorimetery (DSC) and differential thermal analyzer (DTA) were used to analyze the thermal properties and crystallization behavior of the samples at three heating rates of 10, 20 and 30º C/min. The experimental data were fitted to the Avrami model to determine the crystallization behavior. The results showed that the crystallization exotherm became wider and shifted toward a higher temperature range as the heating rate increased. The Avrami analysis also showed that n is about 1, which is related to the same transformation mechanism at different heating rates. The Kissinger method was used to determine the activation energy for the first crystallization peaks. The measured value is approximately 332.67 kJ/g.

Transient behavior of the planar-flow melt spinning process

Planar-flow melt spinning (PFMS) is a single-stage rapid manufacturing technique for producing thin metal sheets or ribbons. Commercial acceptance of PFMS requires ribbons to be cast with uniform thickness to tolerance. The process feeds molten metal through a nozzle onto a moving wheel where a puddle is formed and from which a continuous ribbon is ‘spun’. This study focuses on the time dependent behavior of the process. The dynamics of the process are modeled using unsteady mass balances, combined with a Bernoulli model of flow. Variations over a number of time scales are observed. The time scale over which the process can be treated as ‘quasi-steady’ is identified. Measuring the evolution of the puddle length and ribbon thickness within a cast indicates that the solidification rate also varies with time and a maximum in solidification rate is inferred.

Melting Temperature, Transformation and Metastable Phase Diagram of Rapidly Solidified Ag–Cu Alloys

Cu-Ag samples produced during rapid solidification experiments using a Planar Flow Melt Spinning Process or a levitation casting technique were rapidly heated in a mirror furnace to a variety of temperatures at rates between 100 and 1.6 K/s. The surface of each sample was observed in a confocal laser scanning microscope. Metallographic analyses were performed on the samples by optical and scanning electron microscopy. The rapidly solidified samples melted far below the equilibrium melting point. The melted and resolidified samples mostly consisted of structures similar to those seen in alloys with a miscible gap. It is proposed that this type of behaviour is a result of lattice defects formed during the rapid solidification process. The effect of these defects on the thermodynamic properties was investigated. A metastable phase diagram with a miscibility gap can be constructed below the equilibrium melting point. This could explain the observed phase structure and the melting of the alloy below the equilibrium melting point.

Heat transfer and solidification in planar-flow melt-spinning: high wheelspeeds

Abstract Operation of the planar-flow melt-spinning process in a regime where the wheelspeed is high relative to the (average) solidification rate is studied. A distinct solidification front occurs. An analysis based on the governing energy and momentum equations shows that heat transfer and solidification are only weakly coupled to fluid flow. For long puddles and high wheelspeeds the governing equations decouple, leaving a Stefan problem for the shape of the solidification front and temperature fields. This problem has an analytic solution. The linear front corresponding to thin ribbons is a limiting case. Nonequilibrium kinetics at the freeze interface and undercooling of the melt are included in the general solution. These influences on solidification are thereby examined. Results are compared to previous solidification models and experiments.

Microstructural variation in rapidly solidified ribbons of AgCu and CuMn alloys

Rapidly solidified ribbons of Ag 20.8Cu 79.2, Ag 60.2Cu 39.8 and Cu 67.5Mn 32.5 (at.%) alloys have been produced by the planar flow melt spinning process with different wheel velocities ( V w) and different casting temperatures ( T c). The microstructures of the ribbons were examined by optical microscopy and scanning electron microscopy. An overall assessment of the microstructures shows that the structures of AgCu ribbons consist of four different types: microsegregation-free, banded, dendritic (cellular) and eutectic. The structure of CuMn ribbons consists of a single γ phase with a columnar and equiaxed morphology. The effects of varying V w and T c on the microstructure of the ribbons were studied.

Rapidly solidified ribbons of Fe2C13Cr1SiMo alloys produced by the planar flow melt spinning process

The planar flow melt spinning process has been employed to produce rapidly solidified ribbons of a series of Fe2C13Cr1Si steels with different amounts of Mo added, a constant wheel velocity and different casting temperatures. Metallographic investigations of the ribbons were performed by optical microscopy, scanning electron microscopy and X-ray diffraction. An overall assessment of the microstructures shows that, in the presence of Mo, the microstructure consists of two regions: a chill region and a cellular or dendritic region. The width of the chill region changes with the amount of Mo. The observations indicate that the mechanical properties of ribbons are improved by the addition of Mo to the alloys. It was also found that by increasing the amount of Mo, the lattice parameter of the matrix phase is increased.

Planar-flow spin-casting of molten metals: process behaviour

An experimental study of the planar-flow melt-spinning process was performed in order to gain a better understanding of the steady-state production of microcrystalline and amorphous ribbons. The dependence of the thickness of the ribbon product,T, on process parameters (wheel speed,U, nozzle/wheel gap,G, overpressure, ΔP, nozzle-slot breadth,R, and nozzle-slot width,W) was determined using an apparatus designed to deliver reproducible results. Thicknesses were reproducible to within 5%–8%. Guided by dimensional analysis, the non-dimensional thickness (T/G) was found to depend, within the experimental error, only on a non-dimensional pressure drop (ΔP/ρU2) and slot breadth (R/G) for fixed thermal conditions. Data from the literature and our data, which considerably extend the range, correlate consistently on this basis. In contrast to the steady behaviour, the limits within which a uniform ribbon can be formed depend on a larger set of parameters; this dependence is sketched with the available data. Finally, a variety of observed ribbon surface textures (free meniscus side) is catalogued.

A fluid mechanics model of the planar flow melt spinning process under low reynolds number conditions

A mathematical model for the planar flow melt spinning process was developed under the constraints of low Reynolds numbers. The model shows melt spun ribbon thickness is controlled by chilled wheel speed and nozzle passage flow resistance. A stability criterion was used to determine conditions under which formation of transverse waves on the ribbon free surface is favored.

A mathematical model of the planar flow melt spinning process

The Planar Flow Melt Spinning Process for the Rapid Solidification of metallic materials is analyzed using a mathematical model based on the principles of capillary fluid dynamics and solidification heat transfer. The results suggest the existence of a region of slowly recirculating flow inside the melt puddle which acts as a lubricant between the nozzle and the wheel. Markedly different thermal conditions across the ribbon thickness are also predicted by the model, as are the resultant microstructural variations across such thickness. The results of the model compare well with the available experimental evidence. The model is sufficiently general as to be immediately applicable to the study of other meniscus controlled continuous casting processes.