Liquid Metal Pool Research Articles

Electrically induced reorganization phenomena of liquid metal film printed on biological skin

Liquid metal has been demonstrated to be directly printable on biological skin as physiological measurement elements. However, many fundamental issues remained unclear so far. Here, we disclosed an intriguing phenomenon of electrically induced reorganization of liquid metal film. According to the experiments, when applying an external electric field to liquid metal films which were spray printed on biological skin, it would induce unexpected transformations of the liquid metals among different morphologies and configurations. These include shape shift from a large liquid metal film into a tiny sphere and contraction of liquid metal pool into spherical one. For comprehensively understanding the issues, the impacts of the size, voltage, orientations of the liquid metal electrodes, etc., were clarified. Further, effects of various substrates such as in vitro skin and in vivo skin affecting the liquid metal transformations were experimentally investigated. Compared to the intact tissues, the contraction magnitude of the liquid metal electrode appears weaker on in vivo skin of nude mice under the same electric field. The mechanisms lying behind such phenomena were interpreted through theoretical modeling. Lastly, typical applications of applying the current effect into practical elements such as electrical gating devices were also illustrated as an example. The present findings have both fundamental and practical values, which would help design future technical strategies in fabricating electronically controlled liquid metal electronics on skin.

Sensitivity of driving forces on molten pool behavior and defect formation in high-speed gas tungsten arc welding

The effect of multi-coupled driving forces on molten pool behavior and defect formation in high-current and high-speed gas tungsten arc welding is investigated quantitatively and systematically through combination of sensitivity analysis and experimentally validated numerical modelling. The arc shear stress is the dominant driving force to facilitate free surface deformation of molten pool and backward flow of liquid metal, which masks the effect of Marangoni force. The capillary pressure plays a dominant effect on suppressing free surface deformation. Three dimensionless groups with explicit physical implications are derived to evaluate tendency of high-speed weld bead defect formation using Buckingham π-theorem. The relevant sensitivity analysis shows that arc shear stress and capillary pressure are the most promoting and suppressive factors for defect formation, respectively. High active element concentration induces undercut and humping defects by decreasing capillary pressure.

Evolution of CaO–MgO–Al2O3–CaS–(SiO2) inclusions in H13 die steel during electroslag remelting process

The effect of Al–Mg alloy addition on the cleanliness and CaO–MgO–Al2O3–CaS–(SiO2) inclusions during electroslag remelting of H13 die steel with low oxygen content was investigated by experimental study and thermodynamic calculation. The results show that the oxygen content of consumable electrode (15 × 10−6) was invalid to be reduced after Al–Mg alloy addition during protective gas electroslag remelting (P-ESR) process. In the case of Al–Mg alloy addition during P-ESR process, the oxygen content pick-up and silicon loss of remelted ingot were avoided, and sulphur content was further decreased. CaS content of complex inclusions were decreased significantly after P-ESR process. The type of inclusions was not changed during P-ESR process with Al–Mg alloy addition, except the increase in the concentrations of CaS in individual inclusion. The original oxide inclusions inconsumable electrode transformed to liquid state during P-ESR, and original CaS inclusions were eliminated. The CaS portion in CaS-bearing complex inclusions is the inclusion that formed on the surface of oxide inclusion during the cooling of liquid steel process in liquid metal pool.

Investigation of the Laser-Powder Cladding Effect on Steel Surface Hardening

The investigation was carried out in the laser-technological complex with the power up to 8 kW, ITAM SB RAS. An inert-gas jet was supplied coaxially with the beam. A protective nozzle from which gaseous Ar was injected was used to protect the hardening joint. The parameters of the laser hardening process with the surface alloying was optimized on the samples of low-carbon steel 20, construction steel 45, and spring steel 65G.Special cladding powders containing carbon, manganese, nickel, chromium, molybdenum, tungsten, silicon, boron, and nitrogen were chosen for laser-powder cladding. They are intended for cladding wear-resistant layers onto machine parts, tools and equipment operated under abrasion-wear conditions with moderate shock loading.It was found that an optimal radiation power was 2 kW. Extra water cooling of treated parts is unpractical during laser hardening because it did not improve the hardening effect. The best effect of surface alloying was reached when the powder of rapid tool steel Р6М5 was injected in the liquid metal pool. High hardness of the clad layer remained at further heating up to 550°C. The use of laser thermal treatment and laser-powder cladding provides thermal hardening and enables increasing hardness and hence wear resistance of low-carbon steel parts by 3 - 4 times, whereas the base part remains viscous.

Экспериментальные исследования модели МГД-перемешивателя с постоянными магнитами для алюминиевых печей

A m odel experimental set-up was built aiming to ensure achievable similitude to large scale metal melting furnaces, where electromagnetic stirring is required to reduce the melting time and to achieve thermal and compositional uniformity. The widely used three-phase AC current linear travelling magnetic field inductor is substituted by a new energy-saving concept of a Permanent-Magnet (PM) inductor, consisting of a multitude of cylindrical dipoles, which form a Halbach array and are rotated synchronously. The stirrer creates a very unstable time-dependent flow pattern in the liquid metal pool. The turbulent local velocity was measured, delivering experimental data about time-averaged flow and turbulence intensity as well. Spatial components of velocity were measured by ultrasound Doppler anemometry and by a potential difference probe with an incorporated permanent magnet, delivering mutually verifying and complementary data with higher reliability. The experimental data might be used to validate the full three-dimensional numerical simulations of the stirring produced in actual large scale metal melting furnaces Normal 0 false false false RU X-NONE X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:Обычная таблица; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin-top:0cm; mso-para-margin-right:0cm; mso-para-margin-bottom:10.0pt; mso-para-margin-left:0cm; line-height:115%; mso-pagination:widow-orphan; font-size:11.0pt; font-family:Calibri,sans-serif; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin;}

Experimental and Numerical Analysis of the Deformation of a Liquid Aluminum Free Surface Covered by an Oxide Layer During Induction Melting

In an induction furnace, as a result of electromagnetic forces, the free surface of a liquid aluminum bath deforms and takes the form of a dome. The oxide layer that forms spontaneously on the free surface of aluminum melts may also influence the deformation by exerting an additional friction force on the metal. A non-intrusive experimental technique—Structured Light Fringe Projection—was used to measure the complete surface deformation and its fluctuations, for a varying set of operating parameters—inductor current intensity and initial liquid metal filling level inside the crucible. For an axisymmetric geometry, numerical simulations were carried out to calculate in a single framework: (i) the electromagnetic forces using the A–V formulation, (ii) the free surface deformation using the Volume of Fluid method, and (iii) the turbulent stirring of the metal using a RANS-based k–ω model. The friction force due to the oxide layer was modeled by imposing a pseudo-wall condition on the free surface, which makes the interfacial velocity very small compared to the average liquid metal pool velocity. A marked impact on the dome height due to applied friction force is observed. Finally, comparisons between the predicted and measured domes are presented.

HLM fuel pin bundle experiments in the CIRCE pool facility

Since Lead-cooled Fast Reactors (LFR) have been conceptualized in the frame of GEN IV International Forum (GIF), great interest has focused on the development and testing of new technologies related to HLM nuclear reactors. In this frame the Integral Circulation Experiment (ICE) test section has been installed into the CIRCE pool facility and suitable experiments have been carried out aiming to fully investigate the heat transfer phenomena in grid spaced fuel pin bundles providing experimental data in support of European fast reactor development. In particular, the fuel pin bundle simulator (FPS) cooled by lead bismuth eutectic (LBE), has been conceived with a thermal power of about 1MW and a uniform linear power up to 25kW/m, relevant values for a LFR. It consists of 37 fuel pins (electrically simulated) placed on a hexagonal lattice with a pitch to diameter ratio of 1.8. The FPS was deeply instrumented by several thermocouples. In particular, two sections of the FPS were instrumented in order to evaluate the heat transfer coefficient along the bundle as well as the cladding temperature in different ranks of sub-channels. Nusselt number in the central sub-channel was therefore calculated as a function of the Peclet number and the obtained results were compared to Nusselt numbers obtained from convective heat transfer correlations available in literature on Heavy Liquid Metals (HLM).Results reported in the present work, represent the first set of experimental data concerning fuel pin bundle behaviour in a heavy liquid metal pool, both in forced and natural circulation. A full characterization of the FPS has been experimentally achieved for Peclet numbers in the range of about 500–3000. Obtained experimental data point out a linear trend of Nusselt number as a function of Peclet in agreement with Mikityuk and Ushakov correlations showing a general tendency to underestimate them; in particular, the newly experimental data points are about 25% lower than Nu derived from correlations available in the literature.

Electromagnetic rotation of a liquid metal sphere or pool within a solution

A liquid metal electric motor including a pair of concentric ring electrodes, permanent magnet and electrolyte solution is demonstrated. A liquid metal galinstan sphere, along with a NaOH solution, is stimulated to rotate centrifugally around the central electrode and the rotating speed increases with the voltage. The NaOH solution serves to rapidly remove the oxide on the liquid metal surface, reduce the motion friction and provide impetus to the liquid metal. As the mass of the liquid metal is increased to 12.16 g to form a kidney-like body, its rotating speed appears more controllable and the effect of the electrolytic action in the NaOH solution becomes weak in the range of 0–1.82 V. As the mass of the liquid metal is increased to 18.20 g to form a circular ring-shaped body, the ideal voltage range for controlling the rotating motion of the liquid metal is 0–0.81 V. The metal fluid rotates at a speed of 1.9 r.p.m., even at an extremely low voltage of 0.03 V. The liquid metal electric motor established here can find important applications in chip cooling, liquid metal pumps, material mixing, soft machine realization, etc.

Mixed convection and stratification phenomena in a heavy liquid metal pool

This work deals with an analysis of the first experimental series of tests performed to investigate mixed convection and stratification phenomena in CIRCE HLM large pool. In particular, the tests concern the transition from nominal flow to natural circulation regime, typical of decay heat removal (DHR) regime. To this purpose the CIRCE pool facility has been updated to host a suitable test section in order to reproduce the thermal-hydraulic behaviour of a HLM pool-type reactor. The test section basically consists of an electrical bundle (FPS) made up of 37 pins arranged in a hexagonal wrapped lattice with a pitch diameter ratio of 1.8. Along the FPS active length, three sections were instrumented to monitor the heat transfer coefficient along the bundle as well as the cladding temperatures at different ranks of the sub-channels. This paper reports the experimental data as well as a preliminary analysis and discussion of the results, focusing on the most relevant tests of the campaign, namely Test I (48h) and Test II (97h). Temperatures along three sections of the FPS and at inlet and outlet sections of the main components were reported and the Nusselt number in the FPS sub-channels was investigated together with the void fraction in the riser. Concerning the investigation of in-pool thermal stratification phenomena, the temperatures in the whole LBE pool were monitored at different elevations and radial locations. The analysis of experimental data obtained from Tests I and II underline the occurrence of thermal stratification phenomena in the region placed between the outlet sections of the HX and the DHR, respectively. After the transition to natural circulation, for both tests, this region with temperature stratification moves downwards starting at the exit section of the DHR-system, while upper and lower vessel regions show a uniform temperature.

Mathematical Modeling of ESR Process for Hollow Ingot with Current Supplying Mould

With increasing demand for large cylindrical forgings, a new technology–electroslag remelting (ESR) for direct manufacture of hollow ingots rather than solid ingots has been developed. The main features of the process include a T-shaped current supplying mould (CSM), double power supply, an ingot withdrawing system, a metal level automatic control system based on a level sensor using the electromagnetic eddy current method, and the exchange of a consumable multi-electrode. ANSYS software was used to calculate the fluid flow and heat transfer in the slag bath and metal pool of this ESR hollow ingot process with its T-shaped CSM. The mathematical model was verified by measuring the geometry of the liquid metal pool as observed in the macrostructure of ϕ650 mm (external diameter)/ϕ450 mm (internal diameter) hollow ingots by sulphur print method: the observed shape and depth of the slag bath were consistent with the simulated results. Simulation of the ESR process can improve understanding of the process and allow better operating parameters to be selected.

Three-dimensional magnetohydrodynamic two-phase flow and heat transfer analysis in electroslag remelting process

A transient three-dimensional (3D) coupled mathematical model is developed in this paper in order to explore the electromagnetic, flow, and temperature fields, as well as the solidification in the electroslag remelting (ESR) process. Maxwell's equations are solved by the Finite Volume Method. The Joule heating and electromagnetic force (EMF), the source terms in the energy and momentum equations, are recalculated during each iteration as function of the phase distribution. The movement of the metal droplets is described by the Volume of Fluid (VOF) approach. Additionally, the solidification of the metal is modeled by an enthalpy-based technique, where the mushy zone is treated as a porous medium with a porosity equal to the liquid fraction. The results show that the electric current tends to go through the metal droplet first. The EMF varies with the falling metal droplet, always blocking the motion of the metal droplet. The zone with the highest temperature appears under the outer radius of the inlet. A larger Joule heating density, as well as a higher average temperature of the molten slag, is obtained when the current increases. Bigger metal droplets form with more heat and momentum, resulting in a deeper liquid metal pool.

S0820105 2セル体系ナトリウム燃焼試験における熱影響の評価

A liquid metal sodium leak and pool fire experiment has provided the transient temperature data measured in more than 100 positions for atmospheric gas and structures. The experiment was performed in an air-filled 2-cell geometry that was made by partitioning the room of rectangular cell with an opening between the cells. The analyses of the measured data clarified the basic characteristics of sodium pool combustion and consequential heat and mass transfer in the cells. The data also suggested several features of multi-dimensional thermal-hydraulic behaviors that occurred in the experimental geometry during the fire. The measured data are expected to be utilized for the validation study of numerical sodium fire analysis tools.

Modeling of flow behaviour in a LD vessel by an impinging gas jet

Present study is focused towards development of computational fluid dynamic model of oxygen impingement in the melt pool in case of LD (basic oxygen converter) steelmaking process. 1/30th scaled down model of the 100 ton LD converter has been developed and flow simulation has been performed based on volume of fluid technique, using Fluent as solver engine. Simulation of the steel bath and oxygen is carried out by using water and air, respectively. Effect of process variables on the LD steelmaking practice has been studied and the findings ascertain penetration depth of the oxygen jet into the liquid (metal) pool as a strong function of bath (lance) height, gas flow rate and nozzle exit diameter. Furthermore, an equation is developed by carrying out regression analysis using results obtained from numerical simulation. The study also provides insight into the surface deformation modes, their onsets and transition regimes, which originates due to the gas impingement into the melt pool. Finally, the computed results are compared with the experimental findings for selected cases and good agreement has been found.

An estimate of the order of magnitude of the explosion during a core meltdown-compaction accident for heavy liquid metal fast reactors: A disquieting result updating the Bethe–Tait model

Criticality and recriticality considerations in heavy liquid metal fast reactors (HLMFRs) after a hypothetical core meltdown accident are discussed. Although many aspects of system behaviour in such scenarios can be deduced directly from the classical theory of sodium-cooled fast reactors (SFRs), certain ideas that have been accepted as true for SFRs cannot be extrapolated to HLMFRs without sufficiently careful thought. In this paper, we are concerned, as in SFRs, with fuel compaction, but with one important difference: there would be no boiling of the surrounding heavy liquid metal pool. Utilizing a Bethe–Tait model, it is shown that, due to the power flattening effect of the heavy liquid metal, explosive excursions at least an order of magnitude higher than for SFRs in similar situations are conceivable.

Simulation of Slag-Skin Formation in Electroslag Remelting Using a Volume-of-Fluid Method

A modified volume-of-fluid method is implemented in a fixed-grid, finite-volume model simulating transport phenomena, solidification, and electromagnetics. The VOF model agrees well with published results, and the complete model is used to investigate process variations in the electroslag remelting process, in which liquid metal is melted from a consumable electrode immersed in an electrically resistive slag. The molten metal sinks through the slag cap floating on the liquid metal pool while a slag skin freezes to the mold. Here a VOF tracks slag skin formation and its effects on melt rate with different current levels and ingot diameters.

A Coupled Cellular Automaton–Finite-Element Mathematical Model for the Multiscale Phenomena of Electroslag Remelting H13 Die Steel Ingot

A coupled cellular automaton–finite-element mathematical model has been developed to investigate the multiscale phenomena of the electroslag remelting (ESR) H13 steel ingot. The heat transfer equation is solved to obtain the temperature distribution and liquid metal pool profile by a coarser finite-element (FE) mesh. Then, a regular network of square cells with a much finer scale is drawn for the simulation of microstructure with the cellular automaton (CA) technique. The continuous nucleation, which is based on the Gaussian distribution, is implemented to describe the heterogeneous nucleation. The growth kinetics of the dendritic tip is taken into account by the Kure–Giovanola–Trivedi model. At each time step, the temperature at the CA cell locations is interpolated from the temperature at four adjacent FE elements. The solute transfer is calculated using the FE method. Moreover, the evolution of the multiscale phenomena with growing of the ingot is considered by the varying boundary conditions. A reasonable agreement is demonstrated between the calculation and experiment. The results indicate that the shallow U-shaped metal pool would change to the deep V-shaped metal pool with the growing of the ingot. The vertical columnar grains appear at the bottom of the ingot, and an inverse V-shaped grain structure can be observed at the upper part of the ingot. It can be inferred that improving the undercooling can refine the microstructure and motivate the growing of the columnar grain during the ESR process.

Instabilities in electromagnetic quasilevitation.

We investigate free-surface instabilities occurring in various industrial processes involving liquid metal. Of particular interest is the behavior of the free surface of a pool of liquid metal when it is submitted to an alternating magnetic field. Experimentally, we study the effect of a vertical alternating medium-frequency magnetic field on an initially circular pool. We observe various types of behavior according to magnetic field amplitude, e.g., axisymmetric deformations, azimuthal mode structures, slow radial oscillation of the pool perimeter, and random rotation of the pool around its center. Drop rotation could be attributed to nonsymmetric shape deformations. The effect of oxidation leads to drastic changes in pool behavior. The experimental results are then compared to a linear stability analysis of the free surface of a circular liquid drop.

Modeling of Electromagnetic Field and Liquid Metal Pool Shape in an Electroslag Remelting Process with Two Series-Connected Electrodes

A three-dimensional finite-element model has been developed to understand the electromagnetic field and liquid metal pool shape in an electroslag remelting (ESR) process with two series-connected electrodes. The magnetic vector potential is introduced into the Maxwell’s equations, and the nodal-based method is used to solve a three-dimensional harmonic electromagnetic field. The heat transfer of the solidifying processes of ingot is modeled by a source-based enthalpy method, and the Joule heating is included in an inner source. The results show the main part of the current flows through the slag cap and a little enters into ingot in a two-series-connected electrode ESR system. As the interaction of self-induced and mutual-induced of two electrodes occurs, the skin effect is significantly suppressed by the neighbor effect. A symmetrical pattern of magnetic flux density in a two-series-connected electrode ESR system is displayed. The magnetic flux density between two electrodes is reinforced and reduced at the outside of two electrodes. The maximum Joule heat power density is located at the interface of slag and electrodes, and it decreases with an increase of the electrode immersion depth. The averaged Joule heat power density increases when slag cap thickness is reduced. With the increase of ingot height, the liquid metal pool shape changes from arc shaped to “V” shaped. When the ingot height is more than the diameter in the ESR processes, the liquid metal pool shape is constant.

The influence of laser re-melting and alloying on the structure and properties of the X40CrMov5-l steel surface layer

This paper presents the results of laser re-melting and alloying parameters on the structure and properties of the surface layer of X40CrMoV5-1 hot work tool steels, using a high-power diode laser (HPDL). Investigation indicates the influence of the alloying carbides on the structure and properties of the surface layer of the steel, depending on the kind of alloying carbides and HPDL implemented. Laser alloying of the surface layer of the steel – without introducing alloying additions to the liquid molten metal pool and across the entire range of laser power used – causes a size reduction of the dendritic microstructure in the direction of crystallization, consistent with the direction the heat is being carried away from the laser beam's impact zone. Successful re-melting of the steel without introducing alloying additions into the liquid molten pool in the form of carbide powders causes a slight increase in the properties of the surface layer of the steel in comparison to analogical properties obtained through conventional heat treatment, depending on the laser beam power used for the re-melting. The increase in the hardness of the surface layer obtained throughout HPDL re-melting and alloying with carbides is accompanied by an increase in tribological properties, when compared to X40CrMoV5-1 steels processed with conventional heat treatment.

Characteristics of inclusions in high-Al steel during electroslag remelting process

The characteristics of inclusions in high-Al steel refined by electroslag remelting (ESR) were investigated by image analysis, scanning electron microscopy (SEM), and energy-dispersive spectrometry (EDS). The results show that the size of almost all the inclusions observed in ESR ingots is less than 5 μm. Inclusions smaller than 3 μm take nearly 75% of the total inclusions observed in each ingot. Inclusions observed in ESR ingots are pure AlN as dominating precipitates and some fine spherical Al2O3 inclusions with a size of 1 μm or less. It is also found that protective gas operation and slag deoxidation treatment during ESR process have significant effects on the number of inclusions smaller than 2 μm but little effects on that of inclusions larger than 2 μm. Thermodynamic calculations show that AlN inclusions are unable to precipitate in the liquid metal pool under the present experimental conditions, while the precipitation of AlN inclusions could take place at the solidifying front due to the microsegregation of Al and N in liquid steel during solidification.