Wax pattern structure and method for thin-walled, specially-shaped, large-size single-crystal splash plate casting

Abstract

The application provides a wax mold structure and method for thin-wall special-shaped large-size single-crystal splash baffle casting, which comprises a starting end, a spiral selection section, a first crystal bar, a second crystal bar, a single-crystal splash baffle wax mold piece and a feeding section, the starting end is used for connecting with a pouring assembly, the first crystal bar is connected with the top of the single-crystal splash baffle wax mold piece, the second crystal bar is connected with the bottom of the single-crystal splash baffle wax mold piece, the uppermost end face of the inner circle and the outer circle of the middle circular hole of the flange of the single-crystal splash baffle wax mold piece is pasted with a semi-annular process patch, and a feeding section is arranged at the top and the bottom of the end of the single-crystal splash baffle wax mold piece far away from the crystal bar, and the two feeding sections are not connected. The application controls the single-crystal integrity and metallurgical defects of the casting to obtain a single-crystal splash baffle casting with good metallurgical quality, solves various technical problems in the development process of the casting, and achieves good effects.

Description

Technical Field

[0001] This invention belongs to the field of investment casting technology, specifically to a wax pattern structure and method for casting thin-walled, irregularly shaped, large-size single-crystal splash guards. Background Technology

[0002] Currently, the combustion chamber temperature of high-performance aero-engines internationally ranges from approximately 1950K to 2200K. To ensure a long service life and improve overall combustion performance, both domestic and international manufacturers employ high-efficiency composite cooling technology for their flame tubes. The splash plate is a crucial structural component in this type of high-efficiency composite cooling flame tube. Located at the flame tube head, the flame tube head utilizes an impact-forced convection cooling method. Cooling air enters the convection heat transfer channel formed between the transition section and the splash plate through evenly distributed impact holes on the transition section. It first forces the splash plate to cool it through impact, and then flows outwards. Therefore, the splash plate is subjected to the high-temperature combustion gas in the main combustion zone on one side and the cooling airflow on the other side. The splash plate absorbs a lot of convective and radiative heat, and the wall temperature difference between the cold and hot sides is about 80K to 100K. The working temperature of this advanced structure flame tube splash plate is as high as about 900℃. At the same time, it needs to meet high mechanical properties. Traditional splash plates use solid solution strengthened cobalt-based high temperature alloys, with a maximum temperature resistance of 700℃. Their high-temperature performance, such as high cycle fatigue and creep resistance, is weak and can no longer meet the requirements of advanced aero-engine flame tubes. Therefore, advanced aero-engines have changed the splash plate from cobalt-based high temperature alloys to second-generation single-crystal DD6 alloy. Although this change has greatly increased the temperature of the main combustion zone of the combustion chamber, the unique structural characteristics of the splash plate have greatly increased the manufacturing difficulty. The total height of the splash plate casting is 122mm and the total width is 125mm. The irregular shape of the main body of the casting consists of three conical surfaces with a circumferential wall thickness of 2mm. There is a large circular hole with a diameter of φ80mm in the middle of the conical surface. The small-angle grain boundaries of the castings should not exceed 8°.

[0003] The manufacturing process for single-crystal turbine blades is relatively mature. However, there is a lack of relevant data and reports on the manufacturing process for these large-sized, thin-walled, irregularly shaped single-crystal castings. These castings are large in size, making them prone to twisting and shifting during crystal growth, resulting in large-angle impurities. Their thin walls also make them susceptible to spontaneous nucleation at the corners during directional solidification, leading to impurities. Furthermore, the large circular hole in the center of the casting causes discontinuous crystal growth, increasing the risk of crystal breakage and impurities. The significant difference in wall thickness also results in high structural stress, making them prone to recrystallization defects. Additionally, the solidification high points are susceptible to porosity defects due to insufficient metal feeding. Summary of the Invention

[0004] To address the problems existing in the prior art, this invention provides a wax pattern structure and method for casting thin-walled, irregularly shaped, large-size single-crystal splash guards. By controlling the integrity of the single crystal and metallurgical defects in this type of casting, a single-crystal splash guard casting with good metallurgical quality is obtained, solving various technical problems encountered in the development of this type of casting and achieving excellent results.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a wax mold structure for casting thin-walled, irregularly shaped, large-size single-crystal splash guards, comprising an integrated starting end, a spiral crystal selection section, a first crystal guide bar, a second crystal guide bar, a single-crystal splash guard wax mold, and a feeding section. The starting end is used to connect with the casting assembly. The first crystal guide bar is connected to the top of the single-crystal splash guard wax mold, and the second crystal guide bar is connected to the bottom of the single-crystal splash guard wax mold. The uppermost solidified portion of the inner and outer circles of the central circular hole in the flange of the single-crystal splash guard wax mold is covered with a semi-circular process patch. A feeding section is provided at the top and bottom of the end of the single-crystal splash guard wax mold away from the crystal guide bar, and the two feeding sections are not connected.

[0006] Furthermore, all transition R-shapes at the boss and flange connection points of the single-crystal splash shield wax mold are designed according to the drawings. The outer diameter of the central hole in the flange is designed according to the upper limit of the design, and the inner diameter is designed according to the lower limit of the design.

[0007] Furthermore, the length of the semi-circular process subsidy on the single crystal splash shield wax mold is 1 / 3 of the circumference of the central hole of the flange. The semi-circular process subsidy is removed by grinding after casting heat treatment.

[0008] Furthermore, if the connection between the shrinkage section and the single-crystal splash guard wax mold is circular, then the arc length of the connecting section is 1 / 4 of the circumference of the circular hole in the center of the flange of the single-crystal splash guard wax mold; if the connection between the shrinkage section and the single-crystal splash guard wax mold is not circular, then the length of the connecting section is equivalent to the width of the single-crystal splash guard wax mold; the height of the shrinkage section is 20mm-30mm.

[0009] Furthermore, the flange edge of the single crystal splash shield of the single crystal splash shield wax mold is connected to the spiral crystal selector through the first crystal guide bar, and the thin-walled conical surface of the single crystal splash shield of the single crystal splash shield wax mold is connected to the spiral crystal selector through the second crystal guide bar. The transition R between the first crystal guide bar and the second crystal guide bar and the single crystal splash shield is R10-R30.

[0010] Furthermore, the lower ends of the first and second crystal guides have the same width, the connection width between the upper end of the first crystal guide and the flange edge of the single crystal splash shield is 1 / 6 of the flange circumference, and the connection width between the upper end of the second crystal guide and the thin-walled conical surface of the single crystal splash shield is equivalent to the width of the thin-walled conical surface of the single crystal splash shield.

[0011] The present invention provides a wax mold combined casting structure, including a crystallization base, a casting component and the wax mold structure. The casting component is disposed in the middle of the crystallization base, and multiple wax mold structures are evenly distributed around the casting component on the crystallization base. The starting ends of the multiple wax mold structures are all connected to the outlet of the casting component.

[0012] Furthermore, the casting assembly includes a pouring cup and a sprue located at the bottom of the pouring cup. The outlet of the sprue is connected to the starting end of the wax mold structure. The pouring cup is connected to the shrinkage compensation section at the bottom of the single crystal splash guard wax mold through a connecting rod. When the connecting rod is connected to the shrinkage compensation section, wax material is piled up to form an approximate triangle for reinforcement.

[0013] This invention provides a casting method for a thin-walled, irregularly shaped, large-size single-crystal splash guard, which involves making a shell for the wax mold structure and casting the shell to obtain the thin-walled, irregularly shaped, large-size single-crystal splash guard.

[0014] Furthermore, the prepared shell is cast using the aforementioned wax mold combination casting structure to obtain a thin-walled, irregularly shaped, large-size single-crystal splash guard.

[0015] Compared with the prior art, the present invention has at least the following beneficial effects:

[0016] This invention provides a wax pattern structure for casting thin-walled, irregularly shaped, large-sized single-crystal splash guards. It integrates the starting end, spiral crystal selection section, first crystal guide bar, second crystal guide bar, single-crystal splash guard wax pattern, and feeding section into a single design, resulting in a high-quality wax pattern with good consistency. This ensures the integrity and crystal orientation of the single crystal in the casting, while also improving production efficiency. Furthermore, feeding sections are provided on both the upper and lower end faces of the single-crystal splash guard wax pattern, and a non-closed design concept for the feeding sections is proposed to reduce stress levels and prevent recrystallization. Simultaneously, it proposes... A crystal-drawing scheme for thin-walled castings with discontinuous cross-sections in multiple locations is proposed. A first and second crystal-drawing strip are placed between the spiral crystal selection section and the single-crystal splash guard wax mold, effectively solving the problem of excessive single-crystal integrity in this type of casting. For the problem of porosity at high points during directional solidification in annular thin-walled single-crystal castings, this invention proposes a semi-annular feeding scheme. A semi-annular process patch is applied to the last solidified portion (i.e., the area prone to porosity) on the inner and outer surfaces of the central circular hole in the single-crystal splash guard wax mold flange, effectively solving the problem of porosity at high points during solidification in annular thin-walled single-crystal castings.

[0017] In summary, the wax mold structure of this invention can produce thin-walled, irregularly shaped, large-size single-crystal splash guard castings with fully qualified metallurgical quality. Attached Figure Description

[0018] Figure 1 Schematic diagram of the splash guard casting;

[0019] Figure 2 Schematic diagram of integrated molding of single-crystal splash guard;

[0020] Figure 3 Schematic diagram of solidification high point subsidy;

[0021] Figure 4 Schematic diagram of the seed strip;

[0022] Figure 5 Schematic diagram of wax model assembly scheme. Detailed Implementation

[0023] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0024] like Figures 1-4 As shown, the present invention provides a wax pattern structure for casting thin-walled, irregularly shaped, large-size single-crystal splash guards. To ensure the consistency of wax pattern parts, improve wax pattern quality, and reduce deformation during the wax pattern stage, the starting end, spiral crystal selection section, crystal guide bar, single-crystal splash guard wax pattern parts, and shrinkage compensation section are integrally formed, reducing wax pattern welding. At the same time, it avoids the problem of excessive perpendicularity of the starting end and spiral crystal selector caused by human factors, ensuring the integrity and crystal orientation of the single crystal in the casting.

[0025] The starting end is used to connect to the casting component;

[0026] The crystal guide bar includes a first crystal guide bar and a second crystal guide bar. The first crystal guide bar is connected to the top of the single crystal splash shield wax mold and is used for crystal guiding on the flange edge of the single crystal splash shield. The second crystal guide bar is connected to the bottom of the single crystal splash shield wax mold and is used for crystal guiding on the thin-walled conical surface of the single crystal splash shield.

[0027] All transition radius (R) at the boss and flange connection point of the single-crystal splash shield wax mold are designed according to the drawing to avoid recrystallization defects; the boss is the transition point between the large-diameter and small-diameter sections of the outer wall of the single-crystal splash shield flange; the connection point with the flange is the transition point between the single-crystal splash shield flange and the thin-walled conical surface.

[0028] The center of the flange of the single crystal splash shield wax mold is a round hole. A semi-circular process patch is pasted on the uppermost part of the inner and outer circles of the single crystal splash shield wax mold flange, where solidification high points and loose parts are likely to occur (the last solidified part). The process patch is removed by grinding after casting heat treatment.

[0029] Preferably, the length of the semi-circular process subsidy on the single-crystal splash guard wax mold is approximately 1 / 3 of the circumference of the circular hole in the center of the flange.

[0030] The top and bottom of the single-crystal splash shield wax mold are provided with feeding sections, which are located away from the crystal guide strips. The feeding section at the top of the single-crystal splash shield wax mold cannot be closed. The feeding section must be in a free state to avoid recrystallization defects caused by excessive solidification stress. That is, the two feeding sections are not connected.

[0031] Preferably, if the connection between the feeding section and the casting is circular, the arc length of the feeding section connection is approximately 1 / 4 of the circumference of the circular hole in the center of the flange of the single crystal splash guard wax mold; if the connection between the feeding section and the single crystal splash guard wax mold is not circular, the length of the feeding section connection is equivalent to the width of the single crystal splash guard wax mold; the height of the feeding section is approximately 20-30mm.

[0032] Preferably, during crystal pulling, the crystals selected by the spiral crystal selector are simultaneously introduced into the flange edge and thin-walled conical surface of the single-crystal splash shield wax mold, forming an inverted trapezoidal first crystal puller and an inverted triangular second crystal puller; the first crystal puller smoothly transitions to the flange edge of the single-crystal splash shield, and the second crystal puller smoothly transitions to the thin-walled conical surface, so as to obtain a casting with good single-crystal integrity;

[0033] Under the premise of ensuring the integrity of the single crystal in the casting, the lower diameter of the first crystal guide strip is 8mm, and the width of the connection between the first crystal guide strip and the flange edge should be as small as possible, about 1 / 6 of the circumference, to avoid forming a closed thermal field with the second crystal guide strip, which would affect the temperature field of the casting and thus affect the integrity of the single crystal in the casting; the lower diameter of the second crystal guide strip is 8mm, the upper end is about the same length as the casting, and the height is about 40-50mm.

[0034] Preferably, the transition R between the two lead strands and the casting is typically between R10 and R30.

[0035] Preferably, the outer diameter is designed according to the upper limit of the design, and the inner diameter is designed according to the lower limit of the design.

[0036] like Figure 5 As shown, the present invention also provides a wax mold combination casting structure, which is assembled using the above-mentioned wax mold structure, including a crystallization base, a casting component and the above-mentioned wax mold structure. The casting component is provided in the middle of the crystallization base, and the above-mentioned multiple wax mold structures are evenly distributed along the circumference of the crystallization base. The starting ends of the multiple wax mold structures are all connected to the casting component.

[0037] Preferably, the casting component is set in the middle of the crystallization base, and multiple wax mold structures are set around the casting component. The casting component includes a pouring cup and a sprue set at the bottom of the pouring cup. The sprue is connected to the starting end of the wax mold structure. The pouring cup is connected to the shrinkage compensation section at the bottom of the single crystal splash baffle wax mold through a connecting rod to achieve the fixation and ventilation of the wax mold structure. In order to strengthen the connection between the shrinkage compensation section and the pouring cup, when the connecting rod is connected to the shrinkage compensation section, wax material is piled up to form an approximate triangle for reinforcement.

[0038] This invention also provides a casting method for a thin-walled, irregularly shaped, large-size single-crystal splash guard. The method involves making a shell using the aforementioned wax model structure, casting the prepared shell using the aforementioned wax model combination casting structure, and then casting it using a predetermined directional solidification and melting process. After chemical descrambling, vacuum heat treatment, grinding and polishing, grain size etching, inspection, and non-destructive testing, a casting with good metallurgical quality is obtained.

[0039] Example

[0040] Firstly, in the design of the wax model structure, to ensure the consistency of wax model parts, improve wax model quality, and reduce deformation during the wax modeling process, the starting end, spiral crystal selector section, crystal guide bar, single crystal splash guard, and shrinkage compensation section are integrally molded. This reduces wax model welding and avoids human-caused issues with the perpendicularity of the starting end and spiral crystal selector, ensuring the integrity and crystal orientation of the casting's single crystal. All transitions (R3) at the boss and flange connection points are designed with an upper tolerance of R3.5 to avoid recrystallization defects.

[0041] Secondly, in the design of the seed strips, the radius (R) at the junction of the first seed strip and the casting is designed to be R5; the width of the seed strip at the flange edge is 20mm and the thickness is 1mm to reduce solidification stress. Processing allowances are added to the uppermost end face of the inner circle and the uppermost part of the outer circle (the last solidified area), with a height of 1mm and an arc length of approximately 30mm, to address the porosity problem at solidification high points. These allowances are removed by grinding after heat treatment. The outer circle diameter is designed according to the maximum allowable limit of φ89.5mm, and the inner circle according to the minimum allowable limit of φ79.6mm. The feeding section at the highest solidification point is left in a free state to avoid stress concentration at the highest point of the outer circle.

[0042] Secondly, when assembling the wax mold, a φ200mm crystallization base is used for melting and casting. Due to the large size of the casting, three pieces are assembled in a group, evenly distributed along the circumference of the crystallization base. The casting is 10mm away from the outer circle of the crystallization base to reserve space for shell making.

[0043] Finally, the prepared shell is poured using a predetermined directional solidification and melting process. After chemical descrambling, vacuum heat treatment, grinding and polishing, grain size corrosion inspection, and non-destructive testing, a high-quality casting is obtained.

[0044] This invention employs an integrated wax model design, resulting in high-quality wax models with excellent consistency, ensuring the integrity and crystal orientation of the single crystal in the casting, while simultaneously improving production efficiency. It proposes a design concept where the feeding section cannot be closed to reduce stress levels and prevent recrystallization. A crystal-guiding scheme for thin-walled castings with discontinuous cross-sections in multiple locations is proposed, effectively solving the problem of excessive single crystal integrity in this type of casting. Addressing the issue of porosity at high points during directional solidification in annular thin-walled single-crystal castings, this invention proposes a semi-annular feeding scheme, applying semi-annular process patches to areas prone to porosity, effectively solving the problem of porosity at high points during solidification in annular thin-walled single-crystal castings. Using this invention, large-size, irregularly shaped thin-walled single-crystal splash guard castings with fully qualified metallurgical quality can be produced.

Claims

1. A wax model structure for casting thin-walled, irregularly shaped, large-size single-crystal splash guards, characterized in that, The device includes an integrated starting end, a spiral crystal selection section, a first crystal guide bar, a second crystal guide bar, a single-crystal splash shield wax mold, and a feeding section. The starting end is used to connect with the casting component. The first crystal guide bar is connected to the top of the single-crystal splash shield wax mold, and the second crystal guide bar is connected to the bottom of the single-crystal splash shield wax mold. The uppermost part of the inner and outer circles of the central circular hole in the flange of the single-crystal splash shield wax mold is covered with a semi-circular process patch. The end of the single-crystal splash shield wax mold away from the crystal guide bar has a feeding section at its top and bottom, and the two feeding sections are not connected. The length of the semi-circular process subsidy on the single crystal splash shield wax mold is 1 / 3 of the circumference of the circular hole in the middle of the flange. The semi-circular process subsidy is removed by grinding after casting heat treatment. If the connection between the shrinkage section and the single-crystal splash shield wax mold is circular, then the arc length of the connecting section is 1 / 4 of the circumference of the circular hole in the center of the flange of the single-crystal splash shield wax mold; if the connection between the shrinkage section and the single-crystal splash shield wax mold is not circular, then the length of the connecting section is equivalent to the width of the single-crystal splash shield wax mold; the height of the shrinkage section is 20 mm - 30 mm. The lower ends of the first and second crystal guides have the same width. The connection width between the upper end of the first crystal guide and the flange edge of the single crystal splash shield is 1 / 6 of the flange circumference. The connection width between the upper end of the second crystal guide and the thin-walled conical surface of the single crystal splash shield is equivalent to the width of the thin-walled conical surface of the single crystal splash shield.

2. The wax model structure for casting thin-walled, irregularly shaped, large-size single-crystal splash guards according to claim 1, characterized in that, All transition radius (R) at the boss and flange connection of the single crystal splash shield wax mold part are designed according to the drawing. The outer diameter of the circular hole in the middle of the flange is designed according to the upper limit of the design, and the inner diameter is designed according to the lower limit of the design.

3. The wax model structure for casting thin-walled, irregularly shaped, large-size single-crystal splash guards according to claim 1, characterized in that, The flange edge of the single crystal splash shield of the single crystal splash shield wax mold is connected to the spiral crystal selector through the first crystal guide bar, and the thin-walled conical surface of the single crystal splash shield of the single crystal splash shield wax mold is connected to the spiral crystal selector through the second crystal guide bar. The transition R between the first crystal guide bar and the second crystal guide bar and the single crystal splash shield is R10-R30.

4. A wax mold combined casting structure, characterized in that, The invention includes a crystallization base, a casting component, and a wax mold structure as described in any one of claims 1-3. The casting component is disposed in the middle of the crystallization base, and multiple wax mold structures are evenly distributed around the casting component on the crystallization base. The starting ends of the multiple wax mold structures are all connected to the outlet of the casting component.

5. The wax mold combined casting structure according to claim 4, characterized in that, The casting assembly includes a pouring cup and a sprue located at the bottom of the pouring cup. The outlet of the sprue is connected to the starting end of the wax mold structure. The pouring cup is connected to the shrinkage compensation section at the bottom of the single crystal splash guard wax mold through a connecting rod. When the connecting rod is connected to the shrinkage compensation section, wax material is piled up to form an approximate triangle for reinforcement.

6. A casting method for a thin-walled, irregularly shaped, large-size single-crystal splash guard, characterized in that, The wax mold structure of any one of claims 1-3 is used to make a shell, and the prepared shell is cast to obtain a thin-walled, irregularly shaped, large-size single-crystal splash shield.

7. The casting method of a thin-walled, irregularly shaped, large-size single-crystal splash guard according to claim 6, characterized in that, A wax mold combined casting structure was used to cast the prepared shell to obtain a thin-walled, irregularly shaped, large-size single-crystal splash guard. The wax mold combination casting structure includes a crystallization base, a casting component, and the wax mold structure. The casting component is located in the middle of the crystallization base, and multiple wax mold structures are evenly distributed around the casting component on the crystallization base. The starting ends of multiple wax mold structures are all connected to the outlet of the casting component. The casting assembly includes a pouring cup and a sprue located at the bottom of the pouring cup. The outlet of the sprue is connected to the starting end of the wax mold structure. The pouring cup is connected to the shrinkage compensation section at the bottom of the single crystal splash guard wax mold through a connecting rod. When the connecting rod is connected to the shrinkage compensation section, wax material is piled up to form an approximate triangle for reinforcement.

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