Anti-loosening casting method for guider

Abstract

The invention provides an anti-loosening casting method for a guider, which belongs to the technical field of precision casting and comprises the following steps of: preparing a wax mould according to the shape of the guider, and pasting a process patch at the position with a loosening defect of the wax mould; a mold shell is manufactured on the outer surface of the wax mold pasted through the pasting technology; the mold shell is preheated, and pouring is conducted after preheating to form a casting; and the casting is cooled and cleaned. The process patch is pasted at the position with the loose defect of the wax mold, the problem of surface looseness generated in the solidification process of the casting is solved, and then the loose defect of the surface of the casting can be eliminated.

Description

Technical Field

[0001] The present invention belongs to the technical field of precision casting, and particularly relates to a method for preventing porosity in a guide vane casting. Background Art

[0002] Aero-engine has been developing towards the direction of reducing weight, increasing thrust-to-weight ratio / power-to-weight ratio, improving fuel utilization efficiency, and enhancing reliability, applicability, maintainability and economy. In this process, aero-engine components tend to be highly integrated and thin. The inter-stage guide vane is an integral precision casting composed of multiple complex thin-walled blades integrated into a multi-layer annular structure, and is a composite of the turbine inter-stage casing, the first-stage guide vane of the power turbine and the inter-stage bearing housing.

[0003] Chinese Patent Publication No. CN102513506A discloses a method for preventing porosity in equiaxed crystal superalloy castings. The process steps are as follows: preparing a wax pattern and a shell mold by using a traditional investment precision casting process; heating the shell mold to a certain temperature within the alloy solid-liquid phase line range in a heater of a directional solidification vacuum induction furnace and holding for a certain time; remelting the alloy and pouring it into the cavity of the shell mold, and then pulling it out of the heater at a certain speed.

[0004] The above-mentioned prior art discloses that by controlling the temperature of the upper and lower shell molds, the porosity defects of equiaxed crystal castings of superalloys or structures with high porosity tendency can be effectively reduced or eliminated, thereby improving the qualified rate of castings. However, the difficulty of precision casting for such parts caused by the highly integrated and thin design of components has increased exponentially. Taking a typical inter-stage guide vane as an example, its complex structure directly leads to many problems in the metallurgical quality of this casting, resulting in a low casting qualified rate, high research and development costs, and an unpredictable delivery cycle. Among them, the porosity defect is one of the important factors leading to the scrapping of this part, and has become a technical bottleneck restricting the development of this type of casting.

[0005] Therefore, a method for casting a guide vane with a complex structure and preventing porosity is needed. Summary of the Invention

[0006] In view of the above problems, the present invention provides a method for preventing porosity in a guide vane casting, comprising the following steps:

[0007] Preparing a wax pattern according to the shape of the guide vane, and pasting a process patch at the position of the wax pattern with porosity defects;

[0008] Manufacturing a shell mold on the outer surface of the wax pattern pasted with the process patch;

[0009] Preheating the shell mold, and pouring after preheating to form a casting;

[0010] Cooling the casting, and cleaning the casting.

[0011] Further, the thickness of the position of the wax pattern with porosity defects is significantly smaller than the thickness of the adjacent area, and the process riser is a feeding piece.

[0012] Further, the feeding piece is made of wax.

[0013] Further, the feeding piece is in a stepped shape.

[0014] Further, the feeding piece is in a wedge shape.

[0015] Further, the mold shell is preheated by a zone temperature control method.

[0016] Further, the casting is cooled by zone temperature control.

[0017] Further, the heat dissipation rate of the position of the wax pattern with porosity defects is significantly smaller than the heat dissipation rate of the adjacent area, and the process riser is a heat dissipation fin.

[0018] Further, the heat dissipation fin is a wax sheet with a thickness of 0.5 - 5 mm.

[0019] Further, preparing the wax pattern according to the shape of the guide vane includes the following steps

[0020] Pressing a ceramic core with a ceramic core mold;

[0021] Pressing a guide vane wax pattern with a guide vane wax pattern mold;

[0022] Pressing a gating system wax pattern according to the guide vane wax pattern;

[0023] Assembling the guide vane wax pattern and the gating system wax pattern into an integral wax pattern.

[0024] Further, it further includes the following steps:

[0025] Inspecting the cleaned casting.

[0026] Advantages of the present invention:

[0027] 1. By pasting a process riser at the position of the porosity defect of the wax pattern, the present invention solves the problem of surface porosity generated during the solidification of the casting, and thus can eliminate the surface porosity defect of the casting.

[0028] 2. The present invention prepares a wax pattern according to the shape of the guide vane, and the heat dissipation rate of the position of the wax pattern with porosity defects is significantly smaller than the heat dissipation rate of the adjacent area, and the process riser is a heat dissipation fin; the heat dissipation fin is used to change the local temperature field and improve the heat dissipation capacity, thus solving the problem of surface porosity generated due to slow heat dissipation during the solidification process, and thus can eliminate the surface porosity defect at the connection between the casting runner and the blade.

[0029] 3. The thickness of the position with porosity defects in the wax mold of the present invention is significantly smaller than the thickness of the adjacent area. The process riser is a riser patch to solve the porosity problem of the protrusion, and a top-down riser channel is artificially established to solve the porosity problem in the thin-wall area.

[0030] 4. The present invention controls the temperature of the cast mold after pouring in a differential manner. Specifically, the riser part of the cast mold after pouring and filling is heated, the casting part is moved out of the heating area, and a zoning temperature control method is adopted to control the cooling rate of different areas, optimizing the riser function of the gating system.

[0031] 5. The present invention heats the shell mold in the furnace by a heater zoning temperature control method, controls the temperature of the shell mold to form a stepped temperature field, realizes the temperature gradient at different positions of the shell mold, meets the requirement of sequential risering of the casting, and eliminates the porosity defects on the surface and inside of the casting.

[0032] Other features and advantages of the present invention will be described in the following specification, and, in part, will be obvious from the specification, or will be understood by implementing the present invention. The objectives and other advantages of the present invention can be realized and obtained by the structure pointed out in the specification and the drawings. Brief Description of the Drawings

[0033] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0034] Figure 1 Shows the flow schematic diagram of the anti-porosity casting method for the guide vane in the embodiment of the present invention.

[0035] Figure 2 Shows the three-dimensional structure schematic diagram of the guide vane in the prior art.

[0036] Figure 3 Shows the cross-sectional structure schematic diagram of the guide vane in the prior art.

[0037] Figure 4 Shows the position schematic diagram of the heat dissipation fins in the wax mold of the guide vane in the embodiment of the present invention.

[0038] Figure 5 Shows the position schematic diagram of the riser patch in the wax mold of the guide vane in the embodiment of the present invention.

[0039] Figure 6 Shows the zoning temperature control schematic diagram of the preheating of the guide vane shell mold in the furnace in the embodiment of the present invention.

[0040] Figure 7 The figure shows a schematic diagram of zoned temperature control for the cooling of a guide vane shell in an embodiment of the present invention.

[0041] In the figure, 10 is a blade; 20 is a first flow channel; 30 is a second flow channel; 40 is a heat dissipation fin; 50 is a feeding piece; 60 is a protrusion; 70 is a flange riser; 80 is a casing. Detailed implementation manners

[0042] For the purposes, technical solutions and advantages of the embodiments of the present invention to be more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some but not all of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the protection scope of the present invention.

[0043] Figure 2 The figure shows a three-dimensional structure schematic diagram of a guide vane in the prior art. Refer to Figure 2 , a blade 10 is provided between a first flow channel 20 and a second flow channel 30 of the guide vane. The blade 10 is a hollow blade. A plurality of blades 10 are respectively installed between the first flow channel 20 and the second flow channel 30 in a circumferential array. In the guide vane in this figure, sixteen blades 10 are adopted. Refer to Figure 3 , Figure 3 For Figure 2 the sectional view of, and thus the guide vane can be more intuitively understood.

[0044] The inter-stage guide vane is an integral precision casting composed of a multi-layer annular structure integrated with multiple complex thin-walled blades, and is a composite body of a turbine inter-stage casing, a first-stage guide vane of a power turbine and an inter-stage bearing housing. The present invention is suitable for simple guide vanes and also suitable for complex inter-stage guide vanes.

[0045] Refer to Figure 1 , a method for preventing porosity in the casting of a guide vane includes the following steps:

[0046] Prepare a wax pattern according to the shape of the guide vane, and paste a process subsidy at the position of the wax pattern with porosity defects;

[0047] Make a mold shell on the outer surface of the wax pattern pasted with the process subsidy;

[0048] The mold shell is preheated, and then poured to form a casting; specifically, the outer side of the mold shell corresponding to the pouring system is cotton-wrapped and then the mold shell is placed in a vacuum melting furnace with an in-furnace heating system for preheating. When the mold shell is preheated, the overall temperature field of the mold is controlled by the in-furnace heating of the mold shell partition temperature control method. After the mold shell preheating treatment is completed for a predetermined time as required, the mold shell is transferred to a predetermined position in the pouring furnace for pouring. That is, a heating mechanism is provided in the furnace, and the heating mechanism is specifically a resistance heater or a graphite heater.

[0049] The casting is cooled and cleaned. After the casting is taken out of the furnace, the casting is water-blown and shell-cleaned. At the same time, the heat dissipation fins 40 attached to the connection between the pouring system, the first flow channel 20 and / or the second flow channel 30 and the blade 10 and the stepped or wedge-shaped feeding pieces 50 attached above the protrusions 60 of the first flow channel 20 and / or the second flow channel 30 and / or the casing 80 are cut off, and then the casting is chemically de-cored to remove the residual core in the cavity of the blade 10, so that a hollow integral guide with a complex structure without loose defects can be obtained.

[0050] The casting runner or channels include a first runner 20 and a second runner 30 .

[0051] Furthermore, the heat dissipation speed at the location with the loose defect of the wax mold is significantly lower than the heat dissipation speed of the adjacent area (ie, the location with slow heat dissipation speed), and the process subsidy is the heat dissipation fin 40 .

[0052] like Figure 4 As shown, the present scheme adds heat dissipating fins 40 to the thin-walled area where the blades 10 of the interstage guide device wax mold are connected with the first flow channel 20 and / or the second flow channel 30 (that is, some of the connections have slow heat dissipation and need to add heat dissipating fins 40), and the connection between the blades 10 and the first flow channel 20 and / or the second flow channel 30 is defined as the transition R area. The heat dissipating fins 40 are thin sheet-like heat dissipating fins, and the thickness of the wax sheet is 0.5-5mm. The heat dissipating fins 40 are adhered to the transition R area between the blades 10 and the first flow channel 20 and / or the second flow channel 30 of the interstage guide device wax mold with adhesive wax, and the ceramic shell of the interstage guide device module with the heat dissipating fins 40 is prepared.

[0053] In the above embodiment, another optional implementation is that the heat dissipation fins 40 can be replaced by thin cold iron sheets of the same material or similar material as the casting, or other materials, but any device that can accelerate local heat dissipation is within the scope of protection of the present invention.

[0054] A heat dissipation fin 40 is added at the connection between the blade 10 and the first flow channel 20 and / or the second flow channel 30 to change the local temperature field and improve the heat dissipation capacity, thereby solving the surface looseness problem caused by slow heat dissipation during the solidification process of the transition R zone, thereby eliminating the loose surface defects of the casting flow channel and the blade transition R zone.

[0055] Those skilled in the art should understand that Figure 4 The schematic diagram of the heat dissipation fin pasting shown is only for illustration and not for limiting the scope of this application. The material, shape, thickness of the heat dissipation fin, and the selection of the pasting position are related to the position of the porosity defect of the casting. Those skilled in the art should understand that the pasting process method of the heat dissipation fin can be modified without departing from the scope and spirit of this application. The scope of this application is defined by the appended claims.

[0056] Preparing the wax pattern according to the shape of the guide vane includes the following steps

[0057] Pressing a ceramic core using a ceramic core mold;

[0058] Pressing a guide vane wax pattern using a guide vane wax pattern mold;

[0059] Pressing a gating system wax pattern according to the guide vane wax pattern;

[0060] Assembling the guide vane wax pattern and the gating system wax pattern into an integral wax pattern.

[0061] Specifically, pressing a number of ceramic cores by using a ceramic core mold; pressing a complex structure hollow integral guide vane wax pattern by using a blade guide vane wax pattern mold and trimming the guide vane wax pattern; pasting heat dissipation fins 40 at the connection of the first runner 20 and / or the second runner 30 and the blade 10 of the complex structure hollow integral guide vane wax pattern, and pasting stepped or wedge-shaped feeding pads 50 on the upper surface of the protrusion 60 on the first runner 20 and / or the second runner 30 and / or the casing 80; combining the completed complex structure hollow integral guide vane wax pattern with heat dissipation fins 40 and feeding pads 50 with the gating system wax pattern as required; preparing a mold shell on the outer surface of the blade guide vane wax pattern, ceramic core, and gating system wax pattern as a whole; spraying a coating on the periphery of the blade guide vane wax pattern, ceramic core, and gating system wax pattern combined as a whole and drying and forming; heating to melt and flow out the wax pattern, thereby forming a mold shell.

[0062] The thickness of the position of the wax pattern with porosity defects is significantly smaller than the thickness of the adjacent area (i.e., the thin-walled area), and the process subsidy is the feeding pad 50.

[0063] Furthermore, a feeder sheet 50 is provided between the protrusion 60 and the flange riser 70 of the casing 80 of the guide vane wax pattern. A runner is provided above the flange riser 70 to facilitate pouring. The feeder sheet 50 forms a top-down feeding channel between the protrusion 60 and the flange riser 70 (since this step is still for manufacturing the guide vane wax pattern and the mold shell is made on the outside of the wax pattern, and since the mold shell wraps around the outside of the wax pattern, adding the feeder sheet 50 between the protrusion 60 and the flange riser 70 means that the mold shell forms a feeding channel at the position of the feeder sheet 50), solving the problem of porosity in the protrusion 60.

[0064] The feeder sheet 50 is made of wax. Making it of wax facilitates melting the wax and flowing it out by heating after the subsequent mold shell manufacturing is completed, facilitating subsequent pouring.

[0065] The feeder sheet 50 is in a stepped shape. This increases the cross-sectional area and thus realizes enlarging the feeding channel.

[0066] The feeder sheet 50 is in a wedge shape. This increases the cross-sectional area and thus realizes enlarging the feeding channel.

[0067] As Figure 5 shown, a feeder sheet 50 is added on the upper surface of the first runner 20 and / or the second runner 30 and / or the protrusion 60 of the casing 80. The feeder sheet 50 forms a top-down feeding channel between the protrusion 60 and the flange riser 70 (since this step is still for manufacturing the guide vane wax pattern and the mold shell is made on the outside of the wax pattern, and since the mold shell wraps around the outside of the wax pattern, adding the feeder sheet 50 between the protrusion 60 and the flange riser 70 means that the mold shell forms a feeding channel at the position of the feeder sheet 50), solving the problem of porosity in the protrusion 60 and artificially establishing a top-down feeding channel to solve the porosity problem in the thin-walled area. The feeder sheet 50 is also called a process subsidy.

[0068] Specifically, there are multiple protrusions 60 on the surface of the second runner 30 of the guide vane. The protrusions 60 are protrusion step features. During the solidification of the casting, the position of the second runner 30 solidifies quickly, resulting in insufficient feeding at the position of the thick and large protrusions 60, and serious internal porosity is likely to occur. The porosity problem at the position of the protrusions 60 is solved.

[0069] Those skilled in the art should understand that Figure 5 the schematic diagram of the process subsidy pasting shown is only for illustration and not for limiting the scope of this application. The selection of the shape, thickness, and pasting position of the process subsidy is related to the position of the porosity defect of the casting protrusion 60. Those skilled in the art should understand that the pasting process method of the process subsidy can be modified without departing from the scope and spirit of this application. The scope of this application is defined by the appended claims.

[0070] Refer to Figure 6 , the present invention preheats the mold shell by means of zone temperature control.

[0071] As Figure 6 shown, in this solution, the mold shell is heated in the furnace by means of zone temperature control of the heater, and the temperature of the mold shell is controlled to form a stepped temperature field. That is, a heating mechanism is arranged in the furnace, and the heating mechanism is specifically a resistance heater or a graphite heater. The temperature gradient at different positions of the mold shell is realized to meet the need of sequential feeding of the casting and eliminate the porosity defects on the surface and inside of the casting. As Figure 6 shown, the temperature in zone A is 1200°C to 1350°C. That is, the main reference factors for setting the temperature in zone A are the solid-liquid phase line temperatures of the alloy. Generally, a certain temperature between the solid-liquid phase lines of the alloy is selected to ensure that the alloy liquid at the riser is later than the solidification of the casting, so as to provide an unobstructed feeding channel for the casting; the temperature in zone B is 800°C to 1200°C. That is, the reference for setting the temperature of the heater in zone B includes factors such as the surface grain size of the casting.

[0072] Refer to Figure 7 , the present invention uses zone temperature control to cool the casting.

[0073] As Figure 7 shown, in this solution, the casting mold after pouring is subjected to differential temperature control. Specifically, the riser part of the casting mold after pouring and filling is heated, and part of the casting is moved out of the heating zone. The zone temperature control method is adopted to control the cooling rate of different regions, optimize the feeding function of the gating system, and solve the porosity defect of the casting. As Figure 7 shown, Figure 7 the temperature in zone C is 1200°C to 1350°C, generally the same as the temperature in zone A; Figure 7 the temperature in zone D is normal temperature, that is, zone D follows the natural cooling of the melting furnace hearth temperature.

[0074] In the above embodiment, optionally, another implementation method is a replacement solution for the differential temperature control of the casting mold after pouring: heating the riser part of the casting mold after pouring and filling, and locally blowing inert gas on part of the casting for forced cooling.

[0075] The heat dissipation fin 40 is a wax sheet with a thickness of 0.5 - 5 mm. A wax mold is formed by the thin wax sheet, which is convenient for forming the casting sheet during pouring, and thus convenient for subsequent heat dissipation.

[0076] Cool the casting and clean the casting; include the following steps: perform hot isostatic pressing and heat treatment on the cleaned casting, and then perform casting inspection.

[0077] Hot Isostatic Pressing (HIP) is a process technology that uses the simultaneous action of high temperature and high pressure to subject metal or ceramic products to equal pressure in all directions, enabling the workpieces to be sintered and densified. It has the advantages of stable chemical composition, isotropic mechanical properties, good structural adaptability, and low cost. In hot isostatic pressing, inert gases such as argon and ammonia are generally used as pressure transfer media, and the cladding material is usually metal or glass. The working temperature is generally 1000 - 2200 °C, and the working pressure is often 100 - 200 MPa.

[0078] Heat treatment refers to a metal hot working process in which materials, in the solid state, are subjected to heating, holding, and cooling to obtain the desired microstructure and properties.

[0079] Through the above steps, a guide vane casting with good stability is obtained, and the guide vane casting is inspected.

[0080] Although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

[0081] In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include at least one such feature. In the description of the present invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise specifically defined. In the present invention, unless otherwise clearly specified and limited, terms such as "mounted", "connected", "connected to", "fixed" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or integrated; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the internal communication of two components or the interaction relationship between two components, unless otherwise clearly limited. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

Claims

1. A casting method for preventing the loosening of a guide device, characterized in that, The method includes the following steps: Prepare a wax pattern according to the shape of the guide, and paste a process subsidy at the position of the wax pattern with a porosity defect; Make a mold shell on the outer surface of the wax pattern with the process subsidy pasted; Preheat the mold shell, and perform casting after preheating to form a casting; Cool the casting, and clean the casting.

2. The anti-loosening casting method for a deflector according to claim 1, wherein The thickness of the position of the casting with a porosity defect is significantly smaller than the thickness of the adjacent area, and the process subsidy is a riser patch (50).

3. A method for preventing loosening of a guide vane during casting according to claim 2, characterized in that, The riser patch (50) is made of wax.

4. A method for preventing loosening of a guide vane during casting according to claim 2 or 3, characterized in that The riser patch (50) is stepped.

5. A method for preventing loosening of a deflector during casting according to claim 2 or 3, characterized in that The riser patch (50) is wedge-shaped.

6. A method for preventing loosening of a guide during casting according to claim 1, characterized in that, Preheat the mold shell by means of zone temperature control.

7. A method for preventing loosening of a deflector during casting according to claim 1, characterized in that, Cool the casting by means of zone temperature control.

8. A method for preventing loosening of a guide vane during casting according to claim 1, characterized in that The heat dissipation rate of the position of the casting with a porosity defect is significantly smaller than the heat dissipation rate of the adjacent area, and the process subsidy is a heat dissipation fin (40).

9. A method for preventing loosening of a guide vane during casting according to claim 8, characterized in that, The heat dissipation fin (40) is a wax sheet with a thickness of 0.5 - 5 mm.

10. A method for preventing loosening during casting of a guide device according to claim 1, characterized in that, The step of preparing the wax pattern according to the shape of the guide includes the following steps, Press a ceramic core with a ceramic core mold; Press a guide wax pattern with a guide wax pattern mold; Press a gating system wax pattern according to the guide wax pattern; Assemble the guide wax pattern and the gating system wax pattern into an integral wax pattern.

11. A method for preventing loosening of a guide during casting according to claim 1, characterized in that, It further includes the following steps: Inspect the cleaned casting.

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