Brazed joint of dissimilar materials with a brazed descent line structure and method for manufacturing the same

Abstract

The present invention provides a brazed joint of dissimilar materials with a fastest descent line structure that offers high brazing quality, fewer defects in the brazed joint, and significantly improves the shear strength of the brazed joint, as well as a method for manufacturing the same. [Solution] The brazed joint of dissimilar materials with a velociscity descent structure includes a first brazed base material and a second brazed base material, wherein the first brazed base material has higher wettability to the brazing material than the second brazed base material, and the brazed surface of the second brazed base material is provided with a velociscity descent groove consisting of two symmetrically arranged velociscity descent curved surfaces, the inner surface curve of the velociscity descent curved surfaces satisfies the equation of the velociscity descent. The method for manufacturing the brazed joint includes step S1 of processing a velociscity descent groove on the brazed surface of the second brazed base material, and step S2 of placing the brazing material between the brazed surface of the first brazed base material and the brazed surface of the second brazed base material and brazing them.

Description

Technical Field

[0001] The present disclosure belongs to the technical field of material joining, and specifically relates to a dissimilar material brazed joint with a brachistochrone structure and a manufacturing method thereof.

[0002] [Cross-reference to Related Applications] The present disclosure claims priority based on a Chinese application with an application number of 2024108048089 and a title of "Dissimilar Material Brazed Joint with a Brachistochrone Structure and a Manufacturing Method Thereof" filed with the Chinese Patent Office on June 21, 2024, and all of its contents are incorporated herein by reference.

Background Art

[0003] In the technical field of brazing, dissimilar materials usually refer to materials with differences in physical and chemical properties such as elastic modulus, thermal expansion coefficient, melting point, etc., and examples include ceramics and metals, ferrous metals and non-ferrous metals, copper and stainless steel, etc. Dissimilar material members can achieve a combination of excellent properties of different materials, greatly improving the freedom of structural design, meeting the functional and performance requirements of modern engineering structures, having higher technical and economic value, and having the potential for wide application in various fields. Therefore, reliable joining of dissimilar materials is particularly important.

[0004] However, the joining of dissimilar materials has significant differences in physical, chemical, and mechanical properties between the dissimilar materials, and the differences in metallurgical compatibility during welding, brittle compounds formed by interfacial reactions, and differences in thermal expansion coefficients have a very large impact on the performance of the joint. Therefore, there are mainly the following problems and difficulties in the joining of dissimilar materials.

[0005] 1. When joining dissimilar materials, there are significant differences in wettability, and it is difficult to wet two types of materials simultaneously.

[0006] Conventional brazed joints consist of a pair of approximately parallel planes, and the brazing material flows through the weld gap formed by the two parallel planes. Because the wettability of the brazing material to the two different materials differs, the fluidity and viscosity after melting also differ. As a result, the brazing material does not come into contact with the material on the less wettable side, leading to defects and affecting the performance of the product.

[0007] 2. Due to the large differences in the chemical composition of the dissimilar materials, the interfacial reaction is complex, and problems such as the excessive formation of brittle compounds at the interface are likely to occur.

[0008] 3. Due to the difference in thermal expansion coefficients of dissimilar materials, large residual stresses exist at the interface, making stress relaxation of the joint difficult and prone to cracking after welding.

[0009] Since all of the above problems affect the performance of brazed joints, it is very important to provide dissimilar material brazed joints and methods for manufacturing the same that can achieve efficient and high-quality welding of dissimilar materials.

[0010] In light of the above, we propose this disclosure. [Overview of the project]

[0011] The purpose of this disclosure is to provide a brazed joint of dissimilar materials with a fastest descent line structure that exhibits high brazing quality, fewer defects in the brazed joint, and high joint strength.

[0012] A brazed joint of dissimilar materials with a stochastic descent structure includes a first brazed base material and a second brazed base material, wherein the first brazed base material has higher wettability to the brazing material than the second brazed base material, and the brazed surface of the second brazed base material is provided with a stochastic descent groove consisting of two symmetrically arranged stochastic descent curved surfaces, the inner surface curve of the stochastic descent curved surface satisfies the following equation for stochastic descent, x=r(θ-sinθ), y=r(1-cosθ).

[0013] This disclosure further aims to provide a method for manufacturing a brazed joint of dissimilar materials having the above-described velocitate descent structure. By processing velocitate descent grooves on the surface of a material that is difficult to wet, the flow velocity of the brazing material on the surface of the material that is difficult to wet during brazing, the brazing ratio, and the uniformity of the distribution of residual stress in the brazed joint can be improved, thereby reducing defects in the brazed joint and improving the strength of the joint.

[0014] The method for manufacturing the brazed joint of dissimilar materials with the aforementioned fastest descent line structure includes the following steps.

[0015] Step S1. A rapid descent groove is machined into the brazing surface of the second brazing substrate.

[0016] Step S2. Place the brazing material between the brazing surface of the first brazing substrate and the brazing surface of the second brazing substrate and perform brazing.

[0017] Compared to related technologies, this disclosure has the following beneficial effects.

[0018] According to this disclosure, by providing a rapid descent groove structure on the brazing surface of the second brazing substrate, which is difficult to wet, the brazing material can cover the maximum contact area in the shortest time when flowing over the surface of the difficult-to-wet material. This increases the flow velocity of the brazing material on the surface of the difficult-to-wet material, avoiding defects caused by the brazing material covering and blocking the brazing gap from the surface of the easily wettable material due to the brazing material flowing too quickly on the surface of the easily wettable material. This improves the wettability of the brazing material on the surface of the difficult-to-wet material, improves the uniformity of residual stress in the brazed joint, and avoids cracking due to stress concentration. At the same time, it is possible to increase the contact area between the difficult-to-wet material and the brazing material, and increase the brazing ratio on the surface of the difficult-to-wet material, resulting in high brazing quality of dissimilar material brazed joints, fewer defects in the brazed joint, and high joint strength.

[0019] To more clearly explain the specific embodiments in the present disclosure or the technical solutions in the related art, the drawings necessary for the description of the specific embodiments or the related art will be briefly described below. The drawings to be described are only a part of the embodiments of the present disclosure, and those skilled in the art can obtain other related drawings based on these drawings without using inventive capabilities.

Brief Description of the Drawings

[0020] [Figure 1] It is a schematic configuration diagram of the first interface between the first brazing base material and the second brazing base material according to the present disclosure. [Figure 2] It is a schematic configuration diagram of the second interface between the first brazing base material and the second brazing base material according to the present disclosure. [Figure 3] It is a schematic configuration diagram of the third interface between the first brazing base material and the second brazing base material according to the present disclosure. [Figure 4] It is a schematic configuration diagram of the brazed surface of the second brazing base material according to an embodiment of the present disclosure. [Figure 5] It is a schematic configuration diagram of the mesh structure of the brazed surface of the first brazing base material according to an embodiment of the present disclosure. [Figure 6] It is a schematic configuration diagram of the interface between the first brazing base material and the second brazing base material according to an embodiment of the present disclosure. [Figure 7] It is a schematic configuration diagram of the interface between the first brazing base material and the second brazing base material according to another embodiment of the present disclosure. [Figure 8] It is an electron microscope photograph of the actual object of the bonding interface of the brazed joint according to an embodiment of the present disclosure. [Figure 9] It is an electron microscope photograph of the actual object of the bonding interface of the brazed joint according to another embodiment of the present disclosure. [Figure 10] It is an electron microscope photograph of the actual object of the bonding interface of the brazed joint according to another embodiment of the present disclosure. [Figure 11] It is a schematic configuration diagram of the bonding interface of the brazed joint according to an embodiment of the present disclosure.

Modes for Carrying Out the Invention

[0021] The technical proposal of this disclosure will be clearly and completely described below with reference to the drawings and specific embodiments. The embodiments described below are only a selection of embodiments for illustrating this disclosure and do not represent all embodiments, nor should they be considered to limit the scope of this disclosure. All other embodiments obtained by a person skilled in the art without using their inventive ability, based on the embodiments of this disclosure, also fall within the scope of this disclosure. Where specific conditions are not specified in the embodiments, it is possible to use conventional conditions or conditions recommended by the manufacturer. Where the manufacturer of the reagents or instruments used is not specified, commercially available conventional products may be used.

[0022] As shown in Figures 1, 2, and 3, the first aspect of this disclosure provides a dissimilar material brazed joint with a stochastic descent line structure. This dissimilar material brazed joint with a stochastic descent line structure includes a first brazed base material 1 and a second brazed base material 2, wherein the first brazed base material 1 has higher wettability to the brazing material than the second brazed base material 2, and the brazed surface of the second brazed base material 2 is provided with a stochastic descent line groove 21 consisting of two symmetrically arranged stochastic descent line curves, the inner surface curves of the stochastic descent line curves satisfying the following equation for stochastic descent, x=r(θ-sinθ) and y=r(1-cosθ).

[0023] As shown in Figure 1, the inner surface curve of the velocitate descent curve is the cross-sectional curve at the boundary between the brazed surface of the second brazed base material 2 and the plane perpendicular to the extension direction of the velocitate descent groove 21 and the velocitate descent groove 21.

[0024] The brachistochrone is the curve through which a point mass can slide fastest from point A to point B, provided that two points A and B are placed in a vertical plane and point A is never lower than point B (the point mass is only affected by gravity and has zero initial velocity). In the case of brazed joints, a brachistochrone also exists in the process of a solid brazing alloy droplet moving from one point to another as it flows along the brazed gap. The brachistochrone can be expressed by the parametric equations x=r(θ-sinθ) and y=r(1-cosθ), where r and θ are determined by the position of the endpoints. Therefore, a brachistochrone exists for any two points that have zero initial velocity and are subjected to only one force.

[0025] Conventional brazed joints consist of a pair of approximately parallel planes, and the brazing material flows through the weld gap formed by the two parallel planes. However, in the case of dissimilar joints, the wettability of the brazing material to the two different materials differs, resulting in differences in fluidity and adhesion after melting. As a result, the brazing material does not come into contact with the material on the less wettable side, leading to defects and affecting the performance of the product.

[0026] This disclosure provides a velocity-descent groove structure on the brazing surface of a second brazing substrate that is difficult to wet, thereby adjusting the flow velocity of the brazing material in the brazing gap. This improves the wettability of the brazing material on the surface of the difficult-to-wet material, improves the uniformity of residual stress in the brazed joint, and avoids cracks caused by stress concentration. By providing a velocity-descent groove structure on the surface of the difficult-to-wet material, the brazing material can cover the maximum contact area in the shortest time when flowing over the surface of the difficult-to-wet material. This improves the flow velocity of the brazing material on the surface of the difficult-to-wet material and avoids defects caused by the brazing material covering and blocking the brazing joint from the surface of the easily wettable material due to the brazing material flowing too quickly on the surface of the easily wettable material. At the same time, it is possible to increase the contact area between the difficult-to-wet material and the brazing material, and increase the brazing ratio on the surface of the difficult-to-wet material, thereby improving the performance of dissimilar material brazed joints.

[0027] The dissimilar material brazed joint described herein has advantages such as high brazing quality, fewer defects in the brazed joint, and high joint strength, making it very important for applications involving dissimilar material components.

[0028] As shown in Figure 4, in some specific embodiments of the present disclosure, a plurality of parallel velocity drop grooves 21 are provided on the brazing surface of the second brazing substrate 2, and when the total length of the brazing gap is constant, the number of velocity drop grooves 21 can be increased to reduce the consumption of the brazing material while maintaining the contact area between the brazing material and the less wettable material.

[0029] In some preferred embodiments, multiple rapid descent grooves 21 are evenly distributed on the brazing surface of the second brazing substrate 2 in order to improve the uniformity of the brazing material and stress distribution.

[0030] In some specific embodiments of this disclosure, the vertical distance H and horizontal distance L between the start and end points of the brazing line on the inner surface of the brazing line groove 21, and the size d of the aggregated particles of the brazing material due to the melting of the brazing material used satisfy H≧8d and L≧8d.

[0031] Using the starting point as the origin, the position of the endpoint can be determined and the values ​​of r and θ can be obtained based on the vertical distance H and horizontal distance L between the start and end points of the brazing line. When the vertical distance H and horizontal distance L are 8 times or more the size of the aggregated particles due to the melting of the brazing material, it contributes to improving the joint strength of the brazed joint. If the brazing line groove 21 is too small, the effect of improving joint strength is not significant. If the size of the brazing line groove 21 is too large, the amount of brazing material used increases, leading to higher costs. In some preferred embodiments of this disclosure, the vertical distance H and horizontal distance L satisfy 8d ≤ H ≤ 15d and 8d ≤ L ≤ 15d. Within this range, the joint performs well and does not waste excessive brazing material. For example, H can be any value from among 8d, 9d, 10d, 11d, 12d, 13d, 14d, and 15d, or any two values ​​within that range, and L can be any value from among 8d, 9d, 10d, 11d, 12d, 13d, 14d, and 15d, or any two values ​​within that range.

[0032] In some specific embodiments of the present disclosure, a mesh structure 11 is provided on the brazing surface of the first brazing substrate 1, or a velocitate drop projection 12 is provided on the brazing surface of the first brazing substrate 1 that aligns with the velocitate drop groove 21 and forms a fitting structure.

[0033] In other words, in some embodiments of the present disclosure, the geometric configuration of the joint interface of a dissimilar material brazed joint includes the following: the brazed surface of the first brazed base material 1 is not processed to be planar and the brazed surface of the second brazed base material 2 is provided with a velocisfastest descent groove 21 (Figure 3); the brazed surface of the first brazed base material 1 is a mesh structure 11 and the brazed surface of the second brazed base material 2 is provided with a velocisfastest descent groove 21 (Figure 1); or the brazed surface of the second brazed base material 2 is provided with a velocisfastest descent groove 21 and the brazed surface of the first brazed base material 1 is provided with a velocisfastest descent projection 12 that fits into the velocisfastest descent groove 21 (Figure 2).

[0034] As shown in Figure 5, in some specific embodiments of this disclosure, the mesh structure 11 on the surface of the first brazed substrate 1 is composed of grooves that intersect vertically and horizontally.

[0035] When the brazing surface of the first brazing substrate 1 has a mesh structure 11, the mesh structure 11 reduces the flow velocity of the brazing material on the surface of the easily wettable material, and the fastest descent groove 21 improves the flow velocity of the brazing material on the surface of the less wettable material. Together, these two factors achieve the objective of the brazing material covering both brazing surfaces simultaneously, thereby reducing defects in the brazed joint. The grooves in the mesh structure also serve to store excess brazing material. The mesh structure can increase the surface roughness of the material, increasing the adhesion of the material surface to the brazing material and the contact area between the brazing material and the material. This structure can significantly improve the strength of dissimilar material brazed joints.

[0036] When the brazing surface of the first brazing substrate 1 is provided with a velocitate drop projection 12 that fits into the velocitate drop groove 21, the velocitate drop structure is recessed on the surface of a material that is difficult to wet, increasing the wetting angle and improving wettability. On the surface of a material that is easily wetted, the velocitate drop structure is protruding, decreasing the wetting angle and reducing the wetting speed. With such a structure, a single brazing material channel is formed in the joint, gas is discharged spontaneously, the sparse structure is greatly reduced, impurities are arranged in an orderly manner on the outside of the brazing joint, and the strength of the joint can be improved. Furthermore, compared to cases where the surface of the easily wetted material is flat or has a mesh structure, this structure can reduce the amount of brazing material used, shorten the brazing time, and improve brazing efficiency.

[0037] In some specific embodiments of this disclosure, the surface structures of the first brazed substrate 1 and the second brazed substrate 2 are geometrically arranged on the order of microns.

[0038] In some specific embodiments of this disclosure, a storage groove 211 is provided within the velocity descent groove 21 at the boundary between two symmetrically arranged velocity descent curves to store excess brazing material, thereby increasing the contact area between the material and the brazing material and improving the strength of the joint. The storage groove 211 has a depth of ≥r / 5 and a width of ≥r / 5.

[0039] If the storage groove 211 is too small, the effect of improving shear strength is not significant, and if it is too large, the amount of brazing material used is large, the brazing time is long, the efficiency is low and the cost is high. In some preferred embodiments of this disclosure, the depth of the storage groove 211 is r / 5 to 3r, for example r / 5, r / 4, r / 2, r, 2r, 3r, etc., and the width of the storage groove 211 is r / 5 to 3r, for example r / 5, r / 4, r / 2, r, 2r, 3r, etc.

[0040] In some specific embodiments of this disclosure, the surface structure of the brazed surface of the second brazed substrate 2 has arc-shaped corners to facilitate the flow of brazing material. By forming various arch-shaped structures (velocity drop grooves) and arc-shaped structures on the surface, residual stress generated during brazing can be uniformly distributed, and cracking due to stress concentration can be avoided.

[0041] In some specific embodiments of this disclosure, the first brazing substrate 1 is YG8 or TC4, and / or the second brazing substrate 2 comprises one of PCBN or alumina ceramics.

[0042] In some specific embodiments of this disclosure, the first brazing substrate 1 is YG8 and the second brazing substrate 2 is PCBN.

[0043] In another embodiment of the present disclosure, the first brazing substrate 1 is TC4 and the second brazing substrate 2 is alumina ceramics.

[0044] A second aspect of this disclosure provides a method for manufacturing a dissimilar material brazed joint of a streak-down line structure as described in any one of the embodiments above, the method comprising the following steps:

[0045] Step S1. A rapid descent groove is machined into the brazing surface of the second brazing substrate.

[0046] Step S2. Place the brazing material between the brazing surface of the first brazing substrate and the brazing surface of the second brazing substrate and perform brazing.

[0047] The manufacturing method described herein involves processing a rapid descent groove on the brazing surface of a second brazing substrate that is difficult to wet, thereby increasing the flow velocity of the brazing material on the surface of the difficult-to-wet material, avoiding defects caused by excessively high flow velocity of the brazing material on the surface of the easily wettable material, increasing the contact area between the difficult-to-wet material and the brazing material, and improving the brazing ratio of the material surface. This method significantly improves the brazing quality of dissimilar material brazing joints and improves the strength of the joints.

[0048] In some specific embodiments of the present disclosure, step S1 further includes processing a mesh structure or a brace descender projection onto the brazed surface of the first brazed substrate.

[0049] By processing a mesh structure on the brazing surface of the first brazing substrate, the flow velocity of the brazing material on the surface of the easily wettable material can be reduced, and the difference in flow velocity of the brazing material on the surfaces of the two types of materials can be reduced. As a result, the brazing material covers both types of materials simultaneously, suppressing defects in the brazed joint, and increasing the contact area between the brazing material and the brazing substrate, as well as the roughness of the brazing substrate, thereby improving the brazing ratio and the strength of the joint.

[0050] The strength of the joint can be similarly improved by processing the surface of the first brazing substrate with velocity descent projections that fit into the velocity descent grooves. While a mesh structure is superior in improving joint strength, the velocity descent projections reduce the amount of brazing material used, shorten the brazing time, and improve brazing efficiency compared to a mesh structure.

[0051] In some specific embodiments of the present disclosure, step S1 includes a method for processing the brazed surfaces of the first brazed substrate and the second brazed substrate, which includes a low-speed wire cutting method and / or a short-pulse laser method.

[0052] In some specific embodiments of the present disclosure, step S1 further includes a step of pre-treating the brazing surfaces of the first brazing substrate and the second brazing substrate, the pre-treating method including blasting and / or sanding the brazing surfaces, ultrasonic cleaning, and drying.

[0053] In some specific embodiments of this disclosure, ultrasonic cleaning is performed in acetone, and the ultrasonic cleaning time is 10 to 20 minutes, for example, any value from 10 min, 12 min, 14 min, 15 min, 16 min, 18 min, 20 min, or any two of those values ​​within that range.

[0054] In some specific embodiments of this disclosure, the brazing method includes vacuum brazing and / or induction brazing.

[0055] In some specific embodiments of this disclosure, the first brazing substrate is YG8, the second brazing substrate is PCBN, the brazing material is CuSnTi, the brazing temperature is 800 to 1000°C, for example, any value or any two values ​​from among 800°C, 850°C, 900°C, 950°C, and 1000°C, and the heating rate is 1 to 20°C / min, for example, any value or any two values ​​from among 1°C / min, 3°C / min, 5°C / min, 7°C / min, 10°C / min, 12°C / min, 14°C / min, 16°C / min, 18°C / min, and 20°C / min.

[0056] In some specific embodiments of this disclosure, the first brazing substrate is TC4, the second brazing substrate is alumina ceramics, the brazing material is TiZrCuNi, the brazing temperature is 950 to 1000°C, for example, any value among 950°C, 980°C, and 1000°C or any two of those values, and the heating rate is 1 to 20°C / min, for example, any value among 1°C / min, 3°C / min, 5°C / min, 7°C / min, 10°C / min, 12°C / min, 14°C / min, 16°C / min, 18°C / min, and 20°C / min or any two of those values.

[0057] Several embodiments of this disclosure will be described in detail below using specific examples. Unless otherwise specified, the raw materials used in the examples are commercially available.

[0058] In one embodiment, a PCBN / YG8 brazed joint is fabricated using a low-speed wire cutting machine to create the geometric configuration described in this disclosure, and its interface structure is shown in Figure 6. Brazing is performed using CuSnTi brazing material.

[0059] Step 11: The brazing surfaces of the PCBN and YG8 were pre-treated by blast treatment, then ultrasonically cleaned in acetone for 15 minutes, and finally air-dried.

[0060] Step 12: The brazed surface of the PCBN is processed using a low-speed wire cutting machine, and the formula for the brachistochrone described in this disclosure is imported into CAD drawing software. According to the literature, the size of aggregated particles of the brazing material in commercial CuSnTi brazing material when molten is approximately 2-3 μm. If the angle of the starting point θ is 0°, the angle of the ending point θ is 120°, and the value of r is 20 μm, the vertical distance between the starting point and the ending point is 30 μm, and the horizontal distance is 25 μm. Within the range of this brachistochrone, the particles formed by the aggregation of the brazing material are considered as point masses, and the two brachistochrone curve surfaces on the left and right are connected by a storage groove with a depth of 20 μm and a width of 20 μm, and the equipment automatically processes according to the CAD drawing program.

[0061] Step 13: Process the brazed surface of YG8 using a low-speed wire cutting machine. First, grooves with a width of 20 μm and a depth of 20 μm are made at 20 μm intervals in the transverse direction. Then, the YG8 sample is rotated 90° and grooves with a width of 20 μm and a depth of 20 μm are made at 20 μm intervals in the longitudinal direction to form a mesh structure.

[0062] Step 14: Apply CuSnTi brazing material between the brazing surfaces of the two materials to be brazed, place in a vacuum brazing furnace, and set the vacuum level to 1 × 10⁻⁶. -3 The material was heated to 900°C at a heating rate of 10°C / min in Pa, and then held at that temperature for 2 minutes. After that, it was cooled down to 400°C at a rate of 10°C / s and then cooled in the furnace to obtain a brazed joint.

[0063] Step 15: Once the brazing was complete, the shear strength of the resulting brazed joint was detected using a universal testing machine. The results showed that the welded joint produced in this example reached a shear strength of 269 MPa.

[0064] Optionally, unlike the above embodiment, only steps 11, 14, and 15 of the above embodiment may be performed without any additional processing of the brazed surfaces of PCBN and YG8. After brazing is complete, the strength of the joint is detected, and its shear strength was 147 MPa. By adopting steps 11 to 15, the strength was improved by 83% compared to adopting only steps 11, 14, and 15.

[0065] In some embodiments, unlike steps 11 to 15 above, a short-pulse laser was used to process the brazed surface of the PCBN in order to achieve more precise processing dimensions. The process parameters were a laser power of 300W, a frequency of 1000KHz, a scan speed of 40mm / s, and a processing size of the reservoir groove of depth × width = 4 × 4μm. In this case, the strength of the welded joint was 207MPa, which is a 41% improvement compared to using only steps 11, 14, and 15 above, and a 23% decrease compared to using steps 11 to 15 above. The optimal brazing time in this case was 2min, which is the same as when using steps 11 to 15 above, and the brazing material consumption was 10% lower than when using steps 11 to 15 above.

[0066] In some embodiments, unlike steps 11 to 15 above, the size of the storage groove to be processed was depth × width = 60 × 60 μm. In this case, the strength of the welded joint was 298 MPa, which was a 10.8% improvement in joint strength compared to when steps 11 to 15 were used. However, the welding time was extended to 4 minutes, a 100% increase in time, and the brazing material consumption increased by 82%.

[0067] In another embodiment, the geometric configuration described in this disclosure is fabricated using Al2O3 and TC4 brazed joints with a pulsed laser and a low-speed wire cutter, respectively, and the interface structure is shown in Figure 7. Brazing is performed using commercially available TiZrCuNi brazing material.

[0068] Step 21: Pre-treat the brazing surfaces of the alumina ceramics and TC4 titanium alloy. Pre-treatment involves sanding the brazing surfaces of the materials to be brazed with sandpaper, then ultrasonically cleaning them in acetone for 15 minutes, and finally air drying.

[0069] Step 22: The brazed surfaces of Al2O3 and TC4 were processed using a pulsed laser and a low-speed wire cutter, respectively, and the formula for the brachistochrone described in this disclosure was imported into CAD drawing software. The angle of the starting point θ was 0°, the angle of the ending point θ was 180°, and the value of r was 30 μm. In this case, the vertical distance between the starting and ending points of the brachistochrone was 60 μm, and the horizontal distance was 94.25 μm. After generating the brachistochrone on the left, the brachistochrone on the right of the mirror image was generated, and the interval between the brachistochrone lines, which were closed every two stages (the interval between the left + right stage and the next left + right stage), was 30 μm. A protruding region was processed on the TC4 side of the wettable material, and a recessed brazed surface was processed on the Al2O3 side, and the equipment automatically processed according to the CAD drawing program.

[0070] Step 23: Apply TiZrCuNi brazing material between the brazing surfaces of the two materials to be brazed, place in a vacuum brazing furnace, and set the vacuum level to 1 × 10⁻⁶. -3 The material was heated to 950°C at a heating rate of 10°C / min in Pa, and then held at that temperature for 15 minutes. After that, it was cooled down to 300°C at a rate of 10°C / s and then cooled in the furnace to obtain a brazed joint.

[0071] Step 24: Once the brazing was complete, the shear strength of the resulting joint was detected using a universal testing machine. The results showed that the welded joint produced in this example reached a shear strength of 60 MPa, which is a 50% improvement in strength compared to a welded joint without special treatment.

[0072] Optionally, unlike the above embodiment, only steps 21, 23, and 24 of the above embodiment may be performed without any additional processing of the Al2O3 and TC4 brazing surfaces. After the brazing is complete, the strength of the joint is detected, and its shear strength was 40 MPa.

[0073] In some examples, unlike steps 11 to 15 above, the shape of the joint interface was as shown in Figure 3, the brazed surface of YG8 was not processed, and a rapid descent groove was processed on the brazed surface of PCBN, while other parameters were the same as in steps 11 to 15 above. The shear strength of the fabricated brazed joint was 173 MPa, which was a 17.7% improvement compared to the case where only steps 11, 14, and 15 were used, and a 35.7% decrease compared to the case where steps 11 to 15 were used.

[0074] In some embodiments, the shape of the joint interface differed from steps 11 to 15 above, as shown in Figure 2, and a photograph of the actual product is shown in Figure 8. A velocisfastest descent line projection was machined onto the brazed surface of YG8, and a velocisfastest descent line groove was machined onto the brazed surface of PCBN, while other parameters were the same as in steps 11 to 15 above. The shear strength of the fabricated brazed joint was 192 MPa, which was a 30.6% improvement compared to using only steps 11, 14, and 15 above, and a 28.6% decrease compared to using steps 11 to 15 above. However, the brazing time was 1 min, which was a 100% improvement in speed compared to using steps 11 to 15 above, and the amount of brazing material used was reduced by 72% compared to using steps 11 to 15 above.

[0075] In some embodiments, unlike the above embodiment, a 20 μm × 20 μm storage groove was additionally machined into the velocity drop groove processed on the brazed surface of the PCBN, as shown in Figure 9, while other parameters were the same as in the above embodiment. The shear strength of the fabricated brazed joint was 213 MPa, an 11% improvement compared to the above embodiment. The brazing time was 1.2 min, a 20% increase compared to the above embodiment, and the amount of brazing material used increased by 14% compared to the above embodiment.

[0076] In some examples, unlike steps 11 to 15 above, as shown in Figure 10, a storage groove was not machined within the fastest descent groove processed on the brazed surface of the PCBN, while other parameters were the same as in steps 11 to 15 above. The shear strength of the fabricated brazed joint was 247 MPa, which was 8% lower than when steps 11 to 15 were used. The brazing time was 1.6 min, which was 20% shorter than when steps 11 to 15 were used, and the amount of brazing material used was reduced by 20% compared to when steps 11 to 15 were used.

[0077] In another embodiment, the geometric configuration described in this disclosure was fabricated on the end faces of a stainless steel pipe with an inner diameter of 30 mm and a wall thickness of 6 mm, and a copper pipe with a wall thickness of 5 mm, using a CNC machine tool. As shown in Figure 11, it was welded by induction heating.

[0078] Step 31: Confirm the size of the brachistochrone curve using a copper pipe with a wall thickness of 5 mm. With the starting point angle θ set to 0°, the ending point angle θ set to 180°, and the value of r set to 1.5 mm, the horizontal distance between the starting point and ending point of the brachistochrone curve in this case was 4.71 mm, and the vertical distance was 3 mm. Step 32: Using a CNC machine tool, starting from a point on the outer wall of the stainless steel pipe, a concave surface is turned in the direction from the outer wall to the inner wall, following the brachistochrone curve confirmed in Step 31, and a horizontal table is turned in the direction from the outer wall to the inner wall at the end of the curve.

[0079] Step 33: Using a CNC machine tool, starting from a point on the outer wall of the copper pipe, a convex curve is turned in the outer direction according to the brachistochrone curve confirmed in Step 31, and a horizontal table is turned in the direction from the outer wall to the inner wall.

[0080] Step 34: Place the stainless steel pipe downwards with the concave curved surface facing upwards, and the copper pipe downwards with the convex curved surface facing downwards, butt the two pipes together. Flux-cored silver welding ring (Brand: Zhengzhou Machinery Research Institute Co., Ltd., Symbol: Ag) 25 Install the CuZn (CuZn) by enclosing it in a ring at the joint.

[0081] Step 35: The two tubes obtained in Step 34 are heated by a high-frequency induction heating device with a heating power of 20 kW, placed in an induction heating coil, and heated for 4 seconds. When it is observed that the brazing material flows out from inside the brazing gap, the brazing is complete.

[0082] Optionally, unlike the embodiments described above, the butt joint surface of the brazing gap between the end faces of the stainless steel pipe and the copper pipe was flat, and the other conditions were the same as in Example 9. The brazing time was 7 seconds, which is 75% slower than when steps 11 to 15 were used, and it is clear that the brazing gap structure with the fastest descent line structure can shorten the brazing time and improve brazing efficiency.

[0083] While specific examples have been used to illustrate this disclosure, these examples are merely illustrative and not limiting. Those skilled in the art may modify the technical concepts described in the above examples, or substitute some or all of their technical features, without departing from the spirit and scope of this disclosure. Such modifications or substitutions will not cause the intent of the applicable technical concept to deviate from the scope of the technical concept in each example of this disclosure. Therefore, the claims included hereby encompass all such substitutions and modifications that fall within the scope of this disclosure. [Industrial applicability]

[0084] According to the above proposed technology, by providing a rapid descent groove structure on the brazing surface of the second brazing substrate, which is difficult to wet, the brazing material can cover the maximum contact area in the shortest time when flowing over the surface of the difficult-to-wet material. This increases the flow velocity of the brazing material on the surface of the difficult-to-wet material, avoiding defects caused by the brazing material covering and blocking the brazing gap from the surface of the easily wettable material due to the brazing material flowing too quickly on the surface of the easily wettable material. This improves the wettability of the brazing material on the surface of the difficult-to-wet material, improves the uniformity of residual stress in the brazed joint, and avoids cracking due to stress concentration. At the same time, it increases the contact area between the difficult-to-wet material and the brazing material, and increases the brazing ratio on the surface of the difficult-to-wet material, resulting in high-quality brazing of dissimilar material brazed joints, fewer defects in the brazed joint, and high joint strength. [Explanation of Symbols]

[0085] 1. First brazing base material 11 Mesh structure 12 Fastest descent line protrusion 2. Second brazing base material 21 Fastest descent groove 211 Storage trench

Claims

1. A brazed joint of dissimilar materials with a stochastic descent structure, comprising a first brazed base material and a second brazed base material, wherein the first brazed base material has higher wettability to the brazing material than the second brazed base material, and the brazed surface of the second brazed base material is provided with a stochastic descent groove consisting of two symmetrically arranged stochastic descent curve surfaces, wherein the inner surface curve of the stochastic descent curve surface satisfies the following stochastic descent equation, x = r(θ - sinθ) and y = r(1 - cosθ).

2. A dissimilar material brazed joint with a velocisfiest descent structure according to claim 1, characterized in that a plurality of velocisfiest descent grooves are provided parallel to each other on the brazed surface of the second brazed substrate.

3. The brazed joint of dissimilar materials having a velocisfiest descent structure according to claim 2, characterized in that the plurality of velocisfiest descent grooves are evenly distributed on the brazed surface of the second brazed substrate.

4. The brazed joint of dissimilar materials with a brazed line structure according to claim 1, characterized in that the vertical distance H and the horizontal distance L between the start and end points of the brazed line on the inner surface of the brazed line groove, and the size d of the aggregated particles of the brazing material due to the melting of the brazing material used satisfy H ≥ 8d and L ≥ 8d.

5. A brazed joint of dissimilar materials with a velocisfiest descent structure according to claim 1, characterized in that a mesh structure is provided on the brazed surface of the first brazed substrate, or a velocisfiest descent projection is provided on the brazed surface of the first brazed substrate that aligns with the velocisfiest descent groove to form a fitting structure.

6. The brazed joint of dissimilar materials with the fastest descent line structure according to claim 5, characterized in that the mesh structure on the surface of the first brazed substrate is composed of grooves that intersect vertically and horizontally.

7. a. A storage groove is provided at the boundary between two symmetrically arranged stochastic descent curves within the stochastic descent groove, and the storage groove has a depth of ≥ r / 5 and a width of ≥ r / 5, and b. In the surface structure of the brazed surface of the second brazed substrate, each corner portion is arc-shaped. A brazed joint of dissimilar materials for a velocity descent structure according to any one of claims 1 to 6, characterized by including at least one of features a to b.

8. The first brazing substrate includes one of YG8 and TC4, and / or, the brazed joint of dissimilar materials having a velocity drop structure according to any one of claims 1 to 6, characterized in that the second brazed substrate includes one of PCBN or alumina ceramics.

9. Step S1 involves processing a rapid descent groove on the brazing surface of the second brazing substrate, A method for manufacturing a dissimilar material brazed joint with a velocity drop line structure according to any one of claims 1 to 6, characterized by comprising step S2 of placing a brazing material between the brazing surface of a first brazing substrate and the brazing surface of a second brazing substrate and brazing them together.

10. The method for manufacturing a dissimilar material brazed joint with a velocitate descent structure according to claim 9, characterized in that step S1 further includes processing a mesh structure or velocitate descent projections on the brazed surface of the first brazed substrate.

11. The method for manufacturing a brazed joint of dissimilar materials with a fastest descending line structure according to claim 10, characterized in that step S1 includes a low-speed wire cutting method and / or a short-pulse laser method.

12. A method for manufacturing a dissimilar material brazed joint with a fastest descent line structure according to claim 9, further comprising a step of pre-treating the brazed surfaces of the first brazed substrate and the second brazed substrate before step S1, wherein the pre-treatment method includes blasting and / or sanding the brazed surfaces, ultrasonic cleaning, and drying.

13. The method for manufacturing a dissimilar material brazed joint with a velocity drop structure according to claim 9, characterized in that in step S2, the brazing method includes vacuum brazing and / or induction brazing.

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