Mold core for titanium alloy investment precision casting, preparation method of mold core and post-treatment method for titanium alloy casting
By optimizing the ratio and particle size distribution of fused calcium oxide and yttrium oxide cores, and combining them with a neutral water-resistant binder and an epoxy resin layer, the problems of high strength of yttrium oxide cores and moisture absorption of calcium oxide cores were solved, achieving low-cost, high-efficiency core removal and ensuring casting performance.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-30
- Publication Date
- 2026-03-27
AI Technical Summary
In existing titanium alloy investment casting, yttrium oxide cores are strong, difficult to remove, and costly, while calcium oxide cores are prone to moisture absorption, affecting casting efficiency and cost.
A core was prepared by combining fused calcium oxide and yttrium oxide in a ratio of 8.5:1 to 9.2:1 with a neutral water-resistant binder and an epoxy resin layer. The core was then removed by acid washing with dilute nitric acid using a suitable particle size distribution and preparation method.
It reduces the moisture absorption of the core, improves strength and cleaning efficiency, reduces costs, and can effectively remove cores with complex structures, ensuring the performance of the casting.
Smart Images
Figure CN121732706A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of titanium alloy investment casting technology, and more specifically, to a core for titanium alloy investment casting, its preparation method, and a post-processing method for titanium alloy casting. Background Technology
[0002] Titanium alloys are characterized by low density, high specific strength, and strong corrosion resistance. They also exhibit excellent mechanical properties at both room and high temperatures. Due to their superior comprehensive properties, the demand for titanium alloy castings in the aerospace industry is rapidly increasing. Titanium alloy casting processes include graphite mold casting, sand casting, and investment casting. Among these, investment casting is widely used due to its near-net-shape forming characteristics. The entire process is relatively complex, with four main stages: wax pattern preparation, shell preparation, melting and pouring, and post-finishing, each containing several steps. Ceramic cores are specialized components used in investment casting to form the internal cavity structure of the casting. They work in conjunction with the shell to ensure the dimensional accuracy of the cavity, making them particularly suitable for the precision casting of complex structures such as turbine blades for aero-engines. Ceramic cores possess characteristics such as high temperature resistance, high dimensional accuracy, and high chemical stability.
[0003] In the past, yttrium oxide was often used as the ceramic core material in the shell preparation stage of titanium alloy investment casting. It is heat-resistant, has good dimensional accuracy, and does not react with the molten titanium alloy during pouring. However, yttrium oxide cores have high strength, and are removed using high-pressure water jets. This makes removal difficult when the cavity structure is complex, so it is mostly used for simpler cavity structures. Furthermore, yttrium oxide is expensive, increasing casting costs. Besides yttrium oxide, zirconium oxide and calcium oxide can also be used as core materials, but calcium oxide has poor processability, is prone to moisture absorption, and requires strict drying conditions during investment casting.
[0004] In view of this, the present invention is hereby proposed. Summary of the Invention
[0005] One object of the present invention is to provide a core for investment casting of titanium alloys, which can reduce moisture absorption, has excellent strength, effectively reduces costs, and facilitates cleaning after titanium alloy casting.
[0006] Another object of the present invention is to provide a method for preparing a core for investment casting of titanium alloys.
[0007] Another object of the present invention is to provide a post-treatment method for titanium alloy casting.
[0008] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted: A core for investment casting of titanium alloys is prepared from raw materials including fused calcium oxide, yttrium oxide, and a neutral water-resistant binder; the mass ratio of the fused calcium oxide to the yttrium oxide is (8.5~9.2):1; the particle size distribution of the fused calcium oxide and the yttrium oxide each satisfies the following: the mass percentage of particles smaller than 5μm is ≤3%, the mass percentage of particles between 5 and 44μm is ≥93%, and the mass percentage of particles larger than 44μm is ≤4%.
[0009] In some embodiments, the mass ratio of the fused calcium oxide to the yttrium oxide is (8.8~9):1.
[0010] In some embodiments, the mass ratio of the neutral water-resistant binder to the total mass of the electrofused calcium oxide and yttrium oxide is 1:(6.5~7.5).
[0011] In some embodiments, the surface of the core used for titanium alloy investment casting is further provided with an epoxy resin layer. The thickness of the epoxy resin layer is 1~2mm.
[0012] The method for preparing the titanium alloy investment casting core as described above includes the following steps: Electrofused calcium oxide and yttrium oxide are ground to obtain ground electrofused calcium oxide and yttrium oxide; the ground electrofused calcium oxide and yttrium oxide are mixed with a neutral water-resistant binder to obtain a mixed system; and the mixed system is then used to prepare a core for titanium alloy investment casting.
[0013] In some embodiments, when the core has a complex and slender shape, die casting is used; when the core has a simple shape and a large cross-sectional area, reverse shell method is used; the proportion of neutral water-resistant binder added in the die casting process is less than the proportion of neutral water-resistant binder added in the reverse shell method.
[0014] In some embodiments, during the core preparation process, the ambient temperature is controlled at 20~24°C and the humidity at 30%~50%.
[0015] In some embodiments, an epoxy resin material is coated on the surface of the titanium alloy investment casting core, and then dried to obtain an epoxy resin layer; the drying temperature is 70~85℃, and the drying time is 100~130min.
[0016] A post-treatment method for titanium alloy casting includes removing the casting mold, the casting mold including a core; pickling the core inside the titanium alloy casting using 10%~15% dilute nitric acid at a temperature of 50~60℃; the core being the titanium alloy investment casting core; or the titanium alloy investment casting core obtained by the method. In some embodiments, the casting mold further includes a shell, which is used to remove the outer shell of the titanium alloy casting using a high-pressure water gun.
[0017] In some embodiments, the casting mold further includes a shell, and the method for preparing the shell includes: preparing a wax model on the surface of the core, preparing the shell outside the wax model, and then dewaxing, washing the shell, and firing.
[0018] In some embodiments, when cleaning the wax model with a cleaning agent, a protective wax is applied to the exposed surface of the core. The cleaning agent comprises alkyl glycosides, sodium benzenesulfonate, sodium fatty alcohol ether carboxylate, aminomethylbenzene alcohol, Span 80, Tween 80, and water. The alkyl glycosides comprise 15%–35% by mass, the sodium benzenesulfonate comprises 5%–25% by mass, the sodium fatty alcohol ether carboxylate comprises 15%–40% by mass, and the total content of aminomethylbenzene alcohol, Span 80, and Tween 80 comprises 5%–15% by mass, with the balance being water.
[0019] In some embodiments, the dewaxing temperature is 280~320℃ and the dewaxing time is 2~4h.
[0020] In some embodiments, the cleaning agent used for washing the shell is anhydrous ethanol with a concentration ≥95%.
[0021] In some embodiments, the firing temperature of the shell is 950~1050℃, and the firing time is 100~140min.
[0022] In some embodiments, the method further includes pickling the titanium alloy casting after casting, wherein the acid used for pickling includes HNO3 and HF, and the mass ratio of HNO3 to HF is (14~20):1.
[0023] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) The titanium alloy investment casting core of the present invention, by combining fused calcium oxide and yttrium oxide in appropriate proportion and particle size distribution, can reduce the moisture absorption of the calcium oxide core, ensure its excellent strength, effectively reduce costs, and facilitate cleaning after titanium alloy casting.
[0024] (2) The preparation method of the titanium alloy investment casting core of the present invention is simple and easy to implement. The method can make the obtained titanium alloy investment casting core have excellent mechanical properties and waterproof properties, and can be better cleaned after titanium alloy casting, which is conducive to improving the cleaning efficiency.
[0025] (3) The post-treatment method for titanium alloy casting of the present invention uses a suitable acid solution to clean the core, which can efficiently remove the core while ensuring the performance of the casting. Compared with high-pressure water jet hydraulic removal of the core, it can more effectively remove cores with complex structures. Attached Figure Description
[0026] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.
[0027] Figure 1 These are morphological images of the titanium alloy investment casting core before and after coating with epoxy resin in Embodiment 2 of the present invention, wherein (A) is the morphological image of the core before coating with epoxy resin, and (B) is the morphological image of the core after coating with epoxy resin. Figure 2 This is a morphology diagram of the electrofused calcium oxide of the present invention; Figure 3 This is a schematic diagram of the fracture of the core prepared in Embodiment 2 of the present invention after a bending test; Figure 4 This is a schematic diagram of the shell manufacturing process for the present invention; Figure 5 This is a topographic image of the area near the core after melting and casting according to the present invention; Figure 6 This is a morphological image of the titanium alloy casting after the core has been removed by pickling according to the present invention. Figure 7 This is a morphological image of the titanium alloy casting after the oxide layer has been removed by pickling according to the present invention. Detailed Implementation
[0028] The embodiments of the present invention will be described in detail below with reference to examples. However, those skilled in the art will understand that the following examples are for illustrative purposes only and should not be considered as limiting the scope of the invention. Unless otherwise specified in the examples, conventional conditions or conditions recommended by the manufacturer are followed. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.
[0029] According to one aspect of the present invention, the present invention relates to a core for investment casting of titanium alloys, the core being prepared from raw materials comprising fused calcium oxide, yttrium oxide and a neutral water-resistant binder; the mass ratio of the fused calcium oxide to the yttrium oxide is (8.5~9.2):1; the particle size distribution of the fused calcium oxide and the yttrium oxide each satisfies the following: the mass percentage of particles smaller than 5 μm is ≤3%, the mass percentage of particles between 5 and 44 μm is ≥93%, and the mass percentage of particles larger than 44 μm is ≤4%.
[0030] The titanium alloy investment casting core of the present invention, by combining fused calcium oxide and yttrium oxide in appropriate proportions and particle size distribution, can reduce the moisture absorption of the calcium oxide core, ensure its excellent strength, effectively reduce costs, and facilitate cleaning after titanium alloy casting.
[0031] In some embodiments, the mass ratio of the fused calcium oxide to the yttrium oxide is (8.5~9.2):1, for example, 8.5:1, 8.6:1, 8.7:1, 9:1, 9.2:1, etc. A suitable ratio allows for better synergistic effects, working in conjunction with the binder to ensure the physicochemical properties of the core. In some embodiments, the mass ratio of the fused calcium oxide to the yttrium oxide is (8.8~9):1.
[0032] In some embodiments, the fused calcium oxide comprises, by mass percentage: CaO > 99%, MgO < 0.40%, Al₂O₃ < 0.04%, SiO₂ < 0.09%, and Fe₂O₃ < 0.02%. Electrofusion treatment can remove impurities from the calcium oxide, resulting in fused calcium oxide with better purity.
[0033] In some embodiments, the preparation of fused calcium oxide includes: using high-purity calcium carbonate, crushing it into granules or spheres, and then melting it in an electric furnace under a three-phase electric arc to prepare clinker, thereby obtaining fused calcium oxide.
[0034] In some embodiments, in specific examples, the fused calcium oxide contains, by mass percentage, 99.9% CaO, 0.01% MgO, 0.03% Al2O3, 0.05% SiO2, and 0.01% Fe2O3.
[0035] In some embodiments, yttrium oxide comprises, by mass percentage: Y₂O₃ ≥ 99.5%, MgO < 0.16%, Al₂O₃ < 0.40%, SiO₂ < 0.16%, and Fe₂O₃ < 0.20%. The total amount of MgO, Al₂O₃, SiO₂, Fe₂O₃, and other trace components does not exceed 0.5%.
[0036] In some implementations, in specific embodiments, the yttrium oxide contains, by mass percentage, 99.9% Y2O3, 0.01% MgO, 0.04% Al2O3, 0.04% SiO2, and 0.01% Fe2O3.
[0037] In some embodiments, the particle size distribution of the fused calcium oxide satisfies the following conditions: the mass percentage of particles smaller than 5 μm is ≤3%, for example, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, etc.; the mass percentage of particles from 5 to 44 μm is ≥93%, for example, 93%, 94%, 95%, 96%, 97%, 98%, etc.; and the percentage of particles larger than 44 μm is ≤4%, for example, 1%, 2%, 3%, 4%, etc. In some embodiments, the particle size distribution of the yttrium oxide satisfies the following conditions: the mass percentage of particles smaller than 5 μm is ≤3%, for example, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, etc.; the mass percentage of particles from 5 to 44 μm is ≥93%, for example, 93%, 94%, 95%, 96%, 97%, 98%, etc.; and the percentage of particles larger than 44 μm is ≤4%, for example, 1%, 2%, 3%, 4%, etc. The fused calcium oxide and yttrium oxide of the present invention have suitable particle size distribution and, with a suitable mass ratio, are beneficial to ensuring the mechanical properties of the core.
[0038] In some embodiments, the neutral water-resistant binder of the present invention comprises nano-yttrium oxide sol. In some embodiments, the nano-yttrium oxide sol includes SS-Y14W, with a particle size of 2-8 nm, a content of 14% ± 0.5%, a pH of 7-8, and water as the solvent.
[0039] In some embodiments, the mass ratio of the neutral water-resistant binder to the total mass of the fused calcium oxide and yttrium oxide is 1:(6.5~7.5). The neutral water-resistant binder satisfies the following requirements: no chemical reaction occurs between the neutral water-resistant binder and the refractory matrix (calcium oxide and yttrium oxide); the product generated after high-temperature calcination has high thermochemical stability and does not chemically react with molten titanium; the binder exhibits good flowability, viscosity, and other process properties after mixing with the refractory matrix; the prepared core has certain strength and permeability; the prepared core does not show significant volume change at high temperatures; it is non-toxic, does not harm human health, does not corrode equipment, and is reasonably priced.
[0040] In some embodiments, the surface of the titanium alloy investment casting core is further provided with an epoxy resin layer. The thickness of the epoxy resin layer is 1~2mm (e.g., 1mm, 1.5mm, 2mm, etc.). The epoxy resin layer can improve waterproof performance and increase the strength of the core under low temperature conditions, which helps to prevent the core from cracking and deforming during shell making.
[0041] According to another aspect of the present invention, the present invention also relates to a method for preparing a core for titanium alloy investment casting as described above, comprising the following steps: The fused calcium oxide and yttrium oxide are ground to obtain ground fused calcium oxide and yttrium oxide.
[0042] The ground fused calcium oxide and yttrium oxide are mixed with a neutral water-resistant binder to obtain a mixed system; then the mixed system is used to prepare a core for titanium alloy investment casting.
[0043] The preparation method of the titanium alloy investment casting core of the present invention is simple and easy to implement. The method can make the obtained titanium alloy investment casting core have excellent mechanical properties and waterproof properties, and can be better cleaned after titanium alloy casting, which is conducive to improving the cleaning efficiency.
[0044] In some embodiments, the ground fused calcium oxide and yttrium oxide are mixed and stirred with a neutral water-resistant binder to a suitable viscosity.
[0045] In some embodiments, when the core has a complex and elongated shape, die casting is used; when the core has a simple shape and a large cross-sectional area, a reverse shell method is used. The proportion of neutral water-resistant binder added during the die casting process is less than that used in the reverse shell method. This invention allows for adjusting the amount of neutral water-resistant binder added to prepare core materials of different viscosities when preparing cores of different shapes. For cores with complex and elongated shapes, die casting is used, requiring lower raw material viscosity and a smaller amount of neutral water-resistant binder. For cores with simpler shapes and larger cross-sectional areas, a reverse shell method is used, requiring higher raw material viscosity and a larger amount of neutral water-resistant binder.
[0046] In some embodiments, the present invention uses a reverse shell method to prepare the core, which includes: molding the mixture of the above-ground fused calcium oxide and yttrium oxide with a neutral water-resistant binder, and then calcining it at a temperature of 950~1500℃, such as 950℃, 1000℃, 1050℃, 1100℃, 1200℃, 1300℃, etc.
[0047] In some embodiments, the method for preparing the core by the reverse shell method of the present invention specifically includes: molding the mixture of the above-mentioned ground fused calcium oxide and yttrium oxide with a neutral water-resistant binder, and then calcining it at a temperature of 1100°C.
[0048] In some embodiments, during the core preparation process, the ambient temperature is controlled at 20~24℃, such as 20℃, 22℃, 24℃, etc., and the humidity is controlled at 30%~50%, such as 30%, 35%, 40%, 50%, etc. Since the core has a certain moisture absorption capacity, the ambient humidity should be strictly controlled and kept dry during the core preparation process.
[0049] In some embodiments, the temperature of the mold core during the shell preparation process needs to be controlled at 20-24°C and the humidity at 30%-50%. The process of the mold core participating in shell preparation specifically includes: preparing a wax model on the surface of the mold core, preparing the shell outside the wax model, and then dewaxing, shell washing, and firing. When cleaning the wax model with a cleaning agent, a wax material is coated on the exposed surface of the mold core for protection. The cleaning agent includes alkyl glycosides, sodium benzenesulfonate, and sodium fatty alcohol ether carboxylate, with a water content of less than 10%, such as 1%, 2%, 5%, or 10%. In some embodiments, the dewaxing temperature is 280-320°C, such as 280°C, 290°C, 300°C, 310°C, or 320°C. The dewaxing time is 2-4 hours, such as 2 hours, 3 hours, or 4 hours. In some embodiments, the shell washing agent used is anhydrous ethanol with a concentration ≥95%, such as 95%, 96%, or 97%. In some embodiments, the firing temperature of the mold shell is 950~1050℃, for example 950℃, 980℃, 1000℃, 1020℃, 1050℃, etc.; the firing time is 100~140min, for example 100min, 120min, 130min, 140min, etc. In some embodiments, the mold shell includes two surface layers, one transition layer, six reinforcing layers, and one sealing layer. The surface layers are obtained from raw materials including yttrium oxide powder and a neutral water-resistant binder. The transition layer is prepared from raw materials including aluminum zirconium powder and silica sol. The reinforcing layer and the sealing layer are each prepared independently from raw materials including bauxite powder and silica sol. This invention effectively prevents the fused calcium oxide mold core from absorbing moisture and deforming by using a wax brushing protection process for cleaning the wax mold, an electric dewaxing furnace for the dewaxing process, anhydrous ethanol for cleaning the mold shell, and strict control of ambient temperature and humidity.
[0050] In some embodiments, an epoxy resin material is coated on the surface of the titanium alloy investment casting core, and then dried to obtain an epoxy resin layer. The drying temperature is 70~85℃, for example, 70℃, 75℃, 80℃, 85℃, etc.; the drying time is 100~130min, for example, 100min, 105min, 110min, 120min, 130min, etc. After the core is formed, the epoxy resin material is evenly coated on the surface, and then placed in an oven for drying. Calcium oxide exposed to air is prone to moisture absorption and hydration. The epoxy resin layer can effectively isolate water in the environment and enhance the low-temperature strength of the core.
[0051] According to another aspect of the present invention, the present invention also relates to a post-treatment method for titanium alloy casting, comprising cleaning the casting mold, the casting mold including a core; pickling the core inside the titanium alloy casting, the pickling using dilute nitric acid with a concentration of 10%~15% (e.g., 10%, 11%, 12%, 13%, 14%, 15%, etc.), the pickling temperature being 50~60℃ (e.g., 50℃, 52℃, 55℃, 58℃, 60℃, etc.); the core being a titanium alloy investment casting core obtained by the above method.
[0052] The post-treatment method for titanium alloy casting of the present invention uses a suitable acid solution to clean the core, which can efficiently remove the core while ensuring the performance of the casting. Compared with high-pressure water jet hydraulic removal of the core, it can more effectively remove cores with complex structures.
[0053] The reaction equations for calcium oxide and yttrium oxide with nitric acid are as follows. This process releases heat, and the resulting nitrate dissolves in water. The reaction equations include: CaO + 2HNO3 = Ca(NO3)2 + H2O.
[0054] Y2O2+ 6HNO3= 2Y(NO3)2+ 3H2O.
[0055] After solidification, titanium alloys form a dense oxide film (α layer) on their surface. This oxide film gives the titanium alloy excellent corrosion resistance to common acidic media such as dilute sulfuric acid, hydrochloric acid, and nitric acid. Therefore, the process of removing the fused calcium oxide core using dilute nitric acid will not damage the titanium alloy casting. An oxide layer remains on the casting surface, which is subsequently removed using a specialized pickling process.
[0056] In some embodiments, the casting mold further includes a shell, which is used to remove the outer shell of the titanium alloy casting using a high-pressure water gun.
[0057] In some embodiments, the casting mold further includes a shell, the preparation method of which includes: preparing a wax pattern on the surface of the core, preparing a shell outside the wax pattern, and then dewaxing, washing the shell, and firing; when cleaning the wax pattern with a cleaning agent, coating the surface of the core exposed from the wax pattern with wax material for protection, the cleaning agent includes alkyl glycosides, sodium benzenesulfonate, sodium fatty alcohol ether carboxylate, aminomethylbenzene alcohol, Span 80, Tween 80, and water, wherein the mass content of the alkyl glycosides is 15%~35% (e.g., 15%, 20%, 25%, 30%, 35%, etc.), the mass content of the sodium benzenesulfonate is 5%~25% (e.g., 5%, 10%, 15%, 20%, 25%, etc.), the mass content of the sodium fatty alcohol ether carboxylate is 15%~40% (e.g., 15%, 20%, 25%, 30%, 40%, etc.), the total mass content of the aminomethylbenzene alcohol, Span 80, and Tween 80 is 5%~15% (e.g., 5%, 10%, 15%, etc.), and the balance is water. In some embodiments, the dewaxing temperature is 280~320℃, for example, 280℃, 290℃, 300℃, 310℃, 320℃, etc. The dewaxing time is 2~4h, for example, 2h, 3h, or 4h, etc. In some embodiments, the cleaning agent used for shell washing is anhydrous ethanol with a concentration ≥95%, for example, 95%, 96%, 97%, etc. In some embodiments, the firing temperature of the shell is 950~1050℃, for example, 950℃, 980℃, 1000℃, 1020℃, 1050℃, etc.; the firing time is 100~140min, for example, 100min, 120min, 130min, 140min, etc.
[0058] In some implementations, a physical image of the shell is shown as follows: Figure 4 As shown.
[0059] In some embodiments, the process further includes pickling the titanium alloy casting after casting. The pickling acid consists of HNO3 and HF, with a mass ratio of HNO3 to HF of (14~20):1, such as 14:1, 15:1, 16:1, 20:1, etc. During the pickling process, key dimensions of the casting are measured and monitored every five minutes. After pickling, the surface of the casting shows no abnormalities, the core position dimensions are qualified, and no core displacement or deformation occurs.
[0060] In some embodiments, a vacuum solidification furnace is used for melting and casting the titanium alloy. The preheating temperature of the mold shell is 175~225℃, such as 175℃, 180℃, 190℃, 200℃, 210℃, 225℃, etc., and the preheating time is greater than 2 hours, such as 2.5 hours, 3 hours, etc.; the arc-starting vacuum degree is <0.9Pa, such as 0.5Pa, 0.6Pa, 0.8Pa, etc. The melting vacuum degree is less than 1Pa, such as 0.8Pa, 0.9Pa, etc. The melting voltage is 38~42V, such as 40V, etc. The melting current is 19000~21000A, such as 20000A, etc.
[0061] In some embodiments of the present invention, the titanium alloy melting and casting is carried out in a vacuum solidification furnace, with a shell preheating temperature of 200°C and a preheating time of 2.5 hours; the arc-starting vacuum degree is 0.8 Pa; the melting vacuum degree is 0.8 Pa; the melting voltage is 40 V; and the melting current is 20000 A.
[0062] In one embodiment, the titanium alloy casting method of the present invention includes: (a) Wax film preparation: gating preparation, pouring preparation, wax film pressing, wax film measurement, wax film repair, module assembly, and module cleaning.
[0063] (b) Shell preparation: applying surface coating, applying transition coating, applying reinforcing coating, dewaxing the module, plugging and repairing holes, and firing; after the shell preparation is completed, the furnace is assembled.
[0064] (c) Smelting and casting: material preparation, batching, primary ingot smelting, secondary ingot smelting.
[0065] (d) The secondary ingot is transferred into the furnace mentioned above for further melting, casting, shell cleaning, cutting and sandblasting.
[0066] (e) Repair and maintenance: remove the gating gate, blow sand, pickle, grind, then test the chemical composition, mechanical properties, X-ray inspection, fluorescence inspection, remove defects, repair welding, vacuum annealing, and dimension inspection.
[0067] (f) Final inspection and warehousing: Warehousing, document packaging, document review, certificate of conformity, packaging and shipping.
[0068] The following explanation, combined with specific embodiments and comparative examples, further illustrates the point.
[0069] Example 1 A method for preparing a core for titanium alloy investment casting includes the following steps: (1) Fused calcium oxide and yttrium oxide were ground separately to obtain ground fused calcium oxide and ground yttrium oxide. The particle size distribution of the ground fused calcium oxide was as follows: the mass percentage of particles smaller than 5 μm was 2%, the mass percentage of particles from 5 to 44 μm was 95%, and the mass percentage of particles larger than 44 μm was 3%. The particle size distribution of the ground yttrium oxide was as follows: the mass percentage of particles smaller than 5 μm was 2%, the mass percentage of particles from 5 to 44 μm was 95%, and the mass percentage of particles larger than 44 μm was 3%. (2) The ground fused calcium oxide and ground yttrium oxide are mixed with neutral water-resistant binder (SS-Y14W) to obtain a mixed system; the mass ratio of fused calcium oxide to yttrium oxide is 9:1, and the mass ratio of neutral water-resistant binder to the total mass of fused calcium oxide and yttrium oxide is 1:7; then the core for titanium alloy investment casting is prepared by reverse shell method.
[0070] The ambient temperature for preparing the core for titanium alloy investment casting is 22±2℃ and the humidity is 40%.
[0071] Example 2 A method for preparing a core for titanium alloy investment casting includes the following steps: (1) Fused calcium oxide and yttrium oxide were ground separately to obtain ground fused calcium oxide and ground yttrium oxide. The particle size distribution of the ground fused calcium oxide was as follows: particles smaller than 5 μm accounted for 2% of the mass, particles from 5 to 44 μm accounted for 95% of the mass, and particles larger than 44 μm accounted for 3% of the mass. The particle size distribution of the ground yttrium oxide was as follows: particles from 0 to 5 μm accounted for 2% of the mass, particles from 5 to 44 μm accounted for 95% of the mass, and particles larger than 44 μm accounted for 3% of the mass.
[0072] (2) The ground fused calcium oxide and ground yttrium oxide are mixed with a neutral water-resistant binder (SS-Y14W) to obtain a mixed system; the mass ratio of fused calcium oxide to yttrium oxide is 9:1, and the mass ratio of the neutral water-resistant binder to the total mass of fused calcium oxide and yttrium oxide is 1:7; then the core for titanium alloy investment casting is prepared by the reverse shell method.
[0073] (3) Apply epoxy resin material evenly to the surface of the titanium alloy investment casting core, and then put it into an 80℃ oven for drying for 120 minutes to obtain an epoxy resin layer with a thickness of 1.5mm.
[0074] The morphological images of the titanium alloy investment casting core before and after coating with epoxy resin in this embodiment are as follows: Figure 1 As shown, Figure 1 (A) in the text refers to the area before the epoxy resin layer is applied. Figure 1(B) in the text refers to the core surface after the epoxy resin layer is applied, which gives it a yellowish tint. Electrofused calcium oxide powder, such as... Figure 2 As shown.
[0075] The ambient temperature for preparing the core for titanium alloy investment casting is 22±2℃ and the humidity is 40%.
[0076] Example 3 A method for preparing a core for titanium alloy investment casting includes the following steps: (1) Fused calcium oxide and yttrium oxide were ground separately to obtain ground fused calcium oxide and ground yttrium oxide. The particle size distribution of the ground fused calcium oxide was such that the mass percentage of particles smaller than 5 μm was 1%, the mass percentage of particles between 5 and 44 μm was 98%, and the mass percentage of particles larger than 44 μm was 1%. The particle size distribution of the ground yttrium oxide was such that the mass percentage of particles smaller than 5 μm was 1%, the mass percentage of particles between 5 and 44 μm was 98%, and the mass percentage of particles larger than 44 μm was 1%.
[0077] (2) The ground fused calcium oxide and ground yttrium oxide are mixed with a neutral water-resistant binder to obtain a mixed system; the mass ratio of fused calcium oxide to yttrium oxide is 8.8:1, and the mass ratio of the neutral water-resistant binder to the total mass of fused calcium oxide and yttrium oxide is 1:7; then the core for titanium alloy investment casting is prepared by the reverse shell method.
[0078] (3) Apply epoxy resin material evenly to the surface of the titanium alloy investment casting core, and then put it into a 70℃ oven for drying for 130 minutes to obtain an epoxy resin layer.
[0079] The ambient temperature for preparing the core for titanium alloy investment casting is 22±2℃ and the humidity is 40%.
[0080] Example 4 A post-processing method for titanium alloy casting, comprising: After the titanium alloy casting is melted and poured, the casting mold is cleaned. The casting mold includes a core (using the core of Example 2) and a shell.
[0081] The outer shell of the titanium alloy casting is removed using a high-pressure water gun. The shell preparation method includes: preparing a wax pattern on the surface of the core, preparing the shell outside the wax pattern, and then dewaxing and washing the shell. When cleaning the wax pattern with a cleaning agent, a wax material is coated on the surface of the core exposed from the wax pattern for protection. The cleaning agent includes alkyl glycosides, sodium benzenesulfonate, sodium fatty alcohol ether carboxylate, aminomethylbenzene alcohol, Span 80, Tween 80, and water. The mass content of the alkyl glycosides is 20%, the mass content of sodium benzenesulfonate is 18%, the mass content of sodium fatty alcohol ether carboxylate is 30%, and the total mass content of aminomethylbenzene alcohol, Span 80, and Tween 80 is 10% (mass ratio of 5:2:3), with the balance being water. The dewaxing temperature is 300℃, and the dewaxing time is 3 hours. The cleaning agent used for shell washing is anhydrous ethanol with a concentration of 97%. The shell is baked at 1000℃ for 120 minutes.
[0082] The morphology near the core after melting and casting is as follows Figure 5 As shown, the core structure is intact, without obvious deformation, and there is no reaction with the molten titanium.
[0083] The core inside the titanium alloy casting was pickled using 12% dilute nitric acid at a specific temperature. The morphology of the casting after pickling and core removal is as follows. Figure 6 As shown.
[0084] It also includes: pickling the titanium alloy casting after casting, wherein the pickling acid comprises HNO3 and HF, and the mass ratio of HNO3 to HF is 16:1. The morphology of the casting after pickling to remove the oxide layer is as follows. Figure 7 As shown.
[0085] Example 5 A post-processing method for titanium alloy casting, comprising: After the titanium alloy casting is melted and poured, the casting mold is cleaned. The casting mold includes a core (using the core of Example 2) and a shell.
[0086] The shell on the outside of the titanium alloy casting is removed using a high-pressure water gun. The shell preparation method includes: preparing a wax pattern on the surface of the core, preparing the shell outside the wax pattern, and then dewaxing and washing the shell. When cleaning the wax pattern with a cleaning agent, a wax material is coated on the surface of the core exposed from the wax pattern for protection. The cleaning agent includes alkyl glycosides, sodium benzenesulfonate, and sodium fatty alcohol ether carboxylate, with a water content of less than 9%. The dewaxing temperature is 320℃, and the dewaxing time is 2 hours. The cleaning agent used for shell washing is anhydrous ethanol with a concentration of 95%. The shell is baked at 1050℃ for 100 minutes.
[0087] The core structure remained intact, without significant deformation or reaction with the molten titanium. The core inside the titanium alloy casting was pickled using 15% dilute nitric acid at a specific temperature.
[0088] It also includes: pickling the titanium alloy casting after casting, wherein the acid used for pickling includes HNO3 and HF, and the mass ratio of HNO3 to HF is 20:1.
[0089] Experimental Example The bending strength of the core before and after the epoxy resin coating in Example 2 was tested, and the results are shown in Table 1.
[0090] Table 1 Test Results
[0091] As shown in Table 1, the low-temperature strength of the core increased significantly after applying the epoxy resin layer. This helps prevent the core from cracking and deforming during the shell-making process. After the prepared core breaks, the fracture surface is as follows: Figure 3 As shown. The core prepared by the reverse shell method has a high surface density and a certain strength, which allows coatings and waxes to adhere smoothly to the surface. The internal density is lower and there are cavities. Its advantages include: when the core is subjected to stress and cracks during the shell-making process, there is deformation space inside, which prevents the external deformation of the core from squeezing the shell and causing cracks; it is also beneficial to remove the core after casting, which significantly speeds up the cleaning rate.
[0092] Conventional cores are typically cleaned using high-pressure water jets, but the effectiveness of this method is significantly limited when the core structure is complex. The cores described in the embodiments of this invention offer advantages such as the ability to undergo acid washing for cleaning, making them more suitable for complex structures.
[0093] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.
Claims
1. A core for investment casting of titanium alloys, characterized in that, The titanium alloy investment casting core is prepared from raw materials including fused calcium oxide, yttrium oxide and a neutral water-resistant binder; The mass ratio of the fused calcium oxide to the yttrium oxide is (8.5~9.2):1; The particle size distribution of the fused calcium oxide and the yttrium oxide each satisfies the following: the mass percentage of particles smaller than 5 μm is ≤3%, the mass percentage of particles between 5 and 44 μm is ≥93%, and the mass percentage of particles larger than 44 μm is ≤4%.
2. The core for titanium alloy investment casting according to claim 1, characterized in that, It includes at least one of the following features (1) to (2): (1) The mass ratio of the fused calcium oxide to the yttrium oxide is (8.8~9):1; (2) The ratio of the mass of the neutral water-resistant adhesive to the total mass of the electrofused calcium oxide and yttrium oxide is 1: (6.5~7.5).
3. The core for titanium alloy investment casting according to claim 1, characterized in that, The surface of the core used for titanium alloy investment casting is also provided with an epoxy resin layer; The thickness of the epoxy resin layer is 1~2mm.
4. The method for preparing a core for titanium alloy investment casting as described in any one of claims 1 to 3, characterized in that, Includes the following steps: Fused calcium oxide and yttrium oxide are ground to obtain ground fused calcium oxide and yttrium oxide; The ground fused calcium oxide and yttrium oxide are mixed with a neutral water-resistant binder to obtain a mixed system; then the mixed system is used to prepare a core for titanium alloy investment casting.
5. The method for preparing a core for titanium alloy investment casting according to claim 4, characterized in that, When the core has a complex and slender shape, die casting is used; when the core has a simple shape and a large cross-sectional area, reverse shell forming is used. The proportion of neutral water-resistant binder added in the die casting process for core preparation is lower than that in the reverse shell process for core preparation.
6. The method for preparing a core for titanium alloy investment casting according to claim 4, characterized in that, During the core preparation process, the ambient temperature is controlled at 20~24℃ and the humidity at 30%~50%.
7. The method for preparing a core for titanium alloy investment casting according to claim 4, characterized in that, An epoxy resin material is coated on the surface of the titanium alloy investment casting core, and then dried to obtain an epoxy resin layer; the drying temperature is 70~85℃, and the drying time is 100~130min.
8. A post-treatment method for titanium alloy casting, characterized in that, This includes cleaning the casting mold, which includes a core; pickling the core inside the titanium alloy casting using 10%~15% dilute nitric acid at a temperature of 50~60℃. The core is a titanium alloy investment casting core as described in any one of claims 1 to 3; or a titanium alloy investment casting core obtained by the method described in any one of claims 4 to 7.
9. The method for cleaning the casting mold after titanium alloy casting according to claim 8, characterized in that, It includes at least one of the following features (1) to (3): (1) The casting mold also includes a shell, and the shell outside the titanium alloy casting is removed by a high-pressure water gun; (2) The casting mold also includes a shell, and the method for preparing the shell includes: preparing a wax model on the surface of the core, preparing a shell outside the wax model, and then dewaxing, washing the shell and firing. Preferably, when cleaning the wax model with a cleaning agent, a wax material is applied to the exposed surface of the core to protect it; the cleaning agent includes alkyl glycosides, sodium benzenesulfonate, sodium fatty alcohol ether carboxylate, aminomethylbenzene alcohol, Span 80, Tween 80 and water, wherein the mass content of the alkyl glycosides is 15%~35%, the mass content of the sodium benzenesulfonate is 5%~25%, the mass content of the sodium fatty alcohol ether carboxylate is 15%~40%, the total mass content of the aminomethylbenzene alcohol, Span 80 and Tween 80 is 5%~15%, and the balance is water; Preferably, the dewaxing temperature is 280~320℃, and the dewaxing time is 2~4h; Preferably, the cleaning agent used for washing the shell is anhydrous ethanol with a concentration ≥95%; Preferably, the firing temperature of the shell is 950~1050℃ and the firing time is 100~140min.
10. The method for cleaning the casting mold after titanium alloy casting according to claim 8, characterized in that, Also includes: The titanium alloy castings that have been poured are pickled. The pickling acid solution includes HNO3 and HF, and the mass ratio of HNO3 to HF is (14~20):1.