A blow-out knee for a crucible

Abstract

A blow-out knee (10) for discharging molten metal from a crucible, comprising; a flange (11); a bent portion (12) connected to the flange (11), the bent portion (12) comprising a cavity (16) extending through the bent portion (12); an end portion (13) connected to the bent portion (12), the end portion (13) comprising a cavity (17) extending through the end portion (13); the cavity (16) of the bent portion (12) comprises a bent center axis (X) extending from a first point (A) where the bent portion (12) is connected to the flange (11) to a second point (B) where the bent portion (12) is connected to the end portion (13); the cavity (16) of the bent portion (12) comprises a cross sectional area (A1) at the first point (A) with a nominal diameter (D1); the cavity (17) of the end portion (13) comprises an end center axis (Y) extending from the second point (B) to a third point (C) at the free end of the end portion (13); the cavity (17) of the end portion (13) comprises a cross sectional area (A2) at a fourth point (D) provided on or between the second and third points (B, C) on the end center axis (Y); the cross sectional area (A2) at the fourth point (D) is larger than the cross sectional area (A1) at the first point (A); a cross sectional area of the cavity (17) of the end portion (13) along the end center axis (Y) between the third point (C) and the fourth point (D) is constant.

Description

A BLOW-OUT KNEE FOR A CRUCIBLEField of the invention

[0001] The invention relates to a blow-out knee, and more specifically to a blow-out knee for discharging molten metal from a crucible.Background of the invention

[0002] In metalworking, metal transfer is the process of tapping molten metal from one location and discharge to another, after the metal has been melted and is ready for further processing, such as casting or refining. The molten metal may be poured from the crucible through a spout, or may be more controllably discharged through an opening at the top of the crucible using a pipe. A blow-out knee is the elbow or bent portion of the pipe that allows molten metal to flow out from the crucible at a specific angle. A blow-out knee is also known as a blow-out bend, horse neck or blowout tube.

[0003] The blow-out knee serves several purposes during the discharge process. It helps to guide the molten metal from the crucible into the holding furnace or other collection vessels by angling the metal stream in a controlled manner. The bent shape allows for better control over the direction and angle at which the molten metal exits the crucible. This is important for managing flow and reducing splashing, spillage or dross generation.

[0004] By directing the flow, the blow-out knee helps keep the molten metal in a controlled stream, which can reduce the risk of accidents or damage to nearby equipment. Blow-out knees are themselves known to be exposed to significant wear and tear as the molten metal flows through, and blow-out knees are known to be replaced at regular intervals. All such repairs and replacements affect the efficiency and increase the carbon footprint of the metal transfer process and the parts involved in the process.

[0005] A further problem associated with metal transfer is the generation of dross. Dross generation refers to the formation of unwanted solid impurities or oxides that accumulate on the surface of molten metal during the melting and metal transfer processes. It is common in metalworking, particularly when dealing with metals like aluminum, zinc, lead, or copper. Dross consists primarily of metal oxides and can alsocontain other contaminants, such as slag, dirt, or flux residues. Dross can be included in the molten metal flow, leading to poor-quality castings or finished products due to inclusions of oxides and impurities. Significant amounts of dross are known to be generated and accumulated in existing blow-out knees, and this is a prevailing problem in the art.

[0006] Metal transfer is an age old process in large part based on best practice and established principles, and not much effort has gone into optimizing the various parts involved in the process. As such, the design of blow-out knees in operation today are pretty much based on old principles. There is therefore a need for an improved blowout knee, to optimize the flow of molten metal through the blow-out knee. There is a further need for a blow-out knee to minimize the generation of dross, and maximize the longevity of the blow-out knee. It is an objective of the invention to achieve this and to provide further advantages over the state of the art.Summary of the invention

[0007] It is an object of the invention to mitigate, alleviate or eliminate one or more of the above-identified deficiencies and disadvantages in the prior art and solve at least the above mentioned problem.

[0008] According to a first aspect, there is provided a blow-out knee for discharging molten metal from a crucible. The blow-out knee comprises a flange and a bent portion connected to the flange. The bent portion comprising a cavity extending through the bent portion. An end portion is connected to the bent portion, the end portion comprising a cavity extending through the end portion. The cavity of the bent portion comprises a bent center axis extending from a first point where the bent portion is connected to the flange to a second point where the bent portion is connected to the end portion. The cavity of the bent portion comprises a cross sectional area at the first point with a nominal diameter. The cavity of the end portion comprises an end center axis extending from the second point to a third point at the free end of the end portion. The cavity of the end portion comprises a cross sectional area at a fourth point provided on or between the second and third points on the end center axis. The cross sectional area at the fourth point is larger than the cross sectional area at the first point. A cross sectional area of the cavity of the end portion along the end center axis between the third point and the fourth point is constant.

[0009] According to an embodiment, the cross sectional area at the fourth point is 10- 15% larger than the cross sectional area at the first point.

[0010] According to an embodiment, the cross sectional area increases linearly from the first point to the fourth point.

[0011] According to an embodiment, the third point and the fourth point is coincident and the cross sectional area thus increases from the first point at the flange to the third point at the free end of the end portion.

[0012] According to an embodiment, the bent center axis comprises a curve having a radius.

[0013] According to an embodiment, the radius is in the interval of 2-3 times the nominal diameter of the cross sectional area at the first point.

[0014] According to an embodiment, the flange comprises a level bottom surface and the first point is provided in a plane of the bottom surface.

[0015] According to an embodiment, the radius has a center of curvature provided in the plane of the bottom surface.

[0016] According to an embodiment, the end center axis is straight.Brief description of the figures

[0017] The aspects of the invention, including its particular features and advantages, will be readily understood from the following detailed description and the accompanying figures. The figures are provided to illustrate the general structures of the invention. Like reference numerals refer to like elements throughout.

[0018] Figure 1 shows a perspective view of a first embodiment of a blow-out knee.

[0019] Figure 2 shows a sectional side view of the blow-out knee.Detailed description of the invention

[0020] The invention will now be described with reference to the accompanying figures, in which preferred example embodiments of the invention are shown. Theinvention may, however, be embodied in other forms and should not be construed as limited to the herein disclosed embodiments. The disclosed embodiments are provided to fully convey the scope of the invention to the skilled person.

[0021] It is to be understood that the terminology used herein is for purpose of describing particular embodiments only, and is not intended to be limiting. It should be noted that, as used in the specification and the appended claims, the articles "a", "an" and "the" are intended to mean that there are one or more of the elements or steps unless the context explicitly dictates otherwise. Thus, for example, reference to "a unit" or "the unit" may include several devices, and the like. Furthermore, the words "comprising", "including", "containing" and similar wordings does not exclude other elements or steps.

[0022] Referring to figures 1 and 2, a blow-out knee 10 for discharging molten metal from a crucible is shown. The blow-out knee 10 comprises a flange 11, a bent portion 12 and an end portion 13. The flange 11, bent portion 12 and end portion 13 may preferably be made as a single part. The blow-out knee 10 is preferably cast, made from cast iron or cast steel. The blow-out knee 10 may alternatively comprise parts that are assembled together. The flange 11 connects the blow-out knee 10 to a crucible. The flange 11 may comprise a level bottom surface 14, for ensuring a tight connection to a crucible (not shown). The flange 11 may be connected to the top of the crucible by connection means known in the art of connecting blow-out knees to crucibles. The flange 11 or the crucible is further connected to a straight pipe (also referred to as a blow-out pipe) provided on the inside of the crucible. As the crucible is pressurized, molten metal inside the crucible is forced up through the straight pipe, through the flange 11 and through the bent portion 12 and end portion 13 of the blow-out knee 10. The molten metal exits the blow-out knee 10 at the free end of the end portion 13.

[0023] The blow out-knee 10 may comprise at least one hoisting point 15. More specifically, the bent portion 12 may comprise at least one hoisting point 15, and the end portion 13 may comprise at least one hoisting point 15. The shown blow-out knee 10 comprises two hoisting points 15, both provided on the bent portion 12. If the end portion 13 is longer than the illustrated end portion 13, at least one hoisting point 15 may be provided partly or fully on the end portion 13 as well, ensuring a balanced hoisting of the blow out-knee 10. A hoisting point 15 may be used for lifting the bent portion 12 in balance, and another hoisting point 15 may be used for lifting an assembled blow out-knee 10 in balance.

[0024] The blow-out knee 10 is hollow, and the bent portion 12 and end portion 13 comprise cavities 16,17. The bent portion 12 and end portion 13 may be tubular sections comprising nominal diameters. The cavity 16 of the bent portion 12 extends through the flange 11 and the bent portion 12, and meets the cavity 17 of the end portion 13 where the bent portion 12 and end portion 13 meet. The cavity 17 of the end portion 13 extends through the end portion 13, such that molten metal may be guided through the blow out-knee 10 from the flange 11 to the free end of the end portion 13. The cavity 16 of the bent portion 12 extends along a bent center axis X, and the cavity 17 of the end portion 13 extends along an end center axis Y.

[0025] The shape of the cavities 16,17 may generally correspond to the shape of the outside of the bent portion 12 and end portion 13, respectively, such that the bent portion 12 and end portion 13 comprises generally uniform wall thicknesses. However, the outside of the bent portion 12 and end portion 13 may also deviate from the cavities 16,17, such that the wall thickness of the blow out-knee 10 varies along the length of the blow out-knee 10. E.g. the cavities 16,17 may comprise smooth wall surfaces while the outside of the bent portion 12 and end portion 13 may be more irregular and may comprise e.g. protruding elements such as the at least one hoisting point 15.

[0026] The bent center axis X extends from a first point A located in the area center of a cross sectional area Al of the cavity 16 at the bottom surface 14 of the flange 11. The bent center axis X extends to a second point B located in the area center of a cross sectional area where the bent center axis X meets the end center axis Y at the second point B. The end center axis Y extends from the second point B to a third point C located at the free end of the end portion 13. Point C is thus located at the very end of the end center axis Y, and is located where the end portion 13 is terminated. The bent center axis X and end center axis Y are preferably connected tangentially at the second point B to ensure a smooth flow through the blow-out knee 10.

[0027] A cross sectional area of the cavity 16 of the bent portion 12 increases from the flange 11 to the end portion 13. More precisely, the cross sectional area of the cavity 16 increases from the cross sectional area Al at the bottom surface 14 of the flange 11 along the length of the bent center axis X. The cross sectional area increases up to a cross sectional area A2 at a fourth point D. The fourth point D is provided anywhere along the end center axis Y, including the second and third pointsB,C. The increase in cross sectional area may thus end at point B, but may also continue until point C, or may end anywhere in between point B and point C. The cross sectional area Al is defined as a cross sectional area perpendicular to the bent center axis X at the first point A. The cross sectional area A2 is defined as a cross sectional area perpendicular to the end center axis Y at the fourth point D. If not otherwise described, the term "cross sectional area" refers to a cross sectional area of the cavities 16,17 of the bent portion 12 and end portion 13, normal to the respective center axes.

[0028] Preferably, the increase in the cross sectional area from the cross sectional area Al at the first point A to the cross sectional area A2 at the fourth point D is linear. The cross sectional area Al at the first point A is circular and comprises a nominal diameter DI. The straight pipe provided below the flange 11 commonly comprises an inner circular cross section, and the cross sectional area Al at the first point A preferably corresponds to the cross section of the cavity of the straight pipe, to ensure a smooth flow of molten metal from the straight pipe into the blow-out knee 10. The nominal diameter DI at the first point A is typically in the interval of 60- 120mm, and more preferably in the interval of 80-100mm.

[0029] The cross sectional area A2 at the fourth point D may not be circular, but may preferably be in the interval of 5-20% larger than the cross sectional area Al at the first point A. More preferably, the cross sectional area A2 at the fourth point D is 10- 15% larger than the cross sectional area Al at the first point A. This slight expansion of the cross sectional area of the cavity from the first point A to the fourth point D ensures a smooth flow with minimum of dross generation. Due to the increased cross sectional area, the flow of the molten metal is slowed down, but the small and linear increase in cross sectional area ensures minimum impact on the properties of the molten metal, such that dross generation and corrosion on the blow-out knee 10 is minimized. The increase in cross sectional area from the first point A to the fourth point D of 10-15% ensures the flow of molten metal through the blow-out knee 10 is both steadily and slightly slowed down, providing optimal conditions for the molten metal. As such, there is no risk of pressure build-up in the blow-out knee 10, and the lifetime of the blow-out knee 10 is increased. As the lifetime increases, the carbon footprint of the blow-out knee 10 is reduced.

[0030] The bent center axis X may preferably consist of a radius Rl, but the bent center axis X may also comprise a radius Rl which describes the general curvature of the bent center axis X. The bent center axis X may as such comprise several differentradiuses, including curves and splines. In a preferred embodiment, the radius R1 is dimensioned such that the radius R1 is 2-3 times greater than the nominal diameter DI of the cross sectional area Al at the first point A. The radius R1 is thus preferably at least two times the nominal diameter DI, and at most three times the nominal diameter DI, or anywhere between. This relationship between the nominal dimeter DI and the radius R1 has been found to be particularly advantageous for the flow of molten metal through the bent portion 12. A radius R1 of the bent center axis X of 2- 3 times the nominal diameter DI at the first point A ensures a large enough bend to provide an optimal flow of molten metal through the blow-out knee 10, further leading to less corrosion in the bent portion 12, and less generation of dross.

[0031] The radius R1 preferably has a center of curvature provided in a plane P corresponding to the plane of the bottom surface 14 of the flange 11. This ensures that the bent center axis X of the cavity 16 of the bent portion 12 is normal to the crucible, and / or the straight pipe the blow-out knee 10 is connected to, at the bottom surface 14 of the flange 11. This allows optimal flow of molten metal, but still immediately redirects the flow of molten metal as the metal enters the blow-out knee 10.

[0032] The end center axis Y is preferably straight to ensure a smooth and linear flow of molten metal through the end portion 13. However, the end center axis Y may comprise slight curvatures. If the end center axis Y is straight, it, and generally the end portion 13, is directed at an angle with the plane P of the bottom surface 14. As the length (i.e. the distance from the second point B to the third point C) of the end portion 13 may vary, the end portion 13 may in some embodiments extend past the plane P of the bottom surface 14. In such embodiments, the third point C of the end portion 13 is positioned below the plane P.

[0033] From the fourth point D to the third point C, where the end portion 13 ends, the cross sectional area of the cavity 17 of the end portion 13 is constant. If the fourth point D is located at the second point B, the cross sectional area of the entire cavity 17 of the end portion 13 is constant. Alternatively, if the fourth point D is located at the third point C, the cross sectional area of the cavity 17 of the end portion 13 is increasing all the way through the end portion 13. Both configurations ensure a steady flow of molten metal through the end portion 13.

[0034] While the invention has been described with reference to the embodiments mentioned above, it is to be understood that modifications and variations can bemade without departing from the scope of the present invention, and such modifications and variations shall remain within the field and scope of the invention, as defined by the appended claims.

Claims

Claims1. A blow-out knee (10) for discharging molten metal from a crucible, comprising; a flange (11); a bent portion (12) connected to the flange (11), the bent portion (12) comprising a cavity (16) extending through the bent portion (12); an end portion (13) connected to the bent portion (12), the end portion (13) comprising a cavity (17) extending through the end portion (13); the cavity (16) of the bent portion (12) comprises a bent center axis (X) extending from a first point (A) where the bent portion (12) is connected to the flange (11) to a second point (B) where the bent portion (12) is connected to the end portion (13); the cavity (16) of the bent portion (12) comprises a cross sectional area (Al) at the first point (A) with a nominal diameter (DI); the cavity (17) of the end portion (13) comprises an end center axis (Y) extending from the second point (B) to a third point (C) at the free end of the end portion (13); the cavity (17) of the end portion (13) comprises a cross sectional area (A2) at a fourth point (D) provided on or between the second and third points (B, C) on the end center axis (Y); the cross sectional area (A2) at the fourth point (D) is larger than the cross sectional area (Al) at the first point (A); a cross sectional area of the cavity (17) of the end portion (13) along the end center axis (Y) between the third point (C) and the fourth point (D) is constant.

2. The blow-out knee (10) according to claim 1, wherein the cross sectional area (A2) at the fourth point (D) is 10-15% larger than the cross sectional area (Al) at the first point (A).

3. The blow-out knee (10) according to claim 1 or 2, wherein the cross sectional area increases linearly from the first point (A) to the fourth point (D).

4. The blow-out knee (10) according to any one of the preceding claims, wherein the third point (C) and the fourth point (D) is coincident and the crossio sectional area thus increases from the first point (A) at the flange (11) to the third point (C) at the free end of the end portion (13).

5. The blow-out knee (10) according to any one of the preceding claims, wherein the bent center axis (X) comprises a curve having a radius (Rl).

6. The blow-out knee (10) according to claim 5, wherein the radius (Rl) is in the interval of 2-3 times the nominal diameter (DI) of the cross sectional area (Al) at the first point (A).

7. The blow-out knee (10) according to any one of the preceding claims, wherein the flange (11) comprises a level bottom surface (14) and the first point (A) is provided in a plane (P) of the bottom surface (14).

8. The blow-out knee (10) according to claim 7 when dependent on claim 5 or 6, wherein the radius (Rl) has a center of curvature provided in the plane (P) of the bottom surface (14).

9. The blow-out knee (10) according to any one of the preceding claims, wherein the end center axis (Y) is straight.

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