Multi-energy-field heating device and method for inhibiting cracking of high-strength alloy in printing process

Abstract

The invention discloses a multi-energy-field heating device and method for restraining high-strength alloy from cracking in the printing process, and the device comprises a printing substrate which comprises a working face used for bearing a printed piece; the preheating mechanism is used for heating the printing substrate; the first laser source is used for applying a Gaussian laser beam to the working face so as to form a first light spot on the working face, and the first light spot is used for fusing printing powder for printing forming; the second laser source is used for applying a flat-topped laser beam to the working face so as to form a second light spot on the working face, the diameter of the second light spot is larger than that of the first light spot, and the second light spot completely covers the first light spot; wherein the first laser source and the second laser source move synchronously to ensure that the second light spot covers the first light spot in real time, and the second light spot comprises a preheating area located in front of the movement direction of the first light spot and a heat preservation area located behind the movement direction of the first light spot. According to the method, the temperature gradient is effectively slowed down, and the defects of holes, cracks and the like caused by a high-gradient temperature field and the unbalanced precipitation brittleness problem are avoided.

Description

Technical Field

[0001] The present application belongs to the field of 3D printing technology, and specifically relates to a multi-energy field heating device and method for suppressing cracking during the printing process of high-strength alloys. Background Art

[0002] Based on the characteristics of layer-by-layer cumulative printing and manufacturing, 3D printing technologies such as laser selective melting technology can theoretically print complex structural parts of any material. However, the engineering alloy systems that can be 3D printed and have excellent physical and chemical properties are still very limited. For example, the commercial powder system in aluminum alloy is only AlSi10Mg, and the high-strength 7-series aluminum alloy has encountered great challenges in overcoming cracks in the printing process, forcing people to re-design the complex powder composition for 3D printing.

[0003] In order to overcome defects such as cracks and holes, the existing technology generally adjusts key printing process parameters such as laser power, scanning speed, and scanning spacing to find an optimal process parameter match. However, for high-strength alloys, even through complicated experimental design, it is often difficult to find a reasonable process window to avoid cracking. For high-strength and high-hardness alloy systems (such as Ti alloys) and refractory alloy systems, since their printing process is prone to thermal cracks, how to print their complex components is a challenge that needs to be overcome. Under the existing mature high-strength alloy system, the manufacture of crack-free and high-performance components through 3D printing will further rapidly promote the engineering application of 3D printing technology. Summary of the invention

[0004] The purpose of this application is to provide a multi-energy field heating device and method for suppressing cracking during the printing process of high-strength alloys, so as to solve the technical problems in the prior art that cracks, holes and other problems cannot be overcome when printing high-strength alloy system materials, which affects the engineering application of 3D printing technology.

[0005] In order to achieve the above-mentioned object, the first aspect of the present application provides a multi-energy field heating device for suppressing cracking during the printing process of a high-strength alloy, comprising:

[0006] A printing substrate, including a working surface for carrying a printed part;

[0007] A preheating mechanism, used for heating the printing substrate;

[0008] A first laser source is used to apply a Gaussian laser beam to the working surface to form a first light spot on the working surface, wherein the first light spot is used to melt the printing powder to print and form;

[0009] a second laser source, used for applying a flat-top laser beam to the working surface to form a second light spot on the working surface, wherein the diameter of the second light spot is larger than the first light spot, and the second light spot completely covers the first light spot;

[0010] The first laser source and the second laser source move synchronously to ensure that the second light spot covers the first light spot in real time, and the second light spot includes a preheating area in front of the moving direction of the first light spot and a heat preservation area behind the moving direction.

[0011] In one or more embodiments, the preheating mechanism comprises an electromagnetic induction heating unit, and the preheating temperature of the preheating mechanism is 200-600°C.

[0012] In one or more embodiments, the first light spot is located at a center of the second light spot.

[0013] In one or more embodiments, the printed substrate comprises:

[0014] A panel, one side of which is provided with the working surface, and the other side of which is provided with a heating surface;

[0015] A heating column is arranged at the center of the heating surface, and the diameter of the heating column is 1 / 4 to 1 / 3 of the diameter of the panel;

[0016] Wherein, the electromagnetic induction heating unit is arranged around the heating column, and the heating rate of the electromagnetic induction heating unit is 80-120°C / min; and / or,

[0017] The material of the printing substrate is low carbon steel or low alloy steel with low thermal conductivity.

[0018] In one or more embodiments, the energy of the Gaussian laser beam is 300-500 W, and the diameter of the first light spot is 0.08-0.15 mm; the energy of the flat-top laser beam is 1500-3000 W, and the diameter of the second light spot is 1.5-3.0 mm.

[0019] In one or more embodiments, it further includes:

[0020] A temperature sensor, used to detect the actual temperature of the working surface;

[0021] The controller is used to collect the actual temperature detected by the temperature sensor, and control the output energy of the preheating mechanism, the first laser source and the second laser source based on the actual temperature and a preset target temperature.

[0022] In order to achieve the above-mentioned object, the second aspect of the present application provides a method for inhibiting cracking during the printing process of a high-strength alloy, comprising:

[0023] The printing substrate is heated by a preheating mechanism so that the working surface of the printing substrate reaches a target temperature;

[0024] Applying a Gaussian laser beam and a flat-top laser beam to the working surface simultaneously, and making a second light spot of the flat-top laser beam completely cover the first light spot of the Gaussian laser beam;

[0025] According to the preset printing program, the first light spot and the second light spot are controlled to move synchronously, and the printing powder is melted by the first light spot to print and form, ensuring that the second light spot covers the first light spot in real time, and the second light spot includes a preheating area located in front of the movement direction of the first light spot and a heat preservation area behind the movement direction.

[0026] In one or more embodiments, the target temperature is 200-600° C., and the method for confirming the target temperature includes:

[0027] Selecting an initial experimental temperature based on the melting point of the printing powder;

[0028] Controlling the preheating mechanism to heat the printing substrate to the initial experimental temperature, and then applying a Gaussian laser beam and a flat-top laser beam simultaneously to perform a printing experiment to determine whether the printing material has internal cracks;

[0029] If so, increase the initial experimental temperature by a preset value and repeat the experiment until there are no internal cracks in the printed material, and obtain an intermediate experimental temperature;

[0030] Controlling the preheating mechanism to heat the printing substrate to the intermediate experimental temperature, performing an orthogonal printing experiment with the energy of the Gaussian laser beam and the scanning speed as variables, and determining whether the minimum energy of the Gaussian laser beam is greater than a second threshold when the scanning speed is greater than a first threshold, wherein the minimum energy of the Gaussian laser beam satisfies that the printing material has no internal cracks;

[0031] If not, the intermediate experimental temperature is increased by a preset value and the experiment is repeated until the minimum energy of the Gaussian laser beam is greater than a second threshold when the scanning speed is greater than the first threshold, thereby obtaining the target temperature.

[0032] In one or more embodiments, the first light spot is located at a center of the second light spot.

[0033] In one or more embodiments, the energy of the Gaussian laser beam is 300-500 W, and the diameter of the first light spot is 0.08-0.15 mm; the energy of the flat-top laser beam is 1500-3000 W, and the diameter of the second light spot is 1.5-3.0 mm.

[0034] In one or more embodiments, it further includes:

[0035] The actual temperature of the working surface is acquired in real time during the printing process, and based on the difference between the actual temperature and the target temperature, the output energy of the preheating mechanism, the Gaussian laser beam and the flat-top laser beam is adjusted to keep the working surface at the target temperature.

[0036] Different from the prior art, the beneficial effects of this application are:

[0037] On the one hand, the present application preheats the working surface through a preheating mechanism including an electromagnetic induction heating unit, effectively reducing the temperature difference between the printing area and the non-printing area. On the other hand, overlapping Gaussian laser beams and flat-top laser beams are synchronously applied to the working surface during the printing process, and the two are moved synchronously. The material is sequentially subjected to the preheating of the flat-top laser beam, the printing of the Gaussian laser beam, and the insulation stage of the flat-top laser beam, effectively slowing down the temperature gradient, thereby avoiding defects such as holes and cracks caused by the high-gradient temperature field and the problem of non-equilibrium precipitation brittleness.

[0038] This application greatly expands the printability of mature alloy systems and expands the engineering application space of metal 3D printing. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0040] Figure 1 It is a structural schematic diagram of an embodiment of a multi-energy field heating device for suppressing cracking during the printing process of a high-strength alloy according to the present application;

[0041] Figure 2 is a schematic diagram of the first light spot and the second light spot in this application;

[0042] Figure 3 It is a flow chart of an embodiment of a method for suppressing cracking in a high-strength alloy printing process of the present application;

[0043] Figure 4 It is the confirmation method of the target temperature of this application;

[0044] Figure 5 is a temperature field distribution diagram of the scanning plane in Example 1 of the present application;

[0045] Figure 6 This is a temperature gradient distribution diagram of the longitudinal section in Example 1 of the present application.

[0046] As shown in the figure:

[0047] Printing substrate 10; working surface 101; panel 102; heating surface 103; heating column 104;

[0048] Preheating mechanism 20; electromagnetic induction heating unit 201; resistance wire 202;

[0049] A first laser source 30;

[0050] A second laser source 40;

[0051] First light spot 50;

[0052] Second light spot 60; preheating zone 601; heat preservation zone 602. DETAILED DESCRIPTION

[0053] In order to enable those skilled in the art to better understand the technical solutions in the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without creative work should fall within the scope of protection of the present application.

[0054] For high-strength and high-hardness alloy systems (such as Ti alloys) and refractory alloy systems, since thermal cracks are easily generated during the printing process, how to print their complex components is a challenge that needs to be overcome.

[0055] In order to solve the above problems, the applicant found that the reason why the existing high-strength alloy system has produced thermal cracks during the printing process is that the non-equilibrium physical metallurgical process of high-speed heating and cooling (103-106℃ / s) of the laser forms a high-gradient temperature field (~104℃ / mm), which brings defects such as holes and cracks in the material and non-equilibrium precipitation brittleness.

[0056] In order to solve the above problems, the applicant has developed a new type of multi-energy field heating device for suppressing cracking during the printing process of high-strength alloys. The device can realize real-time preheating of the path to be printed and real-time insulation of the printed path, significantly slowing down the temperature gradient of the printing process, and effectively avoiding the problem of material cracking caused by high gradient temperature field during the printing process.

[0057] Specifically, see Figure 1 , Figure 1 It is a structural schematic diagram of an embodiment of the multi-energy field heating device for suppressing cracking during the printing process of high-strength alloys in the present application.

[0058] like Figure 1 As shown, the device comprises a printing substrate 10, on which a working surface 101 for carrying printed parts is arranged.

[0059] The device also includes a preheating mechanism 20 for heating the printing substrate 10. The preheating mechanism 20 is used to heat the working surface 101 to a preset temperature before printing, thereby reducing the temperature difference between the printing point and the surrounding area during the printing process and slowing down the temperature gradient.

[0060] Specifically, in order to increase the preheating temperature, the preheating mechanism 20 in this embodiment includes an electromagnetic induction heating unit 201, and the preheating temperature is 200-600°C.

[0061] It is understandable that compared with traditional resistance heating, induction heating has a short preheating time, high energy conversion rate, low heat dissipation, is more economical, efficient, green and energy-saving, can achieve higher preheating temperature, and significantly reduce the temperature gradient during printing.

[0062] In order to achieve the best preheating efficiency, the printing substrate 10 in this embodiment includes a panel 102, one side of the panel 102 is arranged with a working surface 101, and the other side is arranged with a heating surface 103; the printing substrate 10 also includes a heating column 104 arranged at the center of the heating surface 103, and the electromagnetic induction heating unit 201 is arranged around the heating column 104 to achieve heating of the panel 102.

[0063] In one embodiment, the panel 102 may be a square panel 102 that matches the molding cavity of the printer, and the diameter of the heating column 104 may be 1 / 4 to 1 / 3 of the side length of the panel 102, thereby ensuring that the heating efficiency of each part of the panel 102 is similar and achieving the best heating effect.

[0064] In other embodiments, based on actual needs, the panel 102 may also adopt other shapes and structures, and the diameter of the heating column 104 may also be adjusted accordingly, and the effect of this embodiment can be achieved.

[0065] In one embodiment, the frequency of the induction coil of the electromagnetic induction heating unit 201 is 30 to 60 kHz, and the output power is 60 to 80 kW, thereby ensuring a heating rate of 80-120°C / min; in other embodiments, the frequency and power of the induction coil can also be adjusted based on actual needs to ensure that the heating rate and the maximum preheating temperature meet the needs, and the effect of this embodiment can be achieved.

[0066] In order to achieve a better preheating effect, the preheating mechanism 20 in this embodiment also includes a resistance wire 202 arranged at the bottom end of the heating column 104, which further improves the preheating efficiency and preheating temperature by superimposing resistance heating and electromagnetic heating.

[0067] Furthermore, in this embodiment, the device includes a first laser source 30 and a second laser source 40, wherein the first laser source 30 is used to apply a Gaussian laser beam to the working surface 101 to form a first light spot 50 on the working surface 101, and the first light spot 50 is used to melt the printing powder for printing and forming; the second laser source 40 is used to apply a flat-top laser beam to the working surface 101 to form a second light spot 60 on the working surface 101, and the diameter of the second light spot 60 is larger than that of the first light spot 50, and the second light spot 60 completely covers the first light spot 50.

[0068] During the printing process, the first laser source 30 and the second laser source 40 move synchronously to ensure that the second light spot 60 covers the first light spot 50 in real time, and the second light spot 60 includes a preheating zone 601 located in front of the movement direction of the first light spot 50 and a heat preservation zone 602 behind the movement direction.

[0069] The energy of Gaussian laser is concentrated at the center, while flat-top laser has the characteristic of uniform energy distribution. This application combines Gaussian laser and flat-top laser, and makes the area of ​​the second light spot 60 of the flat-top laser beam larger than the area of ​​the first light spot 50 of the Gaussian laser. The second light spot 60 completely covers the first light spot 50 and moves synchronously. Please refer to Figure 2 , Figure 2 Schematic diagram of the first light spot 50 and the second light spot 60 in the present application.

[0070] like Figure 2 As shown, during the printing process, the printing powder is melted based on the first light spot 50 to print and form, and the preheating zone 601 in the second light spot 60 located in front of the movement direction x of the first light spot 50 can effectively preheat the material to be printed, and the insulation zone 602 in the second light spot 60 located behind the movement direction x of the first light spot 50 can effectively keep the printed material warm; with the movement of the first light spot 50 and the second light spot 60, the material goes through the processes of preheating, printing, and insulation in sequence, which effectively slows down the temperature gradient of the material, thereby avoiding defects such as holes and cracks caused by the high gradient temperature field and the problem of non-equilibrium precipitation brittleness.

[0071] Specifically, in one embodiment, the energy of the Gaussian laser beam is 300-500 W, and the diameter of the first light spot 50 is 0.08-0.15 mm; the energy of the flat-top laser beam is 1500-3000 W, and the diameter of the second light spot 60 is 1.5-3.0 mm.

[0072] In one embodiment, in order to ensure uniform distribution of the preheating zone 601 and the heat preservation zone 602 and provide the material with sufficient and balanced preheating and heat preservation space, the first light spot 50 can be located at the center of the second light spot 60 .

[0073] In order to perform closed-loop control of the temperature of the processing surface during the processing, in this embodiment, the multi-energy field heating device also includes a temperature sensor (not shown in the figure) and a controller (not shown in the figure). The temperature sensor is used to detect the actual temperature of the working surface 101, and the controller is used to collect the actual temperature detected by the temperature sensor, and based on the actual temperature and the preset target temperature, control the output energy of the preheating mechanism 20, the first laser source 30 and the second laser source 40.

[0074] The temperature sensor may be a thermocouple sensor or a non-contact sensor, and the controller may be a PLC, a single-chip microcomputer, etc., all of which can achieve the effect of this embodiment.

[0075] Based on the multi-energy field heating device of the above-mentioned embodiments, on the one hand, the working surface 101 is preheated by the preheating mechanism 20 including the electromagnetic induction heating unit 201, thereby effectively reducing the temperature difference between the printing area and the non-printing area. On the other hand, during the printing process, a Gaussian laser beam and a flat-top laser beam are synchronously applied to the working surface 101, and the two are made to move synchronously. The material successively goes through the stages of preheating with the flat-top laser beam, printing with the Gaussian laser beam, and heat preservation with the flat-top laser beam, thereby effectively slowing down the temperature gradient, thereby avoiding defects such as holes and cracks caused by the high-gradient temperature field and the problem of non-equilibrium precipitation brittleness.

[0076] This application also provides a method for inhibiting cracking during the printing process of high-strength alloys, see Figure 3 , Figure 3 It is a flow chart of an implementation method of the present application for suppressing cracking during the printing process of high-strength alloys.

[0077] like Figure 3 As shown, the method includes:

[0078] S100, heating the printed substrate by a preheating mechanism so that the working surface of the printed substrate reaches a target temperature.

[0079] S200 , applying a Gaussian laser beam and a flat-top laser beam to the working surface simultaneously, and making the second light spot of the flat-top laser beam completely cover the first light spot of the Gaussian laser beam.

[0080] S300, according to a preset printing program, control the first light spot and the second light spot to move synchronously, melt the printing powder through the first light spot to print and form, ensure that the second light spot covers the first light spot in real time, and the second light spot includes a preheating area located in front of the movement direction of the first light spot and a heat preservation area behind the movement direction.

[0081] It should be understood that the above description of the multi-energy field heating device of the present application is also applicable to the method of suppressing cracking in the high-strength alloy printing process of the present application, and will not be repeated here.

[0082] In one embodiment, the target temperature may be 200-600°C.

[0083] To determine the optimum preheat temperature before starting printing, refer to Figure 4 , Figure 4 This is the method for confirming the target temperature of this application.

[0084] like Figure 4 As shown, the method for determining the target temperature includes:

[0085] S101. Select an initial experimental temperature based on the melting point of the printing powder.

[0086] It can be understood that the higher the melting point of the printing powder, the higher the temperature requirement during printing, and the higher the energy required by the Gaussian laser beam. At this time, in order to reduce the temperature difference between the printing area and the non-printing area, the preset temperature needs to be increased; therefore, the initial experimental temperature can be determined based on the melting point of the printing powder.

[0087] Exemplarily, when the melting point of the printed powder is lower than 1000°C, the initial experimental temperature can be set to 200°C; when the melting point of the printed powder is between 1000 and 2000°C, the initial experimental temperature can be set to 300°C; when the melting point of the printed powder is higher than 2000°C, the initial experimental temperature can be set to 450°C.

[0088] S102, controlling the preheating mechanism to heat the printing substrate to an initial experimental temperature, and then applying a Gaussian laser beam and a flat-top laser beam simultaneously to perform a printing experiment to determine whether the printed material has internal cracks.

[0089] After determining the initial experimental temperature, the printing experiment can be started at the initial experimental temperature. The energy and scanning speed of the Gaussian laser beam and the flat-top laser beam can be preset by referring to the empirical parameters when printing powders with similar material compositions to determine whether the material printed at the initial experimental temperature has internal cracks.

[0090] If cracks are present, they include:

[0091] S103, increasing the initial experimental temperature by a preset value and repeating the experiment until there are no internal cracks in the printed material, thereby obtaining an intermediate experimental temperature.

[0092] If cracks exist inside the material during the printing experiment conducted at the initial experimental temperature, the temperature is increased by a preset value and the experiment is repeated, wherein the preset value can be set based on actual working conditions, for example, can be 40°C.

[0093] As the preheating temperature increases, the temperature gradient of the printing surface gradually decreases until no cracks appear in the printed material. At this time, the intermediate experimental temperature is obtained and the next step of judgment can be carried out.

[0094] S104, controlling the preheating mechanism to heat the printing substrate to an intermediate experimental temperature, performing an orthogonal printing experiment with the energy of the Gaussian laser beam and the scanning speed as variables, and determining whether the minimum energy of the Gaussian laser beam is greater than a second threshold when the scanning speed is greater than a first threshold.

[0095] Among them, the minimum energy of the Gaussian laser beam is required to ensure that the printed material has no internal cracks.

[0096] In the experiments of S102 and S103, the energy and scanning speed of the Gaussian laser beam and the flat-top laser beam are preset based on empirical parameters. Taking into account the balance between printing efficiency, process repeatability and energy consumption, the Gaussian laser beam needs to be as small as possible while meeting the scanning speed requirements to ensure subsequent printing efficiency and process repeatability. If the energy of the Gaussian laser beam is lower than the threshold, although the preset temperature can be lowered, the process repeatability is low. If the energy of the Gaussian laser beam is much higher than the threshold, a higher preheating temperature is required, production energy consumption increases, and there is no unnecessary improvement in the performance of the printed part and printing stability.

[0097] Therefore, an orthogonal printing experiment can be designed with the energy size and scanning speed of the Gaussian laser beam as variables. In the experiment, the scanning speed is set to a value greater than the first threshold, and the energy size of the Gaussian laser beam is gradually reduced until cracks appear inside the printed material. At this time, it is judged whether the minimum energy size of the Gaussian laser beam is greater than the second threshold when there are no cracks inside the printed material.

[0098] If no, include:

[0099] S105, increasing the intermediate experimental temperature by a preset value and repeating the experiment until the minimum energy of the Gaussian laser beam is greater than the second threshold when the scanning speed is greater than the first threshold, thereby obtaining the target temperature.

[0100] If the minimum energy of the Gaussian laser beam is not greater than the second threshold, the preheating temperature can be increased and the experiment can be repeated until the scanning speed is greater than the first threshold and the minimum energy of the Gaussian laser beam is greater than the second threshold, thereby obtaining a target temperature that can achieve a balance between printing efficiency, process repeatability and energy consumption.

[0101] In order to achieve closed-loop control of the temperature of the printing surface during the printing process, the method of this embodiment further includes:

[0102] During the printing process, the actual temperature of the working surface is obtained in real time. Based on the difference between the actual temperature and the target temperature, the output energy of the preheating mechanism, Gaussian laser beam and flat-top laser beam is adjusted to keep the working surface at the target temperature.

[0103] The methods based on the above-mentioned embodiments can effectively slow down the temperature gradient during the printing process while achieving a balance between printing efficiency, process repeatability and energy consumption, thereby avoiding defects such as holes and cracks caused by high-gradient temperature fields and non-equilibrium precipitation brittleness problems.

[0104] The effects of the technical solution of the present application are further described in detail below in conjunction with specific embodiments.

[0105] Embodiment 1:

[0106] In the 316L stainless steel system, 300W Gaussian laser beam and 2000W flat-top laser beam were applied respectively to perform finite element analysis on the temperature field; then 300W Gaussian laser beam and 2000W flat-top laser beam were superimposed to perform finite element analysis on the temperature field, and the results were obtained. Figure 5 and Figure 6 , Figure 5 is the temperature field distribution diagram of the scanning plane in Example 1 of the present application, Figure 6 It is a temperature gradient distribution diagram of the longitudinal section in Example 1 of the present application.

[0107] like Figure 5 As shown, the maximum temperature under a single Gaussian laser beam is 1445°C, while after coupling the Gaussian laser beam and the flat-top laser beam, the maximum temperature increases to 1888°C. At the same time, there is a heating zone with a diameter of about 2 mm, which can realize preheating of the front end of the Gaussian laser beam scanning and insulation of the back end.

[0108] like Figure 6 As shown in the figure, in the case of single Gaussian laser beam and dual laser beam coupling, a 1.87*10 4 ℃ / s, but the area of ​​high temperature gradient zone in the case of double laser beam superposition is much smaller than that in the former, and a wide range of gradual transition zone is formed.

[0109] Therefore, it can be confirmed that the present application can achieve synchronous preheating and heat preservation of materials by superimposing flat-top laser beams, effectively slow down the temperature gradient, and help avoid problems such as material cracking due to high temperature gradients.

[0110] Embodiment 2:

[0111] A 7 series high-strength aluminum alloy was selected as the printing powder, the printing substrate was preheated to 320°C, and overlapping Gaussian laser beams and flat-top laser beams were applied simultaneously, wherein the Gaussian laser beam energy was 400W, the spot diameter was 0.15mm, the flat-top laser beam energy was 2600W, the spot diameter was 3.0mm, and the printing parameter window was: Gaussian laser energy 320-420W; scanning speed 800-1300mm / s.

[0112] The results show that the material can be printed and formed, with no internal cracks and a relative density of 99.95%.

[0113] Embodiment 3:

[0114] Titanium aluminum alloy was selected as the printing powder, the printing substrate was preheated to 500°C, and overlapping Gaussian laser beams and flat-top laser beams were applied simultaneously, wherein the Gaussian laser beam energy was 420W, the spot diameter was 0.10mm, the flat-top laser beam energy was 2600W, the spot diameter was 2.0mm, and the printing parameter window was: Gaussian laser energy 350-450W; scanning speed 720-1200mm / s.

[0115] The results show that the material can be printed and formed, with no internal cracks and a relative density of 99.92%.

[0116] Embodiment 4:

[0117] High-purity tungsten powder was selected as the printing powder, the printing substrate was preheated to 530°C, and overlapping Gaussian laser beams and flat-top laser beams were applied simultaneously, wherein the Gaussian laser beam energy was 400W, the spot diameter was 0.08mm, the flat-top laser beam energy was 2800W, the spot diameter was 1.5mm, and the printing parameter window was: Gaussian laser energy 360-460W; scanning speed 400-850mm / s.

[0118] The results show that the material can be printed and formed, with no internal cracks and a relative density of 99.36%.

[0119] Comparative Example 1:

[0120] The same 7 series high-strength aluminum alloy as in Example 2 was selected as the printing powder, the printing substrate was preheated to 200°C, and overlapping Gaussian laser beams and flat-top laser beams were applied simultaneously, wherein the Gaussian laser beam energy was 400W, the spot diameter was 0.15mm, the flat-top laser beam energy was 2600W, the spot diameter was 3.0mm, and the printing parameter window was: Gaussian laser energy 320-420W; scanning speed 800-1300mm / s.

[0121] The results showed that the material could be printed, but there were high-density cracks inside.

[0122] It is obvious to those skilled in the art that the present application is not limited to the details of the exemplary embodiments described above, and that the present application can be implemented in other specific forms without departing from the spirit or essential features of the present application. Therefore, the embodiments should be regarded as exemplary and non-limiting in all respects, and the scope of the present application is defined by the appended claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims be included in the present application. Any reference numeral in a claim should not be regarded as limiting the claim to which it relates.

[0123] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A multi-energy field heating device for suppressing cracking during the printing process of high-strength alloys, characterized in that: include: A printing substrate, including a working surface for carrying a printed part; A preheating mechanism, used for heating the printing substrate; A first laser source is used to apply a Gaussian laser beam to the working surface to form a first light spot on the working surface, wherein the first light spot is used to melt the printing powder to print and form; a second laser source, used for applying a flat-top laser beam to the working surface to form a second light spot on the working surface, wherein the diameter of the second light spot is larger than the first light spot, and the second light spot completely covers the first light spot; The first laser source and the second laser source move synchronously to ensure that the second light spot covers the first light spot in real time, and the second light spot includes a preheating area in front of the moving direction of the first light spot and a heat preservation area behind the moving direction.

2. The multi-energy field heating device according to claim 1, characterized in that: The preheating mechanism comprises an electromagnetic induction heating unit, and the preheating temperature of the preheating mechanism is 200-600° C.; and / or, The first light spot is located at the center of the second light spot.

3. The multi-energy field heating device according to claim 2, characterized in that: The printing substrate comprises: A panel, one side of which is provided with the working surface, and the other side of which is provided with a heating surface; A heating column is arranged at the center of the heating surface, and the diameter of the heating column is 1 / 4 to 1 / 3 of the diameter of the panel; Wherein, the electromagnetic induction heating unit is arranged around the heating column, and the heating rate of the electromagnetic induction heating unit is 80-120°C / min; and / or, The material of the printing substrate is low carbon steel or low alloy steel with low thermal conductivity.

4. The multi-energy field heating device according to claim 1, characterized in that: The energy of the Gaussian laser beam is 300-500W, and the diameter of the first light spot is 0.08-0.15mm; the energy of the flat-top laser beam is 1500-3000W, and the diameter of the second light spot is 1.5-3.0mm.

5. The multi-energy field heating device according to claim 1, characterized in that: Also includes: A temperature sensor, used to detect the actual temperature of the working surface; The controller is used to collect the actual temperature detected by the temperature sensor, and control the output energy of the preheating mechanism, the first laser source and the second laser source based on the actual temperature and a preset target temperature.

6. A method for inhibiting cracking during the printing process of a high-strength alloy, characterized in that: include: The printing substrate is heated by a preheating mechanism so that the working surface of the printing substrate reaches a target temperature; Applying a Gaussian laser beam and a flat-top laser beam to the working surface simultaneously, and making a second light spot of the flat-top laser beam completely cover the first light spot of the Gaussian laser beam; According to the preset printing program, the first light spot and the second light spot are controlled to move synchronously, and the printing powder is melted by the first light spot to print and form, ensuring that the second light spot covers the first light spot in real time, and the second light spot includes a preheating area located in front of the movement direction of the first light spot and a heat preservation area behind the movement direction.

7. The method according to claim 6, characterized in that The target temperature is 200-600° C., and the method for confirming the target temperature includes: Selecting an initial experimental temperature based on the melting point of the printing powder; Controlling the preheating mechanism to heat the printing substrate to the initial experimental temperature, and then applying a Gaussian laser beam and a flat-top laser beam simultaneously to perform a printing experiment to determine whether the printing material has internal cracks; If so, increase the initial experimental temperature by a preset value and repeat the experiment until there are no internal cracks in the printed material, and obtain an intermediate experimental temperature; Controlling the preheating mechanism to heat the printing substrate to the intermediate experimental temperature, performing an orthogonal printing experiment with the energy of the Gaussian laser beam and the scanning speed as variables, and determining whether the minimum energy of the Gaussian laser beam is greater than a second threshold when the scanning speed is greater than a first threshold, wherein the minimum energy of the Gaussian laser beam satisfies that the printing material has no internal cracks; If not, the intermediate experimental temperature is increased by a preset value and the experiment is repeated until the minimum energy of the Gaussian laser beam is greater than a second threshold when the scanning speed is greater than the first threshold, thereby obtaining the target temperature.

8. The method according to claim 6, characterized in that The first light spot is located at the center of the second light spot.

9. The method according to claim 6, characterized in that The energy of the Gaussian laser beam is 300-500W, and the diameter of the first light spot is 0.08-0.15mm; the energy of the flat-top laser beam is 1500-3000W, and the diameter of the second light spot is 1.5-3.0mm.

10. The method according to claim 6, characterized in that Also includes: The actual temperature of the working surface is acquired in real time during the printing process, and based on the difference between the actual temperature and the target temperature, the output energy of the preheating mechanism, the Gaussian laser beam and the flat-top laser beam is adjusted to keep the working surface at the target temperature.

Images