Showing papers on "Liquid metal published in 1995"

X-ray tube having rotary anode cooled with high thermal conductivity fluid

Abstract: An X-ray tube rotating anode (14) is cooled with a liquid metal (40) functioning as a recirculated heat exchange fluid and/or a metal film in a gap (39) between the anode (14) and a stationary structure. The liquid metal (40) is confined to the gap (39) by (a) a labyrinth (44 or 46) having a coating that is not wetted by the liquid, (b) a magnetic structure (22), or (c) a wick (38). The liquid metal (40) recirculated through the anode (14) is cooled in a heat exchanger located either outside the tube or in the tube so it is surrounded by the anode (14). The heat exchanger in the tube includes a mass of metal in thermal contact with the recirculating liquid metal and including numerous passages (36) for a cooling fluid, e.g. water. A high thermal conductivity path (26, 48, 49) is provided between an anode region (16) bombarded by electrons and a central region of the tube where heat is extracted. In one embodiment the high thermal conductivity is achieved by stacked pyrolytic structures having crystalline axes arranged so there is high heat conductivity radially of the region and lower thermal heat conductivity normal to the high heat conductivity direction.

Method and apparatus for injection molding of semi-solid metals

Abstract: A new method and apparatus for the injection molding of semi-solid materials (SSM). In this process (called Rheomolding), a superheated liquid metal is cooled into the semi-solid state in the barrel of a special vertical injection-molding machine, with the growing dendrites of the solid phase being broken into small and nearly spherical particles by the shearing force generated by the screw and barrel. Compared with the superheated liquid metal, SSM has lower temperature, lower shrinkage and a more stable flow pattern. Therefore, the rheomolding process can produce net-shape metal or metal-matrix-composite parts continuously at lower cost.

Thermal Conductivity of Electrically Conducting Liquids by the Transient Hot-Wire Method

Abstract: A relative transient hot-wire apparatus for the measurement of the thermal conductivity of electrically conducting liquids is described. The instrument consists of a single glass capillary filled with mercury to act as an insulated hot wire. The resistance change in the wire with respect to time is used to obtain the thermal conductivity of the liquid surrounding the wire with an estimated accuracy of ±2%. The most significant advantage of the liquid metal filled glass capillary is its increased temperature limit compared to other types of transient hot-wire cells. The use of the new method at temperatures up to 493 K is shown for several aqueous systems, and new data are reported for propionic acid + water mixtures.

Non-toxic liquid metal composition for use as a mercury substitute

Abstract: Liquid gallium or gallium alloy is utilized as a mercury substitute for a variety of applications. The liquid gallium or gallium alloy is either free of metal oxides or has only very low quantities of metal oxides.

Magnetohydrodynamic flows in ducts with insulating coatings

Abstract: Effective insulation of the electrically conducting channel walls leads to a tolerable magnetohydrodynamic (MHD) pressure drop of liquid metal flows in self-cooled fusion reactor blankets. Such insulation prevents closed current circuits over conducting walls and reduces the total current, which determines the pressure drop and flow distribution caused by the interaction of the flowing liquid metal and the strong plasma-confining magnetic field. Several kinds of insulation are currently under development. One is the so-called flow channel insert technique, where the insulating ceramic is protected against the liquid metal by thin steel sheets. Recently, direct insulating ceramic coatings have been proposed which resist corrosion during the whole operation time of a fusion blanket. It is not necessary that these coatings provide perfect insulation. Even a finite coating resistance is enough to reduce the pressure drop by orders of magnitude. The aim of this paper is to provide material researchers and blanket designers with sufficient data on MHD insulation requirements. Changes in insulation properties occurring during the lifetime of the blanket due to impurities, corrosion, irradiation damage, or the presence of small cracks can be allowed up to a certain limit. The increase in the pressure drop and the change in flowmore » pattern are quantified, if the coating resistance falls below required limits.« less

Gas atomizer with reduced backflow

Abstract: An improved molten metal spray forming atomization ring converter adapted for the spray forming of a refined molten metal from a molten metal refining or melting chamber wherein the molten metal is atomized into tiny molten droplets by gas impingement in a stream of molten metal and to the structure by which the molten metal droplets are preferentially directed to and deposited on a target surface The molten metal spray forming atomization ring converter is adapted to control the flow of liquid metal droplets and to avoid a backflow of such droplets during the gas atomization by providing structure, such as small apertures to the inner diameter of the ring, by providing large holes through the inner diameter and adding a porous metal filter to cover the large holes or by providing a gas supply system independent from the atomization system gas supply, such that a pressure or diffused source of gas is provided at the inner bore These modifications produce a relatively small mass flow of gas sufficient to feed the entrainment requirement of the high speed jets, but sufficiently low enough to avoid preatomization of the liquid metal wherein backsplash of the metal is reduced and/or prevented

Heat transport and solidification in the electromagnetic casting of aluminum alloys: Part I. Experimental measurements on a pilot-scale caster

Abstract: While many investigators have examined electromagnetic and magnetohydrodynamics phenomena in electromagnetic casting (EMC) of aluminum, there appears to be no published work on heat transport and solidification in such casters. This two-part series is an attempt to remedy this deficiency. The first part describes two experimental campaigns, carried out on a pilot-scale electromagnetic caster at Reynolds Metals Company, in which sacrificial thermocouples were used to obtain many data on temperature distributions within the aluminum of a pilot-scale caster and thereby to obtain the shape of the liquid metal pool (sump). The data reveal a strong dependence of temperature distribution and sump depth on casting speed but a relatively weak dependence on the flow rate of the quenching water striking the outside of the ingot.

Steady-state cellular solidification of Al-Cu reinforced with alumina fibers

Abstract: The steady-state directional solidification of aluminum-4.5 wt pct copper and aluminum-1.0 wt pct copper alloys reinforced with parallel,continuous, closely spaced alumina fibers is investigated under growth conditions that produce a plane front or cells in corresponding unreinforced alloys. Specimens were designed to have a central reinforced region surrounded by unreinforced metal of the composite matrix composition. Each was produced by pressure infiltration, subsequently remelted, directionally solidified, and quenched to reveal the liquid/solid metal interface. Both unreinforced and composite sections were characterized to determine solidification front morphology and degree of microsegregation. In the unreinforced portion of the samples, the transition from plane-front to cellular solidification was observed to correspond to a coefficient of diffusion of copper in liquid aluminum of 5 − 10−9 m2 − s−1, in agreement with published values. Cell lengths, analyzed using a finite-difference model of microsegregation, are in agreement with the Bower-Brody-Flemings (BBF) model for cell tip undercooling. In the composite portion of the samples, the alloys solidify free of lateral microsegregation for all solidification conditions investigated, in agreement with theory. The shape of the liquid/solid metal interface near the fibers indicates a much lower fiber/liquid metal interfacial energy than fiber/solid metal interfacial energy. In the composite, plane front solidification is therefore not observed even when plane front solidification obtains in the unreinforced alloy. It is shown that geometrical constraint imposed on deep cells by the fibers causes significant increases in cell tip undercoolings, in agreement with current analyses of deep cell solidification.

Heat Transfer between Bubbles and Molten Wood's Metal

Abstract: In refining processes for steel and some other metals, gas is blown into molten metal from the top, the bottom or simultaneously from the top and bottom of the vessel to promote mixing and chemical reactions. Since the gas is usually injected at a temperature lower than the molten metal temperature, knowledge about the heat transfer between gas and molten metal is required to predict precisely the mixing effect. Present authors previously carried out cold model experiments for bottom injection to investigate the mechanism of convective heat transfer between bubbles and liquid, using cooled gas and water and proposed an empirical correlation for the Nusselt number. In this paper, the mechanism of convective heat transfer between bubbles and molten metal was investigated using molten Wood's metal. The funtional relationship between the Nusselt number and the Peclet number was the same as that for water models although the Prandtl numbers of water and Wood's metal were much different with each other.

Generation of isothermal spreading data and interfacial energy data for liquid reactive metals on ceramic substrates: The copper-titanium/alumina system

Abstract: The sessile drop technique is frequently used to evaluate the wettability and spreadability of liquid metals on ceramic substrates. In this study, the spreading kinetics of copper-20 wt% titanium alloys on polycrystalline alumina were evaluated based on measurements of spreading radius versus time. The process of spreading was monitored by anin situ video recording system. The tests were performed using three different initial metal configurations. It was found that conventional sessile drop testing configurations cannot be used to generate isothermal spreading kinetics data because of significant spreading during the heat-up cycle from the solidus temperature to the test temperature. An improved sessile drop technique was developed which eliminated the non-isothermal experience by introducing the liquid copper to the solid titanium/alumina at the desired testing temperature. Using this technique, only a few seconds of data were lost (while the liquid copper dissolved the solid titanium). Because very limited interfacial energy data exist for the copper-titanium/alumina system, especially at higher titanium concentrations, the equilibrium contact angle, the solid-liquid interfacial energy, and the work of adhesion from 1000 to 1300 °C are also presented.

Metal lubricated plain bearing having a bearing part adjoining a bearing surface wetted with liquid metal during operation

Abstract: The invention is directed to a plain bearing part for a liquid metal lubricated plain bearing, the plain bearing part having a bearing surface that is in contact with a liquid metal during operation. This bearing surface is provided with a layer of a metal effective as diffusion barrier for the liquid metal and which is well wetted with the liquid metal. The layer is applied according to a PVD process.

Thermodynamic Properties of Ternary Liquid Metal Alloys

Abstract: Pseudopotential theory and Gibbs-Bogolyubov variational technique have been generalized to calculate the n-component metal mixture thermodynamics. The Percus-Yevick hard-sphere model was used as a reference system. An effective pair interaction was estimated using the local Animalu-Heine potential in conjunction with the Vashishta-Singwi dielectric function. Minimization of the free energy was performed with respect to the three hard-sphere diameters and the atomic volume. This method was applied to describe the Na-K-Cs and Na-K-Rb liquid alloys at different temperatures and alloy compositions. Good agreement with the available experimental data was observed. The accuracy of the model used improved with increasing temperature, as shown by our results.

On the pressure wave problem in liquid metal targets

Abstract: A liquid metal target for a pulsed spallation neutron source was modelled on the computer to investigate the effect of the high instantaneous power deposition (60 kJ in 1 ps) on the pressure in the liquid and the resulting stress on the container. It was found that for the short pulse duration the resulting stress would be likely to exceed the allowable design stress for steels of the HT-9 type with low nickel content. Adding a small volume fraction of gas bubbles might be a way to suppress almost completely the generation of pressure waves.

Process for treating molten metal during a casting operation using a filter and filter for implementing the process

Abstract: A filter for molten metal comprises a series of at least two refractory mineral material plates which define between them one or more cavities The plates each comprise a series of holes through which the liquid metal passes and by which the liquid metal is filtered At least one of the cavities contains a material for treating the metal, for example a material for inoculating the liquid metal The filter is used among other things to filter and treat molten metals simultaneously and to improve the quality of the metal