CN114260463A - Laser selective melting discharge composite process and equipment - Google Patents
Laser selective melting discharge composite process and equipment Download PDFInfo
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- CN114260463A CN114260463A CN202111362436.1A CN202111362436A CN114260463A CN 114260463 A CN114260463 A CN 114260463A CN 202111362436 A CN202111362436 A CN 202111362436A CN 114260463 A CN114260463 A CN 114260463A
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Abstract
The invention provides a selective laser melting and discharging composite process and equipment, which solve the technical problem of part cracking in the selective laser melting process at present. Meanwhile, the invention provides selective laser melting discharge equipment which is provided with a working box, wherein a laser, a feeding device and a pulse discharge device are arranged inside the working box, a compression device is arranged outside the working box, the pulse discharge device is provided with a substrate assembly, the substrate assembly is sequentially connected with a sensor, a discharge switch and an energy storage capacitor in series, and an oscilloscope is connected with the sensor in parallel. The invention can be widely applied to the technical field of additive manufacturing.
Description
Technical Field
The application belongs to the technical field of additive manufacturing, and particularly relates to a selective laser melting and discharging composite process and device.
Background
Selective Laser Melting (SLM) is a recent advanced manufacturing technique that combines Laser cladding with rapid prototyping. The selective laser melting technology utilizes high-energy beam laser to directly melt metal powder, the metal powder is overlapped layer by layer to form a complex high-performance metal part, the size precision is high, the production efficiency is high, and the like. However, the existing process of melting and preparing the component in the selective laser area still has a plurality of problems, and the problem of serious segregation is caused in the forming process due to the rapid melting and solidification of materials in the preparation process of the part, so that cracks are initiated. Crack initiation in the selective laser melting process is one of key problems restricting SLM technology development and is also a key and hot point problem for study of scholars at home and abroad. The currently used methods are as follows: the substrate preheating, the alloy component adjustment, the heat treatment, the process parameter adjustment and the like are helpful for the part cracking problem in the selective laser melting process, but the crack arrest is still a problem to be solved urgently.
Disclosure of Invention
The invention aims to solve the defects of the background technology, and provides a selective laser melting and discharging composite process and device, wherein under a high-pressure environment, the selective laser melting and the electric heating crack arrest effect are generated at the same time, so that the generation of cracks during part preparation is reduced, the mechanical property of the material is improved, the formability of parts prepared by selective laser melting is effectively improved, and the parts with compact tissues and refined crystal grains are finally obtained.
Therefore, the invention provides a selective laser melting and discharging composite process, which comprises the following specific steps:
(1) assembling a substrate, a heat insulation plate and an insulation plate into a substrate assembly, fixing the substrate assembly on a lifting table in a working box, leading out the substrate assembly along the lifting table through a wire, sequentially connecting a sensor, a discharge switch and an energy storage capacitor in series, and connecting an oscilloscope in parallel with a pulse sensor;
(2) nitrogen is slowly conveyed into the working box through a nitrogen compressor, so that the pressure in the working box maintains a high-pressure environment;
(3) adding alloy powder into a material cylinder, feeding the alloy powder into a feeding box through a feeding pipe by the material cylinder, controlling the feeding box to reach a specified position above a substrate by a controller, triggering a bottom plate of the feeding box to open by a feeding sensor, and feeding the alloy powder onto the substrate;
(4) the energy storage capacitor is slowly charged through the discharging equipment, when the discharging switch is broken down under high voltage, the energy storage capacitor performs pulse discharging on the substrate, current passes through the sensor, current image display is performed through the oscilloscope connected with the sensor in parallel, the oscilloscope is observed, and pulse current density is controlled;
(5) the laser is moved above the substrate by using the controller, and pulse current is introduced to the substrate at the same time, so that the alloy powder on the substrate simultaneously generates an electrothermal effect in the laser melting process, and an electrothermal crack-stopping effect is achieved;
(6) and when the selective laser melting preparation is completed, closing the laser and stopping charging the energy storage capacitor, recovering the residual alloy powder, slowly discharging nitrogen, and taking out the part after air cooling to room temperature.
Preferably, in step (2), the pressure in the working chamber is maintained at 1.5-3.5 MPa.
The invention also provides a laser selective melting discharge device, which is applied to the composite process of the laser selective melting discharge, and is provided with a working box, wherein the upper end inside the working box is provided with a laser, the lower end of the laser is provided with a feeding device, the lower end of the feeding device is provided with a pulse discharge device, the outside of the working box is provided with a compression device, the outside of the working box is also connected with a controller, and the controller is used for controlling the operation of the laser selective melting discharge device.
Preferably, the pulse discharge device is provided with a substrate assembly, the substrate assembly is fixed on a lifting table of the working box, the substrate assembly is connected with the energy storage capacitor, the discharge switch and the pulse sensor in series through a lead, and the pulse sensor is connected with the oscilloscope in parallel.
Preferably, the substrate assembly is provided with a substrate, an insulating plate and a heat insulation plate, the insulating plate is made of epoxy resin materials, and an insulating boss is arranged on the upper surface of the insulating plate and matched with a groove on the lower surface of the heat insulation plate on the upper layer.
Preferably, the heat insulation plate is made of multiple layers of metal foil materials, and a sealing ring is arranged on the upper surface of the heat insulation plate and used for limiting connection of the groove of the substrate.
Preferably, the feeding device is provided with a feeding box, the feeding box is connected with the material cylinder through a feeding pipe, and a feeding sensor is arranged on the feeding pipe.
Preferably, the compression device is provided with a nitrogen compressor, the nitrogen compressor is connected with the work box through an air inlet pipe, and the air inlet pipe is provided with a pressure gauge.
The invention has the beneficial effects that:
(1) the invention relates to a selective laser melting and discharging composite process, which utilizes an energy storage capacitor to carry out high-intensity pulse discharge on a substrate assembly, and an alloy material and a solidified material play a role in an electrothermal crack arrest effect in a rapid solidification process. Under the action of strong pulse current, the crack tip generates strengthening heating to promote the remelting of the tip structure, and a fine structure is formed during subsequent rapid cooling, so that the crack tip is strengthened while the crack problem is improved, and the mechanical property and the formability of the material are improved. The electric heating effect is generated at the tip of the crack, simultaneously, the stress concentration can be eliminated, a quite large compressive stress field is generated, and the potential energy for forming a crack trunk line is inhibited, so that the purpose of crack arrest is achieved. In the pulse discharging process, the electrothermal effect can generate heat, and the heating effect can be realized through the combined action of the insulating plate and the insulating plate, so that the cracks of parts are prevented from being generated, and the stress concentration is reduced. The invention has simple process and low cost, greatly improves the most serious cracking problem of the alloy material in the preparation process, and has great significance for the wide application of the selective laser melting technology.
(2) According to the invention, nitrogen is input into the working box through the nitrogen compressor, so that the selective laser melting preparation process is always maintained in a high-pressure environment, and parts with compact tissues and refined grains are prepared through the combination of the high-pressure environment and selective laser. Meanwhile, based on a high-pressure environment, the feeding is carried out through the material cylinder, and the feeding sensor triggers the bottom plate switch of the feeding box after the feeding box reaches a specified position, so that accurate feeding is facilitated in the preparation process.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the embodiments or the prior art descriptions will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present application, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without inventive exercise.
FIG. 1 is a schematic connection diagram of a selective laser melting and discharging apparatus according to the present invention;
FIG. 2 is a schematic structural diagram of a selective laser melting and discharging apparatus according to the present invention;
FIG. 3 is a schematic view of an insulating plate of the pulse discharge device of the present invention;
FIG. 4 is a schematic view of a heat shield of the pulse discharge apparatus of the present invention;
FIG. 5 is a rear view of a thermally insulated panel of the pulse discharge apparatus of the present invention;
FIG. 6 is a schematic diagram of a substrate of a pulse discharge device according to the present invention;
the symbols in the drawings illustrate that:
1. a work box; 2. a lifting platform; 3. a laser; 4. a feeding box; 5. a feed tube; 6. a substrate; 7. a manometer; 8. a nitrogen compressor; 9. a feed sensor; 10. a material cylinder; 11. an energy storage capacitor; 12. a discharge switch; 13. a pulse sensor; 14. an insulating plate; 15. an insulating boss; 16. a heat insulation plate; 17. a substrate recess; 18. a seal ring; 19. a heat insulation groove; 20. an oscilloscope; 21. and a controller.
Detailed Description
In order to make the technical problems, technical solutions and advantageous effects to be solved by the present application clearer, the present application is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present application and are not intended to limit the present application.
The invention provides a selective laser melting discharge device, which is provided with a working box 1, wherein a laser 3 is arranged at the upper end inside the working box 1, a feeding device is arranged at the lower end of the laser 3 and used for conveying alloy powder, and a pulse discharge device is arranged at the lower end of the feeding device and used for performing pulse discharge on the alloy powder in the selective laser melting preparation process. The outside of the working box 1 is provided with a compression device for conveying compressed nitrogen into the working box 1 to maintain a high-pressure environment. The outside of the work box 1 is also connected with a controller 21, and the controller 21 controls the operation of the selective laser melting discharge device.
The pulse discharge device is provided with a substrate assembly, the substrate assembly is fixed on a lifting platform 2 of the working box 1, the substrate assembly is connected with an energy storage capacitor 11, a discharge switch 12 and a pulse sensor 13 in series through a lead, and the pulse sensor 13 is connected with an oscilloscope 20 in parallel. The energy storage capacitor 11 is charged by the discharge device, and when the high voltage causes the discharge switch 12 to break down, the energy storage capacitor 11 performs pulse discharge on the substrate assembly. The current passes through the pulse sensor 13, and current image display is performed through the oscilloscope 20 connected with the pulse sensor 13 in parallel, so that a pulse discharge process is completed.
Furthermore, the substrate assembly is provided with a substrate 6, an insulating plate 14 and an insulating plate 16, the substrate 6 is fixed on the insulating plate 16 through fastening screws, the insulating plate 16 is connected with the insulating plate 14, and the insulating plate 14 is located at the bottommost layer.
As shown in fig. 3 and 5, the insulating plate 14 is made of an epoxy resin material and functions to insulate an electric current. The upper surface of insulation board 14 is equipped with insulating boss 15, and the thermal-insulated recess 19 cooperation of the thermal-insulated board 16 lower surface on upper strata is with insulation board 16 and 14 zonulae occludens of insulation board, makes things convenient for the accurate locking of insulation board 14 and insulation board 16 position. The heat insulation plate 16 is made of a plurality of layers of metal foil materials, is used for heat insulation and preservation in the selective laser melting preparation process, and can slow down the rapid cooling process so as to reduce the generation of cracks. As shown in fig. 4 and 6, the upper surface of the heat insulation plate 16 is provided with a sealing ring 18 for limiting connection of the substrate groove 17. Moreover, the connection of the sealing ring 18 and the base plate 6 forms a vacuum environment, so that the effect of heat preservation and cooling speed reduction is increased. The cracking of the part during the preparation is mainly caused by the rapid cooling of the material, and the heat loss in the preparation process is greatly reduced through the coupling action of the heat insulation plate 16 and the sealing ring 18.
The feeding device positioned above the pulse discharge device is provided with a feeding box 4 arranged inside the working box 1, the feeding box 4 is connected with a material cylinder 10 arranged outside the working box 1 through a feeding pipe 5, alloy powder in the material cylinder 10 is supplemented to the feeding box 4 through the feeding pipe 5, a feeding sensor 9 is arranged on the feeding pipe 5 and used for sensing the position of the feeding box 4, and the feeding box 4 is matched with the alloy powder to be fed into the substrate 6.
The compression device positioned outside the working box 1 is provided with a nitrogen compressor 8, and the nitrogen compressor 8 sends compressed nitrogen into the working box 1 through an air inlet pipe. The air inlet pipe is provided with a pressure gauge 7 for detecting the pressure inside the work box 1.
Meanwhile, the invention provides a composite process for improving selective laser melting cracking, which comprises the following specific steps:
(1) the substrate 6, the heat insulation plate 16 and the insulation plate 14 are assembled into a substrate assembly, the substrate assembly is fixed on the lifting table 2 in the working box 1, the substrate assembly is led out along the lifting table 2 through a lead and is sequentially connected with the pulse sensor 13, the discharge switch 12 and the energy storage capacitor 11 in series, and the oscilloscope 20 is connected with the pulse sensor 13 in parallel.
(2) Nitrogen is slowly input into the working box 1 through the nitrogen compressor 8, so that the pressure in the working box 1 is maintained at 1.5-3.5Mpa, the selective laser melting preparation process is ensured to be carried out under a high-pressure environment, the organization of parts is compact, the size of the parts is refined, the mechanical property of the materials is improved, and cracking is prevented.
(3) Alloy powder is added into a material cylinder 10, the material cylinder 10 feeds materials into a feeding box 4 through a feeding pipe 5, a controller 21 controls the feeding box 4 to reach a specified position above a base plate 6, and at the moment, a feeding sensor 9 triggers a bottom plate of the feeding box 4 to be opened to feed the alloy powder onto the base plate 6. For the nickel-based high-temperature alloy material, the powder feeding speed is controlled to be 1-2 g/min.
(4) The energy storage capacitor 11 is slowly charged by the discharge device, and when the discharge switch 12 is broken down by high voltage, the energy storage capacitor 11 performs pulse discharge on the substrate assembly. The current passes through the pulse sensor 13, current image display is carried out through the oscilloscope 20 which is connected with the pulse sensor 13 in parallel, the oscilloscope 20 is observed, the pulse current density is controlled to reach a required value, and when the alloy material is nickel-based superalloy powder, the pulse current density is controlled to be 2A-5A/dm 2.
(5) The laser 3 is moved above the substrate 6 by using the controller, the laser power is adjusted to be 1300W-1700W, the scanning speed is 3-6mm/s, and simultaneously the pulse current is introduced to the substrate 6, so that the alloy powder on the substrate 6 simultaneously generates an electrothermal effect in the laser melting process, and the electrothermal crack-stopping effect is achieved. The laser melts the alloy powder, the melted material is combined with the substrate, and the high-intensity pulse current can reduce the generation of cracks and inhibit the expansion of microcracks in the melting process of the alloy material. Meanwhile, the electrothermal effect generates a large amount of compressive stress fields at the tip of the crack, and plays a role in promoting the fusion of the microcracks in the solidified material through the electrothermal effect. In the pulse discharging process, the electrothermal effect can generate heat, and the heating effect can be realized through the combined action of the insulating plate and the insulating plate, so that the cracks of parts are prevented from being generated, and the stress concentration is reduced.
(6) And when the selective laser melting preparation is completed, closing the laser 3 and stopping charging the energy storage capacitor 11, recovering the residual alloy powder, slowly discharging nitrogen, and taking out the part after air cooling to room temperature.
In summary, in the selective laser melting and discharging composite process of the present invention, the energy storage capacitor 11 is used to perform high-intensity pulse discharge on the substrate assembly, and the alloy material and the solidified material have an electrothermal crack arrest effect in the rapid solidification process. Under the action of strong pulse current, the crack tip generates strengthening heating to promote the remelting of the tip structure, and a fine structure is formed during subsequent rapid cooling, so that the crack tip is strengthened while the crack problem is improved, and the mechanical property and the formability of the material are improved. The electric heating effect is generated at the tip of the crack, simultaneously, the stress concentration can be eliminated, a quite large compressive stress field is generated, and the potential energy for forming a crack trunk line is inhibited, so that the purpose of crack arrest is achieved. During the pulse discharge process, the electrothermal effect can generate heat, and the insulating plate 14 and the insulating plate 16 can play a role in heating, so that the generation of part cracks is prevented, and the stress concentration is reduced. The invention has simple process and low cost, greatly improves the most serious cracking problem of the alloy material in the preparation process, and has great significance for the wide application of the selective laser melting technology.
In the invention, nitrogen is also input into the working box 1 through the nitrogen compressor 8, so that the selective laser melting preparation process is always maintained in a high-pressure environment, and parts with compact tissues and refined grains are prepared through the combination of the high-pressure environment and selective laser. Meanwhile, based on a high-pressure environment, the feeding is carried out through the material cylinder 10, and the feeding sensor 9 triggers the feeding box bottom plate 4 to be opened and closed after the feeding box 4 reaches a specified position, so that accurate feeding is facilitated in the preparation process.
The invention has simple process and low cost, greatly improves the most serious cracking problem of the alloy material in the preparation process, and has great significance for the wide application of the selective laser melting technology.
In the description of the present invention, it is to be understood that the terms "upper", "lower", "top", "bottom", "inner", "outer", and the like, indicate orientations and positional relationships based on those shown in the drawings, are only for convenience in describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus, should not be construed as limiting the present invention.
The above description is only exemplary of the present application and should not be taken as limiting the present application, as any modification, equivalent replacement, or improvement made within the spirit and principle of the present application should be included in the protection scope of the present application.
Claims (8)
1. A laser selective melting discharge composite process is characterized by comprising the following steps:
(1) assembling a substrate, a heat insulation plate and an insulation plate into a substrate assembly, fixing the substrate assembly on a lifting table in a working box, leading out the substrate assembly along the lifting table through a wire, sequentially connecting a sensor, a discharge switch and an energy storage capacitor in series, and connecting an oscilloscope in parallel with a pulse sensor;
(2) nitrogen is slowly conveyed into the working box through a nitrogen compressor, so that the pressure in the working box maintains a high-pressure environment;
(3) adding alloy powder into a material cylinder, feeding the alloy powder into a feeding box through a feeding pipe by the material cylinder, controlling the feeding box to reach a specified position above a substrate by a controller, triggering a bottom plate of the feeding box to open by a feeding sensor, and feeding the alloy powder onto the substrate;
(4) the energy storage capacitor is slowly charged through the discharging equipment, when the discharging switch is broken down under high voltage, the energy storage capacitor performs pulse discharging on the substrate, current passes through the sensor, current image display is performed through the oscilloscope connected with the sensor in parallel, the oscilloscope is observed, and pulse current density is controlled;
(5) the laser is moved above the substrate by using the controller, and pulse current is introduced to the substrate at the same time, so that the alloy powder on the substrate simultaneously generates an electrothermal effect in the laser melting process, and an electrothermal crack-stopping effect is achieved;
(6) and when the selective laser melting preparation is completed, closing the laser and stopping charging the energy storage capacitor, recovering the residual alloy powder, slowly discharging nitrogen, and taking out the part after air cooling to room temperature.
2. The selective laser melting and discharging combined process as claimed in claim 1, wherein in the step (2), the pressure in the working chamber is maintained at 1.5-3.5 Mpa.
3. A selective laser melting and discharging device, which is applied to the composite process of selective laser melting and discharging in claim 1, and is characterized in that: the laser selective melting and discharging device is provided with a working box, a laser is arranged at the upper end of the interior of the working box, a feeding device is arranged at the lower end of the laser, a pulse discharging device is arranged at the lower end of the feeding device, a compressing device is arranged outside the working box, a controller is further connected to the exterior of the working box, and the controller controls the operation of the laser selective melting and discharging device.
4. A laser selective melting discharge apparatus as claimed in claim 3, wherein: the pulse discharge device is provided with a substrate assembly, the substrate assembly is fixed on a lifting table of the working box, the substrate assembly is connected with the energy storage capacitor, the discharge switch and the pulse sensor in series through a wire, and the pulse sensor is connected with the oscilloscope in parallel.
5. The selective laser melting discharge apparatus of claim 4, wherein: the base plate assembly is provided with a base plate, an insulating plate and a heat insulation plate, the insulating plate is made of epoxy resin materials, and an insulating boss is arranged on the upper surface of the insulating plate and matched with a groove in the lower surface of the heat insulation plate on the upper layer.
6. The selective laser melting discharge apparatus of claim 5, wherein: the heat insulation plate is made of multiple layers of metal foil materials, and a sealing ring is arranged on the upper surface of the heat insulation plate and used for limiting connection of the groove of the substrate.
7. A laser selective melting discharge apparatus as claimed in claim 3, wherein: the feeding device is provided with a feeding box, the feeding box is connected with the material cylinder through a feeding pipe, and a feeding sensor is arranged on the feeding pipe.
8. A laser selective melting discharge apparatus as claimed in claim 3, wherein: the compression device is provided with a nitrogen compressor, the nitrogen compressor is connected with the work box through an air inlet pipe, and a pressure gauge is arranged on the air inlet pipe.
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| Application Number | Priority Date | Filing Date | Title |
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| CN202111362436.1A CN114260463B (en) | 2021-11-17 | 2021-11-17 | Laser selective melting discharge composite process and equipment |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202111362436.1A CN114260463B (en) | 2021-11-17 | 2021-11-17 | Laser selective melting discharge composite process and equipment |
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| CN114260463A true CN114260463A (en) | 2022-04-01 |
| CN114260463B CN114260463B (en) | 2022-05-27 |
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Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20070142914A1 (en) * | 2005-12-06 | 2007-06-21 | Eric Jones | Laser-produced porous surface |
| CN101215630A (en) * | 2007-12-26 | 2008-07-09 | 燕山大学 | Electromagnetic thermal effect welding seam crack arresting and soldering structure strengthening device |
| CN103602977A (en) * | 2013-09-12 | 2014-02-26 | 南京航空航天大学 | Method and device for refining solidification structure of laser cladding metal coating by pulse current |
| CN108672849A (en) * | 2018-05-23 | 2018-10-19 | 哈尔滨工业大学 | Microbeam electric arc selectivity consolidation and the compound increasing material manufacturing method of electric spark layered milling |
-
2021
- 2021-11-17 CN CN202111362436.1A patent/CN114260463B/en active Active
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20070142914A1 (en) * | 2005-12-06 | 2007-06-21 | Eric Jones | Laser-produced porous surface |
| CN101215630A (en) * | 2007-12-26 | 2008-07-09 | 燕山大学 | Electromagnetic thermal effect welding seam crack arresting and soldering structure strengthening device |
| CN103602977A (en) * | 2013-09-12 | 2014-02-26 | 南京航空航天大学 | Method and device for refining solidification structure of laser cladding metal coating by pulse current |
| CN108672849A (en) * | 2018-05-23 | 2018-10-19 | 哈尔滨工业大学 | Microbeam electric arc selectivity consolidation and the compound increasing material manufacturing method of electric spark layered milling |
Non-Patent Citations (1)
| Title |
|---|
| 白桦: "微弧氧化技术在高压齿轮水泵中的应用", 《哈尔滨工业大学学报》, 31 January 2008 (2008-01-31), pages 47 - 49 * |
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