A nozzle ring casting shell structure and a preparation process thereof

Abstract

The application discloses a nozzle ring casting shell structure and a preparation process. A whole circle of a patch ring is arranged on an inner ring, patch blocks are arranged at each hot spot of an outer ring, a plurality of arc-shaped risers are arranged on the top of the patch ring, the top of the patch block is connected with an arc-shaped runner through a square riser, the arc-shaped risers and the arc-shaped runner in the same radial direction are connected with the same horizontal runner, all the horizontal runners are connected with a flow distribution disc, and the flow distribution disc is connected with a sprue cup. The application greatly improves the yield, reduces the casting stress of the hot spot part, improves the heat radiation environment, is beneficial to the diffusion of heat radiation, reduces the risk of nozzle ring shrinkage and cracks, and adopts a hot spot rolling circle design structure in the longitudinal section size of the patch block, and the hot spot circle diameter of a blade adapter fillet is used to determine the transverse size, which is different from the conventional scheme of only using the hot spot rolling circle method in the longitudinal direction, so that the patch block can accurately compensate the hot spot, and the risk of shrinkage is reduced.

Description

Technical Field

[0001] This invention relates to the field of investment casting technology, and in particular to a nozzle ring casting shell structure and its manufacturing process. Background Technology

[0002] Gas turbines require nozzle rings to adjust airflow direction. The nozzle ring is a crucial component of the gas turbine, needing to maintain overall precision while also ensuring the installation and casting accuracy of the blades. (e.g., nozzle ring...) Figure 1 The nozzle ring (shown) has an inner and outer ring structure. The inner ring 1 and the outer ring 2 are connected by multiple blades 3. The blades in the existing nozzle ring are fixed to the inner and outer rings and are formed by one-time casting. To obtain a high-precision nozzle ring during the casting process, highly complex casting techniques and specialized equipment are required. The nozzle ring has a complex structure with significant differences in wall thickness and small blade cross-sections. During solidification, defects such as incomplete filling, porosity, and cracks are easily generated. Furthermore, the nozzle ring operates under harsh conditions, thus requiring the casting to have excellent metallurgical quality, high comprehensive mechanical properties, and dimensional accuracy, making casting very difficult.

[0003] like Figure 2 As shown, the wall thicknesses of the inner and outer rings and the blades differ significantly, resulting in a large hot spot 17 at the transition fillet where the inner and outer rings connect to the blades. When designing the investment casting process, the feeding effect of the molten metal on this hot spot must be considered first, while simultaneously controlling the casting stress caused by the uneven thickness at the transition fillet. Figure 3 As shown, the existing nozzle ring investment casting process involves adding a full-circle process allowance 16 to the inner and outer rings of the nozzle ring to compensate for the hot spot at the blade transition fillet. This process, to a certain extent, compensates for the hot spot at the blade transition fillet, allowing the blade shape and the inner and outer rings to solidify sequentially. The added allowance is then removed by lathe during subsequent machining. However, because the inner and outer rings become thicker after adding the full-circle allowance, they create a more severe thickness unevenness with the blade, generating greater casting stress during solidification, which easily leads to cracks at the blade root. During casting, the thickened inner and outer rings generate more heat, hindering heat radiation diffusion and easily causing the mold shell to overheat, resulting in the risk of slag inclusions. The increased thickness of the inner and outer rings leads to a low process yield and easily causes the critical working part of the part—the blade—to receive more heat radiation, resulting in poor cooling and porosity.

[0004] To address the limitations of existing technologies in simultaneously addressing issues such as casting stress-induced cracks, hot spot feeding, controlled yield, and mitigation of heat radiation effects, a nozzle ring casting mold structure and manufacturing process are designed. This process separately feeds the hot spot at the blade transition radius, aiming to reduce the unevenness in wall thickness between the inner and outer rings and the blade. It also facilitates the diffusion of heat radiation. This investment casting solution is a targeted approach to addressing the problems of traditional processes. Combined with mold treatment and casting parameters, it solves the problems of blade root cracks, low yield, slag inclusions, and loose blade transition radius in conventional processes, thereby improving the casting qualification rate. Summary of the Invention

[0005] The main objective of this invention is to provide a nozzle ring casting shell structure and its manufacturing process, which can effectively solve the problems in the background art.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: a nozzle ring casting shell structure, comprising a nozzle ring shell and a pouring cup, wherein the nozzle ring shell comprises an inner ring, an outer ring, and blades connecting the inner and outer rings, wherein a full circle of auxiliary rings is provided on the inner side of the inner ring, and auxiliary blocks are provided on the outer side of the outer ring at each hot spot, wherein a plurality of arc-shaped risers are provided on the top of the auxiliary rings, and the top of the auxiliary blocks is connected to an arc-shaped runner through a square riser, wherein the number of arc-shaped runners and arc-shaped risers is the same, and arc-shaped risers and arc-shaped runners in the same radial direction are connected to the same horizontal runner, wherein all horizontal runners are connected to a manifold plate, and the manifold plate is connected to the pouring cup.

[0007] Preferably, the arc-shaped riser is connected to the horizontal runner via an inverted flow-limiting structure.

[0008] Preferably, the inverted flow-limiting structure has the same width as the horizontal runner and its longitudinal section is a necked structure.

[0009] Preferably, triangular bevels are provided at the connection points between the arc-shaped riser and the subsidy ring on both sides.

[0010] Preferably, the horizontal runner has an L-shaped structure, with one end connected to the bottom of the manifold, and the other end connected to the arc-shaped runner via a connecting block, the connecting block being of the same thickness as the arc-shaped runner.

[0011] Preferably, the arc-shaped gating system is connected to at least one auxiliary block.

[0012] Preferably, the outer side of the shell structure is provided with a stepped cotton-filled layer.

[0013] The present invention also provides a manufacturing process for the above-mentioned nozzle ring casting shell structure, which includes the following steps:

[0014] 1) Wax pattern structure design: Calculate the size and position of the hot spot circle at the transition R between the blade and the outer ring in the 3D model of the nozzle ring casting. Use the rolling method to roll out the longitudinal shape and size of the auxiliary block tangentially at a ratio of 1:1.1 according to the longitudinal hot spot circle diameter. Then determine the transverse width of the auxiliary block through the transverse hot spot circle diameter. Use the rolling method to design the auxiliary ring of the inner ring. Based on the thickness and radial dimensions of the inner ring and the top of the auxiliary ring, design the size and quantity of the arc riser according to the feeding principle. Calculate and design the size of the square riser by using the modular method for the auxiliary block and the outer ring.

[0015] 2) Wax model preparation: Prepare wax models of the subsidy block, subsidy ring, arc-shaped riser and square riser designed in step 1), and prepare wax models of the nozzle ring and the sprue;

[0016] 3) Wax mold assembly: Glue and fix the subsidy ring and subsidy block to the corresponding hot joints of the inner and outer rings of the nozzle ring wax mold. Then glue and fix the arc-shaped riser to the subsidy ring, glue the square riser to the subsidy block, and finally connect the horizontal runner on the gating wax mold to the arc-shaped riser and arc-shaped runner.

[0017] 4) Wax trimming: The wax mold structure after tree assembly is trimmed with a wax trimming knife to obtain the nozzle ring wax mold structure;

[0018] 5) Preparation of the mold shell: After the nozzle ring wax mold structure is coated, dewaxed and fired, the nozzle ring casting mold shell is obtained.

[0019] Compared with traditional technologies, the beneficial effects of this invention are as follows: The entire ring of the nozzle ring is fitted with a segmented structure for the blade transition fillet, which greatly improves the yield, reduces the casting stress at the hot spot, improves the thermal radiation environment, facilitates the diffusion of thermal radiation, and reduces the risk of shrinkage and cracking of the nozzle ring. The patch block adopts a rolled hot spot circle design in the longitudinal cross-section, and the transverse dimension is determined by the diameter of the hot spot circle at the blade transition fillet. Unlike conventional solutions that only use the rolled hot spot circle method in the longitudinal direction, this allows the patch block to accurately compensate for shrinkage at the hot spot, further reducing the risk of shrinkage. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of an existing nozzle ring structure;

[0021] Figure 2 This is a schematic diagram of an existing nozzle annular heat exchanger.

[0022] Figure 3 A schematic diagram of the thermal compensation structure of an existing nozzle ring;

[0023] Figure 4 This is a schematic diagram of the overall shell structure of the present invention;

[0024] Figure 5This is a schematic diagram of the shell structure with cotton covering of the present invention;

[0025] Figure 6 This is a schematic diagram showing the longitudinal dimensions of the subsidy block of the present invention;

[0026] Figure 7 This is a schematic diagram showing the lateral dimensions of the subsidy block according to the present invention.

[0027] In the diagram: 1. Inner ring; 2. Outer ring; 3. Blade; 4. Subsidy ring; 5. Subsidy block; 6. Arc-shaped riser; 7. Square riser; 8. Arc-shaped runner; 9. Horizontal runner; 10. Diverter plate; 11. Pour cup; 12. Connecting block; 13. Triangular oblique overlap; 14. Inverted flow-limiting structure; 15. Cotton layer; 16. Process subsidy for the entire ring; 17. Hot spot. Detailed Implementation

[0028] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below in conjunction with specific embodiments.

[0029] like Figure 1 As shown, a nozzle ring casting shell structure is provided, which includes a nozzle ring shell and a pouring cup 11. The nozzle ring shell includes an inner ring 1, an outer ring 2, and a blade 3 connecting the inner ring 1 and the outer ring 2. The inner ring 1 has a full-circle auxiliary ring 4 on its inner side. The outer ring 2 has an auxiliary block 5 at each hot spot 17 on its outer side. The top of the auxiliary ring 4 has several arc-shaped risers 6. The top of the auxiliary block 5 is connected to an arc-shaped runner 8 through a square riser 7. The number of arc-shaped runners 8 and arc-shaped risers 6 is the same. The arc-shaped risers 6 and arc-shaped runners 8 in the same radial direction are connected to the same horizontal runner 9. All horizontal runners 9 are connected to a manifold 10. The manifold 10 is connected to the pouring cup 11. The horizontal runner 9 has an L-shaped structure. One end of the horizontal runner 9 is connected to the bottom of the manifold 10. The other end of the horizontal runner 9 is connected to the arc-shaped runner 8 through a connecting block 12. The connecting block 12 is the same thickness as the arc-shaped runner 8.

[0030] The hot spot 17 at the transition fillet between the inner ring 1 and the blade 3 is usually small, making it less prone to large casting stress and overheating. Therefore, the inner ring 1 is supplemented with a full-circle supplement ring 4. The top of the inner ring 1 is connected to several arc-shaped risers. The size and number of arc-shaped risers are calculated based on the thickness and radial dimension of the top of the inner ring 1 and the supplement ring 4 according to the feeding principle. Triangular bevels 13 are provided on both sides of the arc-shaped riser 6 at the connection with the supplement ring 4 to increase the feeding distance of the arc-shaped riser 6. This ensures that the hot spot 17 at the transition fillet of each blade 3 can receive feeding from the arc-shaped riser 6, thus avoiding shrinkage porosity to a greater extent and reducing the risk of shrinkage porosity in the hot spot 17 of the inner ring 1.

[0031] The number of arc-shaped runners 8 is designed based on the number of arc-shaped risers 6. After the number of arc-shaped risers 6 is calculated, the square risers 7 are connected in batches using the same number of annular runners. The arc-shaped runners 8 are distributed circumferentially. Based on the number of arc-shaped runners 8, each arc-shaped runner 8 is designed to connect multiple square risers 7. In this example, each arc-shaped runner 8 connects risers in four directions, that is, each arc-shaped runner 8 pours molten metal into four auxiliary blocks 5.

[0032] The arc-shaped riser 6 and the horizontal sprue 9 are connected by an inverted flow-limiting structure 14. The inverted flow-limiting structure 14 and the horizontal sprue 9 have the same width and a necked-out longitudinal section. When making the wax model, the inverted flow-limiting structure 14 is prepared by upward drafting. An opposite draft angle is set in the direction of molten metal flow, and the cross-sectional area of ​​the channel through which molten metal flows to the inner ring 1 is reduced. Due to the reduction in the cross-sectional area of ​​molten metal flow, the amount of molten steel entering the inner ring 1 and outer ring 2 can be well controlled during the filling process, thereby ensuring that a large amount of molten metal does not flow from the inner ring 1 into the outer ring 2 through the blade 3, avoiding overheating of the blade 3 shell and causing overheating and shrinkage of the blade 3. The inverted design avoids the molten metal impacting the arc-shaped riser 6 of the inner ring 1 during the filling process, and avoids the inner ring 1 riser shell temperature being too high and heat dissipation being difficult. Meanwhile, since the molten metal enters the blade 3 shell simultaneously in the inner ring 1 and outer ring 2, the feeding channel blockage caused by the blade 3 shell lowering the temperature of the molten metal is avoided. Therefore, the shell firing temperature can be appropriately reduced based on the original parameters, further reducing the risk of slag inclusions in the casting.

[0033] This example also provides a fabrication process for the aforementioned nozzle ring casting shell structure, which includes the following steps:

[0034] 1) Wax pattern structure design: Calculate the size and position of the hot spot circle at the junction R of the blade and the outer ring in the 3D model of the nozzle ring casting. Use the rolling method to roll out the longitudinal shape and size of the auxiliary block 5 tangentially at a ratio of 1:1.1 according to the longitudinal hot spot circle diameter. Then determine the transverse width of the auxiliary block 5 by the transverse hot spot circle diameter. Use the rolling method to design the auxiliary ring 4 of the inner ring 1. Based on the thickness and radial dimension of the top of the inner ring 1 and the auxiliary ring 4, design the size and quantity of the arc riser 6 according to the feeding principle. Calculate and design the size of the square riser 7 by using the modular method for the auxiliary block 5 and the outer ring 2.

[0035] The rounding method, shrinkage compensation principle, and modular method for calculating dimensions used in wax model structure design are all common and conventional technical solutions in existing wax model design, and will not be described in detail in this example.

[0036] 2) Wax model preparation: Prepare the auxiliary block 5, auxiliary ring 4, arc-shaped riser 6 and square riser 7 designed in step 1), and prepare the nozzle ring wax model and the runner wax model. When preparing the nozzle ring wax model, segmented preparation is adopted, and the whole nozzle ring wax model is divided into equal parts. Each blade 3 connects the inner ring 1 section and the outer ring 2 section. The runner wax model includes the pouring cup 11, the runner plate 10, the horizontal runner 9, the arc-shaped runner 8 and other accessory wax models.

[0037] 3) Wax Model Assembly: Attach the subsidy ring 4 and subsidy block 5 to the corresponding hot joints 17 of the inner ring 1 and outer ring 2 of the nozzle ring wax model. Then attach the arc-shaped riser 6 to the subsidy ring 4 and the square riser 7 to the subsidy block 5. Finally, connect the horizontal runner 9 on the gating wax model to the arc-shaped riser 6 and the arc-shaped runner 8. When assembling the tree, first attach the subsidy block 5 to the outer ring 2 section, then attach the square riser 7 to the subsidy block 5, and then attach the equally divided nozzle wax models together to form an integral nozzle wax model. Then, begin attaching the subsidy ring 4, arc-shaped riser 6, and gating.

[0038] 4) Wax trimming: The wax model structure after the tree is assembled is trimmed with a wax trimming knife to obtain the nozzle ring wax model structure.

[0039] 5) Preparation of the mold shell: After the nozzle ring wax mold structure is coated, dewaxed and fired, the nozzle ring casting mold shell is obtained.

[0040] like Figure 2 As shown, a stepped cotton-filled layer 15 is provided on the outside of the mold shell structure. Specifically, the mold shell of the gating system and riser is 13mm thick, and the mold shell of the auxiliary block 5 is 6mm thick, which is a selective stepped cotton-filled structure. The gating system includes a pouring cup 11, a runner 10, a horizontal gating system 9, and an arc-shaped gating system 8, etc. The risers include an arc-shaped riser 6 and a square riser 7. Under the environment of relatively slow heat radiation dissipation of the inner ring 1 and the stepped cotton-filled outer ring 2, the overall sequential solidification is ensured, with the blade 3 part solidifying first, thereby reducing the risk of excessive porosity. With the selection of appropriate mold shell temperature and pouring temperature, the feeding channel of the casting itself is ensured to be unobstructed, and the riser has sufficient feeding capacity for the casting, realizing the sequential solidification of the casting from bottom to top and from the casting to the riser. At the same time, the casting stress at the transition fillet of the blade 3 and the outer ring 2 is reduced, reducing the risk of shrinkage porosity and cracks at the transition fillet. The cotton-wrapping method, combined with the poor heat dissipation of the inner ring 1 of the nozzle ring, achieves an ideal sequential solidification method for investment casting and ensures unobstructed feeding channels.

[0041] The foregoing has only described certain exemplary embodiments of the present invention by way of illustration. Undoubtedly, those skilled in the art can modify the described embodiments in various ways without departing from the spirit and scope of the present invention. Therefore, the foregoing drawings and descriptions are illustrative in nature and should not be construed as limiting the scope of protection of the claims of the present invention.

Claims

1. A nozzle ring casting shell structure, comprising a nozzle ring shell and a pouring cup, wherein the nozzle ring shell includes an inner ring, an outer ring, and blades connecting the inner and outer rings, characterized in that: The inner ring has a full circle of auxiliary rings on its inner side, and auxiliary blocks are set at each hot spot on the outer side of the outer ring. Several arc-shaped risers are set on the top of the auxiliary rings. The top of the auxiliary blocks is connected to the arc-shaped runner through square risers. The number of arc-shaped runners and arc-shaped risers is the same. Arc-shaped risers and arc-shaped runners in the same radial direction are connected to the same horizontal runner. All horizontal runners are connected to the manifold plate. The manifold plate is connected to the pouring cup. The arc-shaped risers and horizontal runners are connected by an inverted flow-limiting structure. The inverted flow-limiting structure is the same width as the horizontal runner and has a necked structure in its longitudinal section. Triangular oblique overlaps are set at the connection between the arc-shaped risers and the auxiliary rings on both sides.

2. The nozzle ring casting shell structure according to claim 1, characterized in that: The horizontal runner has an L-shaped structure. One end of the horizontal runner is connected to the bottom of the distribution plate, and the other end of the horizontal runner is connected to the arc-shaped runner through a connecting block. The connecting block and the arc-shaped runner have the same thickness.

3. The nozzle ring casting shell structure according to claim 1, characterized in that: The arc-shaped gating system connects to at least one auxiliary block.

4. The nozzle ring casting shell structure according to claim 1, characterized in that: The outer side of the shell structure is provided with a stepped cotton-filled layer.

5. A manufacturing process for a nozzle ring casting shell structure as described in any one of claims 1-4, characterized in that: Includes the following steps: 1) Wax pattern structure design: Calculate the size and position of the hot spot circle at the junction R between the blade and the outer ring in the 3D model of the nozzle ring casting. Use the rolling method to roll out the longitudinal shape and size of the auxiliary block tangentially at a ratio of 1:1.1 according to the longitudinal hot spot circle diameter. Then determine the transverse width of the auxiliary block through the transverse hot spot circle diameter. Use the rolling method to design the auxiliary ring of the inner ring. Based on the thickness and radial dimensions of the inner ring and the top of the auxiliary ring, design the size and quantity of the arc riser according to the feeding principle. Calculate and design the size of the square riser by using the modular method for the auxiliary block and the outer ring. 2) Wax model preparation: Prepare wax models of the subsidy block, subsidy ring, arc-shaped riser and square riser designed in step 1), and prepare wax models of the nozzle ring and the sprue; 3) Wax mold assembly: Glue and fix the subsidy ring and subsidy block to the corresponding hot joints of the inner and outer rings of the nozzle ring wax mold. Then glue and fix the arc-shaped riser to the subsidy ring, glue the square riser to the subsidy block, and finally connect the horizontal runner on the gating wax mold to the arc-shaped riser and arc-shaped runner. 4) Wax trimming: The wax model structure after tree assembly is trimmed with a wax trimming knife to obtain the nozzle ring wax model structure; 5) Preparation of the mold shell: After the nozzle ring wax mold structure is coated, dewaxed and fired, the nozzle ring casting mold shell is obtained.

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