High-strength copper alloy for power grid and preparation method thereof

Abstract

The application discloses a high-strength copper alloy for power grid and a preparation method thereof. The copper alloy contains Ti, Si and Cu, wherein the weight percentage of Ti is 0.4%-1.0%, the weight percentage of Si is 0.14%-0.35%, the atomic ratio of Ti and Si is 5:3, and the balance is copper; the copper alloy is composed of a copper matrix and a Ti5Si3 precipitated phase, and the Ti5Si3 precipitated phase is spherical particles with a diameter of 10-50 nm. The strength and electrical conductivity of the Cu-Ti-Si alloy prepared by the application are not inferior to those of a Cu-Ni-Si series alloy, but the raw material cost is lower, and the application of the Cu-Ti-Si alloy in a high-voltage transformer sleeve clamp is facilitated. The alloy preparation process of the application is simple, and does not need complex processes such as solid solution, hot rolling, drawing and the like.

Description

Technical Field

[0001] This invention belongs to the field of alloy technology, specifically a high-strength copper alloy for power grids and its preparation method, and more particularly a novel ternary high-strength and high-elongation conductive copper alloy and its preparation method. Background Technology

[0002] Substations are critical nodes in high-voltage power transmission and transformation systems. The downlead system within a substation is a vital power facility connecting transmission lines and transformer equipment, and its structural safety directly impacts the normal and stable operation of the substation and even the transmission lines. The downlead system consists of downleads, hardware connecting the downleads to the busbars, and hardware connecting the downleads to the main equipment terminals. If a terminal block undergoes plastic deformation or even damage, the main transformer bushing seal will fail, leading to serious consequences such as transformer shutdown and power outages affecting the entire substation. Terminal blocks not only withstand mechanical and wind-driven loads but also require excellent electrical contact to ensure high current flow. Therefore, the materials used for terminal blocks must possess good electrical conductivity, excellent mechanical strength, and good environmental resistance.

[0003] Bushing clamps, a typical form of terminal block, are currently mainly made of H62 brass or T2 copper. The cracking of brass bushing terminals in bushing clamps is primarily due to brass's sensitivity to stress corrosion. Under the combined action of bolt preload and the surrounding corrosive environment, cracks form and rapidly propagate, leading to brittle fracture without warning. Copper bushing clamps have also experienced numerous failures caused by overheating defects. Under the combined action of load and wind load, copper clamps undergo plastic deformation defects, resulting in a large gap between the clamp and the terminal copper head. The reduced effective contact area leads to increased local contact resistance and overheating. This localized overheating further softens the clamp, reducing its strength and causing further plastic deformation. Simultaneously, traditional brass casting processes are energy-intensive and polluting. Brass itself has lower conductivity than pure copper, resulting in heat loss during operation. With the development of transformers towards ultra-high voltage and ultra-large capacity, increasingly higher requirements are being placed on the strength and conductivity of bushing clamp materials.

[0004] In recent years, Cu-Ni-Si alloys have received increasing attention due to their high strength, non-magnetic nature, and lack of Joule heating caused by eddy currents, making them a promising candidate for future development. Typical product models include C70250, C64710, and KLF-125, whose main performance indicators are shown in Table 1 below.

[0005] Table 1 Typical Cu-Ni-Si copper alloys for lead frames and their main performance indicators

[0006]

[0007] Patent documents CN113981267A and CN116640961A disclose the preparation technology of copper alloys for lead frames made of two alloys: Cu-2.4%Ni-0.6%Si-0.2%Mg-0.01%Zn and Cu-(1.0-3.0)%Sn-(0.5-4.0)%Ni-(0.1-5.0)Zn-(≤0.1)%P-(0.005-0.01)%B. Patent document CN108330320B describes a high-performance Cu-Ni-Si alloy leadframe material with a tensile strength of (720-863) MPa and an IACS conductivity of (58-79)%. This material can be obtained through processes such as melting, casting, hot rolling-online quenching, solution treatment, milling, and cold rolling-aging. The material contains Cu-(4.0-9.0)%Ni-(1.0-1.5)%Si-(0.1-0.4)%Ag-(0.05-0.1)%P.

[0008] However, the total amount of various alloying elements added to the above alloys is greater than 2%, and some of them contain expensive strategic metals such as Ag and Ni, which significantly increases the cost of the alloys. Summary of the Invention

[0009] The technical problem to be solved by the present invention is to overcome the defects of the prior art and provide a high-performance low-alloy ternary copper alloy and its preparation method. The copper alloy contains only a small amount of Ti and Si alloying elements, providing a simple and feasible path for the large-scale production of high-strength and high-elongation conductive copper alloys.

[0010] To achieve the above-mentioned objectives, the present invention adopts the following technical solution: a high-strength copper alloy for power grids, the copper alloy containing Ti, Si and Cu, wherein the weight percentage of Ti is 0.4%-1.0%, the weight percentage of Si is 0.14%-0.35%, and the atomic ratio of Ti to Si is 5:3, with the balance being copper; the copper alloy is composed of a copper matrix and Ti5Si3 precipitates, and the Ti5Si3 precipitates are spherical particles with a diameter of 10-50 nm.

[0011] Preferably, the Si weight percentage is 0.1%-0.3%.

[0012] The design concept of the Cu-Ti-Si alloy in this invention is as follows:

[0013] Ti and Si have high solid solubility in the Cu matrix. Even trace amounts of solid solution can cause lattice distortion in the copper matrix, worsening electrical conductivity. Therefore, these two elements are often avoided in conductive copper alloys. The scattering effect of the precipitated second phase on electrons is much smaller than that caused by dissolved atoms. To ensure good conductivity, Ti and Si dissolved in the Cu matrix must precipitate. This invention, through a dual-driven design using in-depth phase diagrams and machine learning models, reveals that characteristic factors such as the content of alloying elements dissolved in the copper matrix, the content of alloying elements in the second phase, the content of the second phase in the alloy, and the formation energy of alloying compound have a significant impact on the hardness and electrical conductivity of the alloy. For the CuTiSi system, it was found that low contents of Ti and Si, due to the low formation energy of the Ti5Si3 compound, have the potential to precipitate during the aging heat treatment stage, forming nanoscale precipitates to purify the copper matrix, improve electrical conductivity, and significantly increase strength. This approach differs from the traditional view that Ti and Si are detrimental to copper conductivity.

[0014] The preparation method of the above-mentioned high-strength copper alloy for power grids includes the following steps:

[0015] 1) Using Cu, Ti and Si as raw materials, they are melted in a medium-frequency vacuum induction melting furnace and then cast into a water-cooled mold for rapid cooling to form an ingot.

[0016] 2) Roll the ingot at dry ice temperature, with a single reduction of 1-2 mm and a total reduction of ≥90%;

[0017] 3) The rolled product is subjected to isothermal aging heat treatment, and after cooling, the copper alloy is obtained.

[0018] The reason this invention does not involve solution treatment is that Ti and Si have high solubility in the copper matrix. Rapid cooling via a water-cooled mold allows Ti and Si elements in the alloy to exist in the ingot in a solid solution form. The reason this invention uses dry ice temperature rolling with a single reduction of 1-2 mm and a total reduction of ≥90% is that copper alloys exhibit significant work hardening at dry ice temperatures. Large deformation processing significantly increases dislocation density, providing rapid diffusion channels for subsequent aging treatment and promoting the formation of Ti and Si compound particles.

[0019] Preferably, in step 1), the melting temperature is 1200-1600℃; the casting temperature is controlled at 1200-1300℃; and the water-cooled mold uses a water-cooled copper mold with a cooling rate higher than 50℃ / s.

[0020] Preferably, in step 3), the heat treatment temperature is 400-600℃; the heat treatment time is 0.5-24h; and after isothermal aging heat treatment, the alloy is cooled by air.

[0021] Compared with the prior art, the copper alloy and its preparation method provided by the present invention have the following beneficial effects:

[0022] (1) The alloy preparation process of the present invention is simple and does not require complex processes such as solution treatment, hot rolling, and drawing.

[0023] (2) The Cu-Ti-Si alloy obtained by this invention has strength and conductivity that are not inferior to the aforementioned Cu-Ni-Si series alloys, but has a lower raw material cost, which is conducive to its application in high-voltage transformer bushing clamps. Attached Figure Description

[0024] Figure 1 This is a tensile stress-strain curve of the alloy of the product in Example 5 of the present invention;

[0025] Figure 2 The transmission electron microscope and energy dispersive spectroscopy (EDS) images of the Ti5Si3 nano-precipitated phase of the product in Example 5 of this invention are shown.

[0026] Figure 3 This is an XRD analysis curve of the nano-precipitated phase of the product in Example 5 of the present invention. Detailed Implementation

[0027] The present invention will be further described below with reference to specific embodiments.

[0028] Example 1

[0029] This embodiment describes a method for preparing a high-strength copper alloy for power grids, and the steps are as follows:

[0030] (1) Using Cu, Ti and Si as raw materials, after melting in a medium-frequency vacuum induction melting furnace, the ingot is poured into a mold to form a casting. The melting temperature is 1600℃ and the casting temperature is controlled at 1300℃. The casting mold is a water-cooled copper mold with a cooling rate of 100℃ / s.

[0031] The weight percentage of Ti is 1.0%, the weight percentage of Si is 0.35%, the atomic ratio of Ti to Si is 5:3, and the balance is copper.

[0032] (2) The ingot is rolled at dry ice temperature, with a single reduction of 1 mm and a total reduction of 90%.

[0033] (3) The rolled sample was subjected to isothermal aging heat treatment at a temperature of 400°C for 4 hours to obtain the copper alloy. After isothermal aging heat treatment, the alloy was cooled by air.

[0034] Example 2

[0035] The difference from Example 1 is that the aging time in step (3) is 24 hours, while other parameters are the same.

[0036] Example 3

[0037] The difference from Example 1 is that the aging time in step (3) is 0.5h, while the other parameters are the same.

[0038] Example 4

[0039] The difference from Example 1 is that the aging temperature in step (3) is 600℃, while the other parameters are the same.

[0040] Example 5

[0041] The difference from Example 1 is that the content (mass percentage) of Ti and Si added in step (1) is 0.40% and 0.14% respectively, the melting temperature is 1300℃, and the casting temperature is controlled at 1200℃; other parameters are the same.

[0042] Example 6

[0043] The difference from Example 1 is that the content (mass percentage) of Ti and Si added in step (1) is 0.8% and 0.28% respectively, while other parameters are the same.

[0044] Comparative Example 1

[0045] The difference from Example 1 is that the melting temperature in step (1) is 1200℃ and the casting temperature is controlled at 1150℃; other parameters are the same.

[0046] Comparative Example 2

[0047] The difference from Example 1 is that the content (mass percentage) of Ti and Si added in step (1) is 1% and 0.2% respectively, while other parameters are the same.

[0048] Comparative Example 3

[0049] The difference from Example 1 is that the content (mass percentage) of Ti and Si added in step (1) is 3% and 1.05% respectively, while other parameters are the same.

[0050] Comparative Example 4

[0051] The difference from Example 1 is that the rolling temperature in step (2) is the liquid nitrogen temperature.

[0052] Comparative Example 5

[0053] The difference from Example 1 is that the rolling temperature in step (2) is room temperature.

[0054] The microstructure of the samples was observed using transmission electron microscopy. Additionally, the hardness of the samples was tested according to the national standard GB / T 4342-1991 "Metallic Materials - Microscopic Vickers Hardness Test Method"; and the room temperature conductivity of the samples was measured according to GB / T 351-1995 "Method for Measurement of Resistivity of Metallic Materials". The detailed results of the above performance tests are shown in Table 2.

[0055] Table 2. Properties of copper alloys obtained in the examples and comparative examples.

[0056]

[0057] As can be seen from the results of Examples 1-6, a high-performance copper alloy can be obtained when prepared according to the technical solution of the present invention. Among them, Figure 1 The stress-strain tensile curve of the alloy obtained in Example 5 shows that its peak strength can reach 741 MPa; Figure 2 The images shown are transmission electron microscope and energy dispersive spectroscopy (EDS) images of the Ti5Si3 nano-precipitates obtained in Example 5. A large number of nano-sized precipitates can be seen, which are mainly composed of Ti and Si elements. Figure 3 The XRD analysis curve of the nanoprecipitated phase obtained in Example 5 clearly indicates the Ti5Si3 second phase.

[0058] By comparing Example 1 and Comparative Example 1, it can be seen that when the smelting and casting temperatures are too low and deviate from the reasonable range required by the present invention, qualified ingots cannot be obtained.

[0059] By comparing Example 1 and Comparative Example 2, it can be seen that when the atomic ratio of Ti and Si does not meet 5:3, the hardness and electrical conductivity of the alloy are not high. The reason is that Ti and Si cannot form Ti5Si3 precipitate phase, and the residual solid solution elements seriously deteriorate the electrical conductivity.

[0060] By comparing Example 1 and Comparative Example 3, it can be seen that even if the atomic ratio of Ti to Si is 5:3, if the total content exceeds the range set by the technical solution of the present invention, the solid solubility of the two does not increase proportionally, and a relatively pure copper matrix cannot be obtained, resulting in a low conductivity of the sample.

[0061] By comparing Example 1 and Comparative Example 4, it can be seen that if the rolling temperature is reduced indiscriminately, the sample will crack severely during the rolling process.

[0062] By comparing Example 1 and Comparative Example 5, it can be seen that if the rolling temperature is too high (e.g., room temperature), the work hardening effect cannot be fully achieved, and Ti and Si are difficult to fully precipitate as Ti5Si3 phase, resulting in poor mechanical and electrical properties of the sample.

Claims

1. A method for preparing a high-strength copper alloy for power grids, characterized in that, The high-strength copper alloy contains Ti, Si and Cu, wherein Ti accounts for 0.4%-1.0% by weight, Si accounts for 0.14%-0.35% by weight, and the atomic ratio of Ti to Si is 5:3, with the balance being copper; the copper alloy is composed of a copper matrix and Ti5Si3 precipitates, and the Ti5Si3 precipitates are spherical particles with a diameter of 10-50 nm; The preparation method of the above-mentioned high-strength copper alloy for power grids includes the following steps: 1) Using Cu, Ti and Si as raw materials, they are melted in a medium-frequency vacuum induction melting furnace and then cast into a water-cooled mold for rapid cooling to form an ingot; 2) Roll the ingot at dry ice temperature, with a single reduction of 1-2 mm and a total reduction of ≥90%; 3) The rolled product is subjected to isothermal aging heat treatment, and after cooling, the copper alloy is obtained. In step 1), the water-cooled mold uses a water-cooled copper mold, and the cooling rate is higher than 50℃ / s; In step 3), the heat treatment temperature is 400-600℃ and the heat treatment time is 0.5-24h.

2. The preparation method according to claim 1, characterized in that, The weight percentage of Si is 0.14%-0.3%.

3. The preparation method according to claim 1, characterized in that, In step 1), the melting temperature is 1200-1600℃.

4. The preparation method according to claim 1, characterized in that, In step 1), the casting temperature is controlled at 1200-1300℃.

5. The preparation method according to claim 1, characterized in that, In step 3), after isothermal aging heat treatment, the alloy is cooled by air.

Images