Investment casting pattern material, preparation method and investment casting method

Abstract

The invention relates to an investment casting pattern material, a preparation method and an investment casting method, in particular to the field of investment casting, and the investment casting pattern material comprises a wax material, petroleum resin, linear low density polyethylene, an ethylene-vinyl acetate copolymer and a filler; the mass ratio of the linear low density polyethylene to the ethylene-vinyl acetate copolymer is 1: (2-4). According to the investment casting mold material provided by the invention, the synthesis of the shrinkage rate, the mechanical property, the thermal stability and the processing property of the mold material is realized by optimizing the formula composition and utilizing the synergistic effect of the linear low-density polyethylene and the ethylene-vinyl acetate copolymer complex in a specific ratio through molecular chain interaction, crystallization behavior regulation and phase structure optimization; and therefore, the precision of investment casting is improved.

Description

Technical Field

[0001] This invention relates to the field of investment casting, specifically to an investment casting mold material and its preparation method, and an investment casting method. Background Technology

[0002] Investment casting, also known as lost-wax casting, begins by creating a wax model, coating it with a layer of refractory material, heating it to melt and flow out, creating a hollow shell. Molten metal is then poured into the shell, and after cooling, the refractory material is removed to obtain the metal casting. Wax modeling is the first step in the entire process, and the quality of the wax material directly affects the quality of both the wax model and the casting. The properties of the wax material are the most important factor affecting the dimensional accuracy of the wax model.

[0003] Currently, there are many types of molding materials used in practice. According to the composition of the matrix material, molding materials can be divided into wax-based molding materials, resin-based molding materials, water-soluble molding materials, etc. Among them, wax-based molding materials are widely used. For example, CN109266021A discloses a composite wax for investment casting, which includes Fischer-Tropsch wax, paraffin wax, methyl acrylate, petrolatum, epoxy resin glue, sodium lignosulfonate, aluminum chloride hexahydrate, and barium ricinoleate.

[0004] 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 reaction vessel and first indirectly heated using a water jacket, with the temperature controlled below 80℃ for localized melting. 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 rpm. After melting, 5-10 parts by weight of tackifying resin and 0-0.01 parts by weight of antioxidant are added and stirred until uniformly mixed. Granulation is then performed using steel strip material selection and forming technology, followed by sieving to obtain the investment casting wax granule mold material.

[0005] However, the current investment casting industry is developing towards precision, complexity, large size, and integral casting of parts, but the existing investment casting mold materials are no longer able to meet the requirements. Investment casting mold materials have defects such as poor toughness and plasticity and substandard shrinkage. Summary of the Invention

[0006] In view of the problems existing in the prior art, the purpose of the present invention is to provide an investment casting mold material and its preparation method, as well as an investment casting method, to solve the defects of poor toughness and plasticity and substandard shrinkage rate of investment casting mold materials.

[0007] To achieve this objective, the present invention adopts the following technical solution:

[0008] In a first aspect, the present invention provides an investment casting mold material, the investment casting mold material comprising:

[0009] Waxes, petroleum resins, linear low-density polyethylene, ethylene-vinyl acetate copolymers, and fillers;

[0010] The mass ratio of the linear low-density polyethylene to the ethylene-vinyl acetate copolymer is 1:(2-4).

[0011] The investment casting mold material provided by this invention optimizes the formulation composition and utilizes the synergistic effect of a specific ratio of linear low-density polyethylene and ethylene-vinyl acetate copolymer complex to achieve a comprehensive improvement in the shrinkage rate, mechanical properties, thermal stability and process performance of the mold material through molecular chain interaction, crystallization behavior regulation and phase structure optimization, thereby improving the accuracy of investment casting.

[0012] As a preferred embodiment of the present invention, the investment casting mold material comprises, by weight, the following:

[0013] The composition consists of 30-40 parts wax, 20-30 parts petroleum resin, 2-5 parts linear low-density polyethylene, 4-20 parts ethylene-vinyl acetate copolymer, and 5-10 parts filler.

[0014] As a preferred technical solution of the present invention, the wax material includes one or a combination of at least two of mineral wax, animal wax or plant wax.

[0015] As a preferred technical solution of the present invention, the petroleum resin includes one or a combination of at least two of the following: C9 petroleum resin, C5 / C9 copolymer petroleum resin, C9 hydrogenated petroleum resin, C5 petroleum resin, or C5 hydrogenated petroleum resin.

[0016] As a preferred embodiment of the present invention, the mass percentage of vinyl acetate-derived structural units in the ethylene-vinyl acetate copolymer is 20-30%.

[0017] As a preferred embodiment of the present invention, the filler includes one or a combination of at least two of the following: cellulose acetate powder, talc powder, or glass fiber.

[0018] In a second aspect, the present invention provides a method for preparing an investment casting mold material as described in the first aspect, the method comprising:

[0019] According to the formula, the wax, linear low-density polyethylene and ethylene-vinyl acetate copolymer are mixed and then subjected to a first heating to obtain a first mixture;

[0020] The first mixture and petroleum resin are subjected to a second heating to obtain a second mixture;

[0021] The second mixture and filler are heated a third time to obtain investment casting mold material.

[0022] As a preferred technical solution of the present invention, the first heating includes: stirring and mixing at 120-130°C for 20-40 minutes;

[0023] Preferably, the second heating includes: stirring and mixing at 120-140°C for 20-40 minutes.

[0024] As a preferred technical solution of the present invention, the third heating includes: stirring and mixing at 110-120°C for 60-80 minutes.

[0025] Thirdly, the present invention provides a method for investment casting, the method comprising: pressing an investment casting mold using an investment casting mold material as described in any one of claims 1-6.

[0026] Compared with existing technical solutions, the present invention has the following beneficial effects:

[0027] (1) The investment casting mold material provided by the present invention improves the hardness and toughness of the mold material through formula optimization, and can ensure that the mold material is easy to demold after injection molding. At the same time, it reduces the shrinkage rate of the mold material, increases the fluidity of the mold material, and facilitates liquid wax injection.

[0028] (2) The investment casting mold material provided by the present invention is a two-phase structure of “LLDPE crystalline region - EVA amorphous region” formed by the combination of linear low-density polyethylene and ethylene-vinyl acetate copolymer. It retains the rigidity of the crystalline phase and utilizes the toughness of the amorphous phase. At the same time, the linear chains of LLDPE and the branched chains of EVA are intertwined to form a semi-interpenetrating network structure, which restricts the free movement of molecular chains during the solidification of the mold material and further reduces shrinkage.

[0029] (3) The penetration (1 / 10mm) of the investment casting mold material provided by the present invention is ≤3.8, the linear shrinkage rate is ≤0.33%, the bending strength is ≤7.5MPa, and the ash content is ≤0.020%.

[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] The current investment casting industry is developing towards precision, complexity, large-scale, and integral casting of components. However, existing investment casting mold materials are no longer sufficient to meet the requirements, exhibiting defects such as poor toughness and plasticity, and substandard shrinkage. Therefore, this invention optimizes the composition and proportion of investment casting mold materials to improve their performance, ensuring low linear shrinkage, penetration, and flexural strength, while also maintaining low ash content. Specifically:

[0033] I. This embodiment provides an investment casting mold material, which includes:

[0034] Waxes, petroleum resins, linear low-density polyethylene, ethylene-vinyl acetate copolymers, and fillers.

[0035] The mass ratio of the linear low-density polyethylene and the ethylene-vinyl acetate copolymer is 1:(2-4), for example, it can be 1:2, 1:2.2, 1:2.4, 1:2.6, 1:2.8, 1:3, 1:3.2, 1:3.4, 1:3.6, 1:3.8 or 1:4, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also acceptable.

[0036] The investment casting mold material comprises, by weight, the following:

[0037] The composition consists of 30-40 parts wax, 20-30 parts petroleum resin, 2-5 parts linear low-density polyethylene, 4-20 parts ethylene-vinyl acetate copolymer, and 5-10 parts filler.

[0038] In this invention, the wax material in the investment casting mold material is 30-40 parts by weight, for example, 30 parts, 31 parts, 32 parts, 33 parts, 34 parts, 35 parts, 36 parts, 37 parts, 38 parts, 39 parts or 40 parts, but is not limited to the listed values. Other unlisted values ​​within this range are also acceptable.

[0039] In this invention, the petroleum resin in the investment casting mold material is 20-30 parts by weight, for example, 20 parts, 21 parts, 22 parts, 23 parts, 24 parts, 25 parts, 26 parts, 27 parts, 28 parts, 29 parts or 30 parts, but is not limited to the listed values. Other unlisted values ​​within this range are also acceptable.

[0040] In this invention, the linear low-density polyethylene in the investment casting mold material 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.

[0041] In this invention, the ethylene-vinyl acetate copolymer in the investment casting mold material is 4-20 parts by weight, for example, 4 parts, 5.6 parts, 7.2 parts, 8.8 parts, 10.4 parts, 12 parts, 13.6 parts, 15.2 parts, 16.8 parts, 18.4 parts, or 20 parts, but is not limited to the listed values. Other unlisted values ​​within this range are also acceptable.

[0042] In this invention, the filler material in the investment casting mold material is 5-10 parts by weight, for example, it can be 5 parts, 5.5 parts, 6 parts, 6.5 parts, 7 parts, 7.5 parts, 8 parts, 8.5 parts, 9 parts, 9.5 parts or 10 parts, but is not limited to the listed values. Other unlisted values ​​within this range are also acceptable.

[0043] The wax material includes one or a combination of at least two of the following: mineral wax, animal wax, or plant wax.

[0044] In this invention, the mineral wax can be selected as lignite wax and / or paraffin wax, with the melting point of paraffin wax being 50-70℃. The specific selection can be made reasonably according to the conventional requirements in the field.

[0045] In this invention, the animal wax can be selected from beeswax or the like, and the selection can be made reasonably according to the conventional requirements in the field.

[0046] In this invention, the plant wax can be selected from candlewood wax, palm wax, etc., and can be reasonably selected according to the conventional requirements in the field.

[0047] The petroleum resin includes one or a combination of at least two of the following: C9 petroleum resin, C5 / C9 copolymer petroleum resin, C9 hydrogenated petroleum resin, C5 petroleum resin, or C5 hydrogenated petroleum resin.

[0048] Linear low-density polyethylene refers to a molecular structure formed by copolymerizing ethylene with a small amount of α-olefins on the main chain of linear ethylene, with short comonomer branches. Specifically, it can be purchased from the market or synthesized according to existing technology in this field, such as commercially available products 6101XR, 1002AY, 0220AA, etc.

[0049] The mass percentage of vinyl acetate-derived structural units in the ethylene-vinyl acetate copolymer is 20-30%, for example, it can be 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29% or 30%, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also acceptable.

[0050] In this invention, VA represents vinyl acetate.

[0051] The filler includes one or a combination of at least two of the following: cellulose acetate powder, talc powder, or glass fiber.

[0052] II. This embodiment provides a method for preparing investment casting mold material, the preparation method comprising:

[0053] According to the formula, the wax, linear low-density polyethylene and ethylene-vinyl acetate copolymer are mixed and then subjected to a first heating to obtain a first mixture;

[0054] The first mixture and petroleum resin are subjected to a second heating to obtain a second mixture;

[0055] The second mixture and filler are heated a third time to obtain investment casting mold material.

[0056] The first heating includes: stirring and mixing at 120-130℃ for 20-40 minutes. The temperature can be, for example, 120℃, 121℃, 122℃, 123℃, 124℃, 125℃, 126℃, 127℃, 128℃, 129℃ or 130℃, etc., and the time can be, for example, 20 minutes, 22 minutes, 24 minutes, 26 minutes, 28 minutes, 30 minutes, 32 minutes, 34 minutes, 36 minutes, 38 minutes or 40 minutes, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also acceptable.

[0057] The second heating includes: stirring and mixing at 120-140℃ for 20-40 minutes. The temperature can be, for example, 120℃, 122℃, 124℃, 126℃, 128℃, 130℃, 132℃, 134℃, 136℃, 138℃ or 140℃, and the time can be, for example, 20 minutes, 22 minutes, 24 minutes, 26 minutes, 28 minutes, 30 minutes, 32 minutes, 34 minutes, 36 minutes, 38 minutes or 40 minutes, but is not limited to the listed values. Other unlisted values ​​within this range are also acceptable.

[0058] The third heating includes stirring and mixing at 110-120℃ for 60-80 minutes. The temperature can be, for example, 110℃, 111℃, 112℃, 113℃, 114℃, 115℃, 116℃, 117℃, 118℃, 119℃ or 120℃, etc., and the time can be, for example, 60 minutes, 62 minutes, 64 minutes, 66 minutes, 68 minutes, 70 minutes, 72 minutes, 74 minutes, 76 minutes, 78 minutes or 80 minutes, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also acceptable.

[0059] In this invention, the stirring speed during mixing can be selected and controlled to be 100-500 r / min, for example, it can be 100 r / min, 140 r / min, 180 r / min, 220 r / min, 260 r / min, 300 r / min, 340 r / min, 380 r / min, 420 r / min, 460 r / min or 500 r / min, etc., but is not limited to the listed values, and other unlisted values ​​within this range also meet the requirements.

[0060] III. This embodiment provides a method for investment casting, which includes: pressing an investment casting mold material into an investment mold.

[0061] IV. To illustrate the excellent performance of the investment casting mold material provided by this invention, the following examples are used for explanation:

[0062] Example 1

[0063] This embodiment provides an investment casting mold material, which comprises, by weight, the following:

[0064] The composition consists of 35 parts wax, 25 parts petroleum resin, 3 parts linear low-density polyethylene (brand name 6101XR), 9 parts ethylene-vinyl acetate copolymer, and 6 parts filler.

[0065] The mass ratio of the linear low-density polyethylene to the ethylene-vinyl acetate copolymer is 1:3;

[0066] The wax material is paraffin wax;

[0067] The petroleum resin is C9 petroleum resin;

[0068] The vinyl acetate-derived structural units in the ethylene-vinyl acetate copolymer comprise 25% by mass.

[0069] The filler is talc.

[0070] The preparation process is as follows:

[0071] According to the formula, the wax, linear low-density polyethylene and ethylene-vinyl acetate copolymer are mixed and then subjected to a first heating to obtain a first mixture;

[0072] The first mixture and petroleum resin are subjected to a second heating to obtain a second mixture;

[0073] The second mixture and filler are heated a third time to obtain investment casting mold material;

[0074] The first heating includes stirring and mixing at 125°C for 30 minutes; the second heating includes stirring and mixing at 130°C for 30 minutes; and the third heating includes stirring and mixing at 115°C for 70 minutes.

[0075] Example 2

[0076] This embodiment provides an investment casting mold material, which comprises, by weight, the following:

[0077] The composition consists of 32 parts wax, 28 parts petroleum resin, 4 parts linear low-density polyethylene (brand name 1002AY), 12 parts ethylene-vinyl acetate copolymer, and 8 parts filler.

[0078] The mass ratio of the linear low-density polyethylene to the ethylene-vinyl acetate copolymer is 1:3;

[0079] The wax material is microcrystalline wax;

[0080] The petroleum resin is C5 petroleum resin;

[0081] The vinyl acetate-derived structural units in the ethylene-vinyl acetate copolymer comprise 28% by mass.

[0082] The filler is cellulose acetate powder.

[0083] The preparation process is as follows:

[0084] According to the formula, the wax, linear low-density polyethylene and ethylene-vinyl acetate copolymer are mixed and then subjected to a first heating to obtain a first mixture;

[0085] The first mixture and petroleum resin are subjected to a second heating to obtain a second mixture;

[0086] The second mixture and filler are heated a third time to obtain investment casting mold material;

[0087] The first heating includes stirring and mixing at 125°C for 30 minutes; the second heating includes stirring and mixing at 130°C for 30 minutes; and the third heating includes stirring and mixing at 115°C for 70 minutes.

[0088] Example 3

[0089] This embodiment provides an investment casting mold material, which comprises, by weight, the following:

[0090] 40 parts wax, 20 parts petroleum resin, 5 parts linear low-density polyethylene (brand name 0220AA), 20 parts ethylene-vinyl acetate copolymer and 10 parts filler;

[0091] The mass ratio of the linear low-density polyethylene to the ethylene-vinyl acetate copolymer is 1:4;

[0092] The wax material is paraffin wax;

[0093] The petroleum resin is a C9 hydrogenated petroleum resin;

[0094] The vinyl acetate-derived structural units in the ethylene-vinyl acetate copolymer comprise 30% by mass.

[0095] The filler is cellulose acetate powder.

[0096] The preparation process is as follows:

[0097] According to the formula, the wax, linear low-density polyethylene and ethylene-vinyl acetate copolymer are mixed and then subjected to a first heating to obtain a first mixture;

[0098] The first mixture and petroleum resin are subjected to a second heating to obtain a second mixture;

[0099] The second mixture and filler are heated a third time to obtain investment casting mold material;

[0100] The first heating includes: stirring and mixing at 130°C for 20 minutes; the second heating includes: stirring and mixing at 120°C for 40 minutes; and the third heating includes: stirring and mixing at 120°C for 60 minutes.

[0101] Example 4

[0102] This embodiment provides an investment casting mold material, which comprises, by weight, the following:

[0103] 30 parts wax, 30 parts petroleum resin, 2 parts linear low-density polyethylene (brand name 6101XR), 4 parts ethylene-vinyl acetate copolymer, and 5 parts filler;

[0104] The mass ratio of the linear low-density polyethylene to the ethylene-vinyl acetate copolymer is 1:2;

[0105] The wax material is paraffin wax;

[0106] The petroleum resin is a C5 hydrogenated petroleum resin;

[0107] The vinyl acetate-derived structural units in the ethylene-vinyl acetate copolymer comprise 20% by mass.

[0108] The filler is talc.

[0109] The preparation process is as follows:

[0110] According to the formula, the wax, linear low-density polyethylene and ethylene-vinyl acetate copolymer are mixed and then subjected to a first heating to obtain a first mixture;

[0111] The first mixture and petroleum resin are subjected to a second heating to obtain a second mixture;

[0112] The second mixture and filler are heated a third time to obtain investment casting mold material;

[0113] The first heating includes stirring and mixing at 120°C for 40 minutes; the second heating includes stirring and mixing at 140°C for 20 minutes; and the third heating includes stirring and mixing at 110°C for 80 minutes.

[0114] Comparative Example 1

[0115] The only difference from Example 1 is that the investment casting mold material does not contain linear low-density polyethylene.

[0116] Comparative Example 2

[0117] The only difference from Example 1 is that the investment casting mold material does not contain ethylene-vinyl acetate copolymer.

[0118] Comparative Example 3

[0119] The only difference from Example 1 is that the mass ratio of linear low-density polyethylene and ethylene-vinyl acetate copolymer is 1:1.

[0120] Comparative Example 4

[0121] The only difference from Example 1 is that the mass ratio of linear low-density polyethylene and ethylene-vinyl acetate copolymer is 1:5.

[0122] Comparative Example 5

[0123] The only difference from Example 1 is that the mass ratio of linear low-density polyethylene and ethylene-vinyl acetate copolymer is 3:1.

[0124] The linear shrinkage and ash content of the investment casting mold materials in the above embodiments and comparative examples were measured according to GB / T 42603.1-2023 Investment Casting Medium Temperature Mold Materials Part 1: Physical Properties Test Methods, and the flexural strength was measured according to GB / T 42603.2-2023 Investment Casting Medium Temperature Mold Materials Part 2: Service Performance Test Methods. Among them, the penetration refers to the depth to which a 100g standard needle penetrates the surface of the mold material within 5 seconds at 25°C. The smaller the penetration value, the greater the surface hardness and the higher the mechanical strength of the mold material. The results are shown in Table 1 below.

[0125] Table 1

[0126]

[0127] As shown in Table 1, the investment casting mold material provided by the present invention, through optimized formulation composition, utilizes the synergistic effect of a specific ratio of linear low-density polyethylene and ethylene-vinyl acetate copolymer complex to achieve a comprehensive improvement in mold material shrinkage, mechanical properties, thermal stability and process performance through molecular chain interaction, crystallization behavior regulation and phase structure optimization, thereby enhancing the accuracy of investment casting.

[0128] 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.

[0129] 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.

[0130] 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 type of investment casting die material, characterized in that, The investment casting mold material includes: Waxes, petroleum resins, linear low-density polyethylene, ethylene-vinyl acetate copolymers, and fillers; The mass ratio of the linear low-density polyethylene to the ethylene-vinyl acetate copolymer is 1:(2-4).

2. The investment casting mold material as described in claim 1, characterized in that, The investment casting mold material comprises, by weight, the following: The composition consists of 30-40 parts wax, 20-30 parts petroleum resin, 2-5 parts linear low-density polyethylene, 4-20 parts ethylene-vinyl acetate copolymer, and 5-10 parts filler.

3. The investment casting mold material as described in claim 1, characterized in that, The wax material includes one or a combination of at least two of the following: mineral wax, animal wax, or plant wax.

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

5. The investment casting mold material as described in claim 1, characterized in that, The vinyl acetate-derived structural units in the ethylene-vinyl acetate copolymer have a mass percentage content of 20-30%.

6. The investment casting mold material as described in claim 1, characterized in that, The filler includes one or a combination of at least two of the following: cellulose acetate powder, talc powder, or glass fiber.

7. A method for preparing an investment casting mold material as described in any one of claims 1-6, characterized in that, The preparation method includes: According to the formula, the wax, linear low-density polyethylene and ethylene-vinyl acetate copolymer are mixed and then subjected to a first heating to obtain a first mixture; The first mixture and petroleum resin are subjected to a second heating to obtain a second mixture; The second mixture and filler are heated a third time to obtain investment casting mold material.

8. The preparation method according to claim 7, characterized in that, The first heating includes: stirring and mixing at 120-130°C for 20-40 minutes; Preferably, the second heating includes: stirring and mixing at 120-140°C for 20-40 minutes.

9. The preparation method according to claim 7, characterized in that, The third heating includes stirring and mixing at 110-120℃ for 60-80 minutes.

10. A method for investment casting, characterized in that, The investment casting method includes: pressing an investment mold using an investment casting mold material as described in any one of claims 1-6.

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