Brazed joint, mixed brazing filler metal of brazed joint and brazed connection method of brazed joint

Abstract

The invention provides a brazed joint, mixed brazing filler metal of the brazed joint and a brazed connection method, and relates to the technical field of braze welding. The mixed brazing filler metal is used for being filled between the first arc to-be-welded face and the second arc to-be-welded face, the mixed brazing filler metal is mixed brazing filler metal AXB100-X composed of brazing filler metal A and brazing filler metal B, X is the percentage of the brazing filler metal A in the mixed brazing filler metal AXB100-X and is larger than or equal to 10 and smaller than or equal to 100, and the melting point temperature of the brazing filler metal A is smaller than that of the brazing filler metal B; the mixed brazing filler metal AXB100-X is divided into a plurality of groups between the arc to-be-welded surfaces, the components of the mixed brazing filler metal AXB100-X in the same group are the same, and the X values of the mixed brazing filler metal AXB100-X from the group of the lowest gravity point to the group of the highest gravity point are sequentially reduced. And the phase remelting temperature in the welding joint is effectively improved, gapless combination between the two arc to-be-welded surfaces is finally achieved, the welding rate is improved, and the obtained brazing joint is better in strength and higher in reliability.

Description

Technical Field

[0001] The invention relates to the technical field of brazing, in particular to a brazing joint and a mixed brazing material and a brazing connection method. Background Art

[0002] At present, the connection of arc surfaces to be welded is widely used in industrial production and other aspects, such as air ducts, shells, heat pipes and other components. Most of these components serve in high temperature and corrosion resistant environments, so there are extremely high requirements for the reliability and stability of arc surface connection joints. The main traditional method used for arc section welding is brazing, that is, placing a brazing material lower than the melting point of the base material between the two arc surfaces, heating the temperature until the brazing material melts, and using the molten liquid brazing material to fill the gap between the arc surfaces to connect the two arc surfaces. However, when the temperature is heated to the point where the brazing material melts, the brazing material becomes molten liquid, such as Figure 1 As shown in (a), since the curvature and radian of the arc surfaces of the two objects are not exactly the same, the gap in the middle is also not exactly the same. The liquid solder will accumulate at the bottom in the direction of gravity. The gap between the two arc surfaces is not completely filled by the molten solder. After cooling, there will still be a large gap on both sides. Figure 1 As shown in (b), the molten solder alone is not sufficient to completely achieve a reliable connection between the two arc surfaces. The interface between the two arc surfaces is not completely filled, resulting in problems such as low service temperature of the welding material, poor bonding and low welding rate. Summary of the invention

[0003] The problem solved by the invention is how to solve the problem of low service temperature of welding materials, poor bonding and low welding rate caused by a large gap between two arc surfaces after arc special-shaped cross-section welding.

[0004] In order to solve the above problems, the present invention provides a brazing joint, a mixed brazing material and a brazing connection method.

[0005] In a first aspect, the present invention provides a mixed solder for filling between a first arc surface to be welded and a second arc surface to be welded, wherein the mixed solder is a mixed solder A composed of solder A and solder B. X B 100-X , where X is the solder A in the mixed solder A X B 100-X The percentage of the mixed solder A is 10≤X≤100, and the melting point of the solder A is lower than the melting point of the solder B. X B 100-X The arc surfaces to be welded are divided into several groups, and the brazing filler metal A is mixed in the same group. X B 100-X The composition is the same, mixed solder A X B 100-X The X values ​​decrease from the group with the lowest gravity point to the group with the highest gravity point.

[0006] Optionally, the mixed filler metal A X B 100-X The X value decreases in equal difference from the group at the lowest point of gravity to the group at the highest point of gravity.

[0007] Optionally, the filler metal A is a silver-based filler metal, a copper-based filler metal, a nickel-based filler metal or a titanium-based filler metal; the filler metal B is a nickel elemental filler metal, a chromium elemental filler metal, a niobium elemental filler metal, a molybdenum elemental filler metal, a palladium elemental filler metal or a nickel-chromium alloy filler metal.

[0008] Optionally, the material of the first arc surface to be welded is stainless steel, carbon steel, aluminum, aluminum alloy, copper, copper alloy, magnesium, magnesium alloy, nickel, nickel alloy or ceramic, and the material of the second arc surface to be welded is stainless steel, carbon steel, aluminum, aluminum alloy, copper, copper alloy, magnesium, magnesium alloy, nickel, nickel alloy or ceramic.

[0009] In a second aspect, the present invention provides a brazing connection method using the mixed filler metal as described in any one of the above, including the following steps:

[0010] Take several groups of mixed filler metals A with different X values X B 100-X Mix with terpineol and arrange them in sequence between the first arc surface to be welded and the second arc surface to be welded, where the mixed filler metal A X B 100-X The X value gradually becomes smaller from the group at the lowest point of gravity to the group at the highest point of gravity;

[0011] Heat to a temperature between the melting point temperature of the filler metal A and the melting point temperature of the filler metal B, and perform vacuum brazing at this temperature to obtain a brazed joint.

[0012] Optionally, it further includes: arranging a foil made of the filler metal B between the first arc surface to be welded and the second arc surface to be welded, and the foil is wrapped by the mixed filler metal A X B 100-X Wrapped.

[0013] Optionally, before the step of heating to a temperature between the melting point temperature of the filler metal A and the melting point temperature of the filler metal B, it further includes: heating to above 400 °C and holding for more than 10 minutes to remove terpineol.

[0014] Optionally, the time of vacuum brazing is 15 - 60 minutes.

[0015] Optionally, after the mixed filler metal A X B 100-X Is mixed with terpineol and arranged between the first arc surface to be welded and the second arc surface to be welded, the following steps are further included: applying a pressure of 0.05 MPa to 0.1 MPa to the first base metal to be welded with the first arc surface to be welded and the second base metal to be welded with the second arc surface to be welded by using a die tooling.

[0016] In a third aspect, the present invention provides a brazed joint, which is made by using the brazing connection method described in any one of the above.

[0017] The beneficial effects of a brazed joint, a hybrid filler metal thereof and a brazing connection method of the present invention are as follows: The filler metal A and the filler metal B form a variable-component hybrid filler metal A X B 100-X , the melting point temperature of the filler metal A is lower than that of the filler metal B, the connection temperature is between the melting point temperature of the filler metal A and the melting point temperature of the filler metal B. During the brazing connection process, after the temperature is raised to the connection temperature, the filler metal A melts, and the filler metal B remains solid. Immediately, the filler metal A undergoes metallurgical bonding with the base metal to be welded and the unfused filler metal B, ensuring that there is always solid filling within the circular arc surface gap between the first circular arc surface to be welded and the second circular arc surface to be welded, avoiding insufficient gap welding caused by the molten filler metal piling up downward due to gravity and leaving large voids at the points with higher gravity unfilled with the filler metal; Since the viscosity of the molten filler metal is related to its melting point, at the same temperature, the lower the melting point, the smaller the viscosity and the better the fluidity, and the higher the melting point, the greater the viscosity, that is, A X B 100-X As the hybrid filler metal rises in the gravity direction with different groups, along with the decrease in the content of the filler metal A and the increase in the content of the filler metal B, the viscosity of the hybrid filler metal during melting gradually increases. The viscosity of the hybrid filler metal in the group at the highest point of gravity is the largest, and the viscosity of the hybrid filler metal in the group at the lowest point of gravity is the smallest, slowing down the tendency of the hybrid filler metal to flow downward along the circular arc surface gap; Moreover, during the brazing process, the low-melting-point filler metal A component undergoes solid solution diffusion towards the high-melting-point filler metal B component. With the increase in the content of the filler metal B, in-situ alloying in each zone is achieved through solid solution diffusion with the molten filler metal A, effectively increasing the remelting temperature of the phases within the welded joint, ultimately achieving gapless bonding between the two circular arc surfaces to be welded, improving the welding rate, obtaining a brazed joint with better strength, realizing "low-temperature connection and high-temperature service", and having higher reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 (a) is a schematic diagram of the gap between the circular arc surfaces to be welded in the background art;

[0019] Figure 1 (b) is a schematic diagram of the circular arc surface gap of the welded joint brazed with molten liquid filler metal in the background art;

[0020] Figure 2 is a schematic diagram of the distribution of the hybrid filler metal A X B 100-X of the embodiment of the present invention between the circular arc surfaces to be welded;

[0021] Figure 3 is a schematic optical microscope diagram of the interface of the brazed joint of Example 1;

[0022] Figure 4 The mixed solder A of Example 2 X B 100-X Schematic diagram of the distribution between the arc surfaces to be soldered

[0023] Figure 5 The mixed solder A of Example 3 X B 100-X Schematic diagram of the distribution of the foil made of solder A and solder B between the arc surfaces to be soldered Detailed implementation manners

[0024] To make the above objects, features and advantages of the present invention more obvious and understandable, the following will describe in detail the specific embodiments of the present invention with reference to the accompanying drawings. Although some embodiments of the present invention are shown in the drawings, it should be understood that the present invention can be implemented in various forms and should not be construed as limited to the embodiments described herein. On the contrary, these embodiments are provided to more thoroughly and completely understand the present invention. It should be understood that the drawings and embodiments of the present invention are only for exemplary purposes and are not used to limit the protection scope of the present invention.

[0025] Unless otherwise defined, all technical and scientific terms used in the present invention have the same meaning as commonly understood by those skilled in the technical field to which the present invention belongs. The terms used in the description of the present invention in the specification are only for the purpose of describing specific implementation manners and are not intended to limit the present invention;

[0026] The term "including" and its variants used herein are open-ended, that is, "including but not limited to"; the term "based on" is "at least partially based on"; the term "one embodiment" means "at least one embodiment"; the term "another embodiment" means "at least one additional embodiment"; the term "some embodiments" means "at least some embodiments"; the term "optionally" means "optional embodiments". The relevant definitions of other terms will be given in the following description. It should be noted that the concepts of "first", "second", etc. mentioned in the present invention are used to distinguish different objects and are not used to describe a specific order or primary-secondary relationship. In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present application, unless otherwise stated, the meaning of "a plurality" is two or more.

[0027] This embodiment provides a brazed joint, its mixed solder and a brazing connection method.

[0028] As Figure 2As shown in the figure, a composite solder provided by an embodiment of the present invention is used to fill between a first arc surface to be welded and a second arc surface to be welded. The composite solder is a composite solder A composed of solder A and solder B X B 100-X , where X is the percentage of solder A in the composite solder A X B 100-X , and 10 ≤ X ≤ 100. The melting point temperature of solder A is lower than that of solder B; the composite solder A X B 100-X is divided into several groups between the arc surfaces to be welded. The composition of the composite solder A X B 100-X in the same group is the same. The X value of the composite solder A X B 100-X decreases sequentially from the group at the lowest point of gravity to the group at the highest point of gravity.

[0029] In this embodiment, solder A and solder B form a variable-composition composite solder A X B 100-X , the melting point temperature of solder A is lower than that of solder B, and the connection temperature is between the melting point temperature of solder A and the melting point temperature of solder B. During the brazing connection process, after the temperature is raised to the connection temperature, solder A melts, and solder B remains solid. Immediately, solder A undergoes metallurgical bonding with the base metal to be welded and the unmelted solder B, ensuring that there is always solid filling in the arc surface gap between the first arc surface to be welded and the second arc surface to be welded, and avoiding insufficient gap welding caused by the molten solder piling up downward due to gravity and leaving large voids at the higher gravity points unfilled with solder; since the viscosity of the molten solder is related to its melting point, at the same temperature, the lower the melting point, the smaller the viscosity and the better the fluidity, and the higher the melting point, the greater the viscosity. That is, A X B 100-X As the composite solder is lifted in the direction of gravity with the group, along with the decrease in the content of solder A and the increase in the content of solder B, the viscosity of the composite solder during melting gradually increases. The viscosity of the composite solder in the group at the highest point of gravity is the largest, and the viscosity of the composite solder in the group at the lowest point of gravity is the smallest, slowing down the tendency of the composite solder to flow downward along the arc surface gap; moreover, during the brazing process, the low-melting-point solder A component undergoes solid solution diffusion to the high-melting-point solder B component. With the increase in the content of solder B, in-situ alloying is achieved zone by zone through solid solution diffusion with the molten solder A, effectively increasing the remelting temperature of the phases in the welded joint, ultimately achieving gapless bonding between the two arc surfaces to be welded, improving the welding rate, obtaining a better strength of the brazed joint, realizing "low-temperature connection and high-temperature service", and having higher reliability.

[0030] Optionally, the X value of the composite solder A X B 100-X decreases in an equal difference from the group at the lowest point of gravity to the group at the highest point of gravity.

[0031] Specifically, as Figure 2 shown, the mixed filler metal A X B 100-X is divided into four groups between the arc surfaces to be welded. The composition of the mixed filler metal A X B 100-X in the same group is the same. The mixed filler metal A 100 B0 of the group at the lowest gravity point, and the groups successively upward are the mixed filler metal A 70 B 30 and the mixed filler metal A 40 B 70 , until the mixed filler metal A 10 B 90 of the group at the highest gravity point. The X value decreases in equal difference.

[0032] Optionally, the filler metal A is a silver-based filler metal, a copper-based filler metal, a nickel-based filler metal or a titanium-based filler metal; the filler metal B is a nickel elemental filler metal, a chromium elemental filler metal, a niobium elemental filler metal, a molybdenum elemental filler metal, a palladium elemental filler metal or a nickel-chromium alloy filler metal.

[0033] In this optional embodiment, the filler metal A is a low melting point filler metal, and the filler metal B is a high melting point filler metal. Specifically, the filler metal A is AgCuTi, CuSn, BNi-2, BNi-5, Ti-Cu alloy, Ni-Ti alloy or TiZrNiCu, etc., and the filler metal B is a transition group elemental element such as Ni, Cr, Nb, Mo, Pd or a high melting point alloy such as Ni-Cr, high entropy alloy.

[0034] Optionally, the material of the first arc surface to be welded is stainless steel, carbon steel, aluminum, aluminum alloy, copper, copper alloy, magnesium, magnesium alloy, nickel, nickel alloy or ceramic, and the material of the second arc surface to be welded is stainless steel, carbon steel, aluminum, aluminum alloy, copper, copper alloy, magnesium, magnesium alloy, nickel, nickel alloy or ceramic.

[0035] In this optional embodiment, the first arc surface to be welded and the second arc surface to be welded can be the same material or different materials.

[0036] A brazing connection method provided by an embodiment of the present invention uses the mixed filler metal described in any one of the above, and includes the following steps:

[0037] Take several groups of mixed filler metals A X B 100-X mixed with terpineol and arrange them successively between the first arc surface to be welded and the second arc surface to be welded, wherein the X value of the mixed filler metal A X B 100-X decreases successively from the group at the lowest gravity point to the group at the highest gravity point;

[0038] Heat to a temperature between the melting point temperature of filler metal A and the melting point temperature of filler metal B, and perform vacuum brazing at this temperature to obtain a brazed joint.

[0039] Specifically, it includes the steps:

[0040] (1) Polish the first arc surface to be welded and the second arc surface to be welded successively with 80-mesh, 240-mesh, 400-mesh, and 800-mesh sandpapers, and then place them in alcohol or acetone for ultrasonic cleaning;

[0041] (2) Take several groups of mixed filler metal A with different X values X B 100-X and mix it with terpineol, and arrange them successively between the first arc surface to be welded and the second arc surface to be welded. Among them, the X value of the mixed filler metal A X B 100-X decreases successively from the group at the lowest point of gravity to the group at the highest point of gravity;

[0042] (3) Assemble in the order of the first arc surface to be welded / mixed filler metal / second arc surface to be welded, and use a mold tooling to apply a certain pressure to the first base metal to be welded with the first arc surface to be welded and the second base metal to be welded with the second arc surface to be welded. By applying pressure, the contact between the two base metals to be welded can be made close, promoting atomic diffusion, so as to ensure that the mixed filler metal can better wet the base metal surface to be welded and fill the joint gap, and finally achieve a firm connection;

[0043] (4) Feed it into a vacuum brazing furnace, heat it at a speed of 10 °C / min to 400 °C and hold for 10 min to remove terpineol; then continue to heat at a speed of 10 °C / min to the connection temperature and hold for 15 - 60 min. Here, the connection temperature should be between the melting point temperature (T A ) of filler metal A and the melting point temperature (T B ) of filler metal B, that is, T A <connection temperature<T B ; finally, cool it to 400 °C at a speed of 5 °C / min and stop heating, and cool it in the furnace to room temperature to obtain a brazed joint.

[0044] Optionally, it further includes: arranging a foil made of filler metal B between the first arc surface to be welded and the second arc surface to be welded, and the foil is wrapped by the mixed filler metal A X B 100-X .

[0045] In this optional embodiment, it is ensured that there is always a solid filling of the foil made of filler metal B in the arc surface gap between the first arc surface to be welded and the second arc surface to be welded. For the variable gap size between the arc surfaces to be welded, the thickness change of the foil made of filler metal B can be adjusted to make a thickness transition, ensuring a good combination between the first arc surface to be welded and the second arc surface to be welded.

[0046] Optionally, before the step of heating to a temperature between the melting point temperature of filler metal A and the melting point temperature of filler metal B, it further includes: heating to above 400 °C and holding for above 10 min to remove terpineol.

[0047] In this optional embodiment, due to its solvent properties, terpineol can dissolve and remove oxides and other contaminants on the metal surfaces of the first arc surface to be welded and the second arc surface to be welded, ensuring the purity of the welding area. At the same time, by heating to above 400 °C and holding for above 10 min, terpineol evaporates, and the protective film formed during the evaporation process of terpineol can prevent the welding area from further oxidizing at high temperatures, protect the solder joints from the erosion of the external environment, and thus extend the service life of the brazed joints.

[0048] Optionally, the time for vacuum brazing is 15 - 60 min.

[0049] Optionally, after mixing filler metal A X B 100-X with terpineol and arranging them between the first arc surface to be welded and the second arc surface to be welded, the following steps are further included: applying a pressure of 0.05 MPa to 0.1 MPa to the first base metal to be welded with the first arc surface to be welded and the second base metal to be welded with the second arc surface to be welded by using a die tooling.

[0050] In this optional embodiment, by applying pressure, the contact between the two base metals to be welded can be made close, promoting atomic diffusion, so as to ensure that the mixed filler metal can better wet the base metal surfaces to be welded and fill the joint gap, and finally achieve a firm connection.

[0051] A brazed joint provided by an embodiment of the present invention is made by using the brazing connection method described in any one of the above.

[0052] The present invention will be further described below in conjunction with specific embodiments.

[0053] Example 1: Using BNi - 5 as filler metal A and Ni as filler metal B to form a mixed filler metal to connect the 2520 stainless steel arc surface

[0054] (1) The 2520 stainless steel arc surface was polished successively with 80 - mesh, 240 - mesh, 400 - mesh, and 800 - mesh sandpapers, and then placed in alcohol for ultrasonic cleaning;

[0055] (2) Four groups of mixed filler metals with different atomic ratios that can achieve in - situ alloying, namely BNi - 5, (BNi - 5) 70 Ni 30 , (BNi - 5) 40 Ni 60 and (BNi - 5) 10 Ni 90After being mixed with terpineol respectively, they are distributed between the first arc surface to be welded and the second arc surface to be welded in seven groups as shown in Figure 2 . Among them, for the mixed filler metal A X B 100-X , the X value decreases successively from the group at the lowest gravity point to the group at the highest gravity point;

[0056] (3) Assemble in the order of 2520 stainless steel arc surface / mixed filler metal (BNi-5) X Ni 100-X / 2520 stainless steel arc surface, and apply a pressure of 0.1 MPa to it using a die and tooling;

[0057] (4) Feed it into a vacuum brazing furnace, heat it to 400 °C at a speed of 10 °C / min and hold for 10 min to remove terpineol; then continue to heat it to 1100 °C at a speed of 10 °C / min and hold for 60 min; finally, cool it to 400 °C at a speed of 5 °C / min to stop heating, and cool it in the furnace to room temperature to obtain a brazed joint.

[0058] Cut the interface of the obtained brazed joint, after grinding and polishing, observe and analyze the joint welding rate using an optical microscope. As shown in Figure 3 , it is increased to nearly 100% welding rate. As shown in Figure 1 (b), when using the direct connection scheme of the conventional filler metal system for the arc structure of this application, it shows a very low welding rate, lower than 30%. This embodiment effectively increases the remelting temperature of the phases in the welded joint, finally realizes the gapless combination between the two arc surfaces to be welded, improves the welding rate, and the obtained brazed joint has better strength and higher reliability.

[0059] Example 2, using Ti-Ni as filler metal A and Al 0.3 CoCrFeNi as filler metal B to form a mixed filler metal to connect the Nb metal arc surface and the SiC ceramic arc surface

[0060] (1) Grind the Nb metal arc surface and the SiC ceramic arc surface successively with 80-mesh, 240-mesh, 400-mesh, and 800-mesh sandpapers, and then place them in acetone for ultrasonic cleaning;

[0061] (2) Mix the low-melting-point filler metal Ti-Ni that can achieve in-situ alloying and the high-melting-point filler metal Al 0.3 CoCrFeNi according to different atomic ratios to form (Ti-Ni) X (Al 0.3 CoCrFeNi) 100-X (10 ≤ X ≤ 100) mixed filler metal. After being mixed with terpineol respectively, they are distributed as shown in Figure 4Are successively distributed between the arc surface of Nb metal and the arc surface of SiC ceramic, wherein the mixed solder (Ti-Ni) X (Al 0.3 CoCrFeNi) 100-X The X value from the group at the lowest point of gravity to the group at the highest point of gravity decreases successively from 100;

[0062] (3) Assemble in the order of SiC ceramic arc surface / mixed solder (Ti-Ni) X (Al 0.3 CoCrFeNi) 100-X / Nb metal arc surface, and apply a pressure of 0.05 MPa to it using a die and fixture;

[0063] (4) Feed it into a vacuum brazing furnace, heat it to 400 °C at a rate of 10 °C / min and hold for 10 min to remove terpineol; then continue to heat it to 1050 °C at a rate of 10 °C / min and hold for 60 min; finally, cool it to 400 °C at a rate of 5 °C / min to stop heating, and cool it in the furnace to room temperature to obtain a brazed joint.

[0064] Example 3, using Cu-Ti as solder A and Nb as solder B to form a mixed solder and using Nb foil to connect the C / C composite arc surface and the GH536 nickel-based superalloy arc surface

[0065] (1) Grind the C / C composite arc surface and the GH536 nickel-based superalloy arc surface successively with 80-mesh, 240-mesh, 400-mesh, and 800-mesh sandpaper, and then place them in acetone for ultrasonic cleaning;

[0066] (2) Mix the low-melting-point solder Cu-Ti that can achieve in-situ alloying and the high-melting-point solder Nb in different atomic ratios to form a (Cu-Ti) X Nb 100-X (10 ≤ X ≤ 100) mixed solder. After mixing with terpineol respectively, they are successively distributed between the C / C composite arc surface and the GH536 nickel-based superalloy arc surface, wherein the mixed solder (Cu-Ti) X Nb 100-X The X value from the group at the lowest point of gravity to the group at the highest point of gravity decreases successively from 100;

[0067] (3) As shown in Figure 5 Assemble in the order of C / C composite arc surface / mixed solder (Cu-Ti) X Nb 100-X / Nb foil / mixed solder (Cu-Ti) X Nb 100-X / GH536 nickel-based superalloy arc surface, and apply a pressure of 0.08 MPa to it using a die and fixture;

[0068] (4) It is sent into a vacuum brazing furnace, heated to 400 °C at a rate of 10 °C / min and held for 10 min to remove terpineol; then it is continuously heated to 1000 °C at a rate of 10 °C / min and held for 15 min; finally, it is cooled to 400 °C at a rate of 5 °C / min to stop heating, and furnace-cooled to room temperature to obtain a brazed joint.

[0069] Although the present invention is disclosed as above, the protection scope of the present invention is not limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention, and these changes and modifications will all fall within the protection scope of the present invention.

Claims

1. A mixed solder, used to fill between a first arc surface to be welded and a second arc surface to be welded, characterized in that: The mixed solder is a mixed solder A composed of solder A and solder B. X B 100-X , wherein X is the solder A in the mixed solder A X B 100-X The percentage of the mixed solder A is 10≤X≤100, and the melting point temperature of the solder A is lower than the melting point temperature of the solder B; X B 100-X The arc surfaces to be welded are divided into several groups, and the mixed solder A in the same group X B 100-X The components of the mixed solder A are the same. X B 100-X The X value decreases from the group with the lowest gravity point to the group with the highest gravity point.

2. The mixed solder according to claim 1, characterized in that: The mixed solder A X B 100-X The X values ​​decrease in an arithmetic progression from the group at the lowest gravity point to the group at the highest gravity point.

3. The mixed solder according to claim 1, characterized in that: The solder A is a silver-based solder, a copper-based solder, a nickel-based solder or a titanium-based solder; the solder B is a nickel solder, a chromium solder, a niobium solder, a molybdenum solder, a palladium solder or a nickel-chromium alloy solder.

4. The mixed solder according to claim 1, characterized in that: The material of the first arc surface to be welded is stainless steel, carbon steel, aluminum, aluminum alloy, copper, copper alloy, magnesium, magnesium alloy, nickel, nickel alloy or ceramic, and the material of the second arc surface to be welded is stainless steel, carbon steel, aluminum, aluminum alloy, copper, copper alloy, magnesium, magnesium alloy, nickel, nickel alloy or ceramic.

5. A brazing connection method, characterized in that: Using the mixed solder according to any one of claims 1 to 4 comprises the following steps: Take several groups of mixed solder A with different X values X B 100-X and pine alcohol, and are sequentially arranged between the first arc surface to be welded and the second arc surface to be welded, wherein the mixed solder A X B 100-X The X value decreases from the group with the lowest gravity point to the group with the highest gravity point; The solder A and the solder B are heated to a temperature between the melting point and the melting point, and vacuum brazing is performed at this temperature to obtain a brazed joint.

6. The brazing connection method according to claim 5, characterized in that: Also includes: The foil material made of the solder B is arranged between the first arc surface to be welded and the second arc surface to be welded. X B 100-X pack.

7. The brazing connection method according to claim 5, characterized in that: Before the step of heating to a temperature between the melting point of the solder A and the melting point of the solder B, the method further includes: heating to above 400° C. and keeping the temperature for more than 10 minutes to remove the terpineol.

8. The brazing connection method according to claim 5, characterized in that: The vacuum brazing time is 15-60 minutes.

9. The brazing connection method according to claim 5, characterized in that: In the mixed solder A X B 100-X After being mixed with the pine oil and arranged between the first arc surface to be welded and the second arc surface to be welded, the following steps are also included: using a mold tooling to apply a pressure of 0.05MPa to 0.1MPa to the first base material to be welded having the first arc surface to be welded and the second base material to be welded having the second arc surface to be welded.

10. A brazing joint, characterized in that: The method is made by the brazing connection method as described in any one of claims 5 to 9.

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