A method for forming the inner cavity of a high-temperature alloy hollow guide vane

Abstract

The present invention relates to the technical field of high-temperature alloy investment casting, and specifically to a method for forming the inner cavity of a high-temperature alloy hollow guide blade. When designing the core mold, the overall inner cavity core is divided into two parts, namely, an exhaust side and an intake side. The inner cavity mold block on the exhaust side is made into a ceramic core mold, and the mold block on the intake side is made into a water-soluble core mold. When preparing the inner cavity core, the ceramic core and the water-soluble core are pressed separately, and the two pressed core parts are combined into a complete core and then a blade wax mold is pressed; the water-soluble core is removed by using the principle that the water-soluble core dissolves in water, and the remaining ceramic core is pressed into a wax mold, with the side close to the intake side as the fixed end and the exhaust side as the free end, and a shell is prepared, and a high-temperature alloy guide blade is prepared by using the method of fixing the ceramic core with the inner cavity shell. The present invention can reduce the casting stress caused by the difference in shrinkage between the ceramic core and the molten metal, and reduce the tendency of blade cracks and recrystallization.

Description

Technical Field

[0001] The invention relates to the technical field of high-temperature alloy investment precision casting, in particular to a method for forming an inner cavity of a high-temperature alloy hollow guide vane. Background Art

[0002] With the continuous increase in gas turbine power and operating temperature, the demand for larger-sized high-temperature alloy hollow guide blades (the size range of guide blades is: length ≥100mm, width ≥60mm, height ≥35mm) is also increasing. However, in the actual production process of large-sized hollow guide blades, defects such as stress cracks, core eccentricity, core leakage, uneven wall thickness, recrystallization and inclusions have always been the main problems limiting the production qualification rate of blades. Summary of the Invention

[0003] In order to solve the difficulties encountered in the production of the above-mentioned hollow guide blades, the purpose of the present invention is to provide a method for forming the inner cavity of a high-temperature alloy hollow guide blade, which adopts a combination of a water-soluble core and a ceramic core to prepare a high-temperature alloy hollow guide blade, which is mainly suitable for high-temperature alloy hollow guide blades with a relatively complex inner cavity structure and an inner cavity width ≥12mm.

[0004] The technical solution of the present invention is:

[0005] A method for forming the inner cavity of a high-temperature alloy hollow guide vane. In the early stage of core mold design, the entire inner cavity core is divided into two molds: an exhaust side and an intake side. The inner cavity mold block on the exhaust side is made into a ceramic core mold, and the mold block on the intake side is made into a water-soluble core mold.

[0006] The method for forming the inner cavity of a high-temperature alloy hollow guide blade is as follows: when preparing the inner cavity core, it is composed of a ceramic core and a water-soluble core, and the ceramic core and the water-soluble core are pressed separately. After the complete core is combined, a blade wax mold is pressed; by utilizing the principle that the water-soluble core dissolves in water, the water-soluble core is removed, and the remaining ceramic core is pressed into a wax mold. The side close to the air inlet edge is used as the fixed end and the exhaust edge as the free end, and then a shell is prepared. The high-temperature alloy guide blade is prepared by fixing the ceramic core with the inner cavity shell.

[0007] In the method for forming the inner cavity of a high-temperature alloy hollow guide vane, when designing the core mold, a ceramic core and a water-soluble core are provided with a combined structure, and the ceramic core is provided with a fixed end structure.

[0008] The method for forming the inner cavity of a high-temperature alloy hollow guide vane is designed to form a high-temperature alloy hollow guide vane with a two-part core, wherein the inner cavity channel of the water-soluble core part is normally used to dry the shell.

[0009] In the method for forming the inner cavity of a high-temperature alloy hollow guide vane, the inner cavity width is ≥12 mm.

[0010] The design concept of the present invention is:

[0011] For high-temperature alloy hollow guide vanes with larger internal cavities, the present invention divides the entire internal cavity core into two molds, one for the exhaust side and the other for the intake side, during the initial core mold design phase. The internal cavity mold blocks on the exhaust side are made into a ceramic core mold, while the mold blocks on the intake side are made into a water-soluble core mold. This invention reduces the size of the high-temperature alloy hollow guide vane core during casting, reduces the casting stress generated during solidification of the molten metal, and improves the controllability of the blade wall thickness. A portion of the casting's internal cavity is formed into a molding shell, and the internal cavity shell is used to secure a portion of the ceramic core to produce the high-temperature alloy hollow guide vane. In this method, the inner cavity of the guide blade is larger, and part of the inner cavity can be replaced by a shell. Compared with the conventional single ceramic core, it can not only reduce the casting stress caused by the shrinkage difference between the ceramic core and the molten metal, but also shorten the distance from the fixed end to the free end of the ceramic core, thereby greatly improving the wall thickness of the blade after casting and reducing the recrystallization tendency of the single crystal blade; at the same time, due to the shrinkage difference between the shell and the ceramic core, reducing the size of the ceramic core can reduce the probability of core breakage and core leakage, which can effectively reduce production costs, improve the metallurgical quality of the guide blade, and increase the qualified rate of blade production.

[0012] The present invention has the following advantages and beneficial effects:

[0013] 1. The present invention replaces the ceramic core with part of the ceramic shell, thereby reducing the production cost of castings.

[0014] 2. The present invention is easy to operate, avoids the deformation problem of large-sized ceramic cores, and can reduce the casting stress caused by the difference in shrinkage between the ceramic core and the molten metal, and can also reduce the recrystallization tendency of single crystal blades.

[0015] 3. The present invention adopts a water-soluble core, which is easy to remove. By positioning the local ceramic core through the inner cavity shell, the ceramic core can be accurately positioned, reducing the defects of core deviation, core leakage, and core breakage in the later casting process, ensuring the control of the blade wall thickness, reducing the deviation of the blade casting wall thickness, and increasing the finished product rate of high-temperature alloy hollow guide blade precision castings. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a schematic diagram of the structure of the high-temperature alloy hollow guide blade of the present invention.

[0017] Figure 2 Schematic diagram of the integral core structure of the high-temperature alloy hollow guide blade.

[0018] Figure 3 It is a schematic diagram of the combined structure of the water-soluble core and the ceramic core of the present invention.

[0019] In the figure, 1 is a water-soluble core, 2 is a ceramic core, 3 is a positioning structure for the fixed end of the ceramic core, and 4 is a matching slot for the positioning structure for the fixed end of the water-soluble core. DETAILED DESCRIPTION

[0020] like Figure 1 As shown, the high-temperature alloy hollow guide blade structure has a large blade size, a transparent inner cavity, and a channel width ≥12mm.

[0021] like Figure 3 As shown, the hollow guide blade integral core ( Figure 2 ) is divided into a water-soluble core 1 and a ceramic core 2, the water-soluble core 1 is used to form an inner cavity on the air inlet side of the hollow guide blade, and the ceramic core 2 is used to form an inner cavity on the exhaust side of the hollow guide blade. The water-soluble core 1 and the ceramic core 2 are connected by the matching slot 4 of the water-soluble core fixed end positioning structure and the ceramic core fixed end positioning structure 3. The matching slot 4 of the water-soluble core fixed end positioning structure is arranged on one side of the water-soluble core 1, and the ceramic core fixed end positioning structure 3 is arranged on one side of the ceramic core 2. The matching slot 4 of the water-soluble core fixed end positioning structure and the ceramic core fixed end positioning structure 3 correspond to each other and are matched and connected (such as: plug-in combination, etc.).

[0022] When designing the mold, the ceramic core 2 and the water-soluble core 1 are designed to correspond to the exhaust side and the air inlet side respectively. The inner cavity block on the exhaust side is made into a ceramic core mold, and the inner cavity block on the air inlet side is made into a water-soluble core mold.

[0023] When preparing the inner cavity core, it is composed of a ceramic core and a water-soluble core. The ceramic core and the water-soluble core are pressed separately, and after they are combined into a complete core, a blade wax mold is pressed.

[0024] After pressing the blade wax mold, the water-soluble core is removed based on the principle that the water-soluble core dissolves in water, and the side of the remaining ceramic core close to the air inlet side is used as the fixed end, and the exhaust side is used as the free end to prepare the shell. A part of the inner cavity shell is formed at the air inlet side where the original water-soluble core was located, and the high-temperature alloy guide blade is prepared by fixing the ceramic core with the inner cavity shell.

[0025] Below, the present invention is further described in detail by examples.

[0026] Example 1

[0027] This embodiment is a case study of using a water-soluble core and a ceramic core to prepare an equiaxed high-temperature alloy hollow guide blade. This blade is relatively large: 305mm long, 260mm wide, and 185mm high. Using a single ceramic core to prepare castings is prone to defects such as cracks, core eccentricity, core leakage, wall thickness tolerances, and inclusions caused by core-shell shrinkage differences. The blade inner cavity core channel was measured to have a width of 43mm. The inner cavity structure of the air intake side can be formed using a shell, while the inner cavity size of the exhaust side is smaller and can be formed using a core. When designing the mold, the overall core is divided into two molds, the exhaust side and the air intake side. The inner cavity mold block on the exhaust side is made into a ceramic core mold, and the mold block on the air intake side is made into a water-soluble core mold. The ceramic core and the water-soluble core are arranged in a combined structure, and the ceramic core is provided with a fixed end positioning structure. When preparing the inner cavity core, a ceramic core and a water-soluble core are pressed separately. The fixed end positioning structure of the ceramic core is partially painted and then combined with the water-soluble core. After the combination, the joints are waxed and deburred, and then a blade wax mold is pressed. The pressed blade wax mold is placed in an aqueous solution with a 10wt% citric acid content to remove the water-soluble core. The side of the remaining ceramic core close to the air inlet side is used as the fixed end, and the exhaust side is used as the free end. After that, a shell is prepared. A portion of the inner cavity shell is formed at the air inlet side where the original water-soluble core was located. The high-temperature alloy guide blade is prepared by using this inner cavity shell to fix the ceramic core.

[0028] The shell is dewaxed, roasted, and pre-burned with cotton before pouring. The cast blades are cleaned, sand-blown, and cored. The blade profile dimensions are qualified, the wall thickness is uniform, the inner cavity surface roughness is 1.20μm, the core coverage rate reaches 100%, and the wall thickness qualification rate reaches 95%.

[0029] Example 2

[0030] This embodiment is a case of preparing a single crystal high-temperature alloy hollow guide blade by combining a water-soluble core and a ceramic core. The blade is relatively large in size: 180mm in length, 115mm in width, and 95mm in height. Using a single ceramic core to prepare castings is prone to defects such as cracks, core deviation, core leakage, wall thickness tolerance, and inclusions caused by core-shell shrinkage differences. The blade inner cavity core channel is measured to have a width of 32mm. The inner cavity structure of the air intake side can be formed by shell molding, while the inner cavity size of the exhaust side is smaller and is formed by the core. When designing the mold, the overall core is divided into two molds, the exhaust side and the air intake side. The inner cavity mold block on the exhaust side is made into a ceramic core mold, and the mold block on the air intake side is made into a water-soluble core mold. The ceramic core and the water-soluble core are set up in a combined structure, and the ceramic core is set up with a fixed end positioning structure. When preparing the inner cavity core, a ceramic core and a water-soluble core are pressed separately. The fixed end positioning structure of the ceramic core is partially painted and then combined with the water-soluble core. After the combination, the joints are waxed and deburred, and then a blade wax mold is pressed. The pressed blade wax mold is placed in an aqueous solution with a 10wt% citric acid content to remove the water-soluble core. The side of the remaining ceramic core close to the air inlet side is used as the fixed end, and the exhaust side is used as the free end. After that, a shell is prepared. A portion of the inner cavity shell is formed at the air inlet side where the original water-soluble core was located. The high-temperature alloy guide blade is prepared by using this inner cavity shell to fix the ceramic core.

[0031] After the shell is dewaxed and fired, single crystal casting and drawing are carried out. After casting, the blades are shell cleaned, sand blown and cored. The blade surface dimensions are qualified, the wall thickness is uniform, the inner cavity surface roughness is 1.38μm, the core coverage rate reaches 100%, the wall thickness qualification rate reaches 95%, and the probability of recrystallization problems in large-sized single crystal hollow guide blades is reduced.

Claims

1. A method for forming the inner cavity of a high-temperature alloy hollow guide vane, characterized in that: In the early stage of core mold design, the whole inner cavity core is divided into two design molds, the exhaust side and the intake side. The inner cavity mold block on the exhaust side is made into a ceramic core mold, and the mold block on the intake side is made into a water-soluble core mold. When preparing the inner cavity core, it is composed of a ceramic core and a water-soluble core, and the ceramic core and the water-soluble core are pressed separately, and after the complete core is combined, a blade wax mold is pressed; the water-soluble core is removed by using the principle that the water-soluble core dissolves in water, and the remaining ceramic core is pressed into a wax mold, and the side close to the air inlet side is used as a fixed end, and the exhaust side is used as a free end, and then a shell is prepared, and a part of the inner cavity shell is formed at the air inlet side where the original water-soluble core is located, and a high-temperature alloy guide blade is prepared by fixing the ceramic core with the inner cavity shell; The water-soluble core is used to form an inner cavity on the air inlet side of the hollow guide blade, and the ceramic core is used to form an inner cavity on the exhaust side of the hollow guide blade. The water-soluble core and the ceramic core are connected via a matching slot of a fixed-end positioning structure of the water-soluble core and a fixed-end positioning structure of the ceramic core. The matching slot of the fixed-end positioning structure of the water-soluble core is arranged on one side of the water-soluble core, and the fixed-end positioning structure of the ceramic core is arranged on one side of the ceramic core. The matching slot of the fixed-end positioning structure of the water-soluble core and the fixed-end positioning structure of the ceramic core correspond to each other and are matched and connected via a plug-in combination. The lumen width is ≥12 mm.

2. The method for forming the inner cavity of a high-temperature alloy hollow guide vane according to claim 1, characterized in that: When designing the core mold, the ceramic core and the water-soluble core are arranged in a combined structure, and the ceramic core is arranged in a fixed end structure.

3. The method for forming the inner cavity of a high-temperature alloy hollow guide vane according to claim 1, characterized in that: The method is designed to form a high-temperature alloy hollow guide vane with a two-part core, and the inner cavity channel of the water-soluble core part is normally used to dry the shell.

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