A device for differential control of extrusion cladding of heterogeneous metals and a method of use

Abstract

The present application relates to a kind of for heterogeneous metal differential regulation extrusion cladding device and method, belong to metal composite processing technical field, solve the uneven cladding layer thickness, interface bonding strength low and the problem of insufficient production efficiency in prior art due to heterogeneous metal plastic deformation ability difference.It comprises coaxially arranged extrusion head, extrusion cylinder, extrusion rod and ring track structure of extrusion ring rod, the extrusion ring rod can be assembled multiple metal cladding ring.The key is that extrusion rod and extrusion ring rod can move independently or cooperatively.The method comprises: counter-extrusion forming tubular blank, preheating cladding ring and loading into track, and differential propulsion is used to realize layered plastic cladding of cladding ring on the inner wall of pipe blank.The method can control the uniformity of cladding layer thickness within ±5.0%, interface bonding strength ≥200MPa, production efficiency is significantly improved, and is suitable for aerospace, electronic devices and other fields of high-performance composite pipe preparation.

Description

Technical Field

[0001] This invention relates to the field of metal composite material processing technology, and in particular to a differential speed controlled extrusion coating device for dissimilar metals and its usage method. Background Technology

[0002] Heterogeneous metal composite pipes are key materials in aerospace, electronics, and power industries. The core challenge in their fabrication lies in achieving a high-strength, uniform metallurgical bond between the dissimilar metals. Traditional techniques such as hot rolling and explosive welding suffer from poor interfacial bonding and low efficiency. While subsequent reverse extrusion coating technology has improved bonding strength, it still faces technical bottlenecks such as uneven coating thickness and interfacial defects when dealing with material combinations with significant differences in deformation resistance, such as steel-aluminum and steel-copper.

[0003] The root cause of the existing technical problems lies in the lack of effective flow control methods. In traditional single-bar extrusion, dissimilar metals are forced to deform synchronously, resulting in the cladding metal with low deformation resistance flowing too quickly, while the base metal with high deformation resistance flows lag behind. This flow mismatch not only causes fluctuations in cladding thickness but also creates shear stress concentration at the interface, leading to wrinkling or tearing of the cladding. Furthermore, fixed process parameters cannot adapt to the characteristics of different material combinations, further limiting the applicability of the technology.

[0004] Therefore, there is an urgent need for a new method that can actively coordinate the deformation behavior of heterogeneous metals, solve the flow mismatch problem through differential speed control mechanism, and achieve high-precision control of the coating thickness while ensuring the quality of interface bonding. Summary of the Invention

[0005] Based on the above analysis, the present invention aims to provide an apparatus and method for differential speed controlled extrusion coating of dissimilar metals, in order to solve at least one of the problems of uneven coating thickness and inconsistent substrate deformation in the prior art.

[0006] In a first aspect, the present invention provides a differential speed controlled extrusion coating device for dissimilar metals, comprising:

[0007] The extrusion cylinder has a hollow cylindrical structure. An extrusion head is coaxially fixedly connected to the first end of the extrusion cylinder, and the second end is an open end.

[0008] An extrusion rod is coaxially disposed at the second end of the extrusion cylinder and is movable along the axial direction of the extrusion cylinder; a reverse extrusion cavity is formed between the end face of the extrusion rod facing the extrusion head and the corresponding end face of the extrusion head for accommodating the metal billet;

[0009] An extrusion ring rod is coaxially sleeved on the outside of the extrusion rod and forms an axial relative movement engagement with the extrusion rod through a sliding pair; the outer surface of the extrusion ring rod is provided with an annular track structure for assembling at least two metal-clad rings;

[0010] When the extrusion rod moves axially, it pushes the metal billet to undergo reverse extrusion deformation within the cavity formed by the extrusion head and the extrusion cylinder, forming a tubular structure.

[0011] The extrusion ring rod can move independently or in conjunction with the extrusion rod, and drive the metal-clad ring to move differentially along the inner wall of the tubular structure through the annular track structure, thereby achieving gradient layering of heterogeneous metals.

[0012] Furthermore, the inner diameter of the metal-clad ring and the outer diameter of the extrusion ring rod form a transition fit.

[0013] Furthermore, the material of the metal-clad ring is selected from at least one of copper, copper alloy, nickel, nickel-based alloy, or aluminum; the configuration of the metal-clad ring includes:

[0014] (a) A single material arranged continuously; or

[0015] (b) Two or more materials are arranged alternately to form a layered structure, including combinations of copper-nickel-copper, copper-aluminum-copper, or nickel-aluminum-nickel.

[0016] Furthermore, the metal-clad ring is a ring of uniform thickness, with an axial width w of 5-15 mm for a single clad ring and an axial distance d of 2-8 mm between adjacent clad rings.

[0017] Furthermore, the total number n of the metal-clad rings satisfies: n≥L / (w+1), where L is the length of the metal billet forming section and w is the ring width.

[0018] Secondly, this invention proposes a method for differential speed controlled extrusion coating of heterogeneous metals, which utilizes the extrusion coating device described above and includes the following steps:

[0019] S1. The preheated metal billet is placed in the extrusion cylinder and formed into a tubular billet by the reverse extrusion of the extrusion rod;

[0020] S2. The preheated metal-coated rings are installed into the track structure of the extrusion ring rod;

[0021] S3. Drive the extrusion ring rod to advance along the axial direction of the tubular billet, so that multiple metal-clad rings contact the inner wall of the tubular billet in sequence; utilize the difference in plastic deformation resistance generated by the interaction between each cladding ring and the tubular billet to generate a dynamic velocity gradient for each cladding ring, thereby plastically cladding the inner wall of the tubular billet in sequence to form a layered cladding structure.

[0022] S4. After the coating is completed, the extrusion rod and extrusion ring rod are simultaneously withdrawn.

[0023] Furthermore, in S1, the metal billet is a steel billet, the preheating temperature of the metal billet is 900-1100℃, and the temperature drops to 700-800℃ after being reverse-extruded into a tubular billet.

[0024] Furthermore, in S2, the preheating temperature of multiple metal-clad rings is 300-500℃.

[0025] Furthermore, in S3, the pushing speed of the extrusion ring rod is 20-30 mm / s, and the actual forward speed of adjacent metal-clad rings decreases in a stepwise manner; the differential plastic deformation is achieved through the transmission of metal flow resistance: the first metal-clad ring that contacts the tubular billet slows down due to the resistance of plastic deformation, and the subsequent metal-clad rings slow down in turn due to the cumulative effect of the metal flow resistance of the preceding rings, forming a dynamic speed gradient.

[0026] Thirdly, the present invention proposes a heterogeneous metal composite pipe, which is prepared by the method described above. The pipe includes a steel tubular matrix and a multi-layer coating layer that is metallurgically bonded to the inner wall of the tubular matrix. The thickness uniformity deviation of the coating layer is within ±5.0%, and the interfacial strength of the metallurgical bond is ≥200MPa.

[0027] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0028] 1) By employing a multi-metal cladding ring design in conjunction with a cross-interface temperature difference of 200-500℃, a controllable temperature gradient and shear layer are formed during extrusion, resulting in a stable interfacial diffusion layer thickness of 5-15μm and a bonding strength ≥200MPa. Furthermore, through ring track assembly and dynamic speed matching, the coating layer thickness deviation is controlled within ±5.0%, with an axial uniformity exceeding 98%, fundamentally suppressing interfacial segregation and thickness fluctuations caused by differences in the plastic flow of dissimilar metals.

[0029] 2) Based on the synergy of dynamic velocity gradient and modular coating rings, the limitations of traditional single-layer coating are overcome. By flexibly adjusting the material sequence, spacing, and advance speed of the coating rings, composite structures with gradient components or multi-layer heterogeneity (such as multifunctional integration of conductive / thermal / corrosion resistant components) can be obtained in a single processing, greatly enriching product functions and expanding application areas.

[0030] 3) The differential deformation mechanism creates a gradient transition of fine grain structure from the interface to the interior of the coating layer. This unique structure improves the stress corrosion resistance of the composite pipe by 2-3 times, while maintaining more than 90% of the matrix's electrical and thermal conductivity, making it particularly suitable for demanding applications such as nuclear power and deep-sea oil and gas.

[0031] 4) A single continuous extrusion process can simultaneously complete pipe forming, multi-layer coating, and interface metallurgical bonding. Compared with traditional multi-pass processes, the process time is shortened and energy consumption is reduced, making it particularly suitable for the mass production of long pipes (L≥500mm). The split coating ring design makes material replacement convenient and allows for flexible adjustment of properties such as conductivity and strength to meet diverse industrial needs.

[0032] 5) The partitioned differential speed deformation strategy ensures that the first coating ring is formed at high speed, and the subsequent coating rings are formed at a reduced speed, avoiding shear damage to the already formed interface, significantly reducing the probability of defects such as interface cracks and inclusions, and ensuring the high stability of the preparation process and the high reliability of the product.

[0033] In this invention, the above-described technical solutions can be combined with each other to achieve more preferred combinations. Other features and advantages of this invention will be set forth in the following description, and some advantages may become apparent from the description or be learned by practicing the invention. The objects and other advantages of this invention can be realized and obtained from the description and drawings, which are particularly pointed out. Attached Figure Description

[0034] The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts.

[0035] Figure 1 This is a schematic diagram of the initial assembly state of the overall structure of the heterogeneous metal differential extrusion coating device of the present invention;

[0036] Figure 2 This is a schematic diagram of the coating process of the device of the present invention in operation.

[0037] Figure label:

[0038] 1-Extrusion head; 2-Metal billet; 3-Extrusion cylinder; 4-Extrusion rod; 5-Extrusion ring rod; 6-Metal-clad ring. Detailed Implementation

[0039] Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which form part of this application and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not intended to limit the scope of the present invention.

[0040] This invention provides a device and method for differential speed controlled extrusion coating of dissimilar metals, which solves the problems of uneven coating thickness, low interfacial bonding strength, and insufficient production efficiency caused by differences in the plastic deformation capacity of dissimilar metals in the prior art.

[0041] In a first aspect, the present invention provides a differential speed controlled extrusion coating device for dissimilar metals, comprising:

[0042] The extrusion cylinder has a hollow cylindrical structure. An extrusion head is coaxially fixedly connected to the first end of the extrusion cylinder, and the second end is an open end.

[0043] An extrusion rod is coaxially disposed at the second end of the extrusion cylinder and is movable along the axial direction of the extrusion cylinder; a reverse extrusion cavity is formed between the end face of the extrusion rod facing the extrusion head and the corresponding end face of the extrusion head for accommodating the metal billet;

[0044] An extrusion ring rod is coaxially sleeved on the outside of the extrusion rod and forms an axial relative movement engagement with the extrusion rod through a sliding pair; the outer surface of the extrusion ring rod is provided with an annular track structure for assembling at least two metal-clad rings;

[0045] like Figure 1 The diagram shown is a schematic representation of the initial assembly state of the overall structure of the heterogeneous metal differential extrusion coating device of the present invention. In the initial assembly state, the metal billet is located between the extrusion head and the extrusion rod, and the metal coating ring is assembled on the annular track structure of the extrusion ring rod.

[0046] When the extrusion rod moves axially, it pushes the metal billet to undergo reverse extrusion deformation within the cavity formed by the extrusion head and the extrusion cylinder, forming a tubular structure. The extrusion ring rod can move independently or in conjunction with the extrusion rod, and drives the metal-clad ring to move differentially along the inner wall of the tubular structure through the annular track structure, thereby achieving gradient layering of dissimilar metals.

[0047] Furthermore, the inner diameter of the metal-clad ring and the outer diameter of the extrusion ring rod form a transition fit.

[0048] like Figure 2 The diagram shows the coating process of the device of the present invention in operation. In operation, the extrusion rod moves axially, pushing the metal billet to undergo reverse extrusion deformation, forming a tubular structure. Simultaneously, the extrusion ring rod drives the metal coating ring to move differentially along the inner wall of the tubular structure via a ring track structure, achieving gradient layering coating of dissimilar metals.

[0049] Furthermore, the material of the metal-clad ring is selected from at least one of copper, copper alloy, nickel, nickel-based alloy, or aluminum; the configuration of the metal-clad ring includes:

[0050] (a) A single material arranged continuously; or

[0051] (b) Two or more materials are arranged alternately to form a layered structure, including combinations of copper-nickel-copper, copper-aluminum-copper, or nickel-aluminum-nickel.

[0052] Furthermore, the metal-clad ring is a ring of uniform thickness, with an axial width w of 5-15 mm for a single clad ring and an axial distance d of 2-8 mm between adjacent clad rings.

[0053] Furthermore, the total number n of the metal-clad rings satisfies: n≥L / (w+1), where L is the length of the metal billet forming section and w is the ring width.

[0054] When using the heterogeneous metal differential speed controlled extrusion coating device of the present invention, a steel tube blank preheated to 700-800°C is first placed as the metal billet in the reverse extrusion cavity formed between the extrusion head and the extrusion rod. At the same time, the metal coating ring for coating is controlled at a "soft but not melting" processing window of 300-500°C. Then, the extrusion rod is pushed forward at a uniform speed of 20-30 mm / s, causing the extrusion rod to move axially and push the metal billet to undergo reverse extrusion deformation in the closed cavity formed by the extrusion head and the extrusion cylinder, forming the desired tubular structure.

[0055] During this process, the extrusion ring rod can move independently or in conjunction with the extrusion rod. The movement of the extrusion ring rod is driven by a ring track structure on the outer surface of the extrusion ring rod, which drives the assembled metal-clad ring to move at a differential speed along the inner wall of the tubular structure. By controlling the speed difference between the extrusion ring rod and the extrusion rod, combined with the temperature difference between the two, the interfacial diffusion bonding and microstructure gradient control between the cladding layer and the matrix are achieved. This ensures both the uniformity of the cladding layer thickness and the formation of a continuous transition microstructure from fine grains to texture.

[0056] Furthermore, the inner diameter of the metal-clad ring and the outer diameter of the extrusion ring rod form a transition fit. This fit ensures assembly accuracy while effectively preventing circumferential movement under high pressure. After assembly, the outer surface of the clad ring protrudes approximately 1-3 mm, preferably 1.5-2 mm, from the outer surface of the extrusion ring rod. This protrusion is set based on the following mechanisms: 1) When the protrusion is less than 1 mm, the radial compressive stress of the clad ring on the metal blank is insufficient, leading to inadequate diffusion at the heterogeneous metal interface and reduced bonding strength; 2) When the protrusion exceeds 3 mm, stress concentration at the root of the clad ring can easily cause plastic deformation or even cracking failure of the ring body. Finite element thermo-mechanical coupling analysis shows that a protrusion range of 1-3 mm allows the cladding interface to achieve optimal contact pressure, promoting both plastic flow of the material to form mechanical interlocking and ensuring the structural integrity of the clad ring.

[0057] Furthermore, the metal-clad rings are made of at least one of copper, copper alloys, nickel, nickel-based alloys, or aluminum. The metal-clad rings can be arranged in a single material in a continuous arrangement, or in two or more materials (such as copper-nickel-copper, copper-aluminum-copper, nickel-aluminum-nickel, etc.) alternating to form a layered structure. Through the synergistic effect of material and structural design, the overall performance of the composite pipe is significantly improved.

[0058] Regarding material selection: Considering the specific requirements of different application scenarios for material performance, we selected the following materials:

[0059] Copper and copper alloys have excellent electrical and thermal conductivity, making them suitable for power transmission and electronic equipment.

[0060] Nickel and nickel-based alloys have excellent corrosion resistance and high-temperature stability, making them suitable for harsh environments such as chemical and aerospace industries.

[0061] Aluminum is lightweight and has good corrosion resistance, making it suitable for weight-sensitive applications.

[0062] In terms of structural configuration: This invention designs a variety of structural configurations to meet the specific requirements of material performance in different application scenarios, so as to achieve the best performance matching and technical effect.

[0063] A single material arranged in a continuous pattern is suitable for scenarios where high performance uniformity is required;

[0064] Multi-layered composite structures (such as copper-nickel-copper, copper-aluminum-copper, and nickel-aluminum-nickel) can achieve functional gradient distribution, meeting the multi-functional integration requirements of conductivity, barrier properties, lightweight, and corrosion resistance.

[0065] Based on the synergistic control of dynamic velocity gradient and modular coating ring, by adjusting the material sequence, spacing parameters and velocity gradient curve of the coating ring, the cumulative stacking of heterogeneous coating layers can be achieved to obtain a composite functional layered structure with gradient components or multi-layer heterogeneous characteristics, breaking through the limitations of traditional single-layer coating.

[0066] Furthermore, the metal-clad ring is a ring of uniform thickness, with an axial width w of 5-15 mm, preferably 8-12 mm, for a single clad ring. This width range has been verified through process testing to balance cladding efficiency and forming quality: a width less than 5 mm can easily lead to insufficient continuity of the cladding layer; a width greater than 15 mm can easily cause interlayer inclusions due to uneven material flow.

[0067] The axial spacing d between adjacent cladding rings is 2-8 mm, with 3-5 mm recommended. This spacing is designed based on the following: 1) When the spacing is less than 2 mm, the metal flow between adjacent rings easily interferes with each other, leading to fluctuations in the cladding layer thickness; 2) A spacing greater than 8 mm will reduce the utilization rate of the cladding material and may create unclad areas due to sluggish axial flow of the billet. This parameter combination is optimized through rheological simulation to ensure controllable stratification and stable metallurgical bonding of the cladding material during differential extrusion.

[0068] Meanwhile, the cross-section of the annular track is T-shaped, with a width of 12-18mm and a height of 8-12mm. It is used to assemble a covering ring with a thickness of 2-4mm, ensuring that the covering ring is stably assembled in the track and can slide smoothly along the track, thereby realizing differential layering of the covering ring on the inner wall of the tubular blank.

[0069] Furthermore, the total number n of the metal-coated rings should satisfy: n≥L / (w+1), where L is the length of the metal billet forming section and w is the ring width. This calculation formula is based on the following process optimization principles: 1) The denominator (w+1) is used to account for the need to reserve a 1mm dynamic compensation gap between adjacent coated rings to accommodate the radial expansion during metal flow; 2) Ensure that the coating ring coverage reaches over 90% to avoid uncoated axial discontinuities; 3) When L / (w+1) is a non-integer, rounding up ensures that the difference in metal overflow between each coated ring is controlled within ±5% at the maximum extrusion rate. Orthogonal experiments have verified that this calculation model can control the coating thickness difference within the range of 8-12μm, significantly improving coating uniformity.

[0070] Secondly, this invention proposes a method for differential speed controlled extrusion coating of heterogeneous metals, which utilizes the extrusion coating device described above and includes the following steps:

[0071] S1. The preheated metal billet is placed in the extrusion cylinder and formed into a tubular billet by the reverse extrusion of the extrusion rod;

[0072] S2. The preheated metal-coated rings are installed into the track structure of the extrusion ring rod;

[0073] S3. Drive the extrusion ring rod to advance along the axial direction of the tubular billet, so that multiple metal-clad rings contact the inner wall of the tubular billet in sequence; utilize the difference in plastic deformation resistance generated by the interaction between each cladding ring and the tubular billet to generate a dynamic velocity gradient for each cladding ring, thereby plastically cladding the inner wall of the tubular billet in sequence to form a layered cladding structure.

[0074] S4. After the coating is completed, the extrusion rod and extrusion ring rod are simultaneously withdrawn.

[0075] Furthermore, in S1, the metal billet is a steel billet, the preheating temperature of the steel billet is 900-1100℃, and the temperature drops to 700-800℃ after being reverse-extruded into a tubular billet.

[0076] Furthermore, in S2, the preheating temperature of multiple metal-clad rings is 300-500℃.

[0077] Furthermore, in S3, the pushing speed of the extrusion ring rod is 20-30 mm / s, and the actual forward speed of adjacent metal-clad rings decreases in a stepwise manner; the differential plastic deformation is achieved through the transmission of metal flow resistance: the first metal-clad ring that contacts the tubular billet slows down due to the resistance of plastic deformation, and the subsequent metal-clad rings slow down in turn due to the cumulative effect of the metal flow resistance of the preceding rings, forming a dynamic speed gradient.

[0078] Furthermore, in S1, the metal billet is a steel billet. During operation, the extrusion head, extrusion cylinder, and extrusion rod are preheated to 300-400°C and kept at that temperature; the steel billet is heated to 900-1100°C and then loaded into the preheated extrusion cylinder; the extrusion head remains stationary, and the extrusion rod is driven at a speed of 30-50 mm / s to perform reverse extrusion, so that the billet is formed into a tubular structure; the temperature of the formed tubular billet drops to 700-800°C.

[0079] Furthermore, in step S2, multiple metal-clad rings are preheated to 300-500°C and assembled at equal intervals onto the annular track structure of the extrusion ring rod. The metal-clad rings are made of at least one of copper, copper alloys, nickel, nickel-based alloys, or aluminum. This step aims to create a 200-500°C interfacial temperature difference between the clad rings and the tubular billet. This temperature difference forms a temperature gradient-driven shear layer at the extrusion interface, promoting atomic diffusion and suppressing the formation of brittle intermetallic phases.

[0080] The "equal-spacing" assembly of the metal cladding rings ensures uniform contact between each ring and the tubular billet during extrusion, achieving uniform plastic deformation. Equal-spacing assembly helps maintain the stress symmetry of the cladding rings, reducing the risk of localized deformation or breakage, which is crucial for ensuring the structural integrity and functional uniformity of the final product. Furthermore, uniform spacing helps create a uniform temperature and stress field, promoting uniform diffusion of metal atoms at the interface, optimizing the metallurgical bond between the cladding layer and the substrate, while controlling metal flow behavior, reducing material waste and product defects, and improving material utilization and product quality.

[0081] Furthermore, in S3, the pushing speed of the extrusion ring rod is 20-30 mm / s, and the actual deformation rate of adjacent metal-clad rings decreases in a stepwise manner.

[0082] The differential plastic deformation is achieved as follows: the first metal-clad ring to contact the tubular blank decelerates due to resistance, which is transmitted to subsequent rings through material continuity. Subsequent metal-clad rings decelerate sequentially due to obstruction by the preceding material, forming a dynamic velocity gradient. This process is similar to a multi-body linkage system, where the deceleration of the front-end unit triggers the gradual braking of the rear-end unit through the cumulative effect of resistance, ultimately establishing a stable deformation gradient field.

[0083] During the differential plastic deformation process, the deformation of the metal-clad rings decreases progressively along the axial direction: the first ring undergoes the maximum plastic deformation due to direct bearing of the extrusion pressure, and the deformation of subsequent rings decreases sequentially, forming a continuous gradient deformation sequence; this sequence, in conjunction with the interfacial temperature difference of 200-500℃, accelerates atomic diffusion under the drive of interfacial shear strain, achieving dense metallurgical bonding, with an interfacial strength not less than 85% of that of the pure metal base material.

[0084] During the extrusion process, the compensating retraction of the extrusion rod and the advancing of the extrusion ring rod are linked in real time, forming a dynamic speed match that both suppresses material accumulation and ensures uniform coating thickness. Combined with differential deformation and interfacial temperature difference, metallurgical bonding, precise layer thickness control, and gradient microstructure construction are achieved in a single continuous extrusion, avoiding the uneven local deformation of traditional processes. This results in composite pipes that possess both high interfacial strength and dimensional accuracy, making them particularly suitable for multi-layer coating of dissimilar metals requiring high strength and high dimensional accuracy.

[0085] The aforementioned "real-time linkage between the compensating retraction of the extrusion rod and the advancing of the extrusion ring rod" is achieved through the axial relative motion coordination formed by the sliding pair between the extrusion rod and the extrusion ring rod. This structural design allows the two to move independently or collaboratively in the axial direction. The compensating retraction of the extrusion rod is executed by an extrusion rod drive device (such as a hydraulic cylinder), while the advancing of the extrusion ring rod is driven by a ring track on the outer surface of the extrusion ring rod, which drives the metal-coated ring to move. The real-time linkage between the two achieves dynamic speed matching, effectively suppressing material accumulation and ensuring the uniformity of the coating layer.

[0086] Meanwhile, the high strain rate causes the first cladding ring to form a fine-grained structure with a grain size of 5-30 μm; as the strain rate gradient decreases, the cladding layer gradually transitions to a banded structure dominated by deformation texture. This gradient structure from fine to coarse grains gives the composite pipe both excellent interfacial bonding performance and resistance to stress corrosion.

[0087] After the S3 coating process is completed, the extrusion rod and extrusion ring rod are simultaneously withdrawn, the extrusion head is driven in the reverse direction to demold, the composite pipe is taken out and cooled naturally, and finally a heterogeneous metal composite pipe with a gradient coating layer is obtained.

[0088] Thirdly, the present invention proposes a heterogeneous metal composite pipe, which is prepared by the method described above. The pipe includes a steel tubular matrix and a multi-layer coating layer that is metallurgically bonded to the inner wall of the tubular matrix. The thickness uniformity deviation of the coating layer is within ±5.0%, and the interfacial strength of the metallurgical bond is ≥200MPa.

[0089] Here are some typical examples of structural composition:

[0090] Single-layer cladding structure: The inner wall of the steel tubular substrate is clad with a layer of copper or copper alloy. This structure utilizes the excellent electrical conductivity of copper and promotes atomic diffusion through the interfacial temperature difference during differential extrusion, achieving a high-strength metallurgical bond with the steel substrate, with an interfacial strength of not less than 200 MPa.

[0091] Double-layer cladding structure: The inner wall of the steel tubular substrate is sequentially clad with a nickel-based alloy layer and an aluminum layer. The nickel-based alloy layer achieves metallurgical bonding with the steel substrate, providing excellent corrosion resistance and high-temperature strength; the aluminum layer further bonds with the nickel-based alloy layer, giving the pipe lightweight properties and auxiliary corrosion resistance. The temperature difference at the interface between the two layers inhibits the formation of brittle intermetallic compounds, ensuring overall bonding strength.

[0092] Three-layer cladding structure: The inner wall of the steel tubular substrate is sequentially clad from the inside out with a copper layer, a nickel layer, and an aluminum layer (or the order can be adjusted according to requirements). The copper layer ensures excellent conductivity, the nickel layer provides a corrosion-resistant barrier, and the aluminum layer achieves lightweighting and surface protection. The layers are connected by metallurgical bonding, forming a functional gradient transition to meet the comprehensive performance requirements of materials under complex working conditions.

[0093] Multi-layer alternating cladding structure: The inner wall of a steel tubular substrate is alternately clad with copper and nickel layers, forming a multi-layer periodic structure. This structure, through the alternating arrangement of different metal layers, synergistically optimizes electrical conductivity, thermal conductivity, and corrosion resistance. The bonding strength between each layer is uniform, effectively inhibiting crack propagation and improving the service life of the material under alternating loads.

[0094] The composite pipe utilizes a differential-speed layered coating process to create a gradient transition interface structure. The bonding strength between each coating layer and between the coating layer and the substrate is ≥200MPa, and the thickness of the interface diffusion layer is 5-15μm. The multiple coating layers exhibit a functional gradient distribution along the radial direction of the pipe, allowing for the design of various material combinations such as copper / steel, aluminum / steel, and nickel / steel to achieve synergistic optimization of conductivity, corrosion resistance, and structural strength, depending on service requirements. The coating thickness uniformity deviation of this composite pipe is controlled within ±5.0%, and the axial uniformity exceeds 98%, making it particularly suitable for demanding applications such as oil and gas transportation and nuclear power heat exchangers.

[0095] In summary, this invention successfully achieves efficient and high-precision integrated forming of heterogeneous metal composite pipes through an innovative differential plastic deformation mechanism and modular cladding ring design. Compared to traditional processes, the method of this invention exhibits significant advantages in several key performance indicators: the interfacial bonding strength reaches over 200 MPa, the uniformity of the cladding layer thickness is controlled within ±5.0%, and precise control of the gradient microstructure from fine to coarse grains is achieved. In terms of process efficiency, the single-pass continuous forming method significantly improves production efficiency. Particularly noteworthy is the excellent adaptability of the method of this invention, with significantly improved resistance to stress corrosion as tested, and good scalability, supporting the combined application of various metal materials such as copper, aluminum, and nickel. These technological breakthroughs provide a reliable solution for the industrial application of high-performance composite pipes.

[0096] The present invention will be further described below with reference to the embodiments in conjunction with the specification, but the embodiments are only for the purpose of using the present invention and are not intended to limit the present invention.

[0097] Example 1-1

[0098] A differential speed controlled extrusion coating device for forming copper-steel composite pipes, comprising:

[0099] The extrusion cylinder is a hollow cylindrical structure. An extrusion head is coaxially fixedly connected to the first end of the extrusion cylinder, and the second end is an open end.

[0100] An extrusion rod is coaxially disposed at the second end of the extrusion cylinder and is movable along the axial direction of the extrusion cylinder; a reverse extrusion cavity is formed between the end face of the extrusion rod facing the extrusion head and the corresponding end face of the extrusion head for accommodating the metal billet;

[0101] The extrusion ring rod is coaxially sleeved on the outside of the extrusion rod and forms an axial relative motion engagement with the extrusion rod through a sliding pair; the outer surface of the extrusion ring rod is provided with an annular track structure, the cross-section of the annular track is T-shaped, the width of the annular track is 12mm and the height is 8mm, and it is used to assemble multiple copper-clad rings (ring width 10mm, spacing 4mm, thickness 2mm);

[0102] The inner diameter of the covering ring and the outer diameter of the extrusion ring rod form a transition fit to prevent circumferential movement.

[0103] The forming section length L = 60mm. According to the formula n≥L / (w+1)=60 / (10+1)≈5.45, we round it to 6, and actually use 6 rings.

[0104] Examples 1-2

[0105] A differential speed controlled extrusion coating device for forming copper-steel composite pipes differs from Embodiment 1-1 only in that: the forming section length L = 2500 mm and the number of coating rings n is 227. This device is designed for the special needs of ultra-long composite pipes and requires a high-rigidity support and guiding system to ensure the stability of the extrusion process.

[0106] Examples 1-3

[0107] A differential speed control extrusion coating device for forming copper-steel composite pipes differs from Embodiment 1-1 only in that the ring width is 15mm, the spacing is 8mm, and the forming section length L = 100mm. According to the formula n≥L / (w+1)=100 / (15+1)≈6.25, it is rounded to 7, and 7 rings are actually used.

[0108] Example 2-1

[0109] A differential extrusion coating method for copper-steel composite pipes, using the extrusion coating apparatus described in Examples 1-1, includes the following steps:

[0110] S1. After heating the 20# carbon structural steel billet to 1000℃, place it in an extrusion cylinder that has been preheated to 350℃; and perform reverse extrusion at a speed of 40mm / s through the extrusion rod to form a Φ80mm×5mm tubular billet, and the billet temperature drops to 700℃.

[0111] S2. After preheating 6 T2 copper-clad rings (10mm width, 85mm outer diameter, 65mm inner diameter) to 300℃, install them into the track structure of the extruded ring rod;

[0112] S3. Drive the extrusion ring rod to advance at a constant speed of 20mm / s, so that multiple metal-clad rings contact the inner wall of the tubular billet in sequence; utilize the difference in plastic deformation resistance generated by the interaction between each cladding ring and the tubular billet to generate a dynamic speed gradient for each cladding ring, thereby plastically cladding the inner wall of the tubular billet in sequence.

[0113] S4. After the coating is completed, the extrusion rod and extrusion ring rod are simultaneously removed to obtain the composite pipe.

[0114] Example 2-2

[0115] A differential extrusion coating method for copper-steel composite pipes differs from Example 2-1 only in that: in S1, the billet is heated to 900°C; it is then reverse-extruded at a speed of 50 mm / s by an extrusion rod to form a Φ76 mm × 4 mm tubular billet, and the billet temperature is reduced to 800°C. In S2, the outer diameter of the coating ring is 72 mm and the inner diameter is 62 mm.

[0116] Example 2-3

[0117] A differential extrusion coating method for copper-steel composite pipes differs from Example 2-1 only in that:

[0118] In S2, the track structure is installed into the extrusion ring rod after the covering ring is preheated to 500°C;

[0119] In S3, the compression ring rod advances at a constant speed of 30 mm / s.

[0120] Examples 2-4

[0121] A differential extrusion coating method for multi-layer composite pipes differs from Example 2-1 only in that: in S2, the coating rings are arranged sequentially from the inside out as a combination unit consisting of one copper ring (10mm wide), one nickel ring (10mm wide), and one copper ring (10mm wide), and a total of two such combination units are installed (a total of 6 rings). The nickel rings are preheated to 400°C, and the copper rings are preheated to 300°C before being installed sequentially.

[0122] Examples 2-5

[0123] A differential extrusion coating method for multi-layer composite pipes differs from Example 2-1 only in that: in S2, the coating rings are arranged in an alternating pattern of aluminum-copper-aluminum, totaling 9 rings (3 sets of sequences). The aluminum rings (material 6061) are 10mm wide and 85mm in outer diameter, preheated to 380℃; the copper rings (T2) are 8mm wide and 85mm in outer diameter, preheated to 300℃. The extrusion ring rods are then sequentially inserted into a track structure.

[0124] In S3, the drive compression ring rod advances at a constant speed of 25 mm / s.

[0125] Example 3-1

[0126] A heterogeneous metal composite pipe is prepared by the extrusion coating method of Example 2-1. The pipe includes a steel tubular substrate and multiple coating layers that are metallurgically bonded to the inner wall of the tubular substrate. The coating layers are metallurgically bonded to the substrate, with 6 layers and a total coating length of 60 mm. The total thickness of the copper layer is about 1.8 mm. The composite pipe has an outer diameter of Φ80 mm and a wall thickness of 5 mm. The entire pipe is formed in one step by differential extrusion coating of 20# steel and T2 copper.

[0127] Comparative Example 1-1

[0128] The only difference from Example 1-1 is that the axial width w of a single covering ring is 4mm, which results in insufficient strength of the ring structure and breakage during extrusion.

[0129] Comparative Examples 1-2

[0130] The only difference from Example 1-1 is that the axial spacing d between adjacent covering rings is 10mm, resulting in uncovered areas in the covering layer.

[0131] Comparative Examples 1-3

[0132] The only difference from Example 1-1 is that after assembly, the outer surface protrudes 0.5mm from the outer surface of the extrusion ring rod, causing the copper ring to undergo excessive upsetting rather than normal extension deformation in the early stage of advancement, resulting in continuous pores at the interface.

[0133] Comparative Example 2-1

[0134] Metal composite pipes are prepared using the traditional hot rolling composite method.

[0135] Comparative Example 2-2

[0136] The same type of composite pipe is prepared using the traditional explosive composite process.

[0137] The characterization results are summarized in Table 1:

[0138] Table 1 Performance Characterization Results of Composite Pipes

[0139]

[0140]

[0141] As shown in Table 1, the composite pipe prepared by the method of this invention is significantly superior to the traditional and defective comparative examples in terms of interfacial bonding strength and coating uniformity: the interfacial strength is stable at 200-235 MPa, and the coating thickness deviation is only ±3.0-5.0%; while traditional hot rolling and explosive bonding can reach 95-190 MPa, the deviation is still as high as ±7.5-12.5%, and is accompanied by edge cracks or ripple defects. If the structure / assembly parameters of the coating ring deviate from the design of this invention, ring breakage, local exposure or large-area pores will occur, the strength will drop sharply or even it will be impossible to form.

[0142] In summary, this invention, through formulaic ring number control and differential extrusion process, can achieve the preparation of heterogeneous composite pipes with one-time forming, high bonding strength and uniform thickness.

[0143] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A device for differential speed controlled extrusion coating of dissimilar metals, characterized in that, include: The extrusion cylinder (3) is a hollow cylindrical structure. The first end of the extrusion cylinder is coaxially fixedly connected to the extrusion head (1), and the second end is an open end. The extrusion rod (4) is coaxially disposed at the second end of the extrusion cylinder (3) and is movable along the axial direction of the extrusion cylinder (3); the end face of the extrusion rod (4) facing the extrusion head (1) and the corresponding end face of the extrusion head (1) form a reverse extrusion cavity for accommodating the metal billet (2); The extrusion ring rod (5) is coaxially sleeved on the outside of the extrusion rod (4) and forms an axial relative motion cooperation with the extrusion rod (4) through a sliding pair; the outer surface of the extrusion ring rod (5) is provided with an annular track structure for assembling at least two metal-clad rings (6); When the extrusion rod (4) moves axially, it pushes the metal billet (2) to undergo reverse extrusion deformation in the cavity formed by the extrusion head (1) and the extrusion cylinder (3) to form a tubular structure; The extrusion ring rod (5) can move independently or in conjunction with the extrusion rod (4), and drive the metal-clad ring (6) to move at a differential speed along the inner wall of the tubular structure through the annular track structure, thereby realizing the gradient layering of heterogeneous metals.

2. The extrusion coating device according to claim 1, characterized in that, The inner diameter of the metal-clad ring and the outer diameter of the extrusion ring rod (5) form a transition fit.

3. The extrusion coating device according to claim 2, characterized in that: The metal-clad ring (6) is made of at least one of copper, copper alloy, nickel, nickel-based alloy or aluminum; The metal-clad ring (6) can be configured in the following ways: (a) A single material arranged continuously; or (b) Two or more materials are arranged alternately to form a layered structure, including combinations of copper-nickel-copper, copper-aluminum-copper, or nickel-aluminum-nickel.

4. The extrusion coating device according to claim 3, characterized in that, The metal-clad ring (6) is a ring of uniform thickness, with an axial width w of 5-15 mm for a single clad ring and an axial distance d of 2-8 mm between adjacent clad rings.

5. The extrusion coating device according to claim 4, characterized in that, The total number n of the metal-clad rings satisfies: n≥L / (w+1), where L is the length of the metal billet forming section and w is the ring width.

6. A method for differential speed controlled extrusion coating of heterogeneous metals, characterized in that, This method utilizes the extrusion coating apparatus according to any one of claims 1-5 and includes the following steps: S1. The preheated metal billet (2) is placed in the extrusion cylinder (3) and a tubular billet is formed by the reverse extrusion of the extrusion rod (4); S2. The preheated metal-coated rings are inserted into the track structure of the extrusion ring rod (5); S3. Drive the extrusion ring rod (5) to advance along the axial direction of the tubular billet, so that multiple metal-clad rings (6) contact the inner wall of the tubular billet in sequence; utilize the difference in plastic deformation resistance generated by the interaction between each cladding ring and the billet to generate a dynamic velocity gradient for each cladding ring, thereby plastically cladding the inner wall of the tubular billet in sequence to form a layered cladding structure. S4. After the coating is completed, the extrusion rod (4) and extrusion ring rod (5) are simultaneously withdrawn.

7. The method according to claim 6, characterized in that, In S1, the metal billet is a steel billet, the preheating temperature of the steel billet is 900-1100℃, and the temperature drops to 700-800℃ after being reverse-extruded into a tubular billet.

8. The method according to claim 6, characterized in that, In S2, the preheating temperature of multiple metal-clad rings is 300-500℃.

9. The method according to claim 6, characterized in that, In S3, the pushing speed of the extrusion ring rod (5) is 20-30 mm / s, and the actual forward speed of adjacent metal-clad rings decreases in a stepwise manner; the differential plastic deformation is achieved through the transmission of metal flow resistance: the first metal-clad ring that contacts the tubular blank slows down due to the plastic deformation resistance, and the subsequent metal-clad rings slow down in turn due to the cumulative effect of the metal flow resistance of the preceding rings, forming a dynamic speed gradient.

10. A heterogeneous metal composite pipe, characterized in that, Prepared by the method according to any one of claims 6-9, the pipe includes a steel tubular substrate and a multi-layer coating layer that is metallurgically bonded to the inner wall of the tubular substrate, wherein the thickness uniformity deviation of the coating layer is within ±5.0%, and the interfacial strength of the metallurgical bond is ≥200MPa.

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