A method for manufacturing a gradient-damping composite pipe

Abstract

The application discloses a manufacturing method of a gradient damping composite pipe to solve the problem of poor damping and sound absorption effect of the existing composite pipe. The manufacturing method comprises the following steps: encapsulating foaming materials in each embedded pipe to obtain a plurality of embedded pipes with different mass fractions of foaming agents; arranging the embedded pipes in an annular gap formed by an outer pipe and an inner pipe, and distributing the embedded pipes in a manner that the mass fraction of the foaming agent decreases layer by layer from the inner wall of the outer pipe to the outer wall of the inner pipe along the radial direction to obtain a first composite pipe blank; the plurality of embedded pipes have at least two different pipe diameters, and the pipe diameters of the embedded pipes decrease layer by layer in the direction from the outer pipe to the inner pipe; or the embedded pipes with smaller pipe diameters are distributed close to the outer wall of the inner pipe and the inner wall of the outer pipe, and the embedded pipes with larger pipe diameters are distributed between two layers of embedded pipes with smaller pipe diameters in the circumferential direction; using an encapsulation plate to block the opening end of the annular gap; and heating the third composite pipe blank through internal spinning to make the foaming materials foam to obtain a gradient damping composite pipe with a foamed metal layer.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of metal pipe processing, in particular to a manufacturing method of gradient damping composite pipe. BACKGROUND

[0002] The foam metal interlayer structure and the foam metal have the characteristics of light weight, high specific steel, sound insulation, shock absorption, heat preservation, and heat insulation. The existing preparation process of the foam metal composite pipe usually adopts inner metal pipe, outer metal pipe and foaming powder located in the middle to form an integrated extrusion, and then heating is performed to make the middle layer foam to form a foam metal layer, so as to obtain a foam metal sandwich composite pipe. However, the foam metal layer structure is single, the mechanical properties in the composite pipe are weak, and the damping and sound absorption effect of the obtained composite pipe is poor. SUMMARY

[0003] The purpose of the present application is to provide a manufacturing method of gradient damping composite pipe for improving the damping and sound absorption effect and mechanical properties of the composite pipe.

[0004] In order to achieve the above purpose, the present application provides the following technical scheme: in the first aspect, the present application provides a manufacturing method of gradient damping composite pipe, comprising:

[0005] providing a metal outer pipe, a metal inner pipe and a plurality of embedded pipes;

[0006] encapsulating foaming material in each embedded pipe, the foaming material comprising foaming agent and metal powder, to obtain a plurality of embedded pipes with different mass fractions of foaming agent;

[0007] arranging the plurality of embedded pipes in the annular gap formed by the metal outer pipe and the metal inner pipe in a close arrangement, so that the plurality of embedded pipes are distributed in the annular gap in a manner that the mass fraction of the foaming agent decreases layer by layer along the radial direction from the inner wall of the metal outer pipe to the outer wall of the metal inner pipe, to obtain a first composite pipe blank; wherein the plurality of embedded pipes have at least two different pipe diameters, and the pipe diameters of the plurality of embedded pipes decrease layer by layer in the direction from the inner wall of the metal outer pipe to the outer wall of the metal inner pipe; or, the embedded pipes with smaller pipe diameters are distributed close to the outer wall of the metal inner pipe and close to the inner wall of the metal outer pipe, and the embedded pipes with larger pipe diameters are distributed between the two layers of embedded pipes with smaller pipe diameters in the circumferential direction;

[0008] sealing the open end of the annular gap with a sealing plate to obtain a second composite pipe blank;

[0009] performing internal spinning processing on the second composite pipe blank to the target wall thickness to obtain a third composite pipe blank;

[0010] heating the third composite pipe blank to make the foaming material foam to obtain a gradient damping composite pipe with a foam metal layer.

[0011] Optionally, in the manufacturing method of the gradient damping composite pipe, after the plurality of embedded pipes are arranged in the annular gap formed by the metal outer pipe and the metal inner pipe, and before the opening end of the annular gap is covered by the packaging plate, the manufacturing method further comprises: filling metal chips into the gap between the outer walls of the plurality of embedded pipes.

[0012] Optionally, in the manufacturing method of the gradient damping composite pipe, the wall thickness of the embedded pipe is 2mm-4mm, and the inner diameter of the embedded pipe is 10mm-30mm.

[0013] Optionally, in the manufacturing method of the gradient damping composite pipe, the temperature for heating the third composite pipe blank is 650℃-1350℃, and the foaming time of the foaming material is 5min-10min.

[0014] Optionally, in the manufacturing method of the gradient damping composite pipe, the packaging plate comprises metal and / or resin.

[0015] The metal outer pipe and the metal inner pipe are both alloy steel pipes or aluminum alloy pipes.

[0016] The embedded pipe is one or more of iron pipe, aluminum pipe, and stainless steel pipe.

[0017] Optionally, in the manufacturing method of the gradient damping composite pipe, the foaming agent in the foaming material is TiH2 with a mass fraction of 1%-2%, and the metal powder is aluminum powder.

[0018] Alternatively, the foaming agent in the foaming material is SrCO3 with a mass fraction of 2%-3%, and the metal powder is iron powder.

[0019] Compared with the traditional way of obtaining a composite pipe by using a single-structure foamed metal interlayer, the present application fills different mass fractions of foaming agents into different inner embedded pipes, respectively, after sealing and welding, arranges the multiple inner embedded pipes in the annular gap formed by the metal outer pipe and the metal inner pipe, and distributes the foaming agents in the radial direction from the inner wall of the metal outer pipe to the outer wall of the metal inner pipe in a manner of gradually decreasing the mass fraction of the foaming agent, so that the foaming material is constrained by the multiple inner embedded pipes and is distributed in various positions in the annular gap, thereby improving the uniformity of the foaming material distribution and the stability of the gradient distribution of the different foaming structures in the composite pipe after foaming. Then, the pipe is spun to the target wall thickness, and finally, the foaming agent is heated to form a foamed metal layer as the core layer of the composite pipe. Due to the different mass fractions of the foaming agent, the porosity after foaming is different, and the porosity of the foamed metal layer obtained can be distributed in a gradient decreasing manner between the metal outer pipe and the metal inner pipe. In addition, the multiple inner embedded pipes have different diameters. When the diameters of the multiple inner embedded pipes gradually decrease in the direction from the inner wall of the metal outer pipe to the outer wall of the metal inner pipe, the larger the diameter, the larger the gap between the adjacent inner embedded pipes. After inner spinning and foaming forming, the gap formed by the inner embedded pipe with a larger diameter is larger, and the porosity is higher. On the contrary, the smaller the diameter, the smaller the gap between the adjacent inner embedded pipes. After inner spinning and foaming forming, the gap formed by the inner embedded pipe with a smaller diameter is smaller, and the porosity is lower. Moreover, the inner embedded pipe with a smaller diameter can provide good structural support and barrier capacity as a support skeleton, so that the gradient damping composite pipe can bear the functions of “preliminary absorption-deep dissipation-structural support” at different positions in the radial direction, form a gradient interception of sound wave / vibration energy, and avoid the problem of weak mechanical properties of a single-porosity material in the composite pipe, thereby ensuring the balance between the strength and the sound absorption and damping performance of the gradient damping composite pipe.When the inner embedded pipes with smaller diameters are distributed close to the outer wall of the metal inner pipe and close to the inner wall of the metal outer pipe, and the inner embedded pipes with larger diameters are distributed in the circumferential direction between the two layers of the inner embedded pipes with smaller diameters, the gradient damping composite pipe constructs different functional layers at different radial positions. The outer layer and the inner layer close to the foam metal layer have smaller gaps between the adjacent inner embedded pipes due to the smaller diameters of the inner embedded pipes, and the multiple inner embedded pipes with smaller diameters can provide good structural support and blocking capacity as a support framework. The middle layer close to the foam metal layer has larger gaps between the adjacent inner embedded pipes due to the larger diameters of the inner embedded pipes, and the inner embedded pipes with larger diameters can provide structural support while having good flexible deformation, which can provide expansion space for the foaming material inside the inner embedded pipes with larger diameters, so that the foam metal layer forms a "hard-soft-hard" radial gradient distribution, and the mass fraction of the foaming agent filled from the outside to the inside is gradually reduced layer by layer, so that the porosity of the foam metal layer decreases in steps from the inner wall of the metal outer pipe to the outer wall of the metal inner pipe, forming a gradient interception of sound waves / vibration energy. Compared with the foam metal layer formed by the inner embedded pipes with the same diameter and the foaming agent material with the same mass fraction, the problem of weak mechanical properties of a single porosity material in the composite pipe is avoided, and the balance between the strength and the damping and sound absorption performance of the gradient damping composite pipe is ensured.

[0020] In a second aspect, the present application further provides a manufacturing method of the gradient damping composite pipe, comprising:

[0021] providing a metal outer pipe, a metal inner pipe, a base and a plurality of metal solid rods, wherein one end of the metal outer pipe and the metal inner pipe is fixed by the base, and an annular filling cavity is formed between the metal outer pipe, the metal inner pipe and the base;

[0022] arranging the plurality of metal solid rods in the annular filling cavity; wherein the plurality of metal solid rods have at least two different diameters, and the diameters of the plurality of metal solid rods decrease layer by layer in the direction from the inner wall of the metal outer pipe to the outer wall of the metal inner pipe; or the metal solid rods with smaller diameters are distributed close to the outer wall of the metal inner pipe and close to the inner wall of the metal outer pipe, and the metal solid rods with larger diameters are distributed in the circumferential direction between the two layers of the metal solid rods with smaller diameters;

[0023] filling the foaming material with different mass fractions of foaming agents into the gaps between the adjacent metal solid rods, so that the mass fraction of the foaming agent of the foaming material in the annular filling cavity decreases layer by layer in the radial direction from the inner wall of the metal outer pipe to the outer wall of the metal inner pipe, and the foaming material comprises a foaming agent and a metal powder;

[0024] sealing the open end of the annular filling cavity with a packaging plate to obtain a fourth composite pipe blank;

[0025] performing internal spinning processing on the fourth composite pipe blank to a target wall thickness to obtain a fifth composite pipe blank;

[0026] The fifth composite pipe blank is heated to make the foaming material foaming to form the gradient damping composite pipe with the foamed metal layer.

[0027] Optionally, in the manufacturing method of the gradient damping composite pipe, the diameter of the metal solid rod is 10mm-30mm.

[0028] Optionally, in the manufacturing method of the gradient damping composite pipe, the temperature for heating the fifth composite pipe blank is 650℃-1350℃, and the foaming time of the foaming material is 5min-10min.

[0029] Optionally, in the manufacturing method of the gradient damping composite pipe, the metal solid rod is an iron rod or an aluminum rod.

[0030] The packaging board comprises metal and / or resin;

[0031] The metal outer pipe and the metal inner pipe are both alloy steel pipes or aluminum alloy pipes.

[0032] Optionally, in the manufacturing method of the gradient damping composite pipe, the foaming agent in the foaming material is TiH2 with a mass fraction of 1%-2%, and the metal powder is aluminum powder.

[0033] Alternatively, the foaming agent in the foaming material is SrCO3 with a mass fraction of 2%-3%, and the metal powder is iron powder.

[0034] Compared with the traditional composite pipe obtained by using a single structure of a foam metal interlayer, the multiple metal solid rods are arranged in the annular filling cavity to form a gap for filling the foaming material which is stably distributed along the radial direction. The foaming material is uniformly distributed in the annular gap by distributing the foaming agent with different mass fractions in the gap between the multiple metal solid rods and sealing welding. The position of the foaming material in the annular gap is constrained by the multiple metal solid rods, and the stability of the gradient distribution of the foaming structure in the composite pipe is improved. After spinning to the target wall thickness and heating and foaming, the foam metal layer is formed as the core layer of the composite pipe. Due to the different mass fractions of the foaming agent and the different diameters of the multiple metal solid rods, the porosity of the foam metal layer is gradiently distributed between the inner metal pipe and the outer metal pipe. When the diameters of the multiple metal solid rods decrease layer by layer from the inner wall of the outer metal pipe to the outer wall of the inner metal pipe, the larger the diameter, the larger the gap between the adjacent metal solid rods. After the inner spinning and foaming forming, the larger the diameter of the metal solid rod, the larger the gap formed at the metal solid rod, and the higher the porosity. On the contrary, the smaller the diameter of the metal solid rod, the smaller the gap between the adjacent metal solid rods. After the inner spinning and foaming forming, the smaller the diameter of the metal solid rod, the smaller the gap formed at the metal solid rod, and the lower the porosity. In combination with the foaming agent with the mass fraction decreasing layer by layer from the outside to the inside, the porosity of the foam metal layer decreases in a stepwise manner from the inner wall of the outer metal pipe to the outer wall of the inner metal pipe (i.e., the porosity of the outer layer is higher, and the porosity of the inner layer is lower). The gradient damping composite pipe forms a gradient interception of sound waves / vibration energy at different positions in the radial direction, so that the comprehensive porosity in the annular filling cavity is large, and the problem of weak mechanical properties of a single porosity material in the gradient damping composite pipe is avoided to ensure the balance between the strength and the damping and sound absorption performance of the gradient damping composite pipe.When the metal solid rods with smaller diameters are distributed close to the outer wall of the metal inner tube and close to the inner wall of the metal outer tube, and the metal solid rods with larger diameters are distributed in the circumferential direction between the two layers of metal solid rods with smaller diameters, the outer layer and the inner layer close to the foam metal layer have smaller gaps between adjacent metal solid rods due to the smaller diameters of the metal solid rods, and less foaming material is filled, and the multiple metal solid rods with smaller diameters can provide good structural support and blocking capacity as a support skeleton; the middle layer close to the foam metal layer has larger gaps between adjacent metal solid rods due to the larger diameters of the metal solid rods, and the metal solid rods with larger diameters can provide structural support, and the larger gaps can fill more foaming material to provide sufficient expansion space for the foaming material, and the pores of the porous structure can disperse and absorb part of the vibration energy, and the mass fraction of the foaming agent filled from the outside to the inside is gradually reduced layer by layer, so that the porosity of the foam metal layer decreases in a stepwise manner from the inner wall of the metal outer tube to the outer wall of the metal inner tube, forming a gradient interception of sound waves / vibration energy, compared with the foam metal layer formed by the metal solid rods with the same diameter and the foaming agent material with the same mass fraction, the problem of weak mechanical properties of a single porosity material in the composite tube is avoided, and the balance between the strength and the vibration absorption performance of the gradient vibration reduction composite tube is ensured. BRIEF DESCRIPTION OF DRAWINGS

[0035] The accompanying drawings, which are included to provide a further understanding of the application and are incorporated in and constitute a part of this application, illustrate embodiments of the application and together with the description serve to explain the application. In the drawings:

[0036] Figure 1 A process flow chart of a manufacturing method of a gradient vibration reduction composite tube provided in an embodiment of the application;

[0037] Figure 2 A schematic diagram of a second distribution mode of an embedded tube or a metal solid rod in a manufacturing method of a gradient vibration reduction composite tube provided in an embodiment of the application;

[0038] Figure 3 A schematic diagram of a third distribution mode of an embedded tube or a metal solid rod in a manufacturing method of a gradient vibration reduction composite tube provided in an embodiment of the application;

[0039] Figure 4 A process flow chart of another manufacturing method of a gradient vibration reduction composite tube provided in an embodiment of the application.

[0040] REFERENCE NUMERALS:

[0041] 1-metal outer tube; 2-metal inner tube; 3-embedded tube. DETAILED DESCRIPTION

[0042] In order to make the technical problems to be solved by the present application, technical solutions and beneficial effects clearer, the present application will be further described in detail below with reference to the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and not intended to limit the present application.

[0043] It should be noted that when an element is referred to as being "fixed" or "disposed" on another element, it can be directly on the other element or indirectly on the other element. When an element is referred to as being "connected" to another element, it can be directly connected to the other element or indirectly connected to the other element.

[0044] In addition, the terms "first", "second" are only for descriptive purposes and should not be construed as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined with "first", "second" can explicitly or implicitly include one or more of the features. In the description of the present application, the meaning of "a plurality of" is two or more, unless otherwise explicitly specified and limited. The meaning of "several" is one or more, unless otherwise explicitly specified and limited.

[0045] In the description of the present application, it should be understood that the terms "upper", "lower", "front", "back", "left", "right" and the like indicate the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and should not be construed as indicating or implying that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore should not be construed as limiting the present application.

[0046] In the description of the present application, it should be noted that unless otherwise explicitly specified and limited, the terms "mounting", "connecting", "connecting" should be understood in a broad sense, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium; it can be the internal communication of two elements or the interaction relationship between two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0047] As shown in Figures 1-3 The manufacturing method of the gradient damping composite pipe provided by the embodiment of the present application comprises:

[0048] Step S100, providing a metal outer pipe 1, a metal inner pipe 2 and a plurality of embedded pipes 3.

[0049] Step S200, encapsulating the foaming material in each embedded tube 3, the foaming material including foaming agent and metal powder, to obtain a plurality of embedded tubes 3 with different mass fractions of foaming agent. Wherein, the foaming agent and metal powder are mixed and then loaded into the embedded tube 3, and a metal block is used to weld and block the two ports of the embedded tube 3. Of course, it can also be bonded or other blocking methods, as long as the metal block is tightly connected with the port of the embedded tube 3 and no leakage of foaming material occurs. For example, the metal block can be made of iron block, aluminum block or other metal materials.

[0050] Step S300, tightly arranging a plurality of embedded tubes 3 in the annular gap formed by the metal outer tube 1 and the metal inner tube 2, so that the plurality of embedded tubes 3 are distributed in the annular gap in a way that the mass fraction of foaming agent decreases layer by layer from the inner wall of the metal outer tube 1 to the outer wall of the metal inner tube 2, to obtain a first composite tube blank. Wherein, the plurality of embedded tubes have at least two different diameters, and the diameters of the plurality of embedded tubes decrease layer by layer in the direction from the inner wall of the metal outer tube to the outer wall of the metal inner tube; or, the embedded tubes with smaller diameters are distributed close to the outer wall of the metal inner tube and close to the inner wall of the metal outer tube, and the embedded tubes with larger diameters are distributed between the two layers of embedded tubes with smaller diameters in the circumferential direction. Specifically, the metal outer tube 1 and the metal inner tube 2 are coaxially placed, and the fixation between the metal outer tube 1 and the metal inner tube 2 can be riveting or other fixation methods, as long as the annular gap formed after the metal outer tube 1 and the metal inner tube 2 are sleeved is fixed.

[0051] Step S400, using an encapsulation plate to block the open end of the annular gap to obtain a second composite tube blank. Wherein, the encapsulation plate and the open end of the annular gap can be connected by welding, bonding or other fixed connection methods, as long as the connection between the encapsulation plate and the open end of the annular gap is tight and no internal material leakage occurs.

[0052] Step S500, inner spinning processing the second composite tube blank to the target wall thickness to obtain a third composite tube blank.

[0053] Step S600, heating the third composite tube blank to make the foaming material foam to obtain a gradient damping composite tube with a foamed metal layer. Specifically, the third composite tube blank can be placed in a mold during the heating and foaming process of the third composite tube blank. For example, the mold can be a cavity structure composed of an outer wall metal tube and an inner wall metal tube. The outer diameter of the third composite tube blank is the same as the inner diameter of the outer wall metal tube, and the inner diameter of the third composite tube blank is the same as the outer diameter of the inner wall metal tube. The cavity structure composed of the outer wall metal tube and the inner wall metal tube constrains the surface of the third composite tube blank to prevent the third composite tube blank from expanding and deforming during the heating and foaming process.

[0054] Compared with the traditional way of obtaining a composite pipe by using a single-structure foamed metal interlayer, the present application fills different mass fractions of foaming agents into different inner embedded pipes 3 respectively, arranges the inner embedded pipes 3 closely in the annular gap formed by the metal outer pipe 1 and the metal inner pipe 2, and distributes the foaming agents in the radial direction from the inner wall of the metal outer pipe 1 to the outer wall of the metal inner pipe 2 in a manner that the mass fraction of the foaming agent decreases layer by layer. The foaming material is constrained by the inner embedded pipes 3, and the foaming material is constrained at each position in the annular gap, which improves the uniformity of the foaming material distribution and the stability of the gradient distribution of the foaming structure in the composite pipe. After spinning to the target wall thickness and finally heating and foaming, the foamed metal layer formed as the core layer of the composite pipe has different porosities due to the different mass fractions of the foaming agents. The inner embedded pipes 3 have different diameters, and the distribution of the inner embedded pipes 3 with different diameters in the radial direction of the annular gap is different. Therefore, the porosity of the foamed metal layer can be distributed in a gradient between the metal inner pipe 2 and the metal outer pipe 1. When the inner embedded pipes 3 have at least two different diameters, the diameter of the inner embedded pipes 3 decreases layer by layer in the direction from the inner wall of the metal outer pipe 1 to the outer wall of the metal inner pipe 2. The larger the diameter, the larger the gap between adjacent inner embedded pipes 3. After inner spinning and foaming, the gap formed by the inner embedded pipes 3 with larger diameters is larger, and the porosity is higher. On the contrary, the smaller the diameter, the smaller the gap between adjacent inner embedded pipes 3. After inner spinning and foaming, the gap formed by the inner embedded pipes 3 with smaller diameters is smaller, and the porosity is lower. In combination with the decreasing mass fraction of the foaming agent filled from the outside to the inside, the porosity of the foamed metal layer decreases in a stepwise manner from the inner wall of the metal outer pipe 1 to the outer wall of the metal inner pipe 2 (i.e., the porosity of the outer layer is higher, and the porosity of the inner layer is lower), so that the gradient damping composite pipe can bear the functions of "preliminary absorption-depth dissipation-structural support" at different positions in the radial direction, form a gradient interception of sound wave / vibration energy, and have a larger overall porosity in the annular gap. Compared with the foamed metal layer formed by the inner embedded pipes 3 with the same diameter and the foaming agent material with the same mass fraction, the performance limitations of a single porosity structure are avoided. When the gradient damping composite pipe is subjected to external vibration, the higher porosity structure in the outer layer provides elastic cushioning effect, compresses, flows, and deforms the medium (air or filling material) in the pores of the porous structure, and deforms the inner embedded pipe 3 as the skeleton of the porous structure, thereby dispersing and absorbing part of the vibration energy, reducing the vibration amplitude transmitted to the inside of the pipe wall, and improving the sound absorption and vibration reduction performance of the gradient damping composite pipe.

[0055] When multiple embedded tubes 3 have at least two different diameters, with the smaller diameter embedded tubes 3 distributed near the outer wall of the inner metal tube 2 and near the inner wall of the outer metal tube 1, and the larger diameter embedded tubes 3 distributed circumferentially between the two layers of smaller diameter embedded tubes 3, the gradient vibration damping composite pipe constructs different functional layers at different radial positions. Due to the smaller diameter of the embedded tubes 3 in the outer and inner layers near the foam metal layer, the gaps between adjacent embedded tubes 3 are smaller, and the multiple smaller diameter embedded tubes 3, acting as a supporting skeleton, can provide good structural support and barrier capabilities. In the middle layer near the foam metal layer, due to the larger diameter of the embedded tubes 3, the gaps between adjacent embedded tubes 3 are larger, and the larger diameter embedded tubes... While providing structural support, tube 3 also exhibits good flexibility and deformation, allowing for expansion space for the foamed material inside the larger-diameter inner tube 3. This results in a radial gradient distribution of the foam metal layer, characterized by a "hard-soft-hard" pattern. Combined with the decreasing mass fraction of the foaming agent from the outside to the inside, the porosity of the foam metal layer decreases radially from the inner wall of the outer metal tube 1 to the outer wall of the inner metal tube 2. This creates a gradient interception of sound wave / vibration energy. Compared to a foam metal layer formed by an inner tube 3 of the same diameter and the same mass fraction of foaming agent, this avoids the problem of weak mechanical properties of materials with single porosity in composite pipes, ensuring a balance between the strength and vibration reduction / sound absorption performance of the gradient vibration damping composite pipe.

[0056] For example, such as Figure 2 As shown, three layers of embedded tubes 3 are arranged radially within the annular gap. From the outside to the inside, they are the first layer, the second layer, and the third layer of embedded tubes 3. The diameter of the three layers of embedded tubes 3 decreases sequentially from the outside to the inside. Each layer of embedded tubes 3 is tightly arranged along the circumference, and the mass fraction of the foaming agent in the foaming material of the same layer of embedded tubes 3 is the same. The mass fraction of the foaming agent in the foaming material of the three layers of embedded tubes 3 decreases sequentially from the outside to the inside. Of course, two, four, or other layers of embedded tubes 3 with different diameters can also be arranged radially within the annular gap.

[0057] like Figure 3 As shown, exemplarily, four layers of embedded tubes 3 are arranged radially in the annular gap. From the outside to the inside, they are the first layer of embedded tubes 3, the second layer of embedded tubes 3, the third layer of embedded tubes 3, and the fourth layer of embedded tubes 3. The diameter of the first layer of embedded tubes 3 is the same as that of the fourth layer of embedded tubes 3, and the diameter of the second layer of embedded tubes 3 is the same as that of the third layer of embedded tubes 3. The diameter of the first layer of embedded tubes 3 is smaller than that of the second layer of embedded tubes 3. Each layer of embedded tubes 3 is arranged closely around the circumference, and the mass fraction of the foaming agent in the foaming material of the same layer of embedded tubes 3 is the same. The mass fraction of the foaming agent in the foaming material of the four layers of embedded tubes 3 decreases sequentially from the outside to the inside. Of course, two, three, five, or other multiple layers of embedded tubes 3 with different diameters can also be arranged radially in the annular gap.

[0058] It should be noted that, due toFigure 2 The arrangement shown has higher comprehensive porosity than Figure 3 The arrangement shown has higher comprehensive porosity than Figure 2 The arrangement shown has better sound absorption effect than Figure 3 The arrangement shown has better sound absorption effect than Figure 3 The arrangement shown has better sound absorption effect than Figure 2 The arrangement shown has better sound absorption effect than

[0059] In some embodiments, after the plurality of embedded pipes 3 are arranged in the annular gap formed by the metal outer pipe 1 and the metal inner pipe 2 in step S300, and before the opening end of the annular gap is sealed by the sealing plate in step S400, the manufacturing method further comprises step S301: filling metal chips in the gap between the outer walls of the plurality of embedded pipes 3. Wherein, the metal chips can be iron chips, aluminum chips or other metal chips, as long as the metal chips can form good metallurgical bonding between the metal outer pipe 1, the metal inner pipe 2 and the embedded pipes 3. By filling metal chips, the relative displacement of the plurality of embedded pipes 3 in the annular gap during the internal spinning process can be limited, and the arrangement is stable and uniform.

[0060] In some embodiments, after the opening end of the annular gap is sealed by the sealing plate in step S400, and before the second composite pipe blank is internally spun in step S500, the manufacturing method further comprises: vacuumizing the plurality of embedded pipes after sealing. In this way, the foaming material in the embedded pipe is prevented from being oxidized by contacting oxygen during the foaming process under high temperature heating.

[0061] Specifically, in the embodiment, the wall thickness of the embedded tube 3 is 2mm-4mm, and the inner diameter of the embedded tube 3 is 10mm-30mm. For example, the wall thickness of the embedded tube 3 can be 2mm, 3mm, 3.5mm, 4mm, etc., and the inner diameter of the embedded tube 3 can be 10mm, 15mm, 20mm, 30mm, etc. The operator can select different sizes of the embedded tube 3 according to the actual work requirements and combined with the arrangement of different structures. The wall thickness of the embedded tube 3 is greater than 2mm, so that the wall thickness of the embedded tube 3 can withstand a certain extrusion strength, avoiding the risk of cracking of the embedded tube 3 during the internal spinning in step S500, resulting in leakage of the inner layer foaming material of the embedded tube 3; the wall thickness of the embedded tube 3 is less than 4mm, so that the embedded tube 3 has a good flexibility and can deform slightly with the expansion of the foaming material in the embedded tube 3 during the foaming process. Considering that the wall thickness of the embedded tube 3 is too large or too small, it will have adverse effects. Therefore, the wall thickness of the embedded tube 3 is selected to be 2mm-4mm to ensure that the embedded tube 3 can withstand a certain extrusion strength while reducing stress concentration in the interface area when the temperature changes or external force acts, so as to ensure the uniformity of the foamed metal layer.

[0062] Specifically, in the embodiment, the foaming agent in the foaming material is TiH2 with a mass fraction of 1%-2%, and the metal powder is aluminum powder. Of course, the foaming agent in the foaming material can also be SrCO3 with a mass fraction of 2%-3%, and the metal powder is iron powder. Of course, other foaming materials can also be used to fill the embedded tube 3, as long as the foaming agent in the foaming material is distributed in the annular gap in the form of gradually decreasing from the inner wall of the metal outer tube 1 to the outer wall of the metal inner tube 2 along the radial direction according to the mass fraction.

[0063] For example, three layers of embedded tubes 3 are arranged in the annular gap along the radial direction, from the outside to the inside, they are the first layer of embedded tube 3, the second layer of embedded tube 3 and the third layer of embedded tube 3, and the mass fraction of the foaming agent TiH2 filled in the three layers of embedded tubes 3 is 2%, 1.5% and 1% respectively; or the mass fraction of the foaming agent SrCO3 filled in the three layers of embedded tubes 3 is 3%, 2.5% and 2% respectively.

[0064] Specifically, in step S600, the temperature for heating the third composite pipe blank is 650-1350°C, and the foaming material is foamed for 5-10 minutes. For example, the temperature for heating the third composite pipe blank can be 650°C, 800°C, 950°C, 1000°C, 1200°C, 1350°C, etc., and the foaming time of the foaming material can be 5 minutes, 6 minutes, 8 minutes, 10 minutes, etc. Since the melting point of the metal powder in the foaming material is usually high, a foaming temperature greater than 650°C can ensure that the metal material is partially melted or semi-melted, the melt viscosity is reduced to provide the flowability basis for the uniform dispersion and expansion of the bubbles, and the uniformity of the pores and the structural stability of the porous structure are ensured. When the foaming temperature is less than 1350°C, the risk of material composition segregation and pore structure collapse of the foamed metal layer due to excessive volatilization and decomposition of the metal melt at high temperature is avoided, and the uniformity of the pores and the structural stability of the porous structure are ensured. Preferably, when the foaming material is TiH2 and Al powder mixed uniformly at room temperature and normal pressure, and then loaded into the embedded pipe 3 for cold extrusion, and the foaming material is blocked in the embedded pipe 3 by the iron block, the foaming temperature of the foaming process is 650°C, and the foaming time is 10 minutes; when the foaming material is SrCO3 and Fe powder mixed uniformly at room temperature and normal pressure, and then loaded into the embedded pipe 3 for cold extrusion, and the foaming material is blocked in the embedded pipe 3 by the iron block, the foaming temperature of the foaming process is 1350°C, and the foaming time is 5 minutes. The operator can select different foaming temperatures and foaming times according to the actual addition of the foaming material, as long as the uniformity of the foamed metal layer after foaming is ensured.

[0065] Specifically, in the present embodiment, the packaging plate comprises metal and / or resin. For example, the packaging plate can be an iron block, an aluminum block or other metal, as long as it can ensure good metallurgical bonding between the packaging plate and the open end of the embedded pipe 3, and can complete the blocking. Of course, the resin has good fluidity before solidification, and can form close physical contact on the metal surface to prevent leakage of the foaming material in the embedded pipe 3.

[0066] Specifically, in the embodiment, the metal outer tube 1 and the metal inner tube 2 are both alloy steel tubes or aluminum alloy tubes; the plurality of embedded tubes 3 are one or more of iron tubes, aluminum tubes, and stainless steel tubes. Among them, the metal outer tube 1 and the metal inner tube 2 can both be alloy steel tubes, aluminum alloy tubes, or other metal tubes, and the embedded tube 3 can be an iron tube, an aluminum tube, or other metal tubes, as long as the foamed metal layer obtained after processing can form a good metallurgical bond between the metal outer tube 1 and the metal inner tube 2. For example, the metal outer tube 1 is an aluminum alloy tube with an outer diameter of 180mm-220mm (preferably, the outer diameter of the metal outer tube 1 is 200mm), and an inner diameter of 160mm-200mm (preferably, the inner diameter of the metal outer tube 1 is 180mm), and the metal inner tube 2 is an aluminum alloy tube with an outer diameter of 50mm-70mm (preferably, the outer diameter of the metal inner tube 2 is 60mm), and an inner diameter of 40mm-60mm (preferably, the inner diameter of the metal inner tube 2 is 50mm); or, the metal outer tube 1 is an alloy steel tube with an outer diameter of 180mm-220mm (preferably, the outer diameter of the metal outer tube 1 is 200mm), and an inner diameter of 60mm-200mm (preferably, the inner diameter of the metal outer tube 1 is 180mm), and the metal inner tube 2 is an alloy steel tube with an outer diameter of 50mm-70mm (preferably, the outer diameter of the metal inner tube 2 is 60mm), and an inner diameter of 40mm-60mm (preferably, the inner diameter of the metal inner tube 2 is 50mm), as long as the radial distance between the inner wall of the metal outer tube 1 and the outer wall of the metal inner tube 2 of the tube blank material obtained by riveting or other processing methods is 60mm.

[0067] Specifically, the embedded tube 3 can be only one of an iron tube, an aluminum tube, and a stainless steel tube; the embedded tube 3 can also be selected from an iron tube and an aluminum tube, or the embedded tube 3 simultaneously has an iron tube, an aluminum tube, and a stainless steel tube.

[0068] As shown in FIGS. 6A and 6B, the embedded tube 3 can be only one of an iron tube, an aluminum tube, and a stainless steel tube; the embedded tube 3 can also be selected from an iron tube and an aluminum tube, or the embedded tube 3 simultaneously has an iron tube, an aluminum tube, and a stainless steel tube. Figure 2 and Figure 3 As shown in FIGS. 6A and 6B, the embedded tube 3 can be only one of an iron tube, an aluminum tube, and a stainless steel tube; the embedded tube 3 can also be selected from an iron tube and an aluminum tube, or the embedded tube 3 simultaneously has an iron tube, an aluminum tube, and a stainless steel tube.

[0069] When the embedded pipe 3 has iron pipes, aluminum pipes and stainless steel pipes, if three layers are arranged in the radial direction in the annular gap, the annular gap is distributed from the outside to the inside in turn as stainless steel pipes, iron pipes and aluminum pipes; if four layers are arranged in the radial direction in the annular gap, the annular gap is distributed from the outside to the inside in turn as stainless steel pipes, iron pipes, aluminum pipes and stainless steel pipes. By such arrangement, since the stainless steel pipes located at the outer layer or the inner layer have good hardness and stable performance at high temperature, they can withstand external mechanical impact, friction or extrusion, avoid the risk of deformation or damage of the internal pipe material, and prolong the service life of the overall structure of the gradient damping composite pipe.

[0070] As shown in Figures 2-4 The embodiment of the present application also provides another manufacturing method of a gradient damping composite pipe, which comprises the following steps:

[0071] In step S100', a metal outer pipe 1, a metal inner pipe 2, a base and a plurality of metal solid rods are provided, wherein one end of the metal outer pipe 1 and the metal inner pipe 2 is fixed by the base, and an annular filling cavity is formed between the metal outer pipe 1, the metal inner pipe 2 and the base.

[0072] In step S200', the plurality of metal solid rods are arranged and arranged in the annular filling cavity; wherein the plurality of metal solid rods have at least two different diameters, and in the direction from the inner wall of the metal outer pipe to the outer wall of the metal inner pipe, the diameters of the plurality of metal solid rods decrease layer by layer; or the metal solid rods with smaller diameters are distributed close to the outer wall of the metal inner pipe and close to the inner wall of the metal outer pipe, and the metal solid rods with larger diameters are distributed between the two layers of metal solid rods with smaller diameters in the circumferential direction.

[0073] In step S300', the foaming material with different mass fractions of foaming agent is filled into the gap between the adjacent metal solid rods, and the foaming material comprises a foaming agent and a metal powder, so that the mass fraction of the foaming agent in the foaming material in the annular filling cavity decreases layer by layer from the inner wall of the metal outer pipe 1 to the outer wall of the metal inner pipe 2 in the radial direction; specifically, the foaming agent and the metal powder are mixed and then filled into the gap between the adjacent metal solid rods.

[0074] In step S400', the opening end of the annular filling cavity is sealed by using a sealing plate to obtain a fourth composite pipe blank.

[0075] In step S500', the fourth composite pipe blank is subjected to internal spinning processing to a target wall thickness to obtain a fifth composite pipe blank.

[0076] In step S600', the fifth composite pipe blank is heated to make the foaming material foam to form a gradient damping composite pipe with a foamed metal layer. Specifically, the fifth composite pipe blank can be placed in a mold during the process of heating and foaming the foaming material. The mold can also have a cavity structure formed by a sleeve joint of an outer wall metal pipe and an inner wall metal pipe. The outer wall diameter of the fifth composite pipe blank is the same as the inner diameter of the outer wall metal pipe, and the inner wall diameter of the fifth composite pipe blank is the same as the outer diameter of the inner wall metal pipe. The cavity structure formed by the sleeve joint of the outer wall metal pipe and the inner wall metal pipe can constrain the surface of the fifth composite pipe blank to prevent the fifth composite pipe blank from expanding and deforming during the heating and foaming process.

[0077] Compared with the traditional way of obtaining a composite pipe by using a single-structure foamed metal interlayer, the present application arranges multiple metal solid rods in the annular filling cavity, so that the annular filling cavity forms a gap for filling foamed material which is stably distributed along the radial direction. By distributing different mass fractions of foaming agent in the gap between the multiple metal solid rods and sealing, the multiple metal solid rods constrain the position of the foamed material in the annular filling cavity, so that the foamed material is uniformly distributed in the annular filling cavity, and after foaming, the stability of the gradient distribution of different foamed structures in the composite pipe is improved. Then, spinning is performed to the target wall thickness, and finally, heating and foaming are performed, so that the foamed metal layer formed as the core layer of the composite pipe has different porosities due to different mass fractions of the foaming agent, and the multiple metal solid rods have different diameters and different radial distribution modes in the annular filling cavity. Therefore, the porosity of the foamed metal layer can be gradiently distributed between the metal inner pipe 2 and the metal outer pipe 1. When the multiple metal solid rods have at least two different diameters, the diameter of the multiple metal solid rods decreases layer by layer in the direction from the inner wall of the metal outer pipe 1 to the outer wall of the metal inner pipe 2. The larger the diameter, the larger the gap between adjacent metal solid rods. After internal spinning and foaming forming, the gap formed at the metal solid rod with a larger diameter is larger, and the porosity is higher. On the contrary, the smaller the diameter, the smaller the gap between adjacent metal solid rods. After internal spinning and foaming forming, the gap formed at the metal solid rod with a smaller diameter is smaller, and the porosity is lower. In combination with the gradually reduced mass fraction of the foaming agent filled from the outside to the inside, the porosity of the foamed metal layer decreases in steps along the radial direction from the inner wall of the metal outer pipe 1 to the outer wall of the metal inner pipe 2 (i.e., the porosity of the outer layer is higher, and the porosity of the inner layer is lower). The gradient damping composite pipe forms gradient interception of sound waves / vibration energy at different positions in the radial direction, so that the overall porosity in the annular filling cavity is large, avoiding the performance limitations of a single porosity structure. When the gradient damping composite pipe is subjected to external vibration, the higher porosity structure in the outer layer provides elastic buffering effect, and the metal solid rod as the skeleton of the porous structure provides support. Compared with the foamed metal layer formed by the metal solid rods with the same diameter and the foaming agent material with the same mass fraction, the problem of weak mechanical properties of a single porosity material in the composite pipe is avoided, so as to reduce the vibration amplitude of the sound waves / vibration transmitted to the inside of the pipe wall, and improve the sound absorption and damping performance of the gradient damping composite pipe.

[0078] When multiple solid metal rods have at least two different diameters, with smaller diameter rods distributed near the outer wall of the inner metal tube and near the inner wall of the outer metal tube, and larger diameter rods distributed circumferentially between the two layers of smaller diameter rods, the gradient vibration damping composite pipe constructs different functional layers at different radial positions. In the outer and inner layers near the foam metal layer, the smaller diameter of the solid metal rods results in smaller gaps between adjacent rods and less foam material is used. Multiple smaller diameter rods, acting as a supporting framework, provide good structural support and insulation. In the middle layer near the foam metal layer, the larger diameter of the solid metal rods results in smaller gaps between adjacent rods. Larger, larger-diameter solid metal rods provide structural support, while the larger gaps in the foam allow for more foaming material to be filled, providing ample expansion space for the foam. The porous structure disperses and absorbs some vibration energy. Combined with the gradual decrease in the mass fraction of the foaming agent from the outside to the inside, the porosity of the foam metal layer decreases radially from the inner wall of the outer metal tube to the outer wall of the inner metal tube, forming a gradient interception of sound wave / vibration energy. Compared to a foam metal layer formed with a solid metal rod of the same diameter and the same mass fraction of foaming agent, this avoids the problem of weak mechanical properties of materials with single porosity in composite pipes, ensuring a balance between the strength and vibration reduction and sound absorption performance of the gradient vibration damping composite pipe.

[0079] For example, such as Figure 2 As shown, three layers of solid metal rods are arranged radially within the annular filling cavity. From the outside to the inside, they are the first, second, and third layers of solid metal rods, with the diameter of the three layers decreasing sequentially from the outside to the inside. Each layer of solid metal rods is tightly arranged along the circumference, and the gaps between the same layers are filled with foaming material containing the same mass fraction of foaming agent. The mass fraction of foaming agent in the foaming material within the annular filling cavity decreases sequentially from the outside to the inside. Of course, two, four, or other layers of solid metal rods with different diameters can also be arranged radially within the annular filling cavity.

[0080] For example, such as Figure 3As shown, four layers of metal solid rods are arranged radially in the annular filling cavity, from outside to inside, they are the first layer of metal solid rods, the second layer of metal solid rods, the third layer of metal solid rods and the fourth layer of metal solid rods, the diameter of the first layer of metal solid rods is the same as that of the fourth layer of metal solid rods, the diameter of the second layer of metal solid rods is the same as that of the third layer of metal solid rods, and the diameter of the first layer of metal solid rods is smaller than that of the second layer of metal solid rods, each layer of metal solid rods is closely arranged along the circumference, and the mass fraction of the foaming agent of the foaming material in the gap between the metal solid rods of the same layer is the same, and the mass fraction of the foaming agent of the foaming material in the annular filling cavity decreases from outside to inside. Of course, two, three, five or more layers of metal solid rods with different diameters can also be arranged radially in the annular filling cavity.

[0081] Specifically, in the embodiment, the temperature for heating the fifth composite pipe blank is 650-1350℃, and the foaming time of the foaming material is 5-10min. For example, the temperature for heating the fifth composite pipe blank can be 650℃, 800℃, 950℃, 1000℃, 1200℃, 1350℃, etc., and the foaming time of the foaming material can be 5min, 6min, 8min, 10min, etc. Since the melting point of the metal powder in the foaming material is usually high, the foaming temperature greater than 650℃ can ensure that the metal material part reaches a molten or semi-molten state, the melt viscosity decreases to provide the flowability basis for the uniform dispersion and expansion of the bubbles, and the uniformity of the pores and the stability of the structure of the formed porous structure are ensured. When the foaming temperature is less than 1350℃, the risk of composition segregation and pore structure collapse of the foam metal layer material caused by excessive volatilization and decomposition of the metal melt at high temperature is avoided, and the uniformity of the pores and the stability of the structure of the formed porous structure are ensured. Preferably, when the foaming material is TiH2 and Al powder mixed uniformly at normal temperature and pressure and filled in the gap between the adjacent metal solid rods for cold extrusion, and the opening end of the annular filling cavity is blocked by the packaging plate, the packaging plate can be made of alloy steel, the foaming temperature of the foaming process is 650℃, and the foaming time is 10min; when the foaming material is SrCO3 and Fe powder mixed uniformly at normal temperature and pressure and filled in the gap between the adjacent metal solid rods for cold extrusion, and the opening end of the annular filling cavity is blocked by the packaging plate, the packaging plate can be made of alloy steel, the foaming temperature of the foaming process is 1350℃, and the foaming time is 5min. The operator can select different foaming temperature and foaming time according to the actual added foaming material, as long as the uniformity of the formed foam metal layer after foaming is ensured.

[0082] Specifically, in the embodiment, the metal solid rod is an iron rod or an aluminum rod; the packaging plate comprises metal and / or resin; the metal outer tube 1 and the metal inner tube 2 are both alloy steel tubes or aluminum alloy tubes. The material and diameter of the metal solid rod are selected according to the material and diameter of the embedded tube 3 in the first embodiment; the packaging plate, the metal outer tube 1 and the metal inner tube 2 are selected to meet the processing requirements of the gradient damping composite tube, and the packaging plate, the metal outer tube 1 and the metal inner tube 2 are described in the first embodiment, which will not be described in detail here.

[0083] Specifically, in the embodiment, the foaming agent in the foaming material is TiH2 with a mass fraction of 1% to 2%, and the metal powder is aluminum powder; or the foaming agent in the foaming material is SrCO3 with a mass fraction of 2% to 3%, and the metal powder is iron powder. Of course, the foaming material can also be mixed with other foaming agents and metal powders, which are not limited here.

[0084] Specifically, in the annular filling cavity, three layers of metal solid rods are arranged in the radial direction, from the outside to the inside, the first layer of metal solid rod, the second layer of metal solid rod and the third layer of metal solid rod, and the mass fraction of the foaming agent TiH2 in the gap between the three layers of metal solid rods is 2%, 1.5% and 1% from the outside to the inside along the radial direction of the annular filling cavity; or the mass fraction of the foaming agent SrCO3 in the gap between the three layers of metal solid rods is 3%, 2.5% and 2% from the outside to the inside along the radial direction of the annular filling cavity.

[0085] In the description of the above embodiments, specific features, structures, materials or characteristics can be combined in any one or more embodiments or examples in a suitable manner.

[0086] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto, any person skilled in the art can easily think of changes or replacements within the technical range disclosed by the present application, which should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A method of manufacturing a gradient-damping composite pipe, characterized by, The manufacturing method comprises the following steps: providing a metal outer tube, a metal inner tube and a plurality of inner embedded tubes; encapsulating foaming material in each of the inner embedded tubes, the foaming material comprising a foaming agent and metal powder, to obtain a plurality of inner embedded tubes with different mass fractions of foaming agent; arranging the plurality of inner embedded tubes in the annular gap formed by the metal outer tube and the metal inner tube in a close arrangement, so that the plurality of inner embedded tubes are distributed in the annular gap in a manner that the mass fraction of the foaming agent decreases layer by layer along the radial direction from the inner wall of the metal outer tube to the outer wall of the metal inner tube, to obtain a first composite tube blank; wherein the plurality of inner embedded tubes have at least two different diameters, and the diameters of the plurality of inner embedded tubes decrease layer by layer in the direction from the inner wall of the metal outer tube to the outer wall of the metal inner tube; or, the inner embedded tubes with smaller diameters are distributed close to the outer wall of the metal inner tube and close to the inner wall of the metal outer tube, and the inner embedded tubes with larger diameters are distributed between the two layers of inner embedded tubes with smaller diameters in the circumferential direction; using an encapsulation plate to seal the open end of the annular gap, to obtain a second composite tube blank; vacuumizing the plurality of inner embedded tubes after sealing; performing internal spinning processing on the second composite tube blank to a target wall thickness, to obtain a third composite tube blank; heating the third composite tube blank to make the foaming material foam, to obtain a gradient damping composite tube with a foamed metal layer, the porosity of the foamed metal layer decreasing in a stepped manner along the radial direction from the inner wall of the metal outer tube to the outer wall of the metal inner tube.

2. The manufacturing method of the gradient-damping composite pipe according to claim 1, characterized by, After arranging the plurality of inner embedded tubes in the annular gap formed by the metal outer tube and the metal inner tube in a close arrangement, and before using the encapsulation plate to cover the open end of the annular gap, the manufacturing method further comprises: filling metal chips into the gap between the outer walls of the plurality of inner embedded tubes.

3. The manufacturing method of the gradient-damping composite pipe according to claim 1 or 2, characterized by, The wall thickness of the inner embedded tube is 2mm-4mm, and the inner diameter of the inner embedded tube is 10mm-30mm.

4. The manufacturing method of the gradient-damping composite pipe according to claim 1, characterized by, The heating temperature of the third composite tube blank is 650℃-1350℃, and the foaming time of the foaming material is 5min-10min.

5. The manufacturing method of the gradient-damping composite pipe according to claim 1, characterized by, The encapsulation plate comprises metal and / or resin; The metal outer tube and the metal inner tube are both alloy steel tubes or aluminum alloy tubes; The inner embedded tube is one or more of iron tube, aluminum tube and stainless steel tube.

6. The method of manufacturing a gradient-damping composite pipe according to claim 1, wherein The foaming agent in the foaming material is TiH2 with a mass fraction of 1%-2%, and the metal powder is aluminum powder; Or, the foaming agent in the foaming material is SrCO3 with a mass fraction of 2%-3%, and the metal powder is iron powder.

7. A method of manufacturing a gradient-damping composite pipe, characterized by The manufacturing method comprises the following steps: providing a metal outer tube, a metal inner tube, a base and a plurality of metal solid rods, wherein one end of the metal outer tube and the metal inner tube is fixed by the base, and an annular filling cavity is formed between the metal outer tube, the metal inner tube and the base; The plurality of metal solid rods are arranged closely in the annular filling cavity; wherein the plurality of metal solid rods have at least two different diameters, and the diameters of the plurality of metal solid rods decrease layer by layer in the direction from the inner wall of the metal outer tube to the outer wall of the metal inner tube; or the metal solid rods with smaller diameters are distributed close to the outer wall of the metal inner tube and close to the inner wall of the metal outer tube, and the metal solid rods with larger diameters are distributed along the circumferential direction between the two layers of metal solid rods with smaller diameters; The foaming material with different mass fractions of foaming agent is filled in the gap between adjacent metal solid rods, and the foaming material comprises a foaming agent and a metal powder, so that the mass fraction of the foaming agent in the foaming material in the annular filling cavity decreases layer by layer in the radial direction from the inner wall of the metal outer tube to the outer wall of the metal inner tube; An encapsulation plate is used to block the open end of the annular filling cavity, to obtain a fourth composite pipe blank; The fourth composite pipe blank is subjected to internal spinning processing to a target wall thickness, to obtain a fifth composite pipe blank; The fifth composite pipe blank is heated, so that the foaming material foams to form a gradient damping composite pipe with a foamed metal layer, and the porosity of the foamed metal layer decreases in a stepped manner in the radial direction from the inner wall of the metal outer tube to the outer wall of the metal inner tube.

8. The manufacturing method of the gradient-damping composite pipe according to claim 7, characterized by, The diameter of the metal solid rod is 10 mm to 30 mm.

9. The manufacturing method of the gradient-damping composite pipe according to claim 7, characterized by, The heating temperature of the fifth composite pipe blank is 650 DEG C to 1350 DEG C, and the foaming time of the foaming material is 5 min to 10 min.

10. The method of manufacturing a gradient-damping composite pipe according to claim 7, wherein The metal solid rod is an iron rod or an aluminum rod; The encapsulation plate comprises metal and / or resin; The metal outer tube and the metal inner tube are both alloy steel tubes or aluminum alloy tubes.

11. The method of manufacturing a gradient-damping composite pipe according to claim 7, wherein The foaming agent in the foaming material is TiH2 with a mass fraction of 1% to 2%, and the metal powder is aluminum powder; Or, the foaming agent in the foaming material is SrCO3 with a mass fraction of 2% to 3%, and the metal powder is iron powder.

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