Dimensional precision control method for heat-resistant stainless steel double-ring hollow gas turbine casing casting

Abstract

The invention provides a size precision control method for a heat-resistant stainless steel double-ring hollow gas turbine casing casting, and particularly relates to the field of gas turbine casing casting. The integrally-cast stainless steel double-ring hollow gas turbine casing is designed by combining a 3D printing heterogeneous composite core and a 3D heterogeneous composite core; according to the 3D printing heterogeneous composite core, zircon sand is adopted for the portion, with the high requirement for refractoriness, in a casing supporting plate, chromite sand is adopted for the portions, with the certain requirement for refractoriness, of an upper flange, a lower flange, an outer ring corner and an inner cavity corner, 3D printing resin sand is adopted for the other portions with the low requirement for refractoriness, and the design of the 3D printing heterogeneous composite core is achieved. According to the 3D printing heterogeneous composite core, when a 3D printing composite core process is designed, topological gridding structure design is adopted, a binding agent is sprayed into a sand layer on the surface of a sand mold and a gridding framework, and the binding agent is not sprayed into a space gridding of the sand mold. And high-dimensional precision control casting of the stainless steel double-ring hollow gas turbine casing casting can be realized.

Description

Technical Field

[0001] The invention relates to the field of gas turbine casing casting, and in particular provides a method for controlling the dimensional accuracy of a heat-resistant stainless steel double-ring hollow gas turbine casing casting. Background Art

[0002] Gas turbines are mainly used in the fields of ship power and energy. They are important strategic equipment for realizing national defense modernization and ensuring national security, and are also important energy equipment that is efficient and environmentally friendly. The casing is an important supporting component of the gas turbine. It connects various components of the gas turbine, the turbine combustion chamber inside, and the exhaust pipe, oil circuit, cooling pipe and other components outside. It is usually made of stainless steel.

[0003] With the continuous development of gas turbine technology, the large-scale and increasingly complex structural design of casing components has become increasingly difficult to achieve through traditional forging and welding processes. Casting has become the preferred process for manufacturing large double-ring hollow gas turbine casings because it can realize the integrated overall forming of complex structures, has good reliability and low cost. Due to the large size, uneven wall thickness and complex shape of large double-ring hollow gas turbine casing castings, conventional casting and post-processing production methods are difficult to ensure the performance, dimensional accuracy and internal and external quality of casing castings. Especially for the dimensional accuracy control of double-ring hollow gas turbine casing castings, due to the large area of ​​non-machined surfaces of the castings, the dimensional accuracy requirements are extremely high; large thin-walled double-ring hollow casing castings are difficult to fill, and the casting structure has multiple slots and multiple stages, which makes sequential solidification difficult. Improper casting process will produce a large number of shrinkage holes and other defects, which are easy to cause casting size deviation after repair; large thin-walled double-ring hollow castings have residual stress after molding, and improper post-processing methods are easy to cause casting deformation. Therefore, it is extremely important to control the dimensional accuracy of large stainless steel double-ring hollow gas turbine casing castings. The problem of dimensional accuracy control has become a difficult problem that must be faced in the manufacturing of stainless steel double-ring hollow gas turbine casing castings. Summary of the invention

[0004] The present invention provides a method for controlling the dimensional accuracy of a heat-resistant stainless steel double-ring hollow gas turbine casing casting. Through the stainless steel double-ring hollow gas turbine casing casting process design and production process control method, high dimensional accuracy controlled casting of the casing casting is achieved, and dimensional over-tolerance and deformation defects of the casting are avoided, thereby obtaining a stainless steel double-ring hollow gas turbine casing casting whose quality meets technical requirements.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] A method for controlling the dimensional accuracy of heat-resistant stainless steel double-ring hollow gas turbine casing castings, wherein the integrally cast stainless steel double-ring hollow gas turbine casing adopts a combination design of 3D printed heterogeneous composite cores and 3D heterogeneous composite cores;

[0007] The 3D printed heterogeneous composite core adopts zircon sand for the parts with higher refractoriness requirements inside the casing support plate, chromite sand for the parts with certain refractoriness requirements such as the upper flange, the lower flange, the outer ring corner, and the inner cavity corner, and 3D printed resin sand is adopted for the remaining parts with lower refractoriness requirements, so as to realize the design of 3D printed heterogeneous composite core;

[0008] The 3D printed heterogeneous composite core adopts a topological grid structure design during the 3D printed composite core process design, so that the sand layer on the surface of the sand mold and the grid skeleton are sprayed with adhesive, and the inside of the sand mold space grid is not sprayed with adhesive.

[0009] Furthermore, the stainless steel is one of: ZG07Cr20Ni10G, ZG1Cr17Ni3, and ZG1Cr11Ni2WMoV.

[0010] Furthermore, the double-ring hollow gas turbine casing structure is composed of an inner ring, an outer ring and a hollow rectifying support plate. The inner ring and the outer ring are both cylindrical in shape, and the wall thickness of the inner ring and the outer ring is 10mm-20mm. A test mounting seat is designed on the outer ring, and the hollow rectifying support plate is 5-15 hollow rectifying support plates, and the wall thickness of the hollow rectifying support plate variable curved surface is 5mm-8mm.

[0011] Furthermore, a hidden riser is added on the top of the hollow rectifier support plate, and an exhaust hole is provided at the thin wall.

[0012] Furthermore, a differentiated scaling design is adopted, with radial scaling ratios of 18‰-25‰, axial scaling ratios of 16‰-25‰, and circumferential scaling ratios of 15‰-25‰;

[0013] Furthermore, during the modeling process, special mortise and tenon type positioning connection methods are designed for the inner cavity support plate, upper flange, lower flange and outer ring corners, and inner cavity corners where zirconium sand and chromite sand cores are required, so as to combine the sand mold and sand core while ensuring high-precision positioning of the casting.

[0014] Furthermore, a special composite casting coating composite coating design is adopted, wherein the composite casting coating is a composite of a water-based zircon powder coating and an alcohol-based zircon powder coating specially developed for 3D printing sand molds; wherein the mass ratio of the water-based zircon powder coating is: zircon powder 71.4%, bentonite 1.1%, RZF 1.1%, resin 3.6%, water asphalt 1.4%, silica sol 3.6%, water 17.8%; the mass ratio of the alcohol-based zircon powder coating is: zircon powder 64.9%, bentonite 2.0%, deionized water 2.0%, modified aluminum magnesium silicate 2 .6%, clay 0.3%, aluminum oxide 0.1%, phenolic resin 0.6%, polyvinyl butyral (PVB) 0.3%, rosin 1.3%, industrial alcohol 19.5%, isopropyl alcohol 3.2%, heavy aromatic solvent oil 3.2%; the composite coating, in order to ensure the overall dimensional accuracy and surface finish of the casing casting, the sand mold is dipped in water-based zircon powder coating to achieve uniform coating of the dead corners of the casting; in order to improve the anti-sand adhesion of the support plate position, the support plate core is sprayed with alcohol-based zircon powder coating, and the overall coating thickness is 0.2-0.3mm.

[0015] The beneficial effects of the present invention are:

[0016] The dimensional accuracy control method of the heat-resistant stainless steel double-ring hollow gas turbine casing casting of the present invention is based on the 3D printing heterogeneous and heterogeneous composite core design, effectively utilizing the advantages of high dimensional accuracy and good forming effect of the 3D printing core, and at the same time successfully solving the problems of high gas emission, poor yield and collapse of the 3D printing core, and the inability of a single printed sand to meet different refractoriness requirements through the heterogeneous and heterogeneous design, thereby realizing high dimensional accuracy controlled casting of the stainless steel double-ring hollow gas turbine casing casting; the reasonable design of the pouring channel, riser, chiller and casting exhaust hole of the casting system reduces the amount of casting subsidy, reduces the gross weight, reduces the overall heat capacity of the casting, and effectively reduces the stainless steel double-ring hollow The shrinkage stress of gas turbine casing castings is used to achieve high dimensional accuracy controlled casting of stainless steel double-ring hollow gas turbine casing castings; considering the dimensional changes caused by liquid shrinkage, solidification shrinkage and solid shrinkage of molten steel, combined with the difference in wall thickness of stainless steel double-ring hollow casing castings and the shrinkage changes of axial structure, different scale ratios are set in radial, axial and circumferential directions to ensure the dimensional accuracy of castings; sand molds and sand cores are connected by mortise and tenon joints to improve the overall dimensional accuracy of the mold and ensure high dimensional accuracy controlled casting of casing castings; special composite coatings are applied on the surface of the mold to further ensure the surface quality of the castings and achieve high dimensional accuracy controlled casting of casing castings. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 Schematic diagram of the inner and outer ring structures.

[0018] Figure 2 Schematic diagram of the hollow rectifier support plate structure.

[0019] Figure 3 Schematic diagram of the inner cavity support plate structure.

[0020] Figure 4 Schematic diagram of the upper flange and lower flange structure.

[0021] Figure 5 Schematic diagram of the outer ring corner and inner cavity corner structure.

[0022] In the figure, 1. outer ring; 2. inner ring; 3. hollow rectifier support plate; 4. inner cavity support plate; 5. upper flange; 6. lower flange; 7. outer ring corner; 8. inner cavity corner. DETAILED DESCRIPTION

[0023] The present invention will be further described below in conjunction with the embodiments and the accompanying drawings, but is not limited thereto.

[0024] Example 1

[0025] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0026] In order to further understand the content of the present invention, the present invention is described in detail in conjunction with the accompanying drawings and embodiments.

[0027] Example 1

[0028] The structure of the stainless steel double-ring hollow gas turbine casing is an inner ring 2 and an outer ring 1, with 8 hollow rectifier support plates 3 in the middle. The maximum outline size of the stainless steel double-ring hollow gas turbine casing is Φ1600×350mm, the side wall thickness is 20mm, the hollow rectifier support plate 3 is 305mm long, 5mm thick, weighs about 700kg, and is made of ZG07Cr20Ni10G.

[0029] The present invention realizes high dimensional precision controlled casting of casing castings through the casting process design and production process control method of stainless steel double-ring hollow gas turbine casing, avoids dimensional over-tolerance and deformation defects of castings, and thus obtains stainless steel double-ring hollow gas turbine casing castings whose dimensional precision and quality meet technical requirements, as follows:

[0030] 1. Casting process design

[0031] (1) 3D printed heterogeneous composite core and 3D printed heterogeneous composite core design:

[0032] The 3D printed sand mold uses modified furan resin as a binder and toluenesulfonic acid as a curing agent. The sand mold is printed by inkjet layer by layer. It has the characteristics of high dimensional accuracy, nearly integrated core, small gas emission, and good yield, which is suitable for the production of large-sized, thin-walled, and complex stainless steel castings. At the same time, composite sand molds are used, and the core of the inner cavity support plate 4 is made of zirconium sand core, and the upper flange 5, lower flange 6, outer ring corner 7, and inner cavity corner 8 are made of chromite sand core. When designing the 3D printing composite core process, a topological grid structure design is adopted, so that the sand layer and grid skeleton on the surface of the sand mold are sprayed with binder to play a role in strength support. No binder is sprayed inside the sand mold space grid, which fundamentally reduces the source of gas emission from the sand mold, increases the permeability and collapse yield of the sand mold without losing strength, and improves the comprehensive performance of the sand mold.

[0033] (2) Reasonable design of pouring channel, riser, chiller and mold vent hole of casting system

[0034] A hidden riser is added to the top of the hollow rectifier support plate 3, and an exhaust hole is set at the thin wall to increase the exhaust channel of the printing core; an external cooling iron is added to reduce the subsidy between the inner ring 2 and the outer ring 1, and the gross weight is reduced by 300kg; the heat capacity is reduced to reduce the shrinkage stress.

[0035] (3) Differentiated scale design:

[0036] In combination with the differences in wall thickness of stainless steel casing castings and the shrinkage changes of the axial structure, different scale ratios are set in the radial, axial and circumferential directions to meet the requirements of casting dimensional accuracy. Combined with the specific casting structure dimensions, the radial scale ratio is 22‰, the axial scale ratio is 18‰, and the circumferential scale ratio is 20‰.

[0037] 2. Production process control

[0038] (1) Design of special sand mold and sand core positioning method

[0039] Taking advantage of the high dimensional accuracy of 3D printed sand molds, the 3D printed sand molds and sand cores at the positions of the inner cavity support plate 4, upper flange 5, lower flange 6, outer ring corner 7, and inner cavity corner 8 are connected by a mortise and tenon type positioning connection method, so as to combine the sand mold and sand core while ensuring high-precision positioning of the casting.

[0040] (2) Design of special composite casting coating

[0041] A specially developed water-based zircon powder coating and an alcohol-based zircon powder coating suitable for 3D printing sand molds are used in combination. The entire sand mold is dipped in water-based zircon powder coating to achieve uniform coating of the coating in the dead corners of the casting mold; in order to improve the anti-sand sticking property of the support plate of the casing, the support plate core is sprayed with alcohol-based zircon powder coating, wherein the mass ratio of the water-based zircon powder coating is: zircon powder 71.4%, bentonite 1.1%, RZF 1.1%, resin 3.6%, water asphalt 1.4%, silica sol 3.6%, water 17.8%; the mass ratio of the alcohol-based zircon powder coating is: zircon powder 64.9%, bentonite 2.0%, deionized water 2.0%, modified aluminum magnesium silicate 2.6%, clay 0.3%, aluminum oxide 0.1%, phenolic resin 0.6%, polyvinyl butyral (PVB) 0.3%, rosin 1.3%, industrial alcohol 19.5%, isopropyl alcohol 3.2%, heavy aromatic solvent oil 3.2%, and the overall coating thickness is 0.2mm.

[0042] Compared with conventional casting methods, the stainless steel double-ring hollow gas turbine casing casting cast by the casting method of the present invention has the dimensional accuracy of the flow channel part improved from ±1.5mm to ±0.8mm, the dimensional accuracy of the support plate part improved from ±1.0mm to ±0.5mm, and the overall concentricity improved from ±3.0mm to ±1.0mm.

[0043] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for controlling the dimensional accuracy of heat-resistant stainless steel double-ring hollow gas turbine casing castings, characterized in that: The integrally cast stainless steel double-ring hollow gas turbine casing adopts a combination design of 3D printed heterogeneous composite core and 3D heterogeneous composite core; The 3D printed heterogeneous composite core adopts zircon sand for the parts with higher refractoriness requirements inside the casing support plate, adopts chromite sand for the parts with certain refractoriness requirements such as the upper flange (5), the lower flange (6), the outer ring corner (7), and the inner cavity corner (8), and adopts 3D printed resin sand for the remaining parts with lower refractoriness requirements, thereby realizing the design of 3D printed heterogeneous composite core; The 3D printed heterogeneous composite core adopts a topological grid structure design during the 3D printed composite core process design, so that the sand layer on the surface of the sand mold and the grid skeleton are sprayed with adhesive, and the inside of the sand mold space grid is not sprayed with adhesive.

2. The method for controlling the dimensional accuracy of heat-resistant stainless steel double-ring hollow gas turbine casing casting according to claim 1 is characterized in that: The stainless steel is one of: ZG07Cr20Ni10G, ZG1Cr17Ni3, and ZG1Cr11Ni2WMoV.

3. The method for controlling the dimensional accuracy of heat-resistant stainless steel double-ring hollow gas turbine casing casting according to claim 1, characterized in that: The double-ring hollow gas turbine casing structure is composed of an inner ring (2), an outer ring (1) and a hollow rectifying support plate (3). The inner ring (2) and the outer ring (1) are both cylindrical in shape, and the wall thickness of the inner ring (2) and the outer ring (1) are both 10 mm to 20 mm. A test mounting seat is designed on the outer ring (1). The hollow rectifying support plate (3) is a plurality of 5 to 15 hollow rectifying support plates, and the wall thickness of the curved surface of the hollow rectifying support plate (3) is 5 mm to 8 mm.

4. The method for controlling the dimensional accuracy of heat-resistant stainless steel double-ring hollow gas turbine casing casting according to claim 1, characterized in that: A concealed riser is added to the top of the hollow rectifying support plate (3), and an exhaust hole is arranged at the thin wall.

5. The method for controlling the dimensional accuracy of heat-resistant stainless steel double-ring hollow gas turbine casing casting according to claim 1, characterized in that: A differentiated scaling design is adopted, with the radial scaling ratio being 18‰-25‰, the axial scaling ratio being 16‰-25‰, and the circumferential scaling ratio being 15‰-25‰.

6. The method for controlling the dimensional accuracy of heat-resistant stainless steel double-ring hollow gas turbine casing casting according to claim 1, characterized in that: During the modeling process, the inner cavity support plate (4), the upper flange (5), the lower flange (6) and the outer ring corner (7), and the inner cavity corner (8) are designed with a special mortise and tenon type positioning connection method using zirconium sand and chromite sand core positions, so as to combine the sand mold and the sand core while ensuring high-precision positioning of the casting.

7. The method for controlling the dimensional accuracy of heat-resistant stainless steel double-ring hollow gas turbine casing casting according to claim 1, characterized in that: A special composite casting coating composite coating design is adopted. The composite casting coating is a specially developed water-based zircon powder coating and an alcohol-based zircon powder coating for 3D printing sand molds. The water-based zircon powder coating has a mass ratio of zircon powder 71.4%, bentonite 1.1%, RZF 1.1%, resin 3.6%, water asphalt 1.4%, silica sol 3.6%, and water 17.8%. The alcohol-based zircon powder coating has a mass ratio of zircon powder 64.9%, bentonite 2.0%, deionized water 2.0%, modified aluminum magnesium silicate 2.6%, clay 0.3%, aluminum oxide 0.1%, phenolic resin 0.6%, polyvinyl butyral (PVB) 0.3%, rosin 1.3%, industrial alcohol 19.5%, isopropyl alcohol 3.2%, and heavy aromatic solvent oil 3.2%. The composite coating is applied on the sand mold as a whole to ensure the overall dimensional accuracy and surface finish of the casing casting. The sand mold is dipped in water-based zircon powder coating to achieve uniform coating of the coating in the dead corners of the casting mold. To improve the anti-sand adhesion of the support plate, the support plate core is sprayed with alcohol-based zircon powder coating, and the overall coating thickness is 0.2-0.3mm.

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