Low-oxygen high-performance tungsten alloy preparation process

Abstract

This invention discloses a low-oxygen, high-performance tungsten alloy preparation process, belonging to the field of metal preparation technology. By adding a certain amount of La2O3 and CeO2 to tungsten powder, and considering that CeO2 has an oxygen-purifying effect at high temperatures, the oxygen content in the cooled tungsten alloy can be minimized, even reaching negative oxygen levels. Through the effective addition of rare earth elements, the performance of pure tungsten can be improved, grains refined, and the recrystallization temperature and strength of the material increased. Furthermore, the toughness of the material can be improved, facilitating subsequent machining and wire drawing. Machining is easier compared to pure tungsten, avoiding defects such as chipping and notches due to the brittleness of pure tungsten, and tool life is more than twice that of pure tungsten; simultaneously, wire breakage is less likely during wire drawing. On the other hand, the final low-oxygen tungsten alloy material can withstand tens of thousands of thermal shock cycles, up from 5,000, and its oxidation resistance is significantly improved, thus meeting the various processing requirements of high-end materials.

Description

Technical Field

[0001] This invention belongs to the field of tungsten alloy preparation technology, and specifically relates to a low-oxygen, high-performance tungsten alloy preparation process. Background Technology

[0002] Tungsten, due to its high melting point (3422℃), possesses excellent electrical and thermal conductivity, as well as a low coefficient of thermal expansion, making it widely used in semiconductors, photovoltaics, medical devices, aerospace, and the nuclear industry. In existing technologies, tungsten alloys are generally made by adding rare earth elements, such as lanthanum, cerium, and yttrium, to a tungsten matrix to improve its properties. This increases the recrystallization temperature of tungsten, improving its processing performance; it also significantly reduces the electron work function, promoting electron emission. Therefore, tungsten can be used as an excellent electrode material, photovoltaic cutting material, single crystal furnace material, sapphire pulling material, and heating material.

[0003] As is well known, impurities have a significant impact on materials in the field of metal material preparation. On the one hand, incomplete impurity removal can accelerate the sintering process, causing premature closure of pores in the sintered matrix and premature completion of sintering. On the other hand, if impurities segregate at grain boundaries, they can easily cause cracking in the material, affecting subsequent processing. Therefore, controlling the content of impurities in materials, especially gaseous elements such as oxygen and nitrogen, is crucial for improving the strength, toughness, and thermal shock resistance of materials.

[0004] However, tungsten alloys often have a high oxygen content, leading to low recrystallization temperatures, low oxidation resistance, and limited thermal shock resistance. Therefore, it is essential to develop a novel tungsten alloy manufacturing process to reduce the oxygen content and thus improve the alloy's performance. Summary of the Invention

[0005] The purpose of this invention is to provide a low-oxygen, high-performance tungsten alloy preparation process, thereby producing high-performance tungsten alloys with low impurity oxygen content, high recrystallization temperature, high oxidation resistance, and long service life of thermal shock materials.

[0006] The technical solution adopted in this invention is a low-oxygen, high-performance tungsten alloy preparation process, which is implemented according to the following steps:

[0007] Step 1, Mixing: Add La2O3 and CeO2 to tungsten powder and mix to obtain a uniformly mixed powder; the content of La2O3 in the mixed powder is 0.5%~1%, and the content of CeO2 is 0.1%~0.5%;

[0008] Step 2, Pressing: The mixed powder is processed using a cold isostatic pressing process to obtain a green body;

[0009] Step 3, sintering: The green blank is sintered to obtain a sintered blank, which achieves near-full densification;

[0010] Step 4, Hot working: The sintered billet is hot-worked to eliminate sintering porosity;

[0011] Step 5, Annealing: Eliminate processing stress, prevent stress cracking, and finally obtain a low-oxygen, high-performance tungsten alloy.

[0012] Furthermore, the tungsten powder is selected with a purity of ≥99.95% and a particle size D50 of 1-3μm, and the La2O3 and CeO2 are selected with a particle size of 0.4μm-0.6μm.

[0013] Further, in step 1, the mixture is mixed in a mixer for 8-12 hours, dried at 80°C and sieved to obtain a uniformly mixed powder.

[0014] Furthermore, during the pressing process in step 2, the pressure is 150MPa-250MPa, and the holding time is 8min-12min.

[0015] Furthermore, step 3 involves sintering in a medium-frequency induction furnace, with high-purity hydrogen as the atmosphere.

[0016] Furthermore, in step 3, sintering is carried out in three stages: a low-temperature pre-sintering stage to remove moisture from the material, a medium-temperature sintering stage to control density, and a high-temperature sintering stage to control grain size.

[0017] Furthermore, in step 3, the temperature of the low-temperature pre-sintering stage is 500℃-1200℃, and the holding time is 2h-4h; the temperature of the medium-temperature sintering stage is 1500℃-1700℃, and the holding time is 6h-8h; the temperature of the high-temperature sintering stage is 2000℃-2400℃, and the holding time is 2h-4h.

[0018] Furthermore, in step 3, the actual density of the sintered billet is greater than 98%TD.

[0019] Furthermore, during hot working in step 4, the billet temperature is 1400℃-1500℃, the deformation is 30%-40% for the first pass, the cumulative processing rate for multiple passes is 60%-80%, and the furnace is reheated for 8-12 minutes between passes.

[0020] Furthermore, in step 5, the annealing temperature is 1200℃-1300℃, and the holding time is 1h-2h.

[0021] The low-oxygen, high-performance tungsten alloy preparation process of this invention involves adding a certain amount of La2O3 and CeO2 to tungsten powder. CeO2, at high temperatures, purifies oxygen and grain boundaries, resulting in a minimum oxygen content, even reaching negative oxygen levels, in the cooled tungsten alloy. During low-oxygen service, the material has low impurity content and is less prone to cracking at grain boundaries. The prepared low-oxygen tungsten alloy material can withstand tens of thousands of thermal shock cycles, up from 5,000, and its oxidation resistance is significantly improved, thus meeting the processing requirements of high-end materials. Furthermore, the addition of CeO2 further increases the recrystallization temperature of the material, reaching 1800℃ (200℃ higher than pure tungsten and 100℃ higher than tungsten-lanthanum alloys with the same content). When used above 1600℃, the material is less prone to deformation and fracture due to irregular grain growth and coarsening.

[0022] Furthermore, by effectively adding rare earth elements, especially CeO2, the properties of pure tungsten can be improved, the grain size refined, and the toughness of the material enhanced, thus facilitating subsequent machining and wire drawing processes. Statistics show that tungsten-lanthanum-cerium alloys are easier to machine than pure tungsten, avoiding defects such as chipping and notches caused by the brittleness of pure tungsten, and tool life is more than twice that of pure tungsten. Simultaneously, during wire drawing, the fine particles of the second phase can anchor grain boundaries, inhibiting abnormal grain growth during high-temperature processing, thereby refining the tungsten grain structure and making the tungsten wire less prone to breakage due to localized stress concentration. Similarly, at high temperatures, rare earth oxide particles can stabilize grain boundaries, prevent grain coarsening, and maintain the material's uniform deformation capacity. Attached Figure Description

[0023] Figure 1 This is a flow chart of the low-oxygen high-performance tungsten alloy preparation process of the present invention;

[0024] Figure 2 This is a 500X metallographic image of the sintered microstructure of a pure tungsten φ80 bar.

[0025] Figure 3 This is a 500X metallographic image of the sintered microstructure of the tungsten alloy φ80 bar prepared according to the present invention;

[0026] Figure 4 This is a SEM image of the sintered microstructure of the tungsten alloy φ80 bar prepared according to the present invention;

[0027] Figure 5 This is a 500X metallographic image of the microstructure of the end face of a pure 40mm tungsten bar annealed at 1500℃.

[0028] Figure 6 This is a 500X metallographic image of the microstructure of the 40mm tungsten alloy bar prepared by this invention after annealing at 1500℃. Detailed Implementation

[0029] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0030] like Figure 1 As shown, the low-oxygen high-performance tungsten alloy preparation process of the present invention includes the following specific steps:

[0031] Step 1: Mixing

[0032] La₂O₃ and CeO₂ were added to tungsten powder and mixed to obtain a uniformly mixed powder. The content of La₂O₃ in the mixed powder was 0.5%–1%, and the content of CeO₂ was 0.1%–0.5%. The tungsten powder was selected with a purity ≥99.95% and a particle size D50 of 1–3 μm. Lanthanum oxide (La₂O₃) and cerium oxide (CeO₂) were mixed with a particle size of approximately 0.5 μm. The mixture was thoroughly mixed in a mixer for 8–12 hours, then dried at 80°C and sieved to obtain a uniformly mixed powder.

[0033] In alloying, mixing is a crucial step. Ensuring material homogeneity at the micro- and nano-levels is key to preventing wire breakage later on. Therefore, selecting appropriate mixing equipment and processes is extremely important.

[0034] In practical implementation, SEM (Sequencing Electron Microscopy) equipment can be used to verify the uniformity of the powder and the second phase of the sintered product. The problem of submicron alloy inhomogeneity can be solved through solid-liquid doping. Specifically, an appropriate amount of cerium nitrate solution is uniformly doped into tungsten powder, and while thoroughly stirred, it is dried at 80°C to obtain doped tungsten alloy powder.

[0035] The addition of CeO2 and La2O3, which are second-phase hard particulate phases, does not react with the tungsten matrix and is insoluble in tungsten. Through dispersion strengthening, the second phase is uniformly distributed on the tungsten matrix. During subsequent deformation, the presence of the second phase leads to the formation of numerous dislocation loops during dislocation slip, thereby increasing the material's strength. Furthermore, the addition of the second phase refines the grains, increasing the material's recrystallization temperature and thus improving its toughness.

[0036] Of course, the addition of CeO2 must be appropriate. Too high a content (above 1%) can lead to fine-grain embrittlement and decreased toughness, while too low a content will result in only a negligible reduction in oxygen content. Similarly, the addition of La2O3 should not be excessive. Too high a content (above 2%) can cause uneven aggregation of La2O3, while too low a content will result in a lack of overall strengthening effect. Therefore, the amount added determines the success of the final result.

[0037] Step 2, Suppression

[0038] The mixed powder is processed by cold isostatic pressing to obtain a green body; during the pressing process, the pressure is 150MPa-250MPa and the holding time is 8min-12min, so that the material has a certain pressure and the relative density of the material can reach about 63%.

[0039] Step 3, Sintering

[0040] The green blank is sintered to obtain a sintered blank, which achieves near-full densification.

[0041] In practice, a medium-frequency induction furnace is used for sintering, with high-purity hydrogen (99.999% purity) as the atmosphere. The low-temperature pre-sintering temperature is 500-1200℃, held for 2-4 hours to remove moisture from the material; the medium-temperature sintering temperature is 1500-1700℃, held for 6-8 hours to remove low-melting-point impurities; and the high-temperature sintering temperature is 2000-2400℃, held for 2-4 hours to achieve near-full densification (>98% TD), control grain growth, and obtain a high-density sintered billet.

[0042] By adding CeO2 to tungsten and lanthanum, the oxygen content in the material can be further reduced, even to the point of being negatively oxygenated. Specifically, after adding CeO2 to tungsten, due to the high-temperature hydrogen atmosphere in the sintering furnace, CeO2 is reduced to Ce2O3, as shown in the following reaction formula:

[0043]

[0044] Below 500℃, the cerium-oxygen ratio strictly follows 2:3. However, above 500℃, the cerium-oxygen ratio changes, reaching as low as 57:43, which creates oxygen vacancies. That is, at high temperatures, the cerium-oxygen ratio of Ce₂O₃ increases, resulting in more oxygen vacancies. During subsequent cooling, to form stable Ce₂O₃, it needs to absorb surrounding oxygen atoms to maintain its structural stability. This leads to the absorption of oxygen atoms from the matrix, even forming negative oxygen atoms, ultimately reducing the oxygen content in the matrix.

[0045] Step 4, Hot working

[0046] Hot working is performed on the sintered billet: the initial temperature is 1400℃-1500℃, and the deformation is 30%-40% in the first pass to break up coarse grains. The cumulative processing rate across multiple passes is 60%-80%, with a reheating period of 8-12 minutes between passes. The initial temperature should not be too low, as this will make the material difficult to deform and prone to cracking; conversely, the initial temperature should not be too high, as this will cause the material to form a wide processing structure during hot working. The main purpose of hot working is to further increase the density of the material, eliminate sintering porosity, and transform the material from an equiaxed sintered structure to a fibrous structure, thereby improving strength and toughness.

[0047] Step 5, Annealing

[0048] After hot working, annealing is performed to eliminate residual stress from the hot working process. The annealing temperature is 1200℃-1300℃, and the holding time is 1h-2h to prevent stress concentration and cracking during subsequent processing. Annealing is mainly for stress relief. Therefore, the temperature should not be too high, as this leads to energy waste and may also pose a risk of grain growth; conversely, the annealing temperature should not be too low, as insufficient stress relief may result in processing cracks.

[0049] To further illustrate the technical solution of the present invention, the following specific embodiments are provided.

[0050] Example 1

[0051] Step 1: Mixing

[0052] La2O3 and CeO2 were added to tungsten powder and mixed to obtain a uniformly mixed powder. The content of La2O3 in the mixed powder was 1%, and the content of CeO2 was 0.5%. The tungsten powder was selected with a purity of ≥99.95% and a particle size D50 of 3μm. The particle size of La2O3 and CeO2 was selected to be 0.4μm.

[0053] The mixture is thoroughly mixed in a mixer for 10 hours, then dried at 80°C and sieved to obtain a uniformly mixed powder.

[0054] Step 2, Suppression

[0055] The mixed powder was processed by cold isostatic pressing to obtain a green body; during the pressing process, the pressure was 250 MPa and the holding time was 8 min.

[0056] Step 3, Sintering

[0057] The green billet is sintered to obtain a sintered billet, which achieves near-full densification, with an actual density greater than 98% TD. In this embodiment, this step ultimately yields a bar with a specification of φ80.

[0058] Sintering was carried out in a medium-frequency induction furnace, with high-purity hydrogen gas used in the atmosphere.

[0059] Sintering is carried out in three stages: low-temperature pre-sintering stage to remove moisture from the material, medium-temperature sintering stage to control density, and high-temperature sintering stage to control grain size.

[0060] The temperature of the low-temperature pre-sintering stage is 800℃, and the holding time is 4 hours; the temperature of the medium-temperature sintering stage is 1500℃, and the holding time is 7 hours; the temperature of the high-temperature sintering stage is 2400℃, and the holding time is 2 hours.

[0061] Step 4, Hot working

[0062] The sintered billet is hot-worked to eliminate sintering porosity. During hot working, the billet temperature is 1450℃, the deformation is 40% for the first pass, and the cumulative processing rate for multiple passes is 60%. A 10-minute reheating period is performed between passes. In this embodiment, an alloy bar with a final diameter of φ40 is obtained in this step.

[0063] Step 5, Annealing

[0064] To eliminate processing stress and prevent stress cracking, the annealing temperature is 1300℃ and held for 1 hour, ultimately yielding a low-oxygen, high-performance tungsten alloy.

[0065] Example 2

[0066] Step 1: Mixing

[0067] La2O3 and CeO2 were added to tungsten powder and mixed to obtain a uniformly mixed powder. The content of La2O3 in the mixed powder was 0.8%, and the content of CeO2 was 0.3%. The tungsten powder was selected with a purity of ≥99.95% and a particle size D50 of 2μm. The particle size of La2O3 and CeO2 was selected to be 0.4μm.

[0068] The mixture is thoroughly mixed in a mixer for 12 hours, then dried at 80°C and sieved to obtain a uniformly mixed powder.

[0069] Step 2, Suppression

[0070] The mixed powder was processed by cold isostatic pressing to obtain a green body; during the pressing process, the pressure was 200 MPa and the holding time was 8 min.

[0071] Step 3, Sintering

[0072] The green billet is sintered to obtain a sintered billet, which achieves near-full densification, with an actual density greater than 98% TD. In this embodiment, this step ultimately yields a bar with a specification of φ80.

[0073] Sintering was carried out in a medium-frequency induction furnace, with high-purity hydrogen gas used in the atmosphere.

[0074] Sintering is carried out in three stages: low-temperature pre-sintering stage to remove moisture from the material, medium-temperature sintering stage to control density, and high-temperature sintering stage to control grain size.

[0075] The temperature of the low-temperature pre-sintering stage is 1200℃, and the holding time is 3 hours; the temperature of the medium-temperature sintering stage is 1500℃, and the holding time is 8 hours; the temperature of the high-temperature sintering stage is 2200℃, and the holding time is 2 hours.

[0076] Step 4, Hot working

[0077] The sintered billet is hot-worked to eliminate sintering porosity. During hot working, the billet temperature is 1500℃, the deformation is 35% for the first pass, and the cumulative processing rate for multiple passes is 60%. A 12-minute reheating period is performed between passes. In this embodiment, an alloy bar with a final diameter of φ40 is obtained in this step.

[0078] Step 5, Annealing

[0079] To eliminate processing stress and prevent stress cracking, the annealing temperature is 1250℃ and held for 1 hour, ultimately yielding a low-oxygen, high-performance tungsten alloy.

[0080] Example 3

[0081] Step 1: Mixing

[0082] La2O3 and CeO2 were added to tungsten powder and mixed to obtain a uniformly mixed powder. The content of La2O3 in the mixed powder was 0.8%, and the content of CeO2 was 0.2%. The tungsten powder was selected with a purity of ≥99.95% and a particle size D50 of 3μm. The particle size of La2O3 and CeO2 was selected to be 0.5μm.

[0083] The mixture is thoroughly mixed in a mixer for 8 hours, then dried at 80°C and sieved to obtain a uniformly mixed powder.

[0084] Step 2, Suppression

[0085] The mixed powder was processed by cold isostatic pressing to obtain a green body; during the pressing process, the pressure was 250 MPa and the holding time was 10 min.

[0086] Step 3, Sintering

[0087] The green billet is sintered to obtain a sintered billet, which achieves near-full densification, with an actual density greater than 98% TD. In this embodiment, this step ultimately yields a bar with a specification of φ80.

[0088] Sintering was carried out in a medium-frequency induction furnace, with high-purity hydrogen gas used in the atmosphere.

[0089] Sintering is carried out in three stages: low-temperature pre-sintering stage to remove moisture from the material, medium-temperature sintering stage to control density, and high-temperature sintering stage to control grain size.

[0090] The temperature of the low-temperature pre-sintering stage is 500℃, and the holding time is 4 hours; the temperature of the medium-temperature sintering stage is 1600℃, and the holding time is 6 hours; the temperature of the high-temperature sintering stage is 2400℃, and the holding time is 3 hours.

[0091] Step 4, Hot working

[0092] The sintered billet is hot-worked to eliminate sintering porosity. During hot working, the billet temperature is 1400℃, the deformation is 40% for the first pass, and the cumulative processing rate for multiple passes is 70%. A reheating period of 8 minutes is performed between passes. In this embodiment, alloy bars with a final specification of φ40 are obtained in this step.

[0093] Step 5, Annealing

[0094] To eliminate processing stress and prevent stress cracking, the annealing temperature is 1300℃ and held for 1 hour, ultimately yielding a low-oxygen, high-performance tungsten alloy.

[0095] Example 4

[0096] Step 1: Mixing

[0097] La2O3 and CeO2 were added to tungsten powder and mixed to obtain a uniformly mixed powder. The content of La2O3 in the mixed powder was 0.75%, and the content of CeO2 was 0.5%. The tungsten powder was selected with a purity of ≥99.95% and a particle size D50 of 2μm. The particle size of La2O3 and CeO2 was selected to be 0.5μm.

[0098] The mixture is thoroughly mixed in a mixer for 10 hours, then dried at 80°C and sieved to obtain a uniformly mixed powder.

[0099] Step 2, Suppression

[0100] The mixed powder was processed by cold isostatic pressing to obtain a green body; during the pressing process, the pressure was 200 MPa and the holding time was 10 min.

[0101] Step 3, Sintering

[0102] The green billet is sintered to obtain a sintered billet, which achieves near-full densification, with an actual density greater than 98% TD. In this embodiment, this step ultimately yields a bar with a specification of φ80.

[0103] Sintering was carried out in a medium-frequency induction furnace, with high-purity hydrogen gas used in the atmosphere.

[0104] Sintering is carried out in three stages: low-temperature pre-sintering stage to remove moisture from the material, medium-temperature sintering stage to control density, and high-temperature sintering stage to control grain size.

[0105] The temperature of the low-temperature pre-sintering stage is 850℃, and the holding time is 3 hours; the temperature of the medium-temperature sintering stage is 1600℃, and the holding time is 7 hours; the temperature of the high-temperature sintering stage is 2200℃, and the holding time is 3 hours.

[0106] Step 4, Hot working

[0107] The sintered billet is hot-worked to eliminate sintering porosity. During hot working, the billet temperature is 1450℃, the deformation is 35% for the first pass, and the cumulative processing rate for multiple passes is 70%. A 10-minute reheating period is performed between passes. In this embodiment, an alloy bar with a final diameter of φ40 is obtained in this step.

[0108] Step 5, Annealing

[0109] To eliminate processing stress and prevent stress cracking, the annealing temperature is 1250℃ and the holding time is 1.5h, ultimately obtaining a low-oxygen, high-performance tungsten alloy.

[0110] Example 5

[0111] Step 1: Mixing

[0112] La2O3 and CeO2 were added to tungsten powder and mixed to obtain a uniformly mixed powder. The content of La2O3 in the mixed powder was 0.75%, and the content of CeO2 was 0.3%. The tungsten powder was selected with a purity of ≥99.95% and a particle size D50 of 1μm. The particle size of La2O3 and CeO2 was selected to be 0.6μm.

[0113] The mixture is thoroughly mixed in a mixer for 10 hours, then dried at 80°C and sieved to obtain a uniformly mixed powder.

[0114] Step 2, Suppression

[0115] The mixed powder was processed by cold isostatic pressing to obtain a green body; during the pressing process, the pressure was 150 MPa and the holding time was 12 min.

[0116] Step 3, Sintering

[0117] The green billet is sintered to obtain a sintered billet, which achieves near-full densification, with an actual density greater than 98% TD. In this embodiment, this step ultimately yields a bar with a specification of φ80.

[0118] Sintering was carried out in a medium-frequency induction furnace, with high-purity hydrogen gas used in the atmosphere.

[0119] Sintering is carried out in three stages: low-temperature pre-sintering stage to remove moisture from the material, medium-temperature sintering stage to control density, and high-temperature sintering stage to control grain size.

[0120] The temperature of the low-temperature pre-sintering stage is 850℃, and the holding time is 2 hours; the temperature of the medium-temperature sintering stage is 1700℃, and the holding time is 7 hours; the temperature of the high-temperature sintering stage is 2000℃, and the holding time is 4 hours.

[0121] Step 4, Hot working

[0122] The sintered billet is hot-worked to eliminate sintering porosity. During hot working, the billet temperature is 1450℃, the deformation is 30% for the first pass, and the cumulative processing rate for multiple passes is 80%. A 10-minute reheating period is performed between passes. In this embodiment, an alloy bar with a final diameter of φ40 is obtained in this step.

[0123] Step 5, Annealing

[0124] To eliminate processing stress and prevent stress cracking, the annealing temperature is 1200℃ and held for 2 hours, ultimately yielding a low-oxygen, high-performance tungsten alloy.

[0125] Example 6

[0126] Step 1: Mixing

[0127] La2O3 and CeO2 were added to tungsten powder and mixed to obtain a uniformly mixed powder. The content of La2O3 in the mixed powder was 0.75%, and the content of CeO2 was 0.1%. The tungsten powder was selected with a purity of ≥99.95% and a particle size D50 of 3μm. The particle size of La2O3 and CeO2 was selected to be 0.6μm.

[0128] The mixture is thoroughly mixed in a mixer for 10 hours, then dried at 80°C and sieved to obtain a uniformly mixed powder.

[0129] Step 2, Suppression

[0130] The mixed powder was processed by cold isostatic pressing to obtain a green body; during the pressing process, the pressure was 250 MPa and the holding time was 12 min.

[0131] Step 3, Sintering

[0132] The green billet is sintered to obtain a sintered billet, which achieves near-full densification, with an actual density greater than 98% TD. In this embodiment, this step ultimately yields a bar with a specification of φ80.

[0133] Sintering was carried out in a medium-frequency induction furnace, with high-purity hydrogen gas used in the atmosphere.

[0134] Sintering is carried out in three stages: low-temperature pre-sintering stage to remove moisture from the material, medium-temperature sintering stage to control density, and high-temperature sintering stage to control grain size.

[0135] The temperature of the low-temperature pre-sintering stage is 850℃, and the holding time is 4 hours; the temperature of the medium-temperature sintering stage is 1700℃, and the holding time is 7 hours; the temperature of the high-temperature sintering stage is 2400℃, and the holding time is 3 hours.

[0136] Step 4, Hot working

[0137] The sintered billet is hot-worked to eliminate sintering porosity. During hot working, the billet temperature is 1500℃, the deformation is 35% for the first pass, and the cumulative processing rate for multiple passes is 80%. A 12-minute reheating period is performed between passes. In this embodiment, an alloy bar with a final diameter of φ40 is obtained in this step.

[0138] Step 5, Annealing

[0139] To eliminate processing stress and prevent stress cracking, the annealing temperature is 1200℃ and held for 2 hours, ultimately yielding a low-oxygen, high-performance tungsten alloy.

[0140] Example 7

[0141] Step 1: Mixing

[0142] La2O3 and CeO2 were added to tungsten powder and mixed to obtain a uniformly mixed powder. The content of La2O3 in the mixed powder was 0.7%, and the content of CeO2 was 0.2%. The tungsten powder was selected with a purity of ≥99.95% and a particle size D50 of 3μm. The particle size of La2O3 and CeO2 was selected to be 0.6μm.

[0143] The mixture is thoroughly mixed in a mixer for 10 hours, then dried at 80°C and sieved to obtain a uniformly mixed powder.

[0144] Step 2, Suppression

[0145] The mixed powder was processed by cold isostatic pressing to obtain a green body; during the pressing process, the pressure was 200 MPa and the holding time was 12 min.

[0146] Step 3, Sintering

[0147] The green billet is sintered to obtain a sintered billet, which achieves near-full densification, with an actual density greater than 98% TD. In this embodiment, this step ultimately yields a bar with a specification of φ80.

[0148] Sintering was carried out in a medium-frequency induction furnace, with high-purity hydrogen gas used in the atmosphere.

[0149] Sintering is carried out in three stages: low-temperature pre-sintering stage to remove moisture from the material, medium-temperature sintering stage to control density, and high-temperature sintering stage to control grain size.

[0150] The temperature of the low-temperature pre-sintering stage is 500℃, and the holding time is 3 hours; the temperature of the medium-temperature sintering stage is 1700℃, and the holding time is 6 hours; the temperature of the high-temperature sintering stage is 2200℃, and the holding time is 4 hours.

[0151] Step 4, Hot working

[0152] The sintered billet is hot-worked to eliminate sintering porosity. During hot working, the billet temperature is 1400℃, the deformation is 35% for the first pass, and the cumulative processing rate for multiple passes is 80%. A reheating period of 8 minutes is performed between passes. In this embodiment, alloy bars with a final specification of φ40 are obtained in this step.

[0153] Step 5, Annealing

[0154] To eliminate processing stress and prevent stress cracking, the annealing temperature is 1250℃ and the holding time is 2 hours, ultimately obtaining a low-oxygen, high-performance tungsten alloy.

[0155] Example 8

[0156] Step 1: Mixing

[0157] La2O3 and CeO2 were added to tungsten powder and mixed to obtain a uniformly mixed powder. The content of La2O3 in the mixed powder was 0.5% and the content of CeO2 was 0.5%. The tungsten powder was selected with a purity of ≥99.95% and a particle size D50 of 3μm. The particle size of La2O3 and CeO2 was selected to be 0.6μm.

[0158] The mixture is thoroughly mixed in a mixer for 10 hours, then dried at 80°C and sieved to obtain a uniformly mixed powder.

[0159] Step 2, Suppression

[0160] The mixed powder was processed by cold isostatic pressing to obtain a green body; during the pressing process, the pressure was 150 MPa and the holding time was 12 min.

[0161] Step 3, Sintering

[0162] The green billet is sintered to obtain a sintered billet, which achieves near-full densification, with an actual density greater than 98% TD. In this embodiment, this step ultimately yields a bar with a specification of φ80.

[0163] Sintering was carried out in a medium-frequency induction furnace, with high-purity hydrogen gas used in the atmosphere.

[0164] Sintering is carried out in three stages: low-temperature pre-sintering stage to remove moisture from the material, medium-temperature sintering stage to control density, and high-temperature sintering stage to control grain size.

[0165] The temperature of the low-temperature pre-sintering stage is 900℃, and the holding time is 2 hours; the temperature of the medium-temperature sintering stage is 1700℃, and the holding time is 7 hours; the temperature of the high-temperature sintering stage is 2000℃, and the holding time is 4 hours.

[0166] Step 4, Hot working

[0167] The sintered billet is hot-worked to eliminate sintering porosity. During hot working, the billet temperature is 1500℃, the deformation is 30% for the first pass, and the cumulative processing rate for multiple passes is 80%. A 10-minute reheating period is performed between passes. In this embodiment, an alloy bar with a final diameter of φ40 is obtained in this step.

[0168] Step 5, Annealing

[0169] To eliminate processing stress and prevent stress cracking, the annealing temperature is 1200℃ and held for 2 hours, ultimately yielding a low-oxygen, high-performance tungsten alloy.

[0170] Example 9

[0171] Step 1: Mixing

[0172] La2O3 and CeO2 were added to tungsten powder and mixed to obtain a uniformly mixed powder. The content of La2O3 in the mixed powder was 0.5%, and the content of CeO2 was 0.3%. The tungsten powder was selected with a purity of ≥99.95% and a particle size D50 of 3μm. The particle size of La2O3 and CeO2 was selected to be 0.6μm.

[0173] The mixture is thoroughly mixed in a mixer for 10 hours, then dried at 80°C and sieved to obtain a uniformly mixed powder.

[0174] Step 2, Suppression

[0175] The mixed powder was processed by cold isostatic pressing to obtain a green body; during the pressing process, the pressure was 200 MPa and the holding time was 8 min.

[0176] Step 3, Sintering

[0177] The green billet is sintered to obtain a sintered billet, which achieves near-full densification, with an actual density greater than 98% TD. In this embodiment, this step ultimately yields a bar with a specification of φ80.

[0178] Sintering was carried out in a medium-frequency induction furnace, with high-purity hydrogen gas used in the atmosphere.

[0179] Sintering is carried out in three stages: low-temperature pre-sintering stage to remove moisture from the material, medium-temperature sintering stage to control density, and high-temperature sintering stage to control grain size.

[0180] The temperature of the low-temperature pre-sintering stage is 1200℃, and the holding time is 3 hours; the temperature of the medium-temperature sintering stage is 1500℃, and the holding time is 8 hours; the temperature of the high-temperature sintering stage is 2200℃, and the holding time is 3 hours.

[0181] Step 4, Hot working

[0182] The sintered billet is hot-worked to eliminate sintering porosity. During hot working, the billet temperature is 1400℃, the deformation is 40% for the first pass, and the cumulative processing rate for multiple passes is 70%. A 10-minute reheating period is performed between passes. In this embodiment, an alloy bar with a final diameter of φ40 is obtained in this step.

[0183] Step 5, Annealing

[0184] To eliminate processing stress and prevent stress cracking, the annealing temperature is 1300℃ and the holding time is 1.5h, ultimately obtaining a low-oxygen, high-performance tungsten alloy.

[0185] To verify the actual effect, the component indicators and microstructure were evaluated.

[0186] The tungsten alloy materials, conforming to normal industry standards, should have an additional oxygen content of less than 50 PPM in addition to the normal formation of La2O3 and Ce2O3, and the content of other impurities should be less than 0.05%. The tungsten alloy materials in the above embodiments all meet these standards.

[0187] Table 1: Statistics of oxide and oxygen content (%) in each example before sintering

[0188]

[0189] Table 2: Statistics of oxide and oxygen content (%) in each example after sintering

[0190]

[0191] As shown in Tables 1 and 2, the amount of oxide added after sintering is slightly less. During the sintering process (temperature above 2000℃), the vapor pressure of rare earth oxides is higher than that of tungsten, so they will volatilize slightly. The addition ratio of La2O3 to CeO2 is 2:1, and when the amount of CeO2 added is 0.3~0.5%, the oxygen content is relatively low, which achieves the expected effect.

[0192] like Figure 2 As shown, the sintered microstructure of a pure tungsten φ80 rod has approximately 1500 grains / mm. 2 .

[0193] like Figure 3 As shown, the sintered microstructure of the tungsten-lanthanum-cerium alloy using this technical solution has a grain number of 5000 grains / mm. 2 .

[0194] pass Figure 2 and Figure 3 The comparison shows that after adding the alloy, the sintered structure of the material is more uniform and fine, and the grain size is more than 3 times that of pure tungsten.

[0195] like Figure 4As shown, the second phase of the tungsten-lanthanum-cerium alloy using this technical solution is uniformly distributed, and the sintering density reaches 18.5 g / cm³. 3 The density reaches 98% of the theoretical density (the density of normal sintered tungsten materials is 95% of the theoretical density). This demonstrates that the addition of alloying elements to tungsten, lanthanum, and cerium significantly refines the grain size and improves both density and uniformity.

[0196] like Figure 5 As shown, a pure tungsten φ40 rod recrystallizes at 1500℃, with approximately 1500 grains / mm. 2， The material exhibits an uneven microstructure, with some areas containing coarse particles approaching 50 μm. This indicates that the material has a relatively low recrystallization temperature in the absence of alloying elements.

[0197] like Figure 6 As shown, the tungsten-lanthanum-cerium alloy using this technical solution exhibits a fine microstructure and narrow grain boundaries at 1500℃, with no recrystallization observed, and the material remains a processed microstructure. Therefore, it is evident that the addition of alloying elements significantly increases the recrystallization temperature of the material, resulting in a finer and more uniform microstructure, achieving the desired effect.

Claims

1. A process for preparing low-oxygen, high-performance tungsten alloys, characterized in that, The specific steps are as follows: Step 1, Mixing: Add La2O3 and CeO2 to tungsten powder and mix to obtain a uniformly mixed powder; the content of La2O3 in the mixed powder is 0.5%~1%, and the content of CeO2 is 0.1%~0.5%; Step 2, Pressing: The mixed powder is processed using a cold isostatic pressing process to obtain a green body; Step 3, sintering: The green blank is sintered to obtain a sintered blank, which achieves near-full densification; Step 4, Hot working: The sintered billet is subjected to hot working treatment to eliminate sintering porosity; Step 5, Annealing: Eliminate processing stress, prevent stress cracking, and finally obtain a low-oxygen, high-performance tungsten alloy; In step 3, high-purity hydrogen is used as the atmosphere.

2. The low-oxygen high-performance tungsten alloy preparation process according to claim 1, characterized in that, The tungsten powder is selected with a purity of ≥99.95% and a particle size D50 of 1-3μm, while the La2O3 and CeO2 are selected with a particle size of 0.4μm-0.6μm.

3. The low-oxygen high-performance tungsten alloy preparation process according to claim 1, characterized in that, In step 1, the mixture is mixed in a mixer for 8-12 hours, then dried at 80°C and sieved to obtain a uniformly mixed powder.

4. The low-oxygen high-performance tungsten alloy preparation process according to claim 1, characterized in that, During the pressing process in step 2, the pressure is 150MPa-250MPa, and the holding time is 8min-12min.

5. The low-oxygen high-performance tungsten alloy preparation process according to claim 1, characterized in that, Step 3 involves sintering in a medium-frequency induction furnace.

6. The low-oxygen high-performance tungsten alloy preparation process according to claim 1, characterized in that, In step 3, sintering is carried out in three stages: low-temperature pre-sintering stage for removing moisture from the material, medium-temperature sintering stage for controlling density, and high-temperature sintering stage for controlling grain size.

7. The low-oxygen high-performance tungsten alloy preparation process according to claim 6, characterized in that, In step 3, the temperature of the low-temperature pre-sintering stage is 500℃-1200℃, and the holding time is 2h-4h; the temperature of the medium-temperature sintering stage is 1500℃-1700℃, and the holding time is 6h-8h; the temperature of the high-temperature sintering stage is 2000℃-2400℃, and the holding time is 2h-4h.

8. The low-oxygen high-performance tungsten alloy preparation process according to claim 1, characterized in that, In step 3, the actual density of the sintered billet is greater than 98%TD.

9. The low-oxygen high-performance tungsten alloy preparation process according to claim 1, characterized in that, During the hot working in step 4, the billet temperature is 1400℃-1500℃, the deformation is 30%-40% for the first pass, the cumulative processing rate for multiple passes is 60-80%, and the furnace is reheated for 8-12 minutes between passes.

10. The low-oxygen high-performance tungsten alloy preparation process according to claim 1, characterized in that, The annealing temperature in step 5 is 1200-1300℃, and the holding time is 1-2 hours.

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