Casting method of gas turbine cover plate

Abstract

The invention relates to the technical field of casting, in particular to a gas turbine cover plate casting method which comprises the steps that a sand core for gas turbine cover plate casting is manufactured, and the sand core is manufactured in a sand-prone area through 3D printing; coating the surface of the manufactured sand core with an anti-burnt-on sand coating; and the sand core coated with the anti-burnt-on sand coating is assembled into a mold in a combined mode, and molten metal pouring is executed. The sand core in the easy-to-burn-on sand area is manufactured through the 3D printing technology, the surface of the sand core is coated with the anti-burn-on sand coating, and the scheme that the chromium ore sand is used for manufacturing the core and the upper half cylinder and the lower half cylinder are combined is combined, so that the size precision and quality of the casting are ensured.

Description

Technical Field

[0001] The present application relates to the field of casting technology, and in particular to a casting method for a gas turbine cover plate. Background Art

[0002] As a technologically advanced and complex power mechanical system, the gas turbine is a prime example of a high-tech-intensive product. It embodies the comprehensive development of multidisciplinary theory and engineering, and stands at the forefront of technological progress in the 21st century. The development of a gas turbine industry that integrates new technologies, new materials, and new processes has become a key indicator of a country's high-tech level and scientific and technological strength, and its strategic significance cannot be underestimated.

[0003] In recent years, with the rise of clean energy and increased environmental awareness, heavy-duty gas turbines have gradually replaced traditional coal-fired power generation and become an emerging power generation technology. Globally, continuous technological advancements have led to the introduction of gas turbine products with improved performance and higher efficiency.

[0004] Developing an efficient gas turbine cover plate casting technology is crucial for increasing the localization of gas turbine generator sets in my country and reducing production costs. This will significantly enhance the market competitiveness of Chinese power generation equipment manufacturers, enabling them to compete with their international counterparts. However, the current gas turbine cover plate casting process suffers from issues such as sand sticking and deformation, resulting in precision that does not meet design requirements. Summary of the Invention

[0005] Based on this, it is necessary to provide a casting method for a gas turbine cover plate to address the problem that during the casting process of the gas turbine cover plate, the accuracy does not meet the design requirements due to sand sticking, deformation, etc.

[0006] A method for casting a gas turbine cover plate, comprising:

[0007] Make sand cores for gas turbine cover casting, and use 3D printing to make sand cores in areas prone to sand adhesion;

[0008] Applying anti-sand sticking coating on the surface of the manufactured sand core;

[0009] The sand core assembly coated with anti-sticking coating is assembled into the mold and the molten metal is poured.

[0010] Preferably, the air duct of the gas turbine cover plate is cored with chromium ore sand.

[0011] Preferably, the scale ratio is determined according to the material properties of the casting;

[0012] According to the shrinkage trend of different parts of the casting during the cooling process, the corresponding positions of the mold are measured.

[0013] Preferably, the air duct of the gas turbine cover plate has the same taper value on both the inner and outer sides.

[0014] Preferably, the casting of the gas turbine cover plate is divided into two parts, an upper part and an lower part, for molding.

[0015] Preferably, the parting surface is selected above the outer ring flange.

[0016] Preferably, the circular hole structure at the junction of the rib plate and the flange below the gas turbine cover plate is formed by using a 3D printed chromium ore sand core.

[0017] Preferably, after the gas turbine cover plate casting is cast, the method further comprises:

[0018] Pre-cleaning is performed, wherein the pre-cleaning includes: unpacking, annealing, cutting risers, normalizing and tempering, gouging / oxygen melting, welding anti-deformation reinforcement, splitting into two halves, eliminating splitting stress, removing reinforcement at room temperature, and marking verification.

[0019] Preferably, during annealing, the temperature is slowly raised to 1000-1100°C and kept at this temperature for at least 8 hours, then slowly cooled to 400-600°C and kept at this temperature for at least 4 hours, and the casting temperature is at least 200°C when cutting the riser.

[0020] The casting method of the gas turbine cover plate provided in this application can solve the problems of sand sticking and casting deformation, ensure that the dimensional accuracy of the casting meets the design requirements, and at the same time reduce manufacturing costs and improve production efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Figure 1 1 is a schematic flow chart of a method for casting a gas turbine cover plate provided in an embodiment of the present application;

[0022] Figure 2 This is a three-dimensional schematic diagram of the cover plate provided in an embodiment of the present application;

[0023] Figure 3 This is a schematic diagram of the chromium ore sand core inlay provided in an embodiment of the present application;

[0024] Figure 4 This is a schematic diagram of the airway chromium ore sand core provided in the embodiment of the present application. DETAILED DESCRIPTION

[0025] To facilitate understanding of the present application, a more comprehensive description of the present application will be provided below with reference to the accompanying drawings. The accompanying drawings illustrate preferred embodiments of the present application. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and comprehensive understanding of the disclosure of the present application.

[0026] It should be noted that when an element is referred to as being "disposed on" another element, it may be directly on the other element or there may be an element centered thereon. When an element is referred to as being "connected to" another element, it may be directly connected to the other element or there may be an element centered thereon. The terms "vertical," "horizontal," "left," "right," "top," "bottom," "bottom end," "top end," and similar expressions used herein are for illustrative purposes only and do not represent the only implementation methods.

[0027] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application pertains. The terms used herein in the specification of this application are intended only to describe specific embodiments and are not intended to limit this application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0028] The following describes the casting method of the gas turbine cover plate provided by the present application in conjunction with specific embodiments. Figure 1 , Figure 1 : is a flow chart of a method for casting a gas turbine cover plate provided in an embodiment of the present application, comprising the following steps:

[0029] S101: Make sand cores for gas turbine cover casting, and use 3D printing to make sand cores in areas prone to sand adhesion.

[0030] First, computer-aided design (CAD) was used based on the cover plate's design requirements. For example, a 3D model of the casting was completed. For complex structural parts, particularly those prone to sand sticking, such as the circular hole at the junction of the rib and flange below the cover plate, chromium ore sand was used for 3D printing core production. The specific steps are as follows:

[0031] Use software to precisely map the overall structure and internal details of the cover. Particularly, areas prone to sand adhesion require detailed annotation of their geometry and dimensions. Furthermore, the 3D model can be converted into a data format suitable for 3D printing. Ensure data accuracy to avoid errors during subsequent processing.

[0032] Furthermore, a high-precision 3D printer was used, using chromium ore sand as the printing material. Chromium ore sand has high refractoriness, strong sintering resistance, and good thermal conductivity, effectively reducing sand sticking to castings. Its excellent thermal conductivity also mitigates cold shut defects in thin-walled air ducts. Furthermore, a 3D-printed chromium ore sand core was used to form the circular hole structure at the junction of the rib plate and flange below the cover plate.

[0033] Furthermore, chromium ore cores are used for the gas ducts in the gas turbine cover. Specifically, the cores are designed based on the specific shape and size of the ducts, ensuring they perfectly match the duct's internal structure. Specialized core-making equipment is used to transform the chromium ore into the desired cores.

[0034] S102: coating an anti-sand sticking coating on the surface of the manufactured sand core.

[0035] To further reduce sand sticking, a layer of specialized, high-temperature, anti-sand coating is evenly applied to the surface of the assembled mold (including the 3D-printed chrome ore sand core and other parts). This process involves selecting an anti-sand coating with excellent adhesion and fire resistance to ensure stability at high temperatures and prevent adverse reactions with the molten metal. After coating, the core can be left to dry naturally in a well-ventilated environment, or oven-dried according to the coating instructions. Ensure the coating is fully cured, forming a protective film.

[0036] S103: Assembling the sand core assembly coated with the anti-sand-sticking coating into a mold, and performing molten metal pouring.

[0037] The 3D-printed sand core is combined with other conventional sand cores and assembled into the mold. The assembly process requires precise positioning and fixation of all components to prevent displacement during the pouring process. Molten metal is then poured into the mold using a pre-configured pouring system. During assembly, all sand cores are preassembled according to design requirements, ensuring a tight fit and seamless fit between components.

[0038] Furthermore, during casting, the volume shrinkage during cooling and solidification is considered to determine the scale ratio. The shrinkage trend of different parts of the casting during cooling can also be considered to design a gradual amount of volume for the corresponding positions of the mold. Specific steps may include the following:

[0039] Shrinkage trend analysis: Based on historical product data and experience with the same material, the shrinkage trend of the casting during cooling is analyzed. Particularly, the shrinkage behavior of uneven thickness areas requires special attention. Based on the analysis results, a gradual tapering design is implemented for different parts of the mold. For example, the tapering is designed to be the same on the inside and outside of the four central airways, with tapering increasing towards the outside and decreasing towards the inside as the airways move outward. This approach helps correct deformation during shrinkage and ensures dimensional stability.

[0040] Furthermore, during casting, the gas turbine cover plate casting can be divided into two parts, upper and lower, for molding. The parting surface can be selected above the outer ring flange, which is convenient for riser placement and cutting and can ensure the integrity and precision of the casting.

[0041] The casting is divided into upper and lower chambers. The lower chamber is responsible for forming the bottom flange of the casting and laying the gating system. The upper chamber is composed of four main parts: an inner ring of 3D-printed cores forming the internal structure and internal riser, and an outer ring of cores forming the outer wall of the casting. During casting, the upper and lower chambers are pre-assembled according to the design requirements and secured with locating pins, clamps, and other tools to ensure that they do not shift or loosen during the entire pouring process.

[0042] Furthermore, after the casting is completed, the application also provides a series of optimized pre-cleaning steps, including unpacking, annealing, cutting the riser (casting temperature at least 200 ° C), normalizing and tempering, gouging / oxygen melting, welding anti-deformation reinforcement, splitting into two halves, eliminating splitting stress, removing the reinforcement at room temperature, and marking verification. Specifically,

[0043] Unpacking: Open the mold and take out the initially formed casting. Make sure that the casting will not be damaged during the operation.

[0044] Annealing: Slowly heat to 1000-1100°C and hold for at least 8 hours, then cool to 400-600°C at a rate not exceeding 70°C / h and hold for at least 4 hours. The purpose is to dissolve M23C6 carbides and prevent brittle fracture.

[0045] Cutting the riser: Ensure that the minimum temperature of the casting is kept above 200℃ before cutting the riser. This can avoid brittle fracture caused by low temperature.

[0046] Normalizing and tempering: Adjust the internal structure of the casting and enhance the material properties. Ensure that the casting has good mechanical properties in subsequent use.

[0047] Air gouging / oxygen fusion treatment: clean up surface defects of castings and ensure that the surface finish meets the requirements.

[0048] Welding anti-deformation reinforcement: Welding reinforcement before splitting to prevent deformation. Ensure that the casting will not undergo uncontrollable deformation during the splitting process.

[0049] Split in half: Split the casting as needed. Ensure that the casting is not damaged during the splitting process.

[0050] Eliminate splitting stress: Eliminate the stress caused by splitting through heat treatment and other means to ensure that the casting will not crack due to stress concentration during subsequent use.

[0051] Remove the anti-deformation reinforcement at room temperature: After the casting has cooled to room temperature, remove the anti-deformation reinforcement to ensure that the surface finish of the casting is not affected.

[0052] Marking verification: Finally check whether the dimensional accuracy meets the design requirements. Ensure that the casting meets all technical indicators.

[0053] The following is a specific implementation method, please refer to Figure 2-Figure 4 , the casting scheme of the gas turbine cover plate provided in the embodiment of the present application is introduced. Figure 2 As shown, Figure 2 This is a three-dimensional schematic diagram of the cover plate provided by the embodiment of the present application. Among them, 1 is a schematic diagram of the structure of the gas turbine cover plate, 2 is the airway structure formed by the airway core, 3 is the inside and outside of the airway, and 4 is the circular hole area. During casting, the upper and lower half-cylinder molding scheme is selected to facilitate the placement and cutting of the subsequent riser. According to the material characteristics, the overall appropriate scale is selected. According to the shrinkage deformation trend in different directions, the different parts are gradually adjusted. The inner and outer sides of the four middle airways are designed with the same adjustment. The adjustment increases from the middle to the outer airways, and the adjustment decreases from the inside to compensate for the shrinkage deformation of the casting during solidification, ensuring that the processing allowance is uniform and controllable.

[0054] like Figure 3-Figure 4 As shown, Figure 2 This is a three-dimensional schematic diagram of the cover provided in the embodiment of this application Figure 3 This is a schematic diagram of the chromium ore sand core inlay provided in the embodiment of the present application. Figure 4 This is a schematic diagram of the airway chromium ore core provided in the embodiment of the present application. Among them, the casting as a whole adopts a molding scheme that combines 3D printing and chromium ore core making. The main body is divided into upper and lower box moldings. The parting surface is selected above the outer ring flange. The lower box 5 is mainly used to form the bottom flange of the casting and lay the pouring system. The upper box core is mainly composed of four parts. The inner ring 3D printed core 6 forms the internal structure of the casting and the inner cavity hidden riser, and the outer ring core forms the outer wall of the casting. Figure 4 As shown, the circular hole 4 at the intersection of the rib and flange below the cover plate is prone to sand adhesion. Therefore, a 3D-printed chrome sand core 8 is used to form this area. Chrome sand has excellent thermal conductivity and strong sintering resistance, effectively reducing sand adhesion in this area. An airway core is designed between the inner and outer ring cores to form the airway structure 2. Because the airway is narrow and prone to sand adhesion, the airway is formed using a chrome sand core 10. Using chrome sand cores ensures airway quality. The inner ring core also has a core head 7, which is matched with the core head 9 to ensure dimensional accuracy.

[0055] The castings are made of ZG13Cr13Ni1, a martensitic heat-resistant steel composed primarily of 13% Cr and 1% Ni. During casting, the two halves are joined into a single unit. Based on historical product structure and production experience with the same material, shrinkage and deformation are common after separation. Compared to traditional 9% Cr heat-resistant steels, 13% Cr materials have more alloying elements, resulting in more pronounced solid solution strengthening, making them more susceptible to cracking during production. Therefore, the traditional pre-cleaning process (unpacking → preheating → riser cutting → normalizing and tempering → gouging / oxygen fusion process information → splitting into two halves → marking and verification) needs to be changed to: unpacking → annealing → riser cutting → normalizing and tempering → gouging / oxygen fusion process information → welding anti-deformation tie bars → splitting into two halves → stress relief → tie bar removal at room temperature → marking and verification.

[0056] After pouring, both the faster-cooling and slower-cooling areas of the casting will produce a severely distorted martensite structure. Some M23C6 carbides may also precipitate along the grain boundaries, making them extremely susceptible to brittle fracture. Traditional preheating processes, set below 650°C, are unable to dissolve the M23C6 carbides. Therefore, the holding temperature must be raised to above 1000°C to melt the precipitated carbides back into the matrix. The annealing process involves heating to 1000-1100°C at a heating rate of <70°C / h and holding for at least 8 hours. The casting is then cooled to 400-600°C at a cooling rate of <70°C / h and held for 4 hours. The casting can then be removed from the furnace and the riser cut. During the cutting process, the minimum temperature of the casting should be controlled above 200°C.

[0057] To address shrinkage caused by the combined effects of casting structure and material properties, anti-deformation reinforcement should be welded on both the upper and lower diameter sides of the single-plate casting before cylinder separation to resist the stress of casting shrinkage. After the casting is split, it should undergo another stress relief heat treatment to eliminate the stress caused by gouging / oxygen melting and the stress of splitting the casting.

[0058] This application uses 3D printing technology to create sand cores that are prone to sand sticking, and applies an anti-sand sticking coating on the surface of the sand core. Combining the chromium ore sand core making process and the upper and lower half-cylinder molding strategy, it effectively overcomes the problems of sand sticking and deformation during the casting of gas turbine cover plates. In response to the problem of shrinkage deformation of castings, this application also designs improved pre-cleaning and heat treatment processes to prevent cracking and deformation. It significantly improves the dimensional accuracy and surface quality of castings, while greatly reducing production costs and enhancing production efficiency, demonstrating its significant application value and huge market potential in industrial production.

[0059] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0060] The above-described embodiments merely represent several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art could make various modifications and improvements without departing from the spirit of the present application, all of which fall within the scope of protection of the present application. Therefore, the scope of protection of the present patent application shall be determined by the appended claims.

Claims

1. A method for casting a gas turbine cover plate, characterized in that: include: Make sand cores for gas turbine cover casting, and use 3D printing to make sand cores in areas prone to sand adhesion; Applying anti-sand sticking coating on the surface of the manufactured sand core; The sand core assembly coated with anti-sticking coating is assembled into the mold and the molten metal is poured.

2. The method for casting a gas turbine cover plate according to claim 1, wherein: The gas channel of the gas turbine cover plate is cored with chromium ore sand.

3. The method for casting a gas turbine cover plate according to claim 1, wherein: include: Determine the scale ratio according to the material properties of the casting; According to the shrinkage trend of different parts of the casting during the cooling process, the corresponding positions of the mold are measured.

4. The method for casting a gas turbine cover plate according to claim 1, wherein: include: The air duct of the gas turbine cover plate has the same taping value on both the inner and outer sides.

5. The method for casting a gas turbine cover plate according to claim 2, wherein: The invention is characterized by comprising: The gas turbine cover casting is divided into two parts, an upper part and an lower part, for molding.

6. The method for casting a gas turbine cover plate according to claim 5, characterized in that: The parting surface is selected above the outer ring flange.

7. The method for casting a gas turbine cover plate according to claim 5, wherein: The circular hole structure at the junction of the rib plate and the flange below the gas turbine cover plate is formed by using a 3D printed chromium ore sand core.

8. The method for casting a gas turbine cover plate according to any one of claims 1 to 7, characterized in that: After the gas turbine cover plate casting is completed, the method further comprises: Pre-cleaning is performed, wherein the pre-cleaning includes: unpacking, annealing, cutting risers, normalizing and tempering, gouging / oxygen melting, welding anti-deformation reinforcement, splitting into two halves, eliminating splitting stress, removing reinforcement at room temperature, and marking verification.

9. The method for casting a gas turbine cover plate according to claim 8, characterized in that: During annealing, slowly heat up to 1000-1100℃ and keep warm for at least 8h, then slowly cool to 400-600℃ and keep warm for at least 4h. The casting temperature should be at least 200℃ when cutting the riser.

Images