Water-soluble salt core material, method of making, and molding die

Abstract

This invention relates to the field of soluble core materials and molding tooling for rubber molding, and discloses a water-soluble salt core material, its preparation method, and a molding die. The water-soluble salt core material comprises a base powder and an optional binder. The base powder consists of potassium nitrate, sodium nitrate, potassium chloride, and sintered mullite, while the binder is anhydrous borax or anhydrous sodium silicate. During preparation, the components are dry-mixed, heated, and stirred at a constant temperature to form a uniform molten slurry, which is then poured into a preheated molding die. After cooling, solidification, and demolding, the salt core is obtained. The molding die includes an upper mold, a middle mold assembly, a lower mold support, and a plug, forming a Y-shaped bifurcated cavity. The upper mold has a gating hole and multiple vent holes. This solution can balance the melt flowability, molding strength, dimensional stability, and water-soluble core removal performance of the salt core, and improves the filling, venting, and demolding effects of the bifurcated salt core.

Description

Technical Field

[0001] This invention relates to the field of soluble core materials and molding tooling for rubber molding, specifically to a water-soluble salt core material, its preparation method, and a molding die. Background Technology

[0002] Hollow, closed rubber sealing products typically feature structures such as enclosed internal cavities, deep cavities, curved transition sections, or bifurcated cavities. During the molding or vulcanization process of these products, a mold core adapted to the shape of the internal cavity is usually pre-prepared. This mold core supports the internal cavity during rubber molding and is removed from the product's internal cavity after molding. Compared to conventional mold cores such as metal cores or sand cores, water-soluble salt mold cores can be removed through water dissolution, making them more suitable for molding rubber products with enclosed or complex internal cavity structures.

[0003] Existing water-soluble salt mold cores are mostly made from single salts or simple mixtures of salts. While these materials possess a certain degree of water solubility, they still have some shortcomings in actual molding and use. On the one hand, single salts or simple mixtures of salts have limited mechanical strength and high-temperature stability, making them prone to cracking, collapse, or localized deformation during handling, molding, and the pressure applied during rubber vulcanization, thus affecting the dimensional accuracy of the inner cavity of the rubber product. On the other hand, some salt mold cores shrink significantly during cooling and solidification, easily leading to defects such as cracking, warping, surface porosity, or looseness, resulting in unstable surface quality of the salt mold core and potentially affecting the molding quality of the inner wall of the rubber product.

[0004] For hollow, closed rubber sealing products with deep cavities, narrow channels, or bifurcated structures, salt-based core materials not only need sufficient molding strength and temperature stability, but also good fluidity in the molten state to ensure complete filling within the mold cavity. If the material system's melting temperature is too high or its fluidity is insufficient, incomplete filling of complex cavities can easily occur; if the material strength is insufficient or cooling shrinkage is large, breakage, deformation, or dimensional deviations can easily occur during demolding, molding, and subsequent rubber vulcanization. Therefore, existing salt-based core materials still struggle to achieve a balance between strength, temperature resistance, melt fluidity, dimensional stability, and water-soluble core-removing performance.

[0005] Furthermore, the molding quality of salt cores is closely related to the manufacturing process and the structure of the molding die. In existing manufacturing processes, insufficient powder mixing uniformity, improper melt temperature control, or insufficient die preheating can easily lead to melt stratification, deposition, uneven filling, or surface defects. For branched or irregularly shaped salt cores, if the parting method, pouring position, venting structure, and demolding structure of the molding die are not properly designed, localized air pockets, material shortages at the ends, or demolding damage can easily occur during pouring, reducing the molding integrity of the salt core. Summary of the Invention

[0006] The purpose of this invention is to provide a water-soluble salt core material, a preparation method, and a molding die, so as to solve the problems of existing salt core materials in that it is difficult to balance strength, temperature resistance stability, melt flowability, dimensional stability, and water-soluble core removal performance, as well as the problems of insufficient filling, poor venting, and easy damage during demolding of complex cavity salt cores.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A water-soluble salt core material includes a base powder and an optional binder; the base powder, by mass percentage, consists of the following components: 10%~50% potassium nitrate, 10%~40% sodium nitrate, 5%~30% potassium chloride, and 10%~40% sintered mullite, and the sum of the mass percentages of each component in the base powder is 100%; the binder is 0~5 parts by mass relative to the total mass of the base powder, and the binder is anhydrous borax or anhydrous sodium silicate.

[0009] Furthermore, the sintered mullite is sintered mullite powder, and the sintered mullite powder is a 200-mesh or 325-mesh powder material.

[0010] Furthermore, the base powder, by mass percentage, is composed of 30%~40% potassium nitrate, 20%~30% sodium nitrate, 15%~25% potassium chloride, and 15%~25% sintered mullite, and the sum of the mass percentages of each component in the base powder is 100%.

[0011] Furthermore, the binder is anhydrous borax, and the binder accounts for 0.5 to 2 parts of the total mass of the base powder.

[0012] The present invention also provides a method for preparing a water-soluble salt mold core material, which is used to prepare the above-mentioned water-soluble salt mold core material. The preparation method includes the following steps:

[0013] Weigh out potassium nitrate, sodium nitrate, potassium chloride and sintered mullite according to the proportions. If a binder is added, weigh out the binder at the same time. Put all components into the mixing equipment and dry mix to obtain a mixed powder.

[0014] The mixed powder is transferred to a melting device, heated to 280℃~350℃, and kept at this temperature while stirring until the mixed powder is completely melted to obtain a uniform melt.

[0015] Preheat the molding die to 80℃~120℃, and inject the uniform molten liquid into the mold cavity of the preheated molding die;

[0016] The uniform molten liquid is cooled and solidified in the mold cavity, and after demolding, a salt mold core is obtained.

[0017] Furthermore, when preparing the mixed powder, the dry mixing time is 10 min to 30 min.

[0018] Furthermore, in preparing the homogeneous melt, the mixed powder is heated to 310℃~330℃ and kept at that temperature while stirring for 5min~20min until the homogeneous melt is free of stratification and sedimentation.

[0019] The present invention also provides a molding die for implementing the above-described preparation method, comprising an upper cover mold, a middle mold assembly, a lower support mold, and a plug; the middle mold assembly includes a first outer parting mold, a second outer parting mold, and an inner core mold, wherein the first outer parting mold and the second outer parting mold are respectively disposed on both sides of the inner core mold; the upper cover mold is disposed above the middle mold assembly, and the lower support mold is disposed below the middle mold assembly; the upper cover mold, the middle mold assembly, the lower support mold, and the plug together form a mold cavity for molding a salt mold core; the mold cavity is a Y-shaped forked cavity; the upper cover mold is provided with a pouring hole communicating with the mold cavity; the upper cover mold is also provided with a first vent hole, a second vent hole, and a third vent hole communicating with the mold cavity; and the plug is disposed at the end opening of the mold cavity.

[0020] Furthermore, the Y-shaped bifurcated cavity is composed of a main cavity segment and two branch cavity segments connected to the main cavity segment. The two branch cavity segments intersect and then connect to the main cavity segment. The casting hole is located above the area where the main cavity segment and the branch cavity segments intersect.

[0021] Furthermore, the first vent hole, the second vent hole, and the third vent hole are spaced apart on the upper cover mold and are respectively connected to the main cavity section and the two branch cavity sections; the plug is detachably inserted into one end of the mold cavity, and the first outer mold parting, the second outer mold parting, and the inner core mold are detachably connected to the lower support mold by bolts.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0023] The water-soluble salt core material provided by this invention comprises a basic powder system of potassium nitrate, sodium nitrate, potassium chloride, and sintered mullite, with the option to add anhydrous borax or anhydrous sodium silicate as a binder. Through the combination of these components, the salt core material maintains its water-soluble core-removing properties while also ensuring good melt flowability, molding strength, temperature stability, and dimensional stability, making it suitable for preparing complex internal cavity salt cores in hollow closed rubber sealing products.

[0024] The preparation method of the present invention controls the uniformity of powder, melting state and casting conditions through steps such as dry mixing of powder, heating and melting, preheating and casting of mold, and cooling and demolding. This helps to reduce melt layering, deposition, uneven filling and local molding defects, and enables the salt mold core to form a predetermined shape more stably.

[0025] The molding die of this invention adopts a combination structure of upper cover mold, middle module, lower support mold and plug, forming a Y-shaped forked cavity, which can meet the casting and molding requirements of forked salt mold cores; by setting pouring holes and venting holes corresponding to the main cavity section and the two branch cavity sections on the upper cover mold, it is beneficial to realize the filling of molten salt material and the venting of the cavity during the casting process; through the plug and split middle module structure, it is easy to demold the salt mold core after cooling and solidification, reducing the risk of damage or breakage of the salt mold core edges and corners during demolding.

[0026] Of course, implementing the various technical solutions of this invention does not necessarily require achieving all of the advantages described above at the same time. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other embodiments can be obtained from these drawings without creative effort.

[0028] Figure 1 This is a schematic diagram of the lower surface structure of the upper cover mold in an embodiment of the present invention;

[0029] Figure 2 This is a schematic diagram of the upper surface structure of the upper cover mold in an embodiment of the present invention;

[0030] Figure 3 This is a schematic diagram of the structure of the middle module, lower support mold, and plug in an embodiment of the present invention;

[0031] Figure 4 for Figure 3 Top view;

[0032] Figure 5 This is a three-dimensional structural diagram of the salt-made mold core in an embodiment of the present invention;

[0033] Figure 6 This is a flowchart of the method for preparing a water-soluble salt mold core in an embodiment of the present invention.

[0034] In the figure, 1-upper cover mold; 2-first outer mold parting; 3-second outer mold parting; 4-inner core mold; 5-lower support mold; 6-plug; 7-pouring hole; 8-first vent hole; 9-second vent hole; 10-third vent hole; 11-salt mold core. Detailed Implementation

[0035] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. It should be understood that the following embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Without departing from the concept of the present invention, those skilled in the art can make adaptive adjustments to the content of each component, the particle size of the powder, the stirring time, the melting temperature, the mold preheating temperature, and the local structure of the mold.

[0036] In the description of this invention, the water-soluble salt core material comprises a base powder and an optional binder. The base powder is composed of potassium nitrate, sodium nitrate, potassium chloride, and sintered mullite, with the sum of the mass percentages of each component being 100%. The binder is 0-5 parts by mass relative to the total mass of the base powder, and can be anhydrous borax or anhydrous sodium silicate. For ease of explanation, unless otherwise specified, all parts mentioned in the following examples refer to parts by mass relative to 100 parts of the total mass of the base powder.

[0037] like Figure 1 and Figure 2 As shown, the molding die used in this invention includes an upper cover mold 1, which is provided with a pouring hole 7, a first venting hole 8, a second venting hole 9 and a third venting hole 10. Figure 1 The lower surface structure of the upper cover mold 1 is shown. Figure 2 The upper surface structure of the upper cover mold 1 is shown. The pouring hole 7 penetrates the upper cover mold 1 and communicates with the mold cavity, and is used to inject molten salt core material into the mold cavity. The first vent hole 8, the second vent hole 9, and the third vent hole 10 are also communicated with the mold cavity, and are used to discharge the gas in the cavity during the pouring process.

[0038] like Figure 3 and Figure 4 As shown, the molding die also includes a middle module, a lower support mold 5, and a plug 6. The middle module includes a first outer mold 2, a second outer mold 3, and an inner core mold 4. The first outer mold 2 and the second outer mold 3 are located on both sides of the inner core mold 4. The upper cover mold 1 is located above the middle module, and the lower support mold 5 is located below the middle module. The upper cover mold 1, the middle module, the lower support mold 5, and the plug 6 together form a mold cavity for molding the salt core 11. The mold cavity is a Y-shaped bifurcated cavity. The inner core mold 4 has a Y-shaped protruding forming part. This Y-shaped protruding forming part cooperates with the opposite forming surfaces of the first outer mold 2 and the second outer mold 3 to form a forming space that matches the shape of the salt core 11.

[0039] The Y-shaped bifurcated cavity includes a main cavity segment and two branch cavity segments connected to the main cavity segment. The two branch cavity segments intersect and then connect to the main cavity segment. A pouring hole 7 is located above the intersection area of ​​the main cavity segment and the branch cavity segments, allowing the molten liquid to flow into the main cavity segment and the two branch cavity segments after entering from the intersection area. A first vent hole 8, a second vent hole 9, and a third vent hole 10 are respectively connected to the main cavity segment and the two branch cavity segments, allowing gas inside the cavity to be discharged through the corresponding vent holes during the molten liquid filling process. A plug 6 is detachably inserted into one end of the mold cavity and cooperates with the upper cover mold 1, the middle mold assembly, and the lower support mold 5 to seal the end opening of the mold cavity.

[0040] The first outer mold 2, the second outer mold 3, and the inner core mold 4 can be detachably connected to the lower mold 5 via bolts. Specifically, mounting holes can be provided on the first outer mold 2, the second outer mold 3, and the inner core mold 4, and threaded connections corresponding to the mounting holes can be provided on the lower mold 5. After the bolts pass through the mounting holes, they are connected to the lower mold 5, thereby keeping the middle mold group relatively stable during the casting process. A positioning assembly can also be provided between the upper mold 1 and the lower mold 5. The positioning assembly includes a positioning pin and a positioning hole that mates with the positioning pin. The positioning pin can be set on one component of the upper mold 1 or the lower mold 5, and the positioning hole can be set on the other corresponding component. When the mold is closed, the positioning pin mates with the positioning hole, keeping the upper mold 1, the middle mold group, and the lower mold 5 in a predetermined positional relationship.

[0041] Example 1

[0042] See Figure 6 This embodiment provides a water-soluble salt core material without the addition of binders and its preparation method.

[0043] Based on a total mass of 100 parts of basic powder, weigh out 35 parts of potassium nitrate, 25 parts of sodium nitrate, 20 parts of potassium chloride, and 20 parts of 200-mesh sintered mullite. Weigh out the above powders separately and put them into a mixing device for dry mixing for 15 minutes to ensure that potassium nitrate, sodium nitrate, potassium chloride, and sintered mullite are evenly dispersed, thus obtaining a mixed powder.

[0044] The mixed powder is transferred to a melting device. This device can be a crucible furnace, an electrically heated melting furnace, or other conventional heating equipment capable of meeting the melting requirements of salt powders. The mixed powder is heated to 320°C and held at this temperature with stirring for 10 minutes to ensure complete melting and obtain a homogeneous melt. The melt state is observed during the melting process. Once the melt exhibits continuous flow and shows no obvious stratification, sedimentation, or unmelted powder, the pouring step begins.

[0045] Before pouring, as follows Figures 1 to 4The molding die assembly is complete. First, the first outer mold 2, the second outer mold 3, and the inner core mold 4 are installed on the lower support mold 5 and fixed with bolts to form the middle mold assembly. Then, the plug 6 is inserted into one end of the mold cavity to seal the end opening. Next, the upper cover mold 1 is placed on top of the middle mold assembly and positioned with the lower support mold 5 using positioning components. The assembled molding die is preheated to 100°C to reduce premature solidification of localized areas caused by excessive temperature differences after the molten liquid is injected into the mold.

[0046] The uniform molten liquid is slowly injected into the mold cavity through the pouring hole 7 on the upper mold 1. After entering the mold cavity, the molten liquid flows from the intersection area of ​​the Y-shaped branch cavities to the main cavity section and the two branch cavity sections. During the filling process, the gas in the mold cavity is discharged through the first vent hole 8, the second vent hole 9, and the third vent hole 10, respectively. After the molten liquid fills the cavity, pouring is stopped, and the mold is allowed to cool naturally to room temperature. After the salt mold core has completely solidified, the upper mold 1, the plug 6, the first outer mold parting 2, the second outer mold parting 3, and the inner core mold 4 are removed in sequence, and the salt mold core 11 is taken out.

[0047] like Figure 5 As shown, the salt mold core 11 prepared in this embodiment has a Y-shaped forked structure, with a main body and two branches. Visual inspection reveals that the salt mold core 11 is intact, without obvious cracks or warping, and has a relatively dense surface without obvious pores. This salt mold core 11 is not easily broken during handling and molding, and can be used to support the internal cavity during the molding of hollow closed rubber sealing products; after rubber vulcanization, the core can be removed by boiling in warm water.

[0048] Example 2

[0049] This embodiment provides a water-soluble salt core material with added anhydrous borax and its preparation method.

[0050] Based on a total mass of 100 parts of base powder, weigh out 35 parts of potassium nitrate, 25 parts of sodium nitrate, 20 parts of potassium chloride, and 20 parts of 200-mesh sintered mullite, and weigh out 1 part of anhydrous borax as a binder. Add the potassium nitrate, sodium nitrate, potassium chloride, sintered mullite, and anhydrous borax to a mixing device and dry mix for 20 minutes to ensure thorough mixing of the anhydrous borax with the base powder and reduce local segregation.

[0051] The mixed powder was transferred to a melting device, heated to 310°C, and kept at this temperature while stirring for 10-15 minutes until a homogeneous melt was formed. Compared with Example 1, the addition of anhydrous borax in this example resulted in better homogeneity of the melt system during the stirring process, and better continuity of the melt surface. The molding die was preheated to 95°C, and then the homogeneous melt was slowly injected into the mold cavity through the gating hole 7.

[0052] During the casting process, the molten liquid enters from the confluence area of ​​the Y-shaped branch cavities and flows to the main cavity section and the two branch cavity sections respectively. The first vent hole 8, the second vent hole 9, and the third vent hole 10 vent the corresponding cavity areas to reduce air accumulation at the branch ends. After the molten liquid fills the mold cavity, it is allowed to cool naturally to room temperature. After cooling, the upper cover mold 1 is removed first, then the plug 6 is removed, and then the bolts connecting the first outer mold part 2, the second outer mold part 3, and the inner core mold 4 are loosened. The mold parts are then disassembled step by step, and the salt mold core 11 is removed.

[0053] The salt-based mold core 11 prepared in this embodiment has a complete shape and a relatively smooth surface, without obvious sand adhesion or peeling. Due to the binding and gap-filling effect of anhydrous borax in the system, the surface density and overall uniformity of the salt-based mold core 11 are good. This salt-based mold core 11 can be used for molding hollow, closed rubber sealing products with Y-shaped bifurcated internal cavities.

[0054] Example 3

[0055] This embodiment provides a water-soluble salt for making mold cores with added anhydrous sodium silicate and a method for preparing the same.

[0056] Based on a total mass of 100 parts of base powder, weigh out 30 parts of potassium nitrate, 30 parts of sodium nitrate, 15 parts of potassium chloride, and 25 parts of 325-mesh sintered mullite, and weigh out 2 parts of anhydrous sodium silicate as a binder. Add the above components to a mixing device for dry mixing for 25 minutes. Since this embodiment uses 325-mesh sintered mullite powder, which has a relatively fine particle size, it is important to ensure that the sintered mullite powder is fully dispersed in the salt powder during the dry mixing process to reduce localized agglomeration.

[0057] The mixed powder was transferred to a melting device, heated to 330°C, and stirred for 15 minutes to obtain a homogeneous melt. During the melting process, anhydrous sodium silicate participated in the formation of a localized bonding phase as the system temperature increased, which is beneficial for improving the bonding stability of the salt-based mold core material. The molding die was preheated to 110°C. After preheating, the homogeneous melt was injected into the mold cavity through the gating hole 7. During the pouring process, continuous and slow feeding was maintained to allow the melt to flow stably along the intersection area of ​​the Y-shaped bifurcated cavities to each cavity segment.

[0058] After the molten liquid fills the mold cavity, it is allowed to cool and solidify naturally within the mold. During demolding, first remove the upper cover mold 1 to expose the upper side of the salt mold core 11; then remove the plug 6 to unblock the end of the mold cavity; subsequently, disassemble the first outer mold 2, the second outer mold 3, and the inner core mold 4 in sequence. This split-type demolding method reduces edge and corner damage caused by directly prying the salt mold core 11.

[0059] The salt-molded core 11 prepared in this embodiment has a relatively complete Y-shaped bifurcation profile, the branch parts are well formed, and there are no obvious large-area loose defects on the surface. This embodiment is suitable for hollow closed rubber sealing products that require high surface integrity of the salt-molded core.

[0060] Example 4

[0061] This embodiment provides a water-soluble salt core material with a relatively high potassium chloride content in the base powder and its preparation method.

[0062] Based on a total mass of 100 parts of base powder, weigh out 40 parts of potassium nitrate, 20 parts of sodium nitrate, 25 parts of potassium chloride, and 15 parts of 200-mesh sintered mullite, and weigh out 0.5 parts of anhydrous borax as a binder. Add all components to a mixing device and dry mix for 20 minutes to obtain a mixed powder. Heat the mixed powder to 325℃ and maintain this temperature while stirring for 10 minutes to obtain a homogeneous melt. Preheat the molding die to 100℃, then pour the homogeneous melt through the gating hole 7. After cooling and solidification, demold to obtain a salt mold core 11.

[0063] In this embodiment, the relatively high potassium chloride content is beneficial for improving the dimensional stability of the salt mold core 11 after cooling. Upon demolding and observation, the main body and two branches of the salt mold core 11 have clear outlines and no obvious warping was observed. This embodiment can be used in scenarios requiring high dimensional stability in the preparation of salt mold cores.

[0064] In all of the above embodiments 1 to 4, the following can be adopted: Figures 1 to 5 The mold shown is used to form the salt core 11. In practical use, the first outer mold 2, the second outer mold 3, the inner core mold 4, and the lower support mold 5 are first cleaned to remove any residue from the mold cavity surface. Then, the inner core mold 4 is placed in the corresponding position of the lower support mold 5, and the first outer mold 2 and the second outer mold 3 are respectively placed on both sides of the inner core mold 4 and connected to the lower support mold 5 with bolts. After the middle module is installed, the plug 6 is inserted into the end opening of the mold cavity to seal the end opening.

[0065] Subsequently, the upper cover mold 1 is placed on top of the middle mold assembly, and the upper cover mold 1 and the lower support mold 5 are positioned using positioning pins and positioning holes, so that the pouring hole 7 is located above the intersection area of ​​the Y-shaped bifurcated cavity. The first vent hole 8, the second vent hole 9, and the third vent hole 10 correspond to the main cavity section and the two branch cavity sections, respectively. After the mold is closed, the entire mold is preheated to the predetermined temperature before pouring the molten liquid. During pouring, the molten liquid enters the mold cavity through the pouring hole 7 and flows along the Y-shaped bifurcated cavity; the gas in the cavity is discharged through the first vent hole 8, the second vent hole 9, and the third vent hole 10. After cooling, the mold is disassembled in the order of upper cover mold 1, plug 6, first outer mold parting 2, second outer mold parting 3, and inner core mold 4, and the salt mold core 11 is removed.

[0066] By combining the above-mentioned molding mold and preparation method, the molten salt mold core material can be stably filled in the Y-shaped bifurcated cavity, and the gas in the cavity can be discharged in time. Therefore, it is suitable for the preparation of salt mold cores for hollow closed rubber sealing products with bifurcated inner cavities.

[0067] Comparative Example 1

[0068] This comparative example does not include sintered mullite; the remaining components and preparation process are basically the same as in Example 1. By mass, 35 parts potassium nitrate, 25 parts sodium nitrate, and 20 parts potassium chloride were weighed, and the salt component ratios were adjusted to ensure the total amount of base powder met the preparation requirements. The powders were mixed, melted, poured, and cooled before demolding.

[0069] Observations revealed that the salt-based mold cores prepared in this comparative example had low overall strength and were prone to breakage during handling or demolding. Under the pressure conditions of rubber vulcanization, they were also prone to local softening or collapse, failing to meet the requirements for internal cavity support in hollow closed rubber sealing products. This indicates that sintered mullite, as an inorganic reinforcing filler, is beneficial for improving the overall strength and temperature stability of salt-based mold cores.

[0070] Comparative Example 2

[0071] This comparative example does not contain potassium chloride; the remaining components and preparation process are basically the same as in Example 1. By mass, 35 parts potassium nitrate, 25 parts sodium nitrate, and 20 parts 200-mesh sintered mullite were weighed, and the proportions of each component were adjusted to ensure the total amount of base powder met the preparation requirements. The powders were mixed, melted, poured, and cooled before demolding.

[0072] Observations revealed that the salt-based mold cores prepared in this comparative example were prone to cracking or warping after cooling, exhibiting poor dimensional stability. This indicates that potassium chloride, in the basic powder system of this invention, can improve the dimensional stability after cooling and molding, and helps reduce the risk of cracking and warping during the cooling process of the salt-based mold cores.

[0073] Comparative Example 3

[0074] This comparative example uses a standard straight-through cavity mold to prepare a Y-shaped branched salt mold core. The salt mold core material formulation and melting preparation process are the same as in Example 1. Because the standard straight-through cavity mold does not have vent holes corresponding to the main cavity section and the two branch cavity sections respectively, when the molten liquid fills the branch area, the gas at the end of the branch is not fully discharged, which easily leads to local air pockets or material shortages.

[0075] In comparison, the present invention Figures 1 to 4When the molding die is used, the pouring hole 7 is located above the intersection area of ​​the Y-shaped bifurcated cavities. The first vent hole 8, the second vent hole 9, and the third vent hole 10 correspond to different cavity segments, which can improve the filling and venting conditions of the Y-shaped bifurcated cavities. Therefore, the molding die of the present invention, when used in conjunction with the water-soluble salt mold core material and preparation method, is more suitable for preparing salt mold cores 11 with bifurcated structures.

[0076] The above examples illustrate the present invention only to aid in understanding it and are not intended to limit the scope of the invention. Those skilled in the art can make various simple deductions, modifications, or substitutions based on the principles of this invention.

Claims

1. A water-soluble salt-based molding core material, characterized in that, Includes base powder and optional binder; The base powder, by mass percentage, consists of the following components: potassium nitrate 10%~50%, sodium nitrate 10%~40%, potassium chloride 5%~30%, and sintered mullite 10%~40%, and the sum of the mass percentages of each component in the base powder is 100%. The binder is 0-5 parts by weight relative to the total mass of the base powder, and the binder is anhydrous borax or anhydrous sodium silicate.

2. The water-soluble salt mold core material according to claim 1, characterized in that, The sintered mullite is sintered mullite powder, and the sintered mullite powder is a 200-mesh or 325-mesh powder material.

3. The water-soluble salt core material according to claim 1, characterized in that, The base powder, by mass percentage, consists of 30%~40% potassium nitrate, 20%~30% sodium nitrate, 15%~25% potassium chloride, and 15%~25% sintered mullite, and the sum of the mass percentages of each component in the base powder is 100%.

4. The water-soluble salt core material according to claim 1, characterized in that, The binder is anhydrous borax, and the binder accounts for 0.5 to 2 parts of the total mass of the base powder.

5. A method for preparing a water-soluble salt mold core, characterized in that, The water-soluble salt core material according to any one of claims 1 to 4 is used, and the preparation method includes the following steps: weighing potassium nitrate, sodium nitrate, potassium chloride and sintered mullite according to the ratio; if a binder is added, weighing the binder at the same time; and putting each component into a mixing device for dry mixing to obtain a mixed powder. The mixed powder is transferred to a melting device, heated to 280℃~350℃, and kept at this temperature while stirring until the mixed powder is completely melted to obtain a uniform melt. Preheat the molding die to 80℃~120℃, and inject the uniform molten liquid into the mold cavity of the preheated molding die; The uniform molten liquid is cooled and solidified in the mold cavity, and after demolding, a salt mold core is obtained.

6. The method for preparing the water-soluble salt mold core according to claim 5, characterized in that, When preparing the mixed powder, the dry mixing time is 10 min to 30 min.

7. The method for preparing the water-soluble salt mold core according to claim 5, characterized in that, In preparing the homogeneous melt, the mixed powder is heated to 310℃~330℃ and kept at that temperature while stirring for 5min~20min until the homogeneous melt is free of stratification and sedimentation.

8. A molding die for implementing the preparation method according to any one of claims 5 to 7, characterized in that, It includes an upper cover mold (1), a middle module, a lower support mold (5), and a plug (6); The middle module includes a first outer mold (2), a second outer mold (3), and an inner core mold (4), wherein the first outer mold (2) and the second outer mold (3) are respectively disposed on both sides of the inner core mold (4); The upper cover mold (1) is located above the middle module, and the lower support mold (5) is located below the middle module. The upper cover mold (1), the middle module, the lower support mold (5), and the plug (6) together form a mold cavity for forming the salt mold core (11). The mold cavity is a Y-shaped bifurcated cavity. The upper cover mold (1) is provided with a pouring hole (7) that communicates with the mold cavity. The upper cover mold (1) is also provided with a first vent hole (8), a second vent hole (9) and a third vent hole (10) that communicate with the mold cavity. The plug (6) is located at the end opening of the mold cavity.

9. The molding die according to claim 8, characterized in that, The Y-shaped bifurcated cavity consists of a main cavity segment and two branch cavity segments connected to the main cavity segment. The two branch cavity segments intersect and then connect to the main cavity segment. The pouring hole (7) is located above the area where the main cavity segment and the branch cavity segments intersect.

10. The molding die according to claim 9, characterized in that, The first vent hole (8), the second vent hole (9) and the third vent hole (10) are spaced apart on the upper cover mold (1) and are respectively connected to the main cavity section and the two branch cavity sections; the plug (6) is detachably inserted into one end of the mold cavity; the first outer mold parting (2), the second outer mold parting (3) and the inner core mold (4) are detachably connected to the lower support mold (5) by bolts.

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