Interlayer ultrasonic impact assisted high-performance CMT arc additive manufacturing method and device

Abstract

The present invention belongs to the technical field of composite additive manufacturing of metal structural parts, and specifically relates to an interlayer ultrasonic impact-assisted high-performance CMT arc additive manufacturing method and device. The present invention realizes the regulation of stress and structure in the forming process of arc additive components through the alternating operation of a cold metal transition arc additive manufacturing control device and a harmonic ultrasonic impact control device, and the strengthening effect is more thorough. The present invention effectively eliminates the residual tensile stress on the interface and produces uniform plastic deformation by performing harmonic ultrasonic impact treatment on the interlayer bonding interface in the CMT arc additive manufacturing process, thereby regulating the size of the primary coarse columnar β crystals and improving the anisotropy of the mechanical properties of the components, so as to achieve the effect of reducing the grain size, eliminating metallurgical defects, and improving strength and plasticity in an integrated manner.

Description

Technical Field

[0001] The present invention belongs to the technical field of composite additive manufacturing of metal structural parts, and specifically relates to an interlayer ultrasonic impact-assisted high-performance CMT arc additive manufacturing method and device. Background Art

[0002] Arc additive manufacturing technology is a digital manufacturing technology that uses the principle of layer-by-layer cladding, uses arc as a heat source, and gradually forms metal parts according to a three-dimensional digital model by adding wire. Compared with the powder accumulation additive manufacturing method, it has significant advantages such as high deposition efficiency, high wire utilization, short overall manufacturing cycle, and low cost. It is especially suitable for the integrated forming of large-sized components. The CMT (cold metal transition) arc additive manufacturing technology uses short arc and reversing wire feeding monitoring under digital control. The front and rear wire feeding systems work together to achieve pulsed wire feeding, which can greatly reduce the generation of welding heat and reduce heat conduction.

[0003] However, during the CMT arc additive forming process, the material undergoes multiple complex thermal cycles, resulting in the accumulation of internal stress and the growth of residual tensile stress, and the formed parts are prone to defects such as deformation and edge collapse; and metallurgical defects such as unfusion, entrapment and precipitation pores, inclusions, etc. are also very easy to produce in the additive process; in addition, from the perspective of the interface scale, the arc additive method will produce through-type coarse columnar crystals along the additive direction. Surface treatment alone cannot make it meet service requirements, and interlayer control treatment is required to inhibit the growth of coarse columnar crystals.

[0004] The ultrasonic impact technology, which was originally used to eliminate residual stress in welds, can also induce a relatively deep and uniform plastic deformation layer on the metal surface. At the same time, it also has significant advantages such as uniform strengthening effect, small surface roughness, high production efficiency and low cost, especially matching the rapid large-scale forming process of arc additive technology. Therefore, we propose a process intervention method for ultrasonic impact in CMT arc additive manufacturing composite interlayers to curb the growth of coarse columnar crystals and integrate strong and tough parts to achieve high-quality production. Summary of the invention

[0005] In view of the above-mentioned deficiencies in the prior art, the purpose of the present invention is to provide an interlayer ultrasonic impact-assisted high-performance CMT arc additive manufacturing method and device, which has a reasonable structural design, convenient operation, and simple applicability; it can realize the integrated strengthening and toughening production of key components in aviation, aerospace, and navigation.

[0006] 1. In order to solve the above technical problems, a high-performance CMT arc additive manufacturing method assisted by interlayer ultrasonic impact is proposed, which performs ultrasonic impact treatment on the interlayer bonding interface in the CMT arc additive manufacturing process, and performs ultrasonic impact treatment on the two side walls after the forming is completed after the whole milling process. In this way, the residual tensile stress on the interface is eliminated, and the forming surface of the component undergoes uniform plastic deformation, the grain structure at the interface is refined, and the periodic uniform distribution of columnar crystals and equiaxed crystals is achieved, thereby effectively blocking the growth of coarse columnar β crystals, improving the anisotropy of the component, and simultaneously improving the strength and toughness of the arc additive component. It mainly includes the following steps:

[0007] 1) The substrate surface is polished to remove the oxide layer and degreased and cleaned with ethanol, then fixed to the working platform and powered on to preheat the substrate;

[0008] 2) Use the CMT arc additive control robot to drive the welding gun to perform additive manufacturing under the unified program control of cold metal transfer; when a layer is formed, stop feeding the wire and extinguish the arc, and wait for the deposited layer to cool naturally.

[0009] 3) When the sensor detects that the temperature at the starting point drops to 200°C, the harmonic ultrasonic impact control robot arm drives the ultrasonic impact head to perform ultrasonic impact strengthening treatment on the formed surface with a large overlap area.

[0010] 4) Repeat steps 2) and 3) to complete the forming and strengthening of each layer, and finally obtain an integrated component;

[0011] 5) After the corrugated protrusions on the two sides of the formed straight wall are milled, the side wall is subjected to ultrasonic impact treatment with the same process parameters using a harmonic ultrasonic impact system to achieve an overall strengthening effect.

[0012] 2. To implement the above method, the present invention proposes an interlayer ultrasonic impact-assisted high-performance CMT arc additive manufacturing device, which includes a cold metal transition arc additive control device and a harmonic ultrasonic impact control device.

[0013] 3. The cold metal transition arc additive control device comprises: a welding gun, an insulating shell, a wire guide tube, a wire feed controller, a CMT arc additive control robot arm, a wire preheating box and a wire feed pipe; the CMT arc additive control robot arm can flexibly control the three-dimensional movement of the welding gun such as feed speed, wire filling path and layer thickness; the wire enters the wire preheating box through the wire feed pipe and adjusts the wire feeding speed through the wire feed controller, and then passes through the wire guide tube to contact the substrate for short circuit and arcing; the wire preheating box is connected to the rotating shaft at the end of the CMT arc additive control robot arm through a set of fastening rivets, and the top of the wire preheating box is connected to the wire feed pipe through an air pipe ferrule; the wire feed controller is connected to the bottom of the wire preheating box through a thread, and controls the pulse feeding of the raw wire through a built-in program; the wire guide tube is fastened to the bottom shell of the wire feed controller by welding; the top of the welding gun is connected to the bottom shell of the wire guide tube by welding, and the insulating shell and the welding gun are detachably connected by a clamp. The key engineering parameters of the CMT arc additive manufacturing process are as follows: peak current is 130A, welding gun feed speed is 0.2-0.5m / min, wire feed speed is 5-10m / min, average voltage is 13V, 99.99vol% pure argon is used as the shielding gas to protect the deposited layer, and the gas flow rate is 20L / min.

[0014] 4. The harmonic ultrasonic impact control device includes: a harmonic vibration controller, a harmonic ultrasonic impact control mechanical arm, an impact gun housing, a fastening nut, a variable amplitude rod, an impact seat sleeve and an impact head; the impact head is a replaceable structure, installed inside the impact seat sleeve, and can move up and down; the impact seat sleeve is fastened to the variable amplitude rod by a thread, and the variable amplitude rod is an inverted cone structure, which plays the role of amplifying the amplitude and is fixed to the impact gun housing by a fastening nut; the impact gun housing is fastened to the bottom of the housing of the harmonic vibration controller by welding; the harmonic vibration controller can adjust the output voltage and current to achieve ultrasonic impact modes with different waveforms, frequencies and amplitudes, and is connected to the rotating shaft at the end of the harmonic ultrasonic impact control mechanical arm through a group of fastening rivets; the harmonic ultrasonic impact control mechanical arm can accurately control the ultrasonic impact head to achieve a large-area overlap feeding strategy. Its key engineering parameters are as follows: operating frequency is 10-90kHz, rated power is 1000W, maximum output amplitude is 50μm, feed speed is consistent with the feed speed of the welding gun in the range of 0.2-0.5m / min, the impact head is replaceable, the diameter range is 2-5mm, and the external force load can be applied by the harmonic ultrasonic impact control robot arm, with a maximum value of 75kN.

[0015] 5. The overlap rate of the ultrasonic impact strengthening treatment is 50% to achieve a uniform strengthening effect; at the same time, a feeding strategy in which the ultrasonic impact path and the wire filling path are perpendicular is adopted to achieve a more dense strengthening effect.

[0016] The present invention can effectively destroy the growth of columnar crystals growing along the additive direction during arc additive manufacturing, forming a microstructure distribution of alternating columnar crystals and equiaxed crystals, thereby reducing the anisotropy of the mechanical properties of arc additive components and improving their strength and toughness. In addition, the ultrasonic shock wave acting on the bonding interface can eliminate microscopic metallurgical defects such as holes and microcracks in the surface layer, thereby improving the density of the formed part; at the same time, it can flatten the bonding interface, reduce the roughness of the bonding interface, and improve the interface bonding strength. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required to be used in the examples or the description of the prior art are briefly introduced below.

[0018] Figure 1 It is a schematic diagram of the overall structure of the device of the present invention;

[0019] Figure 2 This is a partial enlarged schematic diagram of the working area;

[0020] Figure 3 It is a schematic diagram of the interlayer ultrasonic impact feeding strategy of the present invention;

[0021] Figure 4 Schematic diagram of the mechanism of the coarse columnar crystal regulation effect of the present invention;

[0022] Figure 5 This is a microstructure comparison diagram of the actual coarse columnar crystal regulation effect of the present invention.

[0023] Figures are marked: 1. welding gun, 2. insulating shell, 3. wire guide tube, 4. wire feed controller, 5. CMT arc additive control robot, 6. fastening rivets, 7. wire preheating box, 8. wire feed pipe, 9. air pipe ferrule, 10. harmonic vibration controller, 11. harmonic ultrasonic impact control robot, 12. impact gun shell, 13. fastening nut, 14. amplitude transformer, 15. impact seat sleeve, 16. impact head, 17. formed parts, 18. substrate, 19. workbench. DETAILED DESCRIPTION

[0024] The specific implementation modes of the present invention are described below so that those skilled in the art can understand the present invention. However, it should be clear that the present invention is not limited to the scope of the specific implementation modes. For those of ordinary skill in the art, as long as various changes are within the spirit and scope of the present invention as defined and determined by the attached claims, these changes are obvious, and all inventions and creations utilizing the concept of the present invention are protected.

[0025] The present invention performs ultrasonic impact treatment on the interlayer bonding interface in the CMT arc additive manufacturing process to eliminate the residual tensile stress on the interface and cause uniform plastic deformation on the component forming surface. At the same time, the grain structure at the interface is refined and the periodic and uniform distribution of columnar crystals and equiaxed crystals is achieved, thereby effectively blocking the growth of coarse columnar β crystals, improving the anisotropy of the component, and simultaneously improving the strength and toughness of the arc additive component.

[0026] like Figure 1 FIG. 1 is a schematic diagram of the overall structure of the device of the present invention. Figure 2 It is a partial enlarged schematic diagram of the working area, which mainly includes two parts: a cold metal transition arc additive control device and a harmonic ultrasonic impact control device. The cold metal transition arc additive control device can flexibly control the three-dimensional movement of the welding gun 1, such as the feed speed, the wire filling path and the layer thickness, and realize the low heat input CMT arc additive manufacturing of the pulsed welding wire delivery. The harmonic ultrasonic impact control device can accurately control the large-area overlap reinforcement feed path and overlap rate of the ultrasonic impact head 16, and at the same time, by adjusting the output voltage and current of the harmonic vibration controller 10, it can realize ultrasonic impact modes with different waveforms, frequencies and amplitudes, and can realize fast switching of different parameters for different materials. Among them, when forming high-melting-point and easily oxidized metal materials such as titanium alloys, the accompanying argon gas cannot meet the protection requirements, and a simple inert gas protection chamber needs to be installed. Among them, the harmonic ultrasonic impact control device needs to be connected to an external waveform generator box during processing, which is a prior art and is used to generate higher loads and ultrasonic frequency impact signals.

[0027] like Figure 3 The interlayer ultrasonic impact feeding strategy of the present invention is shown. The overlap rate of the ultrasonic impact strengthening treatment is 50% to achieve a uniform strengthening effect; at the same time, the ultrasonic impact path is perpendicular to the wire filling path to achieve a more dense strengthening effect. In order to avoid the impact strengthening layer on both sides being removed after further precision reduction processing, we perform integrated ultrasonic impact strengthening treatment after milling and flattening the side wall to achieve an integrated toughness effect.

[0028] like Figure 4 This is a schematic diagram of the mechanism of the coarse columnar crystal regulation effect of the present invention. Surface ultrasonic impact can effectively refine the top layer grains, while high overlap rate interlayer ultrasonic impact can better regulate the bonding interface state and block the growth of coarse columnar crystals in the additive direction, thereby effectively improving the anisotropy of the additive part.

[0029] Figure 5 This is a microstructure comparison diagram of the actual coarse columnar crystal regulation effect of the present invention. Through the comparison, it can be seen that single-pass surface ultrasonic impact can effectively refine the top layer grains, while high-overlap interlayer ultrasonic impact can better regulate the bonding interface state and block the growth of coarse columnar crystals in the additive direction, thereby effectively improving the anisotropy of the additive part.

[0030] A method for interlayer ultrasonic impact-assisted high-performance CMT arc additive manufacturing using the above-mentioned device is used. After the cold metal transition arc additive control device completes the forming of a layer of material, the temperature sensor monitors the temperature of the deposition layer interface in real time. When its surface temperature drops to 200°C, the harmonic ultrasonic impact control device performs ultrasonic impact strengthening on a large-area overlap of the layer of material, and repeats the above steps until the workpiece is completely formed.

[0031] The following example illustrates: The embodiment specifically includes the following steps:

[0032] The CMT arc additive manufacturing method using metal arc gas shielded welding is used, and the welding wire used is a 6063 aluminum alloy arc additive wire with a diameter of 1.2 mm; the substrate 18 is a 6063 aluminum alloy substrate with a thickness of 10 mm;

[0033] Step S1: polishing the surface of the 6063 aluminum alloy substrate to remove the oxide layer and degreasing and cleaning it with ethanol, then fixing it on the working platform 19 and powering on the substrate 18 to preheat;

[0034] Step S2: The automatic wire feeding device feeds the 6063 aluminum alloy arc additive wire into the wire preheating box 7 through the wire feeding pipe 8 for preliminary preheating;

[0035] Step S3: The CMT arc additive equipment is turned on, the welding gun 1 is powered on, and its key parameters are set as follows: the peak current is 130A, the feeding speed of the welding gun is 0.3m / min, the wire feeding speed is 7.2m / min, the average voltage is 13V, argon is used as the shielding gas, and the gas flow rate is 20L / min. After printing one layer, the wire feeding is stopped and the power is turned off;

[0036] Step S4: After the CMT arc additive equipment completes a certain number of deposition layers on the substrate, when the temperature of the interface of the deposited layer monitored by the temperature sensor drops to 200°C, the harmonic ultrasonic impact control device starts ultrasonic impact strengthening of the large-area overlap of the interface material of the layer: the key parameters are set as follows: the operating frequency is 30kHz, the rated power is 1000W, the output amplitude is 50μm, the feed speed is 0.3m / min, the impact head diameter is 3mm, and the applied load is 25kN;

[0037] Step S5: repeat steps S3 and S4 until the workpiece is completely formed;

[0038] Step S6: After the corrugated protrusions on the two side surfaces of the formed 6063 aluminum alloy straight wall are milled, the side wall is subjected to ultrasonic impact treatment using a harmonic ultrasonic impact system to achieve an overall strengthening effect.

[0039] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. Interlayer ultrasonic impact assisted high-performance CMT arc additive manufacturing method, characterized in that: By performing ultrasonic impact treatment on the interlayer bonding interface of the CMT arc additive manufacturing process, and performing ultrasonic impact treatment on the two side walls after forming, the residual tensile stress on the interface is eliminated, and the component forming surface undergoes uniform plastic deformation, the grain structure at the interface is refined, and the periodic uniform distribution of columnar crystals and equiaxed crystals is achieved, thereby effectively blocking the growth of coarse columnar β crystals, improving the anisotropy of the component, and simultaneously improving the strength and toughness of the arc additive component. The specific steps are as follows: 1) Grind the surface of the substrate to remove the oxide layer and perform degreasing and ethanol cleaning, then fix it to the working platform and power on to preheat the substrate; 2) Use the CMT arc additive control robot to drive the welding gun to perform additive manufacturing under the control of the cold metal transfer unified program; when a layer is formed, stop feeding the wire and extinguish the arc, and wait for the deposited layer to cool naturally; 3) When the sensor detects that the temperature at the starting point drops to 200 °C, the harmonic ultrasonic impact control robot arm drives the ultrasonic impact head to perform ultrasonic impact strengthening treatment on the formed surface with large-area overlap; 4) Repeat steps 2) and 3) to complete the forming and strengthening of each layer, and finally obtain an integrated component; 5) After the corrugated protrusions on the two sides of the formed straight wall are milled, the side wall is subjected to ultrasonic impact treatment using a harmonic ultrasonic impact system with the same engineering parameters as step 3) to achieve an overall strengthening effect; A device for realizing the interlayer ultrasonic impact-assisted high-performance CMT arc additive manufacturing method, comprising a cold metal transition arc additive control device and a harmonic ultrasonic impact control device; The cold metal transition arc additive control device comprises: a welding gun, an insulating shell, a wire guide tube, a wire feeding controller, a CMT arc additive control robot arm, a wire preheating box and a wire feed pipe; the CMT arc additive control robot arm can flexibly control the three-dimensional movement of the welding gun; the wire enters the wire preheating box through the wire feed pipe and adjusts the wire feeding speed through the wire feed controller, and then passes through the wire guide tube to contact the substrate for short circuit and arcing; the wire preheating box is connected to the rotating shaft at the end of the CMT arc additive control robot arm, and the upper part thereof is connected to the wire feed pipe through an air pipe ferrule; the wire feed controller is connected to the bottom of the wire preheating box, and controls the pulse feeding of the raw material wire through a built-in program; the wire guide tube is fastened to the bottom shell of the wire feed controller by welding; the top of the welding gun is connected to the bottom shell of the wire guide tube by welding, and the insulating shell and the welding gun are detachably connected by a clamp; The harmonic ultrasonic impact control device includes: a harmonic vibration controller, a harmonic ultrasonic impact control mechanical arm, an impact gun housing, a fastening nut, a variable amplitude rod, an impact seat sleeve and an impact head; the impact head is a replaceable structure, installed inside the impact seat sleeve, and can move up and down; the impact seat sleeve is fastened to the variable amplitude rod, the variable amplitude rod is an inverted cone structure, plays the role of amplifying the amplitude, and is fixed to the impact gun housing; the impact gun housing is fastened to the bottom of the housing of the harmonic vibration controller; the harmonic vibration controller can adjust the output voltage and current to achieve ultrasonic impact modes with different waveforms, frequencies and amplitudes, and is connected to the rotating shaft at the end of the harmonic ultrasonic impact control mechanical arm; the harmonic ultrasonic impact control mechanical arm can accurately control the ultrasonic impact head to achieve a large-area overlap reinforcement feeding strategy.

2. The method according to claim 1, characterized in that In step 2), the engineering parameters of CMT arc additive manufacturing are as follows: peak current is 130 A, welding gun feed speed is 0.2–0.5 m / min, wire feed speed is 5–10 m / min, average voltage is 13 V, 99.99 vol% pure argon is used as the shielding gas to protect the deposited layer, and the gas flow rate is 20 L / min.

3. The method according to claim 1, characterized in that In step 3), the engineering parameters of the harmonic ultrasonic impact treatment are as follows: the operating frequency is 10-90 kHz, the rated power is 1000 W, the maximum output amplitude is 50 μm, the feed speed is consistent with the feed speed of the welding gun in the range of 0.2-0.5 m / min, the impact head is replaceable, the diameter range is 2-5 mm, and the external force load can be applied by the harmonic ultrasonic impact control robot arm, with a maximum value of 75 kN.

4. The method according to claim 1, characterized in that The overlap rate of ultrasonic impact strengthening treatment is 50% to achieve a uniform strengthening effect; at the same time, a feeding strategy in which the ultrasonic impact path and the wire filling path are perpendicular is adopted to achieve a denser strengthening effect.

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