Preparation process of low-oxygen high-performance tungsten alloy

Abstract

The invention discloses a low-oxygen high-performance tungsten alloy preparation process, and belongs to the technical field of metal preparation. A certain amount of La2O3 and CeO2 are added into tungsten powder, and CeO2 has an oxygen purification effect at a high temperature, so that the oxygen content in the cooled tungsten alloy can reach the minimum and even reach negative oxygen. By means of the effective rare earth element adding amount, on one hand, the performance of pure tungsten can be improved, grains are refined, and the recrystallization temperature and strength of the material are improved; in addition, the toughness of the material can be improved, and subsequent machining, wire drawing and the like are facilitated. Compared with pure tungsten, machining is easier, the defects of edge breakage, notches and the like of materials due to brittleness of the pure tungsten are overcome, and the service life of a cutter is prolonged by more than two times compared with that of the pure tungsten; and meanwhile, the wire is not easy to break during wire drawing processing. And on the other hand, the number of times of the finally prepared low-oxygen tungsten alloy material can be increased to tens of thousands of times from original 5000 times on the service of the thermal shock resistant material, the oxidation resistance of the material is also obviously improved, and various processing requirements of high-end materials are further met.

Description

Technical Field

[0001] The invention belongs to the technical field of tungsten alloy preparation, and in particular relates to a process for preparing a low-oxygen, high-performance tungsten alloy. Background Art

[0002] Tungsten, due to its high melting point (3422°C), possesses excellent electrical and thermal conductivity, a low coefficient of thermal expansion, and many other excellent properties, making it widely used in the semiconductor, photovoltaic, medical, aviation, and nuclear industries. In existing technology, tungsten alloys are typically formed by adding rare earth elements (such as lanthanum, cerium, and yttrium) to a tungsten matrix to improve its properties. This improves the recrystallization temperature of tungsten and its processing properties; it also significantly reduces the electron work function, facilitating electron emission. This makes it suitable for use as an electrode material, photovoltaic cutting material, single crystal furnace, sapphire pulling, and heating materials.

[0003] It's well known that impurities significantly impact metal material preparation. On the one hand, incomplete impurity removal can accelerate the sintering process, causing premature pore closure and premature sintering. On the other hand, if impurities segregate at grain boundaries, they can easily cause cracking in the material, hindering subsequent processing. Therefore, controlling the impurity content in the material, especially gaseous impurities like oxygen and nitrogen, is crucial for improving material strength, toughness, and thermal shock resistance.

[0004] However, the high content of impurity oxygen in tungsten alloys leads to low recrystallization temperature, low oxidation resistance, and low thermal shock resistance. Therefore, it is necessary to provide a new tungsten alloy preparation process to reduce the impurity oxygen content in the material and thus improve the performance of tungsten alloys. Summary of the Invention

[0005] The purpose of the present invention is to provide a low-oxygen high-performance tungsten alloy preparation process, thereby preparing a high-performance tungsten alloy with low impurity oxygen content, high recrystallization temperature, high oxidation resistance and high thermal shock resistance.

[0006] The technical solution adopted by the present invention is a low-oxygen high-performance tungsten alloy preparation process, which is specifically implemented according to the following steps: Step 1: Mixing: La2O3 and CeO2 are added to tungsten powder and mixed to obtain a uniform mixed powder; the content of La2O3 in the mixed powder is 0.5% to 1%, and the content of CeO2 is 0.1% to 0.5%; Step 2: Pressing: The mixed powder is processed by cold isostatic pressing to obtain a green body; Step 3: Sintering: The green compact is sintered to obtain a sintered compact, which is nearly fully densified. Step 4: Heat treatment: heat treatment is performed on the sintered blank to eliminate sintering pores; Step 5: Annealing: Eliminate processing stress, prevent stress cracking, and ultimately obtain low-oxygen high-performance tungsten alloy.

[0007] Furthermore, the tungsten powder is selected with a purity of ≥99.95% and a particle size of 1-3μm (D50), and the La2O3 and CeO2 are selected with a particle size of 0.4um-0.6um.

[0008] Furthermore, in step 1, the mixture is mixed in a mixer for 8 h to 12 h, dried at 80° C. and sieved to obtain a uniformly mixed powder.

[0009] Furthermore, during the pressing treatment in step 2, the pressure is 150MPa-250MPa, and the holding time is 8min-12min.

[0010] Furthermore, in step 3, a medium frequency induction furnace is used for sintering, and high-purity hydrogen is used as the atmosphere.

[0011] Furthermore, the sintering in step 3 is divided into three stages: a low-temperature pre-sintering stage for removing moisture from the material, a medium-temperature sintering stage for controlling density, and a high-temperature sintering stage for controlling grain size.

[0012] Furthermore, in step 3, the temperature of the low-temperature pre-sintering stage is 500℃-1200℃, and the insulation time is 2h-4h; the temperature of the medium-temperature sintering stage is 1500℃-1700℃, and the insulation time is 6h-8h; the temperature of the high-temperature sintering stage is 2000℃-2400℃, and the insulation time is 2h-4h.

[0013] Furthermore, in step 3, the actual density of the sintered compact is greater than 98% TD.

[0014] Furthermore, during the hot working in step 4, the blanking temperature is 1400°C-1500°C, the deformation amount is 30%-40% for the first pass, the cumulative processing rate for multiple passes is 60%-80%, and the furnace is reheated and kept warm for 8min-12min between passes.

[0015] Furthermore, in step 5, the annealing temperature is between 1200° C. and 1300° C., and the temperature is kept for 1 hour to 2 hours.

[0016] The present invention's low-oxygen, high-performance tungsten alloy preparation process involves adding a certain amount of La2O3 and CeO2 to tungsten powder. CeO2 purifies oxygen and grain boundaries at high temperatures, allowing the oxygen content in the tungsten alloy to reach a minimum, even reaching negative oxygen levels, after cooling. When the material is used in low-oxygen conditions, the impurity content is low, and cracking at the grain boundaries is less likely to occur. The resulting low-oxygen tungsten alloy can withstand thermal shock cycles increased from 5,000 to tens of thousands, significantly improving its oxidation resistance and meeting various processing requirements for high-end materials. Furthermore, the addition of CeO2 further increases the material's recrystallization temperature, reaching 1800°C (200°C higher than pure tungsten and 100°C higher than a tungsten-lanthanum alloy with the same CeO2 content). When used at temperatures above 1600°C, the material is less susceptible to deformation and fracture due to irregular grain growth and coarsening.

[0017] Furthermore, effective additions of rare earth elements, particularly CeO2, can improve the properties of pure tungsten, refine the grain size, and enhance the material's toughness, facilitating subsequent machining and wire drawing processes. Statistics show that tungsten-lanthanum-cerium alloys are easier to machine than pure tungsten, avoiding defects like edge collapse and notches caused by the brittle nature of pure tungsten. Furthermore, tool life is more than doubled compared to pure tungsten. Furthermore, during wire drawing, fine second-phase particles pin grain boundaries, inhibiting abnormal grain growth during high-temperature processing. This refines the tungsten grain structure, making the tungsten wire less susceptible to breakage due to localized stress concentration during the drawing process. Similarly, at high temperatures, rare earth oxide particles stabilize grain boundaries, preventing grain coarsening and maintaining the material's uniform deformation capacity. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a process flow chart for preparing low-oxygen, high-performance tungsten alloy according to the present invention; Figure 2 This is a 500X metallographic diagram of the sintered structure of a pure tungsten φ80 rod; Figure 3 This is a 500X metallographic diagram of the sintered structure of the φ80 tungsten alloy rod prepared by the present invention; Figure 4 This is the SEM of the sintered structure of the φ80 tungsten alloy rod prepared by the present invention; Figure 5 This is a 500X metallographic image of the end surface structure of a pure tungsten φ40 bar annealed at 1500°C; Figure 6 This is a 500X metallographic image of the end surface structure of the tungsten alloy φ40 rod prepared by the present invention after annealing at 1500°C. DETAILED DESCRIPTION

[0019] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0020] like Figure 1As shown, the low-oxygen high-performance tungsten alloy preparation process of the present invention includes the following specific steps: Step 1: Mixing La2O3 and CeO2 are added to tungsten powder and mixed to obtain a uniform mixed powder. The La2O3 content in the mixed powder is 0.5%-1%, and the CeO2 content is 0.1%-0.5%. Tungsten powder should have a purity of ≥99.95% and a particle size of 1-3μm (D50). Lanthanum oxide (La2O3) and cerium oxide (CeO2) should have a particle size of approximately 0.5μm. The mixture is thoroughly mixed in a mixer for 8-12 hours, dried at 80°C, and sieved to obtain a uniform mixed powder.

[0021] Mixing and doping alloying elements is a critical step. Ensuring uniformity at the micron and nanometer levels is crucial to preventing subsequent wire breakage. Therefore, selecting the right mixing equipment and process is crucial.

[0022] During specific implementation, the powder uniformity and the uniformity of the second phase of the sintered product can be verified by observing the auxiliary equipment SEM.

[0023] CeO2 and La2O3 are added as a second phase of hard particles that do not react with the tungsten matrix and are insoluble in tungsten. They are evenly distributed throughout the tungsten matrix through second-phase dispersion strengthening. During subsequent deformation, the presence of this second phase causes dislocation slip, forming numerous dislocation loops, thereby increasing the material's strength. Furthermore, the addition of this second phase refines the grain size and raises the material's recrystallization temperature, thereby improving its toughness.

[0024] Of course, CeO2 addition should be appropriate. Excessive CeO2 content (above 1%) can lead to fine-grain embrittlement and reduced toughness, while too low a content can negligibly reduce the oxygen content. Similarly, excessive La2O3 addition should be avoided. Excessive La2O3 content (above 2%) can lead to uneven La2O3 aggregation, while too low a content can lead to insignificant overall strengthening effects. Therefore, the amount added determines the ultimate success of the result.

[0025] Step 2: Press 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 strength and the relative density of the material can reach about 63%.

[0026] Step 3: Sintering The green compact is sintered to obtain a sintered compact, and the sintered compact is nearly fully densified.

[0027] In the specific implementation, a medium-frequency induction furnace is used for sintering, and high-purity hydrogen (purity 99.999%) is used as the atmosphere. The low-temperature pre-sintering temperature is 500-1200°C and the heat preservation is carried out for 2-4 hours to remove moisture from the material; the medium-temperature sintering is carried out at 1500-1700°C and the heat preservation is carried out for 6-8 hours to remove low-melting-point impurities; the high-temperature sintering is carried out at 2000-2400°C and the heat preservation is carried out for 2-4 hours to achieve nearly full densification (>98% TD), control grain growth, and obtain a high-density sintered blank.

[0028] By adding CeO2 to tungsten lanthanum, the oxygen content in the material can be further reduced, even to negative oxygen. Specifically: after adding CeO2 to tungsten, due to the high temperature hydrogen atmosphere in the sintering furnace, CeO2 is reduced to Ce2O3, and the reaction formula is as follows: When the temperature is below 500°C, the cerium-oxygen ratio strictly adheres to 2:3. However, in an environment above 500°C, the cerium-oxygen ratio will change accordingly, reaching a minimum of 57:43, which will form oxygen atom vacancies. That is, at high temperatures, the cerium-oxygen ratio of Ce2O3 increases, forming a large number of oxygen atom vacancies. During the subsequent cooling process, in order to form stable Ce2O3, it needs to absorb other surrounding oxygen atoms to maintain its structural stability. In this way, the oxygen atoms in the matrix are absorbed, and even negative oxygen is formed, which ultimately reduces the oxygen content in the matrix.

[0029] Step 4: Hot working The sintered blank undergoes heat treatment: the starting temperature is 1400°C-1500°C, and the deformation in the first pass is 30%-40% to break up coarse grains. The cumulative processing rate over multiple passes is 60%-80%, with reheating and holding for 8-12 minutes between passes. The starting temperature should not be too low, as this will make the material difficult to deform and prone to cracking. It should also not be too high, as this will result in a wide microstructure during the heat treatment. The purpose of heat treatment is to further increase the material's density and eliminate sintering porosity. The material transforms from sintered equiaxed grains to a fibrous structure, which improves strength and toughness.

[0030] Step 5: Annealing Annealing is performed after hot working to eliminate residual stresses from the process. The material is annealed at a temperature of 1200°C-1300°C for 1-2 hours to prevent stress concentration and cracking during subsequent processing. Annealing is primarily a stress relief annealing. Therefore, the temperature should not be too high, as this wastes energy and may increase the risk of grain growth. It should also not be too low, as this will result in inadequate stress relief and the material may experience cracking during processing.

[0031] In order to further illustrate the technical solutions of the present invention, the following specific embodiments are provided.

[0032] Example 1 Step 1: Mixing La2O3 and CeO2 are added to tungsten powder and mixed to obtain a uniform mixed powder; in the mixed powder, the content of La2O3 is 1%, and the content of CeO2 is 0.5%; the tungsten powder is selected with a purity of ≥99.95% and a particle size of 3μm (D50), and the particle size of La2O3 and CeO2 is selected to be 0.4um.

[0033] The mixture was fully mixed in a mixer for 10 hours, dried at 80°C and sieved to obtain a uniformly mixed powder.

[0034] Step 2: Press The mixed powder is processed by cold isostatic pressing to obtain a green body; during the pressing process, the pressure is 250 MPa and the holding time is 8 minutes.

[0035] Step 3: Sintering The green compact is sintered to obtain a sintered compact, which is nearly fully densified, with an actual density greater than 98% TD. In this step, a rod with a specification of φ80 is finally obtained in this embodiment.

[0036] A medium frequency induction furnace is used for sintering, and high-purity hydrogen is used as the atmosphere.

[0037] Sintering is carried out in three stages: low-temperature pre-sintering to remove moisture from the material, medium-temperature sintering to control density, and high-temperature sintering to control grain size.

[0038] The temperature of the low-temperature pre-sintering stage is 800°C, which is kept warm for 4 hours; the temperature of the medium-temperature sintering stage is 1500°C, which is kept warm for 7 hours; and the temperature of the high-temperature sintering stage is 2400°C, which is kept warm for 2 hours.

[0039] Step 4: Hot working The sintered billet was heat-treated to eliminate sintering porosity. During the heat treatment, the billet temperature was 1450°C, the deformation was 40% for the first pass, and the cumulative processing rate for multiple passes was 60%. Between passes, the billet was reheated and held for 10 minutes. In this step, the alloy bar with a specification of φ40 was finally obtained in this embodiment.

[0040] Step 5: Annealing Eliminate processing stress and prevent stress cracking. Annealing temperature is 1300℃ and kept for 1 hour to finally obtain low-oxygen high-performance tungsten alloy.

[0041] Example 2 Step 1: Mixing La2O3 and CeO2 are added to tungsten powder and mixed to obtain a uniform mixed powder; in the mixed powder, the content of La2O3 is 0.8%, and the content of CeO2 is 0.3%; the tungsten powder is selected with a purity of ≥99.95% and a particle size of 2μm (D50), and the particle size of La2O3 and CeO2 is selected to be 0.4um.

[0042] The mixture was fully mixed in a mixer for 12 hours, dried at 80°C and sieved to obtain a uniformly mixed powder.

[0043] Step 2: Press The mixed powder is processed by cold isostatic pressing to obtain a green body; during the pressing process, the pressure is 200 MPa and the holding time is 8 minutes.

[0044] Step 3: Sintering The green compact is sintered to obtain a sintered compact, which is nearly fully densified, with an actual density greater than 98% TD. In this step, a rod with a specification of φ80 is finally obtained in this embodiment.

[0045] A medium frequency induction furnace is used for sintering, and high-purity hydrogen is used as the atmosphere.

[0046] Sintering is carried out in three stages: low-temperature pre-sintering to remove moisture from the material, medium-temperature sintering to control density, and high-temperature sintering to control grain size.

[0047] The temperature of the low-temperature pre-sintering stage is 1200°C, and the temperature is kept for 3 hours; the temperature of the medium-temperature sintering stage is 1500°C, and the temperature is kept for 8 hours; the temperature of the high-temperature sintering stage is 2200°C, and the temperature is kept for 2 hours.

[0048] Step 4: Hot working The sintered billet was heat-treated to eliminate sintering porosity. During the heat treatment, the billet temperature was 1500°C, the deformation was 35% for the first pass, and the cumulative processing rate for multiple passes was 60%. Between passes, the billet was reheated and held for 12 minutes. In this step, the alloy bar with a specification of φ40 was finally obtained in this embodiment.

[0049] Step 5: Annealing Eliminate processing stress and prevent stress cracking. Annealing temperature is 1250℃ and kept for 1 hour to finally obtain low-oxygen high-performance tungsten alloy.

[0050] Example 3 Step 1: Mixing La2O3 and CeO2 are added to tungsten powder and mixed to obtain a uniform mixed powder; in the mixed powder, the content of La2O3 is 0.8%, and the content of CeO2 is 0.2%; the tungsten powder is selected with a purity of ≥99.95% and a particle size of 3μm (D50), and the particle size of La2O3 and CeO2 is selected to be 0.5um.

[0051] The mixture was fully mixed in a mixer for 8 hours, dried at 80°C and sieved to obtain a uniformly mixed powder.

[0052] Step 2: Press The mixed powder is processed by cold isostatic pressing to obtain a green body; during the pressing process, the pressure is 250 MPa and the holding time is 10 minutes.

[0053] Step 3: Sintering The green compact is sintered to obtain a sintered compact, which is nearly fully densified, with an actual density greater than 98% TD. In this step, a rod with a specification of φ80 is finally obtained in this embodiment.

[0054] A medium frequency induction furnace is used for sintering, and high-purity hydrogen is used as the atmosphere.

[0055] Sintering is carried out in three stages: low-temperature pre-sintering to remove moisture from the material, medium-temperature sintering to control density, and high-temperature sintering to control grain size.

[0056] The temperature of the low-temperature pre-sintering stage is 500°C, and the temperature is kept for 4 hours; the temperature of the medium-temperature sintering stage is 1600°C, and the temperature is kept for 6 hours; the temperature of the high-temperature sintering stage is 2400°C, and the temperature is kept for 3 hours.

[0057] Step 4: Hot working The sintered blank was heat-treated to eliminate sintering porosity. During the heat treatment, the blanking temperature was 1400°C, the deformation was 40% for the first pass, and the cumulative processing rate for multiple passes was 70%. The passes were reheated and held for 8 minutes between passes. In this step, the alloy bar with a specification of φ40 was finally obtained in this embodiment.

[0058] Step 5: Annealing Eliminate processing stress and prevent stress cracking. Annealing temperature is 1300℃ and kept for 1 hour to finally obtain low-oxygen high-performance tungsten alloy.

[0059] Example 4 Step 1: Mixing La2O3 and CeO2 are added to tungsten powder and mixed to obtain a uniform mixed powder; in the mixed powder, the content of La2O3 is 0.75%, and the content of CeO2 is 0.5%; the tungsten powder is selected with a purity of ≥99.95% and a particle size of 2μm (D50), and the particle size of La2O3 and CeO2 is selected to be 0.5um.

[0060] The mixture was fully mixed in a mixer for 10 hours, dried at 80°C and sieved to obtain a uniformly mixed powder.

[0061] Step 2: Press The mixed powder is processed by cold isostatic pressing to obtain a green body; during the pressing process, the pressure is 200 MPa and the holding time is 10 minutes.

[0062] Step 3: Sintering The green compact is sintered to obtain a sintered compact, which is nearly fully densified, with an actual density greater than 98% TD. In this step, a rod with a specification of φ80 is finally obtained in this embodiment.

[0063] A medium frequency induction furnace is used for sintering, and high-purity hydrogen is used as the atmosphere.

[0064] Sintering is carried out in three stages: low-temperature pre-sintering to remove moisture from the material, medium-temperature sintering to control density, and high-temperature sintering to control grain size.

[0065] The temperature of the low-temperature pre-sintering stage is 850°C, which is kept warm for 3 hours; the temperature of the medium-temperature sintering stage is 1600°C, which is kept warm for 7 hours; and the temperature of the high-temperature sintering stage is 2200°C, which is kept warm for 3 hours.

[0066] Step 4: Hot working The sintered billet was heat-treated to eliminate sintering porosity. During the heat treatment, the billet temperature was 1450°C, the deformation was 35% for the first pass, and the cumulative processing rate for multiple passes was 70%. The billet was reheated and held for 10 minutes between passes. In this step, the alloy bar with a specification of φ40 was finally obtained in this embodiment.

[0067] Step 5: Annealing Eliminate processing stress and prevent stress cracking. Annealing temperature is 1250℃ and kept for 1.5h to finally obtain low-oxygen high-performance tungsten alloy.

[0068] Example 5 Step 1: Mixing La2O3 and CeO2 are added to tungsten powder and mixed to obtain a uniform mixed powder; in the mixed powder, the content of La2O3 is 0.75%, and the content of CeO2 is 0.3%; the tungsten powder is selected with a purity of ≥99.95% and a particle size of 1μm (D50), and the particle size of La2O3 and CeO2 is selected to be 0.6um.

[0069] The mixture was fully mixed in a mixer for 10 hours, dried at 80°C and sieved to obtain a uniformly mixed powder.

[0070] Step 2: Press The mixed powder is processed by cold isostatic pressing to obtain a green body; during the pressing process, the pressure is 150 MPaMPa and the holding time is 12 minutes.

[0071] Step 3: Sintering The green compact is sintered to obtain a sintered compact, which is nearly fully densified, with an actual density greater than 98% TD. In this step, a rod with a specification of φ80 is finally obtained in this embodiment.

[0072] A medium frequency induction furnace is used for sintering, and high-purity hydrogen is used as the atmosphere.

[0073] Sintering is carried out in three stages: low-temperature pre-sintering to remove moisture from the material, medium-temperature sintering to control density, and high-temperature sintering to control grain size.

[0074] The temperature of the low-temperature pre-sintering stage is 850°C, which is kept warm for 2 hours; the temperature of the medium-temperature sintering stage is 1700°C, which is kept warm for 7 hours; and the temperature of the high-temperature sintering stage is 2000°C, which is kept warm for 4 hours.

[0075] Step 4: Hot working The sintered billet was heat-treated to eliminate sintering porosity. During the heat treatment, the billet temperature was 1450°C, the deformation was 30% for the first pass, and the cumulative processing rate for multiple passes was 80%. Between passes, the billet was reheated and held for 10 minutes. In this step, the alloy bar with a specification of φ40 was finally obtained.

[0076] Step 5: Annealing Eliminate processing stress and prevent stress cracking. Annealing temperature is 1200℃ and kept for 2h to finally obtain low-oxygen high-performance tungsten alloy.

[0077] Example 6 Step 1: Mixing La2O3 and CeO2 are added to tungsten powder and mixed to obtain a uniform mixed powder; in the mixed powder, the content of La2O3 is 0.75%, and the content of CeO2 is 0.1%; the tungsten powder is selected with a purity of ≥99.95% and a particle size of 3μm (D50), and the particle size of La2O3 and CeO2 is selected to be 0.6um.

[0078] The mixture was fully mixed in a mixer for 10 hours, dried at 80°C and sieved to obtain a uniformly mixed powder.

[0079] Step 2: Press The mixed powder is processed by cold isostatic pressing to obtain a green body; during the pressing process, the pressure is 250 MPa and the holding time is 12 minutes.

[0080] Step 3: Sintering The green compact is sintered to obtain a sintered compact, which is nearly fully densified, with an actual density greater than 98% TD. In this step, a rod with a specification of φ80 is finally obtained in this embodiment.

[0081] A medium frequency induction furnace is used for sintering, and high-purity hydrogen is used as the atmosphere.

[0082] Sintering is carried out in three stages: low-temperature pre-sintering to remove moisture from the material, medium-temperature sintering to control density, and high-temperature sintering to control grain size.

[0083] The temperature of the low-temperature pre-sintering stage is 850°C, which is kept warm for 4 hours; the temperature of the medium-temperature sintering stage is 1700°C, which is kept warm for 7 hours; and the temperature of the high-temperature sintering stage is 2400°C, which is kept warm for 3 hours.

[0084] Step 4: Hot working The sintered billet was heat-treated to eliminate sintering porosity. During the heat treatment, the billet temperature was 1500°C, the deformation was 35% for the first pass, and the cumulative processing rate for multiple passes was 80%. Between passes, the billet was reheated and held for 12 minutes. In this step, the alloy bar with a specification of φ40 was finally obtained in this embodiment.

[0085] Step 5: Annealing Eliminate processing stress and prevent stress cracking. Annealing temperature is 1200℃ and kept for 2h to finally obtain low-oxygen high-performance tungsten alloy.

[0086] Example 7 Step 1: Mixing La2O3 and CeO2 are added to tungsten powder and mixed to obtain a uniform mixed powder; in the mixed powder, the content of La2O3 is 0.7%, and the content of CeO2 is 0.2%; the tungsten powder is selected with a purity of ≥99.95% and a particle size of 3μm (D50), and the particle size of La2O3 and CeO2 is selected to be 0.6um.

[0087] The mixture was fully mixed in a mixer for 10 hours, dried at 80°C and sieved to obtain a uniformly mixed powder.

[0088] Step 2: Press The mixed powder is processed by cold isostatic pressing to obtain a green body; during the pressing process, the pressure is 200 MPa and the holding time is 12 minutes.

[0089] Step 3: Sintering The green compact is sintered to obtain a sintered compact, which is nearly fully densified, with an actual density greater than 98% TD. In this step, a rod with a specification of φ80 is finally obtained in this embodiment.

[0090] A medium frequency induction furnace is used for sintering, and high-purity hydrogen is used as the atmosphere.

[0091] Sintering is carried out in three stages: low-temperature pre-sintering to remove moisture from the material, medium-temperature sintering to control density, and high-temperature sintering to control grain size.

[0092] The temperature of the low-temperature pre-sintering stage is 500°C, which is kept warm for 3 hours; the temperature of the medium-temperature sintering stage is 1700°C, which is kept warm for 6 hours; and the temperature of the high-temperature sintering stage is 2200°C, which is kept warm for 4 hours.

[0093] Step 4: Hot working The sintered billet was heat-treated to eliminate sintering porosity. During the heat treatment, the billet temperature was 1400°C, the deformation was 35% for the first pass, and the cumulative processing rate for multiple passes was 80%. The billet was reheated and held for 8 minutes between passes. In this step, the alloy bar with a specification of φ40 was finally obtained in this embodiment.

[0094] Step 5: Annealing Eliminate processing stress and prevent stress cracking. Annealing temperature is 1250℃ and kept for 2h to finally obtain low-oxygen high-performance tungsten alloy.

[0095] Example 8 Step 1: Mixing La2O3 and CeO2 are added to tungsten powder and mixed to obtain a uniform mixed powder; in the mixed powder, the content of La2O3 is 0.5%, and the content of CeO2 is 0.5%; the tungsten powder is selected with a purity of ≥99.95% and a particle size of 3μm (D50), and the particle size of La2O3 and CeO2 is selected to be 0.6um.

[0096] The mixture was fully mixed in a mixer for 10 hours, dried at 80°C and sieved to obtain a uniformly mixed powder.

[0097] Step 2: Press The mixed powder is processed by cold isostatic pressing to obtain a green body; during the pressing process, the pressure is 150 MPa and the holding time is 12 minutes.

[0098] Step 3: Sintering The green compact is sintered to obtain a sintered compact, which is nearly fully densified, with an actual density greater than 98% TD. In this step, a rod with a specification of φ80 is finally obtained in this embodiment.

[0099] A medium frequency induction furnace is used for sintering, and high-purity hydrogen is used as the atmosphere.

[0100] Sintering is carried out in three stages: low-temperature pre-sintering to remove moisture from the material, medium-temperature sintering to control density, and high-temperature sintering to control grain size.

[0101] The temperature of the low-temperature pre-sintering stage is 900°C, which is kept warm for 2 hours; the temperature of the medium-temperature sintering stage is 1700°C, which is kept warm for 7 hours; and the temperature of the high-temperature sintering stage is 2000°C, which is kept warm for 4 hours.

[0102] Step 4: Hot working The sintered blank was heat-treated to eliminate sintering porosity. During the heat treatment, the blanking temperature was 1500°C, the deformation was 30% for the first pass, and the cumulative processing rate for multiple passes was 80%. Between passes, the blank was reheated and held for 10 minutes. In this step, the alloy bar with a specification of φ40 was finally obtained in this embodiment.

[0103] Step 5: Annealing Eliminate processing stress and prevent stress cracking. Annealing temperature is 1200℃ and kept for 2h to finally obtain low-oxygen high-performance tungsten alloy.

[0104] Example 9 Step 1: Mixing La2O3 and CeO2 are added to tungsten powder and mixed to obtain a uniform mixed powder; in the mixed powder, the content of La2O3 is 0.5%, and the content of CeO2 is 0.3%; the tungsten powder is selected with a purity of ≥99.95% and a particle size of 3μm (D50), and the particle size of La2O3 and CeO2 is selected to be 0.6um.

[0105] The mixture was fully mixed in a mixer for 10 hours, dried at 80°C and sieved to obtain a uniformly mixed powder.

[0106] Step 2: Press The mixed powder is processed by cold isostatic pressing to obtain a green body; during the pressing process, the pressure is 200 MPa and the holding time is 8 minutes.

[0107] Step 3: Sintering The green compact is sintered to obtain a sintered compact, which is nearly fully densified, with an actual density greater than 98% TD. In this step, a rod with a specification of φ80 is finally obtained in this embodiment.

[0108] A medium frequency induction furnace is used for sintering, and high-purity hydrogen is used as the atmosphere.

[0109] Sintering is carried out in three stages: low-temperature pre-sintering to remove moisture from the material, medium-temperature sintering to control density, and high-temperature sintering to control grain size.

[0110] The temperature of the low-temperature pre-sintering stage is 1200°C, which is kept warm for 3 hours; the temperature of the medium-temperature sintering stage is 1500°C, which is kept warm for 8 hours; and the temperature of the high-temperature sintering stage is 2200°C, which is kept warm for 3 hours.

[0111] Step 4: Hot working The sintered blank was heat-treated to eliminate sintering porosity. During the heat treatment, the blanking temperature was 1400°C, the deformation was 40% for the first pass, and the cumulative processing rate for multiple passes was 70%. The blank was reheated and held for 10 minutes between passes. In this step, the alloy bar with a specification of φ40 was finally obtained in this embodiment.

[0112] Step 5: Annealing To eliminate processing stress and prevent stress cracking, the annealing temperature is set at 1300℃ and kept for 1.5h to finally obtain low-oxygen high-performance tungsten alloy.

[0113] In order to test the actual effect, the composition index and microstructure are specially assessed.

[0114] Tungsten alloy materials comply with industry standards. Besides the normal formation of La2O3 and Ce2O3, the additional oxygen content must be less than 50 PPM, and the remaining impurities must be below 0.05%. The tungsten alloy materials in the above examples all meet these standards.

[0115] Table 1: Statistics of oxides and oxygen content in each example before sintering (%) Table 2: Statistics of oxides and oxygen content in each example after sintering (%) It can be seen from Table 1 and Table 2 that the oxide ratio after sintering is slightly less than the added amount. Since the vapor pressure of rare earth oxide is higher than that of tungsten during the sintering process (temperature is higher than 2000℃), it will evaporate slightly. The addition ratio of La2O3 and CeO2 is 2:1, which is appropriate. When the CeO2 addition amount is 0.3~0.5%, the oxygen content is relatively low, achieving the expected effect.

[0116] like Figure 2 As shown, the number of grains in the sintered structure of pure tungsten φ80 rod is about 1500 / mm 2 .

[0117] like Figure 3 As shown, the number of grains in the sintered structure of the tungsten-lanthanum-cerium alloy using this technical solution is 5000 / mm 2 .

[0118] pass Figure 2 and Figure 3 It can be seen from the comparison that after adding the alloy, the sintered structure of the material is uniform and fine, and the grains are more than 3 times that of pure tungsten.

[0119] like Figure 4 As shown in the figure, the second phase of the tungsten-lanthanum-cerium alloy using this technical solution is evenly distributed, and the sintered density reaches 18.5g / cm 3 , reaching 98% of the theoretical density (the density of normal sintered tungsten materials is 95% of the theoretical density). This shows that after adding alloying elements, tungsten, lanthanum, and cerium have obvious grain refinement effects, and the density and uniformity are very good.

[0120] like Figure 5 As shown, pure tungsten φ40 rod has been recrystallized at 1500℃, with the number of grains being about 1500 / mm 2， The material structure is uneven, and some parts are coarse, close to 50um. This shows that without the addition of alloying elements, the recrystallization temperature of the material is relatively low.

[0121] like Figure 6 As shown, the tungsten-lanthanum-cerium alloy using this technical solution exhibits a fine structure and narrow grain boundaries at 1500°C, with no recrystallization observed, and the material retains its processed structure. This demonstrates that the addition of alloying elements significantly increases the material's recrystallization temperature, resulting in a fine, uniform structure, achieving the desired results.

Claims

1. Low oxygen high performance tungsten alloy preparation process, characterized by: To implement it, follow these steps: Step 1, mixing: adding La2O3 and CeO2 to tungsten powder and mixing to obtain a uniform mixed powder; the mixed powder has a La2O3 content of 0.5% to 1% and a CeO2 content of 0.1% to 0.5%; Step 2: Pressing: The mixed powder is processed by cold isostatic pressing to obtain a green body; Step 3, sintering: sintering the green compact to obtain a sintered compact, wherein the sintered compact is nearly fully densified; Step 4, thermal processing: performing thermal processing on the sintered blank to eliminate sintering pores; Step 5: Annealing: Eliminate processing stress, prevent stress cracking, and ultimately obtain low-oxygen high-performance tungsten alloy.

2. The process for preparing low-oxygen high-performance tungsten alloy according to claim 1, wherein: The tungsten powder has a purity of ≥99.95% and a particle size of 1-3 μm (D50), and the La2O3 and CeO2 have a particle size of 0.4 μm-0.6 μm.

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

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

5. The process for preparing low-oxygen high-performance tungsten alloy according to claim 1, wherein: The step 3 is performed by using a medium frequency induction furnace for sintering, and the atmosphere is high-purity hydrogen.

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

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

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

9. The process for preparing low-oxygen high-performance tungsten alloy according to claim 1, wherein: During the hot working in step 4, the blanking temperature is 1400° C.-1500° C., the deformation amount is 30%-40% for the first pass, the cumulative processing rate for multiple passes is 60-80%, and the furnace is reheated and kept warm for 8 minutes-12 minutes between passes.

10. The process for preparing low-oxygen high-performance tungsten alloy according to claim 1, characterized in that: The annealing temperature in step 5 is 1200-1300° C. and the temperature is kept for 1 hour to 2 hours.

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