A method for manufacturing a complex and slender hollow exhaust oil passage sand core

Abstract

The present invention belongs to the technical field of magnesium-aluminum alloy casting, and discloses a method for manufacturing a complex and slender hollow exhaust oil passage sand core, comprising the following steps: step one: designing a three-dimensional model of the oil passage sand core; step two: preparing the oil passage sand core according to the three-dimensional model of the oil passage sand core; step three: removing the residual sand in the exhaust passage of the oil passage sand core; step four: setting an exhaust rope in the exhaust passage of the oil passage sand core through a sand discharge guide rope hole opened at the end of the exhaust passage or on the surface of the oil passage sand core; step five: setting a blocking sand block in the sand discharge guide rope hole, and the blocking sand block is bonded to the inner side wall of the sand discharge guide rope hole through an adhesive pad. The method proposed by the present invention realizes the industrialized production of complex and slender hollow exhaust oil passage sand cores, and solves the problems of complex and slender oil passage pore defects of magnesium and aluminum alloy castings and magnesium alloy combustion caused by gas generation.

Description

Technical Field

[0001] The invention belongs to the technical field of magnesium-aluminum alloy casting, and in particular relates to a method for manufacturing a complex and elongated hollow exhaust oil passage sand core. Background Art

[0002] At present, magnesium and aluminum alloy castings for aircraft engines are constantly developing towards integration and compactness. In particular, the original various external hoses, steel pipes and other oil pipelines are integrated into the castings for casting. The casting of integrated complex oil circuits is extremely difficult. One of the main difficulties in casting complex oil circuits is that the gas generated by the closed oil circuit sand core cannot be discharged, resulting in the appearance of pore defects in the oil circuit wall of the casting that cannot be overcome. For magnesium alloy castings, if the gas pressure is too high, it cannot be discharged and will cause combustion problems.

[0003] There are two main technical solutions to solve the pores in the oil circuit wall. One is to use differential pressure or pressure axe casting, relying on gas pressure to suppress the gas emitted by the oil circuit sand core inside the oil circuit sand core, inhibiting the gas from entering the alloy liquid to form pore defects before the oil circuit solidifies, but this solution cannot completely solve the problem of complex pore defects; the other technical solution is to pre-embed the exhaust aluminum tube or exhaust rope in the mold when preparing the oil circuit core. This solution has a certain degree of operability for thick and simple oil circuit sand cores. During the core making process, the exhaust aluminum tube and exhaust rope will be offset and exposed on the surface of the oil circuit sand core, which is extremely difficult to operate. The qualified rate of oil circuit sand core preparation is very low, and the inner surface of the oil circuit after casting will have defects, and the exhaust effect is not high. For complex and slender oil circuit sand cores, this technical solution is not operational and it is impossible to prepare oil circuit sand cores with exhaust function. Summary of the invention

[0004] Purpose of the invention: Aiming at the complex and slender oil path pore defects of magnesium and aluminum alloy integrated castings and the magnesium alloy combustion problem caused by gas generation, the present invention provides a complex and slender hollow exhaust oil path sand core manufacturing method, which is used to remove the gas generated by the oil path sand core when heated, eliminate the complex and slender oil path pore defects of magnesium and aluminum alloy castings, and the magnesium alloy combustion problem caused by gas generation. .

[0005] The technical solution of the present invention is:

[0006] A method for manufacturing a complex and elongated hollow exhaust oil passage sand core comprises the following steps:

[0007] Step 1: Designing a three-dimensional model of the oil circuit sand core;

[0008] Step 2: preparing the oil circuit sand core according to the three-dimensional model of the oil circuit sand core;

[0009] Step 3: Clear the residual sand in the exhaust channel of the oil sand core;

[0010] Step 4: an exhaust rope is arranged in the exhaust channel of the oil passage sand core through a sand discharge guide rope hole opened at the end of the exhaust channel or on the surface of the oil passage sand core;

[0011] Step 5: a sealing sand block is arranged in the sand discharge guide rope hole, and the sealing sand block is bonded to the inner wall of the sand discharge guide rope hole through an adhesive pad.

[0012] Furthermore, the oil circuit sand core includes, from bottom to top, an integrally formed sand mold body, a process support column and an oil circuit sand core body;

[0013] The sand mold body is connected to the oil circuit sand core body through a plurality of process support columns; the oil circuit sand core body and the process support column are provided with mutually interpenetrating exhaust passages, the exhaust passage in the process support column is located at the center of the process support column, and the exhaust passage in the oil circuit sand core body is arranged along the direction of the oil circuit sand core body;

[0014] The exhaust passage is also connected to the outside of the sand mold body through an exhaust outlet arranged on the surface of the sand mold body;

[0015] A plurality of sand discharge guide rope holes are arranged on the upper surface of the oil passage sand core body, and the sand discharge guide rope holes are connected with the exhaust passage in the oil passage sand core body.

[0016] Furthermore, in the step 2, the oil circuit sand core is prepared by an inkjet 3D printing method.

[0017] Further, in step 3, the residual sand in the exhaust channel is cleared by the following steps:

[0018] Step 1) inserting a hose with a diameter smaller than that of the exhaust channel into the exhaust channel from the sand discharge guide rope hole in turn;

[0019] Step 2) connecting the hose to a dry compressed air pipe, moving the hose forward and backward, and gradually inserting the hose into the depth of the exhaust passage to loosen the unsolidified residual sand;

[0020] Step 3) disconnect the hose from the dry compressed air pipe and connect it to the negative pressure suction pipe to suck out the loose residual sand in the exhaust channel;

[0021] Step 4) Repeat step 3) until the exhaust passage between the two sand discharge guide rope holes is connected;

[0022] Step 5) After all the exhaust channels are connected, connect the hose to the dry compressed air pipe, blow air inward from one sand drainage guide rope hole, and check whether there is gas flowing out from the adjacent sand drainage guide rope hole to complete the penetration inspection of the sand drainage guide rope hole.

[0023] Furthermore, the wall thickness of the oil channel sand core is not less than 5 mm;

[0024] The diameter of the exhaust passage is determined according to the wall thickness of the oil passage sand core, and the value range is 1.5 mm to 6.0 mm.

[0025] Furthermore, in step 4, an exhaust rope is arranged in the exhaust channel in the following manner:

[0026] Use scissors to cut off a corner on both sides of one end of the exhaust rope to form a sharp corner;

[0027] Use refractory cement to glue the upper and lower pieces of the sharp corner together. After the refractory cement is dry, clamp one end of the sharp corner with tweezers, insert it from the end of the exhaust channel of the oil circuit sand core or the sand discharge guide rope hole, and pass it out from the other end of the exhaust channel or the adjacent sand discharge guide rope hole, and cut off the excess length of the exhaust rope and the refractory cement bonding section.

[0028] Furthermore, in the step 5, a refractory felt is provided between the inner surface of the plugging sand block and the exhaust rope; and a coated sand solidification layer is provided on the outer surface of the plugging sand block;

[0029] The refractory felt and the coated sand solidification layer are connected to the inner side wall of the sand discharge guide rope hole on all sides.

[0030] Further, the shape of the sand discharge guide rope hole is a rectangular boss structure, a circular boss structure, an elliptical boss structure, or an arc boss structure;

[0031] The plugging sand block is a rectangular boss structure, a circular boss structure, an elliptical boss structure, or an arc-shaped boss structure that matches the shape of the sand discharge guide rope hole.

[0032] Further, the steps of sealing the sand drain guide rope hole are as follows:

[0033] Step a): laying a layer of refractory felt on the exhaust rope in the sand discharge guide rope hole;

[0034] Step b): applying a layer of refractory clay around the plugging sand block and the lower stage and then inserting it into the sand discharge guide rope hole, wherein the refractory clay forms an adhesive pad after drying;

[0035] Step c): Use a small blowtorch to move back and forth once on the upper surface of the plugging sand block to bake and heat it, and then apply a layer of coated sand solidification layer on the upper surface of the plugging sand block;

[0036] Step d): Repeat step c) cyclically until the sealing shape of the sand drain guide rope hole is consistent with the oil circuit sand core.

[0037] Furthermore, the diameter of the exhaust rope is 0.5 mm to 1 mm smaller than the diameter of the exhaust channel.

[0038] The present invention has the following beneficial effects:

[0039] In order to obtain a complex and slender oil channel sand core with exhaust function, a method for manufacturing a complex and slender hollow exhaust oil channel sand core is provided, and the overall structure of the sand mold body, the oil channel sand core body, and the process support column is designed to facilitate the establishment and continuity of the exhaust channel; the 3D core making method is adopted to realize the molding of the hollow exhaust channel; the method and parameters of the low-pressure blowing of the unsolidified residual sand by the hose and the negative pressure suction are studied experimentally, so as to ensure the removal of residual sand in the exhaust channel and the integrity of the oil channel sand core tube wall; the exhaust rope is a hose woven from refractory materials with a temperature resistance of more than 900 degrees, which can prevent the alloy liquid from flowing into the tube, and allow the gas to enter the exhaust rope tube from the weaving gap, and penetrate the exhaust rope in the hollow exhaust channel, so as to solve the problem that the high-temperature alloy liquid partially damages the thin wall of the oil channel sand core, causing the alloy liquid to drill into the exhaust channel to form a "cast wire" that cannot be cleaned; the sand discharge guide rope hole structure and the sealing method provide a window for cleaning sand and passing the exhaust rope, and the sealing method solves the leakage problem and can introduce the gas emitted by the adhesive pad into the exhaust rope.

[0040] The method proposed in the present invention realizes the industrialized production of complex and slender hollow exhaust oil channel sand cores, solves the problem of complex and slender oil channel pore defects in magnesium and aluminum alloy castings and the combustion of magnesium alloy caused by gas generation. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 This is a cross-sectional view of the oil circuit sand core of the present invention;

[0042] Figure 2 A top view of the oil circuit sand core of the present invention;

[0043] Figure 3 A top view of an accessory casing integrated with a complex oil circuit manufactured by the method described in the present application in an embodiment;

[0044] Figure 4 It is a cross-sectional view of the AA surface of the accessory casing integrated with a complex oil circuit manufactured by the method described in the present application in the embodiment;

[0045] Figure 5 It is a schematic diagram of the connection between the exhaust passage and the exhaust outlet of the accessory case in the embodiment;

[0046] Figure 6 Schematic diagram of the sand discharge guide rope hole of the accessory casing in the embodiment;

[0047] Figure 7 Schematic diagram of plugging the sand discharge guide rope hole of the accessory casing in the embodiment;

[0048] 1-sand mold body, 2-process support column, 3-oil channel sand core body, 4-exhaust rope, 5-adhesive pad, 6-refractory felt, 7-sealing sand block, 8-coated sand solidification layer, 9-exhaust channel, 10-sand discharge guide rope hole, 11-exhaust outlet. DETAILED DESCRIPTION

[0049] This section is an embodiment of the present invention, which is used to explain and illustrate the technical solution of the present invention.

[0050] Figure 1 It is a schematic diagram of the structure of the complex and elongated hollow exhaust oil passage sand core of the present invention; Figure 2 It is a top view;

[0051] like Figure 1 and Figure 2 As shown, the complex and slender hollow exhaust oil circuit sand core includes: a sand mold body, an oil circuit sand core body, a process support column, an exhaust rope, a refractory felt, an adhesive pad, a sealing sand block, and a coated sand solidification layer, wherein the oil circuit sand core body and the process support column center are provided with an exhaust channel, the exhaust channel is a circular pipe, and after the core making is completed, the exhaust channel is filled with unsolidified residual sand that needs to be removed, and the oil circuit sand core body is provided with a sand discharge guide rope hole, the shape of the sand discharge guide rope hole can be a rectangular boss structure, a circular boss structure, an elliptical boss structure, and an arcuate boss structure, and the sealing block sand block structures cooperating with the boss hole are respectively a rectangular boss structure, a circular boss structure, an elliptical boss structure, and an arcuate boss structure.

[0052] The sand mold body is connected to the process support column, the process support column is connected to the oil circuit sand core body, the exhaust rope is connected to the oil circuit sand core body and the inner wall of the exhaust channel of the support column, the exhaust rope is connected to the refractory felt, the refractory felt is connected to the sealing sand block, the sealing sand block is connected to the coated sand solidified layer, the sealing sand block is connected to the inner wall of the sand discharge guide rope hole of the oil circuit sand core body through an adhesive pad, and the refractory felt and the coated sand solidified layer are connected to the inner wall of the sand discharge guide rope hole of the oil circuit sand core body.

[0053] The exhaust rope is connected to the refractory felt, the refractory felt is connected to the sealing sand block, the sealing sand block is connected to the coated sand solidified layer, the sealing sand block is connected to the inner wall of the sand discharge guide rope hole of the oil circuit sand core body through an adhesive pad, and the refractory felt and the coated sand solidified layer are connected to the inner wall of the sand discharge guide rope hole of the oil circuit sand core body.

[0054] A method for manufacturing a complex and elongated hollow exhaust oil passage sand core, the specific implementation steps are as follows:

[0055] Step 1: Design of a three-dimensional model of a complex and slender hollow exhaust oil circuit sand core, including a sand mold body, an oil circuit sand core body, and a process support column. The sand mold body is connected to the process support column, and the process support column is connected to the oil circuit sand core body. The oil circuit sand core body and the process support column are provided with interconnected exhaust channels 9, and the exhaust channel has an exhaust outlet 11 connected to the outside of the sand mold body. The diameter of the exhaust channel can be 1.5mm, 2.5mm, 3.5mm, 4.5mm, or 6.0mm. The wall thickness of the oil circuit sand core body is not less than 5mm. The diameter size of the appropriate exhaust channel can be set according to the outer diameter of the oil circuit sand core body. The oil circuit sand core body is provided with a sand discharge guide rope hole 10.

[0056] Step 2: Use an inkjet printer to prepare the designed complex and elongated hollow exhaust oil channel sand core three-dimensional model into a sand core, and the hollow exhaust channel of the prepared sand core is filled with uncured residual sand to be removed.

[0057] Step 3: Removal of residual sand from the oil circuit sand core and process support column exhaust channel:

[0058] 1) Insert a hose with a diameter smaller than 0.5mm of the exhaust channel into the exhaust channel from the sand discharge guide rope hole in turn;

[0059] 2) Connect the hose to the dry compressed air pipe, set the pressure to 0.1MPa~0.2MPa, move the hose back and forth, and gradually probe forward to a distance of 30mm~40mm to loosen the unsolidified residual sand;

[0060] 3) The hose is connected to the negative pressure suction pipe to suck out the loose residual sand;

[0061] 4) Repeat step 3) until the exhaust channel between the two sand drainage guide rope holes is connected. After all the exhaust channels are connected, connect the hose to the compressed air pipe, blow air from one sand drainage guide rope hole, and check whether there is gas flowing out from the adjacent sand drainage guide rope hole to complete the penetration check of the sand drainage guide rope holes.

[0062] Step 4: Connect the exhaust rope to the inner wall of the exhaust channel of the oil sand core and the support column, that is, insert the exhaust rope into the exhaust channel to prevent the alloy liquid from flowing into the exhaust channel. The diameter of the exhaust rope is 1.0mm, 2.0mm, 3.0mm, 4.0mm, and 5.0mm, which correspond to the exhaust channel diameters of 1.5mm, 2.5mm, 3.5mm, 4.5mm, and 6.0mm respectively; select different exhaust rope diameters according to the exhaust channel diameter; the specific operations are as follows:

[0063] Use scissors to cut off a corner on both sides of one end of the exhaust rope to form a 60-degree sharp angle at one end of the exhaust rope, and then use refractory cement to glue the upper and lower pieces of the sharp angle together. After the refractory cement is dry, use tweezers to clamp one end of the sharp angle, and insert it from the end of the exhaust channel of the oil circuit sand core or the adjacent sand removal guide rope hole. After the exhaust rope is inserted, it is passed out from the other end of the exhaust channel or the adjacent sand removal guide rope hole, and the excess length is cut off. The refractory cement bonding section needs to be cut off.

[0064] Step 5: The exhaust rope is connected to the refractory felt, the refractory felt is connected to the sealing sand block, the sealing sand block is connected to the coated sand solidified layer, the sealing sand block is connected to the inner wall of the sand drain rope hole of the oil circuit sand core through the adhesive pad, the refractory felt and the coated sand solidified layer are connected to the inner wall of the sand drain rope hole of the oil circuit sand core, that is, the sand drain rope hole is sealed. The specific operations are as follows:

[0065] 1) Lay a layer of refractory felt on the exhaust rope in the sand discharge guide rope hole;

[0066] 2) Apply a layer of refractory cement around the plugging sand block and the lower stage, and then install it into the sand discharge guide rope hole. After the refractory cement dries, a bonding pad is formed;

[0067] 3) Use a small blowtorch to move back and forth on the upper surface of the sealing sand block once to bake and heat the upper surface, then apply a layer of coated sand on the upper surface, bake it again, and then apply coated sand again. Repeat this operation until the sealing shape of the sand guide rope hole is consistent with the oil circuit sand core.

[0068] Example 1

[0069] The casing of a certain type of machine accessory is a magnesium alloy casting, which integrates a complex oil circuit. In the early stage of casting development, the oil circuit pore defects and combustion problems could not be solved. The method proposed in the present invention was adopted to solve the above problems and complete the casting development task. The specific operations are as follows:

[0070] Step 1: Overall design of complex and slender hollow exhaust oil channel sand core, such as Figure 3 As shown, it includes 1 sand mold body, 18 complex oil circuit sand core bodies, and 59 process support columns. The sand mold body is connected to the process support columns, and the process support columns are connected to the oil circuit sand core body. The oil circuit sand core body is provided with a hollow exhaust channel, and some process support columns are provided with a hollow exhaust channel. The hollow exhaust channel diameters are 2.5mm and 6mm. The sand core body is provided with 26 sand drainage rope holes. The sand drainage rope holes adopt a rectangular boss structure, a circular boss structure, and an arc boss structure. Since the oil circuit of the casting is complex and numerous, many oil circuit sand core bodies are integrated and designed on the same sand mold body. Figure 3 and Figure 4 Shown is the overall structural schematic diagram and cross-sectional view of a complex and elongated hollow exhaust oil passage sand core case; Figure 5 This is a schematic diagram of the process support column and exhaust channel of the case. Figure 6 Schematic diagram of the sand discharge guide rope hole.

[0071] Step 2: Use an inkjet printer to prepare the designed complex and slender hollow exhaust oil circuit integral sand core three-dimensional model into an integral sand core, and the hollow exhaust channel of the prepared sand core is filled with uncured residual sand to be removed.

[0072] Step 3: Residual sand removal process in the oil circuit sand core and process support column exhaust channel:

[0073] 1) Match the hoses with diameters of 2mm and 5mm to the exhaust channels of corresponding diameters, and insert them into the exhaust channels from the sand discharge guide rope holes in turn;

[0074] 2) Connect the hose to the dry compressed air pipe. For the exhaust channel with a diameter of 2.5mm, set the pressure to 0.15MPa, move the hose back and forth, and gradually probe forward to a distance of 30mm to loosen the uncured residual sand; for the exhaust channel with a diameter of 5mm, set the pressure to 0.2MPa, move the hose back and forth, and gradually probe forward to a distance of 40mm to loosen the uncured residual sand.

[0075] 3) The hose is connected to the negative pressure suction pipe to suck out the loose residual sand;

[0076] 4) Repeat the operation in item "3)" until the exhaust channel between the two sand drainage guide rope holes is connected. After all the exhaust channels are connected, connect the hose to the dry compressed air pipe, blow air from one sand drainage guide rope hole, and check whether there is gas flowing out from the adjacent sand drainage guide rope hole to complete the penetration check of the sand drainage guide rope holes.

[0077] Step 4: Connect the exhaust rope to the inner wall of the exhaust channel of the oil sand core and the support column, that is, insert the exhaust rope into the exhaust channel to prevent the alloy liquid from flowing into the exhaust channel. The specific operations are as follows:

[0078] For the exhaust channel with a diameter of 2.5mm, choose an exhaust rope with a diameter of 2mm. For the exhaust channel with a diameter of 6mm, choose an exhaust rope with a diameter of 5mm. Use scissors to cut off a corner on both sides of one end of the exhaust rope to form a 60-degree sharp angle at one end of the exhaust rope. Then use refractory cement to glue the upper and lower pieces of the sharp angle together. After the refractory cement is dry, use tweezers to clamp one end of the sharp angle and insert it from the end of the discharge channel of the oil circuit sand core or the adjacent sand discharge guide rope hole. After the exhaust rope is inserted, it needs to be passed out from the other end of the discharge channel or the adjacent sand discharge guide rope hole, and the excess length should be cut off. The refractory cement bonding section needs to be cut off.

[0079] Step 5: The exhaust rope is connected to the refractory felt, the refractory felt is connected to the sealing sand block, the sealing sand block is connected to the coated sand solidified layer, the sealing sand block is connected to the inner wall of the sand drain rope hole of the oil circuit sand core through the adhesive pad, the refractory felt and the coated sand solidified layer are connected to the inner wall of the sand drain rope hole of the oil circuit sand core, that is, the sand drain rope hole is sealed. Figure 7 This is a schematic diagram of plugging the sand drainage guide rope hole. The specific operations are as follows:

[0080] 1) Lay a layer of refractory felt on the exhaust rope in the sand discharge guide rope hole;

[0081] 2) Apply a layer of refractory cement around the plugging sand block and the lower stage, and then install it into the sand discharge guide rope. After the refractory cement dries, it forms a bonding pad;

[0082] 3) Use a small blowtorch to move back and forth on the upper surface of the sealing sand block once to bake and heat the upper surface, then apply a layer of coated sand on the upper surface, bake it again, and then apply coated sand again. Repeat this operation until the sealing shape of the sand guide rope hole is consistent with the oil circuit sand core.

[0083] The present invention designs an overall structure including a sand mold body, an oil circuit sand core body and a process support column, which is convenient for establishing and connecting the exhaust channel; inkjet three-dimensional printing is adopted to realize the forming of the hollow exhaust channel; the method and parameters of using a hose to loosen the unsolidified residual sand at low pressure and suck it out at negative pressure are experimentally studied, thereby ensuring the removal of residual sand from the exhaust channel and the integrity of the oil circuit sand core tube wall; the exhaust rope is a hose woven from refractory materials with a temperature resistance of more than 900 degrees, which can block the alloy liquid from flowing into the tube, and allow the gas to enter the exhaust rope tube from the weaving gap, and penetrate the exhaust rope into the hollow exhaust channel, thereby solving the problem that the thin wall of the oil circuit sand core is locally damaged by the high-temperature alloy liquid, causing the alloy liquid to drill into the exhaust channel to form a "cast wire" that cannot be cleaned; the sand discharge guide rope hole structure and the sealing method provide a window for cleaning sand and passing the exhaust rope, and the sealing method solves the leakage problem and can introduce the gas emitted by the adhesive pad into the exhaust rope.

[0084] The method proposed in the present invention realizes the industrialized production of complex and slender hollow exhaust oil channel sand cores, solves the problem of complex and slender oil channel pore defects in magnesium and aluminum alloy castings and the combustion of magnesium alloy caused by gas generation.

Claims

1. A method for manufacturing a complex and elongated hollow exhaust oil passage sand core, characterized in that: The method comprises the following steps: Step 1: Designing a three-dimensional model of the oil circuit sand core; Step 2: Prepare the oil circuit sand core according to the three-dimensional model of the oil circuit sand core; the oil circuit sand core includes an integrally formed sand mold body, a process support column and an oil circuit sand core body from bottom to top; the sand mold body is connected to the oil circuit sand core body through multiple process support columns; the oil circuit sand core body and the process support column are provided with mutually interpenetrating exhaust passages, the exhaust passage in the process support column is located at the center of the process support column, and the exhaust passage in the oil circuit sand core body is arranged along the direction of the oil circuit sand core body; the exhaust passage is also communicated with the outside of the sand mold body through an exhaust outlet arranged on the surface of the sand mold body; a plurality of sand discharge guide rope holes are arranged on the upper surface of the oil circuit sand core body, and the sand discharge guide rope holes are interpenetrating with the exhaust passage in the oil circuit sand core body; Step 3: Clear the residual sand in the exhaust channel of the oil sand core; Step 4: an exhaust rope is arranged in the exhaust channel of the oil passage sand core through a sand discharge guide rope hole opened at the end of the exhaust channel or on the surface of the oil passage sand core; Step 5: a sealing sand block is arranged in the sand discharge guide rope hole, and the sealing sand block is bonded to the inner wall of the sand discharge guide rope hole through an adhesive pad.

2. The method for manufacturing a complex and elongated hollow exhaust oil passage sand core according to claim 1, characterized in that: In the step 2, the oil circuit sand core is prepared by an inkjet 3D printing method.

3. The method for manufacturing a complex and elongated hollow exhaust oil passage sand core according to claim 1, characterized in that: In step 3, the residual sand in the exhaust channel is cleared by the following steps: Step 1) inserting a hose with a diameter smaller than that of the exhaust channel into the exhaust channel from the sand discharge guide rope hole in turn; Step 2) connecting the hose to a dry compressed air pipe, moving the hose forward and backward, and gradually inserting the hose into the depth of the exhaust passage to loosen the unsolidified residual sand; Step 3) disconnect the hose from the dry compressed air pipe and connect it to the negative pressure suction pipe to suck out the loose residual sand in the exhaust channel; Step 4) Repeat step 3) until the exhaust passage between the two sand discharge guide rope holes is connected; Step 5) After all the exhaust channels are connected, connect the hose to the dry compressed air pipe, blow air inward from one sand drainage guide rope hole, and check whether there is gas flowing out from the adjacent sand drainage guide rope hole to complete the penetration inspection of the sand drainage guide rope hole.

4. The method for manufacturing a complex and elongated hollow exhaust oil passage sand core according to claim 1, characterized in that: The wall thickness of the oil channel sand core is not less than 5mm; The diameter of the exhaust passage is determined according to the wall thickness of the oil passage sand core, and the value range is 1.5 mm to 6.0 mm.

5. The method for manufacturing a complex and elongated hollow exhaust oil passage sand core according to claim 1, characterized in that: In the step 4, an exhaust rope is arranged in the exhaust channel in the following manner: Use scissors to cut off a corner on both sides of one end of the exhaust rope to form a sharp corner at one end of the exhaust rope; Use refractory cement to glue the upper and lower pieces of the sharp corner together. After the refractory cement is dry, clamp one end of the sharp corner with tweezers, insert it from the end of the exhaust channel of the oil circuit sand core or the sand discharge guide rope hole, and exit from the other end of the exhaust channel or the adjacent sand discharge guide rope hole, cut off the excess length of the exhaust rope, and cut off the refractory cement bonding section.

6. The method for manufacturing a complex and elongated hollow exhaust oil passage sand core according to claim 1, characterized in that: In the step 5, a refractory felt is provided between the inner surface of the plugging sand block and the exhaust rope; and a coated sand solidification layer is provided on the outer surface of the plugging sand block; The refractory felt and the coated sand solidification layer are connected to the inner side wall of the sand discharge guide rope hole on all sides.

7. The method for manufacturing a complex and elongated hollow exhaust oil passage sand core according to claim 6, characterized in that: The shape of the sand discharge guide rope hole is a rectangular boss structure, a circular boss structure, an elliptical boss structure or an arc boss structure; The plugging sand block is a rectangular boss structure, a circular boss structure, an elliptical boss structure or an arc boss structure that matches the shape of the sand discharge guide rope hole.

8. The method for manufacturing a complex and elongated hollow exhaust oil passage sand core according to claim 7, characterized in that: The steps of plugging the sand drain guide rope hole are as follows: Step a): laying a layer of refractory felt on the exhaust rope in the sand discharge guide rope hole; Step b): applying a layer of refractory clay around the plugging sand block and the lower stage and then inserting it into the sand discharge guide rope hole, wherein the refractory clay forms an adhesive pad after drying; Step c): Use a small blowtorch to move back and forth once on the upper surface of the plugging sand block to bake and heat it, and then apply a layer of coated sand solidification layer on the upper surface of the plugging sand block; Step d): Repeat step c) cyclically until the sealing shape of the sand drain guide rope hole is consistent with the oil circuit sand core.

9. The method for manufacturing a complex and elongated hollow exhaust oil passage sand core according to claim 4, characterized in that: The exhaust rope diameter is smaller than the exhaust channel diameter.

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