CuNiSn alloy, and preparation method and application thereof

Abstract

The application belongs to the technical field of alloy materials, and particularly relates to a CuNiSn alloy and a preparation method and application thereof. The preparation method of the CuNiSn alloy provided by the application comprises the following steps: mixing raw materials according to alloy element proportions, and then sequentially performing melting and pouring to obtain an alloy ingot; performing secondary refining melting on the alloy ingot to obtain a melt; and performing downward continuous casting on the melt to obtain the CuNiSn alloy. The application utilizes the principle of rapid directional solidification (downward continuous casting) to form a rod blank, the alloy rod blank forms a columnar crystal organization growing in parallel with the axial direction under the action of directional solidification, a large number of transverse grain boundaries perpendicular to the stress direction are eliminated, the position of the grain boundary crack initiation is reduced, and the preferred orientation of the crystal grain is beneficial to dislocation slip, so that the elongation of the alloy rod blank is improved.

Description

Technical Field

[0001] This invention belongs to the field of alloy materials technology, specifically relating to a CuNiSn alloy, its preparation method, and its application. Background Technology

[0002] Copper-based alloys, due to their excellent electrical and thermal conductivity, mechanical properties, hot and cold working properties, and wear and corrosion resistance, are widely used in electronic and electrical connectors, elastic elements, and wear- and corrosion-resistant components, and are of significant strategic importance to national economic development. Particularly in the field of critical electronic connectors, CuNiSn alloys, with their high strength, high elasticity, and high wear resistance, have become key materials for core components such as oil well guide rods, electric pump assemblies, and fasteners.

[0003] With the rapid development of high-tech industries, higher demands are being placed on key structural and functional materials. Meanwhile, CuNiSn alloys hold promise as a replacement for toxic CuBe alloys in specialized fields, eliminating the health hazards and thermal instability associated with Be. Therefore, the industry is continuously raising new requirements for the microstructure and properties of CuNiSn alloys, with the core objective of simultaneously improving both strength and ductility.

[0004] Currently, existing technologies mostly employ microalloying as the primary solution, adding specific elements to suppress discontinuous precipitation or strengthen solid solution in order to improve the elongation of CuNiSn alloys. However, this type of method has inherent limitations such as complex processes and difficulty in controlling element composition; if the types and amounts of elements are not properly controlled, although strength may be improved, plasticity is often reduced. Summary of the Invention

[0005] In view of this, the present invention provides a CuNiSn alloy, its preparation method and application. The preparation method provided by the present invention has both high tensile strength and elongation, thus expanding its application range.

[0006] To address the aforementioned technical problems, this invention provides a method for preparing CuNiSn alloy, comprising the following steps: The raw materials are mixed according to the alloy element ratio and then melted and poured in sequence to obtain alloy ingots; The alloy ingot is subjected to secondary refining and melting to obtain a melt; The melt is subjected to bottom-feed continuous casting to obtain the CuNiSn alloy.

[0007] Preferably, the process after the downward continuous casting further includes: homogenizing the alloy obtained after the downward continuous casting to obtain the CuNiSn alloy.

[0008] Preferably, the homogenization treatment is carried out at a temperature of 700~900℃ for 6~10 hours.

[0009] Preferably, the temperature of the downward continuous casting is 1200~1300℃, and the casting speed is 200~300mm / min; the downward continuous casting is carried out under a protective atmosphere, which includes nitrogen or argon.

[0010] Preferably, the downward continuous casting adopts an intermittent pull-stop mode, with a pull-stop time ratio of 0.8 to 1.2:3; The return water temperature for the bottom-feed continuous casting is 23~27℃.

[0011] Preferably, the melting temperature is 1200~1300℃ and the melting time is 30~50min.

[0012] Preferably, the pouring temperature is 1150~1250℃.

[0013] Preferably, the secondary refining and melting temperature is 1200~1300℃ and the time is 40~70min.

[0014] This invention also provides a CuNiSn alloy prepared by the preparation method described above, comprising the following chemical components by mass content: Ni 8~10%; Sn 5.8~7%; Cu balance; The CuNiSn alloy has a tensile strength of 323~380MPa and an elongation of 43.2~63.5%.

[0015] This invention also provides the application of the CuNiSn alloy described above in electronic components or marine engineering.

[0016] This invention provides a method for preparing a CuNiSn alloy, comprising the following steps: mixing raw materials according to the alloy element ratio, followed by sequential melting and casting to obtain an alloy ingot; subjecting the alloy ingot to secondary refining and melting to obtain a melt; and performing downward continuous casting on the melt to obtain the CuNiSn alloy. This invention utilizes the principle of rapid directional solidification (downward continuous casting) to form a rod billet. Under the action of directional solidification, the alloy rod billet forms a columnar crystal structure with parallel axial growth, eliminating a large number of transverse grain boundaries perpendicular to the direction of stress, reducing the sites for intergranular crack initiation, and simultaneously promoting preferred grain orientation which facilitates dislocation slip, thereby improving the elongation of the alloy rod billet. Furthermore, through the synergistic effect of the three-step process of melting and casting + secondary refining + downward continuous casting, this invention successfully achieves a low-segregation, columnar crystal structure in the CuNiSn alloy, resulting in an alloy with both high strength and ultra-high elongation. Attached Figure Description

[0017] Figure 1 This is a photograph of the as-cast Cu9Ni6Sn alloy prepared in Example 1. Figure 2 The images show the microstructures of Example 1 and Comparative Example 1, where (a) is the microstructure of the Cu9Ni6Sn alloy ingot prepared in Comparative Example 1, and (b) is the microstructure of the as-cast Cu9Ni6Sn alloy prepared in Example 1. Figure 3 This is a microstructure diagram of the Cu9Ni5.8Sn alloy prepared in Example 3. Detailed Implementation

[0018] This invention provides a method for preparing CuNiSn alloy, comprising the following steps: The raw materials are mixed according to the alloy element ratio and then melted and poured in sequence to obtain alloy ingots; The alloy ingot is subjected to secondary refining and melting to obtain a melt; The melt is subjected to bottom-feed continuous casting to obtain the CuNiSn alloy.

[0019] In this invention, unless otherwise specified, all materials are commercially available products.

[0020] This invention involves mixing raw materials according to alloy element ratios, followed by sequential melting and casting to obtain alloy ingots. In this invention, the raw materials may include electrolytic copper, electrolytic nickel, and pure tin; the purity of the electrolytic copper may be ≥99.99%, the purity of the electrolytic nickel may be ≥99.99%, and the purity of the pure tin may be ≥99.99%.

[0021] In this invention, the process before mixing may further include: sequentially cutting, drying, and surface degreasing the raw materials; this invention has no special requirements for the cutting, drying, and surface degreasing processes, which can be performed in accordance with conventional methods in the art.

[0022] In this invention, the mixing can be achieved by first adding electrolytic copper and electrolytic nickel to the smelting furnace, and then adding pure tin after they have completely melted; the smelting temperature can be 1200~1300℃, specifically 1230℃, 1250℃ or 1280℃; the smelting time can be 30~50min, specifically 35min, 40min or 45min.

[0023] In this invention, the melting can be carried out under vacuum conditions, and the vacuum degree of the vacuum conditions can be below 10 Pa.

[0024] After the surface of the molten liquid is free of scum and has a mirror-like finish, it is allowed to stand for 1 to 3 minutes before pouring. The pouring temperature can be 1150 to 1250°C, specifically 1180°C, 1200°C, or 1220°C.

[0025] This invention uses a medium-frequency induction furnace for smelting to achieve the refining of raw materials. The vacuum environment can reach below 10 Pa. Under constant temperature conditions, the gases (oxygen, hydrogen, etc.) in the melt are continuously removed. At the same time, after long-term heat preservation and static setting, impurities float to the surface of the melt. The impurity content can be reduced by turning the ingot after casting.

[0026] After obtaining the alloy ingot, the present invention further refines and melts the alloy ingot to obtain a melt. In this invention, the secondary refining and melting process may include: turning the alloy ingot to remove slag and surface oxide scale; the turning thickness can be 0.8~1.2mm, specifically 1mm. The present invention obtains an oxide scale-free ingot through turning, which can significantly reduce the impact of impurity elements on subsequent continuous casting of the alloy.

[0027] In this invention, the secondary refining and melting can be carried out under vacuum conditions, and the vacuum degree can be below 10 Pa; the temperature of the secondary refining and melting can be 1200~1300℃, specifically 1230℃, 1250℃, 1280℃ or 1290℃; the time of the secondary refining and melting can be 40~70min, specifically 45min, 50min, 55min, 60min or 65min.

[0028] The secondary refining and melting process of the present invention is carried out under vacuum conditions. After the surface of the melt is free of scum and has a mirror-like finish, it is kept at a temperature of 5-10 minutes and then purged with argon gas to atmospheric pressure to complete the refining and homogenization of the composition.

[0029] In this invention, the raw materials undergo a first melting process to homogenize the alloying elements and reduce the generation of impurities. The machined ingot is then placed in a continuous casting crucible for a second refining process. After being held at a constant temperature, the melt is thoroughly purified, which greatly ensures the quality of the subsequent continuously cast billet, reduces the segregation of alloying elements and the inclusion of impurity elements, and improves the performance of the billet.

[0030] After obtaining the melt, the present invention performs a bottom-casting process to obtain the CuNiSn alloy. In this invention, the bottom-casting process can be carried out under a protective atmosphere, which may include nitrogen or argon. Copper alloys and graphite are prone to surface oxidation and casting fracture under high-temperature air. The protective atmosphere can inhibit the oxidation of the billet and graphite mold, reduce the wear of the billet surface by particles detached from the inner wall of the graphite, and ensure the brightness of the alloy billet surface. Argon protection allows for the continuous production of copper alloy billets with good surface quality.

[0031] In this invention, the temperature of the downward-drawing continuous casting can be 1200~1300℃, specifically 1220℃, 1250℃, or 1290℃; the casting speed of the downward-drawing continuous casting can be 200~300mm / min, specifically 250mm / min. In this invention, the downward-drawing continuous casting can adopt a pull-stop intermittent mode, with a pull-stop time ratio of 0.8~1.2:3, specifically 1:3; the return water temperature of the downward-drawing continuous casting can be 23~27℃, specifically 25℃. In this invention, the casting speed affects the surface quality of the casting, and the pull-stop intermittent mode and return water temperature result in a more complete solidification structure. Limiting the conditions of the downward-drawing continuous casting within the above ranges can reduce the occurrence of transverse grain boundaries and improve the elongation of the as-cast alloy.

[0032] In this invention, the downward continuous casting can be performed by having the melt flow downwards from the crucible (used for secondary refining and melting) into the graphite crystallizer by gravity, where it is cooled and solidified in a water-cooled copper sleeve to form a rod billet. The rod billet is then pulled downwards by the graphite ingot head to obtain the as-cast CuNiSn alloy.

[0033] In this invention, the process after the downward continuous casting may further include: homogenizing the alloy obtained after the downward continuous casting to obtain the CuNiSn alloy; the homogenization temperature may be 700~900℃, specifically 750℃, 800℃ or 850℃; the homogenization time may be 6~10h, specifically 7h, 8h or 9h.

[0034] In this invention, the homogenization treatment may further include: air-cooling the homogenized alloy to room temperature to obtain the CuNiSn alloy; the room temperature may be 20~35℃ or 25~30℃.

[0035] The preparation method provided by this invention uses bottom-feed continuous casting to control the casting speed and temperature to suppress the precipitation behavior of CuNiSn alloy, and finally obtains an excellent microstructure with uniform structure and fine dendrites, thereby overcoming the long-standing problem of dendrite segregation severely deteriorating the alloy performance of this alloy system; after homogenization treatment, segregation behavior is further reduced, effectively and synergistically improving the strength and plasticity of the alloy.

[0036] This invention also provides a CuNiSn alloy prepared by the preparation method described above, comprising the following chemical components by mass content: Ni 8~10%; Sn 5.8~7%; Cu balance; The CuNiSn alloy has a tensile strength of 323~380MPa and an elongation of 43.2~63.5%.

[0037] In this invention, the CuNiSn alloy comprises 8 to 10% Ni by mass percentage, specifically 8.9% or 9%.

[0038] In this invention, the CuNiSn alloy comprises 5.8 to 7% Sn by mass percentage, specifically 5.8%, 6% or 7%.

[0039] In this invention, the CuNiSn alloy comprises the balance Cu by weight percentage.

[0040] In this invention, the tensile strength of the CuNiSn alloy is 323~380MPa, specifically 368MPa; the elongation of the CuNiSn alloy is 43.2~63.5%, specifically 52.6%.

[0041] The segregation structure of the alloy prepared according to the preparation method provided by the present invention is suppressed, the coarse DP disappears, and the continuous casting billet (CuNiSn alloy) is free of porosity, inclusions and cracks.

[0042] This invention also provides the application of the CuNiSn alloy described above in electronic components or marine engineering.

[0043] To further illustrate the present invention, the technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0044] Example 1 (1) Vacuum casting: Electrolytic copper (Cu≥99.99%), electrolytic nickel (Ni≥99.99%), and pure tin (Sn≥99.99%) are used as raw materials. Before melting, they are cut, dried and degreased. Electrolytic copper and pure nickel are added to the induction melting furnace first. After they are completely melted, pure tin is added. The melting temperature is 1280℃ and the melting time is 30min. Vacuum is drawn throughout the heating and melting process. The vacuum degree is 10Pa. After the surface of the melt is free of slag and has a mirror-like appearance, it is left to stand for 3min before pouring. The pouring temperature is 1220℃. The melt solidifies to obtain an alloy ingot.

[0045] (2) Secondary refining and melting: The alloy ingot is machined by 1 mm to remove slag and surface oxide scale; the machined alloy ingot is placed in a continuous casting crucible, and then vacuumed and heated; the melting temperature is 1290℃ and the melting time is 50 min; vacuum is applied throughout the heating and melting process, with a vacuum degree of less than 10 Pa. After the surface of the melt is free of slag and has a mirror-like appearance, it is kept at a constant temperature for 5 min and then purged with argon gas to atmospheric pressure to obtain the melt.

[0046] (3) Downward continuous casting: After secondary refining and melting, the vacuum valve is closed, and argon gas is continuously supplied for protection during downward continuous casting; the continuous casting temperature is 1290℃, and the continuous casting speed is 200mm / min; the pull-stop intermittent mode is adopted, with a traction and stop time ratio of 1:3, and water-cooled copper sleeves are used for cooling, with the return water temperature controlled at 25℃; the melt solidifies into a rod billet in the crystallizer, and is continuously cast by a graphite dummy bar to obtain... The 8mm as-cast Cu9Ni6Sn alloy comprises 9% Ni, 6% Sn and the balance Cu by mass percentage.

[0047] Example 2 According to Example 1, vacuum casting, secondary refining and melting, and downward continuous casting were performed to obtain as-cast Cu9Ni6Sn alloy; The as-cast Cu9Ni6Sn alloy was homogenized at 800℃ for 6 hours and then air-cooled to room temperature (25℃) to obtain Cu9Ni6Sn alloy.

[0048] Example 3 According to Example 1, vacuum casting, secondary refining and melting, and bottom casting were performed to obtain as-cast Cu9Ni5.8Sn alloy. The difference is that, by mass percentage, the as-cast alloy includes 9% Ni, 5.8% Sn and the balance Cu. The as-cast Cu9Ni5.8Sn alloy was homogenized at 830℃ for 8 hours and then air-cooled to room temperature (25℃) to obtain Cu9Ni5.8Sn alloy.

[0049] Comparative Example 1 (1) Raw material processing: Electrolytic copper (Cu≥99.99%), electrolytic nickel (Ni≥99.99%), and pure tin (Sn≥99.99%) are used as raw materials. Before smelting, they are cut, dried and degreased.

[0050] (2) Melting and casting: First, add electrolytic copper and pure nickel to the induction melting furnace. After they are completely melted, add pure tin. The melting temperature is 1300℃ and the melting time is 30min. Vacuum is drawn throughout the heating and melting process. The vacuum degree is 10Pa. After the surface of the melt is free of slag and has a mirror-like appearance, let it stand for 5min before pouring. The pouring temperature is 1150℃. The melt solidifies to obtain Cu9Ni6Sn alloy ingot. The alloy ingot includes 9%Ni, 6%Sn and the balance Cu by mass percentage.

[0051] Comparative Example 2 (1) Raw material processing: Electrolytic copper (Cu≥99.99%), electrolytic nickel (Ni≥99.99%), and pure tin (Sn≥99.99%) are used as raw materials. Before smelting, they are cut, dried and degreased.

[0052] (2) Melting and casting: First, add electrolytic copper and pure nickel to the induction melting furnace. After they are completely melted, add pure tin. The melting temperature is 1300℃ and the melting time is 50min. Vacuum is drawn throughout the heating and melting process. The vacuum degree is 10Pa. After the surface of the melt is free of slag and has a mirror-like appearance, let it stand for 5min before pouring. The pouring temperature is 1150℃. The melt solidifies to obtain Cu9Ni6Sn alloy ingot. The alloy includes 9%Ni, 6%Sn and the balance Cu by mass percentage.

[0053] (3) Homogenization treatment: The Cu9Ni6Sn alloy ingot was homogenized at 800℃ for 6h and then air-cooled to room temperature (25℃) to obtain Cu9Ni6Sn alloy.

[0054] Figure 1 The image shows the as-cast Cu9Ni6Sn alloy prepared in Example 1. The Cu9Ni6Sn alloys prepared in Examples 1-3 have smooth surfaces, are free of pores, inclusions, and cracks.

[0055] The properties of the alloys prepared in Examples 1-3 and Comparative Examples 1-2 were tested according to the following methods: 1. Alloy microstructure: Test method: Characterization samples were prepared using wire cutting along the continuous casting direction. The samples were then polished using multi-grit sandpaper and abrasives, and the surface was further polished using a three-ion beam. The distribution and morphology of segregation were observed using an inverted metallographic microscope. The resulting microstructure is shown in the figure below. Figure 2 and Figure 3 As shown. Figure 2 The images show the microstructures of Example 1 and Comparative Example 1, where (a) is the microstructure of the Cu9Ni6Sn alloy ingot prepared in Comparative Example 1, and (b) is the microstructure of the as-cast Cu9Ni6Sn alloy prepared in Example 1.

[0056] Depend on Figure 2 It can be seen that in Comparative Example 1, the DP phase is coarse and the segregation is uneven. Casting defects such as porosity and inclusions are prone to occur at the grain boundaries, which can easily lead to problems such as machining cracking. In contrast, in Example 1, the segregation of Sn element is significantly suppressed through directional solidification, the DP phase is suppressed, the segregated structure is refined and evenly distributed, and there are no casting defects.

[0057] Figure 3 The microstructure of the Cu9Ni5.8Sn alloy prepared in Example 3; by Figure 3 It can be seen that the homogenization treatment further eliminated casting defects such as segregation, resulting in extremely high microstructure density, reducing the risk of machining cracks, and providing a good microstructure basis for subsequent plastic processing.

[0058] 2. Mechanical property testing: Test method: The samples were machined into the required sample size using wire cutting and CNC lathe; dog bone-shaped tensile specimens were machined according to the national standard GB / T 228.1~2021; tensile strength and elongation were tested on a WDW~100D universal electronic tensile tester at a tensile rate of 3 mm / min; the test results are listed in Table 1.

[0059] Table 1. Comparison of mechanical properties and segregated microstructure of alloys prepared in Examples 1-3 and Comparative Examples 1-2

[0060] Table 1 shows that Comparative Example 1, due to the lack of bottom-feed continuous casting, produced the following: Figure 2 The segregation and casting defects shown in (a) indicate that the tensile strength and elongation are lower than those in Example 1. The CuNiSn alloys of Examples 1-3 of the present invention improve the casting defects such as segregation and inclusions in the alloy structure through continuous casting and homogenization treatment.

[0061] Compared with the comparative example, the present invention can prepare an alloy structure with smooth surface quality and uniform structure while ensuring performance, and obtain a high-strength and high-elongation CuNiSn alloy. This shows that the preparation method provided by the present invention can suppress segregation and can prepare a CuNiSn alloy that meets the requirements of high-performance copper alloys for key structural and functional materials in the fields of electronic and electrical connectors and elastic elements.

[0062] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, and not all embodiments. People can obtain other embodiments based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for preparing a CuNiSn alloy, characterized in that, Includes the following steps: The raw materials are mixed according to the alloy element ratio and then melted and poured in sequence to obtain alloy ingots; The alloy ingot is then subjected to secondary refining and melting to obtain a melt; The melt is subjected to bottom-feed continuous casting to obtain the CuNiSn alloy.

2. The preparation method according to claim 1, characterized in that, The process after the downward continuous casting also includes: homogenizing the alloy obtained after the downward continuous casting to obtain the CuNiSn alloy.

3. The preparation method according to claim 2, characterized in that, The homogenization process is carried out at a temperature of 700-900℃ for 6-10 hours.

4. The preparation method according to claim 1, characterized in that, The temperature of the downward continuous casting is 1200~1300℃, and the casting speed is 200~300mm / min; the downward continuous casting is carried out under a protective atmosphere, which includes nitrogen or argon.

5. The preparation method according to claim 1 or 4, characterized in that, The lower-draw continuous casting adopts an intermittent pull-stop mode, with a pull-stop time ratio of 0.8~1.2:3; The return water temperature for the bottom-feed continuous casting is 23~27℃.

6. The preparation method according to claim 1, characterized in that, The melting temperature is 1200~1300℃, and the time is 30~50min.

7. The preparation method according to claim 1, characterized in that, The pouring temperature is 1150~1250℃.

8. The preparation method according to claim 1, characterized in that, The secondary refining and melting temperature is 1200~1300℃, and the time is 40~70min.

9. The CuNiSn alloy prepared by the preparation method according to any one of claims 1 to 8, characterized in that, The chemical components include the following mass contents: Ni 8~10%; Sn 5.8~7%; Cu balance; The CuNiSn alloy has a tensile strength of 323~380MPa and an elongation of 43.2~63.5%.

10. The application of the CuNiSn alloy of claim 9 in the fields of electronic components or marine engineering.

Images