Polymer modified ceramic shell material, and preparation method and application thereof

Abstract

The present application relates to the technical field of precision casting, and particularly relates to a polymer modified ceramic shell material, a preparation method and application thereof. The present application aims at the phenomenon of steel leakage and steel contamination caused by insufficient coating performance at the R angle in the current shell manufacturing process, and provides a polymer modified ceramic shell material, so as to solve the problem of small coating amount and poor coating uniformity at the R angle of the wax mold due to structural limitations in the actual production process, thereby improving the phenomenon of shell rupture, steel leakage and steel contamination caused by high-temperature alloy liquid erosion in the pouring process. The technical scheme of the present application can increase the coating amount at the R angle and other difficult-to-coat positions, improve the shell thickness consistency of the R angle and the flat positions on both sides, and reduce the risk of steel leakage and steel contamination.

Description

Technical Field

[0001] This invention relates to the field of precision casting technology, and in particular to a polymer-modified ceramic mold shell material, its preparation method, and its application. Background Technology

[0002] Precision casting has the advantages of wide applicability and is not limited by the size, thickness, or complexity of the casting, making it the main method for manufacturing turbine blades for aero-engines. The precision casting production process includes core preparation, wax pattern preparation and assembly, shell coating, dewaxing and firing, melting and casting, and post-processing. Shell preparation, a crucial step, consists of slurry preparation, slurry coating, sand application, drying, dewaxing and firing, cleaning, and inspection.

[0003] However, with the continuous development of aero-engine technology, aero-engine turbine blades, as core high-temperature resistant components, face greater challenges. Therefore, higher performance requirements are placed on ceramic shells. They must not only possess sufficient high-temperature strength and shell thickness to support the impact of the alloy melt on the shell, but also have a certain degree of yielding to prevent stress-induced recrystallization. Furthermore, since high-temperature alloys contain highly reactive metal elements such as chromium, titanium, and hafnium, it is essential to avoid or minimize reactions between the high-temperature alloy melt and the shell surface layer to ensure the surface quality and metallurgical quality of the casting. Therefore, the shell surface needs high high-temperature chemical inertness. Additionally, the shell thickness needs to be relatively uniform in every part of the shell to obtain a more uniform temperature field during alloy cooling.

[0004] Taking a large turbine guide vane as an example, due to its large size, the alloy molten material flows rapidly and has a strong impact when poured at 1550℃, causing steel bleed-through and leakage in areas where coating is difficult and the shell is relatively fragile. Furthermore, because the R-corners are structurally limited and difficult to coat with slurry, the shell thickness is smaller in the gently sloping areas. During the cooling and solidification of the alloy molten material, the thinner parts cool faster than the thicker parts, damaging the uniformity of the temperature field during cooling. This leads to a shift in grain growth orientation during directional solidification, and in severe cases, product scrap. However, there are currently few reports on polymers improving the coating performance of silica sol ceramic slurries. Summary of the Invention

[0005] A first aspect of the present invention provides a polymer-modified ceramic shell material, the material comprising a face layer material and a back layer material;

[0006] The raw materials for preparing the surface layer material include: a first modified polymer, a first silica sol binder, silica powder, a first defoamer, and a first wetting agent, wherein the mass ratio of the silica powder to the total mass of the remaining raw materials is (3-4):1;

[0007] The raw materials for preparing the backing material include: a second modified polymer, a second silica sol binder, silica powder, fused white alumina powder, a second defoamer, and a second wetting agent. The ratio of the total mass of silica powder and fused white alumina powder to the total mass of the remaining raw materials is (2.5-3.5):1.

[0008] In some embodiments, the first modified polymer and the second modified polymer are both polymers of associative polyurethane and polyacrylate; wherein the molecular weight of the associative polyurethane is 5,000,000 ± 1,000,000 and the pH value is 4.5-9; and the molecular weight of the polyacrylate is 50,000 ± 30,000 and the pH value is 6-9.

[0009] If the relative molecular weight of polyurethane is too small, it will be difficult for it to form a hydrophobic, three-dimensional network structure after its addition, making it difficult to further increase the steric hindrance of the system and optimize the rheological properties of the polymer-modified ceramic slurry. If the kinematic viscosity of polyurethane is too low, it will be difficult to have a significant thickening effect on the ceramic slurry system. If the molecular weight of polyacrylate is too large, it is easy to generate emulsion linkages within the system, reducing stability.

[0010] The first and second modified polymers described in this invention are both mixtures of RM-8W thickener and 5988 acrylic copolymer emulsion. They are mixed thoroughly at a mass ratio of 1:1 before use. They were purchased from Rohm and Haas and Shanghai Kunsheng Adhesives Co., Ltd., respectively.

[0011] The modified polymer is composed of associative polyurethane and polyacrylate. The associative polyurethane is an amphiphilic polymer with hydrophilic and hydrophobic groups capping its long chains on both sides, while the polyacrylate is an oily emulsion. The blending of these two polymers forms a hydrophobic associative three-dimensional network structure, effectively reducing the contact angle between the modified slurry and the oily wax mold surface. Furthermore, the polymer itself also possesses excellent adhesion properties, thus significantly improving the coating performance of the polymer-modified slurry. Plate weight tests on the modified ceramic slurry showed that its weight could be increased from 5g to 20g. Moreover, because the modified polymer forms a three-dimensional network structure within the ceramic slurry, it effectively increases the steric hindrance within the system, thereby increasing the slurry viscosity. However, in actual production, to control the overall module coating quality, the viscosity of the ceramic slurry is generally relatively constant. Therefore, the addition of the polymer reduces the powder-to-liquid ratio to some extent, reducing powder input and achieving cost reduction and efficiency improvement. The modified polymer, as an intermediate additive, is ablated and disappears after dewaxing and calcination. It does not change the performance and composition of the ceramic shell during final casting, and has no impact on the surface quality of the final casting or other related issues.

[0012] In some embodiments, the fused white corundum powder contains ≥99wt% Al2O3; has a D50 of 25.00±5.0; and a density of not less than 3.9 g / cm³. 3 .

[0013] In some embodiments, the total SiO2 content in the silicon powder is not less than 97.5 wt%, the Al2O3 content is ≤1%, the D50 is 20.0 ± 5.0, and the density is not less than 2.3 g / cm³. 3 .

[0014] In some embodiments, the mass ratio of the silicon powder to the white corundum powder is (4-6):1.

[0015] In some embodiments, the SiO2 content in both the first and second silica sol binders is 20-30 wt%.

[0016] Furthermore, the first silica sol binder is Zhejiang Yuda Company's FS1 silica sol binder, and the second silica sol binder is Zhejiang Yuda Company's FS1 silica sol binder.

[0017] In some embodiments, the mass of the first defoamer and the first wetting agent each accounts for 0.1-0.15% of the mass of the first silica sol binder, and the mass of the first modified polymer accounts for 0-10% of the mass of the first silica sol binder.

[0018] In some embodiments, the mass of the second defoamer and the second wetting agent each accounts for 0.1-0.15% of the mass of the second silica sol binder, and the mass of the second modified polymer accounts for 0-10% of the mass of the second silica sol binder.

[0019] In some embodiments, both the first wetting agent and the second wetting agent include at least one of fatty alcohol polyvinyl ether, sodium dodecyl sulfate, sodium dodecyl sulfonate, sodium alkyl naphthalene sulfonate, and fatty alcohol polyethylene glycol ether sulfate.

[0020] Furthermore, both the first and second wetting agents are fatty alcohol polyoxyethylene ethers, specifically LUCRAMUL AG 101 products from Onker Company.

[0021] In some embodiments, both the first defoamer and the second defoamer include at least one of n-octanol, PEG-8 dimethicone water-soluble siloxane, methanethiol, polyether-modified dimethyl polysiloxane copolymer, and tributyl phosphate.

[0022] Furthermore, both the first defoamer and the second defoamer are n-octanol.

[0023] A second aspect of the present invention provides a method for preparing a polymer-modified ceramic shell material, the method comprising:

[0024] (1) Preparation of surface material: Weigh the first silica sol binder, the first defoamer and the first wetting agent into the reactor according to the proportion, stir at 900±100r / min for 10-30min, add the first modified polymer and stir for 10-30min, then add the silica powder, stir for 1-5h and then discharge the material. The viscosity of the surface material in the effluent cup is 10-35s.

[0025] (2) Preparation of back layer material: Weigh the second silica sol binder, the second defoamer and the second wetting agent into the reactor according to the proportion, stir at 900±100r / min for 10-30min, add the second modified polymer and stir for 10-30min, then add silica powder and fused white corundum powder, stir for 1-5h and then discharge the material. The viscosity of the back layer material in the effluent cup is 10-20s.

[0026] A third aspect of the present invention provides the application of a polymer-modified ceramic shell material in the preparation of surface and back slurries for precision casting devices.

[0027] Preferably, in the application described, the surface layer of the polymer-modified ceramic shell material is a single-layer structure, and the back layer is a 7-layer structure, with the 7th layer only coated with slurry and not coated with sand.

[0028] Preferably, in the application described, the wax model is slowly and rotatingly immersed in the surface slurry to prevent air stagnation during coating, ensuring that the slurry is evenly coated on the surface of the wax model; after removing excess slurry, 100# corundum sand is poured on, and the model is placed in a drying room to dry for 12-16 hours before applying the next layer.

[0029] Preferably, in the application described, the module is slowly and rotatingly immersed in the back layer slurry to prevent air entrapment during coating, ensuring that the slurry is evenly coated on the surface layer. After removing excess slurry, 24# corundum abrasive is applied and the surface is dried for 8-12 hours.

[0030] Preferably, in the application described, after the polymer-modified shell coating is completed, it is dewaxed in a steam dewaxing kettle at 160-190°C for more than 5 minutes.

[0031] Preferably, in the aforementioned application, the dewaxed shell is baked at 800°C for more than 4 hours in a high-temperature baking furnace under atmospheric conditions.

[0032] Preferably, in the aforementioned application, the ratio of the thickness of the polymer-modified ceramic shell at the radius (R-corner) to the thickness of the two side planes should be no less than 40%.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] This invention addresses the issues of steel splattering and steel leakage caused by insufficient coating performance at the radius (R) corners during current mold manufacturing processes. It provides a polymer-modified ceramic mold shell material to solve the problem of insufficient coating amount and poor coating uniformity at the R corners of wax molds due to structural limitations during actual production. This improves the situation where high-temperature alloy steel molten material causes mold shell cracking and steel splattering during casting. The technical solution of this invention can increase the coating amount at difficult-to-coat areas such as the R corners, improve the shell thickness consistency between the R corners and the gently sloping sides, and reduce the risk of steel splattering and steel leakage. Attached Figure Description

[0035] Figure 1 This is a diagram demonstrating how modified polymers improve the coating performance of ceramic slurries in areas that are difficult to coat, such as corners. Detailed Implementation

[0036] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0037] Example 1

[0038] The first aspect of this embodiment provides a polymer-modified ceramic shell material, the material comprising a face layer material and a back layer material;

[0039] The raw materials for preparing the surface layer material, by weight, include: 0 parts of the first modified polymer, 100 parts of the first silica sol binder, 400 parts of silica powder, 0.1 parts of the first defoamer, and 0.15 parts of the first wetting agent;

[0040] The raw materials for preparing the backing material, by weight, include: 0 parts of the second modified polymer, 100 parts of the second silica sol binder, 292 parts of silica powder, 58 parts of fused white corundum powder, 0.1 parts of the second defoamer, and 0.15 parts of the second wetting agent.

[0041] The first modified polymer and the second modified polymer are both polymers of associative polyurethane and polyacrylate; wherein the molecular weight of the associative polyurethane is 5,000,000 ± 1,000,000 and the pH value is 4.5-9; the molecular weight of the polyacrylate is 50,000 ± 30,000 and the pH value is 6-9.

[0042] The fused white corundum powder contains ≥99wt% Al2O3; D50 is 25.00±5.0; and density is not less than 3.9g / cm³. 3The silicon powder contains a total SiO2 content of not less than 97.5 wt%, an Al2O3 content of ≤1%, a D50 of 20.0 ± 5.0, and a density of not less than 2.3 g / cm³. 3 .

[0043] The first and second silica sol binders both contain 20-30 wt% SiO2 and are both Zhejiang Yuda FS1 silica sol binders.

[0044] Both the first and second wetting agents are fatty alcohol polyoxyethylene ethers, specifically LUCRAMUL AG 101 products from Onker Company.

[0045] Both the first and second defoamers are n-octanol.

[0046] The second aspect of this embodiment provides a method for preparing a polymer-modified ceramic shell material, the method comprising:

[0047] (1) Preparation of surface material: Weigh the first silica sol binder, the first defoamer and the first wetting agent into the reactor according to the proportion, stir at 900±100r / min for 20min, add the first modified polymer and stir for 20min, then add the fused white corundum powder, stir for 3h and discharge the material. The viscosity of the surface material in the outflow cup is 30s.

[0048] (2) Preparation of back layer material: Weigh the second silica sol binder, the second defoamer and the second wetting agent into the reactor according to the proportion, stir at 900±100r / min for 20min, add the second modified polymer and stir for 20min, then add silica powder and fused white corundum powder, stir for 3h and discharge the material. The viscosity of the back layer material in the effluent cup is 18s.

[0049] Two different angled components, R1 and R5, were used to assemble the wax models. The ceramic slurry described above was then applied, and the application steps are as follows.

[0050] (1) In the application described, the wax model is slowly and rotatingly immersed in the surface slurry to prevent air suffocation during coating, so that the slurry is evenly coated on the surface of the wax model; after removing excess slurry, 100# corundum sand is poured on, and the model is placed in a drying room to dry for 12-16 hours before the next layer is applied.

[0051] (2) In the application described, the module is slowly rotated and immersed in the back layer slurry to prevent air suffocation during coating, so that the slurry is evenly coated on the surface layer. After removing excess slurry, 24# corundum sand is applied and dried for 8-12 hours.

[0052] (3) In the application described above, after the polymer-modified shell coating is completed, it is dewaxed in a steam dewaxing kettle at 160-190℃ for more than 5 minutes.

[0053] (4) In the application described above, the dewaxed shell is baked at 800°C for more than 4 hours in a high-temperature baking furnace in an atmospheric environment.

[0054] Example 2

[0055] This embodiment provides a polymer-modified ceramic shell material, and the specific implementation method is the same as in Embodiment 1, except that...

[0056] The raw materials for preparing the surface layer material, by weight, include: 3 parts of a first modified polymer, 100 parts of a first silica sol binder, 370 parts of silica powder, 0.1 parts of a first defoamer, and 0.15 parts of a first wetting agent;

[0057] The raw materials for preparing the backing material, by weight, include: 3 parts of the second modified polymer, 100 parts of the second silica sol binder, 259 parts of silica powder, 51 parts of fused white corundum powder, 0.1 parts of the second defoamer, and 0.15 parts of...

[0058] Second wetting agent.

[0059] Example 3

[0060] This embodiment provides a polymer-modified ceramic shell material, and the specific implementation method is the same as in Embodiment 1, except that...

[0061] The raw materials for preparing the surface layer material, by weight, include: 5 parts of a first modified polymer, 100 parts of a first silica sol binder, 340 parts of silica powder, 0.1 parts of a first defoamer, and 0.15 parts of a first wetting agent;

[0062] The raw materials for preparing the backing material, by weight, include: 5 parts of the second modified polymer, 100 parts of the second silica sol binder, 234 parts of silica powder, 46 parts of fused white corundum powder, 0.1 parts of the second defoamer, and 0.15 parts of...

[0063] Second wetting agent.

[0064] Example 4

[0065] This embodiment provides a polymer-modified ceramic shell material, and the specific implementation method is the same as in Embodiment 1, except that...

[0066] The raw materials for preparing the surface layer material, by weight, include: 10 parts of a first modified polymer, 100 parts of a first silica sol binder, 300 parts of silica powder, 0.1 parts of a first defoamer, and 0.15 parts of a first wetting agent;

[0067] The raw materials for preparing the backing material, by weight, include: 10 parts of the second modified polymer, 100 parts of the second silica sol binder, 209 parts of silica powder, 41 parts of fused white corundum powder, 0.1 parts of the second defoamer, and 0.15 parts of the second wetting agent.

[0068] Comparative Example 1

[0069] This comparative example provides a polymer-modified ceramic shell material. The specific implementation method is the same as in Example 1, except that two different angle simulation parts, R2.5 and R3, are used for wax model splicing, and the above-mentioned ceramic slurry is used for coating. The coating steps are as follows:

[0070] (1) In the application described, the wax model is slowly and rotatingly immersed in the surface slurry to prevent air suffocation during coating, so that the slurry is evenly coated on the surface of the wax model; after removing excess slurry, 100# corundum sand is poured on, and the model is placed in a drying room to dry for 12-16 hours before the next layer is applied.

[0071] (2) In the application described, the module is slowly rotated and immersed in the back layer slurry to prevent air suffocation during coating, so that the slurry is evenly coated on the surface layer. After removing excess slurry, 24# corundum sand is applied and dried for 8-12 hours.

[0072] (3) In the application described above, after the polymer-modified shell coating is completed, it is dewaxed in a steam dewaxing kettle at 160-190℃ for more than 5 minutes.

[0073] (4) In the application described above, the dewaxed shell is baked at 800°C for more than 4 hours in a high-temperature baking furnace in an atmospheric environment.

[0074] Comparative Example 2

[0075] This comparative example provides a polymer-modified ceramic shell material, with the specific implementation method being the same as in Example 4, except that...

[0076] Wax models were assembled using two different angle simulation parts, R2.5 and R3, and then coated with the aforementioned ceramic slurry. The coating steps are as follows.

[0077] (1) In the application described, the wax model is slowly and rotatingly immersed in the surface slurry to prevent air suffocation during coating, so that the slurry is evenly coated on the surface of the wax model; after removing excess slurry, 100# corundum sand is poured on, and the model is placed in a drying room to dry for 12-16 hours before the next layer is applied.

[0078] (2) In the application described, the module is slowly rotated and immersed in the back layer slurry to prevent air suffocation during coating, so that the slurry is evenly coated on the surface layer. After removing excess slurry, 24# corundum sand is applied and dried for 8-12 hours.

[0079] (3) In the application described above, after the polymer-modified shell coating is completed, it is dewaxed in a steam dewaxing kettle at 160-190℃ for more than 5 minutes.

[0080] (4) In the application described above, the dewaxed shell is baked at 800°C for more than 4 hours in a high-temperature baking furnace in an atmospheric environment.

[0081] Performance testing

[0082] Shell thickness: (1) The shell of the simulated part after baking is longitudinally cut with a grinding wheel, and (2) The shell thickness at the R-corner and the shell thickness at the flat part are measured with an optical microscope;

[0083] Thickness consistency: The ratio of the shell thickness at the R-corner to the shell thickness at the flat part is the thickness consistency.

[0084]

[0085]

[0086] The experimental results above show that the addition of the modified polymer significantly increases the thickness at different R-corners and significantly improves the consistency of thickness between the R-corners and the transition area, reducing the risk of steel leakage and bridging at this location. At the same time, it improves the uniformity of the temperature field and prevents recrystallization at this location.

[0087] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A polymer-modified ceramic shell material, characterized in that, The material includes a surface layer material and a back layer material; The raw materials for preparing the surface layer material include: a first modified polymer, a first silica sol binder, silica powder, a first defoamer, and a first wetting agent, wherein the mass ratio of the silica powder to the total mass of the remaining raw materials is (3-4):1; The raw materials for preparing the backing material include: a second modified polymer, a second silica sol binder, silica powder, fused white corundum powder, a second defoamer, and a second wetting agent, wherein the ratio of the total mass of silica powder and fused white corundum powder to the total mass of the remaining raw materials is (2.5-3.5):1; Both the first modified polymer and the second modified polymer are mixtures of associative polyurethane and polyacrylate; wherein the relative molecular weight of the associative polyurethane is 5,000,000 ± 1,000,000, and the pH value is 4.5-9; the molecular weight of the polyacrylate is 50,000 ± 30,000, and the pH value is 6-9. The first defoamer and the first wetting agent each account for 0.1-0.15% of the mass of the first silica sol binder, and the first modified polymer accounts for 3-10% of the mass of the first silica sol binder. The second defoamer and the second wetting agent each account for 0.1-0.15% of the mass of the second silica sol binder, and the second modified polymer accounts for 3-10% of the mass of the second silica sol binder.

2. The material according to claim 1, characterized in that, The fused white corundum powder contains ≥99wt% Al2O3.

3. The material according to claim 1, characterized in that, The silicon powder contains a total SiO2 content of not less than 97.5 wt%, an Al2O3 content of ≤1 wt%, a D50 of 20.0 ± 5.0 μm, and a density of not less than 2.3 g / cm³. 3 .

4. The material according to claim 1, characterized in that, Both the first wetting agent and the second wetting agent include at least one of fatty alcohol polyoxyethylene ether, sodium dodecyl sulfate, sodium dodecyl sulfonate, sodium alkyl naphthalene sulfonate, and fatty alcohol polyethylene glycol ether sulfate.

5. The material according to claim 1, characterized in that, Both the first defoamer and the second defoamer include at least one of n-octanol, PEG-8 dimethicone water-soluble siloxane, methanethiol, polyether-modified dimethyl polysiloxane copolymer, and tributyl phosphate.

6. A method for preparing a polymer-modified ceramic shell material according to any one of claims 1-5, characterized in that, The preparation method includes: (1) Preparation of surface material: Weigh the first silica sol binder, the first defoamer and the first wetting agent into the reactor according to the proportion, stir at 900±100r / min for 10-30min, add the first modified polymer and stir for 10-30min, then add the silica powder, stir for 1-5h and then discharge the material. The viscosity of the surface material in the effluent cup is 10-35s. (2) Preparation of back layer material: Weigh the second silica sol binder, the second defoamer and the second wetting agent into the reactor according to the proportion, stir at 900±100r / min for 10-30min, add the second modified polymer and stir for 10-30min, then add silica powder and fused white corundum powder, stir for 1-5h and then discharge the material. The viscosity of the back layer material in the effluent cup is 10-20s.

7. The application of the polymer-modified ceramic shell material according to any one of claims 1-5 in the preparation of surface layer slurry and back layer slurry for precision casting devices.

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