A method for preparing wax pattern of special-shaped castings

Abstract

The present invention provides a wax pattern preparation method for special-shaped castings, comprising the following steps: melting, stirring, and standing the wax material; performing segmented wax injection on a mold, wherein three wax injection nozzles are evenly arranged above the wax sample and inject downward, and another wax injection nozzle is located in the middle of the wax sample and injects radially; the segmented wax sample is taken out of the mold together with a urea core, and is shaped and dissolved in water at 20-25°C; the contact surfaces of adjacent segmented wax samples are bonded with AB glue; a sand box is provided outside the wax pattern, gypsum slurry is poured into the sand box, and the bottom of the wax pattern is sealed. By adopting the present invention, a high-precision assembled wax pattern suitable for special-shaped castings with a large aspect ratio can be prepared, the wax pattern segments prepared are easy to position and weld, the assembly process is simple, the assembly difficulty is low, and a complex and closed inner cavity structure of the wax pattern can be prepared at one time; and the problem of inconsistent shrinkage and deformation of the wax pattern during assembly and storage can be well prevented.

Description

Technical Field

[0001] The present application belongs to the technical field of casting wax pattern preparation, and specifically relates to a method for preparing a wax pattern of a special-shaped casting. Background Art

[0002] Wax patterns, also known as wax models, are a common casting method. First, a metal mold of the workpiece is created. Wax is then poured into the mold. Once the wax cools, the wax pattern is removed, resulting in a full-size wax model. Sand is then applied to the surface of the wax model until it reaches a certain thickness. Once the sand adheres to the surface, the wax is placed in water and boiled. The wax melts, leaving a sand shell. This shell is then buried in a sand pit. Liquid metal is then poured along the sand shell. The liquid metal remaining in the sand mold cools and forms the casting.

[0003] At present, the preparation of wax patterns mainly adopts the conventional method, that is, injecting the molten wax into the mold to form it. With the development of precision casting technology, some new wax pattern preparation methods have been developed. For example: the preparation method of investment precision casting wax pattern developed by Harbin Institute of Technology (CN104972063B) is to mix Al2O3 powder and wax material in a mass ratio of 1:2 to obtain a mixture, and press the mold material (mixture) in the wax press machine into the wax pressing mold under the conditions of pressing pressure of 3MPa~5MPa and wax pressing temperature of 90℃~110℃, then maintain the pressure, demould, and naturally cool to room temperature to obtain the investment precision casting wax pattern; the Zhongfu Electromechanical Technology Co., Ltd. developed by Huoshan County The warm wax mold preparation process (CN108607952A) involves adjusting the machine platform or nozzle height so that the nozzle is aligned with the mold's wax injection hole. A qualified urea core is then gently cold-placed into the prepared press mold, ensuring the core head is stable and well-fitted. Molten imported wax is then injected into the press mold through the nozzle to create an investment pattern with a urea core. This pattern is then placed in clean water at a temperature no higher than 26°C, allowing the urea core to dissolve. After the urea core dissolves, the investment pattern is rinsed 2-3 times with clean water to clean the urea. After the wax pattern is removed, the seams and nozzle are trimmed. After passing self-inspection, the pattern is placed in cold water to cool and set, resulting in a medium-temperature wax pattern. However, wax patterns prepared using this method are difficult to apply to special-shaped castings with large aspect ratios (length-to-diameter ratios of no less than 4).

[0004] Although there are documents that disclose assembled wax models, among them, document CN109290515A discloses a split wax mold splicing process: cleaning the mold, placing the qualified split wax mold into the splicing fixture within 30 seconds to prevent the wax mold from cooling and deformation, cleaning the burrs on the bottom surface of the split wax mold before placing it to prevent the wax mold from being unevenly placed, positioning the split wax mold in the splicing fixture, cooling the split wax mold in the splicing fixture for 4-24 hours, cleaning it, heating the bonding wax until it is completely melted, sucking the liquid bonding wax into the straw with a glass pipette, and then blowing out the straw, repeating 3 to 5 times to remove the solid wax remaining in the straw and preheat the straw, injecting wax, splicing the wax parts as a whole, repairing, and cleaning it. However, the operation steps of this scheme are too cumbersome and cannot quickly produce high-precision wax molds suitable for special-shaped castings with large aspect ratios. More importantly, the prepared wax molds are prone to inconsistent shrinkage and deformation during the assembly and storage processes. Summary of the Invention

[0005] The present invention aims to provide a method for preparing a wax pattern for a special-shaped casting, which is at least used to solve the technical problem that the assembled wax pattern is prone to inconsistent shrinkage and deformation during the assembly and storage process.

[0006] The object of the present invention is achieved by adopting the following technical solutions.

[0007] A method for preparing a wax pattern of a special-shaped casting, characterized in that the steps include:

[0008] Step 1: Heat the medium temperature wax to a molten state and keep it warm for 2-2.5 hours;

[0009] Step 2: Transfer the melted wax into the insulation barrel of the wax press, keep it at 65-68°C, and stir it at the bottom, middle, and top of the wax at a stirring speed of 400-500 rpm for 20-25 minutes; Step 3: Let it stand after stirring;

[0010] Step 4: wax injection is performed in sections on the mold. The main pipe of the wax injection tube used is connected to the wax injection machine, and the branch pipe of the wax injection tube is connected to the short glass fiber supply equipment; each wax sample uses four wax injection nozzles, three of which are evenly arranged above the wax sample and inject downward, and the other wax injection nozzle is located in the middle of the wax sample and injects radially; the core of the wax injection mold is made of commercial conventional urea core, and the outside of the urea core is coated with 0.03-0.05mm thick aluminum foil;

[0011] Step 5: After the injection is completed, the segmented wax sample and the urea core are removed from the mold and shaped and dissolved in water at 20-25°C;

[0012] Step 6: Assemble the finalized segmented wax patterns into the desired wax pattern, and bond the contact surfaces of adjacent segmented wax patterns with AB glue;

[0013] Step 7: Place the assembled wax pattern on the base plate, and cover the wax pattern with a sand box, with the lower surface of the sand box flush with the bottom surface of the wax pattern, and the upper surface of the sand box flush with the top surface of the wax pattern;

[0014] Step 8: Pour gypsum slurry into the sand box and place it at room temperature for 10-12 hours after the gypsum slurry solidifies.

[0015] In order to further improve the performance of the prepared wax pattern, a stainless steel tube is axially arranged in the middle of the segmented wax sample, and a plurality of semicircular grooves are radially arranged at the upper and lower ends of the stainless steel tube. After the stainless steel tube is assembled with the mold, the semicircular grooves at the connection part and the mold cover of the mold together form a semicircular hole; during the injection process, the wax material is radially ejected through the semicircular hole to form a wax sample connecting rib, which is ultimately used as an internal casting channel.

[0016] Furthermore, the outer wall of the stainless steel tube is covered with a wax-like layer with a thickness of 2-3 mm, and the wax-like layer on the outer wall of the stainless steel tube, the wax-like connecting ribs and the wax-like main body are connected together to form an integral structure.

[0017] Furthermore, the angle between the generatrix of the stainless steel tube and the axis is 1.5-2 degrees, and the stainless steel tube is thicker at the top and thinner at the bottom.

[0018] To further improve the efficiency of wax pattern preparation and assembly, the stainless steel tubes of adjacent segmented wax samples are connected by socket connection, and the stainless steel tubes in the segmented wax sample at the bottom layer extend downward by 50-60 mm, and the stainless steel tubes in the segmented wax sample at the top layer extend upward by 100-120 mm.

[0019] In order to more efficiently and evenly mix the short glass fibers into the wax material, the acute angle between the main pipe and the branch pipe of the wax material injection pipe is 10-20°.

[0020] Preferably, the ratio of the inner diameters of the main pipe and the branch pipe of the wax injection pipe is 4:1 to 5:1.

[0021] Preferably, the height of the segmented wax-like body is 35-40 times the wall thickness of the segmented wax-like body; the diameter of the wax-like connecting rib is 3-4 times the wall thickness of the segmented wax-like body.

[0022] Furthermore, step 8 further includes: using the positive and negative electrodes of the low-voltage electric heating device to connect the stainless steel tubes at the upper and lower ends of the wax pattern respectively, keeping the power on for 2-3 minutes, and removing the stainless steel tube after the wax-like layer covering the outer wall of the stainless steel tube melts;

[0023] It also includes step 9: sealing the bottom of the wax model, specifically, bonding a solidified gypsum slurry body with a size similar to the portion of the stainless steel pipe extending from the lower end face of the wax model to the hole portion (using a water glass adhesive with a degree of Baume of 54-58 and a modulus of 3.4-3.5, bonding a solidified gypsum slurry body with a size similar to the portion of the steel pipe extending 50-60mm from the lower end face of the wax sample to the lower part of the gypsum casting).

[0024] Preferably, in step 4, the injection pressure is controlled to be 0.5-0.55 MPa, and the injection state is maintained for 3-5 minutes after the wax material is filled.

[0025] Beneficial effects:

[0026] 1. The solution of the present invention can prepare a high-precision assembled wax pattern suitable for special-shaped castings with a large aspect ratio. The outer contour dimensions of the prepared wax pattern are highly accurate, and the prepared wax pattern segments are easy to position and weld. The assembly process is simple and the assembly difficulty is low. The present invention can prepare a wax pattern with a complex and closed inner cavity structure at one time. The aluminum foil wrapped around the outside of the urea core can effectively prevent the impact of high-speed wax material on the urea core. Since the thickness of the aluminum foil is small, the difficulty of demoulding in the later stage is small. For wax patterns that do not need to be welded immediately, the aluminum foil can also be stored on the inner surface of the wax pattern to play a protective and supporting role. The method of the present invention is simple to operate and easy to promote.

[0027] 2. The solution of the present invention can effectively prevent the problem of inconsistent shrinkage and deformation of wax patterns during the molding and storage process;

[0028] 3. The wax mold prepared by the solution of the present invention has good rigidity, high strength and excellent seismic resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 Schematic diagram of the segmented wax sample prepared in the embodiment;

[0030] Figure 2 Schematic diagram of a wax sample composed of segmented wax samples in an embodiment;

[0031] Figure 3 This is the partial structure of the main pipe and branch pipe of the wax injection pipe in the embodiment. DETAILED DESCRIPTION

[0032] The present invention is further described below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described this time are only used to explain the present invention and are not used to limit the present invention. Example 1

[0033] To prepare Figure 1 and Figure 2The wax model shown has a total length of 150 cm, a diameter of 35 cm, and a wall thickness of 4 mm. The wax model is assembled from four wax samples, which are, from top to bottom, the first wax sample 5 (the topmost wax sample) with a thickness of 30 cm, the second wax sample 4 with a thickness of 40 cm, the third wax sample 3 with a thickness of 40 cm, and the fourth wax sample 2 with a thickness of 40 cm. A stainless steel tube 6 is axially arranged in the middle of the first wax sample 5, a stainless steel tube 8 is axially arranged in the middle of the second wax sample 4, a stainless steel tube 9 is axially arranged in the middle of the third wax sample 3, and a stainless steel tube 1 is axially arranged in the middle of the fourth wax sample 2. The stainless steel tube 1 extends downward by 55 mm (i.e., the stainless steel tube 1 is 55 mm longer than the height of the fourth wax sample 2), and the stainless steel tube 6 extends upward by 110 mm (i.e., the stainless steel tube 6 is 110 mm longer than the height of the first wax sample 2). At the upper and lower ends of the stainless steel tubes 8 and 9, there are stainless steel tubes. The ends of the stainless steel tubes are radially arranged with multiple semicircular grooves. The lower end of the stainless steel tube 6, the upper portion of the stainless steel tube 6, the lower portion of the stainless steel tube 1, and the upper end of the stainless steel tube 1 are also radially arranged with multiple semicircular grooves. The outer wall of each stainless steel tube segment is coated with a 2-3mm thick wax-like layer. The wax-like layer on the outer wall of the stainless steel tube, ten wax-like connecting ribs 7, and the wax-like body are connected to form an integral structure (i.e., a segmented wax-like structure). One end of the wax-like connecting rib 7 is connected to the wax-like body and the other end is connected to the wax-like layer on the outer wall of the stainless steel tube. The angle between adjacent wax-like connecting ribs 7 is approximately 36°. Among them, each stainless steel tube segment is provided with an inner concave portion and a convex portion. The convex portion is used to insert into the inner concave portion to achieve a socket connection between adjacent wax-like stainless steel tubes.

[0034] The method for preparing a wax pattern of a special-shaped casting in this embodiment comprises the following steps:

[0035] Step 1: Heat the medium temperature wax to a molten state and keep it warm for 2.3 hours;

[0036] Step 2: Transfer the melted wax into the insulation barrel of the wax press, keep it at 65-68°C, and stir it at the bottom, middle and top of the wax at a stirring speed of 480 rpm for 20-25 minutes;

[0037] Step 3, let it stand after stirring;

[0038] Step 4: wax material is injected in sections on the mold. The mold is designed according to the wax pattern structure and mainly includes an upper mold (upper mold cover), a middle mold and a lower mold (lower mold cover). The upper and lower ends of the middle mold are provided with grooves adapted to the wax sample connecting ribs 7.

[0039] Among them, the core of the mold is made of commercial conventional urea core, the outside of the urea core is coated with 0.04mm thick aluminum foil, and the top and bottom surfaces of the core are provided with semicircular grooves adapted to the wax-like connecting ribs 7, and the inner ends of the semicircular grooves are adapted to the semicircular grooves at the ends of the stainless steel tube 1;

[0040] The main pipe 11 of the wax injection tube is connected to the wax pressing machine, and the branch pipe 12 of the wax injection tube is connected to the short glass fiber supply equipment. The length of the short glass fiber used is 1-3mm. Figure 3 As shown in the figure, the linear arrow represents the wax path, the solid arrow represents the short glass fiber path, the acute angle between the main pipe 11 and the branch pipe 12 of the wax injection tube is 18°, the inner diameter of the main pipe 11 of the wax injection tube is 24 mm, and the inner diameter of the branch pipe 12 of the wax injection tube is 6 mm; each wax sample uses four wax pressing nozzles, three of which are evenly arranged above the wax sample and press downward, and the other wax pressing nozzle is located in the middle of the wax sample and radially presses (in this process, the wax is radially injected through the semicircular groove and flows to the wax sample body to form a wax sample connecting rib); in this step, the injection pressure is controlled to 0.52 MPa, and the injection state is maintained for 5 minutes after the wax is full;

[0041] Step 5: After the injection is completed, the segmented wax samples together with the urea core are taken out of the mold and shaped and the urea core is dissolved in water at 20-25°C; Step 6: The segmented wax samples that have been shaped are assembled into the required wax mold. In addition to the socket connection of the stainless steel pipe, the contact surfaces of the adjacent segmented wax samples are also bonded with AB glue to obtain the following: Figure 2 Wax sample shown;

[0042] Step 7: Place the assembled wax pattern on the base plate, and cover the wax pattern with a sand box, with the lower surface of the sand box flush with the bottom surface of the wax pattern, and the upper surface of the sand box flush with the top surface of the wax pattern;

[0043] Step 8: Pour gypsum slurry into the sand box, and place it at room temperature for 11 hours after the gypsum slurry solidifies. Then use the positive and negative poles of the low-voltage electric heating device to connect the stainless steel tubes at the upper and lower ends of the wax mold respectively. Keep it powered on for 3 minutes. After the wax layer covering the outer wall of the stainless steel tube melts, take out the stainless steel tube. Then seal the bottom of the wax mold. Specifically, glue the gypsum slurry solid body with a size similar to the extension part of the stainless steel tube at the lower end face of the wax mold to the hole part (use a water glass adhesive with a degree of Baume of 54-58 and a modulus of 3.4-3.5 to glue the gypsum slurry solid body similar to the 55mm extension part of the steel tube at the lower end face of the wax sample to the lower part of the gypsum mold).

[0044] The wax mold prepared in this embodiment was subjected to three-dimensional scanning detection, and the deformation of the outer surface profile of the wax mold was found to be 0.03-0.12 mm / 300 mm, and the radial misalignment of the assembled wax mold was 0.05-0.15 mm.

[0045] The present invention can prepare high-precision assembled wax molds suitable for special-shaped castings with large aspect ratios. The outer contour dimensions of the prepared wax mold are highly accurate, and the prepared wax mold segments are easy to position and weld. The assembly process is simple and the assembly difficulty is low. The present invention can prepare a wax mold with a complex and closed inner cavity structure at one time. The aluminum foil wrapped around the outside of the urea core can effectively avoid the impact of high-speed wax material on the urea core. Since the thickness of the aluminum foil is relatively small, the difficulty of demolding in the later stage is small. For wax molds that do not need to be welded immediately, the aluminum foil can also be stored on the inner surface of the wax mold to play a protective and supporting role. The method of the present invention is simple to operate and easy to promote. The scheme of the present invention can well prevent the problem of inconsistent shrinkage and deformation of the wax mold during the assembly and storage process. The scheme of the present invention can prepare a wax mold with good rigidity, high strength and excellent seismic performance.

Claims

1. A method for preparing a wax pattern of a special-shaped casting, characterized in that the steps include: Step 1: Heat the medium temperature wax to a molten state and keep it warm for 2-2.5 hours; Step 2: Transfer the melted wax into the insulation barrel of the wax press, keep it at 65-68°C, and stir it at the bottom, middle and top of the wax at a stirring speed of 400-500 rpm for 20-25 minutes; Step 3, let it stand after stirring; Step 4: wax injection is performed in sections on the mold. The main pipe of the wax injection tube is connected to the wax injection machine, and the branch pipe of the wax injection tube is connected to the short glass fiber supply equipment. Each wax sample uses four wax injection nozzles, three of which are evenly arranged above the wax sample and inject downward, and the other wax injection nozzle is located in the middle of the wax sample and injects radially. The core of the mold is made of urea core, and the outside of the urea core is coated with 0.03-0.05mm thick aluminum foil. Step 5: After the injection is completed, the segmented wax sample and the urea core are removed from the mold and shaped and dissolved in water at 20-25°C; Step 6: Assemble the finalized segmented wax patterns into the desired wax pattern, and bond the contact surfaces of adjacent segmented wax patterns with AB glue; Step 7: Place the assembled wax pattern on the base plate, and cover the wax pattern with a sand box, with the lower surface of the sand box flush with the bottom surface of the wax pattern, and the upper surface of the sand box flush with the top surface of the wax pattern; Step 8: Pour gypsum slurry into the sand box and place it at room temperature for 10-12 hours after the gypsum slurry solidifies; A stainless steel tube is axially arranged in the middle of the segmented wax sample, and multiple semicircular grooves are radially arranged at the upper and lower ends of the stainless steel tube. After the stainless steel tube is assembled with the mold, the semicircular grooves at the connection part and the mold cover of the mold together form a semicircular hole; during the injection process, the wax material is radially ejected through the semicircular groove to form a wax sample connecting rib, which is eventually used as an in-casting channel.

2. The wax-up preparation method according to claim 1, wherein: The outer wall of the stainless steel tube is covered with a wax-like layer with a thickness of 2-3 mm, and the wax-like layer on the outer wall of the stainless steel tube, the wax-like connecting ribs and the wax-like main body are connected together to form an integral structure.

3. The wax-up preparation method according to claim 2, wherein: The included angle between the generatrix of the stainless steel tube and the axis is 0.15-0.2°, and the stainless steel tube is thicker at the top and thinner at the bottom.

4. The wax-up preparation method according to claim 3, wherein: The stainless steel pipes of the adjacent segmented wax samples are connected by a socket connection, and the stainless steel pipe in the segmented wax sample located at the bottom layer extends downward by 50-60 mm, and the stainless steel pipe in the segmented wax sample located at the top layer extends upward by 100-120 mm.

5. The wax-up preparation method according to claim 4, characterized in that: The acute angle between the main pipe and the branch pipe of the wax injection pipe is 10-20 degrees.

6. The wax-up preparation method according to claim 5, characterized in that: The ratio of the inner diameters of the main pipe and the branch pipe of the wax injection pipe is 4:1-5:

1.

7. The wax-up preparation method according to claim 6, characterized in that: The height of the segmented wax-like body is 35-40 times the wall thickness of the segmented wax-like body; the diameter of the wax-like connecting rib is 3-4 times the wall thickness of the segmented wax-like body.

8. The wax-up preparation method according to claim 7, characterized in that: Step 8 also includes: using the positive and negative electrodes of the low-voltage electric heating device to connect the stainless steel tubes at the upper and lower ends of the wax pattern respectively, keeping the power on for 2-3 minutes, and removing the stainless steel tube after the wax-like layer covering the outer wall of the stainless steel tube melts; The method further includes step 9: sealing the bottom of the wax mold, specifically bonding a solidified gypsum slurry having a size similar to that of the extended portion of the stainless steel tube at the lower end surface of the wax mold to the hole.

9. The wax-up preparation method according to any one of claims 1 to 8, characterized in that: In step 4, the injection pressure is controlled at 0.5-0.55 MPa, and the injection state is maintained for 3-5 minutes after the wax material is filled.

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