High-performance precision casting wax and fine preparation method thereof

Abstract

The invention discloses high-performance precision casting wax and a preparation method thereof. The casting wax is prepared from the following raw materials in parts by mass: 20 to 40 parts of paraffin, 0 to 20 parts of lignite wax, 0 to 20 parts of beewax, 0 to 10 parts of polyethylene wax, 5 to 10 parts of stearic acid, 20 to 40 parts of C5 petroleum resin, 10 to 20 parts of C9 petroleum resin, 10 to 20 parts of hydrogenated C9 petroleum resin, 0 to 10 parts of hydrogenated terpene resin, 0 to 40 parts of mannitol, 0 to 14 parts of polymethyl methacrylate, 0 to 5 parts of corn starch and 0 to 5 parts of cellulose acetate. The core innovation point of the invention is as follows: through the synergistic effect of the hydrogenated resin and the high-molecular polymer and in combination with the filling powder in a specific proportion, the thermal expansion coefficient (the shrinkage rate is less than or equal to 0.6%) and the ash content (less than or equal to 0.02%) of the wax material are remarkably reduced, and meanwhile, the bending strength (7-10MPa) and the surface hardness (46-55HD) are improved. The wax material is suitable for precision casting of thick, large and complex castings, solves the problems that the existing wax material is easy to deform, high in shrinkage rate and poor in thermal stability, and has high surface smoothness and dimensional precision.

Description

Technical Field

[0001] The invention relates to the field of investment casting wax materials, and in particular to a high-performance resin-based composite material formula design and a study on the relationship between its structure and performance. Background Art

[0002] Precision casting is an advanced material forming process. Its castings are precise, complex, close to the final shape of the parts, and can be used directly without processing or with little processing. In the precision casting process, the dimensional accuracy of the wax mold directly determines and affects the dimensional accuracy of the final product. Precision casting wax needs to meet the following basic requirements: 1. Melting point: The melting point should be moderate, generally in the range of 60~100℃, to facilitate the preparation of mold materials, molding and demoulding; 2. Fluidity: The mold material should have good fluidity to facilitate filling the mold cavity. In addition, the mold material should also be easy to flow out of the mold shell during dewaxing; 3. Softening point: The temperature at which the mold material begins to soften and deform is called the softening point. Usually, the temperature at which the deformation of the standard sample is 2 mm when heated is used as a scalar. In order to avoid deformation of the mold, the softening point is generally not less than 35-40°C. 4. Shrinkage rate: In order to ensure that the investment mold achieves the required dimensional accuracy, the shrinkage rate of the mold material is required to be small (generally less than 1%) and stable; 5. Strength and surface hardness: In order to avoid damage, fracture or surface scratches of the mold during mold making, shell making, transportation and storage, the mold material is required to have sufficient strength and surface hardness in the solid state; 6. Weldability: The mold material should have good welding performance and welding strength. This will facilitate the assembly of the mold into a mold set, and prevent the welds from breaking during transportation and shell making. 7. Coating property: The mold material should be well wetted by the refractory coating and form a uniform covering layer to facilitate obtaining a shell cavity with clear contours and smooth surface; 8. Ash: The residue after the mold material is burned is called ash. The ash of the mold material remaining in the mold cavity after the shell is fired should be as small as possible to avoid affecting the quality of the casting.

[0003] The demand for model materials in the precision casting process is increasing, especially in the context of precision and complex shapes. Although the existing precision casting wax can meet the general precision casting requirements, it cannot meet the dimensional accuracy and surface quality requirements of thick, complex and large precision castings. Therefore, it is necessary to develop new precision casting wax products. The paraffin-based precision casting wax is prepared by compounding wax materials. Starting from the selection of raw materials and formula design, the paraffin-based wax material is blended and modified. The effects of resin tackifiers, functional modifiers, etc. on the properties of rosin resin on the wax material are investigated. By adjusting the composition and proportion of the wax model material, a new formula scheme is optimized and formed, and finally the purpose of improving the precision of castings is achieved. Summary of the invention

[0004] In view of the defects in the prior art, the purpose of the present invention is to provide a high-strength precision wax material formula and a preparation method thereof, wherein the precision casting wax mold prepared by the formula has excellent thermal stability and high strength.

[0005] The technical solution of the present invention is to provide a high-strength precision casting wax, characterized in that it comprises, by weight: (1) 20-40 parts of paraffin wax; (2) 10-20 parts of montan wax; (3) 0-10 parts of beeswax; (4) 0-5 parts of polyethylene wax; (5) 5-10 parts of stearic acid; (6) Ethylene-vinyl acetate copolymer; (7) 20-40 parts of C5 petroleum resin; (8) 10-20 parts of C9 petroleum resin; (9) 0-10 parts of hydrogenated terpene resin; (10) 0-36 parts of mannitol; (11) 0-14 parts of polymethyl methacrylate; (12) 0-5 parts corn starch; (13) Cellulose acetate 0-5 parts.

[0006] The melting point of the paraffin wax is 60~62℃, which is 60# fully refined paraffin wax. The melting point of the lignite wax is 75~86℃; the melting point of the beeswax is 62~67℃; the melting point of the polyethylene wax is greater than 90℃, and the average relative molecular mass is 1500~2000. The tackifying resin is one or more of C5 petroleum resin, C9 petroleum resin, hydrogenated C9 petroleum resin and terpene resin. Among them, the hydrogenated C9 petroleum resin has a softening point of 100~140℃ and an acid value of <1.0mgKOH / g; the softening point of the terpene resin is 80~90℃ and the iodine value is 40~75. The mannitol is ultra-pure, ≥99.0% (HPLC); the polymethyl methacrylate can pass through a 500 mesh sieve, 25 microns, relative molecular mass; the cellulose acetate passes through a 100 mesh sieve. Mannitol, polymethyl methacrylate and corn starch are added in combination.

[0007] The preparation method of a high-strength investment wax pattern for precision casting of the present invention is carried out according to the following steps: (1) firstly heat paraffin wax, montan wax and beeswax at 90°C, stir continuously until melted, then raise the temperature to 100°C and add polyethylene wax, stir continuously until melted. (2) continue to heat the obtained in step 1 at 100°C, add stearic acid, wait until the stearic acid is completely melted, add ethylene-polyvinyl acetate copolymer, stir continuously and slowly until completely melted, and keep at 100°C for 30-60min. (3) heat the obtained in step 2 to 120°C, add C5 petroleum resin, C9 petroleum resin and hydrogenated terpene resin, stop stirring, keep at 120°C for 90-120min, then cool to 115°C, slowly start stirring, and make the resin completely melted. (4) continue to cool the obtained in step 3 to 100°C, add mannitol powder, polymethyl methacrylate powder and corn starch respectively, start maximum stirring, and keep at 100°C for 60min. (5) The temperature is then lowered to 90° C. and maintained for 60 to 90 minutes to form pellets to obtain the precision casting wax.

[0008] The viscosity of the investment wax prepared by the present invention is between 480 and 640 mPa·s, and the shrinkage is between 0.3 and 0.6%, so that the investment wax has good stability during the casting process; the bending strength of the investment wax is between 7 and 10 Mpa, and the hardness is between 50 and 60, which ensures the high strength and high hardness of the investment wax during the casting process, and can improve the precision of the casting; the ash content of the investment wax is below 0.02%, which ensures that the casting process is pollution-free; the melting point of the investment wax is between 54 and 58 ° C, which is easier to demold during the casting process. The stability, high strength, high hardness, low ash content, suitable melting point, easy demolding, etc. of the investment wax are conducive to improving the efficiency of investment casting. The internal composition of the investment wax provided by the present invention is uniform, the shrinkage rate of each part is uniform, and the wax strength is high. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] none DETAILED DESCRIPTION

[0010] The high-strength precision casting wax of the present invention will be further described in detail below in conjunction with the embodiments of the present invention: Embodiment 1

[0011] A high-strength precision casting wax material, the precision casting wax material comprising the following raw materials in parts by weight: 36 parts of paraffin, 20 parts of montan wax, 6 parts of polyethylene wax, 5 parts of beeswax, 9 parts of stearic acid, 5 parts of ethylene-polyvinyl acetate, 36 parts of C5 petroleum resin, 18 parts of C9 petroleum resin, 12 parts of hydrogenated C9 petroleum resin, 9 parts of hydrogenated terpene resin, 36 parts of mannitol, 14 parts of polymethyl methacrylate and 3 parts of corn starch.

[0012] (1) Heat paraffin wax at 90°C and stir continuously until it melts. Add lignite wax, polyethylene wax and beeswax. Continue heating to 100°C. Add stearic acid and stir continuously until it melts.

[0013] (2) Continue heating the mixture obtained in step 1 at 100°C, add ethylene-polyvinyl acetate, and continue stirring until it is completely melted and keep it at 100°C for 90 minutes.

[0014] (3) Raise the temperature obtained in step 2 to 120°C, continue heating, add C5 petroleum resin, C9 petroleum resin, hydrogenated C9 petroleum resin and hydrogenated terpene resin, stop stirring and keep at 120°C for 60 minutes until the resin is completely melted.

[0015] (4) Cool the mixture obtained in step 3 to 100°C and start stirring. After the resin is evenly mixed, add filler mannitol, polymethyl methacrylate and corn starch in sequence and keep stirring for 40 minutes.

[0016] (5) Continue stirring and heating the product obtained in step 4, then reduce the temperature to 90° C., maintain it at 90° C. for 30 minutes, and then make it into particles to obtain the precision casting wax.

[0017] Embodiment 2

[0018] A high-strength precision casting wax material, the precision casting wax material comprising the following raw materials in parts by weight: 36 parts of paraffin, 20 parts of montan wax, 6 parts of polyethylene wax, 5 parts of beeswax, 9 parts of stearic acid, 5 parts of ethylene-polyvinyl acetate, 36 parts of C5 petroleum resin, 18 parts of C9 petroleum resin, 9 parts of hydrogenated terpene resin, 36 parts of mannitol, 14 parts of polymethyl methacrylate and 3 parts of corn starch.

[0019] (1) Heat paraffin wax at 90°C and stir continuously until it melts. Add lignite wax, polyethylene wax and beeswax. Continue heating to 100°C. Add stearic acid and stir continuously until it melts.

[0020] (2) Continue heating the mixture obtained in step 1 at 100°C, add ethylene-polyvinyl acetate, and continue stirring until it is completely melted and keep it at 100°C for 90 minutes.

[0021] (3) Raise the temperature obtained in step 2 to 120°C, continue heating, add C5 petroleum resin, C9 petroleum resin, hydrogenated C9 petroleum resin and hydrogenated terpene resin, stop stirring and keep at 120°C for 60 minutes until the resin is completely melted.

[0022] (4) Cool the mixture obtained in step 3 to 100°C and start stirring. After the resin is evenly mixed, add filler mannitol, polymethyl methacrylate and corn starch in sequence and keep stirring for 40 minutes.

[0023] (5) Continue stirring and heating the product obtained in step 4, then reduce the temperature to 90° C., maintain it at 90° C. for 30 minutes, and then make it into particles to obtain the precision casting wax.

[0024] Embodiment 3

[0025] A high-strength precision casting wax material, the precision casting wax material comprising the following raw materials in parts by weight: 36 parts of paraffin, 16 parts of montan wax, 6 parts of polyethylene wax, 5 parts of beeswax, 9 parts of stearic acid, 6 parts of ethylene-polyvinyl acetate, 36 parts of C5 petroleum resin, 18 parts of C9 petroleum resin, 9 parts of hydrogenated terpene resin, 36 parts of mannitol, 14 parts of polymethyl methacrylate and 3 parts of corn starch.

[0026] (1) Heat paraffin wax at 90°C and stir continuously until it melts. Add lignite wax, polyethylene wax and beeswax. Continue heating to 100°C. Add stearic acid and stir continuously until it melts.

[0027] (2) Continue heating the mixture obtained in step 1 at 100°C, add ethylene-polyvinyl acetate, and continue stirring until it is completely melted and keep it at 100°C for 90 minutes.

[0028] (3) Raise the temperature obtained in step 2 to 120°C, continue heating, add C5 petroleum resin, C9 petroleum resin, hydrogenated C9 petroleum resin and hydrogenated terpene resin, stop stirring and keep at 120°C for 60 minutes until the resin is completely melted.

[0029] (4) Cool the mixture obtained in step 3 to 100°C and start stirring. After the resin is evenly mixed, add filler mannitol, polymethyl methacrylate powder and corn starch in sequence and keep stirring for 40 minutes.

[0030] (5) Continue stirring and heating the product obtained in step 4, then reduce the temperature to 90° C., maintain it at 90° C. for 30 minutes, and then make it into particles to obtain the precision casting wax.

[0031] Embodiment 4

[0032] A high-strength precision casting wax material, the precision casting wax material comprising the following raw materials in parts by weight: 40 parts of paraffin, 16 parts of montan wax, 6 parts of polyethylene wax, 5 parts of beeswax, 9 parts of stearic acid, 36 parts of C5 petroleum resin, 18 parts of C9 petroleum resin, 9 parts of hydrogenated terpene resin, 18 parts of mannitol, 14 parts of polymethyl methacrylate, 3 parts of corn starch and 3 parts of cellulose acetate.

[0033] (1) Heat paraffin wax at 90°C and stir continuously until it melts. Add lignite wax, polyethylene wax and beeswax. Continue heating to 100°C. Add stearic acid and stir continuously until it melts.

[0034] (2) Continue heating the mixture obtained in step 1 at 100°C, add ethylene-polyvinyl acetate, and continue stirring until it is completely melted and keep it at 100°C for 90 minutes.

[0035] (3) Raise the temperature obtained in step 2 to 120°C, continue heating, add C5 petroleum resin, C9 petroleum resin, hydrogenated C9 petroleum resin and hydrogenated terpene resin, stop stirring and keep at 120°C for 60 minutes until the resin is completely melted.

[0036] (4) Cool the mixture obtained in step 3 to 100°C and start stirring. After the resin is evenly mixed, add filler mannitol, polymethyl methacrylate powder, corn starch and cellulose acetate in sequence and keep stirring for 40 minutes.

[0037] (5) Continue stirring and heating the product obtained in step 4, then reduce the temperature to 90° C., maintain it at 90° C. for 30 minutes, and then make it into particles to obtain the precision casting wax.

[0038] Embodiment 5

[0039] A high-strength precision casting wax material, the precision casting wax material comprising the following raw materials in parts by weight: 36 parts of paraffin wax, 16 parts of montan wax, 6 parts of polyethylene wax, 36 parts of C5 resin, 27 parts of terpene resin, 9 parts of stearic acid, 36 parts of mannitol, 14 parts of polymethyl methacrylate and 3 parts of corn starch.

[0040] (1) Heat paraffin wax at 90°C and stir continuously until it melts. Add lignite wax, polyethylene wax and beeswax. Continue heating to 100°C. Add stearic acid and stir continuously until it melts.

[0041] (2) Continue heating the mixture obtained in step 1 at 100°C, add ethylene-polyvinyl acetate, and continue stirring until it is completely melted and keep it at 100°C for 90 minutes.

[0042] (3) Raise the temperature obtained in step 2 to 120°C, continue heating, add C5 petroleum resin, C9 petroleum resin, hydrogenated C9 petroleum resin and hydrogenated terpene resin, stop stirring and keep at 120°C for 60 minutes until the resin is completely melted.

[0043] (4) Cool the mixture obtained in step 3 to 100°C and start stirring. After the resin is evenly mixed, add filler mannitol, polymethyl methacrylate powder and corn starch in sequence and keep stirring for 40 minutes.

[0044] (5) Continue stirring and heating the product obtained in step 4, then reduce the temperature to 90° C., maintain it at 90° C. for 30 minutes, and then make it into particles to obtain the precision casting wax.

[0045] Comparative Example 1

[0046] A high-strength precision casting wax material, the precision casting wax material comprising the following raw materials in parts by weight: 72 parts of paraffin, 81 parts of C5 petroleum resin, 18 parts of ethylene-polyvinyl acetate, and 18 parts of polymethyl methacrylate.

[0047] (1) Heat paraffin at 90°C and stir continuously until it melts. Add ethylene-polyvinyl acetate first to make it completely melt.

[0048] (2) Raise the temperature obtained in step 1 to 120°C, continue heating, add C5 petroleum resin, stop stirring and keep at 120°C for 60 minutes until the resin is completely melted.

[0049] (3) Cool the mixture obtained in step 2 to 100°C and start stirring. After the resin is evenly mixed, add the filler polymethyl methacrylate powder and keep stirring for 40 minutes.

[0050] (4) Continue stirring and heating the product obtained in step 3, then reduce the temperature to 90° C., maintain it at 90° C. for 30 minutes, and then make it into particles to obtain the precision casting wax.

[0051] Comparative Example 2

[0052] A high-strength precision casting wax material, the precision casting wax material comprising the following raw materials in parts by weight: 36 parts of paraffin wax, 16 parts of montan wax, 6 parts of polyethylene wax, 36 parts of C5 petroleum resin, 18 parts of C9 petroleum resin, 9 parts of hydrogenated terpene resin, 9 parts of stearic acid, 36 parts of mannitol, and 14 parts of polymethyl methacrylate.

[0053] (1) First heat the paraffin at 90°C, stirring continuously until it melts, add the polyethylene wax, continue heating to 100°C, stirring continuously until it melts.

[0054] (2) Raise the temperature obtained in step 1 to 120°C, continue heating, add C5 petroleum resin, stop stirring and keep at 120°C for 60 minutes until the resin is completely melted.

[0055] (3) Cool the mixture obtained in step 2 to 100°C and start stirring. After the resin is evenly mixed, add polymethyl methacrylate powder and keep stirring for 40 minutes.

[0056] (4) Continue stirring and heating the product obtained in step 3, then reduce the temperature to 90° C., maintain it at 90° C. for 30 minutes, and then make it into particles to obtain the precision casting wax.

[0057] Table 1 Performance test data of precision casting wax mold materials of Examples 1-5 and Comparative Examples 1-2 project Melting point(℃) Linear shrinkage (%) Surface hardness (HD / 25℃) Flexural strength (MPa) Viscosity (mPa·s / 90℃) Ash content (%) Embodiment 1 58.05 0.33 55.14 8.69 549.8 ≤ 0.02 Embodiment 2 56.69 0.33 52.17 7.88 515.8 ≤ 0.02 Embodiment 3 55.72 0.29 53.42 8.21 637.6 ≤ 0.02 Embodiment 4 56.82 0.29 46.83 7.01 129.6 ≤ 0.02 Embodiment 5 57.97 0.33 49.50 7.35 480.0 ≤ 0.02 Comparative Example 1 54.18 0.58 32.08 3.42 478.0 ≤ 0.02 Comparative Example 2 55.49 0.88 35.2 6.12 440.2 ≤ 0.02 Result analysis: From the data in the analysis table, it can be seen that the present invention combines paraffin wax and petroleum resin in the above mass fractions, which helps to improve the strength of the wax material for precision casting wax patterns, thereby improving the precision and production efficiency of castings. By compounding hydrogenated C9 petroleum resin (softening point 100~140℃) with hydrogenated terpene resin, a high-density cross-linked network is formed, which improves the thermal stability of the ordinary resin system, improves the hardness of the wax material, and significantly reduces the thermal expansion coefficient. Specifically, with the increase in the amount of petroleum resin added, the bending strength and hardness of the wax material increase. Moreover, the melting is controlled in stages (90℃→100℃→120℃→90℃) to avoid thermal decomposition of the polymer resin, ensure full compatibility between C5 / C9 petroleum resin and hydrogenated resin, and the viscosity of the wax material is stabilized at 480~640mPa·s. Since the hydrogenation reaction saturates the unsaturated double bonds in the terpene resin, the hydrogenated terpene resin has good heat resistance and weather resistance, and thus has higher oxidation resistance and thermal stability. In addition, the hydrogenated terpene resin is hard and brittle, so that the wax material exhibits a typical brittle fracture when it breaks.

[0058] Through nano-dispersion of mannitol, polymethyl methacrylate and corn starch, the flexural strength of the wax material is increased to 7~10 MPa (the comparison is only 3.42~6.12 MPa), and the surface hardness reaches 46~55HD (the traditional wax material is ≤40). At the same time, ethylene-vinyl acetate copolymer (EVA) and stearic acid synergistically improve the fluidity and demoulding properties of the wax material, taking into account both demoulding efficiency and dimensional stability.

[0059] The precision casting wax of the present invention is applied to the precision casting wax casting industry. By replacing the traditional rosin resin with hydrogenated resin, the wax material has a moderate melting point, a small linear shrinkage rate, high hardness, high bending strength, low ash content, moderate viscosity and easy demoulding, etc., which is beneficial to improving the efficiency of investment casting and can be widely used in preparing wax models of high-precision aviation casting structural parts and wax models for other precision casting.

Claims

1. A high-strength precision casting wax, characterized in that: The precision casting wax includes the following components in parts by mass: 20-40 parts of paraffin wax, 0-20 parts of montan wax, 0-20 parts of beeswax, 0-10 parts of polyethylene wax, 5-10 parts of stearic acid, 20-40 parts of C5 petroleum resin, 10-20 parts of C9 petroleum resin, 10-20 parts of hydrogenated C9 petroleum resin, 0-10 parts of hydrogenated terpene resin, 0-40 parts of mannitol, 0-14 parts of polymethyl methacrylate, 0-5 parts of corn starch, and 0-5 parts of cellulose acetate; the total proportion of hydrogenated C9 petroleum resin and hydrogenated terpene resin is 20-30 parts.

2. The precision casting wax according to claim 1, characterized in that: The tackifying resin is at least one of C5 petroleum resin, C9 petroleum resin, hydrogenated C9 petroleum resin and hydrogenated terpene resin. The hydrogenated C9 petroleum resin has a softening point of 100-140°C and an acid value of <1.0 mgKOH / g; the hydrogenated terpene resin has a softening point of 80-90°C and an iodine value of 40-75. The synergistic effect of the two reduces the thermal expansion coefficient of the wax material.

3. The precision casting wax according to claim 1, characterized in that: Mannitol, ultrapure grade, ≥99.0% (HPLC); polymethyl methacrylate, can pass through a 500 mesh sieve, 25 microns; the cellulose acetate, can pass through a 100 mesh sieve. Mannitol, polymethyl methacrylate and corn starch are added in a composite manner, and the mass ratio of the three is (5~8): (3~5): (0.5~1.5). The internal structure of the wax material is homogenized through ultrafine powder dispersion technology (500 mesh sieve), and the flexural strength is increased to 7~10 MPa.

4. The method for preparing the precision casting wax according to any one of claims 1 to 3, characterized in that: The following steps are involved: (1) Add paraffin, beeswax and lignite wax to a beaker, heat at 90°C, and stir continuously until melted; (2) Continue to heat the wax liquid obtained in step 1 at 100°C, add polyethylene wax to melt. Continue to stir until completely melted. Heat to 120°C, add the four resins, and keep at 120°C for 60-120 minutes, stop stirring, and let stand until completely dissolved to form a stable blend system to obtain a basic wax liquid. (3) Cool to 100°C, add mannitol, corn starch and polymethyl methacrylate to the beaker, stir and mix to ensure that the filler is evenly dispersed. The temperature was lowered to 90°C to avoid resin decomposition caused by high temperature, and stirring was maintained at 90°C for 60-90 minutes to obtain precision casting wax.