CN118385687B - A brazing fastest drop line structure joint of heterogeneous materials and its preparation method - Google Patents

Abstract

The invention relates to the technical field of material connection, in particular to a heterogeneous material brazing maximum speed drop line structure joint and a preparation method thereof. The heterogeneous material brazing maximum speed line descending structure joint comprises a first brazing substrate and a second brazing substrate, wherein the wettability of the first brazing substrate to brazing filler metal is superior to that of the second brazing substrate, the surface to be brazed of the second brazing substrate is provided with maximum speed line descending grooves, any one of the maximum speed line descending grooves is composed of two groups of symmetrically arranged maximum speed line descending curved surfaces, and the inner surface curves of the maximum speed line descending curved surfaces conform to the maximum speed line descending equation. The preparation method comprises the following steps: s1, processing a fastest descent line groove on a surface to be brazed of a second brazing substrate; s2, placing the brazing filler metal between the surfaces to be brazed of the first brazing base material and the second brazing base material for brazing, and obtaining the brazing filler metal. The hetero-material brazing maximum speed drop line structure joint provided by the invention has high brazing quality and few brazing seam defects, and can obviously improve the shear strength of the brazing joint.

Description

A brazing fastest drop line structure joint of heterogeneous materials and its preparation method

Technical Field

The invention relates to the technical field of material connection, and in particular to a brazing brazing fastest drop line structure joint of heterogeneous materials and a preparation method thereof.

Background Art

In the field of brazing technology, heterogeneous materials usually refer to materials with large differences in physical and chemical properties such as elastic modulus, thermal expansion coefficient, melting point, etc., such as ceramics and metals, ferrous metals and non-ferrous metals, copper and stainless steel, etc. Heterogeneous material components can achieve excellent performance combinations of different materials, greatly improve the flexibility of structural design, meet the functional and performance requirements of modern engineering structures, have higher technical and economic value, and have broad application prospects in various fields. Therefore, reliable connection of heterogeneous materials is particularly important.

However, when dissimilar materials are connected, due to the great differences in physical, chemical and mechanical properties between the dissimilar materials, the metallurgical compatibility during welding, the brittle compounds formed by the interface reaction and the difference in thermal expansion coefficient have a great influence on the joint performance. Therefore, the connection of dissimilar materials mainly has the following problems and difficulties:

1. When dissimilar materials are connected, the wettability is very different, and it is difficult to wet the two materials at the same time;

A conventional brazed joint is composed of a group of roughly parallel planes. The brazing filler metal flows in the weld formed by the two parallel planes. Due to the different wettability of the brazing filler metal to the two materials, as well as the different fluidity and adhesion after melting, the brazing filler metal often fails to contact the material on the difficult-to-wet side, resulting in defects and affecting product performance.

2. During the interface reaction process, due to the large differences in the chemical composition of heterogeneous materials, problems such as complex interface reactions and excessive generation of brittle interface compounds are likely to occur.

3. The difference in thermal expansion coefficients of dissimilar materials causes large residual stress at the interface, making it difficult to relieve stress in the joint and easily causing post-weld cracks.

The above problems will affect the performance of the brazed joint. It is of great significance to provide a brazed joint of heterogeneous materials and a preparation method thereof to achieve efficient and high-quality welding of heterogeneous materials.

In view of this, the present invention is proposed.

Summary of the invention

The first object of the present invention is to provide a brazed shortest drop line structure joint of heterogeneous materials, the brazing quality of the joint is high, the brazing seam defects are few, and the joint strength is high.

A brazed brazed brazing line structural joint of heterogeneous materials comprises a first brazing substrate and a second brazing substrate, wherein the wettability of the first brazing substrate to the brazing material is better than that of the second brazing substrate, and a brazed line groove is provided on the surface to be brazed of the second brazing substrate, wherein any of the brazed line grooves is composed of two groups of symmetrically arranged brazed line surfaces, and the inner surface curve of the brazed line surface conforms to the brazed line equation: x=r(θ-sinθ); y=r(1-cosθ).

The second object of the present invention is to provide a method for preparing a brazing brazing brazing joint of heterogeneous materials as described above, by machining a brazing brazing groove on the surface of a difficult-to-wet material, thereby increasing the flow rate of the brazing material on the surface of the difficult-to-wet material, the brazing rate and the uniformity of the residual stress distribution at the brazed joint are increased during brazing, thereby reducing brazing seam defects and improving joint strength.

The method for preparing the brazed shortest drop line structure joint of heterogeneous materials comprises the following steps:

S1. Processing the fastest drop line groove on the second brazing substrate to be brazed surface;

S2. Placing a brazing material between the to-be-brazed surfaces of the first brazing substrate and the second brazing substrate for brazing to obtain a product.

Compared with the prior art, the present invention has the following beneficial effects:

The present invention constructs a brazing line groove structure on the surface to be brazed of the second brazing substrate that is difficult to wet, so that the brazing filler metal covers the largest contact area in the shortest time during the flow process on the surface of the difficult-wetting material, thereby increasing the flow rate of the brazing filler metal on the surface of the difficult-wetting material, and avoiding the excessive flow rate of the brazing filler metal on the surface of the easy-wetting material, thereby preventing the brazing filler metal from covering the brazing filler metal surface and blocking the brazing filler metal to cause defects; the wettability of the brazing filler metal on the surface of the difficult-wetting material is improved, the uniformity of the residual stress at the brazing joint is improved, and the cracking problem caused by stress concentration is avoided; at the same time, the contact area between the difficult-wetting material and the brazing filler metal is increased, and the brazing rate on the surface of the difficult-wetting material is increased; the prepared heterogeneous material brazing joint has high brazing quality, few brazing fillet defects, and high connection strength.

BRIEF DESCRIPTION OF THE DRAWINGS

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

FIG1 is a schematic diagram of a first interface structure of a first brazing substrate and a second brazing substrate according to the present invention;

FIG2 is a schematic diagram of a second interface structure between a first brazing substrate and a second brazing substrate according to the present invention;

FIG3 is a schematic diagram of a third interface structure between the first brazing substrate and the second brazing substrate of the present invention;

FIG4 is a schematic structural diagram of a second brazing substrate surface to be welded in one embodiment of the present invention;

FIG5 is a schematic diagram of a grid pattern structure on a surface to be welded of a first brazing substrate in one embodiment of the present invention;

6 is a schematic diagram of the interface structure between the first brazing substrate and the second brazing substrate in Example 1 of the present invention;

7 is a schematic diagram of the interface structure between the first brazing substrate and the second brazing substrate in Example 4 of the present invention;

FIG8 is a physical electron microscope image of the bonding interface of the brazed joint in Example 6 of the present invention;

FIG9 is a physical electron microscope image of the bonding interface of the brazed joint in Example 7 of the present invention;

FIG10 is a physical electron microscope image of the bonding interface of the brazed joint in Example 8 of the present invention;

FIG. 11 is a schematic structural diagram of the bonding interface of the brazed joint in Example 9 of the present invention.

Reference numerals:

1-first brazing substrate; 11-grid pattern; 12-breastistic descent line protrusion; 2-second brazing substrate; 21-breastistic descent line groove; 211-storage tank.

DETAILED DESCRIPTION

The technical scheme of the present invention will be clearly and completely described below in conjunction with the accompanying drawings and specific embodiments, but it will be appreciated by those skilled in the art that the following described embodiments are part of embodiments of the present invention, rather than all embodiments, and are only used to illustrate the present invention, and should not be considered as limiting the scope of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work, all belong to the scope of protection of the present invention. If the specific conditions are not indicated in the embodiments, they are carried out according to the normal conditions or the conditions recommended by the manufacturer. If the manufacturer is not indicated in the reagents or instruments used, they are all conventional products that can be purchased commercially.

As shown in Figures 1, 2 and 3, the first aspect of the present invention provides a brazing brazing brazing line structural joint of heterogeneous materials, including a first brazing substrate 1 and a second brazing substrate 2, the first brazing substrate 1 has better wettability to the brazing material than the second brazing substrate 2, and a brazing line groove 21 is provided on the surface to be brazed of the second brazing substrate 2, and any brazing line groove 21 is composed of two groups of symmetrically arranged brazing line surfaces, and the inner surface curve of the brazing line surface conforms to the brazing line equation: x=r(θ-sinθ); y=r(1-cosθ).

As shown in FIG. 1 , the inner surface curve of the brazed line curve refers to the cross-sectional curve at the intersection of the plane perpendicular to the to-be-brazed surface of the second brazing substrate 2 and the extending direction of the brazed line groove 21 and the brazed line groove 21 .

The brazilian descent line refers to two fixed points A and B on the vertical plane, point A is not lower than point B, so that the particle slides from point A to point B the fastest curve (the particle is only affected by gravity and the initial velocity is zero). For brazed joints, the process of alloy droplets after the solid brazing material melts and flows along the brazing seam from one point to another also has a "bristlian descent line". The brazilian descent line can be expressed in the form of a parametric equation as x=r(θ-sinθ); y=r(1-cosθ), where r and θ are determined by the location of the end points. Therefore, for any two points without initial velocity and subject to a single force, there is a set of "bristlian descent lines".

A conventional brazed joint is composed of a group of roughly parallel planes, and the brazing filler metal flows in the weld formed by the two parallel planes. However, for heterogeneous joints, due to the different wettability of the brazing filler metal to the two materials, as well as the different fluidity and adhesion after melting, the brazing filler metal often fails to contact the material on the difficult-to-wet side, resulting in defects and affecting product performance.

The present invention provides a brazing line groove structure on the surface to be welded of the second brazing substrate which is difficult to wet, and adjusts the flow rate of the solder in the brazing seam, so as to improve the wettability of the solder on the surface of the difficult-wetting material, improve the uniformity of the residual stress at the brazing joint, and avoid cracks caused by stress concentration; by constructing the brazing line structure on the surface of the difficult-wetting material, the solder can cover the largest contact area in the shortest time when flowing on the surface of the difficult-wetting material, increase the flow rate of the solder on the surface of the difficult-wetting material, and avoid the solder flowing too fast on the surface of the easy-wetting material, so as to avoid the soldering seam being blocked by the surface of the easy-wetting material and causing defects; at the same time, the contact area between the difficult-wetting material and the solder can be increased, and the brazing rate on the surface of the difficult-wetting material can be increased, so as to improve the performance of the brazing joint of heterogeneous materials.

The heterogeneous material brazing joint provided by the present invention has the advantages of high brazing quality, few brazing seam defects, high connection strength, etc., and is of great significance to the application of heterogeneous material components.

As shown in Figure 4, in some specific embodiments of the present invention, a plurality of parallel brazed line grooves 21 are provided on the surface to be brazed of the second brazing substrate 2. When the total length of the brazing seam remains unchanged, increasing the number of brazed line grooves 21 can reduce the brazing material consumption while maintaining the contact area between the brazing material and the difficult-to-wet material unchanged.

In some preferred embodiments, a plurality of brazed line grooves 21 are evenly distributed on the to-be-brazed surface of the second brazing substrate 2 to improve the uniformity of the brazing material and stress distribution.

In some substrate embodiments of the present invention, the vertical distance H and horizontal distance L between the starting point and the ending point of the brazilien line on the inner surface of the brazilien line groove 21 and the size d of the solder agglomerate particles when the solder is melted satisfy the following relationship: H≥8d, L≥8d.

Taking the starting point as the origin, the position of the end point can be determined according to the vertical distance H and the horizontal distance L between the starting point and the end point of the brazing line, and the r and θ values can be obtained. The vertical distance H and the horizontal distance L are not less than 8 times the size of the agglomerate particles when the solder is melted, which is helpful to improve the connection strength of the brazed joint. If the brazing line groove 21 is too small, the effect of improving the connection strength is not obvious, but the larger the better. If the size of the brazing line groove 21 is too large, the amount of solder used will increase, which will lead to increased costs. In one embodiment of the present invention, In some preferred embodiments, the vertical distance H and the horizontal distance L satisfy: 8d≤H≤15d, 8d≤L≤15d. Within this range, the performance of the joint is good and not too much solder is wasted. For example, H can be any point value among 8d, 9d, 10d, 11d, 12d, 13d, 14d, and 15d, or a range value consisting of any two point values. L can be any point value among 8d, 9d, 10d, 11d, 12d, 13d, 14d, and 15d, or a range value consisting of any two point values.

In some specific embodiments of the present invention, a grid pattern 11 is provided on the surface to be brazed of the first brazing substrate 1;

Alternatively, a brazing line protrusion 12 is provided on the surface to be brazed of the first brazing substrate 1, and the brazing line protrusion 12 is matched with the brazing line groove 21 to form a meshing structure.

That is, in some embodiments of the present invention, the geometric morphology of the connection interface of the heterogeneous material brazing joint can be: the surface to be brazed of the first brazing substrate 1 is a plane without processing, and the surface to be brazed of the second brazing substrate 2 is provided with a brazed line groove 21 (as shown in FIG3); or the surface to be brazed of the first brazing substrate 1 is a grid pattern 11, and the surface to be brazed of the second brazing substrate 2 is provided with a brazed line groove 21 (as shown in FIG1); or the surface to be brazed of the second brazing substrate 2 is provided with a brazed line groove 21, and the surface to be brazed of the first brazing substrate 1 is provided with a brazed line protrusion 12 meshing with the brazed line groove 21 (FIG. 2).

As shown in FIG. 5 , in some specific embodiments of the present invention, the grid pattern 11 on the surface of the first brazing substrate 1 is composed of crisscrossing grooves.

When the surface to be brazed of the first brazing substrate 1 is provided with a grid pattern 11, the grid pattern 11 can be used to block the flow rate of the brazing material on the surface of the easily wettable material, while the brazing line groove 21 can increase the flow rate of the brazing material on the surface of the difficultly wettable material. The two cooperate to achieve the purpose of simultaneously covering the two surfaces to be brazed with the brazing material, thereby reducing the defects of the brazing seam. The grooves in the grid pattern also have the function of storing excess brazing material. The grid pattern can also increase the roughness of the material surface, increase the adhesion of the material surface to the brazing material, and increase the contact area between the brazing material and the material. This structure can significantly improve the strength of the brazing joint of heterogeneous materials.

When the brazing surface of the first brazing substrate 1 is provided with the brazed line protrusion 12 meshing with the brazed line groove 21, the brazed line structure at the surface of the difficult-to-wet material is concave, the wetting angle is increased, and the wettability is improved. The brazed line structure at the surface of the easy-to-wet material is convex, the wetting angle is reduced, and the wetting speed is reduced. Through this structure, a single brazing material flow channel is formed at the joint, the gas is discharged spontaneously, the looseness is greatly reduced, and the impurities are arranged in order to the outside of the brazing seam, which can improve the joint strength. In addition, compared with the surface of the easy-to-wet material being a plane or a grid pattern, this structure can reduce the amount of brazing material, shorten the brazing time, and improve the brazing efficiency.

In some specific embodiments of the present invention, the surface structures of the first brazing substrate 1 and the second brazing substrate 2 are micrometer-scale geometric morphologies.

In some specific embodiments of the present invention, a storage groove 211 is provided at the intersection of two symmetrically arranged brazing line surfaces in the brazing line groove 21, which is used to store excess solder, while increasing the contact area between the material and the solder and improving the joint strength. The depth of the storage groove 211 is ≥r/5, and the width of the storage groove 211 is ≥r/5.

If the storage tank 211 is too small, the effect of improving the shear strength is not obvious. If it is too large, it will lead to a large amount of solder used, a long brazing time, low efficiency and high cost. In some preferred embodiments of the present invention, the depth of the storage tank 211 is r/5-3r, for example, r/5, r/4, r/2, r, 2r, 3r, etc., and the width of the storage tank 211 is r/5-3r, for example, r/5, r/4, r/2, r, 2r, 3r, etc.

In some specific embodiments of the present invention, in the surface structure of the to-be-welded surface of the second brazing substrate 2, each turning point is transitioned by an arc, so that the brazing material flows smoothly. By forming various arches (breastistic descent line grooves) and arc structures on the surface, the residual stress generated in the brazing process can be evenly distributed, thereby avoiding cracking problems caused by stress concentration.

In some specific embodiments of the present invention, the first brazing substrate 1 includes any one of YG8 and TC4;

And/or, the second brazing substrate 2 includes any one of PCBN and alumina ceramics.

In some specific embodiments of the present invention, the first brazing substrate 1 is YG8, and the second brazing substrate 2 is PCBN.

In some other embodiments of the present invention, the first brazing substrate 1 is TC4, and the second brazing substrate 2 is alumina ceramic.

A second aspect of the present invention provides a method for preparing a heterogeneous material brazing fastest drop line structure joint according to any one of the aforementioned embodiments, comprising the following steps:

S1. Processing the fastest drop line groove on the second brazing substrate to be brazed surface;

S2. Placing a brazing material between the to-be-brazed surfaces of the first brazing substrate and the second brazing substrate for brazing to obtain a product.

The method of the present invention increases the flow rate of the solder on the surface of the difficult-to-wet material by machining the brazing line groove on the surface to be brazed of the difficult-to-wet second brazing substrate, avoids the defects caused by the solder flowing too fast on the surface of the easy-to-wet material, increases the contact area between the difficult-to-wet material and the solder, and improves the brazing rate of the material surface. The method can significantly improve the brazing quality of the brazing joint of heterogeneous materials and improve the joint strength.

In some specific embodiments of the present invention, step S1 further includes a step of processing grid patterns or brazed line protrusions on the surface to be brazed of the first brazing substrate.

Processing grid patterns on the surface to be brazed of the first brazing substrate can reduce the flow rate of the brazing material on the surface of the easily wettable material and reduce the difference in the flow rate of the brazing material on the surfaces of the two materials, so that the brazing material can cover the two materials at the same time, reduce brazing seam defects, and at the same time increase the contact area between the brazing material and the brazing substrate and the roughness of the brazing substrate, increase the brazing rate, and improve the joint strength.

Processing a brazing line protrusion on the surface of the first brazing substrate to mesh with the brazing line groove can also improve the joint strength. Although the grid texture is better in improving the joint strength, compared with the grid texture structure, the brazing line protrusion can reduce the amount of brazing material, shorten the brazing time, and improve the brazing efficiency.

In some specific embodiments of the present invention, in step S1, the processing method of the to-be-brazed surfaces of the first brazing substrate and the second brazing substrate includes a slow-wire cutting method and/or a short-pulse laser method.

In some specific embodiments of the present invention, before step S1, the step of pretreating the surfaces to be brazed of the first brazing substrate and the second brazing substrate is also included, and the pretreatment method includes: sandblasting and/or sandpaper polishing the surfaces to be brazed, ultrasonic cleaning, and drying.

In some specific embodiments of the present invention, ultrasonic cleaning is carried out in acetone, and the ultrasonic cleaning time is 10-20 min, for example, any point value among 10 min, 12 min, 14 min, 15 min, 16 min, 18 min, 20 min, or a range value consisting of any two point values.

In some specific embodiments of the present invention, the brazing method includes vacuum brazing and/or induction brazing.

In some specific embodiments of the present invention, the first brazing substrate is YG8, the second brazing substrate is PCBN, the brazing filler metal is CuSnTi, the brazing temperature is 800-1000°C, for example, any point value among 800°C, 850°C, 900°C, 950°C, 1000°C, or a range value consisting of any two point values, and the heating rate is 1-20°C/min, for example, any point 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, or 20°C/min, or a range value consisting of any two point values.

In some specific embodiments of the present invention, the first brazing substrate is TC4, the second brazing substrate is alumina ceramic, the brazing filler metal is TiZrCuNi, the brazing temperature is 950-1000°C, for example, any point value among 950°C, 980°C, 1000°C or a range value composed of any two point values, and the heating rate is 1-20°C/min, for example, any point 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, 20°C/min or a range value composed of any two point values.

The following is a detailed description of some embodiments of the present invention in conjunction with specific examples. The raw materials used in the examples can be purchased from the market unless otherwise specified.

Example 1

A slow-feed wire cutting machine was used to manufacture the geometric morphology of the present invention on a PCBN/YG8 brazed joint, and the interface structure was shown in FIG6 . CuSnTi brazing filler metal was used for brazing.

Step 1: Pre-treat the surfaces to be welded of PCBN and YG8 by sandblasting, then ultrasonically clean them in acetone for 15 minutes, and finally air dry them naturally.

Step 2: Use a slow-feed wire cutting machine to process the PCBN surface to be welded, and import the brazilian curve formula described in the present invention into the CAD drawing software. According to the literature, the size of the particles of commercial CuSnTi solder agglomerated when the solder is melted is about 2-3μm. Take the starting point θ as 0°, the ending point θ angle as 120°, and the r value as 20μm. At this time, the vertical distance between the starting point and the ending point is 30μm, and the horizontal distance between the starting point and the ending point is 25μm. Within the range of this brazilian curve, the particles formed when the solder agglomerates can be regarded as particles, and the left and right sections of the brazilian curve surfaces are connected by a storage tank with a depth of 20μm and a width of 20μm, which is automatically processed by the equipment according to the CAD drawings and programs.

Step 3: Use a slow-feed wire cutting machine to process the YG8 surface to be welded. First, cut grooves with a width of 20 μm and a depth of 20 μm every 20 μm horizontally. Then rotate the YG8 sample 90° and cut grooves with a width of 20 μm and a depth of 20 μm every 20 μm vertically to form a grid pattern.

Step 4: Pre-coat CuSnTi brazing filler metal between the surfaces of the two materials to be welded, place them in a vacuum brazing furnace, control the vacuum degree to 1×10 ^-3 Pa, heat to 900°C at a heating rate of 10°C/min, keep warm for 2 minutes, then cool to 400°C at a rate of 10°C/s, and then cool with the furnace to obtain a brazed joint.

Step 5: After the brazing is completed, a universal mechanical testing machine is used to test the shear strength of the brazed joint. The results show that the shear strength of the welded joint manufactured using the structure of this embodiment reaches 269 MPa, which is 83% higher than that of comparative example 1.

Example 2

The difference between Example 2 and Example 1 is that in order to achieve a finer processing size, a short pulse laser is used to process the PCBN surface to be welded, and the process parameters are laser power 300W, frequency 1000KHz, scanning speed 40mm/s, and the size of the processed storage tank is depth × width = 4 × 4μm. The strength of the welded joint at this time is 207MPa, which is 41% higher than that of Comparative Example 1 and 23% lower than that of Example 1. The optimal brazing time at this time is 2min, which remains unchanged compared with Example 1, and the consumption of brazing material is reduced by 10% compared with Example 1.

Example 3

The difference between Example 3 and Example 1 is that the size of the processed storage tank is depth × width = 60 × 60 μm. The strength of the welded joint is 298 MPa, which is 10.8% higher than that of Example 1. However, the welding time is 4 minutes, which is 100% longer, and the consumption of brazing material is increased by 82%.

Example 4

Pulse laser and wire cutting machine were used to manufacture the geometric morphology of the present invention at Al ₂ O ₃ and TC4 brazing joints, respectively. The interface structure is shown in FIG. 7 . Commercial TiZrCuNi brazing filler metal was used for brazing.

Step 1: Pre-treat the surfaces to be welded of alumina ceramic and TC4 titanium alloy by grinding and polishing the surfaces to be welded with sandpaper, then ultrasonically clean them in acetone for 15 minutes, and finally air dry them naturally.

Step 2: Use pulse laser and wire cutting machine to process _Al2O3 and _TC4 welding surfaces respectively, and import the brachistocentre formula of the present invention into CAD drawing software. Take the starting point θ as 0°, the ending point θ as 180°, and the r value as 30μm. At this time, the vertical distance between the starting point and the ending point of the brachistocentre is 60μm, and the horizontal distance is 94.25μm. After generating the brachistocentre on the left, generate the brachistocentre on the right by mirroring, and the interval between every two closed _{brachistocentre} segments is 30μm. Process the raised area on the TC4 side of the easily wettable material, and process the concave welding surface on the _Al2O3 side, and the equipment will automatically process according to the CAD drawings and programs.

Step 3: Pre-coat TiZrCuNi solder between the surfaces of the two materials to be welded, put them into a vacuum brazing furnace, control the vacuum degree to 1×10 ^-3 Pa, heat to 950°C at a heating rate of 10°C/min, keep warm for 15 minutes, then cool to 300°C at a rate of 10°C/s, and then cool with the furnace to obtain a brazed joint.

Step 4: After the brazing is completed, a universal mechanical testing machine is used to test the shear strength of the obtained joint. The results show that the shear strength of the welded joint manufactured using the structure of this embodiment reaches 60 MPa, which is 50% higher than that of the welded joint without special treatment.

Example 5

The difference between Example 5 and Example 1 is that the shape of the joint interface is as shown in Figure 3, the surface to be brazed of YG8 is not processed, and the surface to be brazed of PCBN is processed with a fastest drop line groove, and the other parameters are the same as Example 1. The shear strength of the prepared brazed joint is 173 MPa, which is 17.7% higher than that of Comparative Example 1 and 35.7% lower than that of Example 1.

Example 6

The difference between Example 6 and Example 1 is that the shape of the joint interface is as shown in Figure 2, the actual picture is shown in Figure 8, the surface to be brazed of YG8 is machined with a brazed line protrusion, and the surface to be brazed of PCBN is machined with a brazed line groove, and the other parameters are the same as Example 1. The shear strength of the prepared brazed joint is 192 MPa, which is 30.6% higher than that of Comparative Example 1 and 28.6% lower than that of Example 1, but the brazing time is 1 min, which is 100% faster than that of Example 1, and the amount of brazing material is saved by 72% compared with Example 1.

Example 7

The difference between Example 7 and Example 6 is that an additional 20 μm×20 μm material storage groove is processed in the fastest drop line groove of the PCBN surface to be brazed, as shown in Figure 9, and the other parameters are the same as Example 6. The shear strength of the prepared brazed joint is 213 MPa, which is 11% higher than that of Example 6. The brazing time is 1.2 min, which is 20% longer than that of Example 6, and the amount of brazing material is increased by 14% compared with Example 6.

Example 8

The difference between Example 8 and Example 1 is that the material storage tank is not machined in the groove of the fastest drop line machined on the surface to be brazed of PCBN, as shown in Figure 10, and the other parameters are the same as Example 1. The shear strength of the prepared brazed joint is 247MPa, which is 8% lower than that of Example 1. The brazing time is 1.6min, which is 20% shorter than that of Example 1, and the amount of brazing material is reduced by 20% compared with Example 1.

Example 9

The geometric morphology of the present invention was manufactured on the end surface of a stainless steel tube with an inner diameter of 30 mm and a wall thickness of 6 mm and a copper tube with a wall thickness of 5 mm using a CNC lathe. Induction heating was used for welding, as shown in FIG11 .

Step 1: According to the copper tube wall thickness of 5mm, determine the brachistodes curve size. Take the starting point θ as 0°, the ending point θ as 180°, and the r value as 1.5mm. At this time, the horizontal distance between the starting point and the ending point of the brachistodes curve is 4.71mm, and the vertical distance is 3mm.

Step 2: Use a CNC machine tool to take a point on the outer diameter of the stainless steel pipe as the starting point, and rotate and turn a concave surface in the direction of the inner hole according to the fastest descent curve confirmed in step 1, and turn a horizontal platform in the direction of the inner hole at the end point of the curve.

Step 3: Use a CNC machine tool to start from a point on the outer diameter of the copper tube. In the peripheral direction, use the fastest descent curve confirmed in step 1 to rotate and turn a convex surface, and turn a horizontal platform toward the inner hole.

Step 4: Place the stainless steel tube at the bottom with the concave surface facing upwards and the copper tube with the convex surface facing downwards, and connect the two tubes. Sleeve the flux-cored silver solder ring (flux-cored silver solder ring brand: Zhengzhou Machinery Research Institute Co., Ltd., brand: Ag25CuZn) on the joint.

Step 5: Use high-frequency induction heating equipment for heating with a heating power of 20KW. Place the two tubes described in step 4 in the induction heating coil for heating. When the heating time is 4s, solder can be observed to flow out from the inside of the brazing seam, indicating that brazing has been completed.

Comparative Example 1

The difference from Example 1 is that in Example 1, no additional processing is performed on the surfaces to be welded of PCBN and YG8, and only Step 1, Step 4 and Step 5 of Example 1 are performed. After brazing, the joint strength is tested, and the shear strength is 147 MPa.

Comparative Example 2

The difference from Example 4 is that Comparative Example 2 does not perform additional processing on the to-be-welded surfaces of Al ₂ O ₃ and TC4, and only consists of Step 1, Step 3, and Step 4 of Example 4. After brazing, the joint strength is tested, and the shear strength is 40 MPa.

Comparative Example 3

The difference between Comparative Example 3 and Example 9 is that the brazing seam joint surface of the stainless steel tube and the copper tube end surface in Comparative Example 3 is a plane, and the other conditions are the same as Example 9. The brazing time is 7s, which is 75% slower than that in Example 1. The brazing seam structure with the brazing line structure can significantly shorten the brazing time and improve the brazing efficiency.

Although the present invention has been illustrated and described with specific embodiments, it should be appreciated that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Those skilled in the art should understand that the technical solutions described in the above embodiments may be modified, or some or all of the technical features thereof may be replaced by equivalents without departing from the spirit and scope of the present invention. However, these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention. Therefore, this means that all such replacements and modifications within the scope of the present invention are included in the appended claims.

Claims (10)

1. A brazed brazed brazed joint of heterogeneous materials, characterized in that it comprises a first brazing substrate and a second brazing substrate, wherein the wettability of the first brazing substrate to the brazing material is better than that of the second brazing substrate, and a brazed brazed groove is provided on the surface to be brazed of the second brazing substrate, and any of the brazed brazed grooves is composed of two groups of symmetrically arranged brazed brazed surfaces, and the inner surface curve of the brazed brazed surface conforms to the brazed brazed equation: x=r(θ-sinθ), y=r(1-cosθ); A material storage groove is provided at the intersection of two symmetrically arranged brachistocentric curved surfaces in the brachistocentric groove, the depth of the material storage groove is ≥r/5, and the width of the material storage groove is ≥r/5. 2. The brazed brazed brazing fastest drop line structural joint of heterogeneous materials according to claim 1 is characterized in that the vertical distance H and the horizontal distance L between the starting point and the ending point of the fastest drop line on the inner surface of the fastest drop line groove and the size d of the agglomerated particles of the solder when the solder is melted satisfy the following relationship: H≥8d, L≥8d. 3. The brazing fastest drop line structural joint of heterogeneous materials according to claim 1, characterized in that a grid pattern is provided on the surface to be brazed of the first brazing substrate; Alternatively, a brazing line protrusion is provided on the surface to be brazed of the first brazing substrate, and the brazing line protrusion is matched with the brazing line groove to form an engaging structure. 4. The brazing fastest drop line structural joint of heterogeneous materials according to claim 1 is characterized in that each turning point in the surface structure of the to-be-welded surface of the second brazing substrate is transitioned by an arc. 5. The brazing fastest drop line structural joint of heterogeneous materials according to claim 1, characterized in that the first brazing base material comprises any one of YG8 and TC4; And/or, the second brazing substrate includes any one of PCBN and alumina ceramics. 6. The method for preparing the brazed shortest drop line structural joint of heterogeneous materials according to any one of claims 1 to 5, characterized in that it comprises the following steps: S1. Processing the fastest drop line groove on the second brazing substrate to be brazed surface; S2. Placing a brazing material between the to-be-brazed surfaces of the first brazing substrate and the second brazing substrate for brazing to obtain a product. 7. The method for preparing a brazed brazed brazed brazed joint of heterogeneous materials according to claim 6, characterized in that in step S1, it also includes a step of processing a grid pattern or a brazed brazed protrusion on the surface to be brazed of the first brazing substrate. 8. The method for preparing a brazed shortest drop line structural joint of heterogeneous materials according to claim 7, characterized in that in step S1, the processing method includes a slow-wire cutting method and/or a short-pulse laser method. 9. The method for preparing a brazed shortest drop line structural joint of heterogeneous materials according to claim 6 is characterized in that, before step S1, it also includes a step of pretreating the surfaces to be brazed of the first brazing substrate and the second brazing substrate, and the pretreatment method includes: sandblasting and/or sandpaper polishing the surfaces to be brazed, ultrasonic cleaning, and drying. 10. The method for preparing a brazed shortest drop line structural joint of heterogeneous materials according to claim 6, characterized in that in step S2, the brazing method includes vacuum brazing and/or induction brazing.