An aluminum-tin-copper alloy solder and a method of making the same

Abstract

The application provides an aluminum-tin-copper alloy solder and a preparation method thereof, and relates to the technical field of alloys. Specifically, the method comprises the following steps: 1) preparing elemental raw materials of aluminum, tin and copper, mixing and heating the raw materials to obtain a melt; 2) placing an isometric pure aluminum pipe in a mold cylinder, and making the outer wall of the pure aluminum pipe completely adhere to the inner wall of the mold cylinder; continuously performing water cooling treatment on the mold cylinder, and pouring the melt into the pure aluminum pipe to obtain an ingot wrapped by the aluminum pipe; 3) performing homogenization annealing treatment on the ingot wrapped by the aluminum pipe, and then performing turning treatment on the end surface of the ingot and the outer surface of part of the aluminum pipe; and 4) preheating the ingot wrapped by the aluminum pipe and an extrusion die, and extruding the ingot wrapped by the aluminum pipe through the extrusion die to obtain aluminum-tin-copper wire material. The application fills the technical vacancy of aluminum-tin-copper solder products, and solves the technical problem of tin element loss caused by tin element segregation and tin sweat in the preparation of aluminum-tin-copper solder.

Description

Technical Field

[0001] This invention relates to the field of alloy technology, and more specifically, to an aluminum-tin-copper alloy solder and its preparation method. Background Technology

[0002] Engines are increasingly developing towards higher speeds, higher power, lower energy consumption, lighter weight, and higher boost pressure, thus placing higher demands on the performance of their components. Bearings, as a crucial component of engines and internal combustion engines, should possess advantages such as fatigue resistance, wear resistance, anti-galling, corrosion resistance, good compliance, and environmental friendliness. Currently, no single material can simultaneously meet these requirements; therefore, the use of composite materials of bearing alloys and steel to create alloy-steel composite bearing materials is a current hot research and application area.

[0003] Commonly used bearing alloys are tin-based and lead-based, namely the well-known Babbitt alloy. However, with the improvement of equipment performance, operating speed, and increased load, Babbitt alloy bearings have relatively low fatigue strength and high-temperature load-bearing capacity, making them difficult to meet requirements. Copper-based bearings are second-generation products with strong load-bearing capacity and high fatigue resistance, but their conformability and embeddability are poor. Furthermore, copper-based bearings themselves contain lead, which does not meet current environmental protection requirements. Therefore, the international community currently tries to avoid using lead-containing bearing alloys. Aluminum-tin bearings, with their high fatigue strength and long service life, are gradually becoming a new material to replace Babbitt alloy. Al-Sn bearing alloys can be divided into high-tin aluminum alloys (tin content ≥ 20%), medium-tin aluminum alloys (6% < tin content < 20%), and low-tin aluminum alloys (tin content ≤ 6%) according to their Sn content. Studies have found that AlSn20 bearing alloy does not require coating and has excellent interlocking and embedding properties, while also possessing good surface properties and fatigue resistance. Elements such as Mn and Cu can be added to further improve its fatigue performance. Currently, the most widely used alloy is AlSn20Cu. The fatigue strength of AlSn20Cu alloy is approximately 3.5 times that of Babbitt alloy, and its compliance and embedding properties are close to those of Babbitt alloy, while its cost is lower than that of Babbitt alloy.

[0004] Currently, there are no mature application demonstrations of aluminum-tin-copper welding materials in existing technologies, especially for high-tin-content AlSn20Cu welding wire. Besides the limited application range of aluminum-based bearing alloys, a key reason is that the microstructure and properties of AlSn20Cu welding wire differ significantly from conventional aluminum alloy welding materials or Babbitt alloy welding materials, presenting a high level of technical difficulty. To successfully prepare AlSn20Cu welding wire, it is essential to overcome the technical challenges of Sn segregation in the alloy and the easy loss and expulsion of Sn at high temperatures, forming Sn nodules.

[0005] In AlSn20Cu alloys, Al-Sn alloys are typical binary immiscible systems, being miscible in the liquid state but immiscible in the solid state. Furthermore, Al and Sn have significantly different melting points and densities, with Al at 660.45℃ and Sn at 2.7 g / cm³, respectively. 3 Sn (231.96℃, 7.28g / cm³) 3 Therefore, during the solidification of aluminum alloys, low-melting-point Sn is continuously expelled and enriched, gradually accumulating in the higher-temperature regions of the casting. Simultaneously, due to Sn's high density, Sn metal tends to segregate towards the bottom of the casting or the last region to solidify. If the alloy used to produce AlSn20Cu welding wire has significant compositional segregation, it will lead to discontinuities in subsequent production processes, unstable welding wire quality, and a significant impact on the performance of the final bearing alloy material. Therefore, resolving the compositional inhomogeneity problem of AlSn20Cu alloy is one of the keys to successfully preparing welding materials.

[0006] Furthermore, during the solidification process of aluminum-tin-copper alloys, the high tin content forms a continuous tin-rich network that encapsulates the α-Al grains. Interconnected channels exist between these α-Al grains, allowing the Sn phase to flow within them. When these channels extend to the outer surface, the Sn phase may flow to the outside of the matrix. This means that when the alloy temperature rises above 230°C, spherical Sn beads, commonly known as "Sn sweat," will precipitate and condense on the alloy surface. Since aluminum-tin-copper alloys are based on aluminum, and heat treatment of the semi-finished solder materials is necessary to ensure continuity and operability during the solder preparation process (at temperatures exceeding 300°C), directly heat-treating AlSn20Cu alloy without any prior treatment will inevitably produce the "Sn sweat" phenomenon, leading to Sn loss and ultimately resulting in substandard solder composition.

[0007] In view of this, the present invention is hereby proposed. Summary of the Invention

[0008] The primary objective of this invention is to provide a method for preparing aluminum-tin-copper alloy solder, which fills the gap in existing aluminum-tin-copper solder products and solves the problems of tin element segregation and tin element loss caused by the formation of "tin sweat" in the alloy during the preparation process of aluminum-tin-copper solder.

[0009] The second objective of this invention is to provide an aluminum-tin-copper alloy solder, prepared based on the aforementioned method, which can be used in popular fields such as aluminum-based alloy-steel composite bearings or aluminum-tin bearings.

[0010] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted:

[0011] A method for preparing an aluminum-tin-copper alloy solder includes the following steps:

[0012] Step 1: Prepare the metal raw materials of aluminum, tin and copper, which, by mass percentage, include 5.5% to 45% tin, 0.4% to 1.3% copper and the balance aluminum; heat and mix the metal raw materials to obtain a melt;

[0013] Step 2: Insert a pure aluminum tube of equal height into the mold cylinder, with the outer wall of the pure aluminum tube completely fitting the inner wall of the mold cylinder; continuously water-cool the mold cylinder while pouring the melt into the pure aluminum tube, and then obtain an ingot wrapped by the aluminum tube.

[0014] Step 3: Perform homogenization annealing on the ingot wrapped in the aluminum tube; then perform turning on the end face of the ingot and part of the outer surface of the aluminum tube.

[0015] Step 4: Preheat the machined ingot and the extrusion die respectively, and then extrude the ingot wrapped in the aluminum tube through the extrusion die to obtain an aluminum-tin-copper rod with a diameter of 8mm to 12mm.

[0016] An aluminum-tin-copper alloy solder is prepared according to the method described above.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0018] (1) This invention provides a preparation process for aluminum-tin-copper alloy solder, which fills the technical gap in the preparation of aluminum-tin-copper alloy solder products due to the difficulty in obtaining solder products due to tin precipitation. This invention uses pure aluminum tubes as casting shells. Since the melting point of pure aluminum is much higher than that of tin, and pure aluminum also has good machinability, the pure aluminum tubes are wrapped together with the extrusion process to tightly press the pure aluminum and aluminum-tin-copper alloy together. This can effectively prevent the phenomenon of "tin sweat" caused by the temperature exceeding the melting point of tin during the extrusion and subsequent heat treatment of aluminum-tin-copper alloy materials, and avoid the loss of tin elements.

[0019] (2) The present invention first performs homogenization annealing treatment, and then extrudes the aluminum-tin-copper solder. The homogenization annealing treatment causes the tin phase to dissolve and diffuse, and the morphology gradually changes from strip and block to spheroid and aggregate into a network. Then, the shearing action of the extrusion die and the flow of metal are used to stir the solid alloy a second time, so that the tin element is more evenly distributed, the mechanical properties of the structure are improved, and it is also convenient for subsequent rolling processing. Attached Figure Description

[0020] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0021] Figure 1 A schematic diagram of a feasible water-cooled mold is provided.

[0022] Figure 2 A low-magnification cross-sectional view of the aluminum-tin-copper alloy solder prepared in Example 1 is provided;

[0023] Figure 3 Microstructure diagrams of the aluminum-tin-copper alloy solder prepared in Example 1 are provided;

[0024] Figure 4 A high-magnification microstructure image of the center position of the aluminum-tin-copper alloy solder prepared in Example 1 is provided. Detailed Implementation

[0025] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings and specific embodiments. However, those skilled in the art will understand that the embodiments described below are some embodiments of the present invention, but not all embodiments, and are only used to illustrate the present invention, and should not be regarded as limiting the scope of the present invention. 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. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall be followed. Where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be purchased commercially.

[0026] This invention is carried out through the following specific embodiments: a method for preparing an aluminum-tin-copper alloy solder, mainly including the following steps:

[0027] Step 1: Prepare the metal raw materials of aluminum, tin and copper, which, by mass percentage, include 5.5% to 45% tin, 0.4% to 1.3% copper and the balance aluminum; heat and mix the metal raw materials to obtain a melt.

[0028] In this step, the raw materials are formulated and the melt is prepared based on the alloy composition. It should be noted that, based on the technical problem to be solved by this invention, this invention may consist of only three elements: tin, copper, and aluminum, or it may contain other doping elements. However, this invention does not rely on any other doping element to solve the technical problem of tin precipitation.

[0029] In a preferred embodiment, the elemental raw materials, by mass percentage, include, but are not limited to: tin 5.5%, 6%, 7%, 8%, 10%, 15%, 12.5%, 17.5%, 20%, 25%, 30%, 35%, 37.5%, 40%, 42.5%, 45%, copper 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.1%, 1.2%, 1.3%, and the balance aluminum; the mass percentages of tin and copper can be the above-mentioned point values, or any real value within the numerical range formed by any two of the above point values.

[0030] In one preferred embodiment, the elemental raw material can be a metal ingot, or a raw material in any form such as wire, granules, sheet, or plate; the present invention does not impose any restrictions on it.

[0031] In a preferred embodiment, the purity of the elemental raw material should be ≥99%.

[0032] In a preferred embodiment, before performing step one, the method further includes: pre-treating the elemental raw material, the pre-treatment including: cleaning the surface of the elemental raw material with an organic solvent; the organic solvent includes, but is not limited to, ethanol, acetone, methanol, etc.; and drying after cleaning to remove the organic solvent.

[0033] As a preferred embodiment, before performing step one, the method further includes: preheating the elemental raw material at a temperature of 120°C to 180°C for a time of 0.8h to 1.5h.

[0034] In a preferred embodiment, before heating and mixing the elemental raw materials, the method further includes preheating the container to a temperature of 450°C to 550°C.

[0035] In a preferred embodiment, the heating temperature of the elemental raw material is 700℃~720℃; in an optional embodiment, the heating temperature of the elemental raw material includes, but is not limited to, one or any two of the following: 700, 702, 705, 708, 710, 712, 715, 718, 720 (℃).

[0036] In a preferred embodiment, the elemental raw materials are added in the following order: aluminum and copper are melted into a liquid state first, and then tin is added to achieve uniformity of the melt and prevent excessive oxidation of metallic tin.

[0037] In a preferred embodiment, after step one and before step two, the method further includes adding a refining agent to the melt; the amount of the refining agent added is 0.1% to 0.3% of the mass of the melt.

[0038] In a more preferred embodiment, the refining agent includes hexachloroethane; the chlorine atoms in hexachloroethane have a high electronegativity and can interact with metal atoms to form coordinate bonds or covalent bonds, thereby forming metal chloride precipitation; and excess hexachloroethane will decompose at high temperature, avoiding contamination of the molten metal.

[0039] In a preferred embodiment, after step one and before step two, the method further includes: introducing an inert gas into the melt while simultaneously stirring the melt; the inert gas includes at least one of helium, neon, argon, etc.

[0040] In a more preferred embodiment, the flow rate of the inert gas is based on the ability of the melt surface to generate bubbles of 5 mm to 10 mm; the inert gas venting time is 10 min to 15 min.

[0041] Step 2: Insert a pure aluminum tube of equal height into the mold cylinder, with the outer wall of the pure aluminum tube completely fitting the inner wall of the mold cylinder; continuously water-cool the mold cylinder while pouring the melt into the pure aluminum tube, and then obtain an ingot encased in aluminum tube.

[0042] In a preferred embodiment, the inner diameter of the pure aluminum tube is 55mm, the thickness of the pure aluminum tube is 2.5mm, and the height of the pure aluminum tube is 150mm; that is, the outer diameter of the pure aluminum tube is 60mm.

[0043] In a preferred embodiment, the water cooling process includes: mounting a water cooling assembly on the outer wall of the mold cylinder and dissipating heat through various water flow paths.

[0044] As a more preferred implementation method, such as Figure 1 The diagram shows a self-designed water-cooling mold for the water-cooling process described in step two of this invention.

[0045] On the outer side of the cylindrical mold cylinder, the water-cooled mold is sequentially provided with an inner sleeve and a cooling water chamber; wherein, the inner sleeve is made of 45 steel, and the cooling water chamber is welded from steel plate with a thickness of 2mm, and the bottom and top of the cooling water chamber are respectively provided with a water inlet end and a water outlet end; a water inlet pipe is connected to the water inlet end, and a water outlet pipe is connected to the water outlet end, and circulating cooling water flows through the pipe.

[0046] When the water-cooled mold is in operation, the heat of the molten material inside the mold is quickly transferred to the mold during casting, and the heat is quickly carried away by the circulating cooling water, thereby achieving the purpose of water cooling.

[0047] Figure 1The water-cooled mold shown is designed according to the preferred embodiment described above, with parameters such as overall diameter, height, and inner diameter. However, in some other preferred embodiments, those skilled in the art can customize the water-cooled mold based on the structural parameters of the mold cylinder and the pure aluminum tube. Furthermore, Figure 1 The specifications marked in the figures, such as “95”, “55”, “150”, and “170”, are all in mm.

[0048] In a more preferred embodiment, the heat dissipation medium in the water-cooling component is water; and the water circulates within the water-cooling component.

[0049] In a preferred embodiment, the melt obtained in step one is pre-placed in a smelting furnace, and during the casting process in step two, the melt in the smelting furnace is continuously stirred, that is, the uncast melt is continuously stirred.

[0050] As a preferred embodiment, the stirring method can be automatic stirring or manual stirring; automatic stirring is carried out in a smelting furnace equipped with a stirring device, and the stirring blade inserted into the melt is driven by a motor to rotate, thereby stirring the AlSnCu melt to achieve a uniform distribution of components, and the stirring speed is controlled at 20 r / min; manual stirring is carried out by holding a graphite stirring rod and stirring at a uniform speed in one direction, with the stirring speed being such that the melt does not produce obvious splashing.

[0051] In this invention, stirring, water cooling, and casting are performed simultaneously to ensure that the composition of the ingot is mostly uniform, greatly reducing the problem of Sn segregation due to its high density. This is because the densities of Sn, Cu, and Al are significantly different, and the three elements are difficult to combine to form an intermediate phase. In particular, the density difference between Al and Sn, which have higher contents, is huge, and they are immiscible. In a static melt, they are prone to stratification, with the denser Sn and Cu sinking to the bottom and the less dense Al floating to the top, resulting in significant deviations in the composition of the cast ingot. Therefore, physical stirring is used to ensure that the elements in the melt are in a more uniform distribution state. Combined with a water cooling device, the uniformly distributed liquid metal is quickly transformed into a solid state. At the same time, the rapid cooling rate has a grain-refining effect, which improves the microstructure and properties of the alloy.

[0052] In a preferred embodiment, the temperature of the elemental raw material obtained in step one is 700℃~720℃. However, due to the existence of other optional refining operations or unavoidable operation intervals for those skilled in the art, the melt will experience a certain temperature drop during step two; the temperature of the melt in step two is 670℃~700℃.

[0053] As a preferred embodiment, after step two and before step three, the method further includes: performing surface treatment on the ingot wrapped in the aluminum tube to remove the impurity layer on the surface of the ingot; as an optional embodiment, after the ingot wrapped in the aluminum tube has cooled, it is turned by a lathe to remove the surface impurity layer of the ingot; as an optional embodiment, after the surface treatment, the outer diameter of the aluminum tube (containing the ingot) is 57mm to 58mm and the height is 150mm.

[0054] Step 3: Perform homogenization annealing on the ingot wrapped in the aluminum tube; then perform turning on the end face of the ingot and part of the outer surface of the aluminum tube.

[0055] The annealing process of the present invention is diffusion annealing (homogenization annealing), which utilizes long-term heating at high temperature to allow the chemical components inside the metal material to diffuse fully, reduce or eliminate the segregation of chemical components and microstructure in the ingot, and obtain a uniform metallographic structure.

[0056] In a preferred embodiment, the annealing temperature is 250℃~280℃, and the holding time of the annealing is 5h~8h. In an optional embodiment, the annealing temperature includes, but is not limited to, any one or any two of 250, 255, 260, 265, 270, 275, and 280 (℃), and the holding time of the annealing includes, but is not limited to, any one or any two of 5, 5.5, 6, 6.5, 7, 7.5, and 8 (h).

[0057] In a preferred embodiment, after the turning process, the thickness of the aluminum tube is 1mm to 2mm; the impurity layer on the surface of the aluminum tube and the end face of the ingot is removed by turning.

[0058] In a preferred embodiment, the turning length of the end face of the ingot is 1mm to 2mm, and the turning thickness of the outer surface of the aluminum tube is 1mm to 2mm.

[0059] Step 4: Preheat the machined ingot and the extrusion die respectively, and then extrude the ingot wrapped in the aluminum tube through the extrusion die to obtain an aluminum-tin-copper rod with a diameter of 8mm to 12mm.

[0060] In a preferred embodiment, for the ingot encased in the aluminum tube, the preheating temperature is 140℃~160℃, and the preheating time is 0.8h~1.5h. In an optional embodiment, for the ingot encased in the aluminum tube, the preheating temperature includes, but is not limited to, any one or any two of the following values: 140, 142, 144, 145, 146, 148, 150, 152, 154, 155, 156, 158, 160 (℃), and the preheating time includes, but is not limited to, any one or any two of the following values: 0.8, 0.9, 1, 1.1, 1.2, 1.3, 1.4, 1.5 (h).

[0061] In a preferred embodiment, the preheating temperature for the extrusion die is 160℃~200℃, and the preheating time is 0.8h~1.5h. In an optional embodiment, the preheating temperature for the extrusion die includes, but is not limited to, any one or any two of the following numerical ranges: 160, 162, 165, 168, 170, 172, 175, 178, 180, 182, 185, 188, 190, 192, 195, 198, 200 (℃), and the preheating time includes, but is not limited to, any one or any two of the following numerical ranges: 0.8, 0.9, 1, 1.1, 1.2, 1.3, 1.4, 1.5 (h).

[0062] In one preferred embodiment, the inner diameter of the barrel portion of the extrusion die is consistent with the outer diameter of the pure aluminum tube; simultaneously, in another preferred embodiment, by adjusting the diameter of the exit die of the extrusion die, aluminum-tin-copper wires of different diameters can be obtained.

[0063] In a preferred embodiment, the extrusion die is a single-outlet die.

[0064] In a preferred embodiment, the extrusion operation is performed using an extruder at a speed of 3 mm / s to 5 mm / s. Those skilled in the art can adjust the mechanical force or extrusion strength of the extrusion equipment accordingly based on this extrusion speed.

[0065] In a preferred embodiment, the diameter of the aluminum-tin-copper wire obtained in this step includes, but is not limited to, any real value within the range of one or any two of the following: 8, 8.2, 8.5, 8.8, 9, 9.2, 9.5, 9.8, 10, 10.2, 10.5, 10.8, 11, 11.2, 11.5, 11.8, 12 (mm).

[0066] In a preferred embodiment, when the aluminum-tin-copper rod obtained in step four is used as the aluminum-tin-copper alloy solder product, the following step is further included: mechanically scraping the aluminum-tin-copper rod to remove the outer surface of the aluminum tube. This is equivalent to the pure aluminum tube material introduced in step two being merely a process material to avoid solder sweating. When obtaining the aluminum-tin-copper alloy solder product, the pure aluminum tube needs to be removed again to avoid introducing excessive and unnecessary aluminum elements into the solder product.

[0067] In step four of this invention, aluminum-tin-copper rod products with a diameter of 8mm to 12mm are obtained. However, in practical applications, solder products with even smaller diameters are often required. Therefore, this invention also provides the following steps: further processing is performed on the aluminum-tin-copper solder products obtained in step four to obtain more low-diameter aluminum-tin-copper solder products.

[0068] In a preferred embodiment, the present invention provides steps five, six, and seven as follows. It should be noted that steps five, six, and seven are all alternative embodiments. While a high-diameter aluminum-tin-copper alloy solder product has already been obtained in step four, those skilled in the art can also obtain a low-diameter aluminum-tin-copper alloy solder product through any conventional or unconventional diameter reduction process other than steps five, six, and seven.

[0069] Step 5: Roll the aluminum-tin-copper alloy rod to obtain a second aluminum-tin-copper wire with a diameter of 4mm to 7mm.

[0070] In a preferred embodiment, the roll operation can be performed using a continuous rolling mill.

[0071] In a preferred embodiment, the diameter of the second aluminum-tin-copper wire obtained in this step may include, but is not limited to, any real value within the range of one or any two of the following: 4, 4.2, 4.4, 4.6, 4.8, 5, 5.2, 5.4, 5.6, 5.8, 6, 6.2, 6.4, 6.6, 6.8, 7 (mm).

[0072] As a preferred embodiment, similarly, when the second aluminum-tin-copper wire obtained in step five is used as an aluminum-tin-copper alloy solder product, the following steps are also included: mechanically scraping the second aluminum-tin-copper wire and removing the outer surface of the aluminum tube.

[0073] Step 6: Perform a second annealing treatment on the second aluminum-tin-copper additive wire, and then continuously draw it to obtain a third aluminum-tin-copper wire with a diameter of 2.0mm to 3.5mm;

[0074] In a preferred embodiment, the temperature of the second annealing treatment is 330℃~380℃, and the time of the second annealing treatment is 2h~3h. In an optional embodiment, the temperature of the second annealing treatment includes, but is not limited to, any one or any two of the following values: 330, 335, 340, 345, 350, 355, 360, 365, 370, 375, 380 (℃), and the time of the second annealing treatment includes, but is not limited to, any one or any two of the following values: 2, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3 (h).

[0075] In a preferred embodiment, the drawing compression ratio is (1.1 to 1.2):1, based on the cross-sectional area of ​​the wire; wherein the compression ratio refers to the ratio of the cross-sectional area of ​​the aluminum-tin-copper alloy solder before drawing to its cross-sectional area after drawing.

[0076] In a preferred embodiment, the diameter of the third aluminum-tin-copper wire obtained in this step may include, but is not limited to, any real value within the range of one or any two of the following: 2.0, 2.2, 2.4, 2.5, 2.8, 2.9, 3, 3.1, 3.2, 3.3, 3.4, and 3.5 (mm).

[0077] As a preferred embodiment, similarly, when the third aluminum-tin-copper wire obtained in step six is ​​used as an aluminum-tin-copper alloy solder product, the following steps are also included: mechanically scraping the third aluminum-tin-copper wire and removing the outer surface of the aluminum tube.

[0078] In this invention, steps five and six employ rolling and drawing, respectively, to obtain low-diameter solder. This is because, in the preferred embodiment described above, since the preceding product in step five is relatively large, rolling is highly efficient, allowing for a large single-pass processing volume and reducing the risk of wire breakage. The rolled wire has a denser structure, effectively eliminating shrinkage porosity and other defects, thus providing a strength foundation for subsequent drawing. Correspondingly, step six employs drawing, which reduces the diameter while also obtaining a finished solder with better surface quality, whereas rolling typically struggles to produce wires with good surface quality. Under certain specific operating conditions or cost constraints, those skilled in the art may also use drawing for step five or rolling for step six; it is understood that both methods can yield even lower-diameter filamentary aluminum-tin-copper alloy solder.

[0079] Step 7: Perform a third annealing treatment on the third aluminum-tin-copper additive wire, and then continuously draw it to obtain a fourth aluminum-tin-copper wire with a diameter of less than 2.0 mm.

[0080] In a preferred embodiment, the temperature of the third annealing treatment is 330℃~380℃, and the time of the third annealing treatment is 2h~3h. In an optional embodiment, the temperature of the third annealing treatment includes, but is not limited to, any one or any two of the following values: 330, 335, 340, 345, 350, 355, 360, 365, 370, 375, 380 (℃), and the time of the third annealing treatment includes, but is not limited to, any one or any two of the following values: 2, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3 (h).

[0081] In a preferred embodiment, the compression ratio of the drawing is (1.2 to 1.3):1, based on the cross-sectional area of ​​the wire; wherein the compression ratio refers to the ratio of the cross-sectional area of ​​the aluminum-tin-copper alloy solder before drawing to its cross-sectional area after drawing.

[0082] In a preferred embodiment, the diameter of the third aluminum-tin-copper wire obtained in this step may include, but is not limited to, any real value within the range of one or any two of the following: 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, and 2 (mm).

[0083] As a preferred embodiment, similarly, when the fourth aluminum-tin-copper wire obtained in step seven is used as an aluminum-tin-copper alloy solder product, the following steps are also included: mechanically scraping the fourth aluminum-tin-copper wire and removing the outer surface of the aluminum tube.

[0084] As a preferred embodiment, the following post-processing operation can be performed after any of steps four, five, six, and seven: mechanically scraping or ultrasonically cleaning the aluminum-tin-copper alloy solder, and then winding it onto a wire reel or packaging it for storage after drying.

[0085] Example 1

[0086] Step 1: Weigh tin ingots, copper ingots, and aluminum ingots according to the mass fractions of 20%, 1%, and 79%; clean the oil stains on the surface of the metal ingots with acetone, and place them in a drying oven for drying and preheating at 150℃ for 1 hour.

[0087] Step 2: Preheat the crucible using a resistance furnace to 500°C to remove moisture from the crucible; first add the preheated aluminum and copper ingots to the crucible, and after the aluminum and copper ingots melt, add the tin ingots, maintaining the furnace temperature at 720°C.

[0088] Step 3: Add hexachloroethane to the crucible and stir to refine and remove impurities. The amount of hexachloroethane added is 0.2% of the melt mass. After refining, remove the slag from the surface of the melt.

[0089] Step 4: Introduce argon gas into the melt at a flow rate of 2 L / min; stir while introducing the gas for 15 min; remove oxide inclusions from the surface of the melt after the gas is introduced; the temperature of the melt at the end of this step is 680℃.

[0090] Step 5: Casting is carried out using a metal mold with circulating water cooling. A pure aluminum tube with a thickness of 2.5mm is pre-placed inside the mold cylinder. The outer wall of the tube is in contact with the inner wall of the mold cylinder. The inner diameter of the aluminum tube is 55mm, and its height is the same as that of the mold cylinder, which is 150mm.

[0091] Step 6: Pour the casting into the aluminum tube with the water-cooled mold, while continuously stirring the uncast melt from Step 4 to ensure the uniform composition of the ingot.

[0092] Step 7: Place the prepared aluminum-tin-copper rod in a heat treatment furnace for homogenization annealing treatment. The annealing temperature is 260℃ and the holding time is 6h. Remove the furnace and air cool.

[0093] Step 8: Remove the impurity layer from the surface of the aluminum tube and the end face of the ingot using a lathe after annealing. After machining, the outer diameter of the ingot is 58mm and the height is still 150mm.

[0094] Step 9: Place the ingot wrapped in aluminum tube in a resistance furnace for preheating at 150°C for 1 hour. At the same time, preheat the extrusion die at 180°C.

[0095] Step 10: Take a preheated aluminum-tin-copper alloy ingot with an aluminum tube covering and place it in the extrusion barrel. The inner diameter of the extrusion barrel is 60mm, which is the same as the outer diameter of the original aluminum tube. The diameter of the extrusion die is 8mm, and the material is discharged through a single hole.

[0096] Step 11: Operate the extrusion press to extrude and prepare aluminum-tin-copper alloy rods at an extrusion speed of 4 mm / s. Use a take-up frame to take the aluminum-tin-copper rods into coils.

[0097] Step 12: Mechanically scrape the aluminum-tin-copper rod to remove excess aluminum from the outer surface of the tube, then perform ultrasonic cleaning and drying, and finally wind it onto a spool to complete the preparation of AlSn20Cu alloy welding wire.

[0098] Figure 2 A low-magnification cross-sectional view of the 8mm diameter aluminum-tin-copper rod obtained in this embodiment is provided. Figure 3Microstructure images of the aluminum-tin-copper rod obtained in this embodiment are provided; further, the center position of the aluminum-tin-copper rod obtained in this embodiment is magnified for observation, yielding... Figure 4 The high-magnification micrograph of the tissue is shown.

[0099] Example 2

[0100] This embodiment follows steps 12-13 based on step 11 of embodiment 1:

[0101] Step 12: The cooled aluminum-tin-copper welding wire is rolled using a continuous rolling mill to reduce the diameter to 5.6mm.

[0102] Step 13: Place the rolled wire into a heat treatment furnace for annealing at a temperature of 350℃ for 3 hours. After annealing, cool the wire to 200℃ in the furnace and then air-cool it to room temperature. Continuously draw the annealed 5.6mm aluminum-tin-copper wire to 2.4mm. Control the compression ratio of each drawing pass at 1.1:1 (a total of 9 drawing passes are required; the compression ratio of 1.1:1 does not need to be maintained in the 9th pass).

[0103] Step 14: After drawing, the aluminum-tin-copper wire is mechanically scraped, ultrasonically cleaned and dried, and then wound onto a spool to complete the preparation of AlSn20Cu alloy welding wire.

[0104] Example 3

[0105] This embodiment follows step 14 based on step 13 of embodiment 2:

[0106] Step 14: Place the 2.4mm aluminum-tin-copper wire into a heat treatment furnace for annealing at 350℃ for 3 hours. After annealing, cool the furnace to 200℃ and then air-cool to room temperature. Continue to draw the annealed wire to prepare 1.6mm diameter aluminum-tin-copper welding wire. The compression ratio of each drawing pass is controlled at 1.2:1 (a total of 3 drawing passes are conducted, and the compression ratio of 1.2:1 does not need to be maintained in the third pass).

[0107] Step 15: After being drawn, the aluminum-tin-copper solder is mechanically scraped, ultrasonically cleaned and dried, and then wound onto a spool to complete the preparation of AlSn20Cu alloy welding wire.

[0108] Example 4

[0109] The process is basically the same as in Example 2, except that: Step 1: Weigh tin ingots, copper ingots, and aluminum ingots in proportions of 17.5%, 0.07%, and 82.43% by mass.

[0110] Example 5

[0111] The process is basically the same as in Example 3, except that: Step 1: Weigh tin ingots, copper ingots, and aluminum ingots in proportions of 17.5%, 0.07%, and 82.43% by mass.

[0112] Example 6

[0113] It is basically the same as Example 2, except that:

[0114] Step 1: Weigh the tin ingots, copper ingots, and aluminum ingots according to the mass fractions of 22.5%, 1.3%, and 76.2%.

[0115] Example 7

[0116] It is basically the same as Example 3, except that:

[0117] Step 1: Weigh the tin ingots, copper ingots, and aluminum ingots according to the mass fractions of 22.5%, 1.3%, and 76.2%.

[0118] Comparative Example 1

[0119] It is basically the same as Example 2, except that the features of "circulating water cooling" and "water-cooled mold" are removed in steps 5 and 6.

[0120] Comparative Example 2

[0121] It is basically the same as Example 2, except that the stirring operation is cancelled in step 6.

[0122] Test case

[0123] The tensile strength and elongation of the welding wire were tested as follows: The mechanical properties of the wire in different embodiments and comparative examples were tested using a WDW-20E electro-hydraulic servo universal testing machine. Welding wire with a length of 200mm was cut and clamped in the chuck of the testing machine. The loading speed of the testing machine was 2mm / min. The test results were taken as the average value of multiple tests.

[0124] The test results are shown in Table 1 below.

[0125] Table 1

[0126] Example 1 10 102 4.5 Example 2 2.4 180 8.2 Example 3 1.6 203 5.6 Example 4 2.4 134 5.1 Example 5 1.6 150 4.9 Example 6 2.4 197 7.4 Example 7 1.6 215 6.2 Comparative Example 1 2.4 102 3.9 Comparative Example 2 2.4. 71 1.3

[0127] Although the present invention has been illustrated and described with specific embodiments, it should be understood that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; those skilled in the art should understand that modifications can be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein, without departing from the spirit and scope of the present invention; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention; therefore, this means that all such substitutions and modifications that fall within the scope of the present invention are included in the appended claims.

Claims

1. A method for preparing an aluminum-tin-copper alloy solder, characterized in that, The preparation method includes the following steps: Step 1: Prepare the metal raw materials of aluminum, tin and copper, which, by mass percentage, include 5.5%~45% tin, 0.4%~1.3% copper and the balance aluminum; heat and mix the metal raw materials to obtain a melt; Step 2: Insert a pure aluminum tube of equal height into the mold cylinder, with the outer wall of the pure aluminum tube completely fitting the inner wall of the mold cylinder; continuously water-cool the mold cylinder while pouring the melt into the pure aluminum tube, and then obtain an ingot wrapped by the aluminum tube. Step 3: The ingot wrapped in the aluminum tube is subjected to homogenization annealing treatment; then the end face of the ingot and part of the outer surface of the aluminum tube are machined. After the machining treatment, the thickness of the aluminum tube is 1mm~2mm; the annealing temperature is 250℃~280℃, and the annealing holding time is 5h~8h. Step 4: Preheat the machined ingot and the extrusion die respectively, and then extrude the ingot wrapped in the aluminum tube through the extrusion die to obtain an aluminum-tin-copper rod with a diameter of 8mm~12mm. When the aluminum-tin-copper rod material described in step four is used as the aluminum-tin-copper alloy solder, the process further includes: mechanically scraping the aluminum-tin-copper rod material and removing the outer surface of the aluminum tube.

2. The method for preparing the aluminum-tin-copper alloy solder according to claim 1, characterized in that, After step four, the preparation method further includes the following steps: Step 5: Roll the aluminum-tin-copper rod to obtain a second aluminum-tin-copper wire with a diameter of 4mm~7mm; When the second aluminum-tin-copper wire from step five is used as the aluminum-tin-copper alloy solder, the process further includes: mechanically scraping the second aluminum-tin-copper wire and removing the outer surface of the aluminum tube.

3. The method for preparing the aluminum-tin-copper alloy solder according to claim 2, characterized in that, After step five, the preparation method further includes the following steps: Step 6: Perform a second annealing treatment on the second aluminum-tin-copper wire, and then continuously draw it to obtain a third aluminum-tin-copper wire with a diameter of 2.0mm~3.5mm; When the third aluminum-tin-copper wire described in step six is ​​used as the aluminum-tin-copper alloy solder, the process further includes: mechanically scraping the third aluminum-tin-copper wire and removing the outer surface of the aluminum tube.

4. The method for preparing the aluminum-tin-copper alloy solder according to claim 3, characterized in that, The temperature of the second annealing treatment is 330℃~380℃, and the time of the second annealing treatment is 2h~3h.

5. The method for preparing the aluminum-tin-copper alloy solder according to claim 3, characterized in that, For step six: the compression ratio of the drawing is (1.1~1.2):1, based on the cross-sectional area of ​​the wire.

6. The method for preparing the aluminum-tin-copper alloy solder according to claim 3, characterized in that, After step six, the preparation method further includes the following steps: Step 7: Perform a third annealing treatment on the third aluminum-tin-copper wire, and then continuously draw it to obtain a fourth aluminum-tin-copper wire with a diameter of less than 2.0 mm. When the fourth aluminum-tin-copper wire described in step seven is used as the aluminum-tin-copper alloy solder, the process further includes: mechanically scraping the fourth aluminum-tin-copper wire and removing the outer surface of the aluminum tube.

7. The method for preparing the aluminum-tin-copper alloy solder according to claim 6, characterized in that, The temperature of the third annealing treatment is 330℃~380℃, and the time of the third annealing treatment is 2h~3h.

8. The method for preparing the aluminum-tin-copper alloy solder according to claim 6, characterized in that, For step seven: the compression ratio of the drawing is (1.2~1.3):1, based on the cross-sectional area of ​​the wire.

9. The method for preparing the aluminum-tin-copper alloy solder according to claim 1, characterized in that, In step two, the water cooling process includes: loading a water cooling assembly onto the outer wall of the mold cylinder, wherein the heat dissipation medium in the water cooling assembly is water.

10. The method for preparing the aluminum-tin-copper alloy solder according to claim 1, characterized in that, In step two, during the casting process, the uncast melt is continuously stirred.

11. The method for preparing the aluminum-tin-copper alloy solder according to claim 1, characterized in that, The turning length of the end face of the ingot is 1mm to 2mm.

12. The method for preparing the aluminum-tin-copper alloy solder according to claim 1, characterized in that, In step four, the preheating temperature of the machined ingot is 140℃~160℃, and the preheating holding time is 0.8h~1.5h. And / or, the preheating temperature of the extrusion die is 160℃~200℃, and the preheating holding time is 0.8h~1.5h.

13. The aluminum-tin-copper alloy solder prepared by the method for preparing aluminum-tin-copper alloy solder according to any one of claims 1 to 12.

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