4J29 kovar alloy / 304 stainless steel composite board and preparation method thereof

Abstract

The invention discloses a 4J29 kovar alloy / 304 stainless steel composite plate and a preparation method thereof, and belongs to the technical field of metal composite plate production, a 4J29 kovar alloy plate and a 304 stainless steel plate in a cold rolling state are respectively subjected to recrystallization annealing treatment to obtain a soft 4J29 kovar alloy plate and a soft 304 stainless steel plate, then the soft 304 stainless steel plate is used as a base plate, and the 4J29 kovar alloy plate and the soft 304 stainless steel plate are subjected to heat treatment to obtain the 4J29 kovar alloy / 304 stainless steel composite plate. A soft 4J29 kovar alloy plate serves as a compound plate, the surface of the soft 4J29 kovar alloy plate is coated with a layer of water glass to serve as a protective layer, then an explosive layer is laid on the surface of the protective layer in a gradient explosive distribution mode, then explosive cladding is conducted, the composite plate is obtained, a bonding area of the composite plate has the uniform and continuous microwave shape characteristic, the interface bonding rate is larger than or equal to 98.9%, and the bonding strength is larger than 360 MPa. The explosive welding composite board with excellent performance is prepared, and corresponding technical conditions meet industrial production requirements.

Description

Technical Field

[0001] This invention belongs to the field of metal matrix composite material processing, specifically relating to a 4J29 Kovar alloy / 304 stainless steel composite plate and its preparation method. Background Technology

[0002] 4J29 Kovar alloy, a typical iron-based constant expansion alloy, exhibits a stable austenitic structure in the solid state, characterized by a coefficient of thermal expansion similar to borosilicate glass within a temperature range of 20-450 °C. Due to its excellent hermeticity and dimensional stability, 4J29 Kovar alloy is widely used in electronic vacuum devices, semiconductor packaging, aerospace, and medical equipment. In addition, 4J29 Kovar alloy possesses good mechanical properties, corrosion resistance, and weldability. At room temperature, its tensile strength reaches 520 MPa, yield strength is 330 MPa, and elongation is 30%. However, the high Co content in the alloy composition, along with precise component ratios and stringent manufacturing processes, increases its manufacturing cost. 304 stainless steel, a widely used austenitic stainless steel, is suitable for most non-marine, non-strong acid / alkali environments due to its excellent corrosion resistance, mechanical properties, and machinability. Furthermore, 304 stainless steel maintains its strength and stability at high temperatures, making it suitable for applications requiring high-temperature resistance, and it also offers a significant cost advantage compared to 4J29 Kovar alloy.

[0003] Layered metal composites combine two or more metal materials in the same plane, effectively compensating for the shortcomings of a single material while maintaining the performance advantages of the base material. Combining 4J29 Kovar alloy and 304 stainless steel can meet performance requirements while significantly reducing manufacturing costs. However, considering the differences in physical properties between the two materials and the interfacial bonding strength of the composite plate, rolling is not suitable for this process.

[0004] Explosive welding utilizes the immense energy generated during an explosion to cause collisions between two layers of metal, ultimately achieving a metallurgical bond. This method is suitable for composites of metals with significantly different properties, and it removes most impurities during the welding process, improving the quality of the weld joint. The resulting welded plates exhibit high bond strength and excellent subsequent processing properties.

[0005] However, in the actual preparation of explosively welded composite plates, due to the significant difference in the coefficients of thermal expansion between 4J29 Kovar alloy and 304 stainless steel, a large amount of residual stress is generated at the interface during welding, inducing microcracks. Furthermore, the composite plate may undergo macroscopic deformation, such as overall warping. When the thermal stress generated during welding exceeds the interfacial bonding strength, delamination may even occur, leading to welding failure. Moreover, the low thermal conductivity of the two materials easily leads to heat concentration at the interface during the bonding process, increasing the molten zone area and forming a continuous molten layer, resulting in a severe decline in the bonding quality of the composite plate. Therefore, to obtain composite plates with excellent bonding performance, key parameters such as the explosive ratio, dosage, and detonation velocity, as well as the properties, thickness, and spacing of the plates, are required. However, there are currently no reports on the bonding of 4J29 Kovar alloy with dissimilar materials via explosive welding. Therefore, developing a 4J29 Kovar alloy and 304 stainless steel composite technology based on explosive welding is of significant value for promoting the engineering application of this type of structurally functional integrated material. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide a method for preparing 4J29 Kovar alloy / 304 stainless steel composite plates. The invention first involves recrystallizing and annealing cold-rolled 4J29 Kovar alloy plates and 304 stainless steel plates at different temperatures; then, a layer of water glass is applied to the surface of the Kovar alloy plate as a protective layer; a specially formulated low-detonation-velocity expanded ammonium nitrate explosive is laid on the protective layer using a gradient explosive distribution method; finally, explosive welding is performed to obtain a composite plate with a micro-wave interface. The present invention features a simple production process, high yield, and high interfacial bonding strength, meeting the needs of industrial production.

[0007] The second objective of this invention is to provide a 4J29 Kovar alloy / 304 stainless steel composite plate prepared by the above-mentioned preparation method. The 4J29 Kovar alloy / 304 stainless steel composite plate provided by this invention has a uniform and continuous micro-shaped bonding interface, wherein the wavelength and wave height are 390-520 μm and 140-200 μm, respectively. Experiments have shown that this micro-waveform bonding interface results in the optimal bonding performance between the 4J29 Kovar alloy and the 304 stainless steel composite plate.

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] This invention discloses a method for preparing a 4J29 Kovar alloy / 304 stainless steel composite plate. The method involves recrystallizing and annealing cold-rolled 4J29 Kovar alloy plate and 304 stainless steel plate to obtain soft 4J29 Kovar alloy plate and soft 304 stainless steel plate, respectively. The soft 304 stainless steel plate is then used as the substrate, and the soft 4J29 Kovar alloy plate is used as the composite plate. A layer of water glass is coated onto the surface of the soft 4J29 Kovar alloy plate as a protective layer. Then, an explosive layer is laid on the surface of the protective layer using a gradient explosive distribution method. Finally, explosive bonding is performed to obtain the final product.

[0010] The thickness of the explosive layer decreases continuously from the edge of the short side detonation point to the edge of the other side of the short side, wherein the thickness of the edge of the short side detonation point is 40-50 mm, the thickness of the edge of the other side of the short side is 34-39 mm, and the thickness of the edge of the other side of the short side is 6-10 mm smaller than that of the edge of the short side detonation point.

[0011] The explosive has a detonation velocity of 2100-2500 m / s and a saturation of 8-12 mm.

[0012] The preparation method provided by this invention uses cold-rolled 4J29 Kovar alloy plate and 304 stainless steel plate to undergo recrystallization annealing treatment to eliminate work hardening and transform the plates into an annealed (soft) state to adapt to the technical conditions of explosive welding. Then, a layer of water glass is coated on the surface of the soft 4J29 Kovar alloy plate, which can more effectively and uniformly disperse the impact pressure of the explosive and reduce stress concentration. It can effectively improve the surface quality of the composite plate, such as reducing surface burns. Then, the explosive layer is laid in a gradient charge, with the explosive thickness gradually decreasing along the detonation direction. This ensures that the detonation end has sufficient energy density to form an initial waveform interface, and prevents the formation of a large waveform interface due to excess energy during the stable detonation stage. Combined with the specific detonation velocity and saturation explosive of this invention, a micro-waveform interface with a wavelength of 390-520 μm and a wave height of 140-200 μm can be obtained in a controllable manner, resulting in high bonding strength and excellent mechanical properties of the composite plate.

[0013] In this invention, a soft 4J29 Kovar alloy plate obtained by recrystallization annealing of cold-rolled 4J29 Kovar alloy plate is used as the cladding plate. There is no need to use high-manganese explosives to compensate for the strength, and a composite plate with excellent mechanical properties can be obtained. In fact, due to the performance characteristics of the two plates in this invention, if a higher manganese explosive is used, it will lead to excessive melting at the interface, resulting in a decrease in bonding strength; excessive manganese may even cause the cladding plate to tear or be severely deformed.

[0014] Furthermore, the ability to obtain a specific micro-waveform interface, the use of water glass as a protective layer, and the control of the gradient explosive parameters within the limits of this invention are also crucial. During the experimental exploration process, this invention also tried numerous other protective layers such as kraft paper and rubber sheets, but the buffering effect was not as uniform as water glass, and this resulted in a decrease in the surface quality of the final sheet. Moreover, if the gradient explosive parameters are unreasonable, it can lead to disordered interface waveforms, significant changes in waveform size, and the appearance of unbonded or over-melted areas. In addition, excessively thick local explosives can cause tearing or perforation of the cladding; an excessively steep gradient in explosive layer thickness can affect the stable detonation of the explosives and disrupt the continuity of energy transfer.

[0015] In a preferred embodiment, the thickness of the 4J29 Kovar alloy plate is 2.5-4 mm, and the thickness of the 304 stainless steel plate is 9-11 mm.

[0016] In this invention, a 4J29 Kovar alloy plate is used as the cladding plate, and a 304 stainless steel plate is used as the substrate. The thickness of the two plates is controlled within the aforementioned range to obtain a composite plate with an ideal waveform. If the 4J29 Kovar alloy plate is too thin, it will be prone to tearing or perforation during welding, resulting in surface wrinkles. If the cladding plate is too thick, the energy required for the cladding plate to accelerate downward will increase dramatically. Insufficient energy will lead to a decrease in bonding quality. The increased mass of the cladding plate will also increase its kinetic energy, which may cause damage to the substrate upon collision. If the substrate is too thin, it will also tear or bulge due to excessive impact energy. Furthermore, due to insufficient support stiffness, the collision energy will be absorbed by overall deformation rather than used for interface bonding, making it difficult to form an effective bond. If the substrate is too thick, the large stress difference between the substrate near the interface and the substrate far from the interface may induce cracking of the substrate itself.

[0017] In a preferred embodiment, the 4J29 Kovar alloy plate has a length of 420-620 mm and a width of 320-520 mm; the 304 stainless steel plate has a length of 400-600 mm and a width of 300-500 mm.

[0018] In a preferred embodiment, the recrystallization annealing temperature of the 4J29 Kovar alloy plate is 800-900 ℃, and the recrystallization annealing time is 1-2 h; the recrystallization annealing temperature of the 304 stainless steel plate is 1000-1100 ℃, and the recrystallization annealing time is 1-2 h. Controlling the recrystallization annealing temperatures of both plates within the above ranges results in the composite plate with optimal performance.

[0019] In a preferred embodiment, the surfaces to be bonded between the soft 4J29 Kovar alloy plate and the soft 304 stainless steel plate are ground and polished to achieve a surface roughness Ra ≤ 2.5 μm. Grinding and polishing remove the oxide layer and reduce the roughness.

[0020] In a preferred embodiment, the thickness of the protective layer is 2-4 mm. Experiments have shown that only by controlling the thickness of the protective layer within the range of this invention can an ideal uniform micro-wave bonding interface be obtained. If the protective layer is too thick, it will absorb too much energy, resulting in insufficient kinetic energy obtained by the composite plate, which cannot reach the critical collision velocity required to form a metal jet. Ultimately, this leads to a discontinuous, weak wave-like or straight bonding interface, and a significant decrease in bonding strength.

[0021] In a preferred embodiment, the explosive used in the explosive compound has the following composition by mass percentage: 68-82% expanded ammonium nitrate, 2-4% composite oil phase, 3-5% sodium chloride, 3-6% calcium carbonate, 3-6% perlite, 3-5% aluminum powder, and 4-6% rice husk powder.

[0022] In the explosive composition of this invention, an explosive matrix is ​​formed by expanded ammonium nitrate and a composite oil phase. Sodium chloride and calcium carbonate are added to reduce the detonation velocity of the explosive. Perlite and rice husk powder are added to adjust the physical structure and improve the overall bulkiness, which is conducive to detonation. The role of adding aluminum powder is to significantly increase the total work capacity of the explosive and prolong the effective pressure action time through its high heat of explosion and slightly delayed secondary reaction. Through the precise physicochemical synergy among the above explosive components, a stable and controllable detonation output required for explosive welding is achieved, thereby enabling this invention to obtain a uniform and continuous micro-bonded interface.

[0023] In a preferred embodiment, the density of the explosive used in the explosive compound is 0.75-0.9 g / cm³. 3 .

[0024] In actual operation, a gradient explosive method is adopted, in which specially made low-explosion-velocity rock-exploded ammonium nitrate explosive is laid on the protective layer. The thickness of the explosive decreases from the detonation point to the edge of the composite plate. During the laying, the transition is made smooth and without abrupt changes.

[0025] In a preferred embodiment, sand is laid and leveled on an open-air blasting site. An anvil is placed on the leveled sand as a base. A soft 304 stainless steel plate is then placed on the center of the anvil with the bonding surface facing upwards. Supports are placed at the four corners of the base. A soft 4J29 Kovar alloy plate is placed on the support with the bonding surface facing downwards. A layer of water glass is applied to the surface of the soft 4J29 Kovar alloy plate as a protective layer. Cardboard is then used to form a circle around the boundary of the composite plate and secured with tape to serve as an explosive frame. Explosive layers are then laid on the surface of the protective layer using a gradient distribution method. An electronic detonator is installed on one side of the explosive layer and connected to the detonation device via a fuse to detonate the explosive. This detonation process yields the 4J29 Kovar alloy / 304 stainless steel composite plate.

[0026] In a further preferred embodiment, the anvil is made of low-carbon steel, and the length × width × thickness of the anvil is 1500-2000 mm × 1000-1500 mm × 45-50 mm.

[0027] In a further preferred embodiment, the support is made of 304 stainless steel, the diameter of the support is 8-10 mm, preferably 8.5 mm, and the height is 5-7 mm, preferably 6 mm.

[0028] In a further preferred embodiment, the cardboard used for the explosive frame has a thickness of 2-4 mm and a height of 50-55 mm.

[0029] Further optimization involves installing the electronic detonator at the center of the short side of the explosive layer. During actual installation, the lead wire at the tail of the electronic detonator must be protected. The side where the electronic detonator is installed is the side where the detonation point is located.

[0030] The present invention also provides a 4J29 Kovar alloy / 304 stainless steel composite plate prepared by the above preparation method, wherein the 4J29 Kovar alloy / 304 stainless steel composite plate is composed of a 4J29 Kovar alloy layer and a 304 stainless steel layer, wherein the 4J29 Kovar alloy layer and the 304 stainless steel layer have a uniform and continuous waveform bonding interface, wherein the wavelength is 390-520 μm and the wave height is 140-200 μm.

[0031] In a preferred embodiment, the interface bonding rate between the 4J29 Kovar alloy layer and the 304 stainless steel layer in the 4J29 Kovar alloy / 304 stainless steel composite plate is ≥98.9%, and the bonding strength is ≥360 MPa.

[0032] Advantages of this invention:

[0033] This invention uses 304 stainless steel as the substrate and combines it with 4J29 Kovar alloy via explosive welding to obtain a layered metal composite plate. This significantly reduces the application cost while meeting the performance requirements of Kovar alloy under special working conditions. Both 4J29 Kovar alloy and 304 stainless steel are iron-based alloys with excellent metallurgical compatibility, reducing the risk of brittle intermetallic chemical reactions. Furthermore, thanks to the good machinability of 304 stainless steel, the composite plate exhibits high adaptability during subsequent plastic processing. Before explosive welding, the base material undergoes appropriate heat treatment, reducing its work hardening degree and improving its plastic deformation capacity, effectively reducing the risk of fracture due to stress concentration under explosive impact loads. The use of specially formulated low-detonation-velocity expanded ammonium nitrate explosive combined with a gradient charge distribution method is a key process combination for improving the quality of the composite plate. The core advantages of this combination are: 1. By adjusting the explosive ratio, the detonation velocity is controlled within the range required for explosive welding, thus suppressing large wave-shaped interfaces and over-melting caused by excessive impact velocity, while avoiding excessive impact loads that induce microcracks inside the plate; 2. The explosive thickness gradually decreases along the detonation direction, ensuring sufficient energy density at the initiation end to form the initial wave-shaped interface, while preventing large wave-shaped interfaces caused by excess energy during the stable detonation stage. This results in a continuous micro-wave-shaped interface at the weld joint, improving the bonding strength of the composite plate. The bonding area of ​​the 4J29 Kovar alloy and 304 stainless steel composite plate prepared by this invention exhibits uniform and continuous micro-wave-shaped characteristics, with an interface bonding rate greater than or equal to 98.9% and a bonding strength greater than 360 MPa. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of the process structure for explosive welding of 4J29 Kovar alloy and 304 stainless steel.

[0035] Figure 2 The image shows the macroscopic interface of the 4J29 Kovar alloy and 304 stainless steel explosion-bonded composite plate prepared in Example 1. The upper layer, indicated by the shorter arrow, is the 4J29 Kovar alloy layer, and the lower layer, indicated by the longer arrow, is the 304 stainless steel layer. There is a clear dividing line between the two.

[0036] Figure 3 The image shows the microscopic interface of the 4J29 Kovar alloy and 304 stainless steel explosion composite plate prepared in Example 1, wherein the 4J29 Kovar alloy is above the wavy interface and the 304 stainless steel is below it.

[0037] Figure 4 The results of the compression shear test of the 4J29 Kovar alloy and 304 stainless steel explosion composite plate prepared in Example 1 are shown.

[0038] Explanation of reference numerals in the attached drawings: 1. Sand; 2. Anvil; 3. Base plate; 4. Support; 5. Cover plate; 6. Water glass; 7. Cardboard; 8. Explosive; 9. Detonator; 10. Fuse; 11. Detonation device. Detailed Implementation

[0039] The preparation method of the composite plate made of 4J29 Kovar alloy and 304 stainless steel by explosive welding is further described below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are merely preferred examples of the present invention and should not be construed as limiting the present invention. Any equivalent process transformations made based on the content of this specification, or direct or indirect applications in related technical fields, are considered to be included within the scope of patent protection of this invention.

[0040] Example 1

[0041] S1. Cold-rolled 4J29 Kovar alloy sheet and 304 stainless steel sheet were recrystallized and annealed at 850 ℃ and 1050 ℃ respectively for 2 h to soften the sheets. The dimensions of the 4J29 Kovar alloy sheet (thickness × width × length) are 3 × 320 × 420 mm; the dimensions of the 304 stainless steel sheet (thickness × width × length) are 10 × 300 × 400 mm.

[0042] S2. Grind and polish the surfaces of the board to be bonded to remove the oxide layer and make its surface roughness Ra≤2.5 μm.

[0043] S3. Lay sand and level it on the open-air blasting site. Place an anvil made of low-carbon steel as a base on the leveled sand. The dimensions are (thickness × width × length): 50 × 1500 × 2000 mm. Clean the surface of the anvil.

[0044] S4. Using a 304 stainless steel plate as the base plate, place it with the surfaces to be joined facing upwards in the center of the anvil. Place 304 stainless steel support columns with a diameter of 8.5 mm and a height of 6 mm at the four corners of the base plate surface to adjust the distance between the surfaces to be joined. Using a 4J29 Kovar alloy plate as the backing plate, place it with the surfaces to be joined facing downwards on the support, ensuring that the edges of the backing plate and the base plate are parallel.

[0045] S5. Apply a 3 mm thick layer of water glass to the cladding as a protective layer. Use cardboard to form a circle around the edge of the cladding and secure it with tape to create an explosive frame. The cardboard should be 3 mm thick and 50 mm high. Apply a gradient of explosives, laying a specially formulated low-detonation-velocity expanded ammonium nitrate explosive on the protective layer. The explosive thickness decreases from 45 mm to 37 mm from the detonation point towards the edge of the cladding, ensuring a smooth transition without abrupt changes. Install an electronic detonator at the center of the short side of the explosive layer and connect it to the detonation device via a fuse. In this embodiment, the explosive composition is: 75% expanded ammonium nitrate, 3% composite oil phase, 4% sodium chloride, 4% calcium carbonate, 5% perlite, 4% aluminum powder, and 5% rice husk powder. The explosive density is 0.8 g / cm³. 3 Its detonation velocity is 2300 m / s and its saturation is 10 mm.

[0046] S6. After installation, detonate the explosive under safe conditions. The explosive detonation drives the composite plate to collide with the base plate, ultimately resulting in a composite plate of 4J29 Kovar alloy and 304 stainless steel through explosive welding.

[0047] like Figure 3 As shown, the bonding area of ​​the 4J29 Kovar alloy and 304 stainless steel explosion composite plate prepared in this embodiment exhibits a uniform and continuous micro-waveform characteristic, with a wavelength and wave height of 450-510 μm and 170-180 μm, respectively. The interface bonding rate is 99.5% and the bonding strength is 363.9 MPa.

[0048] Example 2

[0049] S1. Cold-rolled 4J29 Kovar alloy sheet and 304 stainless steel sheet were recrystallized and annealed at 850 ℃ and 1050 ℃ respectively for 1.5 h to soften the sheets. The dimensions of the 4J29 Kovar alloy sheet (thickness × width × length) are 2.5 × 420 × 520 mm; the dimensions of the 304 stainless steel sheet (thickness × width × length) are 9 × 400 × 500 mm.

[0050] S2. Grind and polish the surfaces of the board to be bonded to remove the oxide layer and make its surface roughness Ra≤2.5 μm.

[0051] S3. Lay sand and level it on the open-air blasting site. Place an anvil made of low-carbon steel as a base on the leveled sand. The dimensions are (thickness × width × length): 50 × 1500 × 2000 mm. Clean the surface of the anvil.

[0052] S4. Using a 304 stainless steel plate as the base plate, place it with the surfaces to be joined facing upwards in the center of the anvil. Place 304 stainless steel support columns with a diameter of 9 mm and a height of 6.5 mm at the four corners of the base plate surface to adjust the distance between the surfaces to be joined. Using a 4J29 Kovar alloy plate as the backing plate, place it with the surfaces to be joined facing downwards on the support, ensuring that the edges of the backing plate and the base plate are parallel.

[0053] S5. Apply a 2 mm thick layer of water glass to the cladding as a protective layer. Use cardboard to form a circle around the edge of the cladding and secure it with tape to create an explosive frame. The cardboard should be 4 mm thick and 50 mm high. Apply a gradient of explosives, laying a specially formulated low-velocity expanded ammonium nitrate explosive on the protective layer. The explosive thickness decreases from 48 mm to 39 mm from the detonation point towards the edge of the cladding, ensuring a smooth transition without abrupt changes. Install an electronic detonator at the center of the short side of the explosive layer and connect it to the detonation device via a fuse. In this embodiment, the explosive composition is: 73% expanded ammonium nitrate, 4% composite oil phase, 4% sodium chloride, 5% calcium carbonate, 5% perlite, 5% aluminum powder, and 4% rice husk powder. The explosive density is 0.75 g / cm³. 3 Its detonation velocity is 2200 m / s and its saturation is 12 mm.

[0054] S6. After installation, detonate the explosive under safe conditions. The explosive detonation drives the composite plate to collide with the base plate, ultimately resulting in a composite plate of 4J29 Kovar alloy and 304 stainless steel through explosive welding.

[0055] The bonding area of ​​the 4J29 Kovar alloy and 304 stainless steel explosion-bonded composite plate prepared in this embodiment exhibits a uniform and continuous micro-waveform characteristic, with an interface bonding rate of 99.3% and a bonding strength of 366.2 MPa.

[0056] Example 3

[0057] S1. Cold-rolled 4J29 Kovar alloy sheet and 304 stainless steel sheet were recrystallized and annealed at 850 ℃ and 1050 ℃ respectively for 1 h to soften the sheets. The dimensions of the 4J29 Kovar alloy sheet (thickness × width × length) are 4 × 520 × 620 mm; the dimensions of the 304 stainless steel sheet (thickness × width × length) are 11 × 500 × 600 mm.

[0058] S2. Grind and polish the surfaces of the board to be bonded to remove the oxide layer and make its surface roughness Ra≤2.5 μm.

[0059] S3. Lay sand and level it on the open-air blasting site. Place an anvil made of low-carbon steel as a base on the leveled sand. The dimensions are (thickness × width × length): 50 × 1500 × 2000 mm. Clean the surface of the anvil.

[0060] S4. Using a 304 stainless steel plate as the base plate, place it with the surfaces to be joined facing upwards in the center of the anvil. Place 304 stainless steel support columns with a diameter of 8.5 mm and a height of 5.5 mm at the four corners of the base plate surface to adjust the distance between the surfaces to be joined. Using a 4J29 Kovar alloy plate as the backing plate, place it with the surfaces to be joined facing downwards on the support, ensuring that the edges of the backing plate and the base plate are parallel.

[0061] S5. Apply a 4 mm thick layer of water glass as a protective layer to the cladding. Use cardboard to form a circle around the edge of the cladding and secure it with tape to create an explosive frame. The cardboard should be 4 mm thick and 55 mm high. Apply a gradient of explosives, laying a specially formulated low-velocity expanded ammonium nitrate explosive on the protective layer. The explosive thickness decreases from 43 mm to 35 mm from the detonation point towards the edge of the cladding, ensuring a smooth transition without abrupt changes. Install an electronic detonator at the center of the short side of the explosive layer and connect it to the detonation device via a fuse. In this embodiment, the explosive composition is: 77% expanded ammonium nitrate, 4% composite oil phase, 4% sodium chloride, 3% calcium carbonate, 4% perlite, 3% aluminum powder, and 5% rice husk powder. The explosive density is 0.85 g / cm³. 3 Its detonation velocity is 2400 m / s, and its saturation is 8 mm.

[0062] S6. After installation, detonate the explosive under safe conditions. The explosive detonation drives the composite plate to collide with the base plate, ultimately resulting in a composite plate of 4J29 Kovar alloy and 304 stainless steel through explosive welding.

[0063] The bonding area of ​​the 4J29 Kovar alloy and 304 stainless steel explosion-bonded composite plate prepared in this embodiment exhibits a uniform and continuous micro-waveform characteristic, with an interface bonding rate of 99.1% and a bonding strength of 361.8 MPa.

[0064] Example 4

[0065] S1. Cold-rolled 4J29 Kovar alloy sheet and 304 stainless steel sheet were recrystallized and annealed at 850 ℃ and 1050 ℃ respectively for 2 h to soften the sheets. The dimensions of the 4J29 Kovar alloy sheet (thickness × width × length) are 4 × 320 × 420 mm; the dimensions of the 304 stainless steel sheet (thickness × width × length) are 11 × 300 × 400 mm.

[0066] S2. Grind and polish the surfaces of the board to be bonded to remove the oxide layer and make its surface roughness Ra≤2.5 μm.

[0067] S3. Lay sand and level it on the open-air blasting site. Place an anvil made of low-carbon steel as a base on the leveled sand. The dimensions are (thickness × width × length): 50 × 1500 × 2000 mm. Clean the surface of the anvil.

[0068] S4. Using a 304 stainless steel plate as the base plate, place it with the surfaces to be joined facing upwards in the center of the anvil. Place 304 stainless steel support columns with a diameter of 8.5 mm and a height of 7 mm at the four corners of the base plate surface to adjust the distance between the surfaces to be joined. Using a 4J29 Kovar alloy plate as the backing plate, place it with the surfaces to be joined facing downwards on the support, ensuring that the edges of the backing plate and the base plate are parallel.

[0069] S5. Apply a 4 mm thick layer of water glass as a protective layer to the cladding. Use cardboard to form a circle around the edge of the cladding and secure it with tape to create an explosive frame. The cardboard should be 2 mm thick and 55 mm high. Apply a gradient of explosives, laying a specially formulated low-velocity expanded ammonium nitrate explosive on the protective layer. The explosive thickness decreases from 46 mm to 38 mm from the detonation point towards the edge of the cladding, ensuring a smooth transition without abrupt changes. Install an electronic detonator at the center of one side of the short side of the explosive layer and connect it to the detonation device via a fuse. In this embodiment, the explosive composition is: 78% expanded ammonium nitrate, 4% composite oil phase, 4% sodium chloride, 3% calcium carbonate, 3% perlite, 4% aluminum powder, and 4% rice husk powder. The explosive density is 0.9 g / cm³. 3 Its detonation velocity is 2500 m / s, and its saturation is 11 mm.

[0070] S6. After installation, detonate the explosive under safe conditions. The explosive detonation drives the composite plate to collide with the base plate, ultimately resulting in a composite plate of 4J29 Kovar alloy and 304 stainless steel through explosive welding.

[0071] The bonding area of ​​the 4J29 Kovar alloy and 304 stainless steel explosion-bonded composite plate prepared in this embodiment exhibits a uniform and continuous micro-waveform characteristic, with an interface bonding rate of 98.9% and a bonding strength of 364.6 MPa.

[0072] Comparative Example 1

[0073] The comparative example had the same settings as Example 1, except that the annealing temperature of the cold-rolled 304 stainless steel sheet was set to 800 °C. The annealing temperature of the 304 stainless steel sheet did not reach the recrystallization temperature, resulting in incomplete elimination of work hardening and poor plastic deformation capacity. After the explosion, the 304 stainless steel sheet deformed and cracked near the detonation point, leading to the failure of the sheet composite process.

[0074] Comparative Example 2

[0075] The comparative example had the same setup conditions as Example 1, except that the height of the support column was 4 mm. Due to the small spacing between the plates, the acceleration distance of the composite plate was insufficient, resulting in insufficient collision velocity and failure to form an effective metal jet upon collision with the substrate. After explosive welding, a large area of ​​unwelded zone appeared at the interface of the composite plate, with an interface bonding rate of 37.5% and a bonding strength of 167.2 MPa, which was significantly lower than that of Example 1.

[0076] Comparative Example 3

[0077] The comparative example had the same other settings as Example 1, except that a uniform explosive distribution method was used, and the explosive thickness was 41 mm. After the explosive welding was completed, along the detonation direction, the composite plate bonding area evolved from a directly contacting plane to a large wave-shaped interface, with an interface bonding rate of 96.3%. The bonding strength showed significant fluctuations compared to the results of Example 1, with a minimum of 198.8 MPa and a maximum of 359.2 MPa.

[0078] Comparative Example 4

[0079] The comparative example had the same setup conditions as Example 1, except that the explosive used on the buffer layer was commercially available expanded ammonium nitrate rock explosive with a density of 0.95 g / cm³. 3 The detonation velocity was 3500 m / s, and the brisaccharimetry was 14 mm. Compared to the explosive in Example 1, this explosive had a much higher detonation velocity, resulting in excessive energy being absorbed by the composite plate. During the collision, excessive melting occurred at the interface. After the explosive welding was completed, a continuous molten layer with microcracks was formed at the interface of the composite plate. The interface bonding rate was 68.6%, and the bonding strength was 143.5 MPa, which was significantly lower than that of Example 1.

Claims

1. A method for preparing a 4J29 Kovar alloy / 304 stainless steel composite plate, characterized in that: Cold-rolled 4J29 Kovar alloy plate and 304 stainless steel plate are recrystallized and annealed to obtain soft 4J29 Kovar alloy plate and soft 304 stainless steel plate, respectively. Then, the soft 304 stainless steel plate is used as the substrate and the soft 4J29 Kovar alloy plate is used as the cladding plate. After applying a layer of water glass as a protective layer to the surface of the soft 4J29 Kovar alloy plate, an explosive layer is laid on the surface of the protective layer using a gradient explosive distribution method. Then, explosive bonding is performed to obtain the final product. The thickness of the explosive layer decreases continuously from the edge of the short side detonation point to the edge of the other side of the short side, wherein the thickness of the edge of the short side detonation point is 40-50 mm, the thickness of the edge of the other side of the short side is 34-39 mm, and the thickness of the edge of the other side of the short side is 6-10 mm smaller than that of the edge of the short side detonation point. The explosive has a detonation velocity of 2100-2500 m / s and a saturation of 8-12 mm.

2. The method for preparing a 4J29 Kovar alloy / 304 stainless steel composite plate according to claim 1, characterized in that: The thickness of the 4J29 Kovar alloy plate is 2.5-4 mm, and the thickness of the 304 stainless steel plate is 9-11 mm. The 4J29 Kovar alloy plate has a length of 420-620 mm and a width of 320-520 mm; the 304 stainless steel plate has a length of 400-600 mm and a width of 300-500 mm.

3. The method for preparing a 4J29 Kovar alloy / 304 stainless steel composite plate according to claim 1, characterized in that: The recrystallization annealing treatment temperature for the 4J29 Kovar alloy plate is 800-900 ℃, and the recrystallization annealing treatment time is 1-2 h; the recrystallization annealing treatment temperature for the 304 stainless steel plate is 1000-1100 ℃, and the recrystallization annealing treatment time is 1-2 h.

4. The method for preparing a 4J29 Kovar alloy / 304 stainless steel composite plate according to claim 1, characterized in that: The surfaces to be bonded between the soft 4J29 Kovar alloy plate and the soft 304 stainless steel plate are ground and polished to ensure that the surface roughness Ra is ≤ 2.5 μm.

5. The method for preparing a 4J29 Kovar alloy / 304 stainless steel composite plate according to claim 1, characterized in that: The thickness of the protective layer is 2-4 mm.

6. The method for preparing a 4J29 Kovar alloy / 304 stainless steel composite plate according to claim 1, characterized in that: The explosive used in the explosive compound has the following composition by mass percentage: 68-82% expanded ammonium nitrate, 2-4% composite oil phase, 3-5% sodium chloride, 3-6% calcium carbonate, 3-6% perlite, 3-5% aluminum powder, and 4-6% rice husk powder. The density of the explosive used in the explosive compound is 0.75-0.9 g / cm³. 3 .

7. The method for preparing a 4J29 Kovar alloy / 304 stainless steel composite plate according to claim 1, characterized in that: Sand is laid and leveled on the open blasting site. An anvil is placed on the leveled sand as a base. Then, a soft 304 stainless steel plate is placed on the center of the anvil with the bonding side facing upwards. Supports are placed at the four corners of the base. A soft 4J29 Kovar alloy plate is placed on the support with the bonding side facing downwards. A layer of water glass is applied to the surface of the soft 4J29 Kovar alloy plate as a protective layer. Cardboard is used to form a circle around the boundary of the plate and fixed with tape to serve as an explosive frame. Explosive layers are then laid on the surface of the protective layer using a gradient distribution method. An electronic detonator is installed on one side of the explosive layer and connected to the detonation device through a fuse to detonate the explosive. The resulting explosive bonding yields a 4J29 Kovar alloy / 304 stainless steel composite plate.

8. The method for preparing a 4J29 Kovar alloy / 304 stainless steel composite plate according to claim 7, characterized in that: The anvil is made of low-carbon steel, and its length × width × thickness is 1500-2000 mm × 1000-1500 mm × 45-50 mm. The support is made of 304 stainless steel, and has a diameter of 8-10 mm and a height of 5-7 mm. The cardboard used for the explosive frame is 2-4 mm thick and 50-55 mm high; The electronic detonator is installed at the center of the short side of the explosive layer.

9. A 4J29 Kovar alloy / 304 stainless steel composite plate prepared by the preparation method according to any one of claims 1-8, characterized in that: The 4J29 Kovar alloy / 304 stainless steel composite plate is composed of a 4J29 Kovar alloy layer and a 304 stainless steel layer, wherein the 4J29 Kovar alloy layer and the 304 stainless steel layer have a uniform and continuous waveform bonding interface with a wavelength of 390-520 μm and a wave height of 140-200 μm.

10. A 4J29 Kovar alloy / 304 stainless steel composite plate according to claim 9, characterized in that: In the 4J29 Kovar alloy / 304 stainless steel composite plate, the interface bonding rate between the 4J29 Kovar alloy layer and the 304 stainless steel layer is ≥98.9%, and the bonding strength is ≥360 MPa.

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