Large size, assembled yttria refractory material crucible for melting titanium alloy and its preparation method

Abstract

Large size, combined titanium alloy smelting yttria refractory material crucible and its preparation method, belong to the field of oxide ceramic crucible application, in order to reduce the influence of high thermal expansion coefficient of yttria (Y2O3) material crucible, improve the density and erosion resistance and strength of the crucible, and on this basis, the sintering temperature of the crucible can be reduced, 30%-40% of the particle size of 100-200 mesh yttria Y2O3 electric melting mixed powder, 35%-40% of the particle size of 300-400 mesh yttria Y2O3 electric melting mixed powder, 25%-30% of the particle size of 1-3 microns yttria Y2O3 electric melting mixed powder are added into the mixing device, the mechanical stirring speed of the mixing device is 120-150 r / min, the mixing time is 3-5 h, then the grinding ball is added for ball milling, the mixed powder is obtained and the crucible split type monomer is further obtained, the sintered crucible split type monomer is connected according to the hierarchical stacking mode, the yttrium sol is used for bonding and reinforcing the monomer connection to form the crucible, the effect is that the crucible has good thermal shock performance and super high service life characteristics.

Description

Technical Field

[0001] This invention belongs to the field of oxide ceramic crucible applications, specifically relating to large-size, modular yttrium oxide refractory crucibles for titanium alloy melting and their preparation methods. Background Technology

[0002] Titanium alloys are widely used in aerospace, marine, and medical fields due to their low density, high strength, and excellent corrosion resistance. Currently, most titanium alloys are produced using vacuum arc remelting (VAR) or vacuum induction casting (ISM) using graphite molds. While both technologies have their advantages, they are relatively expensive. In contrast, vacuum induction melting using ceramic crucibles offers the possibility of low-cost, large-scale production of titanium alloys. However, due to the high chemical reactivity of titanium alloys, they easily react with the crucible material during melting, contaminating the melt and reducing the crucible's lifespan.

[0003] Yttrium oxide (Y₂O₃), with its high melting point, strong chemical stability, and high thermal conductivity, is an ideal material for making crucibles for melting titanium alloys. Its structural and chemical stability during alloy melting makes its reaction probability with molten titanium alloys much lower than that of ceramic crucibles made from other materials. However, yttrium oxide ceramic crucibles are difficult to sinter, typically requiring sintering temperatures around 1800℃, which is challenging to provide. Furthermore, due to the high sintering requirements, larger and thicker crucibles require even higher sintering temperatures, making the fabrication of large-sized yttrium oxide crucibles even more difficult. In addition, the high coefficient of thermal expansion of yttrium oxide means that under the thermal stress of the melt, the crucible is prone to cracking and failure, leading to crucible waste. Summary of the Invention

[0004] To mitigate the impact of the high thermal expansion coefficient of yttrium oxide (Y₂O₃) material crucibles, improve crucible density, erosion resistance, and strength, and thereby lower the crucible sintering temperature, a crucible preparation method for a combined yttrium oxide refractory material according to some embodiments of this application includes the following steps:

[0005] S1: Add 30%–40% by weight of yttrium oxide (Y₂O₃) fused mixed powder with a particle size of 100–200 mesh, 35%–40% by weight of yttrium oxide (Y₂O₃) fused mixed powder with a particle size of 300–400 mesh, and 25%–30% by weight of yttrium oxide (Y₂O₃) fused mixed powder with a particle size of 1–3 μm to a mixing device. The mixing device is mechanically stirred at a speed of 120–150 r / min. Grinding balls are added for ball milling. Mixing is carried out for 3–5 hours to obtain a mixed powder.

[0006] S2: Add PVA binder solution to the mixed powder;

[0007] S3: After thoroughly and uniformly mixing the mixed powder with the PVA binder, granulate to obtain yttrium oxide (Y2O3) particles;

[0008] S4: Yttrium oxide (Y2O3) particles are loaded into a cold pressing mold and pressed under high pressure to obtain crucible-type split monomers;

[0009] S5: Dry the monomer in the crucible under natural conditions;

[0010] S6: Place the dried monomer in a sintering furnace, heat it to the final sintering temperature of 1660-1760℃, cool it with the furnace, and complete the plastic removal and sintering process to obtain the sintered crucible-type monomer.

[0011] S7: The sintered crucible components are connected in a layered stacking manner, and the joints of the components are bonded and reinforced with yttrium sol to form the crucible.

[0012] According to the crucible preparation method of the combined yttrium oxide refractory material according to some embodiments of this application, the ratio of yttrium oxide Y2O3 electrofused mixed powder with a particle size of 100-200 mesh to yttrium oxide Y2O3 electrofused mixed powder with a particle size of 300-400 mesh to yttrium oxide Y2O3 electrofused mixed powder with a particle size of 1-3 μm is 40:35:25.

[0013] According to the crucible preparation method of the combined yttrium oxide refractory material according to some embodiments of this application, the ratio of yttrium oxide Y2O3 electrofused mixed powder with a particle size of 100-200 mesh to yttrium oxide Y2O3 electrofused mixed powder with a particle size of 300-400 mesh to yttrium oxide Y2O3 electrofused mixed powder with a particle size of 1-3 μm is 35:40:25.

[0014] According to the crucible preparation method of the combined yttrium oxide refractory material according to some embodiments of this application, the ratio of yttrium oxide Y2O3 electrofused mixed powder with a particle size of 100-200 mesh to yttrium oxide Y2O3 electrofused mixed powder with a particle size of 300-400 mesh to yttrium oxide Y2O3 electrofused mixed powder with a particle size of 1-3 μm is 30:40:30.

[0015] According to the crucible preparation method of the combined yttrium oxide refractory material according to some embodiments of this application, the concentration of PVA binder solution in step S2 is 6%, wherein 0.2 to 0.5 g of polyvinyl alcohol (PVA) is prepared for every 10 g of yttrium oxide (Y2O3) electrofused powder.

[0016] According to the crucible preparation method of the combined yttrium oxide refractory material according to some embodiments of this application, in step S4, the material is pressed under a pressure of 160-200 MPa.

[0017] According to the crucible preparation method of the combined yttrium oxide refractory material according to some embodiments of this application, in step S5, the monomer of the crucible is dried in a natural environment for 5 to 7 days.

[0018] According to the crucible preparation method of the combined yttrium oxide refractory material according to some embodiments of this application, in step S6, the heating rate is 0.5-5℃ / min, and the holding time is 6-20h.

[0019] A crucible prepared according to any one of the preparation methods described in some embodiments of this application.

[0020] The crucible described in some embodiments of this application is used for titanium alloy melting.

[0021] Beneficial effects: Large-size, modular yttrium oxide refractory crucibles can be used at temperatures ranging from 1500 to 2100℃, and within this temperature range, they are used as instruments for vacuum melting of titanium alloys. The inner surface of the refractory crucible does not participate in the reaction of active metals or alloys. While improving the purity of the alloy melt, they possess excellent thermal shock resistance and an extremely long service life. They also feature simple preparation processes, low production costs, large melt volume, and high melting efficiency. In some examples, they have demonstrated a good balance between density and strength. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the crucible assembly.

[0023] Figure 2 This is a microstructure diagram of a single crucible unit. Detailed Implementation

[0024] The embodiments of this application are described in detail below with reference to the accompanying drawings, examples of which are shown in the drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout.

[0025] A method for preparing a large-size, modular yttrium oxide refractory crucible for melting titanium alloys is disclosed. By employing a modular design, it not only provides space for stress release but also allows for timely replacement of damaged units, thereby significantly improving melt capacity and melting efficiency. This method is particularly suitable for large-size yttrium oxide refractory crucibles and can be used for melting titanium alloys.

[0026] The method employed in this invention specifically includes the following steps:

[0027] S1: Add 30%–40% of 100–200 mesh yttrium oxide (Y₂O₃) fused powder, 35%–40% of 300–400 mesh yttrium oxide (Y₂O₃) fused powder, and 25%–30% of 1–3 μm yttrium oxide (Y₂O₃) fused powder to a mixing device in descending order of particle size. Then add grinding balls for ball milling to obtain a mixed powder.

[0028] The mixing device has a mechanical stirring speed of 120-150 r / min and a mixing time of 4 hours;

[0029] S2: Prepare a polyvinyl alcohol (PVA) adhesive solution;

[0030] During the molding process, for every 10g of yttrium oxide (Y2O3), an additive of 0.2-0.5g of polyvinyl alcohol (PVA) is prepared, and the concentration of the PVA binder solution is prepared at 6%.

[0031] S3: Granulation of mixed powder and binder;

[0032] S4: The yttrium oxide (Y2O3) particles obtained in step 3 are loaded into a cold pressing mold and pressed under a pressure of 160-200 MPa to obtain crucible-type split monomers.

[0033] S5: Dry the monomer of the crucible obtained in step 4 under natural conditions for 5 to 7 days;

[0034] S6: Place the monomer obtained in step 5 into a sintering furnace, and heat it to the final sintering temperature of 1660-1760℃ at a heating rate of 0.5-5℃ / min. After holding it at that temperature for 6-20 hours, cool it with the furnace to complete the plastic removal and sintering process. This will give you the monomer preparation of the large-size, combined titanium alloy yttrium oxide refractory material and crucible.

[0035] S7: Connect the monomers obtained in step 6 in a layered stacking manner, and use yttrium sol to bond and reinforce the monomer joints.

[0036] In step S1

[0037] Yttrium oxide (Y2O3) electrofused mixed powder with a particle size of 100-200 mesh is prepared by mixing yttrium oxide (Y2O3) electrofused powder with a particle size of 100-200 mesh.

[0038] Yttrium oxide (Y2O3) electrofused mixed powder with a particle size of 300-400 mesh is prepared by mixing yttrium oxide (Y2O3) electrofused powder with a particle size of 300-400 mesh.

[0039] The yttrium oxide (Y₂O₃) electrofused mixed powder with a particle size of 1–3 μm is prepared by mixing yttrium oxide (Y₂O₃) electrofused powder with a particle size of 1–3 μm.

[0040] In this process, three different (particle size) ranges of yttrium oxide (Y2O3) electrofused mixed powder are added to the mixing device in descending order of mass, and then fed into the grinding balls for ball milling.

[0041] Among them, the porous yttrium oxide crucible is a large-size crucible with an outer diameter of 124–133 mm and a height of 218–232 mm.

[0042] The yttrium oxide refractory material and crucible of this invention are assembled from sintered, separate monomers. The yttrium oxide crucible can melt highly reactive refractory metals such as titanium alloys within a temperature range of 1500–2100°C. The separate yttrium oxide monomers are cold-pressed, and the ratio of yttrium oxide (Y₂O₃) electrofused mixed powder with a particle size of 100–200 mesh to yttrium oxide (Y₂O₃) electrofused mixed powder with a particle size of 300–400 mesh to yttrium oxide (Y₂O₃) electrofused mixed powder with a particle size of 1–3 μm is 40:35:25, 35:40:25, or 30:40:30.

[0043] Example 1: A method for preparing a large-size, modular yttrium oxide refractory crucible for melting titanium alloys, comprising the following steps:

[0044] S1: 30% of 100-200 mesh yttrium oxide (Y₂O₃) fused powder, 40% of 300-400 mesh yttrium oxide (Y₂O₃) fused powder, and 30% of 1-3 μm yttrium oxide (Y₂O₃) fused powder are added sequentially to a mixing device in descending order of mass. Then, grinding balls are added for ball milling to obtain a mixed powder. The mixing device is mechanically stirred at 150 r / min for 4 hours.

[0045] S2: Preparation of polyvinyl alcohol (PVA) binder solution: During the molding process, for every 10g of yttrium oxide (Y2O3), 0.5g of polyvinyl alcohol (PVA) is added as an additive, and the concentration of the PVA binder solution is prepared at 6%.

[0046] S3: After mixing the powder and binder, the mixture is granulated. Preferably, the particle size is evenly distributed, and the mixture is sieved to obtain coarse granules with a particle size of 6-10 mesh. The coarse granules are then aged and stored for 24 hours.

[0047] S4: The yttrium oxide (Y2O3) particles obtained in step 3 are loaded into a cold pressing mold and pressed under a pressure of 160 MPa to obtain crucible-type split monomers.

[0048] S5: Dry the monomer of the crucible obtained in step 4 under natural conditions for 7 days.

[0049] S6: Place the monomer obtained in step 5 into a sintering furnace, and heat it to the final sintering temperature of 1760℃ at a heating rate of 5℃ / min. After holding it at that temperature for 9 hours, cool it with the furnace to complete the plastic removal and sintering process. This will give you the monomer preparation of the large-size, combined titanium alloy yttrium oxide refractory material and crucible.

[0050] S7: The monomers obtained in step 6 are stacked in layers, and the joints are reinforced with yttrium sol. The upper part of the resulting crucible can be used repeatedly, while the failed lower part can be replaced. Experiments show that the service life of the combined crucible is more than twenty times that of ordinary crucibles, and the melting performance is not reduced. Preferably, the crucible is a bottom-drain crucible. More preferably, a stopper is provided at the bottom, and the furnace body supports the stopper. After melting, the furnace body's support for the stopper is removed, allowing the melt to drain. The stopper is made of the same material as the crucible.

[0051] Experimental example: The implementation steps were the same as in Example 1, except for the proportion of yttrium oxide (Y2O3) electrofused powder, the sintering temperature was 1760℃, the sintering time was 5h, and the porosity, strength and density of the resulting crucible are shown in Table 1.

[0052] Table 1

[0053]

[0054] The resulting crucible, reinforced by yttrium sol bonding at the monomer joints, provides stress release space through gaps, improving its shock resistance. Furthermore, the gaps largely mitigate cracking caused by the high thermal expansion coefficient of yttrium oxide. In particular, this invention enables the sintering of large-size yttrium oxide (Y₂O₃) electrofused powder crucibles at 1760℃. Table 1 shows that the porosity, strength, and density balance meets the crucible's requirements for density and strength, exhibiting high density and strong resistance to physical erosion. Specifically, for the third set of data, while the porosity and density are the same as the first set, the strength is significantly improved, demonstrating even better balance.

[0055] Table 2 shows the porosity, strength, and density of crucibles obtained by varying the proportions of different particle sizes (particle diameters) of yttrium oxide (Y2O3) electrofused powder at different sintering temperatures.

[0056] Table 2

[0057]

[0058] As shown in Table 2, compared with Table 1, lowering the sintering temperature results in increased porosity and decreased strength and density in Group 1 and Group 2 data. 1760℃ is the sintering temperature with better uniformity.

[0059] In this invention, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0060] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing a crucible for a composite yttrium oxide refractory material, characterized in that, Includes the following steps: S1: Add 30%–40% by weight of yttrium oxide (Y₂O₃) fused mixed powder with a particle size of 100–200 mesh, 35%–40% by weight of yttrium oxide (Y₂O₃) fused mixed powder with a particle size of 300–400 mesh, and 25%–30% by weight of yttrium oxide (Y₂O₃) fused mixed powder with a particle size of 1–3 μm to a mixing device. The mixing device is mechanically stirred at a speed of 120–150 r / min. Grinding balls are added for ball milling. Mixing is carried out for 3–5 hours to obtain a mixed powder. S2: Add PVA binder solution to the mixed powder; S3: After thoroughly and uniformly mixing the mixed powder with the PVA binder, granulate to obtain yttrium oxide (Y2O3) particles; S4: Yttrium oxide (Y2O3) particles are loaded into a cold-pressing mold and pressed under high pressure to obtain crucible-type split monomers, wherein the pressing is carried out at a pressure of 160~200MPa. S5: Dry the monomer in the crucible under natural conditions; S6: Place the dried monomer in a sintering furnace, heat it to the final sintering temperature of 1660~1760℃, cool it with the furnace, and complete the plastic removal and sintering process to obtain the sintered crucible-type monomer. The heating rate is 0.5~5℃ / min, and the holding time is 6~20h. S7: The sintered crucible components are connected in a layered stacking manner, and the joints of the components are bonded and reinforced with yttrium sol to form the crucible.

2. The method for preparing a crucible for the combined yttrium oxide refractory material according to claim 1, characterized in that, The ratio of yttrium oxide (Y2O3) electrofused mixed powder with a particle size of 100~200 mesh to yttrium oxide (Y2O3) electrofused mixed powder with a particle size of 300~400 mesh to yttrium oxide (Y2O3) electrofused mixed powder with a particle size of 1~3 μm is 40:35:

25.

3. The method for preparing a crucible for the combined yttrium oxide refractory material according to claim 1, characterized in that, The ratio of yttrium oxide (Y2O3) electrofused mixed powder with a particle size of 100~200 mesh to yttrium oxide (Y2O3) electrofused mixed powder with a particle size of 300~400 mesh to yttrium oxide (Y2O3) electrofused mixed powder with a particle size of 1~3 μm is 35:40:

25.

4. The method for preparing a crucible for a combined yttrium oxide refractory material according to claim 1, characterized in that, The ratio of yttrium oxide (Y2O3) electrofused mixed powder with a particle size of 100~200 mesh to yttrium oxide (Y2O3) electrofused mixed powder with a particle size of 300~400 mesh to yttrium oxide (Y2O3) electrofused mixed powder with a particle size of 1~3 μm is 30:40:

30.

5. The method for preparing a crucible for a combined yttrium oxide refractory material according to claim 1, characterized in that, In step S2, the concentration of the PVA binder solution is 6%, wherein 0.2 to 0.5 g of polyvinyl alcohol (PVA) is prepared for every 10 g of yttrium oxide (Y2O3) electrofused powder.

6. The method for preparing a crucible for the combined yttrium oxide refractory material according to claim 1, characterized in that, In step S5, the monomer in the crucible is dried under natural conditions for 5 to 7 days.

7. A crucible prepared by the preparation method according to any one of claims 1-6.

8. The use of the large-sized crucible of claim 7 for the melting of titanium alloys.

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