Forming method of active cooling type turbine guider

Abstract

The invention relates to a forming method of an active cooling type turbine guider. The forming method comprises the steps that S1, the hole pattern of a cooling hole is improved; s2, quartz rod improvement: the length and diameter of a quartz rod are determined according to the length and aperture of a cooling hole, and the content of silicon dioxide in the quartz rod is 40-80%; s3, smearing an organic coating, namely coating one end, extending out of the cooling hole, of the quartz rod with an organic coating layer; s4, making a shell by adopting a multi-layer coating process; S5, roasting; and roasting by adopting a gradient roasting process. Through the special design of the cooling holes, the problem that through holes are difficult to form in the 3D printing process is effectively solved. In a traditional manufacturing method, due to the fact that the diameter of a product hole is small, the product hole cannot be in effective contact with a dissolving solution, and a through hole of a wax mold is difficult to form. In the embodiment, the diameter of the middle section of the cooling hole is increased, and the length of the middle section of the cooling hole is limited, so that the supporting wax can be smoothly dissolved and effectively contacted with the dissolving solution, and the quartz rod is prevented from being clamped in the cooling hole due to thermal expansion.

Description

Technical Field

[0001] The invention relates to the technical field of investment casting, in particular to a molding method of an actively cooled turbine guide. Background Art

[0002] In advanced aero-engine technology, turbine blades are core components whose performance is directly related to the overall efficiency and life of the engine. Especially in high-temperature and high-pressure working environments, turbine blades need to withstand the impact of high-temperature combustion gases exceeding 1,000 degrees, which places extremely high demands on the material and cooling design of the blades. To solve this problem, the blades are ingeniously designed as hollow structures, using the cold air introduced from the compressor to circulate inside the blades to achieve efficient cooling, thereby significantly extending the service life of the blades.

[0003] However, the complex inner cavity structure of turbine blades, especially those small and deep cooling holes1 (hole diameter range 0.6mm-1.5mm, hole length over 3mm), poses a severe challenge to traditional manufacturing processes. Traditional forging, machining and other methods are difficult to accurately form such a complex inner cavity, so investment casting has become the mainstream choice. In this process, the quality of the ceramic core directly determines the final quality and pass rate of the casting.

[0004] Traditional processing methods often have the following problems:

[0005] Difficulty in through-hole forming: During the 3D printing process, since the diameter of the product hole is only 0.6-1.5mm, it cannot effectively contact with the dissolving liquid in the later stage, making it difficult to form the through-holes of the wax model.

[0006] The problem of quartz rod fixation and integrity: At high temperatures, due to the inconsistent shrinkage of the mold shell and the quartz rod, stress is easily generated, causing the quartz rod to break.

[0007] Quartz rod breakage caused by dewaxing process: The melting point of 3D printing wax is low, and the traditional dewaxing kettle heats up slowly during steam dewaxing, causing the wax to boil for a long time and the mold shell to vibrate, which in turn causes the quartz rod to break.

[0008] Quality control during shell making and firing: It is necessary to ensure the uniformity of shell making and precise control of temperature during firing to avoid adverse effects on casting quality.

[0009] To this end, we propose a molding method for an actively cooled turbine guide vane. Summary of the invention

[0010] In view of the shortcomings in the above-mentioned existing production technology, the applicant provides a forming method of an actively cooled turbine guide vane. Through the special design of cooling holes, special treatment of quartz rods, application of organic coatings and application of gradient roasting process, the problems existing in the traditional manufacturing method, such as the difficulty in through-hole forming, easy breakage of quartz rods, breakage caused by dewaxing process and difficulty in shell roasting quality control, are effectively solved.

[0011] The technical solution adopted by the present invention is as follows:

[0012] A method for forming an actively cooled turbine guide vane comprises the following steps:

[0013] S1. Improve the cooling hole shape, keep the size of both ends of the cooling hole unchanged, and expand the middle section of the cooling hole;

[0014] S2 quartz rod improvement: the length and diameter of the quartz rod are determined according to the length and diameter of the cooling hole, so that the quartz rod fits tightly with the cooling hole, and at the same time ensures that the content of silicon dioxide in the quartz rod is between 40% and 80%;

[0015] S3, applying an organic coating, and coating an organic coating layer on one end of the quartz rod extending from the cooling hole;

[0016] S4, shell making, using multi-layer coating process to ensure the strength and air permeability of the membrane shell;

[0017] S5. Calcination: The calcination is carried out by using a gradient calcination process, starting from 100-200°C for 15-30 minutes, and then increasing the temperature by 200°C for a period of time until the temperature reaches 750-800°C.

[0018] Furthermore, the design of the cooling hole includes: the diameter of the cooling hole is 0.5-1.5 mm, the depth is at least 3 mm, the diameter of the middle section of the cooling hole is increased to 30%-60% of the diameter, and the length of the middle section of the cooling hole accounts for about 80% of the total length of the cooling hole.

[0019] Furthermore, the quartz rod is composed of silicon dioxide and aluminum oxide, wherein the content of silicon dioxide is between 40% and 80%, and the diameter of the quartz rod is slightly smaller than the diameters of the two ends of the cooling hole.

[0020] Furthermore, at least 2-5 mm is exposed at both ends of the quartz rod for subsequent fixation and coating.

[0021] Furthermore, the organic coating has good high temperature resistance and adhesion, and the coating thickness is controlled between 0.03-0.1 mm.

[0022] Furthermore, the side of the membrane shell close to the blade wax mold is an alumina surface layer, and the back layer is formed by using quartz powder slurry and 24-36 mesh mullite sand, with a total of 6 layers.

[0023] Furthermore, it also includes S6, casting, pouring the molten metal into the membrane shell and naturally cooling and solidifying it.

[0024] Furthermore, it also includes S7, core removal, in which the membrane shell is removed by knocking, and the quartz rod is fully reacted and dissolved by an alkaline solution to achieve demoulding.

[0025] The beneficial effects of the present invention are as follows:

[0026] The invention has a compact and reasonable structure and is easy to operate. Through the special design of cooling holes, special treatment of quartz rods, application of organic coatings and application of gradient baking process, it effectively solves the problems existing in traditional manufacturing methods, such as difficult through-hole forming, easy breakage of quartz rods, breakage caused by dewaxing process and difficult quality control of shell baking. These innovations not only improve the quality of 3D printed castings and the integrity of quartz rods, but also provide new ideas and methods for the manufacture of complex structural parts such as aircraft engine turbine blades.

[0027] At the same time, the present invention also has the following advantages:

[0028] The present invention effectively solves the problem of difficult through-hole forming during 3D printing through the special design of the cooling hole. In the traditional manufacturing method, due to the small diameter of the product hole, it is often impossible to effectively contact the dissolving liquid, resulting in the difficulty of forming the through hole of the wax mold. In this embodiment, by increasing the diameter of the middle section of the cooling hole and limiting its length, it is ensured that the supporting wax can be smoothly dissolved and effectively contact the dissolving liquid, and the quartz rod is prevented from being stuck in the cooling hole due to thermal expansion. This design not only improves the success rate of through-hole forming, but also ensures that the overall structure and performance of the blade are not affected.

[0029] The special treatment of the through-hole quartz rod and the application of organic coating in the present invention effectively solve the problem that the quartz rod is easy to break at high temperature. In the traditional manufacturing method, due to the inconsistent shrinkage of the mold shell and the quartz rod, stress is easily generated, resulting in the breakage of the quartz rod. In this embodiment, by selecting a quartz rod with a suitable ratio of silicon dioxide and aluminum oxide, and applying an organic coating on its surface, the organic coating can be decomposed into carbon dioxide and water at high temperature during the roasting process, thereby reserving a certain gap between the membrane shell and the quartz rod. This design not only ensures the fixing force between the quartz rod and the mold shell, but also avoids the stress caused by inconsistent shrinkage, thereby ensuring the integrity of the quartz rod.

[0030] The present invention effectively optimizes the dewaxing process and improves the quality of castings by applying a gradient roasting process. In the traditional manufacturing method, due to the slow heating rate during the steam dewaxing process in the dewaxing kettle, the wax is in a boiling state for a long time, the mold shell vibrates, and the quartz rod breaks. In this embodiment, a gradient roasting process is used instead of the traditional dewaxing kettle steam dewaxing, and the temperature is gradually increased from a low temperature, which not only quickly discharges the wax, but also avoids the quartz rod from being overstressed and broken due to rapid heating. At the same time, the gradient roasting process also helps to reduce defects such as pores and shrinkage holes generated during the casting process, and improves the overall quality of the casting. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a structural schematic diagram of the present invention.

[0032] Figure 2 It is a schematic diagram of the connection structure between the cooling hole and the quartz rod of the present invention.

[0033] Figure 3 It is a structural schematic diagram of the wax model assembly of the present invention.

[0034] in:

[0035] 1. Cooling hole; 2. Middle section of blade cooling hole; 3. Quartz rod; 4. Blade wax model; 5. Organic coating layer; 6. Wax model assembly. DETAILED DESCRIPTION

[0036] The specific implementation of the present invention will be described below in conjunction with the accompanying drawings.

[0037] like Figure 1-Figure 3 As shown, the present embodiment discloses a rapid prototyping method for an actively cooled turbine guide, especially for the manufacture of hollow turbine blades with multiple small diameter cooling holes 1 (0.6-1.5 mm). The traditional manufacturing method faces problems such as difficulty in molding the cooling holes 1, easy breakage of the quartz rods, fracture caused by the dewaxing process, and difficulty in quality control of shell making and roasting in investment casting 3D printing. The present invention improves the shape of the cooling holes 1, and specially treats the quartz rods 3, and comprehensively optimizes dewaxing and controls shell making and roasting, thereby improving the quality of 3D printed castings and the integrity of the quartz rods.

[0038] In this embodiment, Figure 1 As shown, in order to improve the quality of the product, cooling holes need to be opened on the blade wax mold 4. These cooling holes will play a key role in the subsequent manufacturing process. They are not only channels for cooling air, but also dissolution channels for supporting wax during 3D printing.

[0039] Combined with Figure 1-Figure 3 In this embodiment, a rapid prototyping method for an actively cooled turbine guide vane is disclosed, comprising the following steps:

[0040] S1, cooling hole 1 hole type improvement; in this embodiment, as Figure 2 As shown, during the wax mold design stage, the cooling hole 1 is specially designed. The two ends of the cooling hole 1 maintain the original aperture of 0.5-1.5mm, and the depth is at least 3mm. The middle section of the cooling hole 1 is expanded, that is, the aperture of the middle section 2 of the blade cooling hole is increased by 30%-60% on the basis of the original aperture. At the same time, the length of the middle section 2 of the blade cooling hole is about 80% of the length of the cooling hole 1. By limiting the aperture and length of the middle section 2 of the blade cooling hole, it is possible to avoid the quartz rod 3 from being stuck in the cooling hole 1 due to thermal expansion, and it is also possible to ensure that the supporting wax can be smoothly dissolved and effectively contact the dissolving liquid, while not affecting the overall structure and performance of the blade. Maintaining the original aperture at both ends of the cooling hole 1 facilitates the subsequent insertion and fixation of the quartz rod 3, and ensures the positioning of the cooling hole 1.

[0041] S2. Design of quartz rod 3; the quartz rod should have good high temperature resistance to withstand the high temperature environment in the subsequent casting process, and have a smooth surface. In addition, the quartz rod 3 in this embodiment is composed of silicon dioxide and aluminum oxide, and the content of silicon dioxide is between 40% and 80%. In the quartz rod 3, the content of silicon dioxide is proportional to the expansion coefficient, but inversely proportional to the hardness. However, silicon dioxide will react with alkali solution to melt, so the higher the content of silicon dioxide, the higher the demoulding efficiency; and the content of aluminum oxide is proportional to the hardness, but inversely proportional to the expansion coefficient. In this embodiment, for the slender cooling hole 1, it is relatively difficult to demould, so the content of silicon dioxide in the quartz rod 3 is relatively high. It is because of the high content of silicon dioxide that the expansion coefficient of the quartz rod 3 is large, so it is necessary to set the middle section 2 of the blade cooling hole in the cooling hole 1. At the same time, the smaller the hole diameter and the longer the hole depth, the higher the proportion of silicon dioxide. On the contrary, the content of silicon dioxide can be appropriately reduced. At the same time, in order to ensure the strength of the quartz rod 3, the proportion of aluminum oxide cannot be lower than 20%.

[0042] According to the design size of the cooling hole 1, a quartz rod 3 with a diameter slightly smaller than the diameters of both ends of the cooling hole 1 is selected. This interference connection can ensure that the quartz rod can be smoothly inserted into the cooling hole 1 and sufficient fixing force can be guaranteed.

[0043] At the same time, the length of the quartz rod 3 is determined according to the length of the cooling hole 1, and the customized quartz rods 3 are inserted into the cooling holes 1 of the wax mold one by one, ensuring that both ends of the quartz rod are exposed by at least 2-5 mm. This exposed part will be used for subsequent fixing and coating.

[0044] S3, such as Figure 1 and Figure 3As shown, the quartz rod 3 is coated with organic coating; then, the organic coating is brushed on either end of the quartz rod, and the thickness is controlled to be 0.03-0.1 mm. In this way, after calcination, the organic coating can be decomposed into carbon dioxide and water at high temperature, thereby reserving a certain gap between the membrane shell and the quartz rod. One end of the quartz rod is fixed to the mold shell, and the other end is in a free state due to the existence of the gap, avoiding the stress caused by inconsistent shrinkage and ensuring the integrity of the quartz rod.

[0045] The organic coating layer 5 should have good high temperature resistance and adhesion. In this embodiment, nail polish can be selected as the coating, and its thickness is about 0.03-0.1 mm. Nail polish is not only easy to apply, but also has good hardness and wear resistance after drying. When applying, ensure that the coating is evenly distributed and has sufficient thickness. After the application is completed, let the coating dry naturally.

[0046] S4, shell making, the membrane shell includes a surface layer and a lining layer, the surface layer is 200 mesh alumina slurry; the lining layer has 6 layers, using quartz powder slurry and 24-36 mesh mullite sand; among them, the membrane shell on the side of the membrane shell close to the blade wax mold 4 is an alumina surface layer, the alumina surface layer has high strength and small expansion coefficient, which can ensure the quality of the product.

[0047] By selecting quartz powder slurry and 24-36 mesh mullite sand as the backing layer materials, they have good air permeability and strength.

[0048] Apply the aluminum oxide surface layer evenly on the surface of the wax model to form a thin and uniform surface layer. After the surface layer is dry, the next layer can be applied. On the basis of the surface layer, the back layer material is applied. There are 6 layers of back layer in total, and each layer must be dried after application to ensure the bonding strength between the layers and the overall strength.

[0049] S5, roasting. In this embodiment, a gradient roasting process is used to replace the traditional dewaxing kettle steam dewaxing. Starting from 100-200°C, at this temperature, the wax mold begins to melt and flow out, with a step of 200°C. At 400-500°C, the organic coating layer 5 will be decomposed into CO2 and water by heat, and a certain gap will be reserved between the quartz rod 3 and the membrane shell until the insulation is terminated at 750-800°C, completing the shell making process. This roasting method can not only quickly discharge the wax, but also avoid the quartz rod from being broken due to excessive stress caused by rapid temperature rise.

[0050] By adopting a step-by-step firing process, which is a firing method with gradually increasing temperature, thermal stress concentration and cracking of the mold shell during the heating process can be effectively avoided.

[0051] Firing temperature and holding time: Start holding at 100-200℃ for 15-30min, at this temperature, ensure that the blade wax mold 4 is fully melted, then increase the temperature by 200℃ for a period of time, at 400-500℃, the organic coating layer 5 will be decomposed into CO2 and water by heat, and a certain gap will be reserved between the quartz rod 3 and the membrane shell until the holding is terminated at 750-800℃. The specific holding time is adjusted according to the size and thickness of the mold shell. The mold shell is taken out after cooling to room temperature with the furnace.

[0052] The strength of the mold shell can be enhanced by keeping the temperature at 750-800℃: during the roasting process, the material in the mold shell will undergo a series of physical and chemical changes, which will further improve its strength.

[0053] Reduce casting defects: Through the gradual heating method, defects such as pores and shrinkage holes generated during the casting process can be effectively reduced.

[0054] S6, casting: After the subsequent casting process, the molten metal is poured into the mold shell. After the pouring is completed, the molten metal is allowed to cool and solidify naturally in the mold shell. During the cooling process, the mold shell must be cooled evenly to avoid casting stress.

[0055] S7, core removal: After casting is completed, the mold shell is broken or cut open to remove the casting. Since the cooling hole 1 is an elongated hole, the quartz rod 3 needs to be fully reacted and dissolved by an alkaline solution to achieve demoulding of the quartz rod 3.

[0056] The above description is an explanation of the present invention, not a limitation of the present invention. The scope of the present invention is defined in the claims. Any form of modification may be made within the scope of protection of the present invention.

Claims

1. A method for forming an actively cooled turbine guide vane, characterized in that: The following steps are involved: S1. Improve the cooling hole shape, keep the size of both ends of the cooling hole unchanged, and expand the middle section of the cooling hole; S2 quartz rod improvement: the length and diameter of the quartz rod are determined according to the length and diameter of the cooling hole, so that the quartz rod fits tightly with the cooling hole, and at the same time ensures that the content of silicon dioxide in the quartz rod is between 40% and 80%; S3, applying an organic coating, and coating an organic coating layer on one end of the quartz rod extending from the cooling hole; S4, shell making, using multi-layer coating process to ensure the strength and air permeability of the membrane shell; S5. Calcination: The calcination is carried out by using a gradient calcination process, starting from 100-200°C for 15-30 minutes, and then increasing the temperature by 200°C for a period of time until the temperature reaches 750-800°C.

2. The method for forming an actively cooled turbine guide vane according to claim 1, characterized in that: The design of the cooling hole includes: the diameter of the cooling hole is 0.5-1.5mm, the depth is at least 3mm, the diameter of the middle section of the cooling hole is increased to 30%-60% of the diameter, and the length of the middle section of the cooling hole accounts for about 80% of the total length of the cooling hole.

3. The method for forming an actively cooled turbine guide vane according to claim 2, characterized in that: The quartz rod is composed of silicon dioxide and aluminum oxide, wherein the content of silicon dioxide is between 40% and 80%, and the diameter of the quartz rod is slightly smaller than the diameters of the two ends of the cooling hole.

4. A method for forming an actively cooled turbine guide vane according to any one of claims 1 to 3, characterized in that: Both ends of the quartz rod are exposed by at least 2-5 mm for subsequent fixing and coating.

5. The method for forming an actively cooled turbine guide vane according to claim 4, characterized in that: The organic coating has good high temperature resistance and adhesion, and the coating thickness is controlled between 0.03-0.1 mm.

6. The method for forming an actively cooled turbine guide vane according to claim 5, characterized in that: The side of the membrane shell close to the blade wax mold is an aluminum oxide surface layer, and the back layer is formed by using quartz powder slurry and 24-36 mesh mullite sand, with a total of 6 layers.

7. The method for forming an actively cooled turbine guide vane according to claim 4, characterized in that: It also includes S6, casting, pouring the molten metal into the membrane shell and naturally cooling and solidifying it.

8. The method for forming an actively cooled turbine guide vane according to claim 7, characterized in that: It also includes S7 and core removal, which removes the membrane shell by knocking, and at the same time fully reacts and dissolves the quartz rod through alkaline solution to achieve demoulding.

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