Wax mold, and preparation method and application of investment casting

Abstract

The invention relates to the technical field of investment precision casting, in particular to a wax mold and a preparation method and application of an investment casting. At least one process hole is formed in the wax mold, and the process hole is a through hole; the wax mold is used as a base plane, and the height of the process hole is 15-20 mm; the fabrication hole is provided with a flange, and the thickness of the flange is 5-10 mm; the wax mould further comprises at least one blocking wax piece, and the blocking wax piece is matched with the auxiliary hole in size. According to the method, the mold shell can be effectively prevented from bulging, meanwhile, the produced mold shell process hole is sealed during follow-up mold shell plugging, and welding plugging is not needed after a casting is poured out. And the poured casting has no fabrication hole and does not need repair welding. The purposes that the molding shell for the photosensitive resin is controlled to bulge and deform, and a casting is free of auxiliary holes can be achieved.

Description

Technical Field

[0001] The invention relates to the technical field of investment casting, and in particular to a wax pattern and a preparation method and application of an investment casting. Background Art

[0002] Investment casting technology is a casting technology evolved from the lost wax method. It mainly refers to making a corresponding model with wax and coating the outside of the wax model with refractory materials. Then, heating or high-temperature steam is used to soften the wax and let it flow out of the refractory material to obtain an empty shell wrapped with refractory materials. The shell is baked to ceramicize it and have a certain strength. Then, the required metal material is melted and poured into the empty shell wrapped with refractory materials.

[0003] Photosensitive resin has the characteristics of good surface roughness and high dimensional accuracy, and is widely used in the foundry industry. However, in the production process of investment castings, the shell is not ceramicized and its own structural strength is low. The expansion coefficient of photosensitive resin is much larger than that of the shell, which causes the shell to bulge or even crack during the firing process. Specifically, the bulging of the photosensitive resin shell mainly occurs during the shell firing stage: due to its own unique thermal expansion effect, the photosensitive resin needs to be directly placed in a furnace above 800°C for "flash burning" to reduce its thermal expansion. However, when the shell is prepared with a low number of layers and its own structural strength is low, the thermal expansion of the photosensitive resin will cause the shell to bulge and crack.

[0004] In order to prevent the shell from bulging and deforming, the method of opening process holes is usually adopted, such as Figure 1 As shown in the figure, the process hole connects the shell during shell making, fixes the two walls of the shell, further strengthens the shell, and effectively prevents the shell from deforming. In order to effectively connect the two walls of the shell, the diameter of the process hole is generally The above, so that the shell at the process hole can have a certain strength. However, after the shell is prepared The process holes are often blocked with shell materials, resulting in local heat nodes, which is not conducive to heat dissipation of the shell after pouring, and may affect the metallurgical quality of the casting and cause loose defects. In addition, the process holes formed on the casting are closed by subsequent welding, but due to the large welding area, for thin-walled castings, deformation is easy to occur during welding, resulting in casting size deviation. Weld bumps are also easy to cause the welding "bite edge" position to be polished out of tolerance during grinding, such as Figure 2 shown.

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

[0006] The first purpose of the present invention is to provide a wax mold, which includes process holes and blocking wax parts, which can effectively prevent the mold shell from bulging. At the same time, the mold shell process holes generated are closed during the subsequent mold shell sealing. After the casting is poured, there is no need for welding and sealing. The mold shell after sealing has no process holes, and the cast casting does not need to be repaired by welding to seal the process holes.

[0007] The second purpose of the present invention is to provide a method for preparing an investment casting. The process holes of the mold shell produced by this method can be sealed with a plugging cover after the mold shell is fired. The cast casting has no process holes and does not require repair welding, which can avoid problems such as welding undercut and deformation caused by repair welding of the process holes.

[0008] The third object of the present invention is to provide a method for preparing a wax pattern or an investment casting and its application in preparing an investment casting.

[0009] In order to achieve the above-mentioned purpose of the present invention, the following technical solutions are particularly adopted:

[0010] The present invention first provides a wax mold, on which is arranged at least one process hole, which is a through hole; with the wax mold as a base surface, the height of the process hole is 15 to 20 mm; the process hole has a flange, and the thickness of the flange is 5 to 10 mm; the wax mold also includes at least one plugging wax piece, and the plugging wax piece matches the size of the process hole.

[0011] Furthermore, the inner diameter of the process hole is 6 to 20 mm.

[0012] Furthermore, the plugging wax piece has a step, and the step matches the size of the flange of the process hole.

[0013] Furthermore, the number of the plugging wax pieces is twice the number of the process holes.

[0014] Furthermore, the material of the wax mold, the process hole and the plugging wax piece includes photosensitive resin.

[0015] The present invention further provides a method for preparing an investment casting, using the wax mold, and the method for preparing the investment casting includes the following steps: coating a refractory material on the surface of the wax mold having a process hole, and then firing it to obtain a mold shell; wherein the refractory material on the surface of the process hole forms a mold shell process hole after firing; coating a refractory material on the plugging wax piece, and then firing it to obtain a plugging cover; removing the mold shells at both ends of the mold shell process hole and the mold shell inside the mold shell process hole to obtain the mold shell process hole to be blocked; inserting the plugging cover into the inside of the mold shell process hole to be blocked, and coating the refractory material on the outside of the plugging cover to connect the plugging cover and the mold shell, and pouring after firing to obtain the investment casting.

[0016] Furthermore, the plugging cover matches the size of the shell process hole to be plugged.

[0017] Furthermore, along the diameter direction of the plugging cover, an assembly gap of 0.05-0.2 mm is reserved between the plugging cover and the shell process hole to be plugged.

[0018] Furthermore, the plugging cover is made of the same material as the shell.

[0019] The present invention also provides application of the preparation method of the wax pattern or the investment casting in preparing the investment casting.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] (1) The wax mold provided by the present invention includes process holes and plugging wax parts. The wax mold can effectively prevent the mold shell from bulging. At the same time, the mold shell process holes generated are sealed during the subsequent mold shell sealing. After the casting is poured, there is no need for welding and sealing. The mold shell after sealing has no process holes, and the cast casting does not need to be repaired by welding to seal the process holes.

[0022] (2) In the method for preparing an investment casting provided by the present invention, the process holes of the mold shell can be sealed with a plugging cover after the mold shell is fired, and the cast casting has no process holes and does not require repair welding.

[0023] (3) The method for preparing investment castings provided by the present invention can improve the strength of the mold shell and prevent it from cracking during roasting.

[0024] (4) The method for preparing the investment casting provided by the present invention is simple to operate, and the mold shell can be sealed by a plugging cover, and the purpose of controlling the bulging deformation of the mold shell for photosensitive resin and having no process holes in the casting can be achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0026] Figure 1 This is a picture of opening a process hole on a mold shell in the prior art;

[0027] Figure 2 The picture of the welding nodule of the casting in the prior art;

[0028] Figure 3 A partial schematic diagram of the wax model provided by the present invention;

[0029] Figure 4 A schematic diagram of the structure of the process hole provided by the present invention;

[0030] Figure 5 A schematic diagram of the structure of the shell provided by the present invention;

[0031] Figure 6 A production process flow chart of the plugging cover provided by the present invention;

[0032] Figure 7 A schematic diagram of the structure of the shell process hole to be blocked provided by the present invention;

[0033] Figure 8 A schematic diagram of the structure of the process hole after plugging provided by the present invention;

[0034] Fig. 9 This is a picture of the shell obtained in Comparative Example 1 of the present invention cracking;

[0035] Fig.10 This is a picture showing bulging of the investment casting obtained in Comparative Example 1 of the present invention. DETAILED DESCRIPTION

[0036] 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.

[0037] If there is no special explanation, in the present invention, "the first aspect", "the second aspect", "the third aspect", "the fourth aspect", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or quantity, nor can they be understood as implicitly indicating the importance or quantity of the indicated technical features. Moreover, "the first", "the second", "the third", "the fourth", etc. only serve the purpose of non-exhaustive enumeration and description, and it should be understood that they do not constitute a closed limitation on quantity.

[0038] If there is no special explanation, the "include" and "comprising" mentioned in the present invention represent open-ended or closed-ended expressions. For example, the "include" and "comprising" may represent that other components not listed may also be included or only the listed components may be included or only the listed components may be included.

[0039] If there is no special explanation, in the present invention, "one or more" or "at least one" refers to any one, any two or more of the listed items. Among them, "several" refers to any two or more of the listed items.

[0040] In a first aspect, the present invention provides a wax mold, wherein the wax mold is provided with at least one process hole, such as one, two, three, four, five, six, eight, ten or more, wherein the process hole is a through hole.

[0041] It can be understood that the number of process holes is related to the size of the product. The larger the size, the more process holes there are. It is also related to the product structure. Therefore, the number of process holes can be set according to needs.

[0042] Figure 3 It is a partial schematic diagram (cross-sectional view) of a wax mold with process holes.

[0043] Figure 4 Schematic diagram of the structure of the process hole.

[0044] Taking the wax mold as the base surface, the height of the process hole is 15-20 mm (i.e., the thickness of the process hole on one side of the wax mold is 15-20 mm), including but not limited to any point value of 15 mm, 16 mm, 17 mm, 18 mm, 19 mm, 20 mm or any range value between two of them. That is, the process hole is 15-20 mm higher than the surface of the wax mold, which is convenient for the preparation of the mold shell at the process hole; when the height of the process hole is too low, the mold shell at the process hole is not conducive to preparation, and the formed angle is easy to fall off; when the height of the process hole is too high, the size of the wax piece required for blocking should also be larger, and the raised process hole is also at risk of being easily collided and falling during the transfer of the mold shell.

[0045] The process hole has a flange, and the thickness of the flange is 5 to 10 mm, including but not limited to any point value of 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, 10 mm or a range value between any two of them. The flange refers to the protrusions at both ends of the process hole. The process hole has a flange to facilitate the cleaning of the mold shell at the process hole. If the flange is too small, when removing the mold shell on the surface of the process hole, the step part of the process hole below will be damaged, which is not conducive to the positioning of the blockage; when the flange is too high, there is a risk of introducing broken shells into the mold shell.

[0046] The wax mold further comprises at least one wax plugging piece, such as one, two, three, four, five, six, eight, ten or more wax plugging pieces, wherein the wax plugging piece matches the size of the process hole, and the wax plugging piece is used to form a plugging cover to seal the shell process hole.

[0047] The wax mold provided by the present invention can effectively prevent the shell from bulging, and the shell process holes generated at the same time are sealed during the subsequent shell plugging, and no welding plugging is required after the casting is poured. The shell after plugging has no process holes, and the poured casting does not need to be welded to plug the process holes.

[0048] In some specific implementations, during the three-dimensional model design stage, a process hole with a flange is designed on the model, and the process hole is produced together with the wax model.

[0049] In some specific implementations, a three-dimensional model for the plugging wax piece is designed, and the plugging wax piece (i.e., the outer shell of the plugging cover) is manufactured.

[0050] In some specific embodiments, the inner diameter of the process hole is 6 to 20 mm, including but not limited to any point value of 6 mm, 7 mm, 8 mm, 9 mm, 10 mm, 11 mm, 12 mm, 13 mm, 14 mm, 15 mm, 16 mm, 17 mm, 18 mm, 19 mm, and 20 mm, or a range value between any two of them. If the inner diameter of the process hole is too small, the shell is not easy to prepare, and the connection strength between the inner and outer shells is low, and there is a risk of breakage during the roasting process; if the inner diameter of the process hole is too large, the process hole will affect the final size of the casting for a special-shaped structure or a curved surface structure. Limiting the inner diameter of the process hole within a certain range can not only make the shell process hole have a certain strength, but also avoid affecting the size of the casting.

[0051] In some specific implementations, the plugging wax piece has a step, and the step matches the size of the flange of the process hole, so that the position of the plugging wax piece and the plugging cover can be limited, and the wall thickness of the process hole after plugging can be ensured.

[0052] In some specific implementations, the number of the plugging wax pieces is twice the number of the process holes, that is, each process hole is configured with two plugging wax pieces.

[0053] In some specific implementations, the materials of the wax mold, the process hole and the plugging wax piece include photosensitive resin and other wax material that expands when heated.

[0054] When it is necessary to open a process hole to increase the strength of the mold shell, the above-mentioned wax pattern and the following method for preparing the investment casting can be used.

[0055] In a second aspect, the present invention provides a method for preparing an investment casting, a method for blocking a mold shell process hole, and a method for controlling the bulging deformation of a mold shell (including a mold shell for a photosensitive resin). Using the wax pattern, the method for preparing the investment casting comprises the following steps:

[0056] The surface of the wax mold with process holes is coated with refractory material, and then fired (the wax mold melts during the firing process) to obtain a shell. Figure 5 As shown. Among them, the refractory material on the surface of the process hole is formed into a shell process hole after being roasted. It can be understood that after the shell is made, the original process hole is transformed into a shell process hole.

[0057] The plugging wax piece is coated with a refractory material and then fired (the plugging wax piece melts during the firing process) to obtain a plugging cap. Figure 6 .

[0058] The mold shells at both ends of the mold shell process hole and the mold shell inside the mold shell process hole are removed to obtain the mold shell process hole to be blocked. Figure 7 shown.

[0059] The plugging cap is inserted into the interior of the shell process hole to be plugged, and the refractory material is coated on the outside of the plugging cap, and then baked to obtain the plugged process hole. The structural diagram thereof is shown in Figure 8 As shown. Then pouring is performed to obtain the investment casting. That is, the shell process hole to be blocked is blocked with a plugging cover.

[0060] The method for preparing an investment casting provided by the present invention can effectively prevent the mold shell from bulging, and the mold shell process holes generated at the same time are sealed during the subsequent mold shell sealing. After the casting is poured, welding and sealing are not required, and the investment casting after pouring has no process holes.

[0061] Furthermore, the method for preparing the investment casting provided by the present invention can improve the strength of the shell and prevent it from cracking during firing.

[0062] In addition, the method for preparing the investment casting provided by the present invention is simple to operate, and the mold shell can be sealed by a plugging cover.

[0063] The shell process holes formed after the shell is roasted are sealed with plugging covers, which can achieve the purpose of controlling the expansion and deformation of the shell for photosensitive resin and having no process holes in the casting compared with conventional photosensitive resin process holes.

[0064] In some specific implementations, the plugging cover matches the size of the shell process hole to be plugged.

[0065] In some specific implementations, along the diameter direction of the plugging cover, an assembly gap of 0.05-0.2 mm (eg, 0.1 mm or 0.15 mm) is left between the plugging cover and the shell process hole to be plugged.

[0066] In the present invention, the main function of the plugging cover is to plug the process hole of the shell to be plugged. The material of the plugging cover can be ceramic, metal, etc., as long as it meets the size requirements and does not react with the metal.

[0067] In some specific embodiments, the plugging cover is made of the same material as the shell, that is, the refractory material coated on the wax mold surface is the same as the refractory material coated on the plugging wax piece. This can effectively prevent the deviation caused by the different expansion coefficients of the two during the preheating of the shell.

[0068] In some specific embodiments, during the firing process of preparing the shell, the shells on both sides of the process hole are connected to increase the strength of the shell cavity and prevent the wax pattern (photosensitive resin) from expanding due to heat and causing the shell to bulge and crack.

[0069] In a third aspect, the present invention provides an application of the method for preparing the wax pattern or the investment casting in preparing the investment casting.

[0070] The embodiments of the present invention will be described in detail below in conjunction with the examples, but it will be appreciated by those skilled in the art that the following examples are only used to illustrate the present invention and should not be considered as limiting the scope of the present invention. If no specific conditions are specified in the examples, the conditions are carried out according to normal conditions or the conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments used is not specified, they are all conventional products that can be obtained commercially.

[0071] Example 1

[0072] The present embodiment provides a wax mold, the product name is: front section, the wax mold is provided with 2 process holes, the process holes are through holes, and the inner diameter of the process holes is 12mm. With the wax mold as the base surface, the process hole is 18mm higher than the surface of the wax mold. The process hole has a flange, and the thickness of the flange is 8mm. The wax mold also includes 4 plugging wax parts, the plugging wax parts have steps, and the plugging wax parts match the size of the process holes (the steps and the flanges also match). The materials of the wax mold, the process holes and the plugging wax parts are all photosensitive resins.

[0073] Example 2

[0074] The present embodiment provides a wax mold, the product name is: rear section, and the wax mold is provided with 4 process holes, which are through holes, and the inner diameter of the process holes is 6mm. With the wax mold as the base surface, the process holes are 15mm higher than the surface of the wax mold. The process holes have flanges, and the thickness of the flanges is 5mm. The wax mold also includes 8 plugging wax parts, which have steps, and the plugging wax parts match the size of the process holes (the steps and the flanges also match). The materials of the wax mold, the process holes and the plugging wax parts are all photosensitive resins.

[0075] Example 3

[0076] The present embodiment provides a wax model, the product name is a casing, and three process holes are set on the wax model, the process holes are through holes, and the inner diameter of the process holes is 20mm. With the wax model as the base surface, the process holes are 20mm higher than the surface of the wax model. The process holes have flanges, and the thickness of the flanges is 10mm. The wax model also includes 6 plugging wax parts, the plugging wax parts have steps, and the plugging wax parts match the size of the process holes (the steps and the flanges also match). The materials of the wax model, the process holes and the plugging wax parts are all photosensitive resins.

[0077] Example 4

[0078] This embodiment provides a method for preparing an investment casting, using the wax pattern of embodiment 1, the method for preparing the investment casting comprises the following steps:

[0079] The surface of the wax mold with process holes is coated with refractory materials. Specifically, the surface layer is made of slurry formed by silica sol and zircon powder, and the surface sand is made of white corundum; the back layer is made of slurry formed by coal gangue powder and silica sol, and the back sand is mullite sand. The slurry of the sealing layer is the same as the slurry of the back layer, but only the sealing slurry is used without sanding. Then, the shell is baked to obtain the shell; the refractory material on the surface of the process hole is baked to form the shell process hole.

[0080] The plugging wax piece is coated with a refractory material (the same material as that coated on the wax pattern) and then fired to obtain a plugging cover. The plugging cover is made of the same material as the shell.

[0081] The mold shells at both ends of the mold shell process hole and the mold shell inside the mold shell process hole are removed to obtain the mold shell process hole to be blocked. The plugging cover matches the size of the mold shell process hole to be blocked, and along the diameter direction of the plugging cover, a 0.1mm assembly gap is left between the plugging cover and the mold shell process hole to be blocked.

[0082] The plugging cap is inserted into the interior of the mold shell process hole to be blocked, and the refractory material (the same material coated on the wax pattern) is coated on the outside of the plugging cap. After roasting, it is poured to obtain an investment casting.

[0083] Example 5

[0084] The method for preparing the investment casting provided in this embodiment is basically the same as that of Embodiment 4, except that the wax pattern of Embodiment 2 is used.

[0085] Example 6

[0086] The method for preparing the investment casting provided in this embodiment is basically the same as that of Embodiment 4, except that the wax pattern of Embodiment 3 is used.

[0087] Comparative Example 1

[0088] The wax pattern of this comparative example is substantially the same as that of Example 3, except that it has no process holes. Using the wax pattern of this comparative example, referring to the method for preparing an investment casting of Example 4, an investment casting is prepared.

[0089] Comparative Example 2

[0090] The wax pattern of this comparative example is basically the same as that of Example 3, except that there is no process hole. Using the wax pattern of this comparative example, referring to the method for preparing the investment casting of Example 4, a process hole is opened during shell making to connect the shell and fix the two walls of the shell, wherein the hole diameter is 12 mm, see Figure 1 As shown, an investment casting is produced.

[0091] The bulging and cracking conditions of the mold shells of each embodiment and each comparative example are shown in Table 1.

[0092] Table 1 Shell bulging and cracking of each embodiment and each comparative example

[0093] Group Is the shell bulging? Is the shell cracked? Whether the process hole is repaired by welding Example 4 no no no Example 5 no no no Example 6 no no no Comparative Example 1 yes yes no Comparative Example 2 no no yes

[0094] Among them, the picture of the shell cracking obtained in Comparative Example 1 is shown in Fig. 9 The picture of the investment casting obtained in comparative example 1 that bulges is shown in Fig.10 .

[0095] It can be seen that the present invention can effectively prevent the shell from bulging, improve the shell strength, and avoid cracking during firing, and the cast casting has no process holes and does not require repair welding.

[0096] Although the present invention has been illustrated and described with specific embodiments, it should be appreciated that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Those skilled in the art should understand that the technical solutions described in the above embodiments may be modified, or some or all of the technical features thereof may be replaced by equivalents without departing from the spirit and scope of the present invention. However, these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention. Therefore, this means that all such replacements and modifications within the scope of the present invention are included in the appended claims.

Claims

1. A wax model, characterized in that: The wax mold is provided with at least one process hole, and the process hole is a through hole; Taking the wax mold as the base surface, the height of the process hole is 15 to 20 mm; The process hole has a flange, and the thickness of the flange is 5 to 10 mm; The wax mold further comprises at least one wax plugging piece, and the wax plugging piece matches the size of the process hole.

2. The wax model according to claim 1, characterized in that: The inner diameter of the process hole is 6 to 20 mm.

3. The wax model according to claim 1, characterized in that: The plugging wax piece has a step, and the step matches the size of the flange of the process hole.

4. The wax model according to claim 1, characterized in that: The number of the plugging wax pieces is twice the number of the process holes.

5. The wax model according to any one of claims 1 to 4, characterized in that: The wax model, the process hole and the plugging wax piece are made of photosensitive resin.

6. A method for preparing an investment casting using a wax pattern as claimed in any one of claims 1 to 5, characterized in that: The method for preparing the investment casting comprises the following steps: Coating a refractory material on the surface of the wax mold with process holes, and then baking it to obtain a shell mold; wherein the refractory material on the surface of the process holes forms the shell mold process holes after baking; Coating a refractory material on the plugging wax piece, and then calcining it to obtain a plugging cover; Removing the mold shells at both ends of the mold shell process hole and the mold shell inside the mold shell process hole to obtain the mold shell process hole to be blocked; The plugging cap is inserted into the interior of the mold shell process hole to be blocked, and the refractory material is coated on the outer side of the plugging cap to connect the plugging cap and the mold shell, and then poured after roasting to obtain the investment casting.

7. The method for preparing an investment casting according to claim 6, characterized in that: The plugging cover matches the size of the shell process hole to be plugged.

8. The method for preparing an investment casting according to claim 7, characterized in that: Along the diameter direction of the plugging cover, an assembly gap of 0.05-0.2 mm is reserved between the plugging cover and the shell process hole to be plugged.

9. The method for preparing an investment casting according to claim 6, characterized in that: The plugging cover is made of the same material as the shell.

10. Use of the method for preparing the wax pattern according to any one of claims 1 to 5 or the investment casting according to any one of claims 6 to 9 in preparing investment castings.

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