A ball-type ultrasonic micro-forging assisted additive manufacturing device

Abstract

The present invention relates to the technical field of ultrasonic micro-forging, and provides a ball-type ultrasonic micro-forging assisted additive manufacturing device. It includes: an ultrasonic generator is connected to an ultrasonic transducer in series; the lower end of a hydraulic device is connected to the ultrasonic transducer, the lower end of the ultrasonic transducer is connected to an ultrasonic horn, and the lower end of the ultrasonic horn is connected to a tool head; the lower end of the tool head is connected to an ultrasonic micro-forging head; the ultrasonic micro-forging head is provided with a mounting base, and an arc-shaped groove is arranged inward on one side of the mounting base away from the ultrasonic horn, and a plurality of small balls are evenly arranged on the inner wall of the arc-shaped groove, and the plurality of small balls surround a large ball. The beneficial effects are as follows: adopting a double-layer ball structure, the forging head has a higher degree of freedom of movement, converts sliding friction into rolling friction during the micro-area rolling process, the double-layer balls with ultrasonic vibration have a small contact surface with the additive micro-area, the ultrasonic energy is easy to concentrate, the grain refinement effect is better, and at the same time, the ultrasonic energy transmission depth is greater, and the surface layer and internal tissue uniformity are better improved.

Description

Technical Field

[0001] The present invention relates to the technical field of ultrasonic micro forging, and particularly relates to a ball-type ultrasonic micro forging assisted additive manufacturing device. Background Art

[0002] Additive manufacturing technology is an advanced manufacturing method. It uses a high-energy beam as a heat source, digitizes the data of a three-dimensional model by layering, and then directly forms a three-dimensional solid part in a processing mode of "point-by-point scanning melting - line-by-line scanning and overlapping - layer-by-layer solidification and stacking". In recent years, additive manufacturing technology has developed rapidly, changing the forming modes of traditional manufacturing, such as subtractive manufacturing and isostatic manufacturing. Additive manufacturing technology has a series of advantages, such as a flexible processing method, no need for a specific mold, and a short process flow, and is widely used in fields such as aerospace, medical devices, and polymer materials, especially having unique advantages in the forming of complex structures.

[0003] At present, in the additive manufacturing technology of metal parts using high-energy beams such as lasers and electron beams, due to the extremely short action time between the high-energy beam and the metal material, the material undergoes a violent process of alternating heat and cold, and internal thermal stress and residual stress are extremely likely to be generated in the metal component, and microcracks are easily generated, reducing the toughness of the material; the temperature difference in different regions of the molten pool metal is large, and the degree of superheat is relatively large, especially the superheat temperature at the center is the highest, promoting the formation of columnar crystals, thereby reducing the plasticity of the material. In addition, due to the interaction between liquid metal and various gases during the forming process, pores are extremely likely to be generated in the metal deposition layer, which will not only increase the notch sensitivity, reduce the metal strength, but also reduce the fatigue strength and airtightness of the metal. In order to overcome the internal stress characteristics and tissue characteristics of the rapidly solidified structure, ultrasonic micro forging can be carried out in the hot state after the molten pool solidifies to make up for the above deficiencies of additive manufacturing. Ultrasonic vibration and micro forging treatment of additive manufacturing parts can refine the grains, transform the coarse columnar crystals in the additive manufacturing parts into fine equiaxed crystals, and the acoustic streaming effect and cavitation effect generated by ultrasonic vibration and the pressure of micro forging can reduce or even inhibit the generation of microcracks and pores in the specimen, thereby playing a role in improving the microstructure of the metal material and enhancing the mechanical properties.

[0004] At present, many scholars at home and abroad have proposed several micro-casting and forging integrated process methods based on this: Paul A. Colegrove et al. from Cranfield University in the UK proposed an arc micro-casting and cold rolling step-by-step forming process based on the arc additive manufacturing technology, which reduces the residual stress and deformation existing in traditional arc additive manufacturing. At the same time, through subsequent rolling, the material is reheated during the subsequent deposition process to achieve the purpose of refining grains. However, the effect of roller rolling technology in removing residual stress is poor, it cannot effectively convert tensile stress into compressive stress, nor can it completely eliminate the deformation of components. Moreover, cold rolling requires a large pressure. In addition, it is difficult to process thin-walled parts and parts with complex inner cavities. In addition, the cold rolling mechanism is large in volume, and the cold rolling process is separated from micro-casting, resulting in uneven grain size. The team led by Professor Zhang Haiou of Huazhong University of Science and Technology proposed a micro-casting, forging and synchronous ultra-short process manufacturing technology for large and complex high-end parts to solve this technical problem. It adopts a low-energy consumption forming method of "casting while forging", significantly improving the forming efficiency and obtaining a uniform and ultra-fine equiaxed crystal structure. Integrating multiple processes into one manufacturing unit greatly shortens the manufacturing cycle, reduces production costs and can form large-area forgings at the same time. The team led by Jiang Fengchun of Harbin Engineering University proposed a process of combining ultrasonic and rolling in solving the microstructure and mechanical properties of additive manufacturing. It combines the advantages of high ultrasonic impact frequency and large deformation generated by mechanical rolling. Ultrasonic impact and rolling cause plastic deformation of the metal structure, and then recovery and recrystallization occur, refining the grains while converting the tensile stress on the surface of the component into tensile stress, thus effectively reducing the generation and propagation of cracks and improving the fracture toughness of the material. In addition, the combined action of ultrasonic impact and continuous rolling micro-forging greatly improves the efficiency and action depth of the combined micro-forging. Since the teams led by Professor Zhang Haiou of Huazhong University of Science and Technology and Jiang Fengchun of Harbin Engineering University both install a micro-roller rolling device in the striker groove, inevitably, there are problems of large device structure size and complex structure.

[0005] In view of this, the present invention is proposed. Summary of the Invention

[0006] The purpose of the present invention is to provide a ball-type ultrasonic micro-forging assisted additive manufacturing device to solve the technical problems existing in the prior art.

[0007] To achieve the above object, the technical solution adopted by the present invention is: a ball-type ultrasonic micro-forging assisted additive manufacturing device, comprising: an ultrasonic generator, a hydraulic device, an ultrasonic transducer, an ultrasonic horn, a tool head, and an ultrasonic micro-forging head; wherein, the ultrasonic generator is connected to the ultrasonic transducer by wire; the lower end of the hydraulic device is connected to the ultrasonic transducer, the lower end of the ultrasonic transducer is connected to the ultrasonic horn, and the lower end of the ultrasonic horn is connected to the tool head; the lower end of the tool head is connected to the ultrasonic micro-forging head; the ultrasonic micro-forging head is provided with a mounting base, and an arc-shaped groove is inwardly provided on one side of the mounting base away from the ultrasonic horn, and a plurality of small balls are evenly arranged on the inner wall of the arc-shaped groove, and the plurality of small balls surround a large ball.

[0008] In an alternative embodiment, the plurality of small balls and the large ball are limited in the arc-shaped groove by a sealing ring; wherein, the large ball protrudes from the end faces of the arc-shaped groove and the sealing ring.

[0009] In an alternative embodiment, threaded holes are provided at both ends of the tool head and the ultrasonic horn.

[0010] In an alternative embodiment, the ultrasonic transducer and the ultrasonic horn are connected by a stud; the ultrasonic horn and the tool head are connected by a stud.

[0011] In an alternative embodiment, a threaded rod is provided at the bottom of the mounting base for threaded fastening connection with the threaded hole of the tool head.

[0012] In an alternative embodiment, the ultrasonic generator and the ultrasonic transducer are connected by two lines.

[0013] The beneficial effects of the present invention are as follows:

[0014] The ultrasonic micro forging head of the ball-type ultrasonic micro forging assisted additive manufacturing device adopts a double-layer ball structure. Due to the lack of cooperation of another layer of small balls, in the process of ultrasonic micro forging, the sliding friction between the balls and the additive micro area is large, the wear is large, the service life is short, and the ultrasonic energy is not easily transmitted to the balls, weakening the effect of ultrasonic vibration. In addition, one of the major advantages of the ball-type ultrasonic micro forging assisted additive manufacturing device is that additive manufacturing and ultrasonic micro forging are carried out synchronously. Since the single-layer balls are not easy to roll and the movement freedom is restricted, the advantage of synchronous additive manufacturing and ultrasonic micro forging of this device is greatly weakened. In the double-layer ball structure of the present invention, the sliding friction is transformed into rolling friction during the micro area rolling process, with high precision, small wear, and long service life. Compared with rollers and wheels, the ball-type ultrasonic vibration device has a compact structure, light weight, and more reduced size, which is convenient for cooperating with the ultrasonic device to form micro area vibration. At the same time, the balls in the double-layer ball structure roll more smoothly and have higher freedom, and can roll in any direction of 360 degrees, laying a foundation for the synchronous implementation of additive manufacturing and ultrasonic micro forging of this device. It should be particularly noted that the contact surface between the double-layer balls of ultrasonic vibration and the additive micro area is small, the ultrasonic energy is easy to concentrate, the grain refinement effect is better, the ultrasonic energy transmission depth is greater, and the uniformity of the surface and internal tissues is better improved. Brief Description of the Drawings

[0015] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0016] Figure 1 It is a schematic structural diagram of the ball-type ultrasonic micro forging assisted additive manufacturing device provided in an embodiment of the present invention.

[0017] Figure 2 It is a schematic structural diagram of the assembly of the mounting base, sealing ring and large and small balls provided in an embodiment of the present invention.

[0018] Figure 3 It is a comparison diagram of the tensile strength of the specimens (1, 2, 3) without ultrasonic micro forging and the specimens (4, 5, 6) after ultrasonic micro forging treatment provided in an embodiment of the present invention.

[0019] Among them, the reference numerals are:

[0020] 1 - ultrasonic generator, 2 - hydraulic equipment, 3 - ultrasonic transducer, 4 - ultrasonic horn, 5 - tool head, 6 - ultrasonic micro forging head, 7 - mounting base, 8 - small ball, 9 - large ball, 10 - sealing ring. Detailed Embodiment

[0021] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention clearer and more understandable, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0022] It should be noted that when a component is referred to as "fixed to" or "disposed on" another component, it can be directly or indirectly located on the other component. When a component is referred to as "connected to" another component, it can be directly or indirectly connected to the other component. The orientations or positions indicated by the terms "upper", "lower", "left", "right", "front", "rear", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. are based on the orientations or positions shown in the accompanying drawings, and are only for the convenience of description and cannot be construed as a limitation to the technical solution of the present invention. The terms "first" and "second" are only used for the purpose of convenient description and cannot be construed as indicating or implying relative importance or implicitly indicating the number of technical features. The meaning of "a plurality" is two or more, unless otherwise specifically defined.

[0023] Please refer to the attached Figure 1 , 2. The purpose of this embodiment is to provide a ball-type ultrasonic micro-forging assisted additive manufacturing device, including: an ultrasonic generator 1, a hydraulic device 2, an ultrasonic transducer 3, an ultrasonic horn 4, a tool head 5 and an ultrasonic micro-forging head 6; wherein, the ultrasonic generator 1 is linearly connected to the ultrasonic transducer 3; the lower end of the hydraulic device 2 is connected to the ultrasonic transducer 3, and the hydraulic rod 2 provides a certain pressure for the ultrasonic micro-forging head 6, so as to play a forging role on the surface of the additive manufacturing part; the lower end of the ultrasonic transducer 3 is connected to the ultrasonic horn 4, and the lower end of the ultrasonic horn 4 is connected to the tool head 5; the lower end of the tool head 5 is connected to the ultrasonic micro-forging head 6.

[0024] Specifically, the ultrasonic generator 1 is connected to the ultrasonic transducer 3 through two lines. The ultrasonic generator 1 converts ordinary electrical signals into high-frequency alternating current signals matching the ultrasonic transducer 3, drives the ultrasonic transducer 3 to work, and can also control the current and voltage, playing a role in overload protection. The ultrasonic transducer 3 converts the high-frequency electrical signals into mechanical vibrations and converts electrical energy into mechanical energy. Threaded holes are provided at both ends of the tool head 5 and the ultrasonic horn 4. The ultrasonic transducer 3 and the ultrasonic horn 4 are connected by studs; the ultrasonic horn 4 and the tool head 5 are connected by studs. The ultrasonic horn 4 amplifies and outputs the amplitude output by the ultrasonic transducer 3 and does not consume power itself.

[0025] Further, the tool head 5 transmits the ultrasonic waves amplified by the ultrasonic horn 4 to the ultrasonic micro-forging head 6. The ultrasonic micro-forging head 6 is provided with a mounting base 7. A threaded rod is provided at the bottom of the mounting base 7 for threaded fastening connection with the threaded hole of the tool head 5. On the side of the mounting base 7 away from the ultrasonic horn 4, an arc-shaped groove is provided inward. A plurality of small balls 8 are evenly arranged on the inner wall of the arc-shaped groove, and the plurality of small balls 8 surround the large ball 9. It should be noted that the plurality of small balls 8 and the large ball 9 are limited in the arc-shaped groove by a sealing ring 10; wherein, the large ball 9 protrudes from the end faces of the arc-shaped groove and the sealing ring 10.

[0026] In this embodiment, aiming at the problem of insufficient mechanical properties of the additive component, ultrasonic vibration and micro-forging deformation are introduced into the additive micro-region. The ultrasonic energy and the heat generated by plastic deformation can improve the local molecular motion activity, increase the dislocation movement ability and the defect density, promote the short-time and rapid movement of dislocations for slip and merger, form small-angle grain boundaries and sub-grains, and refine the grains. At the same time, the ultrasonic impact effect can effectively promote the healing and elimination of defects such as as-cast pores, and form a residual compressive stress layer in the cladding layer, effectively improving the performance of the additive component. It is worth mentioning that compared with rollers and wheels, the ball-type ultrasonic vibration device has a compact structure, a smaller size, a higher degree of freedom of movement, and is convenient to cooperate with the ultrasonic device to form a micro-region vibration.

[0027] In the present invention, the double-layer ball structure converts sliding friction into rolling friction during the micro-region rolling process, with high precision, small wear, and long service life. Compared with rollers and wheels, the ball-type ultrasonic vibration device has a compact structure, a light weight, and a more reduced size, and is convenient to cooperate with the ultrasonic device to form a micro-region vibration. At the same time, the double-layer ball structure has smoother ball rolling and a higher degree of freedom, and can realize 360-degree arbitrary-direction rolling, laying a foundation for the realization of the synchronous additive manufacturing and ultrasonic micro-forging of the device. In particular, it should be noted that the contact surface between the double-layer balls of the ultrasonic vibration and the additive micro-region is small, the ultrasonic energy is easy to concentrate, the grain refinement effect is better, the ultrasonic energy transmission depth is greater, and the surface layer and internal tissue uniformity are better improved.

[0028] To further demonstrate the beneficial effects of this embodiment, verification is carried out in an experimental manner. Please refer to the appendix Figure 3 .

[0029] The experiment took whether ultrasonic micro-forging assistance was added during the additive manufacturing process as the experimental variable, and two groups were prepared, one with ultrasonic micro-forging assistance and the other without. The additive manufacturing parameters were set as laser power 1500W, laser scanning speed 17mm / s, step size 1.3mm, powder feeding speed 5.5r / min, and printing thickness 0.6mm / layer. The ultrasonic parameters were set as ultrasonic power 1500W, output frequency 28KHz, and amplitude 8μm. The experimental results showed that the average tensile strength of 316L stainless steel was increased from 659.5MPa to 726.5MPa, which was 10.2% higher than that of the traditional additive manufacturing method and reached the level of forgings. The microstructure of the specimens was observed using an optical microscope. It was found that the grains of the specimens with ultrasonic micro-forging assistance were significantly refined compared to those without ultrasonic micro-forging assistance. The addition of ultrasonic micro-forging caused the dendritic crystals with an average size of 50.4μm in length and 7.5μm in width to break into equiaxed crystals with an average grain size of 3.8μm, and the coarse dendritic crystals were transformed into fine equiaxed crystals. Figure 3 Among them (1, 2, and 3 are specimens without ultrasonic micro-forging, and 4, 5, and 6 are specimens after ultrasonic micro-forging treatment).

[0030] Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A ball-type ultrasonic micro-forging assisted additive manufacturing device, comprising: An ultrasonic generator (1), a hydraulic device (2), an ultrasonic transducer (3), an ultrasonic horn (4), a tool head (5) and an ultrasonic micro forging head (6); wherein, the ultrasonic generator (1) is connected to the ultrasonic transducer (3) by wire; the lower end of the hydraulic device (2) is connected to the ultrasonic transducer (3), the lower end of the ultrasonic transducer (3) is connected to the ultrasonic horn (4), the lower end of the ultrasonic horn (4) is connected to the tool head (5); the lower end of the tool head (5) is connected to the ultrasonic micro forging head (6); It is characterized in that the ultrasonic micro forging head (6) is provided with a mounting base (7), and an arc-shaped groove is arranged inwardly on one side of the mounting base (7) away from the ultrasonic horn (4), and a plurality of small balls (8) are evenly arranged on the inner wall of the arc-shaped groove, and the plurality of small balls (8) surround a large ball (9); The plurality of small balls (8) and the large ball (9) are limited in the arc-shaped groove by a sealing ring (10); wherein, the large ball (9) protrudes from the end faces of the arc-shaped groove and the sealing ring (10); The double-layer balls of ultrasonic vibration have a small contact area with the additive micro region, the ultrasonic energy is easy to concentrate, the grain refinement effect is better, the ultrasonic energy transmission depth is greater, and the uniformity of the surface layer and the internal structure is better improved.

2. The ball-type ultrasonic micro-forging assisted additive manufacturing device according to claim 1, characterized in that Threaded holes are provided at both ends of the tool head (5) and the ultrasonic horn (4).

3. The ball-type ultrasonic micro-forging assisted additive manufacturing device according to claim 1, characterized in that The ultrasonic transducer (3) and the ultrasonic horn (4) are connected by a stud; the ultrasonic horn (4) and the tool head (5) are connected by a stud.

4. The ball-type ultrasonic micro-forging assisted additive manufacturing device according to claim 3, characterized in that A threaded rod is provided at the bottom of the mounting base (7) for threaded fastening connection with the threaded hole of the tool head (5).

5. The ball-type ultrasonic micro-forging assisted additive manufacturing device according to claim 1, characterized in that The ultrasonic generator (1) and the ultrasonic transducer (3) are connected by two lines.

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