An efficient annular-gap vacuum gas atomization nozzle

Abstract

The present invention relates to the technical field of gas atomization powder making, and specifically relates to a high-efficiency annular slit vacuum gas atomization nozzle. After the base and the intermediate bushing of the nozzle are assembled, an annular gas storage chamber is formed between the base and the intermediate bushing; the air inlet hole of the base is communicated with the gas storage chamber, a horizontal air guide hole is opened on the side surface of the intermediate bushing, one end of the air guide hole is communicated with the gas storage chamber, and the other end of the air guide hole is communicated with the inner cavity of the intermediate bushing; the inner bushing is installed in the inner cavity of the intermediate bushing and is coaxial with the intermediate bushing, and an annular slit nozzle air passage is formed between the inner bushing and the inner cavity of the intermediate bushing. The annular slit nozzle air passage is an air passage with a constant cross-section, the width а of the annular slit nozzle air passage is 0.5 mm to 1.5 mm, the value range of the atomization angle α is 45° to 70°, and the diameter D at the lower end outlet of the annular slit nozzle air passage is 13 mm to 17 mm. The present invention is applicable to preparing metal alloy powders with a specific particle size distribution with an average D50 requirement of 25 μm to 65 μm. The nozzle has a simple structure, a high powder output rate, low processing costs, and a long service life.

Description

Technical Field

[0001] The present invention relates to the technical field of gas atomization powder making, and specifically to a high-efficiency annular slit vacuum gas atomization nozzle. Background Art

[0002] The gas atomization powder making technology originated in the 1820s of the 19th century. It uses the impact force of gas on the molten liquid flow to convert the kinetic energy of the gas into the surface energy of the melt, thereby forming fine droplets and solidifying them into powder particles. Initially, the gas atomization powder making technology was mainly used to prepare non-ferrous metal powders such as Al-based and Cu-based. After more than two hundred years of continuous development, this technology has been used for large-scale production of various high-performance metal and alloy powders such as Ni-based, Fe-based, Co-based, and Ti-based, and is widely used in fields such as aerospace, energy power, and mechanical metallurgy.

[0003] The core of the gas atomization technology is to control the process of the gas acting on the metal liquid flow, and this process is achieved through the atomization nozzle. Therefore, the atomization nozzle is the core of the atomization technology and the key component of the atomization equipment. It directly determines the performance of the powder, the powder yield, and the stability of the atomization production process. Currently, the most widely used industrial application is the close-coupled atomization technology, which has a compact structure, the shortest distance from the gas flow outlet to the metal liquid flow, and the energy of the gas flow is maximally converted into the surface energy of the metal droplets, with high atomization efficiency. Scholars from various countries have carried out research on the gas flow field and heat transfer in the atomization process by combining experiments and numerical simulation calculations, and developed different nozzle structures, such as ultrasonic nozzles, Unal nozzles, Nanoval nozzles, and high-pressure gas atomization converging-diverging nozzles, etc. However, the atomization process is a complex physical and chemical process of multi-phase flow coupling. So far, the action mechanism is still unclear, and the design of the nozzle still mainly relies on experience. In actual production, different structures of atomization nozzles are designed and selected according to the characteristics of the melt and the performance requirements of the powder. Summary of the Invention

[0004] The purpose of the present invention is to provide a high-efficiency annular slit vacuum gas atomization nozzle, which is suitable for preparing metal alloy powders with a specific particle size distribution with an average D50 requirement of 25 μm to 65 μm. The nozzle has a simple structure, a high powder yield, low processing costs, and a long service life.

[0005] To achieve the above purpose, the technical solution of the present invention is:

[0006] A high-efficiency annular slit vacuum gas atomization nozzle includes a base, an intermediate bushing, an inner bushing, and a diversion system. The specific structure is as follows:

[0007] The base is a columnar groove structure with an upward opening. A central hole is provided at the bottom thereof, and an air inlet hole is provided on the side thereof; the intermediate bushing is a stepped columnar sleeve structure integrally formed by a columnar groove in the upper part and a cylindrical tube in the lower part coaxially; the intermediate bushing is installed on the base and is coaxial with the base. The intermediate bushing is inserted into the central hole of the base through the lower end of the lower cylindrical tube, and the bottom edge of the upper columnar groove abuts against the upper end of the base and is in close contact. After the base and the intermediate bushing are assembled, an annular gas storage chamber is formed between the base and the intermediate bushing; the air inlet hole of the base is communicated with the gas storage chamber, and a horizontal air guide hole is provided on the side of the lower cylindrical tube of the intermediate bushing. One end of the air guide hole is communicated with the gas storage chamber, and the other end of the air guide hole is communicated with the inner cavity of the intermediate bushing;

[0008] In the inner cavity of the intermediate bushing, the inner wall of the lower cylindrical tube is an integral structure of a columnar section, a contraction section, and an expansion section from top to bottom; the inner bushing is installed in the inner cavity of the intermediate bushing and is coaxial with the intermediate bushing. The inner bushing is an integral structure of an upper columnar part, a middle columnar part, and a lower frustum-shaped part coaxially. The upper columnar part is installed in the upper columnar groove of the intermediate bushing and is closely matched with the inner cavity of the upper columnar groove. The middle columnar part and the lower frustum-shaped part are located in the inner cavity surrounded by the columnar section and the contraction section of the intermediate bushing, and a circumferential slit nozzle air passage is correspondingly formed between them and the inner cavity surrounded by the columnar section and the contraction section;

[0009] The flow guiding system penetrates through the central hole of the inner bushing. The lower end of the flow guiding system is located in the inner cavity formed by the expansion section of the intermediate bushing. The inner wall of the inner bushing is an integral structure of a columnar section and an expansion section from top to bottom. The expansion angle of the expansion section of the inner bushing is the same as that of the expansion section of the lower cylindrical tube of the intermediate bushing, and the expansion section of the lower cylindrical tube of the intermediate bushing is located in the extending direction of the expansion section of the inner bushing.

[0010] For the described high-efficiency circumferential slit vacuum gas atomization nozzle, the outer diameter of the upper columnar groove of the intermediate bushing is larger than the outer diameter of the lower cylindrical tube, and the outer diameter of the lower cylindrical tube is the same as the diameter of the central hole of the base.

[0011] For the described high-efficiency circumferential slit vacuum gas atomization nozzle, the diameter of the central hole at the bottom of the upper columnar groove of the intermediate bushing is the same as the inner diameter of the upper end of the lower cylindrical tube.

[0012] For the described high-efficiency circumferential slit vacuum gas atomization nozzle, the outer diameter of the upper columnar part of the intermediate bushing is larger than the outer diameter of the middle columnar part, the outer diameter of the middle columnar part is the same as the outer diameter of the upper end of the lower frustum-shaped part, and the outer diameter of the upper end of the lower frustum-shaped part is larger than the outer diameter of the lower end of the lower frustum-shaped part.

[0013] The described high-efficiency annular-slot vacuum gas atomization nozzle has an annular-slot nozzle air passage that is an air passage with a constant cross-section. The width а of the annular-slot nozzle air passage is 0.5 mm to 1.5 mm. The angle between the two generatrices in the longitudinal section of the lower frustum-shaped part, or the angle between the two generatrices in the longitudinal section of the contraction section, or the angle between the centerlines of the lower frustum-shaped part and the contraction section is the atomization angle α, and its value range is 45° to 70°. The diameter D at the lower end outlet of the annular-slot nozzle air passage is 13 mm to 17 mm.

[0014] For the described high-efficiency annular-slot vacuum gas atomization nozzle, the lower end outlet of the annular-slot nozzle air passage is located between the expansion section of the inner lining sleeve and the lower cylindrical expansion section of the middle lining sleeve.

[0015] The described high-efficiency annular-slot vacuum gas atomization nozzle has a flow guiding system composed of a ceramic material flow guiding tube, and the inner diameter of the flow guiding tube is φ2 mm to φ5 mm.

[0016] For the described high-efficiency annular-slot vacuum gas atomization nozzle, the air guide holes are evenly distributed on the cylindrical section of the middle lining sleeve, the aperture of which is 1.5 to 2.5 mm, and the number is 15 to 22.

[0017] For the described high-efficiency annular-slot vacuum gas atomization nozzle, the base, the middle lining sleeve, and the inner lining sleeve are made of stainless steel, and the three parts are hermetically connected by welding after assembly.

[0018] For the described high-efficiency annular-slot vacuum gas atomization nozzle, during operation, the atomization gas pressure is used within the range of 2 to 6 MPa; the atomization gas first enters the gas storage chamber from the air inlet hole, then enters the annular-slot nozzle air passage through the air guide holes, and after being accelerated by the annular-slot nozzle air passage, it acts on the alloy melt coming out of the central hole of the flow guiding system, breaking the alloy melt into fine droplets and then solidifying into powder particles.

[0019] The design concept of the present invention:

[0020] Gas atomization powder making is a method of producing powder by using a high-speed gas flow to impact and break a metal or alloy liquid stream, breaking the liquid stream into tiny droplets and rapidly condensing them. In order to improve the atomization efficiency and fragmentation effect, the method of increasing the kinetic energy of the atomizing gas is usually adopted. By means of a complex nozzle air passage design (such as: laval), a subsonic or even supersonic ultra-high atomizing gas flow velocity is generated, and fine powder is obtained by using the high energy of the gas. However, the processing of such a complex air passage is difficult, and it is easy to cause problems such as gas dispersion, large turbulence, and poor stability of the atomization process. Different from the above design idea of increasing the kinetic energy of the atomizing gas, an efficient annular slit vacuum gas atomization nozzle provided by the present invention has an equal cross-section design for the air passage, which can effectively control the gas flow field structure in the recirculation zone. By utilizing the characteristic that the gas moves upward from the stagnation point, the suction pressure is reduced, the melt flow velocity is slowed down, and at the same time, "membrane formation" of the melt is achieved, that is, the melt flows parallel along the bottom after flowing out of the guide pipe, and then forms a film along the gas flow direction and is further broken into alloy powder.

[0021] The advantages and beneficial effects of the present invention are as follows:

[0022] 1. An efficient annular slit vacuum gas atomization nozzle provided by the present invention utilizes the characteristics of the gas flow field structure in the recirculation zone and breaks into alloy powder through "membrane formation and fragmentation" of the melt. Therefore, it can be broken into alloy powder at a lower atomization pressure, greatly saving gas consumption, being beneficial to improving the powder formation rate of medium-sized powder with a D50 requirement of 25μm - 65μm, and at the same time reducing defects such as hollow spheres and satellite spheres generated due to the strong interaction between the high-pressure atomizing gas and the melt, and improving the powder quality.

[0023] 2. An efficient annular slit vacuum gas atomization nozzle provided by the present invention has the characteristics of simple structure, easy processing, reliable use performance, and long service life. Description of the Drawings

[0024] Figure 1 It is a schematic structural diagram of the annular slit vacuum gas atomization nozzle of the present invention.

[0025] In the figure: 1 base, 2 intermediate bushing (21 upper columnar groove, 22 lower cylinder, 23 columnar section, 24 contraction section, 25 expansion section), 3 inner lining bushing (31 columnar section, 32 expansion section, 33 upper columnar part, 34 middle columnar part, 35 lower frustum part), 4 diversion system, 5 gas storage chamber, 6 annular slit nozzle air passage, 7 air guide hole, 8 air inlet hole.

[0026] Figure 2 It is a scanning electron microscope photograph of the Ni25Cr5Al0.5Y alloy powder in Example 1.

[0027] Figure 3 It is a scanning electron microscope photograph of the Co32Ni22Cr8Al0.6Y alloy powder in Example 2. Detailed Embodiments

[0028] See Figure 1 As shown, the high-efficiency circumferential seam vacuum gas atomization nozzle of the present invention is composed of four parts, including a base 1, an intermediate bushing 2, an inner bushing 3, and a diversion system 4. The specific structure is as follows:

[0029] The base 1 is a columnar groove structure with an upward opening. A central hole is provided at the bottom, and an air inlet hole 8 is provided on the side; the intermediate bushing 2 is a stepped columnar sleeve structure integrally formed by an upper columnar groove 21 and a lower cylinder 22 coaxially. The outer diameter of the upper columnar groove 21 is larger than the outer diameter of the lower cylinder 22;

[0030] The intermediate bushing 2 is installed on the base 1 and is coaxial with the base 1. The intermediate bushing 2 is inserted into the central hole of the base 1 through the lower end of the lower cylinder 22. The outer diameter of the lower cylinder 22 is the same as the diameter of the central hole of the base 1. The bottom edge of the upper columnar groove 21 overlaps and is in close contact with the upper end of the base 1. After the base 1 and the intermediate bushing 2 are assembled, a relatively large annular gas storage chamber 5 is formed between the base 1 and the intermediate bushing 2; the air inlet hole 8 of the base 1 is communicated with the gas storage chamber 5. A horizontal air guide hole 7 is provided on the side of the lower cylinder 22. One end of the air guide hole 7 is communicated with the gas storage chamber 5, and the other end of the air guide hole 7 is communicated with the inner cavity of the intermediate bushing 2;

[0031] In the inner cavity of the intermediate bushing 2, the diameter of the central hole at the bottom of the upper columnar groove 21 is the same as the inner diameter of the upper end of the lower cylinder 22. The inner wall of the lower cylinder 22 is an integrally connected structure of a cylindrical section 23, a contraction section 24, and an expansion section 25 from top to bottom; the inner bushing 3 is installed in the inner cavity of the intermediate bushing 2 and is coaxial with the intermediate bushing 2. The inner bushing 3 is a coaxial integral connection structure of an upper columnar part 33, a middle columnar part 34, and a lower frustum part 35. The outer diameter of the upper columnar part 33 is larger than the outer diameter of the middle columnar part 34. The outer diameter of the middle columnar part 34 is the same as the outer diameter of the upper end of the lower frustum part 35. The outer diameter of the upper end of the lower frustum part 35 is larger than the outer diameter of the lower end of the lower frustum part 35; the upper columnar part 33 is installed in the upper columnar groove 21 and is in close fit with the inner cavity of the upper columnar groove 21. The middle columnar part 34 and the lower frustum part 35 are located in the inner cavity surrounded by the cylindrical section 23 and the contraction section 24 of the intermediate bushing 2, and a circumferential seam nozzle air passage 6 is correspondingly formed between them and the inner cavity surrounded by the cylindrical section 23 and the contraction section 24.

[0032] The diversion system 4 passes through the central hole of the inner bushing 3. The inner bushing 3 cooperates with the diversion system 4. The lower end of the diversion system 4 is located in the inner cavity formed by the expansion section 25. The inner wall of the inner bushing 3 is an integrally connected structure of a cylindrical section 31 and an expansion section 32 from top to bottom. The expansion angle of the expansion section 32 of the inner bushing is the same as that of the expansion section 25 of the lower cylinder, and the expansion section 25 of the lower cylinder is located in the extension direction of the expansion section 32 of the inner bushing.

[0033] The annular slit nozzle air passage 6 is an air passage with a constant cross-section. The width а of the annular slit nozzle air passage 6 is 0.5 mm to 1.5 mm. The angle between the two generatrices of the longitudinal section of the lower frustum-shaped part 35 (or the angle between the two generatrices of the longitudinal section of the contraction section 24, or the angle between the centerlines of the lower frustum-shaped part 35 and the contraction section 24) is the atomization angle α, and its value range is 45° to 70°. The diameter D at the lower end outlet of the annular slit nozzle air passage 6 is 13 mm to 17 mm. The lower end outlet of the annular slit nozzle air passage 6 is located between the lining sleeve expansion section 32 and the lower cylindrical expansion section 25.

[0034] The diversion system 4 is composed of a ceramic material diversion pipe, and the inner diameter of the diversion pipe is φ2 mm to φ5 mm. The air guide holes 7 are evenly distributed on the cylindrical section 23 of the intermediate lining sleeve 2, and their aperture diameters are 1.5 to 2.5 mm, and the number is 15 to 22. The base 1, the intermediate lining sleeve 2, and the inner lining sleeve 3 are made of stainless steel, and the three parts are hermetically connected by welding after assembly.

[0035] During operation, the atomizing gas pressure is used within the range of 2 to 6 MPa. The atomizing gas first enters the gas storage chamber 5 from the air inlet hole 8, then enters the annular slit nozzle air passage 6 through the air guide holes 7. After being accelerated by the annular slit nozzle air passage 6, the atomizing gas acts on the alloy melt coming out of the central hole of the diversion system 4, breaking the alloy melt into fine droplets and then solidifying them into powder particles.

[0036] Next, the present invention will be further elaborated in detail through embodiments.

[0037] Embodiment 1:

[0038] As Figure 1 shown, this embodiment provides an efficient annular slit vacuum gas atomization nozzle, which is composed of a base 1, an intermediate lining sleeve 2, an inner lining sleeve 3, and a diversion system 4. After the base 1 and the intermediate lining sleeve 2 are assembled, a gas storage chamber 5 is formed. The intermediate lining sleeve 2 is provided with air guide holes 7. After the intermediate lining sleeve 2 and the inner lining sleeve 3 are assembled, an annular slit nozzle air passage 6 is formed, and the inner lining sleeve 3 cooperates with the diversion system 4.

[0039] The annular slit nozzle air passage 6 is an air passage with a constant cross-section. The width а of the annular slit nozzle air passage 6 is 1.0 mm. The angle formed by the lower centerline of the annular slit nozzle air passage 6 is the atomization angle α, and its value is 50°. The diameter D at the lower end outlet of the annular slit nozzle air passage 6 is 15 mm.

[0040] The diversion system 4 is composed of a BN diversion pipe, and the inner diameter of the diversion pipe is φ3.5 mm. The air guide holes 7 are evenly distributed on the cylindrical section 23 of the intermediate lining sleeve 2, and their aperture diameters are 2.0 mm, and the number is 16. The base 1, the intermediate lining sleeve 2, and the inner lining sleeve 3 are made of stainless steel, and the three parts are hermetically connected by welding after assembly.

[0041] The atomization production of powders is carried out with Ni25Cr5Al0.5Y as the atomization object. The atomization temperature is 1580 °C and the atomization pressure is 4 MPa. The results of Example 1 show that the atomization process is smooth. The yield of powders in the particle size range of 20 μm to 45 μm reaches 58%, and the powders have good sphericity (such as Figure 2 ), and excellent fluidity (18.0 s / 50 g) and apparent density (4.02 g / cm 3 ).

[0042] Example 2:

[0043] The difference from Example 1 is that in Example 2, the width а of the annular slit nozzle air passage 6 is 1.2 mm, the atomization angle α is 45°, and the inner diameter of the draft tube is φ4.0 mm.

[0044] The atomization test of powders is carried out with Co32Ni22Cr8Al0.6Y as the atomization object. The atomization temperature is 1550 °C and the atomization pressure is 3.5 MPa. The results of Example 2 show that the atomization process is smooth. The yield of powders in the particle size range of 45 μm to 63 μm reaches 32%, and the powders have good sphericity (such as Figure 3 ), and excellent fluidity (18.3 s / 50 g) and apparent density (3.92 g / cm 3 ).

Claims

1. An efficient annular slit vacuum gas atomization nozzle, characterized in that, It includes a base, an intermediate bushing, an inner bushing, and a flow guiding system. The specific structure is as follows: The base is a columnar groove structure with an upward opening. A central hole is provided at its bottom, and an air inlet hole is provided on its side. The intermediate bushing is a stepped columnar sleeve structure that is integrally formed by a columnar groove in the upper part and a cylindrical tube in the lower part coaxially. The intermediate bushing is installed on the base and is coaxial with the base. The intermediate bushing is inserted into the central hole of the base through the lower end of the lower cylindrical tube. The bottom edge of the upper columnar groove overlaps and is in close contact with the upper end of the base. After the base and the intermediate bushing are assembled, an annular gas storage chamber is formed between the base and the intermediate bushing. The air inlet hole of the base is communicated with the annular gas storage chamber. A horizontal air guiding hole is provided on the side of the lower cylindrical tube of the intermediate bushing. One end of the air guiding hole is communicated with the annular gas storage chamber, and the other end of the air guiding hole is communicated with the inner cavity of the intermediate bushing. In the inner cavity of the intermediate bushing, the inner wall of the lower cylindrical tube is an integral structure of a columnar section, a contraction section, and an expansion section from top to bottom. The inner bushing is installed in the inner cavity of the intermediate bushing and is coaxial with the intermediate bushing. The inner bushing is a coaxial integral structure of an upper columnar part, a middle columnar part, and a lower frustum-shaped part. The upper columnar part is installed in the upper columnar groove of the intermediate bushing and is closely matched with the inner cavity of the upper columnar groove. The middle columnar part and the lower frustum-shaped part are located in the inner cavity surrounded by the columnar section and the contraction section of the intermediate bushing, and a ring-shaped nozzle air passage is correspondingly formed between them and the inner cavity surrounded by the columnar section and the contraction section. The flow guiding system penetrates through the central hole of the inner bushing. The lower end of the flow guiding system is located in the inner cavity formed by the expansion section of the intermediate bushing. The inner wall of the inner bushing is an integral structure of a columnar section and an expansion section from top to bottom. The expansion angle of the expansion section of the inner bushing is the same as that of the expansion section of the lower cylindrical tube of the intermediate bushing, and the expansion section of the lower cylindrical tube of the intermediate bushing is located in the extension direction of the expansion section of the inner bushing.

2. The high-efficiency annular-gap vacuum gas atomization nozzle according to claim 1, wherein, The outer diameter of the upper columnar groove of the intermediate bushing is larger than the outer diameter of the lower cylindrical tube, and the outer diameter of the lower cylindrical tube is the same as the diameter of the central hole of the base.

3. The high-efficiency annular-gap vacuum gas atomization nozzle according to claim 1, wherein, The diameter of the central hole at the bottom of the upper columnar groove of the intermediate bushing is the same as the inner diameter of the upper end of the lower cylindrical tube.

4. The high-efficiency annular-gap vacuum gas atomization nozzle according to claim 1, wherein The outer diameter of the upper columnar part of the inner bushing is larger than the outer diameter of the middle columnar part. The outer diameter of the middle columnar part is the same as the outer diameter of the upper end of the lower frustum-shaped part. The outer diameter of the upper end of the lower frustum-shaped part is larger than the outer diameter of the lower end of the lower frustum-shaped part.

5. The high-efficiency annular slit vacuum gas atomization nozzle according to claim 1, wherein The ring-shaped nozzle air passage is an air passage with a constant cross-section. The width а of the ring-shaped nozzle air passage is 0.5 mm to 1.5 mm. The angle between the two generatrices in the longitudinal section of the lower frustum-shaped part, or the angle between the two generatrices in the longitudinal section of the contraction section, or the angle between the centerlines of the lower frustum-shaped part and the contraction section, is the atomization angle α, and its value range is 45° to 70°. The diameter D at the lower end outlet of the ring-shaped nozzle air passage is 13 mm to 17 mm.

6. The high-efficiency annular-gap vacuum gas atomization nozzle according to claim 1 or 5, characterized in that, The lower end outlet of the ring-shaped nozzle air passage is located between the expansion section of the inner bushing and the expansion section of the lower cylindrical tube of the intermediate bushing.

7. The high-efficiency annular-gap vacuum gas atomization nozzle according to claim 1, characterized in that, The flow guiding system is composed of a ceramic material flow guiding tube, and the inner diameter of the flow guiding tube is Φ2 mm to Φ5 mm.

8. The high-efficiency annular slit vacuum gas atomization nozzle according to claim 1, wherein, The air guiding holes are evenly distributed on the columnar section of the intermediate bushing. Their pore diameter is 1.5 to 2.5 mm, and the number is 15 to 22.

9. The high-efficiency circumferential seam vacuum gas atomization nozzle according to claim 1, characterized in that, The base, the intermediate bushing, and the inner bushing are made of stainless steel. After the three parts are assembled, they are hermetically connected by welding.

10. The high-efficiency circumferential seam vacuum gas atomization nozzle according to claim 1, characterized in that, During operation, the atomizing gas pressure is used within the range of 2 to 6 MPa; the atomizing gas first enters the annular gas storage chamber from the air inlet hole, and then enters the annular slit nozzle air duct through the air guide hole. After being accelerated by the annular slit nozzle air duct, the atomizing gas acts on the alloy melt flowing out of the central hole of the diversion system, breaking the alloy melt into fine droplets and then solidifying them into powder particles.

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