Large-size wax mold structure and casting process of heavy-duty gas turbine turbine blade with crown

Abstract

The application relates to a heavy-duty engine large-size crown turbine blade wax mold structure and a casting process, wherein the wax mold body is horizontally arranged, one end of the wax mold body is a tenon head, and the other end is a blade crown; a pouring runner is arranged on the outer side of the tenon head, an inner gate communicated with the tenon head is arranged on the pouring runner, and a buffer groove is arranged at the lower end of the pouring runner; a blind riser is arranged on the blade crown, and the blind riser is communicated with the upper end of the pouring runner through an exhaust passage; the upper side of the wax mold body is an air inlet edge, and the lower side of the wax mold body is an air outlet edge; a framework is arranged on the outer side of the wax mold body, an end frame is arranged at one end of the framework close to the blade crown, an end beam is arranged at one end of the framework close to the pouring runner, and the end frame and the end beam are connected through a connecting beam; a limiting beam is arranged between the end beam and the pouring runner, and a ceramic flow resistance block is arranged on the limiting beam; ceramic support rods are additionally arranged on the inner side of the framework when a mold shell is prepared. The application can solve the problems of blade casting products, such as shrinkage of the blade crown, cracks at the blade tip, abnormal surface grains and the like.

Description

Technical Field

[0001] This invention relates to the field of high-temperature alloy investment casting technology for heavy-duty gas turbines, specifically to a wax pattern structure and casting process for large-size crowned turbine blades of heavy-duty gas turbines. Background Technology

[0002] To meet the operational requirements of high-power, high-parameter heavy-duty gas turbines, the last-stage moving blades generally adopt a large-size integrated crowned structure. Compared to uncrowned blades, crowned blades can effectively suppress aerodynamic flutter during high-speed blade rotation, reduce airflow energy loss, and improve the stability of the unit under varying operating conditions. This is currently the mainstream structural form for high-parameter heavy-duty gas turbines. Furthermore, equiaxed crystalline nickel-based superalloys, with their excellent thermal fatigue resistance, resistance to thermal cycling, and good casting adaptability for large-size components, are better suited to the service characteristics of last-stage blades, making them the preferred material for manufacturing large-size crowned moving blades.

[0003] In the existing technology, leading foreign companies have developed mature mass production processes for large-size equiaxed crystal crowned gas turbine blades. Through refined alloy proportioning, zoned solidification control, precise fine-grain casting, and matched heat treatment technologies, they have achieved stable control over the uniformity of blade grain structure, internal defects, and mechanical properties. However, the relevant core processes and parameter systems have long been under technological monopoly and confidentiality. While domestic efforts to domestically produce such blades have made some progress, enabling trial production of small and medium-sized crowned blades, many technical bottlenecks remain for large-size equiaxed crystal crowned turbine blades (800mm and above). This directly leads to high blade scrap rates and poor production stability, specifically:

[0004] 1. Shrinkage at the junction of the leaf crown, leaf body and leaf crown: The leaf crown is a thick-walled structure, and a significant hot spot will form at the junction with the leaf body. Conventional vertical casting systems have problems such as limited feeding channels, poor feeding effect and insufficient supply of molten metal in the later stage of solidification, which easily leads to concentrated shrinkage cavities and regional porosity. Furthermore, it cannot be repaired by hot isostatic pressing or welding, thus leading to the scrapping of the blade.

[0005] II. Blade tip exhaust edge defects: The blade tip is a thin-walled, high-rib structure with a large solidification temperature gradient and concentrated thermal stress. Traditional mold shells have excessively high high-temperature strength and insufficient yielding. The shrinkage of the casting is rigidly constrained, which easily leads to hot cracks and cold cracks. In particular, they are more likely to develop and expand at the sharp corners of the blade tip exhaust edge. In addition, the ultra-long filling path and the impact of molten steel splashing on the mold shell can also easily lead to defects such as cold shuts and cold bead formations on the exhaust edge.

[0006] 3. Abnormal grains on the blade surface: Due to the significant differences in the overall wall thickness of the components, conventional casting processes make it difficult to achieve uniform control of the equiaxed grain structure of the entire blade. Defects such as chilled crystals and columnar crystals are prone to appear on the exhaust edge and intake edge. Thick hot spots are prone to producing structural defects such as coarse grains and columnar crystals, which will seriously reduce the fatigue life and structural stability of the blade.

[0007] Existing processes mostly involve single-point improvements without forming a systematic solution, leading to the recurrence of the aforementioned defects and a persistently low overall blade yield, making it difficult to meet the requirements of high quality, low cost, and stable mass production for heavy-duty gas turbines. Therefore, there is an urgent need to develop a stable, precision-controllable, and high-performance manufacturing technology for large-size equiaxed crystal zone crown gas turbine blades to address the numerous shortcomings of existing technologies.

[0008] Patent CN105364006B discloses a wax model and manufacturing method for a casting system of large-size hollow crowned blades. However, this patent uses a vertical casting method, which generally makes it difficult to avoid the aforementioned problems. Patent CN114130920B discloses a blade crown wax model mold and a crowned turbine blade wax model mold. However, this patent fixes the wax model through structures such as blade crown blocks, blade crown support blocks, and tenon-back sliding blocks at both ends. Furthermore, the aforementioned blade crown blocks and blade crown support blocks are fixed on a base plate, making it difficult to coordinate with the transfer of the wax model. Consequently, it cannot constrain deformation during the transfer of the wax model. In addition, the wax model requires subsequent shell preparation processes, and the shell must also be guaranteed to be resistant to expansion and deformation. Summary of the Invention

[0009] The purpose of this invention is to provide a wax mold structure and casting process for large-size crowned turbine blades of heavy-duty gas turbines, which can fundamentally solve problems such as crown shrinkage porosity, tip cracks, and abnormal surface grains in blade castings, thereby improving the casting qualification rate and production stability.

[0010] The objective of this invention is achieved through the following technical solution:

[0011] A wax model structure for a large-sized crowned turbine blade of a heavy-duty gas turbine includes a wax model body and a frame. The wax model body is horizontally positioned with a tenon head at one end and a blade crown at the other. A casting channel is provided on the outer side of the tenon head, and an inner gate communicating with the tenon head is provided on the casting channel. A buffer groove is provided at the lower end of the casting channel. A hidden riser is provided on the blade crown, and the hidden riser is connected to the upper end of the casting channel through an exhaust channel. The riser modulus of the hidden riser is greater than the thermal modulus of the blade crown. The upper side of the wax model body is an intake side, and the lower side is an exhaust side. The frame is fitted onto the outer side of the wax model body, and an end frame is provided at the end of the frame near the blade crown and an end beam is provided at the end near the casting channel. The end frame and the end beam are connected by a connecting beam. A limiting beam is provided between the end beam and the casting channel, and a ceramic flow-blocking block is provided on the limiting beam. A ceramic support rod is added to the inner side of the frame during the preparation of the mold shell.

[0012] The gating system includes a main gating system, and a pouring cup is provided at the upper end of the main gating system. The dark riser is connected to the pouring cup through a venting channel. The main gating system is provided with an inner gate, and the buffer groove is provided at the lower end of the main gating system.

[0013] The buffer groove is provided with an arc-shaped buffer groove inside.

[0014] The frame is provided with a bracket on its upper side, and the two ends of the bracket are respectively connected to the connecting beams on the corresponding sides. The bracket is provided with an exhaust support column, and the exhaust channel is supported by the exhaust support column.

[0015] The frame is provided with longitudinal reinforcing beams and transverse reinforcing beams, wherein the two ends of the longitudinal reinforcing beams are respectively connected to the connecting beams on the corresponding sides, and the two ends of the transverse reinforcing beams are respectively connected to the longitudinal reinforcing beams on the corresponding sides.

[0016] During the preparation of the shell, a first ceramic support rod is added to the inner side of the connecting beam, and a second ceramic support rod is added to the inner side of the longitudinal reinforcing beam and the transverse reinforcing beam.

[0017] The end frame includes multiple support beams that are centrally connected, and the ends of the support beams are connected to the corresponding ends of the corresponding end beams through corresponding connecting beams.

[0018] After the wax model body forms a shell, the shell has a standard number of layers at the position corresponding to the tenon head. The number of layers of the shell corresponding to the leaf body of the wax model body is less than the standard number of layers, and the number of layers decreases from the leaf root to the leaf crown. The number of layers of the leaf tip connected to the leaf crown is 2 to 3 fewer than the standard number of layers.

[0019] A casting process for the large-size crowned turbine blade wax pattern structure of the heavy-duty gas turbine, comprising the following steps:

[0020] Step 1: Prepare and assemble the wax model body and skeleton;

[0021] Step 2: Prepare the shell, specifically:

[0022] Step 2.1: Apply a top layer of slurry to the surface of the wax model body, then sprinkle top layer sand and let it dry to form the shell surface layer;

[0023] Step 2.2: Prepare a gradient layer on the shell surface layer, wherein the shell corresponding to the tenon head position is the standard layer number, the shell corresponding to the leaf body of the wax model body has fewer layers than the standard layer number, and the layer number decreases from the leaf root to the leaf crown.

[0024] When preparing each gradient layer, first apply gradient layer slurry, then sprinkle gradient layer sand and dry it to form a gradient layer;

[0025] Each gradient layer includes multiple inner transition layers and multiple outer back layers. After any transition layer is dried, a ceramic support rod is added to the inner side of the skeleton, and each ceramic support rod is located on the shell at the position corresponding to the blade basin and back sides.

[0026] Step 2.3: The shell is used after dewaxing and high-temperature firing;

[0027] Step 3: Pour molten metal into the mold shell at the set pouring speed and pouring temperature, wherein the pouring speed of the molten metal is ≥6kg / s. After pouring is completed, vacuum solidification and cooling are performed.

[0028] In step 2.1, the surface slurry is formed by mixing cobalt aluminate, zircon powder and silica sol, and the surface sand is zircon sand;

[0029] In step 2.2, the gradient layer slurry is formed by mixing bauxite and silica sol, and the gradient layer sand is sand.

[0030] In step three, the pouring speed of the molten metal is 6-8 kg / s and the pouring temperature is 1490-1510℃.

[0031] The advantages and positive effects of this invention are as follows:

[0032] 1. This invention addresses the most prominent problems of large-sized crowned blades in heavy-duty gas turbines, including crown shrinkage, tip cracks, and abnormal grain size on the blade surface. The wax mold body employs a horizontal side-injection method, with the ingate positioned on the tenon head surface. A concealed riser is incorporated into the crown section, with the riser modulus exceeding the hot section modulus, thus creating a continuous feeding channel. This effectively solves the shrinkage problems of the crown, blade body, and crown junction. Furthermore, the combination of horizontal side-injection and concealed risers ensures sufficient feeding of the thick-walled hot section of the crown, resulting in an X-ray inspection pass rate of over 90% for the castings. The blade castings exhibit no concentrated shrinkage cavities or regional porosity, and the internal density of the blades meets the requirements for heavy-duty gas turbine operation.

[0033] 2. The downward positioning of the venting edge of the wax mold body in this invention can suppress the rapid cooling and growth of crystal nuclei at the venting edge, ensuring uniform edge grains. The lower end of the casting channel of the wax mold body is provided with an arc-shaped buffer groove, which can eliminate molten metal eddies, slow down the flow rate, and prevent molten metal splashing, thereby avoiding cold-burst defects at the venting edge from the source. Therefore, the blade casting products prepared by this invention have excellent blade surface quality, uniform and stable grains, and no cold shuts, cold bursts, abnormally large grains, or grain boundaries on the blade surface. The surface microstructure uniformity is significantly improved, and the blade fatigue life and reliability are greatly enhanced.

[0034] 3. In the preparation of ceramic shells in this invention, a gradient layer shell is used. The shell uses a standard layer number N for the tenon head and extension section, and a gradient layer number for the blade body. That is, the number of layers decreases from the blade root (i.e., the end near the tenon head) towards the blade crown. This reduces the number of layers in the blade tip area connected to the blade crown by 2 to 3 layers compared to the standard layer number N. This can reduce the local radial strength and rigidity constraint in the blade tip area, greatly improve the yielding property of the blade tip shell, and fully release stress during solidification. As a result, the rate of hot cracking and cold cracking defects in the blade tip is reduced to near zero, thereby greatly reducing the product scrap rate caused by blade tip cracks. At the same time, the gradient layer shell is also conducive to forming a sequential solidification temperature gradient in the blade body.

[0035] 4. The present invention utilizes a skeleton to support the wax model body. In addition to being used for holding and transporting during shell preparation, the skeleton can also constrain the relative positions of various components of the wax model body to prevent deformation. Furthermore, when preparing the shell, ceramic support rods can be added to the inner side of the skeleton to strengthen the support on both sides of the blade basin and back, thereby significantly improving the shell's resistance to expansion and deformation, and ensuring the dimensional accuracy of the casting.

[0036] 5. The present invention uses low-strength and low-cost materials to prepare the shell, and the ceramic support rod used for support and reinforcement is also a conventional material. In addition, the process route of the present invention is compatible with existing investment casting production lines and does not require the addition of large-scale equipment, thus reducing the overall manufacturing cost of the present invention.

[0037] 6. When preparing the shell of this invention, the surface layer uses a grain refiner (cobalt aluminate) + zircon powder + silica sol slurry, which can ensure the surface quality. The transition layer and the back layer (i.e., the gradient layer) are made of aluminum-silicon refractory materials, which can reduce costs and reduce high-temperature strength. This allows the gradient layer shell preparation method of this invention to better meet the requirements of improving the yielding performance of the blade tip area.

[0038] 7. This invention enables the simultaneous control of three major defects: blade crown shrinkage, blade tip cracks, and abnormal grains on the blade surface. This significantly improves the overall casting qualification rate of blades compared to traditional processes, while reducing the cost per piece and stabilizing the production cycle. It can meet the requirements of mass production, high quality, and low cost manufacturing of key components for heavy-duty gas turbines. In addition, the process of this invention is highly versatile and can be applied not only to the last stage moving blades but also to similar large-size crowned blades. Attached Figure Description

[0039] Figure 1 This is a schematic diagram of the wax model body structure of the present invention.

[0040] Figure 2 This is a schematic diagram of the combination of the wax model body and the skeleton of the present invention.

[0041] Figure 3 This is a schematic diagram showing the X-ray inspection of the blade crown and the connection between the blade crown and the blade body in the blade casting product of the present invention.

[0042] Figure 4 This is a schematic diagram of the surface grain structure of the blade casting product of the present invention. Figure 1 ,

[0043] Figure 5 This is a schematic diagram of the surface grain structure of the blade casting product of the present invention. Figure 2 ,

[0044] Figure 6 This is a schematic diagram of the surface grain structure of the blade casting product of the present invention. Figure 3 .

[0045] Among them, 1 is the wax model body, 101 is the tenon head, 102 is the leaf crown, 103 is the venting edge, 104 is the air inlet edge, 105 is the pouring channel, 1051 is the main runner, 1052 is the pouring cup, 1053 is the buffer groove, 1054 is the inner gate, 106 is the hidden riser, and 107 is the venting channel; 2 is the skeleton, 201 is the connecting beam, 202 is the end beam, 203 is the ceramic flow barrier, 204 is the end frame, 205 is the venting support column, 2051 is the bracket, 206 is the longitudinal reinforcing beam, 207 is the transverse reinforcing beam, 208 is the second ceramic support rod, and 209 is the first ceramic support rod. Detailed Implementation

[0046] The invention will now be described in further detail with reference to the accompanying drawings.

[0047] like Figures 1-2 As shown, the present invention includes a wax model body 1 and a skeleton 2, wherein the wax model body 1 is horizontally arranged with a tenon head 101 at one end and a leaf crown portion 102 at the other end; a casting channel 105 is provided on the outer side of the tenon head 101, and an inner gate 1054 communicating with the tenon head 101 is provided on the casting channel 105; a buffer groove portion 1053 is provided at the lower end of the casting channel 105; a hidden riser 106 is provided on the leaf crown portion 102, and the hidden riser 106 is connected to the upper end of the casting channel 105 through a venting channel 107; The wax model body 1 has an air inlet side 104 on the upper side and an air outlet side 103 on the lower side. The skeleton 2 is fitted onto the outside of the wax model body 1, and the skeleton 2 has an end frame 204 near the blade crown 102 and an end beam 202 near the casting channel 105. The end frame 204 and the end beam 202 are connected by a connecting beam 201. A limiting beam is provided between the end beam 202 and the casting channel 105, and a ceramic flow-blocking block 203 is provided on the limiting beam. A ceramic support rod is added to the inner side of the skeleton 2 when preparing the mold shell. The air inlet side 104, the air outlet side 103, the tenon head 101, the blade crown 102, etc. are all technologies known in the art, for example, see patent CN105364006B.

[0048] like Figure 1 As shown, this invention employs a horizontal side-injection method. The ingate 1054 is located on the surface of the tenon head 101, enabling stable flow. A hidden riser 106 is provided at the hot spot of the blade crown 102, and the riser modulus of the hidden riser 106 is greater than the hot spot modulus of the blade crown 102. This ensures that the riser solidifies later than the casting, thereby forming a continuous feeding channel. This can solve the shrinkage porosity problem of the blade crown, blade body, and blade crown transition area in blade castings. The riser modulus and hot spot modulus are both well-known technologies in the art.

[0049] like Figure 1 As shown, the venting edge 103 of the wax model body 1 of the present invention is positioned downwards. This ensures that during wax model assembly, the venting edge 103 of the blades faces downwards and the air intake edge 104 faces upwards. Combined with the coordinated optimization control of the temperature field and flow field, this can suppress the rapid cooling and growth of crystal nuclei on the venting edge 103, ensuring uniform edge grains. The coordinated control of the temperature field and flow field is a well-known technology in the art and can be achieved through the casting equipment control system.

[0050] like Figures 1-2 As shown, the gating channel 105 includes a main gating channel 1051, and a pouring cup 1052 is provided at the upper end of the main gating channel 1051. The dark riser 106 is connected to the pouring cup 1052 through the venting channel 107. The main gating channel 1051 is provided with the inner gate 1054, and the buffer groove 1053 is provided at the lower end of the main gating channel 1051.

[0051] In this embodiment, the buffer groove 1053 forms an arc-shaped buffer groove that connects with the main gating 1051. This can eliminate molten metal eddies, slow down the flow rate of molten metal, and prevent molten metal splashing, thereby avoiding cold bead defects on the exhaust edge 103 from the source.

[0052] like Figure 2 As shown, this invention utilizes a skeleton 2 to support the wax model body 1. The skeleton 2 can be held and transported during shell preparation, and can also constrain the relative positions of the various components of the wax model body 1 to prevent deformation. Ceramic flow-blocking blocks 203 are provided on the limiting beams between the end beams 202 on both sides of the skeleton 2 and the pouring channel 105. This prevents the molten metal from entering the support structure of the skeleton 2, thereby preventing the skeleton 2 from fusing with the casting. During shell preparation, this invention adds ceramic support rods to the vertical arc surfaces on both sides of the blade basin and back of the shell transition layer, and each ceramic support rod is evenly arranged along the blade length direction. This significantly improves the shell's resistance to expansion and deformation, thereby ensuring the dimensional accuracy of the casting.

[0053] like Figure 2 As shown, the upper side of the frame 2 is provided with an exhaust support column 205, and the exhaust channel 107 is supported by the exhaust support column 205.

[0054] like Figure 2 As shown, in this embodiment, the upper side of the frame 2 is provided with a bracket 2051, and both ends of the bracket 2051 are respectively connected to the connecting beam 201 on the corresponding side, and the lower end of the exhaust support column 205 is connected to the bracket 2051.

[0055] like Figure 2 As shown, longitudinal reinforcing beams 206 and transverse reinforcing beams 207 are provided at appropriate positions on the frame 2, wherein the two ends of the longitudinal reinforcing beams 206 are respectively connected to the connecting beams 201 on the corresponding sides, and the two ends of the transverse reinforcing beams 207 are respectively connected to the longitudinal reinforcing beams 206 on the corresponding sides.

[0056] like Figure 2 As shown, during the preparation of the shell, a first ceramic support rod 209 may be added to the inner side of the connecting beam 201, and a second ceramic support rod 208 may be added to the inner side of the longitudinal reinforcing beam 206 and the transverse reinforcing beam 207.

[0057] In this embodiment, positioning slots can be provided on the connecting beam 201, the longitudinal reinforcing beam 206, and the transverse reinforcing beam 207, and the diameter of the positioning slots is larger than the diameter of the ceramic support rods. This allows each ceramic support rod to be inserted into the positioning slot at one end first, and then rotated at the other end until it engages with the surface of the shell transition layer. Other suitable ceramic support rod installation structures can also be used as needed.

[0058] like Figure 2 As shown, in this embodiment, the end frame 204 includes multiple support beams that are centrally connected, and the ends of the support beams are connected to the corresponding ends of the corresponding end beams 202 through corresponding connecting beams 201. In addition, the end of the skeleton 2 near the end frame 204 can be provided with appropriate positioning blocks, positioning beams and other structures as needed to assist in supporting one end of the leaf crown 102 of the wax model body 1.

[0059] The specific casting process of this invention is as follows:

[0060] Step 1: Prepare and assemble the wax model body 1 and the skeleton 2.

[0061] This step specifically involves: pressing the various parts of the wax model body 1 and the skeleton 2 using medium-temperature molding compound, and then bonding and assembling them to form... Figure 2 The combined structure shown is a well-known technology in the field; for example, see patent CN105364006B.

[0062] In this step, it is necessary to ensure that the exhaust edge 103 is facing downwards.

[0063] Step 2: Prepare the ceramic shell, specifically as follows:

[0064] Step 2.1: Apply a surface layer slurry to the surface of the wax model body 1 (together with the skeleton 2), then sprinkle surface layer sand and dry for a set time to form the shell surface layer.

[0065] In this embodiment, the surface slurry is formed by mixing cobalt aluminate, zircon powder, and silica sol in a set ratio, and the surface sand is zircon sand. These materials are known in the art.

[0066] Step 2.2: Prepare the shell with a gradient number of layers, where the tenon head 101 is the standard number of layers, and the number of layers on the blade decreases from the root (i.e. the end near the tenon head) to the crown 102.

[0067] Assuming the standard number of shell layers is N, such as Figure 2 As shown, the wax model body 1 (together with the skeleton 2) can have N layers in the third portion near the tenon head 101, N1 layers in the middle third portion, and N2 layers in the third portion near the crown portion 102 (i.e., the tip region of the leaf), and N > N1 > N2.

[0068] For example, in this embodiment, the wax model body 1 (together with the skeleton 2) has 12 layers (standard number of layers) in the third portion near the pouring channel 105, 11 layers in the middle third portion, and 10 layers in the third portion near the crown 102.

[0069] The specific preparation process in this step is as follows:

[0070] Step 2.2.1: After applying a layer of gradient layer slurry to the shell surface, sprinkle gradient layer sand and dry for a set time to form a gradient layer.

[0071] In this embodiment, the gradient layer slurry is formed by mixing bauxite and silica sol in a set ratio, and the gradient layer sand is cobalt sand. All of the above materials are known in the art.

[0072] Step 2.2.2: Repeat step 2.2.1 until the Mth gradient layer is formed on the surface of the shell and dried. Then, add a ceramic support rod inside the skeleton 2, where M is less than N2.

[0073] In this embodiment, M=4, that is, after the fourth gradient layer is formed on the surface of the shell and dried, a ceramic support rod is added inside the skeleton 2. In addition, in this embodiment, a total of N=12 layers are added, of which layers 2 to 5 are transition layers, layers 6 and above are back layers, and the Mth layer must be a transition layer.

[0074] In this embodiment, as Figure 2 The image shows Φ5mm ceramic support rods installed on the vertical arc surface along the leaf height (i.e., the direction of leaf length) on both sides of the leaf base and back.

[0075] Step 2.2.3: Repeat step 2.2.1 again until an N2 layer (10 layers in this embodiment) gradient layer is formed on the surface of the shell and then dried.

[0076] Step 2.2.4: After applying a gradient layer slurry to two-thirds of the shell surface near the tenon head 101, sprinkle gradient layer sand and dry it to form an N1 layer (11 layers in this embodiment) gradient layer.

[0077] Step 2.2.5: After applying a layer of gradient layer slurry to one-third of the shell surface near the tenon head 101, sprinkle gradient layer sand and dry it to form N layers (12 layers in this embodiment) of gradient layer.

[0078] Step 2.3: The shell is used after dewaxing and high-temperature firing, which is a well-known technology in this field.

[0079] Step 3: Pour molten metal into the mold shell at a set pouring speed and pouring temperature. In this embodiment, the pouring temperature of the molten metal is 1490~1510℃, the pouring speed is controlled at 6.0~8.0kg / s to ensure that the molten metal does not fall back, and the weight of the master alloy is 50kg.

[0080] After the casting is completed, vacuum solidification and cooling are carried out, followed by sand removal, cleaning, cutting of the gating and riser, and inspection. All of the above procedures are well-known technologies.

[0081] The surface of the blade casting product manufactured according to the above process in this embodiment is as follows: Figures 4-6As shown, the X-ray detection results of its leaf crown and the junction of the leaf crown and leaf blade are as follows: Figure 3 As shown, the product has no shrinkage in the leaf crown, no cracks in the leaf tip, and no defects such as chilled crystals, chilled beads, or grain boundaries in the leaf body.

[0082] This invention employs a combination of low-strength, low-cost materials, ceramic support rods for back reinforcement, and a gradient-layer shell construction technique. This achieves a shell that is both strong and flexible. The ceramic support rods reinforce the blade's back side to prevent deformation and bulging. The blade tip is reinforced with gradient layers to reduce strength, improving yielding and releasing thermal stress. This ensures dimensional accuracy and prevents tip cracking at its source. Furthermore, the invention uses low-strength, low-cost shell materials, eliminating the need for expensive special powders. The ceramic support rods are also made of conventional materials. In addition, the process route is compatible with existing investment casting production lines, eliminating the need for additional large-scale equipment. Therefore, the overall manufacturing cost of this invention is significantly reduced.

[0083] The process parameters of this invention are clear, quantifiable, and reproducible. Key parameters such as pouring speed ≥6kg / s and number of gradient layers are quantifiable indicators, while structures such as buffer tanks and hidden risers are reproducible structures. Thus, this invention can be operated without relying on experience, has high process stability, and is suitable for industrial mass production.

Claims

1. A wax mold structure for a large-size crowned turbine blade of a heavy-duty gas turbine, characterized in that: The system includes a wax model body (1) and a skeleton (2), wherein the wax model body (1) is horizontally positioned with a tenon (101) at one end and a crown (102) at the other end; a gating channel (105) is provided on the outer side of the tenon (101), and an inner gate (1054) communicating with the tenon (101) is provided on the gating channel (105), and a buffer groove (1053) is provided at the lower end of the gating channel (105); a hidden riser (106) is provided on the crown (102), and the hidden riser (106) is connected to the upper end of the gating channel (105) through an exhaust channel (107), and the riser modulus of the hidden riser (106) is greater than that of the crown. The heat-limiting module of part (102); the upper side of the wax model body (1) is an air inlet side (104) and the lower side is an exhaust side (103); the skeleton (2) is fitted on the outside of the wax model body (1), and the skeleton (2) is provided with an end frame (204) near the end of the blade crown (102) and an end beam (202) near the end of the casting channel (105), and the end frame (204) and the end beam (202) are connected by a connecting beam (201); a limiting beam is provided between the end beam (202) and the casting channel (105), and a ceramic flow blocking block (203) is provided on the limiting beam; a ceramic support rod is added to the inner side of the skeleton (2) when preparing the shell.

2. The wax mold structure for large-size crowned turbine blades of heavy-duty gas turbines according to claim 1, characterized in that: The gating channel (105) includes a main gating channel (1051), and a pouring cup (1052) is provided at the upper end of the main gating channel (1051). The dark riser (106) is connected to the pouring cup (1052) through an exhaust channel (107). The main gating channel (1051) is provided with an inner gate (1054), and the main gating channel (1051) is provided with a buffer groove (1053) at the lower end.

3. The wax mold structure for large-size crowned turbine blades of heavy-duty gas turbines according to claim 2, characterized in that: The buffer groove (1053) is provided with an arc-shaped buffer groove inside.

4. The wax mold structure for large-size crowned turbine blades of heavy-duty gas turbines according to claim 1, characterized in that: The frame (2) is provided with a bracket (2051) on the upper side, and the two ends of the bracket (2051) are respectively connected to the connecting beam (201) on the corresponding side. The bracket (2051) is provided with an exhaust support column (205), and the exhaust channel (107) is supported by the exhaust support column (205).

5. The wax mold structure for large-size crowned turbine blades of heavy-duty gas turbines according to claim 1, characterized in that: The frame (2) is provided with longitudinal reinforcing beams (206) and transverse reinforcing beams (207), wherein the two ends of the longitudinal reinforcing beams (206) are respectively connected to the connecting beams (201) on the corresponding side, and the two ends of the transverse reinforcing beams (207) are respectively connected to the longitudinal reinforcing beams (206) on the corresponding side.

6. The wax mold structure for large-size crowned turbine blades of heavy-duty gas turbines according to claim 5, characterized in that: During the preparation of the shell, a first ceramic support rod (209) is added to the inner side of the connecting beam (201), and a second ceramic support rod (208) is added to the inner side of the longitudinal reinforcing beam (206) and the transverse reinforcing beam (207).

7. The wax mold structure for large-size crowned turbine blades of heavy-duty gas turbines according to claim 1, characterized in that: The end frame (204) includes multiple support beams that are centrally connected, and the ends of the support beams are connected to the corresponding ends of the corresponding end beams (202) through corresponding connecting beams (201).

8. The wax mold structure for large-size crowned turbine blades of heavy-duty gas turbines according to claim 1, characterized in that: After the wax model body (1) forms a shell, the shell has a standard number of layers at the position corresponding to the tenon head (101). The number of layers of the leaf body part of the shell corresponding to the wax model body (1) is less than the standard number of layers, and the number of layers decreases from the leaf root to the leaf crown (102). The number of layers of the leaf tip connected to the leaf crown (102) is 2 to 3 layers less than the standard number of layers.

9. A casting process for a large-size crowned turbine blade wax model structure for heavy-duty gas turbines according to claim 1, characterized in that: Includes the following steps: Step 1: Prepare and assemble the wax model body (1) and the skeleton (2); Step 2: Prepare the shell, specifically: Step 2.1: Apply a surface layer slurry to the surface of the wax model body (1), then sprinkle surface layer sand and dry it to form the shell surface layer; Step 2.2: Prepare a gradient layer on the shell surface layer, wherein the shell corresponds to the position of the tenon (101) as the standard layer number, the shell corresponds to the leaf body part of the wax model body (1) with a layer number less than the standard layer number, and the layer number decreases from the leaf root to the leaf crown (102); When preparing each gradient layer, first apply gradient layer slurry, then sprinkle gradient layer sand and dry it to form a gradient layer; Each gradient layer includes an inner multi-layer transition layer and an outer multi-layer back layer. After any transition layer is dried, a ceramic support rod is added to the inner side of the skeleton (2), and each ceramic support rod is located on the shell at the position corresponding to the blade basin and the back sides. Step 2.3: The shell is used after dewaxing and high-temperature firing; Step 3: Pour molten metal into the mold shell at the set pouring speed and pouring temperature, wherein the pouring speed of the molten metal is ≥6kg / s. After pouring is completed, vacuum solidification and cooling are performed.

10. The casting process for the large-size crowned turbine blade wax model structure of heavy-duty gas turbines according to claim 9, characterized in that: In step 2.1, the surface slurry is formed by mixing cobalt aluminate, zircon powder and silica sol, and the surface sand is zircon sand; In step 2.2, the gradient layer slurry is formed by mixing bauxite and silica sol, and the gradient layer sand is sand. In step three, the pouring speed of the molten metal is 6-8 kg / s and the pouring temperature is 1490-1510℃.

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