Liquid Metal Stream Research Articles

The Concept of Using 3D Printing Technology in Ceramic Foundry Filter Manufacturing

AbstractThe article presents the concept of using 3D printing technology in ceramic foundry filter manufacturing. They are a crucial component for obtaining an acceptable quality of nickel superalloys by carrying out the process using the precision casting method. Commonly used filters of this type have a number of disadvantages. They are characterized by irregularity of the filtering structure, high brittleness, lack of resistance to mechanical shocks, and impacts of a stream of liquid metal. All these factors create a risk of introducing the material from the damaged filter into the casting mold, which translates into contamination of the casting alloy, and thus the occurrence of casting defects such as nonmetallic inclusions. The hope for a change in this state of affairs is the use of additive manufacturing technology in their production, which by assumption will allow to obtain a product with a repeatable shape, high mechanical resistance, and a specially designed structure regulating the flow of liquid metal into the mold during casting. The suitability of robocasting and binder jetting technology for producing filtration structures was initially assessed. The results have presented the selection of ceramic powder, as well as the development of the composition of the ceramic paste. The parameters of paste preparation and 3D printing individual processes were described. Moreover, the representative microstructures and basic mechanical properties of samples obtained by both of the compared technologies were presented. Furthermore, the final effect of prototype casting filters with a repeatable shape, manufactured with the use of both technologies, was presented, which were transferred for further technological research in a foundry producing critical aircraft engine parts. The possibilities of using each technology in various applications were also discussed.

Modern status and ways of development of round billet production technology by steel continuous casting

Production of round billets by steel continuous casting, widely used for manufacturing seamless pipes, railway wheels and tyres, quality long rolled products etc., is widely spread in the world steel industry. Constant search for improved design of CCM takes place, separate parts of existing machines are being perfected. An analysis of collected in the world practice experience of solving problems, related to production of round continuously casted billets, enables to choose proper technical solutions for each particular situation, to determine rational parameters of technology. History of development of round continuously casted billets production technology considered. Data on their modern producers presented. Peculiarities of steel continuous casting technology, as well as reasons of defects of round continuously casted billets have been discussed. Classification of basic kinds of cracks of round continuously casted billet presented. Basic problems during production of round continuously casted billets relate to ovality formation, mainly because of unevenness of heat-away in the mold. The increased ovality can lead to formation of internal and external cracks. Ways of solving problems of defects formation and ways of round continuously casted billet technology perfection summarized. Application of methods of mathematical simulation for a technology, which enables to produce defectless billets considered. It was shown, that basic measures to decrease number of billet defects, relate to setting rational parameters of temperature-speed mode, transfer to internal mold profile, corresponding to the billet shrinkage. Another measure is elimination of uneven impact of the liquid metal stream on the solidifying shell in the area of small and big radius. A perspective direction of round continuously casted billets production technology perfection is application of soft reduction methods and electromagnetic stirring of the liquid metal.

Low-Pressure Casting of Aluminium AlSi7Mg03 (A356) in Sand and Permanent Molds

Aluminium A356 (AlSi7Mg03) is the most common foundry alloy poured in sand and permanent molds or lost-wax shells. Because of its magnesium content, this alloy responds to a precipitation hardening treatment. The strength and ductility combination of the alloy can be varied at will by changing the temper treatment that follows the solutionizing and quenching of the part. By feeding the mold from the bottom, the low-pressure process provides a tranquil filling of the cavity. A perfect control of the liquid metal stream is provided by programming the pressure rise applied on the melt surface. It compares favorably to the more common gravity casting where a turbulent filling is governed by the geometry of the gating system.

Dissolution and erosion behavior of AISI H13 shot sleeve in high pressure die casting process

In high-pressure die casting process (HPDC), shot sleeve undergoes erosion, wear and soldering due to cyclic thermo-mechanical exposure by the molten casting alloy stream with high temperature and high velocity. Gradual deterioration of sleeve surface during service affects the quality of resultant casting, lives of piston and sleeve. It also results in increased cost and downtime. Objective of this work is to study and reduce sleeve surface damage while casting the components weighing between 20 and 40 kg. As initial survey, the worn-out sleeve was used to perform failure analysis to understand erosion mechanism. Simulation study was conducted to estimate impact force of liquid metal stream on sleeve surface at various sprout angles. Dummy pins were made from same steel that of the sleeve - AISI H13 and their erosion response to different surface conditions such as surface roughness, nitrided case depth, and coating chemistry was investigated. Erosion performance of a dummy pin made from steel with increased molybdenum and reduced silicon content was compared with the pins of AISI H13 steel. The pins were observed intermittently for size, weight loss and any crater formation on the surface. All the pins were characterized after subjecting to a maximum number of 4500 casting made. The pins were characterized for microstructure, chemical composition, and phase analysis. Surface roughness and micro-hardness were also measured. Pin made of DIN 1.2367 steel showed increased resistance against erosion, comparative to the pin made of AISI H13 steel under similar testing condition. TiAlN coated pin outperform all other pins in terms of resistance against erosion. Mechanism of progression of erosion in actual shot sleeve is proposed based on experimental design.

Development of the organization of rational schemes for the use of technogenic waste in the processes of off-treatment of steel intermediate

The results of the experimental verification of the efficiency of complex out-of-furnace treatment of low carbon steel using a test mixture based on man-made waste, which is fed partly to the melting unit at the end of the oxidation period of melting and partly by pouring under a stream of liquid metal. is the use of slag-forming materials obtained by joint heat treatment of mixtures of components containing the above mentioned oxides and carbonaceous material of vegetable origin. Their weight ratio in the initial mixture is determined by the purpose and properties of the finished product. The positive technological effects that are achieved by applying the developed method of after-treatment will in future provide favorable conditions for the effective conduct of microalloying, modification, vacuuming and stable casting of low-quality and ultra-low carbon steel. A slight decrease in the temperature of the steel intermediate in the implementation of the method is about 10 - 15 ° C, which is easily compensated for the installation of the ladle, and a slight increase in electricity consumption is compensated by the effects achieved in the processing of low-carbon steel intermediate. Obtaining a higher degree of desulfurization and deoxidation of steel, as well as reducing the contamination of Al2O3 steel and improving the ecological purity of the process can be achieved by reducing the composition of the SHS used in the first stage of processing, the amount of slag aluminothermal production of ferromanganese and complete exclusion of melting, melting weight ratios of powdered waste production of lime, aluminum-thermal slag production of ferromanganese, sludge neutralization of electrocorundum and carbide cr emnia.

A micro-needle induced strategy for preparation of monodisperse liquid metal droplets in glass capillary microfluidics

Monodisperse micro-sized liquid metal droplets have received considerable attention for developing flexible electronics, microfluidics actuators and reconfigurable devices. Herein we report an innovative and efficient strategy for large-scale preparation of Galinstan liquid metal microdroplets with controllable sizes using a micro-needle induced glass capillary microfluidic device. By inserting a stainless steel micro-needle into the inner liquid metal phase in the glass capillary, the hydrodynamic instability of the liquid metal stream is significantly suppressed to guarantee steady fluid flow before the liquid metal is pinched off by the outer phase flow, giving rise to a stable generation of monodisperse liquid metal microdroplets. The microdroplet size dependence on the flow ratio of the continuous and dispersed-phase is investigated experimentally. A theoretical framework based on the Plateau–Rayleigh instability is proposed to explain the advantage of the micro-needle induced strategy. This strategy has great potential for the generation of high interfacial tension liquid metal emulsions.

Magnetic Properties of NdFeB Alloys Obtained by Gas Atomization Technique

Since Sagawa reported in [1]on the excellent hard magnetic properties of NdFeB permanent magnets, the utilization of anisotropic sintered NdFeB magnets in large motor and generator applications has grown spectacularly. Such hard magnetic material consists of a major tetragonal intermetallic compound (Nd 2 Fe 14 B), with excellent intrinsic hard magnetic properties, and a minor Nd-rich phase. Obviously, the magnetic behavior depends strongly on the microstructure of the magnet material, which in turn is determined by the production process. Microstructural factors affecting the hard magnetic character include the mean and the standard deviation of the grain size distribution, the orientation degree of the grains, the distribution of the Nd-rich phase, and the presence of a residual amount of other secondary phases (e.g. α-Fe, NdFe 4 B 4 , and other borides). All kind of defects in the microstructure, especially soft magnetic phases, can easily deteriorate the hard magnetic properties. It has been reported a slope change in the curve of magnetization as a function of temperature at around 150 K due to a spin reorientation transition (SRT) [2]. Such effect has been carefully analyzed for sintered magnets, since it is essential for the design of sensors, magnetic apparatus or magnetomechanical devices for cryogenic applications [3]. Alternative production routes of NdFeB magnets result in new microstructures whose impact on magnetic properties has to be carefully studied. Inert gas atomization is one of the novel processes under evaluation to produce NdFeB powders [4]. This technique consists on breaking a liquid metal stream into droplets by means of a high velocity inert gas flow. These droplets become spherical particles after solidification. The small size of the droplets, typically in the microns range, and the high velocity of the gas enable a fast heat transfer between both, resulting in high cooling rates and fine microstructures. Using this technique, we have produced several NdFeB alloys. After splitting the as-atomized powders in different size fractions by sieving, their microstructure and magnetic properties have been studied. In this work, we report the magnetic properties as a function of temperature, between 1.8 and 400 K, and of particle size. Fig. 1shows the characteristic microstructure of a single gas atomized NdFeB particle, whose main constituents are Nd 2 Fe 14 Bgrains of a few microns in size. The Inverse Pole Figure (IPF) demonstrates the random crystallographic texture of the material. The cooling rate of gas atomized particles increases when the particle size is reduced. As a result, larger particles exhibit higher microsegregation and, hence, the precipitation of soft magnetic α-Fe phase. On the other hand, smaller particles display finer microstructures. As for the coercive field, it was observed that it increases significantly when the particle size is reduced, reflecting a higher difficulty for reverse domain nucleation (less surface defects, finer grain size, lower volume fraction of secondary soft magnetic phases, etc.). Fig. 2shows the temperature dependency of the saturation magnetization, M s (T). The anomaly, i.e. a slope change of the M s (T) curve, observed around 150 K could be ascribed to the spin-reorentation transition (SRT) mentioned before, which has been reported to occur in the same temperature range when the magnetic field is applied parallel and perpendicularly to the sample direction [2]. In contrast with the measurements performed in single crystals and anisotropic sintered magnets, isotropic gas atomized powders exhibit an increment of saturation magnetization below the split tilt temperature of the SRT. This work has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 720838 (NEOHIRE project).

Fusion and viscosity of molten high-vanadium steels investigation with the aim of perfecting the powder obtaining from liquid state by sputtering

Manufacture of new brands of tool steel by means of powder metallurgy technique has been mastered in Ukraine. High-alloy steels powder is obtained by sputtering liquid metal stream getting out of a batcher through the exhaust outlet of 6 mm in diameter. The average yield of suitable powder makes 60-65%. The reason for the low yield of suitable powder is blocking the exhaust outlet with solid phase and stopping the pouring. The fusion characteristics and viscosity of these steels melts have been studied to work out the rational modes of high-alloy steels sputtering. Experimental researches of the tool steels technological properties have been performed on thermal analysis installation. It has been stated, that the liquidus temperature is the range from 1307-1463°С, and the solidus temperature is the range from 1255-1436°С. Experimental data we used and the formulas for calculation of liquidus temperature depending on the chemical composition have been obtained. The viscosity of the vanadium-containing steel Р0М2СФ10-МП melts has been determined by the method of damped torsional oscillations registration and by the capillary way as well. The melted steel temperature was taken both in the crucible of the induction furnace and in the iron receiver in the course of sputtering under production conditions. The recommendations as to the high-alloy steels sputtering have been developed and introduced in production making it possible to increase the suitable powder yield on the average of 10%

Processing of Cu–Al–Ni Alloy by Spray Atomization and Deposition Process

The present work describes a new route for the preparation of Cu–Al–Ni alloy strips via spray atomization and deposition route. The route consists of atomizing liquid Cu–Al–Ni alloy with a jet of argon gas in a closed chamber, at a pressure of 1 MPa. The semi-solid Cu–Al–Ni droplets are subsequently collected on the steel substrate placed vertically below the liquid metal stream in the atomization chamber to form a three-dimensional preform. The deposit produced on the substrate contains ~ 5% porosity. The microstructural details of the spray deposited Cu–Al–Ni strips explains particularly the presence of porosity, formation of splats during the flight of spray casting and the associated microstructural evolution in Cu–Al–Ni spray deposit are explained.

Effect of Titanium Inoculation on Tribological Properties of High Chromium Cast Iron

Abstract The present investigation focuses on the study of the influence of titanium inoculation on tribological properties of High Chromium Cast Iron. Studies of tribological properties of High Chromium Cast Iron, in particularly the wear resistance are important because of the special application of this material. High Chromium Cast Iron is widely used for parts that require high wear resistance for example the slurry pumps, brick dies, several pieces of mine drilling equipment, rock machining equipment, and similar ones. Presented research described the effects of various amounts of Fe-Ti as an inoculant for wear resistance. The results of wear resistance were collated with microstructural analysis. The melts were conducted in industrial conditions. The inoculation was carried out on the stream of liquid metal. The following amount of inoculants have been used; 0.17% Fe-Ti, 0.33% Fe-Ti and 0.66% Fe-Ti. The tests were performed on the machine type MAN. The assessment of wear resistance was made on the basis of the weight loss. The experimental results indicate that inoculation improve the wear resistance. In every sample after inoculation the wear resistance was at least 20% higher than the reference sample. The best result, thus the smallest wear loss was achieved for inoculation by 0.66% Fe-Ti. There is the correlation between the changing in microstructure and wear resistance. With greater amount of titanium the microstructure is finer. More fine carbides do not crumbling so quickly from the matrix, improving the wear resistance.

A novel metal flow imaging using electrical capacitance tomography

The measurement of gas-liquid metal two phase flow is a challenging task due to the opaqueness and the high temperatures. For instance, during continuous casting of steel the distribution of argon gas and liquid steel in the submerged entry nozzle is of high interest, since it influences the quality of the produced steel. In this paper we present the results of a feasibility study for applying the electrical capacitance tomography (ECT) to detect the outer surface of a liquid metal stream. The results of this study are the basis for the development of a new contactless sensor which should be able to detect the outer shape of a liquid metal jet using ECT and the bubbles inside the jet at the same time with mutual inductance tomography.

Suppression of humping bead in high speed GMAW with external magnetic field

In high speed gas metal arc welding, the higher momentum of backward flowing molten jet in a weld pool contributes to the occurrence of humping bead. In this study, the external magnetic field is exerted to control the fluid flow and its velocity distribution inside the weld pool to suppress the humping bead. The effects of the external magnetic field on the weld pool flow dynamics, arc column and the metal transfer are experimentally investigated. The required excitation current levels to suppress humping bead under different welding conditions are obtained. It is found that the deflection of arc column and liquid metal stream at wire tip can be offset by a suitable backward inclination angle of torch. With appropriate combination of external magnetic flux density and backward inclination angle of torch, a good quality weld bead without humping and spatter can be obtained in high speed GMAW.

A Lorentz force flow meter for application at blast furnaces: design and calibration

AbstractA reference Lorentz force flow meter (LFF) has been developed to measure molten steel mass flow at the end of the runner of an experimental blast furnace. It works according to the principles of Lorentz force velocimetry [1] in which a static magnetic field interacts with a liquid metal stream. The magnetic field lines are generated by an arrangement of permanent magnets and penetrate the entire cross‐section of the flow generating eddy currents and a total Lorentz force inside the melt. This force is proportional to the mass flow of the liquid metal and owing Newton's third law, there is a counter force of the same magnitude acting on the magnet system which is connected to a load cell. For accurate flow rate measurements, a “dry and wet calibration” of the LFF needs to be performed [2]. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Model of Gas Flow Through Porous Refractory Applied to an Upper Tundish Nozzle

Argon gas commonly is injected into the liquid metal stream through the porous refractory walls in many metallurgical processes. In this work, a new model has been developed to investigate gas diffusion through heated porous refractory, including the effects of refractory geometry, the thermal expansion of the gas, temperature-dependent gas viscosity, and possible leakage into unsealed joints. A novel one-way-flow pressure boundary condition has been formulated and implemented to prevent unrealistic flow into the refractory. The complete model is validated with both analytical solutions of 1D test problems and observations of a water bubbling experiment. Then, to demonstrate practical application of this general model, argon gas flow is simulated through a double-slitted upper tundish nozzle during continuous steel casting with a slide-gate system. Realistic liquid steel pressure distributions with the bubbling threshold condition are applied on the inner surface. Parametric studies are conducted to investigate the effects of joint gas leakage, refractory conductivity, permeability, and injection pressure on the resulting gas distributions, gas mass flow rates, and leakage fraction. This new model of porous flow can serve as the first step of a comprehensive multiphase model system.

Electro-hydrodynamic shooting phenomenon of liquid metal stream

We reported an electro-hydrodynamic shooting phenomenon of liquid metal stream. A small voltage direct current electric field would induce ejection of liquid metal inside capillary tube and then shooting into sodium hydroxide solution to form discrete droplets. The shooting velocity has positive relationship with the applied voltage, while the droplet size is dominated by the aperture diameter of the capillary nozzle. Further, the motion of the liquid metal droplets can be flexibly manipulated by the electrodes. This effect suggests an easy going way to generate metal droplets in large quantity, which is important from both fundamental and practical aspects.

The influence of Rolling process on the porosity and wear behavior of Spray-formed Al-6%Si-20%Pb

Spray forming, also called spray casting or spray deposition, is the inert gas atomization of a liquid metal stream into variously sized droplets. These droplets are interrupted by a substrate which collects and solidifies the droplets into coherent, near fully dense perform. The present work concerns with this techniques. This technology was applied to produce Al-6%Si-20%Pb alloys. The spray droplets were deposited over a copper substrate to achieve a disc shape perform. After spray deposition samples were rolled at room temperature on two high rolling mills and total porosity and wear characteristic of spray deposits were studies. The total porosity decreases with the increase in the percentage of reduction in thickness of the samples. Thickness of the samples in both middle and peripheral region. Wear testing of spray formed and rolled Al-Si- Pb alloy were investigated on a pin on disc type wear machine. Wear rate behavior with applied load and increase in percentage of reduction in thickness of samples was observed. Wear rate increased with increasing the load and decreased with increase in percentage of reduction in thickness of the sample. Keyword: Al-Si-Pb alloy, Rolling, Spray forming, Total porosity, Wear characteristic

Effect of Process Parameters on Splat Formation during Impingement of Liquid Metal Droplets over a Cold Substrate

Molten metal droplet impingement is an integral part of droplet based manufacturing processes like spray casting and sprays coating. In these processes, in a single operation, a liquid metal stream is atomized into fine droplets, which impact on a substrate to form a bulk deposit. The properties of casting or coating strongly depend on the shape of splats formed by individual droplets after impingement and solidification. Therefore, considerable research studies have been carried out to characterize individual droplet impact, usually driven by an interest in a particular process. These studies include extensive modeling of droplet deposition, some of which are supported by experimental studies. Most of these modeling activities have focused on the impingement of a droplet on to a surface to predict quantities such as the extent of maximum spread and the final equilibrium diameter, the rate of heat transfer to the substrate, and the solidification rate. Due to interaction of several complex phenomena, comprehensive modeling of the droplet deposition is a challenging task. The flow of liquid droplet upon impingement is itself a complex phenomenon. Heat transfer and solidification occurring concurrently with the flow adds further to the complexity. Thus the present study aims at the development of a comprehensive mathematical model of impingement of liquid metal droplet upon a substrate to understand the effect of process parameters such as initial temperature of droplet, size of droplet and velocity of droplet.

Compatibility of SiCf/SiC composite exposed to liquid Pb–Li flow

SiCf/SiC composites are candidate structural and functional materials for fusion blankets, attractive for their potential application for higher temperature liquid metal blankets compared to the range possible for metallic materials. However, the experimental data on the long term compatibility of SiCf/SiC composites with high temperature liquid metal is inadequate. To acquire parametric data on the compatibility of NITE SiCf/SiC composites with a high temperature liquid metal stream, the corrosion behavior was examined in liquid Pb–Li using a rotating disk apparatus. The materials used in this study were exposed to relative flow velocity of ∼10–37cm/s at 900°C for 1000h. Oxidation layers were detected on the matrix and fiber near the surface exposed to liquid Pb–Li at 900°C for 1000h. Additional results for shorter exposure times and relationship to flow velocity are discussed.

Electric current induced liquid metal flow: Application to coating of micropatterned structures

Although electric fields have been widely used to induce flow of electrolytes, electrically induced long-range flow of metallic liquids has never been reported. Here we show that liquid pure metals can be made to flow in a continuous stream by applying an electric current to an underlying conductive film. This flow occurs in the direction of applied current and is thought to be driven by liquid electromigration. The phenomenon is expected to engender many applications where controlled delivery of a continuous liquid metal stream is desired, such as microfluidics, nanolithography, and patterned conformal coatings. The last application is demonstrated here.

Modelling compressible gas flow near the nozzle of a gas atomiser using a new unified model

In this paper, a unified numerical model is used to simulate the compressible gas flow, during the process of atomisation of liquid, near the atomiser nozzle in gas-only case studies. The flow of the under-expanded gas jets is studied, by analyzing the pressure field, density field and the spatial distribution of Mach number of the gas. The simulated predictions of gas status at the nozzle exit, the radial profile of Pitot pressure, aspiration pressure, and the spatial distribution of the density gradient, are compared with relevant experimental results and an analytical correlation, in order to validate and verify the application of this unified model in the numerical simulation of the gas dynamic behavior during gas atomisation. The simulation results show that the compressible gas flow near the nozzle of a discrete jet atomiser is different from that in a typical annular slit atomiser. Unlike existing models, this new formulation has the potential to be used in future to simulate the simultaneous flow of compressible gas and a weakly compressible liquid metal stream.