A method for welding dissimilar materials
By generating composite material intermediate layer with adjustable linear expansion coefficient and instantaneous liquid phase diffusion welding mechanism in different materials welding, the problems of high thermal stress and high parent material accuracy requirements in different materials welding are solved, and high-quality welding and low-cost welding are achieved.
Patent Information
- Application Number
- CN202211422054.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2022-11-14
- Publication Date
- 2025-08-22
- Estimated Expiration
- 2042-11-14
AI Technical Summary
In the prior art, when welding different materials, especially materials with large linear expansion coefficients, it is difficult to effectively reduce the thermal stress of the joints, and the surface accuracy of the base material is high, which increases welding difficulty and cost.
W-Cu-Ni powder coated with Cu-Ni alloy layer on the surface of tungsten particles and added magnetic Me metal powder to form (W-Cu-Ni)-Me mixed powder. A composite intermediate layer with adjustable linear expansion coefficient is generated in situ in the joint of the heterogeneous material through vacuum diffusion welding, and the combination of high melting point base material and composite intermediate layer is achieved by instantaneous liquid phase diffusion welding mechanism.
Significantly reduce the residual thermal stress of the joint, improve the mechanical properties of the joint, reduce the surface accuracy requirements of the base material, and adapt to welding of a variety of different materials, especially welding materials with large linear expansion coefficients, and the welding temperature is low, reducing costs.
Smart Images
Figure CN115780989B_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of welding and relates to a welding method for dissimilar materials. Background Art
[0002] Connecting dissimilar materials into composite components can maximize the advantages of the respective materials being connected to meet performance requirements. With the development of modern high-parameter equipment, many dissimilar material connection topics have been raised. Due to the differences in elastic modulus and linear expansion coefficients of dissimilar materials, dissimilar material welded joints will generate large thermal stresses. Thermal stress greatly reduces the connection strength and thermal fatigue performance of the joint. Excessive thermal stress can even cause the joint to crack directly after welding. Therefore, for dissimilar material joints, especially those with large differences in linear expansion coefficients, such as welding tungsten to steel, and welding ceramics to metal, how to reduce the thermal stress of the joint is the core issue of dissimilar material welding.
[0003] After years of research and practice, methods have been developed to reduce thermal stress in dissimilar weld joints, including interlayer methods, room-temperature bonding methods, joint geometry modification methods, localized heating methods, joint discretization methods, avoiding tensile loads, phase transformation stress relief methods, and controlled microcracks. Considering factors such as thermal stress reduction effectiveness, process complexity, and adaptability, the interlayer method is the most practical. It also forms the basis for the application of other thermal stress reduction methods. In practice, two types of interlayers are commonly used: soft interlayers, which primarily utilize their lower yield strength to relieve thermal stress in the joint; and hard interlayers, whose linear expansion coefficients lie between the two dissimilar materials and serve as a transition between their physical properties. For example, in joining tungsten to steel, hard materials such as Ti, V, Nb, and Ta, whose thermal expansion coefficients lie between those of tungsten and steel, are often used as interlayers. However, using hard materials as interlayers places high demands on the flatness and surface roughness of both the base metal and the hard interlayer before welding, increasing welding difficulty and processing costs.
[0004] Powders are fluid, and using mixed powders as an intermediate layer for welding dissimilar materials can overcome this problem. During the welding process, the mixed powder intermediate layer is sintered to simultaneously form a composite material intermediate layer in the joint and weld the dissimilar materials. However, it is difficult to achieve high-density sintering of the composite material intermediate layer through solid-phase sintering at welding temperatures, and it is difficult to obtain a composite material intermediate layer with an adjustable thermal expansion coefficient under welding pressure through liquid-phase sintering alone, which is not conducive to optimizing the thermal stress of the joint. In addition, the matrix phase, which occupies most of the volume of the composite material intermediate layer, often uses a hard phase. How to improve the interfacial bonding strength between the composite material intermediate layer and the high-melting-point parent material is also a major challenge. Summary of the Invention
[0005] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a method for welding dissimilar materials, in which a composite material intermediate layer with an adjustable linear expansion coefficient between the two dissimilar materials is generated in situ in the welded dissimilar material joint, and the high melting point base material and the composite material intermediate layer are combined through a transient liquid phase diffusion welding mechanism, thereby achieving high-quality welding between the dissimilar materials, and the surface processing accuracy requirements of the welding base material are not high.
[0006] In order to achieve the above object, the present invention adopts the following technical solutions:
[0007] A method for welding dissimilar materials, comprising the following steps:
[0008] S1, mechanically coating a Cu-Ni alloy layer on the surface of tungsten particles to produce W-Cu-Ni powder;
[0009] S2, adding magnetic Me metal powder to W-Cu-Ni powder and mixing to obtain (W-Cu-Ni)-Me mixed powder;
[0010] S3, pressing the (W-Cu-Ni)-Me mixed powder, copper foil and nickel foil to prepare a laminated sheet;
[0011] S4, assembling the first base material, the nickel sheet, the laminated sheet, and the second base material in the order of first base material / nickel sheet / laminated sheet / second base material into a dissimilar material welded part;
[0012] S5, placing the dissimilar materials to be welded into a vacuum hot pressing furnace for vacuum diffusion welding.
[0013] Optionally, a Cu-Ni alloy layer is mechanically coated on the surface of the tungsten particles by high-energy ball milling.
[0014] Optionally, the components of the W-Cu-Ni powder are calculated by weight as follows: W is 92-97%, and Cu-Ni alloy is 3-8%; the components of the Cu-Ni alloy are calculated by weight as follows: Cu is 90-98%, and Ni is 2-10%.
[0015] Optionally, the components of the (W—Cu—Ni)-Me mixed powder are calculated by weight as follows: W—Cu—Ni is 50-95%, and Me is 5-50%.
[0016] Optionally, the layer structure of the laminated sheet is copper foil / (W-Cu-Ni)-Me mixed powder / copper foil / nickel foil / copper foil.
[0017] Optionally, the layer structure of the dissimilar materials to be welded is first base material / nickel sheet / copper foil / (W-Cu-Ni)-Me mixed powder / copper foil / nickel foil / copper foil / second base material.
[0018] Optionally, the melting point of the second parent material is higher than that of the first parent material.
[0019] Optionally, the thickness of the copper foil is 3-30 microns, the thickness of the nickel foil is 5-60 microns, K≥0.4, and K=nickel foil thickness / (2*copper foil thickness+nickel foil thickness).
[0020] Optionally, the heating temperature of the vacuum diffusion welding is higher than the melting point of the Cu-Ni component in the W-Cu-Ni powder and lower than 1200°C.
[0021] Optionally, a Cu-Ni alloy layer is mechanically coated on the surface of the tungsten particles by high-energy ball milling, with a ball-to-material ratio of 5-12:1, a rotation speed of 200-400 r / min, and a ball milling time of 10-15 h.
[0022] Compared with the prior art, the present invention has the following beneficial effects:
[0023] The present invention provides a method for welding dissimilar materials. In the welded dissimilar material joint, an adjustable composite material intermediate layer with a linear expansion coefficient between the two dissimilar materials is generated in situ, which can significantly reduce the residual thermal stress of the joint and improve the mechanical properties of the joint.
[0024] The welding between the high melting point base material and the composite material middle layer is achieved through the transient liquid phase diffusion welding mechanism, which can achieve a high heat resistance joint at a lower welding temperature;
[0025] The two features of the integrated joint are that the composite material intermediate layer with an adjustable linear expansion coefficient between the two base materials is generated in situ, and the instantaneous liquid phase diffusion welding mechanism is used to weld the high melting point base material and the composite material intermediate layer. This can adapt to the welding of most dissimilar materials, especially the high-quality welding of dissimilar materials with large differences in linear expansion coefficients.
[0026] The requirements for the flatness and roughness of the surface of the base material to be welded are low, which reduces the difficulty of the welding process and the processing cost. BRIEF DESCRIPTION OF THE DRAWINGS
[0027] Figure 1 Shown is a flow chart of a welding method for dissimilar materials according to the present invention;
[0028] Figure 2 The figure shows the morphology of the dissimilar material tungsten / steel welded joint using the present invention;
[0029] Figure 3 Shown is a shear curve diagram of a dissimilar tungsten / steel welded joint welded using the present invention.
[0030] In the figure: 1. Steel base material; 2. Nickel intermediate layer; 3. Composite material intermediate layer; 4. Cu-Ni alloy layer; 5. Tungsten base material. DETAILED DESCRIPTION
[0031] The present invention will be further described below in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention.
[0032] The endpoints of the ranges and any values disclosed herein are not limited to the precise ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.
[0033] For the purposes of this specification and the appended claims, unless otherwise indicated, all numbers expressing amounts, percentages or ratios and other numerical values used in this specification and the appended claims are to be understood as being modified in all instances by the term "about." In addition, all ranges disclosed herein are inclusive and independently combinable.
[0034] like Figures 1 to 3 As shown, a method for welding dissimilar materials includes the following steps:
[0035] S1. Using tungsten powder, copper powder, and nickel powder, all with a purity greater than 99.5% and a mesh size greater than 400 mesh, as raw materials, a W-Cu-Ni mixed powder is prepared by mixing 92-97% tungsten powder, 3-8% copper powder, and 3-8% nickel powder, wherein the copper powder accounts for 90-98% of the total weight of the copper and nickel powders, and the nickel powder accounts for 2-10% of the total weight of the copper and nickel powders. The W-Cu-Ni mixed powder is then subjected to high-energy ball milling at a ball-to-material ratio of 5-12:1, a rotation speed of 200-400 r / min, and a ball milling time of 10-15 hours. After high-energy ball milling, a W-Cu-Ni powder is formed in which the surface of the tungsten particles is mechanically coated with a Cu-Ni alloy layer. The components of the W-Cu-Ni powder, by weight, are: 92-97% W, 3-8% Cu-Ni alloy, and 90-98% Cu, and 2-10% Ni.
[0036] During the high-energy ball milling process, after repeated friction, impact, intrusion and extrusion, the hard tungsten particles are refined, homogenized and mechanically coated with a layer of Cu-Ni alloy. In the subsequent welding process, the Cu-Ni alloy layer melts, and the tungsten particles are metallurgically bonded in the form of liquid phase sintering to form a dense and uniform W-Cu-Ni tungsten-based high-density alloy.
[0037] S2, adding magnetic Me metal powder, such as nickel powder, cobalt powder, iron powder, etc., to the W-Cu-Ni powder, and mixing the powders in a mixer to form a (W-Cu-Ni)-Me mixed powder; the W-Cu-Ni powder accounts for 50-95% of the total weight of the (W-Cu-Ni)-Me mixed powder, and the Me metal powder accounts for 5-50% of the total weight of the (W-Cu-Ni)-Me mixed powder. The mixing speed is 100-150 r / min, and agate balls are added to the mixing tank. The mass of the agate balls is 1 / 5 of the mass of the mixed powder. The mixing time is 30-60 min.
[0038] In this step, the characteristic that the Me metal powder can agglomerate during the powder mixing process due to its magnetic properties is creatively utilized, thereby preparing a (W-Cu-Ni)-Me mixed powder in which a large number of Me metal powder agglomerates are distributed in the W-Cu-Ni powder. In the subsequent welding process, at a suitable temperature, the W-Cu-Ni powder in the (W-Cu-Ni)-Me mixed powder forms a uniform and dense tungsten-based high-density alloy through liquid phase sintering, while the Me metal powder agglomerates form a large number of Me metal clusters distributed in the tungsten-based high-density alloy through solid phase sintering. Since the linear expansion coefficient of the Me metal cluster is higher than that of the tungsten-based high-density alloy, the linear expansion coefficient of the composite material intermediate layer of the tungsten-based high-density alloy + Me metal cluster formed by sintering the (W-Cu-Ni)-Me mixed powder in the weld joint is between the linear expansion coefficients of the tungsten-based high-density alloy and the Me metal cluster, and the linear expansion coefficient of the composite material intermediate layer in the joint can be adjusted by adjusting the content of the Me metal powder in the (W-Cu-Ni)-Me mixed powder, so that the composite material intermediate layer can reduce the thermal stress of the welded joint of different dissimilar materials.
[0039] S3: At room temperature, using a powder metallurgy tableting die, press the (W-Cu-Ni)-Me mixed powder, three copper foils, and one nickel foil into a laminated sheet with a structure of copper foil / (W-Cu-Ni)-Me mixed powder / copper foil / nickel foil / copper foil in the order of copper foil / (W-Cu-Ni)-Me mixed powder / copper foil / nickel foil / copper foil at a pressure exceeding 300 MPa. The copper foil thickness is 3-30 μm, the nickel foil thickness is 5-60 μm, and K is ≥ 0.4, where K = nickel foil thickness / (2 * copper foil thickness + nickel foil thickness). The thickness of the laminated sheet is determined based on the application.
[0040] S4, assembling the first base material, the nickel sheet, the laminated sheet, and the second base material into a dissimilar material welded part according to the order of first base material / nickel sheet / laminated sheet / second base material, that is, assembling the dissimilar material welded part according to the order of first base material / nickel sheet / copper foil / (W-Cu-Ni)-Me mixed powder / copper foil / nickel foil / copper foil / second base material, wherein the melting point of the second base material is higher than that of the first base material; the thickness of the nickel sheet is 0.1 mm to 1 mm; before assembly, grinding the first base material, the second base material, and the nickel sheet to 1000 grit sandpaper, and then ultrasonically cleaning them in alcohol for 15 minutes;
[0041] Since the material composition and stacking structure of the dissimilar materials to be welded are first base material / nickel sheet / copper foil / (W-Cu-Ni)-Me mixed powder / copper foil / nickel foil / copper foil / second base material, the composite material intermediate layer formed during the vacuum diffusion welding process can be combined with the second base material by the mechanism of instantaneous liquid phase diffusion welding, which not only improves the bonding strength between the composite material intermediate layer and the second base material, but also reduces the surface processing accuracy requirements for the second base material.
[0042] S5, placing the dissimilar materials to be welded into a vacuum hot pressing furnace for vacuum diffusion welding; the heating temperature of vacuum diffusion welding is higher than the melting point of the Cu-Ni component in the W-Cu-Ni powder, but lower than 1200°C; an axial pressure of 5-10 MPa is applied during the vacuum diffusion welding process.
[0043] During the welding process, because the heating temperature is higher than the melting point of the Cu-Ni components in the W-Cu-Ni powder, the W-Cu-Ni powder forms a uniform and dense tungsten-based high-density alloy through a liquid-phase sintering process under pressure. Furthermore, because the heating temperature is lower than the melting point of the Me metal, the Me metal powder agglomerates through solid-phase sintering at the welding temperature to form Me metal clusters distributed in the tungsten-based high-density alloy. Therefore, the (W-Cu-Ni)-Me mixed powder forms a composite material intermediate layer in the joint with numerous metal Me clusters distributed in the tungsten-based high-density alloy through the combined action of liquid-phase sintering and solid-phase sintering at the welding temperature.
[0044] The heating temperature is higher than the melting point of the Cu-Ni alloy, which means that the heating temperature must be higher than the melting point of copper. At the heating temperature, the "copper foil / nickel foil / copper foil" located between the middle layer of the composite material and the second base material undergoes the following changes: first, the copper foil melts, and then the nickel foil begins to dissolve and diffuse into the copper liquid to form a Cu-Ni alloy liquid phase. As the content of Ni atoms in the Cu-Ni alloy liquid phase increases, the melting point of the Cu-Ni alloy liquid phase gradually increases and solidifies isothermally to form a Cu-Ni alloy layer. Finally, Ni atoms and Cu atoms continue to diffuse at high temperature at the welding temperature, and the Cu-Ni alloy layer and the remaining nickel layer after dissolution gradually become uniform, forming a Cu-Ni alloy layer with a relatively uniform composition and a high Ni content. That is, instantaneous liquid phase diffusion welding is achieved between the middle layer of the composite material and the second base material. When determining the thickness of copper foil and nickel foil, K is required to be ≥ 0.4, where K = nickel foil thickness / (2 * copper foil thickness + nickel foil thickness). This ensures that the weight percentage of nickel in the Cu-Ni alloy layer is greater than or equal to 0.38, which ensures that the melting point of the Cu-Ni alloy layer is higher than 1250°C. Therefore, at a relatively low welding temperature, a high-melting-point intermediate layer is formed, ensuring the heat resistance of the joint.
[0045] Under a welding temperature not higher than 1200° C. and an axial pressure of 5-10 MPa, the first base material and the nickel sheet are bonded by solid phase diffusion welding, and the nickel sheet and the composite material intermediate layer are bonded by instantaneous liquid phase diffusion welding.
[0046] As can be seen from the above description, the innovative welding method of the present invention is used to weld the first parent material and the second parent material through a composite welding method of solid-phase diffusion welding + instantaneous liquid-phase diffusion welding. At the same time, a composite material intermediate layer having a tungsten-based high-density alloy + Me metal group structure is generated in situ in the joint through the combined action of liquid-phase sintering and solid-phase sintering. These two creative features have many advantages, such as low surface processing requirements for the parent material to be welded and the intermediate layer, good heat resistance of the welded joint, and low thermal stress in the joint. At the same time, the innovative welding method of the present invention is suitable for welding between a variety of dissimilar materials by integrating the two characteristics of in-situ generation of a composite material intermediate layer with an adjustable linear expansion coefficient in the joint and the instantaneous liquid-phase diffusion welding mechanism to achieve welding between the high-melting-point parent material and the composite material intermediate layer.
[0047] Example 1
[0048] like Figure 1 , a method for welding dissimilar materials, comprising the following steps:
[0049] S1, using tungsten powder, copper powder, and nickel powder with a purity greater than 99.5% and a powder mesh greater than 400 mesh as raw materials, and mixing 97% by weight of tungsten powder, 3% by weight of copper powder and 3% by weight of nickel powder to form a W-Cu-Ni mixed powder, wherein the copper powder accounts for 90% by weight of the total weight of the copper powder and the nickel powder, and the nickel powder accounts for 10% by weight of the total weight of the copper powder and the nickel powder; high-energy ball milling is performed on the W-Cu-Ni mixed powder by a high-energy ball milling method, with a ball-to-material ratio of 12:1, a rotation speed of 300 r / min, and a ball milling time of 15 hours, to form a W-Cu-Ni powder with a Cu-Ni alloy layer mechanically plated on the surface of the tungsten particles;
[0050] S2, adding nickel powder to the W-Cu-Ni powder, and mixing the powders in a mixer to form a (W-Cu-Ni)-Ni mixed powder; the W-Cu-Ni powder accounts for 88% of the total weight of the (W-Cu-Ni)-Ni mixed powder, and the nickel powder accounts for 12% of the total weight of the (W-Cu-Ni)-Ni mixed powder; the mixing speed is 150 r / min, and agate balls are added to the mixing tank, the mass of the agate balls is 1 / 5 of the mass of the mixed powder, and the mixing time is 60 min;
[0051] S3, at room temperature, in the stacking order of copper foil / (W-Cu-Ni)-Ni mixed powder / copper foil / nickel foil / copper foil, pressing the (W-Cu-Ni)-Ni mixed powder, three copper foils, and one nickel foil into a laminated sheet having a structure of copper foil / (W-Cu-Ni)-Ni mixed powder / copper foil / nickel foil / copper foil; the copper foil having a thickness of 6 μm and the nickel foil having a thickness of 8 μm, using a general powder metallurgy tableting die, cold pressing the laminated sheet at a pressure of 350 MPa, with a thickness of 0.4 mm;
[0052] S4. Assemble the ferritic steel, nickel sheet, laminated sheet, and tungsten to be welded into a dissimilar material weldment in the order of ferritic steel / nickel sheet / laminated sheet / tungsten, i.e., assemble the dissimilar material weldment in the order of ferritic steel / nickel sheet / copper foil / (W-Cu-Ni)-Ni mixed powder / copper foil / nickel foil / copper foil / tungsten; the nickel sheet is 0.15 mm thick. Prior to assembly, polish the ferritic steel, tungsten, and nickel sheet to 1000 grit sandpaper and then ultrasonically clean them in alcohol for 15 minutes.
[0053] S5, placing the dissimilar materials to be welded into a vacuum hot pressing furnace for vacuum diffusion welding; the heating temperature is 1120°C, and an axial pressure of 5 MPa is applied.
[0054] Depend on Figure 2It can be seen that the tungsten / steel dissimilar material weld joint is composed of steel base material 1, nickel intermediate layer 2, composite material intermediate layer 3, Cu-Ni alloy layer 4 and tungsten base material 5, wherein the composite material intermediate layer 3 is formed by the (W-Cu-Ni)-Ni mixed powder through the combined action of liquid phase sintering and solid phase sintering, and the Cu-Ni alloy layer 4 is formed by copper foil / nickel foil / copper foil as the intermediate layer in the transient liquid phase diffusion welding process.
[0055] The shear strength of the steel / tungsten joint reaches a high of 272MPa. Figure 3 This is the shear curve of the tungsten / steel welded joint. The high shear strength indicates that the steel / tungsten joint has high bonding strength at each interface and low residual stress at each interface.
[0056] Example 2
[0057] like Figure 1 , a method for welding dissimilar materials, comprising the following steps:
[0058] S1, using tungsten powder, copper powder, and nickel powder with a purity greater than 99.5% and a powder mesh greater than 400 mesh as raw materials, and mixing 92% by weight of tungsten powder, 8% by weight of copper powder, and 8% by weight of nickel powder to form a W-Cu-Ni mixed powder, wherein the copper powder accounts for 98% of the total weight of the copper powder and the nickel powder, and the nickel powder accounts for 2% of the total weight of the copper powder and the nickel powder; high-energy ball milling is performed on the W-Cu-Ni mixed powder by a high-energy ball milling method, with a ball-to-material ratio of 5:1, a rotation speed of 400 r / min, and a ball milling time of 10 hours, to form a W-Cu-Ni powder with a Cu-Ni alloy layer mechanically plated on the surface of the tungsten particles;
[0059] S2, adding cobalt powder to the W-Cu-Ni powder, and mixing the powders in a mixer to form a (W-Cu-Ni)-Co mixed powder; the W-Cu-Ni powder accounts for 95% of the total weight of the (W-Cu-Ni)-Co mixed powder, and the cobalt powder accounts for 5% of the total weight of the (W-Cu-Ni)-Co mixed powder. The mixing speed is 100 r / min, and agate balls are added to the mixing tank. The mass of the agate balls is 1 / 5 of the mass of the mixed powder. The mixing time is 30 min;
[0060] S3, at room temperature, in the order of copper foil / (W-Cu-Ni)-Co mixed powder / copper foil / nickel foil / copper foil, pressing the (W-Cu-Ni)-Co mixed powder, three copper foils, and one nickel foil into a laminated sheet having a structure of copper foil / (W-Cu-Ni)-Co mixed powder / copper foil / nickel foil / copper foil; the copper foil having a thickness of 3 μm and the nickel foil having a thickness of 5 μm, using a general powder metallurgy tableting die, cold pressing the laminated sheet at a pressure of 350 MPa, with a thickness of 0.2 mm;
[0061] S4, assembling the carbon steel, nickel sheet, laminated sheet, and tantalum to be welded into a dissimilar material welded part according to the order of carbon steel / nickel sheet / laminated sheet / tantalum, that is, assembling the dissimilar material welded part according to the order of carbon steel / nickel sheet / copper foil / (W-Cu-Ni)-Co mixed powder / copper foil / nickel foil / copper foil / tantalum; the thickness of the nickel sheet is 0.3 mm; before assembly, the carbon steel, tantalum, and nickel sheet need to be polished to 1000 grit sandpaper, and then ultrasonically cleaned in alcohol for 15 minutes;
[0062] S5, placing the dissimilar materials to be welded into a vacuum hot pressing furnace for vacuum diffusion welding; the heating temperature is 1100°C, and an axial pressure of 10 MPa is applied.
[0063] The shear strength of the tantalum / steel joint welded in this example reached 240 MPa.
[0064] Example 3
[0065] like Figure 1 , a method for welding dissimilar materials, comprising the following steps:
[0066] S1, using tungsten powder, copper powder, and nickel powder with a purity greater than 99.5% and a powder mesh greater than 400 mesh as raw materials, 95% of tungsten powder, 5% of copper powder and 5% of nickel powder are mixed to form a W-Cu-Ni mixed powder by weight, wherein the copper powder accounts for 94% of the total weight of the copper powder and the nickel powder, and the nickel powder accounts for 6% of the total weight of the copper powder and the nickel powder; high-energy ball milling is performed on the W-Cu-Ni mixed powder by a high-energy ball milling method, with a ball-to-material ratio of 12:1, a rotation speed of 200 r / min, and a ball milling time of 15 hours, to form a W-Cu-Ni powder with a Cu-Ni alloy layer mechanically plated on the surface of the tungsten particles;
[0067] S2, adding iron powder to the W-Cu-Ni powder, and mixing the powders in a mixer to form a (W-Cu-Ni)-Fe mixed powder; the W-Cu-Ni powder accounts for 50% of the total weight of the (W-Cu-Ni)-Fe mixed powder, and the iron powder accounts for 50% of the total weight of the (W-Cu-Ni)-Fe mixed powder. The mixing speed is 150 r / min, and agate balls are added to the mixing tank. The mass of the agate balls is 1 / 5 of the mass of the mixed powder, and the mixing time is 60 min.
[0068] S3, at room temperature, in the stacking order of copper foil / (W-Cu-Ni)-Fe mixed powder / copper foil / nickel foil / copper foil, pressing the (W-Cu-Ni)-Fe mixed powder, three copper foils, and one nickel foil into a laminated sheet having a structure of copper foil / (W-Cu-Ni)-Fe mixed powder / copper foil / nickel foil / copper foil; the copper foil having a thickness of 30 μm and the nickel foil having a thickness of 60 μm, using a general powder metallurgy tableting die, cold pressing the laminated sheet at a pressure of 350 MPa, with a thickness of 0.3 mm;
[0069] S4, assembling the stainless steel, nickel sheet, laminated sheet, and molybdenum to be welded into a dissimilar material welded part according to the order of stainless steel / nickel sheet / laminated sheet / molybdenum, that is, assembling the dissimilar material welded part according to the order of stainless steel / nickel sheet / copper foil / (W-Cu-Ni)-Fe mixed powder / copper foil / nickel foil / copper foil / molybdenum; the thickness of the nickel sheet is 0.3 mm; before assembly, polishing the stainless steel, molybdenum, and nickel sheet to the size of 1000 sandpaper, and then ultrasonically cleaning them in alcohol for 15 minutes;
[0070] S5, placing the dissimilar materials to be welded into a vacuum hot pressing furnace for vacuum diffusion welding; the heating temperature is 1150°C, and an axial pressure of 5 MPa is applied.
[0071] The shear strength of the stainless steel / molybdenum joint welded in this example reached 263 MPa.
[0072] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.
Claims
1. A method for welding dissimilar materials, characterized in that: The following steps are involved: S1, mechanically coating a Cu-Ni alloy layer on the surface of tungsten particles to produce W-Cu-Ni powder; S2, adding magnetic Me metal powder to W-Cu-Ni powder and mixing to obtain (W-Cu-Ni)-Me mixed powder; S3, pressing the (W-Cu-Ni)-Me mixed powder, copper foil and nickel foil to prepare a laminated sheet; S4, assembling the first base material, the nickel sheet, the laminated sheet, and the second base material in the order of first base material / nickel sheet / laminated sheet / second base material into a dissimilar material welded part; S5, placing the dissimilar materials to be welded into a vacuum hot pressing furnace for vacuum diffusion welding; The W-Cu-Ni powder comprises 92-97% W and 3-8% Cu-Ni alloy by weight; the Cu-Ni alloy comprises 90-98% Cu and 2-10% Ni by weight. The components of the (W-Cu-Ni)-Me mixed powder are calculated by weight percentage: W-Cu-Ni is 50-95%, and Me is 5-50%; The layer structure of the laminated sheet is copper foil / (W-Cu-Ni)-Me mixed powder / copper foil / nickel foil / copper foil.
2. The method for welding dissimilar materials according to claim 1, characterized in that: The Cu-Ni alloy layer was mechanically coated on the surface of tungsten particles by high-energy ball milling.
3. The method for welding dissimilar materials according to claim 1, characterized in that: The second base material has a higher melting point than the first base material.
4. The method for welding dissimilar materials according to claim 1, characterized in that: The thickness of the copper foil is 3-30 microns, the thickness of the nickel foil is 5-60 microns, K≥0.4, K=nickel foil thickness / (2*copper foil thickness+nickel foil thickness).
5. The method for welding dissimilar materials according to claim 1, characterized in that: The heating temperature of vacuum diffusion welding is higher than the melting point of the Cu-Ni component in the W-Cu-Ni powder and lower than 1200°C.
6. The method for welding dissimilar materials according to claim 2, characterized in that: The Cu-Ni alloy layer was mechanically coated on the surface of tungsten particles by high-energy ball milling, with a ball-to-material ratio of 5-12:1, a rotation speed of 200-400 r / min, and a ball milling time of 10-15 h.