An explosive welding method suitable for large-area metal foil / substrate

Abstract

This invention discloses an explosive welding method suitable for large-area metal foil / substrate, comprising: pre-forming threads around the perimeter of the substrate, creating holes symmetrically around the perimeter of the impedance layer, and bonding the metal foil to the lower surface of the impedance plate; sequentially installing the substrate, support plate, impedance plate, heat-absorbing layer, explosive, and detonator from bottom to top; wherein the metal foil, impedance plate, and heat-absorbing layer together form a composite plate; supporting the composite plate with the support plate, using a traction wire to pass through the holes in the impedance plate and fixing the traction wire to fasteners; after laying the prepared explosive on the upper side of the heat-absorbing layer, tightening the fasteners onto the substrate, adjusting the tension of the traction wire by the tightening depth of the fasteners until the middle support plate can be easily pulled out; and installing the detonator at the detonation point of the explosive. This invention avoids the problems of metal foil breakage, wrinkling, deformation, and ablation caused by gap support in explosive welding; and improves the welding quality of the metal foil and substrate.

Description

Technical Field

[0001] This invention belongs to the field of explosive welding technology, and specifically relates to an explosive welding method suitable for large-area metal foils / substrates. Background Technology

[0002] Explosive welding is a solid-state welding technique that uses explosives to drive metal plates in a high-speed, oblique collision, ultimately forming a metallurgical bond between the two metals. The main apparatus for explosive welding consists of a base plate, a cladding plate, gap supports, and explosives. Driven by the energy of the explosives, the cladding plate accelerates continuously between the gaps and finally collides with the base plate at high speed, generating a metal jet. During its motion, the metal jet undergoes melting and interatomic diffusion, ultimately forming a metallurgical bond between the two metals. The collision speed is strictly dependent on the collision spacing; therefore, in actual explosive welding operations, gap supports of uniform height are used to ensure consistent spacing.

[0003] Metal foil generally refers to metal plates with a thickness of less than 200μm. Compared with traditional explosive welding of metal plates, metal foil significantly saves materials, especially precious metals, and can effectively control production costs. In actual explosive welding of metal foil / substrate, the shock wave generated by the explosive explosion easily creates stress concentration on the metal foil surface, leading to deformation or even breakage. Tensile waves can also cause defects such as cracks, pores, and wrinkles. The high-temperature environment at the moment of explosion can also easily ablate the metal foil surface. Currently published patents offer some solutions to these problems. One patent, a method for explosive welding of multilayer tungsten foil to prepare layered composite materials (application number 202210753384.9), uses multilayer tungsten foil instead of a single tungsten plate. Replacing the tungsten plate with multilayer tungsten foil reduces kinetic energy loss at the interface, thereby reducing interfacial plastic deformation. Welding multiple layers of tungsten foil in a single operation can achieve a thicker tungsten coating. However, this method is complex, and better implementation devices exist for other non-hard and brittle metals. A patent for a method of explosive welding of tungsten foil (application number: 202011236548.8) adds a protective plate to the tungsten foil. The protective plate is made of a metal material with a higher wave impedance than the metal foil. The protective plate can effectively reduce the destructive effect of tensile waves. However, the size of the protective plate is too large compared to the tungsten foil, requiring more explosives, which to some extent increases the risk of welding failure. A patent for an explosive welding device for foil with an added pressure-transfer layer (application number: 202210035330.9) adds a pressure-transfer layer between the explosive and the metal foil, using the pressure-transfer layer to transfer the energy generated by the explosion to the foil. The main material of the pressure-transfer layer is salt. In the high-temperature environment of explosive welding, the salt vaporizes and absorbs heat, which can effectively protect the surface of the metal foil from being burned. At the same time, the pressure-transfer layer is simple to make and the cost of salt is low. However, the salt will vaporize rapidly during the explosive welding process. The exposed metal foil is still insufficient to withstand the impact load of the explosive welding process. The problem of easy deformation and breakage of the metal foil cannot be effectively solved. At the same time, the gap support also has a certain impact on the quality of the bonding interface.

[0004] Traditional explosive welding of metal plates utilizes gap supports to ensure consistent spacing. After explosive welding, these gap supports typically remain within the bonding interface. However, due to the sufficient thickness and strength of the base and cladding plates, their actual impact on the interface bonding performance is minimal. But for metal foil plates, due to the thinness of the foil, gap supports can lead to defects such as porosity, cracks, and even interface rupture. Current patents address the issue of easy ablation of the metal foil surface during explosive welding and reduce surface defects such as cracks, porosity, and wrinkles. For small-sized metal foil plates, bonding the foil to a protective plate is often used to ensure consistent spacing, thus avoiding the adverse effects of gap supports. Large-area metal foil plates generally refer to those with a surface area exceeding 1m². 2For metal foil sheets, even when bonded to a protective board, the problem of bending and sagging of the metal foil composite board will only be more severe because the protective board is much heavier than the metal foil sheet. Summary of the Invention

[0005] The purpose of this invention is to provide an explosive welding method suitable for large-area metal foil / substrate. By stretching the metal foil composite plate with a strong constraint device, the spacing during the welding process is ensured to be consistent, and the gap support is eliminated. The welding quality of the composite plate is ensured by installing a functional protective layer. Furthermore, the amount of explosives used is reduced by establishing parameter design criteria.

[0006] The technical solution to achieve the purpose of this invention is as follows:

[0007] An explosive welding method suitable for large-area metal foil / substrate includes:

[0008] Threads are pre-formed around the substrate, and holes are made symmetrically around the wave impedance layer. The metal foil is then bonded to the lower surface of the wave impedance plate.

[0009] The components are installed sequentially from bottom to top: base plate, support plate, wave impedance plate, heat absorption layer, explosive, and detonator. The metal foil plate, wave impedance plate, and heat absorption layer together form a composite plate. The composite plate is supported by the support plate. A traction wire is passed through the holes in the wave impedance plate and fixed to the fastener. After the prepared explosive is laid on the upper side of the heat absorption layer, the fastener is screwed onto the base plate. The tension of the wire is adjusted by the depth of the fastener until the middle support plate can be easily pulled out. The detonator is installed at the detonation point of the explosive.

[0010] The significant advantages of this invention compared to existing technologies are:

[0011] 1) A strong constraint device is used to stretch the wave impedance layer, ensuring that the entire composite panel will not bend or sag, and eliminating the influence of gap supports. 2) The installed functional protective layer avoids deformation and breakage of the metal foil caused by sparse waves and impact loads, and also reduces surface ablation of the metal foil. 3) A design criterion for explosive welding parameters applicable to large-area metal foils and substrates was designed, optimizing the amount of explosives used. Attached Figure Description

[0012] Figure 1 This is a schematic diagram of the explosive welding of the metal foil / substrate of the present invention.

[0013] Figure 2 This is a top view of the explosive welding apparatus for metal foil / substrate of the present invention.

[0014] Figure 3 It is a graph showing the change in collision speed of the composite plate over time.

[0015] Figure 4 This is a diagram showing the explosive welding process of Hastelloy foil and steel cladding.

[0016] In the diagram, 1—foundation, 2—base plate, 3—metal foil plate, 4—support plate, 5—screw, 6—iron wire, 7—wave impedance layer, 8—heat absorption layer, 9—explosive, 10—detonator. Detailed Implementation

[0017] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0018] This invention proposes an explosive welding method suitable for large-area metal foil / substrate, the main steps of which are as follows:

[0019] Step 1: Before the test begins, threads need to be pre-made around the perimeter of the substrate 2, and holes need to be made symmetrically around the perimeter of the wave impedance layer 7. Clean the substrate 2, support plate 4, wave impedance plate 7, and metal foil plate 3 by sanding. The metal foil plate can be sanded with sandpaper. Then clean the surfaces of the substrate 2, metal foil plate 3, and support plate 4 with ethanol solution. Finally, use double-sided tape to bond the metal foil plate 3 to the lower surface of the wave impedance plate 7.

[0020] Step Two, refer to the appendix Figure 1 The components are installed sequentially from bottom to top on a flat foundation 1, in the order of base plate 2, support plate 4, wave impedance plate 7, heat absorption layer 8, explosive 9, and detonator 10. The metal foil plate 3, wave impedance plate 7, and heat absorption layer 8 together form a composite plate. The composite plate is supported by the support plate 4. The wire 6 is passed through the holes in the wave impedance plate 7 and wound around the screw 5 in the direction of screw 5. After the pre-prepared explosive 9 is laid on the upper side of the heat absorption layer 8, the screw 5 is screwed onto the base plate 2. The tension of the wire 6 is adjusted by the depth of screw 5 until the support plate 4 in the middle can be pulled out smoothly. This indicates that the entire composite plate does not bend or sag. Then, the detonator 10 is installed at the detonation point at the center edge.

[0021] Step 3: Explosive preparation; minimum collision velocity for the same type of metal to produce a metal jet. Minimum impact pressure σ b ρ is the tensile strength of the metallic material, ρ is the density of the metallic material, and c is the speed of sound in the metallic material; the minimum collision velocity when dissimilar metallic materials collide to produce a metal jet. To ensure that a metal jet is generated during the collision of dissimilar metals, the minimum collision pressure p is required. min The minimum collision pressure p required to generate metal jets from the collision of dissimilar metal materials needs to be determined. min1 and p min2 The maximum value in, i.e., p min =max(p min1 pmin2 c1 and c2 are the sound velocities of the dissimilar metals, respectively, and ρ1 and ρ2 are the material densities of the dissimilar metals, respectively. The curve of the actual collision velocity versus time is a variable acceleration curve, see attached figure. Figure 3 Considering the thinness of the metal foil and the actual forming effect, V is taken as... pmin 90%, that is, V p , min =90%V pmin This serves as the minimum impact velocity to determine the actual height of the explosive charge. According to the Gurney formula... Determine the mass ratio R of the explosive and the composite plate, where R = m 炸 / (m 箔 +m 阻 +m 热 ), m 炸 m 箔 m 阻 m 热 These are the masses of the explosive, metal foil, wave impedance layer, and heat absorption layer, respectively; Grenfell energy. V D γ is the detonation velocity of the explosive; γ is the polyhedral exponent, which is taken as 3 for emulsion explosives, and m can be obtained. 炸 The explosive is laid on top of the heat-absorbing layer, and its length and width are the same as those of the heat-absorbing layer. Given the density of the explosive, the height h of the explosive can be calculated simultaneously. 炸 The height H between the metal foil and the substrate is 0.2 (h). 炸 +h 箔 ), where h 箔 The thickness of metal foil 3 is given.

[0022] Step 4: Detonate the explosive to complete the explosive welding.

[0023] The diameter of the holes in the wave impedance layer is 1-2 mm larger than the diameter of the iron wire.

[0024] Wherein, the number of openings on each side of the wave impedance layer is n = L / 200, where L is the side length of the wave impedance layer in mm; first, openings are made at the four corners of the wave impedance layer, and a total of n equidistant openings are made on each side.

[0025] Wherein, the depth of the threaded hole on the substrate does not exceed the substrate thickness h. 基 The relationship between the external thread diameter d1 of the screw and the composite plate is as follows: mm; m 炸 m 箔 m 阻 m 热 These are the masses of the explosive, metal foil, wave impedance layer, and heat absorption layer, respectively, in kg / m³. 3 Coefficient k1 = 3 to 8; N is the total number of screws.

[0026] The location of the threaded hole is 50-150 mm away from the wave impedance hole.

[0027] Wherein, the screw length l1 and the substrate thickness h 基 The relationship is: l1 = h 基 +l0, l0 = 20~40mm.

[0028] The wave impedance layer is a lightweight, high wave impedance material. Suitable high wave impedance metals include copper and steel. Its thickness d1 and the metal foil thickness h... 箔 The relationship is d2 = k2h 箔 The coefficient k2 = 3 to 10.

[0029] The heat absorption layer is made of an inexpensive material that is easily decomposed, evaporated, and melted at high temperatures. Materials such as salt, limestone, and graphite can be used. Its thickness d2 and the metal foil thickness h... 箔 The relationship is d3 = k3h 箔 The coefficient k3 = 10 to 30.

[0030] Example

[0031] As attached Figure 1 The diagram shows an explosive welding process for metal foil. The substrate 2 is made of steel and measures 1700mm x 1500mm x 5mm; the metal foil 3 is made of Hastelloy and measures 1200mm x 1000mm x 0.2mm; the wave impedance layer 7 is made of steel and measures 1500mm x 1300mm x 1mm; the heat absorption layer 8 is made of coarse salt and measures 1400mm x 1200mm x 2mm; and the explosive 9 is an emulsion explosive with a detonation velocity of approximately 2800m / s and a density of 0.8g / cm³. 3 The support plate 4 is made of steel. The edge support plate has a size of 1400mm*40mm*2.2mm, and the middle support plate has a size of 1700mm*50mm*2mm. The support plates are all installed along the short side of the wave impedance layer. According to the formula in the technical solution, the laying height of the explosive is 10mm and the gap height is 2mm.

[0032] Before installing the explosive welding device, the substrate, impedance plate, and support plate are polished. Metal foil can be polished with sandpaper to remove the oxide layer from the metal surface. The substrate and support plate surfaces are also cleaned with ethanol solution. Coarse salt is sealed with cardboard and tape, and the silver foil plate and impedance plate, and the impedance plate and coarse salt plate are sequentially bonded with double-sided tape. Before the test, one hole is pre-drilled at each of the four corners of the impedance plate, a total of eight pairs of equidistant holes are pre-drilled along the long side, and a total of seven pairs of equidistant holes are pre-drilled along the short side. The hole diameter is 3mm. Screw holes suitable for standard M6 screws are pre-drilled on the corresponding substrate. The M6 ​​screws are 30mm long, and the upper half needs to have a trapezoidal thread with a pitch of 2mm, while the lower half remains unchanged. Then, proceed according to the attached... Figure 1 Install the components sequentially from bottom to top. Pass the 2mm iron wire 6 through the hole and tightly wrap both ends around the upper half of the M6 ​​screw, with the wrapping direction matching the screw's turning direction. After laying the explosives, tighten the screws until the middle support plate can be easily pulled out. Once the support plate is removed, ignite the detonator 10 to detonate the explosives.

[0033] After the explosive welding was completed, the Hastelloy and steel were successfully welded. The excess part was cut off and the surface of the Hastelloy foil was observed. No large-area cracks, deformations, wrinkles, or ablation were found on the surface of the metal foil.

[0034] The embodiments described in this invention are merely some, not all, of the embodiments, and do not limit the scope of this invention. Other embodiments obtained by those skilled in the art based on the content of this invention without inventive effort are all within the scope of protection of this invention.

Claims

1. A method for explosive welding of large-area metal foil / substrate, characterized in that, include: Threads are pre-formed around the substrate, and holes are made symmetrically around the wave impedance plate. The metal foil is then bonded to the lower surface of the wave impedance plate. The components are installed sequentially from bottom to top: base plate, support plate, wave impedance plate, heat absorption layer, explosive and detonator; the metal foil plate, wave impedance plate and heat absorption layer together form a composite plate; the wave impedance plate is used to reduce the destructive effect of rarefaction waves generated during the welding process and to prevent the metal foil plate from deforming and breaking; the heat absorption layer is used to absorb the heat generated by the explosion of the explosive and to prevent the metal foil from being ablated. The composite plate is supported by a support plate. A traction wire is passed through the holes in the wave impedance plate and fixed to the fastener. After the prepared explosive is laid on the upper side of the heat absorption layer, the fastener is screwed onto the base plate. The tension of the traction wire is adjusted by the depth of the fastener until the middle support plate can be pulled out smoothly. A detonator is installed at the detonation point of the explosive. The height H between the metal foil and the substrate is 0.2 (h). 炸 +h 箔 ), where h 箔 h represents the thickness of the metal foil. 炸 The height of the explosive; The fastener is a screw, and the relationship between the screw's external thread diameter d1 and the composite plate is as follows: Coefficient k1 = 3~8; N is the total number of screws; m 炸 m 箔 m 阻 m 热 These are the masses of the explosive, metal foil, wave impedance plate, and heat absorption layer, respectively. Screw length l1 and substrate thickness h 基 The relationship is: l1 = h 基 +l0, coefficient l0 = 20~40mm; The thickness d1 of the impedance plate and the thickness h of the metal foil plate 箔 The relationship is d2 = k2h 箔 The coefficient k2 = 3 to 10; The thickness of the heat absorption layer d2 and the thickness of the metal foil h 箔 The relationship is d3 = k3h 箔 The coefficient k3 = 10 to 30.

2. The explosive welding method for large-area metal foil / substrate according to claim 1, characterized in that, The height h of the explosive 炸 Obtained through the following process: According to Gurney's formula Determine the mass ratio R of the explosive and the composite plate; Where R = m 炸 / (m 箔 +m 阻 +m 热 ), Grenen V' pmin =0.9*V pmin Where V' pmin V is the minimum collision velocity at the actual height of the explosive. pmin p is the minimum collision velocity when dissimilar metal materials collide to generate a metal jet. min Let V be the minimum collision pressure, c1 and c2 be the sound velocities of the dissimilar metals, and ρ1 and ρ2 be the material densities of the dissimilar metals; D γ is the detonation velocity of the explosive; γ is the polyhedral index. Find m 炸 The length and width of the explosive are the same as the heat-absorbing layer. The height h of the explosive layer can be calculated. 炸 .

3. The explosive welding method for large-area metal foil / substrate according to claim 1, characterized in that, The diameter of the holes on the impedance plate is 1-2 mm larger than the diameter of the traction wire.

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