Micro-channel tube continuous extrusion die and design method

Abstract

This invention relates to a microchannel tube continuous extrusion die and its design method, belonging to the field of metal processing technology. The die consists of a die cavity, a die base plate, a male die, and a female die. The male die has upper and lower flow channels and an inclined male die length channel. The outer side of the male die head is arc-shaped with rounded acute corners. The female die includes a die cavity, an inclined guide slope, an overflow groove, and a discharge port. The arc-shaped surface of the die cavity is equipped with a feed inlet and a plug structure, which can stabilize flow, reduce flow resistance, and prevent overflow and die blockage. Based on the theory of viscous flow in metals, this invention establishes a quantitative model of flow resistance at the inclined rib connection, incorporating the inclination angle, wall thickness, width, length, material viscosity, and flow velocity into the formula. This achieves precise linkage between the extrusion ratio, the number of flow channels, the male die length, and the geometric parameters of the inclined ribs, solving the problems of die design relying on experience, uneven flow field, and frequent product defects.

Description

Technical Field

[0001] This invention relates to a microchannel tube continuous extrusion die and its design method, belonging to the field of metal processing technology. Background Technology

[0002] Continuous extrusion technology, with its significant advantages such as high production efficiency, high material utilization, and uniform product performance, is widely used in the continuous forming and processing of non-ferrous metal tubes and profiles, including aluminum and copper. Microchannel tubes, as a type of high-efficiency heat exchange tube with multiple internal fine channels, are widely used in scenarios with stringent requirements for heat exchange efficiency, structural precision, and reliability, such as automotive air conditioning, new energy vehicle thermal management systems, 3C device heat dissipation modules, refrigeration equipment, and 5G communication filters. Among these, the oblique-ribbed microchannel flat tube, due to its significantly superior heat transfer efficiency and structural strength compared to the traditional straight-ribbed structure, has become the industry trend in the field of microchannel heat exchangers. However, when using continuous extrusion to prepare inclined-rib aluminum alloy microchannel flat tubes, the asymmetric shear flow formed by the angle between the inclined ribs and the extrusion direction makes it impossible to accurately quantify the flow resistance at the inclined joints. In existing technologies, core mold parameters such as extrusion ratio, number of flow dividers, and male die length are all determined by engineers' experience, resulting in a mold debugging cycle of two to three months. When changing to a new product, the mold reuse rate is less than 30%, and defects such as tearing in thin-walled areas and insufficient filling are easily caused by flow velocity differences exceeding 30%. At the same time, insufficient control over the substrate preparation process, unreasonable continuous extrusion mold structure design, lack of a full-process quality control system, and poor compatibility between brazing process and inclined rib structure further exacerbate the instability of product forming, causing frequent welding defects, low mold life, and product qualification rate of less than 85%, which seriously restricts the high-precision, high-stability, and high-efficiency large-scale production of inclined-rib aluminum alloy microchannel flat tubes.

[0003] Therefore, it is urgent to establish a quantitative model of the viscous flow resistance at the inclined connection of the inclined rib microchannel flat tube, form a precise linkage scheme between geometric parameters and mold design, and build a whole-process process collaborative optimization system from substrate preparation to finished product brazing, so as to fundamentally solve the technical problems of mold design relying on experience, uneven flow field distribution, and unstable product quality in the existing continuous extrusion preparation process of inclined rib microchannel tubes. Summary of the Invention

[0004] To address the aforementioned technical problems, the present invention aims to provide a microchannel tube continuous extrusion die and its design method.

[0005] This invention discloses a continuous extrusion molding die, comprising a die cavity, the rear end of which is fixed to a die base plate by bolts. After the die cavity and the die base plate are assembled, an internal cavity is formed for placing a male die and a female die. The core of the male die can be inserted into the die cavity of the female die. The rear end of the die cavity component is bolted to the die base plate component. After the die cavity component and the die base plate component are assembled together, they together form a cavity that allows for stable installation and positioning of the male die component and the female die component. The core component on the male die component extends into and is placed within the die cavity structure of the female die component via a plug-in fit, achieving precise docking between the male and female dies and providing stable structural support and a suitable foundation for the extrusion molding of materials.

[0006] The male mold includes two sets of flow-diverting holes arranged vertically, with an outwardly protruding core mold between the two sets of flow-diverting holes. The core mold contains multiple inclined male mold length channels for material passage, dividing the core mold into multiple male molds. Each male mold extends into the cavity of the female mold, with a forming gap between the male mold and the cavity. The male mold has two sets of flow-diverting holes arranged vertically, with an outwardly protruding core mold between the two sets of flow-diverting holes. The core mold contains multiple inclined male mold length channels for material flow. These inclined male mold length channels replace the straight-through structure of existing technologies, effectively guiding material flow along the inclined direction, significantly improving the uniformity of material flow velocity distribution, and eliminating eddies and localized accumulation. The male mold length channel, while ensuring smooth material transport, divides the core mold into multiple male molds. Each male mold extends into its corresponding mold cavity, and a forming gap is reserved between the male mold and the mold cavity to ensure stable material forming within a limited space. This structure enables material diversion and balanced material distribution, improves material flow stability and forming uniformity, and ensures regular product cross-sectional structure and high dimensional accuracy.

[0007] Furthermore, the outer end faces of the male dies on both sides are arc-shaped, and the acute-angled corners where each male die contacts the male die length channel are rounded. The outer end faces of the male dies on both sides are designed with an arc-shaped structure, and the acute-angled corners where each male die contacts the male die length channel are rounded. The arc-shaped outer end faces can form a smooth, fitting interface with the mating cavity. The rounded corners effectively reduce resistance during material flow, preventing stress concentration and material scraping / retention at corners, eliminating material scraping, retention, and eddy formation, and significantly reducing flow resistance and localized stress concentration. This structure effectively improves material flow smoothness, reduces the risk of mold wear, extends mold life, and ensures a smooth inner wall and regular contour of the molded product, thus improving product molding quality.

[0008] Furthermore, the female mold has a mold-closing cavity on the side near the male mold. The mold-closing cavity includes two sets of inwardly sloping guide slopes, the ends of which communicate with the mold cavity of the female mold. An overflow groove for collecting material is provided on the same side of the guide slopes. An open-shaped discharge port is provided on the female mold at the rear of the mold-closing cavity. The mold-closing cavity is located on the side of the female mold facing the male mold. Inside the mold-closing cavity are two sets of inwardly sloping guide slopes, the ends of which communicate with the mold cavity to guide and convey material. An overflow groove for collecting excess material is provided on the same side of the guide slopes to prevent excess material from affecting the molding quality. An open-shaped discharge port is provided on the female mold at the rear of the mold-closing cavity for smoothly exporting the molded product. During operation, the closing cavity of the female mold is precisely aligned with the male mold. Two sets of guide ramps within the closing cavity direct and smoothly transport the material into the mold cavity. An overflow groove on the same side of the guide ramps promptly collects excess material to prevent overflow accumulation and cavity blockage. The molded product is smoothly discharged through the outlet at the rear of the closing cavity. This structure improves mold closing guidance accuracy and material conveying stability, enabling controllable overflow and continuous discharge, effectively preventing mold blockage, burrs, and channel clogging, and ensuring smooth continuous production.

[0009] Furthermore, the side of the mold cavity that contacts the extrusion wheel is arc-shaped, and at least one feed port is provided on the arc-shaped surface. Each feed port has a plug mounting groove below it for installing a plug. The surface of the plug extends beyond the arc-shaped surface of the mold cavity, and material flows in from the feed port after contacting the upper end of the plug. The side of the mold cavity that contacts the extrusion wheel has an arc-shaped structure, and at least one feed port is arranged on this arc-shaped surface. Below each feed port is a plug mounting groove for assembling the plug. After the plug is installed in the plug mounting groove, its surface is higher than the arc-shaped surface of the mold cavity, guiding and sealing the material, ensuring that the material stably enters the mold cavity through the feed port after contacting the upper end of the plug. During operation, the arc-shaped side of the mold cavity fits snugly against the extrusion roller. The feed inlet on the arc-shaped surface serves as the material inlet. The plug mounting groove below the feed inlet provides stable mounting and positioning for the plug. The structure of the plug protruding from the arc-shaped surface of the mold cavity guides and seals the material, ensuring that the material directionally contacts the upper end of the plug and smoothly flows into the feed inlet. This structure improves the directionality of feeding and the reliability of sealing, preventing material leakage from the side of the feed inlet and ensuring feeding stability and molding consistency during continuous extrusion.

[0010] Furthermore, based on the theory of viscous flow in metals, a quantitative model of flow resistance is constructed at the inclined connection of the male die to determine the precise linkage between the extrusion ratio, the number of flow dividers, the male die length, and the geometric parameters of the inclined ribs. For the asymmetric viscous flow characteristics at the inclined connection of the inclined rib microchannel flat tube, the quantitative model of flow resistance is established, incorporating the geometric parameters of the inclined ribs, including the inclination angle α, wall thickness t, transverse width w, material viscosity μ, and metal velocity v, into the model. The calculation formula is ΔP=K·(α / α0)^a·(t / t0)^b·(w / w0)^c·(l / l0)^d·μ^e·v^f. Through this quantitative model, the precise linkage between the extrusion ratio Λ, the number of flow dividers n, the male die length L, and the geometric parameters of the inclined ribs is achieved, completely solving the problem of mold design relying on trial and error. Parameter K is the drag coefficient, ranging from 0.8 to 1.2, determined through experimental calibration; α0, t0, w0, and l0 are the reference geometric parameters for the tilt angle, wall thickness, transverse width, and tilt section length, respectively; μ is the viscosity of the aluminum alloy at the extrusion temperature, ranging from 8 × 10⁻⁶. -4 Up to 1.2×10 -³Pa·s; v is the metal flow velocity, ranging from 0.5 to 4.0 m / s; exponents a, b, c, and d reflect the influence of tilt angle, wall thickness, width, and length on flow resistance, respectively, with values ​​ranging from a ∈ 0.5 to 1.5, b ∈ 0.3 to 0.7, c ∈ 0.2 to 0.8, and d ∈ 0.4 to 1.2; e is the viscosity correction coefficient, ranging from -1.0 to -0.5; f is the flow velocity exponent, ranging from 1.5 to 2.5. Combining ANSYS Fluent numerical simulation and mold flow channel experiments, K and each exponent were calibrated using the least squares method, ensuring that the relative error between the simulated resistance and the experimental resistance was no greater than 8%.

[0011] The second technical solution of the present invention is a microchannel tube prepared using the aforementioned continuous extrusion molding die, comprising a tube wall, within which multiple through-flow chambers are arranged through multiple inclined sections. These flow chambers are used for the flow of cooling medium, and the inclined sections are arranged at an angle on the inner side of the tube wall. This microchannel tube is manufactured using the aforementioned continuous extrusion molding die, with the tube body being the tube wall structure. Multiple through-flow chambers are formed within the tube wall by the multiple inclined sections, and these flow chambers are used for the flow and transmission of cooling medium. The inclined sections are arranged at an angle on the inner side of the tube wall, stably dividing the internal space and providing a regular channel for medium flow. The inclined sections and flow chambers increase the heat exchange contact area between the cooling medium and the tube wall, enhancing medium turbulence and heat exchange efficiency, improving overall heat exchange performance, while ensuring the structural strength and flow stability of the tube body.

[0012] Furthermore, the wall of the microchannel tube is made of 3-series or 6-series aluminum alloy. 3-series aluminum alloy uses Mn as the core strengthening element, with strict control over impurities such as Fe, Cu, and Mg to achieve a balance of strength, thermal conductivity, and brazing properties. Taking 3003 aluminum alloy as an example, the Mn content is controlled at 1.2% to 1.4%, the Fe content is no more than 0.30%, the Si content is 0.20% to 0.30%, the Cu content is no more than 0.05%, the Mg content is no more than 0.05%, the Zn content is no more than 0.05%, the Ti content is 0.01% to 0.02%, and the balance is Al. Other impurities are individually no more than 0.05% and their total amount is no more than 0.15%. This composition design can form a dispersed Al6Mn phase to achieve solid solution strengthening, while ensuring excellent thermal conductivity and brazing properties. The 6-series aluminum alloys form a Mg2Si strengthening phase with Mg and Si. The Mg content is 0.40% to 0.50%, the Si content is 0.50% to 0.80%, the Mg / Si ratio is about 1:1.1 to 1:3, the Cu content is less than 0.05%, the Mn content is 0.05% to 0.20%, the Fe content is less than 0.15%, and the balance is Al. The total Mg+Si content is 0.8% to 1.5%. This composition is designed to balance strength and brazing properties.

[0013] Furthermore, the inclination angle of the inclined section ranges from 15° to 45°, the wall thickness of the microchannel tube is no greater than 0.5 mm, and the number of channels is no less than 8. The inclined section is arranged on the inner side of the tube wall at an inclination angle of 15° to 45°, forming a ribbed structure. This ribbed structure can improve the heat exchange efficiency by 2 to 3 times compared to a straight ribbed structure, reduce flow resistance by 15% to 20%, and increase compressive strength by more than 30%. Microchannel tubes with a wall thickness of no more than 0.5 mm and no less than 8 channels are suitable for applications such as automotive air conditioning, new energy vehicle thermal management systems, 3C device heat dissipation modules, refrigeration equipment, and 5G communication filters.

[0014] By means of the above-described solution, the present invention has at least the following advantages:

[0015] (1) The mold cavity and the mold base plate of the present invention are spliced ​​to form a precise positioning cavity. The male mold and the female mold are connected to the mold cavity through the mold core, which has high mold closing accuracy and provides a stable structural foundation for continuous extrusion molding, effectively avoiding the problem of mold closing misalignment. The upper and lower molds are precisely aligned by cylindrical positioning pins, further reducing the risk of misalignment and deformation.

[0016] (2) The male mold of this invention adopts a two-part flow channel design with inclined male mold length channels. The inclined channel replaces the straight channel, and the material flows smoothly without eddies or accumulation. Combined with the flow resistance quantification model, the extrusion ratio, the number of flow channels, the length of the male mold and the geometric parameters of the inclined ribs are precisely linked, which ensures that the inclined ribs inside the microchannel tube are formed continuously and the wall thickness is uniform, and the forming accuracy and product consistency are significantly improved.

[0017] (3) The outer arc surface and rounded corner structure of the male mold of this invention reduce the resistance to material erosion and reduce stress concentration and scratch wear; the tungsten steel reinforced mold core improves wear resistance by three times; the lateral support structure counteracts the lateral component force of the inclined ribs and prevents the mold core from shifting. Under the combined effect, the service life of the mold under high temperature and high pressure environment can be increased to more than 130,000 meters.

[0018] (4) The present invention provides a guide slope and an overflow trough in the mold cavity. The guide slope stably guides the material conveying, and the overflow trough collects excess material in time to prevent mold blockage, burrs and channel blockage. The discharge port smoothly discharges the molded product, ensuring smooth continuous production. The petal-shaped four-zone welding chamber design enhances the welding force of the middle seam and reduces the non-welding rate to below 0.5%.

[0019] (5) The mold cavity arc surface of the present invention is matched with the plug and the plug mounting groove. The surface of the plug extends beyond the arc surface to guide and block the material, which ensures stable feeding direction and good sealing performance, effectively preventing material leakage from the side of the feed port, and improving feeding continuity and extrusion molding stability.

[0020] (6) The microchannel tube prepared by the mold of the present invention has an inclined flow chamber formed by the inclined arrangement of the internal inclined section. The inclined flow chamber greatly increases the contact area between the cooling medium and the tube wall, effectively improving heat dissipation and heat exchange efficiency. The heat exchange efficiency is 2 to 3 times higher than that of the straight rib structure, and the overall heat exchange performance is better, meeting the application requirements of high-end thermal management system.

[0021] (7) The mold design method and process parameter system of the present invention are not only applicable to 3003 series inclined rib microchannel flat tubes, but also compatible with 6 series aluminum alloys and harmonica tubes or microchannel flat tubes of different specifications. Only by substituting the flow resistance model into the product drawings to adjust the mold parameters can rapid development be achieved, which has a wide range of industrial application value.

[0022] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, the preferred embodiments of the present invention are described in detail below with reference to the accompanying drawings. Attached Figure Description

[0023] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show a certain embodiment of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This is a schematic diagram of the overall structure of the continuous extrusion molding die of the present invention; Figure 2 yes Figure 1 A cross-sectional view of a continuous extrusion die; Figure 3 This is a schematic diagram of the male die in the continuous extrusion molding die of the present invention; Figure 4 yes Figure 3 A magnified view of a portion of the image; Figure 5 This is a schematic diagram of the structure of the female die in the continuous extrusion molding die of the present invention; Figure 6 This is a schematic diagram of the female die in the continuous extrusion molding die of the present invention from another perspective; Figure 7 This is a schematic diagram of the structure of the mold cavity in the continuous extrusion molding die of the present invention; Figure 8 This is a schematic diagram of the microchannel tube structure of the present invention; Figure 9 This is a schematic diagram of the parameter positions in the microchannel tube viscous flow resistance quantification model of the present invention; In the figure: 1. Mold cavity; 2. Mold base plate; 3. Male mold; 4. Female mold; 5. Core mold; 6. Mold cavity; 7. Diverter hole; 8. Male mold length channel; 9. Male mold head; 10. Mold closing cavity; 11. Guide slope; 12. Overflow groove; 13. Discharge port; 14. Inlet; 15. Plug; 16. Plug mounting groove; 17. Inclined section; 18. Flow chamber; 19. Pipe wall. Detailed Implementation

[0025] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are for illustrative purposes only and are not intended to limit the scope of the invention.

[0026] like Figure 1 and Figure 2 As shown, a continuous extrusion molding die according to an embodiment of the present invention mainly includes four core components: a die cavity 1, a die base plate 2, a male die 3, and a female die 4. The die cavity 1 is the main forming cavity of the continuous extrusion molding die, and its rear end is fastened to the die base plate 2 by multiple bolts. After the die cavity 1 and the die base plate 2 are spliced ​​together, their interiors together form a cavity that can stably accommodate the male die 3 and the female die 4. The die core 5 equipped on the male die 3 extends into and is placed in the die cavity 6 structure inside the female die 4 in a plug-in manner, realizing the precise docking and fit between the male die 3 and the female die 4, providing stable structural support and a fit foundation for the extrusion molding of materials. During operation, the mold cavity 1 and the mold base plate 2 are fastened together by multiple bolts to form a stable assembly structure. The cavity enclosed by the two provides precise positioning and installation support for the male mold 3 and the female mold 4. The mold core 5 of the male mold 3 is inserted into the mold cavity 6 of the female mold 4 in an insert manner to achieve mold closing and positioning. The material enters the mold cavity 6 through a preset path and completes continuous extrusion molding under the cooperation of the mold core 5 and the mold cavity 6. This cooperation structure can improve the coaxiality of mold closing and assembly stability, reduce molding deviation, ensure continuous and reliable extrusion process, and improve product molding accuracy and structural consistency.

[0027] Combination Figure 3 and Figure 4The male mold 3 includes two sets of vertically arranged flow-diverting holes 7, with a protruding core mold 5 between them. The core mold 5 contains multiple inclined male mold length channels 8. Material enters simultaneously through the two sets of vertically distributed flow-diverting holes 7 on the male mold 3, and is directionally conveyed through the multiple male mold length channels 8 inside the protruding core mold 5. The male mold length channels 8 evenly divide the core mold 5 into multiple male mold heads 9, which are distributed along the outer periphery of the core mold 5. The male mold heads 9 extend into the mold cavity 6 of the female mold 4, maintaining a forming gap between them. The inclined male mold length channels 8 replace the straight-through structure in the prior art, effectively guiding the material to flow along the inclined direction, significantly improving the uniformity of material flow velocity distribution, and eliminating eddies and local accumulation phenomena. The male mold length channel 8, while ensuring smooth material transport, divides the core mold 5 into multiple male mold heads 9. Each male mold head 9 can extend into the corresponding mold cavity 6, and a forming gap is reserved between the male mold head 9 and the mold cavity 6 to ensure that the material can be stably formed within a limited space. This structure can realize material diversion and balanced material distribution, improve the stability of material flow and the uniformity of forming, and ensure that the product cross-sectional structure is regular and the dimensional accuracy is high.

[0028] During the molding process, the outer end faces of the two male die heads 9 are arc-shaped, forming a smooth interface with the mating cavity. The acute-angled corners where each male die head 9 contacts the male die length channel 8 are rounded. The rounding radius is determined based on actual working conditions, ranging from 0.1mm to 0.5mm, with the specific value determined comprehensively based on factors such as material viscosity, extrusion speed, and channel size. The arc-shaped outer end faces form a smooth interface with the mating cavity. The rounding treatment effectively reduces flow resistance and local stress concentration when material flows through, avoiding stress concentration and material scraping / retention at corners, eliminating material scraping, retention, and eddy formation, and significantly reducing flow resistance and local stress concentration. This structure effectively improves material flow smoothness, reduces the risk of die wear, extends die life, and ensures a smooth inner wall and regular contour of the molded product, thus improving product molding quality.

[0029] Combination Figure 5 and Figure 6The specific structure of the female mold 4 is described in detail. The female mold 4 has a closing cavity 10 on the side near the male mold 3. The closing cavity 10 includes two sets of inwardly sloping guide slopes 11. The ends of the guide slopes 11 connect to the mold cavity 6 of the female mold 4. An overflow groove 12 for collecting material is located on the same side of the guide slopes 11. An open discharge port 13 is located on the rear side of the closing cavity 10 on the female mold 4. The shape of the closing cavity 10 matches the outer contour of the male mold 3, ensuring precise alignment between the male mold 3 and the female mold 4 during mold closing. The two sets of guide slopes 11 are symmetrically distributed, and the inward sloping angle is designed for material guidance. The sloping angle of the guide slopes 11 is determined to be between 15° and 45° based on the material flow characteristics and extrusion process parameters, specifically matching the sloping angle of the male die head 9. The overflow groove 12 is located on the same side as the guide slope 11, facilitating the collection and discharge of excess material. The depth and width of the overflow groove 12 are determined according to the overflow amount, ensuring that excess material can be discharged smoothly and promptly without accumulating in the molding area. During operation, the mold closing cavity 10 of the female mold 4 is precisely aligned with the male mold 3. The upper and lower guide slopes 11 within the mold closing cavity 10 guide the material in a directional manner and smoothly transport it to the mold cavity 6. The overflow groove 12 on the same side of the guide slope 11 promptly collects excess material to prevent overflow accumulation and cavity blockage. The molded product is smoothly discharged through the outlet 13 on the rear side of the mold closing cavity 10. This structure can improve the mold closing guidance accuracy and material conveying stability, achieve controllable overflow and continuous discharge, effectively prevent mold blockage, burrs, and blockage of the male mold length channel, and ensure smooth continuous production.

[0030] Combination Figure 1 and Figure 7 The feeding structure of the mold cavity 1 is described in detail. The side of the mold cavity 1 that contacts the extrusion roller is arc-shaped, and the arc surface design matches the contour of the extrusion roller. At least one feed port 14 is provided on the arc surface, which serves to guide the material. Each feed port 14 has a plug mounting groove 16 on its lower side for installing a plug 15. The cross-sectional shape of the plug mounting groove 16 matches the shape of the plug 15 to ensure the positioning accuracy of the plug 15 after installation. After the plug 15 is installed in the plug mounting groove 16, the surface of the plug 15 extends beyond the arc surface of the mold cavity 1. The extension height is determined according to the feed rate and is within the range of 0.5mm to 2.0mm. The specific value ensures that the material can stably enter the mold cavity 1 through the feed port 14 after contacting the upper end of the plug 15. During operation, the arc-shaped side of the mold cavity 1 fits snugly against the extrusion roller. The feed inlet 14 on the arc-shaped surface serves as the material inlet. The plug mounting groove 16 below the feed inlet 14 provides stable mounting and positioning for the plug 15. The structure of the plug 15 protruding from the arc-shaped surface of the mold cavity 1 guides and seals the material, ensuring that the material directionally contacts the upper end of the plug 15 and smoothly flows into the feed inlet 14. This structure improves the directionality of feeding and the reliability of sealing, prevents material leakage from the side of the feed inlet, and ensures the feeding stability and molding consistency of the continuous extrusion process.

[0031] In a preferred embodiment, the mold of the present invention further includes a flow resistance quantification model based on the theory of viscous flow in metals. This model is established at the inclined connection of the male die head 9 and is used to determine the precise linkage between the extrusion ratio, the number of diversion holes, the length of the male die, and the geometric parameters of the inclined ribs. A flow resistance quantification model is established for the asymmetric viscous flow characteristics at the inclined connection of the inclined rib microchannel flat tube, see [link to relevant documentation]. Figure 9 The geometric parameters of the inclined ribs, including the inclination angle α, wall thickness t, transverse width w, material viscosity μ, and metal flow velocity v, are incorporated into the model, and the calculation formula is as follows:

[0032] ΔP=K·(α / α0)^a·(t / t0)^b·(w / w0)^c·(l / l0)^d·μ^e·v^f.

[0033] Parameter K is the drag coefficient, ranging from 0.8 to 1.2, determined through experimental calibration; α0, t0, w0, and l0 are the reference geometric parameters for the tilt angle, wall thickness, transverse width, and tilt section length, respectively, with α0 ranging from 2° to 40°, t0 ranging from 0.30 mm to 0.55 mm, w0 ranging from 3.00 mm to 4.50 mm, and l0 ranging from 4.0 mm to 5.50 mm; μ is the viscosity of the aluminum alloy at the extrusion temperature, ranging from 8 × 10⁻⁶. -4 Up to 1.2×10 - ³Pa·s corresponds to a temperature of 400℃±20℃; v is the metal flow velocity, ranging from 0.5 to 4.0 m / s; exponents a, b, c, and d reflect the influence of tilt angle, wall thickness, width, and length on flow resistance, respectively, with values ​​ranging from a∈0.5 to 1.5, b∈0.3 to 0.7, c∈0.2 to 0.8, and d∈0.4 to 1.2; e is the viscosity correction coefficient, ranging from -1.0 to -0.5; f is the flow velocity exponent, ranging from 1.5 to 2.5. Combining ANSYS Fluent numerical simulation and mold flow channel experiments, K and each exponent are calibrated using the least squares method, ensuring that the relative error between simulated and experimental resistance is no greater than 8%. Through this quantitative model, precise linkage between the extrusion ratio Λ, the number of flow channels n, the male mold length L, and the geometric parameters of the inclined ribs is achieved, completely solving the problem of mold design relying on experience-based trial and error.

[0034] Regarding the determination of the core parameters of the mold, based on the flow resistance ΔP and the flat tube discharge flow rate, combined with the requirements for the continuity and uniformity of metal flow, the extrusion ratio Λ is determined to be within the range of 5 ≤ Λ ≤ 100. The specific value of the extrusion ratio Λ is determined according to the number of channels: for harmonica tubes with a low number of channels, 5 ≤ Λ ≤ 20 is used to ensure bite stability and suppress mold dead zones; for flat tubes with a high number of channels, 25 ≤ Λ ≤ 100 is used to promote… <001> Texture formation reduces grain boundary thermal resistance. The number of flow channels n is matched with the number of inclined sections m, satisfying n > m, with a range of 3 ≤ n ≤ 8, to balance flow uniformity and mold cost. The length L of the male die head covers the flow transition zone between the inclined and straight sections, determined by the product of l and α, with a range of 60 mm ≤ L ≤ 180 mm, ensuring sufficient metal flow transition and eliminating velocity differences.

[0035] Combination Figure 8 The microchannel tube is integrally extruded using a continuous extrusion die and includes a tube wall 19. Multiple through-flow chambers 18 are formed within the tube wall 19 via inclined sections 17. These flow chambers 18 facilitate the flow of cooling media. The inclined sections 17 are arranged at an angle on the inner side of the tube wall 19. The tube wall 19 serves as the main load-bearing structure. The inclined sections 17 on the inner side of the tube wall 19 divide the internal space into multiple through-flow chambers 18. The inclined sections 17 and the tube wall form a rib structure. The flow chambers 18 facilitate the flow of cooling media and extend along the tube body. The inclined sections 17 and flow chambers 18 increase the heat exchange contact area between the cooling media and the tube wall 19, enhancing media turbulence and heat exchange efficiency, improving overall heat exchange performance, while ensuring the structural strength and flow stability of the tube body. The inclination angle of the inclined section ranges from 15° to 45°, the wall thickness of the microchannel tube is no more than 0.5 mm, the number of channels is no less than 8, forming an inclined rib structure. This inclined rib structure can improve the heat exchange efficiency by 2 to 3 times compared with the straight rib structure, reduce the flow resistance by 15% to 20%, and increase the compressive strength by more than 30%.

[0036] The walls of the microchannel tubes are made of 3-series or 6-series aluminum alloys. Taking 3003 aluminum alloy as an example, the Mn content is controlled at 1.2% to 1.4%, the Fe content is no more than 0.30%, the Si content is 0.20% to 0.30%, the Cu content is no more than 0.05%, the Mg content is no more than 0.05%, the Zn content is no more than 0.05%, the Ti content is 0.01% to 0.02%, and the balance is Al. Other impurities are individually no more than 0.05% and their total amount is no more than 0.15%. This composition design can form a dispersed Al6Mn phase to achieve solid solution strengthening, while ensuring excellent thermal conductivity and brazing properties. For 6-series aluminum alloys, the Mg content is 0.40% to 0.50%, the Si content is 0.50% to 0.80%, the Mg / Si ratio is approximately 1:1.1 to 1:3, the Cu content is less than 0.05%, the Mn content is 0.05% to 0.20%, the Fe content is less than 0.15%, and the balance is Al. The total Mg+Si content is 0.8% to 1.5%. This composition is designed to balance strength and brazing properties.

[0037] The following example, using the actual fabrication process of a 3003 aluminum alloy inclined rib microchannel flat tube, illustrates the specific application of the continuous extrusion molding die of this invention. This microchannel flat tube is used in automotive air conditioning systems, with a channel count of 12, a wall thickness of 0.4 mm, and an inclination angle of 30°±3°. In the die design stage, the geometric parameters of the inclined ribs are first extracted: inclination angle α is 30°, wall thickness t at the connection is 0.4 mm, and transverse width w is 3.5 mm. The inclination section length l = w / cosα ≈ 4.04 mm is calculated. Then, these geometric parameters are substituted into the flow resistance model ΔP = K·(α / α0)^a·(t / t0)^b·(w / w0)^c·(l / l0)^d·μ^e·v^f for calculation. The calibration parameters are K = 1.0, a = 1.0, b = 0.5, c = 0.5, d = 0.8, e = -0.8, and f = 2.0. The aluminum alloy viscosity μ is taken as 1.0 × 10⁻⁶. - The flow resistance is calculated to be ΔP = 1.8 MPa, with a metal flow velocity v of 1.5 m / s and a pressure of 3 Pa·s (corresponding to an extrusion temperature of 400℃). Based on this flow resistance value and the requirement for continuous metal flow, the extrusion ratio Λ is determined to be 350, the number of branch holes n is 6 (corresponding to m = 4 at the inclined connection), and the length L of the male die head is 120 mm.

[0038] During the continuous extrusion process, the 3003 aluminum alloy rod is first subjected to online grinding. A wire brush is used to remove the oxide layer from the rod surface, with a removal depth of at least 0.1 mm, and the surface roughness is controlled to Ra≤1.6μm. Then, the rod is uniformly heated to 200℃ using high-frequency induction heating, with a temperature control accuracy of ±5℃. The extrusion roller speed is set to 12 rpm, the die preheating temperature is set to 500℃, the extrusion speed reaches 90 m / min, and the extrusion outlet temperature is controlled at 460℃. Quenching employs a staged cooling strategy: first, pre-cooling to 320℃ using high-pressure air mist, then forced cooling to 45℃ in a water bath. The flat tube is arranged at a 45° angle for drying, with the water residue rate controlled below 0.08%. After entering the die, the material enters through the feed inlet 14 on the arc-shaped surface of the die cavity 1, and flows steadily into the die after contacting the upper end of the plug 15 protruding from the arc-shaped surface. After being simultaneously diverted through the upper and lower two-group flow holes 7, the material is evenly conveyed along multiple inclined male die head length channels 8 inside the core mold 5. The male die head length channels 8 extend multiple male die heads 9, which are formed by dividing the core mold 5, into the mold cavity 6, maintaining a forming gap with the mold cavity 6. The arc-shaped end faces and rounded corners of the male die heads 9 on both sides effectively reduce the material flow resistance, avoid scratching and stress concentration, and ensure smooth material conveying. After the material enters the mold cavity 10 of the female mold 4, it is guided into the mold cavity 6 by the upper and lower two-group guide slopes 11. Under the constraint of the male die heads 9 and the mold cavity 6, the material is extruded and formed. The overflow groove 12 on the same side of the guide slope 11 collects excess material in time to prevent overflow accumulation and cavity blockage. The formed product is smoothly discharged through the discharge port 13 on the rear side of the mold cavity 10.

[0039] In the subsequent online processing and testing stage, the microchannel flat tubes undergo online zinc spraying. The zinc spraying current and extrusion speed are dynamically matched according to the formula Y=(0.02X²+1.5X+15) / A, and the zinc layer thickness deviation is controlled within 2.5μm. Then, they are placed in a hot air curing oven for curing at 150℃ and a wind speed of 0.8m / s to ensure full cross-linking of the coating, achieving a cross-cut adhesion grade of 5B. Wall thickness deviation is detected using an online laser diameter gauge with an accuracy of ±0.05mm; weld integrity is detected using eddy current testing, identifying unwelded defects with an accuracy of not less than 0.1mm.

[0040] During the cutting stage, a rolling shearing process is used instead of traditional sawing. Carbide rollers with a hardness of 92 HRC are symmetrically arranged vertically. The roller spacing is set to 1.7 mm, the roller engagement depth is 12% of the flat tube height, the clamping force is 0.8 MPa, and the cutting position accuracy reaches ±0.08 mm. The roller cutting edge is slightly rounded with a radius of 0.2 mm. The roller linear speed and extrusion speed are synchronized at 90 m / min, resulting in a burr-free cut.

[0041] The final microchannel tube product consists of a tube wall 19, inclined sections 17, and through-flow chambers 18. The tube wall 19 is made of 3003 aluminum alloy. The inclined sections 17, arranged at an inclination angle of 30°, divide the internal space, forming 12 through-flow chambers 18. The cooling medium can flow stably along the flow chambers 18, achieving efficient heat exchange. The measured product indicators are as follows: heat exchange efficiency is 2.5 times higher than that of the straight rib structure, flow resistance is reduced by 18%, compressive strength is increased by 32%, wall thickness CV value is 4.2%, brazing qualification rate reaches 99.2%, overall product qualification rate is 98.8%, and the mold shows no significant wear after continuous operation for 140,000 meters.

[0042] Compared to molds designed using traditional empirical methods, which fail to quantify flow resistance to determine the extrusion ratio Λ=300, the number of diversion holes n=4, the male die head length L=80mm, the extrusion speed is only 60m / min, the mold preheating temperature is 530℃, the surface treatment uses single-sided zinc spraying, the cutting uses traditional sawing, and the brazing uses conventional atmospheric brazing, the products produced by this traditional process suffer from problems such as uneven metal flow leading to a 6% non-welding rate, a rib deformation rate of 9%, a zinc layer thickness deviation of 6μm, burrs from sawing, and a brazing failure rate of 8%. The overall product qualification rate is only 78%, and the mold core shifts and shows significant wear after 80,000 meters of operation. The comparative results show that the present invention, through mold design based on flow resistance quantification and synergistic optimization of the entire process, significantly improves the forming stability, product accuracy, and overall performance of the inclined rib microchannel tube, greatly extends the mold life, and improves production efficiency and product qualification rate.

[0043] The continuous extrusion molding die of this invention features stable and reliable overall assembly. The die cavity and die base plate are spliced ​​together to form a precisely positioned cavity. The male and female dies are fitted together by inserting the die core into the die cavity, resulting in high die-closing accuracy and providing a stable structural foundation for continuous extrusion molding, effectively avoiding die-closing misalignment. The male die adopts a two-part flow hole design with an inclined male die head length channel, ensuring smooth material flow without eddies or accumulation. Combined with a flow resistance quantification model, precise linkage between die parameters and rib geometry parameters is achieved, ensuring continuous rib formation and uniform wall thickness within the microchannel tube. The outer arc surface and rounded corner structure of the male die reduce material scouring resistance, minimize stress concentration and scratch wear, and the tungsten steel reinforced die core increases wear resistance by 3 times. The lateral support structure counteracts the lateral force of the ribs, preventing die core displacement. The service life of the die under high temperature and high pressure environments can be extended to over 130,000 meters. The female mold cavity is equipped with a guide slope and an overflow trough. The guide slope stably guides the material transport, while the overflow trough promptly collects excess material. The petal-shaped four-zone welding chamber design enhances the welding force of the center seam, reducing the incomplete welding rate to below 0.5%. The ejector smoothly discharges the molded product, ensuring smooth continuous production. The curved surface of the mold cavity, combined with the plug and plug mounting groove, guides and seals the material beyond the curved surface, ensuring stable feeding direction and good sealing, effectively preventing material leakage from the side of the feed port. The inclined sections inside the microchannel tube form an inclined flow chamber. The inclined flow chamber significantly increases the contact area between the cooling medium and the tube wall, improving heat exchange efficiency by 2 to 3 times compared to a straight rib structure. This meets the application requirements of high-end thermal management systems such as automotive air conditioning, new energy vehicle thermal management systems, 3C device heat dissipation modules, refrigeration equipment, and 5G communication filters. The mold design method and process parameter system of this invention are not only applicable to 3003 series inclined rib microchannel flat tubes, but also adaptable to 6 series aluminum alloys and harmonica tubes or microchannel flat tubes of different specifications. Rapid development can be achieved simply by substituting the mold parameters into the flow resistance model according to the product drawings, and it has a wide range of industrial application value.

[0044] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A continuous extrusion molding die, comprising a die cavity (1), wherein a die base plate (2) is fixed to the rear end of the die cavity (1) by bolts, wherein the die cavity (1) and the die base plate (2) are spliced ​​together to form an internal cavity for placing a male die (3) and a female die (4), wherein the core (5) of the male die (3) can be inserted into the die cavity (6) of the female die (4); The male mold (3) includes at least two sets of symmetrically arranged diversion holes (7), and between the two sets of diversion holes (7) is an outwardly protruding core mold (5). The core mold (5) is provided with multiple non-vertical straight male mold length channels (8). The male mold length channels (8) are used for material passage. The male mold length channels (8) divide the core mold (5) into multiple male mold heads (9). The male mold heads (9) extend into the mold cavity (6) of the female mold (4). There is a forming gap between the male mold head (9) and the mold cavity (6).

2. The continuous extrusion molding die as described in claim 1, characterized in that, The outer end faces of the male mold heads (9) on both sides are arc-shaped, and the acute-angled corners of each male mold head (9) that contact the male mold length channel (8) are rounded.

3. The continuous extrusion molding die as described in claim 1, characterized in that, The female mold (4) has a mold cavity (10) on the side close to the male mold (3). The mold cavity (10) includes two sets of guide slopes (11) that are inclined inward. The end of the guide slope (11) is connected to the mold cavity (6) of the female mold (4). An overflow groove (12) for collecting materials is provided on the same side of the guide slope (11). An open discharge port (13) is provided on the female mold (4) behind the mold cavity (10).

4. The continuous extrusion molding die as described in claim 3, characterized in that, The inclination angle of the guide slope (11) is 15° to 45°.

5. The continuous extrusion molding die as described in claim 1, characterized in that, The side of the mold cavity (1) that contacts the extrusion wheel is arc-shaped. The arc-shaped surface is provided with at least one feed port (14). Each feed port (14) has a plug mounting groove (16) for installing a plug (15) on its lower side. The surface of the plug (15) extends beyond the arc-shaped surface of the mold cavity (1). After the material contacts the upper end of the plug (15), it flows in from the feed port (14).

6. A method for designing a continuous extrusion molding die as described in claim 1 based on a flow resistance quantification model, characterized in that, The specific design steps are as follows: A flow resistance quantification model is established at the inclined connection of the male die head (9). The flow resistance quantification model is used to determine the linkage relationship between the extrusion ratio, the number of diversion holes, the length of the male die, and the geometric parameters of the inclined rib. The flow resistance calculation formula is ΔP=K·(α / α0)^a·(t / t0)^b·(w / w0)^c·(l / l0)^d·μ^e·v^f, where parameter K is the resistance coefficient, with a value range of 0.8 to 1.2, α0, t0, w0, and l0 are the reference geometric parameters of the inclination angle, wall thickness, transverse width, and inclination section length, respectively, and μ is the viscosity of the aluminum alloy at the extrusion temperature, with a value range of 8×10. -4 Up to 1.2×10 - ³Pa·s, where v is the metal flow velocity, ranging from 0.5 to 4.0 m / s; the exponents a, b, c, and d reflect the influence of the tilt angle, wall thickness, width, and length on the flow resistance, respectively, with values ​​ranging from a∈0.5 to 1.5, b∈0.3 to 0.7, c∈0.2 to 0.8, and d∈0.4 to 1.2; e is the viscosity correction factor, ranging from -1.0 to -0.5; and f is the flow velocity exponent, ranging from 1.5 to 2.

5.

7. A microchannel tube prepared using the continuous extrusion molding die according to any one of claims 1 to 5, comprising a tube wall (19), characterized in that, Multiple through flow chambers (18) are provided inside the pipe wall (19) through multiple inclined sections (17). The flow chambers (18) are used for the flow of cooling medium. The inclined sections (17) are arranged in an inclined manner inside the pipe wall (19). The cross-section of the inclined section (17) is rectangular, trapezoidal or arc-shaped. The cross-section of the flow chambers (18) is rectangular, circular or elliptical.

8. The microchannel tube as described in claim 7, characterized in that, The pipe wall (19) is made of 3 series aluminum alloy or 6 series aluminum alloy.

9. The microchannel tube as described in claim 8, characterized in that, When the pipe wall (19) is made of 3-series aluminum alloy, the Mn content is controlled at 1.2% to 1.4%, the Fe content is not greater than 0.30%, the Si content is 0.20% to 0.30%, the Cu content is not greater than 0.05%, the Mg content is not greater than 0.05%, and the balance is Al; when the pipe wall (19) is made of 6-series aluminum alloy, the Mg content is 0.40% to 0.50%, the Si content is 0.50% to 0.80%, the total Mg+Si content is 0.8% to 1.5%, and the balance is Al.

10. The microchannel tube as described in claim 9, characterized in that, The inclination angle of the inclined section (17) ranges from 15° to 45°, the wall thickness of the pipe wall (19) is no more than 0.5 mm, and the number of channels is no less than 8.

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