Composite welded structure

Abstract

The utility model discloses a kind of composite welding structure and its preparation method, composite welding structure includes workpiece and the welding joint fixedly welded with the workpiece, at least the plating layer of welding joint surface is equipped;Wherein, the solder used in the welding joint includes any one or more of copper solder, copper alloy solder, silver solder, silver alloy solder, gold solder, gold alloy solder;The metal plating layer at least includes nickel plating or nickel alloy plating layer.The composite welding structure in the utility model has excellent strength, toughness and corrosion resistance, solves the contradiction of Ni welding brittle and material not corrosion resistant.

Description

Technical Field

[0001] This utility model belongs to the field of welding technology, and specifically relates to a composite welding structure. Background Technology

[0002] In existing welding technologies, nickel solder is a commonly used solder, exhibiting strong resistance to corrosive substances such as acids, alkalis, and salts, thus improving the corrosion resistance and thermal cracking resistance of welded joints. However, while nickel solder has good corrosion resistance, it is prone to Ni-bonded brittleness, resulting in poor joint toughness and low reliability. In contrast, welded joints obtained using materials such as copper, silver, and gold have excellent toughness but are not corrosion-resistant.

[0003] Therefore, overcoming the limitations of using a single material and providing reliable corrosion resistance while ensuring the toughness of the welded joint is a technical problem that urgently needs to be solved in this field. Utility Model Content

[0004] The purpose of this invention is to provide a composite welding structure that has excellent strength, toughness and corrosion resistance, thus resolving the contradiction between Ni welding brittleness and the material's lack of corrosion resistance.

[0005] To achieve the above objectives, the technical solution provided by a specific embodiment of this utility model is as follows:

[0006] A composite welding structure includes a workpiece and a weld joint fixedly welded to the workpiece, wherein at least the surface of the weld joint is provided with a metal plating layer;

[0007] The solder used in the welding joint includes any one or more of copper solder, copper alloy solder, silver solder, silver alloy solder, gold solder, and gold alloy solder.

[0008] The metal coating includes at least a nickel coating or a nickel alloy coating.

[0009] In one or more embodiments of this utility model, the thickness of the metal coating is 30μm-150μm.

[0010] In one or more embodiments of this utility model, the material of the nickel alloy coating includes any one of nickel-phosphorus alloy, nickel-cobalt-phosphorus alloy, nickel-molybdenum alloy, and nickel-tungsten alloy.

[0011] In one or more embodiments of this utility model, the metal coating includes an adhesive layer, a buffer layer, and a protective layer stacked sequentially.

[0012] In one or more embodiments of this utility model, the adhesive layer is a low-phosphorus nickel-phosphorus alloy plating layer.

[0013] In one or more embodiments of this utility model, the material of the buffer layer includes any one of copper, copper alloy, gold, gold alloy, silver, and silver alloy.

[0014] In one or more embodiments of this utility model, the protective layer is a high-phosphorus nickel-phosphorus alloy plating layer.

[0015] In one or more embodiments of this utility model, the protective layer is a nickel-boron alloy plating layer.

[0016] In one or more embodiments of this utility model, the thickness of the adhesive layer is 1μm-3μm; and / or,

[0017] The thickness of the buffer layer is 5μm-15μm; and / or,

[0018] The thickness of the protective layer is 5μm-20μm.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] 1. This utility model combines the high toughness of the solder with the high corrosion resistance of the coating, achieving a unity of strength, toughness and corrosion resistance, and solving the contradiction between Ni solder brittleness and material poor corrosion resistance.

[0021] 2. This utility model optimizes the coating structure by using a "sandwich structure" composed of an adhesive layer, a buffer layer, and a protective layer, while simultaneously optimizing the thickness of each layer. This achieves complementary performance of the materials in each layer, resulting in the final composite coating achieving optimal performance balance and fundamentally solving the technical problem of easy cracking and peeling of a single coating.

[0022] 3. This utility model achieves multi-dimensional coordinated optimization of coating performance by optimizing the doping level in the nickel coating, namely, high ductility of the bottom layer and high corrosion resistance or high hardness of the top layer, which perfectly solves the problem that a single coating layer cannot meet multiple performance requirements at the same time.

[0023] 4. This utility model uses a refined processing technology to treat the welded joint, providing an ideal activated surface for the coating and significantly improving the coating adhesion. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1This is a schematic diagram showing the overall metal plating of the workpiece and the weld joint in a composite welding structure according to an embodiment of the present invention;

[0026] Figure 2 This is a schematic diagram of a composite welding structure in one embodiment of the present invention, in which only the weld joint is provided with a metal plating layer;

[0027] Figure 3 This is a schematic diagram showing that, in one embodiment of the present invention, the workpiece and the welded joint are integrally provided with an adhesive layer, a buffer layer and a protective layer in a composite welding structure.

[0028] Figure 4 This is a schematic diagram of a composite welding structure in one embodiment of the present invention, in which only the weld joint is provided with an adhesive layer, a buffer layer and a protective layer.

[0029] Explanation of key figure labels:

[0030] 1. Workpiece; 2. Welded joint; 3. Metal plating; 30. Adhesive layer; 4. Buffer layer; 5. Protective layer. Detailed Implementation

[0031] To enable those skilled in the art to better understand the technical solutions in this disclosure, the technical solutions in the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this disclosure, and not all embodiments. Based on the embodiments in this disclosure, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this disclosure.

[0032] A specific embodiment of this utility model provides a composite welding structure, such as... Figure 1 As shown, it includes a workpiece 1 and a welded joint 2 fixedly welded to the workpiece 1. At least the surface of the welded joint 2 is provided with a metal plating layer 3. The solder used in the welded joint 2 includes, but is not limited to, any one or more of copper solder, copper alloy solder, silver solder, silver alloy solder, gold solder, and gold alloy solder. The metal plating layer 3 includes at least a nickel plating layer or a nickel alloy plating layer.

[0033] Specifically, while the above-mentioned types of solder have poor corrosion resistance, they possess excellent toughness, which can impart excellent toughness to the welded structure. Metal coatings can provide excellent corrosion resistance to the welded structure. By selecting the right solder and setting the appropriate metal coating, the properties of the solder and coating complement each other, thereby effectively improving the strength, toughness, and corrosion resistance of the welded structure and resolving the contradiction between Ni solder brittleness and the material's poor corrosion resistance. The workpiece can specifically be a stainless steel workpiece.

[0034] It should be noted that, Figure 1The shape of workpiece 1 shown in the illustration is merely an example of one implementation and is not the only limitation on the shape and model of workpiece 1. In reality, the shape and model of workpiece 1 can be selected according to the actual application scenario, such as a tubular workpiece. Figure 1 In this process, the weld joint 2 is formed in the weld groove. In some embodiments, it can be formed directly on the surface of the workpiece 1 or in the gap (weld) where two workpieces 1 to be welded meet.

[0035] like Figure 2 As shown, the specific location of the metal coating can be selected according to the actual application. For example, applying a metal coating to the entire workpiece and welded joint may bring unnecessary costs and affect the non-welded areas of the workpiece. Therefore, it is possible to apply the metal coating to the welded joint or to the welded joint and a small area around the welded joint.

[0036] Furthermore, the thickness of the metal coating is 30μm-150μm, specifically for example, 30μm, 50μm, 70μm, 80μm, 90μm, 100μm, 110μm, 130μm, and 150μm.

[0037] Specifically, by controlling the thickness of the metal coating, the metal coating can cover the microscopic defects on the surface of the welded joint, ensuring that the metal coating can be firmly bonded to the welded joint, thereby improving the toughness and corrosion resistance of the welded structure.

[0038] Furthermore, the materials for the nickel alloy coating include, but are not limited to, any one of nickel-phosphorus alloy, nickel-cobalt-phosphorus alloy, nickel-molybdenum alloy, and nickel-tungsten alloy. Specifically, the nickel alloy coating is any one of nickel-phosphorus alloy coating, nickel-cobalt-phosphorus alloy coating, nickel-molybdenum alloy coating, and nickel-tungsten alloy coating.

[0039] Specifically, choosing the above types of nickel alloys can ensure high bonding strength between the coating and the weld joint, while increasing strength and wear resistance and preventing coating cracking.

[0040] Furthermore, such as Figure 3 and Figure 4As shown, the metal plating layer 3 includes an adhesive layer 30, a buffer layer 4, and a protective layer 5 stacked sequentially. The adhesive layer 30 is a nickel plating layer or a low-phosphorus nickel-phosphorus alloy plating layer, and the phosphorus content in the low-phosphorus nickel-phosphorus alloy plating layer is 1wt.%-3wt.%. The material of the buffer layer 4 includes, but is not limited to, any one of copper, copper alloy, gold, gold alloy, silver, and silver alloy. Specifically, the buffer layer 4 is any one of copper plating layer, copper alloy plating layer, gold plating layer, gold alloy plating layer, silver plating layer, and silver alloy plating layer. The protective layer 5 is a high-phosphorus nickel-phosphorus alloy plating layer, and the phosphorus content in the high-phosphorus nickel-phosphorus alloy plating layer is 9wt.%-12wt.%. Alternatively, the protective layer 5 is a nickel-boron alloy plating layer, and the boron content in the nickel-boron alloy plating layer is 2wt.%-5wt.%.

[0041] Specifically, firstly, the adhesive layer enables a strong bond with the welded joint, improving the stability of the coating; the buffer layer provides high ductility and stress buffering capacity; and the protective layer, located on the outermost layer, provides excellent corrosion resistance.

[0042] Secondly, the phosphorus content in the adhesive layer should be controlled between 1wt.% and 3wt.%, specifically, it can be 1wt.%, 1.5wt.%, 2wt.%, 2.5wt.%, or 3wt.%. If the phosphorus content is too low, the internal stress of the adhesive layer will be high, and the ductility may be reduced, which will affect the adhesion between the adhesive layer and the substrate. If the phosphorus content is too high, the adhesive layer may be too soft, and its hardness and wear resistance will decrease, making it difficult to provide sufficient bonding strength.

[0043] The phosphorus content in the protective layer should be controlled between 9 wt.% and 12 wt.%, specifically 9 wt.%, 10 wt.%, 11 wt.%, or 12 wt.%. Insufficient phosphorus content makes it difficult to form a good amorphous structure, resulting in excessive grain boundaries and reduced corrosion resistance. Furthermore, hardness will also be affected, making it difficult to achieve optimal protective performance. Conversely, excessively high phosphorus content may lead to stress imbalance within the coating, increasing brittleness and making it prone to cracking after stress or heat treatment.

[0044] Nickel-boron alloy coatings possess extremely high hardness, making them suitable for applications requiring exceptional wear resistance. While their corrosion resistance is slightly inferior to nickel-phosphorus alloy coatings, their hardness reaches 700-800 HV in the plated state and can exceed 1000 HV after heat treatment. Specific boron content in nickel-boron alloy coatings can be, for example, 2 wt.%, 3 wt.%, 4 wt.%, or 5 wt.%.

[0045] By specially designing the nickel doping levels in the adhesive layer and the protective layer, this invention achieves multi-dimensional coordinated optimization of coating performance, namely, high ductility of the bottom layer and high corrosion resistance or high hardness of the top layer, perfectly solving the problem that a single coating layer cannot simultaneously meet multiple performance requirements.

[0046] Therefore, by forming a "sandwich" structure with an adhesive layer, a buffer layer, and a protective layer, the properties of each layer of material are complementary, reducing the occurrence of cracking and peeling due to insufficient adhesion or excessive internal stress.

[0047] Furthermore, the thickness of the adhesive layer is 1μm-3μm, specifically 1μm, 1.5μm, 2μm, 2.5μm, and 3μm. This thickness range can cover microscopic defects on the surface of the welded joint and provide reliable adhesion, while avoiding excessive internal stress. The thickness of the buffer layer is 5μm-15μm, specifically 5μm, 8μm, 10μm, 13μm, and 15μm. Buffer layers within this thickness range can effectively absorb and disperse internal stress caused by differences in the thermal expansion coefficients of the coating materials and the deposition process, and are key coating layers to prevent cracking of the final coating. The thickness of the protective layer is 5μm-20μm, specifically 5μm, 8μm, 10μm, 13μm, 15μm, 18μm, and 20μm. This thickness range can provide a reliable corrosion barrier while balancing cost and internal stress control to achieve optimal protective effect.

[0048] The method for preparing the composite welded structure in this utility model includes the following steps:

[0049] Step 1: Take the workpiece and solder, and use the solder to weld the workpiece to form a welded joint.

[0050] Specifically, during welding, brazing or welding methods are used to connect the workpieces to obtain the initial welded structure.

[0051] It should be noted that, Figure 1-4 The shape of workpiece 1 shown in the figure is only for illustration of one embodiment and is not the only limitation on the shape and model of workpiece 1. In fact, the shape and model of workpiece 1 can be selected according to the actual application scenario. In the figure, the welding joint 2 is formed in the welding groove. In some embodiments, it can be formed directly on the surface of workpiece 1 or in the gap (weld) where two workpieces 1 to be welded meet.

[0052] Step 2: Prepare a metal coating on at least the surface of the welded joint to obtain a composite welded structure.

[0053] Specifically, before preparing the metal coating, the welded joint area, especially small or corner locations, is treated with the following refined processes:

[0054] (1) Mechanical treatment: Use a pen-type electric or pneumatic grinder with different shaped fine grinding heads (such as conical or cylindrical) to deburr and grind the weld and remove surface slag.

[0055] (2) Sandblasting: Use a micro sandblasting machine with glass beads or alumina powder of 50-100 mesh to locally sandblast the welding area to increase the surface roughness (Ra is 0.5μm-3.0μm). To prevent damage to non-welding areas, a special sandblasting mold can be used for masking.

[0056] (3) Chemical activation: The treated surface is pickled to remove residual oxides and activate the metal surface, providing an ideal bonding surface for subsequent electroplating. Pickling can be carried out using a mixture of nitric acid and hydrofluoric acid (nitric acid content is 10%-15%), and pickling is performed at room temperature for 10-15 minutes.

[0057] Through the above refined processing, the technical challenges of surface treatment for small and complex workpieces are effectively solved, providing an ideal activated surface for subsequent coatings, thereby significantly improving coating adhesion.

[0058] When preparing a metal coating on the overall surface of a workpiece and welded joint, electroplating, chemical plating, or spraying can be used to deposit the metal coating on its surface.

[0059] Furthermore, the adhesive layer, buffer layer, and protective layer can be prepared by electroplating or electroless plating.

[0060] Specifically, pure nickel plating can be prepared by electroplating. The specific type of electroplating solution can be selected from those containing nickel sulfate (concentration can be controlled at 100g / L-130g / L), nickel chloride (concentration can be controlled at 40g / L-50g / L), boric acid (concentration can be controlled at 35g / L-40g / L), and sodium dodecyl sulfonate (concentration can be controlled at 0.1g / L-0.2g / L).

[0061] Copper plating can be prepared by electroplating. The specific components of the electroplating solution may include copper sulfate (concentration can be controlled at 150g / L-200g / L), sulfuric acid (concentration can be controlled at 30g / L-60g / L), sodium polydisulfide dipropane sulfonate (concentration can be controlled at 0.01g / L-0.1g / L), butynediol (concentration can be controlled at 0.1g / L-1g / L), and hydrochloric acid (providing chloride ions, concentration can be controlled at 20mg / L-50mg / L).

[0062] The gold plating layer can be prepared by electroplating. The specific components of the electroplating solution can include potassium gold cyanide (concentration can be controlled at 8g / L-15g / L), potassium cyanide (concentration can be controlled at 20g / L-35g / L), potassium carbonate (concentration can be controlled at 15g / L-25g / L), citric acid (concentration can be controlled at 5g / L-10g / L), and polyethylene glycol (concentration can be controlled at 0.1g / L-0.3g / L).

[0063] The silver plating layer can be prepared by electroplating. The specific components of the electroplating solution can include potassium silver cyanide (concentration can be controlled at 30g / L-50g / L), potassium cyanide (concentration can be controlled at 60g / L-80g / L), potassium carbonate (concentration can be controlled at 10g / L-20g / L), potassium sulfide (concentration can be controlled at 0.001g / L-0.003g / L), and thiourea (concentration can be controlled at 0.5g / L-1.0g / L).

[0064] Nickel-phosphorus alloy coatings can be prepared using chemical plating methods. Specifically, a chemical plating solution containing nickel salts, reducing agents, complexing agents, stabilizers, and buffers can be selected. The nickel salt concentration can be controlled at 20 g / L-35 g / L, and nickel sulfate or nickel chloride can be chosen. Sodium hypophosphite is selected as the reducing agent, with a concentration controlled at 25 g / L-40 g / L. Sodium hypophosphite reduces nickel ions, causing them to deposit on the workpiece surface. Simultaneously, the phosphorus content in the coating is adjusted by controlling the sodium hypophosphite concentration, specifically based on the desired phosphorus content in the nickel-phosphorus alloy coating. The complexing agent concentration can be controlled at 30 g / L-60 g / L, and citrate, tartrate, or succinate, such as sodium citrate, can be selected. The complexing agent stabilizes nickel ions, preventing spontaneous precipitation in the plating solution. The stabilizer concentration can be controlled at 0.001 g / L-0.01 g / L, used to inhibit spontaneous decomposition of the plating solution and extend its lifespan. Thiourea or lead salts can be selected as stabilizers. An appropriate amount of buffer is used to maintain the pH value of the plating solution within a suitable range (such as pH 4.5-5.5) to ensure the stable progress of the coating deposition process. Specific buffers can be lactic acid or propionic acid.

[0065] Nickel-boron alloy coatings can be prepared using a chemical plating method. Specifically, a chemical plating solution containing nickel salts, a boron source, a complexing agent, a buffer, and a stabilizer can be selected. The concentration of the nickel salt can be controlled at 25 g / L-35 g / L, and nickel sulfate can be a suitable choice. The boron source can be dimethylamine borane, with a concentration controlled at 8 g / L-16 g / L. The complexing agent can be sodium citrate and potassium sodium tartrate, with the sodium citrate concentration controlled at 40 g / L-60 g / L and the potassium sodium tartrate concentration controlled at 10 g / L-20 g / L. Sodium hydroxide can be used as a buffer to adjust the pH of the plating solution to 8.5-10.0. Lead sulfate can be used as a stabilizer, with a concentration controlled at 0.002 g / L-0.005 g / L. Additionally, thiourea at a concentration of 0.01 g / L-0.03 g / L can be added to the plating solution.

[0066] When preparing a coating on the surface of a welded joint, the non-welded areas on the outside of the joint are first masked. This can be done through physical masking, such as using corrosion-resistant electroplating tape, custom-made plastic or rubber molds / clamps, or peelable chemical masks, such as electroplating wax or paint. The masking material must adhere tightly to the workpiece to prevent the electroplating solution or spraying material from seeping in. Then, using brush plating equipment or directional spraying equipment with precision nozzles, electroplating or spraying is performed only on the unmasked welded joint areas to achieve precise control over the coating coverage.

[0067] The present invention will be further described in detail below with reference to specific embodiments.

[0068] Example 1

[0069] In this embodiment, the composite welding structure includes a workpiece and a welding joint connecting the workpiece. The surface of the welding joint is provided with a nickel plating layer with a thickness of 30μm.

[0070] The preparation method of the composite welded structure includes the following steps:

[0071] (1) Take stainless steel workpiece and copper solder, and braze them. The welding can be carried out in a protective gas, such as nitrogen, hydrogen, argon, or a mixture of nitrogen and hydrogen, at a temperature of 1050°C for 5 minutes.

[0072] (2) For the formed weld joint, use a grinder to grind and remove surface burrs and welding slag. Then use 50-mesh alumina powder for sandblasting to make the surface roughness 3.0μm. Then place it in a mixture of nitric acid and hydrofluoric acid (nitric acid content is 10%) for pickling for 10min.

[0073] (3) A nickel plating layer with a thickness of 30 μm is plated on the surface of the welded joint by electroplating. The workpiece is immersed in the electroplating solution and soaked at 60°C for 5.7 h with a current density of 6 A / dm. 2 After cleaning, a composite welded structure was obtained. The electroplating solution used water as a solvent and included nickel sulfate (100 g / L), nickel chloride (45 g / L), boric acid (35 g / L), and sodium dodecyl sulfonate (0.1 g / L).

[0074] Example 2

[0075] The difference between this embodiment and Embodiment 1 is that a nickel-phosphorus alloy coating with a thickness of 150 μm is plated on the surface of the welded joint by chemical nickel plating, and the phosphorus content in the nickel-phosphorus alloy coating is 9 wt.%.

[0076] The electroless plating solution used is water-based and includes nickel sulfate (30 g / L), sodium hypophosphite (33 g / L), sodium citrate (48 g / L), lactic acid (50 g / L), and lead nitrate (0.005 g / L). The plating solution temperature is 90°C.

[0077] Example 3

[0078] In this embodiment, the composite welding structure includes a workpiece and a welded joint connecting the workpieces. An adhesive layer, a buffer layer, and a protective layer are sequentially stacked on the surface of the welded joint. The adhesive layer is a nickel plating layer with a thickness of 1 μm. The buffer layer is a copper plating layer with a thickness of 8 μm. The protective layer is a high-phosphorus nickel-phosphorus alloy layer with a phosphorus content of 9 wt.% and a thickness of 10 μm.

[0079] The preparation method of the composite welded structure includes the following steps:

[0080] (1) Take stainless steel workpiece and copper solder, and braze them. The welding can be carried out in a protective gas, such as nitrogen, hydrogen, argon, or a mixture of nitrogen and hydrogen, at a temperature of 1050°C for 5 minutes.

[0081] (2) For the formed weld joint, use a grinder to grind and remove surface burrs and welding slag. Then use 50-mesh alumina powder for sandblasting to make the surface roughness 3.0μm. Then place it in a mixture of nitric acid and hydrofluoric acid (nitric acid content is 10%) for pickling for 10min.

[0082] (3) An adhesive layer and a buffer layer are plated on the surface of the welded joint by electroplating, and a protective layer is plated by chemical plating to obtain a composite welded structure.

[0083] The electroplating solution used for the bonding layer is water-based and includes nickel sulfate (100 g / L), nickel chloride (45 g / L), boric acid (35 g / L), and sodium dodecyl sulfonate (0.1 g / L). The plating current density is 6 A / dm³. 2 .

[0084] The electroplating solution used for depositing the buffer layer is water-based and includes copper sulfate (150 g / L), sulfuric acid (50 g / L), sodium polydisulfide dipropane sulfonate (0.05 g / L), butynediol (0.5 g / L), and hydrochloric acid (30 g / L). The current density during plating is 3 A / dm³. 2 .

[0085] The chemical plating solution used for applying the protective layer is water-based and includes nickel sulfate (30 g / L), sodium hypophosphite (33 g / L), sodium citrate (48 g / L), lactic acid (50 g / L), and lead nitrate (0.005 g / L). The plating solution temperature is 90°C.

[0086] Example 4

[0087] The difference between this embodiment and Embodiment 3 is that the buffer layer is a gold-plated layer with a thickness of 5 μm.

[0088] The electroplating solution used for the buffer layer is water-based and includes potassium gold cyanide (10 g / L), potassium cyanide (25 g / L), potassium carbonate (20 g / L), citric acid (8 g / L), and polyethylene glycol (0.2 g / L). During plating, the solution temperature is 50°C, and the current density is 2 A / dm³. 2 .

[0089] Example 5

[0090] The difference between this embodiment and Embodiment 3 is that the buffer layer is a silver plating layer with a thickness of 5μm.

[0091] The electroplating solution used for the buffer layer was water-based and included potassium silver cyanide (40 g / L), potassium cyanide (70 g / L), potassium carbonate (15 g / L), potassium sulfide (0.002 g / L), and thiourea (0.8 g / L). The plating was performed at room temperature with a current density of 2 A / dm³. 2 .

[0092] Example 6

[0093] The difference between this embodiment and Embodiment 3 is that the adhesive layer is a low-phosphorus nickel-phosphorus alloy plating with a phosphorus content of 1 wt.% and a thickness of 2 μm. The protective layer is a high-phosphorus nickel-phosphorus alloy plating with a phosphorus content of 10 wt.% and a thickness of 5 μm.

[0094] The electroless plating solution used for the bonding layer is water-based and includes nickel sulfate (35 g / L), sodium hypophosphite (25 g / L), sodium citrate (55 g / L), lactic acid (50 g / L), and lead nitrate (0.003 g / L). The plating solution temperature is 82°C.

[0095] The chemical plating solution used for applying the protective layer is water-based and includes nickel sulfate (25 g / L), sodium hypophosphite (34 g / L), sodium citrate (45 g / L), lactic acid (55 g / L), and lead nitrate (0.006 g / L). The plating solution temperature is 90°C.

[0096] Example 7

[0097] The difference between this embodiment and Embodiment 3 is that the adhesive layer is a low-phosphorus nickel-phosphorus alloy plating with a phosphorus content of 2 wt.% and a thickness of 3 μm. The protective layer is a high-phosphorus nickel-phosphorus alloy plating with a phosphorus content of 12 wt.% and a thickness of 15 μm.

[0098] The electroless plating solution used for the bonding layer is water-based and includes nickel sulfate (35 g / L), sodium hypophosphite (26 g / L), sodium citrate (58 g / L), lactic acid (52 g / L), and lead nitrate (0.002 g / L). The plating solution temperature is 83°C.

[0099] The chemical plating solution used for applying the protective layer is water-based and includes nickel sulfate (20 g / L), sodium hypophosphite (34 g / L), sodium citrate (35 g / L), lactic acid (60 g / L), and lead nitrate (0.008 g / L). The plating solution temperature is 90°C.

[0100] Example 8

[0101] The difference between this embodiment and Embodiment 3 is that the adhesive layer is a low-phosphorus nickel-phosphorus alloy plating with a phosphorus content of 3 wt.% and a thickness of 2 μm. The protective layer is a high-phosphorus nickel-phosphorus alloy plating with a phosphorus content of 11 wt.% and a thickness of 20 μm.

[0102] The electroless plating solution used for the bonding layer is water-based and includes nickel sulfate (35 g / L), sodium hypophosphite (28 g / L), sodium citrate (56 g / L), lactic acid (53 g / L), and lead nitrate (0.003 g / L). The plating solution temperature is 84°C.

[0103] The chemical plating solution used for applying the protective layer is water-based and includes nickel sulfate (20 g / L), sodium hypophosphite (32 g / L), sodium citrate (38 g / L), lactic acid (58 g / L), and lead nitrate (0.007 g / L). The plating solution temperature is 90°C.

[0104] Example 9

[0105] The difference between this embodiment and embodiment 6 is that the protective layer is a nickel-boron alloy plating layer with a boron content of 2 wt.%.

[0106] The chemical plating solution used for the protective layer is an aqueous solvent and includes nickel sulfate (30 g / L), dimethylamine borane (8 g / L), sodium citrate (50 g / L), potassium sodium tartrate (15 g / L), lead nitrate (0.003 g / L), and thiourea (0.02 g / L). Sodium hydroxide is used to adjust the pH of the plating solution to 9.0. The plating solution temperature is 73°C during plating.

[0107] Example 10

[0108] The difference between this embodiment and embodiment 6 is that the protective layer is a nickel-boron alloy plating layer with a boron content of 3 wt.%.

[0109] The chemical plating solution used for the protective layer is an aqueous solvent, comprising nickel sulfate (30 g / L), dimethylamine borane (10 g / L), sodium citrate (50 g / L), potassium sodium tartrate (15 g / L), lead nitrate (0.004 g / L), and thiourea (0.02 g / L). Sodium hydroxide is used to adjust the pH of the plating solution to 9.3. The plating solution temperature is 75°C during plating.

[0110] Example 11

[0111] The difference between this embodiment and embodiment 6 is that the protective layer is a nickel-boron alloy plating layer with a boron content of 5 wt.%.

[0112] The chemical plating solution used for the protective layer is an aqueous solvent, comprising nickel sulfate (30 g / L), dimethylamine borane (14 g / L), sodium citrate (55 g / L), potassium sodium tartrate (18 g / L), lead nitrate (0.005 g / L), and thiourea (0.02 g / L). Sodium hydroxide is used to adjust the pH of the plating solution to 9.8. The plating solution temperature is 78°C during plating.

[0113] Comparative Example 1

[0114] This comparative example uses nickel-based solder as the welding material for welding workpieces. The specific method is as follows:

[0115] (1) Take stainless steel workpiece and nickel-based solder. Here, nickel-based solder with grade BNi-2 is used. Welding is carried out by brazing. Welding can be carried out for 5 minutes at 950°C in a protective gas such as nitrogen, hydrogen, argon, or a mixture of nitrogen and hydrogen.

[0116] (2) After completion, cool to room temperature at a rate of 50℃ / min.

[0117] The toughness and corrosion resistance of the composite welded structures obtained in each embodiment and comparative example were tested. The toughness test mainly tested the fracture resistance, for example, by using the crack tip opening displacement (CTOD) / J integral test, with ISO15653 as a typical standard. The corrosion resistance test used the neutral salt spray test to measure the time of initial corrosion. The anti-detachment test used the scratch method. The test results are shown in Table 1.

[0118] Table 1 Performance test results of composite welded structures

[0119]

[0120] The toughness test result of the nickel solder used in Comparative Example 1 was 22 J, and the corrosion resistance test result was 1487 h. As shown in Table 1, this invention achieves a balance of strength, toughness, and corrosion resistance by using a high-toughness solder to complete the welding and then depositing a coating on the surface of the welded structure, thus resolving the contradiction between the brittleness of Ni solder and the material's poor corrosion resistance. Furthermore, by further optimizing the coating, a "sandwich" structure of an adhesive layer, a buffer layer, and a protective layer is established, achieving complementary properties among the layers. Simultaneously, through special design of the thickness of each layer, precise control of the coating performance is achieved, maximizing the advantages of each layer and resulting in an optimal balance of performance in the final composite coating. This fundamentally solves the technical problem of easy cracking and peeling of a single coating.

[0121] It should be noted that the stainless steel workpiece used in this embodiment of the present invention is only an example of one implementation method. In actual application scenarios, any other initial workpiece material can be used, as long as it is suitable for the welding method provided by this invention.

[0122] It will be apparent to those skilled in the art that this disclosure is not limited to the details of the exemplary embodiments described above, and that this disclosure can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of this disclosure is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within this disclosure. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0123] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A composite welded structure, characterized in that, The composite welding structure includes a workpiece and a welding joint fixedly welded to the workpiece, and at least the surface of the welding joint is provided with a metal plating layer; The solder used in the welding joint includes any one or more of copper solder, copper alloy solder, silver solder, silver alloy solder, gold solder, and gold alloy solder. The metal coating includes at least a nickel coating or a nickel alloy coating.

2. The composite welded structure according to claim 1, characterized in that, The thickness of the metal coating is 30μm-150μm.

3. The composite welded structure according to claim 1, characterized in that, The material of the nickel alloy coating includes any one of nickel-phosphorus alloy, nickel-cobalt-phosphorus alloy, nickel-molybdenum alloy, and nickel-tungsten alloy.

4. The composite welded structure according to claim 1, characterized in that, The metal coating comprises an adhesive layer, a buffer layer, and a protective layer stacked sequentially.

5. The composite welded structure according to claim 4, characterized in that, The adhesive layer is a low-phosphorus nickel-phosphorus alloy plating.

6. The composite welded structure according to claim 4, characterized in that, The material of the buffer layer includes any one of copper, copper alloy, gold, gold alloy, silver, and silver alloy.

7. The composite welded structure according to claim 4, characterized in that, The protective layer is a high-phosphorus nickel-phosphorus alloy plating.

8. The composite welded structure according to claim 4, characterized in that, The protective layer is a nickel-boron alloy plating.

9. The composite welded structure according to claim 4, characterized in that, The thickness of the adhesive layer is 1μm-3μm; and / or, The thickness of the buffer layer is 5μm-15μm; and / or, The thickness of the protective layer is 5μm-20μm.

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