Metal powder manufacturing apparatus and method for manufacturing metal powder

Abstract

To provide a metallic powder manufacturing apparatus capable of manufacturing high-quality metallic powder, and a metallic powder manufacturing method.SOLUTION: A metallic powder manufacturing apparatus 10 has: a molten metal supply part 20 that discharges molten metal 21; a cylindrical body 32 in which a layer 50 of cooling liquid that cools the molten metal 21 is formed on an inner circumferential surface 33; and a cooling liquid guide part 36 that supplies the cooling liquid to an upper inner side of the cylindrical body 32. The circumferential surface 33 on the upper inner side of the cylindrical body 32 has an approximately oval shape.SELECTED DRAWING: Figure 1A

Description

[Technical Field]

[0001] The present invention relates to a metal powder manufacturing apparatus and a method for manufacturing metal powder. [Background technology]

[0002] For example, a metal powder manufacturing apparatus that manufactures metal powder using a so-called gas atomization method and a manufacturing method using the apparatus are known, as shown in Patent Document 1. The conventional apparatus includes a molten metal supply vessel that discharges molten metal, a cylinder installed below the molten metal supply vessel, and a coolant outlet that forms a flow of coolant on the inner surface of the cylinder to cool the molten metal discharged from the molten metal supply vessel.

[0003] The coolant outlet sprays the coolant in a tangential direction to the inner circumferential surface of the cooling cylinder, causing the coolant to flow down while swirling in a circular pattern on the inner circumferential surface of the cooling vessel, forming a coolant layer. The use of the coolant layer is expected to rapidly cool the droplets and produce highly functional metal powder.

[0004] However, conventional methods for producing metal powders sometimes do not allow for rapid cooling of the droplets, and there is a demand for an apparatus and method capable of producing higher quality metal powders. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 11-80812 Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a metal powder manufacturing apparatus and a metal powder manufacturing method that are capable of manufacturing higher quality metal powder. [Means for solving the problem]

[0007] In order to achieve the above object, the metal powder manufacturing apparatus according to the present invention comprises: a molten metal supply unit that discharges molten metal; a cylinder having an inner circumferential surface on which a layer of cooling liquid for cooling the molten metal is formed; a coolant outlet portion for supplying the coolant to the cylindrical body, The metal powder manufacturing apparatus is characterized in that the inner circumferential surface of the inside of the upper part of the cylindrical body has a substantially elliptical shape.

[0008] The metal powder manufacturing apparatus of the present invention can form a coolant layer that flows in a substantially elliptical spiral along the inner circumferential surface of the cylinder. By injecting molten metal droplets into this coolant layer, the molten metal droplets can be cooled more rapidly. The flow velocity of the coolant in the elliptical spiral is faster on the minor axis side of the ellipse and slower on the major axis side. The droplets injected into this coolant layer flow together with the coolant in the coolant layer while their flow velocity changes.

[0009] By flowing the droplets through the coolant layer while changing the flow rate, the vapor film that is thought to be generated around the droplets immediately after contact with the coolant is more easily separated from the droplets, enhancing the rapid cooling effect of the droplets in the coolant layer. By rapidly cooling the droplets in this way, it is possible to produce metal powder with good amorphousness and magnetic properties even at small particle sizes.

[0010] Preferably, the coolant outlet portion has a coolant outlet port that discharges the coolant supplied from the outside of the cylinder so that the coolant flows from the upper part of the cylinder along the inner circumferential surface in a spiral trajectory. With this configuration, a coolant layer can be formed from the coolant outlet port in an elliptical spiral shape from the upper part of the cylinder along the inner circumferential surface toward the lower part, thereby enhancing the rapid cooling effect of the molten metal droplets and enabling the production of metal powder with good amorphous properties and magnetic properties even with a small particle size.

[0011] Preferably, the coolant discharge port is formed in a substantially elliptical shape around the circumference of the cylinder. The coolant discharge port may be formed continuously around the circumference of the cylinder, or may be formed intermittently around the circumference of the cylinder by providing a reinforcing member or the like at the coolant discharge port. By forming the coolant discharge port around the circumference of the cylinder, it becomes easier to form a coolant layer of coolant that flows in an elliptical spiral along the inner circumferential surface of the cylinder.

[0012] Preferably, the coolant outlet portion has a frame body that changes the flow of the coolant from the outside to the inside into a flow along the inner circumferential surface of the cylindrical body, and the frame body has an approximately elliptical inner frame piece with a diameter smaller than the inner circumferential surface of the cylindrical body. With this configuration, a approximately elliptical coolant discharge port can be formed between the inner frame piece and the inner circumferential surface of the cylindrical body. As a result, the coolant can be discharged from the coolant discharge port in an elliptical spiral along the inner circumferential surface of the cylindrical body.

[0013] Preferably, the frame is disposed inside the cylindrical body and defines an inner space through which the coolant flows from the outside to the inside of the cylindrical body, the inner space being formed in a generally elliptical shape along the inner circumferential surface. This configuration allows the coolant to form an elliptical flow along the inner circumferential surface in the inner space. The coolant is discharged downward along the inner circumferential surface and the axis of the cylindrical body, thereby smoothly forming an elliptical spiral coolant layer along the inner circumferential surface.

[0014] Preferably, the coolant outlet portion has an outer forming member that forms an outer space in which the coolant is temporarily stored, the outer forming member being disposed outside the cylindrical body, and the outer space being formed in a substantially elliptical shape. With this configuration, the coolant is introduced into the cylindrical body while swirling in an elliptical shape in the outer space, and a coolant layer of the coolant that flows in an elliptical spiral along the inner circumferential surface of the cylindrical body is easily formed smoothly.

[0015] Preferably, the coolant discharge port is formed between the inner peripheral surface of the cylindrical body and the inner frame piece. The inner peripheral surface of the cylindrical body may be the inner peripheral surface of the cylindrical auxiliary piece. Preferably, the lower end of the passage portion connecting the outer space and the inner space of the coolant lead-out portion is arranged upward along the axis.

[0016] Preferably, the center of the ellipse formed by the inner peripheral surface is shifted so as to be inclined relative to the vertical line as it moves toward the bottom of the cylindrical body. With this configuration, the coolant in the coolant layer formed along the inner peripheral surface flows in an elliptical spiral trajectory that is inclined relative to the vertical direction. This allows the distance of the elliptical spiral along which the coolant flows to be increased. Furthermore, by spraying the molten metal vertically downward, the molten metal droplets can easily enter the coolant layer without impeding the flow of the coolant, facilitating smooth cooling of the droplets.

[0017] Preferably, the ratio of the minor axis to the major axis of the ellipse formed by the inner circumferential surface is equal to or greater than 1.04 and equal to or less than 3.00. With this configuration, it becomes easy to form a coolant layer of uniform thickness while changing the flow rate of the coolant.

[0018] A ring may be formed in a generally elliptical shape along the inner circumferential surface of the lower part of the cylinder. With this configuration, the ring controls the flow of the coolant in the direction along the axis of the cylinder, making it easier to control the thickness of the coolant layer of the coolant flowing in an elliptical spiral along the inner circumferential surface of the cylinder to a constant thickness.

[0019] In order to achieve the above object, the method for producing a metal powder according to the present invention comprises: forming a layer of cooling liquid along an inner circumferential surface of the cylindrical body, the flow rate of which varies; discharging molten metal from a molten metal supply portion toward the layer of the cooling liquid; and flowing the molten metal together with the cooling liquid while varying the flow rate.

[0020] This configuration enhances the effect of rapidly cooling the molten metal droplets, making it possible to produce metal powder with good amorphous properties and magnetic properties even when the particle size is small.

[0021] Preferably, the coolant is caused to flow in a generally elliptical spiral along the inner circumferential surface to form a layer of the coolant. With this configuration, the molten metal droplets flow along the inner circumferential surface while changing their flow speed together with the coolant, thereby enhancing the rapid cooling effect of the molten metal droplets. [Brief explanation of the drawings]

[0022] [Figure 1A] FIG. 1A is a schematic cross-sectional view of a metal powder manufacturing apparatus according to one embodiment of the present invention. [Figure 1B] FIG. 1B is an enlarged cross-sectional view of a main part of the metal powder manufacturing apparatus shown in FIG. 1A. [Figure 1C] FIG. 1C is an enlarged perspective cross-sectional view of a main part of the metal powder manufacturing apparatus shown in FIG. 1A. [Figure 2A] FIG. 2A is a schematic side view of the flow of the coolant in the metal powder manufacturing apparatus shown in FIG. 1A. [Figure 2B] FIG. 2B is a schematic diagram of the flow of the coolant shown in FIG. 2A viewed from the vertical direction. [Figure 3A] FIG. 3A is a schematic diagram showing the configuration of a cylindrical body of the metal powder manufacturing apparatus shown in FIG. 1A. [Figure 3B] FIG. 3B is a schematic diagram showing the configuration of a modified example of the cylindrical body shown in FIG. 1A. [Figure 4] FIG. 4 is a schematic cross-sectional view of a metal powder manufacturing apparatus according to another embodiment of the present invention. [Figure 5A] FIG. 5A is a schematic side view of the flow of cooling water in a conventional metal powder manufacturing apparatus. [Figure 5B] FIG. 5B is a schematic diagram of the flow of cooling water shown in FIG. 5A as viewed from above. DETAILED DESCRIPTION OF THE INVENTION

[0023] Hereinafter, the present invention will be described based on the embodiments shown in the drawings.

[0024] First embodiment 1A, a metal powder manufacturing apparatus 10 according to one embodiment of the present invention is an apparatus for powdering molten metal 21 by atomization (gas atomization) to obtain metal powder composed of a large number of metal particles. This apparatus 10 has a molten metal supply section 20 and a cooling section 30 disposed vertically below the metal supply section 20. In the drawing, the vertical direction is along the Z axis.

[0025] The molten metal supply section 20 has a heat-resistant container 22 that contains molten metal 21. A heating coil 24 is arranged around the outer periphery of the heat-resistant container 22 to heat the molten metal 21 contained inside the container 22 and maintain it in a molten state. A molten metal discharge port 23 is formed at the bottom of the container 22, from which the molten metal 21 is discharged as dripping molten metal 21a toward the inner circumferential surface 33 of a cylindrical body 32 that constitutes the cooling section 30.

[0026] Gas injection nozzles 26 are arranged on the outer side of the outer bottom wall of vessel 22 so as to surround molten metal discharge port 23. Gas injection nozzle 26 is equipped with gas injection ports 27. High-pressure gas is injected from gas injection ports 27 toward dripping molten metal 21a discharged from molten metal discharge port 23. The high-pressure gas is injected obliquely downward from all around the molten metal discharged from molten metal discharge port 23, causing dripping molten metal 21a to form a large number of droplets which are carried along the gas flow toward inner circumferential surface 33 at the top inside of cylinder 32.

[0027] The molten metal 21 may contain any element, for example, at least one of Ti, Fe, Si, B, Cr, P, Cu, Nb, and Zr. These elements are highly active, and molten metal 21 containing these elements is easily oxidized by short-term contact with air, forming an oxide film, making it difficult to pulverize. As described above, the metal powder manufacturing apparatus 10 uses an inert gas as the gas injected from the gas injection port 27 of the gas injection nozzle 26, so that even easily oxidized molten metal 21 can be easily powdered.

[0028] The gas injected from the gas injection port 27 is preferably an inert gas such as nitrogen gas, argon gas, or helium gas, or a reducing gas such as an ammonia decomposition gas, but air may also be used if the molten metal 21 is a metal that is difficult to oxidize.

[0029] 1A has a substantially elliptical cross section (e.g., a cross section substantially perpendicular to the Z axis) that is inclined at an angle θ1 with respect to the axis O of the cylinder 32. If the axis O of the cylinder 32 is inclined at an angle θ2 with respect to the Z axis, the angle θ1 can be expressed as θ1=(90 degrees-θ2).

[0030] In a cross section inclined at an angle θ1 with respect to the axis O of the cylindrical body 32, it is preferable that the major axis of the ellipse of the inner peripheral surface 33 coincides with the direction in which the axis O of the cylindrical body 32 is inclined with respect to the Z axis (vertical line). In other words, it is preferable that the cylindrical body 32 is configured so that the major axis of the ellipse is included in a plane that includes the axis O of the cylindrical body 32 and the Z axis that intersects with the axis O.

[0031] The cylindrical body 32 configured in this manner can be manufactured from a cylindrical material 32α having a circular inner circumferential surface in a cross section perpendicular to the axis O, as shown in Fig. 3A, for example. That is, the cylindrical body 32 shown in Fig. 1A can be formed by cutting the upper and lower portions of the cylindrical material 32α horizontally while tilting the axis O of the cylindrical material 32α at a predetermined angle θ2 with respect to the vertical direction (Z-axis direction). In this embodiment, the inner circumferential surface 33 of the cylindrical body 32 has an approximately elliptical shape of the same size in cross section inclined at an angle θ1 with respect to the axis O, and is formed continuously along the axis O.

[0032] As shown in FIG. 2B, in this embodiment, the ratio of the major axis L3 to the minor axis L2 (L3 / L2) of the ellipse appearing in each horizontal cross section of the inner circumferential surface 33 of the cylindrical body 32 is preferably 1.01 to 3.00, more preferably 1.04 to 2.00, and particularly preferably 1.04 to 1.30. This configuration facilitates the formation of a coolant layer of uniform thickness while varying the flow rate of the coolant (e.g., cooling water). For example, although this varies depending on the flow rate, fluid pressure, and thickness of the coolant layer, when L3 / L2 is 1.04 to 3.00, the speed ratio of the coolant flow rate (maximum speed / minimum speed) can be varied to approximately 1.07 to 1.33.

[0033] As shown in FIG. 1A , a discharge section 34 is provided at the bottom along the axis O of the cylindrical body 32. The discharge section 34 is capable of discharging the metal powder carried in the coolant layer 50 to the outside together with the coolant. The inner diameter of the inner circumferential surface of the discharge section 34 may be smaller than the inner diameter of the inner circumferential surface 33 of the cylindrical body 32, and it is preferable that the inner diameter continuously decreases from the inner circumferential surface 33 of the cylindrical body 32 toward the inner circumferential surface of the discharge section 34. The horizontal cross section of the inner circumferential surface 33 of the cylindrical body 32 does not necessarily have to be elliptical, and may be circular. Preferably, the horizontal cross section of the inner circumferential surface 33 of the cylindrical body 32 is an ellipse of the same size from the top of the cylindrical body 32 along the axis O toward the discharge section 34.

[0034] A coolant outlet 36 is provided at the upper portion of the cylindrical body 32 along the axis O. As shown in FIG. 1B, the coolant outlet 36 has a frame 38 and an outer forming member (outer frame forming member) 45. The outer forming member 45 may be molded integrally with the cylindrical body 32, or may be molded separately from the cylindrical body 32 and attached to the cylindrical body 32.

[0035] The outer forming member 45 forms an outer space 44 outside the inner peripheral surface 33 at the top of the cylindrical body 32. In addition, an auxiliary cylinder 40 is attached to the upper inner peripheral surface of the cylindrical body 32. The auxiliary cylinder 40 may be the upper end opening edge of the cylindrical body 32 itself, but in the example shown, it is molded separately from the cylindrical body 32 and attached to the upper inner peripheral surface of the cylindrical body 32. The inner peripheral surface of the auxiliary cylinder is preferably flush with the inner peripheral surface 33 of the cylindrical body 32, but may be different.

[0036] The frame 38 may be molded integrally with the cylindrical body 32, but is preferably molded separately from the cylindrical body 32. The frame 38 has an inner frame piece 39a disposed inside the inner peripheral surface of the cylindrical body 32, and a frame support piece 39b that intersects with the inner frame piece 39a at a predetermined angle. As shown in FIG. 1C, the frame support piece 39b is a plate piece having a substantially elliptical ring shape, and the inner frame piece 39a has a substantially elliptical cylindrical shape with a central axis Oa that is inclined at an angle θ1 (with respect to the linear axis of the ellipse) from the central opening edge of the substantially elliptical shape of the frame support piece 39b.

[0037] The axis Oa of the inner frame piece 39a shown in Fig. 1C coincides with the axis O of the cylindrical body 32 shown in Fig. 1A, and the horizontal cross section of the outer peripheral surface of the inner frame piece 39a has a similar elliptical shape with a smaller inner diameter than the ellipse of the horizontal cross section of the inner peripheral surface 33 of the cylindrical body 32 (or the inner peripheral surface of the auxiliary cylindrical body 40) shown in Fig. 1A. In other words, the outer peripheral surface of the inner frame piece 39a has a smaller diameter than the inner peripheral surface 33 of the cylindrical body 32 (or the inner peripheral surface of the auxiliary cylindrical body 40) and is parallel to it.

[0038] 1A , the outer diameter portion of frame support piece 39b is attached to the upper end of outer forming member 45 or the upper end of cylindrical body 32. Alternatively, the outer diameter portion of frame support piece 39b may be formed integrally with the upper end of outer forming member 45 or the upper end of cylindrical body 32. The inner diameter portion of frame support piece 39b and inner frame piece 39a, together with the inner circumferential surface of cylindrical body 32, the inner circumferential surface of auxiliary cylindrical body 40, and / or the inner circumferential surface of outer forming member 45, define an inner space 46 inside inner circumferential surface 33 at the top of cylindrical body 32.

[0039] 1B, the outer forming member 45, together with the cylindrical body 32 (including the cylindrical auxiliary piece 40), defines an outer space 44 outside the inner circumferential surface 33 at the top of the cylindrical body 32. The inner space 46 is located radially inside the outer space and communicates with the outer space 44 through the passage portion 42. The upper end of the auxiliary cylindrical body 40 or the cylindrical body 32 is located between the outer space 44 and the inner space so that the passage portion 42 is formed along the axis O of the cylindrical body 32 at or near the top of the outer space 44.

[0040] In this embodiment, the outer space 44 is formed in a substantially elliptical ring shape that continues in the horizontal direction outside the inner circumferential surface 33 of the cylindrical body 32. The inner space 46 is formed in a substantially elliptical ring shape that continues in the horizontal direction inside the inner circumferential surface 33 of the cylindrical body 32 along the inner circumferential surface 33. The passage portion 42 is also formed in a substantially elliptical ring shape that continues in the horizontal direction. The vertical width W1 of the passage portion 42 along the axis O is narrower than the vertical width W2 of the outer space 44 in the axial direction. W1 / W2 is preferably 1 / 2 or less.

[0041] A coolant supply line 37 for introducing coolant is attached to the radially outer side of the outer forming member 45. The connection port from the supply line 37 to the outer space 44 is preferably located lower along the axis O than the passage portion 42.

[0042] In the outer space 44, it is preferable that the coolant flowing in from the supply line 37 flows from below to above the outer space, and that a flow is formed that flows from the passage portion 42 into the inner space 46. In addition, it is preferable that the lower end of the inner frame piece 39a for forming the inner space 46 is located lower along the axis O than the passage portion 42, and a coolant discharge port 52 is formed between the lower end of the inner frame piece 39a and the inner circumferential surface 33 of the cylinder 32 (including the inner circumferential surface of the cylinder auxiliary piece 40). As shown in FIG. 1C, the lower end of the inner frame piece 39a defines an opening that is approximately elliptical in the horizontal plane.

[0043] The inner diameter of the coolant discharge port 52 matches the outer diameter of the inner frame piece 39a, and the outer diameter of the coolant discharge port 52 matches the inner circumferential surface of the cylindrical body 32 (the inner diameter of the cylindrical auxiliary piece 40). In horizontal cross section, the coolant discharge port 52 is preferably formed in the shape of a substantially elliptical ring that continues along the circumferential direction.

[0044] The coolant discharge port 52 is connected to the inner space 46, and the coolant in the inner space 46 is ejected from the coolant discharge port 52 in an elliptical spiral shape toward the inner circumferential surface 33 of the cylindrical body 32. In this embodiment, the radial width of the coolant discharge port 52 is not particularly limited, but corresponds to the thickness of the coolant layer 50 of the coolant flowing along the inner circumferential surface of the cylindrical body 32 and is determined in relation thereto.

[0045] 1A, the axial length L1 of the inner frame piece 39a is determined so that it covers the width W1 of the passage portion 42 in the axial direction O shown in FIG. 1B and so that a coolant discharge port 52 is formed upstream of the position where the molten metal discharged from the molten metal supply portion 20 contacts the cooling layer 50. Also, as shown in FIG. 1A, the axial length L1 of the inner frame piece 39a is determined so that the liquid surface of the coolant layer 50 having a sufficient axial length L0 is exposed on the inner circumferential surface 33 of the cylindrical body 32.

[0046] The length L0 of the coolant layer 50 exposed to the inside along the axis O is preferably 5 to 500 times longer than the axial length L1 of the inner frame piece 39a. The inner diameter (minor axis of the ellipse) of the inner peripheral surface 33 of the cylindrical body 32 is not particularly limited, but is preferably 50 to 500 mm.

[0047] In this embodiment, the coolant supply line 37 may be connected in a tangential direction to the coolant outlet portion 36. The coolant can be caused to flow from the coolant supply line 37 into the outer space 44 so as to rotate in an elliptical spiral around the axis O. The coolant that has flowed in a spiral into the outer space 44 passes through the passage portion 42 and flows into the inner space 46 in a spiral manner.

[0048] In this embodiment, in the coolant outlet portion 36, the coolant is temporarily stored in an outer space 44 disposed outside the cylindrical body 32. The outer space 44 is formed in a substantially elliptical shape. With this configuration, the coolant is introduced into the inner space 46 while swirling in an elliptical shape in the outer space 44.

[0049] In this embodiment, the lower end of the passage 42 is formed higher than the lower end of the outer space 44, so the coolant is first lifted upward while swirling in an elliptical spiral in the outer space 44, and then passes through the passage 42 and enters the inner space 46. By passing through the passage 42, the coolant entering the inner space 46 located inside the upper part of the cylindrical body 32 increases in flow velocity, collides with the inner frame piece 39a of the inner space 46, and changes direction of flow.

[0050] The coolant that passes through the passage 42 provided at the upper part of the cylindrical body 32 and enters the interior of the internal space 46 in an elliptical spiral shape changes its flow downward along the inner frame piece 39a (along the axis O). In addition, the frame support piece 39b blocks the upward flow of the coolant. In the internal space 46, the coolant forms an elliptical ring-shaped flow around the axis O along the inner circumferential surface 33. Furthermore, gravity acts on the coolant downward along the inner circumferential surface 33 (along the axis O), and due to the synergistic effect of gravity, the coolant is discharged from the coolant discharge port 52 so as to flow in a substantially elliptical spiral trajectory along the inner circumferential surface 33. The coolant discharged from the coolant discharge port 52 forms a coolant layer 50 in which the coolant flows in an elliptical spiral shape with a substantially constant thickness along the inner circumferential surface 33.

[0051] 1A, in this embodiment, the coolant is supplied from the coolant outlet 36 to the elliptical inner circumferential surface 33 on the inside of the upper portion of the cylindrical body 32, thereby forming a coolant layer 50 in which the coolant flows in a substantially elliptical spiral along the inner circumferential surface 33 of the cylindrical body 32. By injecting dripping molten metal 21a, which are droplets of the molten metal 21, onto the inner liquid surface of the coolant layer 50, the dripping molten metal 21a can be more rapidly cooled. As shown in FIGS. 2A and 2B, the flow velocity of the elliptical spiral coolant is faster on the minor axis side of the ellipse and slower on the major axis side. Therefore, the dripping molten metal 21a injected into the coolant layer 50 flows through the coolant layer 50 together with the coolant, with the flow velocity changing.

[0052] By flowing the dripping molten metal 21a together with the coolant through the coolant layer 50 while changing the flow rate, the vapor film around the dripping molten metal 21a, which is thought to be generated immediately after contact with the coolant, is easily separated from the dripping molten metal 21, making it easier for the dripping molten metal 21a to be rapidly cooled in the coolant layer 50. By rapidly cooling the dripping molten metal 21a in this way, it is possible to produce metal powder that has good amorphous properties and magnetic properties even when the particle size is small.

[0053] 1A, in this embodiment, the coolant discharge port 52 is formed continuously in a substantially elliptical shape around the circumference of the cylindrical body 32, but it may also be formed intermittently around the circumference of the cylindrical body 32 by providing a reinforcing member or the like to the coolant discharge port 52. By forming the coolant discharge port 52 around the circumference of the cylindrical body 32, a coolant layer 50 of coolant flowing in an elliptical spiral along the inner circumferential surface 33 of the cylindrical body 32 can be formed.

[0054] 1A, in this embodiment, the coolant outlet portion 36 can form a coolant discharge port 52 having a substantially elliptical shape between the inner frame piece 39a and the inner circumferential surface 33 of the cylindrical body 32. As a result, the coolant can be discharged from the coolant discharge port 52, flowing in an elliptical spiral along the inner circumferential surface 33 of the cylindrical body 32.

[0055] 1A, in this embodiment, the center of the ellipse formed by inner circumferential surface 33 is shifted so as to be inclined at an angle θ2 with respect to the vertical line (Z-axis) toward the bottom of cylindrical body 32. As shown in FIG. 2A, the coolant in coolant layer 50 formed along inner circumferential surface 33 flows in an elliptical spiral trajectory that is inclined with respect to the vertical direction (the direction of gravity).

[0056] Therefore, the distance of the elliptical spiral through which the coolant flows can be increased, provided that the length along the Z axis remains the same. Also, by spraying the molten metal in the direction of gravity toward one end of the inner circumferential surface 33 of the cylinder 32 along the major axis of the ellipse, the dripping molten metal 21a can easily enter the inner circumferential surface 33 of the cylinder 32 (coolant layer 50) from the upper end opening of the cylinder 32, and the droplets can be cooled smoothly.

[0057] In the above-described embodiment, the horizontal cross section of the inner surface 33 of the cylindrical body 32 is an ellipse of the same size from the top of the cylindrical body 32 along the axis O toward the discharge portion 34, but the horizontal cross section of the inner surface 33 of the cylindrical body 32 only needs to be approximately elliptical in shape at least at the top of the cylindrical body 32, and may change halfway along the axis O toward the discharge portion 34, for example, gradually changing from an approximately elliptical shape to an approximately circular shape (or other shape).

[0058] Furthermore, the ratio (L3 / L2) of the major axis L3 to the minor axis L2 of the ellipse in the horizontal cross section of the inner peripheral surface 33 of the cylindrical body 32 is preferably constant from the top of the cylindrical body 32 along the axis O toward the discharge portion 34, but may be varied. For example, the ratio (L3 / L2) may be varied so that it decreases or increases from the top of the cylindrical body 32 along the axis O toward the discharge portion 34, or may be varied so that it alternates between the two.

[0059] Furthermore, the horizontal cross section of the inner circumferential surface 33 of the cylindrical body 32 may have the orientation of the major axis of the ellipse gradually change from the upper part of the cylindrical body 32 along the axis O toward the discharge portion 34. For example, in the upper part of the cylindrical body 32, the orientation of the major axis of the ellipse may be aligned with the inclination direction of the axis O of the cylindrical body 32, and in the lower part of the cylindrical body 32, the orientation of the major axis of the ellipse may be changed to be approximately perpendicular to the inclination direction of the axis O of the cylindrical body 32.

[0060] In this embodiment, the predetermined angle θ2 between the axis O of the cylindrical body 32 and the vertical direction is not particularly limited, but is preferably 5 to 45 degrees. By setting the angle within this range, the molten metal 21a dripping from the molten metal discharge port 23 can be easily discharged toward the coolant layer 50 formed on the inner circumferential surface 33 of the cylindrical body 32.

[0061] In this embodiment, the coolant outlet portion 36 is formed so that the frame support piece 39b is horizontal, but is not limited to this as long as it is configured to discharge the coolant layer 50 in an elliptical spiral shape.

[0062] Second embodiment As shown in FIG. 4, the metal powder manufacturing apparatus 110 and the metal powder manufacturing method according to another embodiment of the present invention are the same as those of the first embodiment, except as described below. Common components are given common component names and symbols, and descriptions of some of the common parts are omitted.

[0063] A ring 35 is fixed downstream of the inner circumferential surface 33 of the cylindrical body 32 that constitutes the cooling section 30. The ring 35 functions as a weir (or baffle) on the downstream side of the coolant layer 50 on the inner circumferential surface 33 of the cylindrical body 32. The coolant layer 50 reaches a predetermined thickness because the flow in the direction of the axial center O is blocked by the ring 35, and the coolant layer 50 flows over the ring 35 to the bottom of the cylindrical body 32. By providing the ring 35 on the downstream side of the coolant layer 50, the ring 35 controls the flow of the coolant in the direction along the axial center O of the cylindrical body 32, making it easier to control the thickness of the coolant layer 50 to a constant thickness.

[0064] In this embodiment, the ring 35 is attached at an angle θ1 with respect to the axis O of the cylindrical body 32, and is formed in an elliptical ring shape along the inner peripheral surface 33 of the cylindrical body 32. The radial thickness of the ring 35 corresponds to the radial thickness of the cooling layer 50, and is preferably approximately the same as the radial width of the discharge port 52.

[0065] The present invention is not limited to the above-described embodiment, and various modifications can be made within the scope of the present invention.

[0066] For example, unlike the above-described embodiment, instead of the cylindrical material 32α having a circular inner circumferential surface 33 perpendicular to the axis O shown in FIG. 3A, an elliptical cylindrical material having an approximately elliptical cross section of the inner circumferential surface perpendicular to the axis O may be used as the cylinder 32, as shown in FIG. 3B.

[0067] In the embodiment shown in Fig. 3A, a cylindrical material 32α is cut to form an elliptical inner circumferential surface 33 inclined with respect to the axis O, but as shown in Fig. 3B, a cylindrical material may be used in which the cross section of the inner circumferential surface 33 perpendicular to the axis O is elliptical in advance. Note that, as shown in Fig. 2A, in the first embodiment described above, an elliptical spiral flow is formed in which the center of a horizontal ellipse around the Z axis changes along the axis O of the cylindrical body, but in this embodiment, an elliptical spiral flow is realized in which the center of an ellipse perpendicular to the axis O moves along the axis O along the inner circumferential surface 33 of the cylindrical body. [Example]

[0068] The present invention will be described below in more detail with reference to examples, but the present invention is not limited to these examples.

[0069] Example Using a metal powder production apparatus 10 shown in FIG. 1A in which the angle θ2 is 25 degrees and the ratio (L3 / L2) of the major axis L3 to the minor axis L2 of the circumferential ellipse is 1.10, metal powders consisting of Fe-Si-B (Experiment No. 7), Fe-Si-Nb-B-Cu (Experiment No. 8), Fe-Si-BP-Cu (Experiment No. 10), Fe-Nb-B (Experiment No. 12), Fe-Zr-B (Experiment No. 13), and Fe-Co-Si-BP-Cu (Experiment No. 14) were produced.

[0070] Furthermore, Fe-Co-Si-BP-Cu (Experiment No. 9) was produced using a metal powder production apparatus 10 in which the angle θ2 was 15 degrees and L3 / L2 was 1.04. Furthermore, Fe-Co-Si-BP-Cu (Experiment No. 11) was produced using a metal powder production apparatus 10 in which the angle θ2 was 40 degrees and L3 / L2 was 1.30.

[0071] In each experiment, the melting temperature was 1500°C, the injection gas pressure was 5 MPa, and the gas type used was argon, and the spiral water flow conditions were a pump pressure of 7.5 kPa. In the examples, metal powders were produced with an average particle size of 24.9 to 26.2 μm, which was relatively small and had little variation for each composition. The average particle size was measured using a dry particle size distribution analyzer (HELLOS). In addition, crystal analysis of the metal powders produced in Experiments 7 to 14 was evaluated using powder X-ray diffraction. In the examples, it was confirmed that amorphous metal powders were produced. The magnetic properties of the metal powders were measured by measuring the coercive force (Oe) using an Hc meter. The results are shown in Table 1. The thickness of the coolant layer 50 was 30 mm, and little variation in the axial direction was observed.

[0072] Furthermore, when L3 / L2 was 1.04, the speed ratio (maximum speed / minimum speed) of the coolant flow velocities was approximately 1.07, when L3 / L2 was 1.10, the speed ratio of the coolant flow velocities was approximately 1.16, and when L3 / L2 was 1.30, the speed ratio of the coolant flow velocities was approximately 1.20.

[0073] Reference example 5A and 5B, metal powders (Experiment Nos. 1 to 6) were produced in the same manner as in the Examples, and similar evaluations were performed, except that a metal powder production apparatus was used in which the cross section perpendicular to the axis O of the inner circumferential surface 33 of the cylindrical body 32 was circular (L3 / L2=1.00), and the lower end of the inner frame piece 39a of the coolant outlet portion defined a circular opening in the cross section perpendicular to the axis O, resulting in a circular coolant discharge port 52. The results are shown in Table 1.

[0074] Comparing the Examples and Reference Examples in Table 1, it was confirmed that the magnetic properties of the metal powder were superior to those of the Reference Examples, with the Example having a smaller coercive force than the Reference Examples despite the same composition. This result of superior magnetic properties despite the same pump pressure and flow rate of cooling water as the Reference Examples is thought to be due to the following phenomenon.

[0075] In the metal powder manufacturing apparatus of the reference example, as shown in FIGS. 5A and 5B, the coolant flowing on the inner circumferential surface forms a circular spiral coolant layer. Therefore, the flow rate of the coolant on the inner circumferential surface is considered to be approximately constant (the speed ratio of the coolant flow rates is approximately 1.00). In contrast, in the example, as shown in FIGS. 2A and 2B, the coolant forms a coolant layer 50 with a substantially elliptical spiral. In the elliptical spiral coolant layer 50, the flow rate is slow on the long axis side and fast on the short axis side, so the flow rate changes. Therefore, the molten metal droplets sprayed onto the coolant layer 50 flow with the coolant layer, changing their flow rate. The steam film around the droplets, which is thought to be generated immediately after contact with the coolant, is likely to be easily detached from the droplets due to the change in flow rate, thereby enhancing the rapid cooling effect of the droplets in the coolant layer.

[0076] [Table 1] [Explanation of symbols]

[0077] 10,110… Metal powder manufacturing equipment 20... Molten metal supply section 21... Molten metal 22… Container 23... Molten metal outlet 24... Heating coil 26... Gas injection nozzle 27... Gas nozzle 30,130… Cooling section 32... Cylinder 32α... Cylindrical material 33…Inner peripheral surface 34... Discharge section 35...Ring 36... Coolant outlet 37... Supply line 38…Frame body 39a… Inner frame piece 39b... Frame support piece 40… Cylinder auxiliary piece 42… Passage section 44…Outside space 45...Outer forming member 46… Inner space 50… Coolant layer 52… Coolant discharge port

Claims

1. a molten metal supply unit that discharges molten metal; a cylinder having an inner circumferential surface on which a layer of cooling liquid for cooling the molten metal is formed; a coolant outlet portion for supplying the coolant to an upper inside of the cylindrical body, The inner circumferential surface of the inside of the upper part of the cylindrical body has a substantially elliptical shape, the coolant outlet portion has a frame body that changes the flow of the coolant from the outside to the inside into a flow along the inner circumferential surface of the cylindrical body, the frame body has a substantially elliptical inner frame piece whose diameter is smaller than the inner peripheral surface of the cylindrical body, The metal powder manufacturing apparatus is characterized in that the inner frame piece is inclined so as to follow the axis of the cylindrical body.

2. The metal powder manufacturing apparatus according to claim 1, characterized in that the coolant discharge portion has a coolant discharge port that discharges the coolant supplied from the outside of the cylindrical body so that it flows in a spiral trajectory along the inner surface from the top of the cylindrical body.

3. 3. The metal powder manufacturing apparatus according to claim 2, wherein the coolant discharge port is formed in a substantially elliptical shape around the circumference of the cylindrical body.

4. The frame body has a frame support piece having a substantially elliptical ring shape that intersects with the inner frame piece at a predetermined angle, The lower end of the inner frame piece defines an opening that is substantially elliptical in horizontal plane. The metal powder manufacturing apparatus according to any one of claims 1 to 3.

5. the frame is disposed inside the cylindrical body and defines an inner space through which the cooling liquid flows from the outside to the inside of the cylindrical body; 5. The metal powder manufacturing apparatus according to claim 1, wherein the inner space is formed in a substantially elliptical shape along the inner peripheral surface.

6. the coolant outlet portion has an outer forming member that forms an outer space in which the coolant is temporarily stored, the outer forming member is disposed on the outside of the cylindrical body, 6. The metal powder manufacturing apparatus according to claim 1, wherein the outer space is formed in a substantially elliptical shape.

7. A metal powder manufacturing apparatus as described in any one of claims 1 to 6, characterized in that the center of the ellipse formed by the inner surface is shifted so as to be inclined relative to the vertical line as it moves toward the bottom of the cylindrical body.

8. 8. The metal powder manufacturing apparatus according to claim 1, wherein the ellipse formed by the inner peripheral surface has a ratio of minor axis to major axis of 1.04 or more and 3.00 or less.

9. A process in which, inside a coolant outlet section which is arranged inside the inner surface of a cylinder and has an approximately elliptical inner frame piece which is smaller in diameter than the inner surface and inclined along the axis of the cylinder, coolant flowing in from outside the cylinder is caused to collide with the inner frame piece, changing its direction and forming an elliptical ring-shaped flow of coolant along the inner surface, and the coolant is discharged from the coolant outlet section so that it flows in an approximately elliptical spiral orbit along the inner surface, forming a layer of coolant whose flow rate changes along the inner surface of the cylinder; discharging molten metal from a molten metal supply portion toward the layer of the cooling liquid; and flowing the molten metal together with the cooling liquid while changing the flow rate.

10. 10. The method for producing metal powder according to claim 9, wherein the coolant is caused to flow in a substantially elliptical spiral along the inner circumferential surface to form a layer of the coolant.

Images