A method for manufacturing a titanium alloy casting having a complex internal cavity

Abstract

The application provides a preparation method of a titanium alloy casting with a complex inner cavity. The application utilizes the synergistic effect of a mineralizer and a pore-forming agent to prepare a yttrium oxide-based ceramic core with excellent core removal performance. The mineralizer and the pore-forming agent are reasonably designed to promote the formation of more pores in the core, thereby increasing the solubility of the core. Meanwhile, citric acid and acetic acid are used as core removal liquid by utilizing the complexation reaction mechanism of citric acid and acetic acid with yttrium oxide, which further improves the core removal performance, and the content of yttrium oxide is relatively reduced, thereby reducing the cost. Finally, the titanium alloy casting with a better inner cavity surface quality is obtained.

Description

Technical Field

[0001] This invention belongs to the field of metal casting technology, and in particular relates to a method for preparing titanium alloy castings with complex and irregular internal cavities. Background Technology

[0002] For simple titanium alloy castings, pure yttrium oxide-based ceramic cores fully meet the requirements for physical core removal. However, for titanium alloy castings with complex internal cavities, physical core removal is difficult. Therefore, a preparation method is needed that can improve core removal performance and obtain better surface quality while meeting strength requirements. Summary of the Invention

[0003] To address the problems existing in the prior art, the present invention provides the following technical solution:

[0004] A method for preparing a titanium alloy casting with a complex internal cavity includes the following steps:

[0005] S1. Mix 75-90 wt% yttrium oxide, 0-5 wt% mineralizer, and 0-5 wt% pore-forming agent, and ball mill at 800 rpm for 30 min with a ball-to-material ratio of 1:2. Mix for 2 hours to obtain yttrium oxide-based ceramic premix slurry.

[0006] S2: Mix the yttrium oxide-based ceramic premix slurry obtained in S1 with 10-25 wt% plasticizer, heat to 80-120℃, and stir for 4-12 hours to obtain yttrium oxide-based ceramic core slurry;

[0007] S3: The yttrium oxide-based ceramic core slurry obtained in S2 is used to make yttrium oxide-based ceramic core blanks by hot pressing. The hot pressing temperature is 70-120℃, the mold closing pressure is 40 bar, the slurry injection pressure is 40 bar, the slurry injection time is 40 s, the holding pressure time is 40 s, and the slurry injection speed is 40%.

[0008] S4: Yttrium oxide-based ceramic core blanks are filled into a sagger with micron-sized alumina powder and sintered to obtain yttrium oxide-based ceramic cores;

[0009] S5: The yttrium oxide-based ceramic core obtained in S4 is wax molded and shell-made, and a titanium alloy casting containing the yttrium oxide-based ceramic core is obtained by titanium alloy casting, ultrasonic cleaning and drying.

[0010] S6: Mix 50-60 wt% citric acid, 20-30 wt% acetic acid, and 10-30 wt% other weak acids, and add water to prepare a weak acid core-removing solution of 10-20 g / ml;

[0011] S7: Add the weak acid core-removing liquid to the core-removing kettle, set the pressure to atmospheric pressure, heat to 95-120℃, and then put in the titanium alloy casting containing the yttrium oxide-based ceramic core obtained in S5.

[0012] S8: After the yttrium oxide-based ceramic core of the titanium alloy casting in the core-removing kettle is completely pulverized and removed, rinse 3-4 times and dry to obtain the core-removed titanium alloy casting.

[0013] Furthermore, in S1, the mineralizing agent is at least one or more of titanium dioxide, aluminum oxide, silicon dioxide, lanthanum oxide, cerium dioxide, cristobalite, metallic aluminum powder, silica powder, aluminum silicate, and mullite, and the median particle size of the mineralizing agent is 3 to 40 μm.

[0014] Further, in S1, the pore-forming agent is at least one or more of calcium oxide, calcium carbonate, calcium hydroxide, graphite powder, calcium sulfate, calcium chloride, calcium aluminate, calcium sulfoaluminate, and silicon carbide, and the median particle size of the pore-forming agent is 3 to 40 μm.

[0015] Furthermore, in S1, the sintering process is as follows: sintering temperature is increased from room temperature to 650℃ in 2 hours, then from 650℃ to 1050℃ within 2 hours; the temperature is held at 1050℃ for 1 hour; and the temperature is increased from 1050℃ to 1600℃ in 3 hours, then held at 1600℃ for 2 hours.

[0016] Furthermore, in S2, the plasticizer is prepared by mixing paraffin wax, beeswax and polyethylene in a weight ratio of 91:5:4.

[0017] Furthermore, in S6, the other weak acid is one or a mixture of at least two of carbonic acid, nitrous acid, and phosphoric acid.

[0018] This invention utilizes the synergistic effect of mineralizers and pore-forming agents to prepare yttrium oxide-based ceramic cores with excellent core-removing properties. By rationally designing the mineralizers and pore-forming agents, more pores are formed inside the core, increasing its solubility. Simultaneously, by utilizing the mechanism that citric acid and acetic acid can undergo complexation reactions with yttrium oxide, and using citric acid and acetic acid as core-removing liquids, the core-removing performance is further improved, while the yttrium oxide content is relatively reduced, thus lowering the cost. Ultimately, a titanium alloy casting with better internal cavity surface quality is obtained. Attached Figure Description

[0019] Figure 1 This is a comparison table of the core-removal performance tests of titanium alloy castings in the examples and comparative examples, based on standard number HB5353. Detailed Implementation

[0020] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0021] Example 1

[0022] S1: Add 80wt% yttrium oxide, 1wt% silica as mineralizer, 1wt% lanthanum trioxide as pore-forming agent, 2wt% calcium sulfate, 3wt% calcium aluminate, and 2wt% graphite powder to ball mill at 800 rpm for 240 min to obtain a premix. Mix for 2 hours with a ball-to-material ratio of 1:2 to obtain yttrium oxide-based ceramic premix slurry.

[0023] S2: The yttrium oxide-based ceramic premix slurry obtained in S1 is mixed with 11 wt% plasticizer (made from paraffin wax, beeswax and polyethylene in a ratio of 91:5:4), heated to 80-120°C, and stirred for 8 hours to obtain yttrium oxide-based ceramic core slurry.

[0024] S3: The yttrium oxide-based ceramic core slurry obtained in S2 is used to make yttrium oxide-based ceramic core blanks by hot pressing. The hot pressing temperature is 70-120℃, the mold closing pressure is 40 bar, the slurry injection pressure is 40 bar, the slurry injection time is 40 s, the holding pressure time is 40 s, and the slurry injection speed is 40%.

[0025] S4: Yttrium oxide-based ceramic core blanks are filled into a sagger with micron-sized alumina powder and sintered to obtain yttrium oxide-based ceramic cores;

[0026] S5: The yttrium oxide-based ceramic core obtained in S4 is pressed into a wax mold and a shell is made. The titanium alloy casting with the internal cavity filled by the yttrium oxide-based ceramic core is obtained by centrifugal casting of titanium alloy. After ultrasonic cleaning and drying, its mass is measured as M1.

[0027] S6: Prepare a weak acid core-removing solution of 10-20 g / ml by adding water to a mixture of 55 wt% citric acid, 25 wt% acetic acid, and 20 wt% carbonic acid.

[0028] S7: Add the above weak acid decoupling liquid to the decoupling kettle, set the pressure to atmospheric pressure, heat to 95-120°C, and put in the titanium alloy casting containing yttrium oxide-based ceramic core obtained in S5.

[0029] S8: Observe the titanium alloy casting in the core-removing kettle until the core just begins to pulverize, and record this as the pulverization time. Record the time when the core is completely pulverized as the removal time. Rinse with a water gun 3-4 times to obtain the cored titanium alloy casting. Dry the cored titanium alloy casting and inspect the internal cavities of the casting using a cold light source and an endoscope. If no residual core is found, the casting is ready.

[0030] Example 2

[0031] The difference from Example 1 is that

[0032] S1: Add 80wt% yttrium oxide, mineralizer (1wt% lanthanum trioxide, 1wt% alumina), and pore-forming agent (5wt% calcium oxide, 2wt% graphite powder) to the mixture. Then, ball mill the mixture at 800 rpm / min for 240 min to obtain a premix. Mix the premix for 2 hours with a ball-to-material ratio of 1:2.

[0033] The remaining steps and parameters are the same as in Example 1, and the removal of the yttrium oxide-based ceramic core is completed to obtain the cored titanium alloy casting.

[0034] Comparative Example 1

[0035] The difference from Example 1 is as follows:

[0036] S1: The 89wt% yttrium oxide ceramic powder contains no mineralizers or pore-forming agents.

[0037] The plasticizer was 11 wt%. The mixture was ball-milled at 800 rpm for 240 min to obtain a premix. The ball-to-material ratio was 1:2.

[0038] The remaining steps and parameters are the same as in Example 1, and the removal of the yttrium oxide-based ceramic core is completed to obtain the cored titanium alloy casting.

[0039] Comparative Example 2

[0040] The difference from Example 1 is that

[0041] S1: 89wt% yttrium oxide and ceramic powder (containing no mineralizers or pore-forming agents, and 11% plasticizer) were ball-milled at 800 rpm for 240 min to obtain a premix. The mixture was then mixed for 2 hours with a ball-to-powder ratio of 1:2.

[0042] S6: Prepare a weak acid core-removing solution of 10-20 g / ml by adding water to a mixture of 55 wt% citric acid, 25 wt% acetic acid, and 20 wt% phosphoric acid.

[0043] The remaining steps and parameters are the same as in Example 1, completing the removal of the yttrium oxide-based ceramic core to obtain the cored titanium alloy casting.

[0044] Comparative Example 3

[0045] The difference from Example 1 is as follows:

[0046] S1: Add 84wt% yttrium oxide, 2wt% titanium dioxide, and 3wt% lanthanum trioxide. Without adding a pore-forming agent, ball mill at 800 rpm for 30 min, with a ball-to-material ratio of 1:2, and mix for 2 hours.

[0047] The remaining steps and parameters are the same as in Example 1, and the removal of the yttrium oxide-based ceramic core is completed to obtain the cored titanium alloy casting.

[0048] Comparative Example 4

[0049] The difference from Example 1 is as follows:

[0050] S1: Add 86wt% yttrium oxide, 3wt% alumina, and 2wt% cerium oxide, without adding a pore-forming agent. Ball mill at 800 rpm for 120 min to obtain a premix. Mix for 2 hours, with a ball-to-material ratio of 1:2.

[0051] The remaining steps and parameters are the same as in Example 1, and the removal of the yttrium oxide-based ceramic core is completed to obtain the cored titanium alloy casting.

[0052] Comparative Example 5

[0053] The difference from Example 1 is as follows:

[0054] S1: Add 84wt% yttrium oxide, 3wt% graphite, and 2wt% calcium aluminate, without adding mineralizer. Ball mill at 800 rpm for 120 min to obtain a premix. Mix for 2 hours, with a ball-to-material ratio of 1:2.

[0055] The remaining steps and parameters are the same as in Example 1, and the removal of the yttrium oxide-based ceramic core is completed to obtain the cored titanium alloy casting.

[0056] Comparative Example 6

[0057] The difference from Example 1 is as follows:

[0058] S1: Add 86wt% yttrium oxide and 3wt% calcium oxide, without adding mineralizer. Ball mill at 800 rpm for 120 min to obtain a premix. Mix for 2 hours, with a ball-to-material ratio of 1:2.

[0059] The remaining steps and parameters are the same as in Example 1, and the removal of the yttrium oxide-based ceramic core is completed to obtain the cored titanium alloy casting.

[0060] The core-removal performance of titanium alloy castings with yttrium oxide-based ceramic cores prepared in the examples and comparative examples was tested according to standard number HB5353. The results are as follows: Figure 1 The comparison table shown.

[0061] As shown in the comparison table, the addition of mineralizers reduced the yttrium oxide content to some extent and increased porosity and high / low temperature flexural strength, thus improving core removal efficiency compared to pure yttrium oxide. The addition of pore-forming agents, while increasing porosity, also improved core removal performance due to the hydration effect of calcium-based pore-forming agents and the pore-forming effect of graphite. Furthermore, during sintering, Ca... 2+ Replace Y 3+Lattice distortion occurs, generating oxygen vacancies, promoting grain boundary migration, and forming numerous large pores, while also improving sintering performance. When mineralizers and pore-forming agents are added simultaneously, the porosity is further increased, improving the core-removal effect. Meanwhile, citric acid and acetic acid both react with yttrium oxide, so using citric acid and acetic acid as core-removing solutions also improves core-removal efficiency to some extent. For the core-removed titanium alloy castings, the surface roughness of the inner cavity is generally below 2μm, indicating good surface quality and minimal wall thickness fluctuation.

[0062] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method of producing a titanium alloy casting having a complex internal cavity, characterized by, The method comprises the following steps: S1, mixing 75-90wt% yttria, 0-5wt% mineralizer, 0-5wt% pore-forming agent, ball milling for 30min at a speed of 800rpm, mixing for 2 hours, to obtain a yttria-based ceramic premix slurry; S2, mixing the yttria-based ceramic premix slurry prepared in S1 with 10-25wt% plasticizer, and heating to 80-120℃, stirring and mixing for 4-12 hours, to obtain a yttria-based ceramic core slurry; S3, using the hot-pressing method to prepare a yttria-based ceramic core blank from the yttria-based ceramic core slurry prepared in S2, the hot-pressing temperature is 70-120℃, the closing pressure is 40bar, the injection pressure is 40bar, the injection time is 40s, the holding time is 40s, and the injection speed is 40%; S4, burying the yttria-based ceramic core blank in a kiln with micron-sized alumina powder, and sintering to obtain a yttria-based ceramic core; S5, wax mold pressing and shell making of the yttria-based ceramic core prepared in S4, and titanium alloy casting to obtain a titanium alloy casting containing the yttria-based ceramic core, and ultrasonic cleaning and drying; S6, mixing 50-60wt% citric acid, 20-30wt% acetic acid, and 10-30wt% other weak acids, and adding water to prepare a weak acid core removal liquid with a concentration of 10-20g / ml; S7, adding the weak acid core removal liquid into a core removal kettle, setting the pressure to normal pressure, heating to 95-120℃, and putting the titanium alloy casting containing the yttria-based ceramic core prepared in S5 into the kettle; S8, after the yttria-based ceramic core of the titanium alloy casting in the core removal kettle is completely powdered and removed, rinsing 3-4 times, and drying, to obtain a titanium alloy casting after core removal.

2. A method of producing a titanium alloy casting containing a complex internal cavity according to claim 1, characterized in that, In S1, the mineralizer is at least one or more of titanium dioxide, aluminum oxide, silicon dioxide, lanthanum sesquioxide, cerium dioxide, cristobalite, aluminum powder, silicon powder, aluminum silicate, and mullite, and the median particle size of the mineralizer is 3-40μm.

3. A method of manufacturing a titanium alloy casting containing complex internal cavities according to claim 1, characterized in that, In S1, the pore-forming agent is at least one or more of calcium oxide, calcium carbonate, calcium hydroxide, graphite powder, calcium sulfate, calcium chloride, calcium aluminate, calcium sulfoaluminate, and silicon carbide, and the median particle size of the pore-forming agent is 3-40μm.

4. The method for preparing a titanium alloy casting with a complex internal cavity according to claim 1, characterized in that, In S1, the sintering schedule is 2h from room temperature to 650℃, 2h from 650℃ to 1050℃, 1h at 1050℃, 3h from 1050℃ to 1600℃, and 2h at 1600℃.

5. The method for preparing a titanium alloy casting with a complex internal cavity according to claim 1, characterized in that, In S2, the plasticizer is prepared by mixing paraffin, beeswax, and polyethylene in a weight ratio of 91:5:

4.

6. The method of claim 1, wherein the titanium alloy casting having a complex internal cavity is prepared by the steps of: In S6, the other weak acid is one or a mixture of at least two of carbonic acid, nitrous acid, and phosphoric acid.

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