A brazing experimental device based on a falling tower method simulating a microgravity environment

Abstract

This invention relates to the field of brazing technology, specifically to a brazing experimental apparatus based on the drop tower method to simulate a microgravity environment. It includes a brazing temperature-controlled heating unit, a needle heating unit, a brazing filler metal extrusion mechanism, an image acquisition system, an atmosphere system, and a control system, all fixedly installed within the drop tower's drop chamber. The brazing temperature-controlled heating unit is used to fix and heat the base material to be welded. The needle heating unit is located above it and heats the brazing filler metal until it melts. The brazing filler metal extrusion mechanism quantitatively extrudes the molten filler metal onto the surface of the base material. The image acquisition system records wetting and spreading in a backlit manner. The atmosphere system introduces protective gas and cooling gas. The controller is electrically connected to each mechanism and is used to: control the needle heating unit to heat the brazing filler metal to a preset temperature, and then activate the brazing temperature-controlled heating unit to heat the base material, achieving separate heating; when both reach the set temperature, trigger the drop chamber within the drop tower to fall freely; within 3.6 seconds of descent, the processes of brazing filler metal extrusion, image acquisition, and cooling gas ejection are sequentially performed.

Description

Technical Field

[0001] This invention relates to the field of brazing technology, and more specifically, to a brazing experimental apparatus based on the drop tower method to simulate a microgravity environment. Background Technology

[0002] With the continuous development of space exploration technology, the on-orbit assembly and manufacturing of components for large space stations, as well as the on-orbit repair of damaged parts of spacecraft, have created an urgent need for space connection technology. Brazing, with its significant advantages such as strong process adaptability, high safety, and ease of connecting complex structures, has become one of the key technologies for solving these problems. To simulate a microgravity environment on Earth for studying brazing mechanisms, drop tower experiments are an effective method, utilizing the principle of free fall to provide a short-term microgravity environment of 3.6 seconds for the experimental payload. Currently, some microgravity simulation devices have been used in materials processing experiments. For example, a vacuum chamber combined with a projectile mechanism is used to allow the specimen to fall freely and be heated to achieve material melting; other technologies control the timing of microdroplet ejection and release to achieve microdroplet pursuit and fusion during free fall.

[0003] However, there are still shortcomings when applying the aforementioned existing technologies to microgravity brazing. Under microgravity conditions, the lack of gravity-driven force makes it difficult for liquid brazing filler metal to flow or drip under its own weight. Furthermore, the filler metal is usually pre-assembled onto the base material and relies on natural melting to fill the gaps, making it difficult to actively control the timing and amount of material feeding. Simultaneously, the brazing process requires the filler metal to melt while the base material remains stationary. Under overall heating, the temperatures of the base material and the filler metal are interconnected; the filler metal melts as the base material heats up, which cannot allow the entire melting and spreading process of the filler metal to occur under microgravity conditions. Therefore, it is necessary to design a brazing experimental device based on the drop tower method to simulate a microgravity environment, in order to conduct brazing experiments under simulated microgravity conditions on the ground. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a brazing experimental device based on the drop tower method to simulate a microgravity environment, thus solving the problem of precise control of the brazing process under microgravity conditions.

[0005] This invention provides a brazing experimental device based on the drop tower method to simulate a microgravity environment, including a brazing temperature control heating unit, a needle heating unit, a brazing filler metal extrusion mechanism, an image acquisition system, an atmosphere system, and a controller, all fixedly installed in the drop chamber. The brazing temperature control heating unit is used to fix and heat the base material to be welded; The needle heating unit is located above the brazing temperature control heating unit and is used to place and heat the brazing filler metal, melting it into molten filler metal. The brazing filler metal extrusion mechanism is installed on the needle heating unit and is used to extrude the molten brazing filler metal quantitatively onto the surface of the base material to be welded; The image acquisition system is used to record the wetting and spreading process of the molten solder on the surface of the base material to be soldered; The atmosphere system is connected to the brazing temperature control heating unit and is used to introduce protective gas and cooling gas into the brazing temperature control heating unit. The controller is electrically connected to the brazing temperature control heating unit, the needle heating unit, the brazing filler metal extrusion mechanism, the image acquisition system, and the atmosphere system, respectively. The controller is used to: control the needle heating unit to heat the brazing filler metal to a preset temperature, and start the brazing temperature control heating unit to heat the base material to be welded; when the brazing filler metal and the base material to be welded reach the welding process temperature, trigger the free fall of the drop chamber; during the free fall of the drop chamber, sequentially control the brazing filler metal extrusion mechanism to extrude the molten brazing filler metal quantitatively onto the surface of the base material to be welded, control the image acquisition system to record the wetting and spreading process of the molten brazing filler metal, and control the atmosphere system to introduce cooling gas into the brazing temperature control heating unit.

[0006] Preferably, it also includes a fixed support mechanism, which includes a base plate, a Z-axis scissor lift platform, and a fixed platform; The bottom plate is connected to the bottom of the landing compartment; The Z-axis scissor lift is connected to the base plate. The top of the Z-axis scissor lift is used to install the brazing temperature control heating unit. The height of the Z-axis scissor lift is adjustable and can be locked and fixed. The fixing platform is connected to the base plate, and a fixing plate is provided on the fixing platform for mounting the needle heating unit; The backlight source of the image acquisition system is embedded in the fixed platform, and the high-speed camera in the image acquisition system is mounted on the base plate and located on opposite sides of the brazing temperature control heating unit, respectively, along with the backlight source.

[0007] Preferably, the needle heating unit includes: A connecting frame, which is connected to the fixing plate; A needle-heated steel pipe, the upper end of which is connected to the connecting frame, and the lower end which extends into the interior of the brazing temperature control heating unit; A ceramic tube is coaxially disposed inside the needle heating steel tube. The cavity of the ceramic tube is used to accommodate the brazing filler metal, and an electric heating wire is wound around the outside of the ceramic tube.

[0008] Preferably, the lower end of the ceramic tube has a needle section with a diameter smaller than that of the tube cavity, so that the bottom of the ceramic tube has a stepped structure. The stepped structure matches the stepped hole at the bottom of the needle heating steel tube, and the needle section extends out of the bottom end of the needle heating steel tube and is locked by threads.

[0009] Preferably, the solder extrusion mechanism includes: A linear power assembly, wherein the linear power assembly is mounted on the connecting frame; A ceramic rod is connected to the linear power assembly, and the lower end of the ceramic rod is inserted into the ceramic tube. The linear power assembly drives the ceramic rod to move vertically to extrude the molten solder from the bottom end of the ceramic tube in a measured manner.

[0010] Preferably, the brazing filler metal extrusion mechanism further includes: A positioning sleeve extends through the lower end of the connecting frame, and the upper end of the needle heating steel pipe is inserted into the lower end of the positioning sleeve. A positioning cap is placed on the upper end of the positioning sleeve, and the ceramic rod passes through the positioning cap and extends into the ceramic tube.

[0011] Preferably, the brazing temperature control heating unit includes: A temperature control chamber, wherein heating components are respectively provided in the upper and lower parts of the temperature control chamber, and an air inlet and an air outlet for the protective gas are provided on the side of the temperature control chamber; A temperature sensing element is disposed inside the temperature control chamber and is used to monitor the temperature of the base material to be welded in real time; A cooling air pipe is used to introduce cooling air into the temperature control chamber. The outlet of the cooling air pipe is located inside the temperature control chamber and aligned with the weld seam of the base material to be welded.

[0012] Preferably, the top surface of the temperature control box includes an upper top plate and a lower top plate spaced apart, and the upper top plate and the lower top plate are respectively provided with positioning holes for the needle heating steel pipe to pass through; The positioning hole opening of the lower top plate is provided with a positioning ring; The needle heating unit also includes a mounting base and a sealing ring. The mounting base passes through the positioning hole of the upper top plate and is threadedly connected to the outer side wall of the positioning ring. The sealing ring is embedded in the mounting base and wedge-shapedly engages with the inner side wall of the positioning ring. When the mounting base and the positioning ring are tightened, the sealing ring grips the needle heating steel tube.

[0013] Preferably, observation windows are provided on both opposite sides of the temperature control box, and the backlight source, the observation windows, and the center of the lens of the high-speed camera are arranged collinearly.

[0014] Preferably, the temperature control box is further provided with a base material clamp, which includes a mounting frame and a gasket, and the mounting frame is connected to the inner side wall of the temperature control box; The mounting frame is provided with a first clamping arm and a second clamping arm on opposite sides. The ends of the first clamping arm and the second clamping arm are respectively provided with inverted L-shaped clamping heads. The two inverted L-shaped clamping heads are opposite each other and their horizontal parts face each other. The gasket is located below the horizontal portion of the two inverted L-shaped clamping heads, and the gasket has stop bars on opposite sides; The base material to be welded is placed on the gasket, with its opposite sides limited by the vertical part of the inverted L-shaped clamping head, and its other opposite sides limited by the stop bar, and its upper end abutting against the lower end of the horizontal part.

[0015] The beneficial technical effects of this invention are as follows: This invention provides a brazing experimental device based on the drop tower method to simulate a microgravity environment. The device consists of a brazing temperature-controlled heating unit, a needle heating unit, a brazing filler metal extrusion mechanism, an image acquisition system, an atmosphere system, and a controller, all fixedly installed within a drop chamber in a drop tower. The controller enables timing control. Specifically, independent brazing temperature-controlled heating units and needle heating units are set up. The controller first controls the needle heating unit to heat the brazing filler metal to a preset temperature before activating the brazing temperature-controlled heating unit to heat the base material to be welded. Once both reach the welding process temperature, free fall is triggered. This achieves independent heating and temperature control of the base material and the brazing filler metal, providing a non-contact brazing method under microgravity. It solves the problem of the brazing filler metal melting and spreading prematurely on the base material during overall heating, ensuring that the wetting and spreading process of the brazing filler metal is completed under microgravity conditions. A brazing filler metal extrusion mechanism is installed on the needle heating unit. During free fall, the controller drives it to quantitatively extrude molten brazing filler metal onto the surface of the base material to be welded. This overcomes the feeding challenge of brazing filler metal not being able to flow or drip naturally under gravity in microgravity, achieving active and precise control of the feeding timing and amount, and ensuring the forming quality of the weld joint. Simultaneously, an image acquisition system records the wetting and spreading process, enabling the extraction of quantitative parameters such as spreading radius and wetting angle. The atmosphere system, under the timed control of the controller, introduces cooling gas, achieving rapid solidification after welding, allowing the entire brazing process to be completed in a microgravity environment. In summary, the brazing experimental device achieves multi-dimensional collaborative control and dynamic characterization of the brazing process under a falling tower microgravity environment. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of a brazing experimental device based on the drop tower method to simulate a microgravity environment in one embodiment of the present invention; Figure 2 for Figure 1 A partial cross-sectional diagram; Figure 3 This is a schematic diagram of the structure of a brazing temperature control heating unit in one embodiment of the present invention; Figure 4 This is a schematic diagram of the structure of the base material clamp in one embodiment of the present invention; Figure 5 This is a diagram showing the state of the base material clamped by the base material fixture in one embodiment of the present invention.

[0017] Explanation of reference numerals in the attached figures: 01-Base material to be welded; 1-Brazing temperature control heating unit; 11-Temperature control box; 111-Upper top plate; 112-Lower top plate; 113-Positioning ring; 114-Observation window; 12-Cooling air pipe; 13-Temperature measuring element; 2-Needle heating unit; 21-Connecting frame; 22-Needle heating steel pipe; 23-Ceramic tube; 230-Needle tip section; 24-Mounting base; 25-Sealing ring; 3-Braving metal extrusion mechanism; 31-Linear stroke power assembly; 32-Ceramic rod; 33-Positioning sleeve; 34-Positioning cap; 4-Image acquisition system; 41-Backlight source; 42-High-speed camera; 5-Controller; 6-Fixed support mechanism; 61-Fixed platform; 611-Fixed plate; 62-Z-axis scissor lifting platform; 71-Mounting frame; 72-Shim; 721-Stop bar; 73-First clamping arm; 74-Second clamping arm; 75-Inverted L-shaped clamping head. Detailed Implementation

[0018] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Although some embodiments of the present invention are shown in the drawings, it should be understood that the present invention can be implemented in various forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the present invention. It should be understood that the accompanying drawings and embodiments of the present invention are for illustrative purposes only and are not intended to limit the scope of protection of the present invention.

[0019] The term "comprising" and its variations as used herein are open-ended, meaning "including but not limited to"; the term "based on" means "at least partially based on"; the term "one embodiment" means "at least one embodiment"; the term "another embodiment" means "at least one additional embodiment"; the term "some embodiments" means "at least some embodiments"; and the term "optionally" means "optional embodiments". Definitions of other terms will be given in the following description. It should be noted that the concepts of "first," "second," etc., mentioned in this invention are used only to distinguish different devices, modules, or units, and are not intended to limit the order of functions performed by these devices, modules, or units or their interdependencies.

[0020] It should be noted that the terms "a" and "a plurality of" used in this invention are illustrative rather than restrictive. Those skilled in the art should understand that, unless otherwise expressly indicated in the context, they should be understood as "one or more".

[0021] In related technologies, the Beijing Drop Tower of the National Microgravity Laboratory (NML) is equipped with a drop capsule. The sealing and center-of-gravity adjustment of the capsule are performed by professional technicians from the National Microgravity Laboratory. The sealing process involves mechanically locking the external capsule to create a highly airtight experimental environment. Subsequently, based on data feedback from the balancing system, the deviation angle of the drop capsule in four dimensions is strictly controlled within 0.5° by precisely adjusting the counterweights at the top of the capsule. This reduces the center-of-gravity shift during free fall and suppresses the interference of capsule vibration on the imaging and temperature control systems. After the center-of-gravity is balanced, the drop capsule is transferred to the drop tower recovery area via a dedicated hoisting mechanism and smoothly lifted to an experimental height of 83 m by an electromagnetic adsorption lifting system. During the lifting process, the verticality of the capsule and the operating status of the lifting system are monitored in real time to ensure that there is no additional disturbance during the transfer, thus providing a highly consistent physical environment for subsequent experiments. In the recovery preparation stage, the lifting mechanism deploys a buffer net to the working position to ensure that the center of the net is coaxial with the theoretical descent trajectory of the drop capsule. To ensure the reliable recovery of the landing capsule, technicians must conduct rigorous inspections of the rope net structure, cushioning devices, and their connecting components.

[0022] See Figure 1 and Figure 2 As shown, one embodiment of the present invention provides a brazing experimental apparatus based on the drop tower method to simulate a microgravity environment, including a brazing temperature-controlled heating unit 1, a needle heating unit 2, a brazing filler metal extrusion mechanism 3, an image acquisition system 4, an atmosphere system, and a controller 5, all fixedly installed within the drop chamber. The brazing temperature-controlled heating unit 1 is used to support and heat the base material 01 to be welded. The needle heating unit 2 is located above the brazing temperature-controlled heating unit 1 and is used to contain and heat the brazing filler metal, melting it into molten brazing filler metal. The brazing filler metal extrusion mechanism 3 is installed on the needle heating unit 2 and is used to quantitatively extrude the molten brazing filler metal onto the surface of the base material 01 to be welded. The image acquisition system 4 is used to record the wetting and spreading process of the molten brazing filler metal on the surface of the base material 01 to be welded. The atmosphere system and the brazing temperature-controlled heating unit 1 are connected... The controller 5 is used to introduce protective gas and cooling gas into the brazing temperature control heating unit 1. The controller 5 is electrically connected to the brazing temperature control heating unit 1, the needle heating unit 2, the brazing filler metal extrusion mechanism 3, the image acquisition system 4, and the atmosphere system. The controller 5 is used to: control the needle heating unit 2 to heat the brazing filler metal to the preset temperature, and start the brazing temperature control heating unit 1 to heat the base material 01 to be welded; when the brazing filler metal and the base material 01 to be welded reach the welding process temperature, trigger the free fall of the drop chamber; during the free fall of the drop chamber, the controller sequentially controls the brazing filler metal extrusion mechanism 3 to extrude the molten brazing filler metal quantitatively onto the surface of the base material 01 to be welded, controls the image acquisition system 4 to record the wetting and spreading process of the molten brazing filler metal, and controls the atmosphere system to introduce cooling gas into the brazing temperature control heating unit 1.

[0023] It should be noted that this embodiment achieves independent temperature control of the base material 01 and the brazing filler metal (welding material) by independently setting the brazing temperature control heating unit 1 and the needle heating unit 2 and starting them sequentially by the controller 5 according to a preset time sequence. This provides a method for non-contact brazing under microgravity, solving the problem that the overall heating filler metal would melt and spread prematurely on the base material 01, ensuring that the wetting and spreading process of the filler metal is completed under microgravity. Secondly, this embodiment installs a filler metal extrusion mechanism 3 on the needle heating unit 2, and during free fall, the controller 5 controls it to quantitatively extrude the molten filler metal onto the surface of the base material 01. This overcomes the problem that the molten filler metal cannot flow or drip naturally under gravity under microgravity, achieving active and precise control of the feeding timing and amount, and ensuring the forming quality of the welded joint. Furthermore, in this embodiment, the brazing temperature control heating unit 1, the needle heating unit 2, the brazing filler metal extrusion mechanism 3, and the image acquisition system 4 are all fixedly installed inside the drop chamber. The controller 5 sequentially drives the extrusion, imaging, and cooling actions during free fall, effectively avoiding positional shifts between the needle tip of the needle heating unit 2 and the base material 01 to be welded, as well as image jitter caused by relative movement of the components, thus ensuring the accuracy and repeatability of the experimental data. The image acquisition system 4 can begin recording before the drop chamber begins its descent, specifically for recording the wetting and spreading process of the molten brazing filler metal on the surface of the base material 01 during the drop chamber's descent. In summary, this embodiment, through the synergistic effect of the aforementioned structure and timing control, provides a reliable experimental platform for brazing research under microgravity conditions.

[0024] In one embodiment of the present invention, a fixed support mechanism 6 is further included. The fixed support mechanism 6 includes a base plate, a Z-axis scissor lift platform 62, and a fixed platform 61. The base plate is connected to the bottom of the landing compartment. The Z-axis scissor lift platform 62 is connected to the base plate. The top of the Z-axis scissor lift platform 62 is used to install the brazing temperature control heating unit 1. The height of the Z-axis scissor lift platform 62 is adjustable and can be locked. The fixed platform 61 is connected to the base plate. A fixed plate 611 is provided on the fixed platform 61. The fixed plate 611 is used to install the needle heating unit 2. The backlight source 41 of the image acquisition system 4 is embedded in the fixed platform 61. The high-speed camera 42 in the image acquisition system 4 is installed on the base plate and is located on opposite sides of the brazing temperature control heating unit 1, respectively, as is the backlight source 41.

[0025] Specifically, the Z-axis scissor lift platform 62 is a height-adjustable mechanical support structure composed of interlocking connecting rods. The opening angle of these connecting rods is changed via a drive mechanism such as a drive screw, hydraulic cylinder, or manual lead screw, thereby raising and lowering the platform mounted on top. In this embodiment, the bottom of the Z-axis scissor lift platform 62 is fixed to a base plate, and the brazing temperature control heating unit 1 is fixedly installed on top. Its core function is to precisely adjust the height of the brazing temperature control heating unit 1, that is, to adjust the vertical distance between the bottom end of the needle heating steel pipe 22 (or the bottom end of the ceramic pipe 23) in the needle heating unit 2 and the upper surface of the base material 01 to be welded. Precise control of this distance directly affects the accuracy of the landing point after the molten brazing filler metal is extruded and the initial conditions of the subsequent spreading process.

[0026] It should be noted that this embodiment effectively solves the problems mentioned in the background art, such as the displacement of the needle tip and the base material 01 and the shaking of the camera image caused by the relative movement of the components during free fall, by setting a fixed support mechanism 6 and installing all functional components on the same rigid foundation (the bottom plate is fixedly connected to the bottom of the drop chamber). After the Z-axis scissor lift platform 62 is adjusted to the required height, it is fixed by a locking mechanism to ensure that the relative position of the brazing temperature control heating unit 1 and the bottom plate remains constant during free fall. The fixed platform 61 is directly fixed to the bottom plate, and the fixed plate 611 on it is used to install the needle heating unit 2, so that the spatial relative relationship between the needle heating unit 2 and the brazing temperature control heating unit 1 is locked. At the same time, the backlight source 41 is embedded in the fixed platform 61, and the high-speed camera 42 is installed on the bottom plate, with the two located on opposite sides of the brazing temperature control heating unit 1. During free fall, the optical paths of the backlight source, the observation window and the center of the camera lens remain collinear as pre-calibrated, and will not be subject to relative displacement due to vibration or inertial force. Therefore, the accuracy and repeatability of experimental data acquisition are fundamentally guaranteed, providing a stable imaging basis for the quantitative study of brazing wetting and spreading behavior under microgravity conditions. Furthermore, the height adjustability of the Z-axis scissor-type lifting platform 62 allows the device to be compatible with base materials of different thicknesses or different process gap requirements, enhancing the versatility and practicality of the experimental setup.

[0027] In one embodiment of the present invention, the needle heating unit 2 includes a connecting frame 21, a needle heating steel tube 22, and a ceramic tube 23. The connecting frame 21 is connected to the fixing plate 611; the upper end of the needle heating steel tube 22 is connected to the connecting frame 21, and the lower end extends into the interior of the brazing temperature control heating unit 1; the ceramic tube 23 is coaxially disposed inside the needle heating steel tube 22, the cavity of the ceramic tube 23 is used to accommodate the brazing filler metal, and an electric heating wire is wound around the outside of the ceramic tube 23.

[0028] Specifically, the connecting frame 21 is a rigid frame or plate structure, which is fixed to the fixing plate 611 by bolts or welding. The connecting frame 21 serves as the mounting base for the needle heating unit 2, connecting the entire needle heating unit 2 to the fixed support mechanism 6, ensuring no relative movement between the needle heating unit 2 and the fixing plate 611 during free fall. The upper end of the needle heating steel tube 22 is fixed to the connecting frame 21 by welding, threaded connection, or flange connection. The tube body of the needle heating steel tube 22 extends vertically downwards, with its lower end extending into the temperature control box 11 of the brazed temperature control heating unit 1. The needle heating steel tube 22 not only provides a rigid protective shell for the internal ceramic tube 23 but also serves as a guide and positioning element. The ceramic tube 23 is coaxially arranged within the inner cavity of the needle heating steel tube 22. The cavity of the ceramic tube 23 serves as a container for the brazing filler metal. Its inner diameter is precisely matched with the outer diameter of the ceramic rod 32, allowing the ceramic rod 32 to slide smoothly within the cavity without excessive gaps, thus achieving quantitative extrusion. An electric heating wire (e.g., nickel-chromium alloy resistance wire) is wound around the outside of the ceramic tube 23. This heating wire is electrically connected to the temperature control module in the controller 5 via lead wires. During heating, the heat generated by the heating wire is transferred through the wall of the ceramic tube 23 to the brazing filler metal within the cavity, ensuring uniform heating and melting. Using the ceramic tube 23 as a heating container leverages the high-temperature resistance and non-wetting properties of ceramic materials (especially aluminum alloy brazing filler metal), preventing adhesion or reaction between the brazing filler metal and the container wall, and ensuring smooth extrusion of the melted filler metal. Through this structure, the needle heating unit 2 can not only independently and uniformly heat the brazing filler metal to a preset temperature but also ensure a high-precision coaxial fit between the ceramic rod 32 and the ceramic tube 23, thereby achieving stable and quantitative extrusion of the molten brazing filler metal. This provides a foundation for overcoming the difficulties in brazing filler metal feeding under microgravity conditions and ensuring the quality of welded joints.

[0029] In one embodiment of the present invention, a needle section 230 with a diameter smaller than that of the tube lumen is formed at the lower end of the ceramic tube 23, so that a stepped structure is formed at the bottom of the ceramic tube 23. The stepped structure cooperates with the stepped hole at the bottom of the needle heating steel tube 22, and the needle section 230 extends out of the bottom end of the needle heating steel tube 22 and is locked by threads.

[0030] It should be noted that in this embodiment, a reduced-diameter needle section 230 is provided at the lower end of the ceramic tube 23, forming a stepped fit with the stepped hole at the bottom of the needle-heated steel tube 22. Simultaneously, the needle section 230 extends beyond the bottom end of the needle-heated steel tube 22 and is locked with threads. Specifically, the stepped structure and the stepped hole achieve axial positioning of the ceramic tube 23 within the needle-heated steel tube 22, preventing the ceramic tube 23 from shifting upwards or downwards due to inertia during free fall. The needle section 230 extending beyond the bottom end of the needle-heated steel tube 22 and being locked with threads further secures the ceramic tube 23 and the needle-heated steel tube 22 together, eliminating any relative movement between them and ensuring a constant needle position at the bottom end of the ceramic tube 23. Simultaneously, this structure allows the needle section to be precisely aligned with the weld area of ​​the base material 01 to be welded, ensuring that the molten solder extruded from the needle section falls accurately into the predetermined position, avoiding solder drop point deviation caused by needle section offset. Furthermore, the exposed portion of the needle section 230 facilitates cleaning or replacement of the needle section with a different orifice diameter before the experiment, to accommodate the requirements of different sized solder droplets. In summary, this embodiment, through the aforementioned stepped fit and threaded locking structure, enhances the positioning accuracy and structural reliability of the solder extrusion mechanism under extreme dynamic environments, providing crucial mechanical assurance for the quantitative and targeted extrusion of solder under microgravity conditions.

[0031] In one embodiment of the present invention, the solder extrusion mechanism 3 includes a linear power assembly 31 and a ceramic rod 32. The linear power assembly 31 is mounted on the connecting frame 21. The ceramic rod 32 is connected to the linear power assembly 31 in a transmission manner, and the lower end of the ceramic rod 32 is inserted into the ceramic tube 23. The linear power assembly 31 drives the ceramic rod 32 to move vertically so as to extrude molten solder from the bottom end of the ceramic tube 23 in a quantitative manner.

[0032] Specifically, the linear motion power assembly 31 generates a linear driving force in the vertical direction. Under the command of the controller 5, it drives the ceramic rod 32 to move downward at a set speed and displacement during a preset time period in the free fall process, thereby quantitatively extruding the molten solder inside the ceramic tube 23 from the needle section 230 at the bottom. The linear motion power assembly 31 can use various power sources that can achieve precise displacement control, such as a stepper motor with a lead screw and nut mechanism, a linear motor, a servo cylinder, or an electromagnetic push rod. In this embodiment, a combination of a stepper motor and a lead screw transmission mechanism is used. The stepper motor is mounted on the connecting frame 21, and its output shaft is connected to the lead screw through a coupling. The lead screw is threadedly connected to a guide block, which is fixedly connected to the upper end of the ceramic rod 32. The controller 5 sends pulse signals to the stepper motor to drive the lead screw to rotate, and the guide block drives the ceramic rod 32 to move smoothly along the lead screw axis. Since the rotation angle of the stepper motor is proportional to the number of pulses and the lead of the lead screw is fixed, the displacement of the ceramic rod 32 can be precisely controlled, thereby achieving quantitative adjustment of the extruded solder volume (e.g., forming solder droplets with a diameter of 0.5 mm to 2 mm each time). In addition, the linear motion assembly 31 can also integrate a position sensor to provide real-time feedback on the position of the ceramic rod 32, forming a closed-loop control and further improving the repeatability accuracy of the extrusion volume.

[0033] It should be noted that in this embodiment, a brazing filler metal extrusion mechanism 3 is set on the needle heating unit 2, and its operation is controlled by the controller 5 during free fall. The linear motion power assembly 31 is installed on the connecting frame 21 to provide a precise and controllable linear driving force for the ceramic rod 32; the lower end of the ceramic rod 32 is inserted into the ceramic tube 23 and precisely matches the inner diameter of the ceramic tube 23. When the linear motion power assembly 31 receives the instruction from the controller 5, it drives the ceramic rod 32 to move downward at a set speed and displacement, quantitatively extruding the molten brazing filler metal in the ceramic tube 23 from the bottom needle tip to the surface of the base material 01 to be welded. Since the extrusion action occurs during free fall, the drop chamber is in a microgravity state at this time, and the molten brazing filler metal itself cannot drip. However, this embodiment not only achieves forced feeding of brazing filler metal through active mechanical extrusion, but also can precisely adjust the volume of brazing filler metal extruded each time by controlling the moving distance of the ceramic rod 32, thereby meeting the quantitative control requirements of brazing filler metal usage under different process conditions. Meanwhile, the timing of the brazing filler metal extrusion mechanism 3 is preset by the controller 5, ensuring the synchronous coordination between the brazing filler metal extrusion and the heating state, free fall stage, and subsequent spreading observation of the base material 01 to be welded. In summary, this embodiment overcomes the problem of feeding difficulties in a microgravity environment through the active quantitative extrusion function of the brazing filler metal extrusion mechanism 3, providing a technical means for studying the influence of different amounts of brazing filler metal on wetting and spreading behavior and porosity formation.

[0034] In one embodiment of the present invention, the brazing filler metal extrusion mechanism 3 further includes a positioning sleeve 33 and a positioning cap 34. The positioning sleeve 33 extends through the lower end of the connecting frame 21, and the upper end of the needle heating steel tube 22 is inserted into the lower end of the positioning sleeve 33; the positioning cap 34 covers the upper end of the positioning sleeve 33, and the ceramic rod 32 passes through the positioning cap 34 and extends into the ceramic tube 23.

[0035] It should be noted that in this embodiment, the positioning sleeve 33 penetrates and is fixed to the lower end of the connecting frame 21, and its lower end is inserted and fixed to the upper end of the needle heating steel tube 22, thereby rigidly connecting the needle heating steel tube 22 and the connecting frame 21 into one unit; the positioning cap 34 covers and is fixed to the upper end of the positioning sleeve 33, and the ceramic rod 32 extends into the ceramic tube 23 after passing through the positioning cap 34. The positioning sleeve 33 and the positioning cap 34 together constitute a precision guiding structure: on the one hand, the positioning sleeve 33 ensures the perpendicularity and coaxiality between the needle heating steel tube 22 and the connecting frame 21, so that the needle heating steel tube 22 and the internal ceramic tube 23 maintain a vertical posture; on the other hand, the positioning cap 34 performs secondary centering on the passing position of the ceramic rod 32, ensuring that the ceramic rod 32 can enter the ceramic tube 23 without deviation. Meanwhile, this structure forms a stable load-bearing and guiding support at the bottom of the connecting frame 21, effectively preventing the needle-heated steel pipe 22 from swaying or tilting due to vibration or inertial force during free fall. This ensures the sliding fit accuracy between the ceramic rod 32 and the ceramic tube 23, avoiding additional resistance or brazing filler metal leakage caused by eccentricity during extrusion. Thus, this embodiment enhances the centering reliability and movement stability of the brazing filler metal extrusion mechanism through the synergistic effect of the positioning sleeve 33 and the positioning cap 34, providing precise guidance for the stable and quantitative extrusion of molten brazing filler metal in a microgravity environment.

[0036] See Figure 3 As shown, in one embodiment of the present invention, the brazing temperature control heating unit 1 includes a temperature control chamber 11, a temperature measuring element 13, and a cooling gas pipe 12. Heating components are respectively provided in the upper and lower parts of the temperature control chamber 11, and a protective gas inlet and outlet are provided on the side of the temperature control chamber 11. The temperature measuring element 13 is disposed inside the temperature control chamber 11 and is used to monitor the temperature of the base material 01 to be welded in real time. The cooling gas pipe 12 is used to introduce cooling gas into the temperature control chamber 11, and the outlet of the cooling gas pipe 12 is located inside the temperature control chamber 11 and aligned with the weld seam of the base material 01 to be welded.

[0037] Specifically, the temperature control chamber 11 is a sealed, high-temperature resistant container, with an internal working chamber for accommodating the base material 01 to be welded and the brazing fixture. Heating components (such as resistance heating wires, heating plates, or infrared heating tubes) are respectively installed in the upper and lower parts of the temperature control chamber 11 to ensure uniform heating of the base material 01 during the heating process, avoiding thermal stress deformation or uneven temperature gradients caused by unilateral heating. An air inlet and an air outlet are provided on the side of the temperature control chamber 11. The air inlet is connected to the protective gas outlet of the atmosphere system via a pipeline, used to introduce inert protective gases such as high-purity nitrogen into the temperature control chamber 11 to expel internal air and prevent oxidation of the base material 01 and the brazing filler metal at high temperatures; the air outlet is used to discharge gas from the chamber, maintaining a stable internal atmosphere. Temperature sensing element 13 (e.g., K-type thermocouple, platinum resistance temperature sensor, or infrared temperature probe) is installed inside the temperature control chamber 11. If it is a thermocouple, it needs to contact the surface of the base material 01 to be welded, so as to collect the temperature of the base material 01 in real time and feed the temperature signal back to the temperature control module in the controller 5. The controller 5 adjusts the output power of the heating component according to the set temperature curve to realize closed-loop control of the temperature of the base material 01 to be welded. One end of the cooling gas pipe 12 is connected to the high-pressure cooling gas source of the atmosphere system through a solenoid valve, and the other end extends into the temperature control chamber 11, with its outlet precisely aligned with the weld area of ​​the base material 01 to be welded. When the controller 5 sends an opening command to the solenoid valve according to the preset timing, the high-pressure cooling gas is sprayed through the cooling gas pipe 12 onto the surface of the weld that has just been spread, so that the weld joint solidifies quickly, thereby freezing the spread morphology under microgravity and avoiding tissue changes caused by vibration or gravity recovery when the hull touches the net after landing. The above structure enables the brazing temperature control heating unit 1 to simultaneously possess multiple functions such as uniform heating, atmosphere protection, real-time temperature measurement, and fixed-point rapid cooling, providing a stable and controllable thermal environment for microgravity brazing experiments.

[0038] In one embodiment of the present invention, the top surface of the temperature control box 11 includes an upper top plate 111 and a lower top plate 112 spaced apart, and the upper top plate 111 and the lower top plate 112 are respectively provided with positioning holes for the needle heating steel pipe 22 to pass through. The lower top plate 112 has a positioning hole with a protruding positioning ring 113; the needle heating unit 2 also includes a mounting base 24 and a sealing ring 25. The sealing ring 25 is embedded in the mounting base 24 and wedge-shapedly engages with the inner side wall of the positioning ring 113; the mounting base 24 passes through the positioning hole of the upper top plate 111 and is threadedly connected to the outer side wall of the positioning ring 113. When the mounting base and the positioning ring 113 are tightened, the sealing ring 25 grips the needle heating steel pipe 22.

[0039] See Figure 3As shown, it should be noted that the top surface of the temperature control box 11 adopts a double-layer structure with an upper top plate 111 and a lower top plate 112 spaced apart, forming a certain gap between them. On the one hand, this enhances the rigidity of the top surface and suppresses deformation during free fall; on the other hand, it provides installation and adjustment space for the wedge deformation of the sealing ring 25. The upper part of the mounting base 24 can be connected to a hexagonal nut, or the upper part of the mounting base 24 can be directly machined into a hexagonal head shape. A standard wrench (such as an open-end wrench or a socket wrench) can be used to clamp the hexagonal part to apply torque, thereby obtaining a sufficiently large tightening force. Specifically, the upper top plate 111 and the lower top plate 112 are respectively provided with positioning holes for the needle heating steel tube 22 to pass through. The two positioning holes are coaxially arranged to ensure that the needle heating steel tube 22 remains vertical. The positioning hole opening of the upper top plate 111 is provided with a positioning ring 113 protruding upward. The positioning ring 113 can be independently machined and then welded or threaded onto the upper top plate 111, or it can be integrally formed with the upper top plate 111. The inner wall of the positioning ring 113 has a wedge-shaped inclined surface (e.g., a tapered surface that gradually tapers from top to bottom) that mates with the sealing ring 25. The mounting base 24 is sleeve-shaped, with its lower end passing through the positioning hole of the upper top plate 111. The outer wall of the mounting base 24 has an external thread that mates with the corresponding internal thread on the inner or outer wall of the positioning ring 113. In this embodiment, the external thread of the mounting base 24 mates with the internal thread on the outer wall of the positioning ring 113, that is, the mounting base 24 is sleeved on the outside of the positioning ring 113. The sealing ring 25 (which can be a split structure, with an O-ring on top and a washer with a wedge-shaped outer surface on the bottom) is embedded in an annular mounting groove inside the mounting base 24, with the lower part of the sealing ring 25 extending into the positioning ring 113. The outer wall of the lower part of the sealing ring 25 contacts the wedge-shaped inclined surface of the positioning ring 113, forming a wedge fit. When the operator tightens the mounting base 24 onto the positioning ring 113, the mounting base 24 causes the sealing ring 25 to move downwards. The sealing ring 25 is radially compressed by the wedge-shaped inclined surface of the positioning ring 113, causing it to contract inwards and deform, thus tightly gripping the outer wall of the needle heating steel pipe 22 that passes through it. At the same time, the sealing ring 25 generates clamping force in both the axial and radial directions, achieving an airtight seal for the needle heating steel pipe 22 at the point of penetration into the chamber, and using friction to firmly lock the needle heating steel pipe 22 onto the top surface of the temperature control chamber 11, preventing axial movement or radial swaying of the needle heating steel pipe 22 during free fall. Loosening the mounting base 24 releases the sealing ring 25, allowing the needle heating steel pipe 22 to slide relative to each other for fine-tuning of its height; tightening it simultaneously completes locking and sealing. In addition, the double-layer top plate structure effectively isolates the high temperature inside the chamber from direct heat radiation to the sealing ring 25, extending the service life of the seal. Therefore, this embodiment, through the aforementioned wedge-shaped locking and sealing structure, not only satisfies the airtightness requirements of the temperature control box 11 during operation, but also ensures the fixed position of the needle heating steel pipe 22 under extreme dynamic environments.

[0040] In one embodiment of the present invention, observation windows 114 are provided on both opposite sides of the temperature control box 11, and the backlight source 41, the observation windows 114 and the lens center of the high-speed camera 42 are arranged collinearly.

[0041] It should be noted that in this embodiment, the light emitted by the backlight source 41 enters the temperature control chamber 11 through one observation window 114, penetrates the interface area between the molten solder and the base material 01 to be soldered, and then exits through the other observation window 114 and is received by the high-speed camera 42. Since the backlight source 41 is located on the back of the base material 01 to be soldered, while the high-speed camera 42 is located on the front, this transmissive illumination method makes the wetting front formed by the molten solder on the surface of the base material 01 appear as a clear silhouette outline. The backlight illumination greatly improves the edge contrast, allowing the pixel-level position of the wetting front to be accurately identified. Combined with continuous shooting by the high-speed camera 42 at an adjustable frame rate of 0-500 frames per second, the millisecond-level spreading dynamics of the molten solder under microgravity conditions can be captured, and quantitative parameters such as spreading radius, wetting angle, and spreading speed can be extracted through image analysis. Simultaneously, the collinearity of the three points ensures the consistency of the geometric optical path alignment, avoiding measurement errors caused by viewing angle deviations. Furthermore, the double-layered observation window 114 can also isolate the lens from the high temperature inside the chamber, protecting the equipment. The backlight collinear imaging system provides a high-fidelity and quantifiable dynamic observation method for studying the transient wetting behavior of solder and the formation and suppression mechanism of pores under microgravity.

[0042] In one embodiment of the present invention, a base material clamp is further provided inside the temperature control box 11. The base material clamp includes a mounting frame 71 and a gasket 72. The mounting frame 71 is connected to the inner side wall of the temperature control box 11. A first clamping arm 73 and a second clamping arm 74 are provided on opposite sides of the mounting frame 71. The ends of the first clamping arm 73 and the second clamping arm 74 are respectively provided with inverted L-shaped clamping heads 75. The two inverted L-shaped clamping heads 75 are opposite each other and their horizontal portions face each other. The gasket 72 is provided below the horizontal portions of the two inverted L-shaped clamping heads 75. A stop bar 721 is provided on opposite sides of the gasket 72. The base material 01 to be welded is provided on the gasket 72. Its opposite sides are limited by the vertical portions of the inverted L-shaped clamping heads 75, and its other opposite sides are limited by the stop bar 721. Its upper end abuts against the lower end of the horizontal portion.

[0043] See Figure 4 and Figure 5As shown, specifically, the base material clamp is used to precisely position and clamp the base material 01 to be welded within the temperature control box 11 of the brazing temperature control heating unit 1, so as to ensure that the base material 01 to be welded does not undergo any displacement or deflection during free fall, thereby ensuring that the molten brazing filler metal squeezed from the bottom end of the ceramic tube 23 can accurately fall on the predetermined weld area on the surface of the base material 01 to be welded. The mounting frame 71 is a rigid support, which is fixedly connected to the inner wall of the temperature control box 11 by bolts or welding, providing a mounting base for the entire clamp. The first clamping arm 73 and the second clamping arm 74 extend horizontally from opposite sides of the mounting frame 71, and the ends of the two are respectively fixed with inverted L-shaped clamping heads 75. The two inverted L-shaped clamping heads 75 are arranged in a mirror symmetrical manner, that is, the horizontal parts of the two extend towards each other (relatively set), and the lower end surface of the horizontal part and the inner side surface of the vertical part form a right-angled limiting surface. The gasket 72 is placed horizontally at the bottom of the temperature control box 11 (or fixed to the bottom surface of the temperature control box), and is located directly below the horizontal part of the two inverted L-shaped clamping heads 75. The upper surface of the gasket 72 is used to support the base material 01 to be welded, and its thickness can be selected according to the thickness of the base material 01 to be welded, so as to adjust the height position of the base material 01 to be welded relative to the vertical part of the clamping head. On opposite sides of the gasket 72 (i.e., on both sides perpendicular to the extension direction of the first clamping arm 73 and the second clamping arm 74), there are respectively a stop bar 721, which protrudes upward from the upper surface of the gasket 72.

[0044] When the base material 01 to be welded is placed on the shim 72, its left and right sides are laterally limited by the vertical parts of the two inverted L-shaped clamping heads 75, preventing the base material 01 to be welded from moving left and right in the horizontal plane; its front and back sides (corresponding to the sides of the shim 72 where the stop bar 721 is provided) are limited by the stop bar 721, preventing the base material 01 to be welded from moving back and forth in the horizontal plane; its upper part is limited by the lower end face of the horizontal part of the two inverted L-shaped clamping heads 75, preventing the base material 01 to be welded from moving upward due to weightlessness during free fall. Thus, the six degrees of freedom of the base material 01 to be welded in three-dimensional space are all constrained, achieving complete positioning. The horizontal and vertical parts of the inverted L-shaped clamping heads 75 of the base material fixture are integrated, resulting in a compact structure and high rigidity; secondly, the shim 72 can be replaced with different thicknesses to accommodate base materials 01 of different thicknesses; the stop bar 721 can be designed to be detachable or position-adjustable to accommodate base materials 01 of different widths. This embodiment ensures that the relative position between the base material 01 to be welded and the needle heating unit 2 and the brazing filler metal extrusion mechanism 3 remains unchanged throughout the entire dynamic process of the free fall of the descent chamber and the recovery of the contact net. This provides a solid foundation for the quantitative extrusion and precise spreading of the molten brazing filler metal, and also ensures that the base material 01 to be welded is always located in the center of the field of view in the image recorded by the high-speed camera.

[0045] The following describes in detail the specific operating steps of brazing experiments using the brazing experimental apparatus of the present invention based on the drop tower method to simulate a microgravity environment, with reference to the above-described device embodiments: 1) Power Supply and Connection: Connect the power interfaces of the heating wire of the needle heating unit 2, the heating components of the brazing temperature control heating unit 1, the high-speed camera 42, the solenoid valve of the atmosphere system, the backlight source 41, and the controller 5 to the battery (or external regulated power supply) to ensure sufficient power supply. Connect the communication interfaces of the temperature control module of the needle heating unit 2, the temperature control module of the brazing temperature control heating unit 1, the linear motion power component 31 (e.g., a stepper motor), and the high-speed camera 42 to the controller 5 (or host computer) to the controller.

[0046] 2) Camera optical path calibration: Adjust the center of the lens of the high-speed camera 42, the center of the observation window 114 on the temperature control box 11, and the center of the backlight source 41 to the same axis to ensure that the three points are collinear.

[0047] 3) Execution: When the temperature of the needle heating unit 2 reaches 350-400℃, a remote command is issued by the central control terminal to trigger the formal heating program of the brazing temperature control heating unit 1. Both the brazing temperature control heating unit 1 and the needle heating unit 2 are heated to 550-600℃, and the solder applied to the surface of the base material 01 to be brazed has melted and spread as observed by the high-speed camera 42. The command issuer in the central control room issues the "electromagnetic release" command. The experimental operator presses the electromagnetic release button, the magnetic head is de-energized, and the drop chamber falls freely. Within 0-0.5 seconds after the start of the fall, the controller 5 activates the linear motion power component 31 according to a preset sequence, driving the ceramic rod 32 to move downwards at a set speed, quantitatively extruding the molten solder in the ceramic tube 23 onto the surface of the base material 01 to be brazed. In the following 1-2 seconds, the molten solder continues to spread on the surface of the base material 01 to be brazed, and the high-speed camera 42 continuously records the spreading process at a preset frame rate. After the brazing filler metal was observed to be completely wetted and spread via camera images, within 1 to 3 seconds of the start of the descent, controller 5 triggered the solenoid valve of the atmosphere system, introducing high-pressure cooling nitrogen gas at 2 MPa into the temperature control chamber 11, causing the welded joint to solidify rapidly. At 3.6 seconds into the descent, the drop chamber landed in the buffer rope net, ending the experiment.

[0048] 4) Post-experiment processing: The welded sample was removed, and the image data recorded by the high-speed camera 42 was exported. Parameters such as spreading radius, wetting angle, and spreading speed were extracted using image analysis software. The cooled joint was subjected to CT inspection, airtightness testing, and mechanical property testing to evaluate the brazing quality under microgravity conditions.

[0049] While the present invention has been disclosed above, its scope of protection is not limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention, and all such changes and modifications will fall within the scope of protection of the present invention.

Claims

1. A brazing experimental apparatus based on the drop tower method to simulate a microgravity environment, characterized in that, It includes a brazing temperature control heating unit (1), a needle heating unit (2), a brazing material extrusion mechanism (3), an image acquisition system (4), an atmosphere system, and a controller (5) that are fixedly installed in the landing chamber. The brazing temperature control heating unit (1) is used to fix and heat the base material (01) to be welded. The needle heating unit (2) is located above the brazing temperature control heating unit (1) and is used to place and heat the brazing filler metal to melt it into molten brazing filler metal; The brazing filler metal extrusion mechanism (3) is installed on the needle heating unit (2) and is used to extrude the molten brazing filler metal quantitatively onto the surface of the base material (01) to be welded; The image acquisition system (4) is used to record the wetting and spreading process of the molten solder on the surface of the base material (01) to be soldered; The atmosphere system is connected to the brazing temperature control heating unit (1) and is used to introduce protective gas and cooling gas into the brazing temperature control heating unit (1); The controller (5) is electrically connected to the brazing temperature control heating unit (1), the needle heating unit (2), the brazing filler metal extrusion mechanism (3), the image acquisition system (4), and the atmosphere system, respectively. The controller (5) is used to: control the needle heating unit (2) to heat the brazing filler metal to a preset temperature, start the brazing temperature control heating unit (1) to heat the base material (01) to be welded; when the brazing filler metal and the base material (01) to be welded reach the welding process temperature, trigger the free fall of the drop chamber; during the free fall of the drop chamber, sequentially control the brazing filler metal extrusion mechanism (3) to extrude the molten brazing filler metal quantitatively onto the surface of the base material (01) to be welded, control the image acquisition system (4) to record the wetting and spreading process of the molten brazing filler metal, and control the atmosphere system to introduce cooling gas into the brazing temperature control heating unit (1).

2. The brazing experimental apparatus based on the drop tower method for simulating a microgravity environment according to claim 1, characterized in that, It also includes a fixed support mechanism (6), which includes a base plate, a Z-axis scissor lift platform (62) and a fixed platform (61). The bottom plate is connected to the bottom of the landing compartment; The Z-axis scissor lift (62) is connected to the base plate. The top of the Z-axis scissor lift (62) is used to install the brazing temperature control heating unit (1). The height of the Z-axis scissor lift (62) is adjustable and can be locked and fixed. The fixed platform (61) is connected to the base plate, and a fixed plate (611) is provided on the fixed platform (61). The fixed plate (611) is used to install the needle heating unit (2). The backlight source (41) of the image acquisition system (4) is embedded in the fixed platform (61), and the high-speed camera (42) in the image acquisition system (4) is installed on the base plate and is located on opposite sides of the brazing temperature control heating unit (1) along with the backlight source (41).

3. The brazing experimental apparatus based on the drop tower method for simulating a microgravity environment according to claim 2, characterized in that, The needle heating unit (2) includes: A connecting frame (21) is connected to the fixing plate (611). A needle heating steel pipe (22) is provided, with its upper end connected to the connecting frame (21) and its lower end extending into the interior of the brazing temperature control heating unit (1). A ceramic tube (23) is coaxially disposed inside the needle heating steel tube (22). The cavity of the ceramic tube (23) is used to accommodate the brazing filler metal. An electric heating wire is wound around the outside of the ceramic tube (23).

4. The brazing experimental apparatus based on the drop tower method for simulating a microgravity environment according to claim 3, characterized in that, The lower end of the ceramic tube (23) is formed with a needle section (230) with a diameter smaller than that of the tube cavity, so that the bottom of the ceramic tube (23) forms a stepped structure. The stepped structure and the stepped hole at the bottom of the needle heating steel tube (22) are matched, and the needle section (230) extends out of the bottom end of the needle heating steel tube (22) and is locked by threads.

5. The brazing experimental apparatus based on the drop tower method for simulating a microgravity environment according to claim 4, characterized in that, The brazing filler metal extrusion mechanism (3) includes: A linear power assembly (31) is mounted on the connecting frame (21). A ceramic rod (32) is connected to the linear power assembly (31) for transmission, and the lower end of the ceramic rod (32) is inserted into the ceramic tube (23); The linear power assembly (31) drives the ceramic rod (32) to move vertically to extrude the molten solder from the bottom end of the ceramic tube (23) in a metered manner.

6. The brazing experimental apparatus based on the drop tower method for simulating a microgravity environment according to claim 5, characterized in that, The brazing filler metal extrusion mechanism (3) further includes: Positioning sleeve (33), the positioning sleeve (33) passes through the lower end of the connecting frame (21), and the upper end of the needle heating steel pipe (22) is inserted into the lower end of the positioning sleeve (33); Positioning cap (34) is placed on the upper end of positioning sleeve (33), and ceramic rod (32) passes through positioning cap (34) and extends into ceramic tube (23).

7. The brazing experimental apparatus based on the drop tower method for simulating a microgravity environment according to claim 3, characterized in that, The brazing temperature control heating unit (1) includes: A temperature control box (11) is provided with heating components in the upper and lower parts of the temperature control box (11). An air inlet and an air outlet are provided on the side of the temperature control box (11). The air inlet is used to connect to the protective gas outlet of the atmosphere system, and the air outlet is used to exhaust gas. Temperature sensing element (13), the temperature sensing element (13) is set inside the temperature control box (11) and is used to monitor the temperature of the base material (01) to be welded in real time; Cooling pipe (12) is used to connect to the cooling gas outlet of the atmosphere system. The outlet of the cooling pipe (12) is located inside the temperature control box (11) and aligned with the weld seam of the base material (01) to be welded.

8. The brazing experimental apparatus based on the drop tower method for simulating a microgravity environment according to claim 7, characterized in that, The top surface of the temperature control box (11) includes an upper top plate (111) and a lower top plate (112) spaced apart. The upper top plate (111) and the lower top plate (112) are respectively provided with positioning holes for the needle heating steel pipe (22) to pass through. The positioning hole opening of the lower top plate (112) is provided with a positioning ring (113). The needle heating unit (2) also includes a mounting base (24) and a sealing ring (25). The mounting base (24) passes through the positioning hole of the upper top plate (111) and is threadedly connected to the outer side wall of the positioning ring (113). The sealing ring (25) is embedded in the mounting base (24) and wedge-shapedly engaged with the inner side wall of the positioning ring (113). When the mounting base and the positioning ring (113) are tightened, the sealing ring (25) grips the needle heating steel pipe (22).

9. The brazing experimental apparatus based on the drop tower method for simulating a microgravity environment according to claim 8, characterized in that, The temperature control box (11) has observation windows (114) on both sides. The backlight source (41), the observation window (114) and the lens center of the high-speed camera (42) are arranged in a collinear manner.

10. The brazing experimental apparatus based on the drop tower method for simulating a microgravity environment according to any one of claims 7-9, characterized in that, The temperature control box (11) is also provided with a base material clamp, which includes an installation frame (71) and a gasket (72). The installation frame (71) is connected to the inner wall of the temperature control box (11). The mounting frame (71) has a first clamping arm (73) and a second clamping arm (74) on opposite sides. The ends of the first clamping arm (73) and the second clamping arm (74) are respectively provided with inverted L-shaped clamping heads (75). The two inverted L-shaped clamping heads (75) are opposite to each other and their horizontal portions face each other. The gasket (72) is located below the horizontal portion of the two inverted L-shaped clamping heads (75), and the gasket (72) has stop bars (721) on its opposite sides. The base material to be welded (01) is placed on the gasket (72), and its opposite sides are limited by the vertical part of the inverted L-shaped clamping head (75), and its other opposite sides are limited by the stop bar (721), and its upper end abuts against the lower end of the horizontal part.

Images