A solder and its preparation method

Abstract

This invention provides a brazing filler metal and its preparation method. The preparation method includes the following steps: S100: Melting a matrix alloy, adding reinforcing particles, and continuously stirring to ensure uniform distribution of the reinforcing particles, resulting in a metal solution; S200: Preheating the mold, pouring the metal solution into the mold, and stirring to ensure uniform dispersion of the reinforcing particles; sequentially performing static treatment and cooling treatment to obtain an ingot; S300: Stacking multiple ingots to assemble a composite metal plate; S400: Sequentially performing diffusion welding and rolling on the composite metal plate to obtain the brazing filler metal. The brazing filler metal prepared by this invention can effectively improve the problem of excessive residual stress after brazing.

Description

Technical Field

[0001] This invention relates to the field of brazing materials technology, and more specifically, to a brazing filler metal and its preparation method. Background Technology

[0002] Brazing is widely used for joining dissimilar materials. However, the mismatch in physical properties such as the coefficient of linear expansion and the modulus of elasticity is a common problem in welding dissimilar materials. Direct brazing will inevitably lead to excessive residual stress, which in turn can cause crack initiation or weld cracking. Moreover, the constituent elements of the two materials are quite different. If the brazing filler metal is not selected properly, it will affect the wetting of the base material and the metallurgical reaction.

[0003] Adding reinforcing particles to the brazing filler metal to assist brazing results in an uneven distribution of brazed joint strength. The reinforcing phase at the weld interface includes reinforcing particles and intermetallic compounds generated by metallurgical reactions, while the middle region of the brazed joint only contains reinforcing particles. This leads to a higher content of reinforcing phase at the interface compared to the middle region, resulting in an uneven distribution of brazed joint strength. Summary of the Invention

[0004] To solve at least one of the above problems, the present invention provides a method for preparing brazing filler metal, comprising the following steps: S100: melting a matrix alloy, adding reinforcing particles and continuously stirring to ensure uniform distribution of the reinforcing particles, thereby obtaining a metal solution; S200: preheating the mold, pouring the metal solution into the mold, and stirring to ensure uniform dispersion of the reinforcing particles; sequentially performing static treatment and cooling treatment to obtain an ingot; S300: stacking multiple ingots to assemble a composite metal plate; S400: sequentially performing diffusion welding and rolling on the composite metal plate to obtain brazing filler metal.

[0005] In this technical solution, reinforcing particles are first added to the silver-copper alloy matrix to ensure uniform distribution. Before casting, the mold is preheated to prevent solidification when the molten metal is introduced. Simultaneously, the molten metal is stirred to maintain uniform dispersion of the reinforcing particles. The stirring method can be mechanical stirring, ultrasonic stirring, electromagnetic stirring, or others. Due to the density difference between the reinforcing particles and the matrix alloy, a static settling process allows the reinforcing particles to float or sink, achieving a gradient distribution within the ingot. During assembly, assembly can be performed according to specific requirements, such as stacking two, three, or four ingots; and stacking can be done by bonding the sides with more reinforcing particles together or the sides with fewer reinforcing particles together. Finally, the assembled composite metal plate is diffusion-welded and rolled to obtain the required brazing filler metal.

[0006] Furthermore, the reinforcing particles include a first reinforcing particle or a second reinforcing particle; the first reinforcing particle includes at least one of diamond, tungsten carbide, and silicon carbide; the second reinforcing particle includes at least one of cobalt-containing metal and nickel-containing metal.

[0007] In this technical solution, the reinforcing particles are divided into first reinforcing particles and second reinforcing particles according to their different functions. The first reinforcing particles are used to form a reinforcing phase, which can improve the problem of excessive residual stress. For example, they include diamond, tungsten carbide, and silicon carbide. The second reinforcing particles are used to improve the strength of the brazed interface joint. For example, cobalt-containing metals can improve the strength of the brazed interface of cemented carbide, and nickel-containing metals can improve the strength of the brazed interface of stainless steel.

[0008] Furthermore, the matrix alloy comprises 25-43 parts by mass of copper and 55-74 parts by mass of silver; and / or the reinforcing particles include first reinforcing particles, the amount of which is 5-15% of the volume of the matrix alloy; and / or the reinforcing particles include second reinforcing particles, the amount of which is 1-2% of the mass of the matrix alloy. The amount of reinforcing particles added is small, but after floating or settling, the content in certain areas is higher, which is beneficial for enhancing the brazing effect of the silver-copper alloy matrix.

[0009] Furthermore, the particle size of the reinforcing particles is adjusted according to the density difference 'a' between the reinforcing particles and the matrix alloy. If the density difference 'a' is greater than 25%, the particle size of the reinforcing particles is adjusted to be between 1 μm and 20 μm. If the density difference 'a' is less than 25%, the particle size of the reinforcing particles is adjusted to be between 100 μm and 200 μm. The density difference 'a' is calculated as follows: a = |(ρ1-ρ0) / ρ0|; where a is the density difference between the reinforcing particles and the matrix alloy; ρ1 is the density of the reinforcing particles; and ρ0 is the density of the matrix alloy.

[0010] In this technical solution, the density difference between the reinforcing particles and the matrix alloy varies depending on the material selection. Generally, when the density difference is large, the movement speed of the reinforcing particles will be relatively high when the molten metal is stationary. To control the movement speed of the reinforcing particles, smaller particles are selected for reinforcing particles with large density differences. This is because smaller particles exhibit Brownian motion, which slows their upward movement, ensuring that the molten metal remains stationary for a longer period and facilitating the venting of the molten metal.

[0011] Furthermore, the preheating treatment involves heating the mold to 300°C-400°C; and / or the cooling treatment includes sequentially solidifying the molten metal along the height direction of the mold.

[0012] In this technical solution, the purpose of preheating the mold is to prevent the molten metal from solidifying when it is injected into the mold. Solidification of the molten metal will cause the reinforcing particles to not present a gradient distribution as required. Therefore, it is necessary to preheat the mold to keep the molten metal in a molten state.

[0013] Furthermore, the settling time for the static treatment does not exceed 40 minutes, so that the content of reinforcing particles in the ingot is linearly distributed.

[0014] In this technical solution, the settling time varies depending on the reinforcing particles. Generally, for reinforcing particles with a large density difference, the settling time is shorter; for reinforcing particles with a small density difference, the settling time is appropriately extended. The purpose of this technical solution is to control the reinforcing particle content in the ingot to exhibit a linear distribution, and the settling time can be adjusted according to different reinforcing particles. For reinforcing particles with a small density difference, mechanical vibration is applied along their upward or downward direction during settling to accelerate their movement speed.

[0015] Furthermore, in step S300, the plurality of ingots includes a first ingot and / or a second ingot; wherein the first ingot contains first reinforcing particles; and the second ingot contains second reinforcing particles.

[0016] In this technical solution, assembly can be carried out according to specific needs. For example, when welding cemented carbide and stainless steel, a corresponding second ingot can be selected for assembly. Furthermore, a first ingot can be set in the middle of the second ingot to form a reinforcing phase.

[0017] Furthermore, the multiple ingots include a first ingot; in the first ingot, the end with a higher content of first reinforcing particles is the first reinforcing surface; when stacking them up and down, the first reinforcing surface is positioned close to the center of the composite metal plate.

[0018] In this technical solution, the first ingot includes first reinforcing particles, which are used to form a reinforcing phase and alleviate residual stress after brazing. Therefore, preferably, the first reinforcing surface is positioned close to the center to facilitate the flow of the first reinforcing particles to both brazing surfaces during brazing. For example, when there are an even number of ingots assembled, the first reinforcing surfaces are all positioned close to the center of the composite metal plate; when there are an odd number of ingots assembled, there are no specific requirements for the installation method of the middle ingot.

[0019] Furthermore, the multiple ingots include a second ingot; in the second ingot, the end with a higher content of second reinforcing particles is the second reinforcing surface; when stacking the ingots, the second reinforcing surface is located on the outer surface of the composite metal plate.

[0020] In this technical solution, the second ingot is used to strengthen the brazing surface. Therefore, during the stacking process, the second reinforcing surface should be located on the outer surface of the composite metal plate, and the corresponding second reinforcing particles can be selected according to the different metals being welded. Specifically, a first ingot can also be placed between the two second ingots to alleviate residual stress after welding.

[0021] The present invention also provides a solder sheet, which is prepared by any of the methods provided above. Attached Figure Description

[0022] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings to be used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0024] Figure 1 This is a schematic diagram of the structure of the composite metal plate provided in an embodiment of the present invention.

[0025] Figure 2 This is a schematic diagram of the structure of a composite metal plate provided in another embodiment of the present invention.

[0026] Explanation of reference numerals in the attached figures: 11-first reinforcing particle; 12-second reinforcing particle; 20-matrix alloy. Detailed Implementation

[0027] To make the above-mentioned objectives, features, and advantages of the present invention more apparent and understandable, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] In related technologies, brazing is widely used for joining dissimilar materials. However, the common problem in welding dissimilar materials is the mismatch in physical properties such as the coefficient of linear expansion and the modulus of elasticity. Direct brazing inevitably leads to excessive residual stress, which can cause crack initiation or weld cracking. Moreover, the constituent elements of the two materials differ significantly, and improper selection of brazing filler metal will affect the wetting of the base material and the metallurgical reaction. Currently, two methods are being attempted to address the problem of excessive residual stress.

[0029] The first method uses a soft interlayer with a coefficient of linear expansion between that of dissimilar metals to assist brazing. This method utilizes the moderate coefficient of linear expansion of the soft interlayer to create a transition, reducing the difference in physical properties between the base materials. Furthermore, its good plasticity further releases residual stress. During the welding process, a small amount of interlayer elements dissolves into the brazing filler metal, improving its performance and making the soft interlayer more suitable for welding base materials with large differences in coefficients of linear expansion. In addition, the presence of the interlayer can control the diffusion behavior of elements, preventing the formation of excessive harmful brittle products between base material elements.

[0030] However, due to the addition of an intermediate soft layer to relieve stress, these types of welded joints generally have poor high-temperature strength; the current gradient brazing alloy composition generally has abrupt changes in composition, which inevitably leads to abrupt changes in material properties and still results in large residual stress after welding.

[0031] The second method is to add reinforcing particles to the brazing filler metal to assist brazing. This method uses the low coefficient of linear expansion of the reinforcing particles to neutralize the coefficient of expansion of the brazing filler metal, making it more suitable for welding base materials with large differences in the coefficient of linear expansion. At the same time, the fine grain strengthening and dispersion strengthening effects of the reinforcing particles will greatly improve the joint strength and toughness. The reinforcing phase is usually uniformly dispersed in the material to achieve the best strengthening effect, and there is an optimal value for the content of the reinforcing phase.

[0032] However, the bonding reaction between reinforcing particles and brazing filler metal inevitably consumes a certain amount of brazing filler metal elements, thus affecting the metallurgical reaction at the interface between the brazing filler metal and the base metal. Typically, the metallurgical reaction at the interface generates hard and brittle intermetallic compounds. For welding dissimilar metals, an intermediate layer can often be added to control the formation of brittle phases in the joint and improve joint performance. Appropriate amounts of reinforcing particles can control phase formation and interfacial behavior, preventing excessive formation of intermetallic compounds from affecting weld quality.

[0033] Adding reinforcing particles to brazing filler metal assists in brazing. The reinforcing phase at the weld interface includes reinforcing particles and intermetallic compounds generated by metallurgical reactions, while the middle region of the brazed joint contains only reinforcing particles, resulting in a higher content of reinforcing phase at the interface compared to the middle region. This invention prepares a linear gradient composition brazing filler metal through melting and casting, and then controls the distribution of reinforcing particles in the filler metal through diffusion welding and hot rolling processes. This achieves a linear distribution of the reinforcing phase in the filler metal, thus controlling the distribution position of the reinforcing phase in the brazed joint.

[0034] It is worth mentioning that the filler metal provided in this technical solution is for diffusion welding rather than brazing. During the brazing process, the filler metal melts, and the reinforcing particles are redistributed along with the melted filler metal. However, during diffusion welding, the filler metal does not melt, so the reinforcing particles can maintain their distribution state, thereby achieving the effect of gradient distribution of the reinforcing phase.

[0035] This invention provides a method for preparing brazing filler metal, comprising the following steps: S100: melting a matrix alloy 20, adding reinforcing particles and continuously stirring to ensure uniform distribution of the reinforcing particles, thereby obtaining a metal solution; S200: preheating the mold, pouring the metal solution into the mold, and stirring to ensure uniform dispersion of the reinforcing particles; sequentially performing static treatment and cooling treatment to obtain an ingot; S300: stacking multiple ingots to assemble a composite metal plate; S400: sequentially performing diffusion welding and rolling on the composite metal plate to obtain brazing filler metal.

[0036] In this embodiment, reinforcing particles are first added to the silver-copper alloy matrix to ensure uniform distribution. Before casting, the mold is preheated to prevent solidification when the molten metal is introduced. Simultaneously, the molten metal is stirred to maintain uniform dispersion of the reinforcing particles. The stirring method can be mechanical stirring, ultrasonic stirring, electromagnetic stirring, or others. Due to the density difference between the reinforcing particles and the matrix alloy 20, a static settling process allows the reinforcing particles to float or sink, achieving a gradient distribution within the ingot. During assembly, assembly can be performed according to specific needs, such as stacking two, three, or four ingots; and stacking can be done by bonding the side with more reinforcing particles or the side with fewer reinforcing particles together. Finally, the assembled composite metal plate is diffusion-welded and rolled to obtain the required brazing filler metal.

[0037] Furthermore, the reinforcing particles include a first reinforcing particle 11 or a second reinforcing particle 12; the first reinforcing particle 11 includes at least one of diamond, tungsten carbide, and silicon carbide; the second reinforcing particle 12 includes at least one of cobalt-containing metal and nickel-containing metal.

[0038] In this embodiment, the reinforcing particles are divided into first reinforcing particles 11 and second reinforcing particles 12 according to their different functions. The first reinforcing particles 11 are used to form a reinforcing phase, which can improve the problem of excessive residual stress. For example, they include diamond, tungsten carbide, and silicon carbide. The second reinforcing particles 12 are used to improve the strength of the brazed interface joint. For example, cobalt-containing metal can improve the strength of the brazed interface of cemented carbide, and nickel-containing metal can improve the strength of the brazed interface of stainless steel.

[0039] Furthermore, the matrix alloy 20 includes 25-43 parts by mass of copper and 55-74 parts by mass of silver; and / or the reinforcing particles include a first reinforcing particle 11, the amount of the first reinforcing particle 11 being 5-15% of the volume of the matrix alloy 20; and / or the reinforcing particles include a second reinforcing particle 12, the amount of the second reinforcing particle 12 being 1-2% of the mass of the matrix alloy 20.

[0040] Furthermore, the particle size of the reinforcing particles is adjusted according to the density difference 'a' between the reinforcing particles and the matrix alloy 20. If the density difference 'a' is greater than 25%, the particle size of the reinforcing particles is adjusted to be between 1 μm and 20 μm. If the density difference 'a' is less than 25%, the particle size of the reinforcing particles is adjusted to be between 100 μm and 200 μm. The density difference 'a' is calculated as follows: a = |(ρ1-ρ0) / ρ0|; where a is the density difference between the reinforcing particles and the matrix alloy 20; ρ1 is the density of the reinforcing particles; and ρ0 is the density of the matrix alloy 20.

[0041] In this embodiment, the density difference between the reinforcing particles and the matrix alloy 20 varies depending on the material selection. Generally, when the density difference is large, the movement speed of the reinforcing particles will be relatively high when the metal solution is stationary. To control the movement speed of the reinforcing particles, smaller particles are selected for reinforcing particles with large density differences. This is because small particles exhibit Brownian motion, which slows their buoyancy and ensures that the metal solution remains stationary for a longer period, facilitating the venting of the metal solution. Therefore, when the density difference is greater than 25%, the particle size of the reinforcing particles is controlled between 1 μm and 20 μm; when the density difference is less than 25%, the particle size of the reinforcing particles is controlled between 100 μm and 200 μm. When the density difference is equal to 25%, the particle size of the reinforcing particles can be selected as needed; the density difference is the ratio of the density difference between the reinforcing particles and the matrix alloy 20 to the matrix alloy 20.

[0042] Furthermore, the preheating treatment involves heating the mold to 300°C-400°C; and / or the cooling treatment includes sequentially solidifying the molten metal along the height direction of the mold.

[0043] In this embodiment, the purpose of preheating the mold is to prevent the molten metal from solidifying when it is injected into the mold.

[0044] Solidification can cause the reinforcing particles to not exhibit the required gradient distribution, thus necessitating preheating of the mold. Preheating temperatures can be 300℃, 320℃, 340℃, 360℃, 380℃, or 400℃. The cooling process employs sequential solidification along the height of the mold; for example, the mold can be submerged in water from bottom to top for sequential solidification, effectively improving internal defects in the ingot.

[0045] Furthermore, the settling time for the static treatment does not exceed 40 minutes, so that the content of reinforcing particles in the ingot is linearly distributed.

[0046] In this embodiment, the settling time varies depending on the type of reinforcing particles. Generally, for reinforcing particles with a large density difference, the settling time is shorter; for reinforcing particles with a small density difference, the settling time is appropriately extended. The purpose of the above technical solution is to control the content of reinforcing particles in the ingot to exhibit a linear distribution. The settling time can be adjusted according to different reinforcing particles, preferably not exceeding thirty minutes.

[0047] Furthermore, in step S300, the plurality of ingots includes a first ingot and / or a second ingot; wherein the first ingot contains first reinforcing particles 11; and the second ingot contains second reinforcing particles 12.

[0048] In this embodiment, assembly can be performed according to specific needs. For example, when welding cemented carbide and stainless steel, the corresponding second ingot can be selected for assembly. Furthermore, a first ingot can be set in the middle of the second ingot to form a reinforcing phase.

[0049] Furthermore, the plurality of ingots includes a first ingot; in the first ingot, the end with a higher content of the first reinforcing particles 11 is the first reinforcing surface; when stacking them up and down, the first reinforcing surface is positioned close to the center of the composite metal plate.

[0050] In this embodiment, the first ingot includes first reinforcing particles 11, which are used to form a reinforcing phase and alleviate residual stress after brazing. Therefore, preferably, the first reinforcing surface is positioned close to the center to facilitate the flow of the first reinforcing particles 11 to the two brazing surfaces during brazing. For example, when there are an even number of ingots assembled, the first reinforcing surfaces are all positioned close to the center of the composite metal plate; when there are an odd number of ingots assembled, there are no specific requirements for the installation method of the middle ingot.

[0051] Furthermore, the multiple ingots include a second ingot; in the second ingot, the end with a higher content of the second reinforcing particles 12 is the second reinforcing surface; when stacking the ingots, the second reinforcing surface is located on the outer surface of the composite metal plate.

[0052] In this embodiment, the second ingot is used to strengthen the brazing surface. Therefore, during the stacking process, the second reinforcing surface should be located on the outer surface of the composite metal plate, and the corresponding second reinforcing particles 12 can be selected according to the different metals being welded. Specifically, a first ingot can also be placed between the two second ingots to alleviate residual stress after welding.

[0053] This invention also provides a solder sheet, which is prepared by any of the methods described above.

[0054] Example 1

[0055] See Figure 1This embodiment provides a method for preparing solder, including the following steps:

[0056] S100: Obtain a silver-copper matrix alloy containing 28 parts by mass of copper and 72 parts by mass of silver.

[0057] Copper is first smelted in a medium-frequency furnace. When the copper is completely melted and the temperature of the copper melt reaches 1150-1200℃, silver is added. After the two materials are fully fused together, they are covered with a composite salt prepared by mixing dehydrated borax and boron anhydride in a weight ratio of 7:3.

[0058] Once the temperature drops to 850-900℃, add 1-20μm diamond particles and use electromagnetic and mechanical stirring to ensure uniform distribution of the reinforcing particles, thus obtaining a metal solution. The amount of diamond particles added is 10% of the volume of the metal solution.

[0059] S200: Preheat the mold to 300-400℃. The internal dimensions of the mold are 25mm high, 200mm long, and 80mm wide.

[0060] The molten metal is poured into a mold and stirred to disperse the reinforcing particles evenly; then it is subjected to static treatment and cooling treatment in sequence to obtain an ingot.

[0061] The settling time is 20-40 minutes; diamond has a low density, so it will float during settling. This embodiment uses smaller particles, which exhibit Brownian motion, causing them to float more slowly, ensuring the metal solution can be settling for a longer period and facilitating the venting of the metal solution.

[0062] After standing, the diamonds float to the surface, with a higher diamond content near the top of the mold. The cooling process involves solidifying the molten metal sequentially from bottom to top along the height of the mold.

[0063] After cooling to obtain the ingot, the oxide inclusions on the surface are milled off before it is ready for use.

[0064] S300: The surface of the ingot is cleaned using ultrasound. Two ingots are stacked one on top of the other, with the end having a higher diamond content serving as the first reinforcing surface. The two first reinforcing surfaces are then bonded together to form a composite metal plate.

[0065] S400: Under a protective atmosphere, the composite metal plate is sequentially subjected to diffusion welding and rolling to obtain brazing filler metal.

[0066] Specifically, diffusion welding is carried out in a diffusion welding furnace with a furnace temperature set at 400-600℃, a pressure of 5-30MPa, and a holding time of 1-4 hours.

[0067] After diffusion welding, the composite metal plate is placed in a heating furnace and held at a temperature of 2-4 hours. Then, it is extruded to obtain a composite strip with a thickness of 3-5 mm. The temperature in the heating furnace is 350-450℃. The resulting composite strip is then annealed online and rolled in multiple passes with small ratios to a thin strip with a thickness of 0.2-0.3 mm. The thin strip undergoes pickling, polishing, and other post-treatments to finally obtain a brazing filler metal with a high surface finish.

[0068] Example 2

[0069] This embodiment provides a method for preparing solder, including the following steps:

[0070] S100: Obtain a silver-copper matrix alloy containing 28 parts by mass of copper and 72 parts by mass of silver.

[0071] Copper is first smelted in a medium-frequency furnace. When the copper is completely melted and the temperature of the copper melt reaches 1150-1200℃, silver is added. After the two materials are fully fused together, they are covered with a composite salt prepared by mixing dehydrated borax and boron anhydride in a weight ratio of 7:3.

[0072] Once the temperature drops to 850-900℃, add 1-30μm silicon carbide particles. Use electromagnetic and mechanical stirring to ensure uniform distribution of the reinforcing particles, thus obtaining a metal solution. The amount of silicon carbide particles added is 10% of the volume of the metal solution.

[0073] S200: Preheat the mold to 300-400℃. The internal dimensions of the mold are 25mm high, 200mm long, and 80mm wide.

[0074] The molten metal is poured into a mold and stirred to disperse the reinforcing particles evenly; then it is subjected to static treatment and cooling treatment in sequence to obtain an ingot.

[0075] The settling time is 20-40 minutes. Silicon carbide has a low density, so it will float during settling. This embodiment uses smaller particles; the small particles exhibit Brownian motion, which slows their buoyancy and ensures the metal solution remains set for a longer period, facilitating venting of the metal solution.

[0076] After standing, the silicon carbide floats to the surface, with a higher content of silicon carbide near the top of the mold. The cooling process involves solidifying the molten metal sequentially from bottom to top along the height of the mold.

[0077] After cooling to obtain the ingot, the oxide inclusions on the surface are milled off before it is ready for use.

[0078] S300: The surface of the ingot is cleaned using ultrasound. Two ingots are stacked one on top of the other, with the end having a higher silicon carbide content serving as the first reinforcing surface. The two first reinforcing surfaces are then bonded together to form a composite metal plate.

[0079] S400: Under a protective atmosphere, the composite metal plate is sequentially subjected to diffusion welding and rolling to obtain brazing filler metal.

[0080] Specifically, diffusion welding is carried out in a diffusion welding furnace with a furnace temperature set at 400-600℃, a pressure of 5-30MPa, and a holding time of 1-4 hours.

[0081] After diffusion welding, the composite metal plate is placed in a heating furnace and held at a temperature of 2-4 hours. Then, it is extruded to obtain a composite strip with a thickness of 3-5 mm. The temperature in the heating furnace is 350-450℃. The resulting composite strip is then annealed online and rolled in multiple passes with small ratios to a thin strip with a thickness of 0.2-0.3 mm. The thin strip undergoes pickling, polishing, and other post-treatments to finally obtain a brazing filler metal with a high surface finish.

[0082] Example 3

[0083] This embodiment provides a method for preparing solder, including the following steps:

[0084] S100: Obtain a silver-copper-zinc matrix alloy comprising 40 parts by mass of copper, 55 parts by mass of silver, and 5 parts by mass of zinc.

[0085] Copper is first smelted in a medium-frequency furnace. When the copper is completely melted and the temperature of the copper melt reaches 1150-1200℃, silver is added. After the two materials are fully fused together, they are covered with a composite salt prepared by mixing dehydrated borax and boron anhydride in a weight ratio of 7:3.

[0086] Once the temperature drops to 850-900℃, zinc is added and fusion continues. After the zinc is fully fused, 1-20μm tungsten carbide particles are added, and electromagnetic and mechanical stirring are used to ensure uniform distribution of the reinforcing particles, resulting in a metal solution. The amount of tungsten carbide particles added is 10% of the volume of the metal solution.

[0087] S200: Preheat the mold to 300-400℃. The internal dimensions of the mold are 25mm high, 200mm long, and 80mm wide.

[0088] The molten metal is poured into a mold and stirred to disperse the reinforcing particles evenly; then it is subjected to static treatment and cooling treatment in sequence to obtain an ingot.

[0089] The settling time is 20-40 minutes. Tungsten carbide has a high density, so it will sink during settling. This embodiment uses smaller particles; the small particles exhibit Brownian motion, slowing their settling and ensuring a longer settling time for the molten metal, facilitating venting of the molten metal.

[0090] After standing, the tungsten carbide sinks, with a higher content near the bottom of the mold. The cooling process involves solidifying the molten metal sequentially from bottom to top along the height of the mold.

[0091] After cooling to obtain the ingot, the oxide inclusions on the surface are milled off before it is ready for use.

[0092] S300: The surface of the ingot is cleaned using ultrasound. Two ingots are stacked one on top of the other, with the end having a higher tungsten carbide content serving as the first reinforcing surface. The two first reinforcing surfaces are then bonded together and stacked to obtain a composite metal plate.

[0093] S400: Under a protective atmosphere, the composite metal plate is sequentially subjected to diffusion welding and rolling to obtain brazing filler metal.

[0094] Specifically, diffusion welding is carried out in a diffusion welding furnace with a furnace temperature set at 400-600℃, a pressure of 5-30MPa, and a holding time of 1-4 hours.

[0095] After diffusion welding, the composite metal plate is placed in a heating furnace and held at a temperature of 2-4 hours. Then, it is extruded to obtain a composite strip with a thickness of 3-5 mm. The temperature in the heating furnace is 350-450℃. The resulting composite strip is then annealed online and rolled in multiple passes with small ratios to a thin strip with a thickness of 0.2-0.3 mm. The thin strip undergoes pickling, polishing, and other post-treatments to finally obtain a brazing filler metal with a high surface finish.

[0096] Example 4

[0097] See Figure 2 This embodiment provides a method for preparing solder, including the following steps:

[0098] 1. Preparation of nickel-containing ingot A

[0099] S101: Obtain a silver-copper-zinc-manganese matrix alloy comprising 39 parts by mass of copper, 25 parts by mass of silver, 26 parts by mass of zinc and 10 parts by mass of manganese.

[0100] Copper is first smelted in a medium-frequency furnace. When the copper is completely melted and the temperature of the copper melt reaches 1150-1200℃, silver is added. After the two materials are fully fused, they are covered with a composite salt made of dehydrated borax and boron anhydride in a weight ratio of 7:3, and then manganese is added.

[0101] Once the temperature drops to 850-900℃, zinc is added and fusion continues. After the zinc is fully fused, 400-500μm nickel particles are added, and electromagnetic and mechanical stirring are used to ensure uniform distribution of the reinforcing particles, resulting in a metal solution. The amount of nickel particles added is 3% of the mass of the metal solution.

[0102] S201: Preheat the mold to 300-400℃. The internal dimensions of the mold are 25mm high, 200mm long, and 80mm wide.

[0103] The molten metal is poured into a mold and mechanical vibration is applied while the mold is left to stand. After 5-10 minutes, the heating of the mold is stopped. Then, the mold is left to stand and then cooled to obtain ingot A.

[0104] Nickel particles have a high density, so they sink when left to stand. However, since the density difference between nickel particles and the matrix alloy is small, this embodiment uses larger particles and applies vibration in the same direction as the sinking to accelerate the sinking.

[0105] The nickel content is higher near the bottom of the mold, and the cooling process involves sequentially solidifying the molten metal from bottom to top along the height of the mold.

[0106] After cooling to obtain ingot A, the oxide inclusions on the surface are milled off and it is ready for use.

[0107] 2. Preparation of diamond-containing ingot B

[0108] S102: Obtain a silver-copper-zinc-manganese matrix alloy comprising 39 parts by mass of copper, 25 parts by mass of silver, 26 parts by mass of zinc and 10 parts by mass of manganese.

[0109] Copper is first smelted in a medium-frequency furnace. When the copper is completely melted and the temperature of the copper melt reaches 1150-1200℃, silver is added. After the two materials are fully fused, they are covered with a composite salt made of dehydrated borax and boron anhydride in a weight ratio of 7:3, and then manganese is added.

[0110] Once the temperature drops to 850-900℃, zinc is added and fusion continues. After the zinc is fully fused, 0.1-5μm diamond particles are added, and electromagnetic and mechanical stirring are used to ensure uniform distribution of the reinforcing particles, resulting in a metal solution. The amount of diamond particles added is 20% of the volume of the metal solution.

[0111] S202: Preheat the mold to 300-400℃. The internal dimensions of the mold are 25mm high, 200mm long, and 80mm wide.

[0112] The molten metal is poured into a mold and stirred to disperse the reinforcing particles evenly; then it is subjected to static treatment and cooling treatment in sequence to obtain ingot B.

[0113] The settling time is 3-5 minutes; diamond has a low density, so it will float during settling. This embodiment uses smaller particles, which exhibit Brownian motion, causing them to float more slowly, ensuring the metal solution can be settling for a longer period and facilitating the venting of the metal solution.

[0114] After standing, the diamonds float to the surface, with a higher diamond content near the top of the mold. The cooling process involves solidifying the molten metal sequentially from bottom to top along the height of the mold.

[0115] After cooling to obtain ingot B, the oxide inclusions on the surface are milled off before it is ready for use.

[0116] 3. Preparation of diamond-containing ingots C

[0117] S103: Obtain a silver-copper-zinc-manganese matrix alloy comprising 39 parts by mass of copper, 25 parts by mass of silver, 26 parts by mass of zinc and 10 parts by mass of manganese.

[0118] Copper is first smelted in a medium-frequency furnace. When the copper is completely melted and the temperature of the copper melt reaches 1150-1200℃, silver is added. After the two materials are fully fused, they are covered with a composite salt made of dehydrated borax and boron anhydride in a weight ratio of 7:3, and then manganese is added.

[0119] Once the temperature drops to 850-900℃, zinc is added and fusion continues. After the zinc is fully fused, 200-300μm cobalt particles are added, and electromagnetic and mechanical stirring are used to ensure uniform distribution of the reinforcing particles, resulting in a metal solution. The amount of cobalt particles added is 1% of the mass of the metal solution.

[0120] S203: Preheat the mold to 300-400℃. The internal dimensions of the mold are 25mm high, 200mm long, and 80mm wide.

[0121] The molten metal is poured into a mold and mechanical vibration is applied while the mold is left to stand. After 5-10 minutes, the heating of the mold is stopped. Then, the mold is left to stand and then cooled to obtain ingot C.

[0122] Cobalt particles have a high density, so they sink when left to stand. However, since the density difference between cobalt particles and the matrix alloy is small, this embodiment uses larger particles and applies vibration in the same direction as the sinking to accelerate the sinking.

[0123] The cobalt particles are more abundant near the bottom of the mold, and the cooling process involves sequentially solidifying the molten metal from bottom to top along the height of the mold.

[0124] After cooling to obtain ingot C, the oxide inclusions on the surface are milled off before use.

[0125] After obtaining ingots A, B, and C, perform the following operations:

[0126] S300: Ultrasonic cleaning is used to clean the surfaces of ingots A, B, and C. The three ingots are stacked one on top of the other, with ingot B in the middle. The end with a higher content of the second reinforcing particles 12 is the second reinforcing surface. The two second reinforcing surfaces are set on the outer surface, and the stacked parts are used to obtain a composite metal plate.

[0127] S400: Under a protective atmosphere, the composite metal plate is sequentially subjected to diffusion welding and rolling to obtain brazing filler metal.

[0128] Specifically, diffusion welding is carried out in a diffusion welding furnace with a furnace temperature set at 400-600℃, a pressure of 5-30MPa, and a holding time of 1-4 hours.

[0129] After diffusion welding, the composite metal plate is placed in a heating furnace and held at a temperature of 2-4 hours. Then, it is extruded to obtain a composite strip with a thickness of 3-5 mm. The temperature in the heating furnace is 350-450℃. The resulting composite strip is then annealed online and rolled in multiple passes with small ratios to a thin strip with a thickness of 0.2-0.3 mm. The thin strip undergoes pickling, polishing, and other post-treatments to finally obtain a brazing filler metal with a high surface finish.

[0130] The brazing was performed using the brazing filler metals provided in Examples 1-4, and the experimental data obtained are shown in Table 1.

[0131] Table 1

[0132]

[0133] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a solder, characterized in that, Includes the following steps: S100: Melt the matrix alloy, add reinforcing particles and stir continuously to make the reinforcing particles evenly distributed, to obtain a metal solution; S200: Preheat the mold, pour the molten metal into the mold, and stir to disperse the reinforcing particles evenly; The ingot is obtained by sequentially subjecting it to static treatment and cooling treatment. S300: Stack multiple ingots one on the top and bottom to assemble a composite metal plate; S400: The composite metal plate is sequentially subjected to diffusion welding and rolling to obtain the brazing filler metal; The particle size of the reinforcing particles is adjusted according to the density difference α between the reinforcing particles and the matrix alloy. If the density difference a is greater than 25%, then the particle size of the reinforcing particles is adjusted to be between 1 μm and 20 μm. If the density difference a is less than 25%, then the particle size of the reinforcing particles is adjusted to be between 100μm and 200μm. The density difference 'a' is calculated in the following way: a=∣(ρ1-ρ0) / ρ0∣; Where a is the density difference between the reinforcing particles and the matrix alloy; ρ1 is the density of the reinforcing particles; and ρ0 is the density of the matrix alloy. The settling time for the settling process shall not exceed 40 minutes, so that the content of the reinforcing particles in the ingot is linearly distributed. In step S300, The plurality of ingots includes a first ingot and / or a second ingot; The first ingot contains the first reinforcing particles; The second ingot contains a second reinforcing particle.

2. The preparation method according to claim 1, characterized in that, The reinforcing particles include a first reinforcing particle or a second reinforcing particle; The first reinforcing particle includes at least one of diamond, tungsten carbide, and silicon carbide; The second reinforcing particle includes at least one of cobalt-containing metal and nickel-containing metal.

3. The preparation method according to claim 2, characterized in that, The matrix alloy comprises 25-43 parts by weight of copper and 55-74 parts by weight of silver; and / or The reinforcing particles include first reinforcing particles, the amount of which is 5-20% of the volume of the matrix alloy; and / or The reinforcing particles include second reinforcing particles, the amount of which is 1-2% of the mass of the matrix alloy.

4. The preparation method according to claim 1, characterized in that, The preheating treatment involves heating the mold to 300℃-400℃; and / or The cooling process includes: sequentially solidifying the molten metal along the height direction of the mold.

5. The preparation method according to claim 1, characterized in that, The plurality of ingots includes a first ingot; In the first ingot, the end with a higher content of the first reinforcing particles is the first reinforcing surface; When performing the stacking, the first reinforcing surface is positioned close to the center of the composite metal plate.

6. The preparation method according to claim 4, characterized in that, The plurality of ingots includes a second ingot; In the second ingot, the end with a higher content of the second reinforcing particles is the second reinforcing surface; During the stacking process, the second reinforcing surface is disposed on the outer surface of the composite metal plate.

7. A solder sheet, characterized in that, The solder sheet is prepared by the method described in any one of claims 1-6.

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