An integrated method for interfacial metallurgical bonding and temperature-controlled rolling of composite layer steel pipes

Abstract

This invention discloses an integrated method for interfacial metallurgical bonding and temperature-controlled rolling of composite steel pipes. The method includes composite billet pretreatment, pre-placement of a Ni-Cu-Ti composite alloy gradient transition metallurgical induction layer at the interface, billet pre-clamping and positioning, gradient temperature-controlled preheating, interfacial self-induction metallurgical bonding, synchronous temperature-controlled rolling, interfacial metallurgical strengthening rolling, gradient cooling shaping, and finished product inspection and finishing. This invention achieves atomic-level fusion of the interface through the synergistic effect of the induction layer and self-induction metallurgical bonding. It simultaneously strengthens the interface and calibrates dimensions through fluctuating rolling force, solving the pain points of poor interfacial bonding and process disconnect in existing technologies. Unexpectedly, it achieves effects such as self-release of interfacial stress and improved billet toughness, thereby enhancing the quality and service stability of composite steel pipes and adapting them to harsh working conditions.

Description

Technical Field

[0001] This invention belongs to the field of steel pipe production technology, and particularly relates to an integrated method for metallurgical bonding of composite layer steel pipe interface and temperature-controlled rolling. Background Technology

[0002] Composite-layer steel pipes, due to the complementary properties of their inner and outer layers, are widely used in petroleum, chemical, and power industries. Their core performance depends on the bonding quality of the inner and outer layer interfaces and the overall forming precision. Currently, the preparation of composite-layer steel pipes mostly adopts a step-by-step operation mode of "interface treatment - metallurgical bonding - rolling forming," which has many technical bottlenecks.

[0003] In existing technologies, interfacial metallurgical bonding largely relies on passive atomic diffusion after high-temperature heating, lacking an active induction mechanism. This leads to the easy formation of brittle intermetallic compounds at the interface, resulting in low bonding strength, poor stability, and a tendency for interfacial delamination failure. Furthermore, interface treatment is limited to simple grinding and degreasing, without the establishment of dedicated metallurgical compatibility induction structures, further exacerbating interfacial bonding defects. In addition, existing methods treat metallurgical bonding and temperature-controlled rolling as independent processes, and temperature field fluctuations during their integration can lead to unstable interfacial bonding. Moreover, the rolling process cannot strengthen the already formed metallurgical interface, making it difficult to balance bonding strength and forming accuracy.

[0004] In addition, in the existing rolling process, the cooling process mostly adopts uniform cooling or non-gradient cooling, which easily causes thermal stress between the inner and outer layers of the composite steel pipe, leading to interface cracking; the clamping and positioning device lacks targeted design, which can easily damage the surface of the billet or affect the interface bonding effect, further restricting the finished product quality and production efficiency of the composite layer steel pipe. Summary of the Invention

[0005] The purpose of this invention is to provide an integrated method for metallurgical bonding and temperature-controlled rolling of composite layer steel pipe interfaces to solve the problems mentioned in the background art.

[0006] In view of this, the present invention provides an integrated method for metallurgical bonding and temperature-controlled rolling of composite layer steel pipe interfaces, comprising the following steps: S1. Pretreatment of composite tube blank: Select inner tube and outer tube, grind and degrease the joint surface of the two to remove oxide layer and impurities, and coaxially fit the inner tube into the outer tube to obtain the initial composite tube blank; S2. Pre-formed metallurgical induction layer at the interface: A metallurgical induction layer compatible with both inner and outer tubes is pre-formed on the pre-treated bonding surface to induce inter-diffusion of interfacial atoms and suppress the formation of brittle intermetallic compounds. S3. Pre-clamping and positioning of billet: The initial composite tube billet is placed in a special clamping device to achieve precise axial and radial positioning and clamping, preventing relative displacement of the inner and outer tube layers during rolling. S4. Gradient temperature control preheating: The composite tube blank is preheated by zoned induction heating to form a gradient temperature field from the inside to the outside, so that the metallurgical induction layer reaches the activation temperature first, and the inner and outer tube layers rise to the plastic deformation temperature simultaneously. S5. Interface self-induction metallurgical bonding: Maintaining the stability of the gradient temperature field, guiding the in-situ interdiffusion of atoms at the bonding surface, forming a continuous metallurgical bonding interface without brittle phases. S6. Synchronous temperature-controlled rolling: After the metallurgical bonding is completed, continuous rolling is carried out simultaneously, and the temperature field and rolling parameters are dynamically matched to realize the simultaneous metallurgical bonding and rolling forming. S7. Interface metallurgical strengthening rolling: The bonding interface is activated twice by the periodic fluctuation of rolling force, which strengthens the bonding strength and completes the dimensional calibration. S8. Gradient cooling and shaping: The composite steel pipe is cooled by a reverse gradient cooling method to avoid thermal stress at the interface that could lead to bonding failure. S9. Finished Product Inspection and Finishing: The composite steel pipe is inspected for interface bonding strength and dimensional accuracy. Unqualified parts are repaired to obtain the finished product.

[0007] In a further embodiment of the present invention, in step S2, a metallurgical induction layer is pre-formed using plasma in-situ deposition. During the deposition process, the bonding surface is kept at a constant temperature to ensure that the metallurgical induction layer is tightly bonded to the bonding surface without pores or inclusions. The metallurgical induction layer adopts a multi-layer composite structure, and each layer is metallurgically compatible with the inner and outer tubes. Furthermore, the composition of the metallurgical induction layer transitions in a gradient from one side of the bonding surface to the other, promoting interdiffusion of interfacial atoms and inhibiting the formation of brittle intermetallic compounds.

[0008] In a further embodiment of the present invention, in step S3, the special clamping device includes an axial positioning mechanism and a radial clamping mechanism. The axial positioning mechanism limits the two ends of the composite tube blank, and the radial clamping mechanism adopts a flexible clamping method to fit the outer surface of the composite tube blank, so as to avoid damage to the surface of the tube blank and the pre-placed metallurgical induction layer during the clamping process.

[0009] In a further embodiment of the present invention, in step S4, the partitioned induction heating adopts independent control of inner and outer dual coils. The inner coil corresponds to the heating of the inner tube, and the outer coil corresponds to the heating of the outer tube. By adjusting the coil power differently, a gradient temperature distribution from the inside to the outside of the composite tube blank is achieved, ensuring that the activation temperature of the metallurgical induction layer is lower than the plastic deformation temperature of the inner and outer tubes.

[0010] In a further embodiment of the present invention, in step S5, during the interface self-sensing metallurgical bonding process, the composite tube blank is kept stationary, and the interface temperature and atomic diffusion state are continuously monitored until a continuous metallurgical bonding layer is formed at the interface, ensuring that the bonding layer is free from fracture and brittle phase precipitation.

[0011] In a further embodiment of the present invention, in step S6, the synchronous temperature-controlled rolling adopts multi-pass continuous rolling. After each pass of rolling, the interface temperature of the composite tube blank is detected, and the induction heating power is adjusted according to the detection results to keep the interface temperature within the metallurgical bonding stable range. At the same time, the rolling speed is adjusted to ensure that the rolling forming and metallurgical bonding are carried out synchronously without any disconnection.

[0012] In a further embodiment of the present invention, in step S7, the periodic fluctuation of the rolling force is controlled by pulse, and the fluctuation frequency is matched with the atomic diffusion frequency of the interface. The fluctuation rolling force causes micro-plastic deformation at the interface of the composite tube blank, breaks the atomic diffusion barrier, promotes inter-diffusion of atoms at the interface, and at the same time calibrates the outer diameter and wall thickness of the composite steel pipe to ensure that the dimensional accuracy meets the requirements.

[0013] In a further embodiment of the present invention, in step S8, the gradient cooling and shaping adopts a segmented cooling method. First, the outer layer of the composite steel pipe is cooled to the set temperature and kept at a constant temperature for a period of time. Then, the middle layer and inner layer are gradually cooled. During the cooling process, the interface thermal stress is monitored in real time to avoid thermal stress concentration that could lead to interface cracking.

[0014] In a further embodiment of the present invention, in step S9, the interface bonding strength test adopts a combination of shear strength test and metallographic analysis, the dimensional accuracy test includes outer diameter, wall thickness and roundness test, and the finishing process adopts local grinding and re-rolling methods to avoid damaging the formed metallurgical bonding interface.

[0015] In a further embodiment of the present invention, in step S2, the in-situ deposition method is plasma in-situ deposition, and the bonding surface is kept at a constant temperature during the deposition process to ensure that the metallurgical induced layer is tightly bonded to the bonding surface without pores or inclusions.

[0016] The beneficial effects of this invention are: 1. By combining step S2, "interface pre-placement of metallurgical induction layer," and step S5, "interface self-induced metallurgical bonding," the limitations of existing passive atomic diffusion are overcome. The metallurgical induction layer achieves metallurgical compatibility with both the inner and outer tube layers, actively guiding in-situ interdiffusion of atoms at the bonding surface. Simultaneously, its own compositional characteristics suppress the formation of brittle intermetallic compounds. Combined with stable control of the gradient temperature field, this results in more complete and uniform atomic diffusion at the interface, ultimately forming a continuous, dense, non-porous, and brittle-phase-free metallurgical bonding interface. Compared to existing passive metallurgical bonding without an induction mechanism, the interface bonding strength of this invention effectively avoids failures such as peeling and cracking caused by interface bonding defects during the service life of composite steel pipes, significantly improving the stability and reliability of the interface bonding.

[0017] 2. Achieving integrated and coordinated control of metallurgical bonding and rolling forming significantly improves production efficiency and finished product dimensional accuracy, solving the problems of fragmented and poorly connected processes in the existing technology: Unlike the existing model of "metallurgical bonding and rolling forming being carried out in separate steps", step S4 "gradient temperature control preheating" lays the foundation for subsequent coordinated operations, allowing the metallurgical induction layer to reach the activation temperature first, and the inner and outer tubes to rise to the plastic deformation temperature simultaneously. Then, through step S6 "synchronous temperature control rolling", continuous rolling is carried out simultaneously while the interface metallurgical bonding is completed. The gradient temperature field and rolling speed, rolling direction and other parameters are matched in real time and dynamically, avoiding the problem of unstable interface bonding caused by temperature field fluctuations during process connection in the existing technology. Meanwhile, step S7, "interface metallurgical strengthening rolling," reactivates the formed metallurgical interface through the periodic fluctuation of rolling force, breaks the atomic diffusion barrier, and promotes further interdiffusion of interfacial atoms. While strengthening the interfacial bonding strength, it simultaneously completes the calibration of dimensions such as the outer diameter and wall thickness of the composite steel pipe. This not only eliminates the cumbersome step-by-step operation process and improves production efficiency, but also effectively ensures the dimensional accuracy of the finished product, keeping the dimensional deviation within the lower limit of the industry standard allowable range, thus balancing production efficiency and product quality.

[0018] 3. Step S8, "Gradient Cooling and Shaping," employs a gradient cooling method that reverses the preheating stage, gradually cooling from the outer layer to the inner layer. This effectively alleviates the thermal stress caused by the inconsistent cooling rates between the inner and outer layers of the composite steel pipe, preventing interface cracking due to thermal stress concentration. Step S3, "Bill Pre-clamping and Positioning," uses a dedicated flexible clamping device to achieve precise axial and radial positioning. This prevents relative displacement between the inner and outer layers during rolling and avoids damage to the billet surface and the pre-placed metallurgical induction layer during clamping, providing a stable foundation for interfacial metallurgical bonding. Step S9, "Finished Product Inspection and Finishing," combines shear strength testing with metallographic analysis to accurately detect the interfacial bonding quality. Combined with local grinding and re-rolling finishing methods, this effectively reduces the generation of defective products without damaging the metallurgical bonding interface, increasing the finished product qualification rate and significantly extending the service life of the composite steel pipe. This enables it to adapt to harsh industrial applications such as petroleum and chemical industries, enhancing the product's market competitiveness. Attached Figure Description

[0019] Figure 1 This is a flowchart of the method steps of the present invention. Detailed Implementation

[0020] The technical solutions of the embodiments of this application will be clearly described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application are within the scope of protection of this application.

[0021] In the description of this application, it should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. For ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following drawings denote similar items; therefore, once an item is defined in one drawing, it need not be further discussed in subsequent drawings.

[0022] It should be noted that the terms "first," "second," etc., used in the specification and claims of this application are used to distinguish similar objects and not to describe a specific order or sequence. It should be understood that such use of data can be interchanged where appropriate so that embodiments of this application can be implemented in orders other than those illustrated or described herein, and the objects distinguished by "first," "second," etc., are generally of the same class and are not limited in number; for example, a first object can be one or more. Furthermore, in the specification and claims, "and / or" indicates at least one of the connected objects, and the character " / " generally indicates that the preceding and following objects are in an "or" relationship.

[0023] It should be noted that in the description of this application, the directional terms such as "front, back, up, down, left, right", "horizontal, vertical, horizontal" and "top, bottom" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description. Unless otherwise stated, these directional terms do not indicate or imply that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on the scope of protection of this application. The directional terms "inner" and "outer" refer to the inner and outer contours relative to the outline of each component itself.

[0024] It should be noted that, in this application, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element. Furthermore, it should be noted that the scope of the methods and apparatuses in the embodiments of this application is not limited to performing functions in the order shown or discussed, but may also include performing functions substantially simultaneously or in the reverse order, depending on the functions involved. For example, the described methods may be performed in a different order than described, and various steps may be added, omitted, or combined. Additionally, features described with reference to certain examples may be combined in other examples.

[0025] This embodiment provides an integrated method for metallurgical bonding and temperature-controlled rolling of composite layer steel pipe interfaces, including the following steps: S1. Pre-treatment of Composite Tube Billet: Select inner and outer tubes. Based on the expected service scenarios and performance requirements of the composite steel pipe, rationally select suitable inner and outer tube materials to ensure complementary material properties and basic metallurgical compatibility. The mating surfaces of the two tubes are finely ground and degreased. The grinding process uses a step-by-step grinding technique to remove oxide layers, rust, oil, and various impurities from the mating surfaces, resulting in a uniform and rough surface morphology, improving the contact area and bonding stability for subsequent metallurgical bonding. The degreasing process uses an environmentally friendly degreasing agent, involving immersion and ultrasonic cleaning at room temperature to thoroughly remove residual oil and grinding debris from the mating surfaces, preventing impurities from adversely affecting the interfacial metallurgical bonding. After pre-treatment, a dedicated coaxial positioning device is used to precisely fit the inner tube inside the outer tube, ensuring that the axes of the inner and outer tubes coincide without any offset or tilting, ultimately obtaining a structurally regular and precisely positioned initial composite tube billet. This step, through meticulous pretreatment, lays a clean and stable foundation for subsequent interfacial metallurgical bonding, effectively avoiding interfacial bonding defects caused by incomplete pretreatment, and improving the success rate and stability of subsequent metallurgical bonding.

[0026] S2. Pre-formed metallurgical induction layer at the interface: A metallurgical induction layer that can achieve good metallurgical compatibility with both the inner and outer tubes is pre-formed on the outer surface of the pre-treated inner tube or the inner surface of the outer tube. The metallurgical induction layer is specifically a Ni-Cu-Ti composite alloy layer with a mass ratio of Ni:Cu:Ti=60-70:20-25:5-10 (suitable for most carbon steel and alloy steel composite tube blanks); Alternative scheme (suitable for composite tubes of special materials): Ti-Al-V composite alloy layer with a mass ratio of Ti:Al:V=85-90:5-8:2-5. The function of this metallurgical induction layer is to actively induce interfacial atomic interdiffusion and effectively inhibit the formation of brittle intermetallic compounds, breaking the limitation of existing interfacial metallurgical bonding that relies on passive atomic diffusion. Compared to existing interface treatment methods that do not incorporate any induction structures, this metallurgical induction layer can significantly reduce the energy barrier for interfacial atomic diffusion, promote rapid and uniform diffusion of atoms at the interface between inner and outer tubes, and simultaneously prevent the nucleation and growth of brittle intermetallic compounds through its own composition regulation. This fundamentally improves the quality of interfacial metallurgical bonding and avoids problems such as insufficient bonding strength and easy peeling caused by the presence of brittle phases, providing key support for subsequent self-induction metallurgical bonding of the interface.

[0027] S3. Billet Pre-clamping and Positioning: The initial composite billet after the pre-formed metallurgical induction layer is placed in a dedicated clamping device. This device achieves precise axial and radial positioning and secure clamping of the composite billet, ensuring no relative displacement or loosening between the inner and outer tubes throughout the subsequent gradient temperature-controlled preheating and synchronous temperature-controlled rolling processes. Existing clamping and positioning devices lack specificity, easily leading to billet misalignment and damage, thus affecting the interfacial metallurgical bonding effect. Through precise positioning and clamping, the structural stability of the composite billet is guaranteed in each process, ensuring the uniform distribution of the gradient temperature field, the consistency of interfacial atomic diffusion, and the precision of rolling, providing a stable structural guarantee for the smooth progress of the integrated process.

[0028] S4. Gradient Temperature Controlled Preheating: A zoned induction heating method is used to uniformly preheat the initial composite tube blank. Through precise control of heating parameters, a stable gradient temperature field is formed from the inside to the outside of the composite tube blank. The core requirement is to ensure that the metallurgical induction layer reaches the atomic diffusion activation temperature first, while simultaneously raising the inner and outer tubes to a suitable plastic deformation temperature range, with the temperature difference between them controlled within a reasonable range. This step differs from the single-temperature heating method in existing technologies. The gradient temperature field design ensures that the metallurgical induction layer is fully activated, actively guiding inter-atomic diffusion at the interface and creating optimal temperature conditions for self-induction metallurgical bonding at the interface. It also avoids thermal stress caused by inconsistent heating rates and excessive temperature differences between the inner and outer tubes, preventing tube blank deformation or initial cracks at the interface. Furthermore, it provides suitable plastic conditions for subsequent synchronous temperature-controlled rolling, achieving precise connection between the preheating process and subsequent metallurgical bonding and rolling forming processes.

[0029] S5. Interface Self-Induction Metallurgical Bonding: Under the premise of maintaining a stable gradient temperature field, the activation effect of the metallurgical induction layer is fully utilized to guide the in-situ interdiffusion of atoms at the interface between the inner and outer tubes. This allows the atoms of the inner and outer tubes to penetrate and fuse at the interface, ultimately forming a continuous, dense metallurgical bonding interface free of brittle phases, thus completely completing the interface metallurgical bonding process. This breaks through the limitations of existing technologies where interface metallurgical bonding passively relies on high-temperature heating and lacks an active induction mechanism. Through the synergistic effect of the metallurgical induction layer and the gradient temperature field, the diffusion of atoms at the interface is more complete and uniform, effectively avoiding defects such as porosity, inclusions, and brittle phase precipitation that are prone to occur at the interface in existing technologies. This significantly improves the strength and stability of the interface metallurgical bonding, providing a core guarantee for the overall performance of the composite layer steel pipe.

[0030] S6. Synchronous Temperature-Controlled Rolling: Simultaneously with the completion of interfacial metallurgical bonding, the composite billet is immediately subjected to continuous rolling. During rolling, changes in the gradient temperature field are monitored in real time. Based on the real-time state of the interfacial metallurgical bonding, key rolling parameters such as rolling speed, rolling direction, and rolling force are dynamically adjusted to achieve synchronous and coordinated control of interfacial metallurgical bonding and rolling forming. This solves the technical problems of existing technologies where metallurgical bonding and rolling forming are performed step-by-step, resulting in poor process connections, large temperature field fluctuations, unstable interfacial bonding, and low forming accuracy. Synchronous operation not only eliminates the cumbersome process of step-by-step operations, significantly improving production efficiency, but also ensures the stability of the interfacial metallurgical bonding state during rolling, avoiding secondary damage to the interface caused by process connections, and achieving a dual improvement in bonding quality and forming accuracy.

[0031] S7. Interface Metallurgical Strengthening Rolling: During synchronous temperature-controlled rolling, periodic fluctuations in rolling force are achieved through specialized rolling equipment. These fluctuations are used to reactivate the already formed metallurgical interface, breaking down the barriers to interatomic diffusion and promoting further interdiffusion and fusion of interatomic atoms, thereby strengthening the interatomic metallurgical bond strength. Simultaneously, through precise control of the rolling force, the outer diameter, wall thickness, and other dimensions of the composite tube blank are calibrated to ensure that the dimensional accuracy of the composite steel pipe meets design requirements. In existing technologies, rolling is only used for forming and cannot strengthen the interatomic bond strength. However, this step, through the design of periodic fluctuations in rolling force, achieves the integration of "strengthening the interatomic bond + dimensional calibration," which not only further improves the interatomic bond strength but also ensures the dimensional accuracy of the finished product, effectively solving the pain points of insufficient interatomic bond strength and large dimensional deviations in existing technologies for composite steel pipes.

[0032] S8. Gradient Cooling and Shaping: After rolling, the composite steel pipe is slowly cooled using a gradient cooling method that is the reverse of the preheating stage. This involves gradually cooling from the outer layer to the inner layer, with precise control of cooling parameters to regulate the cooling rate of each layer. This ensures uniform and synchronous cooling of the inner and outer layers, preventing thermal stress caused by excessive temperature differences during cooling. This, in turn, prevents cracking and peeling at the interface due to concentrated thermal stress. Unlike existing technologies that use uniform cooling or no gradient cooling, the reverse gradient cooling design effectively releases internal thermal stress in the composite steel pipe, ensuring the stability of the metallurgical interface. It also prevents deformation of the billet due to thermal stress, ensuring the regularity of the composite steel pipe's shape and dimensional stability, thus guaranteeing the quality of the finished product.

[0033] S9. Finished Product Inspection and Finishing: A comprehensive quality inspection is conducted on the composite steel pipes after cooling and shaping, focusing on two core indicators: interfacial bonding strength and dimensional accuracy. Interfacial bonding strength testing combines shear strength testing and metallographic analysis, accurately quantifying the bonding strength and visually observing the microscopic morphology of the metallurgical bond, ensuring the interface is free of defects such as fractures, brittle phases, and porosity. Dimensional accuracy testing includes checking key dimensions such as outer diameter, wall thickness, and roundness, ensuring that all dimensional parameters meet design standards and industry specifications. For any non-conforming areas discovered during inspection, targeted finishing methods such as local grinding and re-rolling are used to repair the non-conforming areas without damaging the established metallurgical bonding interface, ultimately resulting in a high-quality, stable composite steel pipe. This step, through comprehensive inspection and targeted finishing, effectively reduces the generation of non-conforming products, significantly improves the finished product qualification rate, and ensures the service performance and extends the service life of the composite steel pipes.

[0034] In this embodiment, further, in step S2, a metallurgical induction layer is pre-formed using plasma in-situ deposition. This deposition method has advantages such as high deposition efficiency, tight bonding between the coating and the substrate, and strong controllability of composition. Compared with other deposition methods, it can effectively avoid defects such as detachment and porosity between the metallurgical induction layer and the bonding surface. During the deposition process, the bonding surface is kept at a constant temperature, and the temperature is matched with the composition and thickness of the metallurgical induction layer to ensure that the metallurgical induction layer and the bonding surface are tightly bonded without defects such as porosity and inclusions, further improving the stability and induction effect of the metallurgical induction layer. The metallurgical induction layer adopts a multi-layer composite structure, and each layer achieves good metallurgical compatibility with the inner and outer tubes. From one side of the bonding surface to the other, the composition of the metallurgical induction layer has a gradient transition. This gradient transition structure can further reduce the energy barrier of interfacial atomic diffusion, promote smooth interdiffusion of atoms between the inner and outer tubes, and more effectively suppress the formation of brittle intermetallic compounds, further improving the metallurgical bonding quality and stability of the interface, solving the problems of limited induction effect and easy generation of brittle phases in the existing single-component induction layer.

[0035] The process of generating the metallurgical induced layer is as follows: First, preliminary preparation: complete the pretreatment of the composite tube blank in step S1, and perform fine grinding and degreasing on the selected inner and outer tube mating surfaces to thoroughly remove oxide layers, impurities and oil stains, ensuring that the mating surfaces are clean and rough, laying the foundation for the pre-deposition of the metallurgical induced layer, and avoiding the impact of impurity residue on the deposition quality and performance of the induced layer.

[0036] Secondly, the selection and proportion of the induction layer material: Ni-Cu-Ti composite alloy (mass ratio Ni:Cu:Ti=60-70:20-25:5-10) is selected as the metallurgical induction layer material. This material itself has good resistance to high-temperature oxidation and can achieve good metallurgical compatibility with most carbon steel and alloy steel inner and outer tubes. The Ni element in its composition can improve the resistance to high-temperature oxidation, the Cu element can optimize the plasticity matching, and the Ti element can strengthen the induction performance.

[0037] Plasma in-situ deposition for preparing the induced layer: The prepared Ni-Cu-Ti composite alloy material is precisely deposited on the pretreated bonding surface (outer surface of the inner tube or inner surface of the outer tube) using plasma in-situ deposition. During the deposition process, the deposition power and deposition rate are strictly controlled to ensure that the thickness of the induced layer is uniform (controlled at 50-100μm) and closely adheres to the bonding surface. At the same time, the bonding surface is kept at a constant temperature during the deposition process, with the temperature controlled at 500-550℃. This temperature is precisely matched with the composition and thickness of the induced layer, which not only avoids oxidation of the induced layer due to excessive temperature, but also ensures that the induced layer and the bonding surface achieve preliminary metallurgical bonding, eliminating defects such as porosity and detachment.

[0038] Induced layer gradient transition structure formation: During the deposition process, the composition is precisely controlled by the plasma equipment to form a multi-layer gradient transition structure in the metallurgical induced layer. The first layer (bonding interface) adopts a Ni-Cu-Ti composite alloy layer (basic ratio), the second layer adopts a Ni-Ti transition layer (Ni:Ti=85-90:10-15), and the third layer adopts a Cu-Ti transition layer (Cu:Ti=75-80:20-25). This gradient transition structure can not only reduce the atomic diffusion barrier at the interface, but also unexpectedly achieve a smooth connection of the properties of the inner and outer tube materials, optimize the synergy of plastic deformation, and further enhance the resistance to high-temperature oxidation, so as to avoid the bonding interface being oxidized in subsequent high-temperature processes.

[0039] Finally, post-treatment of the induced layer: After deposition, the surface of the induced layer is lightly polished to remove small protrusions and inclusions, ensuring a smooth surface and further improving its compatibility with subsequent processes, thus completing the pre-positioning of the metallurgical induced layer.

[0040] In this embodiment, further, in step S3, the dedicated clamping device includes an axial positioning mechanism and a radial clamping mechanism, which work together to achieve precise positioning and clamping of the composite tube blank. The axial positioning mechanism precisely limits the two ends of the composite tube blank to prevent displacement in the axial direction and ensure the axial stability of the tube blank during rolling. The radial clamping mechanism adopts a flexible clamping method, using flexible wear-resistant materials to make the clamping contact surface, which closely fits the outer surface of the composite tube blank, avoiding scratches and damage to the surface of the tube blank during clamping. At the same time, it effectively protects the pre-placed metallurgical induction layer from being damaged, solving the problem that existing rigid clamping is prone to damaging the tube blank and the induction layer, and providing a stable and intact billet foundation for subsequent interface metallurgical bonding and rolling forming.

[0041] In this embodiment, further, in step S4, the partitioned induction heating adopts a structure with independent control of inner and outer dual coils. The inner coil precisely heats the inner tube, and the outer coil precisely heats the outer tube. By adjusting the heating power of the inner and outer coils respectively, the gradient temperature distribution of the composite tube blank from the inside to the outside can be precisely controlled. The core control requirement is to ensure that the activation temperature of the metallurgical induction layer is lower than the plastic deformation temperature of the inner and outer tubes. This temperature matching design not only ensures that the metallurgical induction layer can be fully activated and actively guide the interdiffusion of interfacial atoms, but also avoids the inner and outer tubes from undergoing premature plastic deformation due to excessively high temperatures, which would lead to tube blank structure disorder and interface misalignment. This ensures the scientific and rational nature of gradient temperature control preheating and provides a reliable temperature guarantee for the smooth progress of subsequent processes.

[0042] In this embodiment, further, in step S5, during the interface self-sensing metallurgical bonding process, the composite tube blank is kept stationary to avoid problems such as uneven atomic diffusion and misalignment of the bonding surface caused by tube blank movement; at the same time, a dedicated monitoring device is used to continuously monitor the interface temperature and atomic diffusion state, and the monitoring data is fed back in real time. The gradient temperature field parameters are adjusted according to the data to ensure that the interface temperature is always maintained in the optimal range of atomic diffusion (580-620℃ for Ni-Cu-Ti composite alloy layer and 630-670℃ for Ti-Al-V composite alloy layer) until a continuous and dense metallurgical bonding layer is formed at the interface. Metallographic monitoring confirms that the bonding layer has no fractures and no brittle phase precipitation, which completely solves the pain points of the inability to monitor the interface metallurgical bonding process in real time and the difficulty in controlling the bonding quality in the prior art, ensuring that the interface bonding quality of each product can meet the design requirements.

[0043] Step S5 not only enables the bonding interface to achieve uniform penetration and fusion at the atomic level, forming a metallurgical bonding layer without any micropores, microcracks, or brittle phase segregation, but also, combined with the interface's dynamic stress self-release capability, can autonomously buffer and release the thermal and mechanical stress generated at the interface during subsequent gradient cooling, synchronous temperature-controlled rolling, and service processes, avoiding interface cracking and peeling caused by stress concentration. At the same time, it gives the bonding interface excellent thermal shock resistance and stress corrosion resistance. Even under repeated high and low temperature cycles (-50℃ to 600℃) and corrosive media such as strong acids and strong alkalis, it can still maintain the stability and integrity of the interface bonding for a long time, greatly expanding the application scenarios of composite layer steel pipes, making them suitable for harsh and extreme working conditions such as deep sea and high temperature and high pressure.

[0044] In this embodiment, further, in step S6, the synchronous temperature-controlled rolling adopts a multi-pass continuous rolling process. The deformation amount and rolling speed of each rolling pass are precisely calculated and controlled to avoid billet damage or interface bonding failure caused by a single large deformation amount. After each rolling pass, a dedicated temperature measuring device is used to accurately detect the interface temperature of the composite billet. The induction heating power is adjusted in real time according to the detection results to keep the interface temperature within the metallurgical bonding stable range and avoid the adverse effects of temperature fluctuations on the interface bonding quality. At the same time, the rolling speed is dynamically adjusted according to the interface metallurgical bonding state and billet forming situation to ensure that rolling and metallurgical bonding are carried out synchronously without any disconnection. This further improves the forming accuracy and interface bonding stability of the composite steel pipe and solves the problems of temperature runaway and process disconnection that are prone to occur in the multi-pass rolling process in the prior art.

[0045] In this embodiment, further, in step S7, the periodic fluctuation of the rolling force adopts a pulse control method. The pulse frequency can be precisely adjusted according to the atomic diffusion frequency of the interface to ensure that the fluctuation frequency matches the atomic diffusion frequency of the interface, maximizing the secondary activation effect. The fluctuation rolling force causes slight plastic deformation at the interface of the composite tube blank. This micro-plastic deformation can break the atomic diffusion barrier, promote further interdiffusion and fusion of interface atoms, and significantly strengthen the metallurgical bonding strength of the interface. At the same time, the outer diameter and wall thickness of the composite steel pipe are simultaneously calibrated through the periodic fluctuation of the rolling force to ensure that the dimensional accuracy meets the design requirements and industry standards. This achieves the integration of interface strengthening and dimensional calibration, further improving the product quality and market competitiveness of the composite steel pipe.

[0046] In existing technologies, the rolling process is merely a means of forming composite tube blanks. It uses a continuous and constant rolling force to induce plastic deformation in the tube blank, achieving dimensional calibration. This process cannot strengthen the already formed metallurgical interface and may even lead to defects such as microcracks and peeling due to excessive constant rolling force. Furthermore, it cannot simultaneously meet the dual requirements of interface strengthening and dimensional accuracy. In contrast, this step, through the design of periodic fluctuations in rolling force, breaks through the limitations of the existing technology of "constant rolling force forming." With "secondary activation of interface atomic diffusion by fluctuating rolling force + synergistic strengthening by micro-plastic deformation" as the core, it unexpectedly achieves a triple synergistic technical effect of "interface strengthening, precise dimensional calibration, and improved overall toughness of the tube blank." Specifically, this step not only breaks the interfacial atomic diffusion barrier through the periodic fluctuation of rolling force, promoting further full interdiffusion of interfacial atoms and improving the interfacial bonding strength compared to existing technologies, but also unexpectedly refines the grains of the inner and outer layers of the composite tube blank, forming a uniform and fine grain structure. This significantly improves the overall toughness and impact resistance of the composite steel pipe, enhancing its impact toughness. At the same time, it effectively avoids the interfacial defects caused by constant rolling force in existing technologies, achieving a precise match between interfacial strengthening and dimensional accuracy. Furthermore, it unexpectedly endows the composite steel pipe with excellent fatigue resistance, ensuring that the interface remains stable under long-term cyclic loading and is less prone to fatigue cracking.

[0047] In this embodiment, further, in step S8, the gradient cooling and shaping adopts a segmented cooling process. According to the material, size, and interface bonding state of the composite steel pipe, the cooling process is divided into multiple stages. First, the outer layer of the composite steel pipe is cooled to a set temperature and kept at a constant temperature for a period of time, so that the heat from the outer layer can be slowly conducted to the inner layer, alleviating the temperature difference between the inner and outer layers. Then, the middle and inner layers are gradually cooled. The cooling rate of each step is precisely controlled to avoid excessively rapid cooling and the generation of thermal stress. During the cooling process, a special stress monitoring device is used to monitor the interface thermal stress in real time. Once a thermal stress concentration phenomenon is detected, the cooling parameters are immediately adjusted to avoid interface cracking caused by thermal stress concentration. This further improves the finished product quality and structural stability of the composite steel pipe and solves the pain point of easy generation of thermal stress and interface failure during the cooling process in the prior art.

[0048] In this embodiment, further, in step S9, the interface bonding strength detection adopts a combination of shear strength testing and metallographic analysis. The shear strength test uses specialized testing equipment to accurately quantify the shear bonding strength of the interface, ensuring that it meets the design standards. The metallographic analysis uses a microscope to observe the microscopic morphology of the metallurgical bonding of the interface, intuitively judging whether there are defects such as fracture, porosity, and brittle phase precipitation, achieving comprehensive detection of the interface bonding quality. The dimensional accuracy detection includes the detection of key dimensions such as outer diameter, wall thickness, and roundness. High-precision measuring equipment is used to ensure the detection accuracy and avoid dimensional deviations exceeding the allowable range. During the finishing process, local grinding and re-rolling are used to specifically repair the detected dimensional deviations and surface defects. The operating force and method are strictly controlled during the finishing process to avoid damaging the formed metallurgical bonding interface, ensuring that the interface bonding quality and overall performance of the finished product are not affected, further improving the finished product qualification rate.

[0049] In this embodiment, further, in step S2, the in-situ deposition method is plasma in-situ deposition. During the deposition process, the bonding surface is simultaneously kept at a constant temperature, and the temperature is controlled within a range compatible with the composition of the metallurgical induced layer (500-550℃ for Ni-Cu-Ti composite alloy layer, 550-600℃ for Ti-Al-V composite alloy layer). This ensures that the metallurgical induced layer and the bonding surface are tightly bonded without defects such as pores or inclusions. This implementation scheme further optimizes the preparation process of the metallurgical induced layer, improves the bonding stability and induction effect of the metallurgical induced layer, and provides more reliable support for subsequent self-induction metallurgical bonding at the interface.

[0050] The embodiments of this application have been described above with reference to the accompanying drawings. Unless otherwise specified, the embodiments and features in the embodiments of this application can be combined with each other. This application is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of this application without departing from the spirit and scope of the claims, and all of these forms are within the protection scope of this application.

Claims

1. A method of integrated interfacial metallurgical bonding and controlled temperature rolling of a clad steel pipe, characterized by, The method comprises the following steps: S1, composite pipe blank pretreatment: selecting an inner layer pipe and an outer layer pipe, polishing and degreasing the joint surface to remove the oxide layer and impurities, coaxially sleeving the inner layer pipe in the outer layer pipe to obtain an initial composite pipe blank; S2, interface pre-setting a metallurgical induction layer: a layer of metallurgical induction layer compatible with the inner and outer layer pipes is pre-set on the joint surface after pretreatment, which is used to induce interface atomic interdiffusion and inhibit the generation of brittle intermetallic compounds; S3, blank pre-clamping positioning: the initial composite pipe blank is placed in a special clamping device to realize accurate axial and radial positioning and clamping, preventing the relative displacement of the inner and outer layer pipes during rolling; S4, gradient temperature control preheating: the composite pipe blank is preheated by using zoned induction heating to form a gradient temperature field from the inside to the outside, so that the metallurgical induction layer reaches the activation temperature first, and the inner and outer layer pipes are simultaneously raised to the plastic deformation temperature; S5, interface self-induction metallurgical bonding: the gradient temperature field is kept stable to guide the in-situ interdiffusion of the interface atoms, forming a continuous and non-brittle phase metallurgical bonding interface; S6, synchronous temperature control rolling: after the metallurgical bonding is completed, synchronous continuous rolling is carried out, the temperature field and the rolling parameters are dynamically matched, and the metallurgical bonding and rolling forming are carried out synchronously; S7, interface metallurgical strengthening rolling: the bonding interface is activated again by periodic fluctuation of rolling force to strengthen the bonding strength and complete size calibration; S8, gradient cooling shaping: the composite steel pipe is cooled by using reverse gradient cooling method to avoid the generation of thermal stress at the interface, which leads to bonding failure; S9, finished product detection and finishing: the interface bonding strength and size precision of the composite steel pipe are detected, and the unqualified parts are finished to obtain the finished product.

2. The method according to claim 1, wherein the method is characterized by In step S2, the metallurgical induction layer is pre-set by plasma in-situ deposition, and the joint surface is kept at a constant temperature during the deposition process to ensure that the metallurgical induction layer closely matches the joint surface without porosity and inclusion defects. The metallurgical induction layer has a multi-layer composite structure, each layer is metallurgically compatible with the inner and outer layer pipes, and the composition of the metallurgical induction layer gradually transitions from one side of the joint surface to the other side, promoting interface atomic interdiffusion and inhibiting the generation of brittle intermetallic compounds.

3. The method according to claim 1, wherein the method is characterized by In step S3, the special clamping device includes an axial positioning mechanism and a radial clamping mechanism. The axial positioning mechanism limits the two ends of the composite pipe blank, and the radial clamping mechanism uses a flexible clamping method to fit the outer surface of the composite pipe blank, avoiding damage to the surface of the pipe blank and the pre-set metallurgical induction layer during clamping.

4. The method according to claim 1, wherein the method is characterized by In step S4, the zoned induction heating uses inner and outer double coils for independent control. The inner coil corresponds to the inner layer pipe heating, and the outer coil corresponds to the outer layer pipe heating. By differentiating the adjustment of the coil power, the gradient temperature distribution of the composite pipe blank from the inside to the outside is realized, ensuring that the activation temperature of the metallurgical induction layer is lower than the plastic deformation temperature of the inner and outer layer pipes.

5. The method according to claim 1, wherein the method is characterized by In step S5, during the interface self-induction metallurgical bonding process, the composite pipe blank is kept stationary, the interface temperature and atomic diffusion state are continuously monitored, until a continuous metallurgical bonding layer is formed at the interface, ensuring that the bonding layer is free of cracks and brittle phase precipitation.

6. The method according to claim 1, wherein the method is characterized by In step S6, the temperature-controlled synchronous rolling is carried out by multi-pass continuous rolling, the interface temperature of the composite pipe blank is detected after each pass, the induction heating power is adjusted according to the detection result, the interface temperature is maintained in the stable range of metallurgical bonding, the rolling speed is adjusted to ensure that the rolling forming and the metallurgical bonding are synchronized and there is no disconnection phenomenon.

7. The method according to claim 1, wherein the method is characterized by: In step S7, the periodic fluctuation of the rolling force is controlled by pulse, the fluctuation frequency is matched with the interface atomic diffusion frequency, the micro-plastic deformation of the composite pipe blank interface is generated by the fluctuation of the rolling force, the atomic diffusion barrier is broken, the interface atomic interdiffusion is promoted, and the outer diameter and wall thickness of the composite steel pipe are calibrated to ensure that the size precision meets the requirements.

8. The method of claim 1, wherein the method is characterized by: In step S8, the gradient cooling shaping is carried out by segmented cooling, the outer layer of the composite steel pipe is cooled to the set temperature first, then the middle layer and the inner layer are gradually cooled after maintaining the constant temperature for a period of time, the interface thermal stress is monitored in real time during the cooling process to avoid the interface cracking caused by the thermal stress concentration.

9. The method according to claim 1, wherein the method is characterized by, In step S9, the interface bonding strength detection is carried out by combining the shear strength test and the metallographic analysis, the size precision detection includes the outer diameter, wall thickness and roundness detection, the local polishing and re-rolling are used in the trimming process without damaging the formed metallurgical bonding interface.

10. The method of claim 1, wherein the method is characterized by: In step S2, the in-situ deposition method is plasma in-situ deposition, the bonding surface is kept at constant temperature during the deposition process to ensure that the metallurgical induced layer is closely combined with the bonding surface without porosity and inclusion defects.

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