A dynamic self-constrained explosive welding method for preparing a bimetallic composite pipe

Abstract

The present invention relates to the technical field of explosion welding, and discloses a dynamic self-constrained explosion welding method for preparing a bimetallic composite pipe, comprising the following steps: S1, designing a self-constrained system for this method; S2, coaxially placing in sequence from outside to inside: an outer layer of explosive, a base pipe, a clad pipe, a pressure transmission medium, and an inner layer of explosive; connecting industrial detonating cords with different detonation velocities; S3, using a detonator and an industrial detonating cord to form a detonating system; S4, simultaneously detonating the inner layer of explosive and the outer layer of explosive to drive the clad pipe and the base pipe to move towards each other and collide. The present invention proposes a dynamic self-constrained explosion welding method for preparing a bimetallic composite pipe. The present invention utilizes the explosive to drive the clad pipe and the base pipe to collide with each other at opposite velocities, making the kinetic energy of the combined composite pipe zero, realizing self-constrained explosion welding, and completely getting rid of the dependence on external molds.

Description

Technical Field

[0001] The present invention relates to the technical field of explosive welding, and particularly to a dynamic self-constrained explosive welding method for preparing a bimetallic composite pipe. Background Art

[0002] A bimetallic composite pipe is a high-quality composite material that has been widely used in fields such as petroleum, aerospace, chemical industry, and nuclear industry. It economically combines the physical and chemical advantages of the base materials and has excellent comprehensive properties, such as high strength, corrosion resistance, and super thermal conductivity. Explosive welding is one of the most widely used impact welding techniques at present. It uses the violent energy release of explosives to cause a high-speed oblique collision between two welded components, and generates extremely high pressure and temperature at the collision point, ultimately forming a metallurgical bonding interface with high strength. Compared with composite methods such as drawing, expansion jointing, spinning, and thermal diffusion, this method has the advantages of high bonding strength, small heat-affected zone, and no need for complex equipment, and is an irreplaceable bimetallic pipe production technology.

[0003] However, the current traditional explosive welding manufacturing method for bimetallic pipes relies heavily on external heavy molds to restrain the deformation of the composite pipes during implementation to prevent bulging or cracking. Moreover, after several uses, the external molds will undergo large deformations and cannot be used, requiring replacement. In addition, to produce composite pipes of different sizes, different sizes of molds need to be customized, which is very inconvenient and uneconomical, seriously hindering the production and application of explosive-welded bimetallic pipes. To address this problem, Chinese Patent CN202210228304.8 discloses a method and device for explosive welding and manufacturing of dissimilar metal high-wave-impedance self-constrained metal pipes. This method uses water as the pressure transmission medium, which can reduce the strength requirements for external molds to a certain extent, but still must use external molds as strong constraints and cannot achieve true "self-constrained" compounding.

[0004] To solve the above problems, a dynamic self-constrained explosive welding method for preparing a bimetallic composite pipe is proposed in this application. Summary of the Invention

[0005] (I) Object of the Invention

[0006] To solve the technical problems in the background art, the present invention proposes a dynamic self-constrained explosive welding method for preparing a bimetallic composite pipe. The present invention uses explosives to drive the composite pipe and the base pipe to collide with each other at opposite speeds, making the kinetic energy of the combined composite pipe zero, achieving self-constrained explosive welding, and completely getting rid of the dependence on external molds.

[0007] (II) Technical Solution

[0008] To solve the above problems, the present invention provides a dynamic self-constrained explosive welding method for preparing a bimetallic composite pipe, including the following steps:

[0009] S1. This method is designed through a self-constraint system;

[0010] S2. Coaxially place the following components from the outside to the inside: an outer explosive, a base tube, a liner tube, a pressure transmission medium, and an inner explosive; connect industrial detonating cords with different detonation velocities.

[0011] S3. Use a detonating system composed of a detonator and an industrial detonating cord.

[0012] S4. Detonate the inner explosive and the outer explosive simultaneously to drive the liner tube and the base tube to move towards each other and collide.

[0013] Preferably, for the self-constraint system design, based on the law of conservation of momentum and the theory of perfectly inelastic collision, the theoretical collision velocity constraint relationship between the base tube and the liner tube is established as: V b = V f M f / M b ;

[0014] Where:

[0015] V b is the collision velocity of the base tube;

[0016] V f is the collision velocity of the liner tube;

[0017] M f and M b are the masses per unit length of the liner tube and the base tube respectively.

[0018] Preferably, the actual collision velocity of the liner tube is further deduced as:

[0019] Vpb = kVb;

[0020] In the formula: k is the coefficient to offset the influence of residual detonation products and can be determined according to experimental or numerical simulation results;

[0021] Based on the Gurney collision velocity calculation formula, the collision velocity of the liner tube can be determined first, then the collision velocity of the base tube can be calculated, and finally the mass of the outer explosive for constraint can be calculated to establish a self-constraint system for explosive welding of bimetallic tubes.

[0022] Preferably, the value range of k is 1 - 3.

[0023] Preferably, the industrial detonating cord for detonating the outer explosive forms an angle of 60° with the horizontal.

[0024] Preferably, the detonation velocity ratio of the industrial detonating cords for detonating the inner and outer explosives is 1:1.16.

[0025] [[ID=6�]]Preferably, the pressure transmission medium can be water, asphalt, or resin.

[0026] Preferably, for industrial detonating cords with different detonation velocities, one end is evenly tied around the detonator, and among the other ends, 1 is inserted into the inner explosive, and the rest are evenly inserted into the outer explosive, for simultaneously detonating the inner explosive and the outer explosive.

[0027] The above technical solution of the present invention has the following beneficial technical effects:

[0028] 1) From the principle, it realizes the self - constraint of the speed and displacement of the base tube and the composite tube during the explosion welding process, thereby realizing the control of the deformation amount of the composite tube and completely getting rid of the dependence on external molds.

[0029] 2) By continuously extruding the outer wall of the base tube by the detonation products after the explosion of the outer explosive, this method can effectively reduce the circumferential tensile stress near the outer wall of the base tube and avoid the generation of cracks.

[0030] 3) It can be applied to the production of composite tubes of different sizes, with a simple structure and low cost. Description of the Drawings

[0031] Figure 1 It is a sectional view of the experimental arrangement of the present invention.

[0032] Figure 2 It is a top view of the experimental arrangement of the present invention.

[0033] Figure 3 It is a diagram of the experimental results of an embodiment of the present invention.

[0034] Figure 4 It is a diagram of the control experimental results (without applying constraints) of an embodiment of the present invention.

[0035] Figure 5 It is a comparison diagram of the outer diameter of the base tube before and after the experiment of an embodiment of the present invention.

[0036] Reference Signs:

[0037] 1 is the outer explosive; 2 is the base tube; 3 is the composite tube; 4 is the pressure - transmitting medium; 5 is the inner explosive; 6 is the bottom cover; 7 is the top cover; 8 is the industrial detonating cord; 9 is the detonator. Detailed Embodiments

[0038] To make the objectives, technical solutions, and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings. It should be understood that these descriptions are exemplary and are not intended to limit the scope of the present invention. In addition, in the following description, the descriptions of well - known structures and technologies are omitted to avoid unnecessarily confusing the concepts of the present invention.

[0039] As Figure 1-2As shown in the figure, a dynamic self-constrained explosive welding method for preparing a bimetallic composite tube proposed by the present invention includes the following steps:

[0040] S1. The method designs a self-constrained system;

[0041] S2. Coaxially place the following components from the outside to the inside in sequence: an outer layer of explosive 1, a base tube 2, a clad tube 3, a pressure transmission medium 4, and an inner layer of explosive 5; Industrial detonating cords 8 with different detonation velocities are evenly tied around a detonator 9 at one end, and 1 of the other ends is inserted into the inner layer of explosive 5, and the rest are evenly inserted into the outer layer of explosive 1, for simultaneously detonating the inner layer of explosive 5 and the outer layer of explosive 1;

[0042] S3. Use a detonating system composed of the detonator 9 and the industrial detonating cords 8;

[0043] S4. Simultaneously detonate the inner layer of explosive 5 and the outer layer of explosive 1, drive the clad tube 3 and the base tube 2 to move towards each other and collide.

[0044] In an optional embodiment, for the self-constrained system design, based on the law of conservation of momentum and the theory of perfectly inelastic collision, the theoretical collision velocity constraint relationship between the base and the clad tube 3 is established as: V b =V f M f / M b ;

[0045] Where:

[0046] V b is the collision velocity of the base tube 2;

[0047] V f is the collision velocity of the clad tube 3;

[0048] M f and M b are the masses per unit length of the clad tube 3 and the base tube 2 respectively.

[0049] In an optional embodiment, the actual collision velocity of the clad tube 3 is further deduced as:

[0050] Vp b =kV b ;

[0051] In the formula: k is a coefficient to offset the influence of residual detonation products, which can be determined according to experimental or numerical simulation results;

[0052] Based on the Gurney collision velocity calculation formula, the collision velocity of the clad tube 3 can be determined first, then the collision velocity of the base tube 2 can be calculated, and finally the mass of the outer layer of explosive for constraint can be calculated to establish a self-constrained system for explosive welding of bimetallic tubes.

[0053] The value range of k is 1 - 3.

[0054] Among them, the industrial detonating cord 8 for detonating the outer-layer explosive forms an angle of 60° with the horizontal.

[0055] The detonation velocity ratio of the industrial detonating cords 8 for detonating the inner and outer-layer explosives is 1:1.16.

[0056] In an alternative embodiment, the pressure transmission medium 4 can be water, asphalt or resin.

[0057] The base tube, the composite tube and the inner and outer-layer explosives are coaxially arranged. The designed length of the explosives is longer than that of the metal tube to reduce the influence of unstable detonation waves at the detonation end and boundary effects. Industrial detonating cords 8 with different detonation velocities are used. One end is tied around the detonator 9, and the other end is inserted into the heads of the inner and outer-layer explosives for simultaneously detonating the inner and outer-layer explosives. The pressure transmission medium 4 is filled in the gap between the inner-layer explosive 5 and the composite tube 3 to make the shock wave generated by the explosion act on the composite tube 3 evenly and reduce the pressure dissipation. In addition, the top cover 7 is placed above the base tube and the composite tube 3 to prevent the upper detonation products and gases from entering the gap between the tube walls. The spacing distance between the base tube 2 and the composite tube 3 is designed according to the empirical formula (1), where S and δ represent the spacing distance and the thickness of the composite tube 3 respectively.

[0058] S≈(0.5~1)×δ#(1)

[0059] The principle on which the present invention is based is the law of conservation of momentum and the theory of perfectly inelastic collision. The base tube and the composite tube 3 at the moment of collision are regarded as a system. The calculation methods for the collision velocity and the thickness of the outer-layer explosive used for restraint are as follows:

[0060]

[0061]

[0062] Where A * , β, and E are respectively given by formulas (4)-(6);

[0063]

[0064] β = R o / R i #(5)

[0065]

[0066] Where E is the Gurney coefficient of the explosive, M1 / M2, C1 / C2, and N are the unit length masses of the cladding / base tube 2, the inner / outer-layer explosives, and the outer restraint respectively. Ri is the outer diameter of the outer-layer explosive, Ro is the inner diameter of the base tube 2, γ is the effective polytropic index of the explosive, taking 2.5 for emulsion explosive, and D is the detonation velocity of the explosive.

[0067] The velocity of the composite tube obtained after the collision can be calculated by formula (7):

[0068] V c = (V f M f - V b M b ) / (M f + M b ) #(7)

[0069] Assume that the velocity of the composite tube obtained is zero, that is, the optimal constraint effect is achieved. Then, the theoretical relationship between the velocities of the composite tube 3 and the base tube 2 is shown in Equation (8):

[0070] V b = V f M f / M b #(8)

[0071] However, the actual velocity of the base tube 2 should be greater than the theoretical value calculated by Equation (8) to offset the outward expansion deformation of the composite tube caused by the residual explosion products inside the composite tube 3 after the collision, which can be calculated by Equation (9):

[0072] V pb = kV b #(9)

[0073] Where k is the coefficient to offset the influence of the residual detonation products, which can be determined according to the experimental or numerical simulation results, and the value range of k is 1 - 3.

[0074] Before the explosion welding experiment, the collision velocity (Vf) of the composite tube 3 can be calculated from the mass of the inner explosive 5 according to Equations (2) and (6), then the velocity of the base tube 2 (Vpb) can be calculated by Equation (9), and then the mass of the outer explosive for constraint can be calculated from Equations (3) to (6).

[0075] It should be noted that, in combination with Figures 3-5 , as an implementation method:

[0076] For copper tubes and steel tubes, where the copper tube is the composite tube 3 with an outer diameter of 57 mm, a wall thickness of 1.5 mm, and a length of 12 cm; the steel tube is the base tube 2 with an outer diameter of 73 mm, a wall thickness of 8 mm, and a length of 12 cm.

[0077] The explosive used is emulsion explosive, with a density of 0.8 g / m3, a detonation velocity of about 2300 m / s, and the diameter of the inner explosive 5 is 21 mm. From this, the collision velocity of the double tube 3 can be calculated to be 330 m / s, and the collision velocity of the base tube 2 is 108 m / s. Thus, the outer diameter of the outer explosive is calculated to be 83 mm and the inner diameter is 73 mm, that is, the thickness of the outer explosive is determined to be 10 mm. The gap distance between the base and double tubes is 1.5 mm. After grinding and cleaning the surface of the metal tube to be welded with acetone, the metal tube is coaxially placed with the inner and outer explosives on the bottom cover 6. Subsequently, waterproof glue is applied between the double tube 3 and the bottom cover 6 for sealing. Then, water is injected into the gap between the double tube 3 and the inner explosive 5, and the top cover 7 is placed on the upper part. Finally, the initiation system composed of a detonator 9 and industrial detonating cord 8 is installed on the inner and outer explosives.

[0078] The assembled experimental device is placed on the foundation and detonated. After the explosion is completed, the steel pipe and copper pipe are successfully compounded, as Figure 3 shown, and there are no macroscopic defects on the inner and outer surfaces of the compound pipe, and the deformation is small.

[0079] It should be understood that the above specific embodiments of the present invention are only used for exemplary illustration or explanation of the principle of the present invention, and do not constitute a limitation to the present invention. Therefore, any modifications, equivalent replacements, improvements, etc. made without departing from the spirit and scope of the present invention shall be included within the protection scope of the present invention. In addition, the appended claims of the present invention are intended to cover all variations and modification examples falling within the scope and boundaries of the appended claims, or equivalent forms of such scope and boundaries.

Claims

1. A dynamic self-constrained explosive welding method for preparing a bimetallic composite pipe, characterized in that, The method comprises the following steps: S1. The method is designed through a self - constraint system; S2. Place them coaxially from outside to inside in sequence: an outer explosive (1), a base tube (2), a composite tube (3), a pressure - transmitting medium (4), an inner explosive (5); connect industrial detonating cords (8) with different detonation velocities; S3. Use a detonator (9) and an industrial detonating cord (8) to form a detonating system; Use industrial detonating cords (8) with different detonation velocities. One end is tied around the detonator (9), and the other end is inserted into the heads of the inner and outer explosives to simultaneously detonate the inner and outer explosives. Fill the gap between the inner explosive (5) and the composite tube (3) with a pressure - transmitting medium (4) so that the shock wave generated by the explosion acts uniformly on the composite tube (3). Place a top cover (7) above the base tube (2) and the composite tube (3). The spacing distance between the base tube (2) and the composite tube (3) is designed according to empirical formula (1), where S and δ represent the spacing distance and the thickness of the composite tube (3) respectively; S≈(0.5~1)×δ#(1), Based on the principles of the law of conservation of momentum and the theory of perfectly inelastic collision, taking the base and composite tubes (3) at the moment of collision as a system, the calculation methods for the collision velocity and the thickness of the outer explosive used for constraint are as follows: where A * , β, and E are given by formulas (4)-(6) respectively; β = R o / R i #(5) where E is the Gurney coefficient of the explosive, M1 / M2, C1 / C2, and N are the masses per unit length of the cladding / base tube (2), the inner / outer explosives, and the external constraint, respectively, R i is the outer diameter of the outer explosive, R o is the inner diameter of the base tube (2), γ is the effective polytropic exponent of the explosive, 2.5 for emulsion explosives, and D is the detonation velocity of the explosive; The velocity of the composite tube obtained after collision can be calculated by formula (7): V c = (V f M f - V b M b ) f(M f + M b ) #(7) Assume that the velocity of the obtained composite tube is zero, that is, the optimal constraint effect is achieved. Then the theoretical relationship between the velocities of the composite tube 3 and the base tube 2 is shown in formula (8): V b = V f M f / M b #(8) However, the actual velocity of the base tube (2) should be greater than the theoretical value calculated by formula (8) to offset the outward expansion deformation of the composite tube caused by the residual explosion products inside the composite tube (3), which can be calculated by formula (9): V pb = kV b #(9) where k is a coefficient to offset the influence of residual detonation products and can be determined according to experimental or numerical simulation results; Before the explosion welding experiment, the collision velocity (Vf) of the composite tube (3) can be calculated from the mass of the inner explosive (5) according to Equations (2) and (6), and then the velocity (V pb ) of the base tube (2) can be calculated from Equation (9), and then the mass of the outer explosive used for restraint can be calculated from Equations (3) to (6); S4. Simultaneously detonate the inner explosive (5) and the outer explosive (1), drive the composite tube (3) and the base tube (2) to move towards each other and collide.

2. A dynamic self - constraint explosive welding method for preparing a bimetallic composite tube according to claim 1, wherein: Self-constraint system design, based on the law of conservation of momentum and the theory of perfectly inelastic collision, the theoretical collision velocity constraint relationship between the foundation and the double pipe (3) is established as: V b = V f M f / M b ; wherein: V b is the collision velocity of the base tube (2); V f is the collision velocity of the multi-tube (3); M f and M b are the masses of the composite tube (3) and the base tube (2) per unit length, respectively.

3. A dynamic self - constraint explosive welding method for preparing a bimetallic composite tube according to claim 2, wherein: Further deduce that the actual collision velocity of the composite tube (3) is: V pb = kV b ; In the formula: k is a coefficient to offset the influence of residual detonation products and can be determined according to experimental or numerical simulation results; Based on the Gurney collision velocity calculation formula, the collision velocity of the composite tube (3) can be determined first, then the collision velocity of the base tube (2) can be calculated, and finally the mass of the outer explosive (1) used for constraint can be calculated to establish a self - constraint system for the explosive welding of the bimetallic tube.

4. A dynamic self-constrained explosive welding method for preparing a bimetallic composite tube according to claim 3, characterized in that The value range of k is 1 - 3.

5. A dynamic self-constrained explosive welding method for preparing a bimetallic composite pipe according to any one of claims 1-4, characterized in that, Among them, the industrial detonating cord (8) for detonating the outer explosive (1) forms an angle of 60° with the horizontal.

6. The dynamic self-constrained explosive welding method for preparing a bimetallic composite tube according to claim 5, wherein The detonation velocity ratio of the industrial detonating cords (8) for detonating the inner and outer explosives (1) is 1:1.

16.

7. A dynamic self-constrained explosive welding method for preparing a bimetallic composite pipe according to claim 6, characterized in that, The pressure - transmitting medium (4) can be water, asphalt or resin.

8. A dynamic self - constraint explosive welding method for preparing a bimetallic composite tube according to claim 6, wherein: Industrial detonating cords (8) with different detonation velocities, one end of which is evenly tied around the detonator (9), and 1 of the other ends is inserted into the inner explosive (5), and the rest are evenly inserted into the outer explosive (1), are used to simultaneously detonate the inner explosive (5) and the outer explosive (1).

9. A dynamic self-constrained explosive welding method for preparing a bimetallic composite tube according to claim 8, characterized in that The metal tube and the inner and outer explosives are coaxially placed on the bottom cover (6), and the top cover (7) is placed above the base tube and the clad tube.

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