A method for preparing a conformal cooling mold with a copper-steel composite structure

Abstract

This invention belongs to the field of conformal cooling mold technology, specifically relating to a method for preparing a copper-steel composite conformal cooling mold. First, based on the shape of the mold cavity, mold flow and thermal simulation analysis is performed to design a three-dimensional conformal cooling water channel surrounding the cavity. The mold is then divided into several unit blocks. Next, mold steel and copper alloy are prepared, and then heat-treated and machined into individual mold steel blocks and copper alloy blocks. Sub-water channels are machined on each copper alloy block. Subsequently, mutually cooperating protrusions and grooves, as well as a microgroove array for enhanced adhesion, are machined on the contact surfaces of the mold steel blocks and copper alloy blocks. After applying a thermally and electrically conductive adhesive, the mold steel blocks and copper alloy blocks are alternately stacked according to the designed sequence and pressure is applied to form an assembly. Finally, the assembly is cured to obtain the copper-steel composite conformal cooling mold. The preparation method of this invention is simple, easy to operate, and can effectively improve the cooling efficiency of the mold.

Description

Technical Field

[0001] This invention belongs to the field of conformal cooling mold technology, specifically relating to a method for preparing a copper-steel composite conformal cooling mold. Background Technology

[0002] Mold manufacturing technology is one of the most widely used technologies in the manufacturing industry. In the traditional mold manufacturing field, the cooling rate of the mold has always been a key factor affecting product quality and production efficiency. Currently, most molds use a cooling method that involves creating straight cooling channels inside the mold and using circulating water for cooling. However, this traditional cooling method has many drawbacks. On the one hand, straight cooling channels are difficult to fit tightly against the complex curved surfaces of the mold cavity, resulting in uneven cooling. This can cause product deformation due to thermal stress, thus affecting product quality. On the other hand, the cooling rate of traditional cooling methods is not ideal, making it difficult to improve the working efficiency of the mold. To ensure product quality, it is necessary to extend the overall cooling time, thereby increasing production costs.

[0003] Therefore, to prevent product quality issues, conformal cooling channels need to be designed for the mold cavity. The design concept is to ensure the cooling channels align with the component contour, adapting to changes in the product's shape and effectively solving the problem of uneven cooling in traditional cooling methods. However, conformal cooling technology also faces significant challenges: traditional machining methods such as drilling and milling machines cannot manufacture complex internal conformal channels. While 3D printing technology can solve this problem, its equipment is expensive, the performance of printing materials is often inferior to traditional forged and rolled materials, and it suffers from anisotropy and internal defects.

[0004] In existing technologies, conformal cooling molds are basically made of a single material, steel. Some methods use copper inlays or surface copper plating, but these suffer from problems such as easy detachment or insufficient copper layer thickness. Therefore, there is an urgent need for a novel mold manufacturing method that can better combine high thermal conductivity materials with high-strength structural materials in three-dimensional space. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention proposes a method for preparing a copper-steel composite conformal cooling mold. This invention uses mold steel and copper alloy as the mold's constituent materials. First, unit steel blocks and copper alloy blocks are machined. Then, CNC machining is used to create three-dimensional conformal cooling water channels on the copper alloy unit blocks, enabling them to form conformal cooling water channels surrounding the mold cavity after assembly. Finally, conductive adhesive is used to connect the mold for integrated molding. The mold's exterior is made of mold steel, forming the mold's support structure and outer contour. The mold's interior is made of a high thermal conductivity copper alloy, embedded within the external mold steel structure to form three-dimensional conformal cooling channels. This method is simple, easy to operate, effectively improves mold cooling efficiency, and possesses excellent mechanical properties.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a method for preparing a conformal cooling mold with a copper-steel composite structure, comprising the following steps: S1. Based on the shape of the mold cavity, perform mold flow and thermal simulation analysis, design a three-dimensional conformal cooling water channel around the cavity, and divide the mold into several unit blocks. Among them, the inner unit block near the water channel is a copper alloy block, and the outer unit block away from the water channel is a mold steel block. S2. Prepare mold steel and copper alloy, heat treat them separately, and then machine them into mold steel blocks and copper alloy blocks respectively. On each copper alloy block, use CNC machining to machine sub-channels that make up part of the three-dimensional conformal cooling water channel. S3. A micro-texture structure is machined on the contact surface of each mold steel block and copper alloy block to make mutual cooperation. The micro-texture structure includes protrusions and grooves for assembly positioning, and an array of micro-grooves for enhancing adhesion. S4. Sandblast the contact surfaces of each mold steel block and copper alloy block, clean and dry them, and then apply a thermally and electrically conductive adhesive. S5. Stack the mold steel blocks and copper alloy blocks alternately in the design order and apply pressure to form an assembly. The sub-water channels of each copper alloy block together form a complete three-dimensional conformal cooling water channel. S6. The assembly is cured to obtain the conformal cooling mold of the copper-steel composite structure.

[0007] Preferably, in step S2, the mold steel is H13 steel, and its composition by mass percentage is: C: 0.32~0.45%, Si: 0.80~1.20%, Mn: 0.20~0.50%, Cr: 4.75~5.50%, Mo: 1.10~1.75%, V: 0.80~1.20%, with the balance being Fe and unavoidable impurity elements, of which P≤0.001% and S≤0.001%. Preferably, in the heat treatment process of the mold steel, the mold steel is annealed at 850°C, then solution-treated at 1000~1080°C for 1~2 h, water-cooled to room temperature, and then tempered three times at 500~650°C, each time holding at the temperature for 2~4 h, and air-cooled to room temperature.

[0008] Preferably, in step S2, the copper alloy is a C18150 zirconium-chromium copper alloy or a beryllium copper alloy; during the heat treatment of the copper alloy, the copper alloy is solution-treated at 760~1000 ℃ for 1~2 hours, water-cooled to room temperature, and then held at 315~520 ℃ for 2~4 hours.

[0009] Preferably, in step S3, the depth of the microgroove array is 20~50μm, the width is 50~100μm, and it is distributed in a cross-grid pattern.

[0010] Preferably, in step S4, the thermally and electrically conductive adhesive is an adhesive with epoxy resin as the matrix and silver powder as the filler.

[0011] Preferably, in step S4, a layer of silane coupling agent is coated on the contact surface before coating the conductive adhesive.

[0012] Preferably, in step S4, the thickness of the thermally and electrically conductive adhesive coating is 80~100μm.

[0013] Preferably, in step S6, during the curing process, the curing temperature is 80~120℃ and the temperature is maintained for 1~4 hours.

[0014] Compared with the prior art, the present invention has the following beneficial technical effects: This invention utilizes high thermal conductivity materials such as beryllium copper and zirconium-chromium copper as the materials for the flexible cooling water channels. Their thermal conductivity is far higher than that of mold steel, enabling rapid heat removal from the mold cavity, achieving fast and uniform cooling, significantly shortening the molding cycle, and improving product quality. The mold exterior is constructed of high-performance mold steel such as H13, ensuring high overall strength, high hardness, and wear resistance, resulting in a long service life. A segmented machining-integral welding strategy overcomes the manufacturing bottleneck of complex internal cavity structures, avoiding the use of expensive 3D printing equipment. The machining and vacuum diffusion welding processes used are mature, highly reliable, and suitable for mass production. Finite element analysis demonstrates that this structure effectively reduces thermal stress concentration during mold operation.

[0015] To more clearly illustrate the technical solutions of the embodiments of this disclosure, the accompanying drawings of the embodiments will be briefly described below. It should be understood that the drawings described below only relate to some embodiments of this disclosure and are not intended to limit this disclosure, wherein: Figure 1 This is a three-dimensional conformal cooling water channel diagram of the conformal cooling mold of copper-steel composite structure provided by the present invention.

[0016] Figure 2 This is a physical image of the copper-steel composite conformal cooling mold provided in Embodiment 1 of the present invention.

[0017] Figure 3 The temperature field change during the cooling process provided in Embodiment 1 of the present invention is shown in (a) as a schematic diagram of the overall temperature of the mold and (b) as a schematic diagram of the temperature of the cross-section of the mold.

[0018] Figure 4 The temperature field change during the cooling process provided in Comparative Example 1 of the present invention is shown in (a) as a schematic diagram of the overall temperature of the mold and (b) as a schematic diagram of the temperature of the cross-section of the mold.

[0019] Figure 5 This is a physical image of the device provided in Comparative Example 2 of this invention, which has undergone thermal cycling testing. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of the embodiments of this disclosure clearer, the technical solutions of the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this disclosure. All other embodiments obtained by those skilled in the art based on the described embodiments of this disclosure without creative effort are also within the scope of protection of this disclosure.

[0021] Unless otherwise defined, all terms used herein (including technical and scientific terms) shall have the same meaning as commonly understood by one of ordinary skill in the art to which this subject matter pertains. It will be further understood that terms such as those defined in commonly used dictionaries shall be interpreted as having meanings consistent with their meanings in the context of the specification and in the relevant art, and shall not be interpreted in an idealized or overly formal form unless otherwise explicitly defined herein.

[0022] The term "embodiment" as used herein means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of the phrase "embodiment" in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0023] This invention provides a method for preparing a conformal cooling mold with a copper-steel composite structure, comprising the following steps: S1. Based on the shape of the mold cavity, perform mold flow and thermal simulation analysis, design a three-dimensional conformal cooling water channel around the cavity, and divide the mold into several unit blocks. Among them, the inner unit block near the water channel is a copper alloy block, and the outer unit block away from the water channel is a mold steel block. Specifically, the thickness of the divided unit blocks is not limited, as long as it is suitable for machining.

[0024] S2. Prepare mold steel and copper alloy, heat treat them separately, and then machine them into mold steel blocks and copper alloy blocks respectively. On each copper alloy block, use CNC machining to machine sub-channels that form part of the three-dimensional conformal cooling water channel. Specifically, in step S2, the mold steel is H13 steel or other mold steel, and its composition by mass percentage is: C: 0.32~0.45%, Si: 0.80~1.20%, Mn: 0.20~0.50%, Cr: 4.75~5.50%, Mo: 1.10~1.75%, V: 0.80~1.20%, with the balance being Fe and unavoidable impurity elements, of which P≤0.001% and S≤0.001%; ​​during the heat treatment of the mold steel, the mold steel is annealed at 850℃, then solution-treated at 1000~1080℃ for 1~2 h, water-cooled to room temperature, and then tempered three times at 500~650℃, each time holding at that temperature for 2~4 h, and air-cooled to room temperature; Specifically, in step S2, the copper alloy is C18150 zirconium-chromium copper alloy, beryllium copper alloy, or other copper alloys; the C18150 zirconium-chromium copper alloy composition consists of the following elements by mass percentage: Cr: 0.50~1.20%, Zr: 0.03~0.30%, with the balance being Cu and unavoidable impurity elements, of which Al≤0.001% and Pb≤0.001%; ​​the beryllium copper alloy composition consists of the following elements by mass percentage: Be: 0.40~0.70%, Ni: 1.40~2.20%, with the balance being Cu and unavoidable impurity elements, of which Al≤0.001% and Pb≤0.001%; ​​during the heat treatment of the copper alloy, the copper alloy is solution-treated at 760~1000 ℃ for 1~2 h, water-cooled to room temperature, and then held at 315~520 ℃ for 2~4 h.

[0025] S3. A microtextured structure is machined on the contact surface of each mold steel block and copper alloy block to make mutual cooperation. The microtextured structure includes protrusions and grooves for assembly positioning, and a microgroove array for enhancing adhesion. The depth of the microgroove array is preferably 20~50μm, more preferably 30~40μm, and the width is preferably 50~100μm, more preferably 60~80μm. The microgroove array is distributed in a cross-grid pattern, which increases the bonding area and forms a mechanical anchoring effect. The fitting accuracy between the protrusions and grooves is 0.01~0.02mm, which is used for initial positioning during assembly. S4. The contact surfaces of the steel blocks and copper alloy blocks of each mold are sandblasted using 100-mesh white corundum sand at a sandblasting pressure of 0.5 MPa to achieve a surface roughness Ra of 1~3μm. Then, the surfaces are ultrasonically cleaned with acetone and anhydrous ethanol for 15 min in sequence, and dried in an oven at 80℃ for 30 min. A layer of silane coupling agent (KH-560, 2% ethanol solution) is uniformly coated on the dried contact surfaces to enhance interfacial bonding. After being left to air dry at room temperature for 15 min, a thermally and electrically conductive adhesive is applied. The coating thickness is preferably 80~100μm, for example, 80μm, 85μm, 90μm, 95μm, or 100μm. In some embodiments of the present invention, the oxide layer on the surface of the copper alloy can be partially removed by the microgroove array designed to enhance adhesion. After sandblasting and ultrasonic cleaning, hydroxyl, carboxyl and other groups are formed on the surface of the microgroove, which form chemical bonds with the coated silane coupling agent, and then cross-link with the active groups in the thermally and electrically conductive adhesive.

[0026] In some embodiments of the present invention, the thermally and electrically conductive adhesive used is an adhesive with epoxy resin as the matrix and silver powder as the filler, such as Master Bond EP17HTND-CCM, which has a thermal conductivity of 1.44 W·m⁻¹·K⁻¹ and an applicable temperature range of -62℃ to 316℃. Alternatively, the thermally and electrically conductive adhesive can be a conductive adhesive with epoxy resin as the matrix and graphite as the filler, such as Master Bond EP5G-80.

[0027] S5. Stack the mold steel blocks and copper alloy blocks alternately in the design order and apply a pressure of 2~5 MPa to form an assembly. The sub-water channels of each copper alloy block together form a complete three-dimensional conformal cooling water channel. The thickness of the adhesive layer in the assembly is 50~80μm.

[0028] S6. The assembly is cured at 80~120℃ for 1~4h to obtain the conformal cooling mold of the copper-steel composite structure.

[0029] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments thereof:

[0030] Example 1 This embodiment prepares a copper-steel composite conformal cooling mold, using H13 mold steel, whose composition consists of the following elements by mass percentage: C: 0.38%, Si: 1.20%, Mn: 0.40%, Cr: 5.00%, Mo: 1.30%, V: 0.85%, with the balance being Fe and unavoidable impurity elements, among which P≤0.001% and S≤0.001%; ​​and C18150 zirconium-chromium-copper alloy, whose composition consists of the following elements by mass percentage: Cr: 0.80%, Zr: 0.25%, with the balance being Cu and unavoidable impurity elements, among which Al≤0.001% and Pb≤0.001%; Specifically, the following steps are included: (1) Design according to the shape of the mold cavity, such as Figure 2 The mold is divided into 20 unit blocks of appropriate thickness, with the inner unit blocks near the water channel being copper alloy blocks and the outer unit blocks away from the water channel being mold steel blocks. Each unit block is 20 mm thick.

[0031] (2) The H13 mold steel was annealed at 850 ℃, then solution treated at 1080 ℃ for 1 hour, then water-cooled to room temperature, and then tempered three times at 600 ℃, holding for 4 hours each time, and then air-cooled to room temperature. The C18150 zirconium chromium copper alloy was solution treated at 1000 ℃ for 1 hour, then water-cooled to room temperature, and then held at 500 ℃ for 4 hours.

[0032] (3) H13 mold steel and C18150 zirconium chromium copper alloy are respectively machined into mold steel blocks and copper alloy blocks, and CNC machined into sub-water channels that form part of the three-dimensional conformal cooling water channels on each copper alloy block. The sub-water channel has a cross-sectional diameter of 8 mm.

[0033] (4) On the contact surfaces of each mold steel block and copper alloy block, a micro-textured structure is processed to cooperate with each other. A positioning protrusion with a diameter of 2 mm and a height of 0.5 mm is processed at the four corners of the contact surface, and a positioning groove is processed to cooperate with it. The fitting accuracy is 0.01 mm. A cross-grid micro-groove array is processed in the remaining area of ​​the contact surface. The micro-groove depth is 40 μm, the width is 80 μm, and the groove spacing is 200 μm. (5) Sandblasting is performed on the contact surfaces of each unit block using 100-mesh white corundum sand at a sandblasting pressure of 0.5 MPa to achieve a surface roughness Ra of 2 μm. Then, the surface is ultrasonically cleaned with acetone and anhydrous ethanol for 15 min, dried in an oven at 80℃ for 30 min, and a layer of silane coupling agent is uniformly coated on the dried contact surfaces. After being left to air dry at room temperature for 15 min, a thermally conductive and electrically conductive adhesive (Master Bond EP17HTND-CCM) is applied with a coating thickness of 100 μm. (6) After applying the thermally and electrically conductive adhesive, the unit blocks are stacked alternately in sequence. The copper alloy block and the mold steel block are precisely aligned through the positioning protrusions and grooves. A pressure of 3 MPa is applied to both ends of the assembly. After the assembly is formed, the adhesive layer thickness is 55 μm. (7) Place the assembly in a constant temperature oven and cure it at 100 °C for 2 h. Then air cool it to room temperature to obtain a copper-steel composite conformal cooling mold.

[0034] (8) After heat treatment, the final assembly is precision machined to obtain a conformal cooling mold with a C18150 zirconium chromium copper / H13 steel composite structure.

[0035] The conformal cooling mold with a C18150 zirconium-chromium-copper / H13 steel composite structure prepared in this embodiment is shown in the schematic diagram below. Figure 1 As shown in the picture, the actual product is as follows. Figure 2 As shown. The conformal cooling mold of the prepared C18150 zirconium-chromium-copper / H13 steel composite structure was tested for temperature and stress fields using finite element simulation, as shown. Figure 3 As shown, when the initial temperature is 700 ℃, after 60s of cooling, the highest temperature of the C18150 zirconium chromium copper and H13 mold connection surface is 335 ℃; the temperature near the cooling water channel is uniform. Compared with traditional molds, the temperature distribution of the mold of this invention is more uniform, effectively reducing the occurrence of "hot spots" and "cooling blind spots", reducing the temperature difference on the mold surface, and improving cooling efficiency.

[0036] The sample was cyclicated 500 times between room temperature and 200 ℃ (heating rate 10 ℃ / min, holding temperature for 30 min, forced air cooling), and the interface was checked by ultrasonic C-scan. There was no debonding or cracks at the interface.

[0037] Comparative Example 1 This comparative example provides a method for preparing H13 steel, the steps of which are basically the same as those in Example 1, except that all unit blocks in this comparative example are H13 steel. Everything else is exactly the same as in Example 1.

[0038] The temperature field of the conformal cooling mold made of H13 steel in this comparative example was analyzed by finite element simulation, such as... Figure 5 As shown, after cooling from 700 ℃ for 60 seconds, the highest temperature of the H13 steel mold was 485 ℃, which is higher than the highest surface temperature of the C18150 zirconium chromium copper / H13 mold in Example 1 (335 ℃). Calculations show that the cooling rate of the C18150 zirconium chromium copper / H13 mold is approximately 70% higher than that of the H13 steel mold.

[0039] Comparative Example 2 This comparative example prepares a copper-steel composite conformal cooling mold using H13 mold steel and C18150 zirconium-chromium copper. The steps are basically the same as in Example 1, except that in step (4), the contact surfaces of the mold steel blocks and copper alloy blocks are not machined with microgroove arrays, and only the positioning protrusions and grooves are retained. The rest is exactly the same as in Example 1.

[0040] Test results showed that interfacial microcracks appeared after 300 thermal cycles, such as... Figure 5 As shown, the protrusions and grooves on the contact surface, as well as the microgroove array for enhancing adhesion, significantly improve the interfacial bonding strength and thermal fatigue life.

[0041] The above description is only a preferred embodiment of 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 principle 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 method for preparing a conformal cooling mold with a copper-steel composite structure, characterized in that, Includes the following steps: S1. Based on the shape of the mold cavity, perform mold flow and thermal simulation analysis, design a three-dimensional conformal cooling water channel around the cavity, and divide the mold into several unit blocks. Among them, the inner unit block near the water channel is a copper alloy block, and the outer unit block away from the water channel is a mold steel block. S2. Prepare mold steel and copper alloy, heat treat them separately, and then machine them into mold steel blocks and copper alloy blocks respectively. On each copper alloy block, use CNC machining to machine sub-channels that make up part of the three-dimensional conformal cooling water channel. S3. A micro-texture structure is machined on the contact surface of each mold steel block and copper alloy block to make mutual cooperation. The micro-texture structure includes protrusions and grooves for assembly positioning, and an array of micro-grooves for enhancing adhesion. S4. Sandblast the contact surfaces of each mold steel block and copper alloy block, clean and dry them, and then apply a thermally and electrically conductive adhesive. S5. Stack the mold steel blocks and copper alloy blocks alternately in the design order and apply pressure to form an assembly. The sub-water channels of each copper alloy block together form a complete three-dimensional conformal cooling water channel. S6. The assembly is cured to obtain the conformal cooling mold of the copper-steel composite structure.

2. The method for preparing a conformal cooling mold with a copper-steel composite structure according to claim 1, characterized in that, In step S2, the mold steel is H13 steel, and its composition by mass percentage is: C: 0.32~0.45%, Si: 0.80~1.20%, Mn: 0.20~0.50%, Cr: 4.75~5.50%, Mo: 1.10~1.75%, V: 0.80~1.20%, with the balance being Fe and unavoidable impurity elements, of which P≤0.001% and S≤0.001%.

3. The method for preparing a conformal cooling mold with a copper-steel composite structure according to claim 2, characterized in that, During the heat treatment of the mold steel, the mold steel is annealed at 850 ℃, then solution-treated at 1000~1080 ℃ for 1~2 hours, water-cooled to room temperature, and then tempered three times at 500~650 ℃, each time holding at the temperature for 2~4 hours, and air-cooled to room temperature.

4. The method for preparing a conformal cooling mold with a copper-steel composite structure according to claim 1, characterized in that, In step S2, the copper alloy is C18150 zirconium-chromium copper alloy or beryllium copper alloy; during the heat treatment of the copper alloy, the copper alloy is solution-treated at 760~1000 ℃ for 1~2 h, water-cooled to room temperature, and then held at 315~520 ℃ for 2~4 h.

5. The method for preparing a conformal cooling mold with a copper-steel composite structure according to claim 1, characterized in that, In step S3, the depth of the microgroove array is 20~50 μm and the width is 50~100 μm, and it is distributed in a cross-grid pattern.

6. The method for preparing a conformal cooling mold with a copper-steel composite structure according to claim 1, characterized in that, In step S4, the thermally and electrically conductive adhesive is an adhesive with epoxy resin as the matrix and silver powder as the filler.

7. The method for preparing a conformal cooling mold with a copper-steel composite structure according to claim 1, characterized in that, In step S4, a layer of silane coupling agent is coated on the contact surface before the conductive adhesive is applied.

8. The method for preparing a conformal cooling mold with a copper-steel composite structure according to claim 1, characterized in that, In step S4, the thickness of the thermally and electrically conductive adhesive coating is 80~100μm.

9. The method for preparing a conformal cooling mold with a copper-steel composite structure according to claim 1, characterized in that, In step S6, during the curing process, the curing temperature is 80~120℃ and the temperature is maintained for 1~4 hours.

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