Copper alloy and method for producing the same

Abstract

The present invention discloses a copper alloy and a method for manufacturing the same. The composition of the copper alloy includes Cu: 85% - 92 wt.%, Ni: 0.5 - 1.5 wt.%, Si: 0.2 - 0.8 wt.%, Sn: 0.05 - 0.15 wt.%, Cr: 0.1 - 0.8 wt.%, Zr: 0.01 - 0.5 wt.%, Mg: 0.01 - 0.3 wt.%, and the balance is Zn. In the present invention, by simultaneously adding elements such as Ni, Si, Cr, and Zr to the Cu-Zn-Sn alloy system, the purpose of composite precipitation strengthening is achieved. Further, the present invention utilizes composite precipitation strengthening to control the precipitation order and the size of the precipitation phase of Ni, Cr, Zr, and Si, so that the material obtains good bending characteristics and stress relaxation resistance characteristics.

Description

Technical Field

[0001] The present invention relates to the technical field of copper alloys, and more specifically, to the technical field of copper alloys with high stress relaxation resistance characteristics.

Background Art

[0002] Copper alloys used in connectors, terminals, relays, etc. are required to have good electrical conductivity, yield strength, and stress relaxation resistance levels in order to meet the requirements for current or signal conduction and ensure reliability for long-term use.

[0003] Currently, the copper alloys used in the market are mainly solid-solution strengthened types represented by bronze and brass, and precipitation strengthened types represented by CuNiSi. Bronze can achieve better strength levels due to the action of the Sn element, but it cannot obtain high electrical conductivity, and the electrical conductivity is generally 20% IACS or less. In addition, since Sn metal is expensive, the price of bronze materials is always high. The CuNiSi material can obtain better comprehensive performance by utilizing the precipitation strengthening of Ni and Si elements, but the cost is relatively high due to the price of the metal.

[0004] In Japanese Patent Application Laid-Open Nos. H5-33087 and 2006-283060, a method of adding Ni, Fe, and P elements to a Cu-Zn-Sn alloy system has been designed and developed to facilitate recycling, and the purpose of improving the characteristics of the Cu-Zn-Sn alloy is achieved by utilizing the precipitation strengthening mechanisms of Ni-P and Fe-P. However, the precipitation strengthening effect is not obvious, and sufficient comprehensive performance cannot be obtained. In Japanese Patent Nos. 3953357 and 3717321, the stress relaxation resistance characteristics of the material are improved by adding Ni elements to the Cu-Zn-Sn alloy system to form NiSn intermetallic compounds or finely controlling the ratio of (Fe + Ni) / P. However, only the ratio of Ni / Sn is considered, and the interaction of Ni, Sn, and P elements is not considered, so the purpose of good stress relaxation resistance characteristics cannot be completely achieved.

[0005] In U.S. Patent No. 9,653,191, Fe, Co, and P elements are added to the Cu-Zn-Sn system to obtain a material with good bending characteristics and stress relaxation resistance. However, due to the price of the Co element, this alloy system cannot obtain the advantage of low cost. Chinese Patent No. 10,511,2715 adds Ni and Si elements to the Cu-Zn system to obtain an alloy material with advantages in terms of cost and improved performance. However, since the Zn content of the alloy system is too high (10-20%), this alloy system has a very high possibility of problems such as stress corrosion and low conductivity.

Summary of the Invention

Problems to be Solved by the Invention

[0006] The object of the present invention is to provide a copper alloy and a method for manufacturing the same in order to solve the disadvantages of the prior art.

[0007] The technical solution adopted by the present invention is as follows. The composition contains Cu: 85-92 wt.%, Ni: 0.5-1.5 wt.%, Si: 0.2-0.8 wt.%, Sn: 0.05-0.15 wt.%, Cr: 0.1-0.8 wt.%, Zr: 0.01-0.5 wt.%, Mg: 0.01-0.3 wt.%, and the balance is Zn and unavoidable impurities, and contains NiSi phase and Cr3Si phase, the size of the NiSi phase is 30 nm or less, and the size of the Cr3Si phase is 40-100 nm. It is a copper alloy.

[0008] According to the copper alloy of the present invention, the NiSi phase and the copper alloy matrix show a coherent relationship.

[0009] According to the copper alloy of the present invention, the composition further contains at least one element of Co, Fe, P, Re, and Mn with a total amount of 2.0 wt.% or less, Co: 0.01%-1.0 wt.%, Fe: 0.01%-1.0 wt.%, P: 0.001%-0.05 wt.%, Re: 0.0001%-0.05 wt.%.

[0010] According to the copper alloy of the present invention, the strip of the copper alloy has a yield strength of 550 MPa or more, a conductivity of 35% IACS% or more, and a stress relaxation rate of 25% or less when kept at 150 °C for 1000 hours.

[0011] According to the copper alloy of the present invention, the 90° bend formability of the strip of the copper alloy has a value of R / t ≤ 1 in the GW direction and a value of R / t ≤ 1 in the BW direction, and the 180° bend formability of the strip of the copper alloy has a value of R / t ≤ 2 in the GW direction and a value of R / t ≤ 2 in the BW direction.

[0012] According to the copper alloy of the present invention, the size of the NiSi phase is 10 nm or less.

[0013] According to the copper alloy of the present invention, the copper alloy can be used for manufacturing the terminals of connectors.

[0014] According to the manufacturing method of the copper alloy of the present invention, (1) Melting and casting: a step of melting and forging at a melting temperature of 1200 - 1280 °C and a casting temperature of 1180 - 1250 °C; (2) Preheating: a step of preheating at 800 - 1050 °C for 6 - 10 h to sufficiently homogenize the ingot; (3) Hot rolling: controlling the rolling reduction amount to 85% or more, controlling the slab temperature during rolling to 800 °C or more, and minimizing the precipitation of phase particles such as phases Ni, Si, Cr, etc. during hot rolling; (4) Water quenching: controlling the temperature of the hot - rolled slab to 800 °C or more, performing high - speed on - line water quenching at a cooling water temperature of 30 - 45 °C and an on - line water quenching speed of 30 - 50 m / min, making the temperature difference between the front end and the rear end of the slab before water quenching 40 °C or less, thereby facilitating subsequent aging treatment and solution treatment, and ensuring the uniformity of the performance of the entire finished rolled material; (5) Surface machining: a step of cutting 0.5 - 1.2 mm from each of the upper and lower surfaces of the hot - rolled plate; (6) First cold rolling: a step of controlling the total cold rolling reduction amount to 80% or more to facilitate subsequent aging treatment; (7) Primary aging treatment: at an aging treatment temperature of 350 - 480 °C for 6 - 15 h, Cr3Si phase with a size of 40 - 100 nm is precipitated, and the Cr3Si phase plays a role in suppressing the growth of crystal grains during solution heat treatment. Step and, (8) Online solution treatment: at an online solution temperature of 800 - 950 °C and an online solution rate of 10 - 60 m / min, precipitated phases during hot rolling and water quenching are fully dissolved into the copper matrix. Step and, (9) Secondary cold rolling: controlling the total reduction of cold rolling to 30 - 70%. Step and, (10) Secondary aging treatment: at an aging treatment temperature of 400 - 550 °C for 6 - 15 h, NiSi phase with a size of ≤ 30 nm that is coherent with the copper alloy matrix is precipitated. It includes the step of,

[0015] According to the method for manufacturing a copper alloy of the present invention, the melting and casting method in the step (1) is vertical casting or horizontal continuous casting, and for horizontal continuous casting, a heating and cooling composite mold (HCCM) horizontal continuous casting process is used.

[0016] According to the method for manufacturing a copper alloy of the present invention, the Cr3Si phase is precipitated after the primary aging treatment, and the NiSi phase is precipitated after the secondary aging treatment.

Advantages of the Invention

[0017] Compared with the prior art, the present invention has the following advantages.

[0018] 1. In the Cu - Zn - Sn alloy system, in order to achieve the purpose of composite precipitation strengthening, elements such as Ni, Si, Cr, and Zr are added simultaneously. Thereby, while maintaining the solid solution strengthening effect of the Zn or Sn element, the composite precipitation strengthening of Ni, Si, Cr, and Zr can maximize the strength and stress relaxation resistance characteristics while minimizing the influence on conductivity.

[0019] 2. The present invention can obtain good bending characteristics and stress relaxation resistance characteristics because it utilizes composite precipitation strengthening to control the precipitation sequence of Ni, Cr, Zr, Si and the size of the precipitated phase.

[0020] 3. Since the alloy system of the present invention contains a relatively high content of Zn and other elements, its cost is advantageous compared to ordinary bronze and CuNiSi systems.

[0021] 4. By controlling the size of the precipitation phase so that the size of the NiSi phase is 30 nm or less and the size of the Cr3Si phase is 40 - 100 nm, the effect of precipitation strengthening is enhanced, and the strength of the alloy is further improved.

[0022] 5. Co, Fe, P, Re, and Mn elements are added to the copper alloy. Mg, Co, and Fe play a role in refining the crystal grains and can promote the precipitation of a smaller and denser NiSi phase. P and Re can purify the melt during smelting, refine the crystal grains, and thereby improve the strength and conductivity of the alloy.

Brief Description of the Drawings

[0023]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Modes for Carrying Out the Invention

[0024] To enable those skilled in the art to better understand the technical solutions provided by the present invention, the following will be described in relation to specific examples.

[0025] In the present invention, Ni, Si, and Cr elements are added to the copper alloy material. During the aging treatment, the Ni element and the Si element form a NiSi metal compound phase, and the Cr element and the Si element form a Cr3Si phase. The NiSi phase mainly plays a role in improving the strength and conductivity of this alloy. After the solution treatment of the alloy, it completely dissolves in the copper matrix to form a supersaturated solid solution. During the subsequent aging treatment, the Ni and Si solute elements from the matrix are precipitated in the form of NiSi metal compounds from the solute enrichment region due to the combined action of the aging treatment temperature and the cold rolling strain energy storage, and are dispersed and distributed in the matrix. The NiSi phase suppresses the movement of dislocations and grain boundaries and improves the strength of the alloy. On the other hand, the precipitation of the NiSi phase purifies the matrix, reduces the degree of lattice strain of the copper phase, weakens the degree of scattering of moving electrons, and significantly improves the conductivity of the alloy. A small amount of Cr3Si phase is generated during the casting and crystallization of the alloy, and during the subsequent primary aging treatment, finely dispersed Cr3Si phases (40 nm ≤ size ≤ 100 nm) are precipitated from the matrix.

[0026] The Cr3Si phase can increase the recrystallization temperature and high-temperature softening resistance of the alloy. The Cr3Si phase dispersed and distributed during solution treatment can inhibit the growth of crystal grains and refine the crystal grains. In addition, the Cr3Si phase is the primary phase. During the secondary aging treatment of the alloy, the finely dispersed Cr3Si phase functions as the nucleation and precipitation center of the NiSi phase, promotes the precipitation of the NiSi phase and the refinement of the size of the NiSi phase, can more firmly bond the NiSi phase and the copper matrix, and shows a coherent relationship with the matrix. Due to the precipitation strengthening, dislocation strengthening, and fine grain strengthening effects of the Cr3Si phase and the NiSi phase, the strength of the alloy is greatly improved. The more uniform and dense the distribution of the NiSi phase and the Cr3Si phase, the better the precipitation strengthening effect and the greater the improvement in strength. The size of the Cr3Si phase affects the size and distribution of the NiSi phase during subsequent secondary aging treatment. The coarser the Cr3Si phase (size ≥ 100 nm), the more unevenly distributed and less dense it is, the larger the size of the NiSi phase, the more unevenly distributed and less dense it is. On the other hand, the finer the Cr3Si phase (size ≤ 40 nm), the less likely the precipitation of the NiSi phase occurs, the weaker the precipitation strengthening effect, and the lower the strength of the alloy. Also, if the size of the NiSi phase is too large, the precipitation strengthening effect also weakens, and the strength of the alloy decreases.

[0027] Mg, Co, and Fe play a role in refining crystal grains and can promote the precipitation of smaller and denser NiSi phases. P and Re can purify the melt during smelting, refine crystal grains, and thereby improve the strength and conductivity of the alloy.

[0028] The raw materials were formulated like the copper alloys shown in the components of each example, Comparative Example 1, and Comparative Example 2 in Table 1, and samples were manufactured in the following steps. (1) Vertical semi-continuous casting was used to cast an ingot with a specification of 720×220 mm at a casting temperature of 1190°C. (2) Preheating: The heating temperature was 930°C and it was held for 8 h. (3) Hot rolling: Hot rolling was carried out from 220 mm to 18 mm. (4) Water quenching: Online water quenching was carried out at a slab temperature of 850°C, a cooling water temperature of 38°C, and a quenching rate of 40 m / min. (5) Surface machining: Machining was carried out up to 0.6 mm and 16.2 mm in the up and down directions. (6) First cold rolling: Cold rolling was carried out from 16.2 mm to 0.4 mm. (7) First aging treatment temperature: The aging treatment temperature was 400°C and it was held for 5 h. (8) Online solution treatment: Online solution treatment was carried out at a solution temperature of 830°C and a solution rate of 35 m / min. (9) Second cold rolling: Cold rolling was carried out from 0.4 mm to 0.2 mm. (10) Second aging treatment temperature: The aging treatment temperature was 420°C and it was held for 8 h.

[0029]

Table 1

[0030] Among these, Comparative Example 3 is C51900 tin phosphor bronze and Comparative Example 4 is C26000 brass.

[0031] As shown in FIGS. 1 to 5, FIG. 1 is a scanning electron microscope image of the copper alloy of Example 1, FIGS. 2 to 4 are element distribution diagrams of the copper alloy of Example 1, and FIG. 5 is a transmission electron microscope image of the copper alloy of Example 1. As is clear from the figures, the precipitation phases of the copper alloy manufactured in Example 1 are Cr3Si phase and NiSi phase, respectively. The size of the Cr3Si phase is about 50 nm, the size of the NiSi phase is about 5 nm, and the NiSi phase is uniformly distributed in the copper alloy matrix.

[0032] For the strip samples of the seven manufactured example alloys and four comparative example alloys, the mechanical properties, conductivity, stress relaxation resistance properties, and bending properties were tested respectively.

[0033] The room temperature tensile test was carried out in accordance with 'ISO 6892-1 Metallic materials - Tensile testing - Part 1: Method of test at room temperature' using an electronic universal tensile testing machine. Using a dogbone sample with an effective test width of 20 mm, the tensile speed was set to 5 mm / min.

[0034] The conductivity test complies with "GB / T 32791 Eddy current test method for electrical conductivity of copper and copper alloys", and this detector is an eddy current type metal conductivity meter.

[0035] The stress relaxation resistance property test complies with "GB / T0120-2013 Tensile stress relaxation test method for metallic materials", samples are taken parallel to the rolling direction, the initial load stress value is 80% of the 0.2% yield strength, the test temperature is 150 °C, and the time is 1000 h.

[0036] The bending property test complies with "ISO 7438 Metallic materials - Bending test", and is carried out on a bending testing machine. The samples are 10 mm in width and 50 mm in length.

[0037] The size and performance test results of the precipitation phases of each example and comparative example are shown in Table 2.

[0038]

Table 2

Claims

1. The composition contains: Cu: 85 - 92 wt.%, Ni: 0.5 - 1.5 wt.%, Si: 0.2 - 0.8 wt.%, Sn: 0.05 - 0.15 wt.%, Cr: 0.1 - 0.8 wt.%, Zr: 0.01 - 0.5 wt.%, Mg: 0.01 - 0.3 wt.%, the balance being Zn and inevitable impurities, contains NiSi phase and Cr3Si phase, the size of the NiSi phase is 30 nm or less, and the size of the Cr3Si phase is 40 - 100 nm, a copper alloy characterized by this.

2. The copper alloy according to claim 1, characterized in that the NiSi phase and the copper alloy matrix exhibit a coherent relationship.

3. The composition further contains at least one element of Co, Fe, P, Re, and Mn with a total amount of 2.0 wt.% or less, Co: 0.01% - 1.0 wt.%, Fe: 0.01% - 1.0 wt.%, P: 0.001% - 0.05 wt.%, Re: 0.0001% - 0.05 wt.%, the copper alloy according to claim 2, characterized by this.

4. The strip of the copper alloy has a yield strength of 550 MPa or more, a conductivity of 35% IACS% or more, and a stress relaxation rate of 25% or less when kept at 150 °C for 1000 hours, the copper alloy according to claim 3, characterized by this.

5. The 90° bending workability of the strip of the copper alloy has a value of R / t ≤ 1 in the GW direction and a value of R / t ≤ 1 in the BW direction, and the 180° bending workability of the strip of the copper alloy has a value of R / t ≤ 2 in the GW direction and a value of R / t ≤ 2 in the BW direction, the copper alloy according to claim 4, characterized by this.

6. The size of the NiSi phase is 10 nm or less, the copper alloy according to claim 1, characterized by this.

7. The copper alloy is used for manufacturing the terminals of connectors, the copper alloy according to claim 1, characterized by this.

8. (1) Melting and casting: A step of melting and forging at a melting temperature of 1200 - 1280 °C and a casting temperature of 1180 - 1250 °C, (2) Preheating: A step of preheating at 800 - 1050 °C for 6 - 10 h, (3) Hot rolling: A step of controlling the rolling reduction amount to 85% or more and controlling the slab temperature during rolling to 800 °C or more, (4) Water quenching: Controlling the temperature of the hot-rolled slab to 800 °C or more, performing high-speed on-line water quenching at a cooling water temperature of 30 - 45 °C and an on-line water quenching speed of 30 - 50 m / min, and making the temperature difference between the front end and the end of the slab before water quenching 40 °C or less. (5)Surface machining: a step of machining 0.5 to 1.2 mm from each of the upper and lower surfaces of the hot-rolled plate; (6)Primary cold rolling: a step of controlling the total reduction ratio of cold rolling to 80% or more; (7)Primary aging treatment: a step of setting the aging treatment temperature to 350 to 480 °C and the time to 6 to 15 h; (8)Online solution treatment: a step of performing online solution treatment at an online solution temperature of 800 to 950 °C and an online solution rate of 10 to 60 m / min; (9)Secondary cold rolling: a step of controlling the total reduction ratio of cold rolling to 30 to 70%; (10)Secondary aging treatment: a step of setting the aging treatment temperature to 400 to 550 °C and the time to 6 to 15 h, characterized in that the method for producing a copper alloy according to any one of claims 1 to 7 includes the above steps.

9. The method for producing a copper alloy according to claim 8, characterized in that the melting and casting method in step (1) is vertical casting or horizontal continuous casting.

10. The method for producing a copper alloy according to claim 8, characterized in that Cr3Si phase is precipitated after the primary aging treatment, and NiSi phase is precipitated after the secondary aging treatment.

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