An arc additive manufacturing device and additive manufacturing process combining a circular arc and a Laval nozzle

Abstract

The present invention discloses an arc additive device and additive process combining an annular arc and Laval, comprising a Laval nozzle, an annular tungsten electrode, a lifting mechanism, and a workbench. The lifting mechanism is connected to one end of the Laval nozzle for controlling the movement of the Laval nozzle. The Laval nozzle comprises a Laval nozzle contraction end and a Laval nozzle throat. The annular tungsten electrode is connected to the Laval nozzle throat on a side away from the Laval nozzle contraction end. A substrate is placed on the workbench, the substrate being larger than the annular tungsten electrode. Air inlets are provided on both sides of the top of the Laval nozzle, and a feeding mechanism is also provided on the Laval nozzle. The presence of the Laval utility nozzle significantly improves the bonding strength of additive manufacturing while avoiding the disadvantage of coarse grains caused by excessive heat input, reducing the occurrence of product cracks. The presence of the annular arc increases the additive area, greatly improving the additive efficiency.

Description

Technical Field

[0001] The present invention relates to the technical field of additive manufacturing equipment, and in particular to an arc additive device combining an annular arc and Laval. Background Art

[0002] Additive manufacturing technology is a revolutionary manufacturing technology that has overturned traditional subtractive manufacturing methods. Metal additive manufacturing, in particular, as a revolutionary and advanced manufacturing technology, is widely used in related fields such as aerospace, biomedicine, industrial molds, and power energy.

[0003] Arc additive manufacturing (AM) uses an electric arc to melt wire and deposit the molten metal layer by layer in a line-surface-solid configuration based on a three-dimensional model of the product. This process solidifies and forms a metal component. This process offers advantages such as high wire utilization, low cost, freedom from part size constraints within the build cylinder or vacuum chamber, and ease of repair. However, existing technologies using arc AM require high heat input, resulting in coarse grains, poor mechanical properties, and a tendency to crack. Summary of the Invention

[0004] In order to overcome the above problems existing in the prior art, the present invention proposes an arc material adding device that combines an annular arc and Laval.

[0005] The technical solution adopted by the present invention to solve its technical problems is: an arc additive device that combines an annular arc and Laval, including a Laval nozzle, an annular tungsten electrode, a lifting mechanism, and a workbench. The lifting mechanism is connected to one end of the Laval nozzle for controlling the movement of the Laval nozzle. The Laval nozzle includes a Laval nozzle contraction end and a Laval nozzle throat. The annular tungsten electrode is connected to the side of the Laval nozzle throat away from the Laval nozzle contraction end. A substrate is placed on the workbench, and the size of the substrate is larger than that of the annular tungsten electrode. Air inlets are provided on both sides of the top of the Laval nozzle, and a feeding mechanism is also provided on the Laval nozzle.

[0006] In the above-mentioned arc additive device combining annular arc and Laval, the feeding mechanism includes a wire feeding structure, which is located above the central axis of the Laval nozzle and is used to feed the welding wire to the bottom of the Laval nozzle.

[0007] In the above-mentioned annular arc and Laval composite arc additive device, the feeding mechanism includes a particle powder inlet, and the particle powder inlet is located on the side of the contraction end of the Laval nozzle.

[0008] In the above-mentioned annular arc and Laval composite arc additive device, the Laval nozzle and the annular arc are both placed perpendicular to the substrate.

[0009] In the above-mentioned arc additive device combining annular arc and Laval, the cross-sectional area of the Laval nozzle convergence end gradually decreases toward the Laval nozzle throat, the convergence angle of the Laval nozzle convergence end is 30°-60°, the Laval nozzle throat is straight cylindrical, and the diameter ratio of the Laval nozzle convergence end to the Laval nozzle throat is 2-2.5:1.

[0010] In the above-mentioned annular arc and Laval composite arc additive device, the annular tungsten electrode is connected to the Laval nozzle through a nylon insulating sleeve.

[0011] In the above-mentioned annular arc and Laval composite arc additive device, the annular tungsten electrode is connected to the nylon insulator through threads, and the upper end of the annular tungsten electrode and the lower end of the nylon insulating sleeve are both provided with threads.

[0012] The additive process of any of the above-mentioned annular arc and Laval composite arc additive devices comprises the following steps:

[0013] Step 1: Adjust the position of the Laval nozzle using the lifting mechanism so that the distance between the annular tungsten electrode at the bottom of the Laval nozzle and the substrate is 5-8 mm. Ensure that the Laval nozzle is placed perpendicular to the substrate at a 90° angle.

[0014] Step 2: Open the gas supply device, supply the protective gas into the Laval nozzle from the gas inlet, and discharge the gas from the Laval nozzle throat;

[0015] Step 3, adjust welding parameters and feeding speed;

[0016] Step 4: Start the welding power supply to feed the material, and energize the annular tungsten electrode to start adding material;

[0017] Step 5: After the material addition is completed, turn off the welding power supply, feeding mechanism and gas feeding device in sequence.

[0018] In the additive process of the above-mentioned annular arc and Laval composite arc additive device, the feeding speed in step 3 varies according to the feeding state. When the feeding material is welding wire, the feeding speed is 2-8 m / min; when the feeding material is granular powder, the feeding speed is 0.1-1.2 g / s.

[0019] The beneficial effect of the present invention is that the Laval nozzle sprays the shielding gas into the annular arc area at a supersonic speed, the annular arc heats the substrate and the additive material at the same time, the arc heating forms an annular melting zone on the surface of the substrate, and the accelerated additive material collides with the arc heating zone at a supersonic high speed to refine the grains in the molten pool. Under the action of the impact force and arc heating, the mixed bonding characteristics of melting (metallurgical) bonding and solid-state bonding are realized, which significantly improves the bonding strength of additive manufacturing, while avoiding the disadvantage of coarse grains caused by excessive heat input, and reducing the occurrence of product cracks. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The present invention will be further described below with reference to the accompanying drawings and examples.

[0021] Figure 1 This is a schematic diagram of Example 1 of the present invention;

[0022] Figure 2 This is a schematic diagram of Example 2 of the present invention;

[0023] Figure 3 It is the curved iron plate of the present invention.

[0024] In the figure, 1. wire feeding structure, 2. air inlet, 3. welding wire, 4. Laval nozzle contraction end, 5. Laval nozzle throat, 6. annular tungsten electrode, 7. annular arc, 8. base plate, 9. nylon insulating sleeve, 10. lifting mechanism, 11. up and down adjustment knob, 12. front and back adjustment knob, 13. workbench, 14. curved iron plate, 15. granular powder inlet, 16. granular powder. DETAILED DESCRIPTION

[0025] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0026] The present invention discloses an arc additive device that combines an annular arc and Laval, including a Laval nozzle, an annular tungsten electrode 6, a lifting mechanism 10, and a workbench 13. The lifting mechanism 10 is connected to one end of the Laval nozzle through an arc-shaped iron plate 14 for controlling the movement of the Laval nozzle. The lifting mechanism 10 is provided with an up and down adjustment knob 11 and a front and back adjustment knob 12. The up and down adjustment knob 11 and the front and back adjustment knob 12 can be used to control the up and down, front and back movement of the lifting mechanism 10, thereby driving the movement of the Laval nozzle. In this embodiment, a small welding manipulator of Huafei CNC is used, model HC-2*2. Any lifting mechanism on the market that can achieve this function can be used, so the structure of the lifting mechanism is not described here.

[0027] The Laval nozzle includes a Laval nozzle convergence end 4 and a Laval nozzle throat 5. The middle part of the tungsten electrode is evacuated, leaving only the tungsten electrode circular shell to form an annular tungsten electrode 6. The annular tungsten electrode 6 is threadedly connected to the Laval nozzle throat 5 on the side away from the Laval nozzle convergence end 4 through a nylon insulator 9. A substrate 8 is placed on the workbench 13. The size of the substrate 8 is larger than that of the annular tungsten electrode 6. Air inlets 2 are provided on both sides of the top of the Laval nozzle.

[0028] The cross-sectional area of the Laval nozzle convergence end 4 gradually decreases toward the Laval nozzle throat 5. The convergence angle of the Laval nozzle convergence end 4 is 30°-60°. The Laval nozzle throat 5 is in a straight cylindrical shape. The diameter ratio of the Laval nozzle convergence end 4 to the Laval nozzle throat 5 is 2-2.5:1.

[0029] Example 1

[0030] like Figure 1 As shown, the welding gun shield used in ordinary arc additive manufacturing is replaced with a Laval nozzle structure, the air inlet 2 is connected to the gas feeding device, and the protective gas argon is introduced from the air inlet 2. A wire feeding structure 1 is provided above the central axis of the Laval nozzle, and the wire feeding structure 1 is used to feed the welding wire 3 to the bottom of the Laval nozzle. The outlet end of the Laval nozzle is a coaxial annular tungsten electrode 6, as shown in FIG. Figure 1 As shown, the shielding gas can be accelerated from subsonic speed to supersonic speed, and the annular tungsten electrode 6 forms an annular arc 7. The annular arc 7 heats the substrate 8 to form an annular melting zone, which greatly accelerates the efficiency of arc additive manufacturing.

[0031] During operation, the protective gas used in this embodiment is pure Ar gas with a flow rate of 15-20 L / min, and the following steps are included:

[0032] (1) Fix the Laval nozzle on the lifting mechanism through the arc iron plate, and adjust the position of the Laval nozzle by the up and down adjustment knob and the front and back adjustment knob so that the annular tungsten electrode is placed 5-8mm above the substrate. If it is less than 5mm, the molten pool will be in a semi-molten state, and the strength after welding will decrease; if it is higher than 8mm, the arc height will be too large, which will burn the tungsten electrode and cause tungsten to be clamped in the workpiece after the material is added, resulting in defects in the workpiece structure and performance;

[0033] (2) Confirm that the Laval nozzle is placed at a 90° vertical angle to the substrate. If the additive is performed at a non-vertical angle, the bonding effect between the particles and the substrate will be reduced, ultimately weakening the strength of the material;

[0034] (3) Open the gas supply device, feed the protective gas into the Laval nozzle from the gas inlet, and discharge the gas from the Laval nozzle throat;

[0035] (4) Adjust the welding parameters, welding current is 80A-260A, and wire feeding speed is 2-8m / min;

[0036] (5) Start the welding power supply to feed the wire and energize the annular tungsten electrode to start adding material;

[0037] (6) After the addition is completed, turn off the welding power supply and gas supply device in sequence.

[0038] The gas flow through the Laval nozzle transitions from subsonic to supersonic, significantly increasing the gas velocity. This in turn reduces the size of the molten droplets formed by the melting wire, prompting them to impact the molten pool at a faster rate, thus refining the molten pool grain size and improving the material strength. When the welding current is 80A-260A, the wire feed speed is 2-8m / min, and the welding heat input reaches 1.2kJ / cm-4.8kJ / cm, grain refinement occurs, and the tensile strength of the additively manufactured structure can be increased by over 30%.

[0039] Example 2

[0040] like Figure 2 As shown, the arc additive structure of Example 1 is further improved, and granular powder is used instead of welding wire for arc additive, and the wire feeding structure is cancelled. A granular powder inlet 15 is set at the contraction end of the Laval nozzle, and the Laval nozzle is used as a conveying channel for the granular powder. The granular powder is fed into the contraction end of the Laval nozzle. Similar to the principle of cold spraying, the granular powder 16 is spherical powder. The high-pressure gas generated by the Laval nozzle is used to accelerate the micron-sized particles so that they impact the annular arc area at a supersonic speed. The annular arc formed by the annular tungsten electrode 6 heats the substrate and preheats the powder at the same time, so that Under the action of multiple strong impact forces and arc heating, the particle powder realizes the mixed bonding characteristics of melting bonding and solid-state bonding, overcoming the poor plasticity caused by the dominant mechanical bonding and less metallurgical bonding in the interface bonding of ordinary cold spray deposits. At the same time, the annular melting zone formed by the annular arc is impacted by high-speed moving powder particles during the crystallization process. With additional energy, it will be refined during crystallization, making the grains smaller, and the bonding strength of additive manufacturing is significantly improved. At the same time, it avoids the disadvantages of coarse grains caused by excessive heat input, reducing the occurrence of product cracks.

[0041] In this example, the protective gas used is pure Ar gas, and the compressed gas pressure is 0.5-1.2MPa. The following steps are included:

[0042] (1) Fix the Laval nozzle on the lifting mechanism through the arc iron plate, and adjust the position of the Laval nozzle by the up and down adjustment knob and the front and back adjustment knob so that the annular tungsten electrode is placed 5-8mm above the substrate. If it is less than 5mm, the molten pool will be in a semi-molten state, and the strength after welding will decrease; if it is higher than 8mm, the arc height will be too large, which will burn the tungsten electrode and cause tungsten to be clamped in the workpiece after the material is added, resulting in defects in the workpiece structure and performance;

[0043] (2) Confirm that the Laval nozzle is placed at a 90° vertical angle to the substrate. If the additive is performed at a non-vertical angle, the bonding effect between the particles and the substrate will be reduced, ultimately weakening the strength of the material;

[0044] (3) Turn on the gas delivery device, and the compressed and preheated gas is delivered to the front end of the Laval channel. The compressed gas (0.5-1.2 MPa) is accelerated to a flow rate of 1.5-2 Mach (400-600 m / s) in the Laval nozzle, and the preheated gas temperature reaches 500-600°C. The higher the gas pressure and temperature, the greater the speed of the powder particles, and the better the performance of the material obtained by the additive manufacturing process.

[0045] (4) When the preheated gas comes out of the annular tungsten electrode and contacts the surface of the substrate, heat transfer occurs between the gas and the substrate, and the substrate is preheated (for example, the preheating temperature of a magnesium substrate is generally 150-200°C; if high-temperature preheating is required, such as the preheating temperature of a carbon steel substrate is generally 800-850°C, it can be heated by a resistance furnace).

[0046] (5) Adjust the welding parameters, the welding current is 80A-260A, turn on the powder feeding device, the powder feeding rate is 0.1-1.2g / s, the powder fed is mixed with the compressed preheated gas and then sent to the annular tungsten electrode at a high speed. The powder used is a spherical powder of 300-500 mesh. Irregular powder is more easily oxidized during the spraying process and its fluidity is not as good as that of spherical powder.

[0047] (6) Turn on the welding power supply to energize the tungsten electrode for material addition;

[0048] (7) After the addition is completed, turn off the welding power supply, powder feeding mechanism and gas feeding device in sequence.

[0049] When the powder feed rate reaches 0.1-1.2g / s and the welding heat input reaches 1.0kJ / cm-3.8kJ / cm, the grain refinement is obvious and the tensile strength of the additively manufactured structure can be increased by more than 40%.

[0050] The above embodiments are merely exemplary embodiments of the present invention and are not intended to limit the scope of the present invention. The scope of protection of the present invention is defined by the claims. Those skilled in the art may make various modifications or equivalent substitutions to the present invention within the spirit and scope of protection of the present invention, and such modifications or equivalent substitutions shall also be deemed to fall within the scope of protection of the present invention.

Claims

1. An arc additive device combining a toroidal arc and Laval arc, characterized by: The device comprises a Laval nozzle, an annular tungsten electrode, a lifting mechanism, and a workbench. The lifting mechanism is connected to one end of the Laval nozzle for controlling the movement of the Laval nozzle. The Laval nozzle comprises a Laval nozzle contraction end and a Laval nozzle throat. The annular tungsten electrode is connected to the side of the Laval nozzle throat away from the Laval nozzle contraction end. A substrate is placed on the workbench. The substrate is larger than the annular tungsten electrode. Air inlets are provided on both sides of the top of the Laval nozzle. The Laval nozzle is also provided with a feeding mechanism. The Laval nozzle and the annular arc are both placed perpendicular to the substrate; The cross-sectional area of the Laval nozzle convergent end gradually decreases toward the Laval nozzle throat, the convergence angle of the Laval nozzle convergent end is 30°-60°, the Laval nozzle throat is straight, and the diameter ratio of the Laval nozzle convergent end to the Laval nozzle throat is 2-2.5:1; The annular tungsten electrode is connected to the Laval nozzle through a nylon insulating sleeve.

2. The annular arc and Laval composite arc additive device according to claim 1, characterized in that: The feeding mechanism includes a wire feeding structure, which is located above the central axis of the Laval nozzle and is used to feed the welding wire to the bottom of the Laval nozzle.

3. The annular arc and Laval composite arc additive device according to claim 1, characterized in that: The feeding mechanism comprises a particle powder inlet, and the particle powder inlet is located on one side of the contraction end of the Laval nozzle.

4. The annular arc and Laval composite arc additive device according to claim 1, characterized in that: The annular tungsten pole is connected to the nylon insulator through threads, and the upper end of the annular tungsten pole and the lower end of the nylon insulating sleeve are both provided with threads.

5. An additive process according to any one of claims 1 to 4, wherein the arc additive device of the annular arc and Laval composite is characterized in that: The steps include: Step 1: Adjust the position of the Laval nozzle using the lifting mechanism so that the distance between the annular tungsten electrode at the bottom of the Laval nozzle and the substrate is 5-8 mm. Ensure that the Laval nozzle is placed perpendicular to the substrate at a 90° angle. Step 2: Open the gas supply device, supply the protective gas into the Laval nozzle from the gas inlet, and discharge the gas from the Laval nozzle throat; Step 3, adjust the welding parameters and feeding speed, the welding current is 80A-260A; Step 4: Start the welding power supply to feed the material, and energize the annular tungsten electrode to start adding material; Step 5: After the material addition is completed, turn off the welding power supply, feeding mechanism and gas feeding device in sequence.

6. The additive process of the annular arc and Laval composite arc additive device according to claim 5, characterized in that: The feeding speed in step 3 varies according to the feeding state. When the feeding material is welding wire, the feeding speed is 2-8 m / min; when the feeding material is granular powder, the feeding speed is 0.1-1.2 g / s.

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