Preparation method of titanium alloy casting with complex inner cavity

Abstract

According to the preparation method of the titanium alloy casting containing the complex inner cavity, the yttrium oxide-based ceramic core with the excellent depoling performance is prepared through the synergistic effect of the mineralizing agent and the pore forming agent, more air holes are promoted to be formed in the core by reasonably designing the mineralizing agent and the pore forming agent, and the solubility of the core is improved; meanwhile, the mechanism that citric acid and acetic acid can be subjected to complex reaction with yttrium oxide is matched and utilized, citric acid and acetic acid are used as depoling liquid, the depoling performance is further improved, the content of yttrium oxide is relatively reduced, and the cost is reduced; and finally, the titanium alloy casting with better inner cavity surface quality is obtained.

Description

Technical Field

[0001] The invention belongs to the technical field of metal casting, and in particular relates to a method for preparing a titanium alloy casting containing a complex and special-shaped inner cavity. Background Art

[0002] For simple titanium alloy castings, pure yttria-based ceramic cores fully meet the physical core removal requirements. However, for titanium alloy castings with complex internal cavities, physical core removal is difficult. It is necessary to provide a preparation method that can meet the strength requirements while improving the core removal performance and obtaining better surface quality. Summary of the invention

[0003] In view of the problems existing in the prior art, the present invention provides the following technical solutions:

[0004] A method for preparing a titanium alloy casting containing a complex inner cavity comprises the following steps:

[0005] S1. 75-90wt% of yttrium oxide, 0-5wt% of mineralizer, and 0-5wt% of pore former are mixed, ball milled at a speed of 800rpm for 30min, with a ball-to-material ratio of 1:2, and mixed for 2 hours to obtain a yttrium oxide-based ceramic premixed slurry;

[0006] S2: mixing the yttrium oxide-based ceramic premixed slurry prepared in S1 with 10-25 wt% of a plasticizer, heating the mixture to 80-120° C., and stirring the mixture for 4-12 hours to prepare a yttrium oxide-based ceramic core slurry;

[0007] S3: the yttrium oxide-based ceramic core slurry prepared in S2 is made into a yttrium oxide-based ceramic core blank by hot pressing, the hot pressing temperature is 70-120° C., the mold closing pressure is 40 bar, the grouting pressure is 40 bar, the grouting time is 40 s, the pressure holding time is 40 s, and the grouting speed is 40%;

[0008] S4: using micron-sized aluminum oxide powder to bury the yttrium oxide-based ceramic core blank in a sagger, and sintering to obtain a yttrium oxide-based ceramic core;

[0009] S5: the yttrium oxide-based ceramic core prepared in S4 is subjected to wax mold pressing and shell forming, and a titanium alloy casting containing the yttrium oxide-based ceramic core is prepared by titanium alloy casting, and then ultrasonically cleaned and dried;

[0010] S6: 50-60 wt % of citric acid, 20-30 wt % of acetic acid, and 10-30 wt % of other weak acids are mixed, and water is added to prepare a 10-20 g / ml weak acid core stripping liquid;

[0011] S7: adding a weak acid core-removing liquid into the core-removing kettle, setting the pressure to normal pressure, heating to 95-120° C., and placing the titanium alloy casting containing the yttria-based ceramic core prepared in S5;

[0012] S8: After the yttria-based ceramic core of the titanium alloy casting in the core-removing kettle is completely pulverized and removed, the core-removing process is performed, and ...

[0013] Further, in S1, the mineralizer is at least one or more of titanium dioxide, aluminum oxide, silicon dioxide, lanthanum trioxide, cerium dioxide, cristobalite, metal aluminum powder, silicon powder, aluminum silicate, and mullite, and the median particle size of the mineralizer is 3 to 40 μm.

[0014] Furthermore, 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 system is as follows: the temperature is raised from room temperature to 650°C in 2h, and then from 650°C to 1050°C in 2h; the temperature is kept at 1050°C for 1h; the temperature is raised from 1050°C to 1600°C in 3h, and then the temperature is kept at 1600°C for 2h.

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

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

[0018] The present invention utilizes the synergistic effect of a mineralizer and a pore-forming agent to prepare an yttria-based ceramic core with excellent core-removal performance, and promotes the formation of more pores inside the core by reasonably designing the mineralizer and the pore-forming agent, thereby increasing the solubility of the core; at the same time, by utilizing the mechanism that both citric acid and acetic acid can react with yttria to form a complex, citric acid and acetic acid are used as core-removal liquids, thereby further improving the core-removal performance, and at the same time, the yttria content is relatively reduced, thereby reducing the cost; and finally, a titanium alloy casting with better inner cavity surface quality is obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a comparison table of the core removal performance tests of the titanium alloy castings of the embodiments and comparative examples according to standard number HB5353. DETAILED DESCRIPTION

[0020] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0021] Example 1

[0022] S1: 80wt% yttrium oxide, 1wt% silica and 1wt% lanthanum trioxide as mineralizers, 2wt% calcium sulfate, 3wt% calcium aluminate and 2wt% graphite powder as pore-forming agents were ball-milled at 800rpm for 240min to obtain a premix, which was mixed for 2 hours with a ball-to-material ratio of 1:2 to obtain a yttrium oxide-based ceramic premix slurry;

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

[0024] S3: The yttrium oxide-based ceramic core slurry prepared in S2 is made into a yttrium oxide-based ceramic core blank by hot pressing, the hot pressing temperature is 70-120° C., the mold closing pressure is 40 bar, the grouting pressure is 40 bar, the grouting time is 40 s, the holding time is 40 s, and the grouting speed is 40%;

[0025] S4: using micron-sized aluminum oxide powder to bury the yttrium oxide-based ceramic core blank in a sagger, and sintering to obtain a yttrium oxide-based ceramic core;

[0026] S5: The yttria-based ceramic core obtained in S4 is subjected to wax mold pressing and shell forming, and a titanium alloy casting with an internal cavity filled with the yttria-based ceramic core is obtained by centrifugal casting of titanium alloy, and then ultrasonically cleaned and dried, and its mass is measured to be M1;

[0027] S6: adding water to a plurality of weak acids according to 55 wt % of citric acid, 25 wt % of acetic acid, and 20 wt % of carbonic acid to prepare a 10-20 g / ml weak acid stripping liquid;

[0028] S7: adding the above-mentioned weak acid core-removing liquid into the core-removing kettle, setting the pressure to normal pressure, heating to 95-120° C., and placing the titanium alloy casting containing the yttria-based ceramic core prepared in S5;

[0029] S8: Observe the core of the titanium alloy casting in the core removal kettle and observe when it starts to pulverize, which is recorded as the pulverization time, and when it is completely pulverized, it is recorded as the removal time. Rinse with a water gun 3 to 4 times to obtain the titanium alloy casting after core removal; dry the titanium alloy casting after core removal, and inspect the internal cavity of the casting with a cold light source and an endoscope, and check if there is no residual core.

[0030] Example 2

[0031] The difference from Example 1 is

[0032] S1: 80wt% yttrium oxide, mineralizer (1wt% lanthanum trioxide, 1wt% alumina) and pore-forming agent (5wt% calcium oxide, 2wt% graphite powder) were added, and ball-milled at a speed of 800rpm / min for 240min to obtain a premix, and mixed for 2 hours, with a ball-to-material ratio of 1:2;

[0033] The remaining steps and parameters are the same as those in Example 1, and the yttria-based ceramic core is removed to obtain a titanium alloy casting after core removal.

[0034] Comparative Example 1

[0035] The difference from Example 1 is:

[0036] S1: 89wt% of yttrium oxide and ceramic powder without any mineralizer and pore-forming agent,

[0037] The plasticizer was 11 wt%, ball milled at 800 rpm / min for 240 min, and the premix was mixed for 2 hours, with a ball-to-material ratio of 1:2;

[0038] The remaining steps and parameters are the same as those in Example 1, and the yttria-based ceramic core is removed to obtain a titanium alloy casting after core removal.

[0039] Comparative Example 2

[0040] The difference from Example 1 is

[0041] S1: 89wt% yttrium oxide and ceramic powder without any mineralizer and pore former, and 11% plasticizer) were ball-milled at 800rpm for 240min to obtain a premix, and mixed for 2 hours, with a ball-to-material ratio of 1:2;

[0042] S6: Add water to prepare a weak acid stripping solution of 10-20 g / ml, with the ratio of 55 wt% citric acid, 25 wt% acetic acid, and 20 wt% phosphoric acid.

[0043] The remaining steps and parameters are the same as those in Example 1, and the yttria-based ceramic core is removed to obtain a titanium alloy casting after core removal.

[0044] Comparative Example 3

[0045] The difference from Example 1 is:

[0046] S1: 84wt% yttrium oxide, 2wt% titanium dioxide, and 3wt% lanthanum trioxide were added. No pore-forming agent was added, and the mixture was ball-milled at 800rpm for 30min, with a ball-to-material ratio of 1:2, and mixed for 2 hours;

[0047] The remaining steps and parameters are the same as those in Example 1, and the yttria-based ceramic core is removed to obtain a titanium alloy casting after core removal.

[0048] Comparative Example 4

[0049] The difference from Example 1 is:

[0050] S1: 86wt% yttrium oxide, 3wt% alumina, 2wt% cerium oxide, without pore-forming agent, were ball-milled at 800rpm for 120min to obtain a premix, which was mixed for 2 hours, with a ball-to-material ratio of 1:2;

[0051] The remaining steps and parameters are the same as those in Example 1, and the yttria-based ceramic core is removed to obtain a titanium alloy casting after core removal.

[0052] Comparative Example 5

[0053] The difference from Example 1 is:

[0054] S1: 84wt% yttrium oxide, 3wt% graphite, 2wt% calcium aluminate, without adding mineralizer, ball milled at 800rpm for 120min, and the premix was mixed for 2 hours, with a ball-to-material ratio of 1:2;

[0055] The remaining steps and parameters are the same as those in Example 1, and the yttria-based ceramic core is removed to obtain a titanium alloy casting after core removal.

[0056] Comparative Example 6

[0057] The difference from Example 1 is:

[0058] S1: 86 wt% yttrium oxide and 3 wt% calcium oxide were added without adding mineralizer. The mixture was ball milled at 800 rpm for 120 min to obtain a premix, which was mixed for 2 hours with a ball-to-material ratio of 1:2.

[0059] The remaining steps and parameters are the same as those in Example 1, and the yttria-based ceramic core is removed to obtain a titanium alloy casting after core removal.

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

[0061] As shown in the comparison table, after adding the mineralizer, the yttrium oxide content is reduced to a certain extent, and the porosity and high and low temperature flexural strength are increased. Compared with pure yttrium oxide, the core removal efficiency is improved. After adding the pore-forming agent, the porosity is improved, and the hydration of the calcium-based pore-forming agent and the pore-forming effect of graphite jointly improve the core removal performance. In addition, during the sintering process, Ca 2+ Replace Y 3+, lattice distortion occurs, oxygen vacancies are generated, grain boundary migration is promoted, a large number of coarse pores are formed, and the sintering performance is also improved; when the mineralizer and pore-forming agent are added at the same time, the porosity is further improved and the core removal effect is improved. At the same time, citric acid and acetic acid will react with yttrium oxide, so citric acid and acetic acid are used as core removal liquids, and the core removal efficiency is also improved to a certain extent. For titanium alloy castings after core removal, the surface line roughness of the inner cavity is basically below 2μm, the surface quality is good, and the wall thickness does not fluctuate much.

[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 principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a titanium alloy casting containing a complex inner cavity, characterized in that: The steps include: S1. 75-90wt% of yttrium oxide, 0-5wt% of mineralizer, and 0-5wt% of pore former are mixed, ball milled at a speed of 800rpm for 30min, with a ball-to-material ratio of 1:2, and mixed for 2 hours to obtain a yttrium oxide-based ceramic premixed slurry; S2: mixing the yttrium oxide-based ceramic premixed slurry prepared in S1 with 10-25 wt% of a plasticizer, heating the mixture to 80-120° C., and stirring the mixture for 4-12 hours to prepare a yttrium oxide-based ceramic core slurry; S3: the yttrium oxide-based ceramic core slurry prepared in S2 is made into a yttrium oxide-based ceramic core blank by hot pressing, the hot pressing temperature is 70-120° C., the mold closing pressure is 40 bar, the grouting pressure is 40 bar, the grouting time is 40 s, the pressure holding time is 40 s, and the grouting speed is 40%; S4: using micron-sized aluminum oxide powder to bury the yttrium oxide-based ceramic core blank in a sagger, and sintering to obtain a yttrium oxide-based ceramic core; S5: the yttrium oxide-based ceramic core prepared in S4 is subjected to wax mold pressing and shell forming, and a titanium alloy casting containing the yttrium oxide-based ceramic core is prepared by titanium alloy casting, and then ultrasonically cleaned and dried; S6: 50-60 wt % of citric acid, 20-30 wt % of acetic acid, and 10-30 wt % of other weak acids are mixed, and water is added to prepare a 10-20 g / ml weak acid core stripping liquid; S7: adding a weak acid core-removing liquid into the core-removing kettle, setting the pressure to normal pressure, heating to 95-120° C., and placing the titanium alloy casting containing the yttria-based ceramic core prepared in S5; S8: After the yttria-based ceramic core of the titanium alloy casting in the core-removing kettle is completely pulverized and removed, the core-removing process is performed and the core-removing process is performed, and the core-removing process is performed and the core-removing process is performed.

2. The method for preparing a titanium alloy casting containing a complex inner 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 trioxide, cerium dioxide, cristobalite, metal aluminum powder, silicon powder, aluminum silicate, and mullite, and the median particle size of the mineralizer is 3 to 40 μm.

3. The method for preparing a titanium alloy casting containing a complex inner cavity 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 to 40 μm.

4. The method for preparing a titanium alloy casting containing a complex inner cavity according to claim 1, characterized in that: In S1, the sintering system is as follows: the temperature is raised from room temperature to 650°C in 2 h, and then from 650°C to 1050°C in 2 h; the temperature is kept at 1050°C for 1 h; the temperature is raised from 1050°C to 1600°C in 3 h, and then the temperature is kept at 1600°C for 2 h.

5. The method for preparing a titanium alloy casting containing a complex inner 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 for preparing a titanium alloy casting containing a complex inner cavity according to claim 1, characterized in that: In S6, the other weak acid is one of carbonic acid, nitrous acid, and phosphoric acid, or a mixture of at least two of them.

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