Laser additive and casting combined forming method for shape follow-up waterway mold

Abstract

The invention discloses a laser additive machining and casting combined forming method for a shape follow-up waterway mold, the shape follow-up waterway mold is split into a forming layer, a cooling pipeline and a supporting layer, step-by-step and process-by-process machining is carried out, the splitting form is that the whole mold is split layer by layer from outside to inside, and the forming layer of laser additive machining is provided with an internal cavity; the arrangement of the three-dimensional conformal waterways can be carried out in the cavity, and the supporting layer can be directly formed in the cavity through casting. Firstly, a forming layer is designed into a structural layer with the equal wall thickness, and laser printing is conducted; then, the selected pipe is machined into a three-dimensional conformal waterway matched with the forming layer through a split-channel and segmented bending process in cooperation with different segmented machining temperatures; and finally, the three-dimensional conformal waterway is arranged in a cavity of the forming layer, the supporting layer is machined through casting, combined forming of the mold is finally completed, and the problems that the internal stress of a laser additive printing piece is uneven, the pipe wall roughness of the conformal waterway is high, and the overall additive manufacturing and machining cost is high are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of laser processing die forming, and particularly relates to a laser additive and casting combined forming method for a conformal cooling channel die. Background Art

[0002] The cooling channels of traditional dies are usually in a straight cross-shaped network, with relatively low cooling efficiency and often uneven cooling for large and complex-structured parts. The conformal cooling channels, on the other hand, can be designed according to the shape of the mold core / cavity, with high cooling efficiency and uniform cooling. Such conformal cooling channel dies can effectively prevent the deformation of parts caused by uneven cooling and shorten the cooling time, thereby improving the yield and production efficiency of parts. Although conformal cooling channel dies have their unique advantages, at present, conformal cooling channel dies have not been able to replace traditional cooling channel dies. The reason is that due to the complexity of the water channel structure, conformal cooling channel dies usually need to be processed by laser additive manufacturing methods. Compared with the production process of traditional dies, there are still some technical problems in the laser additive manufacturing process of conformal cooling channel dies. The main problems are as follows: 1. The rapid heating and rapid cooling during laser processing can cause large non-uniform residual stresses inside the material, and in severe cases, the die may crack directly; 2. The surface roughness of the die manufactured by laser additive manufacturing, including the water channel surface, is relatively high. Scaling is likely to occur on the rough water channel surface, and it is very difficult to process the surface roughness of the water channel by general processing methods; 3. The cost of laser additive manufacturing is still relatively high.

[0003] In response to these problems, the existing solutions are as follows: 1. When using the laser additive manufacturing method to process conformal cooling channel dies, the process parameters such as laser power, scanning spacing, scanning speed, layer thickness, etc. are usually adjusted and optimized to reduce the residual stress inside the part. However, it cannot solve the problem of uneven stress caused by the complex structure of the part. Even if the laser additive manufacturing process parameters are adjusted, cracks may occur in some local areas (such as stress concentration positions) of the conformal cooling channel die. Moreover, by using laser additive manufacturing to process the conformal cooling channel die as a whole, the problems of high surface roughness of the water channel and high manufacturing cost cannot be solved.

[0004] 2. Other methods are adopted to process conformal cooling channel molds, such as metal powder pressing and sintering forming (recorded in the patent document CN104741884B), split machining and assembly forming (recorded in the patent document CN102744328A), and laser additive forming with a conformal cooling channel mold surface on a substrate (recorded in the patent document CN108421898B). These methods all reduce the manufacturing cost to varying degrees, and the disadvantages of each method are also significant. Metal powder pressing and sintering forming will introduce resin, resulting in shrinkage of the mold during the sintering and debinding process. Non-uniform shrinkage at different positions will cause serious deformation, and there will also be problems in terms of the density, strength, and subsequent mold life of the mold after sintering. Split machining and assembly forming have certain advantages for simple conformal cooling channel molds, but for complex conformal cooling channel molds, the machining difficulty of the water channels is very high, and the processing cost will no longer have an advantage. Laser additive forming with a conformal cooling channel mold surface on a substrate, although saving some printing costs, does not solve the problems of non-uniform residual stress cracking and high roughness of the water channel surface. Summary of the Invention

[0005] The present invention provides a combined forming method of laser additive manufacturing and casting for a conformal cooling channel mold, which disassembles the conformal cooling channel mold into a forming layer, a cooling pipeline, and a support layer and processes them step by step and by different processes, solving a series of problems such as non-uniform internal stress in laser additive printed parts, high roughness of the walls of the conformal cooling channels, and high overall additive manufacturing processing costs.

[0006] To achieve the above object, the present invention adopts the following technical solutions: The present invention provides a combined forming method of laser additive manufacturing and casting for a conformal cooling channel mold, and the conformal cooling channel mold is composed of a forming layer, a cooling pipeline, and a support layer; The forming layer has a structure with a hollow interior and an open bottom. The forming surface at the top of the forming layer has an outer shape structure corresponding to the workpiece. The forming layer is a structure layer formed by laser printing with equal wall thickness and high symmetry; The cooling pipeline is a three-dimensional conformal cooling channel formed by plastic forming a pipe to have the same shape as the inner surface of the forming surface, and the processed cooling pipeline is attached to the inner surface of the forming surface; By means of casting, molten metal liquid is directly poured into the cavity of the forming layer to form, forming a support layer, which plays a supporting role for the forming layer, and at the same time fixes the cooling pipeline between the support layer and the forming layer.

[0007] Adopting the above technical solutions: The forming layer is mainly used for the forming of parts (such as injection molded parts, die castings, etc.). Therefore, the forming surface of the forming layer should have all the external features corresponding to the parts. The cooling pipeline is a three-dimensional conformal waterway in the mold, and its external structure is similar to the forming surface, and it will be laid along the forming surface. The support layer will support the forming layer and at the same time fix the cooling pipeline between the support layer and the forming layer.

[0008] The present invention disassembles the conformal waterway mold into a forming layer, a cooling pipeline, and a support layer and processes them step by step and by different processes. The disassembly form is to disassemble the entire mold layer by layer from the outside to the inside. The above disassembly form or structure is not arbitrary, but is determined according to the combined forming process in the present invention. Due to the layer-by-layer disassembly structure, the forming layer processed by laser additive manufacturing has an internal cavity. In addition to arranging the three-dimensional conformal waterway in the cavity, more importantly, the support layer can be directly cast in the cavity. First, following the principle of the simplest structure and minimizing and equalizing the internal stress of laser additive manufacturing, the forming layer is designed into a structural layer with equal wall thickness and is laser printed; then, through the process of bending in sections and different section processing temperatures, the selected pipe is processed into a three-dimensional conformal waterway (conformal cooling pipeline); finally, the support layer is cast and processed to finally complete the combined forming of the conformal waterway mold. The processing processes involved in the present invention, such as laser additive processing, pipe plastic processing, and casting forming, are clearly sequenced and interrelated, which is beneficial to forming a complete production line, and the process flow is consistent with the structure disassembly form in the logical order.

[0009] Further, the support layer and the forming layer are made of the same material. During the casting process of the support layer, cooling is carried out through the cooling pipeline and a cooling box located outside the forming layer.

[0010] Further, during the casting process of the support layer, the temperature of the coolant in the cooling pipeline and the cooling box is 300 - 400 °C, the flow rate of the coolant in the cooling pipeline is 0.2 - 1 m 3 / h, and the flow rate of the coolant in the cooling box is 0.8 - 4 m 3 / h.

[0011] Further, before casting the support layer, coolant is introduced into the cooling pipeline and the cooling box to pre-treat the forming layer and the cooling pipeline, and keep it warm at 300 - 400 °C.

[0012] Further, after casting the support layer, the support layer is completely cooled and solidified in the coolant environment of the cooling pipeline and the cooling box. Subsequently, the coolant in the cooling pipeline and the cooling box are removed, and the conformal waterway mold is slowly cooled to room temperature in the air environment.

[0013] Further, before casting, an external fixing component is used to horizontally fix the forming layer, and the opening of the forming layer faces upward.

[0014] The support layer is formed by casting. The molten metal liquid is directly poured into the cavity of the forming layer to form. The problem solved here is the processing cost. Compared with laser additive manufacturing, using casting to process the support layer can greatly reduce the processing cost. The casting material is selected to be the same as that of the forming layer. During the casting process, the high-temperature liquid metal can flow and fill the gap between the cooling pipeline and the forming layer. As it cools and forms, the cooling pipeline is fixed and the entire forming layer is supported. In the casting process, some casting defects will be generated inside the support layer or at the interface between the forming layer and the cooling pipeline, which will slightly affect the cooling performance and the strength of the support layer, but will not affect the overall function and strength of the forming layer, and the strength of the support layer is not crucial.

[0015] During the casting process of the support layer, cooling is required. In addition to the cooling pipeline itself being used as a cooling component in the casting process, the present invention also adds a cooling box outside the forming layer. The cooling box is connected to an external coolant water circuit to ensure that the temperature remains stable during the cooling process. In addition, during the casting process, the forming layer needs to be horizontally fixed by an external fixing component. The purpose of cooling is, on the one hand, to prevent the high-temperature molten metal from penetrating the forming layer or the cooling pipeline. On the other hand, it is to prevent the forming layer from generating thermal deformation or thermal cracks during the casting process. Therefore, the temperature of the coolant cannot be too low. If the coolant temperature is too low, after the forming layer is heated by the casting liquid, it is very likely to be quenched in the too-low coolant, thus generating thermal cracks. The temperature of the coolant is set at 300 - 400 °C, and an oil medium can be selected as the coolant. During the cooling process, the molten metal liquid for casting first conducts heat to the cooling pipeline and the forming layer, and then to the coolant. The coolant is connected to an external circulation pipeline, and the continuously flowing coolant finally takes away the heat and cools. The flow rate of the cooling pipeline is 0.2 - 1 m 3 / h, and the flow rate of the cooling box is 0.8 - 4 m 3 / h.

[0016] Furthermore, the thickness of the forming layer is 5 - 20 mm.

[0017] The thickness of the forming layer can be determined by comprehensively considering the cooling effect and the processing difficulty. According to the layer-by-layer rule of the conformal cooling channel mold of the present invention, the layer inside the forming layer is the cooling pipeline, and the innermost layer is the support layer. Therefore, the thickness of the forming layer will directly affect the cooling efficiency of the product during the future mold production. The thinner the forming layer, the closer the cooling pipeline is to the forming surface of the mold, and the better the cooling effect. However, during the laser printing process, the thinner the wall surface of the forming layer, the more prone to deformation, the more difficult the processing, and the corresponding strength of the forming layer will also be affected, which will affect the service reliability of the subsequent mold. On the contrary, the cooling effect of the cooling pipeline on the product through the forming layer is worse. After multiple experimental verifications, the preferred range of the thickness of the forming layer in the present invention is 5-20 mm.

[0018] Furthermore, the forming layer is formed by laser additive printing on the substrate. The substrate has the same material as the forming layer. During the laser additive printing process, the substrate is preheated to 200-450 °C.

[0019] Furthermore, during the laser additive printing process, the laser power is 200-350 W, the scanning speed is 800-1200 mm / s, the scanning spacing is 0.08-0.12 mm, and the layer thickness of the printing is 30-50 μm.

[0020] The forming layer in the present invention has a dual role: in the mold processing of parts, it is used for the forming of parts; during the casting process, it serves as the outer mold for casting and is used for the casting forming of the support layer.

[0021] Manufacture the forming layer, which is processed by selective laser additive manufacturing of a powder bed. The problem to be solved in this step is the residual stress problem inside the workpiece. To solve this problem, on the one hand, the process is optimized, including the substrate preheating temperature, laser power, scanning speed, scanning spacing, etc., and on the other hand, the design and selection of the forming layer are carried out. The former mainly solves the thermal stress problem brought about by the process. The thermal stress is mainly related to the "rapid heating and rapid cooling" in the laser additive process. After preheating the substrate, the cooling rate of the printed part can be effectively reduced, thereby reducing the stress caused by rapid cooling. The laser power is directly related to the heat input. The greater the laser power, the more heat is input into the scanning area per unit time, which will cause the temperature of the molten pool to rise, and a greater temperature gradient and thermal stress will be generated during cooling. A higher scanning rate will result in a faster cooling rate of the molten pool and greater thermal stress. Usually, the next scan has a certain heat input effect on the previous scan layer. At a larger scanning spacing, this heat input will be less, so the cooling rate of the previous scan layer will be faster, corresponding to greater thermal stress. The latter mainly solves the structural thermal stress problem brought about by structural factors. During the laser additive manufacturing process, due to the inconsistent thickness of different positions of the printed part, different cooling rates of different parts after printing, or the asymmetry of the printed part structure, uneven internal stress in the printed part after cooling will generate structural thermal stress. Therefore, the design of the forming layer should follow two elements: one is that the thickness of the forming layer is uniform; the other is that the forming layer has higher symmetry. In this way, the structural thermal stress of the printed part can be minimized, and the occurrence of cracking of the printed part can be more effectively prevented.

[0022] Combined with the process in the present invention, the structure of the forming layer is designed. Its design principle is to follow the simplest structure on the premise of ensuring consistency with the shape of the workpiece. One is uniform thickness, and the other is structural symmetry. The smaller and more uniform the structural stress generated by laser additive processing is. In the overall laser additive manufacturing guided by the product structure, it is very difficult to keep the wall thickness of the printed part consistent, and the symmetry of the structure is not high, which will inevitably introduce greater structural stress. Different from this, in the present invention patent, laser additive manufacturing with minimized structural thermal stress is adopted, and the forming layer is designed into a structural layer with equal wall thickness and high symmetry and then laser printed. Here, it should be particularly noted that the overall laser additive manufacturing guided by the product structure only performs 3D printing based on the overall structure of the product itself. Different from this, laser additive manufacturing with minimized structural stress is to design the printed part before laser additive manufacturing, so as to minimize the internal stress of the printed part. In the present invention patent, according to the splitting rule, the forming layer itself is not structurally fixed and can be independently split and designed according to requirements. Here, the forming layer is split and designed based on the minimization of structural thermal stress.

[0023] In the forming layer of the present invention, the laser additive manufacturing process is as follows: 1. The design of the forming layer follows the principle of the simplest structure, ensuring uniform thickness of the forming layer and high structural symmetry; 2. Use 3D drawing software to model the 3D model and export the model in STL file format for subsequent processing; 3. Use slicing software to slice the 3D model and set parameters such as the printing layer thickness; 4. According to the sliced file, print and form the printed part layer by layer along a specific scanning path. Argon is used for protection throughout the additive manufacturing process and the oxygen content needs to be strictly controlled. The purity of argon is ≥99.99%, and the oxygen content in the protective atmosphere is controlled within 100 ppm.

[0024] Furthermore, the pipe is processed into a three-dimensional conformal waterway through the bending process. The bending process is carried out in sections according to the shape, curvature, etc. Different bending temperatures are selected under different curvatures, and the higher the curvature value, the higher the corresponding bending temperature.

[0025] The cooling pipeline has a dual role: in the processing of the mold to produce parts, it is used to cool the parts; during the casting process, it is used to cool the pipeline itself and its surroundings to prevent the pipe from melting.

[0026] When the cooling pipeline is processed and formed, a suitable pipe is selected and a three-dimensional conformal waterway with the same shape as the inner surface of the forming surface is processed through plastic forming. The problem solved in this step is the roughness problem of the conformal waterway. After disassembling the mold of the conformal waterway, only parameters such as the material of the pipe and the inner wall roughness need to be screened. Therefore, the roughness problem of the conformal waterway will not exist. The basic method of plastically processing the pipe into a conformal waterway is to bend the pipe. For simple structures, only one or two bending processes are required; for complex structures, three or more bending processes are required. In particular, for the processing of variable curvature arcs, when the curvature change is small, it can be approximated as a middle curvature for unified bending. When the curvature change is large, multiple bends need to be carried out in sections.

[0027] During the processing of the variable curvature arc of the cooling pipeline, under different positions and different curvatures, bending will cause uneven stress distribution inside the pipeline, and in severe cases, it may even cause problems such as wrinkling and cracking of the cooling pipeline. To solve this problem, the relationship between curvature and plastic processing needs to be considered. At large curvatures, the corresponding temperature is increased during bending to promote plastic deformation and facilitate stress release. Therefore, different bending temperatures are selected under different curvatures, so that the cooling pipeline generates uniform internal stress after plastic processing, preventing local wrinkling or cracking of the pipeline.

[0028] After processing and forming, the size and curvature of the cooling pipeline are consistent with the inner surface of the forming surface, and it can be attached to the inner surface of the forming layer after processing and forming. The cooling pipeline is simplified as much as possible. For example, adjacent pipelines are arranged at equal intervals. Without special restrictions, the pipelines adopt a unified pipe diameter, and the pipelines are integrally processed without welding, etc.

[0029] Compared with the prior art, the present invention has the following beneficial effects: (1) The present invention disassembles the conformal waterway mold into a forming layer, a cooling pipeline, and a support layer and processes them step by step and by different processes. The disassembly form is to disassemble the entire mold layer by layer from the outside to the inside. The above disassembly form or structure is not arbitrary, but is determined according to the combined forming process in the present invention. Due to the layer-by-layer disassembly structure, the formed layer processed by laser additive manufacturing has an internal cavity. In addition to arranging the three-dimensional conformal waterway in the cavity, more importantly, the support layer can be directly cast in the cavity.

[0030] (2) The forming layer with equal wall thickness and high symmetry is manufactured by powder bed laser additive manufacturing, so that the internal stress of the forming layer is uniform, avoiding stress concentration, preventing cracks from occurring in the mold during laser additive manufacturing, and improving the reliability of this part of the conformal waterway mold manufactured by laser additive manufacturing.

[0031] (3) Through the process of bending in different channels and segments, combined with different segment processing temperatures, the selected pipe is processed into a three-dimensional conformal waterway (conformal cooling pipeline). The conformal waterway can select the pipe according to requirements, such as pipe material, pipe diameter, inner wall roughness of the pipe, etc., to ensure that the surface of the conformal waterway has a low roughness after the mold is formed, so that the conformal waterway cools stably and does not scale.

[0032] (4) By casting to process the support layer and finally completing the combined forming of the conformal waterway mold, compared with the full-size integral forming of the conformal waterway mold by laser additive manufacturing, through the combined forming of laser additive manufacturing and casting, the laser additive printing amount is greatly reduced, and the production cost can be effectively reduced on the basis of maintaining the complete function of the conformal waterway mold.

[0033] (5) The processing processes involved in the invention, such as laser additive manufacturing, plastic processing of pipes, and casting forming, are clearly sequenced and interrelated. For example, the front and back of the forming layer are respectively related to laser additive manufacturing and casting forming, and the front and back of the cooling pipeline are respectively related to plastic processing of pipes and casting forming, etc., which is conducive to forming a complete production line, and the process flow is consistent with the structure disassembly form in the logical order. Description of the Drawings

[0034] The following further elaborates on the present invention in detail in conjunction with the drawings and specific embodiments.

[0035] Figure 1 It is a schematic structural diagram of the conformal waterway mold formed by the combination of laser additive manufacturing and casting in the present invention; Figure 2 Schematic diagram of laser additive manufacturing of the forming layer in the present invention; Figure 3 Schematic diagram of the processing flow of the cooling pipeline in the present invention; Figure 4 Schematic diagram of the casting process of the support layer in the present invention; Among them, the specific reference numerals are as follows: Forming layer 1, substrate 1-1, support layer 2, cooling pipeline 3, copper pipe 3-1, planar parallel pipeline 3-2 after the first bending process, three-dimensional conformal pipeline 3-3 after the second bending process, cooling pipeline liquid inlet 3-4, cooling pipeline liquid outlet 3-5, forming surface 4, forming layer support frame 5, fastening bolt 5-1, gasket 5-2, cooling box 6, cooling box liquid inlet 6-1, cooling box liquid outlet 6-2. Specific embodiments

[0036] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0037] In the embodiments of the present invention, a method of combining laser additive manufacturing and casting is used to process the core or cavity of a conformal waterway mold, hereinafter collectively referred to as a conformal waterway mold. Figure 1 For the combined-formed conformal waterway mold, according to the splitting rules of the present invention, the whole mold can be split into three parts: forming layer 1, support layer 2, and cooling pipeline 3. Although this embodiment takes the core of a certain mold as an example, this invention patent is applicable to the combined processing and forming of all other conformal waterway molds.

[0038] The forming surface 4 of the forming layer 1 of the conformal waterway mold is consistent with the outer shape of the workpiece and is used for shaping the workpiece. In this embodiment, only the arc surface of the forming layer 1 is regarded as the forming surface 4, and the cooling pipeline 3 is mainly laid according to the shape of the forming surface 4. However, the present invention does not limit the number of forming surfaces 4. In other embodiments, there can be multiple forming surfaces 4 to meet the requirements of different workpieces, and corresponding cooling pipelines 3 can be laid on different forming surfaces 4. For example, in this embodiment, in addition to the upper forming surface 4, the four side surfaces can all be set as the forming surface 4 according to the requirements of the workpiece.

[0039] In this embodiment, according to the design and selection rules of the forming surface 4, the thickness of each different position of the forming layer 1 of the conformal cooling channel mold is the same, and the structure has high symmetry, so that the residual stress inside the forming layer 1 can be kept uniform after subsequent laser additive manufacturing. However, the present invention does not strictly limit this condition. For extremely fine structures on the outer surface of the forming layer 1, such as narrow strip-shaped protrusions, etc., when the height of the protrusion is greater than the thickness of other positions and the narrow protrusion cannot be grooved, this condition cannot be satisfied and can be not restricted.

[0040] In this embodiment, the length and width of the forming layer 1 of the conformal cooling channel mold are both 160 mm, the height is 80 mm, and the thickness is 5 mm. The thickness of the forming layer 1 is directly related to the cooling efficiency of the mold. The thicker the thickness, the farther the cooling pipeline 3 is from the forming surface 4, and the lower the cooling efficiency. However, the thinner the thickness, the greater the difficulty of laser additive manufacturing of the forming layer 1. For thin-walled parts, during laser additive manufacturing, deformation or cracking is likely to occur due to the accumulation of internal stress. Therefore, in other embodiments, the thickness of the forming layer 1 of the conformal cooling channel mold can be determined according to the cooling effect and the situation during the laser additive manufacturing process.

[0041] In this embodiment, the forming layer 1 of the conformal cooling channel mold is formed by powder bed laser selective additive manufacturing, and the material of the forming layer 1 is selected as H13 steel. However, the present invention does not limit the material used for the forming layer 1. In other embodiments, mold steel materials from different grades such as H13, S136, P20, NAK80, 718, HPM38, 420, etc. can be selected. However, there are basic requirements for the specifications of the printing powders of different materials. The powder particle size is 15 - 53 μm, the powder oxygen content ≤ 100 ppm, and the powder Hall flow rate ≤ 25 s / 50 g.

[0042] In this embodiment, the forming layer 1 of the conformal cooling channel mold is subjected to laser additive printing on the substrate 1-1. The material of the substrate 1-1 is the same as that of the forming layer 1 for printing, both being H13. In order to reduce the internal stress in laser additive manufacturing and obtain a forming layer 1 with high density and low porosity, the substrate 1-1 needs to be preheated to 300 °C, the laser power is 280 W, the scanning speed is 800 mm / s, the scanning spacing is 0.08 mm, and the printing layer thickness is set to 50 μm. In other embodiments, the process parameters of laser additive manufacturing will be different. In addition, the entire additive manufacturing process is protected by argon, and the argon purity ≥ 99.99%, and the oxygen content in the protective atmosphere is controlled within the range of 100 ppm.

[0043] In this embodiment, for the laser additive manufacturing path of the conformal cooling channel mold forming layer 1, the printing of each planar layer is performed in the counterclockwise direction, and in terms of height, the printing is from bottom to top. However, the present invention does not limit the printing path. In other embodiments, the printing path can be adjusted to reduce the internal stress generated by laser additive manufacturing.

[0044] In this embodiment, the material of the cooling pipeline 3 of the conformal cooling channel mold is selected as a copper pipe 3-1. The inner diameter of the copper pipe 3-1 is 10 mm, the wall thickness of the copper pipe 3-1 is 3 mm, and the surface roughness Ra of the inner wall of the copper pipe 3-1 is 3.2 μm. Using the copper pipe 3-1 with a low-roughness inner wall as the cooling pipeline can, on the one hand, improve the heat transfer efficiency, and on the other hand, prevent pipeline blockage.

[0045] In this embodiment, the copper pipe 3-1 used for the cooling pipeline 3 of the conformal cooling channel mold is straight. In order to be able to fit the inner surface of the forming surface 4, the straight copper pipe 3-1 needs to be bent. First, the straight copper pipe 3-1 is bent once to form equally spaced planar parallel pipelines 3-2. The spacing between the planar parallel pipelines 3-2 is 20 mm, and the connection between pipes is an arc. In the first bending, since the curvature at the bending corner position is relatively large, the bending process needs to be carried out at a temperature of 200 °C. Then, the planar parallel pipelines 3-2 are bent a second time to form a three-dimensional conformal pipeline 3-3. The straight-line distance between the heads and tails of the arc segments of the conformal pipeline 3-3 is 150 mm. In the second bending, according to different curvatures, it can be roughly divided into two sections for bending. For the small-curvature section, the bending can be carried out at room temperature. For the large-curvature section, the temperature needs to be raised to 100 °C for bending. The three-dimensional conformal pipeline 3-3 is fitted to the inner surface of the forming surface 4 as the cooling pipeline 3 of the conformal cooling channel mold.

[0046] In this embodiment, the forming surface 4 of the conformal cooling channel mold forming layer 1 is a variable arc surface. Therefore, in the process of processing the planar parallel pipelines 3-2 into three-dimensional conformal pipelines 3-3, the arcs are segmented, and segmented processing and forming are carried out according to the curvatures of different segments to obtain pipelines with the same shape as the forming surface 4.

[0047] In this embodiment, the bending process of the cooling pipeline 3 is relatively simple. In other embodiments, in the case of particularly large bending deformation, the pipe can be preheated to 400 - 500 °C to prevent the pipe from cracking during the plastic processing. In particular, for complex bending processes, specific molds can be made for the conformal forming of the pipe.

[0048] In this embodiment, the conformal cooling channel mold support layer 2 is formed by casting. Before casting, the conformal cooling channel mold forming layer 1 needs to be placed in the cooling box 6 and fixed horizontally. The forming layer support frame 5 is used to fix the conformal cooling channel mold forming layer 1. During the fixing process, the cavity opening of the forming layer 1 faces upward. After horizontal testing, when the casting surface is completely horizontal, it is fixed with fastening bolts 5-1. A gasket 5-2 is provided between the fastening bolts 5-1 and the forming layer 1 to prevent the tightening force of the bolts from damaging the outer surface of the forming layer 1. The main purpose of the forming layer support frame 5 is to fix the forming layer 1. In the present invention, it is not limited to such a support frame for fixing.

[0049] In this embodiment, the casting material is selected as the same material as the forming layer 1, H13 steel. The melting point of H13 steel is usually 1450 °C. Then, during the casting process of the conformal cooling channel mold support layer 2, it is necessary to cool the forming layer 1 and the cooling pipeline 3 to prevent the H13 steel liquid from penetrating through the forming layer 1 or the cooling pipeline 3. The cooling box 6 is used for the placement and circulation of the coolant, connecting the cooling box liquid inlet 6-1 and the cooling box liquid outlet 6-2. The cooling pipeline 3 is used for the circulation of the coolant, connecting the cooling pipeline liquid inlet 3-4 and the cooling pipeline liquid outlet 3-5. The coolant is selected as an oil medium, and the oil temperature is 400 °C. Before casting, the forming layer 1 and the cooling pipeline 3 need to be placed in the coolant for a certain period of time to keep warm so that their overall temperature reaches 400 °C. On the one hand, it can prevent thermal cracks from occurring in the forming layer 1 during the casting process. On the other hand, it can prevent the fluidity of the H13 steel liquid from deteriorating under rapid cooling, resulting in interface void defects due to incomplete coating of the steel pipe. During casting, the flow rate of the cooling pipeline 3 is selected as 0.3 m 3 / h. The flow rate of the cooling box 6 is selected as 1.8 m 3 / h. After casting, the support layer 2 is completely cooled and solidified in a coolant environment at 400 °C. Subsequently, the coolant is removed, and the mold is slowly cooled from 400 °C to room temperature in an air environment. Finally, the combined forming of the conformal cooling channel mold is completed.

[0050] In the present invention, the conformal cooling channel mold is formed by combining laser additive manufacturing and casting in a segmented manner. After the mold is formed, heat treatment, surface secondary processing, etc. are required, and these operations can adopt conventional process flows.

[0051] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A laser additive and casting combined forming method for a conformal water channel mold, characterized in that, The conformal cooling channel mold is composed of a forming layer, a cooling pipeline, and a support layer; The forming layer has a hollow interior and an open bottom structure. The forming surface at the top of the forming layer has an outer shape structure corresponding to the workpiece. The forming layer is a structure layer with equal wall thickness and high symmetry formed by laser printing; The cooling pipeline is a three-dimensional conformal cooling channel processed by plastic forming of a pipe to have the same shape as the inner surface of the forming surface. The processed cooling pipeline is attached to the inner surface of the forming surface; In a casting method, molten metal liquid is directly poured into the cavity of the forming layer for molding to form a support layer, which plays a supporting role for the forming layer and at the same time fixes the cooling pipeline between the support layer and the forming layer.

2. The laser additive and casting combined forming method of the conformal water channel mold according to claim 1, characterized in that, The support layer and the forming layer are made of the same material. During the casting process of the support layer, cooling is carried out through the cooling pipeline and a cooling box located outside the forming layer.

3. The laser additive and casting combined forming method of the conformal water channel mold according to claim 2, characterized in that During the casting process of the support layer, the temperature of the coolant in the cooling pipeline and the cooling tank is 300-400 °C, the flow rate of the coolant in the cooling pipeline is 0.2-1 m 3 / h, and the flow rate of the coolant in the cooling tank is 0.8-4 m 3 / h.

4. The laser additive and casting combined forming method of the conformal water channel mold according to claim 3, characterized in that Before casting the support layer, coolant is introduced into the cooling pipeline and the cooling box to pre-treat the forming layer and the cooling pipeline and keep it warm at 300 - 400 °C.

5. The laser additive and casting combined forming method of the conformal water channel mold according to any one of claims 1-4, characterized in that, After casting the support layer, the support layer is completely cooled and solidified in the coolant environment of the cooling pipeline and the cooling box. Subsequently, the coolant in the cooling pipeline and the cooling box is removed, and the conformal cooling channel mold is slowly cooled to room temperature in the air environment.

6. The laser additive and casting combined forming method of the conformal water channel mold according to claim 5, characterized in that Before casting, an external fixing component is used to horizontally fix the forming layer, and the opening of the forming layer faces upward.

7. The laser additive and casting combined forming method of the conformal water channel mold according to claim 1, characterized in that, The thickness of the forming layer is 5 - 20 mm.

8. The laser additive and casting combined forming method of the conformal water channel mold according to claim 1, characterized in that, The forming layer is formed by laser additive printing on a substrate. The substrate and the forming layer are made of the same material. During the laser additive printing process, the substrate is preheated to 200 - 450 °C.

9. The laser additive and casting combined forming method of the conformal water channel mold according to claim 8, characterized in that, During the laser additive printing process, the laser power is 200 - 350 W, the scanning speed is 800 - 1200 mm / s, the scanning pitch is 0.08 - 0.12 mm, and the printing layer thickness is 30 - 50 μm.

10. The laser additive and casting combined forming method of the conformal water channel mold according to claim 1, characterized in that The pipe is processed into a three-dimensional conformal cooling channel through a bending process. The bending process is carried out in sections according to the shape, curvature, etc. Different bending temperatures are selected under different curvatures, and the curvature value and the bending temperature value are positively correlated.

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