A method for eliminating loose defects of tilted leaf crowns

Abstract

The present invention relates to a method and a wax mold module for eliminating the loose defect of the blade crown position of a turbine blade, and belongs to the field of turbine blade casting technology. The method comprises: step S1, preparing a blade wax mold, the blade wax mold comprising a crystal selection section, a blade crown, a blade body, and a tenon that are integrally formed and connected in sequence, and a groove is formed along the contour shape of the blade crown at the connection between the crystal selection section and the blade crown; step S2, assembling multiple blade wax molds to form a wax mold module; step S3, using the wax mold module to prepare a casting shell, so that the inner surface of the casting shell and the corresponding position of the groove of the blade wax mold form a blocking protrusion; step S4, assembling the casting shell and the inner cavity core to form a casting module, and forming a crystal growth channel between the casting shell blocking protrusion and the inner cavity core; step S5, pouring molten metal into the casting module, and through directional solidification, the molten metal starts crystal growth from the blade crown end, so as to prepare a turbine blade with no loose defects in the blade crown.

Description

Technical Field

[0001] The present invention relates to the technical field of turbine blade casting, and in particular to a method for eliminating loose defects of a blade crown at an inclined angle and a wax mold module. Background Art

[0002] As the direct power component of an aircraft, aircraft engines determine its stability and economy. With the development trend of high-power, low-fuel-consumption aircraft engines with high thrust-to-weight ratios, and the continuous increase in turbine inlet temperatures, aircraft engine designs are becoming increasingly complex. As a key component at the hot end of an aircraft engine, turbine blades are also experiencing increasing operating temperatures, leading to a wider range of turbine blade designs. The most common design is the shrouded structure for low-pressure and power turbine components. However, this shroud structure is prone to porosity defects during the casting process due to insufficient shrinkage compensation, resulting in unqualified turbine blades. Summary of the Invention

[0003] In view of the above analysis, the embodiments of the present invention aim to provide a method for eliminating the loose defect of the inclined blade shroud and a wax mold module to solve the problem that the blade shroud position of the hollow blade is prone to loose defects due to insufficient shrinkage compensation.

[0004] In one aspect, an embodiment of the present invention provides a method for eliminating a loose defect in a turbine blade shroud position, comprising:

[0005] Step S1, preparing a blade wax mold, the blade wax mold including a crystal selection section, a blade crown, a blade body, and a tenon that are connected in sequence and are integrally formed, and a groove is formed at the connection between the crystal selection section and the blade crown along the blade crown contour;

[0006] Step S2, assembling a plurality of blade wax models to form a wax model module, wherein the plurality of blade wax models are distributed in a circumferential direction around the center of the wax model module;

[0007] Step S3, preparing a casting shell using a wax mold assembly, so that a barrier protrusion is formed at a position corresponding to the groove of the blade wax mold on the inner surface of the casting shell;

[0008] Step S4, assembling the casting shell and the inner cavity core to form a casting module, and forming a crystal growth channel between the blocking protrusion of the casting shell and the inner cavity core;

[0009] Step S5 , pouring molten metal into the casting mold, and causing the molten metal to selectively grow from the blade shroud end through directional solidification, thereby preparing a hollow shrouded turbine blade with no loose defects in the blade shroud.

[0010] Furthermore, in step S1, when preparing the blade wax mold, the distance between the bottom of the groove and the inner cavity core is controlled to be 0.5-1 mm, so that the width of the selective crystal growth channel is 0.5-1 mm.

[0011] Furthermore, the blade crown is tilted relative to the blade body; in step S2, when assembling the wax mold module, the edge of the highest solidification point of the blade crown is directed toward the center of the wax mold module and forms an angle with the radial direction of the wax mold module, and a shrinkage wax block is set next to the edge of the highest solidification point of the blade crown.

[0012] Furthermore, when assembling the wax mold module, the edge of the highest solidification point of the blade crown is oriented toward the center of the wax mold module, and the angle between the radial line connecting the edge and the center of the wax mold module and the edge itself is 45°.

[0013] Furthermore, in step S1, when preparing the blade wax model, a portion of the edge of the highest solidification point of the blade crown close to the center of the wax model module is further extended outward along the inclination direction of the blade crown to be raised, and the raised edge is further extended outward in the horizontal direction to form a feeding platform of a predetermined width; in step S2, when assembling the wax model module, the feeding wax block is set on the feeding platform.

[0014] Furthermore, in step S2, when assembling the wax pattern module, a feeding wax block is bonded to the feeding platform. The feeding wax block is a rectangular parallelepiped and is vertically arranged to the feeding platform. The bonding surface of the feeding wax block matches the size of the feeding platform.

[0015] Furthermore, in step S2, when assembling the wax mold module, a thermal insulation wax mold sleeve is set in the space formed by multiple blade wax molds, so that the thermal insulation wax mold sleeve is located in the center of the wax mold module and is spaced apart from the blade wax mold.

[0016] Furthermore, the distance between the outer surface of the insulating wax pattern sleeve and the feeding wax block of the blade crown is maintained at 25 to 30 mm, and the upper surface of the insulating wax pattern sleeve is higher than the feeding wax block by no less than 20 mm.

[0017] Furthermore, in step S5, the casting module is placed in a heating device. When the casting module reaches a predetermined temperature and is kept warm, the molten metal is poured into the casting module. The casting module is pulled out and separated from the heating device so that the molten metal begins to directionally solidify from the blade crown end, and the pulling rate is controlled to 3 to 5 mm / min.

[0018] On the other hand, an embodiment of the present invention also provides a wax mold module for eliminating the loose defects of blade crowns with inclined angles, which includes: a pouring gate, an upper runner, multiple blade wax molds, an insulating wax mold sleeve, and a base; the pouring gate is connected to the upper runner, the upper runner and the base are spaced apart, and multiple blade wax molds are connected between the upper runner and the base; the insulating wax mold sleeve is connected to the base, and the pouring gate, upper runner, insulating wax mold sleeve and base are concentrically arranged; multiple blade wax molds are evenly arranged around the insulating wax mold sleeve; wherein, the blade wax mold includes a crystal selection section, a blade crown, a blade body and a tenon connected in sequence, the crystal selection section is connected to the base, and the tenon is connected to the upper runner; a groove is provided at the connection between the crystal selection section and the blade crown along the contour shape of the blade crown.

[0019] Compared with the prior art, the method of the present invention can achieve at least one of the following beneficial effects:

[0020] 1. During the directional solidification process, the blade of the present invention undergoes selective growth starting from the shroud end. When preparing the blade wax mold, a groove is provided along the shroud contour at the junction of the selective growth section and the blade wax mold. This creates a barrier protrusion on the inner surface of the casting shell, corresponding to the groove. This prevents the shroud from feeding the selective runner below it during directional solidification of the molten metal within the shell, thereby reducing the degree of looseness in the blade shroud. Furthermore, the placement of the barrier protrusion at the selective runner does not affect or alter the structure of the turbine blade formed by casting.

[0021] 2. The present invention controls the distance between the bottom of the groove at the connection between the crystal selection section and the blade crown and the inner cavity core to be 0.5 to 1 mm, so that a crystal selection growth channel with extremely small width is formed between the barrier protrusion on the inner surface of the shell and the inner cavity core, ensuring that the grains can grow smoothly from the crystal selection runner to the blade body to prepare hollow blades; at the same time, the shrinkage of the blade crown body to the crystal selection runner is blocked.

[0022] 3. The present invention directs the highest solidification point edge of the inclined blade crown toward the center of the wax mold module and forms an angle with the radial direction of the wax mold module, so that the projection of the edge in the radial direction of the wax mold module has a certain distance. This facilitates the use of the radial temperature gradient of the casting module during directional solidification to cause the edge of the blade crown to solidify and feed sequentially in the radial direction. A feeding block is provided at the last solidification position to effectively feed the blade crown, thereby further eliminating the looseness defect of the blade crown.

[0023] 4. The present invention arranges an insulating wax mold sleeve at the center of the wax mold module, so that a cylindrical ceramic shell insulation layer is formed in the central area of ​​the casting module. In the subsequent directional solidification process of the molten metal in the shell, the radial heat dissipation is blocked, and the cooling rate of the central area of ​​the casting module is slowed down, thereby increasing the temperature gradient in the radial direction of the casting module, which is beneficial for the blade crown to solidify sequentially in the direction of the radial temperature gradient and complete shrinkage compensation, so as to eliminate the loose defects of the blade crown and improve the casting qualification rate of the turbine blade with the inclined angle blade crown structure.

[0024] In the present invention, the above-mentioned technical solutions can be combined with each other to achieve more preferred combinations. Other features and advantages of the present invention will be described in the following description, and some advantages will become apparent from the description or be learned through practice of the present invention. The objectives and other advantages of the present invention can be realized and obtained through the contents particularly pointed out in the description and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The accompanying drawings are only for the purpose of illustrating particular embodiments and are not to be considered limiting of the present invention. Like reference symbols denote like parts throughout the drawings.

[0026] Figure 1 Schematic diagram of the structure of blade wax molds in some embodiments of the present invention.

[0027] Figure 2 yes Figure 1 A magnified view of the crown of the leaf wax model.

[0028] Figure 3 Schematic diagram of the structure of the leaf crown of some embodiments of the present invention.

[0029] Figure 4 Schematic diagram of the structure of wax mold modules according to some embodiments of the present invention.

[0030] Figure 5 yes Figure 4 Schematic diagram of the partial structure of the middle wax mold module.

[0031] Figure 6 Schematic cross-sectional view of a wax mold assembly according to some embodiments of the present invention.

[0032] Figure 7 This is a partial photo of the leaf crown prepared in Example 1 of the present invention.

[0033] Figure 8 This is a partial photo of the leaf crown prepared in Comparative Example 1 of the present invention.

[0034] Description of reference numerals:

[0035] 10. Blade wax mold; 11. Crystal selection section; 12. Blade crown; 13. Blade body; 14. Tenon; 15. Groove; 16. Core positioning hole; 17. Extension section; 18. Feeding platform; 20. Feeding wax block; 30. Base; 40. Insulation wax mold sleeve; 50. Pouring gate; 60. Upper runner. DETAILED DESCRIPTION

[0036] The preferred embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings, wherein the accompanying drawings constitute a part of this application and are used together with the embodiments of the present invention to illustrate the principles of the present invention, and are not used to limit the scope of the present invention.

[0037] A turbine blade consists of a tenon, a blade body, and a shroud, all connected in sequence. The tenon is used to connect to the turbine, and the shroud is located at the end of the blade body away from the turbine. The shroud is tilted relative to the blade body. During turbine blade casting, the shroud is tilted at a certain angle to the horizontal. This structure facilitates longitudinal shrinkage compensation during directional solidification. However, this tilted shroud inevitably has an edge at its highest point in the longitudinal direction, making it prone to porosity defects during directional solidification.

[0038] To this end, an embodiment of the present invention provides a method for eliminating the loose defect at the shroud position of a turbine blade, thereby eliminating the loose defect at the shroud position and improving the casting qualification rate of the turbine blade. The method for eliminating the loose defect at the shroud position of a turbine blade according to an embodiment of the present invention comprises the following steps:

[0039] Step S1, prepare a blade wax mold, such as Figure 1 As shown, the blade wax mold 10 includes an integrally formed crystal selection section 11, a blade crown 12, a blade body 13, and a tenon 14 that are sequentially connected. A groove 15 is formed along the contour of the blade crown 12 at the connection between the crystal selection section 11 and the blade crown 12.

[0040] Step S2, assembling a plurality of blade wax models 10 to form a wax model module, wherein the plurality of blade wax models 10 are distributed in a circumferential direction around the center of the wax model module;

[0041] Step S3, preparing a casting shell using a wax mold assembly, so that a barrier protrusion is formed at a position corresponding to the groove of the blade wax mold on the inner surface of the casting shell;

[0042] Step S4, assembling the casting shell and the inner cavity core to form a casting module, and forming a crystal growth channel between the blocking protrusion of the casting shell and the inner cavity core;

[0043] Step S5 , pouring molten metal into the casting mold, and causing the molten metal to selectively grow from the blade shroud end through directional solidification, thereby preparing a hollow shrouded turbine blade with no loose defects in the blade shroud.

[0044] Using the method of the embodiment of the present invention, such as Figure 1As shown, when preparing the blade wax mold 10 in step S1, the crystal selection section 11 is set at the end of the blade crown 12 away from the blade body 13, so that the crystal selection runner in the casting shell prepared using the blade wax mold 10 is adjacent to the blade crown structure of the blade itself, so that the blade starts to grow from the blade crown end during the directional solidification process.

[0045] like Figure 1 and Figure 2 As shown, when preparing a blade wax mold 10, the present invention provides a groove 15 along the contour of the blade shroud 12 at the junction of the crystal selection section 11 and the blade shroud 12. This creates a blocking protrusion on the inner surface of the casting shell produced from this blade wax mold 10, corresponding to the groove 15. This reduces the thickness of the shell's crystal selection runner at this location. This prevents the blade shroud from feeding the crystal selection runner below it during directional solidification of the molten metal within the shell, thereby reducing the degree of porosity in the blade shroud. Furthermore, the blocking protrusion is located at the crystal selection runner and does not affect or alter the structure of the turbine blade formed by casting.

[0046] It should be noted that the blade prepared in the present invention is a hollow blade. In order to form the inner cavity of the hollow blade, the casting shell and the inner cavity core are assembled to form a casting module, so that when the molten metal is poured, the molten metal is filled between the casting shell and the inner cavity core, and the blade cavity is formed at the position of the inner cavity core to cast a hollow blade.

[0047] In step S2, a wax mold module is assembled using the blade wax mold 10. In some embodiments, Figure 4 and Figure 5 As shown, the wax mold assembly includes multiple blade wax molds 10, a pouring gate 50, an upper runner 60, and a base 30. When assembling the wax mold assembly, multiple blade wax molds 10 are arranged between the base 30 and the upper runner 60 along the circumferential direction of the base 30 (only one blade wax mold 10 is shown in the figure), the crystal selection section 11 of the blade wax mold 10 is connected to the base 30, the tenon 14 is connected to the upper runner 60, and the pouring gate 50 is connected to the upper runner 60, and the pouring gate 50, the upper runner 60 and the base 30 are concentrically arranged.

[0048] Furthermore, in step S3, when the wax mold assembly is used to prepare the casting shell, a cavity having the same structure and dimensions as the wax mold assembly can be formed within the casting shell, thereby obtaining a turbine blade having the same structure as the blade wax mold 10 through casting. Furthermore, the cavity within the casting shell includes, from bottom to top, interconnected crystallization runners, shroud cavities, and blade body cavities, so that after pouring molten metal, the blade grows sequentially from the crystallization runners to the shroud, blade body, and tenon, thereby producing the blade.

[0049] Furthermore, to produce a hollow turbine blade with a shroud, in step S4, the casting shell and the inner cavity core are assembled to form a casting mold assembly, with a cavity formed between the casting shell and the inner cavity core. Because the blade wax mold 10 has a groove 15 formed at the junction of the crystal selection section 11 and the blade shroud 12, and a blocking protrusion is formed at a corresponding position on the inner surface of the casting shell, when the casting shell and the inner cavity core are assembled, the top area of ​​the crystal selection runner formed by the blocking protrusion can block the upper blade shroud from feeding the crystal selection runner during directional solidification, thereby reducing the looseness of the blade shroud.

[0050] In some embodiments, in step S1 , when preparing the blade wax mold 10 , the distance between the bottom of the groove 15 and the inner cavity core is controlled to be 0.5-1 mm, so that the width of the selective crystal growth channel is 0.5-1 mm.

[0051] To prevent the blocking protrusions on the inner surface of the casting shell from completely blocking the connection between the selection runner and the airfoil shell above it, an embodiment of the present invention creates a minimal gap between the bottom of the groove 15 and the inner core during the preparation of the blade wax mold 10. Specifically, a minimal gap is created between the blocking protrusions of the casting shell and the inner core, forming a selective growth channel. This not only blocks the airfoil body from feeding the selection runner, but also ensures that grains within the selection runner can smoothly grow through this gap into the airfoil and blade body. If the gap is too large, it will be difficult to block the airfoil from feeding the selection runner; if the gap is too small, it will be difficult for grains to smoothly grow from the selection runner to the airfoil.

[0052] In addition, for solid blades, when preparing the blade wax mold 10, a groove 15 can also be set at the connection between the crystal selection section 11 and the blade crown 12, and the distance between the bottoms of the grooves 15 on the opposite sides of the crystal selection section is 0.5 to 1 mm, so that a crystal selection growth channel with a thickness of 0.5 to 1 mm is formed through the opposite blocking protrusions on both sides at the corresponding position in the casting shell, which can block the shrinkage of the blade crown on the crystal selection runner, and at the same time ensure that the grains can smoothly grow from the crystal selection runner to the blade body.

[0053] In some embodiments, when preparing the blade wax mold 10, molten paraffin can be injected into the mold and solidified to form the blade wax mold 10. To obtain the blade wax mold 10 with the above structure, when designing the mold, a groove cutting portion protruding from the mold surface is designed along the blade crown contour at the connection between the crystal selection section and the blade crown. The blade wax mold 10 with the groove 15 is then pressed through the groove cutting portion.

[0054] In some embodiments, when preparing the blade wax mold 10, symmetrical positioning protrusions can be set on the inner surface of the mold at positions corresponding to the crystal selection sections, and the inner cavity core can be fixedly clamped inside the mold by the positioning protrusions on both sides. This ensures that the relative position between the blade wax mold 10 and the inner cavity core is maintained when preparing the blade wax mold 10, so as to facilitate positioning of the casting shell and the inner cavity core when preparing the casting shell.

[0055] At the same time, the distance between the bottom of the groove 15 of the blade wax model 10 and the inner cavity core is ensured by controlling the height of the groove cutting line in the mold. For example, by controlling the height of the groove cutting part in the mold to be 0.5 to 1 mm lower than the height of the positioning protrusion, the distance between the bottom of the groove of the blade wax model 10 and the inner cavity core is ensured to be 0.5 to 1 mm.

[0056] Further, if Figure 1 and Figure 2 As shown, due to the positioning protrusions provided within the mold, a core positioning hole 16 is formed in the crystal selection section of the blade wax mold 10. The core positioning hole 16 is located on the side of the groove 15 away from the blade body 13. By providing the core positioning hole 16, the present invention can form a core positioning protrusion on the inner surface of the casting shell when preparing it. The core positioning protrusions can be used to position the two sides of the inner core cavity, thereby avoiding uneven thickness on both sides of the inner core cavity of the hollow blade formed by casting.

[0057] For example, two groups of core positioning holes 16 may be provided, and the two groups of core positioning holes 16 are symmetrically and evenly distributed on both sides of the blade wax mold. The diameter of the core positioning holes 16 may be 2-3 mm.

[0058] In some embodiments, after the blade wax mold 10 is prepared, it is trimmed and a thick layer of paraffin wax is applied to the bottom of the core positioning hole 16. This creates a gap between the core positioning protrusion on the inner surface of the casting shell and the inner core. This allows for a certain amount of movement between the casting shell and the inner core during the heating and cooling process of the turbine blade casting, when the casting shell and the inner core change in size due to thermal expansion and contraction, thereby preventing contact deformation and fracture. For example, the thickness of the paraffin wax layer at the bottom of the core positioning hole 16 can be 0.1 to 0.2 mm.

[0059] In some embodiments, as Figure 3 As shown, the shroud 12 is approximately a parallelogram, wherein two opposite edges are serrated.

[0060] Because the blade shroud 12 is tilted relative to the blade body 13, one side edge of the blade shroud 12 is at the highest point of solidification. In step S2, when assembling the wax mold assembly, the highest point of solidification of the blade shroud 12 is oriented toward the center of the wax mold assembly and forms an angle with the radial direction of the wax mold assembly. A feeding wax block is then placed next to the highest point of solidification of the blade shroud 12, so that the feeding wax block is located near the center of the wax mold assembly.

[0061] Specifically, such as Figure 4 and Figure 5 As shown, the edge of the highest solidification point of the leaf crown 12 is toward the center of the wax mold module, and a feeding wax block 20 is provided next to the edge; Figure 6 As shown, the edge of the highest solidification point of the blade shroud 12 forms an angle with the radial direction of the wax mold module, so that the projection of the edge in the radial direction of the wax mold module has a certain distance.

[0062] The present invention directs the edge of the highest solidification point of the blade shroud 12 toward the center of the wax mold module and forms an angle with the radial direction of the wax mold module, so that the edge is not perpendicular to the radial direction of the wax mold module, and the projection of the edge in the radial direction of the wax mold module has a certain distance, so that during directional solidification, the radial temperature gradient of the casting module is utilized to make the edge of the blade shroud solidify in radial order, thereby completing effective sequential shrinkage feeding of the blade shroud; at the same time, a shrinkage wax block is arranged at the last solidification position, so that a shrinkage block is formed in the casting module at the last solidification position of the blade shroud, so that the shrinkage block is located near the center of the casting module, so as to effectively feed the edge of the highest solidification point of the blade shroud; at the same time, the vertical design of the rectangular-shaped shrinkage block also plays a radial heat insulation role of the shrinkage block, thereby improving the radial temperature gradient of the blade shroud structure and ensuring radial sequential solidification of the blade shroud.

[0063] In some embodiments, when assembling the wax mold module, the angle between the radial line connecting the edge of the highest solidification point of the blade crown and the center of the wax mold module and the edge itself is 45°, so that the projected length of the edge on the radial line is longer, thereby increasing the temperature gradient between the end point of the edge of the blade crown away from the center of the module and the end point close to the center of the module during directional solidification, so that the edge solidifies and shrinks sequentially in the direction of the temperature gradient, thereby reducing the looseness defect of the blade crown.

[0064] Specifically, such as Figure 6 As shown, the angle a between the endpoint of the highest solidification point edge of the leaf crown 12 close to the center of the wax mold module and the edge itself can be made to be 45°; or, the angle b between the endpoint of the highest solidification point edge of the leaf crown 12 away from the center of the wax mold module and the edge itself can be made to be 45°; or, the angle between any point in the middle of the highest solidification point edge of the leaf crown 12 and the edge itself can be made to be 45°.

[0065] In some embodiments, in step S1, when preparing the blade wax mold 10, a portion of the edge of the highest solidification point of the blade crown 12 close to the center of the wax mold module is further extended outward along the inclination direction of the blade crown 12 to be raised, and the raised edge is further extended outward in the horizontal direction to form a feeding platform of a predetermined width; in step S2, when assembling the wax mold module, the feeding wax block is placed on the feeding platform.

[0066] Specifically, such as Figure 2 and Figure 3 As shown, a portion of the edge of the highest solidification point of the blade crown 12 near the center of the wax mold continues to extend along the inclination direction of the blade crown 12 to form an extension section 17, thereby raising the portion of the edge of the blade crown 12 near the center of the mold. After the extension section 17 is formed, the edge of the extension section 17 continues to extend horizontally away from the blade crown to form a feeding platform 18. Figure 2 As shown, the feeding wax block 20 is disposed on the feeding platform 18 .

[0067] The present invention extends and raises the blade shroud edge to form an extended section before installing the feeding platform. This prevents the feeding platform from directly contacting the blade shroud edge. This prevents excess molten wax from flowing into the blade shroud during the bonding of the feeding wax block, potentially affecting the original structure of the blade shroud in the wax mold and, in turn, the structure of the resulting turbine blade shroud. Furthermore, the extended section also allows the corresponding feeding runner in the casting shell to further feed the blade shroud, reducing porosity defects in the blade shroud.

[0068] In some embodiments, the length of the extension section 17 is 1 / 2 the length of the edge of the highest solidification point of the blade crown 12, and the width of the extension section 17 along the inclination direction of the blade crown 12 is 2-3 mm. If the width of the extension section 17 is too large, the feeding wax block 20 will not directly feed the blade crown 12 during the subsequent directional solidification. If the width is too small, it will be difficult to fill the feeding wax pattern 20 with molten paraffin when bonding, resulting in inconvenient operation.

[0069] In some embodiments, in step S2, when assembling the wax pattern module, the feeding wax block 20 is bonded to the feeding platform 18. Figure 1 and Figure 2 As shown, the feeding wax block 20 is a rectangular parallelepiped. The feeding wax block 20 and the feeding platform 18 are arranged perpendicularly, and the bonding surface of the feeding wax block 20 matches the size of the feeding platform 18.

[0070] The embodiments of the present invention use a rectangular parallelepiped feeding wax block, which is positioned close to and along the edge of the highest freezing point of the leaf crown. Compared to feeding blocks of other shapes, the vertically designed rectangular parallelepiped large-area feeding block maximizes the radial heat insulation function of the feeding block and provides a large volumetric feeding capacity. This allows the feeding block to effectively feed the edge of the highest freezing point of the leaf crown during subsequent directional solidification, thereby improving the feeding effect.

[0071] In some embodiments, the length of the feeding platform 18 is 1 / 2 the length of the edge of the highest solidification point of the blade shroud 12; the width of the feeding platform 18 is 3-4 mm, that is, the thickness of the feeding wax block 20 is 3-4 mm, and the height of the feeding wax block is 15-18 mm. If the thickness or height of the feeding wax block 20 is too small, the feeding effect will be insufficient, and the radial thermal insulation effect will be insufficient. If the thickness or height of the feeding wax block 20 is too large, it will generate large stress during directional solidification shrinkage, causing deformation of the blade shroud of the turbine blade.

[0072] In some embodiments, when bonding the feeding wax block 20 to the feeding platform 18 and preparing the extension section 17 and the feeding platform 18, molten paraffin can be used to fill and trim the joints of the adjacent structures after bonding to ensure a smooth transition at the transition position.

[0073] In some embodiments, in step S2, Figure 4 and Figure 5 As shown, when assembling the wax mold module, a heat-insulating wax mold sleeve 40 is set in the space formed by multiple blade wax molds 10, so that the heat-insulating wax mold sleeve 40 is located in the center of the wax mold module and is spaced apart from the blade wax mold 10.

[0074] The present invention arranges an insulating wax mold sleeve 40 in the center of the wax mold module, thereby forming a cylindrical ceramic insulation layer in the central area of ​​the casting module, blocking radial heat dissipation during directional solidification, slowing down the cooling rate of the central area of ​​the casting module, thereby increasing the temperature gradient in the radial direction of the casting module, which is beneficial to the sequential solidification of the blade crown in the direction of the radial temperature gradient and effective sequential shrinkage compensation.

[0075] It should be noted that the position of the insulating wax mold sleeve 40 in the casting module forms a cavity after dewaxing, and the cavity and the ceramic shell outside it form a ceramic insulating layer, which plays a radial heat insulation role; and because the insulating wax mold sleeve 40 of the present invention is not connected to the upper runner 60 above, the molten metal cannot enter the cavity when pouring the molten metal, thereby avoiding the waste of molten metal.

[0076] In some embodiments, as Figure 5As shown, the distance L between the outer surface of the insulating wax pattern sleeve 40 and the feeding wax block 20 of the blade crown is maintained at 25 to 30 mm, and the upper surface of the insulating wax pattern sleeve 40 is at least 20 mm higher than the height H of the feeding wax block 20. If the height of the insulating wax pattern sleeve 40 is too low or the distance from the feeding wax block 20 is too large, the insulating layer will not provide radial insulation for the feeding block during subsequent directional solidification, resulting in a rapid drop in the feeding block temperature and a decrease in the radial temperature gradient of the casting module, which is not conducive to the sequential solidification and feeding of the blade crown along the radial direction of the casting module. If the distance between the insulating wax pattern sleeve 40 and the feeding wax block 20 is too small, the insulating wax pattern sleeve 40 and the feeding wax block 20 will easily stick together during the preparation of the casting shell, affecting the drying of the shell.

[0077] In some embodiments, in step S5, the casting module is placed in a heating device. When the casting module reaches a predetermined temperature and is kept warm, the molten metal is poured into the casting module. The casting module is pulled out and separated from the heating device so that the molten metal begins to directionally solidify from the blade crown end, and the pulling rate is controlled to 3 to 5 mm / min.

[0078] The present invention ensures that the inclined blade crown structure can solidify and complete shrinkage feeding in sequence according to the axial and radial temperature gradient directions by selecting a suitable pulling rate. If the pulling rate is too high or too low, it will affect the temperature gradient and solidification sequence of the blade along the axial and radial directions of the casting module during the directional solidification process, and the shrinkage feeding design cannot complete solidification and shrinkage feeding in the axial and radial directions of the casting module.

[0079] The embodiment of the present invention also provides a wax mold module for eliminating the loose defect of the tilt angle blade crown, such as Figure 4 and Figure 5 As shown, the wax mold assembly includes: a pouring gate 50, an upper runner 60, a plurality of blade wax molds 10, a heat-insulating wax mold sleeve 40, and a base 30. The pouring gate 50 is connected to the upper runner 60, and the upper runner 60 is spaced apart from the base 30. The plurality of blade wax molds 10 are connected between the upper runner 60 and the base 30; the heat-insulating wax mold sleeve 40 is connected to the base 30, and the pouring gate 50, the upper runner 60, the heat-insulating wax mold sleeve 40 and the base 30 are concentrically arranged; the plurality of blade wax molds 10 are evenly arranged around the heat-insulating wax mold sleeve 40; wherein, as shown in FIG. Figure 1 and Figure 2 As shown, the blade wax mold 10 includes a crystal selection section 11, a blade crown 12, a blade body 13 and a tenon 14 connected in sequence. The crystal selection section 11 is connected to the base 30, and the tenon 14 is connected to the upper runner 60. The connection between the crystal selection section 11 and the blade crown 12 is provided with a groove 15 extending along the contour shape of the blade crown 12.

[0080] In addition, the structure of the wax mold module is the same as that in the above embodiment and will not be repeated here.

[0081] The method for eliminating the loose defect of the inclined angle blade crown of the present invention is further described below with reference to specific embodiments.

[0082] Example 1

[0083] The method of this embodiment is used to cast turbine working blades with an inclined blade crown structure. The turbine working blades are hollow blades with crowns. The planar shape of the blade crown is approximately a parallelogram. The sizes of adjacent edges are 30 mm and 40 mm, and the 40 mm long edge is serrated. When the blade crown is placed vertically, the angle between it and the horizontal direction is 40°.

[0084] The method of this embodiment includes:

[0085] S1, prepare a blade wax model 10. Figure 1 As shown, the blade wax model 10 comprises a sequentially connected crystal selection section 11, a shroud 12, a blade body 13, and a tenon 14. A groove 15 is formed at the junction of the crystal selection section 11 and the shroud 12, following the contour of the shroud 12. The distance between the bottom of the groove 15 and the inner core is 0.5 mm. Two sets of core positioning holes 16 with a diameter of 2 mm are provided in the blade wax model 10.

[0086] S2, assemble multiple blade wax molds 10 to form Figure 4 Wax model set shown.

[0087] The edge of the highest solidified point of the crown 12 of the blade wax model 10 is 30 mm long. This edge is extended and raised by 15 mm near the center of the wax model assembly to form an extension section 17. Extension section 17 is 15 mm long and 2 mm wide. The edge of extension section 17 is further extended horizontally to form a feeding platform 18. The width of feeding platform 18 is 3 mm.

[0088] A rectangular parallelepiped feeding wax block 20 is pressed, the size of which is 15 mm x 15 mm x 3 mm. A feeding wax block 20 of the same size is vertically bonded to the feeding platform 18 .

[0089] A base 30 with a diameter of 300 mm was selected for the wax mold assembly. The feeding wax block 20 was positioned toward the center of the wax mold. The inner endpoint of the highest solidified edge of the shroud 12, near the mold center, and the radial line connecting the inner endpoint and the mold center formed a 45° angle with the edge. The feeding wax block 20 was positioned near the center of the wax mold.

[0090] A 90mm diameter insulation wax mold sleeve 40 is set at the center of the wax mold module. Its thickness is 5mm, its upper edge is 20mm higher than the shrinkage wax block 20, and its outer surface is kept at a distance of 25mm from the shrinkage wax block 20.

[0091] S3, using the wax mold assembly to prepare a casting shell.

[0092] S4, assembling the casting shell and the inner cavity core to form a casting module.

[0093] S5: Molten metal is poured into the casting mold and directional solidification is performed to cause selective crystal growth of the molten metal from the blade shroud end, thereby producing a hollow shrouded turbine blade with no loose shroud defects. The pulling rate during directional solidification is 4 mm / min.

[0094] Comparative Example 1

[0095] The turbine working blades are cast using a traditional casting method, and the method of selective crystal growth starting from the tenon section is adopted. No groove 15 is set in the crystal selection section, nor is an insulating wax mold sleeve 40. The edge of the highest point of the blade crown solidification is perpendicular to the radial direction of the wax mold module, and a cylindrical shrinkage block is set next to the edge to feed the blade crown.

[0096] The blade crowns of the turbine blades prepared in Example 1 and Comparative Example 1 were observed. Figure 7 and Figure 8 As shown, there is no loose defect at the edge of the leaf crown of Example 1, while there are a large number of loose defects at the edge of the leaf crown of Comparative Example 1.

[0097] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by any technician familiar with this technical field within the technical scope disclosed by the present invention should be covered by the scope of protection of the present invention.

Claims

1. A method for eliminating the loose defect of the turbine blade shroud position, characterized in that: include: Step S1, preparing a blade wax mold, wherein the blade wax mold includes a crystal selection section, a blade crown, a blade body, and a tenon that are connected in sequence and are integrally formed, and a groove is formed at the connection between the crystal selection section and the blade crown along the contour of the blade crown; Step S2, assembling a plurality of the blade wax models to form a wax model module, wherein the plurality of the blade wax models are distributed in a circumferential direction around the center of the wax model module; Step S3, preparing a casting shell using the wax mold assembly, so that a barrier protrusion is formed at a position corresponding to the groove of the blade wax mold on the inner surface of the casting shell; Step S4, assembling the casting shell and the inner cavity core to form a casting module, and forming a crystal growth channel between the blocking protrusion of the casting shell and the inner cavity core; Step S5 , pouring molten metal into the casting mold, and causing the molten metal to selectively grow from the blade shroud end through directional solidification, so as to prepare a hollow shrouded turbine blade with no loose defects in the blade shroud.

2. The method according to claim 1, characterized in that In step S1, when preparing the blade wax mold, the distance between the bottom of the groove and the inner cavity core is controlled to be 0.5-1 mm, so that the width of the selective crystal growth channel is 0.5-1 mm.

3. The method according to claim 1, characterized in that The blade crown is arranged obliquely relative to the blade body; In step S2, when assembling the wax mold module, the edge of the highest solidification point of the leaf crown is oriented toward the center of the wax mold module and forms an angle with the radial direction of the wax mold module, and a shrinkage wax block is set next to the edge of the highest solidification point of the leaf crown.

4. The method according to claim 3, characterized in that When assembling the wax mold assembly, the edge of the highest solidification point of the leaf crown is oriented toward the center of the wax mold assembly, and the angle between the radial line connecting the edge and the center of the wax mold assembly and the edge itself is 45°.

5. The method according to claim 3, characterized in that In step S1, when preparing the blade wax model, a portion of the edge of the highest solidification point of the blade crown close to the center of the wax model module is further extended outward along the inclined direction of the blade crown to increase height, and the heightened edge is further extended outward in the horizontal direction to form a feeding platform of a predetermined width; In step S2, when assembling the wax pattern module, the feeding wax block is placed on the feeding platform.

6. The method according to claim 5, characterized in that In step S2, when assembling the wax pattern module, the feeding wax block is bonded to the feeding platform. The feeding wax block is a rectangular parallelepiped and is arranged perpendicular to the feeding platform. The bonding surface of the feeding wax block matches the size of the feeding platform.

7. The method according to claim 1, characterized in that In step S2, when assembling the wax mold module, a heat-insulating wax mold sleeve is set in the space formed by the multiple blade wax molds, so that the heat-insulating wax mold sleeve is located in the center of the wax mold module and is spaced apart from the blade wax mold.

8. The method according to claim 7, characterized in that The distance between the outer surface of the insulating wax pattern sleeve and the shrinkage wax block of the leaf crown is maintained at 25-30 mm, and the upper surface of the insulating wax pattern sleeve is higher than the shrinkage wax block by no less than 20 mm.

9. The method according to any one of claims 1 to 8, characterized in that In step S5, the casting mold is placed in a heating device, and when the casting mold reaches a predetermined temperature and is kept warm, the molten metal is poured into the casting mold; The casting mold is pulled out and separated from the heating device so that the molten metal starts to directionally solidify from the blade crown end, and the pulling rate is controlled to be 3-5 mm / min.

10. A wax mold module for eliminating loose defects of inclined blade crowns, characterized in that: include: Sprue, upper runner, multiple blade wax molds, insulation wax mold sleeve, base; The pouring gate is connected to the upper runner, the upper runner is spaced apart from the base, and the plurality of blade wax molds are connected between the upper runner and the base; The thermal insulation wax mold sleeve is connected to the base, and the pouring port, the upper runner, the thermal insulation wax mold sleeve and the base are concentrically arranged; The plurality of blade wax models are evenly arranged around the heat-insulating wax model sleeve; Among them, the blade wax mold includes a crystal selection section, a blade crown, a blade body and a tenon connected in sequence, the crystal selection section is connected to the base, and the tenon is connected to the upper runner; the connection between the crystal selection section and the blade crown is provided with a groove along the contour shape of the blade crown, so that the inner surface of the casting shell prepared by the wax mold module and the corresponding position of the groove of the blade wax mold form a blocking protrusion, the casting shell and the inner cavity core are assembled to form a casting module, and a crystal selection growth channel is formed between the casting shell blocking protrusion and the inner cavity core.

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