Impeller for metal melt and stirring body for metal melt

Abstract

This impeller for a metal melt is provided with: a center section including a through-hole extending from a lower surface to an upper surface along a rotational axis; a plurality of stirring blades protruding radially outward from the central portion; and a plurality of grooves provided in the lower surface and extending from the through holes to the tips of the corresponding stirring blades. The stirring blade includes a first guide surface and a second guide surface connected to the upper surface and the lower surface. When viewed toward the lower surface, the first guide surface is located at a position advancing from the groove in the circumferential direction of the impeller, and the second guide surface is located at a position retracting from the groove in the circumferential direction of the impeller. The first guide surface is inclined with respect to the lower surface so as to advance in the circumferential direction of the impeller from the lower surface to the upper surface.

Description

Technical Field

[0001] The present invention relates to an impeller for molten metal and a stirring body for molten metal. Background Art

[0002] Generally speaking, before casting with a metal material such as an aluminum alloy, a degassing treatment is performed to remove impurities such as hydrogen or oxides contained in the molten metal (for example, refer to patent documents 1 to 5). During the degassing treatment, the molten metal such as the aluminum alloy retained in the degassing treatment tank is stirred by rotating the molten metal stirring body, while blowing gas such as argon or nitrogen is blown into the molten metal. The blown gas is transformed into bubbles from the outer peripheral end of the molten metal impeller installed at the front end of the shaft of the molten metal stirring body and is blown into the molten metal. By rotating the molten metal impeller, the bubbles of the blown gas are miniaturized. The miniaturized bubbles take in impurities in the molten metal and make them float. In this way, impurities are removed from the molten metal.

[0003] The impeller for the molten metal may be arranged at a relatively deep position in the degassing tank. In this case, the stirring of the molten metal at the relatively shallow position becomes insufficient, and the efficiency of the degassing treatment of the molten metal may be reduced.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Laid-Open No. 6-273074

[0007] Patent Document 2: Japanese Patent Application Laid-Open No. 2003-130557

[0008] Patent Document 3: Japanese Patent No. 4672067

[0009] Patent Document 4: Japanese Patent No. 5032521

[0010] Patent Document 5: Japanese Patent No. 6196533 Summary of the Invention

[0011] Problems to be solved by the invention

[0012] The present invention has been made in consideration of this point, and an object of the present invention is to provide an impeller for molten metal and a stirring body for molten metal that can improve the efficiency of degassing treatment of molten metal.

[0013] Means for solving problems

[0014] [1] The present invention may be an impeller for molten metal, comprising an upper surface and a lower surface perpendicular to the axis of rotation, wherein:

[0015] a central portion including a through hole extending from the lower surface along the rotation axis to the upper surface;

[0016] a plurality of stirring blades protruding radially outward from the central portion; and

[0017] a plurality of grooves provided on the lower surface and extending from the through hole to the corresponding front ends of the stirring blades;

[0018] The stirring blade includes a first guide surface and a second guide surface connected to the upper surface and the lower surface,

[0019] When viewed toward the lower surface, the first guide surface is located at a position forward from the groove in the circumferential direction of the impeller, and the second guide surface is located at a position backward from the groove in the circumferential direction of the impeller.

[0020] The first guide surface is inclined relative to the lower surface so as to advance along the impeller circumferential direction from the lower surface toward the upper surface.

[0021] [2] The present invention may also be as follows:

[0022] The impeller for molten metal according to [1], wherein

[0023] The second guide surface is inclined relative to the lower surface so as to advance along the impeller circumferential direction from the lower surface toward the upper surface.

[0024] [3] The present invention may also be as follows:

[0025] The impeller for molten metal according to [1] or [2], wherein:

[0026] When viewed toward the lower surface, the impeller circumferential direction is counterclockwise.

[0027] [4] The present invention may also be as follows:

[0028] The impeller for molten metal according to any one of [1] to [3], wherein

[0029] The upper surface is inclined relative to the lower surface so as to be away from the lower surface from the front end of the stirring blade toward the center portion.

[0030] [5] The present invention may also be as follows:

[0031] The impeller for molten metal according to any one of [1] to [4], wherein

[0032] The groove includes: a first side wall connected to the lower surface; a second side wall connected to the lower surface and located at a position retreated from the first side wall along the circumferential direction of the impeller; and a top wall connected to the first side wall and the second side wall;

[0033] The second side wall is inclined relative to the lower surface so as to advance along the impeller circumferential direction from the lower surface toward the top wall.

[0034] [6] The present invention may also be as follows:

[0035] The impeller for molten metal according to [5], wherein

[0036] The first side wall is formed perpendicularly to the lower surface.

[0037] [7] The present invention may also be as follows:

[0038] The impeller for molten metal according to any one of [1] to [6], wherein

[0039] The number of the stirring blades is 2.

[0040] [8] The present invention may also be as follows:

[0041] The impeller for molten metal according to [7], wherein:

[0042] The central portion includes a protrusion that protrudes from the upper surface and extends the through hole.

[0043] [9] The present invention may also be as follows:

[0044] The impeller for molten metal according to [8], wherein:

[0045] The upper surface is inclined relative to the lower surface so as to be away from the lower surface from the front end of the stirring blade toward the protrusion.

[0046]

[10] The present invention may also be as follows:

[0047] The impeller for molten metal according to any one of [7] to [9], wherein:

[0048] The direction in which the stirring blade protrudes from the central portion is defined as a blade protruding direction,

[0049] The center portion has a dimension greater than a dimension of a front end of the stirring blade in a direction perpendicular to a protruding direction of the blade.

[0050]

[11] The present invention may also be a stirring body for molten metal, comprising:

[0051] Axis; and

[0052] The impeller for molten metal according to any one of [1] to

[10] is attached to the lower end portion of the shaft.

[0053] Effects of the Invention

[0054] According to the present invention, the efficiency of the degassing treatment of the molten metal can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Figure 1 This is a schematic diagram showing a state where the impeller for molten metal according to the first embodiment of the present invention is used in a degassing apparatus.

[0056] Figure 2 It is a perspective view showing an impeller for molten metal according to a first embodiment of the present invention.

[0057] Figure 3 Looking toward the lower surface Figure 2 A bottom view of an impeller for a molten metal is shown.

[0058] Figure 4 yes Figure 3 AA line section view.

[0059] Figure 5 yes Figure 4 BB line cross-sectional view.

[0060] Figure 6 It is a perspective view showing an impeller for molten metal according to a second embodiment of the present invention.

[0061] Figure 7 Looking toward the lower surface Figure 6 A bottom view of an impeller for a molten metal is shown.

[0062] Figure 8 yes Figure 7 CC line cross-sectional view.

[0063] Figure 9 Yes Figure 6 A perspective view of a modified example of the impeller for molten metal shown.

[0064] Figure 10 Yes Figure 9 A bottom view of a modified example of an impeller for molten metal. DETAILED DESCRIPTION

[0065] Hereinafter, an impeller for molten metal and a stirring body for molten metal according to embodiments of the present invention will be described with reference to the drawings.

[0066] (First embodiment)

[0067] use Figures 1 to 5 An impeller for molten metal and a stirring body for molten metal according to a first embodiment of the present invention will be described.

[0068] First, use Figure 1 A degassing apparatus 1 using the molten metal impeller 20 of this embodiment will be described. The degassing apparatus 1 is an apparatus for performing a degassing process to remove impurities such as hydrogen and oxides contained in a molten metal before casting a metal material such as an aluminum alloy.

[0069] like Figure 1 As shown, the degassing device 1 includes a degassing tank 2 in which a molten metal is stored and a molten metal stirring body 10 for stirring the molten metal stored in the degassing tank 2. The molten metal stirring body 10 is rotatably mounted on the degassing tank 2 around a rotation axis X. The molten metal stirring body 10 is connected to a rotation drive device (not shown) to stir the molten metal stored in the degassing tank 2. The molten metal is heated in the degassing tank 2. Figure 1 Indicated by the reference symbol M in the etc.

[0070] The stirring body 10 for molten metal includes a shaft 11 extending along a rotation axis X and an impeller 20 for molten metal. The impeller 20 for molten metal is mounted on the lower end 11a of the shaft 11, and the shaft 11 and the impeller 20 for molten metal rotate integrally. The mounting structure of the shaft 11 and the impeller 20 for molten metal is arbitrary. For example, the shaft 11 may be screwed to the impeller 20 for molten metal. Alternatively, the shaft 11 may be bonded to the impeller 20 using an adhesive or the like, or may be fixed to the impeller 20 by a fitting structure.

[0071] The impeller 20 for molten metal is configured to blow a gas G such as argon or nitrogen into the molten metal. The shaft 11 includes a gas flow path 12 connected to a gas supply device (not shown) (see FIG. Figure 4 The shaft 11 is inserted into the through hole 31 of the impeller 20 for molten metal, which will be described later. A nozzle 13 communicating with the gas flow path 12 is formed at the lower end 11a of the shaft 11 (see Figure 3 、 Figure 4 The blown gas G passing through the gas flow path 12 is ejected from the ejection port 13 and is blown into the metal melt through the groove 50 described later.

[0072] The shaft 11 and the impeller 20 for the molten metal can be formed of at least one material selected from, for example, silicon nitride-based ceramics, Sialon-based ceramics, silicon carbide-based ceramics, carbon ceramics, and carbon. More specifically, the shaft 11 and the impeller 20 for the molten metal can be formed of the following materials: silicon nitride-based ceramics or Sialon-based ceramics formed by sintering silicon nitride powder with a sintering aid; silicon carbide-based ceramics composed of a silicon carbide sintered body formed by sintering silicon carbide powder with a sintering aid; a silicon nitride-bonded silicon carbide sintered body containing 50% or more silicon carbide by weight; carbon ceramics formed by sintering a mixture of carbon, silicon carbide, boron carbide, and the like; and other materials.

[0073] Next, use Figures 2 to 5 The molten metal impeller 20 of this embodiment will be described.

[0074] like Figures 2 to 4 As shown, the impeller 20 for molten metal includes a lower surface 21 and an upper surface 22 perpendicular to the rotation axis X. The upper surface 22 is inclined relative to the lower surface 21, as will be described later.

[0075] The molten metal impeller 20 includes a central portion 30 , a plurality of stirring blades 40 , and a plurality of grooves 50 .

[0076] The central portion 30 includes a through-hole 31 . The through-hole 31 extends from the lower surface 21 to the upper surface 22 along the rotation axis X. The through-hole 31 penetrates the central portion 30 . The lower end portion 11 a of the shaft 11 is inserted into the through-hole 31 .

[0077] like Figure 3 and Figure 4 As shown, the through hole 31 includes a first circular hole portion 32 and a second circular hole portion 33. The first circular hole portion 32 opens at the upper surface 22. The second circular hole portion 33 is located below the first circular hole portion 32 and opens at the lower surface 21. The first circular hole portion 32 and the second circular hole portion 33 can be formed into a cylindrical shape centered on the rotation axis X and formed concentrically. The diameter of the second circular hole portion 33 can be larger than the diameter of the first circular hole portion 32.

[0078] like Figure 4 As shown, the lower end portion 11a of the shaft 11 is inserted into the first circular hole portion 32. Alternatively, an internal thread (not shown) may be formed on the wall surface of the first circular hole portion 32, and an external thread may be formed on the lower end portion 11a of the shaft 11. In this case, the shaft 11 and the central portion 30 are threadedly engaged, and the shaft 11 and the molten metal impeller 20 can be screwed together.

[0079] The wall height h1 of the first circular hole 32 may be equal to the diameter d1 of the impeller 20 for molten metal (see Figure 3 and Figure 4) or greater, and may also be greater than 5%. By setting height h1 to be greater than 3% of diameter d1, the fastening strength between shaft 11 and impeller 20 for molten metal can be increased, preventing the impeller 20 from accidentally detaching from shaft 11. Furthermore, by setting height h1 to be less than 15% of diameter d1, space saving can be achieved. From this perspective, height h1 may be greater than 3% and less than 15% of diameter d1, or may be greater than 5% and less than 10% of diameter d1.

[0080] Next, the stirring blade 40 will be described.

[0081] like Figure 2 and Figure 3 As shown, the stirring blades 40 are formed in a manner protruding outward in the radial direction from the central portion 30. The number of stirring blades 40 constituting the impeller 20 for molten metal of this embodiment is 8. However, the number of stirring blades 40 is arbitrary as long as it is 2 or more. The stirring blades 40 are arranged at equal angular intervals in the impeller circumferential direction D1 described later. In this embodiment, the stirring blades 40 are arranged at intervals of 45°. In addition, the width w1 (refer to Figure 3 and Figure 5 ) may be the diameter d2 of the second circular hole portion 33 of the through hole 31 (see Figure 3 and Figure 4 ) is greater than or equal to 0.3 times and less than or equal to 0.8 times the diameter d2 of the second circular hole portion 33 of the through hole 31, or may be greater than or equal to 0.4 times and less than or equal to 0.7 times the diameter d2 of the second circular hole portion 33 of the through hole 31. By setting the width w1 to the above range, the strength of the stirring blade 40 can be improved. In addition, by ensuring the width of the stirring blade 40, a flow of the blown gas G toward the radial outward can be formed inside the groove 50. It is also possible to form a flow of the molten material toward the radial outward along with the flow of the blown gas G. By setting the width w1 to less than or equal to 0.8 times the diameter d2, the strength of the impeller 20 for molten metal can be improved. In addition, the width w1 of the stirring blade 40 is the width of the stirring blade 40 at the lower surface 21. The width w1 of the stirring blade 40 can be constant along the radial direction. By using 8 stirring blades 40 to constitute the impeller 20 for molten metal, the flow of the molten metal from the top to the bottom of the impeller 20 for molten metal can be continuously formed and strengthened. Therefore, the stirring efficiency can be improved.

[0082] like Figure 2 and Figure 3As shown, the stirring blade 40 includes a first guide surface 41 and a second guide surface 42. The first guide surface 41 and the second guide surface 42 are connected to the upper surface 22 and the lower surface 21. In this embodiment, the lower edge of the first guide surface 41 is connected to the lower surface 21, and the upper edge of the first guide surface 41 is connected to the upper surface 22. Similarly, the lower edge of the second guide surface 42 is connected to the lower surface 21, and the upper edge of the second guide surface 42 is connected to the upper surface 22.

[0083] like Figure 3 and Figure 5 As shown, when viewed toward the lower surface 21, the first guide surface 41 is located at a position forward from the groove 50 along the impeller circumferential direction D1. When viewed toward the lower surface 21, the second guide surface 42 is located at a position backward from the groove 50 along the impeller circumferential direction D1. Figure 5 As shown in FIG. 4 , when viewed in the radial direction along the stirring blade 40 , the second guide surface 42 is located on the opposite side to the first guide surface 41 . Figure 3 As shown, the impeller circumferential direction D1 is a direction along the circumference of the circle centered on the rotation axis X. When viewed toward the lower surface 21, the impeller circumferential direction D1 may also be a counterclockwise direction. In this embodiment, as shown in FIG. Figure 3 As shown, the impeller circumferential direction D1, as viewed toward the lower surface 21, represents the rotational direction of the impeller 20 for molten metal. In this case, the first guide surface 41 is positioned forward of the second guide surface 42 in the rotational direction, while the second guide surface 42 is positioned backward of the first guide surface 41 in the rotational direction. In other words, the direction from the second guide surface 42 toward the first guide surface 41 along the circumference centered on the rotation axis X represents the rotational direction of the impeller 20 for molten metal.

[0084] like Figure 5 As shown, the first guide surface 41 is inclined relative to the lower surface 21 in a manner that advances along the impeller circumferential direction D1 from the lower surface 21 to the upper surface 22. That is, the first guide surface 41 is inclined relative to the lower surface 21 in a manner that the upper edge of the first guide surface 41 is displaced relative to the lower edge of the first guide surface 41 along the impeller circumferential direction D1. Figure 5 In the example shown, the first guide surface 41 is inclined so as to shift leftward from the lower surface 21 toward the upper surface 22. In other words, the first guide surface 41 is formed so as to extend in the direction of rotation from the lower surface 21 to the upper surface 22. Thus, the first guide surface 41 is configured to guide the molten metal downward when the molten metal impeller 20 rotates.

[0085] The angle θ1 formed by the first guide surface 41 and the extension of the lower surface 21 can be arbitrarily set within a range of 30° or more and less than 90°. By setting θ1 to 30° or more, the stirring function of the molten metal can be improved. By setting θ1 to less than 90°, the rotational resistance of the impeller 20 for the molten metal can be reduced. For example, the angle θ1 can be 45° or 60°. Figure 5 , an example in which the angle θ1 is 60° is shown.

[0086] like Figure 5 As shown, the second guide surface 42 is inclined relative to the lower surface 21 in a manner that advances along the impeller circumferential direction D1 from the lower surface 21 to the upper surface 22. That is, the second guide surface 42 is inclined relative to the lower surface 21 in a manner that the upper edge of the second guide surface 42 is displaced relative to the lower edge of the second guide surface 42 along the impeller circumferential direction D1. Figure 5 In the example shown, the second guide surface 42 is inclined so as to shift leftward from the lower surface 21 toward the upper surface 22. In other words, the second guide surface 42 is formed so as to extend in the direction of rotation from the lower surface 21 to the upper surface 22. Thus, the second guide surface 42 is configured to draw in the molten metal from above as the molten metal impeller 20 rotates.

[0087] The angle θ2 formed by the second guide surface 42 and the lower surface 21 can be arbitrarily set within the range of 30° to 90°. By setting θ2 to 30° or more, the stirring function of the molten metal can be improved. By making θ2 less than 90°, the rotational resistance of the impeller 20 for the molten metal can be reduced. For example, the angle θ2 can be 45° or 60°. The angle θ2 can be equal to the angle θ1. Figure 5 In the example shown, angle θ2 is 60°. Angle θ2 can also be set to an angle different from angle θ1. In this case, from the perspective of smoothly stirring the molten metal in the vertical direction, angle θ2 can be within ±10° or ±5° relative to angle θ1. Setting angle θ2 within this range can further enhance the stirring function of the molten metal.

[0088] like Figures 2 to 4 As shown, the stirring blade 40 includes a front end surface 43. The front end surface 43 is connected to the upper surface 22 and the lower surface 21, and is connected to the first guide surface 41 and the second guide surface 42 mentioned above. The front end surface 43 constitutes the outer peripheral end surface of the impeller 20 for molten metal. Figure 3 , an example is shown in which the front end surface 43 is formed as a portion of a cylindrical surface centered on the rotation axis X. However, the front end surface 43 may extend linearly in a direction perpendicular to the radial direction when viewed toward the lower surface 21 .

[0089] like Figure 4As shown, the upper surface 22 of the impeller 20 for molten metal is inclined relative to the lower surface 21, away from the lower surface 21, from the front end surface 43 of the stirring blade 40 toward the central portion 30. As a result, the thickness of the stirring blade 40 gradually increases from the front end surface 43 toward the central portion 30. The upper surface 22 can be formed into a generally flat conical surface. The angle θ4 of the upper surface 22 relative to the lower surface 21 can be greater than 1° and less than 45°, or greater than 2° and less than 20°, or greater than 3° and less than 10°. By setting the angle θ4 to greater than 1°, it is possible to prevent the molten metal from remaining on the upper surface 22 when the molten metal is discharged from the degassing tank 2. By setting the angle θ4 to less than 45°, it is possible to prevent the thickness of the central portion 30 of the impeller 20 for molten metal from increasing, and space saving can also be achieved.

[0090] Next, the groove 50 will be described.

[0091] like Figures 3 to 5 As shown, grooves 50 are provided on the lower surface 21 of the impeller 20 for molten metal. A groove 50 is formed in each stirring blade 40, with one groove 50 formed for each stirring blade 40. The grooves 50 extend radially from the through-hole 31 to the front end surface 43 of the corresponding stirring blade 40. More specifically, the grooves 50 extend from the second circular hole 33 described above to the front end surface 43 of the stirring blade 40. In this manner, a plurality of grooves 50 are formed radially on the lower surface 21.

[0092] In addition, if Figure 3 As shown, when viewed toward the lower surface, the area occupied by all the grooves 50 in the lower surface 21 (described later) of the impeller 20 for molten metal can be greater than 0.5 times and less than 10.0 times the area occupied by the second circular hole portion 33 (described later) of the through-hole 31, or can be greater than 1.5 times and less than 6.0 times the area occupied by the second circular hole portion 33 (described later) of the through-hole 31. By setting the area occupied by all the grooves 50 to be greater than 0.5 times the area occupied by the second circular hole portion 33, the release amount of the blown gas G at the front end surface 43 of the stirring blade 40 can be increased, and the degassing function can be improved. In addition, by setting the area occupied by the grooves 50 to be less than 10.0 times the area occupied by the second circular hole portion 33, the radially outward blown gas G can be suppressed from being retained inside the grooves 50, forming an efficient laminar flow. It is also possible to form a radially outward flow of the melt along with the flow of the blown gas G.

[0093] The width w2 of the groove 50 (see Figure 3 and Figure 5) can be greater than 0.2 times and less than 0.8 times the width w1 of the stirring blade 40, or can be greater than 0.3 times and less than 0.4 times the width w1 of the stirring blade 40. By setting the width w2 to be greater than 0.2 times the width w1, the area of the groove 50 can be ensured on the lower surface 21 of the metal melt impeller 20, thereby improving the degassing function. By setting the width w2 to be less than 0.8 times the width w1, the strength of the metal melt impeller 20 can be improved. In addition, the width of the groove 50 can be constant along the radial direction, but it can also vary. For example, the width of the groove 50 can gradually narrow from the through-hole 31 to the front end surface 43, or it can gradually widen. In this case, the width of the groove 50 can also vary within the range of the numerical examples above. In addition, when the width w2 of the groove 50 is not constant, the "average value" of the width measured at 10 equally spaced points from the connection point with the second circular hole portion 33 to the connection point with the front end surface 43 is defined as the width w2. These ten points include a connection point with the second circular hole portion 33 and a connection point with the front end surface 43. The width w2 is the width of the groove 50 at the lower surface 21.

[0094] The depth h2 of the groove 50 (see Figure 5 ) can be the thickness t1 of the stirring blade 40 at the front end surface 43 (refer to Figure 4 ) or greater than 0.3 times and less than 0.7 times the thickness t1 of the stirring blade 40 at the front end surface 43. Setting the depth h2 to be greater than or equal to 0.3 times the thickness t1 ensures a sufficient cross-sectional area for the groove 50, improving the degassing function. Setting the depth h2 to be less than or equal to 0.7 times the thickness t1 improves the strength of the impeller 20 for molten metal. Thickness t1 is the thickness of the front end surface 43 at the center of the groove 50 in the width direction.

[0095] like Figure 5 As shown, the groove 50 includes a first side wall 51, a second side wall 52 and a top wall 53. The first side wall 51 and the second side wall 52 are connected to the lower surface 21.

[0096] The first side wall 51 is located at a position that is advanced in the impeller circumferential direction D1 compared to the second side wall 52. In other words, the first side wall 51 is located at a position that is advanced in the rotation direction compared to the second side wall 52. Figure 5 The left side is shown. The first side wall 51 does not need to be formed perpendicular to the lower surface 21. The first side wall 51 may also be formed as a plane perpendicular to the lower surface 21. The so-called perpendicular plane is not limited to a plane that is strictly perpendicular to the lower surface 21, but also includes a plane that is inclined at an angle within ±5° relative to the perpendicular plane.

[0097] The second side wall 52 is located at a position set back in the impeller circumferential direction D1 compared to the first side wall 51. In other words, the second side wall 52 is located at a position set back in the rotation direction compared to the first side wall 51. Figure 5 Right side shown.

[0098] The second side wall 52 can be inclined relative to the lower surface 21 in a manner that advances along the impeller circumferential direction D1 from the lower surface 21 to the top wall 53. That is, the second side wall 52 can be inclined relative to the lower surface 21 in a manner that the upper edge of the second side wall 52 is displaced relative to the lower edge of the second side wall 52 along the impeller circumferential direction D1. The upper edge of the second side wall 52 is connected to the top wall 53, and the lower edge of the second side wall 52 is connected to the lower surface 21. Figure 5 In the example shown, the second side wall 52 is inclined so as to shift leftward from the lower surface 21 toward the top wall 53. In other words, the second side wall 52 is formed so as to advance in the direction of rotation from the lower surface 21 toward the top wall 53. This facilitates the entry of the molten metal into the groove 50 during rotation of the impeller 20, and prevents the downward release of the blown gas G flowing radially outward within the groove 50. The second side wall 52 can be formed as a flat surface inclined relative to the lower surface 21.

[0099] The angle θ3 formed by the second side wall 52 and the extension surface of the lower surface 21 can be arbitrarily set within the range of more than 30° and less than 90°. By setting θ3 to more than 30°, when the impeller 20 for molten metal rotates, the molten metal can easily enter the groove 50, and the release of the blown gas G from the groove 50 to the bottom can be suppressed. For example, the angle θ3 can be 45° or 60°. The angle θ3 can be equal to the angle θ2. The angle θ3 can also be set to an angle different from the angle θ2. In this case, the angle θ3 can deviate from the angle θ2 within the range of ±10°, within the range of ±5°, or within the range of ±3°. By setting the angle θ3 within this range, the second guide surface 42 and the second side wall 52 can be configured to be nearly parallel, and the change in thickness between the second guide surface 42 and the second side wall 52 can be suppressed. Therefore, damage caused by uneven temperature can be prevented, and the strength of the impeller 20 for molten metal can be improved. Figure 5 , an example is shown in which angle θ3 is equal to angle θ2 and is 60°. Furthermore, by setting angle θ3 to less than 90°, a laminar flow of the blown gas G toward the radially outward direction is easily formed within the groove 50. Therefore, the flow rate of the blown gas G within the groove 50 can be increased. Based on these viewpoints, angle θ3 can be greater than 35° and less than 80°, or greater than 40° and less than 75°.

[0100] The top wall 53 is connected to the first side wall 51 and the second side wall 52. The top wall 53 is arranged above the first side wall 51 and the second side wall 52. The top wall 53 can be formed in a curved shape so as to protrude toward the upper surface 22. The top wall 53 can be formed so as to constitute a portion of the cylindrical surface.

[0101] Next, the operation of this embodiment having such a structure will be described.

[0102] During the degassing process, the molten metal such as aluminum alloy stored in the degassing tank 2 is stirred by rotating the molten metal stirring body 10. Figure 3 As shown, the impeller 20 for molten metal rotates in the impeller circumferential direction D1 when viewed toward the lower surface 21. The first guide surface 41 of the stirring blade 40 is located at a position that is forward in the rotation direction relative to the second guide surface 42, so that Figure 5 As shown in FIG. 4 , the molten metal present in the vicinity of the first guide surface 41 is guided downward. Figure 1 As shown, a downward flow of the molten metal is formed near the molten metal impeller 20, causing the molten metal to descend toward the bottom of the degassing tank 2. An upward flow of the molten metal is formed on the outer peripheral wall of the degassing tank 2. This creates a vertically circulating flow of the molten metal within the degassing tank 2, stirring the entire molten metal within the degassing tank 2.

[0103] During the degassing treatment, a gas G such as argon or nitrogen is blown into the molten metal while stirring the molten metal. Figure 3 and Figure 4 As shown, the blown gas G passing through the gas flow path 12 in the shaft 11 reaches the ejection port 13 formed on the lower surface 21 of the shaft 11 and is ejected from the ejection port 13 into the second circular hole portion 33 of the impeller 20 for molten metal. The blown gas G is distributed from the second circular hole portion 33 to each groove 50 and flows radially outward in each groove 50. Figure 5 As shown, the rotation of the molten metal impeller 20 causes the molten metal to enter the groove 50. This prevents the blown gas G within the groove 50 from being released downward from the groove 50, maintaining the flow path of the blown gas G flowing radially outward. The blown gas G flowing within the groove 50 is transformed into bubbles and blown into the molten metal from the front end 43 of each stirring blade 40. The bubbles of the blown gas G are sheared by the rotating stirring blades 40 and are atomized. The atomized bubbles draw impurities from the molten metal, and the buoyancy of the bubbles and the flow of the molten metal cause the impurities to float upward. This removes impurities from the molten metal.

[0104] Thus, according to this embodiment, the first guide surface 41 of the stirring blade 40 of the molten metal impeller 20 is inclined relative to the lower surface 21 so as to advance along the impeller circumferential direction D1 from the lower surface 21 toward the upper surface 22. Thus, when the molten metal impeller 20 rotates in the impeller circumferential direction D1, the molten metal present near the first guide surface 41 can be guided downward. This creates a downward flow of the molten metal, and a vertical circulation flow can be formed within the degassing tank 2. The blown gas G, which passes through the groove 50 provided on the lower surface 21 of the molten metal impeller 20, can be blown into the stirred molten metal from the front end surface 43 of the stirring blade 40. As a result, the blown gas G can be blown into the entire molten metal, thereby improving the efficiency of the molten metal degassing treatment.

[0105] Furthermore, according to this embodiment, the second guide surface 42 is inclined relative to the lower surface 21 so as to extend from the lower surface 21 toward the upper surface 22 along the impeller circumferential direction D1. This allows the molten metal above the impeller 20 to be smoothly guided into the vicinity of the second guide surface 42. This enhances the downward flow of the molten metal and the vertical circulation within the degassing tank 2. Furthermore, the first and second guide surfaces 41, 42 are inclined relative to the lower surface 21 so as to extend from the lower surface 21 toward the upper surface 22 along the impeller circumferential direction D1. Therefore, when the impeller 20 is made of ceramic, thermal shock caused by uneven thickness during firing or use can be prevented, thereby preventing damage.

[0106] Furthermore, according to this embodiment, the impeller circumferential direction D1 is counterclockwise when viewed toward the lower surface 21. Consequently, the first guide surface 41, which is inclined relative to the lower surface 21 so as to advance along the impeller circumferential direction D1 from the lower surface 21 toward the upper surface 22, can be positioned further in the rotational direction than the second guide surface 42. This allows for a downward flow of the molten metal and a vertical circulation flow within the degassing tank 2.

[0107] Furthermore, according to this embodiment, the upper surface 22 of the molten metal impeller 20 is inclined relative to the lower surface 21, moving away from the lower surface 21 from the front end surface 43 of the stirring blade 40 toward the center portion 30. This prevents the molten metal from accumulating near the upper surface 22. Specifically, if molten metal remains on the upper surface 22 when the molten metal is discharged from the degassing tank 2, the molten metal will cool and solidify on the upper surface 22, potentially requiring removal of the solid matter. However, according to this embodiment, by inclining the upper surface 22 relative to the lower surface 21, the molten metal can be prevented from remaining on the upper surface 22. Consequently, the work of removing the solid matter from the molten metal remaining on the upper surface 22 can be reduced or eliminated.

[0108] Furthermore, according to this embodiment, the second sidewall 52 of the groove 50 is positioned set back from the first sidewall 51 in the impeller circumferential direction D1 and is inclined relative to the lower surface 21 so as to advance in the impeller circumferential direction D1 from the lower surface 21 to the top wall 53. Thus, when the molten metal impeller 20 rotates in the impeller circumferential direction D1, the molten metal can smoothly enter the groove 50. The molten metal entering the groove 50 can suppress the blown gas G within the groove 50 from being released downward from the groove 50, and the flow path of the blown gas G flowing radially outward can be maintained. Therefore, the blown gas G can smoothly flow radially outward, be atomized, and be blown into the molten metal from the tip surface 43 of each stirring blade 40.

[0109] Furthermore, according to this embodiment, the first sidewall 51 of the groove 50 is formed perpendicularly to the lower surface 21. This prevents the blown gas G within the groove 50 from being released downward from the groove 50, and maintains a flow path for the blown gas G flowing radially outward within the groove 50. Consequently, the blown gas G can flow smoothly radially outward, and the blown gas G can be atomized and blown into the molten metal from the front end surface 43 of each stirring blade 40.

[0110] In addition, in the above-mentioned embodiment, the example in which the impeller circumferential direction D1 is counterclockwise when viewed toward the lower surface 21 is described. However, the present invention is not limited thereto, and the impeller circumferential direction D1 may also be a clockwise direction when viewed toward the lower surface 21. In this case, Figure 5 The thick arrow indicating the impeller circumferential direction D1 is now pointing to the right. Figure 5 The cross-sectional shape of the stirring blade 40 shown is reversed left to right. In this case, the first guide surface 41 is located forward of the groove 50 along the impeller circumferential direction D1, and the second guide surface 42 is located backward of the groove 50 along the impeller circumferential direction D1. By rotating the molten metal impeller 20 clockwise when viewed toward the lower surface 21, a downward flow of the molten metal can be formed.

[0111] (Second embodiment)

[0112] Next, use Figures 6 to 10 An impeller for molten metal and a stirring body for molten metal according to a second embodiment of the present invention will be described.

[0113] exist Figures 6 to 10 The second embodiment shown in the figure is different mainly in that the number of stirring blades constituting the impeller for molten metal is two, and the other structures are the same as those of the first embodiment. Figures 1 to 5 The first embodiment shown is substantially the same. Figures 6 to 10 In the Figures 1 to 5 The same parts as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted.

[0114] like Figure 6 and Figure 7 As shown, the number of stirring blades 40 constituting the impeller 20 for molten metal in this embodiment is two. The two stirring blades 40 protrude from the central portion 30 in opposite directions. The stirring blades 40 are arranged at 180° intervals and in a straight line. The direction in which each stirring blade 40 protrudes from the central portion 30 is referred to as the blade protrusion direction D2. The blade protrusion direction D2 is along the radial direction. The groove 50 may extend along the blade protrusion direction D2.

[0115] The width w3 of the groove 50 (see Figure 7 ) can be the width w4 of the stirring blade 40 (refer to Figure 7 ) is 0.05 times or more and 0.9 times or less, and may be the width w4 of the stirring blade 40 (refer to Figure 7 ) is greater than 0.1 times and less than 0.4 times. By setting the width w3 to be greater than 0.05 times the width w4, the area of the groove 50 can be ensured on the lower surface 21 of the impeller 20 for molten metal, and the degassing function can be improved. By setting the width w3 to be less than 0.9 times the width w4, the strength of the impeller 20 for molten metal can be improved. In addition, the width w3 of the groove 50 can be constant along the blade protrusion direction D2, but it can also be different. For example, the width w3 of the groove 50 can gradually narrow from the through hole 31 to the front end surface 43, or it can gradually widen. The width w3 of the groove 50 in this case can also vary within the range of the above-mentioned numerical examples. In addition, the width w3 is the width of the groove 50 at the lower surface 21. The width w4 of the stirring blade 40 is the width of the stirring blade 40 at the lower surface 21. The width w4 of the stirring blade 40 can be constant along the radial direction.

[0116] In addition, the width w4 of the stirring blade 40 may be the diameter d2 of the second circular hole portion 33 of the through hole 31 (see Figure 7 and Figure 8 ), and may be between 1.0 times and 1.8 times the diameter d2 of the second circular hole portion 33 of the through-hole 31. By setting the width w4 to the above range, the strength of the stirring blade 40 can be improved on the lower surface 21 of the molten metal impeller 20. In addition, by ensuring the width of the stirring blade 40, a flow of the blown gas G toward the radial outward can be formed within the groove 50. This flow of the blown gas G can also form a flow of the melt toward the radial outward. By setting the width w4 to be less than 2.0 times the diameter d2, the strength of the molten metal impeller 20 can be improved.

[0117] like Figure 7 As shown, when viewed toward the lower surface 21, the dimension w5 of the central portion 30 in a direction perpendicular to the blade protruding direction D2 of the stirring blade 40 may be equal to the width w6 of the front end surface 43 of the stirring blade 40. The dimension w5 is the dimension of the central portion 30 at a position passing through the center (rotation axis X) of the through hole 31. More specifically, the impeller 20 for molten metal includes a pair of side surfaces 23. Each side surface 23 is connected to the lower surface 21 and the upper surface 22. As shown in FIG. Figure 7 As shown, the side surface 23 can be formed along the blade protrusion direction D2. That is, each side surface 23 can extend parallel to the blade protrusion direction D2 and can be perpendicular to the lower surface 21. The side surface 23 is formed in the central portion 30, but can also extend from the central portion 30 to the stirring blade 40. Figure 6 As shown, the side surface 23 may be sandwiched between the guide surfaces 41, 42 and the upper surface 22 or the lower surface 21. For example, the first guide surface 41 may be connected to the upper surface 22 via the side surface 23, and the second guide surface 42 may be connected to the lower surface 21 via the side surface 23. Width w6 is the overall width of the stirring blade 40.

[0118] like Figure 6 and Figure 8 As shown, the central portion 30 includes a protrusion 60 protruding upward from the upper surface 22. The protrusion 60 is provided in a ring shape around the through hole 31, so that the through hole 31 is extended upward. In this case, the insertion depth of the shaft 11 into the first circular hole portion 32 of the through hole 31 can be deepened. For example, when the first circular hole portion 32 is formed with an internal thread, the number of thread teeth can be increased. In addition, the wall height dimension of the first circular hole portion 32 of this embodiment can also be the same as Figure 3 The wall height dimension h1 of the first circular hole portions 32 shown is the same.

[0119] The upper surface 22 of the impeller 20 for molten metal is inclined relative to the lower surface 21 in a manner away from the lower surface 21 from the front end surface 43 of the stirring blade 40 to the protrusion 60. As a result, the thickness of the stirring blade 40 gradually increases from the front end surface 43 to the central portion 30. In this embodiment, the angle of the upper surface 22 relative to the lower surface 21 can be Figure 4 The angle θ4 shown is the same.

[0120] like Figure 7 As shown, a first chamfered surface 44 may be formed between the first guide surface 41 and the lower surface 21 of the stirring blade 40. The first chamfered surface 44 is formed on the inner circumference of the first guide surface 41. This prevents the stirring blade 40 from forming an angular corner. Figure 6 As shown, a second chamfered surface 45 may be formed between the second guide surface 42 and the lower surface 21 of the stirring blade 40 . The second chamfered surface 45 is formed on the inner peripheral side of the second guide surface 42 .

[0121] Thus, according to this embodiment, the number of stirring blades 40 constituting the impeller 20 for molten metal is two. This simplifies the structure of the impeller 20 for molten metal and reduces the weight of the impeller 20 for molten metal. Furthermore, the storage space can be reduced.

[0122] Furthermore, according to this embodiment, the central portion 30 includes a protrusion 60 protruding from the upper surface 22, and the protrusion 60 extends the through-hole 31. This allows the shaft 11 to be inserted deeper into the through-hole 31, thereby stabilizing the attachment of the shaft 11 to the impeller 20 for molten metal. Furthermore, the stirring blade 40 can be made thinner, thereby reducing the weight of the impeller 20 for molten metal.

[0123] Furthermore, according to this embodiment, the upper surface 22 of the molten metal impeller 20 is inclined relative to the lower surface 21, moving away from the lower surface 21 from the front end surface 43 of the stirring blade 40 toward the protrusion 60. This prevents the molten metal from accumulating near the upper surface 22. Specifically, if molten metal remains on the upper surface 22 when the molten metal is discharged from the degassing tank 2, the molten metal will cool and solidify on the upper surface 22, potentially requiring removal of the solid matter. However, according to this embodiment, by inclining the upper surface 22 relative to the lower surface 21, the molten metal can be prevented from remaining on the upper surface 22. Consequently, the work of removing the solid matter from the molten metal remaining on the upper surface 22 can be reduced or eliminated.

[0124] In addition, in the above embodiment, the example in which the dimension w5 of the central portion 30 in the direction perpendicular to the blade protruding direction D2 is equal to the width w6 of the front end surface 43 of the stirring blade 40 is described. However, the present invention is not limited to this. For example, Figure 9and Figure 10 As shown, in the direction perpendicular to the blade protruding direction D2, the dimension w5 of the central portion 30 may be larger than the width w6 of the front end surface 43 of the stirring blade 40. In this case, the mechanical strength of the central portion 30 can be improved, and the attachment of the shaft 11 and the impeller 20 for molten metal can be stabilized. In addition, the rotational resistance of the impeller 20 for molten metal can be reduced. Figure 10 In the illustrated example, the side surfaces 23 of the impeller 20 for molten metal, when viewed toward the lower surface 21, do not necessarily lie along the blade protruding direction D2. More specifically, the side surfaces 23 may include two inclined side surfaces 23a formed away from the groove 50 from the stirring blades 40 toward the center 30, and a cylindrical side surface 23b formed between the two inclined side surfaces 23a. The cylindrical side surface 23b may also constitute a portion of a cylindrical surface centered on the rotation axis X, and may be concentric with the first and second circular hole portions 32, 33 of the through-hole 31. The inclined side surfaces 23a and the cylindrical side surface 23b may also be perpendicular to the lower surface 21.

[0125] The present invention is not limited to the above-mentioned embodiments and modifications, and can be embodied by modifying the constituent elements within the scope of the present invention in the implementation stage. In addition, various inventions can be formed by appropriate combinations of multiple constituent elements disclosed in the above-mentioned embodiments and modifications (including combinations of modifications with each other).

Claims

1. An impeller for molten metal, comprising an upper surface and a lower surface perpendicular to a rotation axis, characterized in that: have: a central portion including a through hole extending from the lower surface along the rotation axis to the upper surface; a plurality of stirring blades protruding radially outward from the central portion; as well as a plurality of grooves provided on the lower surface and extending from the through hole to the corresponding front ends of the stirring blades; The stirring blade includes a first guide surface and a second guide surface connected to the upper surface and the lower surface, When viewed toward the lower surface, the first guide surface is located at a position forward from the groove in the circumferential direction of the impeller, and the second guide surface is located at a position backward from the groove in the circumferential direction of the impeller. The first guide surface is inclined relative to the lower surface so as to advance along the impeller circumferential direction from the lower surface toward the upper surface.

2. The impeller for molten metal according to claim 1, characterized in that: The second guide surface is inclined relative to the lower surface so as to advance along the impeller circumferential direction from the lower surface toward the upper surface.

3. The impeller for molten metal according to claim 1 or 2, characterized in that: When viewed toward the lower surface, the impeller circumferential direction is counterclockwise.

4. The impeller for molten metal according to claim 1 or 2, characterized in that: The upper surface is inclined relative to the lower surface so as to be away from the lower surface from the front end of the stirring blade toward the center portion.

5. The impeller for molten metal according to claim 1 or 2, characterized in that: The groove includes: a first side wall connected to the lower surface; a second side wall connected to the lower surface and located at a position retreated along the circumferential direction of the impeller compared to the first side wall; and a top wall connected to the first side wall and the second side wall; The second side wall is inclined relative to the lower surface so as to advance along the impeller circumferential direction from the lower surface toward the top wall.

6. The impeller for molten metal according to claim 5, characterized in that: The first side wall is formed perpendicularly to the lower surface.

7. The impeller for molten metal according to claim 1 or 2, characterized in that: The number of the stirring blades is 2.

8. The impeller for molten metal according to claim 7, characterized in that: The central portion includes a protrusion that protrudes from the upper surface and extends the through hole.

9. The impeller for molten metal according to claim 8, characterized in that: The upper surface is inclined relative to the lower surface so as to be away from the lower surface from the front end of the stirring blade toward the protrusion.

10. The impeller for molten metal according to claim 7, characterized in that: The direction in which the stirring blade protrudes from the central portion is defined as a blade protruding direction, The center portion has a dimension greater than a dimension of a front end of the stirring blade in a direction perpendicular to a protruding direction of the blade.

11. A stirring body for molten metal, characterized in that: have: Axis; and The impeller for molten metal according to claim 1 or 2, which is mounted on the lower end portion of the shaft.

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