A method for ceramic and metal low-thermal-damage brazing connection based on coupling joule heat local heating of a heat-conductive base material

Abstract

The application relates to a ceramic and metal low-heat-damage brazing connection method based on local heating of a heat-conducting base material coupled with Joule heat, which comprises the following steps: pretreating a base material and a brazing filler metal sheet, and assembling the base material and the brazing filler metal sheet into a brazing piece in the mode of heat-conducting base material / brazing filler metal / metal base material; connecting two ends of an electric conductor to the positive and negative poles of a direct-current power supply respectively, placing the brazing piece above the electric conductor, and making the heat-conducting base material directly contact the electric conductor, with the metal base material being located at the far end of the electric conductor; powering the electric conductor, adjusting the current and voltage to make the electric conductor and the heat-conducting base material reach a preset temperature, monitoring the surface temperature of the electric conductor by using a temperature measuring device, and welding the brazing piece. The application utilizes Joule heat to rapidly heat, combines with an ultra-short holding time, greatly compresses the welding cycle, combines with a unique assembly mode, significantly reduces the welding heat input, and has a simple process flow, low equipment investment and strong controllability.

Description

Technical Field

[0001] The embodiments of the present invention relate to the field of welding technology, and in particular to a method for low-heat-damage brazing of ceramics and metals based on local Joule heating coupled to a thermally conductive base material. Background Technology

[0002] High-temperature composite materials (such as C / C and C / SiC composites) have become core candidate materials for hot-end components of aero-engines and structural components of spacecraft due to their excellent properties such as high specific strength, high specific modulus, high temperature resistance, and corrosion resistance. However, due to their poor plasticity and difficulty in machining, they cannot be used as components on their own and need to be connected with a metal matrix. Reliable connection between the two is one of the key technologies for achieving lightweight and high-temperature service in high-end equipment. However, during the welding process, the properties of metals make them sensitive to heat input. Excessive heating can easily lead to grain growth, residual stress accumulation, and deterioration of interfacial bonding, which poses a severe challenge to the brazing connection of composite material components.

[0003] Existing brazing technologies for composite materials and dissimilar metals generally suffer from problems such as poor heat input orientation, severe thermal damage to the heat-sensitive base material, unstable joint performance, and low process efficiency, making it difficult to balance connection reliability and base material integrity.

[0004] Therefore, developing a brazing method that can achieve differentiated thermal protection for dissimilar materials, is simple in process, and is suitable for engineering applications has become a technical problem that urgently needs to be solved in this field.

[0005] Therefore, it is necessary to improve one or more of the problems existing in the above-mentioned related technical solutions.

[0006] It should be noted that this section is intended to provide background or context for the technical solutions of the invention as set forth in the claims. The description herein does not imply acceptance as prior art simply because it is included in this section. Summary of the Invention

[0007] The purpose of this invention is to provide a method for low-heat-damage brazing of ceramics and metals based on local Joule heating coupled with a thermally conductive base material, thereby solving at least to some extent one or more problems caused by the limitations and defects of related technologies.

[0008] This invention provides a method for low-heat-damage brazing of ceramics and metals based on localized Joule heating coupled with a thermally conductive base material, comprising: S1, pre-treat the base material and brazing filler metal sheet, and assemble them into the parts to be brazed in the manner of thermally conductive base material / brazing filler metal / metal base material; S2, connect the two ends of the conductor to the positive and negative terminals of the DC power supply respectively, place the workpiece to be brazed above the conductor, and make the thermally conductive base material directly contact the conductor, with the metal base material located at the far end of the conductor, to set up a vacuum or protective gas environment for the workpiece to be brazed. S3: Power is applied to the conductor, and the current and voltage are adjusted to raise the temperature of the conductor and the heat-conducting base material to the preset temperature. The surface temperature of the conductor is monitored using a temperature measuring device, and the workpiece to be brazed is then welded.

[0009] In this invention, the thermally conductive base material is one of C / C composite material, SiC ceramic, Al2O3 ceramic, Si3N4, BN, C / SiC, and SiC / SiC.

[0010] In this invention, the metal base material is one of high-temperature alloys, high-entropy alloys, Nb alloys, and Fe alloys.

[0011] In this invention, the solder sheet is one of high-entropy solder, nickel-based solder, silver-based solder, and copper-based solder.

[0012] In this invention, the thickness of the solder sheet is 50μm to 200μm.

[0013] In this invention, the conductor is one of carbon cloth, carbon paper, and carbon felt.

[0014] In this invention, in step S3, after the conductor is used to keep the joint of the workpiece to be brazed warm for a preset time, the conductor is directly stopped from being energized or the current and voltage are controlled to drop to zero at a preset rate.

[0015] In this invention, the rate of decrease of the current is 1-300A / s, and the rate of decrease of the voltage is 1-100V / s.

[0016] In this invention, in step S3, the heat preservation time of the joint of the workpiece to be brazed is 3-300s.

[0017] The technical solution provided by this invention may include the following beneficial effects: In this invention, Joule heating is used for rapid heating, combined with an ultra-short holding time, which greatly reduces the welding cycle; combined with a unique assembly method, welding heat input is significantly reduced; the process is simple, requires little equipment investment, and is highly controllable. Attached Figure Description

[0018] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this disclosure and, together with the description, serve to explain the principles of this disclosure. It is obvious that the drawings described below are merely some embodiments of this disclosure, and those skilled in the art can obtain other drawings based on these drawings without any inventive effort.

[0019] Figure 1 This diagram illustrates a process flow of a ceramic-metal brazing connection method based on localized Joule heating coupled with a thermally conductive base material, according to an exemplary embodiment of the present invention. Figure 2 This diagram illustrates the assembly of the fixture and sample used in this invention. Figure 3 The current-voltage curves over time used in Experiment Example 1 of this invention are shown. Figure 4 The temperature change curve of the conductor surface in Experiment Example 1 of the present invention is shown. Figure 5 The microstructure of C / C—FeCoNiAlCuTi—Nb prepared in Experimental Example 1 of the present invention is shown. Detailed Implementation

[0020] Exemplary embodiments will now be described more fully with reference to the accompanying drawings. However, these exemplary embodiments can be implemented in many forms and should not be construed as limited to the examples set forth herein; rather, they are provided so that the invention will be more comprehensive and complete, and will fully convey the concept of the exemplary embodiments to those skilled in the art. The described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

[0021] Furthermore, the accompanying drawings are merely illustrative diagrams of embodiments of the present invention and are not necessarily drawn to scale. The same reference numerals in the drawings denote the same or similar parts, and therefore repeated descriptions of them will be omitted. Some block diagrams shown in the drawings are functional entities and do not necessarily correspond to physically or logically independent entities.

[0022] This example embodiment provides a method for low-heat-damage brazing of ceramics and metals based on localized Joule heating coupled to a thermally conductive base material. (Refer to...) Figure 1 As shown, the welding method includes the following steps: S1. The base material and brazing filler metal sheet are pre-treated and assembled into the parts to be brazed in the manner of thermally conductive base material / brazing filler metal / metal base material. The pre-treatment includes grinding the base material and brazing filler metal sheet to remove impurities from the surface of the base material.

[0023] S2, connect the two ends of the conductor to the positive and negative terminals of the DC power supply respectively, place the workpiece to be brazed above the conductor, and ensure that the thermally conductive base material is in direct contact with the conductor, while the metal base material is located at the far end of the conductor, thus creating a vacuum or protective gas environment for the workpiece to be brazed.

[0024] S3: Power is applied to the conductor, and the current and voltage are adjusted to raise the temperature of the conductor and the heat-conducting base material to the preset temperature. The surface temperature of the conductor is monitored using a temperature measuring device, and the workpiece to be brazed is then welded.

[0025] This invention utilizes Joule heating for rapid heating, combined with ultra-short holding time, to significantly reduce the welding cycle; combined with a unique assembly method, it significantly reduces welding heat input; the process is simple, requires little equipment investment, and is highly controllable.

[0026] Specific Implementation Method 1: This implementation method is a low-heat-damage brazing connection method for ceramics and metals based on localized Joule heating coupled with a thermally conductive base material, and is implemented according to the following steps: Step 1: Grind the C / C composite material, Nb metal and TiNiCrFeCu solder sheet to remove impurities from the surface of the base material, and assemble them into the parts to be brazed in the manner of C / C composite material / TiNiCrFeCu solder sheet / Nb metal.

[0027] Step 2: Connect the two ends of the conductive carbon felt to the positive and negative terminals of the DC power supply, respectively. Place the assembled workpiece to be brazed on top of the conductor, with the carbon felt in direct contact with the C / C composite material and the Nb metal matrix located at the far end of the carbon felt, creating a vacuum, protective gas, or air environment for the workpiece to be brazed.

[0028] Step 3: Apply direct current to the carbon felt, adjusting the current and voltage to heat the conductor and the thermally conductive base material. Monitor the surface temperature of the conductor using a temperature measuring device. Maintain a constant current or voltage to keep the joint of the parts to be brazed at this temperature for a period of time. Then, either stop the power supply or control the current and voltage to drop to zero at a certain rate to complete the brazing connection.

[0029] Specific Implementation Method Two: This implementation method differs from Specific Implementation Method One in that the thickness of the TiNiCrFeCu solder sheet mentioned in step one is 50μm ~ 200μm. Everything else is the same as in Specific Implementation Method One.

[0030] Specific Implementation Method 3: This implementation method differs from Specific Implementation Methods 1 and 2 in that the conductor mentioned in step 2 is carbon cloth or carbon paper. Everything else is the same as in Specific Implementation Methods 1 and 2.

[0031] Specific Implementation Method Four: This implementation method differs from Specific Implementation Methods One to Three in that the protective gas mentioned in step two is nitrogen or argon. Everything else is the same as in Specific Implementation Methods One to Three.

[0032] Specific Implementation Method Five: This implementation method differs from Specific Implementation Methods One to Four in that the surface temperature of the conductor described in step three is 1200℃ to 1500℃. Everything else is the same as in Specific Implementation Methods One to Four. Additionally, the surface temperature of the conductor can be 1300℃, 1400℃, etc., but is not limited to these.

[0033] Specific Implementation Method Six: This implementation method differs from Specific Implementation Methods One to Five in that the current reduction rate in step three is 1-300 A / s, and the voltage reduction rate is 1-100 V / s. Everything else is the same as in Specific Implementation Methods One to Five. Furthermore, the current reduction rate can also be 10 A / s, 50 A / s, 100 A / s, 150 A / s, 200 A / s, etc., but is not limited to these; the voltage reduction rate can also be 10 V / s, 20 V / s, 50 V / s, 80 V / s, etc., but is not limited to these.

[0034] Specific Implementation Method Seven: This implementation method differs from Specific Implementation Methods One to Six in that the heat preservation time described in step three is 3-300 seconds. Everything else is the same as in Specific Implementation Methods One to Six. The heat preservation time can also be 20 seconds, 50 seconds, 100 seconds, 200 seconds, etc., but is not limited to these.

[0035] The beneficial effects of the present invention are verified using the following embodiments: Experimental Example 1: A method for low-heat-damage brazing of ceramics and metals based on localized Joule heating coupled with a thermally conductive base material is carried out according to the following steps: Step 1: Grind the C / C composite material, Nb metal and FeCoNiAlCuTi solder sheet to remove impurities from the base material surface, and assemble them into the parts to be brazed in the manner of C / C composite material / FeCoNiAlCuTi solder sheet / Nb metal.

[0036] Step 2: Connect the two ends of the conductive carbon felt to the positive and negative terminals of a DC power supply, respectively. Place the assembled workpiece from Step 1 above the conductor, with the carbon felt in direct contact with the C / C composite material. The Nb metal matrix is ​​located at the far end of the carbon felt, creating a vacuum of 10 for the workpiece. -1 Pa environment.

[0037] Step 3, press Figure 3 The process parameters shown apply current to the carbon felt, and the surface temperature of the carbon felt is monitored. The joint to be brazed is held at this temperature for 40 seconds, then the current is stopped, completing the brazing connection. In this embodiment, the shear strength of the brazed joint between the C / C composite material and the Nb alloy is tested to be 35.5 MPa.

[0038] Figure 2 The assembly fixture used in this embodiment, such as Figure 2 As shown, the thermally conductive C / C composite material is in direct contact with the conductor, while the heat-sensitive material (metallic material) is placed at the far end of the heat source.

[0039] Apply as Figure 3 The voltage and current shown control the surface temperature of the conductor as follows: Figure 4 As shown in the figure, Joule heating can achieve rapid heating and high welding efficiency.

[0040] Figure 5 The image shows the microstructure of the brazed joint of C / C composite material and Nb alloy obtained in this embodiment. As can be observed from the image, the weld has no obvious cracks or pores, the joint is well bonded, and an effective connection is achieved.

[0041] Experimental Example 2: The difference between this experimental example and Experimental Example 1 is that the protective environment in step 2 is an argon atmosphere, while the rest is the same as Experimental Example 1.

[0042] Experiment Example 3: The difference between this experiment example and Experiment Example 1 is that the heat preservation time in step 3 is 20 seconds, while the rest is the same as Experiment Example 1.

[0043] The beneficial effects of this invention include: (1) By using Joule heating to rapidly raise the temperature and combining it with ultra-short holding time, the welding cycle is greatly reduced.

[0044] This invention employs Joule heating, directly connecting the conductor to a DC power supply and placing it in contact with the heat-conducting substrate. This enables rapid start-up and efficient heat conduction during the heating process, eliminating the lengthy preheating and heat radiation conduction processes required in traditional furnace brazing, thus significantly shortening the heating cycle. Furthermore, the holding time of the brazed joint is precisely controlled within 300 seconds, further reducing the welding cycle and improving welding efficiency.

[0045] (2) By utilizing Joule heating for local heating and combining it with a unique assembly method, the heat input for welding is significantly reduced.

[0046] This invention specifically uses a single-sided heat source to achieve localized heating through Joule heating, treating the metal in the joint as a "cold end" that only receives a small amount of conductive heat for a short period of time. This design fundamentally avoids thermal damage problems such as grain growth, residual stress accumulation, and interface degradation caused by continuous high temperature on the metal base material, and preserves the mechanical properties of metals such as high-temperature alloys, Nb alloys, and high-entropy alloys to the greatest extent, which is of key significance for the connection of dissimilar materials.

[0047] (3) The process is simple, the equipment investment is small, and the operation is highly controllable.

[0048] This invention eliminates the need for additional complex auxiliary equipment such as cooling water circulation and large-scale thermal radiation heating devices, resulting in a simple equipment system and low initial investment costs. Furthermore, the process flow is clear and easy to operate. By adjusting the current and voltage parameters of the DC power supply, the heating rate can be precisely controlled. Combined with real-time monitoring of the conductor surface temperature using temperature measuring equipment, precise control of brazing temperature and holding time can be achieved.

[0049] It should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise" that may appear in the above description indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the embodiments of the present invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of the present invention.

[0050] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of embodiments of the present invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0051] In the embodiments of this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0052] In embodiments of the present invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature may include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature include the first feature being directly above or diagonally above the second feature, or simply indicating that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature include the first feature being directly below or diagonally below the second feature, or simply indicating that the first feature is at a lower horizontal level than the second feature.

[0053] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. In addition, those skilled in the art can combine and integrate the different embodiments or examples described in this specification.

[0054] Other embodiments of the invention will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This application is intended to cover any variations, uses, or adaptations of the invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not disclosed herein. The specification and examples are to be considered exemplary only, and the true scope and spirit of the invention are indicated by the appended claims.

Claims

1. A method for low-heat-damage brazing of ceramics and metals based on localized Joule heating coupled with a thermally conductive base material, characterized in that, include: S1, pre-treat the base material and brazing filler metal sheet, and assemble them into the parts to be brazed in the manner of thermally conductive base material / brazing filler metal / metal base material; S2, connect the two ends of the conductor to the positive and negative terminals of the DC power supply respectively, place the workpiece to be brazed above the conductor, and make the thermally conductive base material directly contact the conductor, with the metal base material located at the far end of the conductor, to set up a vacuum or protective gas environment for the workpiece to be brazed. S3: Power is applied to the conductor, and the current and voltage are adjusted to raise the temperature of the conductor and the heat-conducting base material to the preset temperature. The surface temperature of the conductor is monitored using a temperature measuring device, and the workpiece to be brazed is then welded.

2. The brazing connection method according to claim 1, characterized in that, The thermally conductive substrate is one of C / C composite material, SiC ceramic, Al2O3 ceramic, Si3N4, BN, C / SiC, and SiC / SiC.

3. The brazing connection method according to claim 1, characterized in that, The metal substrate is one of high-temperature alloys, high-entropy alloys, Nb alloys, and Fe alloys.

4. The brazing connection method according to claim 1, characterized in that, The solder sheet is one of high-entropy solder, nickel-based solder, silver-based solder, and copper-based solder.

5. The brazing connection method according to claim 1, characterized in that, The thickness of the solder sheet is 50μm to 200μm.

6. The brazing connection method according to claim 1, characterized in that, The conductor is one of carbon cloth, carbon paper, and carbon felt.

7. The brazing connection method according to any one of claims 1 to 6, characterized in that, In S3, after the conductor is used to keep the joint of the workpiece to be brazed warm for a preset time, the conductor is directly stopped from being energized or the current and voltage are controlled to drop to zero at a preset rate.

8. The brazing connection method according to claim 7, characterized in that, The rate of decrease of the current is 1-300 A / s, and the rate of decrease of the voltage is 1-100 V / s.

9. The brazing connection method according to claim 7, characterized in that, In S3, the heat preservation time of the joint of the workpiece to be brazed is 3-300s.

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