A kind of thickness control material for investment casting and preparation method, investment casting method

Abstract

This invention relates to a thickness-fixed die material for investment casting and its preparation method, as well as an investment casting method, specifically relating to the field of investment casting. The thickness-fixed die material for investment casting comprises: microcrystalline wax, polyolefin wax, ethylene-vinyl acetate copolymer (EVA), elastomer, and petroleum resin. The thickness-fixed die material for investment casting provided by this invention achieves simultaneous improvement in hardness and toughness by utilizing the synergistic effect between the components within the die material, resulting in a material that is both hard and tough. It can bend naturally when the wax sheet is bent without creases or breakage, exhibiting excellent performance. The resulting die material has a penetration (25℃, 0.1mm) ≤ 8.5 and a bending strength ≥ 10.8MPa.

Description

Technical Field

[0001] This invention relates to the field of investment casting, specifically to a fixed-thickness die material for investment casting and its preparation method, as well as an investment casting method. Background Technology

[0002] Precision casting is an advanced material forming process that produces castings that are precise, complex, and close to the final shape of the parts, and can be used directly with little or no machining.

[0003] In precision casting, the mold material is a key material used to manufacture wax patterns. Its main function is to form a precise wax pattern through a specific process, providing a foundation for subsequent casting production.

[0004] For example, CN113150564A discloses an investment casting mold material for jewelry casting and its preparation method. The components of the investment casting mold material include 20-50% microcrystalline wax, 10-30% paraffin wax, 0.5-3% plant wax, 10-20% poly(α-methylstyrene) resin, 5-15% tackifying resin, 4-10% paste refiner, and 0.5-5% modified SEBS thermoplastic elastomer. The preparation method includes the following steps: first, by mixing SEBS thermoplastic elastomer and polypropylene, a modified SEBS thermoplastic elastomer is obtained; then, paraffin wax and microcrystalline wax are mixed with the modified SEBS thermoplastic elastomer to obtain a base wax / modified SEBS thermoplastic elastomer composite material; finally, plant wax, poly(α-methylstyrene) resin, tackifying resin, and paste refiner are mixed to obtain the investment casting mold material.

[0005] CN118185326A discloses an investment casting mold material, its preparation method, and its application. According to the method, 40-60 parts by weight of paraffin wax are placed in a reactor and first partially melted using indirect heating with a water jacket, with the temperature controlled below 80℃. The mixture is then heated to 100-120℃, and 5-10 parts by weight of lignite wax and 10-20 parts by weight of graphene-modified maleic anhydride-vinyl acetate copolymer are added sequentially. The mixture is stirred and mixed at 50-100 r / min. After melting, 5-10 parts by weight of tackifying resin and 0-0.01 parts by weight of antioxidant are added and stirred until homogeneous. The mixture is then granulated using steel strip selection and forming technology, and sieved to obtain the investment casting wax granule mold material. This mold material exhibits good thermal stability, low penetration and linear shrinkage, high flexural strength, and low ash content, effectively meeting the requirements of high dimensional accuracy and high surface quality for precision castings.

[0006] The molding material is heated and mixed before being poured into a mold, where it cools and solidifies to form a wax pattern. The precision and stability of the wax pattern directly affect the quality of the final casting. Currently, in investment casting, it is usually necessary to use a fixed-thickness molding material to precisely control the thickness of specific locations on the investment pattern. However, the molding materials currently used are difficult to balance in terms of both hardness and toughness, resulting in defects such as creases or even breakage when bent during use. Summary of the Invention

[0007] In view of the problems existing in the prior art, the purpose of the present invention is to provide a fixed-thickness die material for investment casting and a preparation method thereof, as well as an investment casting method, so as to solve the defects of the die material that it is difficult to simultaneously achieve both hardness and toughness, and that it may have creases or even break when bent during use.

[0008] To achieve this objective, the present invention adopts the following technical solution:

[0009] In a first aspect, the present invention provides a thickness-fixed die material for investment casting, the thickness-fixed die material for investment casting comprising:

[0010] Microcrystalline wax, polyolefin wax, ethylene-vinyl acetate copolymer (EVA), elastomers, and petroleum resins.

[0011] The thickness mold material for investment casting provided by this invention achieves simultaneous improvement in hardness and toughness by utilizing the synergistic cooperation between the components within the mold material. It has the effect of being both hard and tough, and can bend naturally when the wax sheet is bent without creases or breakage, thus exhibiting excellent performance.

[0012] As a preferred embodiment of the present invention, the thickness-fixed die material for investment casting comprises, by weight, the following:

[0013] 40-60 parts of microcrystalline wax;

[0014] 10-15 parts of polyolefin wax;

[0015] 2-5 parts of ethylene-vinyl acetate copolymer (EVA);

[0016] 6-10 parts elastomer;

[0017] 1-5 parts of petroleum resin.

[0018] As a preferred technical solution of the present invention, the microcrystalline wax includes one or a combination of at least two of the following: 70# microcrystalline wax, 75# microcrystalline wax, 80# microcrystalline wax, 85# microcrystalline wax or 90# microcrystalline wax.

[0019] As a preferred embodiment of the present invention, the polyolefin wax includes one or a combination of at least two of polyethylene wax, oxidized polyethylene wax, or polypropylene wax.

[0020] As a preferred embodiment of the present invention, the VA content of the ethylene-vinyl acetate copolymer EVA is 15-25%.

[0021] As a preferred embodiment of the present invention, the elastomer includes: SEBS thermoplastic elastomer and / or polyurethane elastomer.

[0022] As a preferred technical solution of the present invention, the petroleum resin includes one or a combination of at least two of the following: C5 petroleum resin, hydrogenated C5 petroleum resin, C9 petroleum resin, hydrogenated C9 petroleum resin, or C5 / C9 copolymer petroleum resin.

[0023] In a second aspect, the present invention provides a method for preparing a thickness-fixed die material for investment casting as described in the first aspect, the method comprising: mixing ingredients according to a formula in parts by weight, followed by heating and mixing to obtain a thickness-fixed die material for investment casting.

[0024] As a preferred technical solution of the present invention, the heating and mixing method includes: high-shear mixing.

[0025] Preferably, the shearing speed of the high-shear mixing is 1000-2000 r / min.

[0026] Preferably, the high-shear mixing time is 20-30 minutes.

[0027] Thirdly, the present invention provides a method for investment casting, wherein the thickness of the wax pattern is adjusted using a fixed-thickness die material as described in the first aspect for investment casting.

[0028] Compared with existing technical solutions, the present invention has the following beneficial effects:

[0029] The microcrystalline wax in the thickness mold material provided by this invention provides a rigid framework and crystal nucleus template, while the polyolefin wax provides flexible molecular chains and interface connections. Through three major mechanisms—crystal refinement, intermolecular force enhancement, and network structure construction—a balance between rigidity and flexibility is achieved. Petroleum resin constructs a rigid supporting framework to provide hardness and thermal stability, while the elastomer absorbs impact energy and optimizes the interface structure through flexible molecular chains to provide toughness. The two are matched in proportion, structure, and process synergy to form an interpenetrating network system that combines rigidity and flexibility. Ethylene-vinyl acetate copolymer (EVA) constructs an elastic network together with the elastomer through flexible molecular chains, solving the problem of wax mold brittleness. At the same time, it restricts shrinkage and improves dimensional accuracy by using molecular chain entanglement.

[0030] The present invention will now be described in further detail. However, the examples described below are merely simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention is determined by the claims. Detailed Implementation

[0031] To better illustrate the present invention and facilitate understanding of its technical solutions, typical but non-limiting embodiments of the present invention are as follows:

[0032] In precision casting, wax pattern material is a key material used to manufacture wax patterns. Its main function is to form a precise wax pattern through a specific process, providing a foundation for subsequent casting production. The wax pattern material is heated, mixed, and then poured into a mold, where it cools and solidifies to form the wax pattern. The accuracy and stability of the wax pattern directly affect the quality of the final casting. Currently, in investment casting, thickness-controlled molding materials are typically used to precisely control the thickness of specific locations on the investment pattern. However, current molding materials often suffer from a difficulty in simultaneously achieving both hardness and toughness, leading to defects such as creases or even breakage during bending. Therefore, this invention optimizes the molding material composition formula to simultaneously achieve both hardness and toughness, thereby expanding the application range of the molding material, as detailed below:

[0033] I. This embodiment provides a thickness-fixed die material for investment casting, the thickness-fixed die material for investment casting comprising:

[0034] Microcrystalline wax, polyolefin wax, ethylene-vinyl acetate copolymer (EVA), elastomers, and petroleum resins.

[0035] In this invention, the thickness-fixed die material is prepared by mixing the raw materials and then pressing them into various required shapes such as plates, rods, and blocks according to actual needs. These are used as thickness-fixed materials in investment casting. For example, molten wax is pressed into wax sheets with uniform thickness (such as 0.5mm, 2mm, etc.) and smooth surface by a precision wax press.

[0036] The thickness-fixed die material used for investment casting comprises, by weight, the following:

[0037] 40-60 parts of microcrystalline wax;

[0038] 10-15 parts of polyolefin wax;

[0039] 2-5 parts of ethylene-vinyl acetate copolymer (EVA);

[0040] 6-10 parts elastomer;

[0041] 1-5 parts of petroleum resin.

[0042] In this invention, the microcrystalline wax in the thickness die material used for investment casting is 40-60 parts by weight, for example, 40 parts, 42 parts, 44 parts, 46 parts, 48 ​​parts, 50 parts, 52 parts, 54 parts, 56 parts, 58 parts or 60 parts, but is not limited to the listed values. Other unlisted values ​​within this range are also acceptable.

[0043] In this invention, the polyolefin wax in the thickness die material used for investment casting is 10-15 parts by weight, for example, 10 parts, 10.5 parts, 11 parts, 11.5 parts, 12 parts, 12.5 parts, 13 parts, 13.5 parts, 14 parts, 14.5 parts or 15 parts, but is not limited to the listed values. Other unlisted values ​​within this range are also acceptable.

[0044] In this invention, the ethylene-vinyl acetate copolymer (EVA) in the thickness die material used for investment casting is 2-5 parts by weight, for example, 2 parts, 2.3 parts, 2.6 parts, 2.9 parts, 3.2 parts, 3.5 parts, 3.8 parts, 4.1 parts, 4.4 parts, 4.7 parts, or 5 parts, but is not limited to the listed values. Other unlisted values ​​within this range are also acceptable.

[0045] In this invention, the elastomer in the thickness die material used for investment casting is 6-10 parts by weight, for example, 6 parts, 6.4 parts, 6.8 parts, 7.2 parts, 7.6 parts, 8 parts, 8.4 parts, 8.8 parts, 9.2 parts, 9.6 parts, or 10 parts, but is not limited to the listed values. Other unlisted values ​​within this range are also acceptable.

[0046] In this invention, the petroleum resin in the thickness die material used for investment casting is 1-5 parts by weight, for example, it can be 1 part, 1.4 parts, 1.8 parts, 2.2 parts, 2.6 parts, 3 parts, 3.4 parts, 3.8 parts, 4.2 parts, 4.6 parts or 5 parts, but is not limited to the listed values. Other unlisted values ​​within this range are also acceptable.

[0047] The microcrystalline wax includes one or a combination of at least two of the following: 70# microcrystalline wax, 75# microcrystalline wax, 80# microcrystalline wax, 85# microcrystalline wax or 90# microcrystalline wax.

[0048] For example, the combination of microcrystalline wax can be selected as: a combination of 70# microcrystalline wax and 75# microcrystalline wax, a combination of 75# microcrystalline wax and 80# microcrystalline wax, a combination of 80# microcrystalline wax and 85# microcrystalline wax, a combination of 85# microcrystalline wax and 90# microcrystalline wax, etc.

[0049] The polyolefin wax includes one or a combination of at least two of polyethylene wax, oxidized polyethylene wax, or polypropylene wax.

[0050] For example, the combination of polyolefin waxes may be selected as: a combination of polyethylene wax and oxidized polyethylene wax, a combination of oxidized polyethylene wax and polypropylene wax, a combination of polyethylene wax and polypropylene wax, etc.

[0051] In this invention, the polyolefin wax can be synthesized using existing technology or can be purchased directly from commercially available products, such as polyethylene wax (CAS No. 9002-88-4), oxidized polyethylene wax (CAS No. 95465-93-3), and polypropylene wax (CAS No. 9003-07-0).

[0052] The VA content of the ethylene-vinyl acetate copolymer EVA is 15-25%, for example, it can be 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24% or 25%, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also acceptable.

[0053] In this invention, VA content refers to the VA content in ethylene-vinyl acetate copolymer EVA, which is determined by thermogravimetric analysis.

[0054] The elastomer includes: SEBS thermoplastic elastomer and / or polyurethane elastomer.

[0055] The petroleum resin includes one or a combination of at least two of the following: C5 petroleum resin, hydrogenated C5 petroleum resin, C9 petroleum resin, hydrogenated C9 petroleum resin, or C5 / C9 copolymer petroleum resin.

[0056] For example, the combination of petroleum resins may be selected as: a combination of C5 petroleum resin and hydrogenated C5 petroleum resin, a combination of hydrogenated C5 petroleum resin and C9 petroleum resin, a combination of C9 petroleum resin and hydrogenated C9 petroleum resin, a combination of C9 petroleum resin and C5 / C9 copolymer petroleum resin, a combination of C5 petroleum resin and C5 / C9 copolymer petroleum resin, etc.

[0057] II. This embodiment provides a method for preparing a thickness-fixed die material for investment casting. The preparation method includes: mixing materials according to a formula in parts by weight, followed by heating and mixing to obtain a thickness-fixed die material for investment casting.

[0058] In this invention, the order of adding each material and the heating temperature during the heating and mixing process are designed based on the physicochemical properties of each raw material, ensuring that the mixing of each raw material is achieved without affecting its properties.

[0059] The heating and mixing method includes high-shear mixing.

[0060] In this invention, high-shear mixing can enhance interfacial penetration of components, improve compatibility, and enhance the mechanical properties of materials.

[0061] The shearing speed of the high-shear mixing is 1000-2000 r / min, for example, it can be 1000 r / min, 1100 r / min, 1200 r / min, 1300 r / min, 1400 r / min, 1500 r / min, 1600 r / min, 1700 r / min, 1800 r / min, 1900 r / min or 2000 r / min, but is not limited to the listed values. Other unlisted values ​​within this range are also acceptable.

[0062] The high-shear mixing time is 20-30 min, for example, it can be 20 min, 21 min, 22 min, 23 min, 24 min, 25 min, 26 min, 27 min, 28 min, 29 min or 30 min, but is not limited to the listed values. Other unlisted values ​​within this range are also acceptable.

[0063] III. This embodiment provides a method for investment casting, wherein the thickness of the wax pattern is adjusted by using a fixed-thickness mold material for investment casting.

[0064] IV. To illustrate the effect of the present invention in providing a thickness-fixed die material for investment casting that balances hardness and toughness, the following example is used for explanation:

[0065] Example 1

[0066] This embodiment provides a thickness-fixed die material for investment casting, wherein the thickness-fixed die material for investment casting comprises, by weight, the following:

[0067] 50 parts microcrystalline wax;

[0068] 12 parts of polyolefin wax;

[0069] 3.5 parts of ethylene-vinyl acetate copolymer (EVA);

[0070] 8 parts elastomer;

[0071] 3 parts petroleum resin;

[0072] The microcrystalline wax is 70# microcrystalline wax;

[0073] The polyolefin wax is polyethylene wax (CAS No. 9002-88-4).

[0074] The VA content of the ethylene-vinyl acetate copolymer EVA is 20%;

[0075] The elastomer is SEBS thermoplastic elastomer;

[0076] The petroleum resin is C5 petroleum resin;

[0077] The preparation process is as follows: ingredients are prepared according to the weight formula, and then heated and mixed to obtain a fixed thickness mold material for investment casting.

[0078] The heating and mixing method includes: high-shear mixing; the high-shear mixing speed is 1500 r / min; the high-shear mixing time is 25 min.

[0079] Example 2

[0080] This embodiment provides a thickness-fixed die material for investment casting, wherein the thickness-fixed die material for investment casting comprises, by weight, the following:

[0081] 40 parts microcrystalline wax;

[0082] 15 parts of polyolefin wax;

[0083] 2 parts of ethylene-vinyl acetate copolymer (EVA);

[0084] 10 parts elastomer;

[0085] 1 part petroleum resin;

[0086] The microcrystalline wax is 80# microcrystalline wax;

[0087] The polyolefin wax is oxidized polyethylene wax (CAS No. 95465-93-3).

[0088] The VA content of the ethylene-vinyl acetate copolymer EVA is 15%;

[0089] The elastomer is a polyurethane elastomer;

[0090] The petroleum resin is a C5 / C9 copolymer petroleum resin;

[0091] The preparation process is as follows: ingredients are prepared according to the weight formula, and then heated and mixed to obtain a fixed thickness mold material for investment casting.

[0092] The heating and mixing method includes: high-shear mixing; the high-shear mixing speed is 1000 r / min; the high-shear mixing time is 30 min.

[0093] Example 3

[0094] This embodiment provides a thickness-fixed die material for investment casting, wherein the thickness-fixed die material for investment casting comprises, by weight, the following:

[0095] 60 parts microcrystalline wax;

[0096] 10 parts of polyolefin wax;

[0097] 5 parts of ethylene-vinyl acetate copolymer EVA;

[0098] 6 parts elastomer;

[0099] 5 parts petroleum resin;

[0100] The microcrystalline wax is 85# microcrystalline wax;

[0101] The polyolefin wax is a polypropylene wax (CAS No. 9003-07-0).

[0102] The VA content of the ethylene-vinyl acetate copolymer EVA is 25%;

[0103] The elastomer is a polyurethane elastomer;

[0104] The petroleum resin is hydrogenated C9 petroleum resin;

[0105] The preparation process is as follows: ingredients are prepared according to the weight formula, and then heated and mixed to obtain a fixed thickness mold material for investment casting.

[0106] The heating and mixing method includes: high-shear mixing; the high-shear mixing speed is 2000 r / min; the high-shear mixing time is 20 min.

[0107] Example 4

[0108] The only difference from Example 1 is that the microcrystalline wax in the thickness die used for investment casting is 30 parts by weight.

[0109] Example 5

[0110] The only difference from Example 1 is that the microcrystalline wax in the thickness die used for investment casting is 70 parts by weight.

[0111] Example 6

[0112] The only difference from Example 1 is that the polyolefin wax in the thickness die used for investment casting is 20 parts by weight.

[0113] Example 7

[0114] The only difference from Example 1 is that the polyolefin wax in the thickness die used for investment casting is 5 parts by weight.

[0115] Example 8

[0116] The only difference from Example 1 is that the ethylene-vinyl acetate copolymer EVA in the thickness die used for investment casting is 1 part by weight.

[0117] Example 9

[0118] The only difference from Example 1 is that the ethylene-vinyl acetate copolymer EVA in the thickness die used for investment casting is 8 parts by weight.

[0119] Example 10

[0120] The only difference from Example 1 is that the elastomer in the fixed-thickness die material used for investment casting is 4 parts by weight.

[0121] Example 11

[0122] The only difference from Example 1 is that the elastomer in the thickness die used for investment casting is 15 parts by weight.

[0123] Example 12

[0124] The only difference from Example 1 is that the petroleum resin in the thickness die used for investment casting is 0.5 parts by weight.

[0125] Example 13

[0126] The only difference from Example 1 is that the petroleum resin in the thickness die used for investment casting is 10 parts by weight.

[0127] Example 14

[0128] The only difference from Example 1 is that the heating and mixing is carried out by stirring, with a stirring speed of 200 r / min and a mixing time of 2 h.

[0129] Comparative Example 1

[0130] The only difference from Example 1 is that the microcrystalline wax is replaced with an equal amount of 60# fully refined paraffin wax.

[0131] Comparative Example 2

[0132] The only difference from Example 1 is that the microcrystalline wax is replaced with an equal amount of carnauba wax.

[0133] Comparative Example 3

[0134] The only difference from Example 1 is that the microcrystalline wax is replaced with an equal amount of lignite wax.

[0135] Comparative Example 4

[0136] The only difference from Example 1 is that the polyolefin wax is replaced with an equal amount of Fischer-Tropsch wax.

[0137] Comparative Example 5

[0138] The only difference from Example 1 is that no elastomer is added.

[0139] Comparative Example 6

[0140] The only difference from Example 1 is that the petroleum resin is replaced with an equal amount of hydrogenated terpene resin.

[0141] The molding materials obtained from the above embodiments and comparative examples were subjected to performance tests, and the results are shown in Table 1 below.

[0142] Table 1

[0143]

[0144] In the table: the bending strength test is conducted in accordance with GB / T 14235.2; the penetration test is conducted in accordance with the test standard GB / T4985-2010.

[0145] As shown in Table 1, the solution provided by this invention achieves simultaneous improvement in hardness and toughness by utilizing the synergistic effect between the components within the molding material, resulting in a material that is both hard and tough. It can bend naturally when the wax sheet is bent without creases or breakage, exhibiting excellent performance. Replacing or omitting some components of this invention will lead to a significant deterioration in the performance of the molding material, which is detrimental to its use. The resulting molding material has a penetration (25℃, 0.1mm) ≤ 8.5 and a bending strength ≥ 10.8MPa. In the preferred embodiment, the molding material has a penetration (25℃, 0.1mm) ≤ 6 and a bending strength ≥ 14.5MPa.

[0146] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0147] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0148] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A dimensionally stable moulding material for use in investment casting, characterised in that, The thickness-fixed die material used for investment casting includes: Microcrystalline wax, polyolefin wax, ethylene-vinyl acetate copolymer (EVA), elastomers, and petroleum resins.

2. The exfoliated graphite composition of claim 1 wherein the exfoliated graphite composition has a density of 0.1 to 0.3 g / cm3. The thickness-fixed die material for investment casting comprises, by weight, the following: 40-60 parts of microcrystalline wax; 10-15 parts of polyolefin wax; 2-5 parts of ethylene-vinyl acetate copolymer (EVA); 6-10 parts elastomer; 1-5 parts of petroleum resin.

3. The thickness-fixed die material for investment casting as described in claim 1, characterized in that, The microcrystalline wax includes one or a combination of at least two of the following: 70# microcrystalline wax, 75# microcrystalline wax, 80# microcrystalline wax, 85# microcrystalline wax, or 90# microcrystalline wax.

4. The thickness-fixed die material for investment casting as described in claim 1, characterized in that, The polyolefin wax includes one or a combination of at least two of the following: polyethylene wax, oxidized polyethylene wax, or polypropylene wax.

5. The thickness-fixed die material for investment casting as described in claim 1, characterized in that, The VA content of the ethylene-vinyl acetate copolymer EVA is 15-25%.

6. The thickness-fixed die material for investment casting as described in claim 1, characterized in that, The elastomer includes: SEBS thermoplastic elastomer and / or polyurethane elastomer.

7. The thickness-fixed die material for investment casting as described in claim 1, characterized in that, The petroleum resin includes one or a combination of at least two of the following: C5 petroleum resin, hydrogenated C5 petroleum resin, C9 petroleum resin, hydrogenated C9 petroleum resin, or C5 / C9 copolymer petroleum resin.

8. A method for preparing a thickness-fixed die material for investment casting as described in any one of claims 1-7, characterized in that, The preparation method includes: mixing ingredients according to a formula in parts by weight, followed by heating and mixing to obtain a fixed-thickness mold material for investment casting.

9. The preparation method according to claim 8, characterized in that, The heating and mixing method includes: high-shear mixing; Preferably, the shearing speed of the high-shear mixing is 1000-2000 r / min; Preferably, the high-shear mixing time is 20-30 minutes.

10. A method for investment casting, characterized in that, The investment casting method uses a thickness-fixed mold material as described in any one of claims 1-7 to adjust the thickness of the wax pattern.

Images