Preparation method of high-temperature alloy single crystal blade controlled by radiation heat transfer assisted by mold shell

Abstract

The invention discloses a preparation method of a high-temperature alloy single crystal blade controlled by mould shell auxiliary radiation heat transfer, which comprises the following steps: providing one or more auxiliary radiation partition plates, and the ratio of the thermal diffusion coefficient of the auxiliary radiation partition plates to the thermal diffusion coefficient of a mould shell is more than or equal to 0.6 and less than or equal to 1.5; defining a preset position on the mold shell, wherein the preset position is a defect-prone part, corresponding to the mold cavity of the mold shell, on the high-temperature alloy single crystal blade; the auxiliary radiation partition plate is arranged at the preset position of the mold shell; the high-temperature alloy single crystal blade is prepared in directional solidification equipment by adopting a mold shell provided with an auxiliary radiation partition plate. The auxiliary radiation partition plates are arranged at the characteristic positions of the mold shell, so that the temperature field inclination degree caused by the difference of heat dissipation conditions on the surface of the mold shell can be reduced, the uniformity of the temperature fields in the horizontal direction at the multiple characteristic positions of the blade casting is improved, and the forming tendency of mixed crystal and freckle defects is reduced.

Description

Technical Field

[0001] This invention relates to the field of casting, and more particularly to a method for preparing high-temperature alloy single-crystal blades with mold shell-assisted radiative heat transfer control. Background Technology

[0002] Aero-engines and heavy-duty gas turbines are of critical strategic importance to the development of the equipment manufacturing industry. Turbine blades are the core components of the hot end of these two engines, and their high-temperature performance directly determines the operating efficiency and safe service life of the engines. To achieve higher high-temperature mechanical properties, turbine blades require a single-crystal structure. Due to the complex hollow geometry of turbine blades, they are generally prepared using investment casting with Bridgman directional solidification. The Bridgman process can be further divided into High-Rate Solidification (HRS) and liquid metal cooling. HRS is more widely used in industry due to its simple equipment and convenient operation. In HRS, the heating element in the furnace heats the mold shell and the poured molten metal through thermal radiation, and during the downward pull, heat is dissipated to the cooler furnace wall for cooling and solidification. Thermal radiation between the furnace cavity and the mold shell in HRS is a key factor determining the temperature field of the molten metal and even the solidification process. Due to the complex geometry of the mold shell, the heat dissipation on the surface of the mold shell changes significantly during the casting process, especially after the crystallizer is pulled down. This leads to a substantial increase in the gap between the hot and cold zones of the furnace (before the water-cooled crystallizer is pulled down, the gap is the narrow slit between the water-cooled crystallizer and the furnace hot and cold zone partition; after the water-cooled crystallizer is pulled down, the gap is the gap between the furnace hot and cold zone partition and the mold shell, and between the blades within the mold shell). This results in vertical radiative heat flow within the furnace, causing uneven temperature distribution on the mold shell, which already has an uneven radiative temperature field. This temperature field inhomogeneity causes a deviation in the directionality of the blade casting solidification, resulting in fluctuations in the macroscopic morphology and width of the mushy zone. The macroscopic morphology of the mushy zone corresponds to the tendency for the formation of impurities and freckles; the more inclined the solid-liquid interface, the easier it is for impurities and freckle defects to form. The width of the mushy zone corresponds to the primary dendrite spacing and freckle defects; a lower width reduces the primary dendrite spacing and inhibits freckle formation. This increases the risk of casting defects such as impurities and freckles in blade castings. Currently, the yield rate of single-crystal blades in my country is relatively low, therefore, developing methods for efficiently controlling the solidification process of single-crystal blades is particularly important.

[0003] Temperature field and defect regulation during Bridgman directional solidification have always been key areas of research in single-crystal blade fabrication. A research team at RWTH Aachen University in Germany balanced the non-uniformity of the temperature field on the mold surface by placing heat-conducting blocks at locations with rapid heat dissipation. This effectively suppressed the formation of impurity defects at the longer edge plates of the blade casting. A research team at Northwestern Polytechnical University designed a mold with non-uniform thickness. By covering the tenon with a thicker mold, they suppressed the premature heat dissipation effect of the local mold during the pulling process, thus mitigating the impact of non-uniform radiative temperature field on impurity formation at the tenon. A research team at the Institute of Metal Research, Chinese Academy of Sciences, used a method of placing heating blocks at the center of the mold assembly to compensate for the radiative heat dissipation generated vertically along the furnace chamber. This improved the "shadowing effect" of the solidification temperature field in large-diameter furnaces and mold assemblies, suppressing the formation of freckle defects. The research team at Tsinghua University used a variable pulling rate method. By adjusting the process parameters in real time during directional solidification, they matched the pulling rate with the solid-liquid interface propulsion rate, thereby reducing the impact of the non-uniformity of the mold shell temperature field on the solidification process.

[0004] It is evident that efficient control of heat transfer during blade manufacturing is crucial. However, current methods focus on "specific analysis for specific situations," which may require long-term iterative design for blade castings with specific geometries or process design based on a large amount of experimental data to establish a dataset. This makes it difficult to achieve low-cost, universal application for blades with different geometric characteristics.

[0005] Therefore, those skilled in the art are dedicated to developing a more universal method for preparing high-temperature alloy single-crystal blades based on radiation heat dissipation control. By improving the design of the mold shell geometry, the radiation heat transfer between the furnace cavity and the mold shell is optimized, thereby achieving optimized adjustment of the macroscopic solid-liquid interface morphology and width during the solidification process of the molten metal in the mold shell, and thus achieving the purpose of eliminating casting defects such as freckles and impurities. Summary of the Invention

[0006] In view of the above-mentioned deficiencies of the prior art, the technical problem to be solved by the present invention is how to develop a more universal temperature field and defect adjustment method applicable to the preparation of single crystal blades by Bridgman directional solidification.

[0007] To achieve the above objectives, the present invention provides a method for preparing high-temperature alloy single-crystal blades with mold-assisted radiative heat transfer control, comprising the following steps: One or more auxiliary radiation partitions are provided, wherein the ratio of the thermal diffusivity of the auxiliary radiation partitions to the thermal diffusivity of the mold shell is greater than or equal to 0.6 and less than or equal to 1.5; A preset position is defined on the mold shell, and the preset position is the defect-prone part on the high-temperature alloy single crystal blade corresponding to the cavity of the mold shell; The auxiliary radiation partition is positioned at the preset location on the mold shell; High-temperature alloy single-crystal blades are prepared in a directional solidification apparatus using the mold shell equipped with the auxiliary radiation partition.

[0008] Furthermore, the auxiliary radiation partition is provided with a through hole that matches the outer contour of the mold shell and the central support column of the mold shell at the preset position.

[0009] Furthermore, the auxiliary radiation baffle is configured such that its projected outer contour on the horizontal plane can completely cover the outer contour of the water-cooled crystallizer.

[0010] Furthermore, the thermal conductivity of the auxiliary radiative baffle is less than or equal to 1 W / mK.

[0011] Furthermore, the mold shell includes a third feature position and a second feature position, and the preset position is located at the connection between the third feature position and the second feature position.

[0012] Furthermore, the preset position is located at the second feature position.

[0013] Furthermore, the mold shell includes a first feature position, and the preset position is located at the first feature position.

[0014] Furthermore, the thickness of the auxiliary radiation partition is set to be less than or equal to the thickness of the mold shell, and the thickness difference between the auxiliary radiation partition and the mold shell is greater than or equal to 1 mm and less than or equal to 2 mm.

[0015] Furthermore, the directional solidification device includes a furnace hot and cold zone partition, and the horizontal distance between the auxiliary radiant partition and the furnace hot and cold zone partition is set to be less than or equal to 10 mm.

[0016] Furthermore, a segmented variable-speed pulling process is used to prepare high-temperature alloy single-crystal blades in the directional solidification equipment, and the speed change position of the segmented variable-speed pulling is determined according to the setting position of the auxiliary radiation partition.

[0017] The technical effects of this invention are as follows: (1) By setting auxiliary radiation baffles at the characteristic positions of the mold shell, the degree of temperature field tilt caused by the difference in heat dissipation conditions on the surface of the mold shell can be reduced, and the uniformity of the horizontal temperature field at multiple characteristic positions of the mold shell and blade casting can be improved (because the vertical radiation of the device center is blocked, the uniformity of the horizontal radiation temperature field is improved, thereby improving the uniformity of the horizontal temperature field of the mold shell and casting), thereby reducing the tendency of impurity crystals and freckle defects to form.

[0018] Furthermore, when the thermal diffusivity is similar, the unsteady thermal conductivity of the mold shell and the auxiliary radiative baffle exhibits similar characteristics, thereby synchronizing the temperature changes of the auxiliary radiative baffle and the mold shell connected to it. This avoids the auxiliary radiative baffle and the mold shell being in different heat dissipation stages, which would cause additional temperature differences and lead to deviations in the control of radiative heat transfer by the auxiliary radiative baffle and the solidification process of the blade. In addition, the radiation-assisted baffles on the mold shell, due to their low thermal conductivity, create a large temperature difference between the top and bottom, blocking the high-temperature surface of the mold shell in the hot zone from radiating heat to the lower-temperature furnace cavity and the cooled part of the mold shell. This fundamentally weakens the additional radiative heat dissipation of the mold shell surface in the vertical direction, thereby improving the uniformity of the horizontal temperature field and reducing the unevenness of the horizontal temperature field of the mold shell caused by the different degrees of heat loss between the center and the edge of the mold shell during the pulling process.

[0019] Furthermore, the geometry and design criteria of the auxiliary radiating baffle on the blade mold shell in this method are relatively simple and easy to implement, and have good universality.

[0020] (2) Setting auxiliary radiant baffles at the characteristic positions of the mold shell can improve the allowable rate during the drawing process of the blade casting. By effectively improving the heat preservation effect of the mold shell and blade casting above the auxiliary radiant baffle and the heat dissipation effect of the mold shell and blade casting below the auxiliary radiant baffle, the mold shell and blade casting can be drawn down at a higher rate. Using a larger overall drawing rate can shorten the time that the high-temperature alloy melt is under high-temperature heating conditions, reduce the burn-off of alloy elements in the melt, reduce the reaction time between the mold shell and core and the alloy, and improve the production efficiency of single crystal blades.

[0021] (3) The setting of auxiliary radiant baffles can increase the vertical temperature gradient of the blade body and tenon in the blade casting, thereby increasing the primary dendrite spacing of the blade body and tenon in the casting, thus improving the high-temperature mechanical properties of the key load-bearing parts of the single crystal blade. When the radiant baffle moves to the hot and cold zone baffle in the furnace, it hinders the vertical transmission of heat radiation: reducing the heat dissipation from the mold shell surface above the auxiliary radiant baffle to the cold zone, and at the same time reducing the absorption of radiant heat from the hot zone by the mold shell below the auxiliary radiant baffle, thereby increasing the vertical temperature gradient of the mold shell surface and even the blade casting.

[0022] The following will further explain the concept, specific structure, and technical effects of the present invention in conjunction with the accompanying drawings, so as to fully understand the purpose, features, and effects of the present invention. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the HRS directional solidification device according to a preferred embodiment of the present invention; Figure 2 This is a schematic diagram of the structure of the auxiliary radiation partition 12 in the blade mold shell according to a preferred embodiment of the present invention; Figure 3 This is a schematic diagram illustrating the physical concept of the macroscopic solid-liquid interface height difference involved in this invention. Figure 4 This is a comparison of simulation results of temperature field uniformity during directional solidification of single-crystal blades in a preferred embodiment of the present invention; Figure 5 This is a schematic diagram of the auxiliary radiation partition after removing the mold shell and the corresponding part of the central support column of the mold shell according to a preferred embodiment of the present invention; Among them, 1-furnace top cover; 2-hot zone heating element; 3-mold shell; 4-furnace hot and cold zone partition; 5-water-cooled crystallizer; 6-cold zone furnace cavity; 7-pull-out mechanism; 8-Riser; 9-Central support of the mold shell; 10-First characteristic position; 11-Second characteristic position; 12-Auxiliary radial baffle; 13-Third characteristic position; 14-Mold shell base; A - Macroscopic solid-liquid interface location; B - Solid-liquid interface height difference. Detailed Implementation

[0024] The following description, with reference to the accompanying drawings, illustrates several preferred embodiments of the present invention to make its technical content clearer and easier to understand. The present invention can be embodied in many different forms, and the scope of protection of the present invention is not limited to the embodiments mentioned herein.

[0025] In the accompanying drawings, components with the same structure are indicated by the same numerical designation, and components with similar structures or functions are indicated by similar numerical designations. The dimensions and thicknesses of each component shown in the drawings are arbitrary, and the present invention does not limit the dimensions and thicknesses of each component. To make the illustrations clearer, the thickness of some components has been appropriately exaggerated in the drawings.

[0026] like Figure 1The diagram shown is a schematic representation of a device for the HRS-based directional solidification of single-crystal blades according to a preferred embodiment of this application. The device includes: a furnace top cover 1, a hot zone heating element 2, a mold shell 3, a furnace hot and cold zone partition 4, a water-cooled crystallizer 5, a cold zone furnace cavity 6, and a pulling mechanism 7. The furnace hot and cold zone partition 4 is located in the middle of the device. The hot zone heating element 2 is located above the furnace hot and cold zone partition 4, and the cold zone furnace cavity 6 is located below the furnace hot and cold zone partition 4. The furnace top cover 1 is located at the top of the device. The mold shell 3 is placed on the water-cooled crystallizer 5 via a mold shell base 14 at its bottom. The water-cooled crystallizer 5 is connected to the pulling mechanism 7.

[0027] like Figure 2 This is a schematic diagram of the auxiliary radiation baffle 12 in the mold shell 3 according to a preferred embodiment of the present invention. The mold shell 3 is supported by a central support column 9, and both the mold shell 3 and the central support column 9 are connected to the mold shell base 14. The auxiliary radiation baffle 12 is provided on the mold shell 3. The mold shell 3 may include structures such as a first feature position 10, a second feature position 11, a third feature position 13, and a riser 8. Among them, the first feature position 10 corresponds to the tenon edge plate area of ​​the blade casting, the second feature position 11 corresponds to the blade body area of ​​the blade casting, and the third feature position 13 corresponds to the transition section area of ​​the blade casting.

[0028] A method for preparing high-temperature alloy single-crystal blades with mold-assisted radiative heat transfer control includes the following steps: One or more auxiliary radiative baffles 12 are provided, and the ratio of the thermal diffusivity of the auxiliary radiative baffle 12 to that of the mold shell 3 is greater than or equal to 0.6 and less than or equal to 1.5. When the thermal diffusivity is similar, the unsteady thermal conductivity of the mold shell 3 and the auxiliary radiative baffle 12 exhibits similar characteristics, thereby synchronizing the temperature changes of the auxiliary radiative baffle 12 and the mold shell 3 connected to it. This can avoid the additional temperature difference caused by the auxiliary radiative baffle 12 and the mold shell 3 being in different heat dissipation stages, and the resulting deviation between the control of radiative heat transfer by the auxiliary radiative baffle 12 and the solidification process of the blade. A preset position is defined on the mold shell 3. The preset position is the defect-prone part on the high-temperature alloy single crystal blade corresponding to the cavity of the mold shell 3, including the tenon edge plate of the blade casting, the blade body of the blade casting, the transition section of the blade casting, and other characteristic positions of the blade casting. The auxiliary radiation partition 12 is set at a preset position on the mold shell 3; High-temperature alloy single-crystal blades are prepared in a directional solidification apparatus using the mold shell equipped with the auxiliary radiation partition.

[0029] In some embodiments, a material that can maintain its structural strength throughout the entire blade drawing process (process duration equal to blade casting height / drawing rate) at a high temperature of 1500°C is selected as the material of the auxiliary radiative baffle 12; if the geometry of the auxiliary radiative baffle 12 changes due to high temperature, it can no longer exert its effect of isolating radiative heat transfer due to its geometry.

[0030] In some embodiments, the auxiliary radiation partition 12 is a ceramic fiber board.

[0031] In some embodiments, the auxiliary radiant baffle 12 is made of a material with a thermal conductivity of less than or equal to 1 W / mK, so that a large temperature difference is generated between the upper and lower surfaces of the auxiliary radiant baffle 12. This can block the high-temperature surface of the mold shell 3 in the hot zone from radiating heat to the cooled low-temperature surface and the cold zone of the furnace cavity 6, fundamentally reducing the additional radiative heat dissipation of the mold shell 3 surface in the vertical direction. This reduces the temperature field non-uniformity of the mold shell 3 caused by the different degrees of heat loss between the center and the edge of the mold shell 3 during the pulling process. The furnace cavity is heated from the top and cooled from the bottom by radiation. Because there are large gaps between each blade in the mold shell 3, radiative heat transfer occurs from the hot zone to the cold zone during the pulling process. This radiative heat transfer is characterized by a large amount of heat transfer at the center of the furnace and a small amount at the edge. This results in greater heat dissipation at the center and less heat dissipation at the edge, i.e., poor temperature uniformity in the horizontal direction. The auxiliary radiant baffle 12 blocks the radiative heat dissipation in the vertical direction, thereby improving the temperature field uniformity in the horizontal direction.

[0032] In some embodiments, the density of the auxiliary radiation partition 12 is greater than or equal to 1800 kg / m³. 3 And less than or equal to 2700 kg / m 3 Between these conditions, the specific heat capacity of the auxiliary radiant baffle 12 is greater than or equal to 800 J / kg-K and less than or equal to 1200 J / kg-K, so that the heat absorbed or lost by the auxiliary radiant baffle 12 cannot be quickly conducted to other parts of the mold shell 3, and the heat transfer is still dominated by thermal radiation.

[0033] In some embodiments, the distribution location of defects in high-temperature alloy single-crystal blades is defined by the prototype casting of blades, and the distribution location of defects in high-temperature alloy single-crystal blades is defined as the preset location of the auxiliary radiation partition 12.

[0034] In some embodiments, the auxiliary radiation partition 12 is disposed at a position corresponding to a change in the cross-sectional area of ​​the high-temperature alloy single crystal blade exceeding 1.2 times and a discontinuous change in cross-sectional area.

[0035] In some embodiments, the length of the transition section of the blade casting is greater than the thickness of the furnace hot and cold zone partition 4, and the auxiliary radiation partition 12 is disposed above the mold base 14, and the vertical distance between the auxiliary radiation partition 12 and the mold base 14 is greater than or equal to the thickness of the furnace hot and cold zone partition 4.

[0036] In some embodiments, the auxiliary radiation partition 12 is disposed at the position where the third feature position 13 is connected to the second feature position 11.

[0037] The mold base 14 has a large cross-sectional area, which can block the radiative heat dissipation from the hot zone to the cold zone. When the mold base 14 is completely pulled out below the furnace hot and cold zone partition 4, the radiative temperature field of the furnace will change, and the vertical radiative heat transfer will be greatly enhanced. The radiative temperature field at these locations will change significantly because the mold base 14 is fully inserted into the cold zone furnace cavity 6 and the cross-sectional area increases significantly. Defects are prone to occur in the blade casting structure above these locations. By setting auxiliary radiative partitions 12 at these locations, the vertical radiative heat transfer can be reduced, thereby reducing blade casting defects.

[0038] In some embodiments, the auxiliary radiation partition 12 is disposed at a position where the mold shell 3 protrudes more than 20 mm above its lower geometry in the horizontal direction.

[0039] In some embodiments, the auxiliary radiation partition 12 is disposed at the position of the first feature position 10; In these locations, heat on the surface of the mold shell 3 is lost in large quantities to the cold area in the form of thermal radiation along the vertical direction, which easily leads to defects.

[0040] In some embodiments, the auxiliary radiation partition 12 is disposed at a position of the mold shell 3 with a thin-walled tapered geometry. The position with the thin-walled tapered geometry is susceptible to disturbance and may produce defects with severe non-uniformity, such as freckle defects.

[0041] In some embodiments, the auxiliary radiating baffle 12 is disposed at the second feature position 11, and the blade body region of the blade casting corresponding to the second feature position 11 has a thin-walled tapering geometry.

[0042] Freckle defects mainly occur at locations with thin-walled tapering geometry on the blade casting, while impurities mainly occur at locations that protrude significantly in the horizontal direction. Placing auxiliary radiation baffles 12 at these corresponding locations on the mold shell 3 can reduce the radiative transfer of temperature from the hot zone to the cold zone in the vertical direction, thereby increasing the temperature gradient in the vertical direction and thus helping to suppress freckle and impurity defects.

[0043] The primary dendrite spacing determines the final mechanical properties of the blade. According to the strength design principles of blades, a higher primary dendrite spacing is generally required at the blade body. In addition, the temperature gradient will be significantly reduced at locations where the cross-section of the mold shell 3 increases abruptly (such as at the first feature position 10). Therefore, setting auxiliary baffles at these locations can reduce the temperature transfer from the hot zone to the cold zone in the vertical direction, thereby increasing the temperature gradient in the vertical direction and thus increasing the primary dendrite spacing at these two locations to improve strength.

[0044] In some embodiments, the vertical spacing between the auxiliary radiation partitions 12 is set to be greater than or equal to 30 mm.

[0045] In some embodiments, for small aircraft blades with a blade body length of 100 mm, the number of auxiliary radiating baffles 12 provided does not exceed 3.

[0046] In some embodiments, the shape and size of the auxiliary radiation partition 12 are determined according to the outer contour of the mold shell 3 and the central support column 9 of the mold shell at a preset position. The auxiliary radiation partition 12 is provided with a through hole that matches the outer contour of the mold shell 3 and the central support column 9 of the mold shell at its preset position, so that the through hole on the auxiliary radiation partition 12 can fit snugly around the outer contour of the mold shell 3 and the central support column 9 of the mold shell at its preset position, thereby enabling the projected contour of the auxiliary radiation partition 12 on the horizontal plane to cover all gaps between adjacent blades in the mold shell 3.

[0047] In some embodiments, the auxiliary radiation partition 12 is configured such that its projected outer contour on a horizontal plane can completely cover the outer contour of the water-cooled crystallizer 5.

[0048] Radiation is transferred from a high-temperature surface to a low-temperature surface. The temperature of the mold shell 3 in the hot zone of the furnace is relatively high, while the wall temperature of the water-cooled crystallizer 5 and the cold zone furnace cavity 6 is relatively low. The temperature of the mold shell base 14 is also relatively low because it is in close contact with the water-cooled crystallizer 5. The high-temperature surface of the mold shell 3 in the hot zone of the furnace will radiate heat to the mold shell base 14, resulting in a lower temperature near the center of the device. Therefore, through the design of the shape and size of the auxiliary radiation baffle 12, the auxiliary radiation baffle 12 can completely block the vertical radiation heat dissipation from the mold shell 3 to the mold shell base 14 in the horizontal direction.

[0049] In some embodiments, the water-cooled crystallizer 5 is a regular circle, and the auxiliary radiation partition 12 is configured to be the same regular circle as the water-cooled crystallizer 5.

[0050] In some embodiments, the distance between the outer edge of the auxiliary radiant baffle 12 and the outer edge of the mold shell 3 is set to be greater than or equal to 20 mm, so that when the horizontal distance between the outer edge of the mold shell 3 and the furnace hot and cold zone baffle 4 is greater than or equal to 30 mm, the auxiliary radiant baffle 12 can still prevent direct radiative heat transfer between the hot zone and the cold zone.

[0051] In some embodiments, the horizontal distance between the auxiliary radiant baffle 12 and the furnace hot and cold zone baffle 4 is set to be less than or equal to 10 mm, thereby preventing direct radiative heat transfer between the hot and cold zones.

[0052] In some embodiments, the horizontal distance between the auxiliary radiant baffle 12 and the furnace hot and cold zone baffle 4 is set to be greater than or equal to 3 mm, so that the auxiliary radiant baffle 12 structure will not come into contact with the furnace hot and cold zone baffle 4 of the furnace cavity during the pulling down process of the mold shell 3.

[0053] In some embodiments, the horizontal distance between the water-cooled crystallizer 5 and the furnace hot and cold zone partition 4 is greater than or equal to 20 mm. In this case, the horizontal distance between the auxiliary radiation partition 12 and the furnace hot and cold zone partition 4 is set to be greater than or equal to 10 mm, so that the auxiliary radiation partition 12 structure will not come into contact with the furnace hot and cold zone partition 4 during the pulling down of the mold shell 3.

[0054] In some embodiments, the thickness of the auxiliary radiation partition 12 is set to be less than or equal to the thickness of the mold shell 3, and the difference between the two thicknesses is greater than or equal to 1 mm and less than or equal to 2 mm, so that a sufficiently large temperature gradient can be generated above and below the auxiliary radiation partition 12. The reason for generating the temperature gradient is that the partition has a low thermal conductivity, so the thinner it is, the larger the temperature gradient generated. The larger the temperature gradient, the more it can change the current radiation temperature field and increase the primary dendrite spacing. However, if it is too thin, it will break due to stress. Therefore, by limiting the thickness as described above, a sufficient temperature gradient is generated without breaking.

[0055] In some embodiments, the method for setting the auxiliary radiation partition 12 at a preset position of the mold shell 3 is as follows: after the mold shell 3 is prepared or after the partial slurry coating process is completed, according to the outer contour of the mold shell 3 and the central support column 9 of the mold shell at the preset position of the auxiliary radiation partition 12, a through hole is cut out of the auxiliary radiation partition 12 to fit and wrap the outer contour of the mold shell 3 and the central support column 9 of the mold shell at its preset position, and then spliced ​​with the mold shell 3 and the central support column 9 of the mold shell at its preset position. The auxiliary radiation partition 12 is fixedly connected to the surface of the mold shell 3 with an adhesive such as silica sol, and then high temperature baking is performed to completely fix the auxiliary radiation partition 12 on the mold shell 3 and the central support column 9 of the mold shell.

[0056] In some embodiments, the auxiliary radiation partition 12 is cut into three pieces and then spliced ​​with the mold shell 3 and the central support column 9 at its preset position, thereby achieving a fit and wrapping of the outer contour of the mold shell 3 and the central support column 9 at its preset position.

[0057] In some embodiments, the method of setting the auxiliary radiation partition 12 at a preset position of the mold shell 3 is as follows: the auxiliary radiation partition 12 and the mold shell 3 are prepared and assembled simultaneously. When the wax mold surface is halfway through the process of applying slurry and coating sand, the thin mica sheet is cut into a geometric shape that can fit the outer contour of the mold shell 3 and the central support column 9 of the mold shell at the preset position of the auxiliary radiation partition 12. The cut thin mica sheet is then fixed to the surface of the mold shell 3 and the central support column 9 of the mold shell after applying slurry with silica sol. The shell-making process, such as applying slurry and coating sand, is then further completed to realize the integrated preparation and assembly of the auxiliary radiation partition 12 and the mold shell 3.

[0058] In some embodiments, depending on the location of the auxiliary radiating baffle, a segmented speed-varying method is used for the pulling process, enabling the blades to be fabricated at a higher overall pulling rate, as detailed below: The first auxiliary radiation partition 12 is set at the position where the third feature position 13 is connected to the second feature position 11. Below the first auxiliary radiation partition 12 is the crystal selection section. The crystal selection section still sets the pulling rate according to the original process pulling rate process window to ensure the success rate of crystal selection. The last auxiliary radiant baffle 12 is set at the first characteristic position 10. Between the first auxiliary heat insulation plate 12 and the last auxiliary radiant baffle 12, a pulling rate of no more than 2.5 mm / min is added to the original pulling rate process window as a new pulling rate. Above the last auxiliary radiation partition plate 12, a new pulling rate is adopted, which is an increase of no more than 1.5 mm / min on the original pulling rate process window.

[0059] At the location where the auxiliary radiation partition 12 is set, it is better to gradually transition the change in the pulling rate by using a smaller step size.

[0060] By setting auxiliary radiating baffles 12 at characteristic locations on the mold shell 3, the heat preservation effect of the mold shell 3 and blade casting above the auxiliary radiating baffles 12 and the heat dissipation effect of the mold shell 3 and blade casting below the auxiliary radiating baffles 12 can be effectively improved. This allows the mold shell 3 and blade casting to be drawn down at a higher drawing rate without easily generating defects. It improves the overall drawing rate, shortens the time required for the high-temperature alloy melt to be under high-temperature heating conditions, reduces the burn-off of alloy elements in the melt, reduces the reaction time between the mold shell 3 and the core and the alloy, and improves the production efficiency of high-temperature alloy single crystal blades.

[0061] In some embodiments, the fabrication of high-temperature alloy single-crystal blades with mold-assisted radiation heat dissipation control is carried out through the following steps: 1.1) Based on the structure of the furnace chamber of the device, the dimensions of the furnace hot and cold zone partition 4 are obtained by measurement or the drawings of the furnace chamber. In some embodiments, the inner cavity of the furnace chamber is a regular cylinder, and the furnace hot and cold zone partition 4 is a perforated disc with a diameter of Φ130mm for the central hole of the disc. 1.2) Determine the size and shape of the water-cooled crystallizer 5 at the center of the furnace. In some embodiments, the water-cooled crystallizer 5 is a regular circle, and the size of the water-cooled crystallizer 5 is Φ120mm. 1.3) Based on the dimensions of the water-cooled crystallizer 5 and the hot and cold zone partitions, the dimensions of the auxiliary radiation partition 12 are determined. In some embodiments, the auxiliary radiation partition 12 is selected as a Φ120mm disc. The area that the disc can cover extends from the center of the mold shell 3 of a set of three molds to the outer edge of the mold shell base plate 4 (or the entire geometry of the mold shell 3). When the auxiliary radiation partition 12 is pulled down to the furnace hot and cold zone partition 4, a horizontal distance of 5mm is left between it and the furnace hot and cold zone partition 4. 1.4) The auxiliary heat insulation board is made of ceramic fiber board. The mold shell 3 and the auxiliary radiant partition 12 are manufactured separately and then assembled together. The portions of the mold shell 3 and the central support column 9 at predetermined positions on the auxiliary radiant partition 12 need to be removed to ensure that the closed geometry of the auxiliary radiant partition 12 intersects with the closed geometry of the mold shell 3 and the central support column 9. For example... Figure 5 The diagram shown is a schematic of the auxiliary radiation partition 12 after removing the corresponding parts of the mold shell 3 and the central support column 9 of the mold shell. Specifically, it is a schematic diagram of one-third of a set of three molds. The two white areas correspond to the mold shell 3 and the central support column 9 of the mold shell. The remaining shaded part after removing these two parts is one-third of the auxiliary radiation partition 12. It is cut into three pieces and then placed on the mold shell 3 and the central support column 9 of the mold shell. It is fixed and connected to the surface of the mold shell 3 and the central support column 9 of the mold shell with silica sol. It is then fired at high temperature to make the ceramic fiber board completely fixed with the same thermal properties as the mold shell 3.

[0062] 1.5) The thickness of the auxiliary radiation partition 12 is 5mm, which is the same as the standard thickness of the mold shell 3.

[0063] In some embodiments, the auxiliary radiation baffle 12 extends outward from the center of the entire mold shell 3 in a horizontal direction. The geometry of the auxiliary radiation baffle 12 requires that the mold shell 3 and the corresponding part of the mold shell central support 9 be removed, and the remaining part can completely include the geometry of the blade mold shell 3 in the horizontal direction.

[0064] The role of the auxiliary radiative baffle 12 in radiative heat dissipation of the mold shell 3 and temperature field control during the directional solidification process of the blades is quantitatively evaluated using numerical simulation. The horizontal uniformity of the temperature field is described by the solid-liquid interface height difference B, the physical meaning of which is as follows: Figure 3 As shown, this represents the height difference between the highest and lowest points of the liquidus isothermal surface. During the downward pulling process of the mold shell 3, the complex geometric structure of its surface causes differences in the rate of heat dissipation at various locations within the mold shell 3. Due to the temperature distribution differences within the mold shell 3, the advancing rate of the macroscopic solid-liquid interface position A also varies, resulting in localized upward or downward convexity at the macroscopic solid-liquid interface position A. The overall macroscopic solid-liquid interface position A exhibits a complex structure, with its highest point representing the strongest heat dissipation and its lowest point representing the weakest heat dissipation.

[0065] The high-temperature alloy single-crystal blade preparation method with shell-assisted radiation heat dissipation control proposed in this invention shows that the degree of temperature field tilt during the directional solidification process of the blade is compared with the original process method. Figure 4 As shown, we can conclude from this: When macroscopic solid-liquid interface position A enters the second characteristic position 11 (corresponding to...) Figure 4 The upper paste-like area is located at 80 mm, while the height of the bottom of the blade casting is corresponding to... Figure 4 The upper pasty zone is 0 mm, which is the height of the starting point of the blade casting blade body from the bottom of the blade casting (80 mm). The solidification temperature field of the blade gradually begins to tilt significantly, and reaches its highest point when the solid-liquid interface enters the blade tenon. The auxiliary radiation baffle 12 disposed between the third feature position 13 and the second feature position 11 can significantly reduce the degree of temperature field tilt at the second feature position 11; When macroscopic solid-liquid interface position A enters the first characteristic position 10 (corresponding to...) Figure 4 The auxiliary radiation baffle 12 set at the position of the first feature position 10 (the height coordinate of the upper pasty region is about 130 mm) can still reduce the tilt of the solid-liquid interface and reduce the risk of impurity crystal formation.

[0066] The preferred embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection defined by the claims.

Claims

1. A method for preparing high-temperature alloy single-crystal blades with mold-assisted radiative heat transfer control, characterized in that, Includes the following steps: One or more auxiliary radiation partitions are provided, wherein the ratio of the thermal diffusivity of the auxiliary radiation partitions to the thermal diffusivity of the mold shell is greater than or equal to 0.6 and less than or equal to 1.5; A preset position is defined on the mold shell, and the preset position is the defect-prone part on the high-temperature alloy single crystal blade corresponding to the cavity of the mold shell; The auxiliary radiation partition is positioned at the preset location on the mold shell; High-temperature alloy single-crystal blades are prepared in a directional solidification apparatus using the mold shell equipped with the auxiliary radiation partition.

2. The method for preparing high-temperature alloy single-crystal blades with mold-assisted radiative heat transfer control as described in claim 1, characterized in that, The auxiliary radiation partition has through holes that match the outer contour of the mold shell and the central support column of the mold shell at the preset position.

3. The method for preparing high-temperature alloy single-crystal blades with mold-assisted radiative heat transfer control as described in claim 1, characterized in that, The auxiliary radiation baffle is configured such that its projected outer contour on the horizontal plane can completely cover the outer contour of the water-cooled crystallizer.

4. The method for preparing high-temperature alloy single-crystal blades with mold-assisted radiative heat transfer control as described in claim 1, characterized in that, The thermal conductivity of the auxiliary radiative baffle is less than or equal to 1 W / mK.

5. The method for preparing high-temperature alloy single-crystal blades with mold-assisted radiative heat transfer control as described in claim 1, characterized in that, The mold shell includes a third feature position and a second feature position, and the preset position is located at the connection between the third feature position and the second feature position.

6. The method for preparing high-temperature alloy single-crystal blades with mold-assisted radiative heat transfer control as described in claim 1, characterized in that, The preset position is located at the second feature position.

7. The method for preparing high-temperature alloy single-crystal blades with mold-assisted radiative heat transfer control as described in claim 1, characterized in that, The mold shell includes a first feature position, and the preset position is located at the first feature position.

8. The method for preparing high-temperature alloy single-crystal blades with mold-assisted radiative heat transfer control as described in claim 1, characterized in that, The thickness of the auxiliary radiation partition is set to be less than or equal to the thickness of the mold shell, and the thickness difference between the auxiliary radiation partition and the mold shell is greater than or equal to 1 mm and less than or equal to 2 mm.

9. The method for preparing high-temperature alloy single-crystal blades with mold-assisted radiative heat transfer control as described in claim 1, characterized in that, The directional solidification device includes a furnace hot and cold zone partition, and the horizontal distance between the auxiliary radiant partition and the furnace hot and cold zone partition is set to be less than or equal to 10 mm.

10. The method for preparing high-temperature alloy single-crystal blades with mold-assisted radiative heat transfer control as described in claim 1, characterized in that, High-temperature alloy single-crystal blades are prepared in the directional solidification equipment using a segmented variable-speed pulling process, wherein the speed change position of the segmented variable-speed pulling is determined according to the setting position of the auxiliary radiation partition.

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