Preparation method of special-shaped hole in ceramic core

Abstract

The invention belongs to the field of ceramic cores in the fields of aerospace, electronic information, precision investment casting and the like, and particularly relates to a preparation method of a special-shaped hole in a ceramic core. The method sequentially comprises the following steps that 1, a refractory metal pore-forming part is designed and machined according to requirements; 2, a refractory metal pore-forming component composite ceramic core is prepared, and a corresponding refractory metal pore-forming component is placed at the position where a special-shaped hole needs to be formed; and step 3, sintering the ceramic core, removing the refractory metal pore-forming component through high-temperature oxidation and sublimation, and forming the special-shaped hole in the ceramic core. The refractory metal is adopted as the template to prepare the special-shaped hole in the ceramic core, and the problems that the special-shaped hole in the ceramic core is difficult to machine and auxiliary materials are difficult to remove are solved.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of ceramic cores used in aerospace, electronic information, precision investment casting and the like, in particular to a preparation method of a special-shaped hole in a ceramic core. BACKGROUND

[0002] With the continuous development of the scientific and technological level of human society, the demand is also continuously improved; people also put forward higher requirements on the performance of the turbine blade of the aero-engine. With the increase of the turbine inlet temperature, the cooling effect has a greater and greater influence on the use effect of the blade, and the internal cavity structure of the air-cooled blade is becoming more and more complex, so the structure of the ceramic core also becomes more and more complex, and the frequency of using special-shaped holes in the design of the ceramic core is also increasing. When the special-shaped hole is machined by using ordinary mechanical machining or embedding a ceramic rod, it is difficult to guarantee the machining precision and the yield in the machining process; when the ceramic rod is removed by using the embedding method, the ceramic rod is easy to break due to adhesion with the core material and cannot be completely removed, which will cause the ceramic core to be scrapped. SUMMARY

[0003] The purpose of the present application is to provide a preparation method of a special-shaped hole in a ceramic core, which solves the problem of difficult machining of the special-shaped hole in the ceramic core, and can realize the machining of complex special-shaped holes by the method; at the same time, the method can also realize the machining of simple holes while improving the yield.

[0004] In order to achieve the above purpose, the present application adopts the following technical scheme:

[0005] A preparation method of a special-shaped hole in a ceramic core, sequentially comprising the following steps:

[0006] Step 1, designing and machining a refractory metal hole-making part according to requirements;

[0007] Step 2, preparing a refractory metal hole-making part composite ceramic core, placing the corresponding refractory metal hole-making part at the position where the special-shaped hole needs to be formed;

[0008] Step 3, sintering the ceramic core, removing the refractory metal hole-making part by high-temperature oxidation and sublimation to form a special-shaped hole in the ceramic core.

[0009] The preparation method of the special-shaped hole in the ceramic core, the metal material used for the refractory metal hole-making part is molybdenum, tungsten, rhenium, niobium, tantalum or hafnium, and after determining the selected refractory metal, the refractory metal hole-making part is directly prepared.

[0010] The preparation method of the special-shaped hole in the ceramic core, the shape and size of the refractory metal hole-making part are machined according to the requirements of the special-shaped hole, and the diameter of the special-shaped hole is 0.001mm-10mm.

[0011] The refractory metal pore-forming part is directly processed by using refractory metal wires with different diameters, and the diameter of the refractory metal wire is 0.001mm-10mm.

[0012] The refractory metal pore-forming part is made by mechanical processing or casting.

[0013] In step 2, the refractory metal pore-forming part is directly put into the ceramic core for processing, or is compounded after the ceramic core is pressed.

[0014] In step 3, the refractory metal pore-forming part is compounded with the ceramic core for two-stage sintering: the first-stage sintering is heated to 400-500℃, and the temperature is kept for 1-4 hours; the second-stage sintering is heated to 1100-1300℃, and the temperature is kept for 1-6 hours, the refractory metal pore-forming part is removed, the special-shaped hole is formed, and the ceramic core is cooled in the furnace after keeping the temperature.

[0015] The design idea of the application is that the refractory metal is used as a pore-forming precursor, the refractory metal oxide is sublimated, the refractory metal is removed in a specific step, and the special-shaped hole with a specific shape and size is formed.

[0016] Compared with the prior art, the special-shaped hole preparation method has the following advantages and beneficial effects:

[0017] The application can simply realize the preparation of the ceramic core with special requirements for the special-shaped hole, the special-shaped hole is formed by oxidation and sublimation of the pore-forming metal in a heat treatment process, the problems of difficult machining of the special-shaped hole and product scrapping are solved, and the problems of fracture of the ceramic rod and incomplete removal of the ceramic rod caused by adhesion of the ceramic rod to the core material are solved, which causes the ceramic core to be scrapped. Meanwhile, the process and method provided by the application can be popularized to the production of other types of products, and has a wide prospect. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 The core with a special-shaped hole is shown in the drawing. DETAILED DESCRIPTION

[0019] In the implementation process, the application provides a preparation method of a special-shaped hole in a ceramic core, which comprises the following steps in sequence: step 1, a refractory metal pore-forming part is designed and processed according to requirements; step 2, the refractory metal pore-forming part is compounded with a ceramic core; and step 3, the ceramic core is sintered, the refractory metal pore-forming part is removed by high-temperature oxidation, and the special-shaped hole is formed in the ceramic core.

[0020] The application will be further described below in combination with the following embodiments.

[0021] Example 1

[0022] In this embodiment, a method for preparing a special-shaped hole in a ceramic core comprises the following steps:

[0023] Step 1: Design and process refractory metal hole-forming parts according to requirements:

[0024] Select pure molybdenum wire with a diameter of 0.50 mm; the surface of the wire after drawing is gray-black coated with drawing lubricant, and the molybdenum wire is cut into several specified lengths using wire cutting;

[0025] First, soak the molybdenum wire in acetone / alcohol (volume ratio 1:1) for ultrasonic cleaning for 100 seconds to remove oil stains brought about by wire cutting; after cleaning, dry the molybdenum wire in an oven or use a hair dryer to dry it;

[0026] Then manually grind the surface step by step using metallographic sandpaper; the final sandpaper grinding mesh should reach 1200#, and the ends of the molybdenum wire should be rounded and polished;

[0027] Finally, use a mechanical processing device to process the molybdenum wire into a specified special shape, soak the special-shaped molybdenum wire in alcohol for ultrasonic cleaning for 100 seconds, and dry the cleaned molybdenum wire in an oven or use a hair dryer to dry it.

[0028] Step 2: Preparation of refractory metal hole-forming part composite ceramic core:

[0029] Place the cleaned and dried special-shaped molybdenum wire at the position where the special-shaped hole needs to be formed according to the design requirements to prepare the composite ceramic core.

[0030] Step 3: Sintering of ceramic core, removal of refractory metal hole-forming part by high temperature oxidation and sublimation to form special-shaped hole in ceramic core.

[0031] Refractory metal hole-forming part composite ceramic core 190°C into the furnace;

[0032] Heat to 450°C and keep for 2 hours;

[0033] Heat to 1200°C and keep for 3 hours to remove the refractory metal hole-forming part and form the special-shaped hole;

[0034] After keeping, cool down in the furnace.

[0035] As shown in Figure 1 the refractory metal hole-forming part is completely removed, and the special-shaped hole has high size precision.

[0036] Example 2

[0037] In this embodiment, a method for preparing a special-shaped hole in a ceramic core comprises the following steps:

[0038] Step 1, design and process refractory metal pore-forming parts according to requirements:

[0039] Select pure metal molybdenum wire, diameter 0.95mm; the surface of the wire after drawing is covered with gray-black drawing lubricant, and the molybdenum wire is cut into several specified length molybdenum wires by wire cutting;

[0040] First, soak the molybdenum wire in acetone / alcohol (1:1 by volume) for 100 seconds and clean it with ultrasonic cleaning to remove oil stains brought by wire cutting. After cleaning, dry the molybdenum wire in an oven or use a hair dryer to dry it.

[0041] Then, manually grind the surface step by step using metallographic sandpaper. The final sandpaper grinding mesh should reach 1200#, and the ends of the molybdenum wire should be rounded and polished.

[0042] Finally, use a mechanical processing device to process the molybdenum wire into a specified profile. Soak the profiled molybdenum wire in alcohol for 90 seconds and clean it with ultrasonic cleaning. After cleaning, dry the molybdenum wire in an oven or use a hair dryer to dry it.

[0043] Step 2, preparation of refractory metal pore-forming part composite ceramic core:

[0044] Place the cleaned and dried profiled molybdenum wire at the desired location to form a profiled hole for composite ceramic core preparation according to design requirements.

[0045] Step 3, sintering of ceramic core, removal of refractory metal pore-forming part by high temperature oxidation and sublimation to form profiled hole in ceramic core.

[0046] Refractory metal pore-forming part composite ceramic core 190℃ into the furnace;

[0047] Heat to 450℃, keep for 3 hours;

[0048] Heat to 1200℃, keep for 5 hours, remove refractory metal pore-forming part, form profiled hole;

[0049] After keeping, cool down in the furnace.

[0050] The refractory metal pore-forming part is completely removed, and the profiled hole has high dimensional accuracy.

[0051] Example 3

[0052] In this embodiment, a method for preparing a profiled hole in a ceramic core includes the following steps:

[0053] Step 1, design and process refractory metal pore-forming parts according to requirements:

[0054] Select pure metal molybdenum wire, diameter 2.00mm; the surface of the wire after drawing is covered with gray-black drawing lubricant, and the molybdenum wire is cut into several specified length molybdenum wires by wire cutting;

[0055] Firstly, the molybdenum wire is soaked in acetone / alcohol (volume ratio 1:1) for ultrasonic cleaning for 100 seconds to remove oil stains caused by wire cutting, and then the cleaned molybdenum wire is dried in an oven or dried by a hair dryer;

[0056] Then, the surface of the molybdenum wire is ground by using metallographic sandpaper step by step, and the final sandpaper grinding mesh number is 1200#, and the two ends of the molybdenum wire are rounded and polished;

[0057] Finally, the molybdenum wire is processed into a specified profile by using a mechanical processing device, and the profiled molybdenum wire is soaked in alcohol for ultrasonic cleaning for 90 seconds, and then the cleaned molybdenum wire is dried in an oven or dried by a hair dryer.

[0058] Step 2, preparation of refractory metal pore-forming part composite ceramic core:

[0059] The dried profiled molybdenum wire is placed at the position where the profiled hole is required to be formed according to the design requirements for preparation of the composite ceramic core.

[0060] Step 3, sintering of the ceramic core, and removal of the refractory metal pore-forming part to form a profiled hole in the ceramic core by high-temperature oxidation and sublimation.

[0061] The refractory metal pore-forming part composite ceramic core is put into the furnace at 190℃;

[0062] The temperature is raised to 500℃ and kept for 3 hours;

[0063] The temperature is raised to 1300℃ and kept for 3 hours to remove the refractory metal pore-forming part and form a profiled hole;

[0064] After keeping the temperature, the furnace is cooled.

[0065] The refractory metal pore-forming part is completely removed, and the profiled hole has high size precision.

[0066] The implementation results show that the profiled hole in the ceramic core is prepared by using a refractory metal as a template, which solves the problems of difficult processing of the profiled hole in the ceramic core and difficult removal of auxiliary materials.

[0067] The above examples are only for illustrating the technical concept and characteristics of the present application, and the purpose is to enable those skilled in the art to understand the content of the present application and implement it, and cannot limit the protection scope of the present application. Any equivalent changes or modifications made according to the spirit and essence of the present application shall be covered within the protection scope of the present application.

Claims

1. A method of producing a shaped hole in a ceramic core, characterized by, The method comprises the following steps in sequence: Step 1: designing and processing refractory metal hole forming parts according to requirements; Step 2: preparing the refractory metal hole forming part composite ceramic core, and placing the corresponding refractory metal hole forming part at a position where a special-shaped hole needs to be formed; Step 3: sintering the ceramic core, removing the refractory metal hole forming part through high-temperature oxidation and sublimation, and forming a special-shaped hole in the ceramic core.

2. The method of claim 1, wherein the step of forming the irregular hole is performed by a method comprising: (a) forming a first hole in the ceramic core; (b) forming a second hole in the ceramic core; and (c) forming a third hole in the ceramic core. The metal material used in the refractory metal hole forming part is molybdenum, tungsten, rhenium, niobium, tantalum or hafnium, and after the selected refractory metal is determined, the refractory metal hole forming part is directly prepared.

3. The method of claim 2, wherein the step of forming the irregular hole is performed by a method comprising: (a) forming a first hole in the ceramic core; (b) forming a second hole in the ceramic core; and (c) forming a third hole in the ceramic core. The shape and size of the refractory metal hole forming part are processed according to the requirements of the special-shaped hole, and the diameter of the special-shaped hole is 0.001mm-10mm.

4. The method of claim 3, wherein the step of forming the irregular hole is performed by a method comprising: (a) forming a first hole in the ceramic core; (b) forming a second hole in the ceramic core; and (c) forming a third hole in the ceramic core. The refractory metal hole forming part is directly processed by using refractory metal wires with different diameters, and the diameter of the refractory metal wire is 0.001mm-10mm.

5. The method of claim 3, wherein the step of forming the irregular hole is performed by a method comprising: (a) forming a first hole in the ceramic core; (b) forming a second hole in the ceramic core; and (c) forming a third hole in the ceramic core. The refractory metal hole forming part is prepared by mechanical processing or melting and casting.

6. The method of claim 1, wherein the step of forming the irregular shape comprises the steps of: forming a first irregular shape in the ceramic core; and forming a second irregular shape in the ceramic core. In step 2, the refractory metal hole forming part is directly placed in the ceramic core for processing, or the ceramic core is pressed and then compounded.

7. The method of claim 1, wherein the step of forming the irregular shape comprises the steps of: forming a first irregular shape in the ceramic core; and forming a second irregular shape in the ceramic core. In step 3, the refractory metal hole forming part composite ceramic core is sintered in two stages: the first stage is sintered to 400-500℃, and the temperature is kept for 1-4 hours; the second stage is sintered to 1100-1300℃, and the temperature is kept for 1-6 hours to remove the refractory metal hole forming part and form a special-shaped hole; and the temperature is kept and then the furnace is cooled.

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