Large-size combined yttrium oxide refractory crucible for titanium alloy smelting and preparation method thereof

Abstract

The invention discloses a large-size combined yttrium oxide refractory crucible for titanium alloy smelting and a preparation method thereof, belongs to the field of application of oxide ceramic crucibles, and aims to reduce the influence of a high thermal expansion coefficient of a yttrium oxide (Y2O3) material crucible, improve the compactness, anti-scouring capability and strength of the crucible and reduce the sintering temperature of the crucible on the basis. The method comprises the following steps: adding 30-40% by mass of yttrium oxide Y2O3 electric smelting mixed powder with the granularity of 100-200 meshes, 35-40% by mass of yttrium oxide Y2O3 electric smelting mixed powder with the granularity of 300-400 meshes and 25-30% by mass of yttrium oxide Y2O3 electric smelting mixed powder with the granularity of 1-3 microns into a material mixing device, mixing for 3-5 hours at the mechanical stirring rotating speed of the material mixing device of 120-150 r / min, then adding grinding balls for ball milling to obtain mixed powder and further obtain a crucible split type monomer; sintered split type single bodies of the crucible are connected in a layered stacking mode, yttrium sol is adopted for bonding and reinforcing the joints of the single bodies to form the crucible, and the crucible has the advantages of being good in thermal shock resistance and ultra-long in service life.

Description

Technical Field

[0001] The invention belongs to the application field of oxide ceramic crucibles, and in particular relates to a large-size, combined yttria refractory crucible for smelting titanium alloys and a preparation method thereof. Background Art

[0002] Titanium alloys are widely used in aerospace, marine, medical and other fields due to their low density, high strength and excellent corrosion resistance. At present, most titanium alloys are mainly produced by vacuum arc remelting (VAR) technology or vacuum induction melting (ISM) technology using graphite molds. Although these two technologies have their own advantages, the cost is relatively high. In contrast, the vacuum induction melting method using ceramic crucibles makes it possible to produce titanium alloys at low cost and on a large scale. However, due to the high chemical activity of titanium alloys, they easily react with the crucible material during the melting process, which not only contaminates the melt but also reduces the service life of the crucible.

[0003] Yttrium oxide (Y2O3) is an ideal material for making crucibles for melting titanium alloys due to its high melting point, strong chemical stability and high thermal conductivity. The structural and chemical stability it exhibits during the alloy melting process makes the probability of reaction with molten titanium alloy much lower than that of ceramic crucibles made of other materials. However, yttrium oxide ceramic crucibles are difficult to sinter, and the sintering temperature is usually required to be around 1800°C, and it is difficult to provide such a high temperature environment. In addition, due to the high sintering requirements, the larger and thicker the crucible, the higher the sintering temperature required, so large-sized yttrium oxide crucibles are more difficult to prepare. In addition, the high thermal expansion coefficient of yttrium oxide means that under the thermal stress of the melt, the crucible is prone to cracks and failure, resulting in waste of crucibles. Summary of the invention

[0004] In order to reduce the influence of the high thermal expansion coefficient of the yttrium oxide (Y2O3) crucible, improve the compactness, anti-scouring ability and strength of the crucible, and on this basis reduce the sintering temperature of the crucible. According to some embodiments of the present application, the method for preparing a combined yttrium oxide refractory crucible includes the following steps:

[0005] S1: 30% to 40% by weight of yttrium oxide Y2O3 fused mixed powder with a particle size of 100 to 200 mesh, 35% to 40% by weight of yttrium oxide Y2O3 fused mixed powder with a particle size of 300 to 400 mesh, and 25% to 30% by weight of yttrium oxide Y2O3 fused mixed powder with a particle size of 1 to 3 μm are added to a mixing device, the mechanical stirring speed of the mixing device is 120 to 150 r / min, grinding balls are added for ball milling, and the mixing is performed for 3 to 5 hours to obtain a mixed powder;

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

[0007] S3: fully and evenly mix the mixed powder and the PVA binder and then granulate to obtain yttrium oxide Y2O3 particles;

[0008] S4: Yttrium oxide Y2O3 particles are placed in a cold pressing mold and pressed under high pressure to obtain a crucible split monomer;

[0009] S5: drying the monomer in the crucible under natural environment;

[0010] S6: placing the dried monomer in a sintering furnace, heating it to a final sintering temperature of 1660-1760° C., cooling it along with the furnace, completing the plastic removal and sintering process, and obtaining a sintered crucible split monomer;

[0011] S7: Connect the sintered split crucible monomers in a layered stacking manner, and use yttrium sol to bond and reinforce the monomer joints to form a crucible.

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

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

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

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

[0016] According to the method for preparing a crucible of a combined yttria refractory material in some embodiments of the present application, in step S4, pressing is performed at a pressure of 160 to 200 MPa.

[0017] According to the method for preparing a crucible of a combined yttria refractory material in some embodiments of the present application, in step S5, the crucible monomer is dried in a natural environment for 5 to 7 days.

[0018] According to the method for preparing a crucible of a combined yttria refractory material in some embodiments of the present application, in step S6, the heating rate is 0.5 to 5°C / min, and the temperature is kept for 6 to 20 hours.

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

[0020] The crucible according to some embodiments of the present application is used for melting titanium alloy.

[0021] Beneficial effects: The large-sized, combined yttria refractory crucible has a use temperature of 1500-2100°C, and is used as a tool for vacuum melting of titanium alloys under this temperature environment. The inner surface of the refractory crucible does not participate in the reaction of active metals or alloys. On the basis of improving the purity of the alloy melt, it has the characteristics of good thermal shock resistance and ultra-high service life, and has the advantages of simple preparation process, low preparation cost, large melt volume, high melting efficiency, etc. In some examples, it shows a better balance between density and strength. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0023] Figure 2 It is the microstructure diagram of the crucible monomer. DETAILED DESCRIPTION

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

[0025] A method for preparing a large-sized, modular yttria refractory crucible for melting titanium alloys, which adopts a split modular design, can not only provide space for stress release, but also replace damaged units in time, thereby greatly improving the melt capacity and melting efficiency. It is particularly suitable for large-sized yttria refractory crucibles and can be used for melting titanium alloys.

[0026] The method adopted by the present invention specifically comprises the following steps:

[0027] S1: adding 30% to 40% of 100-200 mesh yttrium oxide Y2O3 fused powder, 35% to 40% of 300-400 mesh yttrium oxide Y2O3 fused powder, and 25% to 30% of 1-3 μm yttrium oxide Y2O3 fused powder into a mixing device in descending order of particle size, and then adding grinding balls for ball milling to obtain a mixed powder;

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

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

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

[0031] S3: Mixing the mixed powder and the binder and then granulating;

[0032] S4: placing the yttrium oxide Y2O3 particles obtained in step 3 into a cold pressing mold, and pressing at a pressure of 160 to 200 MPa to obtain a crucible split monomer;

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

[0034] S6: placing the monomer obtained in step 5 in a sintering furnace, heating it to a final sintering temperature of 1660-1760°C at a heating rate of 0.5-5°C / min, keeping it warm for 6-20 hours, and then cooling it with the furnace to complete the plastic discharge and sintering process, thereby obtaining the monomer preparation of the large-size, combined yttrium oxide refractory material and crucible for smelting titanium alloys.

[0035] S7: The monomers prepared in step 6 are connected in a layered stacking manner, and yttrium sol is used to bond and reinforce the monomer connections.

[0036] Among them, in step S1

[0037] The yttrium oxide Y2O3 fused mixed powder with a particle size (particle diameter) of 100 to 200 meshes is prepared by mixing yttrium oxide Y2O3 fused mixed powder with a particle size of 100 to 200 meshes.

[0038] The yttrium oxide Y2O3 fused mixed powder with a particle size of 300-400 meshes is prepared by mixing yttrium oxide Y2O3 fused powder with a particle size of 300-400 meshes.

[0039] The yttrium oxide Y2O3 fused mixed powder with a particle size of 1 to 3 μm is prepared by mixing yttrium oxide Y2O3 fused powder with a particle size of 1 to 3 μm.

[0040] Among them, yttrium oxide Y2O3 fused mixed powders of three different (particle size) particle size ranges are added into the mixing device in sequence according to mass from large to small, and then enter the grinding ball for ball milling.

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

[0042] The crucible yttria refractory material and crucible of the present invention are composed of split monomers after sintering, and the yttria crucible can melt high-activity refractory metals such as titanium alloys within a temperature range of 1500-2100° C. The yttria split monomers are formed by cold pressing, and the mass ratio of yttria Y2O3 fused mixed powder with a particle size of 100-200 meshes: yttria Y2O3 fused mixed powder with a particle size of 300-400 meshes: yttria Y2O3 fused mixed powder with a particle size of 1-3 μm is 40:35:25 or 35:40:25 or 30:40:30.

[0043] Embodiment 1: A method for preparing a large-sized, modular yttria refractory crucible for smelting titanium alloys, comprising the following steps:

[0044] S1: Add 30% 100-200 mesh yttrium oxide Y2O3 fused powder, 40% 300-400 mesh yttrium oxide Y2O3 fused powder, and 30% 1-3μm yttrium oxide Y2O3 fused powder to the mixing device in descending order of mass, and then add grinding balls for ball milling to obtain a mixed powder. The mechanical stirring speed of the mixing device is 150r / min, and the mixing is performed for 4 hours;

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

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

[0047] S4: The yttrium oxide Y2O3 particles prepared in step 3 are placed in a cold pressing mold and pressed at a pressure of 160 MPa to obtain a crucible split monomer.

[0048] S5: Dry the monomer in the crucible prepared in step 4 under natural environment for 7 days.

[0049] S6: placing the monomer obtained in step 5 in a sintering furnace, heating it to a final sintering temperature of 1760°C at a heating rate of 5°C / min, keeping it warm for 9 hours, and then cooling it with the furnace to complete the plastic removal and sintering process, thereby obtaining the monomer preparation of the large-size, combined yttrium oxide refractory material and crucible for smelting titanium alloys.

[0050] S7: The monomers obtained in step 6 are spliced ​​in a layered stacking manner, and the monomer joints are bonded and reinforced with yttrium sol. The upper part of the obtained crucible can be used continuously for many times, and the failed part of the lower part can be replaced. According to experiments, the service life of the combined crucible is more than twenty times that of an ordinary crucible, and the smelting performance will not be reduced. Preferably, the crucible is a bottom-leaking crucible, and more preferably, a plug is provided at the bottom, and the furnace body supports the plug. After smelting, the support of the furnace body to the plug is cancelled, so that the melt can be discharged. Among them, the plug is formed of the same material as the crucible.

[0051] Experimental Example: The implementation steps are the same as those in Example 1, except for the proportion of yttrium oxide Y2O3 fused powder, the sintering temperature is 1760°C, the sintering time is 5h, and the porosity, strength and density of the obtained crucible are shown in Table 1.

[0052] Table 1

[0053]

[0054] The obtained crucible is bonded and reinforced by yttrium sol at the monomer connection, so the gap provides stress release space, so that the anti-seismic performance of the crucible is improved, and the crack phenomenon caused by the high thermal expansion coefficient of yttrium oxide can be overcome to a considerable extent by the gap. In particular, the present invention can complete the sintering of a large-size yttrium oxide Y2O3 electric melting powder material crucible at 1760°C, and it can be seen from Table 1 that the balance of porosity, strength and density reflected therein can meet the compactness and strength requirements of the crucible, and the high density is strong in resisting physical erosion and erosion. Among them, for the third group of data, it has the same porosity and density as the first group of data, but the strength is greatly improved, and its balance effect is better.

[0055] At different sintering temperatures, the proportions of different particle sizes (particle diameters) of yttrium oxide Y2O3 fused powder, the porosity, strength and density of the resulting crucible are shown in Table 2.

[0056] Table 2

[0057]

[0058] It can be seen from Table 2 that when the sintering temperature is lowered, the porosity of the first and second groups of data increases, while the strength and density decrease compared with those in Table 1. 1760°C is the sintering temperature with a better balance effect.

[0059] In the present invention, the terms "one embodiment", "some embodiments", "examples", "specific examples" or "some examples" etc. mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the described specific features, structures, materials or characteristics may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0060] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical solutions and inventive concepts of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A method for preparing a combined yttria refractory crucible, It is characterized in that The steps include: S1: 30% to 40% by weight of yttrium oxide Y with a particle size of 100 to 200 mesh 2 O 3 Electrofusion mixed powder, 35% to 40% yttrium oxide Y with a particle size of 300 to 400 mesh 2 O 3 Electrofusion mixed powder, 25% to 30% yttrium oxide Y with a particle size of 1 to 3 μm 2 O 3 The electro-melted mixed powder is added to a mixing device, the mechanical stirring speed of the mixing device is 120-150 r / min, grinding balls are added for ball milling, and the mixture is mixed for 3-5 hours to obtain a mixed powder; S2: adding PVA binder solution to the mixed powder; S3: The mixed powder is fully and evenly mixed with the PVA binder and then granulated to obtain yttrium oxide Y 2 O 3 Particles; S4: Yttrium oxide Y 2 O 3 The particles are loaded into a cold pressing mold and pressed under high pressure to obtain a crucible split monomer; S5: drying the monomer in the crucible under natural environment; S6: placing the dried monomer in a sintering furnace, heating it to a final sintering temperature of 1660-1760° C., cooling it along with the furnace, completing the plastic removal and sintering process, and obtaining a sintered crucible split monomer; S7: Connect the sintered split crucible monomers in a layered stacking manner, and use yttrium sol to bond and reinforce the monomer joints to form a crucible.

2. The method for preparing a combined yttria refractory crucible according to claim 1, It is characterized in that Yttrium oxide Y with a particle size of 100 to 200 mesh by mass 2 O 3 Electrofusion mixed powder: particle size is 300-400 mesh yttrium oxide Y 2 O 3 Electrofusion mixed powder: particle size is 1-3μm yttrium oxide Y 2 O 3 Electrofusion mixed powder = 40:35:

25.

3. The method for preparing a combined yttria refractory crucible according to claim 1, It is characterized in that Yttrium oxide Y with a particle size of 100 to 200 mesh by mass 2 O 3 Electrofusion mixed powder: particle size is 300-400 mesh yttrium oxide Y 2 O 3 Electrofusion mixed powder: particle size is 1-3μm yttrium oxide Y 2 O 3 Electrofusion mixed powder = 35:40:

25.

4. The method for preparing a combined yttria refractory crucible according to claim 1, It is characterized in that Yttrium oxide Y with a particle size of 100 to 200 mesh by mass 2 O 3 Electrofusion mixed powder: particle size is 300-400 mesh yttrium oxide Y 2 O 3 Electrofusion mixed powder: particle size is 1-3μm yttrium oxide Y 2 O 3 Electrofusion mixed powder = 30:40:

30.

5. The method for preparing a combined yttria refractory crucible according to claim 1, It is characterized in that In step S2, the concentration of the PVA binder solution is 6%, wherein, for every 10g of yttrium oxide Y 2 O 3 The electro-fused powder is configured with 0.2 to 0.5 g of polyvinyl alcohol (PVA).

6. The method for preparing a combined yttria refractory crucible according to claim 1, It is characterized in that In step S4, pressing is performed at a pressure of 160 to 200 MPa.

7. The method for preparing a combined yttria refractory crucible according to claim 1, It is characterized in that In step S5, the monomers in the crucible are dried in a natural environment for 5 to 7 days.

8. The method for preparing a combined yttria refractory crucible according to claim 1, It is characterized in that In step S6, the heating rate is 0.5 to 5°C / min, and the temperature is kept for 6 to 20 hours.

9. A crucible prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the large-sized crucible according to claim 9 for melting titanium alloy.

Images