A water-soluble salt core material, its preparation method and application

Abstract

The present invention discloses a water-soluble salt core material, a preparation method thereof and an application. The composition of the water-soluble salt core material of the present invention includes a water-soluble inorganic salt and a binder, and the mass percentage of the water-soluble inorganic salt to the binder is 60% - 90%: 10% - 40%; the binder at least includes bentonite. The preparation method of the water-soluble salt core material of the present invention comprises the following steps: (1) mixing the inorganic salt and the binder; (2) adding water and mixing to obtain an extrusion feed; (3) extruding and molding to obtain a salt core green body; (4) drying and sintering to obtain a salt core material. The water-soluble salt core material prepared by the present invention has high strength, excellent water-soluble disintegration performance, good plasticity, excellent molding performance, and can prepare a water-soluble salt core with a complex structure and a small diameter through an extrusion molding process. The raw materials used in the present invention have low prices, the molding process and equipment are simple, and the manufacturing cost is low.

Description

Technical Field

[0001] The present invention belongs to the technical field of aluminum alloy casting, and particularly relates to a water-soluble salt core material, a preparation method thereof and an application thereof. Background Art

[0002] In precision aluminum alloy castings in various fields such as automobiles, aerospace, petrochemicals, etc., for those channel structural parts with complex shapes, they usually cannot be manufactured by traditional machining and other forming methods. The method used in industry is to form complex channel structural parts through core casting. However, the current core materials for casting mainly use sand cores made of natural sand as the matrix material and mixed with other additive materials, which have many problems. Not only is the strength relatively low, the surface accuracy is poor, but also the collapsibility is not good, making it difficult to clean the casting, and even impossible to clean. In addition, when casting and forming complex channel structural castings, the combined sand cores used not only greatly increase the difficulty of cleaning, but also the combination and lapping of the sand cores are extremely cumbersome, and it is also difficult to prepare and form more complex and fine sand cores. Therefore, the sand cores used for complex channel structural parts cannot meet the casting requirements of many precision aluminum alloy castings.

[0003] The water-soluble salt core technology refers to a technology that uses water-soluble alkali metal salts (mainly including chlorides represented by sodium chloride and potassium chloride, sulfates represented by sodium sulfate, carbonates represented by sodium carbonate and potassium carbonate, as well as nitrates, phosphates, etc.) as the matrix material, and then adds other auxiliary materials to make a casting core. The water-soluble salt core has high strength, good surface accuracy, excellent water-soluble collapsibility, and does not corrode the casting. The core can be washed with water flow to quickly complete the cleaning of the casting.

[0004] Currently, the most common methods for preparing water-soluble salt cores are melt casting molding and pressing and sintering molding. Melt casting molding is a casting molding method in which the alkali metal salt is heated to above the melting point and then poured into a mold. Pressing and sintering molding is to mix salt powder with other materials, and then prepare a salt core green body with a certain strength through pressing molding, and obtain a salt core product through processes such as degreasing, sintering, and post-treatment. The water-soluble salt cores prepared by melt casting molding and pressing and sintering molding have very high strength, and can already meet the requirements of aluminum alloy die casting, and the collapsibility is also better than that of traditional sand cores. However, for aluminum alloy castings with three-dimensional spatial distribution, fine water-cooled or oil-cooled channels, these two molding methods are difficult to prepare the required water-soluble salt cores.

[0005] CN 106670376A discloses a high-strength composite salt core for low-melting-point alloy casting. The composite salt core is made of a low-melting-point inorganic salt (one of potassium nitrate and sodium nitrate), or a combination of a low-melting-point inorganic salt and a high-melting-point inorganic salt (one of potassium chloride, potassium bromide, sodium chloride and sodium bromide), and then a reinforcement including one or more of bentonite, kaolin, high-alumina bauxite, quartz powder, glass fiber powder, refractory mud powder, and Dalin sand is added to prepare the salt core by melt casting. The salt core is a composite salt core prepared from a single low-melting-point salt and a reinforcement, or a composite salt core prepared from a mixture of a low-melting-point salt and a high-melting-point salt and a reinforcement. The melting temperature of the composite salt core prepared from a single low-melting-point salt is determined by the melting point of the low-melting-point salt; however, the composite salt core prepared from a low-melting-point salt and a high-melting-point salt will form a eutectic temperature lower than the melting point of the low-melting-point salt, and the molar percentage of the low-melting-point salt and the high-melting-point salt in the composite salt core is 70mol%-100mol%:0-30mol%. This composition is near its eutectic temperature or in a region close to the low-melting-point salt. Therefore, the initial melting temperature of the composite salt core prepared is between the melting point of the low-melting-point inorganic salt and the eutectic temperature (lower than the melting point of the low-melting-point inorganic salt). Therefore, the composite salt core prepared from the single low-melting-point salt and the composite salt core prepared from the low-melting-point salt and the high-melting-point salt are only suitable for casting low-melting-point alloys, such as magnesium alloys and zinc alloys, due to their low melting temperatures.

[0006] CN112222363A discloses a die-cast water-soluble salt core. It uses raw materials consisting of 60%-80% sodium chloride (mass percentage, the same below); 2%-8% sodium sulfate; 2%-8% aluminum oxide; 10%-20% aluminum carbide; and 2%-8% zirconium oxide. After mixing uniformly, the mixture is heated to a molten state, poured into a runner, and pressed into a mold to form the salt core.

[0007] CN1739883A discloses a method for preparing a soluble salt core for squeeze casting, which uses sodium chloride as the base material of the salt core, water glass as the binder, and high-alumina bauxite as the reinforcing phase, and prepares the water-soluble salt core by compression molding.

[0008] The aforementioned water-soluble salt cores are prepared using either melt casting or press sintering. Both methods produce salt cores with high strength and a certain degree of water-soluble disintegration. However, these water-soluble salt core materials also suffer from shortcomings such as low melting points or poor disintegration properties. For aluminum alloy castings with three-dimensionally distributed, tiny water-cooled or oil-cooled channels, these two materials and molding methods make it difficult to produce the required water-soluble salt cores. Therefore, finding a new water-soluble salt core material and molding process is extremely important. Summary of the Invention

[0009] Aiming at the deficiencies of existing salt core materials and their preparation processes, the present invention provides a water-soluble salt core material, its preparation method and application. Through the design of the composition and forming process of the salt core, a water-soluble salt core required for aluminum alloy castings with three-dimensional spatial distribution and fine water-cooled or oil-cooled channels can be prepared, and it has sufficient strength, excellent water-soluble collapsibility and high surface quality.

[0010] In order to achieve the above object, the present invention adopts the following scheme:

[0011] A water-soluble salt core material, the composition of the water-soluble salt core material includes water-soluble inorganic salts and binders, and the mass percentage of the water-soluble inorganic salts to the binder is 60%-90%: 10%-40%; the binder includes at least bentonite.

[0012] Preferably, the water-soluble inorganic salt is a single salt with a high melting point, and its particle size mesh number is 100-1250 mesh;

[0013] Preferably, the water-soluble inorganic salt includes one of sodium chloride, potassium chloride, sodium sulfate or potassium sulfate.

[0014] Preferably, the binder includes two or more of organic binders and inorganic binders, and one of them is bentonite; the particle size mesh number of the inorganic binder is 400-1250 mesh.

[0015] Further preferably, the organic binder is phenolic resin; the inorganic binders are bentonite, kaolin, and phosphate.

[0016] Preferably, the binder is bentonite and kaolin; further preferably, the mass percentage of the water-soluble inorganic salt, bentonite and kaolin is 90%-60%: 5%-20%: 5%-20%.

[0017] Preferably, the binder is bentonite, kaolin and phosphate; further preferably, the mass percentage of the water-soluble inorganic salt, bentonite, kaolin and phosphate is 85%-60%: 5%-20%: 5%-10%: 5%-10%.

[0018] Preferably, the water-soluble salt core material is prepared by an extrusion molding method and has a three-dimensional complex structure.

[0019] The preparation method of the above-mentioned water-soluble salt core includes the following steps:

[0020] (1) Powder mixing treatment

[0021] Mix the water-soluble inorganic salts and the binder evenly to obtain a mixed salt powder;

[0022] (2) Preparation of extrusion feed

[0023] Water is added to the mixed salt powder and mixed evenly to obtain an extrusion feedstock.

[0024] (3) Preparation of the salt core green body

[0025] The extrusion feedstock is used to prepare a salt core green body by an extrusion molding method.

[0026] (4) Sintering and shaping of the salt core green body

[0027] After drying the salt core green body, it is sintered and shaped to obtain a water-soluble salt core material.

[0028] Preferably, in step (2), the addition amount of water is 20%-40% of the mass of the extrusion feedstock.

[0029] Preferably, in step (4), the drying temperature is 60-100°C and the drying time is 3-12 h.

[0030] Preferably, in step (4), the sintering and shaping temperature is: holding at 100-200°C for 1-3 h, holding at 250-350°C for 1-3 h, and holding at 350-450°C for 1-3 h.

[0031] Application of the above water-soluble salt core material in aluminum alloy casting.

[0032] The advantages of the present invention mainly include:

[0033] (1) The salt core prepared by the present invention has excellent comprehensive performance: it has high strength, high surface quality, and excellent water-soluble collapsibility.

[0034] (2) The salt core of the present invention has good formability: the salt core material has excellent plasticity (good formability), and a three-dimensional spatially distributed and fine water-soluble salt core can be obtained through an extrusion molding process.

[0035] (3) The salt core of the present invention has low preparation cost: the raw materials are inexpensive, the molding process and equipment are simple, and the preparation cost is low. Brief description of the drawings

[0036] Figure 1 It is a process flow chart of the preparation of the water-soluble salt core material of the present invention.

[0037] Figure 2 It is a sintering process diagram of the water-soluble salt core material of the present invention.

[0038] Figure 3 It is a structural diagram of the three-dimensional spatially distributed and fine water-soluble salt core of the present invention. Detailed implementation manners

[0039] The water-soluble salt core material and preparation method of the present invention include, but are not limited to, the components and preparation methods in the following specific embodiments. To make the objectives, solutions, technologies, and advantages of the present invention clearer, the present invention will be specifically introduced below in conjunction with the accompanying drawings and specific implementation manners.

[0040] As Figure 1 shown is the process flow chart of the preparation of the water-soluble salt core. It includes the following steps:

[0041] (1) Powder mixing treatment

[0042] Weigh the water-soluble inorganic salt and the binder according to the mass percentage of 60%-90%: 10%-40%. After grinding the salt powder to make fine salt powder with a particle size (screened) of 100-1250 mesh, mix it evenly with the binder to obtain mixed salt powder.

[0043] (2) Preparation of extrusion feed

[0044] Add an appropriate amount of water to the mixed salt powder and mix it evenly again to obtain extrusion feed.

[0045] (3) Preparation of salt core green body

[0046] Prepare the extrusion feed by extrusion molding to obtain a small salt core green body with the required three-dimensional spatial distribution. Its structure diagram is as Figure 3 shown.

[0047] (4) Sintering and shaping of salt core green body

[0048] After drying the salt core green body to have a certain strength, sinter and shape it in a heat treatment furnace to obtain a water-soluble salt core product.

[0049] In the following embodiments, the particle size of the inorganic salt is 100-1250 mesh; the mesh number of bentonite is 400-1250 mesh; the mesh number of kaolin is 400-1250 mesh; the mesh number of phosphate is 400-1250 mesh; the viscosity of phenolic resin is 10-28.1 mp·s.

[0050] In the following embodiments, the wire diameter of the three-dimensional spatial distribution and small water-soluble salt core structure formed by extrusion molding is 5 mm, the diameter (top view) is 20 cm, and the vertical height is 40 cm / 6 turns.

[0051] Example 1

[0052] Preparation of water-soluble salt core material: 95 parts by mass of sodium chloride inorganic salt + 5 parts by mass of bentonite.

[0053] After mixing the weighed sodium chloride inorganic salt and bentonite evenly, 20% by mass of water was added to make an extrusion feedstock. Since the content of bentonite was low, the formability of the salt core raw material was very poor, and the extrusion feedstock could not be used to prepare the salt core green body by extrusion molding.

[0054] Example 2

[0055] Preparation of water-soluble salt core material: 90 parts by mass of sodium chloride inorganic salt + 10 parts by mass of bentonite.

[0056] After mixing the weighed sodium chloride inorganic salt and bentonite evenly, 25% by mass of water was added to make an extrusion feedstock; the extrusion feedstock was extruded in an extruder to form a salt core green body with the required diameter and shape ( Figure 3 ), the salt core composition of this ratio could extrude the salt core green body, but the formability was still poor, and the surface of the extruded salt core green body had many wrinkles; the extruded salt core green body was kept at 60 °C for 3 h; the salt core was put into a heat treatment furnace for sintering to obtain the final salt core product. The sintering process is as follows Figure 2 shown (the sintering temperatures of the following other examples are all referred to Figure 2 ).

[0057] By preparing standard cylindrical salt core specimens (GB / T 2684—2009) (the same in the following examples), the average compressive strength of the salt core was measured to be 10 MPa, and the average water-soluble time was 15 min.

[0058] Example 3

[0059] Preparation of water-soluble salt core material: 80 parts by mass of potassium chloride inorganic salt + 20 parts by mass of bentonite.

[0060] After mixing the weighed potassium chloride inorganic salt and bentonite evenly, 25% by mass of water was added to make an extrusion feedstock; the extrusion feedstock was extruded in an extruder to form a salt core green body with the required diameter and shape ( Figure 3 ); the salt core composition of this ratio could extrude the salt core green body, but the formability was slightly poor, and the surface of the extruded salt core green body had certain wrinkles; the extruded salt core green body was kept at 60 °C for 6 h; the salt core was put into a heat treatment furnace for sintering to obtain the final salt core product.

[0061] The average compressive strength of the standard cylindrical salt core specimen was measured to be 12 MPa, and the average water-soluble time was 40 min.

[0062] Example 4

[0063] Preparation of water-soluble salt core material: 70 parts by mass of sodium sulfate inorganic salt + 30 parts by mass of bentonite.

[0064] After uniformly mixing the weighed sodium sulfate inorganic salt and bentonite, add water with a mass percentage of 30% to make an extrusion feed; extrude the extrusion feed in an extruder to obtain a salt core green body with the required diameter and shape ( Figure 3 ); The salt core composition in this proportion can extrude a salt core green body, and the formability is good, and there are fewer wrinkles on the surface of the extruded salt core green body; Keep the extruded salt core green body at 80 °C for 6 hours; Put the salt core into a heat treatment furnace for sintering to obtain the final salt core product.

[0065] The average compressive strength of the standard cylindrical salt core specimens was measured to be 15 MPa, and the average water solubility time was 120 min.

[0066] Example 5

[0067] Preparation of water-soluble salt core material: 60 parts by mass of potassium sulfate inorganic salt + 40 parts by mass of bentonite.

[0068] After uniformly mixing the weighed potassium sulfate inorganic salt and bentonite, add water with a mass percentage of 40% to make an extrusion feed; extrude the extrusion feed in an extruder to obtain a salt core green body with the required diameter and shape ( Figure 3 ); The salt core composition in this proportion can extrude a salt core green body, and the formability is excellent, and the surface quality of the extruded salt core green body is good; Keep the extruded salt core green body at 100 °C for 12 hours; Put the salt core into a heat treatment furnace for sintering to obtain the final salt core product.

[0069] The average compressive strength of the standard cylindrical salt core specimens was measured to be 17 MPa, and the average water solubility time was 300 min.

[0070] Example 6

[0071] Preparation of water-soluble salt core material: 50 parts by mass of potassium sulfate inorganic salt + 50 parts by mass of bentonite.

[0072] After uniformly mixing the weighed potassium sulfate inorganic salt and bentonite, add water with a mass percentage of 40% to make an extrusion feed; extrude the extrusion feed in an extruder to obtain a salt core green body with the required diameter and shape ( Figure 3 ); The salt core composition in this proportion can extrude a salt core green body, and the formability is excellent, and the surface quality of the extruded salt core green body is good; However, due to the too high content of the binder and the too low content of the inorganic salt, the finally obtained salt core product cannot be water-soluble after drying and sintering.

[0073] Example 7

[0074] Preparation of water-soluble salt core material: 70 parts by mass of sodium chloride inorganic salt + 30 parts by mass of kaolin.

[0075] After mixing the weighed sodium chloride inorganic salt and kaolin evenly, add 20% water by mass to make an extrusion feedstock. Since the formability of the salt core raw material is very poor, the extrusion feedstock cannot be used to prepare a salt core green body by extrusion molding.

[0076] Example 8

[0077] Preparation of water-soluble salt core material: 90 parts by mass of sodium chloride inorganic salt + 5 parts by mass of bentonite + 5 parts by mass of kaolin.

[0078] After mixing the weighed sodium chloride inorganic salt with bentonite and kaolin evenly, add 20% water by mass to make an extrusion feedstock; extrude the extrusion feedstock in an extruder to obtain a salt core green body with the required diameter and shape ( Figure 3 ); The salt core composition in this proportion can extrude a salt core green body, but the formability is very poor, and there are many wrinkles on the surface of the extruded salt core green body; keep the extruded salt core green body at 60 °C for 3 h; put the salt core into a heat treatment furnace for sintering to obtain the final salt core product.

[0079] It is measured that the average compressive strength of the standard cylindrical salt core sample is 6 MPa, and the average water-soluble time is 10 min.

[0080] Example 9

[0081] Preparation of water-soluble salt core material: 80 parts by mass of potassium chloride inorganic salt + 10 parts by mass of bentonite + 10 parts by mass of kaolin.

[0082] After mixing the weighed potassium chloride inorganic salt with bentonite and kaolin evenly, add 25% by mass to make an extrusion feedstock; extrude the extrusion feedstock in an extruder to obtain a salt core green body with the required diameter and shape ( Figure 3 ); The salt core composition in this proportion can extrude a salt core green body, but the formability is poor, and there are many wrinkles on the surface of the extruded salt core green body; keep the extruded salt core green body at 60 °C for 6 h; put the salt core into a heat treatment furnace for sintering to obtain the final salt core product.

[0083] It is measured that the average compressive strength of the standard cylindrical salt core sample is 13 MPa, and the average water-soluble time is 30 min.

[0084] Example 10

[0085] Preparation of water-soluble salt core material: 70 parts by mass of sodium sulfate inorganic salt + 20 parts by mass of bentonite + 10 parts by mass of phenolic resin.

[0086] After mixing the weighed sodium sulfate inorganic salt with bentonite and phenolic resin evenly, add 25% water by mass to make an extrusion feedstock; extrude the extrusion feedstock in an extruder to obtain a salt core green body with the required diameter and shape ( Figure 3) This proportion of the salt core composition can extrude a green salt core blank with good formability and fewer wrinkles on the surface of the extruded green salt core blank; the extruded green salt core blank is kept at 80 °C for 6 h; the salt core is put into a heat treatment furnace for sintering to obtain the final salt core product.

[0087] The average compressive strength of the standard cylindrical salt core specimens measured is 20 MPa, and the average water solubility time is 150 min.

[0088] Example 11

[0089] Preparation of water-soluble salt core material: 60 parts by mass of potassium sulfate inorganic salt + 30 parts by mass of bentonite + 10 parts by mass of phosphate.

[0090] After mixing the weighed potassium sulfate inorganic salt with bentonite and phosphate evenly, 30% by mass of water is added to make an extrusion feed; the extrusion feed is extruded in an extruder to obtain a green salt core blank with the required diameter and shape ( Figure 3 ) This proportion of the salt core composition can extrude a green salt core blank with good formability and very few wrinkles on the surface of the extruded green salt core blank; the extruded green salt core blank is kept at 100 °C for 12 h; the salt core is put into a heat treatment furnace for sintering to obtain the final salt core product.

[0091] The average compressive strength of the standard cylindrical salt core specimens measured is 22 MPa, and the average water solubility time is 400 min.

[0092] Example 12

[0093] Preparation of water-soluble salt core material: 80 parts by mass of sodium chloride inorganic salt + 10 parts by mass of bentonite + 5 parts by mass of kaolin + 5 parts by mass of phenolic resin.

[0094] After mixing the weighed sodium chloride inorganic salt with bentonite, kaolin and phenolic resin evenly, 20% by mass of water is added to make an extrusion feed; the extrusion feed is extruded in an extruder to obtain a green salt core blank with the required diameter and shape ( Figure 3 ) This proportion of the salt core composition can extrude a green salt core blank, but the formability is still poor and there are also more wrinkles on the surface of the extruded green salt core blank; the extruded green salt core blank is kept at 60 °C for 12 h; the salt core is put into a heat treatment furnace for sintering to obtain the final salt core product.

[0095] The average compressive strength of the standard cylindrical salt core specimens measured is 14 MPa, and the average water solubility time is 90 min.

[0096] Example 13

[0097] Preparation of water-soluble salt core material: 70 parts by mass of potassium chloride inorganic salt + 10 parts by mass of bentonite + 10 parts by mass of kaolin + 10 parts by mass of phosphate.

[0098] After uniformly mixing the weighed potassium chloride inorganic salt with bentonite, kaolin, and phosphate, add water with a mass percentage of 20% to make an extrusion feedstock; extrude the extrusion feedstock in an extruder to obtain a green salt core blank with the required diameter and shape ( Figure 3 ); The salt core composition in this proportion can extrude a green salt core blank with good formability and less surface wrinkles on the extruded green salt core blank; Keep the extruded green salt core blank at 80 °C for 6 hours; Put the salt core into a heat treatment furnace for sintering to obtain the final salt core product.

[0099] The average compressive strength of the standard cylindrical salt core specimen was measured to be 21 MPa, and the average water-soluble time was 100 min.

[0100] Example 14

[0101] Preparation of water-soluble salt core material: 70 parts by mass of potassium chloride inorganic salt + 10 parts by mass of bentonite + 20 parts by mass of phosphate.

[0102] After uniformly mixing the weighed potassium chloride inorganic salt with bentonite phosphate, add water with a mass percentage of 20% to make an extrusion feedstock; extrude the extrusion feedstock in an extruder to obtain a green salt core blank with the required diameter and shape ( Figure 3 ); The salt core composition in this proportion can extrude a green salt core blank with good formability and less surface wrinkles on the extruded green salt core blank; Keep the extruded green salt core blank at 80 °C for 6 hours; Put the salt core into a heat treatment furnace for sintering to obtain the final salt core product.

[0103] The average compressive strength of the standard cylindrical salt core specimen was measured to be 25 MPa, and the average water-soluble time was 200 min.

[0104] Example 15

[0105] Preparation of water-soluble salt core material: 60 parts by mass of sodium sulfate inorganic salt + 20 parts by mass of bentonite + 10 parts by mass of kaolin + 10 parts by mass of phenolic resin.

[0106] After uniformly mixing the weighed sodium sulfate inorganic salt with bentonite, kaolin, and phenolic resin, add water with a mass percentage of 25% to make an extrusion feedstock; extrude the extrusion feedstock in an extruder to obtain a green salt core blank with the required diameter and shape ( Figure 3 ); The salt core composition in this proportion can extrude a green salt core blank with good formability and very few surface wrinkles on the extruded green salt core blank; Keep the extruded green salt core blank at 100 °C for 12 hours; Put the salt core into a heat treatment furnace for sintering to obtain the final salt core product.

[0107] The average compressive strength of the standard cylindrical salt core specimen was measured to be 23 MPa, and the average water-soluble time was 350 min.

[0108] Example 16

[0109] Preparation of water-soluble salt core material: 60 parts by mass of potassium sulfate inorganic salt + 20 parts by mass of bentonite + 10 parts by mass of phenolic resin + 10 parts by mass of phosphate.

[0110] After uniformly mixing the weighed potassium sulfate inorganic salt with bentonite, phenolic resin, and phosphate, add water with a mass percentage of 20% to make an extrusion feed; extrude the extrusion feed in an extruder to obtain a salt core green body with the required diameter and shape ( Figure 3 ); The salt core composition in this proportion can extrude a salt core green body with good formability and very few wrinkles on the surface of the extruded salt core green body; Keep the extruded salt core green body at 100 °C for 12 h; Put the salt core into a heat treatment furnace for sintering to obtain the final salt core product.

[0111] The average compressive strength of the standard cylindrical salt core specimens was measured to be 28 MPa, and the average water-soluble time was 500 min.

[0112] Data analysis

[0113] It can be seen from the above embodiments that by compounding inorganic salts and binders in appropriate ratios, the present invention can prepare high-strength and highly water-soluble salt core materials through extrusion molding; If the binder content is too high or too low, the purpose of the present invention cannot be achieved; The purpose of the present invention cannot be achieved without bentonite either.

[0114] The preparation method of Example 9 refers to Example 3. The difference is that in Example 3, a single bentonite binder is used to prepare the salt core, while in Example 9, bentonite and kaolin are mixed to prepare the salt core, and the binder ratios of the two examples are the same. The compressive strength of the salt core prepared in Example 9 is increased from 12 MPa in Example 3 to 13 MPa, and the water-soluble time is reduced from 40 min to 30 min. This shows that the mixed use of bentonite and kaolin in the present invention has better effects.

[0115] The preparation method of Example 13 refers to Example 4. The difference is that in Example 4, a single bentonite binder is used to prepare the salt core, while in Example 13, bentonite, kaolin, and phosphate are mixed to prepare the salt core, and the binder ratios of the two examples are the same. The compressive strength of the salt core prepared in Example 13 is increased from 15 MPa in Example 4 to 21 MPa, and the water-soluble time is reduced from 120 min to 100 min. This shows that the mixed use of bentonite, kaolin, and phosphate in the present invention has better effects.

[0116] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited by the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principle of the present invention shall be equivalent replacement methods and are all included in the protection scope of the present invention.

Claims

1. A water-soluble salt core material, characterized in that, The composition of the water-soluble salt core material includes water-soluble inorganic salts and a binder. The mass percentage of the water-soluble inorganic salts to the binder is 60% - 90%: 10% - 40%. The binder includes more than two of bentonite, kaolin, phosphate, and phenolic resin, and one of them is bentonite.

2. The water-soluble salt core material according to claim 1, characterized in that, The water-soluble inorganic salt is a high-melting single salt with a particle size of 100 - 1250 mesh. The water-soluble inorganic salt includes one of sodium chloride, potassium chloride, sodium sulfate, or potassium sulfate.

3. The water-soluble salt core material according to claim 1, wherein, The particle size of the bentonite, kaolin, and phosphate is 400 - 1250 mesh.

4. The water-soluble salt core material according to claim 1, wherein The binder is bentonite and kaolin. The mass percentage of the water-soluble inorganic salt, bentonite, and kaolin is 90% - 60%: 5% - 20%: 5% - 20%.

5. The water-soluble salt core material according to claim 1, characterized in that, The binder is bentonite, kaolin, and phosphate. The mass percentage of the water-soluble inorganic salt, bentonite, kaolin, and phosphate is 85% - 60%: 5% - 20%: 5% - 10%: 5% - 10%.

6. The water-soluble salt core material according to claim 1, wherein The water-soluble salt core material is prepared by an extrusion molding method.

7. The preparation method of the water-soluble salt core according to any one of claims 1-6, characterized in that, It includes the following steps: (1) Powder mixing treatment Mix the water-soluble inorganic salts and the binder evenly to obtain a mixed salt powder. (2) Preparation of extrusion feed Add water to the mixed salt powder and mix evenly to obtain an extrusion feed. (3) Preparation of salt core green body Prepare the salt core green body from the extrusion feed by an extrusion molding method. (4) Sintering and shaping of the salt core green body After drying the salt core green body, sinter and shape it to obtain the water-soluble salt core material.

8. The preparation method according to claim 7, wherein In step (2), the addition amount of water is 20% - 40% of the mass of the extrusion feed. In step (4), the drying temperature is 60 - 100 °C, and the drying time is 3 - 12 h. The sintering and shaping temperature is: keep warm at 100 - 200 °C for 1 - 3 h, keep warm at 250 - 350 °C for 1 - 3 h, and keep warm at 350 - 450 °C for 1 - 3 h.

9. Application of the water-soluble salt core material according to any one of claims 1 - 6 in aluminum alloy casting.

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