High-strength conductive free-cutting elastic copper alloy and preparation method and application thereof

Abstract

The invention belongs to the field of copper alloy materials, and discloses a high-strength conductive free-cutting elastic copper alloy which comprises 0.5 wt%-3 wt% of Ni, 0.1 wt%-2 wt% of Pb, 0.1 wt%-0.3 wt% of P, 0.01 wt%-0.5 wt% of Si and the balance Cu. The preparation method comprises the following steps: weighing pure copper, pure nickel, pure silicon, pure lead and a copper-phosphorus intermediate alloy according to a mass ratio, melting in a heating furnace, and casting an alloy melt into a cast ingot; and then homogenizing treatment, first-time cold deformation treatment, first-time aging treatment, second-time cold deformation treatment, second-time aging treatment, third-time cold deformation treatment and annealing treatment are sequentially carried out, and the high-strength conductive elastic copper alloy is obtained. The Si element is added into the components of the alloy, precipitation of Ni5P4 phase particles can be accelerated through addition of the Si element, particle coarsening is inhibited, and the strength and performance of the copper alloy are more excellent.

Description

Technical Field

[0001] The invention belongs to the field of copper alloys, and in particular relates to a high-strength conductive and easy-to-cut elastic copper alloy and a preparation method and application thereof. Background Art

[0002] C19160 copper alloy is an alloy material with high corrosion resistance, tensile strength, yield strength, high conductivity, easy cutting and other excellent properties. It is currently widely used to replace beryllium copper alloy with the same performance and lower cost. C19160 copper alloy is usually used as a material for electrical contacts, elastic elements and connectors due to its good comprehensive performance advantages, easy cutting performance, conductivity and tensile strength, and is generally used in the production of electronic connector components.

[0003] The element composition of C19160 alloy is mainly Ni: 0.80-1.20%, Pb: 0.80-1.20%, P: 0.15-0.30% and the balance of copper. It has excellent strength and electrical conductivity and good cutting performance. Although this alloy has the above advantages, its comprehensive performance needs to be strengthened, especially the stress relaxation performance. Summary of the invention

[0004] The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art and provide a high-strength conductive and easy-to-cut elastic copper alloy with high strength, excellent conductivity, excellent stress relaxation performance and excellent corrosion resistance, and a preparation method thereof.

[0005] In order to solve the above technical problems, the technical solution proposed by the present invention is: A high-strength conductive and easy-to-cut elastic copper alloy, which comprises, by mass percentage, 0.5wt%-3wt% Ni, 0.1wt%-0.3wt% P, 0.1wt%-2wt% Pb, 0.01wt%-0.5wt% Si, and the balance is Cu. The Si content cannot be too low, otherwise the stress relaxation performance will not be significantly improved, nor can it be too high, otherwise the electrical conductivity of the alloy will be greatly reduced; the Pb content cannot be too low, otherwise the cutting performance of the alloy will be slightly affected, and the Pb content cannot be too high, otherwise the mechanical properties of the alloy will deteriorate.

[0006] Preferably, the mass content of Si element in the above-mentioned high-strength, conductive and easy-to-cut elastic copper alloy is not higher than 0.2wt%.

[0007] The above-mentioned high-strength conductive and easy-to-cut elastic copper alloy preferably has a ratio of Ni element content to the sum of P and Si element contents of Ni: (P + Si) = 2-6, and further preferably Ni: (P + Si) = 2.5-6, a ratio of Ni element content to P element content of Ni: P = 3-10, so as to achieve a better precipitation strengthening effect, a ratio of Ni element content to Si element content of Ni: Si = 10-30, and the addition of trace Si has little effect on the conductivity while hindering the coarsening of precipitated phases such as Ni5P4 and Ni3P during stress relaxation, while the fine precipitates have a more significant effect on dislocation inhibition.

[0008] The above-mentioned high-strength conductive and easy-to-cut elastic copper alloy preferably has an electrical conductivity of 50-75% IACS, a tensile strength of 600-710 MPa, and an elongation of 3-10%; and the stress relaxation resistance can reach 70%-85% after loading at 150°C for 100 hours.

[0009] As a general inventive concept, the present invention also provides a method for preparing the above-mentioned high-strength conductive free-cutting elastic copper alloy, comprising the following steps: (1) pure copper, pure nickel, pure silicon, pure lead and copper-phosphorus master alloy are weighed according to mass ratio, placed in a heating furnace for melting, and then the alloy melt is cast into an ingot to obtain an ingot billet; (2) homogenizing the ingot obtained in step (1); the main purpose is to eliminate defects caused by casting; (3) The ingot after homogenization treatment in step (2) is subjected to the first cold deformation treatment, the first aging treatment, the second cold deformation treatment, the second aging treatment, the third cold deformation treatment, and the annealing treatment in sequence to obtain the high-strength conductive elastic copper alloy. The multi-stage aging treatment can promote the precipitation of the precipitate phase particles and avoid the coarsening of the precipitate phase, thereby achieving an effect of increasing the strength; that is, the multi-stage aging treatment adopted in the present application can promote the precipitation of the precipitate phase in the matrix, while avoiding the growth of the precipitate phase, making the precipitation strengthening more significant, and at the same time, the fine precipitate phase can effectively pin dislocations, thereby improving the strength and stress relaxation resistance of the alloy. The main purpose of the annealing treatment is to increase the density of the Ni-P clusters and reduce the internal stress while having almost no effect on the mechanical properties.

[0010] In the above-mentioned preparation method, preferably, in step (1), the temperature in the furnace is first raised to 1500-1600°C, and an inert gas is filled into the furnace. Then, pure copper, pure nickel and pure silicon are placed in the heating furnace, and the melt temperature in the furnace is controlled to be 1600-1800°C. After the raw materials are completely melted, the temperature in the furnace is adjusted to 1300-1350°C, and then lead and copper-phosphorus master alloy are added for smelting to form an alloy melt.

[0011] In the above preparation method, preferably, in step (2), the temperature of the homogenization treatment is 900-950° C. and the time is 2-4 hours.

[0012] In the above preparation method, preferably, in step (3), the first cold deformation treatment is a cold rolling deformation treatment, which is carried out in multiple passes, and the deformation amount of each cold rolling pass is controlled to be 10-20%, and the deformation strain rate is 0.5-10s -1 The total deformation of cold rolling deformation treatment is 60%-70%. In the first cold deformation treatment, a larger deformation is beneficial to the precipitation of precipitation phase.

[0013] In the above preparation method, preferably, in step (3), the temperature of the first aging treatment is 400-500°C, and the time is 0.5-10 h; the temperature of the second aging treatment is 350-450°C, and the time is 0.5-10 h.

[0014] In the above preparation method, preferably, in step (3), the second cold deformation treatment is room temperature cold deformation treatment, the total deformation amount is 50-60%, and the deformation strain rate is 0.5-10s -1 The third cold deformation treatment is room temperature cold deformation treatment, with a total deformation of 50-60% and a deformation strain rate of 0.5-10s -1 .

[0015] In the above preparation method, preferably, in step (3), the annealing treatment is performed at a temperature of 200-300° C. and for a time of 0.5-2 h.

[0016] As a general inventive concept, the present invention also provides an application of the above-mentioned high-strength conductive and easy-to-cut elastic copper alloy or the high-strength conductive and easy-to-cut elastic copper alloy prepared by the above-mentioned preparation method in electrical contacts, elastic elements or connectors.

[0017] Compared with the prior art, the advantages of the present invention are: (1) The present invention adds Si element to the alloy composition. The addition of Si element can accelerate the precipitation of Ni5P4 phase particles and inhibit the coarsening of particles, thereby making the strength and performance of the copper alloy more excellent.

[0018] (2) The present invention promotes the precipitation of nano-sized Ni5P4 phase from the matrix through multi-stage combined aging treatment, thereby ensuring excellent mechanical properties while having excellent electrical conductivity. At the same time, the smaller precipitated phase can improve the alloy's resistance to stress relaxation, and the use of low-temperature annealing treatment can promote Ni-P clustering.

[0019] (3) The present invention can effectively inhibit the coarsening of Ni5P4 during long-term stress relaxation at 150°C by adding Si, effectively hinder dislocation movement, and improve the alloy's stress relaxation resistance.

[0020] (4) The high-strength conductive elastic copper alloy of the present invention has an electrical conductivity of 50%-75% IACS, a tensile strength of 600-710 MPa, and an elongation of 3%-10%. After loading at 150°C for 100 hours, the stress relaxation resistance can reach 70%-85%, and can be used in electrical contacts, elastic elements or connectors. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 The microstructure of the alloy in the homogenized state in Example 4 of the present invention; Figure 2 The microstructure of the alloy after secondary cold deformation in Example 4 of the present invention; Figure 3 This is the fracture morphology of the alloy after three cold deformations in Example 4 of the present invention. DETAILED DESCRIPTION

[0022] In order to facilitate the understanding of the present invention, the present invention will be described more comprehensively and carefully in combination with preferred embodiments below, but the protection scope of the present invention is not limited to the following specific embodiments.

[0023] Unless otherwise defined, all the professional terms used below have the same meanings as those generally understood by those skilled in the art. The professional terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention.

[0024] Unless otherwise specified, all reagents and raw materials used in the present invention are commercially available products or products that can be prepared by known methods.

[0025] Embodiment 1: The invention discloses a high-strength, conductive, easy-to-cut elastic copper alloy, which comprises, by mass percentage, 1.2 wt% Ni, 0.50 wt% Pb, 0.15% P, 0.05 wt% Si, and the remainder Cu and other inevitable impurities.

[0026] The preparation method of the high-strength conductive and easy-to-cut elastic copper alloy of this embodiment comprises the following steps: (1) First, raise the temperature in the furnace to 1550°C, put pure copper, pure nickel and pure silicon into the heating furnace for melting, and control the melt temperature in the furnace to be 1650°C. After the raw materials are completely melted, adjust the temperature to 1300°C, and then add pure lead and copper-phosphorus intermediate alloy for smelting. After smelting evenly, an alloy melt is formed, and then the alloy melt is cast into an ingot to obtain an ingot billet.

[0027] (2) The ingot obtained in step (1) is placed in a furnace for annealing and homogenization treatment at a temperature of 900° C. for 4 h.

[0028] (3) The ingot obtained after step (2) is subjected to the first cold deformation treatment, wherein the cold rolling deformation amount of the cold deformation treatment is 70%, the deformation amount of each cold rolling is controlled to be 10%, and the deformation strain rate is 10s -1 .

[0029] (4) The plate obtained after step (3) is subjected to the first aging treatment, the aging treatment temperature is 450° C., and the treatment time is 1 hour.

[0030] (5) The plate obtained after step (4) is subjected to a second room temperature cold deformation treatment, with a total deformation of 60%, a deformation of 10% per pass, and a deformation strain rate of 5 s -1 .

[0031] (6) The plate obtained after step (5) is subjected to a second aging treatment, wherein the second aging treatment temperature is 400° C. and the treatment time is 1 hour.

[0032] (7) The plate obtained after step (6) is subjected to a third room temperature cold deformation treatment, with a total deformation of 60%, a deformation of 10% per pass, and a deformation strain rate of 5 s -1 .

[0033] (8) The plate obtained after step (7) is annealed at 200° C. for 1 h to obtain a high-strength, conductive, easy-to-cut elastic copper alloy.

[0034] Embodiment 2: The invention discloses a high-strength, conductive, easy-to-cut elastic copper alloy, which comprises, by mass percentage, 0.5wt% Ni, 1.00wt% Pb, 0.15% P, 0.05wt% Si, and the remainder is Cu and other inevitable impurities.

[0035] The preparation method of the high-strength conductive and easy-to-cut elastic copper alloy of this embodiment comprises the following steps: (1) First, raise the temperature in the furnace to 1600°C, put pure copper, pure nickel and pure silicon into the heating furnace for melting, and control the melt temperature in the furnace to be 1700°C. After the raw materials are completely melted, adjust the temperature to 1300°C, and then add pure lead and copper-phosphorus intermediate alloy for smelting. After smelting evenly, an alloy melt is formed, and then the alloy melt is cast into an ingot to obtain an ingot billet.

[0036] (2) The ingot obtained in step (1) is placed in a furnace for annealing and homogenization treatment at a temperature of 900° C. for 4 h.

[0037] (3) The ingot obtained after step (2) is subjected to the first cold deformation treatment, wherein the cold rolling deformation amount of the cold deformation treatment is 70%, the pass deformation amount is 10%, and the deformation strain rate is 5s -1 .

[0038] (4) The plate obtained after step (3) is subjected to the first aging treatment, the aging treatment temperature is 450° C., and the treatment time is 1 hour.

[0039] (5) The plate obtained after step (4) is subjected to a second room temperature cold deformation treatment, with a total deformation of 60%, a pass deformation of 10%, and a deformation strain rate of 5s -1 .

[0040] (6) The plate obtained after step (5) is subjected to a second aging treatment, wherein the second aging treatment temperature is 400° C. and the treatment time is 1 hour.

[0041] (7) The plate obtained after step (6) is subjected to a third cold deformation treatment, with a total deformation of 60%, a deformation of each cold rolling pass controlled to 10%, and a deformation strain rate of 10s -1 .

[0042] (8) The plate obtained after step (7) is annealed at 200° C. for 1 h to obtain a high-strength, conductive, easy-to-cut elastic copper alloy.

[0043] Embodiment 3: The invention discloses a high-strength, conductive, easy-to-cut elastic copper alloy, which comprises, by mass percentage, 1.00wt% Ni, 1.00wt% Pb, 0.15% P, 0.25wt% Si, and the remainder Cu and other inevitable impurities.

[0044] The preparation method of the high-strength conductive and easy-to-cut elastic copper alloy of this embodiment comprises the following steps: (1) First, raise the temperature in the furnace to 1550°C, put pure copper, pure nickel and pure silicon into the heating furnace for melting, and control the melt temperature in the furnace to be 1750°C. After the raw materials are completely melted, adjust the temperature to 1350°C, and then add pure lead and copper-phosphorus intermediate alloy for smelting. After smelting evenly, an alloy melt is formed, and then the alloy melt is cast into an ingot to obtain an ingot billet.

[0045] (2) The ingot obtained in step (1) is placed in a furnace for annealing and homogenization treatment at a temperature of 900° C. for 4 h.

[0046] (3) The ingot obtained after step (2) is subjected to the first cold deformation treatment, wherein the cold rolling deformation amount of the cold deformation treatment is 70%, the pass deformation amount is 10%, and the deformation strain rate is 5s -1 .

[0047] (4) The plate obtained after step (3) is subjected to the first aging treatment, the aging treatment temperature is 500° C., and the treatment time is 1 hour.

[0048] (5) The plate obtained after step (4) is subjected to a second cold deformation treatment, with a total deformation of 60%, a deformation of each cold rolling pass controlled to 10%, and a deformation strain rate of 10s -1 .

[0049] (6) The plate obtained after step (5) is subjected to a second aging treatment, wherein the second aging treatment temperature is 400° C. and the treatment time is 1 hour.

[0050] (7) The plate obtained after step (6) is subjected to a third cold deformation treatment, with a total deformation of 60%, a deformation of each cold rolling pass controlled to 10%, and a deformation strain rate of 10s -1 .

[0051] (8) The plate obtained after step (7) is annealed at 300° C. for 1 h to obtain a high-strength, conductive, easy-to-cut elastic copper alloy.

[0052] Embodiment 4: The invention discloses a high-strength, conductive, easy-to-cut elastic copper alloy, which comprises, by mass percentage, 1.00wt% Ni, 1.00wt% Pb, 0.25% P, 0.10wt% Si, and the remainder Cu and other inevitable impurities.

[0053] The preparation method of the high-strength conductive and easy-to-cut elastic copper alloy of this embodiment comprises the following steps: (1) First, raise the temperature in the furnace to 1550°C, put pure copper, pure nickel and pure silicon into the heating furnace for melting, and control the melt temperature in the furnace to 1800°C. After the raw materials are completely melted, adjust the temperature to 1350°C, and then add pure lead and copper-phosphorus intermediate alloy for melting. After uniform melting, an alloy melt is formed, and then the alloy melt is cast into an ingot to obtain an ingot billet.

[0054] (2) The ingot obtained in step (1) is placed in a furnace for annealing and homogenization treatment at a temperature of 900°C for 4 hours. The microstructure of the alloy in homogenized state is as follows: Figure 1 shown.

[0055] (3) The ingot obtained after step (2) is subjected to the first cold deformation treatment, wherein the cold rolling deformation amount of the cold deformation treatment is 70%, the secondary deformation amount is 10%, and the deformation strain rate is 5s -1 .

[0056] (4) The plate obtained after step (3) is subjected to the first aging treatment, the aging treatment temperature is 450° C., and the treatment time is 1 hour.

[0057] (5) The plate obtained after step (4) is subjected to a second cold deformation treatment, with a total deformation of 60%, a secondary deformation of 10%, and a deformation strain rate of 5s-1 The microstructure of secondary cold deformation is as follows: Figure 2 shown.

[0058] (6) The plate obtained after step (5) is subjected to a second aging treatment, wherein the second aging treatment temperature is 400° C. and the treatment time is 1 hour.

[0059] (7) The plate obtained after step (6) is subjected to a third cold deformation treatment, with a total deformation of 60%, a deformation of each cold rolling pass controlled to 10%, and a deformation strain rate of 10s -1 The fracture morphology after three cold deformations is shown in Figure 3 shown.

[0060] (8) The plate obtained after step (7) is annealed at 300° C. for 1 h to obtain a high-strength, conductive, easy-to-cut elastic copper alloy.

[0061] Comparative Example 1: The composition of the copper alloy of this comparative example, in terms of mass percentage, includes: Ni: 1.20%, Pb: 0.50%, P: 0.35%, Si: 0.05%, and the remainder is copper and other inevitable impurities. The preparation method of the copper alloy of this comparative example is the same as that of Example 1.

[0062] Comparative Example 2: The composition of the copper alloy of this comparative example, in terms of mass percentage, includes: Ni: 0.50%; Pb: 1.00%; P: 0.15%; the remainder is copper and other unavoidable impurities. The preparation method of the copper alloy of this comparative example is the same as that of Example 2 except that silicon is not added in step (1), and the other steps are exactly the same as those of Example 2.

[0063] Comparative Example 3: The composition of the copper alloy of this comparative example, in terms of mass percentage, includes: Ni: 1.00%, Pb: 1.00%, P: 0.30%, Si: 0.25%; the rest is copper and other inevitable impurities. The preparation method of the copper alloy of this comparative example is the same as that of Example 3.

[0064] Comparative Example 4: The composition of the copper alloy of this comparative example, in terms of mass percentage, includes: Ni: 1.00%; Pb: 1.00%; P: 0.25%; Si: 0.10%; the rest is copper and other unavoidable impurities. The difference between this comparative example and Example 4 is that the aging temperature is different. The first aging temperature of this comparative example is 550°C, and the temperature of the second aging treatment is 500°C. The other processes and parameters are the same as those of Example 4.

[0065] The compositions of the high-strength conductive and free-cutting elastic copper alloys of the above-mentioned embodiments and comparative examples are shown in Table 1. According to the national standards of the People's Republic of China (GB / T 32791-2016, GB / T 4340.1-2009, GB / T 228.1-2021, GB / T3956-2008, GB / T 10120-2013, GB / T 41509-2022), the electrical conductivity, Vickers hardness, tensile strength, elongation, stress relaxation resistance, and cutting performance of the embodiments and comparative examples were tested respectively, and the results are shown in Table 2.

[0066] Table 1 Element composition of copper alloys of Examples 1-4 and Comparative Examples 1-4 (%)

[0067] Table 2 Physical properties of copper alloys of Examples 1-4 and Comparative Examples 1-4

[0068] According to the data analysis of the embodiments and comparative examples in Table 2, compared with comparative example 1, embodiment 1 has an increased phosphorus content in comparative example 1, and a phosphorus content exceeding 0.3% will cause the electrical conductivity of the alloy to decrease significantly. Compared with comparative example 2, embodiment 2 does not add silicon in comparative example 2, and the strength of the alloy decreases. The reason is that silicon can better precipitate nickel-phosphorus compounds, inhibit particle coarsening, and make the alloy performance superior. Compared with comparative example 3, embodiment 3 has a slightly higher content of P element in comparative example 3, Ni: (P+Si) = 1.8, which results in a large amount of P element unable to form nickel-phosphorus compounds and precipitate, and unable to achieve a good precipitation strengthening effect, which seriously affects the electrical conductivity of the alloy. Compared with comparative example 4, embodiment 4 has different aging treatment parameters and the performance is also very different. Compared with comparative example 4, the aging temperature in embodiment 4 is lower, the precipitated particles are finer, the strengthening effect is obvious, and the lower aging temperature will retain more dislocation structures.

Claims

1. A high-strength, conductive, easy-to-cut elastic copper alloy, characterized in that: Calculated in mass percentage, its composition includes: Ni: 0.5wt%-3wt%, Pb: 0.1wt%-2wt%, P: 0.1wt%-0.3wt%, Si: 0.01wt%-0.5wt%, and the balance is Cu.

2. The high-strength, conductive, free-cutting elastic copper alloy according to claim 1, characterized in that: The mass content of Si element is not higher than 0.2wt%.

3. The high-strength, conductive, free-cutting elastic copper alloy according to claim 1, characterized in that: The ratio of Ni element content to the sum of P and Si element content is Ni: (P+Si) = 2.5-6, the ratio of Ni element content to P element content is Ni: P = 3-10, and the ratio of Ni element content to Si element content is Ni: Si = 10-30.

4. A method for preparing a high-strength, conductive, free-cutting elastic copper alloy as claimed in any one of claims 1 to 3, characterized in that: The following steps are involved: (1) pure copper, pure nickel, pure silicon, pure lead and copper-phosphorus master alloy are weighed according to mass ratio, placed in a heating furnace for melting, and then the alloy melt is cast into an ingot to obtain an ingot billet; (2) homogenizing the ingot obtained in step (1); (3) The ingot after the homogenization treatment in step (2) is subjected to a first cold deformation treatment, a first aging treatment, a second cold deformation treatment, a second aging treatment, a third cold deformation treatment, and an annealing treatment in sequence to obtain the high-strength conductive elastic copper alloy.

5. The preparation method according to claim 4, characterized in that: In step (1), the temperature in the furnace is first raised to 1500-1600°C, and then pure copper, pure nickel and pure silicon are placed in the heating furnace, and the melt temperature in the furnace is controlled to be 1600-1800°C. After the raw materials are completely melted, the temperature in the furnace is adjusted to 1300-1350°C, and then lead and copper-phosphorus master alloy are added for smelting to form an alloy melt.

6. The preparation method according to claim 4, characterized in that: In step (2), the temperature of the homogenization treatment is 900-950°C and the time is 2-4 hours.

7. The preparation method according to claim 4, characterized in that: In step (3), the first cold deformation treatment is a cold rolling deformation treatment, which is carried out in multiple passes. The deformation amount of each cold rolling pass is controlled to be 10-20%, and the deformation strain rate is 0.5-10s -1 The total deformation of cold rolling deformation treatment is 60%-70%.

8. The preparation method according to claim 4, characterized in that: In step (3), the temperature of the first aging treatment is 400-500°C, and the time is 0.5-10 h; the temperature of the second aging treatment is 350-450°C, and the time is 0.5-10 h; the second cold deformation treatment is room temperature cold deformation treatment, the total deformation is 50-60%, and the deformation strain rate is 0.5-10s -1 The third cold deformation treatment is room temperature cold deformation treatment, with a total deformation of 50-60% and a deformation strain rate of 0.5-10s -1 .

9. The preparation method according to claim 4, characterized in that: In step (3), the annealing treatment is carried out at a temperature of 200-300°C and for a time of 0.5-2h.

10. Use of the high-strength, conductive, free-cutting elastic copper alloy according to any one of claims 1 to 3 or the high-strength, conductive, free-cutting elastic copper alloy prepared by the preparation method according to any one of claims 4 to 9 in electrical contacts, elastic elements or connectors.

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