Manufacturing method of copper-aluminum composite pipe

Abstract

The invention provides a method for manufacturing a copper-aluminum composite pipe, which comprises the following steps of: preheating a copper pipe to 600-620 DEG C, and conveying the copper pipe to a graphite mold filled with inert gas; the medium-frequency aluminum melting furnace heats an aluminum raw material to 700-730 DEG C, the aluminum raw material is injected into the copper pipe in the graphite mold, the aluminum solution wraps the outer surface of the copper pipe, and then the cast copper pipe is pulled out of the graphite mold. And a cooling mechanism is used for cooling twice, and the copper-aluminum composite pipe is obtained. By preheating the copper pipe and cooperating with inert gas protection, temperature difference impact and oxidation interference are reduced, and it is guaranteed that molten aluminum is evenly spread; molten aluminum is heated, silicon is added, the liquidity and wettability of the molten aluminum are improved, and CuAl2 brittle phase nucleation is inhibited; a layered cooling mechanism is matched to precisely regulate and control the temperature gradient, and local stress concentration is avoided; and finally, through cooperative control of technological parameters and a dynamic model, the copper-aluminum interface bonding strength and the plasticity of the composite pipe are improved, the interface defect problem is solved, and the copper-aluminum composite pipe with high reliability and long service life is obtained.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of copper-aluminum composite pipe, and particularly to a manufacturing method of copper-aluminum composite pipe. BACKGROUND

[0002] The copper-aluminum composite pipe has been widely used in heat exchangers, refrigeration equipment and other related fields due to its unique material properties, which not only inherits the high thermal conductivity of copper, but also combines the lightweight characteristics and low-cost advantages of aluminum. However, traditional preparation methods such as mechanical compounding and explosive welding face many challenges in actual operation: complex process flow, high operation difficulty, easy oxidation reaction at the interface, and low bonding strength, which seriously affect the quality and performance of the composite pipe. Although the solid-liquid compounding method can theoretically achieve metallurgical bonding between copper and aluminum, the significant difference in melting points between copper (melting point of 1083℃) and aluminum (melting point of 660℃) makes it easy to form brittle phases or defects at the interface during actual operation, further weakening the overall performance of the composite pipe. At present, although the continuous solid-liquid compounding casting process has made some progress in technology, it still cannot effectively solve the problem of interface control during the synchronous compounding of copper and aluminum, and this technical bottleneck needs to be broken through. SUMMARY

[0003] The present application aims to at least solve the technical problems existing in the prior art that the large difference in melting points between copper (1083℃) and aluminum (660℃) easily leads to interface brittle phases or defects, and particularly innovatively proposes a manufacturing method of copper-aluminum composite pipe.

[0004] In order to achieve the above-mentioned purpose of the present application, a manufacturing method of copper-aluminum composite pipe is provided, which is applied to a manufacturing device of copper-aluminum composite pipe, and the manufacturing device of copper-aluminum composite pipe comprises a medium-frequency aluminum melting furnace, a pouring mechanism, a graphite mold, a cooling mechanism, a feeding driving mechanism and a traction mechanism.

[0005] The pouring mechanism is in communication with the medium-frequency aluminum melting furnace and is used for pouring the aluminum solution in the medium-frequency aluminum melting furnace onto the copper pipe in the graphite mold; the cooling mechanism is used for cooling the copper pipe after pouring the aluminum solution; the feeding driving mechanism is used for conveying the copper pipe into the graphite mold; and the traction mechanism is used for continuously pulling out the copper-aluminum composite pipe from the graphite mold.

[0006] The method comprises the following steps:

[0007] S1, removing the oxide layer on the surface of the copper pipe and drying it in a nitrogen environment;

[0008] S2, preheating the copper pipe to 600-620℃, conveying it into the graphite mold through the feeding driving mechanism, and introducing inert gas into the copper pipe;

[0009] S3, heating and melting the aluminum raw material by an aluminum solution frequency melting furnace to obtain an aluminum solution, and heating the aluminum solution to 700-730℃, and then pouring the aluminum solution into the copper pipe in the graphite mold through the pouring mechanism, so that the aluminum solution is coated on the outer surface of the copper pipe, and the traction mechanism continuously pulls out the copper pipe with the poured aluminum solution from the graphite mold;

[0010] S4, using the cooling mechanism to cool the copper pipe with the poured aluminum solution for the first time, so that the aluminum solution rapidly nucleates on the outer surface of the copper pipe, and a bonding interface is formed on the copper pipe;

[0011] S5, using the cooling mechanism to cool the copper pipe after the bonding interface is formed for the second time, and controlling the cooling speed to be within 10-20℃ / s to inhibit the growth of CuAl2 brittle phase, so as to obtain a copper-aluminum composite pipe.

[0012] As an optional embodiment of the present application, optionally, the temperature of the bonding interface in step S4 is between 620-640℃.

[0013] As an optional embodiment of the present application, optionally, a temperature acquisition unit and an interface diffusion controlled parabolic growth kinetics model are arranged in the cooling mechanism in step S4, the interface diffusion controlled parabolic growth kinetics model is used to quantitatively describe the growth kinetics behavior of the bonding interface under high temperature conditions, and the cooling rate is adjusted in real time according to the temperature data of the surface of the copper pipe acquired by the temperature acquisition unit.

[0014] As an optional embodiment of the present application, optionally, the expression of the interface diffusion controlled parabolic growth kinetics model is:

[0015]

[0016] J=-D dc / dx

[0017]

[0018] Wherein, D represents the diffusion coefficient, D0 represents a constant of the material itself property, Q represents the activation energy, R represents the gas constant, T represents the absolute temperature, J represents the diffusion flux, δ represents the bonding interface thickness, k represents the temperature constant, and t represents the time.

[0019] As an optional embodiment of the present application, optionally, controlling the cooling speed to be within 10-20℃ / s in step S5 includes:

[0020] S501, acquiring temperature data of different points in the graphite mold;

[0021] S502, compare the temperature data with the set temperature curve value by using the interface diffusion controlled parabolic growth kinetics model, and obtain a deviation value;

[0022] S503, calculate the required cooling water flow based on the deviation value, control the cooling mechanism based on the cooling water flow, and adjust the size of the cooling water flow in real time by using the cooling mechanism.

[0023] As an optional embodiment of the present application, the cooling mechanism comprises:

[0024] A primary water cooling jacket is arranged outside the graphite mold.

[0025] A primary water cooling thermocouple hole is arranged on the graphite mold.

[0026] A secondary water cooling jacket is arranged on the graphite mold and outside the primary water cooling jacket.

[0027] A secondary water cooling thermocouple hole is arranged on the graphite mold.

[0028] As an optional embodiment of the present application, the cooling mechanism further comprises a spray, which is arranged near the end of the graphite mold.

[0029] As an optional embodiment of the present application, the temperature of the cooling water sprayed by the spray is below 40℃.

[0030] As an optional embodiment of the present application, the aluminum solution obtained in step S3 contains 0.5-1.2% of silicon.

[0031] As an optional embodiment of the present application, the casting mechanism comprises a ceramic pipe, an electromagnetic pump and a sprue.

[0032] The ceramic pipe is used to communicate the intermediate frequency aluminum melting furnace with the sprue, the electromagnetic pump is arranged on the ceramic pipe, which is used to pump the aluminum solution in the intermediate frequency aluminum melting furnace to the sprue through the ceramic pipe, and then uniformly cast to the copper pipe in the graphite mold pulled by the traction mechanism.

[0033] The present application has the beneficial effects that: the present application effectively reduces the temperature difference impact and oxidation interference when the molten aluminum contacts the copper pipe by preheating the copper pipe to 600-620 DEG C and cooperating with inert gas protection, guarantees the uniform coating of the molten aluminum on the copper surface; the molten aluminum is heated to 700-730 DEG C and 0.5-1.2 % silicon element is added, which improves the flowability of the molten aluminum and the wettability of the molten aluminum and copper, and simultaneously inhibits the nucleation of CuAl2 brittle phase; the twice cooling process is adopted, the first rapid cooling makes the molten aluminum crystallize on the copper pipe surface to realize the preliminary metallurgical bonding (temperature 620-640 DEG C), the cooling rate is adjusted in real time through the parabolic growth kinetics model of interface diffusion control, and the bonding interface thickness is controlled; the second cooling controls the rate within 10-20 DEG C / s to further inhibit the growth of brittle phase; the temperature gradient is accurately controlled through the layered cooling mechanism (primary water cooling jacket, secondary water cooling jacket and end spraying), and the local stress concentration is avoided; finally, the copper-aluminum interface bonding strength and the plasticity of the composite pipe are significantly improved through the cooperative control of the process parameters and the kinetics model, the interface defect problem caused by the melting point difference is effectively solved, and the copper-aluminum composite pipe with high reliability and long service life is obtained.

[0034] Additional aspects and advantages of the application will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following and the description or be learned by practice of the application. BRIEF DESCRIPTION OF DRAWINGS

[0035] The above and / or additional aspects and advantages of the present application will become apparent and be readily appreciated from the description of the embodiments, given by reference to the following drawings: Figure 1 is a flow chart of a method for manufacturing a copper-aluminum composite pipe according to the present application; Figure 2 is a sectional view of a manufacturing device for a copper-aluminum composite pipe according to the present application; Figure 3 is a schematic view of the position of a secondary water cooling thermocouple hole in a manufacturing device for a copper-aluminum composite pipe according to the present application; Figure 4 is a statistical graph of the relationship between temperature and time in a manufacturing device for a copper-aluminum composite pipe according to the present application.

[0036] In the figure: 1, intermediate frequency aluminum melting furnace, 2, electromagnetic pump, 3, ceramic pipeline, 4, copper pipe, 5, feeding driving mechanism, 6, graphite mold, 7, preheating coil, 8, pouring gate, 9, primary water cooling jacket, 10, primary water cooling thermocouple hole, 11, secondary water cooling jacket, 12, secondary water cooling thermocouple hole, 13, secondary water cooling thermocouple hole, 14, spraying, 15, traction mechanism, 16, secondary water cooling thermocouple hole, 17, secondary water cooling thermocouple hole, 18, secondary water cooling jacket. DETAILED DESCRIPTION

[0037] The following describes embodiments of the present invention in detail. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended only to explain the present invention and are not to be construed as limiting the present invention.

[0038] like Figure 1 As shown, a method for manufacturing a copper-aluminum composite pipe is applied to a copper-aluminum composite pipe manufacturing device, which includes a medium-frequency aluminum melting furnace 1, a casting mechanism, a graphite mold 6, a cooling mechanism, a feeding drive mechanism 5, and a traction mechanism 15;

[0039] The casting mechanism is connected to the medium frequency aluminum melting furnace 1 and is used to cast the aluminum solution in the medium frequency aluminum melting furnace 1 onto the copper tube 4 in the graphite mold 6; the cooling mechanism is used to cool the copper tube 4 after the aluminum solution is cast; the feeding drive mechanism 5 is used to transport the copper tube 4 into the graphite mold 6; the traction mechanism 15 is used to continuously pull the copper-aluminum composite pipe out of the graphite mold 6;

[0040] like Figure 2 As shown, it should be noted that a preheating coil 7 is installed outside the input end of the graphite mold 6. This maintains the temperature of the copper tube 4 in the mold between 600°C and 620°C, ensuring that the aluminum solution quickly crystallizes upon contact with the copper tube, forming a stable bonding interface. The design of the preheating coil 7 not only improves production efficiency but also effectively reduces energy consumption, making the entire production process more environmentally friendly and economical.

[0041] The feeding drive mechanism 5 in this embodiment includes a feeding wheel and a drive motor. The feeding wheel is driven by the drive motor to continuously and stably feed the copper tube 4 into the graphite mold 6. The design of this feeding device ensures the stability and accuracy of the copper tube before casting, further improving the quality of the copper-aluminum composite pipe.

[0042] The traction mechanism 15 in this embodiment includes a traction wheel and a drive motor. Driven by the drive, the traction wheel continuously and stably pulls the cooled copper tube, which has been cast with molten aluminum, out of the graphite mold 6. This traction mechanism design ensures the stability and continuity of the composite tube during the cooling process, avoiding product quality issues caused by tube deformation or breakage.

[0043] The method comprises:

[0044] S1, removing the oxide layer on the surface of the copper tube 4 and drying it under a nitrogen environment;

[0045] It is necessary to explain in step S1 that the oxide on the surface of the copper pipe is completely removed by physical or chemical methods, which is crucial for the subsequent metallurgical bonding between copper and aluminum. Drying in a nitrogen environment can effectively prevent the copper pipe from being oxidized again during the processing process, ensuring the cleanliness of the copper pipe surface. Specifically, the surface of the copper pipe (outer diameter 16-60 mm) is treated by sand blasting (roughness Ra 3.2-6.3 μm), then immersed in a 10% citric acid solution to remove the oxide layer, and dried in a nitrogen environment.

[0046] S2, preheat the copper pipe 4 to 600-620℃, transport it into the graphite mold 6 through the feeding drive mechanism 5, and pass inert gas into the copper pipe 4;

[0047] It is necessary to explain in step S2 that the copper pipe is preheated to the specified temperature range and accurately fed into the graphite mold 6 by the feeding drive mechanism 5, which ensures the temperature stability of the copper pipe during the subsequent casting step. At the same time, the inert gas passed into the copper pipe 4 effectively isolates the oxygen in the air, avoiding the reaction of the copper pipe with oxygen at high temperature, further ensuring the cleanliness of the surface of the copper pipe 4 and the quality of the composite pipe. In addition, the use of inert gas also helps to reduce the oxidation of the aluminum solution during the casting process, improving the bonding strength of the aluminum solution and the copper pipe.

[0048] Specifically, the copper pipe is preheated to 600-620℃ (lower than the melting point of aluminum but close to its solidus), placed on the core shaft of the continuous casting machine, and the inert gas (N2) is passed into the core shaft for protection.

[0049] S3, heat and melt the aluminum raw material by the intermediate frequency melting aluminum furnace 1 to obtain the aluminum solution, heat the aluminum solution to 700-730℃, and then pour the aluminum solution into the copper pipe 4 in the graphite mold 6 through the casting mechanism, so that the aluminum solution is coated on the outer surface of the copper pipe 4, and the traction mechanism 15 continuously pulls out the copper pipe 4 with the cast aluminum solution from the graphite mold 6;

[0050] It is necessary to explain in step S3 that during the pouring process of the aluminum solution, the electromagnetic pump 2 is precisely controlled to ensure that the aluminum solution is poured onto the copper pipe 4 with stable flow and pressure, forming a uniform aluminum layer. In this step, the use of the electromagnetic pump 2 not only improves the precision of the aluminum solution pouring, but also effectively avoids the splashing and waste of the aluminum solution during the pouring process, further improving the production efficiency and quality of the copper-aluminum composite pipe. At the same time, the continuous traction of the traction mechanism 15 ensures the stable movement of the copper pipe 4 during the casting process, avoiding the problem of uneven thickness of the aluminum layer caused by the stagnation or uneven movement of the copper pipe.

[0051] Specifically, the molten aluminum (containing 0.5-1.2% Si, temperature 700-730℃) is injected into the annular gate 8 through the electromagnetic pump 2, while the outer surface of the preheated copper pipe 4 is coated.

[0052] S4, the cooling mechanism is used to cool the copper pipe 4 with cast aluminum solution for the first time, so that the aluminum solution nucleates rapidly on the outer surface of the copper pipe 4, and a bonding interface is formed on the copper pipe 4;

[0053] It should be noted in step S4 that the purpose of the first cooling is to make the aluminum solution nucleate rapidly on the outer surface of the copper pipe, forming a preliminary metallurgical bonding interface. Through rapid cooling, the solidification process of the aluminum solution can be effectively controlled, so that a fine and uniform grain structure is formed, thereby improving the mechanical properties and corrosion resistance of the composite pipe.

[0054] Specifically, the first zone: the first water cooling jacket 9 (cooling intensity 0.3-0.5L / min), so that the aluminum solution nucleates rapidly on the surface of the copper pipe 4, forming a bonding interface (interface temperature 620-640℃). The temperature sensor implanted in this zone feeds back data to the control system in real time, which is converted into an electrical signal to the electromagnetic proportional valve through calculation, and the flow of the first water cooling is adjusted in real time. During the operation of the system, the parameters of the controller, such as proportional coefficient, integral time and differential time, are gradually adjusted according to the actual temperature control effect, so as to achieve the best control performance, so that the surface temperature of the pipe can quickly and stably approach the set value with small fluctuations.

[0055] S5, the cooling mechanism is used to cool the copper pipe 4 after the bonding interface is formed for the second time, and the cooling speed is controlled within 10-20℃ / s to inhibit the growth of CuAl2 brittle phase and obtain copper-aluminum composite pipe.

[0056] It should be noted in step S5 that the purpose of the second cooling is to further consolidate the bonding between the aluminum solution and the copper pipe and inhibit the growth of CuAl2 brittle phase, thereby improving the overall performance of the composite pipe. By precisely controlling the cooling speed, the ideal microstructure of the aluminum solution during solidification can be ensured, which not only guarantees the strength of the composite pipe, but also improves its plasticity and corrosion resistance.

[0057] As Figure 3As shown, specifically, the second zone: secondary water cooling jacket 11, composed of two groups, control aluminum layer to 10-20 ℃ / s rate of cooling, inhibit CuAl2 brittle phase growth. In this area of graphite graphite mold 6 implantation of 4 temperature sensors, evenly distributed in four locations, real-time detection of temperature at each location. Control system receives temperature sensor signals, compared with the set temperature curve value, then according to the deviation value calculated the required cooling water flow, and send corresponding control signal to electromagnetic proportional valve, real-time adjustment of the size of the cooling water flow. Cooling water path: including cooling water pipeline, water pump, etc., for cooling water to provide circulation channel, so that the cooling water can flow through the water cooling jacket, take away heat.

[0058] The length of the secondary cooling zone is 300 mm, and the pulling speed range is 450-900 mm / min.

[0059] As an optional embodiment of the present application, the temperature of the bonding interface in step S4 is between 620-640℃.

[0060] It should be noted that in the process of manufacturing copper-aluminum composite pipe, the formation of the bonding interface is a key step. The temperature of the bonding interface is controlled between 620-640℃. The selection of this temperature range is based on the interaction of the aluminum solution and the copper pipe and the physical properties of the materials. At this temperature, the aluminum solution can rapidly nucleate on the surface of the copper pipe, forming a uniform and dense bonding interface. This bonding interface enhances the bonding force between the aluminum solution and the copper pipe.

[0061] As an optional embodiment of the present application, the cooling mechanism in step S4 is provided with a temperature acquisition unit and an interface diffusion controlled parabolic growth kinetics model. The interface diffusion controlled parabolic growth kinetics model is used to quantitatively describe the growth kinetics behavior of the bonding interface under high temperature conditions, and the cooling rate is adjusted in real time according to the temperature data of the surface of the copper pipe 4 collected by the temperature acquisition unit.

[0062] It should be noted that the temperature acquisition unit provided in the cooling mechanism can monitor the temperature change of the surface of the copper pipe 4 in real time, providing accurate data input for the interface diffusion controlled parabolic growth kinetics model. Through the analysis of the temperature data, the model can accurately calculate the growth rate of the bonding interface and adjust the cooling rate in real time as needed to ensure that the thickness and quality of the bonding interface meet the expected requirements. This design not only improves the production accuracy of the copper-aluminum composite pipe, but also helps to optimize the production process, reduce energy consumption and production cost.

[0063] As an optional embodiment of the present application, the expression of the interface diffusion controlled parabolic growth kinetics model is:

[0064]

[0065] J = -D dc / dx

[0066]

[0067] where D is the diffusion coefficient, D0 is a constant representing the intrinsic property of the material, Q is the activation energy, R is the gas constant, T is the absolute temperature, J is the diffusion flux, δ is the thickness of the reaction interface, k is a temperature constant, and t is time.

[0068] As Figure 4 illustrated, it is necessary to note that:

[0069] Derivation of the interface diffusion coefficient based on Fick's law

[0070] Fick's first law describes that under steady-state diffusion conditions, the diffusion flux J (the amount of substance per unit area per unit time) is proportional to the concentration gradient dc / dx,

[0071] In actual diffusion processes, the diffusion coefficient D is closely related to the temperature T, and the diffusion process needs to overcome a certain energy barrier (activation energy Q). According to the theory of thermodynamics and kinetics, the relationship between the diffusion coefficient D and the temperature T can be described by the Arrhenius equation.

[0072] The physical meaning of the formula is: the higher the temperature, the higher the energy of the molecules, the more molecules that can overcome the activation energy required for diffusion, the larger the diffusion coefficient, and the faster the diffusion rate. In practical applications, the diffusion coefficient D at different temperatures is usually measured through experiments, and then a linear fitting of lnD and 1 / T is performed, and the activation energy Q is calculated according to the slope of the fitting straight line -Q / R.

[0073] Establish the relationship between the thickness of the reaction interface δ and the time t:

[0074] Consider a diffusion-controlled growth process of the reaction interface. Assume that the growth of the reaction interface is dominated by the diffusion process, i.e., the increase in the thickness of the reaction interface is due to the diffusion of the material from one side to the other side through the interface and the reaction caused by the diffusion.

[0075] In the case of one-dimensional diffusion, according to Fick's second law:

[0076] To simplify the problem, some approximations and boundary conditions are adopted. Assume that at the beginning of the diffusion (t=0), the concentration c at the reaction interface is c0 (the initial concentration), and as time goes on, the diffusion causes the reaction interface to gradually thicken.

[0077] By solving Fick's second law (a relatively complex mathematical process, usually using similarity transformation and other methods), under certain boundary conditions (such as semi-infinite diffusion body and other conditions), the relationship between the interface thickness δ and time t satisfies the parabolic law, i.e. δ 2 is proportional to t.

[0078] Let δ 2 = 4D t (the coefficient 4 here is determined by specific mathematical solution and boundary conditions), and take the square root of both sides to get:

[0079] Since D is a constant related to temperature, we can associate it with a new constant k related to temperature, let Thus the relationship between the interface thickness δ and time t is obtained:

[0080] As an optional embodiment of the present application, the cooling speed is optionally controlled to be within 10-20℃ / s in step S5, including:

[0081] S501, collecting temperature data of different points in the graphite mold 6;

[0082] As shown in Figure 3 , it is necessary to explain in step S501 that the temperature data of different points in the graphite mold is monitored and recorded in real time by the multiple temperature sensors arranged in the graphite mold 6. These data are the key basis for subsequent adjustment of the cooling speed and ensuring uniformity of cooling. The distribution of temperature sensors should take into account the geometric shape of the copper-aluminum composite pipe and the cooling demand to ensure that the temperature change of the pipe during the cooling process can be accurately reflected. The setting position of the temperature sensor in this embodiment is shown in Figure 3 .

[0083] S502, comparing the temperature data with the set temperature curve value by using the parabolic growth kinetics model of interface diffusion control to obtain a deviation value;

[0084] It is necessary to explain in step S502 that the parabolic growth kinetics model of interface diffusion control can compare the real-time collected temperature data with the preset ideal temperature curve to calculate the deviation value. This step is the key to accurately control the cooling speed, which ensures that the cooling process can be carried out according to the predetermined parameters, thereby optimizing the microstructure and overall performance of the copper-aluminum composite pipe.

[0085] The specific comparison process involves comparing the actual temperature values collected by the temperature sensors with the ideal temperature values preset in the model one by one to calculate the temperature deviation of each monitoring point. These deviation values are then input into the control system as the basis for adjusting the cooling water flow.

[0086] S503、based on the deviation value, calculate the required cooling water flow, based on the cooling water flow control the cooling mechanism, using the cooling mechanism to adjust the size of the cooling water flow in real time.

[0087] In step S503, it needs to be explained: the control system according to the deviation value, through the preset algorithm to calculate the required cooling water flow. This calculation process takes into account a number of factors, including the size of the deviation value, the requirement of cooling speed and the performance of cooling mechanism, etc. The calculated cooling water flow is then converted into control signal, sent to electromagnetic proportional valve and other actuators, real-time adjustment of the size of the cooling water flow. Through this precise feedback control mechanism, it can ensure that the cooling process in accordance with the predetermined parameters, so as to optimize the microstructure and overall performance of copper aluminum composite pipe. This design not only improves the production efficiency, but also helps to reduce energy consumption and production cost, enhance the market competitiveness of products.

[0088] The above-mentioned algorithm for calculating the required cooling water flow algorithm is: based on PID (proportional-integral-derivative) control algorithm. PID control algorithm is a classical control strategy, widely used in various industrial control systems. In the present invention, PID control algorithm is used to calculate the required cooling water flow according to the temperature deviation value. Specifically, the PID controller receives the deviation value from the temperature sensor as input, and then through the calculation of the three links of proportion, integral and differential, outputs a control signal to adjust the cooling water flow. The proportional link can quickly respond to the change of the deviation value, so that the cooling water flow quickly approaches the target value; the integral link can eliminate the cumulative effect of the deviation value, ensure that the cooling water flow remains stable for a long time; the differential link can predict the trend of the deviation value, adjust the cooling water flow in advance, avoid overshoot and oscillation. By adjusting the parameters of the PID controller (proportionality coefficient, integral time and differential time), the precise control of the cooling water flow can be realized, so as to optimize the cooling process and overall performance of copper aluminum composite pipe.

[0089] As an optional embodiment of the present invention, optionally, the cooling mechanism comprises:

[0090] Primary water cooling jacket 9, set in the graphite mold 6 outside;

[0091] Primary water cooling thermocouple hole 10, set in the graphite mold 6;

[0092] Secondary water cooling jacket 11, 18, set in the graphite mold 6, and located outside the primary water cooling jacket 9;

[0093] Secondary water cooling thermocouple hole 12, 13, 16, 17, set in the graphite mold 6.

[0094] As Figure 2 shown, the primary water cooling jacket 9 and the secondary water cooling jackets 11, 18 are installed on the graphite mold 6 from left to right for staged cooling of the copper-aluminum composite pipe. The primary water cooling jacket 9 is mainly responsible for preliminary rapid cooling to reduce the temperature of the pipe and preliminarily solidify the aluminum solution. The secondary water cooling jackets 11, 18 are responsible for further precise cooling by controlling the cooling speed and temperature gradient to optimize the microstructure and performance of the pipe. This staged cooling design makes the cooling process more flexible and controllable, which helps to improve the overall quality and production efficiency of the copper-aluminum composite pipe.

[0095] In practical applications, the specific configuration and operating parameters of the cooling mechanism will be adjusted according to the specifications of the copper-aluminum composite pipe, production requirements, and performance of the production equipment, etc. For example, the cooling water flow, cooling speed, and cooling time of the primary water cooling jacket 9 and the secondary water cooling jackets 11, 18 can be adjusted according to the diameter, wall thickness, and required strength and plasticity of the pipe. At the same time, the accuracy and real-time of temperature monitoring can be improved by optimizing the layout and number of temperature sensors, thereby further improving the control accuracy and stability of the cooling process.

[0096] In summary, the present application successfully optimizes the microstructure and overall performance of the copper-aluminum composite pipe by precisely controlling the cooling speed and temperature gradient, combined with the design of staged cooling. This manufacturing method not only improves the strength, plasticity, and corrosion resistance of the pipe, but also helps to reduce production costs and improve production efficiency.

[0097] The primary water cooling thermocouple hole 10 and the secondary water cooling jackets 11, 18 are used to install temperature sensors to monitor the temperature changes of the pipe during the cooling process in real time. These temperature sensors are connected to the control system and can transmit the collected temperature data to the control system in real time. The control system calculates the required cooling water flow according to the preset algorithm and temperature data, and adjusts the electromagnetic proportional valve and other actuators to control the size of the cooling water flow in real time, thereby realizing precise control of the cooling speed and temperature gradient. This design ensures that the cooling process can be carried out according to the predetermined parameters, optimizing the microstructure and overall performance of the copper-aluminum composite pipe.

[0098] As an optional embodiment of the present application, the cooling mechanism further comprises a spray 14 arranged near the end of the graphite mold 6.

[0099] As Figure 2As shown, the spray 14 of the present embodiment is a ring-shaped structure arranged at the end of the graphite mold 6, used for the final cooling and cleaning of the copper-aluminum composite pipe. The spray 14 sprays cooling water uniformly on the surface of the pipe through nozzles, taking away the residual heat and cleaning the impurities and oxides on the surface of the pipe. This design not only improves the cooling efficiency, but also helps to improve the surface quality of the pipe, making it smoother and neater.

[0100] In practical applications, the spray 14 is used in cooperation with other cooling mechanisms (such as the primary water cooling jacket 9 and the secondary water cooling jackets 11, 18) to complete the cooling process of the copper-aluminum composite pipe. By precisely controlling the parameters and synergistic effects of each cooling mechanism, the cooling speed and temperature gradient can be precisely controlled, thereby optimizing the microstructure and overall performance of the pipe. This production method not only improves the strength, plasticity, and corrosion resistance of the pipe, but also helps to reduce production costs and improve production efficiency.

[0101] As an optional embodiment of the present application, the temperature of the cooling water sprayed by the spray 14 is below 40℃.

[0102] It should be noted that the temperature of the cooling water sprayed by the spray 14 is controlled below 40℃, mainly to avoid the thermal shock or influence on the microstructure of the copper-aluminum composite pipe caused by excessively high cooling water temperature. The selection of cooling water temperature needs to consider factors such as the material of the pipe, the requirement of cooling speed, and the cooling effect, to ensure that the cooling process can proceed smoothly, while achieving the expected cooling effect and pipe performance.

[0103] In practical applications, the final temperature of the copper-aluminum composite pipe is reduced to room temperature or close to room temperature by using the spray below 40℃, thereby completing the entire cooling process.

[0104] As an optional embodiment of the present application, the aluminum solution obtained in step S3 contains 0.5-1.2% of silicon.

[0105] It should be noted that 0.5-1.2% of silicon is added to the aluminum solution, mainly to improve the mechanical properties and corrosion resistance of the copper-aluminum composite pipe. The addition of silicon can refine the grain structure of aluminum, improve the strength and hardness of the pipe. At the same time, silicon can form compounds with aluminum, enhancing the corrosion resistance of the pipe and prolonging its service life. Through experiments and optimization, the optimal range of silicon addition is determined to ensure that the copper-aluminum composite pipe has excellent mechanical properties and corrosion resistance.

[0106] When preparing the aluminum solution, silicon is added to the molten aluminum in a suitable form (such as silicon powder, silicon particles, etc.), and is subjected to thorough stirring and mixing to ensure that the silicon is uniformly distributed in the aluminum solution. Subsequently, the subsequent casting and composite processes are carried out according to the established process flow, and finally the copper-aluminum composite pipe with excellent performance is obtained.

[0107] As an optional embodiment of the present application, the casting mechanism comprises a ceramic pipe 3, an electromagnetic pump 2 and a sprue 8;

[0108] The ceramic pipe 3 is used to communicate the intermediate frequency aluminum melting furnace 1 with the sprue 8, and the electromagnetic pump 2 is arranged on the ceramic pipe 3, which is used to pump the aluminum solution in the intermediate frequency aluminum melting furnace 1 to the sprue 8 through the ceramic pipe 3, and then uniformly cast onto the copper pipe 4 in the graphite mold 6 pulled by the traction mechanism 15 through the sprue 8.

[0109] It should be noted that the ceramic pipe 3 has good high-temperature resistance and chemical stability, which can withstand the high temperature of the aluminum solution and prevent it from chemical reaction. At the same time, the inner wall of the ceramic pipe 3 is smooth, which helps to reduce the resistance of the aluminum solution in the conveying process and ensure that the aluminum solution can be smoothly pumped to the sprue 8. The electromagnetic pump 2 drives the delivery of the aluminum solution by electromagnetic force, which has the advantages of precise control of flow and stable delivery. By adjusting the working parameters of the electromagnetic pump 2, the delivery speed and flow of the aluminum solution can be precisely controlled, so as to ensure that the aluminum solution can be uniformly cast onto the copper pipe 4 in the graphite mold 6, forming a good composite interface.

[0110] Although the embodiments of the present application have been shown and described, those of ordinary skill in the art can understand that various changes, modifications, replacements and variations can be made to these embodiments without departing from the principles and purposes of the present application, and the scope of the present application is defined by the claims and their equivalents.

Claims

1. A method for manufacturing a copper-aluminum composite pipe, characterized in that: The method is applied to a copper-aluminum composite pipe manufacturing device, which comprises a medium-frequency aluminum melting furnace (1), a casting mechanism, a graphite mold (6), a cooling mechanism, a feeding drive mechanism (5), and a traction mechanism (15); The casting mechanism is connected to the medium-frequency aluminum melting furnace (1) and is used to cast the aluminum solution in the medium-frequency aluminum melting furnace (1) onto the copper tube (4) in the graphite mold (6); the cooling mechanism is used to cool the copper tube (4) after the aluminum solution is cast; the feeding drive mechanism (5) is used to transport the copper tube (4) into the graphite mold (6); and the traction mechanism (15) is used to continuously pull the copper-aluminum composite pipe out of the graphite mold (6); The method comprises: S1, removing the oxide layer on the surface of the copper tube (4) and drying it under a nitrogen environment; S2, preheating the copper tube (4) to 600-620° C., conveying it to the graphite mold (6) through the feeding drive mechanism (5), and introducing inert gas into the copper tube (4); S3, heating and melting the aluminum raw material in a medium-frequency aluminum melting furnace (1) to obtain an aluminum solution, and heating the aluminum solution to 700-730° C., and then injecting the aluminum solution into the copper tube (4) in the graphite mold (6) through the casting mechanism, so that the aluminum solution is coated on the outer surface of the copper tube (4), and the pulling mechanism (15) continuously pulls the copper tube (4) with the cast aluminum solution out of the graphite mold (6); S4, using the cooling mechanism to perform a first cooling on the copper tube (4) on which the aluminum solution has been cast, so that the aluminum solution rapidly nucleates on the outer surface of the copper tube (4) and forms a bonding interface on the copper tube (4); S5. Using the cooling mechanism to perform a second cooling on the copper tube (4) after the bonding interface is formed, the cooling rate is controlled within 10-20° C. / s to suppress the growth of the CuAl2 brittle phase and obtain a copper-aluminum composite tube.

2. The method for manufacturing the copper-aluminum composite pipe according to claim 1, wherein: In step S4, the temperature of the bonding interface is between 620-640°C.

3. The method for manufacturing the copper-aluminum composite pipe according to claim 2, wherein: In step S4, a temperature acquisition unit and a parabolic growth kinetics model controlled by interface diffusion are provided in the cooling mechanism. The parabolic growth kinetics model controlled by interface diffusion is used to quantitatively describe the growth kinetics behavior of the bonding interface under high temperature conditions, and to adjust the cooling rate in real time according to the temperature data of the surface of the copper tube (4) collected by the temperature acquisition unit.

4. The method for manufacturing the copper-aluminum composite pipe according to claim 3, wherein: The expression of the parabolic growth kinetic model controlled by interface diffusion is: J=-D dc / dx Where D represents the diffusion coefficient, D0 represents the constant of the material itself, Q represents the activation energy, R represents the gas constant, T represents the absolute temperature, J represents the diffusion flux, δ represents the thickness of the bonding interface, k represents the temperature constant, and t represents time.

5. The method for manufacturing the copper-aluminum composite pipe according to claim 3 or 4, characterized in that: In step S5, controlling the cooling rate to be within 10-20°C / s includes: S501, collecting temperature data at different points in the graphite mold (6); S502, using the parabolic growth kinetics model controlled by interface diffusion to compare the temperature data with a set temperature curve value to obtain a deviation value; S503 : Calculate the required cooling water flow rate based on the deviation value, control the cooling mechanism based on the cooling water flow rate, and use the cooling mechanism to adjust the cooling water flow rate in real time.

6. The method for manufacturing the copper-aluminum composite pipe according to claim 1, 2, 3 or 4, characterized in that: The cooling mechanism comprises: A primary water cooling jacket (9) is arranged outside the graphite mold (6); A primary water-cooled thermocouple hole (10) is provided on the graphite mold (6); A secondary water cooling jacket (11, 18) is provided on the graphite mold (6) and is located outside the primary water cooling jacket (9); Secondary water-cooled thermocouple holes (12, 13, 16, 17) are provided on the graphite mold (6).

7. The method for manufacturing the copper-aluminum composite pipe according to claim 6, wherein: The cooling mechanism further comprises a spray (14) which is arranged near the end of the graphite mold (6).

8. The method for manufacturing the copper-aluminum composite pipe according to claim 7, wherein: The temperature of the cooling water sprayed by the spray (14) is below 40°C.

9. The method for manufacturing the copper-aluminum composite pipe according to claim 1, wherein: The aluminum solution obtained in step S3 contains 0.5-1.2% silicon.

10. The method for manufacturing the copper-aluminum composite pipe according to claim 1, wherein: The casting mechanism comprises a ceramic pipe (3), an electromagnetic pump (2) and a gate (8); The ceramic pipe (3) is used to connect the medium-frequency aluminum melting furnace (1) with the pouring gate (8); the electromagnetic pump (2) is arranged on the ceramic pipe (3) and is used to pump the aluminum solution in the medium-frequency aluminum melting furnace (1) to the pouring gate (8) through the ceramic pipe (3), and uniformly pour the aluminum solution from the pouring gate (8) onto the copper tube (4) in the graphite mold (6) uniformly pulled by the pulling mechanism (15).

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