A solder powder and its preparation method and application

Abstract

The invention relates to a solder powder and a preparation method and application thereof, and belongs to the technical field of welding materials. The solder powder of the invention comprises a copper-phosphorus alloy powder and a copper-based alloy powder, the melting points of the copper-phosphorus alloy powder and the copper-based alloy powder are close, the copper-phosphorus alloy powder is a eutectic component, and after melting in the brazing process, the copper-phosphorus alloy powder can contact the surface of the copper-based alloy powder through capillary action and undergo an in-situ synthesis reaction, forming a high-melting-point AlP intermetallic compound in the brazing seam, which can improve the temperature resistance of the brazing seam joint and make the brazing seam have higher strength at high temperature.

Description

Technical Field

[0001] The invention relates to solder powder and a preparation method and application thereof, belonging to the technical field of welding materials. Background Art

[0002] Brazing is the process of using a brazing filler metal with a lower melting point than the base metal to be welded, which reacts chemically with the base metal to achieve the purpose of connecting the base metals. The melting point of the brazing filler metal must be lower than that of the material to be welded, and it is particularly suitable for welding complex and heterogeneous materials.

[0003] During the brazing process, the brazing filler metal melts and fills the gap through capillary action, and undergoes diffusion metallurgical reaction with the base material to be welded at the interface. The melting point of the brazing filler metal is low, and low-melting-point intermetallic compounds are formed during the reaction with the base material. The operating temperature of the brazed joint is subject to the melting temperature of the brazing filler metal, and the temperature resistance of the brazed joint is weaker than that of fusion welding and diffusion welding.

[0004] In the machining industry, tools, drills, and grinders are very likely to heat up during machining. Excessive local temperature can cause the mechanical properties of brazed joints to deteriorate, leading to tool failure. With the advancement of technology, there are more and more scenarios where mechanical equipment replaces manual labor in harsh environments. A large number of complex working conditions require components to withstand high temperatures and maintain mechanical properties at a certain temperature.

[0005] Traditional solder can control the melting point and fluidity by adjusting the composition. Low melting elements will form a large amount of low melting point solid solution phase or intermetallic compounds while reducing the melting point of solder, resulting in a decrease in the high temperature mechanical properties of the brazed joint. At the same time, increasing the melting point of solder is not conducive to the welding process, especially for tempered and quenched metals. Too high welding temperature will affect the mechanical properties of the alloy. Thin-walled and complex components are more sensitive to temperature, and high temperature welding is very likely to cause stress deformation.

[0006] Therefore, there is an urgent need to develop a solder powder with low brazing temperature and good heat resistance of the brazed joint. Summary of the invention

[0007] The object of the present invention is to provide a solder powder with low soldering temperature and good heat resistance of the soldered joint.

[0008] The second object of the present invention is to provide a method for preparing solder powder.

[0009] The third object of the present invention is to provide a use of solder powder in brazing.

[0010] In order to achieve the above objectives, the technical solution adopted by the solder powder of the present invention is:

[0011] A solder powder comprises a copper-phosphorus alloy powder and a copper-based alloy powder, wherein the copper-phosphorus alloy powder is mainly composed of copper and phosphorus, and the mass fraction of the phosphorus in the copper-phosphorus alloy powder is 6-8%; the copper-based alloy powder is a copper-aluminum alloy powder and / or a copper-zinc-aluminum alloy powder; the copper-aluminum alloy powder is mainly composed of copper and aluminum, and the mass fraction of the aluminum in the copper-aluminum alloy powder is 32-42%; the copper-zinc-aluminum alloy powder is mainly composed of copper, zinc and aluminum, and the mass fraction of the aluminum in the copper-zinc-aluminum alloy powder is 28-40%; the molar ratio of the phosphorus in the copper-phosphorus alloy powder to the aluminum in the copper-based alloy powder is 1:(1-1.9).

[0012] The solder powder of the present invention comprises copper-phosphorus alloy powder and copper-based alloy powder. The melting points of the copper-phosphorus alloy powder and the copper-based alloy powder are close. The copper-phosphorus alloy powder is a eutectic component. After melting in the brazing process, it can contact the surface of the copper-based alloy powder through capillary action and undergo an in-situ synthesis reaction to form a high-melting-point AlP intermetallic compound in the brazing seam. AlP is a compound with strong ionic bond. The Al positive ion is located at the node position of the face-centered cubic lattice, and the P negative ion is located at the center of a 1 / 8 small cube in the cube. In order to form a stable valence electron layer, there are strong covalent electrons and covalent bonds between the P negative ions, and the Al positive ion and the P negative ion are still ionic bonded. Since the diffusion reaction free energy of P and Al is low and the reaction trend is obvious, an intermetallic compound AlP with a melting point higher than 2000°C is formed during the reaction process, which can improve the temperature resistance of the brazing seam joint and make the brazing seam have higher strength at high temperature. When the solder powder of the present invention is used for brazing, the brazing temperature is 750-800°C, and the brazing joint can meet high-temperature applications above 900°C.

[0013] The reasons why low-melting solder has poor temperature resistance are as follows: (1) The solder has a low melting point, even much lower than the melting point of the base material. Due to the limitation of solder composition, the mechanical properties of the base material cannot be fully utilized at high temperatures. (2) The reaction between the solder and the base material produces a chemical metallurgical reaction, which easily produces low-melting-point intermetallic compounds, affecting the high-temperature mechanical properties of the joint.

[0014] The reasons for the poor processability of high-temperature solder are as follows: (1) The high temperature of solder can easily damage the base material and reduce its physical properties. (2) The high solder welding temperature places high demands on equipment and energy consumption, which does not meet the requirements of green development.

[0015] If the molar ratio of phosphorus in copper-phosphorus alloy powder to aluminum in copper-based alloy powder is greater than 1:1 (for example, 1:0.5), the P element in the joint will be consumed, resulting in the appearance of a large amount of low-melting-point Cu3P phase, which will reduce the temperature resistance of the welded joint. If the molar ratio is less than 1:1.9 (for example, 1:2), excessive low-melting-point CuAl intermetallic compounds will be generated, reducing the temperature resistance of the welded joint.

[0016] Preferably, the mass fraction of zinc in the copper-zinc-aluminum alloy powder is 3-10%. When the mass fraction of zinc in the copper-zinc-aluminum alloy powder is 3-10%, the liquidus temperature of the copper-zinc-aluminum alloy powder can be close to the liquidus temperature of the copper-phosphorus alloy powder.

[0017] Preferably, the copper-aluminum alloy powder further comprises silicon, and the mass fraction of silicon in the copper-aluminum alloy powder is not greater than 1.2%. When the mass fraction of silicon in the copper-aluminum alloy powder is greater than 1.2%, a low melting point Al-Si phase will be generated during welding, affecting the temperature resistance of the welded joint.

[0018] Preferably, the copper-aluminum alloy powder further comprises zinc, and the mass fraction of zinc in the copper-aluminum alloy powder is not greater than 2%. When the mass fraction of zinc in the copper-aluminum alloy powder is greater than 2%, the liquidus temperature of the copper-aluminum alloy powder will differ greatly from that of the copper-phosphorus alloy powder.

[0019] Preferably, the copper-aluminum alloy powder further comprises tin, and the mass fraction of tin in the copper-aluminum alloy powder is not greater than 2%. When the mass fraction of tin in the copper-aluminum alloy powder is greater than 2%, the low melting point phase will increase during welding, affecting the temperature resistance of the welded joint.

[0020] Preferably, the copper-aluminum alloy powder further comprises iron, and the mass fraction of the iron in the copper-aluminum alloy powder is not greater than 2%. When the mass fraction of the iron in the copper-aluminum alloy powder is greater than 2%, the melting point of the copper-aluminum alloy powder will be too high.

[0021] Preferably, the copper-zinc-aluminum alloy powder further comprises silicon, and the mass fraction of silicon in the copper-zinc-aluminum alloy powder is not greater than 1.2%. When the mass fraction of silicon in the copper-zinc-aluminum alloy powder is greater than 1.2%, a low melting point Al-Si phase will be generated during welding, affecting the temperature resistance of the welded joint.

[0022] Preferably, the copper-zinc-aluminum alloy powder further comprises tin, and the mass fraction of tin in the copper-zinc-aluminum alloy powder is not greater than 2%. When the mass fraction of tin in the copper-zinc-aluminum alloy powder is greater than 2%, the low melting point phase will increase during welding, affecting the temperature resistance of the welded joint.

[0023] Preferably, the copper-zinc-aluminum alloy powder further comprises iron, and the mass fraction of the iron in the copper-zinc-aluminum alloy powder is not greater than 2%. When the mass fraction of the iron in the copper-zinc-aluminum alloy powder is greater than 2%, the melting point of the copper-zinc-aluminum alloy powder will be too high.

[0024] Preferably, the solder powder has a particle size of 200 mesh or finer. When the solder powder has a particle size of 200 mesh or finer, the materials can be mixed more evenly and have the advantages of large surface area and high activity.

[0025] Preferably, the liquidus temperature of the copper-phosphorus alloy powder is 718-740°C. For example, the liquidus temperature of the copper-phosphorus alloy powder is 721-731°C. Preferably, the liquidus temperature of the copper-aluminum alloy powder is 650-780°C. For example, the liquidus temperature of the copper-aluminum alloy powder is 655-773°C. Preferably, the liquidus temperature of the copper-zinc-aluminum alloy powder is 650-780°C. For example, the liquidus temperature of the copper-zinc-aluminum alloy powder is 756°C.

[0026] The technical solution adopted by the method for preparing the solder powder of the present invention is:

[0027] The method for preparing the solder powder as described above comprises the following steps: mixing copper-phosphorus alloy powder and copper-based alloy powder evenly to obtain the solder powder.

[0028] The method for preparing the solder powder of the invention is simple to operate, the solder powder prepared has a low soldering temperature, and the solder joint has good heat resistance.

[0029] Preferably, the copper-phosphorus alloy powder has a particle size of 200 mesh or finer.

[0030] Preferably, the particle size of the copper-based alloy powder is 200 mesh or finer.

[0031] Preferably, the oxygen content of the copper-phosphorus alloy powder is not greater than 2000 ppm. If the oxygen content of the copper-phosphorus alloy powder is too high, the performance of the welded joint will be deteriorated, affecting the welding effect.

[0032] Preferably, the oxygen content of the copper-based alloy powder is not greater than 2000 ppm. If the oxygen content of the copper-based alloy powder is too high, the performance of the welded joint will be deteriorated, affecting the welding effect.

[0033] The technical solution adopted by the application of the solder powder of the present invention in brazing is:

[0034] The brazing filler metal powder as described above is used in brazing.

[0035] When the solder powder of the present invention is used for brazing, the copper-phosphorus alloy powder is melted first during the brazing process. Since phosphorus has a self-brazing effect and the copper-phosphorus alloy powder is a eutectic component, it has good fluidity after melting. At the brazing temperature, the copper-phosphorus melt reacts with the semi-solid copper-based alloy powder (copper-aluminum alloy powder and / or copper-zinc-aluminum alloy powder) through capillary action to generate a large amount of AlP high-temperature intermetallic compounds, which can improve the temperature resistance of the brazed joint and make the brazed joint still have a certain strength at high temperature.

[0036] Preferably, the application is using the brazing filler metal powder for brazing of metal materials.

[0037] Preferably, the metal material is a copper-based metal material.

[0038] When solder powder is used for welding, it can be used alone as solder, or it can be used with a brazing flux or made into solder paste. When using flame or high-frequency welding, solder powder needs to be used with a brazing flux; when using vacuum brazing, solder powder can be used alone; when welding under a protective atmosphere, solder powder can be used alone or with a brazing flux. DETAILED DESCRIPTION

[0039] The technical solution of the present invention is further described below in conjunction with specific embodiments.

[0040] 1. The specific embodiments of the solder powder of the present invention are as follows:

[0041] Example 1

[0042] The solder powder of this embodiment is composed of copper-phosphorus alloy powder and copper-based alloy powder; the copper-phosphorus alloy powder is prepared by atomization method, and is composed of copper and phosphorus elements, the mass fraction of phosphorus element is 7.2%, the mass fraction of copper element is 92.8%, and the liquidus temperature of the copper-phosphorus alloy powder is 721°C; the copper-based alloy powder is copper-aluminum alloy powder, which is prepared by atomization method, and is composed of copper and aluminum elements, the mass fraction of aluminum element is 37%, the mass fraction of copper element is 63%, and the liquidus temperature of the copper-aluminum alloy powder is 738°C; the particle size of the copper-phosphorus alloy powder is 200 mesh or finer, and the oxygen content is less than 2000ppm; the particle size of the copper-based alloy powder is 200 mesh or finer, and the oxygen content is less than 2000ppm; the molar ratio of the phosphorus element in the copper-phosphorus alloy powder to the aluminum element in the copper-based alloy powder is 1:1.4.

[0043] Example 2

[0044] The solder powder of this embodiment is composed of copper-phosphorus alloy powder and copper-based alloy powder; the copper-phosphorus alloy powder is prepared by atomization method, and is composed of copper and phosphorus elements, the mass fraction of phosphorus element is 7.2%, the mass fraction of copper element is 92.8%, and the liquidus temperature of the copper-phosphorus alloy powder is 721°C; the copper-based alloy powder is copper-aluminum alloy powder, which is prepared by atomization method, and is composed of copper and aluminum elements, the mass fraction of aluminum element is 42%, the mass fraction of copper element is 58%, and the liquidus temperature of the copper-aluminum alloy powder is 684°C; the particle size of the copper-phosphorus alloy powder is 200 mesh or finer, and the oxygen content is less than 1000ppm; the particle size of the copper-based alloy powder is 200 mesh or finer, and the oxygen content is less than 1000ppm; the molar ratio of the phosphorus element in the copper-phosphorus alloy powder to the aluminum element in the copper-based alloy powder is 1:1.6.

[0045] Example 3

[0046] The solder powder of this embodiment is composed of copper-phosphorus alloy powder and copper-based alloy powder; the copper-phosphorus alloy powder is prepared by mechanical crushing, and is composed of copper and phosphorus elements, the mass fraction of phosphorus element is 7%, the mass fraction of copper element is 93%, and the liquidus temperature of the copper-phosphorus alloy powder is 733°C; the copper-based alloy powder is copper-aluminum alloy powder, which is prepared by mechanical crushing, and is composed of copper and aluminum elements, the mass fraction of aluminum element is 32%, the mass fraction of copper element is 68%, and the liquidus temperature of the copper-aluminum alloy powder is 773°C; the particle size of the copper-phosphorus alloy powder is 200 mesh or finer, and the oxygen content is less than 2000ppm; the particle size of the copper-based alloy powder is 200 mesh or finer, and the oxygen content is less than 2000ppm; the molar ratio of the phosphorus element in the copper-phosphorus alloy powder to the aluminum element in the copper-based alloy powder is 1:1.6.

[0047] Example 4

[0048] The solder powder of this embodiment is composed of copper-phosphorus alloy powder and copper-based alloy powder; the copper-phosphorus alloy powder is prepared by atomization method, and is composed of copper and phosphorus elements, the mass fraction of phosphorus element is 8%, the mass fraction of copper element is 92%, and the liquidus temperature of the copper-phosphorus alloy powder is 724°C; the copper-based alloy powder is copper-zinc-aluminum alloy powder, which is prepared by atomization method, and is composed of copper, zinc and aluminum elements, the mass fraction of aluminum element is 33%, the mass fraction of zinc element is 6%, the mass fraction of copper element is 61%, and the liquidus temperature of the copper-zinc-aluminum alloy powder is 756°C; the particle size of the copper-phosphorus alloy powder is 200 mesh or finer, and the oxygen content is less than 2000ppm; the particle size of the copper-based alloy powder is 200 mesh or finer, and the oxygen content is less than 2000ppm; the molar ratio of phosphorus element in the copper-phosphorus alloy powder to aluminum element in the copper-based alloy powder is 1:1.35.

[0049] Example 5

[0050] The solder powder of this embodiment is composed of copper-phosphorus alloy powder and copper-based alloy powder; the copper-phosphorus alloy powder is prepared by atomization method, and is composed of copper and phosphorus elements, the mass fraction of phosphorus element is 6%, the mass fraction of copper element is 94%, and the liquidus temperature of the copper-phosphorus alloy powder is 731°C; the copper-based alloy powder is composed of copper-aluminum alloy powder and copper-zinc-aluminum alloy powder with a mass ratio of 1:1, wherein the copper-aluminum alloy powder is prepared by atomization method, and is composed of copper and aluminum elements, the mass fraction of aluminum element is 40%, the mass fraction of copper element is 60%, and the liquidus temperature of the copper-aluminum alloy powder is 731°C. The liquidus temperature is 689°C; the copper-zinc-aluminum alloy powder is prepared by an atomization method, and is composed of copper, zinc and aluminum elements, the mass fraction of the aluminum element is 33%, the mass fraction of the zinc element is 6%, the mass fraction of the copper element is 61%, and the liquidus temperature of the copper-zinc-aluminum alloy powder is 756°C; the particle size of the copper-phosphorus alloy powder is finer than 200 mesh, and the oxygen content is less than 1000ppm; the particle size of the copper-based alloy powder is finer than 200 mesh, and the oxygen content is less than 1000ppm; the molar ratio of the phosphorus element in the copper-phosphorus alloy powder to the aluminum element in the copper-based alloy powder is 1:1.9.

[0051] Example 6

[0052] The only difference between the solder powder of this embodiment and the solder powder of Example 3 is that the copper-aluminum alloy powder in the solder powder of this embodiment is composed of copper, silicon, tin, iron and aluminum elements, the mass fraction of the aluminum element is 42%, the mass fraction of the zinc element is 2%, the mass fraction of the silicon element is 1.2%, the mass fraction of the tin element is 2%, the mass fraction of the iron element is 2%, the mass fraction of the copper element is 50.8%, and the liquidus temperature of the copper-aluminum alloy powder is 655°C.

[0053] Example 7

[0054] The only difference between the solder powder of this embodiment and the solder powder of Example 4 is that the mass fraction of the aluminum element in the copper-zinc-aluminum alloy powder in the solder powder of this embodiment is 40%, the mass fraction of the zinc element is 10%, the mass fraction of the copper element is 50%, the liquidus temperature of the copper-zinc-aluminum alloy powder is 665°C; and the molar ratio of the phosphorus element in the copper-phosphorus alloy powder to the aluminum element in the copper-based alloy powder is 1:1.

[0055] Example 8

[0056] The only difference between the solder powder of this embodiment and the solder powder of Example 4 is that the copper-zinc-aluminum alloy powder in the solder powder of this embodiment is composed of copper, zinc, silicon, tin, iron and aluminum elements, the mass fraction of the aluminum element is 28%, the mass fraction of the zinc element is 3%, the mass fraction of the silicon element is 1.2%, the mass fraction of the tin element is 2%, the mass fraction of the iron element is 2%, the mass fraction of the copper element is 63.8%, and the liquidus temperature of the copper-zinc-aluminum alloy powder is 735°C.

[0057] Comparative Example 1

[0058] The difference between the solder powder of this comparative example and the solder powder of Example 3 is that the mass fraction of aluminum element in the copper-aluminum alloy powder of this comparative example is 30%, the mass fraction of copper element is 70%, and the liquidus temperature of the copper-aluminum alloy powder is 824°C.

[0059] Comparative Example 2

[0060] The only difference between the solder powder of this comparative example and the solder powder of Example 3 is that the mass fraction of aluminum element in the copper-aluminum alloy powder in the solder powder of this comparative example is 44%, the mass fraction of copper element is 56%, and the liquidus temperature of the copper-aluminum alloy powder is 618°C.

[0061] Comparative Example 3

[0062] The only difference between the solder powder of this comparative example and the solder powder of Example 7 is that the mass fraction of aluminum element in the copper-zinc-aluminum alloy powder in the solder powder of this comparative example is 42%, the mass fraction of copper element is 48%, and the liquidus temperature of the copper-zinc-aluminum alloy powder is 638°C.

[0063] Comparative Example 4

[0064] The only difference between the solder powder of this comparative example and the solder powder of Example 7 is that the mass fraction of aluminum element in the copper-zinc-aluminum alloy powder in the solder powder of this comparative example is 26%, the mass fraction of copper element is 64%, and the liquidus temperature of the copper-zinc-aluminum alloy powder is 825°C.

[0065] Comparative Example 5

[0066] The difference between the solder powder of this comparative example and the solder powder of Example 4 is that the mass fraction of phosphorus in the copper-phosphorus alloy powder of this comparative example is 10%, the mass fraction of copper is 90%, and the liquidus temperature of the copper-phosphorus alloy powder is 817°C.

[0067] Comparative Example 6

[0068] The difference between the solder powder of this comparative example and the solder powder of Example 5 is that the mass fraction of phosphorus element in the copper-phosphorus alloy powder of this comparative example is 5%, the mass fraction of copper element is 95%, and the liquidus temperature of the copper-phosphorus alloy powder is 884°C.

[0069] 2. The specific embodiment of the method for preparing the solder powder of the present invention is as follows:

[0070] The preparation method of the solder powder of this embodiment is the preparation method of any solder powder in Embodiments 1-8, and specifically comprises the following steps: the copper-phosphorus alloy powder and the copper-based alloy powder in any solder powder in Embodiments 1-8 are mixed uniformly by using a three-dimensional mixer.

[0071] 3. Specific examples of the application of the solder powder of the present invention in brazing are as follows:

[0072] Example 9

[0073] The application of the solder powder of this embodiment in brazing specifically comprises the following steps:

[0074] The solder powder and the brazing agent of Example 1 are mixed uniformly in a mass ratio of 7:3 to obtain a solder, and then the solder is placed at the overlapping interface of the copper sheet to be welded, and the solder and the copper sheet to be welded are heated to 760-780°C by a high-frequency heating machine, the solder is melted, and then the heating is stopped to complete the brazing. The brazing agent used in this embodiment is composed of cesium fluoroaluminate, cryolite and boron oxide in a mass ratio of 2.5:3:4.5.

[0075] Example 10

[0076] The application of the solder powder of this embodiment in brazing specifically comprises the following steps:

[0077] The solder powder and colloid of Example 2 are mixed uniformly in a mass ratio of 8:1 to obtain a solder paste, and then the solder paste is applied to the overlapping interface of the copper sheet to be welded, and then placed in a vacuum brazing furnace for welding, the heating rate in the vacuum brazing furnace is 50°C / min, and the brazing temperature is 750-780°C. The colloid used in this embodiment is composed of polyvinyl butyral (when polyvinyl butyral is made into an ethanol solution with a mass fraction of 10%, the viscosity is 80mPa·s) and a solvent, the mass fraction of polyvinyl butyral in the colloid is 5%, and the solvent is composed of ethanol, methanol and ethylene glycol butyl ether with a mass ratio of 30:25:40.

[0078] Embodiment 11

[0079] The application of the solder powder of this embodiment in brazing specifically comprises the following steps:

[0080] The solder powder, flux and colloid of Example 1 are mixed uniformly in a mass ratio of 7:1.5:1.5 to obtain a solder paste, and then the solder paste is applied to the overlapping interface of the copper sheet to be welded, and then the joint is heated with a flame gun. When the joint temperature is heated to 780-800°C, the solder powder in the solder paste melts and the brazing is completed. The flux used in this embodiment is composed of cesium fluoroaluminate, cryolite and boron oxide in a mass ratio of 2.5:3:4.5. The colloid used in this embodiment is composed of polyvinyl butyral with a viscosity of 80s and a solvent, the mass fraction of polyvinyl butyral in the colloid is 5%, and the solvent is composed of ethanol, methanol and ethylene glycol butyl ether.

[0081] Example 12

[0082] The application of the solder powder of this embodiment in brazing specifically comprises the following steps:

[0083] The solder powder and the flux of Example 3 are mixed uniformly in a mass ratio of 9.5:0.5 to obtain a solder, and then the solder is placed at the overlap interface of the copper sheet to be welded, and then placed in a protective atmosphere furnace to heat the solder and the copper sheet to be welded to 780-800°C, the solder is melted, and then the heating is stopped to complete the brazing. The flux used in this embodiment is composed of cesium fluoroaluminate, cryolite and boron oxide in a mass ratio of 3:3:4.

[0084] Example 13

[0085] The application of the solder powder of this embodiment in brazing specifically comprises the following steps:

[0086] The solder powder and the flux of Example 4 are mixed uniformly in a mass ratio of 9.5:0.5 to obtain a solder, and then the solder is placed at the overlap interface of the copper sheet to be welded, and then placed in a protective atmosphere furnace to heat the solder and the copper sheet to be welded to 780-800°C, the solder is melted, and then the heating is stopped to complete the brazing. The flux used in this embodiment is composed of cesium fluoroaluminate, cryolite and boron oxide in a mass ratio of 3:3:4.

[0087] Embodiment 14

[0088] The application of the solder powder of this embodiment in brazing specifically comprises the following steps:

[0089] The solder powder of Example 5 is placed at the overlapping interface of the copper sheets to be welded, and then placed in a protective atmosphere furnace to heat the solder powder and the copper sheets to be welded to 780-800° C., the solder melts, and then the heating is stopped to complete the brazing.

[0090] Embodiment 15

[0091] The application of the solder powder of this embodiment in brazing specifically comprises the following steps:

[0092] The solder powder of Example 6 is placed at the overlapping interface of the copper sheets to be welded, and then placed in a protective atmosphere furnace to heat the solder powder and the copper sheets to be welded to 750-780°C. The solder melts, and then heating is stopped to complete the brazing.

[0093] Example 16

[0094] The application of the solder powder of this embodiment in brazing specifically comprises the following steps:

[0095] The solder powder of Example 7 is placed at the overlapping interface of the copper sheets to be welded, and then placed in a protective atmosphere furnace to heat the solder powder and the copper sheets to be welded to 750-770°C until the solder melts, and then heating is stopped to complete brazing.

[0096] Embodiment 17

[0097] The application of the solder powder of this embodiment in brazing specifically comprises the following steps:

[0098] The solder powder of Example 8 is placed at the overlapping interface of the copper sheets to be welded, and then placed in a protective atmosphere furnace to heat the solder powder and the copper sheets to be welded to 780-800°C until the solder melts, and then heating is stopped to complete brazing.

[0099] Experimental example

[0100] In order to evaluate the performance of the solder powder of Examples 1-8, the brazed copper sheets in Examples 9-17 were heated to 900°C to observe whether the solder flowed out and whether the weld cracked and deformed. At the same time, the tensile strength of the brazed joint at high temperature (900°C) was tested. The tensile strength test method was carried out in accordance with the provisions of the standard GB / T 11363-2008 "Test Method for Strength of Brazed Joints". At the same time, in order to compare with commercially available solders and the solder powders of Comparative Examples 1-6, copper-based solder BCu92P (the solder consists of copper and phosphorus, the mass fraction of phosphorus is 7.5-8.1%, the solidus temperature of the solder is 710°C, and the liquidus temperature is 720°C), silver-based solder BAg25CuZn (the solder consists of silver, copper and zinc, the mass fraction of silver is 24-26%, the mass fraction of copper is 39-41%, the mass fraction of zinc is 33-37%, and the solidus temperature of the solder is 700°C, The liquidus temperature is 790°C), copper-based brazing material BCu54Zn (the brazing material is composed of copper and zinc elements, the mass fraction of copper element is 53-55%, the solidus temperature of the brazing material is 885°C, and the liquidus temperature is 888°C) are used for brazing of copper sheets according to the method of Example 16, and the brazing temperatures are 750°C, 840°C, and 930°C respectively. The brazing material powders of Comparative Examples 1-6 are used for brazing of copper sheets according to the method of Example 16, and the brazing temperatures are 860°C, 650°C, 680°C, 860°C, 850°C, and 920°C respectively. After brazing, the brazed copper sheets are heated to 900°C by the above method, and the brazing is observed to see whether the brazing material flows out and whether the weld is cracked and deformed, and the tensile strength of the brazed joint at high temperature (900°C) is tested.

[0101] The performance of the welds and joints obtained when welding copper sheets using the solder powders of Examples 1-8 (i.e., the welds and joints obtained in Examples 9-17) and the performance of the welds and joints obtained when welding copper sheets using the solder powders of copper-based solder BCu92P, silver-based solder BAg25CuZn, copper-based solder BCu54Zn, and comparative examples 1-6 are shown in Table 1.

[0102] Table 1 Properties of welds and joints obtained by brazing copper sheets with different brazing filler metal powders

[0103]

[0104]

[0105] Note: / indicates that the test cannot be performed.

[0106] At the same time, when the solder powder and colloid of Example 2 in Example 10 are mixed in a mass ratio of (7.5-9): (1-2.5) to prepare solder paste, when the prepared solder paste is used to braze copper sheets according to the method of Example 10, the obtained welds and joints have similar performance to the welds and joints obtained in Example 10. When the copper-phosphorus alloy powder and the copper-aluminum alloy powder in the solder powder of Example 2 are both prepared by mechanical crushing, when the solder powder and colloid are mixed in a mass ratio of (6-7.5): (2.5-4) to prepare solder paste according to the method of Example 10, when the prepared solder paste is used to braze copper sheets according to the method of Example 10, the obtained welds and joints have similar performance to the welds and joints obtained in Example 10. When the copper-phosphorus alloy powder and the copper-aluminum alloy powder in the solder powder of Example 1 are both prepared by mechanical crushing, when the solder powder, the brazing agent and the colloid are mixed in a mass ratio of 6:1.5:3.5 according to the method in Example 11 to prepare the solder paste, and when the prepared solder paste is used to braze the copper sheet according to the method of Example 11, the performance of the obtained welds and joints are similar to those of the welds and joints obtained in Example 11.

[0107] It can be seen from the above test results that when the brazing filler metal powder of Examples 1-8 is used to braze the copper sheet, a large amount of AlP intermetallic compounds with a temperature exceeding 2000°C are synthesized in situ in the brazing seam during the brazing process, and the remaining unreacted Al and other elements form a high-temperature copper-based solid solution phase, which increases the melting temperature of the brazing seam. Therefore, when the brazing seam is heated to 900°C, the brazing filler metal does not melt, the weld does not deform, and a certain strength can still be maintained. However, the liquidus temperatures of the copper-phosphorus alloy powder and the copper-based alloy powder in the brazing filler metal powder of Comparative Examples 1-6 are quite different, and copper-phosphorus or copper-based alloy is lost during the melting process, resulting in the inability to effectively form high-melting-point AlP intermetallic compounds.

Claims

1. A solder powder, characterized in that: The invention comprises copper-phosphorus alloy powder and copper-based alloy powder, wherein the copper-phosphorus alloy powder is mainly composed of copper and phosphorus, and the mass fraction of phosphorus in the copper-phosphorus alloy powder is 6-8%; the copper-based alloy powder is copper-aluminum alloy powder and / or copper-zinc-aluminum alloy powder; the copper-aluminum alloy powder is mainly composed of copper and aluminum, and the mass fraction of aluminum in the copper-aluminum alloy powder is 32-42%; the copper-zinc-aluminum alloy powder is mainly composed of copper, zinc and aluminum, and the mass fraction of aluminum in the copper-zinc-aluminum alloy powder is 28-40%; the molar ratio of phosphorus in the copper-phosphorus alloy powder to aluminum in the copper-based alloy powder is 1:(1-1.9); the mass fraction of zinc in the copper-zinc-aluminum alloy powder is 3-10%.

2. The solder powder according to claim 1, wherein The copper-aluminum alloy powder also includes silicon element, and the mass fraction of silicon element in the copper-aluminum alloy powder is not greater than 1.2%.

3. The solder powder according to claim 1, wherein The copper-aluminum alloy powder also includes zinc element, and the mass fraction of the zinc element in the copper-aluminum alloy powder is not greater than 2%.

4. The solder powder according to claim 1, wherein The copper-aluminum alloy powder also includes tin element, and the mass fraction of the tin element in the copper-aluminum alloy powder is not greater than 2%.

5. The solder powder according to claim 1, wherein The copper-aluminum alloy powder also includes iron, and the mass fraction of the iron in the copper-aluminum alloy powder is not greater than 2%.

6. The solder powder according to any one of claims 1 to 5, characterized in that The copper-zinc-aluminum alloy powder also includes silicon element, and the mass fraction of silicon element in the copper-zinc-aluminum alloy powder is not greater than 1.2%.

7. The solder powder according to any one of claims 1 to 5, characterized in that The copper-zinc-aluminum alloy powder also includes tin element, and the mass fraction of the tin element in the copper-zinc-aluminum alloy powder is not greater than 2%; the copper-zinc-aluminum alloy powder also includes iron element, and the mass fraction of the iron element in the copper-zinc-aluminum alloy powder is not greater than 2%.

8. A method for preparing a solder powder according to any one of claims 1 to 7, characterized in that: The following steps are involved: The copper-phosphorus alloy powder and the copper-based alloy powder are mixed evenly to obtain the product.

9. Use of the solder powder according to any one of claims 1 to 7 in brazing.

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