Investment material for casting large thick-wall parts and preparation method thereof

Abstract

The invention discloses an investment material for casting large thick-wall parts. The investment material comprises the following components in percentage by weight: 30%-60% of petroleum wax, 30%-60% of tackifying resin, 1%-15% of synthetic wax and 1%-10% of a first high-molecular polymer. According to the investment material disclosed by the invention, the components are adopted, and the first high-molecular polymer is added, so that intertwining and crosslinking of molecular chains are realized, and the strength of an unsolidified layer in a thick-wall part of an investment is improved. And after the fired mold is demolded and freely cooled, the surface of the fired mold has a lower recess or shrinkage recess or even has no surface recess. In addition, the bending strength of the investment material is also improved.

Description

Technical Field

[0001] The invention belongs to the field of investment casting, and in particular relates to an investment material technology for casting large thick-walled parts and a preparation method thereof. Background Art

[0002] Investment casting is also known as lost wax precision casting. It uses fusible molds to make molten mold pieces and form molds. Then multiple layers of refractory materials are coated on the surface of the mold. After drying and solidification, the mold material of the mold is heated and melted out of the mold shell. After the mold shell is roasted at high temperature, molten metal is poured into it to obtain investment castings.

[0003] The first step in investment casting production is to press the investment pattern, which is used to form the model of the cavity in the refractory shell. Therefore, in order to obtain castings with high dimensional accuracy and surface finish, the investment casting mold material should first have high dimensional accuracy and surface finish. Therefore, the investment pattern material is an important material in precision casting and plays a key role in the quality of the casting. When pressing a large thick-walled investment pattern, the thick and large parts on the investment pattern are pressure-maintained and cooled in the mold. After a certain pressure-maintaining time and cooling time, the investment pattern is removed from the mold. The surface of the investment pattern in contact with the inner cavity of the mold has solidified, while the inside of the thick-walled investment pattern has not yet solidified and may still be in a liquid state. Since the strength of the solidified layer on the surface of the investment pattern is not high, there is a relatively closed space between the solidified layer on the surface of the investment pattern and the unsolidified liquid layer inside the investment pattern. As the body of the investment pattern shrinks, a negative pressure is generated inside the wax pattern. This negative pressure is less than the atmospheric pressure. The solidified layer on the surface of the investment pattern is in contact with the atmospheric pressure, and the atmospheric pressure is greater than the pressure inside the thick part of the investment pattern. Therefore, after the investment pattern is separated from the mold and cooled freely, depressions or shrinkages form on the surface of the thick part, resulting in surface quality defects of the investment pattern. In subsequent processes, the depressions or shrinkages on the surface of the investment pattern need to be repaired before entering the next process, which greatly reduces production efficiency.

[0004] The information disclosed in this background technology section is only intended to enhance the understanding of the overall background of the invention and should not be regarded as an acknowledgment or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art. Summary of the invention

[0005] The object of the present invention is to provide an investment material for casting large thick-walled parts, which has lower surface depression or shrinkage limit, higher bending strength, smaller linear shrinkage rate and higher dimensional accuracy.

[0006] In order to achieve the above-mentioned purpose, a technical solution provided by a specific embodiment of the present invention is as follows: a kind of investment pattern material for casting large thick-walled parts, comprising the following components in terms of weight percentage: petroleum wax: 30%-60%, tackifying resin: 30%-60%, synthetic wax 1%-15%, and a first high molecular polymer: 1%-10%.

[0007] In one or more embodiments of the present invention, the petroleum wax is selected from one or more of 56# fully refined paraffin, 58# fully refined paraffin, 60# fully refined paraffin, 62# semi-refined paraffin, 62# fully refined paraffin, 64# semi-refined paraffin, 64# fully refined paraffin, 66# semi-refined paraffin, 66# fully refined paraffin, 70# semi-refined paraffin, 70# fully refined paraffin, 70# microcrystalline wax, 75# microcrystalline wax, 80# microcrystalline wax, 85# microcrystalline wax and 90# microcrystalline wax.

[0008] In one or more embodiments of the present invention, the tackifying resin is selected from one or more of aliphatic petroleum resins, hydrogenated aliphatic petroleum resins, aromatic petroleum resins, hydrogenated aromatic petroleum resins, aliphatic-aromatic copolymer petroleum resins, hydrogenated aliphatic-aromatic copolymer petroleum resins, terpene resins and their derivatives, rosin resins and their derivatives, phenolic resins and their derivatives.

[0009] In one or more embodiments of the present invention, the Ring and Ball softening point of the tackifying resin is between 70°C and 140°C.

[0010] In one or more embodiments of the present invention, the Ring and Ball softening point of the tackifying resin is between 90°C and 125°C.

[0011] In one or more embodiments of the present invention, the synthetic wax is selected from one or more of 70# Fischer-Tropsch wax, 80# Fischer-Tropsch wax, 90# Fischer-Tropsch wax, 100# Fischer-Tropsch wax, homopolymer polyethylene wax, cracked polyethylene wax, polyester wax and maleic anhydride grafted polyethylene wax.

[0012] In one or more embodiments of the present invention, the first high molecular polymer is selected from one or more of ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer, ethylene-propylene copolymer, ethylene-butene copolymer, random polypropylene, polyolefin and α-olefin copolymer.

[0013] In one or more embodiments of the present invention, the molecular weight of the first high molecular weight polymer is between 30,000 and 100,000.

[0014] In one or more embodiments of the present invention, the molecular weight of the first high molecular weight polymer is between 50,000 and 100,000.

[0015] Another specific embodiment of the present invention provides a method for preparing an investment material for casting a large thick-walled component, which comprises:

[0016] The petroleum wax and the first high molecular polymer are heated and stirred at a temperature of 120° C. to melt into a uniform and transparent first liquid mixture;

[0017] Adding a tackifying resin to the first liquid mixture, controlling the temperature to be between 110° C. and 130° C. and stirring until the mixture melts into a uniform and transparent second liquid mixture;

[0018] Adding synthetic wax to the second liquid mixture, controlling the temperature to be between 100° C. and 120° C. and stirring until all the materials are completely melted, filtering with a 200-mesh filter, and discharging the materials for molding; obtaining the investment mold material for casting large thick-walled parts;

[0019] The content of the first high molecular weight polymer is 1% to 10%. The content of the first high molecular weight polymer is 1% to 10%. The content of the first high molecular weight polymer is 1% to 10%.

[0020] Compared with the prior art, the investment pattern material of the present invention adopts the above-mentioned components, adds the first high molecular polymer and the tackifying resin, realizes the entanglement and cross-linking of the molecular chains, accelerates the cooling speed of the thick wall of the investment pattern during the pressure holding stage in the mold, improves the strength of the inner layer of the thick wall part of the investment pattern, and after the investment pattern is demolded and freely cooled, the surface of the investment pattern has a lower depression or shrinkage or even no surface depression. The first high molecular polymer also improves the bending strength of the investment pattern material. DETAILED DESCRIPTION

[0021] In order to enable those skilled in the art to better understand the technical solutions in the present invention, the technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0022] In one embodiment of the present invention, a large thick-walled component casting investment material includes the following components in terms of weight percentage: petroleum wax: 30%-60%, tackifying resin: 30%-60%, synthetic wax: 1%-15%, and a first high molecular polymer: 1%-10%.

[0023] In this embodiment, the investment pattern material of the present invention adopts the above-mentioned components, adds a tackifying resin and a first high molecular polymer, realizes the entanglement and cross-linking of molecular chains, and improves the strength of the unsolidified layer inside the thick wall part of the investment pattern. After the investment pattern is demolded and cooled freely, the surface of the investment pattern has a lower depression or shrinkage or even no surface depression. In addition, the bending strength of the investment pattern material is improved through the action of the first high molecular polymer.

[0024] In one embodiment, in order to improve the flowability of the investment pattern material, petroleum wax with low melting viscosity is added to the investment pattern material. For example, the petroleum wax can be selected from one or more of 56# fully refined paraffin, 58# fully refined paraffin, 60# fully refined paraffin, 62# semi-refined paraffin, 62# fully refined paraffin, 64# semi-refined paraffin, 64# fully refined paraffin, 66# semi-refined paraffin, 66# fully refined paraffin, 70# semi-refined paraffin, 70# fully refined paraffin, 70# microcrystalline wax, 75# microcrystalline wax, 80# microcrystalline wax, 85# microcrystalline wax and 90# microcrystalline wax.

[0025] In one embodiment, the tackifying resin is selected from one or more of aliphatic petroleum resin, hydrogenated aliphatic petroleum resin, aromatic petroleum resin, hydrogenated aromatic petroleum resin, aliphatic-aromatic copolymerized petroleum resin, hydrogenated aliphatic-aromatic copolymerized petroleum resin, terpene resin and its derivatives, rosin resin and its derivatives, phenolic resin and its derivatives. The tackifying resin can refine the crystallization of petroleum wax and reduce the linear shrinkage of the investment material.

[0026] Furthermore, the ring and ball softening point of the tackifying resin of the present invention is between 70°C and 140°C, which has the effect of refining the crystallization of petroleum wax and reducing the linear shrinkage of the material. Preferably, the ring and ball softening point of the tackifying resin can be controlled at 90°C to 125°C.

[0027] In one embodiment, the synthetic wax is selected from one or more of 70# Fischer-Tropsch wax, 80# Fischer-Tropsch wax, 90# Fischer-Tropsch wax, 100# Fischer-Tropsch wax, homopolymerized polyethylene wax, cracked polyethylene wax, polyester wax, and maleic anhydride grafted polyethylene wax. The synthetic wax has the function of increasing the melting point and surface finish of the investment pattern material.

[0028] In order to reduce the surface depression of the thick wall part of the large thick wall component investment mold, a first high molecular polymer is added to the investment mold material. The first high molecular polymer is selected from one or more of ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer, ethylene-propylene copolymer, ethylene-butene copolymer, random polypropylene, polyolefin and α-olefin copolymer.

[0029] Furthermore, the molecular weight of the first high molecular weight polymer is between 30000 and 100000. Preferably, the molecular weight of the first high molecular weight polymer is between 50000 and 100000.

[0030] A method for preparing an investment material for casting large thick-walled parts in another embodiment of the present invention includes steps S1-S3.

[0031] Step S1, heating and stirring the petroleum wax and the first high molecular polymer at a temperature of 120° C.-140° C. to melt into a uniform and transparent first liquid mixture.

[0032] Specifically, in step S1, the petroleum wax can be selected from one or more of 56# fully refined paraffin, 58# fully refined paraffin, 60# fully refined paraffin, 62# semi-refined paraffin, 62# fully refined paraffin, 64# semi-refined paraffin, 64# fully refined paraffin, 66# semi-refined paraffin, 66# fully refined paraffin, 70# semi-refined paraffin, 70# fully refined paraffin, 70# microcrystalline wax, 75# microcrystalline wax, 80# microcrystalline wax, 85# microcrystalline wax and 90# microcrystalline wax.

[0033] The first high molecular polymer can be selected from one or more of ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer, ethylene-propylene copolymer, ethylene-butene copolymer, random polypropylene, polyolefin and α-olefin copolymer. The molecular weight of the first high molecular polymer is between 30000-100000. Preferably, the molecular weight of the first high molecular polymer is between 50000-100000.

[0034] In step S2, a tackifying resin is added to the first liquid mixture, and the temperature is controlled between 110° C. and 130° C. and stirred until it melts into a uniform and transparent second liquid mixture.

[0035] Specifically, in step S2, the tackifying resin can be selected from one or more of aliphatic petroleum resin, hydrogenated aliphatic petroleum resin, aromatic petroleum resin, hydrogenated aromatic petroleum resin, aliphatic-aromatic copolymer petroleum resin, hydrogenated aliphatic-aromatic copolymer petroleum resin, terpene resin and its derivatives, rosin resin and its derivatives, phenolic resin and its derivatives.

[0036] The ring and ball softening point of the tackifying resin is between 70°C and 140°C. The ring and ball softening point of the tackifying resin can be controlled at 90°C to 125°C.

[0037] In step S3, synthetic wax is added to the second liquid mixture, and the temperature is controlled to be between 100° C. and 120° C. for stirring until all the materials are completely melted, and then filtered with a 200-mesh filter and discharged for molding; thus, an investment mold material for casting large thick-walled parts is obtained.

[0038] Specifically, in step S3, the synthetic wax can be selected from one or more of 70# Fischer-Tropsch wax, 80# Fischer-Tropsch wax, 90# Fischer-Tropsch wax, 100# Fischer-Tropsch wax, homopolymer polyethylene wax, cracked polyethylene wax, polyester wax and maleic anhydride grafted polyethylene wax.

[0039] The content of the first high molecular weight polymer is 1% to 10%. The content of the first high molecular weight polymer is 1% to 10%. The content of the first high molecular weight polymer is 1% to 10%.

[0040] The present invention is further described below in conjunction with specific embodiments and comparative examples.

[0041] Example 1

[0042] The raw materials are calculated by weight: petroleum wax: 30 parts of 62# fully refined paraffin wax; tackifying resin: 55 parts of C5-C9 copolymerized hydrogenated petroleum resin; synthetic wax: 12 parts of 70# Fischer-Tropsch wax; first high molecular polymer: 3 parts of ethylene-vinyl acetate.

[0043] Preparation method: 30 parts of 62# fully refined paraffin wax and 3 parts of ethylene-vinyl acetate are heated and stirred at 120°C to melt into a uniform and transparent first liquid mixture.

[0044] Add 55 parts of C5-C9 copolymerized hydrogenated petroleum resin to the first liquid mixture, control the temperature at 110° C. and stir until it melts into a uniform and transparent second liquid mixture.

[0045] Add 12 parts of 70# Fischer-Tropsch wax to the second liquid mixture, control the temperature at 100°C and stir until all the materials are completely melted, filter with a 200-mesh filter, and discharge the materials for molding; obtain the investment mold material for casting large thick-walled parts.

[0046] Example 2

[0047] The raw materials are calculated by weight: petroleum wax: 40 parts of 62# fully refined paraffin wax; tackifying resin: 50 parts of C9 hydrogenated petroleum resin; synthetic wax: 5 parts of homopolymer polyethylene wax; first high molecular polymer: 5 parts of ethylene-butene copolymer.

[0048] Preparation method: 40 parts of 62# fully refined paraffin wax and 5 parts of ethylene-butene copolymer are heated and stirred at 130°C to melt into a uniform and transparent first liquid mixture.

[0049] Add 50 parts of C9 hydrogenated petroleum resin to the first liquid mixture, control the temperature at 130°C and stir until it melts into a uniform and transparent second liquid mixture.

[0050] Add 5 parts of homopolymer polyethylene wax to the second liquid mixture, control the temperature at 120° C. and stir until all the materials are completely melted, filter with a 200-mesh filter, and discharge the materials for molding; obtain the investment mold material for casting large thick-walled parts.

[0051] Example 3

[0052] The raw materials are calculated by weight: petroleum wax: 35 parts of 62# fully refined paraffin wax; tackifying resin: 30 parts of terpene resin; synthetic wax: 7 parts of cracked polyethylene wax; first high molecular polymer: 8 parts of ethylene-acrylic acid copolymer.

[0053] Preparation method: 35 parts of 62# fully refined paraffin wax and 8 parts of ethylene-acrylic acid copolymer are heated and stirred at 140°C to melt into a uniform and transparent first liquid mixture.

[0054] 30 parts of terpene resin were added to the first liquid mixture, and the temperature was controlled at 120° C. and stirred until it melted into a uniform and transparent second liquid mixture.

[0055] Add 7 parts of cracked polyethylene wax to the second liquid mixture, control the temperature at 115° C. and stir until all the materials are completely melted, filter with a 200-mesh filter, and discharge the materials for molding; obtain the investment mold material for casting large thick-walled parts.

[0056] Example 4

[0057] The raw materials are calculated by weight: petroleum wax: 30 parts of 62# fully refined paraffin wax; tackifying resin: 50 parts of polymerized rosin resin; synthetic wax: 9 parts of polyester wax; first high molecular polymer: 6 parts of polyolefin.

[0058] Preparation method: 30 parts of 62# fully refined paraffin wax and 6 parts of polyolefin are heated, stirred and melted at 140°C to form a uniform and transparent first liquid mixture.

[0059] Add 50 parts of polymerized rosin resin to the first liquid mixture, control the temperature at 120° C. and stir until it melts into a uniform and transparent second liquid mixture.

[0060] Add 9 parts of polyester wax to the second liquid mixture, control the temperature at 115° C. and stir until all the materials are completely melted, filter with a 200-mesh filter, and discharge the materials for molding; obtain the investment mold material for casting large thick-walled parts.

[0061] Comparative Example 1

[0062] The raw materials are calculated by weight: hydrogenated microcrystalline wax: 30 parts; paraffin wax: 30 parts by weight; petroleum resin: 25 parts by weight; high molecular polymer with an average molecular weight of 10,000: 5 parts; and vegetable wax: 10 parts.

[0063] Comparative Example 2

[0064] The raw materials are calculated by weight: microcrystalline wax: 40 parts; terpene resin: 20 parts; PE wax: 15 parts; carnauba wax: 20 parts; candelilla wax: 5 parts.

[0065] The investment materials of Examples 1-4 and Comparative Examples 1-2 were tested, and the test results are shown in Table 1 below.

[0066] Table 1 Test results of Examples 1-4 and Comparative Examples 1-2

[0067]

[0068] As can be seen from the above table, the range of surface depression of Examples 1-4 of the present invention is between 0.19 mm and 0.25 mm, which is much smaller than the surface depression of Comparative Example 1-2 of 0.58 mm to 0.63 mm. The bending strength of Examples 1-4 is greater than that of Comparative Example 1-2. It can be seen that the investment material for casting large thick-walled parts prepared by the present invention has lower surface depression or shrinkage limit, higher bending strength, lower linear shrinkage rate, and higher dimensional accuracy.

[0069] In summary, the investment pattern material of the present invention adopts the above-mentioned components, adds the first high molecular polymer and the tackifying resin, and the intertwining and cross-linking of the molecular chains of the first high molecular polymer accelerates the cooling speed of the investment pattern thick wall during the pressure holding stage in the mold, improves the strength of the unsolidified layer inside the thick wall part of the investment pattern, and after the investment pattern is demolded and freely cooled, the investment pattern surface has a lower depression or shrinkage or even no surface depression. In addition, the first high molecular polymer also improves the bending strength of the investment pattern material.

[0070] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

[0071] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. An investment material for casting large thick-walled parts, characterized in that: The invention comprises the following components in terms of weight percentage: petroleum wax: 30%-60%, tackifying resin: 30%-60%, synthetic wax: 1%-15%, and first high molecular polymer: 1%-10%.

2. The investment material for casting large thick-walled parts according to claim 1, characterized in that: The petroleum wax is selected from one or more of 56# fully refined paraffin, 58# fully refined paraffin, 60# fully refined paraffin, 62# semi-refined paraffin, 62# fully refined paraffin, 64# semi-refined paraffin, 64# fully refined paraffin, 66# semi-refined paraffin, 66# fully refined paraffin, 70# semi-refined paraffin, 70# fully refined paraffin, 70# microcrystalline wax, 75# microcrystalline wax, 80# microcrystalline wax, 85# microcrystalline wax and 90# microcrystalline wax.

3. The investment material for casting large thick-walled parts according to claim 1, characterized in that: The tackifying resin is selected from one or more of aliphatic petroleum resin, hydrogenated aliphatic petroleum resin, aromatic petroleum resin, hydrogenated aromatic petroleum resin, aliphatic-aromatic copolymer petroleum resin, hydrogenated aliphatic-aromatic copolymer petroleum resin, terpene resin and its derivatives, rosin resin and its derivatives, phenolic resin and its derivatives.

4. The investment material for casting large thick-walled parts according to claim 1, characterized in that: The ring and ball softening point of the tackifying resin is between 70°C and 140°C.

5. The investment material for casting large thick-walled parts according to claim 4, characterized in that: The ring and ball softening point of the tackifying resin is between 90°C and 125°C.

6. The investment material for casting large thick-walled parts according to claim 1, characterized in that: The synthetic wax is selected from one or more of 70# Fischer-Tropsch wax, 80# Fischer-Tropsch wax, 90# Fischer-Tropsch wax, 100# Fischer-Tropsch wax, homopolymer polyethylene wax, cracked polyethylene wax, polyester wax and maleic anhydride grafted polyethylene wax.

7. The investment material for casting large thick-walled parts according to claim 1, characterized in that: The first high molecular polymer is selected from one or more of ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer, ethylene-propylene copolymer, ethylene-butene copolymer, random polypropylene, polyolefin and α-olefin copolymer.

8. The investment material for casting large thick-walled parts according to claim 1, characterized in that: The molecular weight of the first high molecular weight polymer is between 30,000 and 100,000.

9. The investment material for casting large thick-walled parts according to claim 8, characterized in that: The molecular weight of the first high molecular weight polymer is between 50,000 and 100,000.

10. A method for preparing an investment material for casting a large thick-walled component, characterized in that: include: The petroleum wax and the first high molecular polymer are heated and stirred at a temperature of 120° C. to melt into a uniform and transparent first liquid mixture; Adding a tackifying resin to the first liquid mixture, controlling the temperature to be between 110° C. and 130° C. and stirring until the mixture melts into a uniform and transparent second liquid mixture; Adding synthetic wax to the second liquid mixture, controlling the temperature to be between 100° C. and 120° C. and stirring until all the materials are completely melted, filtering with a 200-mesh filter, and discharging the materials for molding; obtaining the investment mold material for casting large thick-walled parts; The content of the first high molecular weight polymer is 1% to 10%. The content of the first high molecular weight polymer is 1% to 10%. The content of the first high molecular weight polymer is 1% to 10%.

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