Seed selector, seed selection method and wax pattern assembly for secondary orientation control

Abstract

The application discloses a selector for secondary orientation control, and belongs to the technical field of single crystal casting, which comprises a first seeding section, a secondary seeding section and a selecting section which are sequentially connected along a directional solidification growth path; the first seeding section is a prism structure with a thickness direction; the secondary seeding section is located between the first seeding section and the selecting section, and extends obliquely relative to the height direction of the first seeding section and has a thickness direction corresponding to the first seeding section; the selecting section is used for screening single crystal grains; the application makes columnar crystals continue to compete for growth along the obliquely extending direction through the secondary seeding section, thereby screening the secondary orientation corresponding to the thickness direction in the columnar crystals, and realizing secondary orientation control of single crystal casting.

Description

Technical Field

[0001] This application relates to the field of precision casting technology for single-crystal castings, specifically to a crystal selector, crystal selection method, and wax mold assembly for secondary orientation control. Background Technology

[0002] With the ever-increasing performance requirements of aero-engines, high-temperature alloy castings such as turbine blades typically require directional solidification or single-crystal casting processes to improve their creep resistance, fatigue performance, and microstructural stability under high-temperature service environments. In the preparation of single-crystal castings, the crystal selection method is a commonly used single-crystal formation technique. This method typically involves using a crystal-inducing segment to allow multiple columnar crystals to compete for growth along the directional solidification direction, and then using structures such as spiral crystal-selecting segments to select individual grains from these columnar crystals, thereby obtaining a single-crystal casting.

[0003] However, existing crystal selectors primarily focus on primary orientation control and individual grain selection in single-crystal castings. Specifically, the existing seeding section is typically used to select columnar crystals that preferentially grow along the directional solidification direction, while the spiral selection section is used to eliminate other grains and retain a single grain. While this type of structure can achieve the fabrication of single-crystal castings, its ability to select columnar crystals in the lateral direction is weak, making it difficult to obtain single-crystal castings with the desired secondary orientation.

[0004] For castings such as single-crystal turbine blades with clear service orientation requirements, secondary orientation can affect the blade's mechanical properties and service reliability. In existing technologies, the seed crystal method is typically used to control secondary orientation. This involves placing a single-crystal seed crystal with a predetermined orientation in the mold shell or wax pattern, allowing the casting to grow epitaxially on the seed crystal. However, the seed crystal method has high requirements for the seed crystal's installation position, orientation accuracy, and pouring process control. It is also prone to problems such as melt backflow and the formation of impurities in the gap between the seed crystal and the mold shell, increasing process complexity and quality control difficulty.

[0005] Therefore, there is an urgent need to provide a crystal selector for secondary orientation control, which can further screen secondary orientations during the competitive growth of columnar crystals and single crystal screening without relying on seed crystals, thereby achieving effective control of secondary orientation of single crystal castings. Summary of the Invention

[0006] This application provides a crystal selector, a crystal selection method, and a wax mold assembly for secondary orientation control, in order to solve the technical problem that the prior art is unable to effectively screen and control the secondary orientation of single crystal castings.

[0007] According to one aspect of this application, a crystal selector for secondary orientation control is provided, comprising a first crystal-leading segment, a secondary crystal-leading segment, and a crystal-selecting segment sequentially connected along a directional solidification growth path; the first crystal-leading segment has a flattened prismatic structure, and the thickness direction of the first crystal-leading segment is the secondary orientation control direction of the crystal selector; the secondary crystal-leading segment is located between the first crystal-leading segment and the crystal-selecting segment, and the secondary crystal-leading segment extends obliquely relative to the height direction of the first crystal-leading segment; the secondary crystal-leading segment is used to enable columnar crystals to continue competitive growth along the oblique extension direction during directional solidification, so as to screen the secondary orientations in the columnar crystals that correspond to the secondary orientation control direction; the crystal-selecting segment is used to screen out individual grains from the columnar crystals after screening by the secondary crystal-leading segment.

[0008] Optionally, both the first and second seed segments are rectangular cross-section channels, and the thickness direction of the first seed segment is consistent with the thickness direction of the second seed segment.

[0009] Optionally, the extension direction of the secondary seeding segment forms an angle of 0° to 70° with the normal direction of the height and width of the first seeding segment.

[0010] Optionally, the first seed segment has a height dimension of 15mm to 35mm, the second seed segment has a height dimension of 15mm to 20mm, and both the first and second seed segments have a thickness dimension of 4mm to 6mm.

[0011] Optionally, the crystal selection section is a spiral crystal selection section, and the inlet of the spiral crystal selection section is connected to the outlet of the secondary crystal selection section.

[0012] According to another aspect of this application, a method for crystal selection with controllable secondary orientation is also provided, comprising the following steps: A crystal selector is fabricated, comprising a first crystal-guiding section, a second crystal-guiding section, and a crystal-selecting section sequentially connected along the directional solidification growth path. The first crystal-guiding section is a prismatic structure with a thickness direction. The second crystal-guiding section is located between the first crystal-guiding section and the crystal-selecting section, extending obliquely relative to the height direction of the first crystal-guiding section. The casting wax model and the crystal selector are set according to a preset angular relationship, so that the secondary orientation reference direction of the casting wax model is parallel to the thickness direction of the crystal selector. The casting wax model with the crystal selector is combined with the gating system to form a wax model module, and the wax is then... The mold assembly is used to form a shell, and liquid metal is poured into the shell and solidified in a directional manner, so that the liquid metal solidifies and grows sequentially along the first crystal-leading section, the second crystal-leading section and the crystal-selecting section. The first crystal-leading section is used to screen the primary orientation of columnar crystals, the second crystal-leading section is used to screen the secondary orientation of columnar crystals corresponding to the thickness direction of the crystal selector by changing the heat flow direction formed by the inclined extension, and the crystal-selecting section is used to screen out individual grains from the columnar crystals after the screening by the second crystal-leading section, so as to obtain a single crystal casting with controllable secondary orientation.

[0013] Optionally, the single-crystal casting is a single-crystal turbine blade, the casting wax model is a blade wax model, and the secondary orientation reference direction is the chord direction or the average chord direction of the blade wax model.

[0014] Optionally, setting the casting wax model and the crystal selector according to a preset angular relationship includes: splicing the blade wax model and the crystal selector, or pressing the blade wax model and the crystal selector together using a mold; when splicing or pressing the blade wax model and the crystal selector together, making the chord direction or average chord direction of the blade wax model parallel to the thickness direction of the crystal selector, so that a preset angular relationship for secondary orientation control is formed between the blade wax model and the crystal selector.

[0015] According to another aspect of this application, a wax model assembly is also provided, including a cast wax model and a crystal selector; the crystal selector includes a first crystal-leading segment, a secondary crystal-leading segment, and a crystal-selecting segment connected sequentially along a directional solidification growth path, the first crystal-leading segment is a prismatic structure with a thickness direction, the secondary crystal-leading segment is located between the first crystal-leading segment and the crystal-selecting segment, and extends obliquely relative to the height direction of the first crystal-leading segment, and the secondary crystal-leading segment has a thickness direction corresponding to the first crystal-leading segment; the cast wax model is connected to or integrally formed with the crystal selector, and the secondary orientation reference direction of the cast wax model is parallel to the thickness direction of the crystal selector.

[0016] Optionally, the wax pattern part corresponding to the first crystal-initiating segment, the wax pattern part corresponding to the second crystal-initiating segment, the wax pattern part corresponding to the crystal selection segment, and the casting wax pattern are connected sequentially along the directional solidification growth path. The first crystal-initiating segment is set at one end of the crystal selector near the directional solidification initiation side, and the crystal selection segment is set at one end of the crystal selector near the casting wax pattern cavity.

[0017] In summary, this application includes at least one of the following beneficial technical effects: This scheme adds a secondary crystal-guiding section between the first crystal-guiding section and the crystal-selecting section, and extends the secondary crystal-guiding section at an angle relative to the height of the first crystal-guiding section. This allows the columnar crystals, after completing the first orientation screening, to not directly enter the crystal-selecting section for single-crystal screening, but instead to continue competitive growth within the angled secondary crystal-guiding section. The first crystal-guiding section has a flat prismatic structure, and its thickness direction serves as the secondary orientation control direction for the crystal selector, providing a clear structural reference for subsequent secondary orientation screening. The thickness direction of the secondary crystal-guiding section is consistent with the secondary orientation control direction, and its angled extension structure alters the heat flow direction during the continued growth of the columnar crystals, allowing the columnar crystals to continue competitive growth along the angled extension direction within the secondary crystal-guiding section. This further screens the secondary orientations within the columnar crystals that correspond to the secondary orientation control direction. After secondary orientation screening, the columnar crystals then enter the crystal-selecting section, where single grains are selected from multiple columnar crystals. Therefore, this application enables the crystal selector to simultaneously achieve primary orientation screening, secondary orientation control, and individual grain screening without using seed crystals, thereby reducing the installation accuracy requirements, impurity risk, and process complexity associated with the seed crystal method.

[0018] In addition to the purposes, features, and advantages described above, this application has other purposes, features, and advantages. A further detailed description of this application will be provided below with reference to the figures. Attached Figure Description

[0019] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings: Figure 1 This is a schematic diagram of the crystal selector for secondary orientation control of single-crystal castings in this application. Figure 2 for Figure 1 Side view; Figure 3 for Figure 1 Top view.

[0020] Legend: 1. First crystal-initiating segment; 2. Secondary crystal-initiating segment; 3. Crystal selection segment. Detailed Implementation

[0021] The embodiments of this application are described in detail below with reference to the accompanying drawings; however, this application may be implemented in a variety of different ways as defined and covered below.

[0022] The following is in conjunction with the appendix Figure 1-3 This application will be described in further detail.

[0023] This application discloses a crystal selector, a crystal selection method, and a wax mold assembly for secondary orientation control.

[0024] Reference Figure 1 The crystal selector for secondary orientation control includes a first crystal-guiding section 1, a secondary crystal-guiding section 2, and a crystal-selecting section 3 connected sequentially along the directional solidification growth path. The first crystal-guiding section 1 has a flat prismatic structure, and the thickness direction of the first crystal-guiding section 1 is the secondary orientation control direction of the crystal selector. The secondary crystal-guiding section 2 is located between the first crystal-guiding section 1 and the crystal-selecting section 3, and the secondary crystal-guiding section 2 extends obliquely relative to the height direction of the first crystal-guiding section 1. The secondary crystal-guiding section 2 is used to make the columnar crystals continue to grow competitively along the oblique extension direction during the directional solidification process, so as to screen the secondary orientations in the columnar crystals that correspond to the secondary orientation control direction. The crystal-selecting section 3 is used to screen out individual grains from the columnar crystals after being screened by the secondary crystal-guiding section 2.

[0025] In this embodiment, the crystal selector used for secondary orientation control is mainly used in the directional solidification forming process of high-temperature alloy single crystal castings, especially suitable for castings such as single crystal turbine blades that have high requirements for grain orientation. The crystal selector is arranged sequentially along the directional solidification growth path, with a first crystal-leading section 1, a secondary crystal-leading section 2, and a crystal-selecting section 3. The directional solidification growth path can be understood as the growth path in which liquid metal gradually solidifies from the initial solidification side towards the casting cavity within the mold shell and forms columnar crystals. The first crystal-leading section 1 is located near the starting side of directional solidification, so that multiple initial grains compete to grow under the action of directional heat flow, thereby preferentially retaining columnar crystals with a more suitable primary orientation. The first crystal-leading section 1 adopts a flat prismatic structure, and its thickness direction is the secondary orientation control direction of the crystal selector. This secondary orientation control direction can be used as the structural reference direction for subsequent secondary orientation screening. Compared with ordinary cylindrical crystal-leading sections, this flat prismatic structure can form a more defined lateral reference, so that the columnar crystals have stable geometric constraints and heat flow boundaries when entering the subsequent secondary crystal-leading section 2.

[0026] The secondary crystal-guiding segment 2 connects the first crystal-guiding segment 1 and the selection segment 3, and extends at an angle relative to the height direction of the first crystal-guiding segment 1. This ensures that after the columnar crystal undergoes initial orientation screening in the first crystal-guiding segment 1, it does not directly enter the selection segment 3 for single-crystal screening, but instead first enters the secondary crystal-guiding segment 2, which has an angled growth path, to continue competitive growth. During directional solidification, the angled extension of the secondary crystal-guiding segment 2 changes the heat flow direction as the columnar crystal continues to grow, subjecting it to growth constraints different from those in the first crystal-guiding segment 1 within the angled channel. Simultaneously, the thickness direction of the secondary crystal-guiding segment 2 aligns with the secondary orientation control direction, allowing the secondary orientation control direction determined by the first crystal-guiding segment 1 to extend to the secondary crystal-guiding segment 2 and serve as the corresponding direction for secondary orientation screening. The secondary crystal-guiding segment 2 can screen the columnar crystals for secondary orientations corresponding to the secondary orientation control direction during their continued competitive growth, making it easier for columnar crystals that better meet the predetermined secondary orientation requirements to continue growing, while columnar crystals with larger orientation deviations are gradually eliminated through competition.

[0027] The crystal selection section 3 is positioned after the secondary crystal-guiding section 2. It receives the columnar crystals that have been screened by the secondary crystal-guiding section 2 and continues to screen individual grains from multiple columnar crystals through spatial constraint and competitive growth. The crystal selector does not rely solely on the crystal selection section 3 to complete traditional single-crystal screening; instead, a secondary crystal-guiding section 2 is added before the crystal selection section 3 to perform secondary orientation screening. This allows the columnar crystals to sequentially undergo primary orientation screening, secondary orientation screening, and individual grain screening. Through this structure, the crystal selector can control the secondary orientation of single-crystal castings without using seed crystals, reducing the risks associated with seed crystal installation, orientation calibration, and the generation of impurities during casting. It also helps improve the orientation consistency and forming stability of single-crystal castings.

[0028] In one embodiment, both the first crystal-leading segment 1 and the second crystal-leading segment 2 are rectangular cross-section channels. The rectangular cross-section channels have a width direction and a thickness direction, and the dimension of the rectangular cross-section channel along the thickness direction is smaller than the dimension along the width direction.

[0029] The height direction corresponds to the directional solidification growth path, while the width and thickness directions are two transverse directions perpendicular to the height direction. The rectangular cross-section channel has a smaller dimension along the thickness direction than along the width direction, making the first crystal-guiding segment 1 and the second crystal-guiding segment 2 have an overall flat structure. When columnar crystals compete to grow along the directional solidification growth path in the first crystal-guiding segment 1, they are constrained by the boundary formed by the sidewalls of the rectangular channel, making the growth state of the columnar crystals before entering the second crystal-guiding segment 2 more stable. The second crystal-guiding segment 2 also adopts a rectangular cross-section channel, and its thickness direction is consistent with the thickness direction of the first crystal-guiding segment 1, so that the thickness direction determined by the first crystal-guiding segment 1 can continue continuously into the second crystal-guiding segment 2, avoiding the weakening of the secondary orientation screening effect due to the inconsistency of the transverse directions of the two segments.

[0030] In one embodiment, the extension direction of the secondary seeding segment 2 forms an angle of 0° to 70° with the normal direction of the height and width direction of the first seeding segment 1.

[0031] In this embodiment, the secondary crystal-guiding segment 2 does not continue to extend linearly along the height direction of the first crystal-guiding segment 1, but is inclined relative to the height direction of the first crystal-guiding segment 1. By setting this inclined angle, the columnar crystal, after passing through the first orientation screening of the first crystal-guiding segment 1, is guided by the inclined channel when entering the secondary crystal-guiding segment 2, changing its continued growth direction. This causes the heat flow direction during the directional solidification process to change in accordance with the extension direction of the secondary crystal-guiding segment 2. Since the thickness direction of the secondary crystal-guiding segment 2 is consistent with the secondary orientation control direction, when the columnar crystal continues to grow competitively in the inclined extension direction, it can further undergo secondary orientation screening around the secondary orientation control direction.

[0032] When the tilt angle of the secondary seeding segment 2 is too small, the directional change of the secondary seeding segment 2 relative to the first seeding segment 1 is not significant. As the columnar crystal continues to grow within it, it mainly maintains its original height direction, resulting in a weak secondary orientation screening effect. When the tilt angle is too large, the growth path of the columnar crystal as it enters the secondary seeding segment 2 changes too drastically, easily affecting the continuous and stable growth of the columnar crystal. Limiting the angle between the extension direction of the secondary seeding segment 2 and the height direction of the first seeding segment 1 to 0° to 70° ensures that the columnar crystal can continuously enter the secondary seeding segment 2 while providing sufficient tilt guidance, thereby enhancing the secondary orientation screening effect.

[0033] Reference Figure 2 and Figure 3In one embodiment, the first seed section 1 has a height dimension of 15mm to 35mm, the second seed section 2 has a height dimension of 15mm to 20mm, and the first seed section 1 and the second seed section 2 both have a thickness dimension of 4mm to 6mm.

[0034] In this embodiment, the first crystal-guiding segment 1 is set to a height dimension of 15mm to 35mm. This dimension range provides sufficient growth distance for the primary orientation competition growth of columnar crystals, allowing the initially formed multiple grains to compete fully under the action of directional solidification heat flow, thereby preferentially retaining columnar crystals that grow stably along the directional solidification growth path. If the height dimension of the first crystal-guiding segment 1 is too small, the competitive growth among columnar crystals will be insufficient, and the number and orientation state of the grains subsequently entering the secondary crystal-guiding segment 2 may not be stable enough. If the height dimension of the first crystal-guiding segment 1 is too large, it will increase the overall height of the crystal selector and the module layout space, which is not conducive to the compact design of the wax mold assembly and the mold shell structure. The height dimension of the secondary crystal-guiding segment 2 is set to a height dimension of 15mm to 20mm. This dimension allows the columnar crystals to have a certain distance to continue competing growth after entering the secondary crystal-guiding segment 2, so that the secondary crystal-guiding segment 2 can filter the secondary orientation of the columnar crystals through the change in heat flow direction formed by the inclined extension. The secondary crystal-guiding segment 2 is not a simple transition connection segment, but a functional segment for columnar crystals to continue growing and competing within the inclined channel. Both the first crystal-leading section 1 and the second crystal-leading section 2 are set to a thickness of 4 mm to 6 mm. The thickness direction is used to determine the secondary orientation control direction of the crystal selector. The size of this direction affects both the forming stability of the channel and the lateral competitive growth state of the columnar crystals within the channel. When the thickness direction dimension is too small, the stability of channel forming, wax mold pressing, and shell making processes may decrease; when the thickness direction dimension is too large, the boundary constraint effect of the thickness direction on the columnar crystals is weakened, which is not conducive to forming a clear secondary orientation screening criterion.

[0035] In one embodiment, the crystal selection section 3 is a spiral crystal selection section, and the inlet of the spiral crystal selection section is connected to the outlet of the secondary crystal selection section 2.

[0036] In this embodiment, the inlet of the spiral crystal selection section is connected to the outlet of the secondary crystal selection section 2, allowing columnar crystals that have undergone primary orientation screening by the first crystal selection section 1 and secondary orientation screening by the secondary crystal selection section 2 to continue growing within the spiral crystal selection section. The spiral crystal selection section has a curved, extended crystal selection channel. After entering the spiral crystal selection section, multiple columnar crystals are constrained by the spatial morphology of the spiral channel and continue to compete for growth. Columnar crystals whose growth direction and position are more adapted to the spiral channel can continue to grow forward, while other columnar crystals are gradually eliminated as their growth space is gradually squeezed out, ultimately resulting in a single grain. The spiral crystal selection section does not perform all orientation control alone, but rather works in conjunction with the first crystal selection section 1 and the secondary crystal selection section 2 located at its front end.

[0037] The crystal selection method with controllable secondary orientation includes the following steps: Prepare or provide a crystal selector, the crystal selector comprising a first crystal-leading segment 1, a secondary crystal-leading segment 2 and a crystal-selecting segment 3 connected sequentially along a directional solidification growth path, the first crystal-leading segment 1 having a flat prism structure, the thickness direction of the first crystal-leading segment 1 being the secondary orientation control direction of the crystal selector, the secondary crystal-leading segment 2 being located between the first crystal-leading segment 1 and the crystal-selecting segment 3, and extending obliquely relative to the height direction of the first crystal-leading segment 1; Set the casting wax model and the crystal selector according to a preset angular relationship, so that the secondary orientation reference direction of the casting wax model is parallel to the secondary orientation control direction of the crystal selector; The casting wax model equipped with a crystal selector is combined with the gating system to form a wax model module, and the wax model module is then shelled to obtain the mold shell; Liquid metal is poured into the mold shell and solidified in a directional manner, so that the liquid metal solidifies and grows sequentially along the first crystal-initiating section 1, the second crystal-initiating section 2 and the crystal-selecting section 3. The first crystal-guiding section 1 is used to screen the primary orientation of columnar crystals. The second crystal-guiding section 2 is used to screen the secondary orientation of columnar crystals corresponding to the secondary orientation control direction of the crystal selector by changing the heat flow direction formed by the inclined extension. The crystal-selecting section 3 is used to screen out individual grains from the columnar crystals after screening by the second crystal-guiding section 2, so as to obtain a single crystal casting with controllable secondary orientation.

[0038] In this embodiment, firstly, a crystal selector having a first crystal-leading segment 1, a secondary crystal-leading segment 2, and a crystal-selecting segment 3 is prepared or provided. This crystal selector can be obtained by wax molding, die forming, or other methods suitable for investment casting. The first crystal-leading segment 1, the secondary crystal-leading segment 2, and the crystal-selecting segment 3 are sequentially connected along the directional solidification growth path, allowing the liquid metal to pass through each of the above functional segments sequentially during directional solidification. The first crystal-leading segment 1 has a flat prismatic structure, and the thickness direction of the first crystal-leading segment 1 is the secondary orientation control direction of the crystal selector. The secondary crystal-leading segment 2 connects the first crystal-leading segment 1 and the crystal-selecting segment 3, and extends obliquely relative to the height direction of the first crystal-leading segment 1, so that the columnar crystals can enter the oblique growth channel after passing through the first crystal-leading segment 1 to continue competitive growth.

[0039] After obtaining the crystal selector, the casting wax model and the crystal selector are set according to a preset angular relationship, so that the secondary orientation reference direction of the casting wax model is parallel to the secondary orientation control direction of the crystal selector. The preset angular relationship refers to the relative orientation between the casting structure direction and the secondary orientation control direction of the crystal selector determined in advance during the wax model stage, and is not adjusted after casting. By establishing this angular relationship during the wax model stage, the secondary orientation control direction of the crystal selector can correspond to the final secondary orientation direction that the casting needs to control during subsequent directional solidification, thus providing a directional basis for the secondary orientation of columnar crystals in the secondary crystal-leading section 2.

[0040] Then, the wax model of the casting equipped with the crystal selector is combined with the gating system to form a wax model module. The wax model module is then shell-made to obtain a refractory material shell. After shell-making, conventional investment casting processes such as dewaxing and firing can be performed to create cavities and channels within the shell that correspond to the wax model, crystal selector, and gating system. During casting, liquid metal is injected into the shell and directionally solidified, allowing the liquid metal to solidify and grow sequentially along the first crystal-initiating section 1, the second crystal-initiating section 2, and the crystal-selecting section 3. During directional solidification, the first seeding section 1 screens the primary orientation of columnar crystals, preferentially retaining those more suitable for growth along the directional solidification growth path. As the columnar crystals continue into the second seeding section 2, the internal heat flow direction and the direction of continued growth of the columnar crystals change due to the inclined extension of the second seeding section 2 relative to the height of the first seeding section 1. This causes the columnar crystals to continue competing for growth within the inclined channel, and the secondary orientations corresponding to the secondary orientation control direction of the crystal selector are screened. The columnar crystals screened by the second seeding section 2 then enter the selection section 3, where individual grains are further selected from multiple columnar crystals. Through this method, controlled secondary orientation can be achieved in single-crystal castings while forming a single-crystal structure, without relying on a single-crystal seed crystal. This reduces the process difficulty associated with seed crystal installation and orientation calibration, and lowers the risk of impurities forming at the seed crystal and mold shell mating positions.

[0041] In one embodiment, the single-crystal casting is a single-crystal turbine blade, the casting wax model is a blade wax model, and the secondary orientation reference direction is the chord direction or average chord direction of the blade wax model.

[0042] In this embodiment, the single-crystal casting can specifically be a single-crystal turbine blade for an aero-engine, and the casting wax model is correspondingly a blade wax model. Single-crystal turbine blades are subjected to high-temperature combustion gas erosion, centrifugal loads, and complex aerodynamic loads during service. Their crystal orientation has a significant impact on the blade's creep and fatigue performance. For single-crystal turbine blades, primary orientation mainly reflects the correspondence between the main crystal growth direction and the blade's height direction or stacking axis direction, while secondary orientation mainly reflects the correspondence between the blade's transverse structural direction and the crystal's transverse orientation. Since blades typically have a twisted shape and the blade cross-section varies along the height direction, the chord direction of the blade wax model can be used as the secondary orientation reference direction. When the chord direction varies at different height positions of the blade, the average chord direction of the blade wax model can also be used as the secondary orientation reference direction. By determining the chord or average chord direction of the blade wax mold as the secondary orientation reference direction, a clear corresponding reference can be provided for the secondary orientation control direction of the subsequent crystal selector in the wax mold stage. This allows the screening results of the secondary orientation of columnar crystals in the secondary crystal-leading section 2 to match the actual structural direction that the blade needs to control. As a result, the final single-crystal turbine blade not only obtains a single-crystal structure, but its secondary orientation can also be controlled around the chord or average chord direction of the blade.

[0043] In one embodiment, setting the casting wax model and the crystal selector according to a preset angular relationship includes either splicing the blade wax model and the crystal selector together, or integrally pressing the blade wax model and the crystal selector together using a mold. When using the splicing method, the blade wax model and the crystal selector wax model can be prepared separately first, and then positioned using a splicing fixture to make the chord direction or average chord direction of the blade wax model parallel to the secondary orientation control direction of the crystal selector, and then the blade wax model and the crystal selector are fixedly connected. The splicing fixture can limit the relative angle between the blade wax model and the crystal selector through positioning grooves, positioning surfaces, limiting blocks, or other positioning structures to reduce angular deviations caused by manual splicing. When using the integral pressing method, the relative orientation of the blade forming cavity and the crystal selector forming cavity can be preset in the wax model pressing mold, so that the chord direction or average chord direction of the blade forming cavity is parallel to the direction used to form the secondary orientation control direction in the crystal selector forming cavity, thereby directly forming an integral structure of the blade wax model and the crystal selector with a preset angular relationship during the pressing process. In the above manner, the correspondence between the secondary orientation reference direction of the blade and the secondary orientation control direction of the crystal selector can be stably established in the wax model stage, so that in the subsequent shell making, casting and directional solidification process, the secondary crystal-leading section 2 can screen the secondary orientation of columnar crystals according to the preset direction.

[0044] The wax model assembly includes a cast wax model and a crystal selector. The crystal selector includes a first crystal-leading section 1, a secondary crystal-leading section 2, and a crystal-selecting section 3 connected sequentially along the directional solidification growth path. The first crystal-leading section 1 has a flat prism-shaped structure, and the thickness direction of the first crystal-leading section 1 is the secondary orientation control direction of the crystal selector. The secondary crystal-leading section 2 is located between the first crystal-leading section 1 and the crystal-selecting section 3, and extends obliquely relative to the height direction of the first crystal-leading section 1. The thickness direction of the secondary crystal-leading section 2 is consistent with the secondary orientation control direction. The cast wax model is connected to or integrally formed with the crystal selector, and the secondary orientation reference direction of the cast wax model is parallel to the secondary orientation control direction of the crystal selector.

[0045] In this embodiment, the wax model assembly is used in subsequent tree assembly, shell making, and directional solidification casting processes. It includes a casting wax model and a crystal selector. The casting wax model is used to form the shape of the single-crystal casting, and the crystal selector is used to perform orientation screening and single-crystal screening of columnar crystals before they enter the casting forming area during directional solidification. The casting wax model and the crystal selector can be connected by a subsequent splicing method, or they can be directly integrally formed during the wax model pressing process. When using the splicing method, the casting wax model and the crystal selector wax model can be prepared separately first, and then connected after positioning with tooling. When using the integral forming method, an integral wax model assembly can be directly pressed by using the preset relative orientation of the casting wax model forming cavity and the crystal selector forming cavity in the mold. Regardless of whether the splicing method or the integral forming method is used, the secondary orientation reference direction of the casting wax model must be parallel to the secondary orientation control direction of the crystal selector. After subsequent shell making, dewaxing, and directional solidification casting, the secondary orientation control direction of the crystal selector can maintain a corresponding relationship with the secondary orientation direction that the casting needs to control. This allows the secondary crystal-inducing segment 2 to screen the secondary orientation corresponding to this direction during the continued competitive growth of columnar crystals, thereby giving the final single crystal casting a better secondary orientation control effect.

[0046] In one embodiment, the first crystal-leading segment 1, the second crystal-leading segment 2, the crystal-selecting segment 3, and the casting wax model are connected sequentially along the directional solidification growth path. The first crystal-leading segment 1 is located at one end of the crystal selector near the directional solidification initiation side, and the crystal-selecting segment 3 is located at one end of the crystal selector near the casting wax model.

[0047] The first crystal-guiding section 1, the second crystal-guiding section 2, the crystal-selecting section 3, and the casting wax model are arranged sequentially according to the crystal growth sequence during directional solidification, forming a continuous solidification growth path between the crystal selector and the casting wax model. The first crystal-guiding section 1 is located at the end of the crystal selector closest to the directional solidification initiation side, i.e., near the cooling end or the initial crystallization region. It is used to initially receive multiple columnar crystals grown from the initial solidification region and provide growth space for the primary orientation competition of the columnar crystals. The second crystal-guiding section 2 is connected after the first crystal-guiding section 1, allowing the columnar crystals initially screened by the first crystal-guiding section 1 to continue growing in the inclined channel, thus performing secondary orientation screening before entering the crystal-selecting section 3. The crystal-selecting section 3 is located at the end of the crystal selector closest to the casting wax model and is adjacent to it. This allows the columnar crystals screened by the second crystal-guiding section 2 to continue entering the crystal-selecting section 3 and be screened into individual grains. These individual grains then continue epitaxial growth towards the corresponding forming region of the casting wax model. Through the above arrangement, the wax model assembly has a clear crystal growth path from the direction solidification initiation side to the casting wax model, so that the first crystal-introducing segment 1, the second crystal-introducing segment 2 and the crystal-selecting segment 3 can play their roles in the order of first orientation screening, then second orientation screening and then single crystal screening, avoiding the instability of crystal selection effect caused by the reversal of the positions of each functional segment or unclear connection.

[0048] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A crystal selector for secondary orientation control, characterized in that: It includes a first crystal-initiating segment (1), a second crystal-initiating segment (2), and a crystal-selecting segment (3) that are connected sequentially along the directional solidification growth path; The first crystal-leading segment (1) has a flat prism-shaped structure. The height direction of the first crystal-leading segment (1) is the primary orientation control direction, and the thickness direction of the first crystal-leading segment (1) is the secondary orientation control direction. The secondary crystal-introducing segment (2) is located between the first crystal-introducing segment (1) and the crystal-selecting segment (3), and the secondary crystal-introducing segment (2) extends at an angle relative to the height direction of the first crystal-introducing segment (1); The secondary crystallization segment (2) is used to make columnar crystals continue to grow competitively along the inclined extension direction during the directional solidification process, so as to screen the secondary orientations in the columnar crystals that correspond to the secondary orientation control direction. The crystal selection section (3) is used to select individual crystals from the columnar crystals after the secondary crystal selection section (2).

2. The crystal selector for secondary orientation control according to claim 1, characterized in that: Both the first crystal-introducing segment (1) and the second crystal-introducing segment (2) are rectangular cross-section channels. The rectangular cross-section channels have a width direction and a thickness direction, and the dimension of the rectangular cross-section channel along the thickness direction is smaller than the dimension along the width direction.

3. The crystal selector for secondary orientation control according to claim 1, characterized in that: The extension direction of the secondary seeding segment (2) forms an angle of 0° to 70° with the normal of the height and width directions of the first seeding segment (1).

4. The crystal selector for secondary orientation control according to claim 1, characterized in that: The first seed section (1) has a height dimension of 15mm to 35mm, and the second seed section (2) has a height dimension of 15mm to 20mm. The first seed section (1) and the second seed section (2) have the same thickness dimension, which is 4mm to 6mm.

5. The crystal selector for secondary orientation control according to claim 1, characterized in that: The crystal selection section (3) is a spiral crystal selection section, and the inlet of the spiral crystal selection section is connected to the outlet of the secondary crystal selection section (2).

6. A method for crystal selection with controllable secondary orientation, characterized in that: Includes the following steps: A crystal selector is fabricated. The crystal selector includes a first crystal-leading segment (1), a second crystal-leading segment (2), and a crystal-selecting segment (3) that are connected sequentially along the directional solidification growth path. The first crystal-leading segment (1) is a prismatic structure with a thickness direction. The height direction of the first crystal-leading segment (1) is the primary orientation control direction, and the thickness direction of the first crystal-leading segment (1) is the secondary orientation control direction. The second crystal-leading segment (2) is located between the first crystal-leading segment (1) and the crystal-selecting segment (3) and extends at an angle relative to the height direction of the first crystal-leading segment (1). Set the casting wax model and the crystal selector according to a preset angular relationship, so that the secondary orientation reference direction of the casting wax model is parallel to the secondary orientation control direction of the crystal selector; The casting wax model equipped with a crystal selector is combined with the gating system to form a wax model module, and the wax model module is then shelled to obtain the mold shell; Liquid metal is poured into the mold shell and directional solidification is carried out, so that the liquid metal solidifies and grows sequentially along the first crystal-initiating section (1), the second crystal-initiating section (2) and the crystal-selecting section (3); The first crystal-introducing segment (1) is used to screen the primary orientation of columnar crystals. The second crystal-introducing segment (2) is used to screen the secondary orientation of columnar crystals corresponding to the secondary orientation control direction by changing the heat flow direction formed by the inclined extension. The crystal-selecting segment (3) is used to screen out individual grains from columnar crystals after screening by the second crystal-introducing segment (2) in order to obtain single crystal castings with controllable secondary orientation.

7. The method for controllable secondary orientation of single-crystal castings according to claim 6, characterized in that: The single-crystal casting is a single-crystal turbine blade, the casting wax model is a blade wax model, and the secondary orientation reference direction is the chord direction or average chord direction of the blade wax model.

8. The method for controllable secondary orientation of single-crystal castings according to claim 7, characterized in that: The casting wax model and the crystal selector are set according to a preset angular relationship, including: The blade wax model is spliced ​​with the crystal selector, or the blade wax model and the crystal selector are pressed together by a mold. When the blade wax mold is spliced ​​or integrally pressed with the crystal selector, the chord direction or average chord direction of the blade wax mold is made parallel to the secondary orientation control direction of the crystal selector, so that a preset angular relationship for secondary orientation control is formed between the blade wax mold and the crystal selector.

9. A wax model assembly, characterized in that: This includes casting wax models and crystal selectors; The crystal selector includes a first crystal-leading section (1), a secondary crystal-leading section (2), and a crystal-selecting section (3) connected sequentially along the directional solidification growth path. The first crystal-leading section (1) has a flat prism structure. The thickness direction of the first crystal-leading section (1) is the secondary orientation control direction of the crystal selector. The secondary crystal-leading section (2) is located between the first crystal-leading section (1) and the crystal-selecting section (3), and extends obliquely relative to the height direction of the first crystal-leading section (1). The thickness direction of the secondary crystal-leading section (2) is consistent with the secondary orientation control direction. The casting wax model is connected to or integrally formed with the crystal selector, and the secondary orientation reference direction of the casting wax model is parallel to the secondary orientation control direction of the crystal selector.

10. The wax mold assembly according to claim 9, characterized in that: The wax pattern part corresponding to the first crystal-leading section (1), the wax pattern part corresponding to the second crystal-leading section (2), the wax pattern part corresponding to the crystal selection section (3), and the casting wax pattern are connected sequentially along the directional solidification growth path. The first crystal-leading section (1) is set at one end of the crystal selector near the directional solidification start side, and the crystal selection section (3) is set at one end of the crystal selector near the casting wax pattern cavity.

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