Degassing machine shaft

Abstract

The present invention relates to a degasser shaft for treating molten metal with gas, the shaft comprising: (a) a first end connectable to a drive for rotating the shaft about a longitudinal axis, the first end having a first end outer diameter; (b) a second end having a second end outer diameter connectable to the rotor; the outer diameter of the second end is regarded as the minimum shaft outer diameter close to the rotor; and (c) a passage through which gas flows from the first end to the second end, the passage defined by the inner diameter of the degasser shaft; wherein the degasser shaft has a first portion located at or towards the first end and comprising a first tapered section having a cross-sectional area decreasing towards the second end, and optionally a first constant cross-section section extending from the first tapered section towards the first end, the first part comprises 48% to 100% of the total length of the degasser shaft; and wherein at least the first conical section of the degasser shaft is made of a ceramic composite material.

Description

Technical Field

[0001] The invention relates to a degassing shaft and application of the degassing shaft to degas molten metal, in particular molten aluminum, molten magnesium and alloys thereof. Background Art

[0002] During the degassing process, an inert gas is pumped into the aluminum melt to remove hydrogen and prevent subsequent porosity in the casting. In the rotary degassing method, an inert or chemically inactive gas is purged through a rotating shaft and rotor. The energy of the rotating shaft and rotor causes the formation of a large number of fine bubbles, providing a very high surface area to volume ratio. The large surface area promotes rapid and efficient diffusion of hydrogen into the bubbles, thereby making the activity of hydrogen in the liquid and gas phases equal and removing hydrogen from the melt quickly.

[0003] There are a variety of degassing processes, many of which require the shaft to rotate at high speeds, which results in vibration and high-frequency cyclic bending loads and stresses being imposed on the shaft, concentrated at the end toward the motor connection. Graphite and carbon composite shafts are favored for these types of applications due to their low density, high stiffness, and excellent bending strength compared to shafts made from ceramic composites. However, while graphite shafts have good mechanical properties in these applications, they are susceptible to oxidative corrosion and mechanical erosion when in contact with air atmospheres and molten metals, respectively, resulting in graphite shafts having to be replaced regularly.

[0004] EP 3 180 455 in the name of Pyrotek Corporation addresses this problem by impregnating the carbon composite component with an antioxidant chemical such as the phosphate based oxidation inhibitors disclosed in US 4,439,491.

[0005] WO2022 / 129612, filed in the name of Foseco International Ltd., deals with the rigors of injecting metal additives into molten iron and using gas to carry the metal in powder form into the molten iron, the gas pressure preventing the iron from returning to the rotor shaft. WO2022 / 129612 places a ceramic composite sleeve on a graphite shaft (which would otherwise dissolve in the molten iron) so that the graphite shaft can provide good mechanical properties while the ceramic composite can provide improved resistance to oxidative corrosion and erosion. The graphite shaft and the ceramic composite sleeve are tapered to achieve a close fit between the graphite shaft and the ceramic composite sleeve. However, the mismatch in the coefficient of thermal expansion between the graphite shaft and the ceramic composite sleeve can cause the sealing integrity between the shaft and the sleeve to deteriorate, thereby shortening the working life of the shaft / sleeve combination.

[0006] WO 2004 / 029307 A1 discloses a degasser shaft which tapers towards the rotor head. Thus, the peripheral speed of the shaft in the molten metal decreases with increasing depth, which is believed to minimize undesirable eddy currents. WO 2004 / 029307 A1 does not define the material of the shaft.

[0007] Despite these advances, there remains a need for improved degasser shafts that have longer operating life; that can be manufactured without complex materials or processes; and that can be used in high frequency cyclic loading or stress applications (also known as fatigue applications). Summary of the invention

[0008] In a first aspect of the invention there is provided a degasser shaft for treating molten metal with a gas, the shaft comprising;

[0009] (a) a first end connectable to a drive for rotating the shaft about a longitudinal axis, the first end having a first end outer diameter;

[0010] (b) a second end having a second end outer diameter, and the second end

[0011] may be connected to the rotor; or

[0012] Integral to the rotor, the second end outer diameter being considered to be the smallest shaft outer diameter proximate to the rotor; and

[0013] (c) a passage through which gas flows from the first end to the second end, the passage being defined by an inner diameter of the degasser shaft;

[0014] wherein the degasser shaft has a first portion, the first portion being located at or toward the first end and comprising a first tapered section and an optional first constant cross-section section, the cross-sectional area of ​​the first tapered section decreasing toward the second end, the first constant cross-section section extending from the first tapered section toward the first end and having a constant cross-sectional area, the first portion comprising between 48% and 100% of the total length of the degasser shaft; and wherein at least the first tapered section of the degasser shaft is constructed of a ceramic composite material.

[0015] "Tapered" refers to a reduction in cross-sectional area, and such reduction may be linear or smooth, such as flaring from a first cross-sectional area to a second cross-sectional area so as to smoothly approach the first cross-sectional area and / or the second cross-sectional area.

[0016] The conical section is preferably frustoconical. The constant cross-section section is preferably cylindrical.

[0017] In some embodiments, the degasser shaft further comprises one or both of the following:

[0018] a first constant cross-sectional section (having a constant cross-sectional area) that is larger than the minimum cross-sectional area of ​​the degasser shaft and extends continuously from the first tapered section toward the first end; and

[0019] A second constant cross-section segment (having a constant cross-sectional area) extending continuously from the first tapered segment toward the second end.

[0020] In some embodiments, the shaft is comprised of a first portion and an optional second constant cross-section segment. The first portion may include a tapered segment including a tapered segment with an optional constant segment having a cross-sectional area greater than the smallest cross-sectional area of ​​the degasser shaft (e.g., a first cylindrical segment and an intermediate cylindrical segment disposed between the frustoconical segments).

[0021] The degasser shaft of the present invention has a long operating life because the shaft is resistant to both oxidative corrosion, melt mechanical erosion and premature mechanical failure. Although the innovative design features can be applied to any material suitable for use as a degasser shaft, it is particularly advantageous when the degasser shaft is made of a ceramic composite material. Counterintuitively, the goal of extending operating life can be improved by using a composite material that generally has a lower bending fatigue strength than graphite-based compositions.

[0022] The conical (e.g., truncated conical) portion may include one or more conical segments that constitute at least 50% or at least 60% or at least 70% or at least 80% or at least 90% or 100% of the total length of the first portion. The conical segment may include one or more conical segments and an intermediate constant cross-section segment (excluding the first constant cross-section segment or the second constant cross-section segment), the intermediate constant cross-section segment constituting at least 50% or at least 60% or at least 70% or at least 80% or at least 90% or 100% of the total length of the degasser shaft. In some embodiments, one of the plurality of conical segments constitutes no more than 90% or no more than 80% or no more than 70% or no more than 60% of the total length of the degasser shaft. The longer the one or more conical segments, the smaller the angle of incidence with the axis, thereby avoiding local stress concentration if and when the conical segment abuts the optional constant cross-section segment of the degasser shaft.

[0023] For the purpose of the present invention, the constant cross-section segment includes a cylindrical and polygonal prism or any other suitable shape with a constant cross-sectional area. In some embodiments, the constant cross-section segment includes a cylinder. In other embodiments, the constant cross-section segment includes a prismatic polygon, preferably with at least 5 edges, and preferably with at least 7 edges or at least 8 edges. In the embodiment where the constant segment includes a polygonal prism (e.g., a hexagonal prism), the constant cross-section segment can cooperate with a tightening tool (e.g., a wrench) to fasten the degasser shaft to a motor or rotor or its connector. Preferably, the constant cross-section segment does not include any acute angles (e.g., less than 90° or less than 60°) to avoid any stress concentration points in the shaft (e.g., a pentagon or hexagon). The constant portion is preferably symmetrical around the central axis of the degasser shaft. In some embodiments, the constant cross-section segment includes a degasser shaft cross-sectional area, which is at least 5% or at least 8% or at least 10% or at least 12% or at least 15% or at least 20% larger than the minimum cross-sectional area of ​​the degasser shaft adjacent to or at the second end.

[0024] The first portion may comprise at least 50% or at least 52% or at least 55% or at least 58% or at least 60% or at least 70% or at least 80% or at least 90% or at least 95% or 100% of the total length of the degasser shaft. In some embodiments, the first portion may be no more than 90% or no more than 80% or no more than 70% or no more than 60% of the total length of the degasser shaft. A larger first portion may help minimize local areas of concentrated stress and increase shaft stiffness during operation, while a smaller first portion may reduce shaft weight.

[0025] The first constant segment, when present, may represent >0% to 50% of the total length of the shaft; or 5% to 40%; or 10% to 30%. Typically, the first constant segment is at least 5 mm, or at least 10 mm, or at least 20 mm. The first constant segment is typically no more than 1000 mm, or no more than 800 mm, or no more than 600 mm, or no more than 500 mm, or no more than 400 mm. In some embodiments, the first constant segment comprises a melt-line of the shaft.

[0026] When the first portion does not extend over the entire length of the shaft, the remainder of the shaft (not part of the first portion) may include a second constant segment (including a cylindrical segment or a polygonal prism segment) defined by the second end diameter and extending from the first portion to the second end. The second end outer diameter is generally the smallest diameter (or effective diameter) of the shaft.

[0027] The second constant segment, when present, may represent >0% to 52% of the total length of the shaft. Typically, the second constant segment is at least 5 mm or at least 10 mm or at least 20 mm or at least 40 mm or at least 60 mm. The first constant segment is typically no more than 1000 mm or no more than 800 mm or no more than 600 mm or no more than 500 mm or no more than 400 mm.

[0028] The first shaft end outer diameter is typically the largest outer diameter of the shaft. In some embodiments, the first shaft end outer diameter defines a first constant section of the shaft extending from the end of the tapered section toward the first end of the shaft.

[0029] In other embodiments, the first portion includes two or more tapered portions connecting the first shaft end diameter to the second shaft end outer diameter. The outer diameter of the tapered portions can gradually decrease as they advance toward the second end of the shaft. Each tapered portion can be separated by one or more constant segments. The benefit of this "step down" structure is that the shaft outer diameter (and thus stiffness) of each portion of the shaft can be customized to offset local vibrations and therefore offset stresses along the degasser shaft under operating conditions.

[0030] In some embodiments, the first constant section extends to the first end of the shaft.

[0031] The motor guard or housing associated with the motor may be such that the outer diameter of the first end needs to be smaller than the maximum outer diameter of the shaft to enable the first shaft end to fit within these auxiliary components of the degasser system. In these embodiments, the first end outer diameter may be continuously connected to the maximum outer diameter of the shaft by a tapered section.

[0032] Connectors and seamless connectivity

[0033] The first end of the shaft may be connected to the motor and the second end of the shaft may be connected to the rotor. The connection to the motor and / or the rotor may be a male connector; a female connector; or any other suitable connection mechanism.

[0034] In some embodiments, the first end is connectable to the motor via a female connector. The female connector can be a spiral threaded coupling device (e.g., a spiral threaded cavity). In order to reduce stress concentration around the female connector, the female connector preferably includes an arcuate bridging connector to the passage. The arcuate bridging connector preferably has a radius of at least 5 mm or at least 10 mm. The arcuate bridging connector can also be incorporated into the male connector. When there is a seamless connection between the shaft and the rotor (or a flange connection with an increased shaft diameter), the second end considered is considered to be the minimum diameter of the shaft near the rotor. This ensures that the second end does not include any tapered expansion of the device toward the wider diameter of the rotor, and the rotor is generally disc-shaped.

[0035] Degasser shaft size

[0036] The degasser shaft is preferably a monolithic structure. In some embodiments, the degasser shaft extends from the inner diameter of the defined passage and extends to the outer diameter. The outer surface of the degasser shaft is defined by the outer diameter of the shaft. In operation, the outer surface of the degasser shaft is in contact with the molten metal in the submerged zone and the hot air atmosphere in the nearby non-submerged zone, and the thickness of the degasser rotor (i.e., outer shaft diameter-inner shaft diameter) provides excellent oxidation corrosion resistance and erosion resistance compared to a graphite shaft of the same thickness (with or in combination with an oxidation corrosion protection sleeve). Superior oxidation resistance and erosion corrosion resistance can also make the shaft wall thinner to reduce the weight of the shaft while maintaining sufficient oxidation resistance and erosion resistance.

[0037] The length of the degasser shaft is measured from the first end to the second end along the central axis. The length does not include an extension belonging to a connector (e.g., a male connector). When the second end of the degasser shaft includes a rotor (i.e., the rotor is integral with the shaft or seamlessly connected (e.g., a one-piece construction)), the second end is considered to terminate at the location where the minimum shaft diameter is closest to the rotor. Therefore, the tapered flange component whose diameter increases toward the end of the shaft to match the rotor diameter is not included in the shaft length calculation.

[0038] The length of the degasser shaft typically ranges from at least 250 mm to no more than 2500 mm, and typically no more than 2200 mm or no more than 2000 mm. The length of the shaft can be determined based on the requirements of the degassing system. However, at a certain speed, once the shaft length extends to 2000 mm and above, the vibration-derived stress on the degasser shaft will increase significantly and shorten its durability.

[0039] Degasser shafts can be divided into three categories, as shown in Table 1 below:

[0040] Table 1

[0041]

[0042] As shown in Table 1, as the degasser shaft becomes longer, the speed at which it operates decreases. This is at least partially related to increased rotordynamic instabilities, which increase the speed of a long shaft, which translates into additional stresses placed on the longer degasser shaft.

[0043] For long shafts, the maximum outer diameter of the shaft (D 最大值 ) is typically between 125 mm and 200 mm. In some embodiments, the maximum outer diameter is at least 130 mm or at least 140 mm or at least 150 mm or at least 160 mm. For a constant cross-sectional weight, the larger the diameter, the higher the cross-sectional moment of inertia, and the harder the shaft at that location. The minimum outer diameter (D 最小值 ) is usually between 60mm and 150mm. The difference between the maximum and minimum outer diameters of the shaft (D最大值 -D 最小值 ) is typically at least 20 mm or at least 25 mm or at least 30 mm or at least 35 mm or at least 40 mm or at least 45 mm or at least 50 mm or at least 55 mm or at least 60 mm. 最大值 -D 最小值 Usually no more than 150mm or no more than 100mm.

[0044] For medium shafts, the maximum outer diameter of the shaft (D 最大值 ) is typically between 100 mm and 150 mm. In some embodiments, the maximum outer diameter is at least 110 mm or at least 115 mm or at least 120 mm or at least 125 mm. The minimum outer diameter (D 最小值 ) is usually between 60mm and 120mm. The difference between the maximum and minimum outer diameters of the shaft (D 最大值 -D 最小值 ) is typically at least 20 mm or at least 25 mm or at least 30 mm or at least 35 mm or at least 40 mm or at least 45 mm or at least 50 mm. In some embodiments, D 最大值 -D 最小值 Not larger than 90mm.

[0045] For short shafts, the maximum outer diameter of the shaft (D 最大值 ) is typically between 60 mm and 100 mm. In some embodiments, the maximum outer diameter is at least 65 mm or at least 70 mm or at least 75 mm or at least 80 mm. The minimum outer diameter (D 最小值 ) is usually between 40mm and 80mm. The difference between the maximum and minimum outer diameters of the shaft (D 最大值 -D 最小值 ) is typically at least 10 mm or at least 15 mm or at least 20 mm or at least 25 mm or at least 30 mm or at least 35 mm or at least 40 mm. 最大值 -D 最小值 Usually no more than 60mm.

[0046] In some embodiments, the outer diameter of the first end may be greater than D 最大值 As small as 100mm or as small as 50mm.

[0047] In some embodiments, D 最大值 With D 最小值 The ratio of is at least 1.1 or at least 1.2 or at least 1.3 or at least 1.4 or at least 1.5 or at least 1.6 or at least 1.7 or at least 1.8. 最大值 With D 最小值 The ratio is usually no more than 5 or no more than 4 or no more than 3 or no more than 2. The higher D 最大值 With D最小值 The ratio promotes distribution of weight toward the top (ie, first end) of the shaft, thereby reducing the tendency of the shaft to vibrate excessively during operation, reducing stresses and higher thicknesses at the weld line.

[0048] In some embodiments, the minimum shaft outer diameter and the minimum wall thickness (D 最小值 / wall 最小值 ) is at least 2.7 or at least 2.9 or at least 3.1 or at least 3.3. The higher the ratio, the harder the shaft and the lighter the weight.

[0049] In some embodiments, the ratio of the maximum outer diameter to the minimum outer diameter of the degasser shaft is in a range of 1.05:1 to 3.0:1, or in a range of 1.1:1 to 2.5:1, or in a range of 1.2:1 to 2.0:1.

[0050] The largest shaft outer diameter is usually located at the first end or around the weld line. The smallest shaft outer diameter is usually at or around the second end of the shaft.

[0051] In some embodiments, the degassing shaft includes an angle of incidence between the tapered section and the constant cross-section section (or central axis) that is no greater than 16°, no greater than 15°, no greater than 14°, or no greater than 13°, or no greater than 12°, or no greater than 10°. Larger angles of incidence may cause bending stresses to concentrate at the intersection, leading to potential mechanical failure. The angle of incidence is greater than 0°, and is typically at least 0.3°, or at least 0.5°, or at least 1.0°, or at least 2.0°, or at least 3.0°, or at least 4.0°, or at least 5.0°, to enable the desired change in shaft diameter to achieve stiffness and weight targets.

[0052] The internal diameter of the shaft (i.e., passage) can be in the range of 10mm to 80mm or 12mm to 70mm or 15mm to 60mm or 18mm to 50mm or 20mm to 40mm. In some embodiments, the internal diameter of the shaft is at least 25mm or at least 30mm or at least 40mm. Larger internal diameter can achieve one or both of a larger external diameter and a thinner wall thickness. For constant cross-sectional weight, a larger external diameter contributes to a harder shaft, and thinner walls contribute to a lower degasser shaft weight. The internal diameter can be constant along the length of the shaft, or the internal diameter can change as the internal diameter is reduced along the shaft from the first end to the second end. When the first end or the second end include a female connector, the internal diameter is measured in the cavity next to the female connector.

[0053] The minimum shaft wall thickness is generally at least 12mm or at least 15mm or at least 18mm or at least 20mm or at least 22mm or at least 25mm or at least 27mm or at least 30mm or at least 35mm or at least 40mm. The minimum shaft wall thickness is generally positioned toward the second end of the degasser shaft, and generally corresponds to the minimum outer diameter of the degasser shaft. For the major shaft, the minimum wall thickness is generally in the range of 20mm to 45mm or 22mm to 42mm or 25mm to 40mm. For the medium shaft, the minimum wall thickness is generally in the range of 14mm to 25mm or 16mm to 22mm or 17mm to 21mm. For the minor shaft, the minimum wall thickness is generally in the range of 10mm to 17mm or 11mm to 16mm or 12mm to 15mm.

[0054] The maximum shaft wall thickness is usually no more than 80mm or no more than 70mm or no more than 60mm. The maximum shaft wall thickness is usually positioned toward the first end of the degasser shaft, and usually corresponds to one or about position (e.g., ± 50mm) of the weld line (melt line) of the degasser shaft. According to the total length of the shaft and the degasser system configuration, the weld line is usually located between 40mm and 500mm from the first end of the degasser shaft, and in the first part. When the degasser shaft is connected to the motor using a female connector, the weld line is preferably located below the female connector, and is preferably located at least 20mm or at least 40mm below the female connector. Due to corrosion stress concentration, weld lines and female connectors are potential weak areas. Therefore, these areas are preferably separated.

[0055] In some embodiments, the wall thickness at the second end of the shaft is in the range of 12 to 60 mm, or 14 to 50 mm, or 16 to 40 mm; and the wall thickness at the first end or weld line is in the range of 20 to 80 mm, or 22 to 70 mm, or 24 to 60 mm. In some embodiments, the ratio of the minimum shaft thickness (second end) to the maximum shaft thickness (first end or weld line) is in the range of at least 0.3 to less than 1.0, or in the range of 0.4 to less than 0.95, or in the range of at least 0.5 to less than 0.90, or in the range of at least 0.6 to less than 0.85. In some embodiments, the maximum wall thickness (wall thickness) of the degasser shaft is in the range of 12 to 60 mm, or 14 to 50 mm, or 16 to 40 mm; and the wall thickness at the first end or weld line is in the range of 20 to 80 mm, or 22 to 70 mm, or 24 to 60 mm. In some embodiments, the ratio of the minimum shaft thickness (second end) to the maximum shaft thickness (first end or weld line) is in the range of at least 0.3 to less than 1.0, or in the range of 0.4 to less than 0.95, or in the range of at least 0.5 to less than 0.90, or in the range of at least 0.6 to less than 0.85. 最大值 ) is located at or near (e.g., within 10 mm) the location where the degasser shaft has the largest outer diameter, and the minimum wall thickness (wall 最小值 ) is located at or near the second end (e.g., within 10 mm), and wherein the wall 最小值 / wall 最大值The ratio is in the range of 0.75 to 1.0 or in the range of 0.80 to 0.95. By maintaining a relatively similar wall thickness while increasing the diameter of the shaft, weight can be removed from the shaft while the oxidative corrosion resistance of the ceramic composite enables the relatively thin wall thickness to provide adequate oxidative corrosion resistance.

[0056] In some embodiments, D 最大值 / D 最小值 Greater than 1.3, and the wall 最小值 / wall 最大值 In the range of 0.80 to 1.0.

[0057] In some embodiments, the wall thickness of the shaft varies along the length of the shaft. In some embodiments, the wall thickness is greatest toward the first end and thinnest toward the second end. In some embodiments, the wall thickness is greatest at or near the weld line and thinnest toward the second end. The difference in thickness between the thinnest wall and the thickest wall is typically between 10% and 300%, or between 20% and 200%, or between 30% and 100% of the thinnest wall. By varying the thickness of the shaft along the length of the shaft, greater oxidation corrosion resistance and stress resistance (e.g., thicker walls) and vibration minimization can be applied where needed without unnecessarily increasing the weight of the shaft.

[0058] In a preferred embodiment, the degasser shaft comprises:

[0059] a. Overall length, between 250 and 2200 mm;

[0060] b. a first constant section comprising a length in the range of 0 to 600 mm (or 10 mm to 500 mm);

[0061] c. a tapered section adjoining said optional further constant section, the tapered section comprising a diameter that decreases as said tapered section extends toward said second end, said tapered section comprising an axial length in the range of 100 to 2200 mm;

[0062] d. Optional second constant segment

[0063] e. The diameter of the first shaft end is in the range of 60 to 180 mm;

[0064] f. a second shaft end diameter in the range of 45 to 140 mm; and

[0065] g. Channel diameter, in the range of 10 to 60 mm.

[0066] The degasser shaft preferably comprises a ceramic composite material.

[0067] In another preferred embodiment, the short degasser shaft comprises:

[0068] a. Overall length, between 250mm and 600mm (or 280mm and 500mm);

[0069] b. a first constant section comprising a length in the range of 50 to 100 mm;

[0070] c. a tapered section adjacent to the first constant section, the tapered section comprising a diameter that decreases as the tapered section extends toward the second end, the tapered section comprising an axial length in the range of 100 mm to 400 mm;

[0071] d. an optional second constant segment;

[0072] e. The diameter of the first shaft end is in the range of 60 mm to 90 mm;

[0073] f. a second shaft end diameter in the range of 45 mm to 70 mm; and

[0074] g. Channel diameter, in the range of 10mm to 25mm.

[0075] The minimum wall thickness of the short degasser shaft may be in the range of 10 mm to 24 mm, or 12 mm to 22 mm, or 14 mm to 20 mm. The maximum wall thickness may be in the range of 18 mm to 32 mm, or 20 mm to 30 mm, or 22 mm to 28 mm.

[0076] In a preferred embodiment, the mid-size degasser shaft comprises:

[0077] a. Total length, between 500mm and 1500mm;

[0078] b. an optional first constant segment extending from or near the first end, the length of the first constant segment being in the range of 0 mm to 400 mm;

[0079] c. a tapered section adjacent to said optional first constant section, said tapered section comprising a diameter that decreases as said tapered section extends toward said second end when said first constant section is present, said tapered section comprising an axial length in the range of 500 mm to 1500 mm;

[0080] d. an optional second constant section extending continuously from said tapered section to the second end;

[0081] e. The diameter of the first shaft end is in the range of 70 mm to 150 mm (or 80 mm to 140 mm);

[0082] f. a second shaft end diameter in the range of 50 mm to 130 mm (or 60 mm to 120 mm); and

[0083] g. Channel diameter, in the range of 10 mm to 50 mm (or 15 mm to 40 mm).

[0084] The minimum wall thickness of the medium degasser shaft may be in the range of 20 mm to 34 mm, or 22 mm to 32 mm, or 24 mm to 30 mm. The maximum wall thickness may be in the range of 27 mm to 42 mm, or 29 mm to 40 mm, or 31 mm to 38 mm.

[0085] In a preferred embodiment, the long degasser shaft comprises:

[0086] a. Overall length, between 1500mm and 2200mm;

[0087] b. a first constant section extending from or near the first end and including a length in the range of 100 mm to 600 mm (or 120 mm to 500 mm);

[0088] c. a first tapered section continuously adjacent to the first constant section, the first tapered section comprising a diameter that decreases as the tapered section extends toward the second end, the tapered section comprising an axial length in the range of 400 mm to 2200 mm;

[0089] d. An optional second constant section extending continuously from the tapered section to the second end;

[0090] e. an optional second tapered section, continuously adjacent to the end of the first constant section and extending continuously to the first end, and comprising a length of 0 mm to 600 mm (or 10 mm to 500 mm or 120 mm to 350 mm);

[0091] f. The diameter of the first shaft end is in the range of 80 mm to 200 mm (or 90 mm to 180 mm);

[0092] g. a second shaft end diameter in the range of 80 mm to 140 mm; and

[0093] h. Channel diameter, in the range of 10 mm to 60 mm.

[0094] The minimum wall thickness of the long degasser shaft may be in the range of 10 mm to 24 mm, or 12 mm to 22 mm, or 14 mm to 20 mm. The maximum wall thickness may be in the range of 18 mm to 32 mm, or 20 mm to 30 mm, or 22 mm to 28 mm.

[0095] The inner diameter of the degasser shaft defining the passage can be at least 12mm or at least 14mm or at least 16mm or at least 18mm or at least 20mm or at least 22mm or at least 24mm or at least 26mm. The maximum inner diameter of the passage is usually no more than 70mm, or no more than 65mm, or no more than 60mm, or no more than 55mm, or no more than 50mm. The degasser shaft preferably includes a ceramic composite material or is composed of a ceramic composite material. In some embodiments, the degasser shaft does not include any parts or components made mainly of graphite (e.g., at least 50 wt % or at least 80 wt % or at least 98 wt %). Although the graphite parts have good mechanical properties, such as rigidity, they have poor resistance to oxidation corrosion.

[0096] The degasser shaft of the present invention is compatible with a range of degasser systems, including Foseco FDU degasser, STAS degasser, Novelis ALPUR degasser and Hertwich degasser systems. Advantageously, the shaft of the present invention not only provides mechanical durability at varying rotational speeds, but the degasser shaft has excellent resistance to oxidative corrosion to ensure a longer working life.

[0097] Ceramic Composites

[0098] Ceramic composites may include composites comprising refractory particles and graphite flakes in an inorganic (e.g., glass and / or mullite) or organic binder matrix (e.g., ceramic carbon composites). The refractory particles may include any suitable refractory material having suitable mechanical strength, oxidation resistance, erosion resistance, thermal shock resistance, and impact resistance. Suitable particles may include carbides, including silicon carbide; nitrides, including silicon nitride; aluminum oxide, zirconium oxide, and aluminosilicates. The refractory particles are preferably crystalline or partially crystalline. The function of the graphite flakes is primarily to enhance machinability during manufacturing while providing strength to the material. In some embodiments, the ceramic composite may include inorganic fibers, which may enhance the flexural strength of the composite.

[0099] The ceramic composite material can be formed by a ceramic composite precursor material bonded by clay or resin. The ceramic composite formed by a composite precursor bonded by clay can include refractory particles embedded in an aluminosilicate matrix. The aluminosilicate matrix can be glassy and / or crystalline (e.g., mullite). The aluminosilicate matrix is ​​defined as a matrix containing at least 60% by weight, at least 70% by weight, or at least 80% by weight of aluminum oxide + silicon dioxide. The ceramic composite formed by a ceramic composite precursor bonded by a resin can include refractory particles embedded in a carbon matrix.

[0100] Examples of suitable ceramic composites are disclosed in WO2022013523, which is hereby disclosed by reference. Ceramic composites generally have superior resistance to oxidative corrosion compared to carbon composites or graphite-based shafts. However, ceramic composites cannot directly replace graphite and carbon composites due to their higher density and reduced mechanical properties (including lower stiffness and flexural strength).

[0101] The ceramic composite material may be coated or impregnated using compositions and methods known to those skilled in the art.

[0102] Composite material properties

[0103] The ceramic composite material typically comprises a density of at least 1.90 g / cc, or at least 2.0 g / cc, or at least 2.1 g / cc, or at least 2.2 g / cc. The upper limit is typically limited by the refractory material used in the composite material, but is typically less than 2.5 g / cc. Ceramic composite materials comprising a carbon matrix typically have a lower density than clay / glass bonded ceramic composite materials due to the lower density of carbon.

[0104] The stiffness of a material can be determined by its Young's modulus. The Young's modulus of a composite material is typically significantly lower than that of a graphite-based material, which has a Young's modulus of about 10 to 20 GPa. In contrast, the Young's modulus of a ceramic composite can vary with the addition of ingredients, and is typically between 0.5 (or 1.0 or 2.0) and 20 GPa, with many ceramic compositions having a Young's modulus of less than 10 GPa or less than 8 GPa or less than 6 GPa. In one embodiment, the Young's modulus of a ceramic composite is in the range of 0.5 GPa to 10 GPa.

[0105] Tensile bending strength or flexural strength is an index of the ability of a material to withstand cyclic bending stress before mechanical failure, i.e. an index of bending fatigue strength. In one embodiment, the flexural strength of a ceramic composite is in the range of 5MPa to 30MPa. The flexural strength of a ceramic composite can be at least 8MPa or at least 10MPa or at least 12MPa or at least 14MPa, with an upper limit of no more than 30MPa or no more than 25MPa or no more than 20MPa. As known to those skilled in the art, by controlling the particle size and porosity of the composite material, the flexural strength of the ceramic composite, and more importantly, the flexural fatigue strength, can be increased to the upper limit of the scope. The flexural strength of graphite materials is generally greater than the flexural strength of ceramic composites, in the range of 18MPa to 36MPa, and for a given number of cycles and at a given stress ratio, its flexural fatigue strength follows a similar trend.

[0106] operate

[0107] The natural frequency of a shaft is an important design consideration because the amplitude of shaft vibration increases significantly as the shaft speed approaches the shaft's natural frequency. The increase in vibration increases the stress on the shaft, which can lead to premature mechanical failure of the shaft. Therefore, it is desirable that the natural frequency of the shaft be higher than the target operating speed, preferably at least 30% higher.

[0108] There are many factors that can affect the natural frequency of the degasser shaft, including:

[0109] ·Shaft length (shorter shaft = higher natural frequency)

[0110] The weight of the shaft (increased weight = lower natural frequency)

[0111] Shaft stiffness (increased stiffness = higher natural frequency)

[0112] The stiffness of the shaft may be affected by the design of the shaft, including the moment of inertia of the shaft cross section, with the larger the diameter, the harder the shaft. However, an increase in the weight of the shaft may result in a decrease in the natural frequency. The choice of material may also significantly affect the natural frequency of the shaft, with harder materials causing the shaft to have a higher natural frequency. The applicant has found that, through a combination of design modifications and material selection, not only can a longer shaft (e.g., greater than 1.5 m) be produced, it has a natural frequency high enough to enable the shaft to run at a target speed under conditions of high density (>2 g / cc) low stiffness (<10 GPa) materials, the target speed being sufficiently lower than the natural frequency to avoid any vibration amplification. In addition, this purpose can be achieved by a ceramic composite material that can enhance the oxidation corrosion resistance and erosion resistance of the shaft, especially compared to a graphite-based shaft.

[0113] The natural frequency of a long (ie, greater than 1500 mm in length) degasser shaft may be in the range of 150 rpm to 500 rpm, or 200 rpm to 480 rpm, or 250 rpm to 450 rpm.

[0114] In a second aspect of the invention, there is provided a method for degassing a molten metal melt, the method comprising immersing a degassing device into the molten metal melt, the degassing device comprising a degassing shaft according to the first aspect of the invention, and wherein the rotational speed of the degassing shaft is lower than the natural frequency of the shaft.

[0115] The rotational speed of the degassing shaft is preferably at least 20 rpm or at least 40 rpm or at least 50 rpm below the natural frequency of the shaft.

[0116] In one embodiment, the shaft length is in the range of 1.5 to 2.2 meters, or at least 1.8 to 2.2 meters, or at least 1.9 to 2.1 meters, and the natural frequency of the shaft is greater than 300 rpm, or 350 rpm, or 400 rpm.

[0117] When the cross-sectional area of ​​the shaft is not circular, the reference diameter includes the effective diameter. The effective diameter is considered to be the diameter of a circle having the same cross-sectional area as the non-circular shape.

[0118] For purposes of the present invention, a conical segment includes a truncated conical segment and a polygonal prism that includes a cross-sectional area that decreases from one end to the other. For example, a segment of a pyramid would be considered a conical segment. However, in some embodiments, the conical segment does not include any flat surfaces.

[0119] Throughout this specification, flexural strength and transverse flexural strength are used interchangeably.

[0120] For the avoidance of doubt, it should be noted that in this specification, the term "comprising" in relation to a composition is considered to have the meaning of including, containing or possessing, and allows for the presence of other ingredients. The terms "comprising" and "including" should be understood in a similar manner. It should also be noted that no requirement is made for any composition in which the sum of the components exceeds 100%.

[0121] Furthermore, it should be understood that the use of oxide names such as alumina and silica in the compositions does not imply that these materials are in a particular stoichiometric form, but rather refers to the composition of the composite in which the relevant elements are expressed as oxides. It should be understood that the elements may also exist in non-oxide forms.

[0122] For the purposes of the present invention, the length of the tapered section is taken to be the axial length.

[0123] For purposes of the present invention, the degasser shaft is separate and distinct from the degasser shaft sleeve.

[0124] The term "portion" is used to refer to one or more segments.

[0125] Unless otherwise stated or implied, references to diameters are references to outside diameters.

[0126] The determination of minimum and maximum wall thickness of the shaft does not include any measurements around the connection points to the motor or rotor, nor does it include any flange areas immediately adjacent to the rotor. BRIEF DESCRIPTION OF THE DRAWINGS

[0127] Figure 1 is a schematic diagram of a degasser shaft design with a connectable rotor according to the present invention.

[0128] Figure 2 There is no rotor Figure 1 A cross-sectional view of the degasser shaft design and an exploded view showing the female connection portion.

[0129] Figure 3Schematic diagram of the degasser shaft design of Comparative Example 1 (CE-1).

[0130] Figure 4 Schematic diagram of the degasser shaft design of Example 2.

[0131] Figure 5 Schematic diagram of the degasser shaft design of Example 5 and Example 6.

[0132] Figure 6 Schematic diagram of the degasser shaft design of Example 3.

[0133] Figure 7 It's a mechanical failure Figure 3 Photo of the degasser shaft design.

[0134] Figure 8 This is the design diagram of Comparative Example 5 (CE-5).

[0135] Fig. 9 This is the design diagram of Comparative Example 6 (CE-6).

[0136] Fig.10 This is the design drawing of Example 7. DETAILED DESCRIPTION

[0137] The invention is illustrated by reference to a frustoconical conical section and an optional cylindrical section, but the invention is not limited thereto.

[0138] The degasser shaft of the present invention is manufactured using conventional techniques, wherein the raw materials are mixed, dried and filled into a mold, then pressed and sintered or fired at high temperature (e.g., >1000° C.) for a sufficient time to sinter or otherwise harden the binder and ceramic composite together. The degasser shaft preferably comprises one or both of a material and a unitary structure.

[0139] See also Figure 1 and Figure 2 , a schematic diagram of a degasser shaft 10 and a cross-section 110 thereof are shown. The shaft has a first end 20 that can be connected to a motor. The connection is a female connection 50, which may include a helical threaded portion 50 that is suitable for receiving a complementary male connection (not shown) of a motor or a device connected to a motor. In order to avoid stress concentration in the female connector during operation, the connector includes a circular or arcuate transition section 58 located between the helical threaded portion and the channel 100. The degasser shaft also has a second end 30, which second end 30 may include a rotor 40 of one-piece construction, wherein the rotor is seamlessly connected to the shaft. Alternatively, as Figure 2 As shown, the second end of the degasser shaft may include a male helically threaded portion forming a connector 70 that may be connected to a complementary helically threaded female connector (not shown) of the rotor.

[0140] The first end 20 comprises the maximum diameter (D 第一 The second end 30 comprises the smallest diameter (D 第二 ).

[0141] The degasser shaft has an outer diameter 80 and an inner diameter 90 that define a passage 100 extending from the first end 20 to the second end 30. The outer diameter of the degasser shaft defines a frustum of a right circular cone that extends the overall length (L 总 ) (i.e., the length of the male connector is not included in the overall length of the degasser shaft).

[0142] The inner diameter of the degasser tube can be limited by a cylindrical portion and / or a frustoconical portion. In order to increase the rigidity of the degasser shaft, the outer diameter can be increased. In order to avoid the associated increase in the weight of the shaft, the inner diameter can also be increased in at least some parts of the shaft. One or more cylindrical or conical (i.e., frustoconical) mandrels can be used to cooperate with a mold that limits the outer diameter of the shaft to form a channel. In some embodiments, the channel has a cross-sectional area increased from the first end of the maximum diameter point (e.g., weld mark) of the degasser shaft. This minimizes the wall thickness difference between the minimum wall thickness and the maximum wall thickness, thereby helping to remove weight from the degasser shaft. In some embodiments, the wall thickness is the thickest at the maximum diameter point of the degasser shaft.

[0143] In operation, the degasser shaft is located in a vessel containing molten metal. Depending on the degasser arrangement, the degasser shaft will be immersed in the molten metal up to the so-called "weld line", the level of the shaft comprising the interface between the molten level and the gaseous atmosphere above. The weld line 60 of the shaft is exposed to the most oxidatively corrosive environment and, therefore, the degasser shaft is weakened by oxidative corrosion and is susceptible to mechanical failure at this point. In order to mitigate the risk of mechanical failure of the degasser shaft around the weld line, the wall thickness of the shaft may be greater in this portion of the degasser shaft than in other portions of the degasser shaft.

[0144] Figure 3 and Figure 4 Shows Figure 1 and Figure 2 A variation of a frustoconical degasser shaft of 450 wherein the first portion 310, 410 comprises a cylindrical portion 320, 420 and a frustoconical portion 330, 430. The frustoconical portion adjoins a cylindrical portion 340, 440 extending to a second end of the degasser 450.

[0145] like Figure 4As shown, the wall thickness of the shaft is greatest at the cylindrical portion 420 where the weld mark is located and is smallest at the cylindrical portion 440 at the second end of the degasser shaft 450. This structure provides the greatest resistance to oxidative corrosion at the location where oxidative corrosion is most severe, namely at the interface between the gas atmosphere and the molten metal. In other embodiments (e.g., some shorter shafts), the weld mark can be located in the first portion of the lower half or lower third of the shaft. Preferably, the weld mark is located at an outer diameter of the shaft that is greater than the minimum outer diameter of the shaft, and preferably, the weld mark is located at a shaft wall thickness that is greater than the minimum shaft wall thickness.

[0146] Figure 3 The degasser shaft design 300 is a comparative example because the first portion 310 does not extend the total length (L 总 ) of the required portion. The result is that (i) the stiffness of the degasser shaft is lower due to the relatively small outer diameter of the degasser shaft (SD) in the lower cylindrical portion 340; and (ii) relative to Figure 4 The corresponding connection angle 460 in FIG. 4 is smaller than the connection angle 350 between the frustoconical portion and the cylindrical portion 340. These differences are Figure 4 The first part of the degasser shaft is Figure 3 The degasser axis is longer (P2>P1) and Figure 4 The frustoconical part of Figure 3 Depending on the operating conditions, the combination of these two design features can significantly reduce stress concentrations on the degassing shaft portion, thereby reducing the frequency of mechanical failures in the shaft. Figure 7 Shows something like Figure 3 The location of mechanical failure of the short degasser shaft type design is located at and around the intersection of the frustoconical portion 710 and the cylindrical portion 720.

[0147] When the rotor is seamlessly connected to the degasser shaft 300, the radius R defining the tapered shoulder of the rotor 360 will determine what the second end of the shaft 370 is considered to be.

[0148] Figure 4 The design structure can maintain Figure 1 and Figure 2 The design of the 420 provides similar (if not better) performance because for medium and longer shafts, the weld line is positioned within the cylindrical portion 420, thereby keeping the weld line at the maximum diameter of the degasser shaft. Although the length of the cylindrical portion 420 (L c )and Figure 3 The cylindrical portion 320 is the same as in FIG. 1 , but the length (L t ) is significantly longer than Figure 3 The tapered portion 330 in the embodiment of the present invention contributes to higher rigidity.

[0149] Furthermore, the relatively small cylindrical portion 440 adjacent the second end of the degasser shaft 450 has been shown not to significantly impede performance, which may be at least partially offset by the lower weight of that portion compared to its frustoconical counterpart.

[0150] In addition, the inner diameter of the channel from the first end ID1 to the inner diameter of the second end ID2 can be widened to reduce the weight of the degasser shaft. This is particularly advantageous in longer degasser shafts where the total weight and weight distribution of the degasser shaft can affect the natural frequency of the degasser shaft in operation. The inner diameter of the channel at the first end ID1 can be measured directly below any female connection cavity 470 that may be present. The channel 480 can be cylindrical, in which case the wall thickness of the degasser shaft is greatest at the weld mark of the medium and longer shafts located within the cylindrical portion 420, thereby increasing the oxidation resistance of the shaft at the point where protection is most needed. If desired, the shaft can also have a tapered channel to reduce the overall shaft weight.

[0151] Figure 5 and Figure 6 Further variations of the design are provided within the scope of the present invention. Figure 5 Degasser shaft design and Figure 4 The difference is that the cylindrical portion 420 is partially replaced by a frustoconical portion 525, which tapers from the cylindrical portion to the first end of the degasser shaft. This causes the cylindrical portion 520 to be offset from the first end. This construction can enable the first end of the degasser shaft to be assembled into an existing degasser device, which can include a safety guard and a housing component, as well as reduce the overall weight of the shaft. In addition, for medium and long shafts, the maximum outer diameter of the shaft can be maintained around the weld mark at or around the cylindrical portion. Alternatively, the weld mark can be located at the upper portion of the frustoconical portion 530. It will be understood that the degasser device can be configured to accept a conventional shaft with a smaller outer diameter.

[0152] Figure 6 A shaft 600 is shown with a design variation that still includes a first portion 610 that includes a first cylindrical portion at the top of a shaft 620. The first portion also includes a frustoconical portion that includes a cascade or step-down portion that includes a series of cylindrical portions 640, 660, 680 of reduced diameter that separate a series of frustoconical portions 630, 650, 670, 690 of reduced diameter.

[0153] The specific design features of the degasser shaft will depend on the operating environment to which the degasser shaft will be exposed, and the properties of the corrosion- and erosion-resistant ceramic composite material required to extend the operating life of the degasser shaft. Short shafts (e.g., less than 600 mm in length) typically operate at high rotational speeds, and the focus of the shaft design is on reducing stress concentrations due to deflection of the shaft, particularly shafts with relatively low stiffness (i.e., relatively low Young's modulus). Increasing the shaft diameter and minimizing stress concentration points are typically design priorities. For longer shafts, avoiding excessive vibration that causes elevated stress levels in the shaft is typically a focus, with shaft weight and weight distribution being further design priorities.

[0154] The scope of the present invention is not limited to the specific embodiments shown herein. Those skilled in the art will be able to easily use the teachings herein to produce various modifications and variations that fall within the scope of the present invention.

[0155] Example

[0156] A number of shaft designs were evaluated under simulated conditions. It is important to note that for the purposes of the experiment, the end of the shaft with the short rotor was considered to be the largest diameter of the rotor, rather than the smallest diameter of the shaft close to the rotor. Given that the weight of this additional section is similar, the results are still valid for comparison purposes.

[0157] Short degasser shaft

[0158] The short degasser shaft designs shown in Table 2 were capable of operating between 700 rpm and 1000 rpm and their maximum stress levels and maximum displacements under a 25N load were compared.

[0159] The shaft is made of a ceramic carbon composite material from Molten Metal Systems GmbH, which contains about 65 weight percent refractory particles (about 40 weight percent SiC, the remainder mostly consisting of alumina and aluminosilicate particles) and about 35 weight percent carbon matrix and graphite flakes, and has a density of 2.2 g / cc, a Young's modulus of 3 GPa, and a flexural strength of 11 MPa.

[0160] Reference Figure 3 and Figure 4 , the geometries of different degasser shaft designs are provided in Table 2.

[0161] Table 2 (measurement unit: mm)

[0162]

[0163] + The frustoconical portion comprises a cylindrical segment having an outer diameter smaller than that of the first cylindrical segment but having an outer diameter larger than that of the second cylindrical segment.

[0164] Table 3

[0165] Maximum stress (MPa) Maximum displacement(mm) CE-1 0.70 0.34 1 0.28 0.23 2 0.35 0.32 3 0.35 0.32 CE-2 0.45 0.35

[0166] As shown in Tables 2 and 3, designs 1 to 3 have the lowest maximum stress and the lowest maximum displacement when subjected to a 25N load. The comparative examples have higher maximum stress and displacement levels and are therefore more susceptible to mechanical failure. Despite these excellent mechanical properties, the corrosion resistance of graphite is significantly lower than that of the ceramic composite. While CE-1 and CE-2 have relatively high first sections, their truncated conical sections are relatively small, resulting in relatively high angles of incidence, which may contribute to the high maximum stress levels achieved with these designs.

[0167] Long degasser shaft

[0168] Although the Young's modulus is 3 GPa, the ceramic composite used is similar in composition and properties to the short degasser shaft. Table 4 provides the properties of the ceramic composite. The natural frequency of the degasser shaft was determined when the shaft was connected to the rotor. The weight of the rotor was 5.8 kg, except for sample CE-4, which weighed 4.5 kg. This is due to the fact that this rotor was made of graphite instead of ceramic composite, while the other rotors were made of ceramic composite. The frequency response analysis of the shaft and rotor to determine the natural frequency was based on a 1 kg lateral excitation at the bottom of the rotor and 0% damping was applied. The damping usually produced by the liquid affects the amplitude of the vibration, but does not affect the value of the natural frequency. For 0% damping, the shaft rotates in air.

[0169] As shown in Table 4, the conventional cylindrical shaft (CE-3) made of ceramic composite material has a low natural frequency, which is not suitable for operation at a rotation speed of 220 rpm or higher, so as not to easily amplify vibration. In contrast, the natural frequency of a similar size degasser shaft made of graphite is 550 rpm. The increase in natural frequency can be attributed to the rigidity (e.g., high Young's modulus) and lighter (e.g., low density) properties of graphite.

[0170] The tapered degasser shaft (4) enables to reduce the weight of the degasser shaft and the natural frequency of the degasser shaft is increased to 260 rpm despite the reduced diameter of the shaft at the second end. In Examples 5 and 6, the natural frequency of the degasser shaft is further increased by increasing the diameter of the degasser shaft at the first end, although this results in an increase in the weight of the degasser shaft compared to Example 3. The degasser shaft weights of Examples 3 to 5 are all lower than the ceramic composite degasser shaft of Comparative Example 3 (CE-3). The wider diameter of Examples 3 to 5 is combined with the lower minimum wall thickness to achieve this lower degasser shaft weight.

[0171] Table 4 (measurement unit: mm)

[0172]

[0173] * In terms of corrosion resistance, OOO>OO>O

[0174] Service life

[0175] The service life of graphite shafts is generally determined by mechanical failure due to corrosion, while the service life of ceramic composite shafts is determined by mechanical failure due to fatigue.

[0176] Fatigue testing was performed to determine how the inventive design increases the service life of ceramic composite shafts by increasing rigidity, targeting weight distribution, and avoiding stress concentrations.

[0177] Fatigue testing equipment

[0178] a. Setup: The fatigue testing machine consists of a fixture with a shaft assembly. The shaft is fixed at a top coupling, connected to the fixture (rig), and has a bottom coupling that moves horizontally, causing deflections that simulate application conditions.

[0179] b. Loading: A set deflection is applied to the shaft through horizontal movement of the bottom coupling. The shaft does not rotate but circulates through horizontal deflection.

[0180] Testing Procedure:

[0181] a. Specimen Preparation: Six test specimens were made for each design variant.

[0182] b. Offset Determination: The cycle speed was empirically confirmed at 600-800 cycles per minute (cpm) by using a frequency response plot and by a laser measurement device.

[0183] c. Cyclic load curve: Deflection is applied to the shaft at a given cycle speed. The equipment cycle speed only affects the test duration, as the deflection is fixed.

[0184] d. Test Duration: The duration of the fatigue test is not predetermined, the test is continued until the shaft fails. After 1,000,000 (1M) cycles at a deflection of 1.8 mm, the shaft is exposed to increasing deflections of 3.0 mm to accelerate shaft failure.

[0185] Test execution:

[0186] a. Cyclic Loading: Start the fatigue test and subject the specimen to cyclic loading at the specified CPM and specified deflection.

[0187] b. Data Collection: When the shaft breaks, the proximity sensor will register, indicating the failure, and the number of cycles completed by each specimen until failure will be recorded.

[0188] Data Analysis:

[0189] a. Fatigue life assessment: The number of cycles each specimen endures before failure is recorded, representing the fatigue life of each design variant.

[0190] b. Failure criteria: Specimens with visible cracks or complete fracture are considered to be failures.

[0191] c. Statistical analysis: The number of cycles sustained and the percentage of shafts that failed were calculated for each design variant to assess the relative resistance of the designs.

[0192] d. Interpretation of results: The design with the highest number of cycles is considered to be the most resilient and capable of having a longer service life in operation, excluding other factors such as axle weight.

[0193] Design variants:

[0194] Fatigue testing was performed on three design variations of the ceramic composite material using the previous examples.

[0195] Comparative Example 5 Figure 8 ) is the axis of the first portion included outside the scope of the present invention, wherein the frustoconical portion includes an incident angle that is relatively acute to the adjacent cylindrical portion. Fig. 9 ) is a shaft having a constant shaft diameter (except for the flange portion at the second end). Example 7 ( Fig.10 ) is an axis within the scope of the present invention.

[0196] Fatigue test results

[0197] As shown in Table 5, Comparative Example 5 was only able to last 20 cycles at 600 cpm with a horizontal deflection of 3.0 mm. While the shaft design was able to last significantly longer at a lower horizontal deflection (1.8 mm) and associated stresses, this was still less than 20% of the cyclic service life (on average) of the conventional cylindrical shaft of Comparative Example 6.

[0198] Table 5

[0199]

[0200] In Experiment Nos. 9 and 11, the shaft design of the present invention (Example 7) had a slightly lower operating cycle life than Comparative Example 6, while Experiment No. 10 revealed a premature failure that may be a feature of manufacturing variation (e.g., non-uniform material filling). However, the premature failure was still more than twice the average cycle life of Comparative Example 5.

[0201] The indication that Experiment No. 10 is an anomaly is supported by the fact that Experiment No. 10 failed approximately 50 mm below the threaded connection to the motor (i.e., approximately 105 mm from the first end), while Experiments 6 to 8 (CE-6) and 9 and 11 (Example 7) all failed at the threaded internal connection point (i.e., approximately 57 mm from the first end). The different failure location of Experiment No. 10 compared to the other experiments of the same design indicates an inconsistency in the composite material rather than an inherent design weakness.

[0202] All of Experiments 1 to 5 failed at the intersection of the tapered and cylindrical portions below the internal threaded section toward the first end (approximately 105 mm from the first end), indicating a stress concentration in this area.

[0203] It is noted that Example 7 has an arcuate bridge connection with a radius of 2 mm. Therefore, increasing this radius to at least 5 mm would be expected to further increase the useful life of the shaft, as the increased radius would be expected to reduce stress in this area.

[0204] While the design of Example 7 (excluding Experiment 10) has a cycle life comparable to the cylindrical shaft of CE-6, the lower weight (17% reduction) of the design of Example 7 compared to CE-6 has the advantage of placing a lower load on the motor, and therefore, motor maintenance (e.g., bearing changes) will be significantly reduced, while achieving a greater than 5-fold increase in shaft life before mechanical failure compared to the shaft of CE-5. The shaft design of the present invention can reduce the total maintenance cost (repair and replacement) of the degassing system over the life cycle of the shaft. The relatively light shaft is also easier to install and has lower energy consumption.

Claims

1. A degasser shaft for treating molten metal using gas, the shaft comprising; (d) a first end connectable to a driver for rotating the shaft about the longitudinal axis, the first end having a first end outer diameter; (e) a second end, the second end having a second end outer diameter, the second end may be connected to the rotor; or is formed integrally with the rotor, the second end outer diameter being considered as the smallest shaft outer diameter close to the rotor; and (f) a passage through which the gas flows from the first end to the second end, the passage being defined by an inner diameter of the degasser shaft; in, The degasser shaft has a first portion, the first portion is located at or toward the first end, and the first portion includes a first tapered section and an optional first constant section section, the cross-sectional area of ​​the first tapered section decreases toward the second end, the first constant section section extends from the first tapered section toward the first end, the first portion includes 48% to 100% of the total length of the degasser shaft; and wherein at least the first tapered section of the degasser shaft is composed of a ceramic composite material.

2. The degasser shaft according to claim 1, wherein: The degasser shaft also includes one or two of the following: a first constant cross-section section having a cross-sectional area greater than a minimum cross-sectional area of ​​the degasser shaft and extending continuously from the first tapered section toward the first end; and A second constant cross-section section extending continuously from the first tapered section toward the second end.

3. The degasser shaft according to claim 2, wherein: The second constant cross-section section has a cross-sectional area equal to the smallest cross-sectional area of ​​the degasser shaft.

4. The degasser shaft according to claim 1, wherein: The first tapered section extends from the minimum shaft outer diameter to a maximum shaft outer diameter, and the second tapered section extends from the maximum shaft outer diameter and decreases in cross-sectional area toward the first end.

5. The degasser shaft according to claim 4, wherein: A constant cross-section section is provided between the first tapered section and the second tapered section.

6. The degasser shaft according to claim 4 or 5, wherein: The first tapered section includes two or more tapered sections separated by two or more constant cross-section sections.

7. The degasser shaft according to claim 6, wherein: The two or more constant cross-section segments have an outer diameter that decreases as the first portion progresses toward the second end of the shaft.

8. The degasser shaft according to any one of claims 2 to 7, wherein The first portion ranges from 50% to 90% of the total length of the degasser shaft, and the second constant cross-section ranges from 10% to 50% of the total length of the degasser shaft.

9. The degasser shaft according to any one of claims 1 to 8, wherein The first portion includes one or more tapered sections that constitute 40% to 90% of the total length of the degasser shaft.

10. The degasser shaft according to claim 9, wherein: The one or more tapered sections constitute at least 50% of the total length of the degasser shaft.

11. The degasser shaft according to any one of claims 2 to 10, wherein An incident angle between the tapered section and the second constant cross-section section is greater than 0° and not greater than 16°.

12. The degasser shaft of claim 11, wherein: An incident angle between the tapered section and the second constant cross-section section is greater than 2° and not greater than 10°.

13. The degasser shaft according to any one of claims 1 to 12, wherein The shaft further includes a weld mark located at a maximum outer diameter of the shaft.

14. The degasser shaft according to any one of claims 1 to 13, wherein A ratio of the minimum shaft wall thickness to the maximum shaft wall thickness is in the range of at least 0.3 and less than 0.

90.

15. The degasser shaft of claim 14, wherein: A ratio of the minimum shaft wall thickness to the maximum shaft wall thickness is in a range of at least 0.5 and less than 0.

85.

16. The degasser shaft according to any one of claims 1 to 15, wherein The maximum outer diameter of the shaft is D 最大值 Subtract the smallest outer diameter of the shaft, D 最小值 In the range of 10 to 100 mm.

17. The degasser shaft of claim 16, wherein: D 最大值 -D 最小值 At least 30mm.

18. The degasser shaft of claim 16, wherein: D 最大值 -D 最小值 At least 40mm.

19. The degasser shaft according to any one of claims 1 to 18, wherein The length of the shaft is greater than 1500 mm.

20. The degasser shaft according to any one of claims 1 to 18, wherein The degasser shaft has: Overall length, between 250 mm and 2200 mm; an optional first constant cross-section segment comprising a length in the range of 0 mm to 600 mm; a tapered section adjacent to the first section of constant cross-section, the tapered section having an outer diameter that decreases as the tapered section extends toward the second end when the first section of constant cross-section is present, the tapered section having an axial length in the range of 100 mm to 2200 mm; · Optional second constant cross-section segment; The outer diameter of the first shaft end is in the range of 60 mm to 180 mm; The outer diameter of the second shaft end is in the range of 45 mm to 140 mm; and Channel diameter, in the range of 10 mm to 60 mm.

21. A degasser shaft according to any one of claims 1 to 18, wherein The degasser shaft has: Overall length, between 1500 mm and 2200 mm; The first constant cross-section segment comprises a length in the range of 100 mm to 600 mm; a first tapered section, continuously adjoining said first section of constant cross-section, comprising an outer diameter that decreases as said tapered section extends towards said second end, said tapered section comprising an axial length in the range of 400 mm to 2200 mm; · Optional second constant part segment; an optional second tapered section continuously adjoining the end of the first constant section section and extending continuously to the first end, and the second tapered section comprises a length of 0 mm to 500 mm; The outer diameter of the first shaft end is in the range of 80 mm to 180 mm; The outer diameter of the second shaft end is in the range of 80 mm to 150 mm; and Channel diameter, in the range of 10 mm to 60 mm.

22. A degasser shaft according to any one of claims 1 to 18, wherein The degasser shaft has: Total length, between 500mm and 1500mm; the first constant cross-section segment comprising a length in the range of 0 mm to 500 mm; a tapered section adjacent to the first section of constant cross-section, the tapered section, when present, comprising an outer diameter that decreases as the tapered section extends toward the second end, the tapered section comprising an axial length in the range of 500 mm to 1500 mm; The outer diameter of the first shaft end is in the range of 70 mm to 150 mm; The outer diameter of the second shaft end is in the range of 50 mm to 130 mm; and Channel diameter, in the range of 10 mm to 50 mm.

23. A degasser shaft according to any one of claims 1 to 18, wherein The degasser shaft comprises: Overall length, between 250 and 600 mm; a first constant cross-section section comprising a length in the range of 50 mm to 100 mm; a tapered section adjacent to the first constant section, the tapered section comprising an outer diameter that decreases as the tapered section extends toward the second end, the tapered section comprising an axial length in the range of 100 mm to 400 mm; · Optional second constant cross-section segment; The outer diameter of the first shaft end is in the range of 60 mm to 90 mm; The second shaft end outer diameter is in the range of 45 mm to 70 mm; and Channel diameter, in the range of 10 mm to 25 mm.

24. A degasser shaft according to any one of claims 20 to 23, wherein Maximum shaft outer diameter (D 最大值 ) and the minimum shaft outer diameter (D 最小值 ) is at least 1.

2.

25. The degasser shaft of claim 24, wherein: Maximum shaft outer diameter D 最大值 The minimum shaft outer diameter D 最小值 The ratio is at least 1.

4.

26. A degasser shaft according to any one of claims 1 to 23, wherein The first end is connectable to a motor via a female connection.

27. The degasser shaft of claim 26, wherein: The female connection comprises a threaded coupling in which the helical threads and the passage of the shaft are connected by an arcuate bridging connection.

28. The degasser shaft of claim 27, wherein: The arcuate bridging connection has a radius of at least 5 mm.

29. A degasser shaft according to any one of the preceding claims, wherein The maximum wall thickness of the degasser shaft is 最大值 Located at or towards the location where the degasser shaft has the largest outer diameter and the minimum wall thickness of the degasser shaft, i.e., the wall 最小值 at or toward the second end, and wherein the wall 最小值 / wall 最大值 The ratio is in the range of 0.75 to 1.

0.

30. The degasser shaft of claim 29, wherein: wall 最小值 / wall 最大值 The ratio is in the range of 0.80 to 0.

95.

31. A degasser shaft according to claim 29 or 30, wherein D 最大值 / D 最小值 Greater than 1.

3.

32. The degasser shaft of claim 31, wherein D 最大值 / D 最小值 Greater than 1.

4.

33. A degasser shaft according to any one of the preceding claims, wherein The density of the ceramic composite is in the range of 1.9 g / cc to 2.5 g / cc.

34. A degasser shaft according to any one of the preceding claims, wherein The ceramic composite material has a Young's modulus in a range of 0.5 GPa to 10 GPa.

35. A degasser shaft according to any one of the preceding claims, wherein The ceramic composite material has a transverse bending strength (TBS) in the range of 5 MPa to 30 MPa.

36. A degasser shaft according to any preceding claim, comprising a shaft length of at least 1500mm and a natural frequency in the range of 250 rpm to 500 rpm.

37. A method for degassing a molten metal melt, the method comprising immersing a degasser into the molten metal melt, the degasser comprising a degasser shaft according to any preceding claim.

38. The method of claim 37, wherein: The rotational speed of the degasser shaft is lower than the natural frequency of the degasser shaft.

39. The method according to claim 37 or 38, wherein: The surface of the molten metal melt meets the degasser shaft at a weld mark located where the shaft's outer diameter is greater than the minimum shaft outer diameter.

40. The method according to any one of claims 37 to 39, wherein: The shaft wall thickness at the weld line is greater than the minimum shaft wall thickness below the weld line.

41. Use of a degasser shaft as claimed in any one of claims 1 to 36 for processing molten metal.

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