Pouring system and forming method of starting turbine casting with complex structure

Abstract

The invention relates to the field of investment casting, and particularly discloses a pouring system and a forming method of a starting turbine casting with a complex structure, the pouring system comprises a pouring cup, a feeding head and a starting turbine wax mould, an annular blade main ceramic core is arranged in the wax mould, blade insertion cavities are evenly distributed in the circumference of the blade main ceramic core, and blade inner cavity ceramic cores are inserted into the insertion cavities; a spigot is arranged between the sprue cup and the feeding head, and the lower end of the feeding head is connected with the top surface of the starting turbine wax mold; the method comprises the steps of ceramic core manufacturing, wax mold pressing, wax mold assembly, shell manufacturing, dewaxing, shell cotton wrapping, roasting, vacuum melting and pouring and aftertreatment. Through the combined structure of the integral blade main ceramic core and the plug-in blade inner cavity ceramic core and the fused quartz shell manufacturing process, the problems that a complex blade inner cavity ceramic core is difficult to position and prone to core shift and core breakage are solved, the defects of looseness, cracks, slag inclusion and the like are effectively reduced, the size precision and the yield of castings are improved, and the production cost is reduced. And stable batch production of high-temperature alloy starting turbine castings with complex structures is realized.

Description

Technical Field

[0001] This invention relates to the field of investment casting, specifically a gating system and forming method for a complex structure starting turbine casting. Background Technology

[0002] The existing turbine casting is a key component for a certain type of aerospace rocket engine. It serves as the "power starter" for the rocket engine, guiding it from a standstill to stable operation. Its core function is to drive the engine's turbopump to its operating speed, delivering high-pressure propellant to the combustion chamber, making it a crucial device for engine startup. The casting has a highly complex structure, with overall dimensions of 185*185*35mm. It consists of a turbine disk, a mounting plate, and 56 evenly distributed circumferential blades. The blades are hollow, and the overall wall thickness is only 1mm.

[0003] The current mainstream manufacturing method is investment casting, but due to its complex structure, dispersed hot spots, and large differences in wall thickness in different areas of the casting, metallurgical defects such as porosity, cracks, and slag inclusions are very easy to occur during casting production. In addition, the blades are densely distributed, the casting space is narrow, and the inner cavity cannot be directly shelled and coated. When using ceramic core molding, the positioning of the ceramic core is difficult, and problems such as ceramic core misalignment and core breakage often occur. The dimensional accuracy is poor, and the tolerance of blade profile and wall thickness is difficult to guarantee. The scrap rate of castings is high, the production cost is high, and it is difficult to achieve mass production and stable delivery.

[0004] To address these issues, this application proposes a casting system and molding method for complex-structure starting turbine castings. Summary of the Invention

[0005] To address the existing problems, this invention provides a casting system and molding method for complex structure starting turbine castings, which can effectively solve the problems mentioned in the background art.

[0006] To solve the above problems, the present invention adopts the following technical solution: A gating system for a complex-structure starting turbine casting includes a pouring cup, a feeding riser, and a starting turbine wax model. The starting turbine wax model contains an annular blade core, and the blade core has several blade cavities evenly distributed around its circumference. Blade inner cores are inserted into the blade cavities. A stop is provided between the pouring cup and the feeding riser, and the lower end of the feeding riser is connected to the top surface of the starting turbine wax model.

[0007] Preferably, the annular inner wall of the blade's main ceramic core is provided with three positioning grooves.

[0008] Preferably, the ceramic core inside the blade cavity is provided with a positioning notch.

[0009] Preferably, a supporting ceramic rod is welded to the lower end of the turbine disk of the starting turbine wax mold, and the bottom surface of the supporting ceramic rod in the height direction is kept flush with the bottom of the ceramic core of the blade cavity.

[0010] This invention further provides a method for investment casting of a complex-structure starting turbine casting, comprising the following steps: S1. Preparation of wax mold and ceramic core mold: According to the starting turbine casting drawing, metal molds are made, and wax molds, blade inner cavity ceramic core molds and blade main ceramic core molds are made respectively. S1. Ceramic core manufacturing: Press the inner ceramic core of the blade according to the manufactured inner ceramic core mold, and press the main ceramic core of the blade according to the main ceramic core mold. S1. Pressing wax molds: Medium-temperature filling wax is used to press wax molds. The wax temperature is controlled at 65-75℃, the injection pressure is 5-8 bar, and the wax flow rate is 80-120 cc / s. The starting turbine wax mold and the corresponding gating and riser system wax mold are pressed separately. The main ceramic core of the blade is placed in the designated position in the mold cavity before the wax mold is pressed. The inner cavity ceramic core of the blade is inserted into the pre-made wax mold cavity after the wax mold is pressed. S2, Wax Model Assembly Tree: The gating and riser system is sequentially welded into the starting turbine wax model using an electrothermal welding knife to form a wax model module for a complex starting turbine structure; S3. Shell making: An 8-10mm thick silica sol precision casting ceramic shell is coated on the surface of the starting turbine wax mold assembly. The shell surface layer is made of zircon powder, and the shell reinforcement layer is made of fused silica. This shell configuration has a small expansion rate and good matching with the ceramic core. It can ensure that the shell has good surface quality and sufficient shell strength, and also ensure that the shell has good collapsibility after casting. The wax is removed by steam dewaxing kettle at a temperature of not less than 180℃ and a pressure of 8-10 bar to obtain the shell cavity to be cast. S4. Molding shell insulation: The molding shell is covered with insulation cotton. The insulation cotton in the gating and riser system area of ​​the molding shell is 13mm thick, while the starting turbine casting body area is not covered with insulation cotton. S5. Shell firing: After the insulation cotton is wrapped, place the formed ceramic filter screen at the stop below the pouring cup of the shell, and then put the shell into a special shell firing furnace to preheat it to the appropriate pouring temperature. S6. Melting and casting: After the master alloy ingot is melted into molten metal in a three-chamber vacuum melting furnace, it is poured into the preheated starting turbine shell cavity. The molten metal is poured to the middle position of the stop below the pouring cup to ensure effective feeding of the starting turbine casting body. S7. Post-processing: After the cast mold solidifies and cools, the shell is removed, the excess gating and riser system is cut off, and after subsequent finishing, grinding, sandblasting and heat treatment, a complex structure starting turbine casting is obtained.

[0011] Compared with the prior art, the beneficial effects of the present invention are as follows: by combining the integral blade main ceramic core and the insert-type blade inner cavity ceramic core design and the fused silica shell manufacturing process, the problem of difficult positioning of the complex blade inner cavity ceramic core is effectively solved, the risk of core deviation and core breakage is significantly reduced, the matching between the shell and the ceramic core is improved, and the dimensional accuracy of the casting is guaranteed; metallurgical defects such as porosity, cracks and slag inclusions are reduced, the casting qualification rate is improved, and stable batch production is achieved. The casting qualification rate can reach more than 80%, which is suitable for the engineering application of high-temperature alloy complex structure starting turbine castings. Attached Figure Description

[0012] Figure 1 This is a schematic diagram of the starting turbine casting structure; Figure 2 for Figure 1 A side view; Figure 3 for Figure 2 Schematic diagram of the AA section; Figure 4 This is a schematic diagram of the ceramic core structure inside the blade cavity in this invention; Figure 5 This is a schematic diagram of the main ceramic core structure of the blade in this invention; Figure 6 This is a schematic diagram of the starting turbine wax model structure in this invention; Figure 7 for Figure 6 A plan view; Figure 8 for Figure 7 BB cross-sectional diagram; Figure 9 This is a schematic diagram of the casting system of the present invention.

[0013] In the diagram: 100, starting turbine; 101, turbine disc; 102, mounting plate; 103, small blade; 1, pouring cup; 2, feeding riser; 3, starting turbine wax model; 4, blade main ceramic core; 5, positioning groove; 6, blade inner cavity ceramic core; 7, positioning notch; 8, stop; 9, supporting ceramic rod. Detailed Implementation

[0014] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0015] like Figure 1-3The diagram shows a structural schematic of a complex starting turbine casting for a certain type of aerospace rocket engine. The starting turbine 100 includes a turbine disk 101, a mounting plate 102, and several small blades 103 evenly distributed around the circumference. There are fifty-six small blades 103 in the starting turbine 100. The small blades 103 are hollow blind hole structures, and the turbine disk 101 and the mounting plate 102 are connected by a ring of small blades 103 evenly distributed around the circumference.

[0016] Specifically, this embodiment provides a gating system for a complex-structure starting turbine casting, such as... Figure 4-9 As shown, the gating system includes a pouring cup 1, a feeding riser 2, and a starting turbine wax mold 3. The starting turbine wax mold 3 contains an annular blade core 4, which forms the overall shape and channel contour dimensions of fifty-six blades evenly distributed around the circumference. The annular inner wall of the blade core 4 has three positioning grooves 5 for positioning the blade core 4. Fifty-six blade insertion cavities are evenly distributed around the circumference of the blade core 4. Blade inner cavity cores 6 are inserted into these blade insertion cavities. Each blade inner cavity core 6 is a single core, used to form the inner cavity of a small blade on the starting turbine wax mold 3. One blade inner cavity core 6 is inserted at the position of one small blade. The blade inner cavity cores 6 are evenly distributed around the circumference, and their dimensions partially match those of the small blade cavities. Positioning notches are also provided on the blade inner cavity cores 6. 7. The positioning notch 7 is used for positioning the ceramic core. After the starting turbine wax mold 3 is manufactured on the basis of the main ceramic core 4 of the blade, the pouring cup 1 and the feeding riser 2 are welded onto the starting turbine wax mold 3 to form the starting turbine wax mold 3 module. A stop 8 is provided between the pouring cup 1 and the feeding riser 2. The upper end of the stop 8 is connected to the lower end of the pouring cup 1, the upper end of the feeding riser 2 is connected to the lower end of the stop 8, and the lower end of the feeding riser 2 is connected to the upper end face of the starting turbine wax mold 3. The pouring cup 1 is used for the molten steel to flow in during pouring. A supporting ceramic rod 9 is welded to the lower end of the turbine disk of the starting turbine wax mold 3. The bottom surface of the supporting ceramic rod 9 in the height direction is kept flush with the bottom of the ceramic core 6 of the blade cavity. The supporting ceramic rod 9 is used to resist the impact of the molten metal on the bottom shell of the turbine disk during the melting and pouring process and to ensure the dimensional stability of the shell.

[0017] Based on the aforementioned wax pattern module of a complex structure starting turbine casting for a certain type of aerospace rocket engine, this invention further provides a method for investment casting of a complex structure starting turbine casting, comprising the following steps: Preparation of wax mold and ceramic core mold: Metal molds are made according to the starting turbine casting drawings, and wax molds, blade inner cavity ceramic core 6 molds and blade main ceramic core 4 molds are made respectively. Ceramic core manufacturing: The inner ceramic core 6 of the blade is pressed according to the mold of the manufactured inner ceramic core 6 of the blade, and the main ceramic core 4 of the blade is pressed according to the mold of the main ceramic core 4 of the blade. Each of this type of starting turbine products requires a total of one main ceramic core 4 of the blade and a total of fifty-six inner ceramic cores 6 of the blade. Pressing the wax mold: The wax mold is pressed using medium-temperature filling wax material. The wax material temperature is controlled at 65-75℃, the injection pressure is 5-8 bar, and the wax flow rate is 80-120 cc / s. The starting turbine wax mold 3 and the corresponding gating and riser system wax mold are pressed separately. The blade main ceramic core 4 is placed in the designated position in the mold cavity before the wax mold is pressed. The blade inner cavity ceramic core 6 is inserted into the pre-made wax mold cavity after the wax mold is pressed. They are combined to form the complete starting turbine wax mold 3.

[0018] Wax mold assembly: The gating and riser system is sequentially welded onto the starting turbine wax mold 3 using an electrothermal welding knife, forming a structure as shown below. Figure 6 The wax mold module of the complex structure starting turbine product shown; Shell making: An 8-10mm thick silica sol precision casting ceramic shell is coated on the surface of the starting turbine wax mold assembly. The shell surface layer is made of zircon powder, and the shell reinforcement layer is made of fused silica. This shell configuration has a very small expansion rate and good matching with the ceramic core. It can ensure that the shell has good surface quality and sufficient shell strength, and also ensure that the shell has good collapsibility after casting. The wax is removed by steam dewaxing kettle at a temperature of not less than 180℃ and a pressure of 8-10 bar, thereby obtaining the shell cavity to be cast. Molding shell insulation: The molding shell is covered with insulation cotton. The insulation cotton covering the gating and riser system area of ​​the molding shell is 13mm thick, while the starting turbine casting body area is not covered with insulation cotton. Shell firing: Place a molded foam ceramic filter screen at the stop 8 below the mold pouring cup 1 after the insulation cotton is wrapped, and then put the mold into a special shell firing furnace to preheat to the appropriate pouring temperature. Melting and casting: After the master alloy ingot is melted into molten metal in a three-chamber vacuum melting furnace, it is poured into the preheated starting turbine shell cavity. The molten metal is poured to the middle position of the stop 8 below the pouring cup 1 to ensure effective feeding of the starting turbine casting body. Post-processing: After the cast metal mold solidifies and cools, the shell is removed, the excess gating and riser system is cut off, and then the complex structure starting turbine casting is obtained through subsequent finishing, grinding, sandblasting, heat treatment and other operations.

[0019] The working principle of this invention is as follows: a special starting turbine wax mold 3 and a ceramic core mold are designed. The ceramic core mold is used to manufacture a special blade ceramic core to form the blade outline and cavity structure of the starting turbine wax mold 3. The specific wax model is produced by combining ceramic cores. The gating and riser system is then welded onto the wax model assembly in sequence. By designing a shell system with zircon powder on the surface and reinforced fused silica material, and using a molding master alloy ingot and a three-chamber vacuum melting furnace for melting and casting, a qualified starting turbine casting with a complex structure is finally produced.

[0020] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0021] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A gating system for a complex-structure starting turbine casting, the gating system comprising a pouring cup, a feeding riser, and a starting turbine wax model, characterized in that, The starting turbine wax mold has an annular blade core, and the blade core has several blade cavities evenly distributed around its circumference. Blade inner cores are inserted into the blade cavities. A stop is provided between the pouring cup and the feeding riser. The lower end of the feeding riser is connected to the top surface of the starting turbine wax mold.

2. The casting system for a complex structure starting turbine casting according to claim 1, characterized in that, The blade's main ceramic core has a positioning groove on its annular inner wall.

3. The casting system for a complex structure starting turbine casting according to claim 1, characterized in that, The inner ceramic core of the blade is provided with a positioning notch.

4. The casting system for a complex structure starting turbine casting according to claim 1, characterized in that, The turbine disk of the starting turbine wax model is welded with a supporting ceramic rod at the lower end, and the bottom surface of the supporting ceramic rod in the height direction is kept flush with the bottom of the ceramic core of the blade cavity.

5. A method for investment casting of a complex-structure starting turbine casting, characterized in that, Includes the following steps: S1. Preparation of wax mold and ceramic core mold: According to the starting turbine casting drawing, metal molds are made, and wax molds, blade inner cavity ceramic core molds and blade main ceramic core molds are made respectively. S1. Ceramic core manufacturing: Press the inner ceramic core of the blade according to the manufactured inner ceramic core mold, and press the main ceramic core of the blade according to the main ceramic core mold. S1. Pressing wax molds: Medium-temperature filling wax is used to press wax molds. The wax temperature is controlled at 65-75℃, the injection pressure is 5-8 bar, and the wax flow rate is 80-120 cc / s. The starting turbine wax mold and the corresponding gating and riser system wax mold are pressed separately. The main ceramic core of the blade is placed in the designated position in the mold cavity before the wax mold is pressed. The inner cavity ceramic core of the blade is inserted into the pre-made wax mold cavity after the wax mold is pressed. S2, Wax Model Assembly Tree: The gating and riser system is sequentially welded into the starting turbine wax model using an electrothermal welding knife to form a wax model module for a complex starting turbine structure; S3. Shell making: Apply an 8-10mm thick silica sol precision casting ceramic shell to the surface of the starting turbine wax mold module. The shell surface layer is made of zircon powder material, and the shell reinforcement layer is made of fused silica material. The wax is removed by steam dewaxing kettle at a temperature of not less than 180℃ and a pressure of 8-10 bar to obtain the shell cavity to be poured. S4. Molding shell insulation: The molding shell is covered with insulation cotton. The insulation cotton in the gating and riser system area of ​​the molding shell is 13mm thick, while the starting turbine casting body area is not covered with insulation cotton. S5. Shell firing: After the insulation cotton is wrapped, place the formed ceramic filter screen at the stop below the pouring cup of the shell, and then put the shell into a special shell firing furnace to preheat it to the appropriate pouring temperature. S6. Melting and casting: After the master alloy ingot is melted into molten metal in a three-chamber vacuum melting furnace, it is poured into the preheated starting turbine shell cavity. The molten metal is poured to the middle position of the stop below the pouring cup to ensure effective feeding of the starting turbine casting body. S7. Post-processing: After the cast mold solidifies and cools, the shell is removed, the excess gating and riser system is cut off, and after subsequent finishing, grinding, sandblasting and heat treatment, a complex structure starting turbine casting is obtained.

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