Annular narrow channel casting forming method

Abstract

The invention relates to the technical field of casting forming, in particular to a forming method for a circular narrow-channel casting. The annular narrow channel casting forming method comprises the following steps that S1, a plurality of split mold cores are put into a wax mold, and after positioning wax pressing and cooling shaping are conducted in sequence, a wax piece A is obtained; wherein the split mold core comprises a ceramic mold core, a fixed end, a free end and a soluble mold core; the fixed end is located at one end of the ceramic core, the free end is located at the other end of the ceramic core, and the ceramic core and the soluble core are connected through the free end; a wax layer is arranged on the surface of the free end; s2, a soluble and lost mold core in the wax piece A is removed, and a wax piece B is obtained; s3, the wax piece B is sequentially subjected to slurry spraying, sand hanging and steam dewaxing, and a mold shell is obtained; s4, molten metal is poured into the mold shell, after cooling, the mold shell, the fixed end and the free end are removed, the ceramic mold core is removed, and after sand blasting, an annular narrow-channel casting is obtained; the method improves the qualification rate of castings.

Description

Technical Field

[0001] The invention relates to the technical field of casting and molding, in particular to a method for molding a circular narrow channel casting. Background Art

[0002] With the increasing demand for lightweight metal parts in the aviation and aerospace fields, metal castings tend to be integrated and complex. Investment casting is widely used in aircraft engines as a molding method for complex structural castings.

[0003] The molding of investment castings generally includes the preparation of wax patterns, shells, dewaxing, roasting, melting and pouring. For narrow channel castings, the shell molding method is a major difficulty in the development of castings. The investment casting shell is a repetition of the process of "coating-sanding-drying", but for castings with structures such as long holes and narrow channels, it is difficult to cast when the ratio of hole depth to hole diameter H / d≥5 and the ratio of the depth to length and width of the narrow channel is greater than a certain ratio. As the number of shell making layers increases, the sand particle size increases, and it is not easy to apply paint and sand at narrow apertures or channels. In addition, the inside of the shell is not fully dried, which can easily cause leakage inside the holes and narrow channels during the melting and pouring process.

[0004] At present, ceramic cores are usually used for such narrow channel locations. However, for large-sized annular parts, the overall ceramic core production method is relatively difficult, and split ceramic cores are usually spliced ​​into a whole circle for molding during the wax mold stage. Considering the deformation of the ceramic core during sintering and the yielding of the alloy liquid during solidification and shrinkage, the ceramic core is very likely to crack due to stress during wax mold pressing and subsequent melting and pouring. At the same time, there is a gap at the joint of the split ceramic core in the narrow channel, which will form a metal batch seam after pouring. The batch seam is difficult to visually observe and trim during the subsequent casting trimming process, resulting in a high scrap rate for the casting.

[0005] In view of this, this invention is proposed. Summary of the invention

[0006] The purpose of the present invention is to provide a method for forming a circular ring-shaped narrow channel casting, optimize the forming method of a large-size circular ring-shaped narrow channel structure casting, avoid leakage inside the long hole and the narrow channel during the pouring process, and form metal batch seams after pouring, thereby improving the qualified rate of castings.

[0007] In order to achieve the above-mentioned purpose of the present invention, the following technical solutions are particularly adopted:

[0008] The present invention provides a method for forming a circular narrow channel casting, comprising the following steps:

[0009] S1, placing several split cores into a wax mold, positioning and wax pressing and cooling and shaping in sequence to obtain a wax part A;

[0010] The split core comprises: a ceramic core, a fixed end, a free end and a soluble core; the fixed end is located at one end of the ceramic core, the free end is located at the other end of the ceramic core, the ceramic core and the soluble core are connected via the free end; a wax layer is provided on the surface of the free end;

[0011] S2, removing the soluble lost core in the wax part A to obtain a wax part B;

[0012] S3, sequentially subjecting the wax part B to slurry spraying, sand hanging and steam dewaxing to obtain a mold shell;

[0013] S4, pouring molten metal into the mold shell, removing the mold shell, the fixed end and the free end after cooling, removing the ceramic core, and obtaining the annular narrow channel casting after sandblasting.

[0014] Furthermore, the difference between the outer diameter and the inner diameter of the circular narrow channel casting is 8 to 10 mm, and the outer diameter is >350 mm;

[0015] And / or, the annular narrow channel casting comprises a flow channel and a plurality of blade-shaped holes connected to the flow channel, the diameter of the blade-shaped holes is 7.5-10 mm, and the ratio of hole depth to hole diameter is ≥5.

[0016] Furthermore, in step S1, a plurality of split cores are evenly distributed in the wax mold to form a ring.

[0017] Further, in step S1, the ceramic core is a slender structure;

[0018] And / or, the diameter of the ceramic core is 7.5-10 mm.

[0019] Further, in step S1, the fixed end includes a diamond structure;

[0020] And / or, the maximum cross-sectional width of the fixed end is greater than the maximum diameter of the ceramic core.

[0021] Further, in step S1, the free end comprises a dovetail structure;

[0022] And / or, the height of the free end is 4.5-5.5 mm, and the width of the free end is less than or equal to the maximum diameter of the ceramic core.

[0023] Furthermore, in step S1, the thickness of the wax layer is 0.45-0.55 mm.

[0024] Further, in step S1, the material of the ceramic core, the fixed end and the free end includes a silicon-based material;

[0025] And / or, the material of the soluble core includes a wax material soluble in water or acidic substances.

[0026] Furthermore, in step S2, removing the soluble lost core in the wax part A comprises: soaking in an acidic solution.

[0027] Furthermore, in step S4, removing the ceramic core includes: soaking in an alkaline solution.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] The circular ring-shaped narrow channel casting molding method of the present invention adopts a ceramic core to mold the long hole structure in the narrow channel of the casting, and the flow channel connected thereto is molded by a mold shell, and the two together form a complex structure inside the narrow channel; the molding method of a large-size circular ring-shaped narrow channel structure is optimized, on the one hand, the problem of casting leakage caused by the difficulty in drying the long hole and narrow channel of the mold shell and uneven coating is solved, and on the other hand, the metal batch seam formed by the ceramic core inside the mold shell is avoided, thereby improving the qualified rate of castings and greatly reducing the production cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0031] Figure 1 It is a schematic diagram of the split core structure of the present invention.

[0032] Figure 2 It is a cross-sectional view of the wax piece A of the present invention.

[0033] Figure 3 It is a schematic diagram of the complete circular ring structure of the wax piece B of the present invention.

[0034] Figure 4 It is a schematic structural diagram of the wax piece B and the mold shell of the present invention.

[0035] Reference numerals:

[0036] 1-fixed end; 2-ceramic core; 3-soluble core; 4-free end; 5-wax material; 6-mold shell. DETAILED DESCRIPTION

[0037] The technical scheme of the present invention will be clearly and completely described below in conjunction with the accompanying drawings and specific embodiments, but it will be understood by those skilled in the art that the following described embodiments are part of embodiments of the present invention, rather than all embodiments, and are only used to illustrate the present invention, and should not be considered as limiting the scope of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work are within the scope of protection of the present invention. If specific conditions are not specified in the embodiments, they are carried out according to normal conditions or conditions recommended by the manufacturer. If the manufacturer is not specified in the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0038] The method for forming a circular narrow channel casting according to an embodiment of the present invention is described in detail below.

[0039] See also Figure 1 , Figure 2 , Figure 3 and Figure 4 In some embodiments of the present invention, a method for forming a circular narrow channel casting is provided, comprising the following steps:

[0040] S1, placing several split cores into a wax mold, positioning and wax pressing and cooling and shaping in sequence to obtain a wax part A;

[0041] The split core comprises: a ceramic core 2, a fixed end 1, a free end 4 and a soluble core 3; the fixed end 1 is located at one end of the ceramic core 2, the free end 4 is located at the other end of the ceramic core 2, and the ceramic core 2 and the soluble core 3 are connected via the free end 4; a wax layer is provided on the surface of the free end 4;

[0042] S2, removing the soluble lost core 3 in the wax part A to obtain the wax part B;

[0043] S3, sequentially subjecting the wax part B to slurry spraying, sanding and steam dewaxing to obtain a mold shell 6;

[0044] S4, pouring molten metal into the mold shell 6, after cooling, removing the mold shell 6, the fixed end 1 and the free end 4, removing the ceramic core 2, and obtaining a circular narrow channel casting after sandblasting.

[0045] In some embodiments of the present invention, the difference between the outer diameter and the inner diameter of the circular narrow channel casting is 8 to 10 mm (for example, it can be 8 mm, 8.5 mm, 9 mm, 9.5 mm, 10 mm, etc.), and the outer diameter is greater than 350 mm (for example, it can be 400 mm, 500 mm, etc.);

[0046] The annular narrow channel casting includes a flow channel and a plurality of blade-shaped holes connected to the flow channel, the diameter of the blade-shaped holes is 7.5 to 10 mm (for example, 7.5 mm, 8 mm, 8.5 mm, 9 mm, 9.5 mm, 10 mm, etc.), and the ratio of the hole depth to the hole diameter is ≥5 (for example, 5, 6, 7, etc.);

[0047] Preferably, the minimum wall thickness of the annular narrow channel casting is in the range of 1.5 to 2.1 mm.

[0048] The circular narrow channel casting of the present invention has a compact structure, a gap between the inner and outer rings of 8 to 10 mm, an outer diameter size of >350 mm, and a narrow channel formed between the inner and outer rings comprising a flow channel and a plurality of evenly distributed long and deep blade-shaped holes (long hole structure). The blade-shaped holes are connected to the flow channel, the aperture of the blade-shaped holes is 7.5 to 10 mm, and the ratio of the hole depth to the aperture is ≥5. The complex narrow channel poses a relatively large challenge to the casting molding.

[0049] The long and deep blade-shaped holes in the narrow channel of the casting of the present invention are formed by a ceramic core, and the flow channel connected thereto is formed by a mold shell 6, and the two together form a complex structure inside the narrow channel; the mold shell molding of the large-size circular narrow channel structure is optimized, which solves the problems of casting leakage caused by the difficulty in drying the long holes and narrow channels of the mold shell and uneven coating on the one hand, and avoids the metal batch seams formed by the ceramic core inside the mold shell on the other hand, thereby improving the qualified rate of castings and greatly reducing production costs.

[0050] See also Figure 1 According to the narrow channel cavity structure of the casting, a split core is designed, a long hole structure is formed by the ceramic core 2, a flow channel structure is formed by the soluble core 3, and the ceramic core 2 and the soluble core 3 are connected by a free end 4 to form a narrow channel structure;

[0051] See also Figure 2 and Figure 3 , put the split core into the wax mold, inject wax material, position and press the wax in the wax mold through the fixed end 1 and the soluble core 3, and after cooling and shaping, obtain the wax part A;

[0052] The soluble core 3 in the wax piece A is removed to obtain the wax piece B. At this time, the free end 4 is exposed at the flow channel position, the wax material 5 completely wraps the ceramic core 2, the fixed end 1 is exposed on the outer surface of the wax piece B, and the free end 4 is exposed in the flow channel cavity;

[0053] See also Figure 4, the wax part B is sequentially subjected to slurry spraying, sand hanging and steam dewaxing, and the wax material 5 is melted and flows out, and finally a mold shell 6 with a cavity is obtained; wherein, the fixed end 1 is wrapped by the mold shell 6, and the free end 4 has a gap with the mold shell 6 because of the wax layer previously provided, which can not only limit the ceramic core 2, but also leave a certain distance when the ceramic core 2 expands due to heat, so as to avoid the ceramic core 2 and the mold shell 6 from interfering with each other and causing fracture. The above operations finally obtain a mold shell 6 with a narrow flow channel cavity;

[0054] The molten metal is poured into the mold shell 6. After cooling, the long hole structure is obtained by removing the ceramic core 2, the narrow channel is obtained by removing the mold shell 6, and the circular narrow channel casting is obtained after sandblasting.

[0055] In some embodiments of the present invention, in step S1, a plurality of split cores are evenly distributed in the wax mold to form a ring.

[0056] In some embodiments of the present invention, in step S1, the ceramic core 2 is a slender structure; the diameter of the ceramic core 2 is 7.5 to 10 mm (for example, it can be 7.5 mm, 8 mm, 8.5 mm, 9 mm, 9.5 mm, 10 mm, etc.); a long hole structure is formed by the ceramic core 2 with a slender structure and a diameter of 7.5 to 10 mm.

[0057] In some embodiments of the present invention, in step S1 , the fixed end 1 includes a diamond structure; and the maximum width of the cross section of the fixed end 1 is greater than the maximum diameter of the ceramic core 2 .

[0058] In some embodiments of the present invention, in step S1 , the free end 4 comprises a dovetail structure; the height of the free end 4 is 4.5 to 5.5 mm, preferably 5 mm; and the width of the free end 4 is less than or equal to the maximum diameter of the ceramic core 2 .

[0059] In some embodiments of the present invention, the soluble core 3 is arc-shaped.

[0060] In some embodiments of the present invention, in step S1, the thickness of the wax layer is 0.45 to 0.55 mm (for example, it can be 0.45 mm, 0.5 mm, 0.55 mm, etc.), preferably, the thickness of the wax layer is 0.5 mm; preferably, the surface of the free end 4 is brushed with wax to form a wax layer on the surface of the free end 4.

[0061] In some embodiments of the present invention, in step S1, the material of the ceramic core 2, the fixed end 1 and the free end 4 includes a silicon-based material; the ceramic core 2, the fixed end 1 and the free end 4 are pressed by a mold and then sintered.

[0062] The present invention does not impose strict restrictions on the specific type of silicon-based materials, and any silicon-based material that can be used to prepare ceramic cores is sufficient.

[0063] In some embodiments of the present invention, the material of the soluble core 3 includes wax material that is soluble in water or acidic substances.

[0064] A flow channel structure is formed through the soluble lost core 3, and the width is 8 to 10 mm. The ceramic core 2 and the soluble lost core 3 are connected through the free end 4 to form a narrow channel structure.

[0065] In some embodiments of the present invention, in step S2, removing the soluble lost core 3 in the wax part A comprises: soaking in an acidic solution; preferably, the acidic solution comprises a solution containing citric acid.

[0066] The split core is placed in the wax mold and evenly arranged to form a whole ring. The wax is positioned and pressed in the wax mold through the fixed end 1 and the soluble core 3. After cooling and shaping, it is placed in a solution containing citric acid for immersion, and the soluble core 3 is removed. After the soluble core 3 is completely dissolved, the free end 4 leaks out of the flow channel position, and the wax material 5 wraps the ceramic core 2 in a whole ring. The fixed end 1 and the free end 4 are exposed on the outer surface of the wax part B and the flow channel cavity respectively.

[0067] In some embodiments of the present invention, in step S3, the wax part B is subjected to the steps of multiple slurry spraying and sanding; preferably, the number of slurry spraying and sanding is 9 times, wherein the first 5 layers of sanding are corundum sand with a particle size of 100 mesh, and the next 4 layers of sanding are mullite sand with a particle size of 16-30 mesh, and the slurry is prepared by using silica sol as a binder, and zircon powder is added and stirred and mixed; after the slurry spraying and sanding are completed, steam dewaxing is carried out at 145-155°C in a dewaxing kettle, and the wax material 5 flows out along the ceramic core 2 and the mold shell 6 after melting, and finally a mold shell 6 with a cavity is obtained; wherein, the fixed end 1 is wrapped by the mold shell 6, and the free end 4 has a gap of 0.45-0.55mm with the mold shell 6 due to the previous wax brushing treatment, which can not only limit the ceramic core 2, but also leave a certain distance when the ceramic core 2 expands due to heat, so as to avoid interference between the ceramic core 2 and the mold shell 6 and cause breakage, and the above operations finally obtain a mold shell 6 with a narrow flow channel cavity.

[0068] In some embodiments of the present invention, in step S4, the method of removing the mold shell 6, the fixed end 1 and the free end 4 includes using a high-pressure water shell cleaning method.

[0069] In some embodiments of the present invention, in step S4, removing the ceramic core 2 comprises: immersing the ceramic core 2 in an alkaline solution; the long hole structure is obtained after the ceramic core 2 is corroded by immersion in a strong alkali.

[0070] After pouring and cooling, the mold shell 6 on the casting surface and the fixed end 1 and free end 4 exposed on the casting surface are removed by high-pressure water cleaning, and the remaining ceramic core 2 in the narrow channel is removed by strong alkali corrosion.

[0071] In some embodiments of the present invention, in step S4, a vacuum induction melting furnace is used to melt the master alloy rod to obtain molten metal; the molten metal is poured into the mold shell 6;

[0072] After pouring, the mold shell 6 is cooled, and the mold shell 6 and the fixed end 1 and free end 4 exposed on the surface are removed by high-pressure water cleaning. The remaining ceramic core 2 is removed by strong alkali corrosion, and finally the casting is obtained after sandblasting.

[0073] Example 1

[0074] The method for forming a circular narrow channel casting provided in this embodiment includes the following steps:

[0075] S1. Designing a split core according to the narrow channel cavity structure of the circular narrow channel casting;

[0076] The split core comprises: a ceramic core 2, a fixed end 1, a free end 4 and a soluble core 3; the fixed end 1 is located at one end of the ceramic core 2, the free end 4 is located at the other end of the ceramic core 2, and the ceramic core 2 and the soluble core 3 are connected via the free end 4;

[0077] The ceramic core 2 is a slender structure with a diameter of 7.5 to 10 mm;

[0078] The fixed end 1 is a diamond-shaped structure, and the maximum width of the cross section of the fixed end 1 is greater than the maximum diameter of the ceramic core 2;

[0079] The free end 4 is a dovetail structure, the height of the free end 4 is 5 mm, and the width of the free end 4 is less than or equal to the maximum diameter of the ceramic core 2; the surface of the free end 4 is waxed to form a wax layer with a thickness of 0.5 mm on the surface of the free end 4;

[0080] The soluble lost core 3 is arc-shaped;

[0081] The material of the ceramic core 2, the fixed end 1 and the free end 4 includes silicon-based material;

[0082] The material of the soluble core 3 includes a wax material soluble in water or acidic substances;

[0083] Put several split cores into the wax mold and evenly place them to form a whole ring. Position and press the wax in the wax mold through the fixed end 1 and the soluble core 3. After cooling and shaping, a wax part A is obtained.

[0084] S2, soaking the wax part A in a solution containing citric acid, removing the soluble core 3, and obtaining the wax part B;

[0085] S3, the wax part B is subjected to a step of multiple slurry spraying and sanding, wherein the first 5 layers of sanding are corundum sand with a particle size of 100 mesh, and the next 4 layers of sanding are mullite sand with a particle size of 16-30 mesh, and the slurry is prepared by mixing silica sol as a binder and adding zircon powder; after the slurry spraying and sanding are completed, steam dewaxing is carried out at 150° C. in a dewaxing kettle to obtain a mold shell 6 with a cavity;

[0086] S4, using a vacuum induction melting furnace to melt the master alloy rod to obtain molten metal; pouring the molten metal into a mold shell 6 with a mold cavity, after cooling, removing the mold shell 6, the fixed end 1 and the free end 4 by high-pressure water cleaning, soaking and corroding the ceramic core 2 with a strong alkaline solution, and obtaining a circular narrow channel casting after sandblasting;

[0087] The difference between the outer diameter and the inner diameter of the circular narrow channel casting is 8 to 10 mm, and the outer diameter is >350 mm; the circular narrow channel casting includes a flow channel and a plurality of blade-shaped holes connected to the flow channel, the diameter of the blade-shaped holes is 7.5 to 10 mm, and the ratio of the hole depth to the hole diameter is ≥5; the minimum wall thickness range of the circular narrow channel casting is 1.5 to 2.1 mm.

[0088] The circular narrow channel casting molding method optimizes the mold shell molding of a large-size circular narrow channel structure. On the one hand, it solves the problems of casting leakage caused by the difficulty in drying the long holes and narrow channels of the mold shell and uneven coating, and on the other hand, it avoids the metal batch seams formed by the ceramic core inside the mold shell.

[0089] Compared with the method in which long hole and narrow channel structures are formed by multi-jointed split ceramic cores, the problems of metal seams formed at the joints of the ceramic cores and broken ceramic cores have not been effectively solved; the circular narrow channel casting molding method increases the casting qualification rate from 20% to 90%, greatly reducing production costs.

[0090] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for forming a circular narrow channel casting, characterized in that: The steps include: S1, placing several split cores into a wax mold, positioning and wax pressing and cooling and shaping in sequence to obtain a wax part A; The split core comprises: a ceramic core, a fixed end, a free end and a soluble core; the fixed end is located at one end of the ceramic core, the free end is located at the other end of the ceramic core, the ceramic core and the soluble core are connected via the free end; a wax layer is provided on the surface of the free end; S2, removing the soluble lost core in the wax part A to obtain a wax part B; S3, sequentially subjecting the wax part B to slurry spraying, sand hanging and steam dewaxing to obtain a mold shell; S4, pouring molten metal into the mold shell, removing the mold shell, the fixed end and the free end after cooling, removing the ceramic core, and obtaining the annular narrow channel casting after sandblasting.

2. The method for forming a circular narrow channel casting according to claim 1, characterized in that: The difference between the outer diameter and the inner diameter of the circular narrow channel casting is 8 to 10 mm, and the outer diameter is greater than 350 mm; And / or, the annular narrow channel casting comprises a flow channel and a plurality of blade-shaped holes connected to the flow channel, the diameter of the blade-shaped holes is 7.5-10 mm, and the ratio of hole depth to hole diameter is ≥5.

3. The method for forming a circular narrow channel casting according to claim 1, characterized in that: In step S1, a plurality of split cores are evenly distributed in the wax mold to form a ring.

4. The method for forming a circular narrow channel casting according to claim 1, characterized in that: In step S1, the ceramic core is a slender structure; And / or, the diameter of the ceramic core is 7.5-10 mm.

5. The method for forming a circular narrow channel casting according to claim 1, characterized in that: In step S1, the fixed end includes a diamond structure; And / or, the maximum cross-sectional width of the fixed end is greater than the maximum diameter of the ceramic core.

6. The method for forming a circular narrow channel casting according to claim 1, characterized in that: In step S1, the free end includes a dovetail structure; And / or, the height of the free end is 4.5-5.5 mm, and the width of the free end is less than or equal to the maximum diameter of the ceramic core.

7. The method for forming a circular narrow channel casting according to claim 1, characterized in that: In step S1, the thickness of the wax layer is 0.45-0.55 mm.

8. The method for forming a circular narrow channel casting according to claim 1, characterized in that: In step S1, the material of the ceramic core, the fixed end and the free end includes silicon-based material; And / or, the material of the soluble core includes a wax material soluble in water or acidic substances.

9. The method for forming a circular narrow channel casting according to claim 1, characterized in that: In step S2, removing the soluble lost core in the wax part A includes: soaking in an acidic solution.

10. The method for forming a circular narrow channel casting according to claim 1, characterized in that: In step S4, removing the ceramic core includes: soaking in an alkaline solution.

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