Molten metal degassing device and molten metal degassing system

Abstract

The utility model relates to a molten metal degassing device and a molten metal degassing system. The device comprises: a hollow shaft; a rotor comprising a top portion and a base portion separated by a gap, the rotor being connected to the hollow shaft; a range of 3 to 8 supports, each of which extends radially outward and is connected to the top portion and the base portion; a manifold portion wherein a gas flow from the hollow shaft enters through an opening in the top portion and the gas flow is radially distributed through a mixing zone inlet; a mixing zone continuous with the mixing zone inlet and laterally offset from the manifold portion for a flow of gas from the manifold portion; a cutout portion located between a rotational volume envelope of the rotor and a periphery of the rotor.

Description

Technical Field

[0001] The utility model relates to a molten metal degassing device, which is used to: first form a vortex to transport additives from the vortex to the molten metal; then form and distribute fine bubbles of fluxing gas in the entire molten metal. The utility model also relates to a molten metal processing system including the molten metal degassing device and a process for processing molten metal using the molten metal degassing device or the molten metal processing system. Background Art

[0002] Molten metals such as aluminum contain many impurities before casting, which, if not removed, can result in high scrap losses during casting or 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 an inert or reactive gas mixture (i.e., fluxing gas) into molten aluminum is a common technique used to remove the above impurities. The removal rate of these impurities depends largely on how the fluxing gas is injected into the molten metal. Optimum performance in this type of metal treatment process is achieved when fine bubbles are generated, thereby forming a large interfacial contact area for the metal treatment reaction to occur, and when these bubbles are distributed in a uniform manner throughout the cross-sectional area available for the metal flow.

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

[0005] In addition to adding gas, other treatment agents can also be added to the molten melt to assist grain refinement or modify the microstructure and performance of the resulting cast metal and alloy. Metal treatment agents can be added to the vortex, so that they are easily dispersed throughout the melt. Any turbulence in the melt will cause the introduction of air, which will subsequently cause oxides to form in the metal. Therefore, the vortex is only used in a small section of the processing cycle, and once the mixing stage is completed, the vortex stops (for example, by applying a baffle). The rotor blades pump the liquid to form a vortex, and in doing so, a vacuum chamber is generated behind the blades, which is pressurized after the next blade arrives. An efficient rotor will form a vortex and disperse the treatment agent as quickly as possible to keep the turbulence in the melt to a minimum. Then, degassing and reaction product removal are practiced in the melt. Using a rotor to form both a vortex for efficient addition of processing agents and then a vortex for efficient distribution of fine bubbles creates an inherent challenge in rotor design in that the intense mixing required to form a vortex conflicts with the need to distribute fine bubbles within the melt without a vortex that would cause deleterious re-entrainment of gases and impurities.

[0006] As the size of the crucible or refractory lined vessel increases (over 800mm in diameter, up to 1.5 tonnes of aluminium, less commonly 3 tonnes of aluminium and in extreme cases 10 tonnes of aluminium), eddy currents become more difficult to achieve. As rotational speed increases, the rotor head needs to increase in diameter and height (hence increased weight, and thus increased vibration and cyclic shaft stresses) to achieve the desired eddy currents, and therefore increased head erosion. All of the above factors have driven the redesign of the head so that the generation of eddy currents remains fast and deep, while the increase in weight and rotational speed is minimised.

[0007] As such, there is an increasing need for a rotor that can efficiently form a vortex in a body of molten metal and then also efficiently distribute fine bubbles therein.

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

[0009] Thus, there remains room for improvement in rotor designs and systems for processing molten metals, particularly for processing in larger capacity vessels. Utility Model Content

[0010] In a first aspect of the present invention, a molten metal degassing device is provided, the molten metal degassing device comprising:

[0011] a. a hollow shaft for conveying a gas flow (eg, fluxing gas);

[0012] b. a rotor 10 comprising a top portion 20 and a base portion 30 separated by a gap, the rotor being connected to the hollow shaft;

[0013] c. 3 to 8 support members 40, each of which extends radially outward and is connected to the top portion 20 and the base portion 30;

[0014] d. a manifold portion 50 wherein the gas flow from the hollow shaft enters through an opening 60 in the top portion 20 and the gas flow is radially distributed through a mixing zone inlet 70;

[0015] e. a mixing zone 90 continuous with the mixing zone inlet 70 and radially offset from the manifold portion; the top portion 20 and the base portion 30 and the adjacent support member 40 each extend radially outward from the manifold portion 50 to form the mixing zone 90, the mixing zone 90 forming at least a portion of the void, the peripheral edges of the top portion 20, the base portion 30 and the adjacent support member 40 defining a mixing zone outlet 100; and

[0016] f. a cutout portion 80, said cutout portion being located between the rotation volume envelope / envelope of the rotor and the periphery of the rotor,

[0017] The cutout portion 80 occupies a range between 25% and 75% of the rotational volume of the rotor.

[0018] Preferably, in use, the gas flow from the manifold portion 50 counter-currently contacts the molten metal flow entering from the mixing zone outlet 100. The resulting metal and gas dispersion is then radially discharged from the mixing zone 90 through the mixing zone outlet 100.

[0019] 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 R of the rotor is in the range of greater than 0.0 to 0.70. Although L1:L2 can have a negative ratio, these results occur when the mixing zone inlet feeds directly into the cutout portion, thereby bypassing the mixing zone. In addition, this arrangement also results in the support member not extending completely radially, thereby reducing the ability of the rotor to pump the molten metal dispersion in the circumferential direction, thereby reducing the vortex formation efficiency of the rotor.

[0020] Preferably, the ratio of L1:L2 is at least 0.05 or at least 0.10 or at least 0.20 or at least 0.30. Generally, the higher the ratio, the larger the two-dimensional occupied area of ​​the mixing zone. Preferably, the ratio of L1:L2 is not greater than 0.60 or not greater than 0.50 or not greater than 0.40 or not greater than 0.38 or not greater than 0.35. Too high a ratio may result in a reduced ability of the rotor to move the molten metal dispersion in a circumferential direction to facilitate eddy formation.

[0021] 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 the mixing zone outlet share the same focus of circles of different radii). In some embodiments, the cross-sectional area of ​​the mixing zone outlet is greater than the cross-sectional area of ​​the mixing zone inlet.

[0022] The device of the utility model is capable of operating in an initial vortex formation mode to effectively form a vortex. This is achieved by the depth of the cutout portion, which enables a large amount of molten metal to rotate in the same direction around the axis of the hollow shaft, thereby promoting the formation of a vortex, using which the metal treatment agent can be effectively distributed in the molten metal mass. As the volume (and inner diameter) of the container (e.g., crucible) increases, vortex formation becomes increasingly difficult. Therefore, there is an increasing demand for a degassing device that can effectively form a vortex in a larger container while also providing acceptable flux gas dispersion efficiency.

[0023] 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 the plurality of supports 40 forces the molten metal into each mixing zone 90 to form a high shear force region, in which fine bubbles are formed and uniformly distributed as the mixture is ejected from the mixing zone into the molten metal body.

[0024] High shear force refers to the force generated by the collision of a flow of molten metal in a body moving in one direction with a flow of gas moving in the opposite direction. For example, when the impeller (i.e., support) of the rotor rotates, the molten metal flows in the same direction as the impeller at a speed that is less than the speed of rotation of the impeller. However, the rotor speed and the molten metal speed are usually not much different, so the shear force is relatively low compared to the collision of fluids in opposite directions that occurs in the mixing zone of the rotor of the utility model. The greater the difference between the two speeds of the molten metal and the fluxing gas, the greater the ability to divide the fluxing gas into fine bubbles by shear force.

[0025] Although some conventional rotors inject fluxing gas through small holes between the rotor blades, the volume of high shear is relatively low because once the fluxing gas is injected into the molten metal, it is carried downstream in a circumferential direction around the central axis of the rotor. The mixing efficiency can be improved by forming a mixing zone in which the molten metal can mix with the fluxing gas before leaving the mixing zone.

[0026] As the rotation of the impeller draws the molten metal into the mixing zone, the collision flow of the gas and molten metal from the manifold section creates a shear force that drives the formation of fine bubbles within the mixed molten metal phase, which are then ejected into the body of the molten metal. It is this collision period between the molten metal and the gas that causes the greatest shear force and has the greatest impact on the efficiency and effectiveness of the formation and distribution of fine bubbles within the molten metal.

[0027] The same rotational force that drives the molten metal mass in the same rotational direction to assist in vortex formation (in vortex formation mode) also drives a portion of the molten metal mass into the high shear mixing zone in the gas dispersion mode. The volume of molten metal and the duration of the molten metal in the mixing zone will determine the efficiency of fine bubble formation and distribution, which will thereby affect the degassing efficiency.

[0028] Generally, the larger the mixing zone, the better the degassing efficiency, and the larger the cutout, the better the vortex formation efficiency. Consideration of this common concept is that sufficient mixing zone outlets and cutout areas are required to promote the required high shear environment and flow pattern, thereby improving mixing and vortex formation efficiency. Rotors with between 3 and 8 support members provide such an environment.

[0029] The final rotor design may be a compromise between the mixing and vortexing capabilities of the rotor for the characteristics of the molten metal being processed and the geometry of the vessel holding the molten metal.

[0030] Mixed Zone

[0031] The mixing zone is where the molten metal stream and fluxing gas stream preferably first contact. The contact is a countercurrent contact that preferably produces a high shear contact to produce fine bubbles dispersed within the molten metal.

[0032] The mixing zone forms at least a portion of the gap between the top portion and the base portion. In some embodiments, the mixing zone consists of the gap between the top portion and the base portion. In other embodiments, the manifold portion includes a portion of the gap before the gap extends radially laterally. In these embodiments, the diameter of the manifold portion can be widened adjacent to the opening in the top portion. The mixing zone inlet typically includes a height that is lower than the height of the manifold portion. The mixing zone height can be in the range of 20mm to 100mm; or 30mm to 80mm; or 40mm to 60mm.

[0033] Because the mixing zone defines a space for gas from the manifold section to flow radially outward in a lateral direction (molten metal is drawn into the mixing zone from the opposite direction, i.e., through the mixing zone outlet), the mixing zone possesses 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 top and base cutout portions and two supports.

[0034] Each mixing zone is defined by a top portion and 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 that is not defined by adjacent supports (e.g., in the form of a single annular space with multiple outlets between supports) can be more correctly defined as an expanded manifold portion (see comparative example C-5). The expanded manifold portion is at the expense of reducing the mixing zone area. It has been found that the mixing performance provided by the expanded manifold portion is relatively poor, which indicates that, in addition to mixing via countercurrent flow of the fluid, the shearing action of the supports on the fluid and its restriction on flow contribute to increasing turbulence, thereby increasing the mixing efficiency of the rotor.

[0035] The height of the top portion may taper from the opening 60 to the periphery of the support. Alternatively, the top portion may extend horizontally from the opening to maximize the rotational volume of the rotor.

[0036] In some embodiments, the mixing zone extends to the periphery of the rotating zone. In other embodiments, the mixing zone only partially extends to the rotating zone.

[0037] Preferably, the cross-sectional area of ​​the mixing zone has the rotor rotation area (π×D 2 / 4) of at least 4% or at least 5% or at least 8% or at least 10% or at least 12% or at least 15% of the lower limit range and no more than 50% or no more than 40% or no more than 35% or no more than 30% of the upper limit. 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 inlet and outlet of the mixing zone. Similarly, the volume of the mixing zone can have a lower limit of at least 1% or at least 2% or at least 3% or at least 4% or at least 5% of the total rotating volume and an upper limit of no more than 25% or no more than 20% or no more than 15%.

[0038] In some embodiments, the cross-sectional area of ​​the mixing zone may be at least 20% or at least 22% or at least 24% or at least 26% or at least 28% or at least 30% or at least 32% or at least 34% or at least 36% or at least 38% or at least 40% of the rotor's rotating area.

[0039] The volume of the mixing zone may 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 rotating volume of the rotor. The larger the cross-sectional area (or volume) of the mixing zone, the greater the proportion of the high shear zone environment that the molten metal is exposed to where the molten metal collides with the gas flowing into the mixing zone from the manifold portion of the rotor.

[0040] The height of the mixing zone is typically in the range of 20 mm to 100 mm, depending on the specific application of the device. The width of the mixing zone (measured between the supports) is controlled by the number of supports in the rotor, but is typically at least 20 mm and may extend to 100 mm or more, particularly towards the outlet end of the mixing zone.

[0041] The mixing zone outlet is large enough to allow the molten metal to enter the mixing zone before exiting along with the dispersed fine bubbles of fluxing gas. The minimum transverse dimension (e.g., height or width) is preferably at least 28 mm or at least 30 mm or at least 35 mm or at least 40 mm. The maximum transverse dimension of the outlet is typically no more than 125 mm or no more than 100 mm or no more than 80 mm or no more than 60 mm. Too small a size results in clogging of the outlet and difficulty in cleaning the outlet during maintenance, while too large an outlet can result in a reduced shear rate between the fluxing gas and the molten metal or an increased tendency for components to be transported away through the channel, thereby reducing mixing efficiency.

[0042] In some embodiments, each mixing zone outlet 100 spans at least 50% of the circumference between the circumferential ends of an adjacent pair of support members 40 .

[0043] Manifold section

[0044] The manifold section is used to distribute fluxing gas from the hollow shaft to a mixing zone laterally offset relative to the manifold section. The manifold section is preferably continuous with the mixing zone inlet. Under normal operation (using a standard design, i.e., expansion of the manifold section is not at the expense of the mixing zone section), 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.

[0045] The manifold portion is coherently engaged with the gas leaving the hollow shaft. The manifold portion is generally defined by a base portion and a top portion and a plurality of supports, which are combined to provide a plurality of mixing zone inlets from which the manifold portion distributes gas. Although the base portion of the rotor is generally solid and has no openings, in some embodiments, the base portion may include a small central hole, which is an artifact of the manufacturing process. In some embodiments, the base portion does not include an opening. In other embodiments, the base portion 30 includes an opening that is not large enough to allow molten metal to be sucked into the opening and mixed with the gas in the rotor manifold portion. In other embodiments, the base portion includes an opening that is less than 28 mm or less than 25 mm or less than 20 mm, so that the opening is not used as an inlet for the molten metal to mix with the gas in the manifold portion. Typically, the opening size is too narrow to cause it to be covered by scum during operation, thereby effectively closing the opening in use.

[0046] Although there is no limitation on the shape of the manifold portion, the manifold portion generally comprises a circular cross-sectional area from a top view of the rotor. However, to maximize the cross-sectional area of ​​the mixing zone, the effective diameter of the manifold portion may be no greater than 100 mm, or no greater than 80 mm, or no greater than 60 mm, or no greater than 50 mm, or no greater than 40 mm. The diameter of the manifold portion is generally at least 10 mm, or at least 20 mm, or at least 30 mm. A smaller inlet diameter may increase the effective rate of fluxing gas entering the mixing zone, thereby increasing the degree of high shear, thereby increasing the formation of fine bubbles. However, for the practicality of cleaning the rotor, a minimum inlet diameter may be required.

[0047] Depending on the application, the height of the manifold portion between the top portion and the base portion is typically in the range of 20 mm to 200 mm. In some embodiments, the height of the manifold portion is at least 25 mm, or at least 30 mm, or at least 35 mm. The greater the height of the manifold portion, the greater the potential height of the entrance to the mixing zone, thereby expanding the interfacial contact area between the molten metal and the gas, thereby enhancing the formation of fine bubbles. In addition, a larger mixing zone entrance height is more likely to avoid scum blockage and is also easier to clean.

[0048] In some embodiments, the manifold portion includes a top component having an inner diameter ID-T and a base component having an inner diameter ID-B. The top component is generally associated with the portion of the connector that is adjacent to the hollow shaft. The base portion is generally associated with the portion adjacent to the mixing zone inlet. The ID-T of the manifold portion may be the same as ID-B, or may be greater than or less than ID-B.

[0049] The ratio of the diameter of the rotor to the height of the rotor may be in the range of 1.5 to 5.0 or 1.7 to 4.0 (eg, 180 mm / 105 mm to 160 mm / 65 mm).

[0050] Multiple supports

[0051] Between 3 and 8 supports connect the top and base portions and form a portion of the manifold portion and the mixing zone. A smaller number of supports results in a relatively large mixing zone, and thus a high shear environment cannot be easily formed to promote effective mixing, wherein the passage of fluxing gas or molten metal can pass through the mixing zone without achieving adequate mixing. In addition, with fewer supports, the material flow pattern between the supports is not conducive to promoting eddy flow.

[0052] Having a greater number of supports results in a greater proportion of the rotor comprising supports, thereby increasing weight and reducing the potential size of the mixing zone and cut-out portion. In some embodiments, the rotor may comprise 3 or 4 or 5 or 6 or 7 or 8 supports. In a preferred embodiment, the rotor comprises in the range of 4 to 6 supports.

[0053] In some embodiments, a support member connects the top portion and the base portion adjacent the mixing zone inlet, wherein the support member separates a plurality of mixing zones having a plurality of mixing zone inlets.

[0054] In other embodiments, the cutout portion extends at least partially between the radial supports so that at least a portion of the supports distal to the manifold portion is in the form of a blade that does not include a circumferentially adjacent top or base portion. In these embodiments, the mixing zone typically occupies a relatively low portion of the rotating area.

[0055] In other embodiments, the cutout portions extend between the radial supports so that the supports have circumferentially adjacent top or base portions. In these embodiments, the mixing zone typically occupies a relatively high portion of the rotating area.

[0056] The supports typically extend radially from the manifold portion. Due to the radial arrangement of the supports, the inlet to the mixing zone typically has a smaller cross-sectional area than the outlet of the mixing zone. The size of the supports is typically determined by mechanical and erosion performance considerations. In a preferred embodiment, the minimum cross-sectional thickness of the supports is less than 20 mm, or less than 18 mm, or less than 16 mm, or less than 14 mm. The minimum support member thickness is preferably at least 6 mm, or at least 8 mm, or at least 10 mm, or at least 12 mm, or at least 14 mm, to provide sufficient corrosion and erosion resistance to enable the rotor to have a sufficiently long service life.

[0057] To assist in reducing the thickness of the support, the support is preferably made of a carbon ceramic composite material, which has excellent corrosion resistance compared to a graphite rotor. Reducing the thickness of the support enables the mixing zone to be increased and / or the cutout portion to be increased, thereby assisting in enhancing the degassing efficiency and / or the vortex formation efficiency.

[0058] In some embodiments, the average thickness of the support 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 is at least 10 mm, or at least 11 mm, or at least 12 mm, or at least 13 mm, or at least 14 mm, or at least 15 mm.

[0059] In some embodiments, the support member tapers from top to bottom, or vice versa. For example, one end of the support member may have a thickness of 12 mm, while the other end may have a thickness of 7 mm.

[0060] In some embodiments, at least some or all of the sections of the support member taper from a proximal position of the central axis to a distal position of the central axis (i.e., the height of the support member decreases as the support member extends radially outward). Alternatively, some or all of the sections of the support member maintain a constant height. The height of the support member can vary from 30 mm to the full height of the rotor (e.g., up to 200 mm).

[0061] The support preferably extends from the mixing zone inlet and extends to the periphery of the rotating zone. The support starts at the mixing zone outlet and extends to the periphery of the rotating zone.

[0062] Cutting part

[0063] The cutout portion is preferably continuous with the mixing zone outlet. The cutout portion block is located between the rotor's rotating volume envelope and the rotor's periphery. For clarity, the cutout portion does not include the manifold portion.

[0064] The cutout portions (e.g., top and base) represent the difference between the rotating area of ​​the rotor of diameter D and the top / bottom view profile of the rotor (i.e., the cutout portions are cutouts 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 position, so that from a top view of the rotor, the top cutout portion and the base cutout portion completely overlap each other. Having completely overlapping cutout portions enables the mixing zone area to be maximized.

[0065] For completeness, note that the gap between the top portion and the base portion is within the perimeter.The perimeter of the rotor may be defined as being bounded by the smallest geometric surface connecting the perimeter of the top portion with the perimeter of the base portion.

[0066] In some embodiments, fluid flow modeling can determine that if there is misalignment between the top cut portion and the base cut portion (i.e., the top cut portion and the bottom cut portion can partially overlap), an increased high shear region can be achieved to a certain extent. In other embodiments, fluid flow modeling can indicate that an increased high shear region can be achieved with perfect alignment between the top cut portion and the base cut portion.

[0067] The percentage area of ​​the cutout portion of the rotor will be equal to the minimum of the cutout portions in the top portion and the base portion. Therefore, if the top portion has a 5% cutout portion relative to the rotating area and the base portion has an 8% cutout portion relative to the rotating area, the rotor will be considered to have a 5% cutout area percentage. If there is no cutout portion in the base portion or the top portion, the cutout portion will be considered to be 0%. If the cutout portion has no supports, the cutout portion will also be considered to be 0% because without supports, the cutout portion will not have the ability to rotationally move the fluid to form a vortex. The volume percentage of the cutout portion can be determined by multiplying the minimum percentage area of ​​the cutout portion in the base portion or the top portion and multiplying that area by the average height of the top portion and the base portion adjacent to the top and base cutout portions.

[0068] In one embodiment, the number of top cutout portions is the same as the number of base cutout portions. In some embodiments, the number of top cutout portions is different from the number of base cutout portions. Although a single cutout (top and bottom) is typically made between adjacent supports, several cutouts may also be made between adjacent supports.

[0069] The cutout portion can be symmetrical or asymmetrical. The cutout portion can be part-circular or parabolic or linear. The advantage of a part-circular cutout is that it can be easily machined into the rotor. The greater depth of the cutout portion enables the rotor to move more molten metal between the supports, which function as rotor blades. The more molten metal that can be moved in the circumferential direction, the easier it is for the rotor to form eddies around the rotating hollow shaft.

[0070] In one embodiment, the cutout portion includes: a first length, the 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 central axis of the rotor; and a second length, the second length extending from the turning point and extending along the periphery of the cutout portion to the peripheral end of the adjacent support member defining the cutout portion, the first length being greater than the second length.

[0071] The rotor is preferably configured so that the second length of each cut-out portion is the leading edge of the rotor. It has been found that this configuration enhances vortex formation.

[0072] 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.

[0073] In some embodiments, the ratio of the area of ​​the cutout 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 regime in the mixing zone allows a higher proportion of the rotor to be devoted to improving the formation of vortices.

[0074] For purposes of the present invention, the cross-sectional area of ​​each component (including support, manifold portion, mixing zone) is the cross-sectional area as viewed from the top cross section ("top view") presented in a plane normal to the hollow axis.

[0075] In some embodiments, the cross-sectional area of ​​the cutout portion comprises a range between 20% and 70% of the rotor rotation area. In some embodiments, the cross-sectional area of ​​the cutout portion comprises 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 rotation area. The increase in the area percentage of the cutout portion enhances the vortex formation efficiency of the rotor.

[0076] In some embodiments, the volume of the cutout portion comprises a range between 26% and 70% of the rotational volume of the rotor. In some embodiments, the volume of the cutout portion comprises 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 rotational volume of the rotor.

[0077] In some embodiments, the cutout portion extends greater than 50% of the rotor radius (i.e., a linear line extending from the center of the rotor to the periphery of the rotating zone is considered as the radius of the rotor, and the cutout portion extends greater than 50% of the distance along the line from the periphery of the rotating zone toward the center of the rotor) 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 depth of the cutout, the greater the ability of the rotor to increase the efficiency of vortex formation.

[0078] In other embodiments, the cross-sectional area of ​​the cutout portion and the mixing zone comprises a range between 50% and 90% of the rotational area of ​​the rotor. In some embodiments, the cross-sectional area of ​​the cutout portion and the mixing zone comprises 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 rotational area of ​​the rotor.

[0079] In some embodiments, the volume of the cutout portion and the mixing zone comprises a range between 30% and 80% of the rotational volume of the rotor. In some embodiments, the volume of the cutout portion and the mixing zone comprises 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% or at least 46% of the rotational volume of the rotor.

[0080] In some embodiments, the rotor support thickness is controlled by stress analysis so that the size of the support can be reduced with a corresponding increase in the size of the cutout portion and / or the mixing zone. An advantage of increasing the mixing zone and the cutout portion is that this also contributes to a reduction in rotor weight because the reduction in support and top / base portion thickness results in an increase in the functional size of the rotor dedicated to mixing and swirl efficiency. The use of carbon ceramic composites in constructing the rotor enables the use of a smaller volume of material than graphite due to their excellent erosion resistance.

[0081] In some embodiments, the cutout portion comprises a stepped structure, wherein the cutout portion comprises a portion between the mixing zone outlet and the rotating area / volume and a portion above the mixing zone top and between the support members extending upward. Other cutout portions may also be present below the mixing zone base and between the support members extending downward. By using one or both of the spaces above and below the mixing zone top and base, the mixing zone size for obtaining the desired high shear environment may also be able to maximize the cutout volume. For example, the top portion adjacent to the opening ID-T may extend vertically downward along the top of the manifold, then radially extend outward (horizontally or at an angle thereto), and the support members extend vertically above the radial top portion, extending partially or entirely to the height of the opening. A portion of the support member may be gradually reduced (i.e., height reduction) toward the periphery of the rotating zone. In other embodiments, from the proximal side of the opening to the periphery of the rotating zone, the support height may remain constant.

[0082] manufacture

[0083] The shaft and rotor may be formed separately and connected together by releasable connection means such as threads on each of the rotor and shaft. Alternatively, the shaft and rotor may be formed as an integral one-piece hollow shaft and rotor.

[0084] The rotor may be machined from a solid block of material from which the manifold portion, mixing zone, and cutout portion are machined. Alternatively, the rotor may also be formed using molding and pressing techniques (e.g., isostatic pressing), particularly if the rotor configuration is not readily obtainable by machining alone. Specifically, a rotor design that seeks to maximize the volume percentage of the cutout portion and mixing zone relative to the total volume of the rotating volume is most likely to be achieved using molding techniques or 3D printing manufacturing techniques.

[0085] In one embodiment, the hollow shaft portion includes at least a portion of the top portion of the rotor. This enables the remainder of the rotor to be machined from a single piece. Greater design flexibility can be achieved when constructing the support and mixing zone without the top portion being in the way. To facilitate this construction, the rotor portion may include a male connector for engaging with a female connector on the hollow shaft portion.

[0086] The rotor may then undergo heat treatment to produce the final product. Additional machining may also be performed on the component. The rotor may also be coated with any aggressive and / or anti-scum coatings.

[0087] The rotor and shaft may be made of graphite or a carbon ceramic composite. In some embodiments, the rotor includes or consists of a carbon ceramic composite. Carbon ceramic composites have the advantage of being more resistant to corrosion and erosion than graphite. Thus, the support members and walls of the rotor may have a reduced thickness to increase the volume of the mixing zone and the cutout portion, thereby improving the dual-function performance of the rotor. An example of a suitable carbon ceramic composite is Roton available from Molten Metal System Co., Ltd. TM A series of carbon ceramic composite materials.

[0088] Carbon ceramic composites can include:

[0089] 30 to 70 wt.% ceramic matrix;

[0090] 30 to 70 wt. % carbon material; and

[0091] 0 to 15 wt% additives.

[0092] The ceramic matrix is ​​preferably selected for its combination of thermal and mechanical properties and may be selected from the group consisting of: silicon dioxide; aluminum oxide; carbides of Si, Ti, W, Ta, Nb, Zr, Hf, V, Cr, Mo; silicon nitride; magnesia; zirconium oxide; boron nitride; aluminum nitride; or combinations thereof.

[0093] The ceramic matrix may include silicon carbide, for example, beta silicon carbide and / or alpha silicon carbide.

[0094] The carbon material is preferably graphite and / or a carbonaceous material derivable from an organic binder used to form the composite material.

[0095] Additives may include silicon metal, FeSi, aluminum, boron, aluminum silicate (eg, clay), borax, and / or boric acid.

[0096] Molten Metal Degassing Systems

[0097] In a second aspect of the present invention, a molten metal degassing system is provided, the molten metal degassing system comprising an apparatus according to the first aspect of the present invention and a molten metal container. The molten metal container may comprise an inner diameter of at least 650 mm, or at least 800 mm, or at least 850 mm, or at least 900 mm, or at least 1000 mm, or at least 1100 mm, or at least 1200 mm, or at least 1300 mm, or at least 1400 mm, or at least 1500 mm. The maximum inner diameter of the molten metal container may be affected by various technical and commercial considerations, but is expected to be no more than 2000 mm, or no more than 1500 mm.

[0098] In some embodiments, the rotor diameter R D With the container inner diameter VD The ratio of is in the range of 0.18 to 0.37 (e.g., 180mm / 960mm to 260mm / 700mm). D V D 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 are particularly advantageous (eg a 300 mm diameter rotor in a vessel with an inner diameter of 1500 mm).

[0099] Technology

[0100] In a third aspect of the present invention, a process for degassing molten metal using the molten metal degassing system according to the second aspect of the present invention is provided, wherein the rotor of the device rotates at a speed greater than 300 rpm, greater than 350 rpm, greater than 400 rpm, greater than 450 rpm, or greater than 500 rpm during the vortex formation mode, and then rotates at a speed less than the speed in the vortex formation mode in the degassing mode. Preferably, the degassing mode speed is at least 50 rpm, at least 75 rpm, at least 100 rpm, at least 125 rpm, or at least 150 rpm slower than the vortex formation mode.

[0101] Due to the excellent overall vortex formation and degassing efficiency of the rotor, the average speed of the rotor in these two modes can be lower than the average speed of other rotors in the prior art. In one embodiment, the average speed of the rotor does not exceed 500rpm or does not exceed 475rpm or does not exceed 450rpm or does not exceed 425rpm or does not exceed 400rpm. Alternatively, by maintaining a speed close to that of the rotor operated in the prior art, excellent vortex and / or mixing efficiency can be achieved.

[0102] In some embodiments, the average rotor speed (i.e., speed in vortex mode + speed in degassing mode divided by 2) to obtain a vortex depth of at least 550 mm and a fluxing gas fraction of at least 80% v / v within 40 seconds (under the conditions outlined in the experimental section) is no more than 600 rpm, or no more than 580 rpm, or no more than 570 rpm, or no more than 565, or no more than 550 rpm.

[0103] In some embodiments, to obtain a vortex depth of at least 400 mm after 15 seconds and a residual O of no more than 20% v / v after 450 seconds, 2 The average rotor speed (i.e., speed in vortex mode + speed in degassing mode divided by 2) for the content (under the conditions outlined in the experimental part) does not exceed 450 rpm or does not exceed 425 rpm or does not exceed 400 rpm or does not exceed 375 or does not exceed 350 rpm or does not exceed 325 rpm.

[0104] Rotor

[0105] In a third aspect of the present invention, there is provided a rotor as defined in the first aspect of the present invention.

[0106] Rotation Area

[0107] The rotational area is defined as the "top view" area covered by the rotor as it rotates about its axis of rotation in a two-dimensional plane. The rotational area can be defined as π × D 2 / 4, where D is the diameter of the rotor.

[0108] Volume of rotation

[0109] The volume of revolution is defined as the volume covered by the rotor as it rotates about its axis of revolution in a two-dimensional plane. The volume of revolution can be calculated by determining the 3D envelope resulting from the rotation of the rotor in a two-dimensional plane. The envelope typically includes a cylindrical portion toward the base portion and may include a frustoconical portion toward the top portion, wherein the rotor top portion tapers downward from an opening adjacent to a peripheral edge toward the top portion.

[0110] Rotation Volume Envelope

[0111] The volume of revolution envelope is defined as the envelope that contains the volume of revolution.

[0112] The rotating area and volume are preferably the sum of the various components of the rotor (eg, manifold+support+mixing zone+top section+base section+cutout section).

[0113] For the purpose of defining the area of ​​revolution, volume of revolution and envelope of volume of revolution, the axis of revolution is the geometric axis extending through the centre of the base portion and the centre of the top portion. This coincides with the geometric axis extending through the centre of the hollow shaft. BRIEF DESCRIPTION OF THE DRAWINGS

[0114] Figure 1a and Figure 1b They are a side view and a perspective view of a rotor (Example 7) of the present invention, respectively, illustrating the rotor rotation volume.

[0115] Figure 1c is a top view of a rotor (Example 7), illustrating the rotating cross-sectional area of ​​the rotor.

[0116] Figure 2a and Figure 2b They are respectively a stereoscopic view and a cross-sectional top view of the rotor (Example 4) of the present invention.

[0117] Figure 3a and Figure 3b They are respectively a side view and a cross-sectional top view of the rotor (Example 1) of the present invention.

[0118] Figure 4a and Figure 4b They are respectively a side view and a cross-sectional top view of the rotor (Example 2) of the present invention.

[0119] Figure 5a and Figure 5b They are respectively a side view and a cross-sectional top view of the rotor (Example 3) of the present invention.

[0120] Figure 6a and Figure 6b They are respectively a side view and a cross-sectional top view of the rotor (Example 5) of the present invention.

[0121] Figure 7a and Figure 7b They are respectively a side view and a cross-sectional top view of the rotor (Example 6) of the present invention.

[0122] Figure 8a and Figure 8b They are respectively a side view and a cross-sectional top view of the rotor (Example 7) of the present invention.

[0123] Figure 9a and Figure 9b They are respectively a sectional side view and a sectional top view of the rotor (Example 8) of the present invention.

[0124] Fig.10a and Fig.10b It is a cross-sectional top view and a stereoscopic view of the rotor (Example 9) of the present invention.

[0125] Figures 11a to 11c They are a sectional side view, a perspective view, and a sectional top view of a rotor of the prior art (Comparative Example C-1), respectively.

[0126] Fig.12a and Figure 12b They are a sectional side view and a sectional top view, respectively, of a rotor of the prior art (Comparative Example C-2).

[0127] Fig.13a and Fig.13b They are a sectional side view and a sectional top view, respectively, of a rotor of the prior art (Comparative Example C-3).

[0128] Fig.14a and Fig.14b They are a sectional side view and a sectional top view, respectively, of a rotor of the prior art (Comparative Example C-4).

[0129] Fig.15a and Fig.15b They are respectively a perspective view and a cross-sectional top view of a rotor of the prior art (Comparative Example C-5).

[0130] Fig.16a and Fig.16b It is a cross-sectional side view of a vessel used as part of the molten metal degassing system of the present invention.

[0131] All cross-sectional top views are taken from the midpoint of the height of the mixing zone. DETAILED DESCRIPTION

[0132] refer to Figure 1a and Figure 1b , illustrates the rotation volume envelope of the rotor (Example 7), which includes a cylindrical portion A and a truncated conical portion B, the truncated conical portion B includes five cutout portions C1, and illustrates the rotation volume of the cutout portions. Figure 1c The cross-sectional area of ​​the rotor including five cutout portions C2 is illustrated, illustrating the rotational cross-sectional area of ​​the cutout portions. The rotational volume can be calculated by calculating the volume of the cylindrical component and the frustoconical component and adding them together. Although there is a trend to increase the rotational volume of the rotor to meet the needs of larger process vessels, the increase in size and speed creates increased mechanical and erosion stresses on the rotor. To avoid these stresses, which can shorten the operating life of the rotor, more erosion-resistant materials and innovative rotor designs can be used. Figure 1b The portion indicated by reference numeral C1 extends from the rotor's rotation volume envelope to the rotor's periphery and represents a rotor cutout portion that contributes to the rotor's vortex formation efficiency. The utility model aims to increase the rotor's vortex formation efficiency while maintaining acceptable mixing efficiency.

[0133] use" Professional 2023” 3D CAD software determines the rotating area and rotating volume of the rotor and its components. As indicated in Table 2, the volume component of the cutout portion of Example 6 accounts for 54% of the total rotating volume, of which the mixing zone accounts for 5% of the total rotating volume of the rotor.

[0134] refer to Figure 2a to Figure 2b , illustrates a rotor 10 for degassing molten metals, 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, and five supports 40 extend radially outward from the central axis of the rotor and connect the top portion 20 and the base portion 30 together.

[0135] The fluxing gas is supplied to an opening 60 in the top portion 20 that is continuous with the manifold portion 50. From the opening 60 to the periphery of the support, the height of the top portion may taper. The base portion typically has a flat outer base. The inner portions of the bottom portion and the top portion may include contours consistent with machining tools used to remove material during the one-piece block construction process. The manifold portion is typically cylindrical or frustoconical in shape. The diameter of the manifold portion 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 greater than the diameter of the opening 60. The fluxing gas is distributed laterally from the manifold portion through the mixing zone inlet 70 into the mixing zone 90, which forms at least a portion of the void between the top portion 20 and the base portion 30. In embodiments where the opening and the manifold portion have the same diameter, the mixing zone and the void may consist of the same space.

[0136] like Figure 2b As indicated in the cross-sectional top view in FIG. 1 , there are five mixing zones 90, each having a mixing zone inlet 70 and a mixing zone outlet 100. The outlet dimension S2 is greater than the inlet dimension S1. When the rotor is operating, the larger outlet dimension facilitates the entry of molten metal into the mixing zone. In other embodiments, the inlet and outlet diameters may be the same (e.g., Figure 3b , Example 1).

[0137] The mixing zone outlet 100 is at least partially defined by a cut-out 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 thus the rotating area may be defined as π×D 2 / 4, where D is the diameter of the rotor. The boundary of the rotating area is given by Figure 2b The dashed circle with a diameter of 220 mm is shown as an example.

[0138] It has been found that an increase in the volume (or cross-sectional area) of the mixing zone is associated with an increase in the degassing efficiency, which is the amount of air in the molten metal container ( Fig.16a and Fig.16b ) is measured by the volume percent distribution of fluxing gas in the rotor. It has also been found that an increase in the cutout portion 80 in the rotor is associated with an improvement in vortex formation, as measured by the depth of the vortex in the molten metal container after a specified time.

[0139] In order to maximize degassing and vortex formation performance, it is desirable to reduce the ratio of cross-sectional area / volume occupied by the manifold and the support. In the case of the support, the circumferential thickness T1 of the periphery of the support 40 can be reduced. In addition, the maximum thickness of the support can be reduced. In some embodiments, the thickness of the rotor is substantially uniform (e.g., Fig.10a and Fig.10b , Example 9).

[0140] 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 extending mixing zone can be formed by Fig.10a The linear profile between adjacent supports indicated by the dashed lines 200 in , 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 so that the supports are higher than the extended top portions. In this configuration, additional rotating flow is obtained from the supports, which act as rotor blades above the top portion of the mixing zone. Compared to examples such as Example 4 ( Figure 2a This has the advantage of reducing the weight of the rotor and partially offsetting the rotational volume loss for the mixing zone compared to the top portion extending to the top of the rotor as exemplified in FIG. 1. In the case of a top portion thickness of 15 mm, the height of the top cutout portion may be in the range of about 20 mm to 50 mm, depending on the total height of the rotor.

[0141] experiment

[0142] Simulation Modeling

[0143] Using molten aluminum alloy (AlSi7Mg0.3) and nitrogen, a computer gas-fluid dynamics model (Flow3D TM Software) to evaluate the vortex formation performance and gas diffusion performance of a series of rotors. The diameter of each rotor is 220 mm. The height of each rotor is 95 mm. The difference is that the comparative example C-1 ( Fig.11a and Fig.11b ) and Comparative Example C-4 ( Fig.14a and Fig.14b ) was 85 mm in height. The base portion thickness of Examples 1 to 8 was 15 mm. For Examples 1 to 7, the top portion / support gradually tapers from a height of 95 mm to a height of 60 mm at the periphery of the rotating zone. In Example 8, the top portion / support gradually tapers from a height of 95 mm to a height of 70 mm at the periphery of the rotating zone. The height H of the mixing zone was 30 mm for Examples 1 to 7 and 55 mm for Example 8.

[0144] The degassing efficiency was determined by placing the rotor at an immersion depth of 700 mm (150 mm from the bottom) in a container of 784 mm inner diameter with baffles (600 mm long x 135 mm wide x 30 mm thick) placed parallel to the axis at a distance of approximately 45 mm, and measuring the volume percentage occupied by the fluxing gas bubbles after degassing at a rotation speed of 450 rpm for a time of 15 seconds. The higher the volume percentage occupied, the more efficient the degassing process.

[0145] The vortex formation efficiency was determined under similar conditions (except for the absence of baffles and a rotor speed of 680 rpm) where the depth of the vortex from the surface was measured after the system was in vortex formation mode for 40 seconds.

[0146] Basin test

[0147] Preparation of the basin:

[0148] A cylindrical container of dimensions 1000 mm in diameter and 1000 mm in height was filled with water up to a height of 700 mm. The primary oxygen meter was located at 100 mm from the bottom of the container, while the auxiliary oxygen meter was located at 500 mm from the bottom.

[0149] Initially, water was washed with O 2 saturated until it reaches a concentration of 17 ppm. 2 When the concentration drops to 17-15ppm, start N 2 The degassing process was carried out using different impeller designs and a rotation speed of 300 rpm.

[0150] Data from the oxygen meter were recorded every 50 seconds until the total duration reached 450 seconds. 2 The impeller design with the content is considered to be the most efficient design.

[0151] In a cylindrical container filled with water up to a height of 700 mm, vortices were generated using different impeller designs and a rotation speed of 450 rpm. The vortex progress was video recorded (the camera was placed in a fixed position) and reviewed later to determine the vortex progress measured in seconds in increments of 100 mm. The time taken to achieve a vortex depth of 400 mm when the rotor was operated at 450 rpm is recorded in Table 2. The shorter the time, the more efficient the rotor is in forming the vortex.

[0152] result

[0153] As indicated in Tables 1 and 2, both the vortex formation and flux gas dispersion efficiency of the rotor design of the present invention are superior to the comparative examples of the prior art.

[0154] The superior vortex formation characteristics of the rotor design of the present invention can be attributed to the relatively large fraction of the rotor volume occupied by the cutout portion, with examples including cutout portions ranging from 29% to 64% of the total rotating volume of the rotor. In addition, despite the relatively low proportion of the mixing zone volume (and cross-sectional area), surprisingly, the rotor also possesses more efficient mixing properties, such as lower residual O 2 This is at least partly due to the formation of turbulent mixing between the molten metal and the gas in the countercurrent arrangement.

[0155] In Comparative Example C-1 ( Fig.11a and Fig.11b ), the high mixing zone size enables excellent mixing efficiency, however the cutouts are unable to deliver sufficient volume of molten metal-fluxing gas dispersion to effectively form a vortex. In fact, according to the definition of the cutout, Comparative Example C-1 does not include a cutout, as only the top portion of the rotor includes a cutout. Therefore, it is not surprising that this rotor design has the worst vortex formation performance (Table 2).

[0156] Comparative Example C-3 ( Fig.13a and Fig.13b ) despite including a similar mixing zone size as the rotor in Example 4, has significantly lower mixing efficiency. It is believed that having fewer but larger mixing zones is detrimental to promoting high shear zones because the larger mixing zone size enables some fluxing gas to be transported through the mixing zone without being effectively dispersed into the molten metal stream. In addition, the reduced number of supports used as blades reduces further dispersion of the fluxing gas within the cutout area. Therefore, there is a balance between the proportion of the rotor allocated to the mixing zone and the number of mixing zones to enable a sufficiently high shear environment.

[0157] In Comparative Example C-4 ( Fig.14a and Fig.14b ), the fluxing gas and molten metal have a greater tendency to flow in the lateral direction due to the centrifugal lateral forces that both are subjected to once entering the central mixing zone. The degree of counterflow is believed to be relatively low because the lateral passages provide a path of lower resistance and lower shear rate. In contrast, the mixing zone of the present invention forces the gas and molten metal to collide in opposite lateral directions (high shear counterflow), wherein the forward flow is only achieved after the force of the fluxing gas flow drives the molten metal-gas dispersion back from the mixing zone outlet against the flow of the incoming molten metal flow.

[0158] In Comparative Example C-5 ( Fig.15a and Fig.15b ), the base manifold inner diameter (ID-B) has been increased to extend almost to the periphery 200 of the rotor. The supports 210 that do exist are located at the periphery of the rotor. The positions of the supports are such that the rotor has no mixing zone. The space between adjacent supports is occupied by the cutout portions 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 poorer than in the design of the present invention.

[0159] Table 1 (Dimensions, unit: mm)

[0160]

[0161] It is clear from Table 2 that an increase in the percentage of cutout area is associated with an increase in vortex efficiency in both the simulation modeling and the water basin test. Likewise, an increase in the mixing area is associated with an increase in mixing efficiency.

[0162] As illustrated in Examples 1 to 3 (symmetric) and Examples 6 and 7 (asymmetric), the size of the cutout can be maximized by reducing the relative sizes of the support, manifold section, and mixing zone (top-down perspective). Maintaining a sufficient proportion of the high shear mixing zone is expected to maintain acceptable dispersion efficiency. From the results, the symmetric rotor appears to perform slightly better than the asymmetric rotor from a vortex formation performance perspective.

[0163] Compared to the rotor of Example 4, Example 8 includes a higher proportion of mixing zones and cutout portions. This is achieved by reducing the proportion of the support and manifold portions of the rotor. As a result, both vortex and dispersion efficiency can be expected to be improved relative to Example 4. However, the experimental results show that although the vortex formation efficiency is improved, the vortex formation efficiency is improved at 0. 2 The dispersion efficiency measured in the residual content of 100 rpm was adversely affected. This may be a result of the rotor design creating additional surface area in the degassing mode (300 rpm) resulting in increased oxygen reabsorption. This emphasizes the need to be able to balance the rotor design with the specific application, including vessel size and configuration. In addition, the optimal degassing rotor speed should be selected to minimize oxygen reabsorption.

[0164] It should be noted that for commercial reasons, a balance needs to be struck between manufacturability, durability, swirl and dispersion efficiency performance. The use of carbon ceramic composites allows for greater design flexibility due to the material's greater resistance to erosion and the ability to create designs with larger cutout and mixing zone volumes relative to the total rotating volume.

[0165] Effect of mixing zone size.

[0166] For example, the only O in Example 8 with a content of 20% or more is recorded. 2 The results of the content (Table 2). The mixing zone size of Example 8 has the highest outlet dimension S2. In addition, Example 8 has an increased mixing zone height compared to the other examples. This emphasizes that the narrower mixing zone promotes improved mixing, which is consistent with the increase in turbulence in the mixing zone indicated by the theory underlying the Reynolds number.

[0167] Although Comparative Example C-2 has the narrowest mixing zone size (35 mm), the deoxygenation efficiency of this rotor is still lower than all rotors under the present invention, thereby highlighting that the base opening of Comparative Example C-2 has a negative impact on the deoxygenation efficiency relative to the design of the present invention.

[0168] It should be understood that modifications and variations can be made without departing from the spirit and scope of the novel concepts of the present invention.

[0169]

[0170] The present invention relates to but is not limited to the following exemplary aspects:

[0171] Clause 1. A molten metal degassing device, characterized in that the molten metal degassing device comprises:

[0172] A hollow shaft, the hollow shaft being used to convey a gas flow;

[0173] 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 comprises an opening 60 for allowing gas to enter from the hollow shaft;

[0174] In the range of 3 to 8 support members 40, each of which extends radially outward and is connected to the top portion 20 and the base portion 30;

[0175] a manifold portion 50 for radially distributing gas from the hollow shaft through a mixing zone inlet 70;

[0176] a mixing zone 90 continuous with the mixing zone inlet 70 and radially offset from the manifold portion, wherein the top portion 20 and the base portion 30 and adjacent support members 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 peripheral edges of the top portion 20, the base portion 30 and adjacent support members 40 define a mixing zone outlet 100; and

[0177] a cutout portion 80, the cutout portion being located between the rotor's rotation volume envelope and the rotor's periphery,

[0178] Therein, the cutout portion 80 is within a range between 25% and 75% of the rotational volume of the rotor.

[0179] Clause 2. The molten metal degassing device according to Clause 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 0.0 to 0.38.

[0180] Clause 3. A molten metal degassing device according to any of the preceding clauses, characterized in that the minimum transverse dimension of the mixing zone outlet 100 is at least 28 mm.

[0181] Clause 4. A molten metal degassing device according to any of the preceding clauses, characterized in that the base portion 30 does not comprise an opening.

[0182] Clause 5. A molten metal degassing apparatus according to any of the preceding clauses, wherein the base portion 30 comprises an opening which is not large enough to allow molten metal to be drawn into the opening and mix with the gas in the manifold portion.

[0183] Clause 6. A molten metal degassing device according to any of the preceding clauses, 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 .

[0184] Clause 7. The molten metal degassing device according to any of the preceding clauses, characterized in that the cut-out portion 80 comprises at least 26% of the rotational volume of the rotor.

[0185] Clause 8. A molten metal degassing device according to any one of the preceding clauses, characterised in that the cross-sectional area of ​​the mixing zone is at least 5% of the rotational area of ​​the rotor.

[0186] Clause 9. A molten metal degassing device according to any one of the preceding clauses, characterized in that the volume of the mixing zone is in the range between 1% and 25% of the rotational volume of the rotor.

[0187] Clause 10. The molten metal degassing apparatus of Clause 9, wherein the volume of the mixing zone is at least 3% of the rotational volume of the rotor.

[0188] Clause 11. The molten metal degassing device according to any one of the preceding clauses, characterized in that the sum of the volume of the mixing zone and the volume of the cutout portion is in the range of 30% to 80% of the rotational volume of the rotor.

[0189] Clause 12. A molten metal degassing device according to any one of the preceding clauses, characterized in that the sum of the volume of the mixing zone and the volume of the cut-out portion is at least 36% of the rotational volume of the rotor.

[0190] Clause 13. A molten metal degassing device according to any one of the preceding clauses, characterized in that the sum of the cross-sectional area of ​​the mixing zone and the cross-sectional area of ​​the cutout portion is in the range of 50% to 90% of the rotation area of ​​the rotor.

[0191] Clause 14. A molten metal degassing device according to any one of the preceding clauses, characterized in that the sum of the cross-sectional area of ​​the mixing zone and the cross-sectional area of ​​the cut-out portion is at least 59% of the rotational area of ​​the rotor.

[0192] Clause 15. A molten metal degassing device according to any one of the preceding clauses, wherein the ratio of the cross-sectional area of ​​the cutout portion to the cross-sectional area of ​​the mixing zone is 1.0 or greater.

[0193] Clause 16. A molten metal degassing apparatus according to any one of the preceding clauses, wherein the cross-sectional area of ​​the manifold portion does not exceed 10% of the rotational area of ​​the rotor.

[0194] Clause 17. The molten metal degassing device according to any of the preceding clauses, characterized in that each of the support members 40 comprises a circumferential thickness T1 in the range of 8 mm to 20 mm.

[0195] Clause 18. The molten metal degassing apparatus according to any of the preceding clauses, wherein each mixing zone outlet 100 spans at least 50% of the circumference between the circumferential ends of an adjacent pair of support members 40.

[0196] Clause 19. A molten metal degassing device according to any of the preceding clauses, characterized in that the cut-out portion 80 comprises: a first length, the first length extending from the periphery of the cut-out portion originating from the peripheral end of the support member to a turning point of the cut-out portion closest to the central axis of the rotor; and a second length, the second length extending from the turning point to the peripheral end of the adjacent support member defining the cut-out portion, the first length being greater than the second length.

[0197] Clause 20. The molten metal degassing device according to any of the preceding clauses, characterized in that the cut-out portion 80 extends over a distance greater than 50% of the radius of the rotor.

[0198] Clause 21. A molten metal degassing device according to any of the preceding clauses, wherein the cut-out portion 80 extends to more than 55% of the radius of the rotor.

[0199] Clause 22. The molten metal degassing device according to any of the preceding clauses, characterized in that the rotor 10 comprises or consists of a carbon-ceramic composite material.

[0200] Clause 23. A molten metal degassing apparatus according to any one of the preceding clauses, wherein each mixing zone inlet 70 forms a portion of a circumference of a circle having a radius not exceeding 50 mm.

[0201] Clause 24. A molten metal degassing system, characterized in that the molten metal degassing system comprises a molten metal degassing device according to any one of Clauses 1 to 23 and a container for molten metal.

[0202] Clause 25. A molten metal degassing system according to Clause 24, wherein the inner diameter of the container is in the range of 600 mm to 2000 mm.

[0203] Clause 26. The molten metal degassing system of Clause 25, wherein a ratio of the diameter of the rotor to the inner diameter of the vessel is in the range of 0.18 to 0.30.

[0204] Clause 27. The molten metal degassing system according to Clause 25, characterized in that the ratio of the diameter of the rotor 10 to the inner diameter of the container is less than 0.23.

[0205] Clause 28. A molten metal degassing system according to any one of clauses 25 to 27, wherein the inner diameter of the vessel is at least 1000 mm.

[0206] Clause 29. A process for degassing molten metal using the molten metal degassing apparatus according to any one of clauses 1 to 23 or the molten metal degassing system according to any one of clauses 24 to 28.

[0207] Clause 30. The process of Clause 29, wherein the rotor rotates at a first speed greater than 300 rpm in the vortex forming mode.

[0208] Clause 31. The process of clause 30, wherein after rotating in the vortexing mode, the rotor is rotated at a second speed in a degassing mode, wherein the second speed is at least 50 rpm lower than the first speed.

[0209] Clause 32. A process according to clause 31, wherein for a 220 mm diameter rotor in a 1000 mm diameter vessel filled to a level of 700 mm with water, in order to obtain a vortex depth of at least 400 mm after 15 seconds and a residual O of not more than 20% v / v after 450 seconds, 2 The average of the first speed and the second speed of the content does not exceed 450 rpm, and the container is provided with oxygen probes arranged at 100 mm and 500 mm from the bottom of the container.

[0210] Clause 33. The process of clause 32, wherein the average of the first speed and the second speed does not exceed 500 rpm.

Claims

1. A molten metal degassing device, characterized in that: The molten metal degassing device comprises: A hollow shaft, the hollow shaft being used to convey a gas flow; 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) comprises an opening (60) for allowing gas to enter from the hollow shaft; In the range of 3 to 8 support members (40), each of which extends radially outward and is connected to the top portion (20) and the base portion (30); a manifold portion (50) for radially distributing gas from the hollow shaft through a mixing zone inlet (70); a mixing zone (90) continuous with the mixing zone inlet (70) and radially offset from the manifold portion, wherein the top portion (20) and the base portion (30) and adjacent support members (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 peripheral edges of the top portion (20), the base portion (30) and adjacent support members (40) define a mixing zone outlet (100); and a cutout portion (80) located between a rotation volume envelope of the rotor and a periphery of the rotor, Wherein, the cutout portion (80) is within a range between 25% and 75% of the rotational volume of the rotor.

2. The molten metal degassing device 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 0.0 to 0.

38.

3. The molten metal degassing device according to claim 1, characterized in that: The mixing zone outlet (100) has a minimum transverse dimension of at least 28 mm.

4. The molten metal degassing device according to claim 1, characterized in that the base portion (30) does not include an opening.

5. The molten metal degassing device according to claim 1, characterized in that: The base portion (30) includes an opening that is not large enough to allow molten metal to be drawn into the opening and mix with gas in the manifold portion.

6. The molten metal degassing device according to claim 1, 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 molten metal degassing device according to claim 1, characterized in that: The cut-out portion (80) comprises at least 26% of the rotational volume of the rotor.

8. The molten metal degassing device according to claim 1, characterized in that: The cross-sectional area of ​​the mixing zone is at least 5% of the rotational area of ​​the rotor.

9. The molten metal degassing device according to claim 1, characterized in that: The volume of the mixing zone is in the range of between 1% and 25% of the rotational volume of the rotor.

10. The molten metal degassing device 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 molten metal degassing device according to claim 1, characterized in that: A sum of a volume of the mixing zone and a volume of the cutout portion is in a range of 30% to 80% of a rotation volume of the rotor.

12. The molten metal degassing device according to claim 1, characterized in that: The sum of the volume of the mixing zone and the volume of the cutout portion is at least 36% of the rotational volume of the rotor.

13. The molten metal degassing device according to claim 1, characterized in that: A sum of a cross-sectional area of ​​the mixing zone and a cross-sectional area of ​​the cutout portion is in a range of 50% to 90% of a rotation area of ​​the rotor.

14. The molten metal degassing device according to claim 1, characterized in that: The sum of the cross-sectional area of ​​the mixing zone and the cross-sectional area of ​​the cutout portion is at least 59% of the rotational area of ​​the rotor.

15. The molten metal degassing device according to claim 1, characterized in that: A ratio of a cross-sectional area of ​​the cutout portion to a cross-sectional area of ​​the mixing zone is 1.0 or more.

16. The molten metal degassing device according to claim 1, characterized in that: The cross-sectional area of ​​the manifold portion does not exceed 10% of the rotational area of ​​the rotor.

17. The molten metal degassing device according to claim 1, characterized in that: Each of the supports (40) comprises a circumferential thickness (T1) in the range of 8 mm to 20 mm.

18. The molten metal degassing device according to claim 1, characterized in that: Each mixing zone outlet (100) spans at least 50% of the circumference between the circumferential ends of an adjacent pair of support members (40).

19. The molten metal degassing device according to claim 1, characterized in that: The cutout portion (80) includes: a first length, the 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 central axis of the rotor; and a second length, the second length extending from the turning point to the peripheral end of the adjacent support member defining the cutout portion, the first length being greater than the second length.

20. The molten metal degassing device according to claim 1, characterized in that: The cut-out portion (80) extends over a distance greater than 50% of the radius of the rotor.

21. The molten metal degassing device according to claim 1, characterized in that: The cutout portion (80) extends to greater than 55% of the radius of the rotor.

22. The molten metal degassing device according to claim 1, characterized in that: Each mixing zone inlet (70) forms a portion of the circumference of a circle having a radius not exceeding 50 mm.

23. A molten metal degassing system, characterized in that: The molten metal degassing system comprises a molten metal degassing device according to any one of claims 1 to 22 and a container for molten metal.

24. The molten metal degassing system according to claim 23, characterized in that The inner diameter of the container is in the range of 600 mm to 2000 mm.

25. The molten metal degassing system according to claim 24, characterized in that The ratio of the diameter of the rotor to the inner diameter of the container is in the range of 0.18 to 0.

30.

26. The molten metal degassing system according to claim 24, characterized in that The ratio of the diameter of the rotor (10) to the inner diameter of the container is less than 0.

23.

27. A molten metal degassing system according to any one of claims 24 to 26, characterized in that The inner diameter of the container is at least 1000 mm.

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