Molten metal degassing device

Abstract

A molten metal degasser comprises: a hollow shaft for a flow of gas; a rotor (10) comprising a top portion and a base portion (30) separated by a gap and connected to the shaft, the top portion (20) comprising an opening (60) for allowing gas to enter from the shaft; 3 to 8 supports (40) each extending radially outward and connected to the top and base portions (20); a manifold portion (50) for distributing gas through the mixing zone inlet (70); a mixing zone (90) adjoining the mixing zone inlet (70) wherein the top and base portions (20, 30) and adjacent supports (40) each extend radially outward from the manifold portion (50) to form the mixing zone (90); a cutout portion (80) located between a rotational volume envelope of the rotor and a periphery of the rotor, where the cutout portion (80) is in a range between 25% and 75% of the rotational volume.

Description

Technical Field

[0001] This invention relates to a molten metal degassing apparatus for: firstly, forming a vortex from which an additive is conveyed to the molten metal; and then forming and distributing fine bubbles of fluxing gases throughout the molten metal. The invention also relates to a molten metal processing system including the aforementioned molten metal degassing apparatus, and a process for processing molten metal using the aforementioned molten metal degassing apparatus or molten metal processing system. Background Technology

[0002] Molten metals such as aluminum contain many impurities before casting. If these impurities are not removed, they will cause high scrap losses during casting, or result in poor quality metal products. Typical undesirable impurities that need to be removed include dissolved hydrogen, alkali or alkaline earth elements, and undissolved non-metallic inclusions.

[0003] Injecting a mixture of inert or reactive gases (i.e., fluxing gases) into molten aluminum is a common technique for removing the aforementioned impurities. The removal rate of these impurities depends largely on how the fluxing gas is injected into the molten metal. Optimal performance is achieved in this type of metal processing when fine bubbles are generated, thus creating a large interfacial contact area for the metal processing reaction to occur, and when these bubbles are distributed uniformly across the entire cross-sectional area available for the metal flow.

[0004] Processes are known that use rotating impellers to inject gas into a bulk of molten metal without the use of a filter bed. The impellers used in these processes function to generate small bubbles and distribute them evenly throughout the entire volume of the metal to be treated, or to create a metal flow pattern such that all the metal to be treated passes through some portion of the rotating impeller. They also have some beneficial effects on metal cleanliness by removing undissolved particulate impurities or inclusions primarily through flotation. However, the reliability of this inclusion removal process is variable due to the turbulence on the treated metal surface associated with the rotating impeller. This turbulence tends to re-carry inclusions as well as floating scum.

[0005] In addition to adding gases, other processing agents can be added to the molten melt to aid in grain refinement or modify the microstructure and properties of the resulting cast metals and alloys. Metal processing agents can be added to the vortex, allowing for easy dispersion throughout the melt. Any turbulence in the melt will introduce air, subsequently causing oxide formation in the metal. Therefore, vortices are employed only for a short portion of the processing cycle, and are stopped once the mixing phase is complete (e.g., by applying baffles). The rotor blades pump the liquid to create vortices, and in doing so, a vacuum chamber is created behind the blades, which is pressurized after the next blade arrives. An efficient rotor will create vortices and disperse the processing agent as quickly as possible to minimize turbulence in the melt. Degassing and removal of reaction products are then carried out in the melt. Using a rotor to create both vortices for efficient addition of processing agents and vortices for efficient distribution of fine bubbles presents an inherent challenge in rotor design: the intense mixing required to create vortices contradicts the need to distribute fine bubbles in the melt without creating vortices that cause harmful re-entrainment of gases and impurities.

[0006] As the size of the crucible or refractory-lined vessel increases (diameters exceeding 800 mm, up to 1.5 tons of aluminum, less commonly 3 tons, and in extreme cases 10 tons), eddy currents become more difficult to achieve. With increasing rotational speed, the rotor head needs to increase in diameter and height (and thus weight, leading to increased vibration and cyclic shaft stress) to achieve the desired eddy currents, resulting in increased head erosion. All of these factors have driven a redesign of the head that allows eddy current generation to remain rapid and deep, while minimizing the increases in weight and rotational speed.

[0007] Therefore, there is an increasing need for a rotor that can efficiently generate eddies in the molten metal body and then efficiently distribute tiny bubbles within it.

[0008] US 8,281,964 partially addresses this need by disclosing a rotor in which molten metal is drawn into an opening in the rotor base and mixed with gas before being ejected outward through radial channels. While this rotor design enables generally acceptable gas distribution and vortex formation, there remains a need to improve the performance of dual-function rotors, particularly in terms of improving vortex formation efficiency.

[0009] Therefore, there is still room for improvement in rotor design and systems for handling molten metal, especially for handling in larger capacity vessels. Summary of the Invention

[0010] In a first aspect of the present invention, a molten metal degassing apparatus is provided, the molten metal degassing apparatus comprising: a. A hollow shaft for conveying a gas stream (e.g., fluxing gas); b. A rotor comprising a top portion and a base portion separated by a gap, the rotor being connected to the hollow shaft; c. A range of 3 to 8 support members, each of which extends radially outward and connects to the top portion and the base portion; d. Manifold section, wherein a gas flow from the hollow shaft enters through an opening in the top section, and the gas flow is radially distributed through a mixing zone inlet; e. A mixing zone adjacent to and radially offset from the manifold portion; the top portion, the base portion, and the adjacent support each extend radially outward from the manifold portion to form the mixing zone, the mixing zone forming at least a portion of the void, and the peripheral edges of the top portion, the base portion, and the adjacent support define a mixing zone outlet; and f. A cut portion, said cut portion being located between the rotational volume envelope of the rotor and the periphery of the rotor. The cut portion occupies between 25% and 75% of the rotor's rotating volume.

[0011] In another embodiment, the present invention relates to a molten metal degassing apparatus, the molten metal degassing apparatus comprising: a. A hollow shaft, said hollow shaft being used to transport a gas flow; b. A rotor comprising a top portion and a base portion separated by a gap, wherein the rotor is connected to the hollow shaft, wherein the top portion includes an opening for allowing gas to enter from the hollow shaft; c. A range of 3 to 8 support members, each of which extends radially outward and connects to the top portion and the base portion; d. A manifold section for radially distributing gas from the hollow shaft through a mixing zone inlet; e. A mixing zone adjacent to and radially offset from the manifold portion, wherein the top portion, the base portion, and the adjacent support each extend radially outward from the manifold portion to form the mixing zone, wherein the mixing zone forms at least a portion of the void, and wherein the peripheral edges of the top portion, the base portion, and the adjacent support define a mixing zone outlet; and f. A cut portion (80) located between the rotational volume envelope of the rotor and the periphery of the rotor, wherein the cut portion is in the range of 25% to 75% of the rotational volume of the rotor.

[0012] Preferably, in use, the gas flow from the manifold section (50) and the molten metal flow entering from the mixing zone outlet (100) come into countercurrent contact. The resulting metal and gas dispersion is then radially discharged from the mixing zone (90) through the mixing zone outlet (100).

[0013] In some embodiments, the ratio of the minimum radial length (L1) between the mixing zone inlet (70) and the mixing zone outlet (100) to the minimum radial length (L2) between the mixing zone inlet (70) and the periphery of the rotor (L2) is in the range of greater than 0.0 to 0.70. Although L1:L2 can have negative ratios, these results occur when the mixing zone inlet is fed directly into the cut portion, thereby bypassing the mixing zone. In addition, this arrangement also results in the support not extending radially in full, thereby reducing the rotor's ability to pump molten metal dispersion in the circumferential direction, and thus reducing the rotor's eddy current formation efficiency.

[0014] Preferably, the L1:L2 ratio is at least 0.05, at least 0.10, at least 0.20, or at least 0.30. Generally, the higher the ratio, the larger the two-dimensional area occupied by the mixing zone. Preferably, the L1:L2 ratio is not greater than 0.60, 0.50, 0.40, 0.38, or 0.35. An excessively high ratio can reduce the rotor's ability to move the molten metal dispersion circumferentially to facilitate vortex formation.

[0015] In some embodiments, the radial length from the mixing zone inlet to the mixing zone outlet increases as the mixing zone outlet approaches the support (e.g., Figure 9b In other embodiments, the radial length from the mixing zone inlet to the mixing zone outlet is constant (e.g., the mixing zone inlet and outlet share the same center of circles with different radii). In some embodiments, the cross-sectional area of ​​the mixing zone outlet is larger than the cross-sectional area of ​​the mixing zone inlet.

[0016] The apparatus of the present invention is capable of operating in an initial vortex-forming mode to effectively generate vortices. This is achieved through the depth of the cut portion, which allows a large amount of molten metal to rotate in the same direction about the axis of the hollow shaft, thereby facilitating vortex formation. Using the vortex, the metal processing agent can be effectively distributed within the molten metal mass. As the volume (and inner diameter) of the container (e.g., a crucible) increases, vortex formation becomes increasingly difficult. Therefore, there is a growing demand for degassing apparatuses capable of effectively generating vortices in larger containers while also providing acceptable fluxing gas dispersion efficiency.

[0017] The apparatus of the present invention is also capable of forming an effective gas-molten metal mixing zone at the interface where the gas is being distributed radially outward through the manifold portion (50), and wherein the rotational action of the rotor blades (i.e., the supports) formed by a plurality of supports (40) forces the molten metal into each mixing zone (90) to form a high shear force region in which the formation and homogeneous distribution of fine bubbles are facilitated as the mixture is ejected from the mixing zone into the molten metal body.

[0018] High shear force refers to the force generated by the collision between a flow of molten metal moving in one direction and a flow of gas moving in the opposite direction within a bulk. For example, when the impeller of a rotor (i.e., the support) rotates, the molten metal flows in the same direction as the impeller at a speed less than the impeller's rotational speed. However, the difference between the rotor speed and the molten metal speed is usually small, resulting in relatively low shear force compared to the collision of fluids in opposite directions within the mixing zone of the rotor of the present invention. The greater the difference between these two speeds of the molten metal and the fluxing gas, the stronger the ability of the fluxing gas to be broken into fine bubbles by shear force.

[0019] While some conventional rotors inject fluxing gas through orifices between rotor blades, the volume for high-shear applications is relatively low because once the fluxing gas is injected into the molten metal, it is carried along the circumferential direction around the rotor's central axis. Mixing efficiency can be improved by forming a mixing zone, where the molten metal can mix with the fluxing gas before leaving the mixing zone.

[0020] As the impeller rotates and draws molten metal into the mixing zone, the collision flow of gas and molten metal from the manifold generates shear force. This shear force drives the formation of tiny bubbles within the mixed molten metal phase, which are then ejected into the bulk of the molten metal. It is precisely during this collision period between the molten metal and the gas that the greatest shear force is generated, and it has the greatest impact on the efficiency and effectiveness of the formation and distribution of tiny bubbles within the molten metal.

[0021] The same rotational force that drives the molten metal mass in the same rotational direction to assist vortex formation (in vortex formation mode) also drives a portion of the molten metal mass into the high-shear mixing zone in gas dispersion mode. The volume of the molten metal and the duration of the molten metal in the mixing zone will determine the efficiency of fine bubble formation and distribution, thereby affecting the degassing efficiency.

[0022] Generally, a larger mixing zone results in better degassing efficiency, and a larger cut-out section results in better vortex formation efficiency. The consideration behind this common design is the need for sufficient mixing zone outlets and cut-out zones to create the desired high-shear environment and flow pattern, thereby improving mixing and vortex formation efficiency. Rotors with supports between 3 and 8 provide such an environment.

[0023] The final rotor design can be a compromise between the characteristics of the molten metal being processed and the geometry of the container holding the molten metal, in terms of the rotor's mixing and eddy current generation capabilities.

[0024] Mixed Zone The mixing zone is where the molten metal flow and the fluxing gas flow preferably come into contact first. This contact is a countercurrent contact, which preferably produces a high-shear contact to generate fine bubbles dispersed within the molten metal.

[0025] The mixing zone forms at least a portion of the void between the top and base portions. In some embodiments, the mixing zone consists of the void between the top and base portions. In other embodiments, the manifold portion includes the portion of the void before the void extends laterally in a radial pattern. In these embodiments, the diameter of the manifold portion may widen adjacent to the opening in the top portion. The mixing zone inlet typically includes a height lower than the height of the manifold portion. The mixing zone height may range from 20 mm to 100 mm; or 30 mm to 80 mm; or 40 mm to 60 mm.

[0026] Because the mixing zone defines the space for the gas from the manifold section to flow radially outward in the lateral direction (the molten metal is drawn into the mixing zone from the opposite direction (i.e., through the mixing zone outlet)), the mixing zone has a high-shear environment that promotes the formation and dispersion of small bubbles within the molten metal. Each mixing zone preferably has one outlet. The outlet and inlet of each mixing zone preferably include a top cutout portion and a base cutout portion, as well as two supports.

[0027] Each mixing zone is defined by a top portion, a base portion, and a gap between adjacent radially extending supports. In some embodiments, each mixing zone is separated by adjacent supports. A mixing zone not defined by adjacent supports (e.g., in the form of a single annular space with multiple outlets between supports) can be more accurately defined as an enlarged manifold section (see Comparative Example C-5). The enlarged manifold section comes at the cost of a reduced mixing zone area. It has been found that the mixing performance provided by the enlarged manifold section is relatively poor, suggesting that, in addition to mixing via countercurrent flow of the fluid, the shearing effect of the supports on the fluid and their confinement of the flow contribute to increased turbulence, thus increasing the mixing efficiency of the rotor.

[0028] The height of the top portion can gradually decrease from the opening (60) toward the periphery of the support. Alternatively, the top portion can extend horizontally from the opening to maximize the rotational volume of the rotor.

[0029] In some implementations, the mixing zone extends to the periphery of the rotating zone. In other implementations, the mixing zone extends only partially to the rotating zone.

[0030] Preferably, the cross-sectional area of ​​the mixing zone has the rotor rotation area (π*D) 2 The lower limit of the mixing zone is at least 4%, at least 5%, at least 8%, at least 10%, at least 12%, or at least 15%, and the upper limit is no more than 50%, no more than 40%, no more than 35%, or no more than 30%. The cross-sectional area of ​​the mixing zone (taken from the midpoint of the mixing zone height) is measured from a top view of the rotor and represents the area in which the base portion and the top portion cover the mixing zone inlet and outlet. Similarly, the volume of the mixing zone may have a lower limit of at least 1%, at least 2%, at least 3%, at least 4%, or at least 5%, and an upper limit of no more than 25%, no more than 20%, or no more than 15%, of the total rotating volume.

[0031] In some embodiments, the cross-sectional area of ​​the mixing zone may be at least 20%, at least 22%, at least 24%, at least 26%, at least 28%, at least 30%, at least 32%, at least 34%, at least 36%, at least 38%, or at least 40% of the rotor's rotating area.

[0032] The volume of the mixing zone can be at least 2% or at least 3% or at least 4% or at least 5% or at least 6% or at least 7% or at least 8% or at least 9% or at least 10% of the total rotating volume. In some embodiments, the mixing zone is no more than 15% or no more than 12% or no more than 10% or no more than 8% or no more than 7% of the rotor rotating volume. The larger the cross-sectional area (or volume) of the mixing zone, the greater the proportion of the molten metal exposed to the high-shear environment in which the molten metal collides with the gas flowing into the mixing zone from the manifold portion of the rotor.

[0033] Depending on the specific application of the device, the height of the mixing zone typically ranges from 20 mm to 100 mm. The width of the mixing zone (measured between the supports) is controlled by the number of supports within the rotor, but is typically at least 20 mm and can extend to 100 mm or more, especially towards the outlet end of the mixing zone.

[0034] The mixing zone outlet is large enough to allow molten metal to enter the mixing zone before it leaves along with the dispersed fine bubbles of fluxing gas. The minimum lateral dimension (e.g., height or width) is preferably at least 28 mm, 30 mm, 35 mm, or 40 mm. The maximum lateral dimension of the outlet typically does not exceed 125 mm, 100 mm, 80 mm, or 60 mm. Too small a dimension leads to outlet blockage and difficulty in cleaning the outlet during maintenance, while too large a dimension can result in a reduced shear rate between the fluxing gas and molten metal or an increased tendency for components to escape through the channel, thus reducing mixing efficiency.

[0035] In some implementations, each mixing zone outlet (100) spans at least 50% of the circumference between the circumferential ends of an adjacent pair of supports (40).

[0036] manifold section The manifold section is used to distribute fluxing gas from the hollow shaft to a mixing zone that is laterally offset relative to the manifold section. The manifold section is preferably adjacent to the inlet of the mixing zone. Under normal operation (using a standard design, i.e., the expansion of the manifold section does not come at the expense of the mixing zone section), very little or no molten metal enters the manifold section, and the pressurized fluxing gas prevents molten metal from flowing through the mixing zone into the manifold section.

[0037] The manifold section is coherently engaged with the gas exiting the hollow shaft. The manifold section is typically defined by a base section and a top section, along with multiple supports that combine to provide multiple mixing zone inlets from which the manifold section dispenses gas. While the base section of the rotor is typically solid and without openings, in some embodiments, the base section may include a small central bore, which is an artifact of the manufacturing process. In some embodiments, the base section does not include an opening. In other embodiments, the base section 30 includes an opening that is not large enough to allow molten metal to be drawn into the opening and mixed with the gas in the rotor manifold section during operation. In other embodiments, the base section includes an opening smaller than 28 mm, 25 mm, or 20 mm, such that the opening is not used as an inlet for mixing molten metal with the gas in the manifold section. Typically, an opening size that is too narrow causes it to be covered by scum during operation, thus effectively sealing the opening in use.

[0038] While there are no restrictions on the shape of the manifold section, it typically comprises a circular cross-sectional area when viewed from the rotor's top view. However, to maximize the cross-sectional area of ​​the mixing zone, the effective diameter of the manifold section can be no greater than 100 mm, 80 mm, 60 mm, 50 mm, or 40 mm. The diameter of the manifold section is typically at least 10 mm, 20 mm, or 30 mm. A smaller inlet diameter can increase the effective rate of flux gas entering the mixing zone, thus increasing the degree of shear and consequently increasing the formation of fine bubbles. However, for practical use in cleaning the rotor, a minimum inlet diameter may be required.

[0039] Depending on the application, the height of the manifold section between the top and base portions typically ranges from 20 mm to 200 mm. In some embodiments, the height of the manifold section is at least 25 mm, at least 30 mm, or at least 35 mm. A greater manifold section height results in a greater potential height for the inlet to the mixing zone, thereby increasing the interfacial contact area between the molten metal and the gas, and thus enhancing the formation of fine bubbles. Additionally, a larger mixing zone inlet height makes it easier to avoid scum clogging and is easier to clean.

[0040] In some embodiments, the manifold portion includes a top component with an inner diameter (ID-T) and a base component with an inner diameter (ID-B). The top component is typically associated with a portion immediately adjacent to and connected to the hollow shaft. The base component is typically associated with a portion immediately adjacent to the mixing zone inlet. The ID-T of the manifold portion may be the same as, greater than, or less than, ID-B.

[0041] The ratio of the rotor diameter to the rotor height can be in the range of 1.5 to 5.0 or 1.7 to 4.0 (e.g., 180mm / 105mm to 160mm / 65mm).

[0042] Multiple support components The supports between 3 and 8 connect the top and base portions, forming part of the manifold and mixing zone. A smaller number of supports results in a relatively large mixing zone, making it difficult to easily create a high-shear environment conducive to effective mixing, where channels for fluxing gas or molten metal can pass through the mixing zone without achieving sufficient mixing. Furthermore, with fewer supports, the material flow pattern between the supports is not conducive to inducing eddies.

[0043] Having a greater number of supports results in a larger proportion of the rotor including the supports, thereby increasing weight and reducing the potential size of the mixing zone and the cut-out portion. In some embodiments, the rotor may include 3, 4, 5, 6, 7, or 8 supports. In a preferred embodiment, the rotor includes 4 to 6 supports.

[0044] In some embodiments, the support member is connected adjacent to the top portion and the base portion to the mixing zone inlet, wherein the support member separates multiple mixing zones having multiple mixing zone inlets.

[0045] In other embodiments, the cut-out portion extends at least partially between the radial supports, such that at least a portion of the supports located distal to the manifold portion is blade-shaped, excluding the adjacent top or base portion in the circumferential direction. In these embodiments, the mixing zone typically occupies a relatively low portion of the rotational area.

[0046] In other embodiments, the cut-out portions extend between the radial supports, such that the supports have adjacent top or base portions in the circumferential direction. In these embodiments, the mixing zone typically occupies a relatively high portion of the rotational area.

[0047] The supports typically extend radially from the manifold section. Due to the radial arrangement of the supports, the inlet of the mixing zone generally has a smaller cross-sectional area than the outlet of the mixing zone. The dimensions of the supports are typically determined by mechanical and corrosion performance considerations. In a preferred embodiment, the minimum cross-sectional thickness of the supports is less than 20 mm, less than 18 mm, less than 16 mm, or less than 14 mm. The minimum support thickness is preferably at least 6 mm, at least 8 mm, at least 10 mm, at least 12 mm, or at least 14 mm to provide sufficient corrosion and erosion resistance, allowing the rotor to have a sufficiently long service life.

[0048] To help reduce the thickness of the support component, it is preferably made of carbon-ceramic composite material, which has superior corrosion resistance compared to graphite rotors. Reducing the thickness of the support component allows for an increase in the mixing zone and / or an increase in the slit portion, thereby helping to enhance degassing efficiency and / or eddy current formation efficiency.

[0049] In some embodiments, the average thickness of the support member is in the range of 10 mm to 20 mm, or in the range of 11 mm to 18 mm, or in the range of 12 mm to 16 mm. Preferably, the average thickness of the support member is at least 10 mm, at least 11 mm, at least 12 mm, at least 13 mm, at least 14 mm, or at least 15 mm.

[0050] In some implementations, the support gradually tapers from top to bottom, or vice versa. For example, one end of the support may have a thickness of 12 mm, while the other end may have a thickness of 7 mm.

[0051] In some embodiments, at least part or all of the support member gradually tapers from the proximal side to the distal side of the central axis (i.e., the height of the support member decreases as the support member extends radially outward). Alternatively, part or all of the support member maintains a constant height. The height of the support member can vary from 30 mm to the entire height of the rotor (e.g., up to 200 mm).

[0052] The support members preferably extend from the inlet of the mixing zone and into the periphery of the rotating zone. The length of the support members decreases from the outlet of the mixing zone to the periphery of the rotating zone.

[0053] Incision part The cut-out portion is preferably adjacent to the mixing zone outlet. The cut-out portion block is located between the rotor's rotating volume envelope and the rotor's periphery. For clarity, the cut-out portion does not include the manifold portion.

[0054] The cutouts (e.g., at the top and base) represent the difference between the rotating region of the rotor with diameter D and the top / bottom view profile of the rotor (i.e., the cutouts are cuts removed from a circle of diameter D to obtain the top view profile shape of the rotor). Each portion can be of any shape and size. Preferably, each cutout portion has the same shape and size. Preferably, the top cutout portion and the base cutout portion have the same size and location such that, viewed from the top view of the rotor, the top cutout portion and the base cutout portion completely overlap each other. Having completely overlapping cutout portions allows the mixing zone area to be maximized.

[0055] For completeness, note that the gap between the top and base portions is within the perimeter. The rotor's perimeter can be defined by the smallest geometric surface connecting the perimeter of the top portion and the perimeter of the base portion.

[0056] In some implementations, fluid flow modeling can determine that an increased high-shear region can be obtained to some extent if the top cut portion is not aligned with the base cut portion (i.e., the top cut portion and the bottom cut portion may partially overlap). In other implementations, fluid flow modeling can indicate that an increased high-shear region can be obtained when the top cut portion and the base cut portion are perfectly aligned.

[0057] The percentage of the cut area of ​​the rotor will be equal to the minimum percentage of the cut area in the top and base portions. Therefore, if the top portion has a 5% cut area relative to the rotational area and the base portion has an 8% cut area relative to the rotational area, the rotor will be considered to have a 5% cut area percentage. If the base or top portion has no cut area, the cut area will be considered 0%. If the cut area has no support, it will also be considered 0%, because without support, the cut area will not have the ability to rotate the fluid to form vortices. The volume percentage of the cut area can be determined by multiplying the minimum percentage of the cut area in the base or top portion by the average height of the top and base portions adjacent to the top and base cut areas.

[0058] In one embodiment, the number of top cutouts is the same as the number of base cutouts. In some embodiments, the number of top cutouts differs from the number of base cutouts. While typically a single cutout (top and bottom) is made between adjacent supports, several cutouts may also be made between adjacent supports.

[0059] The cut can be symmetrical or asymmetrical. The cut can be partially circular, parabolic, or linear. A partially circular cut has the advantage of being easy to machine into a rotor. A greater depth of cut allows the rotor to move more molten metal between the supports, which act as rotor blades. The more molten metal that can move circumferentially, the easier it is for the rotor to form vortices around the rotating hollow shaft.

[0060] In one embodiment, the cutout portion includes: a first length extending from the periphery of the cutout portion originating from the peripheral end of the support member to a turning point of the cutout portion closest to the rotor central axis; and a second length extending from the turning point and along the periphery of the cutout portion to the peripheral end of an adjacent support member defining the cutout portion, wherein the first length is greater than the second length.

[0061] The rotor is preferably configured such that the second length of each cut portion is the leading edge of the rotor. This configuration has been found to enhance vortex formation.

[0062] In this embodiment, the ratio of the first length to the second length is preferably in the range of greater than 1 to 5.0, and more preferably in the range of greater than 1.2 to 2.5.

[0063] In some implementations, the ratio of the area of ​​the cut portion to the area of ​​the mixing zone is 1.0 or greater, or 1.2 or greater, or 1.4 or greater, or 1.6 or greater, or 1.8 or greater. The excellent mixing efficiency of the countercurrent flow in the mixing zone allows a higher proportion of the rotor to be dedicated to improving vortex formation.

[0064] For the purposes of this invention, the cross-sectional area of ​​each component (including the support, manifold portion, and mixing zone) is the cross-sectional area as seen from a top cross-section (“top view”) presenting a plane orthogonal to the hollow axis.

[0065] In some embodiments, the cross-sectional area of ​​the cut portion ranges from 20% to 70% of the rotor's rotating area. In some embodiments, the cross-sectional area of ​​the cut portion includes at least 25% or at least 28% or at least 30% or at least 33% or at least 35% or at least 38% or at least 40% or at least 42% or at least 45% or at least 48% or at least 50% or at least 52% or at least 53% or at least 54% or at least 55% or at least 56% or at least 57% or at least 58% or at least 59% of the rotor's rotating area. Increasing the percentage of the cut portion's area enhances the rotor's eddy current formation efficiency.

[0066] In some embodiments, the volume of the cut-out portion ranges between 26% and 70% of the rotor's rotating volume. In some embodiments, the volume of the cut-out portion includes at least 28% or at least 30% or at least 35% or at least 36% or at least 37% or at least 38% or at least 39% or at least 40% or at least 41% or at least 42% or at least 43% or at least 44% or at least 45% of the rotor's rotating volume.

[0067] In some implementations, the cut-out portion extends beyond 50% of the rotor radius (i.e., a linear line extending from the rotor center to the periphery of the rotating area is considered the rotor radius, and the cut-out portion extends along this line from the periphery of the rotating area toward the rotor center by a distance greater than 50%), or greater than 51%, or greater than 52%, or greater than 53%, or greater than 54%, or greater than 55%, or greater than 56%, or greater than 57%, or greater than 58%. The greater the cut-out depth, the stronger the rotor's ability to increase eddy current formation efficiency.

[0068] In other embodiments, the cross-sectional area of ​​the cut portion and the mixing zone includes a range between 50% and 90% of the rotor's rotating area. In some embodiments, the cross-sectional area of ​​the cut portion and the mixing zone includes at least 59% or at least 60% or at least 61% or at least 62% or at least 63% or at least 64% or at least 65% or at least 66% or at least 67% or at least 68% or at least 70% of the rotor's rotating area.

[0069] In some embodiments, the volume of the cut portion and the mixing zone comprises between 30% and 80% of the rotor's rotating volume. In some embodiments, the volume of the cut portion and the mixing zone comprises at least 36%, at least 37%, at least 38%, at least 39%, at least 40%, at least 41%, at least 42%, at least 43%, at least 44%, at least 45%, or at least 46% of the rotor's rotating volume.

[0070] In some implementations, the rotor support thickness is controlled by stress analysis, allowing the support size to decrease as the size of the cut-out portion and / or mixing zone increases accordingly. The advantage of increasing the size of the mixing zone and cut-out portion is that this also contributes to a reduction in rotor weight, as the reduced thickness of the support and top / base portions leads to an increase in the functional size of the rotor dedicated to mixing and eddy current efficiency. Due to the excellent corrosion resistance of carbon-ceramic composites, the use of carbon-ceramic composites in rotor construction allows for the use of materials with smaller volumes than graphite.

[0071] In some embodiments, the cutout portion includes a stepped configuration, comprising a portion between the mixing zone outlet and the rotation area / volume, and a portion above the top of the mixing zone and between the upwardly extending support. Other cutout portions may also exist below the base of the mixing zone and between the downwardly extending support. The ability to maximize the cutout volume can also be achieved by using one or both of the spaces above and below the top and base of the mixing zone to obtain the desired high-shear environment of the mixing zone. For example, the top portion adjacent to the opening (ID-T) may extend vertically downward along the top of the manifold and then radially outward (horizontally or at an angle), while the support extends vertically above the radial top portion, partially or entirely reaching the height of the opening. A portion of the support may taper downward toward the periphery of the rotation zone (i.e., the height decreases). In other embodiments, the support height may remain constant from the proximal side of the opening to the periphery of the rotation zone.

[0072] manufacture The shaft and rotor can be formed separately and connected together by a releasable connection such as threads on each of the rotor and shaft. Alternatively, the shaft and rotor can be formed as a single, one-piece hollow shaft and rotor.

[0073] The rotor can be machined from a solid block of material, from which the manifold portion, mixing zone, and cutout portion are machined. Alternatively, the rotor can also be formed using molding and pressing techniques (e.g., isostatic pressing), especially if the rotor structure cannot be easily obtained solely through machining. Specifically, rotor designs that seek to maximize the volume percentage of the cutout portion and mixing zone relative to the total volume of the rotating volume are most likely to be achieved using molding or 3D printing manufacturing techniques.

[0074] In one embodiment, the hollow shaft portion includes at least a portion of the top portion of the rotor. This allows the remainder of the rotor to be machined from a single block. Greater design flexibility is possible when constructing the supports and mixing zone without hindering the top portion. To facilitate this construction, the rotor portion may include a male connector for engaging with a female connector on the hollow shaft portion.

[0075] The rotor can then undergo heat treatment to produce the final product. Additional machining of the components is also possible. The rotor can also be coated with any corrosive and / or anti-scum-forming coating.

[0076] The rotor and shaft can be made of graphite or carbon-ceramic composite materials. In some embodiments, the rotor comprises or is composed of carbon-ceramic composite materials. Carbon-ceramic composite materials have the advantage of being more resistant to corrosion and erosion than graphite. Thus, the rotor's supports and walls can have reduced thickness to increase the volume of the mixing zone and the cut-out portion, thereby improving the rotor's dual-function performance. An example of a suitable carbon-ceramic composite material is Roton, available from Molten Metal Systems, Inc. TM A series of carbon ceramic composite materials.

[0077] Carbon ceramic composite materials may include: 30 to 70% by weight of ceramic matrix; 30 to 70% by weight of carbon materials; and 0 to 15% by weight of additives.

[0078] The ceramic matrix is ​​preferably selected for its combination of thermal and mechanical properties and can be selected from the group consisting of: silicon dioxide; aluminum oxide; carbides of silicon (Si), titanium (Ti), tungsten (W), tantalum (Ta), niobium (Nb), zirconium (Zr), hafnium (Hf), vanadium (V), chromium (Cr), molybdenum (Mo); silicon nitride; magnesia; zirconium oxide; boron nitride; aluminum nitride; or combinations thereof.

[0079] The ceramic matrix may include silicon carbide, for example, β silicon carbide and / or α silicon carbide.

[0080] The carbon material is preferably graphite and / or a carbon-containing material that can be derived from an organic binder used to form the composite material.

[0081] Additives may include silicon metal, iron silicon (FeSi), aluminum, boron, aluminum silicate (e.g., clay), borax and / or boric acid.

[0082] Molten metal degassing system In a second aspect of the invention, a molten metal degassing system is provided, comprising an apparatus according to a first aspect of the invention and a molten metal container. The molten metal container may include an inner diameter of at least 650 mm, at least 800 mm, at least 900 mm, at least 1000 mm, at least 1100 mm, at least 1200 mm, at least 1300 mm, at least 1400 mm, or at least 1500 mm. The maximum inner diameter of the molten metal container may be influenced by various technical and commercial considerations, but is expected to not exceed 2000 mm or 1500 mm.

[0083] In some implementations, the rotor diameter R D With the inner diameter V of the container DThe ratio is in the range of 0.18 to 0.37 (e.g., 180mm / 960mm to 260mm / 700mm). The rotor of the present invention has a ratio of R... D V D It is particularly advantageous when the value is less than 0.30 or less than 0.27 or less than 0.25 or less than 0.24 or less than 0.23 or less than 0.22 (e.g., a rotor with a diameter of 300 mm in a container with an inner diameter of 1500 mm).

[0084] process In a third aspect of the invention, a process is provided for degassing molten metal using a molten metal degassing system according to a second aspect of the invention, wherein the rotor of the device rotates at a speed greater than 300 rpm, 350 rpm, 400 rpm, 450 rpm, or 500 rpm during a vortex forming mode, and then rotates at a speed lower than that in the degassing mode. Preferably, the degassing mode speed is at least 50 rpm, 75 rpm, 100 rpm, 125 rpm, or 150 rpm slower than that in the vortex forming mode.

[0085] Due to the rotor's excellent overall vortex formation and degassing efficiency, the average rotor speed in both modes can be lower than the average speed of other rotors in the prior art. In one embodiment, the average rotor speed does not exceed 500 rpm, 475 rpm, 450 rpm, 425 rpm, or 400 rpm. Alternatively, excellent vortex and / or mixing efficiency can be achieved by maintaining a speed similar to that of rotors operating in the prior art.

[0086] In some implementations, in order to obtain a vortex depth of at least 550 mm and a fluxing gas percentage of at least 80% v / v (under the conditions outlined in the experimental section) within 40 seconds, the average rotor speed (i.e., the speed in vortex mode + the speed in degassing mode divided by 2) shall not exceed 600 rpm or 580 rpm or 570 rpm or 565 rpm or 550 rpm.

[0087] In some implementations, in order to obtain a vortex depth of at least 400 mm after 15 seconds and a residual O2 content of no more than 20% v / v after 450 seconds (under the conditions outlined in the experimental section), the average rotor speed (i.e., the speed in vortex mode + the speed in degassing mode divided by 2) is no more than 450 rpm or no more than 425 rpm or no more than 400 rpm or no more than 375 rpm or no more than 350 rpm or no more than 325 rpm.

[0088] Rotor In a third aspect of the invention, a rotor as defined in the first aspect of the invention is provided.

[0089] Rotation area The area of ​​rotation is defined as the area of ​​the "top view" covered by the rotor as it rotates about its axis of rotation in a two-dimensional plane. The area of ​​rotation can be defined as π*D 2 / 4, where D is the diameter of the rotor.

[0090] Rotational volume Rotational volume is defined as the volume covered by the rotor as it rotates about a rotation axis in a two-dimensional plane. Rotational volume can be calculated by determining the 3D envelope generated by the rotor's rotation in the two-dimensional plane. The envelope typically includes a cylindrical portion toward the base portion and may include a truncated conical portion toward the top portion, wherein the rotor's top portion gradually tapers downwards from the peripheral edge of the adjacent opening toward the top portion.

[0091] Rotational volume envelope The envelope of a rotating volume is defined as the envelope that contains the rotating volume.

[0092] The rotation area and volume are preferably the sum of the individual components of the rotor (e.g., manifold + support + mixing zone + top portion + base portion + cut-out portion).

[0093] To define the area of ​​revolution, the volume of revolution, and the envelope of the volume of revolution, the axis of revolution is a geometric axis extending through the center of the basal portion and the center of the top portion. This coincides with the geometric axis extending through the center of the hollow axis. Attached Figure Description

[0094] Figure 1a and Figure 1b These are a side view and a perspective view of the rotor (Example 7) of the present invention, illustrating the rotating volume of the rotor.

[0095] Figure 1c This is a top view of the rotor (Example 7), illustrating the rotating cross-sectional area of ​​the rotor.

[0096] Figure 2a and Figure 2b These are, respectively, a perspective view and a top cross-sectional view of the rotor (Example 4) of the present invention.

[0097] Figure 3a and Figure 3b These are, respectively, a side view and a top cross-sectional view of the rotor (Example 1) of the present invention.

[0098] Figure 4a and Figure 4b These are, respectively, a side view and a top view of the rotor (Example 2) of the present invention.

[0099] Figure 5a and Figure 5b These are, respectively, a side view and a top view of the rotor (Example 3) of the present invention.

[0100] Figure 6a and Figure 6b These are, respectively, a side view and a top cross-sectional view of the rotor (Example 5) of the present invention.

[0101] Figure 7a and Figure 7b These are, respectively, a side view and a top cross-sectional view of the rotor (Example 6) of the present invention.

[0102] Figure 8a and Figure 8b These are, respectively, a side view and a top cross-sectional view of the rotor (Example 7) of the present invention.

[0103] Figure 9a and Figure 9b These are, respectively, a cross-sectional side view and a cross-sectional top view of the rotor (Example 8) of the present invention.

[0104] Figure 10a and Figure 10b These are a top view and a perspective view of the rotor (Example 9) of the present invention.

[0105] Figures 11a to 11c These are, respectively, a cross-sectional side view, a perspective view, and a cross-sectional top view of a prior art rotor (comparative example C-1).

[0106] Figure 12a and Figure 12b These are, respectively, a side view and a top view of a cross-section of a prior art rotor (comparative example C-2).

[0107] Figure 13a and Figure 13b These are, respectively, a side view and a top view of a cross-section of a prior art rotor (comparative example C-3).

[0108] Figure 14a and Figure 14b These are, respectively, a side view and a top view of a cross-section of a prior art rotor (comparative example C-4).

[0109] Figure 15a and Figure 15b These are, respectively, a perspective view and a top cross-sectional view of a prior art rotor (comparative example C-5).

[0110] Figure 16a and Figure 16b This is a cross-sectional side view of a container used as part of the molten metal degassing system of the present invention.

[0111] All top views of the cross sections are taken from the midpoint of the height of the mixed zone. Detailed Implementation

[0112] refer to Figure 1a and Figure 1b The following illustrates the rotational volume envelope of a rotor (Example 6), which includes a cylindrical portion (A) and a truncated conical portion (B), and the cylindrical portion (A) and the truncated conical portion (B) include five cut-out portions (C1), illustrating the rotational volume of the cut-out portions. Figure 1c The cross-sectional area of ​​the rotor, including the five cut sections (C2), is illustrated, as is the rotating cross-sectional area of ​​the cut sections. The rotating volume can be calculated by calculating the volumes of the cylindrical and truncated conical components and adding them together. While there is a trend towards increasing the rotating volume of rotors to meet the needs of larger processing containers, the increase in size and speed generates increased mechanical and corrosive stresses on the rotor. To avoid these stresses that could shorten the rotor's service life, more corrosion-resistant materials and innovative rotor designs can be used. Figure 1a and Figure 1b The dark shaded area extends from the rotor's rotating volume envelope to the rotor's periphery and represents the rotor cutouts that contribute to the rotor's eddy current formation efficiency. The objective of this invention is to increase the rotor's eddy current formation efficiency while maintaining acceptable mixing efficiency.

[0113] Using "Autodesk" ® Inventor ® The Professional 2023 3D CAD software was used to determine the rotating area and rotating volume of the rotor and its components. As indicated in Table 2, the volume component of the cut-out portion in Example 6 accounts for 54% of the total rotating volume, while the mixed zone accounts for 5% of the total rotating volume of the rotor.

[0114] refer to Figures 2a to 2b An example is illustrated of a rotor (10) for degassing molten metal, including but not limited to aluminum, magnesium, and steel. The rotor includes a top portion (20) and a base portion (30) separated by a void space, while five support members (40) extend outwardly from the central axis of the rotor in a radial manner and connect the top and base portions (20, 30) together.

[0115] Fluxing gas is supplied to an opening (60) in the top portion (20) adjacent to the manifold portion (50). The height of the top portion may gradually decrease from the opening (60) toward the periphery of the support. The base portion typically has a flat outer base. The inner portions of the bottom and top portions may contain a profile consistent with a machining tool used to remove material during the one-piece block construction process. The manifold portion is typically cylindrical or truncated conical in shape. The diameter of the manifold (50) may be the same as or different from the diameter of the opening (60). In some embodiments, the diameter of the manifold portion is larger than the diameter of the opening (60). Fluxing gas is laterally distributed from the manifold portion through a mixing zone inlet 70 into a mixing zone 90, which forms at least a portion of the void between the top portion (20) and the base portion (30). In embodiments in which the opening and the manifold portion have the same diameter, the mixing zone and the void may consist of the same space.

[0116] like Figure 2b As indicated in the top cross-sectional view, there are five mixing zones (90), each with an inlet (70) and an outlet (100). The diameter of the outlet (S2) is larger than the diameter of the inlet (S1). The larger outlet diameter facilitates the entry of molten metal into the mixing zone during rotor operation. In other embodiments, the inlet and outlet diameters may be the same (e.g., Figure 3b Example 1).

[0117] The mixing zone outlet (100) is at least partially defined by a cutout portion (80) formed from the rotating area of ​​the rotor. The rotating area is defined as the area covered by the rotor as it rotates in a two-dimensional plane, and therefore the rotating area can be defined as π*D. 2 / 4, where D is the diameter of the rotor. The boundary of the rotating area is defined by Figure 2b The dashed circle in the image is an example, with a diameter of 220 mm.

[0118] It has been found that an increase in the volume (or cross-sectional area) of the mixing zone is correlated with an increase in degassing efficiency, which is determined by the molten metal container after a specific time. Figure 16a and Figure 16b The volume percentage distribution of the fluxing gas inside the rotor was measured. It has also been found that an increase in the cut portion (80) in the rotor is associated with improved vortex formation, which is measured by the depth of the vortex inside the molten metal container after a specific time.

[0119] To maximize degassing and vortex formation performance, it is desirable to reduce the cross-sectional area / volume ratio occupied by the manifold section and the support. Regarding the support, the circumferential thickness (T1) around the periphery of the support (40) can be reduced. Additionally, the maximum thickness of the support can be reduced. In some embodiments, the rotor thickness is substantially uniform (e.g., Figures 10a and 10b). Figure 10b(Example 9).

[0120] In some embodiments, the mixing zone can be increased by radially extending the top and base portions of the rotor. The outlet of each radially extended mixing zone can be a linear profile between adjacent supports, indicated by the dashed line (200) in Figure 10a, to form a pentagonal mixing zone separated by five supports. Alternatively, the mixing zone can extend radially outward by the same length (L1) to form an annular (top view) mixing zone separated by five supports. The height of the top portion can be aligned with the height of the mixing zone and extend radially in the horizontal plane such that the supports are higher than the extended top portion. In this configuration, additional rotational flow is obtained from the supports, which act as rotor blades above the top portions of the mixing zone. Similar to Example 4 ( Figure 2a Compared to the top portion extending to the top of the rotor illustrated in [example], this has the advantage of reducing rotor weight and partially offsetting the rotational volume loss for the mixing zone. With a top portion thickness of 15 mm, the height of the top cut-out portion can range from approximately 20 mm to 50 mm, depending on the total height of the rotor.

[0121] experiment Simulation modeling Using molten aluminum alloy (AlSi7Mg0.3) and nitrogen, a computer-aided gas-fluid dynamics model (Flow3D) was employed. TM The software was used to evaluate the eddy current generation and gas diffusion performance of a series of rotors. Each rotor had a diameter of 220 mm and a height of 95 mm. The comparison example C-1 (…) Figure 11a and Figure 11b ) and Comparison Example C-4 ( Figure 14a and Figure 14b The height of the top portion / support is 85 mm. The thickness of the base portion in Examples 1 to 8 is 15 mm. For Examples 1 to 7, the top portion / support gradually decreases in height from 95 mm to 60 mm at the periphery of the rotating area. In Example 8, the top portion / support gradually decreases in height from 95 mm to 70 mm at the periphery of the rotating area. The height (H) of the mixing zone is 30 mm for Examples 1 to 7 and 55 mm for Example 8.

[0122] Degassing efficiency was determined by immersing the rotor in a container with an inner diameter of 784 mm (600 mm long × 135 mm wide × 30 mm thick) at a depth of 700 mm (150 mm from the bottom) with a baffle (600 mm long × 135 mm wide × 30 mm thick) placed parallel to the axis at a distance of approximately 45 mm. The volume percentage occupied by flux gas bubbles was measured after degassing at a rotation speed of 450 rpm for 15 seconds. A higher volume percentage indicates a more efficient degassing process.

[0123] The eddy current forming efficiency was determined under similar conditions (except for the absence of baffles and a rotor speed of 680 rpm), where the depth of the eddy currents from the surface was measured after the system was in eddy current forming mode for 40 seconds.

[0124] Water basin test Preparation of the water basin: A cylindrical container with a diameter of 1000 mm and a height of 1000 mm is filled with water to a height of 700 mm. The main oxygen meter is located 100 mm from the bottom of the container, while the auxiliary oxygen meter is located 500 mm from the bottom.

[0125] Initially, the water is saturated with O2 until it reaches a concentration of 17 ppm. When the O2 concentration drops to 17-15 ppm, the N2 degassing process begins. This process is carried out using different impeller designs and a rotation speed of 300 rpm.

[0126] Data from the oxygen meter was recorded every 50 seconds until the total duration reached 450 seconds. The impeller design that could reduce O2 levels most quickly was considered the most efficient.

[0127] In a cylindrical container filled with water up to 700 mm high, vortices were generated using different impeller designs and a rotation speed of 450 rpm. The vortex process was video-recorded (cameras were placed in fixed positions) and later reviewed to determine the vortex progress in increments of 100 mm, measured in seconds. Table 2 records the time taken to achieve a vortex depth of 400 mm when the rotor operates at 450 rpm. The shorter the time, the higher the efficiency of the rotor in generating vortices.

[0128] result As indicated in Tables 1 and 2, the rotor design of the present invention outperforms both the eddy current formation and flux gas dispersion efficiency of the prior art comparative examples.

[0129] The superior eddy current forming characteristics of the rotor design of this invention can be attributed to the relatively large proportion of the cut-out portion in the rotor volume, with examples including cut-out portions ranging from 29% to 64% of the total rotor rotating volume. Furthermore, surprisingly, despite the relatively low proportion of the mixing zone volume (and cross-sectional area), the rotor also exhibits more efficient mixing performance, as indicated by a lower residual O2 content (Table 2). This is at least partly attributed to the formation of turbulent mixing between the molten metal and gas in the countercurrent arrangement.

[0130] In comparison example C-1( Figure 11a and Figure 11bIn this design, a large mixing zone size can achieve excellent mixing efficiency; however, the cut-out section cannot deliver a sufficient volume of molten metal-fluxing gas dispersion to effectively form vortices. In fact, according to the definition of a cut-out section, Comparative Example C-1 does not include a cut-out section, as only the top portion of the rotor contains one. Therefore, it is not surprising that this rotor design has the worst vortex-forming performance (Table 2).

[0131] Compare Example C-3 ( Figure 13a and Figure 13b Although it includes a similar mixing zone size to the rotor in Example 4, it has a significantly lower mixing efficiency. It is argued that a smaller but larger mixing zone is detrimental to achieving a high shear zone because the larger mixing zone size allows some fluxing gas to be transported through the mixing zone without being effectively dispersed into the molten metal stream. Additionally, the reduced number of supports used as blades reduces further dispersion of the fluxing gas within the cut-out region. Therefore, a balance must be struck between the proportion of rotor space allocated to the mixing zone and the number of mixing zones to achieve a sufficiently high shear environment.

[0132] In comparison example C-4 ( Figure 14a and Figure 14b In this invention, since both the gas and molten metal are subjected to centrifugal lateral forces once they enter the central mixing zone, the fluxing gas and molten metal have a greater tendency to flow in the lateral direction. The degree of counterflow is considered relatively low because the lateral channels provide a path with lower resistance and lower shear rate. In contrast, the mixing zone of this invention forces the gas and molten metal to collide in opposite lateral directions (high-shear counterflow), where coflow is only achieved after the force of the fluxing gas flow drives the molten metal-gas dispersion to flow back from the mixing zone outlet against the flow of the incoming molten metal flow.

[0133] In comparison example C-5 ( Figure 15a and Figure 15b In this design, the base manifold inner diameter (ID-B) has been increased to almost extend to the periphery of the rotor (200). A support (210) is present at the periphery of the rotor. The position of the support results in no mixing zone on the rotor. The space between adjacent supports is occupied by a cutout portion (80), rather than the top and base portions (20, 30) and adjacent supports (40) each extending radially outward to form a mixing zone (90). As a result, vortex formation and mixing efficiency are poor compared to the design of this invention.

[0134] Table 1 (Dimensions, unit: mm)

[0135] Table 2 clearly shows that in both simulation modeling and basin experiments, an increase in the percentage of cut area is associated with an increase in eddy current efficiency. Similarly, an increase in the mixing zone is associated with an increase in mixing efficiency.

[0136] As illustrated in Examples 1 to 3 (symmetric) and Examples 6 and 7 (asymmetric), the size of the cut can be maximized by reducing the relative sizes of the support, manifold section, and mixing zone (from a top-down perspective). Maintaining a sufficient proportion of the high-shear mixing zone is expected to preserve acceptable dispersion efficiency. From the results, the symmetric rotor appears to perform slightly better than the asymmetric rotor in terms of eddy current forming performance.

[0137] Compared to the rotor of Example 4, Example 8 includes a higher proportion of mixing zone and cut-out section. This is achieved by reducing the proportion of the rotor's support and manifold sections. As a result, improvements in both vortex formation and dispersion efficiency can be expected compared to Example 4. However, experimental results show that while vortex formation efficiency is improved, dispersion efficiency measured in residual O2 content is adversely affected. This is likely a consequence of the rotor design creating additional surface area in degassing mode (300 rpm), leading to increased oxygen reabsorption. This underscores the need to balance rotor design with specific applications, including container size and configuration. Furthermore, an optimal degassing rotor speed should be selected to minimize oxygen reabsorption.

[0138] It should be noted that a balance needs to be struck between manufacturability, durability, eddy current, and dispersion efficiency for commercial reasons. The use of carbon-ceramic composites allows for greater design flexibility due to their enhanced erosion resistance, and the ability to create designs with larger cut-out and mixing zone volumes relative to the total rotational volume.

[0139] The effect of the size of the mixing zone.

[0140] For example, the results for the only O2 content of 20% or higher in Example 8 were recorded (Table 2). Example 8 had the highest mixing zone size (S2). Additionally, Example 8 had an increased mixing zone height compared to the other examples. This highlights that the narrower mixing zone contributes to improved mixing, consistent with the increased turbulence in the mixing zone indicated by the underlying theory via the Reynolds number.

[0141] Although Comparative Example C-2 has the narrowest mixing zone size (35 mm), its deoxygenation efficiency is still lower than that of all rotors under the present invention, thus highlighting that the base opening of Comparative Example C-2 has a negative impact on deoxygenation efficiency relative to the design of the present invention.

[0142] It should be understood that modifications and variations can be made without departing from the spirit and scope of the novel concept of this invention.

[0143] Table 2

Claims

1. A molten metal degassing device, characterized in that, The molten metal degassing device includes: a. A hollow shaft used for conveying a gas flow; b. A rotor (10) comprising a top portion (20) and a base portion (30) separated by a gap, wherein the rotor is connected to the hollow shaft, wherein the top portion (20) includes an opening (60) for allowing gas to enter from the hollow shaft; c. Support members (40) in the range of 3 to 8, each of which extends radially outward and connects to the top portion (20) and the base portion (30); d. Manifold section (50) for radially distributing gas from the hollow shaft through a mixing zone inlet (70); e. A mixing zone (90) adjacent to and radially offset from the manifold inlet (70), wherein the top and base portions (20, 30) and the adjacent support (40) each extend radially outward from the manifold portion (50) to form the mixing zone (90), wherein the mixing zone forms at least a portion of the void, wherein the peripheral edges of the top and base portions (20, 30) and the adjacent support (40) define a mixing zone outlet (100); and f. A cut portion (80), said cut portion being located between the rotational volume envelope of the rotor and the periphery of the rotor. The cut portion (80) is located between 25% and 75% of the rotating volume of the rotor.

2. The apparatus according to claim 1, characterized in that, The ratio of the minimum radial length (L1) between the mixing zone inlet (70) and the mixing zone outlet (100) to the minimum radial length (L2) between the mixing zone inlet (70) and the periphery of the rotor (10) is in the range of greater than 0.0 to 0.

38.

3. The apparatus according to any one of the preceding claims, characterized in that, The minimum lateral dimension of the mixing zone outlet (100) is at least 28 mm.

4. The apparatus according to any one of the preceding claims, characterized in that, The base portion (30) does not include an opening, or the base portion (30) includes an opening that is not large enough to allow molten metal to be drawn into the opening and mixed with gas in the manifold portion of the rotor during operation.

5. The apparatus according to any one of the preceding claims, characterized in that, The base portion (30) includes an opening with a diameter of less than 28 mm.

6. The apparatus according to any one of the preceding claims, characterized in that, The cross-sectional area of ​​the mixing zone outlet (100) is greater than the cross-sectional area of ​​the mixing zone inlet (70).

7. The apparatus according to any one of the preceding claims, characterized in that, The cut-out portion (80) of the rotor (10) comprises at least 26% of the rotor's rotational volume.

8. The apparatus according to any one of the preceding claims, characterized in that, The cross-sectional area of ​​the mixing zone is at least 5% of the rotational area of ​​the rotor.

9. The apparatus according to any one of the preceding claims, characterized in that, The volume of the mixing zone is between 1% and 25% of the rotating volume of the rotor.

10. The apparatus according to claim 9, characterized in that, The volume of the mixing zone is at least 3% of the rotational volume of the rotor.

11. The apparatus according to any one of the preceding claims, characterized in that, The sum of the volume of the mixing zone and the volume of the cut portion is in the range of 30% to 80% of the rotating volume of the rotor.

12. The molten metal degassing apparatus according to any one of the preceding claims, characterized in that, The sum of the volume of the mixing zone and the volume of the cut portion is at least 36% of the rotational volume of the rotor.

13. The molten metal degassing apparatus according to any one of the preceding claims, characterized in that, The sum of the cross-sectional area of ​​the mixing zone and the cross-sectional area of ​​the cut portion is in the range of 50% to 90% of the rotating area of ​​the rotor.

14. The molten metal degassing apparatus according to any one of the preceding claims, characterized in that, The sum of the cross-sectional area of ​​the mixing zone and the cross-sectional area of ​​the cut portion is at least 59% of the rotational area of ​​the rotor.

15. The molten metal degassing apparatus according to any one of the preceding claims, characterized in that, The ratio of the cross-sectional area of ​​the cut portion to the cross-sectional area of ​​the mixing zone is 1.0 or greater.

16. The molten metal degassing apparatus according to any one of the preceding claims, characterized in that, The cross-sectional area of ​​the manifold portion accounts for no more than 10% of the rotating area of ​​the rotor.

17. The molten metal degassing apparatus according to any one of the preceding claims, characterized in that, Each of the support members (40) includes a circumferential thickness (T1) in the range of 8 mm to 20 mm.

18. The molten metal degassing apparatus according to any one of the preceding claims, characterized in that, Each mixing zone outlet (100) spans at least 50% of the circumference between the circumferential ends of an adjacent pair of supports (40).

19. The molten metal degassing apparatus according to any one of the preceding claims, characterized in that, The cut portion (80) includes: a first length extending from the periphery of the cut portion originating from the peripheral end of the support member to a turning point of the cut portion closest to the central axis of the rotor; and a second length extending from the turning point to the peripheral end of an adjacent support member defining the cut portion, the first length being greater than the second length.

20. The molten metal degassing apparatus according to any one of the preceding claims, characterized in that, The cut portion (80) extends over a distance greater than 50% of the radius of the rotor.

21. The molten metal degassing apparatus according to any one of the preceding claims, characterized in that, The cut portion (80) extends to be greater than 55% of the radius of the rotor.

22. The molten metal degassing apparatus according to any one of the preceding claims, characterized in that, The rotor (10) comprises or is composed of carbon ceramic composite material.

23. The molten metal degassing apparatus according to any one of the preceding claims, characterized in that, Each mixing zone inlet (70) forms part of a circumference with a radius not exceeding 50 mm.

24. A molten metal degassing system, characterized in that, The molten metal degassing system includes a molten metal degassing device according to any one of the preceding claims and a container for molten metal.

25. The molten metal degassing system according to claim 24, characterized in that, The inner diameter of the container is in the range of 600mm to 2000mm.

26. The molten metal degassing system according to claim 25, characterized in that, The ratio of the rotor's diameter to the container's inner diameter is in the range of 0.18 to 0.

30.

27. The molten metal degassing system according to claim 26, characterized in that, The ratio of the diameter of the rotor (10) to the inner diameter of the container is less than 0.

23.

28. The molten metal degassing system according to any one of claims 24 to 27, characterized in that, The inner diameter of the container is at least 1000 mm.

29. A process for degassing molten metal using a molten metal degassing device according to any one of claims 1 to 23 or a molten metal degassing system according to any one of claims 24 to 28.

30. The process according to claim 29, characterized in that, The rotor rotates at a first speed greater than 300 rpm in vortex formation mode.

31. The process according to claim 30, characterized in that, After rotating in the vortex-forming mode, the rotor rotates in the degassing mode at a second speed, which is at least 50 rpm slower than the first speed.

32. The process according to claim 31, characterized in that, For a 220mm diameter rotor placed in a 1000mm diameter container filled with 700mm of water, with oxygen meters in the water located 100mm and 500mm from the bottom of the container, in order to obtain a vortex depth of at least 400mm after 15 seconds and a residual O2 content of no more than 20% v / v after 450 seconds, the average rotor speed of the average speed of the first speed and the second speed shall not exceed 450 rpm.

33. The process according to claim 32, characterized in that, The average speed of the first speed and the second speed does not exceed 500 rpm.

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