Process for improving the density of tungsten-nickel-copper alloy by low-temperature cryogenic treatment
By employing cryogenic treatment and vacuum heating processes, the problem of density discrepancies in tungsten-nickel-copper alloys was resolved, resulting in high bonding strength and improved mechanical properties that meet standard requirements.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- XIAN HUASHAN TUNGSTEN PROD CO LTD
- Filing Date
- 2023-12-27
- Publication Date
- 2026-07-21
AI Technical Summary
Existing technologies have problems with density in the production of tungsten-nickel-copper alloys. In particular, the poor wettability of copper and tungsten leads to weak bonding, and repeated sintering cannot effectively improve the density, resulting in substandard products.
The process employs a cryogenic treatment, which includes liquid nitrogen cryogenic treatment and vacuum heating after the first sintering, combined with a stirring mixer and the use of paraffin wax, to ensure that the tungsten-copper alloy is fully miscible at high temperatures and rapidly cooled, preserving its microstructure and removing harmful hydrogen elements.
It improves the bonding strength and density of tungsten-nickel-copper alloy, enhances mechanical properties, prevents alloy cracking, and meets the density requirements of American Standard ASTM T 21014.
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Figure CN117947299B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of powder metallurgy technology, specifically to a process for increasing the density of tungsten-nickel-copper alloys through cryogenic treatment. Background Technology
[0002] Tungsten-nickel-copper alloys are formed by adding nickel and copper to tungsten, or by adding other metallic elements. Typically, the nickel to copper ratio in tungsten-nickel-copper alloys is 3:2. Tungsten-nickel-copper alloys are non-ferromagnetic and have relatively good electrical and thermal conductivity, making them suitable for applications with special requirements, such as gyroscope rotors and components of other devices and instruments that operate under magnetic fields, electrical contacts in high-voltage electrical switches, and electrodes for electrical discharge machining. However, due to the poor wettability of both copper and tungsten, density discrepancies frequently occur during the production of tungsten-nickel-copper alloys. To eliminate this problem, most companies use repeated sintering methods. However, this method can only treat severely under-sintered tungsten-nickel-copper alloys with incorrect density to achieve the required density. It has no effect on un-under-sintered tungsten-nickel-copper alloys with incorrect density; repeated sintering cannot improve the sintered density, leading to product defects and significant economic losses for companies.
[0003] Therefore, in order to reduce density discrepancies caused by under-sintering and minimize losses, existing technologies often employ cold treatment after preliminary sintering to improve hardness, toughness, and fatigue impact resistance. Essentially, this increases the sintering density of the alloy. For example, the patent document CN102534353B describes a low-chromium multi-element alloy casting and its preparation method, which uses oil cooling to lower the surface temperature of the low-chromium multi-element alloy casting ball to below 250°C. However, this involves a small amount of tungsten-nickel-copper alloy, with most bonding relying on iron sintering. Therefore, for high-content, high-density tungsten-nickel-copper alloys, the sintering density during oil cooling can still lead to the separation of tungsten and copper, resulting in a loose bond between their microstructures. Thus, a better process is needed to address the poor compatibility of tungsten and copper during the cooling process. Summary of the Invention
[0004] In view of this, the present invention provides a process for improving the density of tungsten-nickel-copper alloy through cryogenic treatment, which not only enables the tungsten-copper alloy to have higher bonding strength, but also removes harmful hydrogen elements from the tungsten-nickel-copper alloy, effectively improving the density of the tungsten-nickel-copper alloy.
[0005] This invention provides a process for increasing the density of tungsten-nickel-copper alloy by cryogenic treatment, which includes a first calcination and a second calcination of the tungsten-nickel-copper alloy. After the first calcination and before the second calcination, a liquid nitrogen cryogenic treatment is performed, and the treatment time of the liquid nitrogen cryogenic treatment is 5-30 seconds. The tungsten-nickel-copper alloy comprises 90%-97% tungsten metal and 3%-10% nickel metal and copper metal, wherein the ratio of nickel to copper is 2:1-2.5:1.
[0006] After the first high-temperature heating treatment, the tungsten alloy and copper alloy are fully miscible at high temperature, and tungsten and copper can form a tightly bonded microstructure. The key technical point of this invention is to use liquid nitrogen for rapid low-temperature cooling of the tungsten-copper microstructure to fully preserve this microstructure. Then, vacuum heating is performed to remove the harmful hydrogen elements introduced into the nickel-copper alloy during the first sintering process, thereby increasing the density of the tungsten-nickel-copper alloy and improving the overall mechanical properties of the tungsten-nickel-copper alloy, thus solving the problem of insufficient density in nickel-free copper alloys.
[0007] The underlying principle behind the preservation of the microstructure by cryogenic liquid nitrogen cooling described above lies in the fact that high-temperature heating allows tungsten and copper to fully dissolve, forming a solid solution. At high temperatures, the mutual solubility of the solid solution is usually supersaturated, meaning the solute concentration is much higher than the solubility in equilibrium. Therefore, when the tungsten-nickel-copper alloy is rapidly cooled, the solute atoms are forced to remain in the solid solution under non-equilibrium conditions, forming a supersaturated state. This supersaturated state plays an important role in preserving the microstructure. Rapid cooling can limit the time for solute atoms to rearrange in the solid solution and hinder grain growth and phase separation. The rapid decrease in cooling rate can cause atoms to be fixed in their original positions, limiting grain size growth and phase interface formation. Therefore, rapid cryogenic cooling with liquid nitrogen effectively preserves the microstructure formed by mutual solubility at high temperatures.
[0008] Furthermore, the raw materials for the tungsten-nickel-copper alloy are tungsten powder, nickel powder, and copper powder, and the tungsten-nickel-copper alloy is pretreated through a mixing process before the first calcination.
[0009] Furthermore, the specific steps of the powder mixing process are as follows: Weigh tungsten powder, nickel powder, and copper powder, and put them into a stirring mixer for dry grinding and mixing to obtain a mixed powder. Add paraffin wax to the mixed powder, heat and mix evenly, and then mold it to obtain an alloy billet.
[0010] Furthermore, the dry grinding and mixing time is 3 hours, and the paraffin wax accounts for 2% of the weight of the mixed powder.
[0011] Through the above steps, the mixing time is greatly shortened by using a stirring mixer. After mixing, 2% paraffin is added, melted at a certain temperature and mixed evenly to facilitate the molding of tungsten-nickel-copper alloy, followed by degumming.
[0012] Furthermore, the sintering atmosphere for the first calcination is hydrogen.
[0013] Furthermore, the calcination temperature for the first calcination is 1300℃-1380℃, and the holding time is 60min-90min.
[0014] Furthermore, the sintering atmosphere during the second calcination is a vacuum.
[0015] Furthermore, the vacuum degree of the second calcination is 10. -1 Pa~10 -2 Pa.
[0016] Furthermore, the sintering temperature of the second sintering is 900℃-1000℃, and the holding time is 3h-7h.
[0017] In summary, this application has at least one of the following beneficial technical effects compared with the prior art: 1. The present invention can effectively preserve the microstructure of tungsten-nickel-copper alloy under high temperature after using liquid nitrogen cryogenic treatment. Through reasonable liquid nitrogen cryogenic immersion and vacuum heating treatment, not only is the bonding between tungsten and copper better, but also the harmful hydrogen elements on the nickel-copper alloy phase are removed, thus solving the problems of low bonding density and poor mechanical properties of tungsten-nickel-copper alloy in one fell swoop.
[0018] 2. The present invention also effectively shortens the mixing time by using a stirring mixer and adds paraffin wax to the mixture to ensure the formation of the tungsten nickel copper alloy powder blank, which is convenient for subsequent molding and degumming processes and will not deform. Therefore, it is extremely convenient for the firing of alloy powder.
[0019] 3. In the second calcination of this invention, the temperature is reduced to below 1100℃ to ensure that the tungsten-nickel-copper alloy does not re-enter the solid solution state. Therefore, harmful hydrogen is removed without damaging the alloy density, which enhances the mechanical properties of the tungsten-nickel-copper alloy and prevents the alloy from cracking. Attached Figure Description
[0020] Figure 1 This is a microstructure image of the tungsten-nickel-copper alloy blank in Embodiment 1 of the present invention; Figure 2 This is a microstructure image of the finished tungsten-nickel-copper alloy obtained after furnace cooling in Embodiment 1 of the present invention. Figure 3 This is a microstructure image of the tungsten-nickel-copper alloy blank in Example 7 of the present invention; Figure 4 This is a microstructure image of the finished tungsten-nickel-copper alloy obtained after furnace cooling in Example 7 of the present invention. Figure 5This is a microstructure image of the tungsten-nickel-copper alloy blank in Embodiment 8 of the present invention; Figure 6 This is a microstructure image of the finished tungsten-nickel-copper alloy obtained after furnace cooling in Embodiment 8 of the present invention. Figure 7 This is a line graph showing the alloy density between Embodiments 1 to 6 and Comparative Examples 1 to 4 of the present invention. Detailed Implementation
[0021] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the following will be described in conjunction with the accompanying drawings of the embodiments of the present invention. Figure 1-4 The technical solutions of the embodiments of the present invention will be clearly and completely described herein. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the described embodiments of the present invention are within the scope of protection of the present invention.
[0022] The following will provide a detailed and clear explanation of how the present invention is specifically implemented, thereby demonstrating that the present application has the aforementioned beneficial effects; Firstly, the alloy targeted by the process of this invention is a tungsten-nickel-copper alloy, in which the tungsten alloy accounts for more than 90%.
[0023] The specific implementation steps of this process are as follows: Step 1: Weigh the raw materials according to the ratio of 90%-97% tungsten powder, 3%-10% nickel powder and copper powder, where the mass ratio of nickel powder to copper powder is 2:1-2.5:1. Then, dry grind the tungsten powder, nickel powder and copper powder in a mixer for 3 hours. After mixing, add 2% by weight of paraffin wax to the mixture and heat it until the paraffin wax melts and mixes evenly with the mixture. Then, use a molding method to press the mixture into a 20mm×200mm (diameter×length) tungsten-nickel-copper alloy blank. After that, perform debinding treatment to obtain the tungsten-nickel-copper alloy pressed blank.
[0024] In this step, the tungsten powder, nickel powder, and copper powder are all commercially available pure alloy powders without any other additional substances. The paraffin wax is mixed during the heating stage and heating is stopped when the paraffin wax is no longer visible. After the mixture is evenly mixed, the temperature is lowered before the alloy pressing blank is pressed. The pressing shape is designed according to the required workpiece.
[0025] Step 2: Place the tungsten-nickel-copper alloy pressed billet in a muffle furnace and introduce hydrogen gas to keep the tungsten-nickel-copper alloy pressed billet in a hydrogen atmosphere. Heat the billet to 1300℃-1380℃ and hold it for 60min-90min to obtain a tungsten-nickel-copper alloy rough billet.
[0026] The main purpose of this step is to mix tungsten metal powder and copper metal powder to form a tightly bonded structure. Therefore, the heating time should be slightly adjusted depending on the material and heating conditions.
[0027] Step 3: Remove the tungsten-nickel-copper alloy billet from the muffle furnace and subject it to cryogenic treatment with liquid nitrogen. The high-temperature tungsten-nickel-copper alloy billet is completely immersed in liquid nitrogen for 5-30 seconds. In this step, the tungsten-nickel-copper alloy must be subjected to liquid nitrogen cryogenic treatment at a very fast speed to avoid excessive temperature drop due to natural cooling. The immersion time should also be controlled, and the shorter the better.
[0028] Step 4: The nickel-free copper blank, after being cryogenically treated with liquid nitrogen, is subjected to vacuum heating at a temperature of 900℃-1000℃ and a vacuum degree of 10. -1 Pa~10 -2 Pa, hold for 3-7 hours, then turn off the heating and allow to cool naturally to obtain a tungsten-nickel-copper alloy.
[0029] This step primarily removes harmful hydrogen substances from the nickel-copper alloy, thereby enhancing its mechanical properties.
[0030] The following method uses more detailed and strict specifications, including the component ratios, temperature, time, and other variables in each step, to prepare the corresponding tungsten-nickel-copper alloy and measure its density.
[0031] Example 1 This embodiment provides a process for improving the density of tungsten-nickel-copper alloys through cryogenic treatment. The specific implementation method is as follows: Step 1: Weigh the raw materials according to the ratio of 90% tungsten powder, 7% nickel powder, and 3% copper powder. Then, dry grind the tungsten powder, nickel powder, and copper powder in a mixer for 3 hours. After mixing, add 2% paraffin wax by weight of the total mixture and heat until the paraffin wax melts and mixes evenly with the mixture. Then, use a molding method to press the mixture into a 20mm×200mm (diameter×length) tungsten-nickel-copper alloy blank. After debinding, the tungsten-nickel-copper alloy pressed blank is obtained.
[0032] Step 2: Place the tungsten-nickel-copper alloy pressed billet in a muffle furnace and introduce hydrogen gas to keep the tungsten-nickel-copper alloy pressed billet in a hydrogen atmosphere. Heat the billet to 1300℃ and hold for 90 minutes to obtain a tungsten-nickel-copper alloy rough billet.
[0033] Step 3: Remove the tungsten-nickel-copper alloy blank from the muffle furnace and subject it to liquid nitrogen cryogenic treatment. The high-temperature tungsten-nickel-copper alloy blank is completely immersed in liquid nitrogen for 5 seconds. Step 4: The nickel-free copper blank, after being cryogenically treated with liquid nitrogen, is subjected to vacuum heating at a temperature of 1000℃ and a vacuum degree of 10. -2 Pa, heat treatment time is 7h, then heating is turned off, and after natural cooling, tungsten-nickel-copper alloy is obtained.
[0034] Example 2 The difference between this embodiment and Embodiment 1 is that the duration of the liquid nitrogen cryogenic treatment has been changed. The specific changes are as follows: Step 3: Remove the tungsten-nickel-copper alloy blank from the muffle furnace and subject it to liquid nitrogen cryogenic treatment. The high-temperature tungsten-nickel-copper alloy blank is completely immersed in liquid nitrogen for 10 seconds. Example 3 The difference between this embodiment and Embodiment 1 is that the duration of the liquid nitrogen cryogenic treatment has been changed. The specific changes are as follows: Step 3: Remove the tungsten-nickel-copper alloy billet from the muffle furnace and subject it to cryogenic treatment with liquid nitrogen. The high-temperature tungsten-nickel-copper alloy billet is completely immersed in liquid nitrogen for 15 seconds. Example 4 The difference between this embodiment and Embodiment 1 is that the duration of the liquid nitrogen cryogenic treatment has been changed. The specific changes are as follows: Step 3: Remove the tungsten-nickel-copper alloy blank from the muffle furnace and subject it to cryogenic treatment with liquid nitrogen. The high-temperature tungsten-nickel-copper alloy blank is completely immersed in liquid nitrogen for 20 seconds. Example 5 The difference between this embodiment and Embodiment 1 is that the duration of the liquid nitrogen cryogenic treatment has been changed. The specific changes are as follows: Step 3: Remove the tungsten-nickel-copper alloy blank from the muffle furnace and subject it to cryogenic treatment with liquid nitrogen. The high-temperature tungsten-nickel-copper alloy blank is completely immersed in liquid nitrogen for 25 seconds. Example 6 The difference between this embodiment and Embodiment 1 is that the duration of the liquid nitrogen cryogenic treatment has been changed. The specific changes are as follows: Step 3: Remove the tungsten-nickel-copper alloy billet from the muffle furnace and subject it to cryogenic treatment with liquid nitrogen. The high-temperature tungsten-nickel-copper alloy billet is completely immersed in liquid nitrogen for 30 seconds. Example 7 This embodiment alters the proportions of each component in the tungsten-nickel-copper alloy and changes the pressing model. Accordingly, to obtain a tungsten-nickel-copper alloy with higher alloy density, relevant parameters are adjusted. The specific implementation steps are as follows: This embodiment provides a process for improving the density of tungsten-nickel-copper alloys through cryogenic treatment. The specific implementation method is as follows: Step 1: Weigh the raw materials according to the ratio of 93% tungsten powder, 4.7% nickel powder, and 2.3% copper powder. Then, dry grind the tungsten powder, nickel powder, and copper powder in a mixer for 3 hours. After mixing, add 2% paraffin wax by weight of the total mixture and heat until the paraffin wax melts and mixes evenly with the mixture. Then, use a molding method to press the mixture into a 30mm×100mm (diameter×length) tungsten-nickel-copper alloy blank. After debinding, the tungsten-nickel-copper alloy pressed blank is obtained.
[0035] Step 2: Place the tungsten-nickel-copper alloy pressed billet in a muffle furnace and introduce hydrogen gas to keep the tungsten-nickel-copper alloy pressed billet in a hydrogen atmosphere. Heat the billet to 1360℃ and hold for 70 minutes to obtain a tungsten-nickel-copper alloy rough billet.
[0036] Step 3: Remove the tungsten-nickel-copper alloy blank from the muffle furnace and subject it to liquid nitrogen cryogenic treatment. The high-temperature tungsten-nickel-copper alloy blank is completely immersed in liquid nitrogen for 5 seconds. Step 4: The nickel-free copper blank, after being cryogenically treated with liquid nitrogen, is subjected to vacuum heating at a temperature of 1000℃ and a vacuum degree of 10. -1 Pa, heat treatment time is 5h, then heating is turned off, and after natural cooling, tungsten-nickel-copper alloy is obtained.
[0037] Example 8 This embodiment alters the proportions of each component in the tungsten-nickel-copper alloy and changes the pressing model. Accordingly, to obtain a tungsten-nickel-copper alloy with higher alloy density, relevant parameters are adjusted. The specific implementation steps are as follows: This embodiment provides a process for improving the density of tungsten-nickel-copper alloys through cryogenic treatment. The specific implementation method is as follows: Step 1: Weigh the raw materials according to the ratio of 95% tungsten powder, 3.4% nickel powder, and 1.6% copper powder. Then, dry grind the tungsten powder, nickel powder, and copper powder in a mixer for 3 hours. After mixing, add 2% paraffin wax by weight of the total mixture and heat until the paraffin wax melts and mixes evenly with the mixture. Then, use a molding method to press the mixture into a 40mm×150mm (diameter×length) tungsten-nickel-copper alloy blank. After debinding, the tungsten-nickel-copper alloy pressed blank is obtained.
[0038] Step 2: Place the tungsten-nickel-copper alloy pressed billet in a muffle furnace and introduce hydrogen gas to keep the tungsten-nickel-copper alloy pressed billet in a hydrogen atmosphere. Heat the billet to 1380℃ and hold for 60 minutes to obtain a tungsten-nickel-copper alloy rough billet.
[0039] Step 3: Remove the tungsten-nickel-copper alloy blank from the muffle furnace and subject it to liquid nitrogen cryogenic treatment. The high-temperature tungsten-nickel-copper alloy blank is completely immersed in liquid nitrogen for 5 seconds. Step 4: The nickel-free copper blank, after being cryogenically treated with liquid nitrogen, is subjected to vacuum heating at a temperature of 1100℃ and a vacuum degree of 10. -2 Pa, heat treatment time is 3h, then heating is turned off, and after natural cooling, tungsten-nickel-copper alloy is obtained.
[0040] Example 9 This embodiment alters the proportions of each component in the tungsten-nickel-copper alloy and changes the pressing model. Accordingly, to obtain a tungsten-nickel-copper alloy with higher alloy density, relevant parameters are adjusted. The specific implementation steps are as follows: This embodiment provides a process for improving the density of tungsten-nickel-copper alloys through cryogenic treatment. The specific implementation method is as follows: Step 1: Weigh the raw materials according to the ratio of 97% tungsten powder, 2% nickel powder, and 1% copper powder. Then, dry grind the tungsten powder, nickel powder, and copper powder in a mixer for 3 hours. After mixing, add 2% paraffin wax by weight of the total mixture and heat until the paraffin wax melts and mixes evenly with the mixture. Then, use a molding method to press the mixture into a 40mm×150mm (diameter×length) tungsten-nickel-copper alloy blank. After debinding, the tungsten-nickel-copper alloy pressed blank is obtained.
[0041] Step 2: Place the tungsten-nickel-copper alloy pressed billet in a muffle furnace and introduce hydrogen gas to keep the tungsten-nickel-copper alloy pressed billet in a hydrogen atmosphere. Heat the billet to 1370℃ and hold for 80 minutes to obtain a tungsten-nickel-copper alloy rough billet.
[0042] Step 3: Remove the tungsten-nickel-copper alloy blank from the muffle furnace and subject it to liquid nitrogen cryogenic treatment. The high-temperature tungsten-nickel-copper alloy blank is completely immersed in liquid nitrogen for 5 seconds. Step 4: The nickel-free copper blank, after being cryogenically treated with liquid nitrogen, is subjected to vacuum heating at a temperature of 1100℃ and a vacuum degree of 10. -2 Pa, heat treatment time is 4 hours, then heating is turned off, and after natural cooling, tungsten-nickel-copper alloy is obtained.
[0043] Comparative Example 1 This comparative example investigates the effect of shorter liquid nitrogen cryogenic treatment on the alloy density of tungsten-nickel-copper alloys. The liquid nitrogen treatment time was varied, and the specific implementation steps are as follows: Step 1: Weigh the raw materials according to the ratio of 90% tungsten powder, 7% nickel powder, and 3% copper powder. Then, dry grind the tungsten powder, nickel powder, and copper powder in a mixer for 3 hours. After mixing, add 2% paraffin wax by weight of the total mixture and heat until the paraffin wax melts and mixes evenly with the mixture. Then, use a molding method to press the mixture into a 20mm×200mm (diameter×length) tungsten-nickel-copper alloy blank. After debinding, the tungsten-nickel-copper alloy pressed blank is obtained.
[0044] Step 2: Place the tungsten-nickel-copper alloy pressed billet in a muffle furnace and introduce hydrogen gas to keep the tungsten-nickel-copper alloy pressed billet in a hydrogen atmosphere. Heat the billet to 1300℃ and hold for 90 minutes to obtain a tungsten-nickel-copper alloy rough billet.
[0045] Step 3: Remove the tungsten-nickel-copper alloy blank from the muffle furnace and subject it to cryogenic treatment with liquid nitrogen. The high-temperature tungsten-nickel-copper alloy blank is completely immersed in liquid nitrogen for 3 seconds. Step 4: The nickel-free copper blank, after being cryogenically treated with liquid nitrogen, is subjected to vacuum heating at a temperature of 1000℃ and a vacuum degree of 10. -2 Pa, heat treatment time is 7h, then heating is turned off, and after natural cooling, tungsten-nickel-copper alloy is obtained.
[0046] Comparative Example 2 The difference between this comparative example and Comparative Example 1 is that the liquid nitrogen treatment time was reduced. The specific changes are as follows: Step 3: Remove the tungsten-nickel-copper alloy blank from the muffle furnace and subject it to cryogenic treatment with liquid nitrogen. The high-temperature tungsten-nickel-copper alloy blank is completely immersed in liquid nitrogen for 2 seconds.
[0047] Comparative Example 3 This comparative example investigates the effect of prolonged liquid nitrogen cryogenic treatment on the alloy density of tungsten-nickel-copper alloys. The liquid nitrogen treatment time was varied, and the specific implementation steps are as follows: Step 1: Weigh the raw materials according to the ratio of 90% tungsten powder, 7% nickel powder, and 3% copper powder. Then, dry grind the tungsten powder, nickel powder, and copper powder in a mixer for 3 hours. After mixing, add 2% paraffin wax by weight of the total mixture and heat until the paraffin wax melts and mixes evenly with the mixture. Then, use a molding method to press the mixture into a 20mm×200mm (diameter×length) tungsten-nickel-copper alloy blank. After debinding, the tungsten-nickel-copper alloy pressed blank is obtained.
[0048] Step 2: Place the tungsten-nickel-copper alloy pressed billet in a muffle furnace and introduce hydrogen gas to keep the tungsten-nickel-copper alloy pressed billet in a hydrogen atmosphere. Heat the billet to 1300℃ and hold for 90 minutes to obtain a tungsten-nickel-copper alloy rough billet.
[0049] Step 3: Remove the tungsten-nickel-copper alloy billet from the muffle furnace and subject it to cryogenic treatment with liquid nitrogen. The high-temperature tungsten-nickel-copper alloy billet is completely immersed in liquid nitrogen for 35 seconds. Step 4: The nickel-free copper blank, after being cryogenically treated with liquid nitrogen, is subjected to vacuum heating at a temperature of 1000℃ and a vacuum degree of 10. -2 Pa, heat treatment time is 7h, then heating is turned off, and after natural cooling, tungsten-nickel-copper alloy is obtained.
[0050] Comparative Example 4 The difference between this comparative example and Comparative Example 3 is that the liquid nitrogen treatment time was increased. The specific changes are as follows: Step 3: Remove the tungsten-nickel-copper alloy blank from the muffle furnace and subject it to cryogenic treatment with liquid nitrogen. The high-temperature tungsten-nickel-copper alloy blank is completely immersed in liquid nitrogen for 40 seconds.
[0051] Experiments and Analysis The alloy density of the tungsten-nickel-copper alloys in the above embodiments and comparative examples was tested according to the American standard AMST 21014 "Tungsten matrix metals, high density".
[0052] The following is the test data. In Example 1, parallel experiments were conducted on tungsten-nickel-copper alloy blanks that had not undergone liquid nitrogen cryogenic treatment after step two. The results showed an alloy density of 16.6 g / cm³. 3 .
[0053] The finished tungsten-nickel-copper alloy of Example 1 has an alloy density of 17.0 g / cm³. 3 It meets the requirements of AMS T 21014 "Tungsten-based metals, high density" at 17.05±0.2 g / cm³. 3 Requirements.
[0054] In Example 7, parallel experiments were conducted on tungsten-nickel-copper alloy blanks that had not undergone liquid nitrogen cryogenic treatment after step two. The results showed an alloy density of 17.3 g / cm³. 3 .
[0055] The finished tungsten-nickel-copper alloy of Example 7 has an alloy density of 17.05 g / cm³. 3 It meets the requirements of AMS T 21014 "Tungsten-based metals, high density" at 17.05±0.35 g / cm³. 3 Requirements.
[0056] In Example 8, parallel experiments were conducted on tungsten-nickel-copper alloy blanks that had not undergone liquid nitrogen cryogenic treatment after step two. The results showed an alloy density of 17.7 g / cm³. 3 .
[0057] The finished tungsten-nickel-copper alloy of Example 8 has an alloy density of 18.05 g / cm³. 3 It meets the requirements of AMS T 21014 "Tungsten-based metals, high density" at 18.05±0.2 g / cm³. 3 Requirements.
[0058] In Example 9, parallel experiments were conducted on tungsten-nickel-copper alloy blanks that had not undergone liquid nitrogen cryogenic treatment after step two. The results showed an alloy density of 18.15 g / cm³. 3 .
[0059] The finished tungsten-nickel-copper alloy of Example 9 has an alloy density of 18.35 g / cm³. 3 It meets the requirements of AMS T 21014 "Tungsten-based metals, high density" at 18.55±0.3 g / cm³. 3 Requirements.
[0060] analyze Figure 1 This is a microstructure image of the tungsten-nickel-copper alloy rod from step three of Example 1. Figure 1 It can be seen that the tungsten particles in the microstructure of the tungsten-nickel-copper alloy rod have been spheroidized, but there are many pores, indicating that the sintering degree of the 90 tungsten-nickel-copper alloy rod is appropriate, but the density is not up to standard.
[0061] Figure 2 The image shows the microstructure of the tungsten-nickel-copper alloy rods obtained after furnace cooling in Example 1. Figure 2 and Figure 1 The comparison shows that the porosity of the tungsten particles in the tungsten-nickel-copper alloy rod is significantly reduced, and the density of the tungsten-nickel-copper alloy rod is increased. This indicates that the process of the present invention improves the density inconsistency in the tungsten-nickel-copper alloy and increases the density of the tungsten-nickel-copper alloy.
[0062] Figure 3 This is a microstructure image of the tungsten-nickel-copper alloy rod from step three of Example 7. Figure 3 It can be seen that the tungsten particles in the microstructure of the tungsten-nickel-copper alloy rod have been spheroidized, but there are many pores, indicating that the sintering degree of the tungsten-nickel-copper alloy rod is appropriate, but the density is not right.
[0063] Figure 4 The image shows the microstructure of the tungsten-nickel-copper alloy rods obtained after furnace cooling in Example 7. Figure 4 and Figure 3The comparison shows that the porosity of the tungsten particles in the tungsten-nickel-copper alloy rod is significantly reduced, and the density of the tungsten-nickel-copper alloy rod is increased. This indicates that the process of the present invention improves the density inconsistency in the tungsten-nickel-copper alloy and increases the density of the tungsten-nickel-copper alloy.
[0064] Figure 5 This is a microstructure image of the tungsten-nickel-copper alloy rod from step three of Example 8. Figure 5 It can be seen that the tungsten particles in the microstructure of the tungsten-nickel-copper alloy rod have been spheroidized, but there are many pores, indicating that the sintering degree of the tungsten-nickel-copper alloy rod is appropriate, but the density is not right.
[0065] Figure 6 The image shows the microstructure of the tungsten-nickel-copper alloy rod obtained after furnace cooling in step four of Example 8. Figure 6 and Figure 5 The comparison shows that the porosity of the tungsten particles in the tungsten-nickel-copper alloy rod is significantly reduced, and the density of the tungsten-nickel-copper alloy rod is increased. This indicates that the process of the present invention improves the density inconsistency in the tungsten-nickel-copper alloy and increases the density of the tungsten-nickel-copper alloy.
[0066] Figure 7 The graphs show the alloy density of Examples 1 to 6 and Comparative Examples 1 to 4. Figure 7 As can be seen, with the increase of liquid nitrogen treatment time, the alloy density deviates more and more from the specifications of the standard alloy. After the time exceeds 30 seconds, the alloy density of the tungsten-nickel-copper alloy no longer meets the requirements of 17.05±0.2 g / cm³ in the American standard AMS T 21014 "Tungsten-based metals, high density". 3 The requirement is that excessive liquid nitrogen cold piercing will cause the grains in the alloy to be too small and the grains to be distributed in layers, thus affecting the toughness of the material and making the tungsten particles have larger pores.
[0067] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.
Claims
1. A process for increasing the density of tungsten-nickel-copper alloy by cryogenic deep treatment at low temperature, comprising first calcination and second calcination of the tungsten-nickel-copper alloy, characterized in that, After the first calcination and before the second calcination, a liquid nitrogen cryogenic treatment was performed, in which the high-temperature tungsten-nickel-copper alloy blank was completely immersed in liquid nitrogen for 5-30 seconds. The first calcination temperature was 1300℃-1380℃, and the holding time was 60-90 minutes. The second calcination temperature was 900℃-1000℃, and the holding time was 3-7 hours. The tungsten-nickel-copper alloy comprises 90%-97% tungsten metal and 3%-10% nickel and copper metal, wherein the ratio of nickel to copper is 2:1-2.5:
1. The raw materials for the tungsten-nickel-copper alloy are tungsten powder, nickel powder and copper powder. The tungsten-nickel-copper alloy is pretreated by a powder mixing process before the first calcination. The specific steps of the powder mixing process are as follows: Weigh tungsten powder, nickel powder, and copper powder, and put them into a stirring mixer for dry grinding and mixing to obtain a mixed powder. Add paraffin wax to the mixed powder, heat and mix evenly, and then mold it to obtain an alloy billet.
2. The process for increasing the density of tungsten nickel copper alloy by cryogenic deep cooling treatment as claimed in claim 1 wherein the process is carried out at a temperature in the range of 1000C to 1200C. The dry grinding and mixing time is 3 hours, and the paraffin wax accounts for 2% of the weight of the mixed powder.
3. The process for increasing the density of tungsten-nickel-copper alloy by cryogenic treatment as described in claim 1, characterized in that: The sintering atmosphere for the first calcination is hydrogen.
4. The process for increasing the density of tungsten-nickel-copper alloy by cryogenic treatment as described in claim 1, characterized in that: The sintering atmosphere for the second calcination is a vacuum.
5. The process for increasing the density of tungsten-nickel-copper alloy by cryogenic treatment as described in claim 4, characterized in that: The vacuum degree of the second calcination is 10 -1 Pa 10 -2 Pa.