Metal degassing system

Abstract

A metal degassing system (2) configured for degassing a liquid or solid metal (3), the metal degassing system comprises an electrical power supply (4), an electrolyzer unit (12), and a control system (6) connected to the electrical power supply (4) and the electrolyzer unit (12), the electrolyzer unit comprising an anode (14), a cathode (18), and an electrolyte (16), wherein the electrolyte comprises or consists of a proton exchange membrane and wherein the electrolyzer unit comprises an electrolyzer housing (24) including a separating wall (26) having a first surface (30) including an electrolyte-gas interface and a second surface (32) including an electrolyte-metal interface, the cathode (18) positioned on said first surface (30).

Description

[0001] P2961PC00

[0002] METAL DEGASSING SYSTEM

[0003] The present invention relates to a system for degassing metallic alloys.

[0004] The casting process of certain metal products often necessitates melting and maintaining molten metal at temperatures ranging from 600°C to 1200°C, or higher, depending on the specific metal physical properties, raw material, and process parameters. Some molten metals and alloys such as aluminum, magnesium, and copper alloys can contain dissolved gases such as hydrogen and oxygen and / or impurities, which may adversely affect both the manufacturing process and the final properties of the metal product [1]: D. E. J. Talbot, “Effects of Hydrogen in Aluminium, Magnesium, Copper, and Their Alloys", International Metallurgical Reviews, Volume 20, Issue 1 , 166-184. In addition, the absorption process of some of these gases directly contribute to the formation of oxides layers, hydrides and impurities during melting and maintaining the molten metal.

[0005] Efforts to diminish the levels of these dissolved gases or impurities in molten metal baths are one of the main industrial and manufacturing challenges. There is a need to purify molten metals by eliminating gases and / or impurities, thereby ensuring the production of high-quality molten metal with optimal physical and mechanical characteristics.

[0006] Porosity formation in metallic alloys during solidification are critical issues that affect negatively the mechanical properties and integrity of cast materials. The porosity formation can be drastically increased by the amount of dissolved hydrogen content in the molten metal before solidification. Hydrogen, being the smallest and most diffusive atom, can easily dissolve in molten metal during the melting and casting processes. In addition, the oxidation reactions between water vapor and molten metal can also contribute to increase of dissolved hydrogen contents in the molten metal. However, during solidification, its solubility in the solid phase significantly reduces, leading to the excess hydrogen being expelled from the solidifying front. This expulsion often results in the formation of hydrogen-induced porosity, as the hydrogen gas cannot escape quickly enough and becomes trapped within the solidifying metals and alloys. These pores can significantly weaken the material by acting as stress concentrators, thereby reducing its ductility, fatigue resistance, conductivity and tensile strength. Addressing the hydrogen or oxygen contents problem and controlling porosity formation are thus essential for improving the quality and performance of many metallic alloys, requiring careful control of casting conditions, alloy composition, and post-processing treatments to minimize these defects. These properties are critical for many industrial applications. P2961PC00

[0007] In addition to the formation of porosity, the interaction between hydrogen and oxygen within the molten metal plays a critical role. These interactions can significantly influence the overall quality and integrity of the final cast product. When hydrogen is present in the molten metal, it can lead to the formation of undesirable gas porosity. Oxygen, on the other hand, can react with other elements within the metal, potentially leading to the formation of oxides. These oxides can act as nucleation sites for porosity and other defects. Moreover, the interaction between hydrogen and oxygen within the molten metal significantly influences the oxidation process at the interface between the molten metal and the atmosphere. This interaction can lead to the formation of an oxide layer, which presents several drawbacks.

[0008] One of the primary issues is metal loss due to oxidation, resulting in increased metal waste during melting Oxide defects can also form, compromising the integrity of the cast product. For example, during the direct chill casting of aluminum alloys, surface skin oxide layers form on the molten metal. These oxide layers are a primary cause of casting defects, such as vertical folds. These oxides can lead to the formation of vertical and relatively deep (~10 mm) cracks on the ingot surface. Such defects enhance the formation of both cold and hot cracks, further increasing metal waste due to the need to scalp several millimeters from the ingot surface.

[0009] This defect occurrence contributes to higher production and energy costs. By minimizing the formation of oxides and porosity, the overall quality of the cast product can be significantly improved, leading to more efficient and cost-effective manufacturing processes.

[0010] [2] Davis, J.L., Mendez, P.F. (2016). Wrinkling Phenomena to Explain Vertical Fold Defects in DC-Cast Al-Mg4.5. In: Grandfield, J.F., Eskin, D.G. (eds) Essential Readings in Light Metals. Springer, Cham, https: / / doi.org / 10.1007 / 978-3-319-48228-6_99

[0011] Therefore, controlling the levels of hydrogen and oxygen during the melting and casting processes is important to minimize the above-mentioned problems and ensure a high-quality metal product.

[0012] The degassing process is a critical step in reducing the hydrogen content in metallic alloys such as aluminum, magnesium and copper alloys to mitigate porosity formation during solidification. This process involves the removal of dissolved hydrogen gas from the molten metal before it is cast into shapes. Various methods can be employed for degassing, including vacuum degassing, inert gas flushing, and the addition of chemical degassers. Vacuum degassing works by reducing the pressure over the molten metal, thereby encouraging the dissolved hydrogen to come out of solution and escape as gas. Inert gas flushing involves bubbling a chemically inert gas, such as argon or nitrogen, through the molten metal. This gas P2961PC00 picks up dissolved hydrogen and carries it to the surface, where it can be vented away. Chemical degassers, on the other hand, react with hydrogen to form volatile compounds that can be easily removed from the melt. By effectively reducing the hydrogen content in the alloy, these degassing techniques can significantly decrease the risk of porosity formation and improve the material's overall physical and mechanical properties. These solutions however face limitations. Gas flushing, as the most common method, is costly due to necessity for large volumes of inert gasses. Its efficiency is also usually limited to up to 60%.

[0013] In view of the foregoing, it is an object of the invention to provide a metal degassing that is efficient in removing gas from molten metal or from solid metal, yet that is economical to operate.

[0014] It is advantageous to provide a liquid metal degassing that is easy to scale and implement in metal casting systems with different production rates and different configurations.

[0015] It is advantageous to provide a metal degassing that is economical to install and maintain.

[0016] It is advantageous to provide a metal degassing that is compact.

[0017] Objects of the invention have been achieved by providing systems according to the independent claims.

[0018] Dependent claims set out various advantageous features of embodiments of the invention.

[0019] Disclosed herein according to a first aspect, is a metal casting system configured for producing a liquid metal, the metal casting system comprising a container for the liquid metal and a metal degassing system configured for degassing the liquid metal, the metal degassing system being implemented in the metal casting system, wherein the metal degassing system comprises an electrical power supply, an electrolyzer unit, and a control system connected to the electrical power supply and the electrolyzer unit, the electrolyzer unit comprising an anode, a cathode, and an electrolyte, wherein the electrolyte comprises or consists of a proton exchange membrane and wherein the electrolyzer unit comprises an electrolyzer housing including a separating wall comprising the electrolyte, the separating wall having a first surface including an electrolyte-gas interface and a second surface including an electrolyte-metal interface, the cathode positioned on the first surface, wherein the first surface is configured for surrounding an inner chamber of the electrolyzer housing such that the cathode is separated from the liquid metal, the anode being in contact with the liquid metal. P2961PC00

[0020] Also disclosed herein, is a metal degassing system configured for degassing a liquid metal, the metal degassing system comprises an electrical power supply, an electrolyzer unit, and a control system connected to the electrical power supply and the electrolyzer unit, the electrolyzer unit comprising an anode, a cathode, and an electrolyte, wherein the electrolyte comprises or consists of a proton exchange membrane and wherein the electrolyzer unit comprises an electrolyzer housing including a separating wall comprising the electrolyte, the separating wall having a first surface including an electrolyte-gas interface and a second surface including an electrolyte-metal interface, the cathode positioned on the first surface, wherein the first surface is configured for surrounding an inner chamber of the electrolyzer housing such that the cathode is separated from the liquid metal, wherein the anode is mounted on the electrolyzer housing, the anode being in contact with the liquid metal.

[0021] Also disclosed herein according to a second aspect is a metal degassing system configured for degassing a solid metal, the metal degassing system comprises an electrical power supply, an electrolyzer unit, and a control system connected to the electrical power supply and the electrolyzer unit, the electrolyzer unit comprising an anode, a cathode, and an electrolyte, wherein the electrolyte comprises or consists of a proton exchange membrane defining a separating wall having a first surface including an electrolyte-gas interface and a second surface including an electrolyte-metal interface, the cathode positioned on the first surface.

[0022] In an advantageous embodiment, the cathode comprises a conductive cathode coating formed on the inner surface of the electrolyte.

[0023] In an advantageous embodiment, the conductive coating comprises a catalyst selected from any one or more of platinum, palladium, nickel, graphite.

[0024] In an advantageous embodiment, the anode comprises a conductive material such as carbonbased material, for instance a graphite electrode to provide electrons to the metal.

[0025] In an advantageous embodiment, the proton exchange membrane comprises or consists of a material selected from any one or more of Ceramic Proton Conductors, Perovskite Oxides, Phosphate-Based Ceramic Membranes, Silicon Carbide (SiC) Membranes, Carbon-Based Materials, and Refractory Metal Oxides.

[0026] In an advantageous embodiment, the separating wall of the electrolyzer housing is formed at least partially by the electrolyte and further by an insulator.

[0027] In an advantageous embodiment, a material of the insulator is selected from a material comprising or consisting of ceramics such as alumina, zirconia. P2961PC00

[0028] In an advantageous embodiment, the anode is mounted on the electrolyzer housing.

[0029] In an advantageous embodiment, the anode is mounted against a bottom wall of the electrolyzer housing.

[0030] In an advantageous embodiment, the electrolyzer units include electrical circuit interconnections including an interconnection to the cathode within the housing and an interconnection to the anode through the housing, the anode separated from the cathode by an anode interconnection insulator extending through housing.

[0031] In an advantageous embodiment, the control system further comprises sensors including a liquid or solid metal temperature sensor and a gas concentration sensor configured for measuring a gas concentration in the liquid metal, for instance a hydrogen concentration or a temperature sensor.

[0032] In an advantageous embodiment, the control system is configured to generate a pulsed electrical current to the anode and cathode.

[0033] In an advantageous embodiment, the control system is configured to generate the pulsed electrical current at a frequency of in a range of 0.1 to 100 Hz and a maximum pulsed voltage in a range of 0.5V and 10V.

[0034] In an advantageous embodiment, the control system includes physical models based on control, digital twins, statistical models, or Al-based models for improved control of outputs such as pulsing, electrical potential, and currents, based on at least one process input, such as but not limited to alloy composition and temperature.

[0035] In an advantageous embodiment, a plurality of electrolyzer units are combined for implementation in the metal casting system.

[0036] In an advantageous embodiment, the electrolyzer unit or plurality of electrolyzer units is / are configured for positioning in the metal casting system at various positions between an input end of the molten liquid metal in the metal casting system to an output unit of the molten liquid metal within the metal casting system.

[0037] In an advantageous embodiment, the electrolyzer unit or multiple electrolyzer units are configured for positioning on the surface of a solid metal at various locations, which can be heated or preheated in a furnace. P2961PC00

[0038] In an advantageous embodiment of the metal casting system, the container comprises a crucible.

[0039] In an advantageous embodiment, the crucible comprises an insulation.

[0040] In an advantageous embodiment of the metal casting system, the container further comprises a liquid metal transfer channel and a liquid metal output unit, wherein the liquid metal transfer channel is positioned between the crucible and the liquid metal output unit.

[0041] In an advantageous embodiment of the solid metal degassing system, the system further comprises a heating device connected to the control system and configured for heating of the solid metal.

[0042] In an advantageous embodiment, the heating device is embedded in, or mounted on, the electrolyte, or wherein the heating device is a separate unit from the electrolyte.

[0043] In an advantageous embodiment of the solid metal degassing system, the system is configured for degassing a section of a tubular solid metal pipe or container, the electrolyte comprising a curved shaped for conforming to an inner or outer surface of the tubular solid metal pipe or container.

[0044] In an advantageous embodiment, the control system and electrical power supply are configured to apply a voltage in a range or 0.5V to 2V.

[0045] Further advantageous features of the invention will be apparent from the following detailed description of embodiments of the invention and the accompanying illustrations.

[0046] Figure 1a is a schematic diagram of an electrolytic metal degassing system showing the electrical reactions and functioning principal of embodiments of the present invention;

[0047] Figure 1 b is another schematic diagram of an electrolytic metal degassing system according to an embodiment of the invention illustrating the functioning principal;

[0048] Figure 2 is a schematic diagram of an electrolytic metal degassing system according to an embodiment of the invention;

[0049] Figures 3a to 3d are schematic diagrams of a metal casting system implementing a metal P2961PC00 degassing system according to embodiments of the invention, figures 3a to 3d each showing different configurations of implementation of the metal degassing system in metal casting systems according to different variants;

[0050] Figures 4a to 4d are schematic diagrams of an electrolytic metal degassing system according to embodiments of the invention for degassing a solid metal, the illustrated examples showing different variants configured for degassing a section of solid pipe or reservoir, for instance a solid section of piping used for the transport of gaseous or liquid hydrocarbons.

[0051] Referring to the figures, a metal degassing system 2 according to embodiments of the invention is configured, according to a first aspect, for degassing of liquid metals (figures 1a and 1b to 3d), and according to a second aspect, for degassing of solid metals (figures 1a and 4a to 4c).

[0052] In the first aspect, a metal casting system 100 is configured for producing molten liquid metal for purification and casting into solid metal 1 output by the metal casting system 100. The metal casting system 100 comprises a furnace or heating device for melting liquid metal from raw product input into the metal casting system, and some form of container of the molten liquid metal 3, typically known as a crucible 102 having insulation 103 for reducing the heat transfer from the molten metal contained in the crucible to the outside of the crucible. The raw product input may include recycled or remelted metal. The molten liquid metal 3 may be poured out of the crucible 102 into a liquid metal output unit 106, for instance typically a casting unit for solidifying the liquid metal into ingots or for pouring in a continuous casting process, for instance for the production of metal sheets or rods. The metal casting system may comprise a liquid metal transfer channel 104 between the crucible 102 and the liquid metal output unit 106.

[0053] Such metal casting systems 100 are perse well known and do not need to be further described herein.

[0054] The metal degassing system 2 according to the embodiments of the invention comprises an electrical power supply 4, a control system 6, and an electrolyzer unit 12.

[0055] The control system 6 is connected to the electrical power supply 4 and the electrolyzer unit 12 and controls the power supply to the electrolyzer unit 12. The control system 6 includes a control unit 8 and one or more sensors 10 connected to the control unit 8.

[0056] The sensors 10 may include a temperature sensor for measuring the temperature of the metal P2961PC00

[0057] 3. The sensors may include additional sensors, in particular a gas concentration sensor for measuring the concentration of a gas in the liquid metal subject to the degassing process carried out by the metal degassing system 2. The gas concentration sensor may in particular comprise a hydrogen concentration sensor and / or an oxygen concentration sensor.

[0058] The electrolyzer unit 12 comprises an anode 14, a cathode 18 and an electrolyte 16 between the anode and the cathode.

[0059] The anode 14 is positioned in contact with the molten or solid metal and the cathode is positioned in contact with a gaseous environment. The electrolyte 16 separates the cathode 18 from the liquid or solid metal 3 and is advantageously in the form of a proton exchange membrane, an outer or first surface 32 of the proton exchange membrane being in contact with the liquid or solid metal 3 and an inner or second surface of the proton exchange membrane being in contact with the cathode 18.

[0060] The proton exchange membrane may advantageously be selected from Ceramic Proton Conductors, Perovskite Oxides, Phosphate-Based Ceramic Membranes, Silicon Carbide (SiC) Membranes, Carbon-Based Materials, and Refractory Metal Oxides. Other solid perovskite materials may be provided as proton exchange membrane materials.

[0061] The cathode 18 may comprise a conductive catalytic coating 20 for conducting electrical current to the cathode and promoting reaction of protons passing through the proton exchange membrane with electrons supplied by the electrical current to form H2 or H2O exhaust gas emitted on the cathode side. The material of the conductive catalytic coating 20 is configured to enhance the kinetics of cathodic reactions and may for instance comprise or consist of Platinum, Palladium, or Nickel. The cathode may have a porous, meshed structure, or other patterned structures with passages allowing the cathode reaction gas to escape from the cathode and increase the reaction surface.

[0062] The anode 14 for liquid metal degassing embodiments may in particular be in the form of a graphite electrode. In variants the anode may however be formed of various other materials based on carbon, conductive ceramics, or other high temperatures conductive materials per se known for use as high temperature electrodes. The anode may be coated by other materials as protective layer or by a catalyzer. The anode may have various simple or complex shapes, and / or have a porous, meshed structure, or other patterned structures.

[0063] The gas emitted by the cathode may include other reduction product gases binding with the P2961PC00 hydrogen protons.

[0064] The anode and cathode are interconnected via electrical interconnections to the electrical power supply 4, the current flowing through the anode and cathode being controlled by the control system 6 for driving the degassing operation.

[0065] In an advantageous embodiment, the control system 6 may be configured to supply a pulsed current. Preferred parameters of the pulsed current are in a range from 0.01 to 100 kHz, preferably in a range from 0.1 to 100 Hz.

[0066] The electrolyzer unit comprises an electrolyzer body or housing 24 having a separating wall 26 with an inner or first surface that forms an electrolyte-gas interface or cathode-gas interface, and an outer or second surface 32 that forms an electrolyte-liquid metal interface. It may be noted that a thin layer of insulation (such as porous ceramic) may be provided on the outer or second surface 32 to increase the durability of the cathode. For the liquid metal degassing embodiments, the inner surface may have various smooth or patterned, simple or complex geometrical shapes, surrounding an inner chamber 28, or one or more gas escape channel(s) that is (are) thus separated from the molten liquid metal 3.

[0067] The control unit may be configured to adjust the process parameters such as current, voltage, or frequency based on desired degassing kinetics, desired level of hydrogen content, type of alloy, number of electrolyzer units, and measured parameters such as air humidity, temperature, gas concentration in the molten alloy or solid metal, and other process conditions.

[0068] In an example of liquid metal degassing, for instance liquid aluminium degassing, the current applied by the control system is preferably in a range of 1A to 10A, preferably 2A-10A, for instance in a range of 5A-10A, for a proton exchange membrane (PEM) with a surface area of 100cm2, (i.e. the separating wall 26 of the electrolyzer body 24 with a surface area of 100cm2). For the degassing of solid metals, for instance solid steel, one is limited by the diffusion rate of Hydrogen in the solid metal.

[0069] An electrolyzer unit with a 100cm2PEM separating wall 26 can treat about 4 kg of molten aluminum alloy per minute. This means that an industrial machine capable of treating 10 tons per hour, would need about 4000cm2of PEM surface area. The total current will thus amount to 80 A (if we assume a conservative 2A current per 100cm2PEM).

[0070] The current over time controlled by the control system does not vary much, since liquid is P2961PC00 constantly fed into the system bringing more hydrogen and H diffusion is fast in the liquid. One may assume that it can be halved over time.

[0071] A typical voltage applied by the control system is quite low, about 0.5-2 V, although the voltage can be higher in order to overcome the resistivity of the various components

[0072] In an example of solid metal degassing, the current applied by the control system is preferably in a range of a few mA up to 100mA. For instance, for diffusible H concentrations in the embrittling range (~1-5 ppm) one should expect currents starting at few 10s of mA (e.g. 50mA) at the start and this current goes lower as the hydrogen is depleted, reaching few-mA (e.g. 5mA) for a 100cm2electrolyzer extraction area, namely the PEM surface area of the separating wall. The dropping rate of hydrogen is correlated with 1 / - t (1 over square root of time).

[0073] The impact of current over time is higher in a solid compared to a liquid metal due to lower diffusion of H in the solid metal compared to liquid metal, it can be reduced by a factor of 5 to 10.

[0074] The voltage applied to obtained the desired current for hydrogen degassing of solid metals is in also selected to be in range of about 0.5-2V, although the selected voltage can be higher in order to overcome the resistivity of the various components.

[0075] It may be noted that the control system imposes a voltage, as opposed to measuring a voltage as one would find in a hydrogen sensing system.

[0076] In an embodiment for liquid metal degassing, the electrolyzer housing 24 may advantageously comprise a substantially tubular shape with the separating wall comprising a peripheral wall 26a forming the perimeter of the tubular shape, and a bottom wall 26b that closes a bottom of the tubular shaped peripheral wall. The peripheral wall 26a extends from the bottom wall to a top end 26c that may comprise an outlet for the gases produced on the cathode side, as well as passages for electrical interconnections to the cathode and to the anode (if mounted on the housing, depending on the embodiment).

[0077] The electrolyzer unit 12 may in particular comprise a connection interface (not shown) that allows removable interconnection of the electrical interconnections at the interface such that the electrolyzer unit can be connected and disconnected to the control and power supply for instance for maintenance or replacement. P2961PC00

[0078] The electrolyzer housing 24 may include insulators 34 or insulating portions at the top end, or bottom end or at intermediate positions forming part of the structural portions of the separating wall 26. The insulator may for instance comprise or consist of a ceramic such as alumina, zirconia, or Silicon Nitride.

[0079] In an advantageous embodiment for liquid metal degassing, the anode may be mounted on the electrolyzer housing 24, the anode separated from the cathode 18 by an insulator forming a cathode to anode bottom insulator 34a.

[0080] The proton exchange membrane forming the electrolyte 16 may form all or only portions of the electrolyzer housing separating peripheral wall 26a configured to be inserted into the molten liquid metal 3 and in contact therewith during the liquid metal degassing process.

[0081] The cathode 18 may advantageously coat the inner side of the housing, in particular the portion of the housing separating wall formed by the electrolyte 16 or comprising the electrolyte 16.

[0082] In an advantageous embodiment for liquid metal degassing, the electrolyzer housing may have a substantially circular tubular shape, however other shapes such as square, rectangular, polygonal or irregular shapes may be provided without departing from the scope of the invention.

[0083] In a preferred embodiment for liquid metal degassing, the anode 14 is directly mounted on an outer side of the electrolyzer housing 24 and the electrical connection to the anode may pass through the inner chamber 28 from the top end 26c of the housing, separated from the cathode 18 and interconnections to the cathode by an insulator, for instance a tubular shaped insulator 34c. In variants, however, it is possible to provide the anode as a separate component that is not coupled to the electrolyzer housing 24 for instance in the form of a graphite rod that is inserted in the liquid metal separated from the combined electrolyzer housing 24, electrolyte 16 and cathode 18 (see figure 1 b) that form a separate unit.

[0084] In the case of implementation of the electrolyzer unit in molten liquid metal 3 in a metal casting system 100, there may be a plurality of electrolyzer units 12 inserted in the molten liquid depending on the volume of the molten liquid and the production flow rate of molten liquid from the input of the metal casting system to the output 106. It is possible in this regard to have a different number of anode units 14 and cathode units 16, 18, 24 in variants with the anode unit separated from the cathode unit. P2961PC00

[0085] The electrolyzer unit may thus be configured as a cartridge whereby the number of cartridges inserted into the molten liquid for degassing depends on the desired power input into the metal degassing system which depends on the rate of the gas to be extracted from the liquid metal.

[0086] The degassing may be performed offline in the furnace or crucible 102 for instance as illustrated in figure 3a. The number of degassing cartridges (i.e. the number of electrolyzer units 12) inserted in the molten liquid metal 3 may depend on the desired rate and efficiency of degassing as well as the volume of liquid metal contained in the crucible.

[0087] The electrolyzer unit may also be implemented in an inline manner for instance as illustrated in figures 3b and 3c, for instance installed within a liquid metal transfer channel 104 between the source of liquid metal in the crucible 102 and the liquid metal casting unit 106.

[0088] The liquid metal casting unit 106 may for instance comprise a casting die for casting metal billets or ingots, or may comprise a continuous casting unit as illustrated in figure 3c. In embodiments, the electrolyzer unit may also be installed in the output I casting unit 106, for instance in the molten liquid flowing in the continuous casting process.

[0089] More generally, the electrolyzer unit may be positioned in various positions between the input of the liquid metal forming process to an output of the process prior to transformation to solid metal. The configuration of the electrolyzer unit as a cartridge connectable to an electrical power supply 4 and a control system 6 that may be inserted in a molten liquid 3 allows great flexibility and modularity, including the possibility to scale up with a varying plurality of cartridges depending on the performance requirements and production scale of the metal case system. Such flexibility and modularity allow inter alia easy and efficient integration in an optimal manner in existing liquid metal processing systems.

[0090] The process efficiency may be assisted by generating forced convection, for instance by providing the metal casting system with a mixing device (e.g., a stirrer) configured for stirring the molten liquid metal.

[0091] Embodiments of the present invention thus allow to efficiently reduce the amount of a dissolved gas (and / or various impurities) or decrease the formation of oxides or further absorption of gases in a molten metal bath by electrolysis degassing. In particular, the dissolved gas may comprise hydrogen and the molten metal bath may comprise aluminum alloys (containing any amount of Zn, Cu, Mg, Mn, Cr, Li, ... thereof), copper alloys, magnesium alloys or other metallics or intermetallic alloys. The degassing may also serve to protect molten metal from P2961PC00 further oxidation on its surface with atmosphere containing hydrogen, oxygen, or their compounds such as 02, H2 or H20. It can also be used to reduce other impurities, such as hydrides or oxides.

[0092] Embodiments of this invention may provide methods for reducing an amount of a dissolved gas in a molten metal bath or, methods for degassing molten metals. That can also be used to influence the oxidation reaction on the surface to reduce the oxidation of molten alloy with direct contact with the atmosphere containing oxygen or hydrogen compounds. The process can work even at passivation at given applied potentials. Embodiments may include operating electrolysis in the molten metal in various installations such as:

[0093] Melting furnace

[0094] Holding furnace

[0095] Transferring trough or tube

[0096] Dedicated degassing unit

[0097] Launder

[0098] Crucible

[0099] Direct chill, permanent or any kind of mold.

[0100] Embodiments of the invention may also operate inside a direct chill casting mold, or other kind of mold or very close to the solidification front, before solidification stage or event. The application of such a process can include agitation, stirring, ultrasonic waves, vibration or any kind of metal movement.

[0101] The dissolved gas may comprise oxygen, hydrogen, combinations thereof or any kind of their compounds. For example, the dissolved gas may be or may comprise hydrogen in atomic form or appear as a form of protons or any hydrogen compounds.

[0102] The molten metal bath may comprise aluminum alloys, lithium alloys, copper alloys, zinc alloys, steel alloys, magnesium alloys and the like, or mixtures and / or combinations thereof (e.g., including various alloys of aluminum, copper, zinc, steel, magnesium, etc.).

[0103] Reducing the dissolved H content in molten metal can advantageously reduce the oxidation process of metal by passivation process through changing the oxide layer growth morphologies. Because the oxidation process of Al can include following reaction of H2O + M

[0104] MxOy + H (dissolved), for example for aluminum H2O + Al -> AI2O3 + H (dissolved), application of hydrogen electrolysis will bring more driving force for the oxidation process. However, as oxidation rate is predominantly governed by kinetical aspect such as shape and P2961PC00 morphology of the oxide layer. This may reduce metal loss and oxide formation in the furnace or on the surface of liquid metal in the direct chill casting. That results in the reduce the formation of some defects such as cracks, oxide induced porosities and vertical folds during casting and solidification.

[0105] According to the second aspect, embodiments of the present invention also encompass the degassing of solid metals. In particular, hydrogen represents a significant concern regarding hydrogen embrittlement in metallic alloys, for instance in steel. Given that steel is increasingly being utilized in hydrogen containers and high-pressure pipes, embodiments of the invention may be effectively applied for hydrogen removal from solid metals that are subject to hydrogen diffusion and embrittlement.

[0106] Referring to figures 4a to 4c, examples of implementation of a metal degassing system for in situ degassing of a solid section of pipe, for instance of a pipeline for the transport of hydrogen, combustible fuels or other hydrogen containing chemicals in liquid or gaseous form, are illustrated. In addition to the previously described features of the metal degassing system, the solid metal degassing system comprises a heating device 36 configured to heat the solid metal 3 during degassing to increase the rate of degassing, in other words to improve the efficiency of the degassing process. The heating device 36 may be embedded in the proton exchange membrane (figure 4a), or mounted on the proton exchange membrane, thermally coupled to the solid metal 3. The heating device may also be provided as a separate unit for coupling to the solid metal, for instance as schematically illustrated in figures 4b and 4c. Heating advantageously accelerates the hydrogen diffusion and thus degassing.

[0107] Various heating devices may be provided employing perse well known heating technologies, for instance induction heating, radiation heating, electrical resistive heating, and fluid convention heating.

[0108] In the illustrated embodiments of figures 4a to 4c, the proton exchange membrane electrolyte 16 of the electrolyzer unit 12 is provided with a shape that conforms to the surface of the solid metal section 3 against which it is placed, for instance a curved shape configured to be placed along a certain section of tubular metal pipe that needs to be degassed.

[0109] In the embodiment of figures 4a and 4b, the electrolyte 16 is mounted on an outer side of the section of pipe, whereas in the embodiment of figure 4c the electrolyte 16 is mounted on an inner side of the section of pipe. In the latter embodiment, the system may further comprise a ventilation or vacuum pump unit connected to the interior of the pipe to evacuate the hydrogen P2961PC00 extracted by the degassing process.

[0110] One can often remove hydrogen from solid metal parts (a “bake-out” or vacuum anneal) and thereby reduce risk of hydrogen-embrittlement. Thermal bake-out or vacuum annealing is a well-established and effective way to reduce diffusible hydrogen and mitigate embrittlement risk. The limitations or drawbacks of such techniques are multifold, such as: treatments often can only be performed ex-situ whereby parts have to be moved to a special facility, which adds costs due to disassembly typical bake temperatures can be very high and are in the 175-750 °C range depending on the metal alloy high temperatures accelerate degassing but risk grain growth, oxidation, or mechanical property changes large vacuum furnaces or controlled atmosphere furnaces may be needed the cost and time scale for large or complex-shaped parts is high

[0111] According to embodiments of the invention, the solid metal degassing system enables on-site, in-situ hydrogen removal, without disassembly or transfer to a furnace. Because the process can be applied frequently and directly at the point of use, hydrogen is extracted before it penetrates deeply into the material. This has several advantages: Reduced hydrogen trapping: frequent treatment prevents accumulation in deep traps. Lower operating temperatures: process can be effective at milder conditions, avoiding heat-induced changes to the alloy microstructure. Operational convenience: in-situ treatment eliminates costly downtime, logistics, and specialized vacuum equipment. Scalability: suitable for continuous operation, for instance on pipelines.

[0112] The shape of the cathode can be adapted to the shape of the solid metal part. Since the solid metal part is conductive, there is no need for any particular anode other than an electrical contact to the solid metal part. P2961PC00

[0113] List of references

[0114] Solid metal 1

[0115] Molten (liquid) metal 3

[0116] Free surface 5

[0117] Metal casting system 100

[0118] Furnace

[0119] Crucible 102

[0120] Insulation 103

[0121] Liquid metal transfer channel 104

[0122] Liquid metal casting unit 106

[0123] Billet casting unit

[0124] Casting die I mold

[0125] Continuous casting unit

[0126] Metal degassing system 2

[0127] Electrical power supply 4

[0128] Control system 6

[0129] Control unit 8

[0130] Sensors 10

[0131] Temperature sensor Gas concentration sensor e.g. hydrogen concentration sensor

[0132] Electrolyzer unit 12

[0133] Anode 14

[0134] Graphite electrode

[0135] Electrolyte 16

[0136] Proton exchange membrane

[0137] Cathode 18

[0138] Cathode coating 20

[0139] -^Catalytic coating

[0140] Electrical circuit interconnections 22

[0141] Electrolyzer housing 24

[0142] Separating wall 26

[0143] Peripheral wall 26a Bottom wall 26b Top end 26c Inner chamber 28

[0144] First surface 30

[0145] -> Electrolyte - gas interface Inner surface second surface 32

[0146] -> Electrolyte - liquid metal interface

[0147] Outer surface

[0148] Insulators 34

[0149] Cathode to Anode bottom Insulator 34a e.g. alumina, zirconia

[0150] Cathode to Anode top Insulator 34b

[0151] Heating device 36

Claims

P2961PC00Claims1. A metal casting system (100) configured for producing a liquid metal (3), the metal casting system comprising a container for the liquid metal and a metal degassing system configured for degassing the liquid metal, the metal degassing system (2) being implemented in the metal casting system (100), wherein the metal degassing system comprises an electrical power supply (4), an electrolyzer unit (12), and a control system (6) connected to the electrical power supply (4) and the electrolyzer unit (12), the electrolyzer unit comprising an anode (14), a cathode (18), and an electrolyte (16), wherein the electrolyte comprises or consists of a proton exchange membrane and wherein the electrolyzer unit comprises an electrolyzer housing (24) including a separating wall (26) comprising the electrolyte, the separating wall having a first surface (30) including an electrolyte-gas interface and a second surface (32) including an electrolyte-metal interface, the cathode (18) positioned on the first surface (30), wherein the first surface is configured for surrounding an inner chamber (28) of the electrolyzer housing such that the cathode is separated from the liquid metal (3), the anode being in contact with the liquid metal.

2. The metal casting system according to the preceding claim, wherein the anode is mounted on the electrolyzer housing.

3. The metal casting system according to any preceding claim wherein the cathode (18) comprises a conductive cathode coating (20) formed on the inner surface of the electrolyte (16).

4. The metal casting system of the preceding claim wherein the conductive coating comprises a catalyst selected from any one or more of platinum, palladium, nickel, graphite.

5. The metal casting system of any preceding claim wherein the anode (14) comprises a conductive material such as carbon-based material, for instance a graphite electrode to provide electrons to the metal.

6. The metal casting system of any preceding claim wherein the proton exchange membrane comprises or consists of a material selected from any one or more of Ceramic Proton Conductors, Perovskite Oxides, Phosphate-Based Ceramic Membranes, Silicon Carbide (SiC) Membranes, Carbon-Based Materials, and Refractory Metal Oxides.

7. The metal casting system of any preceding claim wherein the separating wall (26) of the electrolyzer housing is formed at least partially by the electrolyte (16) and further by anP2961PC00 insulator (34).

8. The metal casting system of the preceding claim wherein a material of the insulator is selected from a material comprising or consisting of ceramics such as alumina, or zirconia.

9. The metal casting system of any preceding claim wherein electrolyzer units (12) include electrical circuit interconnections including an interconnection to the cathode (18) within the housing (24) and an interconnection to the anode through the housing, the anode separated from the cathode by an anode interconnection insulator (34c) extending through housing (24).

10. The metal casting system of any preceding claim wherein the control system (6) further comprises sensors (10) including a liquid or solid metal temperature sensor and a gas concentration sensor configured for measuring a gas concentration in the liquid metal (3), for instance a hydrogen concentration or a temperature sensor.11 . The metal casting system of any preceding claim wherein the control system (6) is configured to generate a pulsed electrical current to the anode and cathode.

12. The metal casting system of the preceding claim wherein the control system (6) is configured to generate the pulsed electrical current at frequency of in a range of 0.1 to 100 Hz and a maximum pulsed voltage in a range of 0.5V to 10V.

13. The metal casting system according to any preceding claim wherein a plurality of electrolyzer units (12) are combined and configured for implementation in the metal casting system.

14. The metal casting system according to any preceding claim wherein the metal casting system (100) further comprises a furnace configured for melting liquid metal from raw product input into the metal casting system.

15. The metal casting system according to any preceding claim wherein the container comprises a crucible (102).

16. The metal casting system according to the preceding claim wherein the crucible (102) comprises an insulation (102).

17. The metal casting system according to any one of the two directly preceding claim wherein the container further comprises a liquid metal transfer channel (104) and a liquid metal output unit (106), wherein the liquid metal transfer channel is positioned between the crucible and the liquid metal output unit.19P2961PC0018. The metal casting system according to the preceding claim wherein the electrolyzer unit or plurality of electrolyzer units is / are configured for positioning in the metal casting system at various positions between an input end of the molten liquid metal in the metal casting system to an output unit (106) of the molten liquid metal within the metal casting system (100).

19. A metal degassing system (2) configured for degassing a liquid metal (3), the metal degassing system comprises an electrical power supply (4), an electrolyzer unit (12), and a control system (6) connected to the electrical power supply (4) and the electrolyzer unit (12), the electrolyzer unit comprising an anode (14), a cathode (18), and an electrolyte (16), wherein the electrolyte comprises or consists of a proton exchange membrane and wherein the electrolyzer unit comprises an electrolyzer housing (24) including a separating wall (26) comprising the electrolyte, the separating wall having a first surface (30) including an electrolyte-gas interface and a second surface (32) including an electrolyte-metal interface, the cathode (18) positioned on the first surface (30), wherein the first surface is configured for surrounding an inner chamber (28) of the electrolyzer housing such that the cathode is separated from the liquid metal (3), wherein the anode is mounted on the electrolyzer housing, the anode being in contact with the liquid metal.

20. The metal degassing system according to the preceding claim wherein the cathode (18) comprises a conductive cathode coating (20) formed on the inner surface of the electrolyte (16).

21. The metal degassing system of the preceding claim wherein the conductive coating comprises a catalyst selected from any one or more of platinum, palladium, nickel, graphite.

22. The metal degassing system of any one of claims 18 - 20 wherein the anode (14) comprises a conductive material such as carbon-based material, for instance a graphite electrode to provide electrons to the metal.

23. The metal degassing system of any any one of claims 18 - 21 wherein the proton exchange membrane comprises or consists of a material selected from any one or more of Ceramic Proton Conductors, Perovskite Oxides, Phosphate-Based Ceramic Membranes, Silicon Carbide (SiC) Membranes, Carbon-Based Materials, and Refractory Metal Oxides.

24. The metal degassing system of any one of claims 18 - 22 wherein the separating wall (26) of the electrolyzer housing is formed at least partially by the electrolyte (16) and further by an insulator (34).20P2961PC0025. The metal degassing system of the preceding claim wherein a material of the insulator is selected from a material comprising or consisting of ceramics such as alumina, zirconia.

26. The metal degassing system of any one of claims 18 - 24 wherein electrolyzer units (12) include electrical circuit interconnections including an interconnection to the cathode (18) within the housing (24) and an interconnection to the anode through the housing, the anode separated from the cathode by an anode interconnection insulator (34c) extending through housing (24).

27. The metal degassing system of any one of claims 18 - 25 wherein the control system (6) further comprises sensors (10) including a liquid or solid metal temperature sensor and a gas concentration sensor configured for measuring a gas concentration in the liquid metal (3), for instance a hydrogen concentration or a temperature sensor.

28. The metal degassing system of any one of claims 18 - 26 wherein the control system (6) is configured to generate a pulsed electrical current to the anode and cathode.

29. The metal degassing system of the preceding claim wherein the control system (6) is configured to generate the pulsed electrical current at frequency of in a range of 0.1 to 100 Hz and a maximum pulsed voltage in a range of 0.5V to 10V.

30. A metal degassing system (2) configured for degassing a solid metal (3), the metal degassing system comprises an electrical power supply (4), an electrolyzer unit (12), and a control system (6) connected to the electrical power supply (4) and the electrolyzer unit (12), the electrolyzer unit comprising an anode (14), a cathode (18), and an electrolyte (16), wherein the electrolyte comprises or consists of a proton exchange membrane defining a separating wall (26) having a first surface (30) including an electrolyte-gas interface and a second surface (32) including an electrolyte-metal interface, the cathode (18) positioned on the first surface (30).

31. The system according to the preceding claim wherein the cathode (18) comprises a conductive cathode coating (20) formed on said first surface.

32. The system of the preceding claim wherein the conductive coating comprises a catalyst selected from any one or more of platinum, palladium, nickel, graphite.

33. The system of any preceding claim 30-32 wherein the anode (14) comprises a conductive metal contact for direct conductive connection to the solid metal.21P2961PC0034. The system of any preceding claim 30-33 wherein the proton exchange membrane comprises or consists of a material selected from any one or more of Ceramic Proton Conductors, Perovskite Oxides, Phosphate-Based Ceramic Membranes, Silicon Carbide (SiC) Membranes, Carbon-Based Materials, and Refractory Metal Oxides.

35. The system of any preceding claim 30-34 wherein the separating wall (26) of the electrolyzer housing is formed at least partially by the electrolyte (16) and further by an insulator (34).

36. The system of the preceding claim wherein a material of the insulator is selected from a material comprising or consisting of ceramics such as alumina, zirconia.

37. The system of any preceding claim 30-36 wherein the control system (6) further comprises a metal temperature sensor.

38. The system of any preceding claim 30-37 wherein the control system (6) is configured to generate a pulsed electrical current to the anode and cathode.

39. The system of the preceding claim wherein the pulsed electrical current has a frequency of in a range of 0.1 to 100 Hz and a maximum pulsed voltage in a range of 0.5V or 10V.

40. The system of any preceding claim 30-39 further comprising a heating device connected to the control system and configured for heating of the solid metal.

41. The system of the preceding claim wherein the heating device is embedded in, or mounted on, the electrolyte, or wherein the heating device is a separate unit from the electrolyte.

42. The system of any preceding claim 30-41 configured for degassing a section of a tubular solid metal pipe or container, the electrolyte comprising a curved shaped for conforming to an inner or outer surface of the tubular solid metal pipe or container.

43. The system of any preceding claim wherein the control system and electrical power supply are configured to apply a voltage in a range or 0.5V to 2V.

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