A method for producing a tungsten-copper alloy

Abstract

This invention relates to a method for preparing a tungsten-copper alloy, comprising the following steps: According to the composition requirements of the tungsten-copper alloy to be prepared, metallic copper powder, copper oxide powder, and metallic tungsten powder are taken, mixed evenly, and then molded to obtain a pressed blank; the pressed blank is pre-sintered at 750-980℃ under vacuum or inert atmosphere to obtain a first tungsten-copper ingot; the first tungsten-copper ingot is sintered at 1000-1050℃ under hydrogen atmosphere to obtain a second tungsten-copper ingot; the second tungsten-copper ingot is re-pressed to obtain a re-pressed ingot; the re-pressed ingot is hot-extruded to obtain an extruded blank; the extruded blank is rolled to obtain a strip-shaped tungsten-copper alloy. The preparation method of this invention can obtain a high-density tungsten-copper alloy, and can prepare a high-tungsten-content dense tungsten-copper alloy with a tungsten content of 80% or higher. Furthermore, the tungsten-copper alloy obtained by this invention can reach a thickness of about 1 mm and has excellent physical and mechanical properties.

Description

Technical Field

[0001] This invention relates to a method for preparing a tungsten-copper alloy, and more particularly to a method for preparing a dense tungsten-copper alloy, belonging to the field of alloys. Background Technology

[0002] As shown in the tungsten-copper binary phase diagram, the solubility of metallic tungsten and copper is very low, even in the liquid state, almost zero at room temperature. These two metals cannot form alloys, but only hybrid composites, i.e., tungsten-copper pseudo-alloys. Tungsten-copper composites exhibit the superposition and combination of the intrinsic physical properties of the two constituent elements. This characteristic allows for flexible design of their composition, thereby enabling the design and adjustment of their performance, maximizing the strengths and minimizing the weaknesses of the constituent elements. Tungsten-copper composites, composed of highly conductive copper and highly arc-resistant tungsten, possess excellent arc-erosion resistance, making them superior electrode materials for electrical contacts, resistance welding, electrical discharge machining, and plasma spraying. Recent applications include high-speed solid seals and components in various instruments requiring non-magnetic, low-expansion, high-elastic modulus, and radiation shielding properties. Tungsten-copper pseudoalloys, composed of copper (high electrical and thermal conductivity, high ductility) and tungsten (low coefficient of thermal expansion, high temperature resistance), combine the advantages of good electrical and thermal conductivity, low coefficient of thermal expansion, and high softening temperature. This allows them to meet the stringent requirements of large-scale integrated circuits and high-power devices for connectors and wiring. Furthermore, these properties enable them to be well-matched with different semiconductor materials in microelectronic devices, thus avoiding thermal fatigue damage caused by thermal stress.

[0003] Therefore, tungsten-copper composites have become an upgraded replacement product for electronic packaging and computer central processing systems, lead frames for large-scale integrated circuits, heat sink substrates for solid-state microwave tubes, connectors, and microelectronic housing materials. The combination of high thermal conductivity copper and high-temperature strength tungsten gives tungsten-copper composites excellent thermal shock resistance, ablation resistance, and high-temperature cavitation resistance, making them superior materials for rocket nozzles. Tungsten-copper composites have broad application prospects in electrical, electronic, nuclear energy, and military fields.

[0004] Due to the significant difference in melting points between copper and tungsten, and the fact that they can only form pseudo-alloys, they are generally produced using powder metallurgy. Porosity and lack of density are common characteristics of powder metallurgy products. Pores are neither copper nor tungsten, and they reduce the properties of both copper and tungsten, thus reducing the properties of tungsten-copper composites. Eliminating porosity and increasing the density of tungsten-copper composites is a perpetually important research topic for tungsten-copper scientists. In industrial production, densification methods for tungsten-copper composites mainly include: melt infiltration, activated sintering, and hot isostatic pressing. While these methods are effective, they are far from ideal, and still suffer from the following problems: 1. The processes are complex or the equipment is expensive, resulting in low production efficiency and high costs; 2. For applications requiring strict density control, the porosity is still too high, and the density is not ideal.

[0005] Achieving comprehensive improvements in the performance of dense tungsten copper is a key objective for critical applications and has always been a challenging issue in the industry. Solving this problem has not only engineering application value but also theoretical value. Particularly in the electronics industry, tungsten copper sheets used for packaging, with a thickness of only about 1mm and a high tungsten content, face numerous limitations in achieving density, making it a significant industry challenge. Summary of the Invention

[0006] In view of the shortcomings of the prior art, the purpose of this invention is to provide a method for preparing a high-density tungsten-copper alloy.

[0007] To solve the above-mentioned technical problems, the technical solution of the present invention is as follows:

[0008] A method for preparing a tungsten-copper alloy includes the following steps:

[0009] S1. According to the composition requirements of the tungsten-copper alloy to be prepared, take metallic copper powder, copper oxide powder and metallic tungsten powder, mix them evenly, and then mold them to obtain a compact.

[0010] The copper element from the copper powder accounts for 63-95 wt% of the copper element in the tungsten-copper alloy to be prepared, and the remaining copper element in the tungsten-copper alloy to be prepared comes from the copper oxide powder.

[0011] S2. The pressed blank is pre-sintered at 750-980℃ for 120-240 min under vacuum or inert atmosphere to obtain the first tungsten copper ingot;

[0012] S3. The first tungsten copper ingot is sintered at 1000-1050℃ for 150-240 min under hydrogen atmosphere to obtain the second tungsten copper ingot.

[0013] S4. The second tungsten-copper ingot is repressed to obtain a repressed ingot;

[0014] S5. The compounded ingot is hot-extruded to obtain an extruded billet;

[0015] S6. The extruded billet is rolled to obtain a strip-shaped tungsten-copper alloy.

[0016] During pre-sintering, copper oxide powder and metallic copper powder react to form cuprous oxide, which makes oxygen more dispersed in the ingot. Subsequently, cuprous oxide has a strong activating sintering effect during sintering in a reducing atmosphere, resulting in more significant sintering shrinkage and higher density in tungsten copper. More importantly, the activating sintering significantly improves the toughness and ductility of the tungsten copper sintered billet, which is beneficial for subsequent rolling, increases the yield of the product, and yields high-performance tungsten copper alloy products.

[0017] Further, in S1, the median particle size D50 of the copper powder is ≤45μm, preferably 37-45μm, and preferably, the copper powder is electrolytic copper powder; the median particle size D50 of the copper oxide powder is 1-10μm, preferably 2-8μm; and the median particle size D50 of the tungsten powder is 3-7μm, preferably 4-6μm.

[0018] This invention has found that neither coarse nor fine copper powder can achieve the desired effect. Coarse copper powder is detrimental to the uniform distribution of copper and tungsten. Fine copper powder is prone to agglomeration and uneven distribution, and it is also prone to delamination during molding in S1, which is detrimental to improving the yield of the product.

[0019] Copper oxide powder with a median particle size (D50) of 1-10 μm ensures sufficient copper oxidation, facilitating accurate calculation of copper and oxygen content. Copper oxide powder that is too coarse makes it difficult to guarantee sufficient copper oxidation, as the central portion of coarse particles is unlikely to form cuprous oxide. Copper oxide powder that is too fine, such as nano-copper oxide powder, is prone to agglomeration, resulting in uneven distribution of copper and tungsten.

[0020] Further, in S1, the copper element from the copper powder accounts for 78-82 wt% of the copper element in the tungsten-copper alloy to be prepared, and the remaining copper element in the tungsten-copper alloy to be prepared comes from the copper oxide powder (that is, the copper content in the copper oxide powder [equivalent mass fraction of copper oxide powder] is 18-22 wt% of the copper content in the tungsten-copper alloy to be prepared, and the amount of copper oxide powder added can be determined by conversion).

[0021] This invention has found that neither excessively high nor low equivalent mass fractions of copper oxide powder can achieve the most ideal results. When the equivalent mass fraction of copper oxide powder is below 18 wt%, the improvement in the toughness and ductility of the second tungsten copper ingot decreases, making it more prone to cracking during subsequent rolling and resulting in a decrease in yield. When the equivalent mass fraction of copper oxide powder is above 22 wt%, the oxygen content in the compact is too high, which increases the difficulty of reduction and deoxidation during sintering in a hydrogen reducing atmosphere, making it easier for residual oxygen to remain and reducing the sintering quality of tungsten copper.

[0022] Furthermore, the unit pressure during compression molding in S1 is less than the unit pressure during re-compression in S4.

[0023] Furthermore, in S1, the tungsten content in the tungsten-copper alloy to be prepared is 63-95 wt%. The copper content in the tungsten-copper alloy to be prepared is 5-37 wt%.

[0024] Preferably, in S1, the concentration is 2.0-2.5 t / cm 2 Compression molding under unit pressure, more preferably at 2.2-2.4 t / cm 2 Molded under unit pressure.

[0025] Generally, higher pressure helps to obtain a denser compact in compression molding. However, in the specific case of this invention, the research found that the unit pressure of S1 is not necessarily better the higher it is. Excessive unit pressure may lead to a decrease in product quality and toughness. The possible reasons are: if the unit pressure is too high, the compact density increases, but the porosity is too small, reducing the channels for hydrogen to enter in S3. Hydrogen cannot fully enter for reduction, resulting in high oxygen content in the product, loss of activation sintering effect, decreased toughness, and ultimately low yield.

[0026] Furthermore, in S4, at 7.7-8.0 t / cm 2 The pressure is repressurized under a unit pressure, more preferably at 7.8-7.9 t / cm². 2 The pressure is repressurized under the unit pressure.

[0027] Compression molding under a relatively small molding pressure can satisfy the requirements of strength transfer and molding, and also leave a certain gap in the compact to facilitate the smooth entry of hydrogen and the timely discharge of water vapor generated during the subsequent reduction sintering process. By using a larger re-compression pressure, the density of the second tungsten copper ingot can be greatly improved, usually resulting in a relative density of over 97%.

[0028] Furthermore, in S2, the pre-sintering temperature is 945-955℃, and even further, it is 948-952℃, and the pre-sintering time is 150-180min, and even further, it is 160-170min.

[0029] Furthermore, in S3, the sintering temperature is 1010-1040℃, and even further, it is 1020-1030℃, and the sintering time is 180-210min, and even further, it is 190-200min.

[0030] Furthermore, in S4, the thickness of the compounded ingot is 40-300mm, and even more specifically 80-200mm.

[0031] Further, in step S5, the compounded ingot is preheated to 945-955°C, and the extrusion cylinder and die are preheated to 845-855°C. The compounded ingot is then placed in the die for hot extrusion; preferably, the temperature is 7.5-8.5 t / cm. 2 Hot extrusion is performed under unit pressure.

[0032] This invention reveals that when the preheating temperature of the extrusion cylinder and die is below 845°C, the heat from the re-pressed ingot is easily and significantly conducted to the die and extrusion cylinder, causing them to heat up and then rapidly cool down. This results in a rapid increase in extrusion resistance, making extrusion unsuccessful, and the die and extrusion cylinder are also prone to deformation. By preheating the re-pressed ingot, extrusion cylinder, and die to the aforementioned temperature, the extrusion resistance of the re-pressed ingot can be sufficiently low, allowing for sufficient deformation. During deformation, porosity is eliminated, thereby increasing the density of the tungsten copper. After hot extrusion, the relative density of the extruded billet can exceed 99%, and the porosity volume fraction is less than 1%, which is quite high.

[0033] Optionally, the ingot is heated and held at 945-955℃ for 90-120 minutes, and the extrusion cylinder and die are held at 845-855℃ for 210-240 minutes before being used for hot extrusion.

[0034] Preferably, the thickness of the extruded blank is 6-10 mm.

[0035] Furthermore, in S6, the rolling process includes at least one hot rolling process and at least one cold rolling process, with the hot rolling process and the cold rolling process being performed alternately to obtain a tungsten-copper alloy of the desired thickness.

[0036] Preferably, a first hot rolling is performed at 600-650°C (more preferably 610-640°C), followed by a first cold rolling, then a second hot rolling at 600-650°C (more preferably 610-640°C), and finally a second cold rolling. Generally, the relative density reaches at least 99.30% after the first hot rolling, at least 99.44% after the first cold rolling, at least 99.65% after the second hot rolling, and at least 99.74% after the second cold rolling.

[0037] Optionally, the rolling speed is 54-62 m / s and the rolling force is 1000-1200 kN.

[0038] Furthermore, in S6, the thickness of the tungsten-copper alloy is 0.5-2 mm, and even more specifically 0.8-1.2 mm.

[0039] Furthermore, after S6, the tungsten-copper alloy is cut into tungsten-copper sheets as needed.

[0040] Optionally, the tungsten-copper alloy has a density ≥99.6%, a hardness ≥97HRB, a conductivity ≥45.2%IACS, and an oxygen content ≤0.035wt%.

[0041] The preparation method of this invention can obtain highly dense tungsten-copper alloys, and can prepare high-tungsten-content dense tungsten-copper alloys with a tungsten content of 70% or higher. Furthermore, the tungsten-copper alloys obtained by this invention can reach a thickness of approximately 1 mm and possess excellent physical and mechanical properties.

[0042] This invention breaks with traditional thinking by using metallic copper powder, copper oxide powder and tungsten powder as starting materials to press a compact, pre-sinter it and then sinter it, which can effectively activate the sintering process and prepare it for subsequent rolling to obtain high-density tungsten copper products. At the same time, the addition of re-pressing and extrusion processes can effectively eliminate porosity and improve density. Detailed Implementation

[0043] The present invention will be described in detail below with reference to embodiments. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of the present invention can be combined with each other.

[0044] Example 1

[0045] In this embodiment, the preparation method of the tungsten-copper alloy includes the following steps:

[0046] S1. According to the composition requirements of the tungsten-copper alloy to be prepared, take metallic copper powder, copper oxide powder and metallic tungsten powder, mix them evenly, and then mold them to obtain a compact.

[0047] The copper element from the copper powder accounts for 80 wt% of the copper element in the tungsten-copper alloy to be prepared (referred to as "Cu" in the table), and the remaining copper element in the tungsten-copper alloy to be prepared comes from the copper oxide powder, that is, the copper element from the copper oxide powder accounts for 20 wt% of the copper content in the tungsten-copper alloy to be prepared; the tungsten content in the tungsten-copper alloy to be prepared (referred to as "W" in the table) is 80 wt%, and the balance is copper.

[0048] S2. The pressed blank is pre-sintered under vacuum at 950°C (referred to as "T1" in the table) for 165 min (referred to as "t1" in the table) to obtain the first tungsten copper ingot;

[0049] S3. The first tungsten copper ingot is reduced and sintered at 1025℃ (referred to as "T2" in the table) for 195 min (referred to as "t2" in the table) under a hydrogen atmosphere to obtain the second tungsten copper ingot.

[0050] S4. The second tungsten copper ingot is repressed to obtain a repressed ingot with a thickness of 280mm;

[0051] S5. The compounded ingot is hot-extruded to obtain an extruded billet with a thickness of 9mm;

[0052] S6. The extruded billet is rolled to obtain a strip-shaped tungsten-copper alloy (product).

[0053] In S1, the copper powder is electrolytic copper powder with a median particle size D50 (referred to as "D1" in the table) of 40 μm; the copper oxide powder has a median particle size D50 (referred to as "D2" in the table) of 5 μm; and the tungsten powder has a median particle size D50 of 4 μm.

[0054] In S1, at 2.2 t / cm 2 Compression molding under unit pressure, in S4, at 7.8 t / cm 2 The pressure is repressurized under the unit pressure.

[0055] In step S5, the compounded ingot is preheated at 950℃ (referred to as "T4" in the table) for 105 min (referred to as "t4" in the table), and the extrusion cylinder and die are preheated at 850℃ (referred to as "T3" in the table) for 225 min (referred to as "t3" in the table). The compounded ingot is then placed in the die for hot extrusion; at 8.0 t / cm 2 Hot extrusion is performed under unit pressure.

[0056] In S6, the rolling process includes two hot rolling processes and two cold rolling processes, which are performed alternately. Specifically, the first hot rolling is performed at 630°C, followed by the first cold rolling, then the second hot rolling at 630°C, followed by the second cold rolling.

[0057] The rolling speed is 58 m / s and the rolling force is 1100 kN.

[0058] In S6, the thickness of the tungsten-copper alloy is 0.8 mm.

[0059] The obtained tungsten-copper alloy (product) has a yield (referred to as "C" in the table) of 90.8%, a relative density (referred to as "ρ" in the table) of 99.75%, a hardness (referred to as "R") of HRB97.7, a conductivity (referred to as "σ" in the table) of 45.7% IACS, and an oxygen content (referred to as "O" in the table) of 0.032wt%.

[0060] The yield rate is calculated as follows: the relative density of the finished product must exceed 97%, and the yield rate is calculated as the mass of the tungsten copper alloy product / the total mass of the raw materials * 100%.

[0061] The hardness of tungsten-copper alloys is measured according to the following standard: GB / T230.1-2018 Rockwell Hardness Test for Metallic Materials.

[0062] The electrical conductivity of tungsten-copper alloys is measured according to the following standard: GB / T 35392-2017 Nondestructive testing method for determining electrical conductivity by electromagnetic (eddy current) method.

[0063] Example 2-27

[0064] Example 1 is repeated, except for the differences shown in Table 1.

[0065] Comparative Examples 1-22

[0066] Example 1 is repeated, except for the differences shown in Table 2.

[0067] Comparative Example 23

[0068] Repeat Example 1, except that pre-sintering is not performed.

[0069] Comparative Example 24

[0070] Repeat Example 1, except that: no re-compression is performed.

[0071] Comparative Example 25

[0072] Repeat Example 1, except that hot extrusion is not performed.

[0073] Comparative Example 26

[0074] Repeat Example 1, except that rolling is not performed.

[0075] Comparative Example 27

[0076] Repeat Example 1, except that copper oxide powder is not added.

[0077] For details of the process parameters of Examples 1-27 and Comparative Examples 1-27, please refer to Table 1 and Table 2.

[0078]

[0079]

[0080]

[0081]

[0082] In Table 4, 1 This indicates that the material has not undergone hot rolling or cold rolling.

[0083] As shown in Tables 1-4, the tungsten-copper alloy prepared by the method of the present invention has excellent electrical conductivity, hardness, density, and low oxygen content, and has a high yield.

[0084] In the prior art [1], the relative density of the tungsten-copper alloy obtained after liquid phase sintering and two extrusions can only reach 99.15%. In the prior art [2], the relative density of the tungsten-copper alloy can only reach 98.6%.

[0085] Existing technology [1]: Yu Yang, Li Daren, Wang Erde, et al. Study on hot deformation densification process and microstructure properties of tungsten copper [J]. Powder Metallurgy Technology, 2009, 27(1):3.

[0086] Existing technology[2]: Liu B, Chen J, Xie J. Fabrication of W / Cu20 CompositeMaterials with Nearly Full Density by Particle Size Distribution Method[J]. Rare Metal Materials&Engineering, 2010, 39(1):17-21.

[0087] Examples 28-29 and Comparative Examples 28-31

[0088] Example 1 was repeated, with the only difference shown in Table 5. The properties of the resulting tungsten-copper alloy are also shown in Table 5.

[0089] Table 5 Summary of differences in process parameters and product performance in Examples 1, 28-29 and Comparative Examples 28-29

[0090]

[0091] In Table 5, 2 The pressed blank exhibits delamination and is deemed unusable.

[0092] As shown in Table 5, controlling the molding pressure in S1 helps to improve the yield and obtain tungsten-copper alloy products with higher density, electrical conductivity and hardness.

[0093] The above embodiments should be understood as being used only to illustrate the present invention more clearly, and not to limit the scope of the present invention. After reading the present invention, any modifications of the present invention in various equivalent forms by those skilled in the art fall within the scope defined by the appended claims.

Claims

1. A method for preparing a tungsten-copper alloy, characterized in that, Includes the following steps: S1. According to the composition requirements of the tungsten-copper alloy to be prepared, take metallic copper powder, copper oxide powder and metallic tungsten powder, mix them evenly, and then mold them to obtain a compact. The copper element from the copper powder accounts for 63-95 wt% of the copper element in the tungsten-copper alloy to be prepared, and the remaining copper element in the tungsten-copper alloy to be prepared comes from the copper oxide powder. S2. The pressed blank is pre-sintered at 750-980℃ for 120-240 min under vacuum or inert atmosphere to obtain the first tungsten copper ingot; S3. The first tungsten copper ingot is sintered at 1000-1050℃ for 150-240 min under hydrogen atmosphere to obtain the second tungsten copper ingot. S4. The second tungsten-copper ingot is repressed to obtain a repressed ingot; S5. The compounded ingot is hot-extruded to obtain an extruded billet; S6. The extruded billet is rolled to obtain a strip-shaped tungsten-copper alloy.

2. The preparation method according to claim 1, characterized in that, In S1, the median particle size D50 of the copper powder is ≤45μm; the median particle size D50 of the copper oxide powder is 1-10μm; and the median particle size D50 of the tungsten powder is 3-7μm.

3. The preparation method according to claim 1, characterized in that, In S1, the copper element from the copper powder accounts for 78-82 wt% of the copper element in the tungsten-copper alloy to be prepared, and the remaining copper element in the tungsten-copper alloy to be prepared comes from the copper oxide powder.

4. The preparation method according to claim 1, characterized in that, The unit pressure during compression molding in S1 is less than the unit pressure during re-compression in S4; and / or, the tungsten content in the tungsten-copper alloy to be prepared is 63-95 wt%.

5. The preparation method according to claim 4, characterized in that, In S1, at 2.0-2.5 t / cm 2 Molding under unit pressure; in S4, at 7.7-8.0 t / cm 2 The pressure is repressurized under the unit pressure.

6. The preparation method according to claim 1, characterized in that, In S2, the pre-sintering temperature is 945-955℃ and the pre-sintering time is 150-180min; and / or, in S3, the sintering temperature is 1010-1040℃ and the sintering time is 180-210min.

7. The preparation method according to any one of claims 1-6, characterized in that, In S4, the thickness of the compound-pressed ingot is 40-300mm.

8. The preparation method according to any one of claims 1-6, characterized in that, In step S5, the compounded ingot is preheated to 945-955°C, the extrusion cylinder and the die are preheated to 845-855°C, and then the compounded ingot is placed in the die for hot extrusion.

9. The preparation method according to any one of claims 1-6, characterized in that, In S6, the rolling process includes at least one hot rolling process and at least one cold rolling process, with the hot rolling process and the cold rolling process being performed alternately in sequence.

10. The preparation method according to claim 9, characterized in that, In S6, the first hot rolling is carried out at 600-650℃, followed by the first cold rolling, then the second hot rolling at 600-650℃, and then the second cold rolling.

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