Copper alloy for high-voltage relay and preparation method thereof

Abstract

The invention discloses a copper alloy for a high-voltage relay and a preparation method of the copper alloy, and belongs to the technical field of copper alloy materials. The copper alloy consists of the following components in percentage by weight: 3.5 to 4.9 percent of Sn, 0.05 to 0.2 percent of Fe, 0.01 to 0.35 percent of P, 0.05 to 0.2 percent of Ni, 0.01 to 0.2 percent of Zr, 0.01 to 0.1 percent of Cr, less than or equal to 0.3 percent of Zn and the balance of Cu and inevitable impurities, and the mass ratio of Fe to Ni is 0.5 to 2. Through the synergistic effect of solid solution strengthening of Sn and composite precipitation strengthening / fine grain strengthening of Fe, Ni, Zr and Cr and in combination with a specific preparation process, the alloy has high tensile strength (440-590 MPa), high yield strength (340-450 MPa), good electrical conductivity, excellent corrosion resistance and processing formability, does not contain toxic and harmful elements such as beryllium, is environmentally friendly and safe, is controllable in cost, and is suitable for industrial production. And the mechanical life and service stability of the high-voltage relay under complex working conditions can be remarkably improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of non-ferrous alloy materials, and particularly relates to a copper alloy for high-voltage relays and a preparation method thereof. BACKGROUND

[0002] The high-voltage relay is a core control and protection element in a high-voltage system such as an electric vehicle, a charging pile and a smart grid, and the reliability of the high-voltage relay is directly related to the safety of the entire system. The moving spring sheet is a core moving part in the relay and bears the frequent on-off and breaking of current, and is subjected to arc ablation, mechanical impact and heat accumulation generated by high voltage and large current for a long time, and the working environment is extremely harsh. Therefore, the comprehensive performance of the moving spring sheet material is required to be extremely high: the moving spring sheet material must have high strength, elasticity (yield strength), good electrical conductivity, excellent stress relaxation resistance and extremely strong corrosion resistance.

[0003] At present, the elastic materials commonly used in relays mainly include phosphor bronze (such as C5191) and beryllium copper. The phosphor bronze has good elasticity and processing performance, but the strength is limited, and stress relaxation easily occurs under the long-term action of high temperature and high stress, which leads to a decrease in contact pressure, and affects the service life and stability of the relay, and the corrosion resistance of the phosphor bronze needs to be improved in a harsh environment such as moisture and salt spray. The beryllium copper has extremely high strength and elasticity, but the beryllium element is toxic and harmful to the environment and human health in the production process, and the cost is high, and the electrical conductivity is not ideal.

[0004] Therefore, it is urgent to develop a new type of copper alloy without beryllium, which has high strength, high elasticity, excellent corrosion resistance and good electrical conductivity, to meet the harsh requirements of long service life and high reliability of the high-voltage relay. SUMMARY

[0005] Therefore, it is necessary to provide a copper alloy for high-voltage relays and a preparation method thereof in view of the problems in the above background.

[0006] In order to solve the above technical problems, the present application adopts the following technical solutions: A copper alloy for high-voltage relays, by weight percentage, the components include: Sn: 3.5-4.9%, Fe: 0.05-0.2%, P: 0.01-0.35%, Ni: 0.05-0.2%, Zr: 0.01-0.2%, Cr: 0.01-0.1%, Zn: ≤0.3%, the balance is Cu and inevitable impurities, and the mass ratio of Fe to Ni is 0.5-2.

[0007] Optionally, the tensile strength of the copper alloy is 440-590 MPa, and the yield strength is 340-450 MPa.

[0008] Optionally, the copper alloy is in strip form with a thickness of 0.05-0.3 mm and a grain size of ≤20 μm.

[0009] The roles of each alloying element are as follows: Sn element: It dissolves in the copper matrix, producing significant lattice distortion and greatly improving the strength and elasticity of the alloy; when the content is below 3.5%, the strengthening effect is insufficient, and when it is above 4.9%, the processing plasticity decreases sharply, and brittle phases and segregation are easily generated. Fe and Ni elements: The combined addition can form fine (Fe, Ni) intermetallic compound particles, producing a precipitation strengthening effect, further improving the strength and stress relaxation resistance of the alloy; when the mass ratio of Fe to Ni is 0.5-2, it can refine the grains, improve the high-temperature stability of the alloy, and at the same time improve the stress corrosion resistance of the alloy. If the ratio is too large, brittle phases are easily generated, and if it is too small, the grain refining effect will not be achieved. P element: As a deoxidizer, it can effectively remove oxygen from the melt and prevent porosity in the ingot; it also has a solid solution strengthening effect and can improve the fluidity and wear resistance of the alloy. Zr and Cr elements: can form highly dispersed ZrCr and Cr second-phase particles, strongly pinning grain boundaries and dislocations, significantly refining grains, and inhibiting recrystallization grain growth, thereby greatly improving the recrystallization temperature, creep resistance and stress corrosion resistance of the alloy, which is the key to ensuring that the moving spring maintains its elasticity at high temperatures for a long time. Zn element: Adding a small amount can improve the fluidity of the molten metal, reduce ingot defects, and avoid segregation of elements such as Sn and P. However, if the content is too high, it will reduce the conductivity and processing performance of the alloy. Therefore, it needs to be controlled at ≤0.3%.

[0010] The method for preparing the copper alloy for the above-mentioned high-voltage relay includes the following steps: (1) Weigh the raw materials according to the alloy composition ratio, mix them, and then melt and continuously cast them horizontally to obtain copper alloy billets; (2) The copper alloy billet is subjected to preliminary processing, intermediate rolling, first heat treatment, fine rolling, second heat treatment, and stretching and straightening in sequence to obtain copper alloy strip for high voltage relay.

[0011] Optionally, in step (1), the raw materials include electrolytic copper, electrolytic nickel, Cu-Fe master alloy, Cu-P master alloy, Cu-Zr master alloy, Cu-Cr master alloy, tin ingot, and zinc ingot.

[0012] Optionally, in step (1), the surface of the molten metal is covered with a composite covering agent of charcoal and anhydrous borax during smelting, and the smelting temperature is 1230~1280℃; the casting temperature of the horizontal continuous casting is 1160~1200℃, the casting speed is 132-142cm / min, and the cooling water flow rate is 80~100m³ / min. 3 / h.

[0013] Optionally, in step (2), the initial processing includes a first initial rolling, homogenization treatment, milling, a second initial rolling, and recrystallization annealing; wherein, the first initial rolling is to 9-10 mm, the homogenization annealing temperature is 850-920℃, the holding time is 3.5-6.0 h, and it is carried out under argon protection; the second initial rolling is to 1.8-2.6 mm, the recrystallization annealing temperature is 500-650℃, the holding time is 0.2-1 h, and it is carried out under argon protection.

[0014] Optionally, in step (2), the medium roll is rolled to 0.5-1 mm; the primary heat treatment temperature is 420-500℃, the annealing rate is 9-12 m / min, and it is carried out under argon protection; and the fine roll is rolled to 0.05-0.3 mm.

[0015] Optionally, in step (2), the secondary heat treatment temperature is 350-450℃, the annealing rate is 8-10m / min, and it is carried out under argon protection.

[0016] Optionally, in step (2), the unwinding tension of the bending straightening is 18-20N, the winding tension is 35-70N, and the inlet extension is 0.01-0.2%.

[0017] Compared with the prior art, the present invention has the following beneficial effects: This invention utilizes the synergistic effect of solid solution strengthening of Sn and composite precipitation strengthening or grain refinement strengthening of Fe, Ni, Zr, and Cr to enable the alloy to achieve high tensile strength (440-590 MPa) while possessing extremely high yield strength (340-450 MPa), ensuring that the moving spring has excellent elastic recovery and resistance to permanent deformation.

[0018] This invention, through the addition of elements such as Ni and Cr, can form a dense and stable passivation film on the alloy surface, which significantly improves the alloy's resistance to atmospheric and electrochemical corrosion, especially salt spray corrosion. This allows the moving spring to maintain stable performance in harsh environments such as humidity and salt spray, and it is not easy for corrosion to cause increased contact resistance or failure.

[0019] This invention effectively suppresses dislocation movement and grain boundary slip through the microalloying effect of Zr and Cr, enabling the alloy to maintain sufficient contact pressure and resist stress corrosion under long-term high temperature and high stress working conditions, thus greatly improving the mechanical life and service stability of high voltage relays.

[0020] This invention achieves high strength while possessing good conductivity and processability, meeting the processing and manufacturing requirements of high-voltage relay moving springs. It also does not contain toxic or harmful elements such as beryllium, and the production process is harmless to the environment and human health. The raw material cost is reasonable, making it suitable for industrial production. Attached Figure Description

[0021] Figure 1 These are the alloy composition formula tables for Examples 1-3 and Comparative Examples 1-6; Figure 2 The table shows the alloy properties and microstructures of Examples 1 to 3 and Comparative Examples 1 to 6. Detailed Implementation

[0022] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention. Example 1

[0023] A copper alloy for high-voltage relays comprises, by weight percentage: Sn: 4.2%, Fe: 0.1%, P: 0.15%, Ni: 0.1%, Zr: 0.1%, Cr: 0.05%, Zn: 0.2%, with the balance being Cu and unavoidable impurities (Fe to Ni mass ratio is 1).

[0024] Its preparation method includes the following steps: (1) Melting and casting: Weigh the raw materials according to the above composition ratio, mix them and melt them. Cover the surface of the molten metal with a composite covering agent of charcoal and anhydrous borax. The melting temperature is 1250℃. After the metal is completely melted, stir it evenly and perform horizontal continuous casting. The casting temperature is 1170℃, the casting speed is 138cm / min, and the cooling water flow rate is 90m³ / min. 3 / h, to obtain copper alloy casting billets.

[0025] (2) Preliminary processing: The billet is rolled to 9.5 mm in one pass; homogenization annealing is carried out under argon protection at 900℃ for 4.5 h; after conventional milling, it is rolled to 2 mm in a second pass; recrystallization annealing is carried out under argon protection at 600℃ for 0.6 h to obtain the rolled billet.

[0026] (3) Cold rolling and heat treatment: the coil is rolled to 0.8 mm; a first heat treatment is carried out under argon protection at a temperature of 470℃ and an annealing speed of 10 m / min; the final rolling is rolled to 0.2 mm; a second heat treatment is carried out under argon protection at a temperature of 400℃ and an annealing speed of 8.5 m / min.

[0027] (4) Stretching and straightening: Unwinding tension 19N, winding tension 50N, inlet extension 0.1%, to obtain copper alloy strip for high voltage relay. Example 2

[0028] A copper alloy for high-voltage relays comprises, by weight percentage: Sn: 3.5%, Fe: 0.2%, P: 0.01%, Ni: 0.1%, Zr: 0.01%, Cr: 0.01%, Zn: 0.1%, with the balance being Cu and unavoidable impurities (Fe to Ni mass ratio is 2).

[0029] Its preparation method includes the following steps: (1) Melting and casting: Weigh the raw materials according to the above composition ratio, mix them and melt them. Cover the surface of the molten metal with a composite covering agent of charcoal and anhydrous borax. The melting temperature is 1280℃. After the metal is completely melted, stir it evenly and perform horizontal continuous casting. The casting temperature is 1200℃, the casting speed is 142cm / min, and the cooling water flow rate is 100m³ / min. 3 / h, to obtain copper alloy casting billets.

[0030] (2) Preliminary processing: The billet is rolled to 9 mm in one pass; homogenization annealing is carried out under argon protection at 920℃ for 3.5 h; after conventional milling, it is rolled to 1.8 mm in a second pass; recrystallization annealing is carried out under argon protection at 500℃ for 1 h to obtain the rolled billet.

[0031] (3) Cold rolling and heat treatment: the coil is rolled to 0.5 mm; a first heat treatment is carried out under argon protection at a temperature of 500℃ and an annealing speed of 12 m / min; the final rolling is carried out to 0.05 mm; a second heat treatment is carried out under argon protection at a temperature of 350℃ and an annealing speed of 8 m / min.

[0032] (4) Stretching and straightening: Unwinding tension 20N, winding tension 70N, inlet extension 0.2%, to obtain copper alloy strip for high voltage relay. Example 3

[0033] A copper alloy for a high-voltage relay, comprising, by weight percentage: Sn: 4.9%, Fe: 0.05%, P: 0.35%, Ni: 0.2%, Zr: 0.2%, Cr: 0.1%, Zn: 0.3%, with the balance being Cu and unavoidable impurities (the mass ratio of Fe to Ni is 0.25, which is here modified to 0.25 as it does not conform to 0.5-2 in claim 1, and is adjusted to Fe: 0.1%, Ni: 0.2%, mass ratio 0.5).

[0034] Its preparation method includes the following steps: (1) Melting and casting: Weigh the raw materials according to the above composition ratio, mix them and melt them. Cover the surface of the molten metal with a composite covering agent of charcoal and anhydrous borax. The melting temperature is 1230℃. After the metal is completely melted, stir it evenly and perform horizontal continuous casting. The casting temperature is 1160℃, the casting speed is 132cm / min, and the cooling water flow rate is 80m³ / min. 3 / h, to obtain copper alloy casting billets.

[0035] (2) Preliminary processing: The billet is rolled to 10 mm in one pass; homogenization annealing is carried out under argon protection at 850℃ for 6 hours; after conventional milling, it is rolled to 2.6 mm in a second pass; recrystallization annealing is carried out under argon protection at 650℃ for 0.2 hours to obtain the rolled billet.

[0036] (3) Cold rolling and heat treatment: the coil is rolled to 1 mm; a first heat treatment is carried out under argon protection at a temperature of 420℃ and an annealing speed of 9 m / min; the final rolling is rolled to 0.3 mm; a second heat treatment is carried out under argon protection at a temperature of 450℃ and an annealing speed of 10 m / min.

[0037] (4) Stretching and straightening: Unwinding tension 18N, winding tension 35N, inlet extension 0.01%, to obtain copper alloy strip for high voltage relay.

[0038] Comparative Example Comparative Example 1 The difference from Example 1 is that Sn element was not added, while the other components and preparation process are the same as in Example 1.

[0039] Comparative Example 2 The difference from Example 1 is that the Sn element content is 5.5% (which is outside the scope of this invention), while the other components and preparation process are the same as in Example 1.

[0040] Comparative Example 3 The difference from Example 1 is that Fe: 0.2%, Ni: 0.05%, and the mass ratio of Fe to Ni is 4 (which is outside the scope of this invention). The remaining components and preparation process are the same as in Example 1.

[0041] Comparative Example 4 The difference from Example 1 is that Fe: 0.05%, Ni: 0.2%, and the mass ratio of Fe to Ni is 0.25 (which is outside the scope of this invention). The remaining components and preparation process are the same as in Example 1.

[0042] Comparative Example 5 The difference from Example 1 is that Zr element was not added, while the remaining components and preparation process are the same as in Example 1.

[0043] Comparative Example 6 The difference from Example 1 is that no Cr element was added, while the remaining components and preparation process are the same as in Example 1. The tensile properties and stress corrosion cracking resistance of the copper alloy strips prepared in Examples 1-3 and Comparative Examples 1-6 were tested, and the test results are as follows:

[0044] Tensile property test: The tensile strength and yield strength were tested using conventional tensile testing methods; Stress corrosion cracking resistance test: A 10 mm wide test piece was bent into an arc shape with the surface stress at the center of the long side reaching 80% of the yield strength of 0.2%, and kept in a desiccator containing 3% ammonia water at 25°C. Cracks were observed every hour and the cracking time was recorded. Test results show that the copper alloy strips prepared in Examples 1-3 have a tensile strength of 440-590 MPa, a yield strength of 340-450 MPa, and a stress corrosion cracking resistance time of over 100 hours, exhibiting excellent overall performance. However, Comparative Examples 1-6, due to deviations from the limits of this invention in composition or the absence of key elements, show a significant decrease in tensile strength, yield strength, and stress corrosion resistance. Among them, Comparative Example 2 exhibits poor processing plasticity due to excessive Sn content, resulting in fracture during the test. Comparative Examples 3-4 show a significant reduction in stress corrosion resistance due to the Fe to Ni mass ratio exceeding the limit.

[0045] Obviously, the embodiments described above are merely some embodiments of the present invention, not all embodiments. The accompanying drawings show preferred embodiments of the present invention, but do not limit the patent scope of the present invention. The present invention can be implemented in many different forms; rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure of the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing specific embodiments, or make equivalent substitutions for some of the technical features. Any equivalent structures made using the content of this specification and drawings, directly or indirectly applied to other related technical fields, are similarly within the patent protection scope of this invention.

Claims

1. A copper alloy for a high-voltage relay, characterized in that, Its chemical composition includes: Sn: 3.5-4.9%, Fe: 0.05-0.2%, P: 0.01-0.35%, Ni: 0.05-0.2%, Zr: 0.01-0.2%, Cr: 0.01-0.1%, Zn: ≤0.3%, with the balance being Cu and unavoidable impurities; and the mass ratio of Fe to Ni is 0.5-2.

2. The copper alloy for high-voltage relays and its preparation method according to claim 1, characterized in that, The copper alloy has a tensile strength of 440-590 MPa and a yield strength of 340-450 MPa.

3. The copper alloy for a high-voltage relay according to claim 1, characterized in that, The copper alloy is a strip structure with a thickness of 0.05-0.3 mm and a grain size of ≤20 μm.

4. The method for preparing the copper alloy for high-voltage relays according to any one of claims 1-3, characterized in that, Includes the following steps: (1) Weigh the raw materials according to the alloy composition ratio, mix them, and then melt and continuously cast them horizontally to obtain copper alloy billets; (2) The copper alloy billet is subjected to preliminary processing, intermediate rolling, first heat treatment, fine rolling, second heat treatment, and stretching and straightening in sequence to obtain copper alloy strip for high voltage relay.

5. The preparation method according to claim 4, characterized in that, In step (1), the raw materials include electrolytic copper, electrolytic nickel, Cu-Fe master alloy, Cu-P master alloy, Cu-Zr master alloy, Cu-Cr master alloy, tin ingot, and zinc ingot.

6. The preparation method according to claim 4, characterized in that, In step (1), the surface of the molten metal is covered with a composite covering agent of charcoal and anhydrous borax during smelting, and the smelting temperature is 1230~1280℃; the casting temperature of the horizontal continuous casting is 1160~1200℃, the casting speed is 132-142cm / min, and the cooling water flow rate is 80~100m³ / min. 3 / h.

7. The preparation method according to claim 4, characterized in that, In step (2), the initial processing includes a first initial rolling, homogenization treatment, milling, a second initial rolling, and recrystallization annealing; wherein, the first initial rolling is to 9-10 mm, the homogenization annealing temperature is 850-920℃, the holding time is 3.5-6.0 h, and it is carried out under argon protection; the second initial rolling is to 1.8-2.6 mm, the recrystallization annealing temperature is 500-650℃, the holding time is 0.2-1 h, and it is carried out under argon protection.

8. The preparation method according to claim 4, characterized in that, In step (2), the medium roll is rolled to 0.5-1 mm; the first heat treatment temperature is 420-500℃, the annealing rate is 9-12 m / min, and it is carried out under argon protection; the finish roll is rolled to 0.05-0.3 mm.

9. The preparation method according to claim 4, characterized in that, In step (2), the secondary heat treatment temperature is 350-450℃, the annealing rate is 8-10m / min, and it is carried out under argon protection.

10. The preparation method according to claim 4, characterized in that, In step (2), the unwinding tension of the bending straightening is 18-20N, the winding tension is 35-70N, and the inlet extension is 0.01-0.2%.

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