Ceramic mold with surface microstructure and structure optimization method and application thereof

Abstract

The invention discloses a ceramic mold with a surface microstructure and a structure optimization method and application of the ceramic mold, and belongs to the technical field of metal casting. A mathematical model between a longitudinal temperature gradient and surface microstructure parameters is constructed, the surface structure shape of the ceramic mold is adjusted through surface microstructure design and mathematical model driving quantitative optimization, heat transfer and heat dissipation paths during casting alloy solidification are effectively improved, a thermal field is actively regulated and controlled by locally adapting to complex geometric requirements, and the surface structure shape of the ceramic mold is adjusted. According to the invention, effective control of the overall longitudinal temperature gradient is realized, the problems of insufficient temperature gradient, non-uniform structure and defects caused by structural limitation of a traditional ceramic shell are systematically solved, and an innovative technical path is provided for low-cost manufacturing of high-performance single crystal blades.

Description

Technical Field

[0001] The present invention belongs to the technical field of metal casting, and relates to a ceramic mold with a surface microstructure, and a method and application for optimizing its structure. Background Art

[0002] The manufacturing material of gas turbine turbine blades is mainly superalloy to meet the stringent requirements of working in extreme high-temperature environments. Under high-temperature conditions, the grain boundaries inside traditional polycrystalline materials will act as weakening points, resulting in a significant decrease in the strength and stiffness of the materials, which cannot meet the performance requirements of gas turbine turbine blades. Therefore, single-crystal blades came into being. By eliminating all grain boundaries, single-crystal blades significantly improve the temperature-bearing capacity and creep performance of the alloy, and have become the main type of current gas turbine turbine blades. The manufacturing of single-crystal blades relies on advanced directional solidification technology, which establishes a temperature gradient with a specific direction inside the mold. During the solidification process, the heat flow is made perpendicular to the solidification interface and exported in a single direction. This special heat conduction mode promotes the growth of crystals along the direction opposite to the heat flow, and finally forms a columnar crystal or single-crystal structure with a specific orientation. This preparation process is crucial for the successful manufacturing of superalloy single-crystal blades.

[0003] However, the directional solidification technology also faces a series of challenges in the preparation process of single-crystal blades. Among them, problems such as non-uniform microstructure and large grains are particularly prominent. In addition, defects such as stray crystals and freckles often appear. The stray crystal defect refers to the formation of unexpected grains during the manufacturing process of single-crystal blades due to the complexity of solidification conditions. These unexpected grains destroy the integrity of the single-crystal structure of the blade, thereby affecting its high-temperature performance and reliability. The freckle defect usually appears on the vertical outer surface of the casting, presenting as continuous or intermittent slender chain-like parallel to the gravity direction, and is composed of many fine grains with disordered orientations. These defects not only seriously reduce the high-temperature mechanical properties of the blade, but also cannot be eliminated by subsequent heat treatment, thus greatly affecting the qualification rate of turbine blades. Research results show that a high longitudinal temperature gradient can effectively inhibit the formation of the above defects and simultaneously prepare directional columnar crystals with uniform organization and fine grains.

[0004] Further analysis reveals that the reduction of the longitudinal temperature gradient of the blade is mainly related to the material and structural characteristics of the ceramic mold. During the directional solidification process, the main role of the ceramic mold is to provide a stable heat conduction path to control the solidification process of the molten metal. When the superalloy molten metal is injected into the ceramic mold, it will start to cool and solidify. During this process, the material and structural characteristics of the ceramic mold play a decisive role in the heat conduction path and rate. As Figure 1As shown in the figure, during the directional solidification process, after the heat of the molten metal of the blade is conducted to the ceramic mold, since the transverse comprehensive heat transfer coefficient of the traditional ceramic mold with smooth inner and outer walls is less than the longitudinal comprehensive heat transfer coefficient, the heat will quickly conduct along the longitudinal direction of the ceramic mold. This results in a decrease in the temperature difference between the unsolidified region and the solidified region of the casting, and further reduces the longitudinal temperature gradient at the solidification front during the directional solidification of the blade. This change directly leads to the coarsening of the blade grains, the increase of the dendrite spacing, and the non-uniformity of the microstructure. Chinese patent application with the publication number CN110252958A discloses a method for preparing a blade mold that suppresses the hetero-crystal defects of the flange based on the hollow / porous structure of the flange. By setting the hollow / porous structure at specific positions of the mold, the direct regulation of the temperature gradient during the directional solidification process is achieved. However, due to the geometric differences in regions such as the blade body, blade root, and blade tip of the blade, the requirements for the temperature gradient are different, and the currently disclosed ceramic molds cannot meet the differential heat dissipation requirements of the casting. Summary of the Invention

[0005] Aiming at the problems existing in the prior art, the present invention provides a ceramic mold with a surface microstructure, its structure optimization method and application, so as to solve the technical problems that the ceramic mold in the prior art cannot meet the differential heat dissipation requirements of the casting, the microstructure of the casting is non-uniform, and hetero-crystal defects are easily generated.

[0006] The present invention is realized through the following technical solutions: A method for optimizing the structure of a ceramic mold with a surface microstructure, comprising the following steps: S1: Establish a basic directional solidification temperature field by using a ceramic mold with a smooth outer surface; S2: Obtain the longitudinal temperature gradient when the blade to be cast undergoes directional solidification on the ceramic mold with a surface microstructure, and establish a mathematical model between the longitudinal temperature gradient and the surface microstructure parameters; optimize the basic directional solidification temperature field based on the mathematical model, and obtain the microstructure of the blade to be cast under the optimized basic directional solidification temperature field; S3: If the microstructure of the blade to be cast under the optimized basic directional solidification temperature field is non-uniform or defective, adjust the surface microstructure parameters, and repeat S2 until the microstructure of the blade to be cast meets the requirements, and complete the structure optimization of the ceramic mold with a surface microstructure; the surface microstructure parameters include: the structural shape, structural size, and arrangement mode of the surface microstructure.

[0007] Preferably, in S1, the method of establishing the basic directional solidification temperature field by using a ceramic mold with a smooth outer surface is as follows: on the ceramic mold with a smooth outer surface, at least 10 temperature measurement zones are divided according to the shape change characteristics of the casting and the process requirements, and the simulated directional solidification temperature field of each temperature measurement zone is calculated through numerical simulation; and an actual directional solidification experiment is carried out by using the ceramic mold with a smooth outer surface, the actual temperature data of each temperature measurement zone are measured in real time, and the actual directional solidification temperature field of the directional solidification process is established according to the actual temperature data; the simulated directional solidification temperature field is used to adjust the actual directional solidification temperature field to complete the establishment of the basic directional solidification temperature field.

[0008] Preferably, 15 of the temperature measurement zones are divided according to the shape change characteristics of the casting and the process requirements.

[0009] Preferably, the method of using the simulated directional solidification temperature field to adjust the actual directional solidification temperature field to complete the establishment of the basic directional solidification temperature field is as follows: if the temperature error between the actual directional solidification temperature field and the simulated directional solidification temperature field of any one temperature measurement zone is greater than 10%, the heat transfer parameters are adjusted, and the simulated directional solidification temperature field is adjusted according to the actual directional solidification temperature field so that the temperature errors between the actual directional solidification temperature fields and the simulated directional solidification temperature fields of all temperature measurement zones are not greater than 10%, the adjustment of the simulated directional solidification temperature field is completed, and the establishment of the basic directional solidification temperature field is realized.

[0010] Preferably, in S2, the longitudinal temperature gradient is obtained through the thermal conductivity, heat conduction and heat transfer coefficient, radiation heat transfer coefficient, specific heat, latent heat of solidification, and the density, solidus temperature, and liquidus temperature of the alloy.

[0011] Preferably, the thermal conductivity includes the thermal conductivity of the ceramic shell and the thermal conductivity of the non-shell medium; the radiation heat transfer coefficient includes the radiation heat transfer coefficient of the ceramic shell and the radiation heat transfer coefficient of the non-shell medium.

[0012] Preferably, the structural shape of the surface microstructure includes a square or a regular hexagon.

[0013] A ceramic mold with a surface microstructure is optimized by the above structural optimization method; the ceramic mold includes a ceramic mold body, a hollow chamber is arranged inside the ceramic mold body, and a plurality of grooves with geometric configurations are arranged on the outer wall of the ceramic mold body; the shape of the hollow chamber is the same as the shape of the blade to be cast.

[0014] Preferably, the ceramic mold body is prepared by binder jetting.

[0015] The application of the above-mentioned ceramic mold with a surface microstructure in casting blades.

[0016] Compared with the prior art, the present invention has the following beneficial technical effects: In the first aspect, the present invention discloses a structural optimization method for a ceramic mold with a surface microstructure. This optimization method relates the longitudinal temperature gradient during directional solidification to the structural parameters of the ceramic mold with a surface microstructure. The surface microstructure parameters include the structural shape, structural size, and arrangement pattern. A mathematical model between the longitudinal temperature gradient and the surface microstructure parameters is constructed. Through surface microstructure design, the thermal field is actively regulated, quantitative optimization is driven by the mathematical model, and local adaptation to complex geometric requirements is achieved, systematically solving the problems of insufficient temperature gradient, non-uniform microstructure, and defects caused by structural limitations in traditional ceramic shells, providing an innovative technical path for the low-cost manufacturing of high-performance single crystal blades.

[0017] Furthermore, on the ceramic mold with a smooth outer surface, at least 10 temperature measurement zones are divided according to the shape change characteristics of the casting and process requirements. The simulated directional solidification temperature field of each temperature measurement zone is obtained through numerical simulation. Here, by measuring the temperature in zones, the influence of local characteristics of the casting (such as thin walls, abrupt cross-sections) on the thermal field can be captured, effectively achieving the optimization of the temperature gradient.

[0018] Furthermore, 15 of the said temperature measurement zones are divided according to the shape change characteristics of the casting and process requirements, which can fully realize the individual monitoring of the temperature gradient in different blade regions and improve the accuracy of optimization.

[0019] Furthermore, the actual directional solidification temperature field is adjusted using the simulated directional solidification temperature field to complete the establishment of the basic directional solidification temperature field. Specifically: If the temperature error between the actual directional solidification temperature field and the simulated directional solidification temperature field in any one temperature measurement zone is greater than 10%, then the heat transfer parameters are adjusted, and the simulated directional solidification temperature field is adjusted using the actual directional solidification temperature field, so that the temperature error between the actual directional solidification temperature field and the simulated directional solidification temperature field in all temperature measurement zones is not greater than 10%, completing the adjustment of the simulated directional solidification temperature field and realizing the establishment of the basic directional solidification temperature field. By setting a temperature error threshold of 10%, the consistency between the simulated directional solidification temperature field and the actual directional solidification temperature field can be effectively ensured, ensuring the accuracy of optimization.

[0020] Furthermore, in S2, the longitudinal temperature gradient is obtained through the thermal conductivity, heat transfer coefficient, radiation heat transfer coefficient, specific heat, latent heat of solidification, and the density, solidus temperature, and liquidus temperature of the alloy, effectively achieving high-precision prediction of the temperature gradient, active control of the microstructure, and dynamic optimization of process parameters.

[0021] Second aspect, the present invention also discloses a ceramic mold with a surface microstructure, which is optimized by the above-mentioned structure optimization method. The surface of the ceramic mold is provided with grooves of geometric configuration, and the grooves of geometric configuration are the surface microstructure in the present invention. The ceramic mold optimized by this method can change the heat conduction route, realize the uniformity of heat transfer and heat dissipation during the directional solidification of the casting alloy, improve the temperature gradient of the traditional ceramic mold, meet the differentiated requirements of different positions of the blade, and then realize the grain refinement and microstructure optimization of the blade, inhibit the generation of heterocrystalline defects, and improve the tissue uniformity and overall performance of the alloy blade; In addition, the grooves on the surface of the optimized ceramic mold also increase the outer wall surface area of the mold, strengthening the radiation heat dissipation. In addition, due to the enhanced fluid disturbance in the grooves for heat transfer, this groove design also strengthens the convective heat transfer. In actual working conditions, the depth, width and distribution density of the grooves can be optimized to targetedly reduce the thermal resistance of specific areas, improve the local cooling rate and temperature gradient, enhance the stability of dendritic directional growth, and reduce the heterocrystalline defect rate. In addition, the chamber shape of the ceramic mold in the present invention is exactly the same as that of the blade, ensuring uniform melt filling and reducing local undercooling or overheating caused by poor contact between the mold shell and the melt. Through the optimization of the groove structure, the ceramic mold systematically solves the problems of insufficient temperature gradient and solidification defects caused by structural limitations of the traditional mold, providing an innovative solution for the efficient and low-cost manufacturing of single crystal blades of superalloys. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention, and therefore should not be regarded as limiting the scope. For those of ordinary skill in the art, other related drawings can be obtained based on these drawings without creative efforts.

[0023] Figure 1 Schematic diagram of the heat conduction route of a traditional ceramic mold with a smooth outer wall; Figure 2 Schematic flow chart of the structure optimization method of a ceramic mold with a surface microstructure in the present invention; Figure 3 Front view (A), right view (B) and top view (C) of the ceramic mold in Embodiment 3 of the present invention; Figure 4 Schematic diagram of the heat conduction route of the ceramic mold in Embodiment 3 of the present invention; Figure 5 Temperature simulation results on the ceramic mold during casting using the ceramic mold in Embodiment 3 of the present invention; Figure 6Front view (A), right view (B), and top view (C) of the ceramic mold in Embodiment 4 of the present invention; Figure 7 Partial enlarged schematic view of the outer wall of the ceramic mold in Embodiment 4 of the present invention; Figure 8 Schematic diagram of the heat conduction route of the ceramic mold in Embodiment 4 of the present invention; Figure 9 Temperature simulation result on the ceramic mold during pouring using the ceramic mold in Embodiment 4 of the present invention; Figure 10 Front view (A), right view (B), and top view (C) of the ceramic mold in Embodiment 5 of the present invention; Figure 11 Partial enlarged schematic view of the outer wall of the ceramic mold in Embodiment 5 of the present invention; Figure 12 Schematic diagram of the heat conduction route of the ceramic mold in Embodiment 5 of the present invention; Figure 13 Temperature simulation result on the ceramic mold during pouring using the ceramic mold in Embodiment 5 of the present invention.

[0024] Wherein, 1, ceramic mold body; 2, hollow chamber; 3, groove. Detailed implementation manners

[0025] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. Usually, the components of the embodiments of the present invention described and illustrated in the accompanying drawings herein can be arranged and designed in various different configurations.

[0026] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed present invention, but merely represents selected embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0027] It should be noted that: similar reference numerals and letters denote similar items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings.

[0028] In the description of the embodiments of the present invention, it should be noted that if terms such as "upper", "lower", "horizontal", "inner", etc. are used to indicate the orientation or positional relationship, it is based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship in which the invention product is usually placed during use. This is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation to the present invention. In addition, terms such as "first", "second", etc. are only used for distinguishing descriptions and cannot be understood as indicating or implying relative importance.

[0029] In addition, if the term "horizontal" appears, it does not mean that the component is required to be absolutely horizontal, but it can be slightly inclined. For example, "horizontal" only means that its direction is more horizontal relative to "vertical", and does not mean that the structure must be completely horizontal, but it can be slightly inclined.

[0030] In the description of the embodiments of the present invention, it should also be noted that unless otherwise clearly specified and limited, if terms such as "set", "installed", "connected", "connected" are used, they should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0031] The following further describes the present invention in detail with reference to the drawings: Embodiment 1 As Figure 2 shown, the present invention discloses a method for optimizing the structure of a ceramic mold with a surface microstructure, including the following steps: S1: Establish a basic directional solidification temperature field using a ceramic mold with a smooth outer surface; S2: Obtain the longitudinal temperature gradient when the blade to be cast undergoes directional solidification on a ceramic mold with a surface microstructure, and establish a mathematical model between the longitudinal temperature gradient and the surface microstructure parameters; optimize the basic directional solidification temperature field based on the mathematical model, and obtain the microstructure of the blade to be cast under the optimized basic directional solidification temperature field; S3: If the microstructure of the blade to be cast is uneven or defective under the optimized basic directional solidification temperature field, adjust the surface microstructure parameters, and repeat step S2 until the microstructure of the blade to be cast meets the requirements, thus completing the structure optimization of the ceramic mold with a surface microstructure.

[0032] The surface microstructure in the present invention refers to the grooved geometric configuration provided on the outer wall of the ceramic mold. Through the optimization of this microstructure, specific optimizations include the optimization of the structure shape, structure size, and arrangement method, so as to optimize the heat transfer path and improve the longitudinal temperature gradient.

[0033] For the above optimization method, in step S1, the establishment of the basic directional solidification temperature field by using a ceramic mold with a smooth outer surface is specifically as follows: on the ceramic mold with a smooth outer surface, at least 10 temperature measurement zones are divided according to the shape change characteristics of the casting and the process requirements, and the simulated directional solidification temperature field of each temperature measurement zone is calculated through numerical simulation; and an actual directional solidification experiment is carried out by using the ceramic mold with a smooth outer surface, the actual temperature data of each temperature measurement zone is measured in real time by using the infrared temperature measurement method, and the actual directional solidification temperature field of the directional solidification process is established according to the actual temperature data; the ceramic mold with a smooth outer surface mentioned in the present invention refers to the traditional ceramic mold, and its outer wall is not provided with any microstructure and is a smooth outer wall. Preferably, at least 15 temperature measurement zones can also be set, so that the optimization result is more accurate.

[0034] Furthermore, the actual directional solidification temperature field is adjusted by using the simulated directional solidification temperature field to complete the establishment of the basic directional solidification temperature field. Specifically, this process is as follows: if the temperature error between the actual directional solidification temperature field and the simulated directional solidification temperature field of any one temperature measurement zone is greater than 10%, the heat transfer parameters are adjusted, and the simulated directional solidification temperature field is adjusted according to the actual directional solidification temperature field, so that the temperature error between the actual directional solidification temperature fields and the simulated directional solidification temperature fields of all temperature measurement zones is not greater than 10%, that is, the simulated temperature field is made to approach the actual temperature field by increasing or decreasing the heat transfer parameters, the adjustment of the simulated directional solidification temperature field is completed, and the establishment of the basic directional solidification temperature field is realized.

[0035] In step S2, the variables of the mathematical model include the thermal conductivity, heat transfer coefficient of heat conduction, radiation heat transfer coefficient, specific heat, latent heat of solidification, alloy density, and solid / liquidus temperature of the alloy. Further, the thermal conductivity includes the thermal conductivity of the ceramic shell and the thermal conductivity of the non-shell medium; the radiation heat transfer coefficient includes the radiation heat transfer coefficient of the ceramic shell and the radiation heat transfer coefficient of the non-shell medium.

[0036] The surface microstructure parameters include: the structure shape, structure size, and arrangement method of the surface microstructure. The structure shape of the surface microstructure includes a square or a regular hexagon, or other regular geometric shapes. The arrangement method can be square close-packed or triangular close-packed. The square close-packed refers to the structural form in which each row and each column are aligned and arranged, such as Figures 3 - 4In the arrangement form, triangular close packing means that the grooves in each row are located between the two closest grooves in the upper row and also between the two closest grooves in the lower row, as shown in Figures 6 - 8 and Figures 10 - 12 the arrangement form in.

[0037] In step S3, specifically, aiming to optimize the microstructure of the alloy blade to be cast and eliminate defects such as stray grains and freckles, the basic directional solidification temperature field obtained in step S1 is optimized according to the mathematical model established in step S3, and the microstructure of the blade to be cast under the optimized basic directional solidification temperature field is obtained; it is judged whether the microstructure of the blade to be cast under the optimized basic directional solidification temperature field is uneven or defective. If so, the surface microstructure parameters of the ceramic mold with a surface microstructure are changed, and then step S2 is repeated until the grain size, orientation and structure meet the requirements and there are no defects such as stray grains. When the grain size, orientation and structure meet the requirements and there are no defects such as stray grains, the modified surface microstructure parameters are saved, that is, the structure optimization of the ceramic mold with a surface microstructure is completed.

[0038] Embodiment 2 The present invention also discloses a ceramic mold with a surface microstructure, as shown in Figure 3 shown, including a ceramic mold body 1. A hollow chamber 2 is provided inside the ceramic mold body 1, and a plurality of grooves 3 with geometric configurations are provided on the outer wall of the ceramic mold body 1; the shape of the hollow chamber 2 is consistent with the shape of the blade to be cast; the structural shape, structural size and arrangement mode of the grooves 3 with geometric configurations are optimized and determined according to the method in Embodiment 1 of the present invention. Of course, in this embodiment, the shape of the groove 3 is square, and this shape is only an example for explaining the technical solution of the present invention. The shape of the groove 3 can also be other, and can be optimized and determined according to actual working conditions.

[0039] The ceramic mold body 1 is made by binder jetting, and the groove 3 is integrally provided with the ceramic mold body 1.

[0040] The wall thickness of the ceramic mold body 1 is uniform, and the wall thickness at the thickest part of the ceramic mold body 1 is the minimum thickness to ensure the mechanical properties of the ceramic mold, that is, the minimum ceramic mold thickness when the ceramic mold does not break or crack during the alloy casting process.

[0041] In addition, a seed selector base is provided at the bottom of the ceramic mold body 1 for seed selection and supporting the integral ceramic mold. The seed selector base is also integrally provided with the ceramic mold body 1.

[0042] The method of the present invention uses a ceramic mold with a surface microstructure manufactured by a binder jet additive manufacturing process. On the premise that the mechanical strength of the ceramic mold meets the requirements of alloy casting, the design of the surface microstructure of the ceramic mold is realized, breaking through the design shackles that a traditional ceramic mold with a smooth outer wall cannot increase the temperature gradient at the directional solidification front of the casting, and the structure of the ceramic mold is designed to avoid problems such as high operation difficulty caused by indirectly increasing the longitudinal temperature gradient. The ceramic mold with a surface microstructure in the present invention can be processed by additive manufacturing technology, solving the problem that it is difficult to prepare complex microstructures by traditional processes, effectively shortening the production cycle and improving production efficiency. Moreover, the ceramic mold with a surface microstructure in the present invention can also effectively reduce the volume and weight of the ceramic mold, save ceramic powder, and reduce costs.

[0043] The ceramic mold with a surface microstructure prepared by the above method includes a ceramic mold body 1. A hollow chamber 2 is provided inside the ceramic mold body 1, and a plurality of grooves 3 with geometric configurations are provided on the outer wall of the ceramic mold body 1. Among them, the hollow chamber 2 is the internal working part, and the hollow chamber 2 is used to form the outer shape of the alloy blade, and its shape should be consistent with the structure of the alloy blade. The grooves 3 are used to control the uniformity of the alloy directional solidification temperature field and increase the longitudinal temperature gradient at the alloy solidification front. The thickness of the ceramic mold body 1, the depth of the grooves 3, and the thickness of the bottom of the grooves 3 from the inner wall of the hollow chamber 2 are all carefully designed to maintain the strength of the ceramic mold body 1 and prevent it from breaking under the action of the directional solidification pressure.

[0044] Meanwhile, the present invention also discloses a cast blade, which is prepared by casting with the above-mentioned ceramic mold with a surface microstructure. Due to the optimization of the surface microstructure of the ceramic mold, the microstructure of the cast blade has good uniformity and no tissue defects.

[0045] Example 3 In this example, a gas turbine blade is selected as the part for precision casting. According to the method for optimizing the structure of a ceramic mold with a surface microstructure described in the present invention, as Figure 3 shown, a plurality of grooves 3 with a size of 2 mm × 2 mm are designed on the surface of the ceramic mold body 1. The depth of the grooves 3 is 5 mm, and the arrangement method is square close-packed. The thickness of the bottom of the grooves 3 from the inner wall of the ceramic mold body 1 is 5 mm, that is, the overall thickness of the ceramic mold body 1 is 10 mm. The heat preservation temperature of the ceramic mold is 1500 °C, and the pulling rate is 3 mm / min.

[0046] The heat conduction path of this example, as Figure 4 shown, is from Figure 4It can be seen that, compared with the traditional ceramic mold with a smooth outer wall, this heat conduction path is longer, which reduces the heat conduction rate in the longitudinal direction to a certain extent, increases the longitudinal temperature gradient, that is, increases the longitudinal temperature gradient of the mold shell.

[0047] In addition, Figure 5 Figure [X] shows the temperature simulation results on the ceramic mold during pouring using the ceramic mold in Embodiment 3 of the present invention. It can be seen from Figure 5 that for the gas turbine blade prepared using the ceramic mold with surface microstructures in this embodiment, the microstructure is more uniform compared with the traditional ceramic mold with a smooth outer wall, but the change of the solidification front is not obvious.

[0048] Embodiment 4 In this embodiment, a gas turbine blade is selected as the part for precision casting. According to a method for optimizing the structure of a ceramic mold with surface microstructures of the present invention, as shown in Figures 6 - 7 Figure [X], a plurality of square grooves 3 with a size of 2 mm × 2 mm are designed on the surface of the ceramic mold body 1. The depth of the groove 3 is 5 mm, and the arrangement method is triangular close packing. The thickness of the bottom of the groove 3 from the inner wall of the ceramic mold body 1 is 5 mm, that is, the overall thickness of the ceramic mold body 1 is 10 mm. The heat preservation temperature of the ceramic mold is 1500 °C, and the drawing rate is 3 mm / min.

[0049] The heat conduction path of this embodiment, as shown in Figure 8 Figure [X], it can be seen from Figure 8 that compared with the square close packing in Embodiment 1, the heat conduction path of this embodiment is longer, and thus the heat conduction in the longitudinal direction can be reduced to a greater extent, increasing the longitudinal temperature gradient, that is, increasing the longitudinal temperature gradient of the mold shell.

[0050] In addition, Figure 9 Figure [X] shows the temperature simulation results on the ceramic mold during pouring using the ceramic mold in Embodiment 4 of the present invention. It can be seen from Figure 9 that for the gas turbine blade prepared using the ceramic mold with surface microstructures in this embodiment, the microstructure is more uniform compared with the traditional ceramic mold with a smooth outer wall, and the solidification front tends to be horizontal.

[0051] Embodiment 5 In this embodiment, a gas turbine blade is selected as the part for precision casting. According to a method for optimizing the structure of a ceramic mold with surface microstructures of the present invention, as shown in Figures 10 - 11As shown, a plurality of regular hexagonal grooves 3 with a spacing of 1 mm are designed on the surface of the ceramic mold body 1. The depth of the groove 3 is 5 mm, the side length of the regular hexagonal groove 3 is 2 mm, and the arrangement method is triangular close packing. The thickness of the bottom of the groove 3 from the inner wall of the ceramic mold body 1 is 5 mm, that is, the overall thickness of the ceramic mold body 1 is 10 mm. The heat preservation temperature of the ceramic mold is 1500 °C, and the drawing rate is 3 mm / min.

[0052] The heat conduction path of this embodiment is as Figure 12 shown, and it can be seen from Figure 12 that the heat conduction path of this embodiment is more complex than that of Embodiment 1 and Embodiment 2. Furthermore, the heat conduction in the longitudinal direction can be reduced to a greater extent, resulting in a relatively large increase in the longitudinal temperature gradient, that is, the longitudinal temperature gradient of the mold shell is increased.

[0053] In addition, Figure 13 Figure Figure 13 shows the temperature simulation results on the ceramic mold during casting using the ceramic mold in Embodiment 5 of the present invention. It can be seen from

[0054] that for the gas turbine blade prepared using the ceramic mold with surface microstructure in this embodiment, the microstructure of the blade is more uniform, and the solidification front tends to be horizontal. The above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for optimizing the structure of a ceramic casting mold having a surface microstructure, characterized in that: The following steps are involved: S1: Use a ceramic mold with a smooth outer surface to establish a basic directional solidification temperature field; S2: obtaining a longitudinal temperature gradient of a blade to be cast during directional solidification on a ceramic mold having a surface microstructure, and establishing a mathematical model between the longitudinal temperature gradient and surface microstructure parameters; Optimizing the basic directional solidification temperature field based on the mathematical model, and obtaining the microstructure of the blade to be cast under the optimized basic directional solidification temperature field; S3: If the microstructure of the blade to be cast is uneven or defective under the optimized basic directional solidification temperature field, the surface microstructure parameters are adjusted and S2 is repeated until the microstructure of the blade to be cast meets the requirements, thereby completing the structural optimization of the ceramic casting mold with a surface microstructure; the surface microstructure parameters include structural shape, structural size and arrangement.

2. The method for optimizing the structure of a ceramic casting mold having a surface microstructure according to claim 1, characterized in that: In S1, the method of establishing a basic directional solidification temperature field using a ceramic mold with a smooth outer surface is specifically as follows: on a ceramic mold with a smooth outer surface, at least 10 temperature measurement zones are divided according to the shape change characteristics of the casting and the process requirements, and a simulated directional solidification temperature field of each temperature measurement zone is obtained through numerical simulation; and an actual directional solidification experiment is performed using the ceramic mold with a smooth outer surface to obtain actual temperature data of each temperature measurement zone, and an actual directional solidification temperature field of the directional solidification process is established based on the actual temperature data; The actual directional solidification temperature field is adjusted using the simulated directional solidification temperature field to complete the establishment of the basic directional solidification temperature field.

3. The method for optimizing the structure of a ceramic casting mold having a surface microstructure according to claim 2, characterized in that: According to the shape change characteristics of the casting and the process requirements, 15 temperature measurement zones are divided.

4. The method for optimizing the structure of a ceramic casting mold having a surface microstructure according to claim 2, characterized in that: The actual directional solidification temperature field is adjusted by using the simulated directional solidification temperature field to complete the establishment of the basic directional solidification temperature field. Specifically, if the temperature error between the actual directional solidification temperature field and the simulated directional solidification temperature field in any temperature measuring zone is greater than 10%, the heat transfer parameters are adjusted, and the simulated directional solidification temperature field is adjusted by using the actual directional solidification temperature field, so that the temperature errors between the actual directional solidification temperature field and the simulated directional solidification temperature field in all temperature measuring zones are not greater than 10%, and the adjustment of the simulated directional solidification temperature field is completed to achieve the establishment of the basic directional solidification temperature field.

5. The method for optimizing the structure of a ceramic casting mold having a surface microstructure according to claim 1, characterized in that: In S2, the longitudinal temperature gradient is obtained through the thermal conductivity coefficient, the thermal conduction heat transfer coefficient, the radiation heat transfer coefficient, the specific heat, the solidification latent heat, and the density, solidus temperature, and liquidus temperature of the alloy.

6. The method for optimizing the structure of a ceramic casting mold having a surface microstructure according to claim 5, characterized in that: The thermal conductivity coefficient includes the thermal conductivity coefficient of the ceramic shell and the thermal conductivity coefficient of the non-shell medium; the radiation heat transfer coefficient includes the radiation heat transfer coefficient of the ceramic shell and the radiation heat transfer coefficient of the non-shell medium.

7. The method for optimizing the structure of a ceramic casting mold having a surface microstructure according to claim 1, characterized in that: The surface microstructure has a structural shape including a square or a regular hexagon.

8. A ceramic casting mold having a surface microstructure, characterized in that: The ceramic mold is optimized by the structural optimization method described in any one of claims 1 to 7; the ceramic mold comprises a ceramic mold body (1), a hollow chamber (2) is provided inside the ceramic mold body (1), and a plurality of geometrically configured grooves (3) are provided on the outer wall of the ceramic mold body (1); the shape of the hollow chamber (2) is consistent with the shape of the blade to be cast.

9. The ceramic casting mold with a surface microstructure according to claim 8, characterized in that: The ceramic casting mold body (1) is manufactured by binder spraying.

10. Use of a ceramic casting mold with a surface microstructure as claimed in any one of claims 8 to 9 in casting blades.

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