A kind of easy-to-cut high-conductivity copper alloy and its preparation method

Abstract

The invention discloses a free-cutting and highly conductive copper alloy. The mass percentages of the components of the copper alloy are as follows: Ni: 0.5-1.5%, P: 0.05-0.2%, Pb: 0.1-0.3%, Te: 0.05-0.5%, Co: 0.01-0.3%, Zn: 0.01-0.5%, and the balance is Cu. The number of Pb particles in the copper alloy is 4000-11000 per mm 2 The copper alloy has good cutting performance, high electrical conductivity and strong mechanical properties. The present invention also discloses a method for preparing the easy-to-cut and highly conductive copper alloy.

Description

Technical Field

[0001] The present invention belongs to the technical field of copper alloys, and in particular relates to an easy-to-cut and highly conductive copper alloy and a preparation method thereof. Background Art

[0002] The Cu-Ni-P-Pb series alloys have excellent processing properties and can be turned, milled, drilled, and cryogenically processed. They also have excellent corrosion resistance and can withstand erosion by various corrosive media, such as salt spray corrosion and acid corrosion. They have high electrical and thermal conductivity, making them suitable for the manufacture of electrical components such as electronic connectors, jacks, and terminals. They have low contact resistance and are suitable for high current transmission. They have good brazing properties and can be connected through processes such as brazing. In short, the Cu-Ni-P-Pb series alloys are high-performance copper alloys suitable for the manufacture of high-performance electronic connectors, jacks, terminals, and other electrical components. Therefore, the Cu-Ni-P-Pb series alloys are currently the main choice for split-slot terminals in new energy vehicle connectors.

[0003] Chinese patent number CN1688732A discloses an age-hardenable copper-based alloy and method for producing commercial strip products in the form of strip, sheet, wire, foil, tubing, powder, or castings. The strip products are used in applications requiring high yield strength and adequate electrical conductivity. The alloy is particularly suitable for use in circuit connectors and interconnects. The alloy comprises Cu-Ti-X, where X is selected from Ni, Fe, Sn, P, Al, Zn, Si, Pb, Be, Mn, Mg, Ag, As, Sb, Zr, B, Cr, and Co, and combinations thereof. The alloy provides an excellent combination of yield strength and electrical conductivity, as well as excellent stress relaxation resistance. The yield strength is at least 724 MPa (105 ksi), and the electrical conductivity is at least 50% IACS.

[0004] Chinese Patent No. CN104884651A discloses a machinable, precipitation-hardenable copper alloy comprising 1 to 4.1 wt.% Ni; 0.3 to 3.0 wt.% Si; 0.4 to 4.0 wt.% Pb; not more than 0.5 wt.% Sn; not more than 0.5 wt.% Cr; not more than 0.5 wt.% Zn; not more than 0.5 wt.% Zr; not more than 0.1 wt.% Fe; not more than 0.3 wt.% P; and unavoidable impurities, with the remainder consisting essentially of Cu. The disclosure further relates to a production method for obtaining a semi-finished copper alloy product comprising the copper alloy. The copper alloy product can be used to manufacture electrical connectors, such as jacks and pins.

[0005] However, the copper-based alloys disclosed in the above two patents have poor cutting performance and their electrical conductivity needs to be further improved. In the prior art, since most of the split slot terminals are small in size, the general size is between And below, at the same time, the Cu-Ni-P-Pb series alloys have poor plasticity during hot extrusion, and generally require a low extrusion ratio for batch extrusion processing, which leads to a long processing flow. After multiple cold deformation plastic processing and softening heat treatment processes, Pb particles are prone to aggregation, resulting in reduced material cutting performance. Wires are prone to sticking to the knife and producing long curled spring chips during the processing of split slot terminals, which to a certain extent affects the production and processing efficiency and product surface finish. Summary of the Invention

[0006] The invention discloses a free-cutting high-conductivity copper alloy with good cutting performance, high conductivity and strong mechanical properties.

[0007] A specific embodiment of the present invention provides a free-cutting and highly conductive copper alloy, wherein the mass percentages of the components of the copper alloy are as follows: Ni: 0.5-1.5%, P: 0.05-0.2%, Pb: 0.1-0.3%, Te: 0.05-0.5%, Co: 0.01-0.3%, Zn: 0.01-0.5%, and the balance is Cu and impurity elements;

[0008] The number of Pb particles in the copper alloy is 4000-11000 / mm 2 .

[0009] The purpose of adding the Pb element provided in the specific embodiment of the present invention is mainly to improve the cutting performance of the material. The present invention controls the upper limit of Pb to 0.3%, greatly reducing the risk of hot extrusion cracking of the material due to the addition of the Pb element, and can achieve extrusion conditions with a large extrusion ratio. On the one hand, extrusion with a large extrusion ratio is beneficial to grain refinement, and the mechanical properties and structural uniformity of the material are improved; on the other hand, the Pb particles are refined, and the number of softening annealing times during the process of wire processing to finished products is reduced, and the tendency of Pb particles to aggregate is greatly reduced, thereby making the number of lead particles in the copper alloy 4000-11000 / mm 2 Therefore, strict control of Pb in the present invention can further improve the thermal deformation processing performance and cutting performance of the material.

[0010] The purpose of adding the Co element provided in the specific embodiment of the present invention is to further improve the material's electrical conductivity and meet the high electrical conductivity requirements of connector products. The present invention reduces the material's electrical conductivity after adding elements such as P, B, and Zn. Therefore, to compensate for the above-mentioned problem, the material's electrical conductivity is improved by adding the Co element. The upper limit of the Co element addition is controlled at 0.3%. If the Co addition is too high, on the one hand, the mechanical properties of the material will be reduced, and on the other hand, the required solid solution temperature of the material will be increased. Under high temperature conditions, the grains will easily grow, increasing the structural inhomogeneity. At the same time, it will promote the aggregation of Pb particles and reduce the material's cutting performance.

[0011] The present invention is based on Cu-Ni-P alloy, in which Ni element and P element form NiP compound, which serves as the main precipitation strengthening phase, so that the material has high strength to meet the requirements of split slot terminal plugging and unplugging. The lower limit of Ni element is controlled at more than 0.5%. On the one hand, Ni element can be dissolved in the Cu matrix to achieve a good solid solution strengthening effect. On the other hand, it ensures the amount of NiP precipitation phase formed, which plays a good precipitation strengthening effect. The upper limit of Ni element is controlled at 1.5%. Considering that too high Ni element content will increase the material's resistance to thermal deformation processing, increase the difficulty of extrusion, and reduce the plasticity of the material, which is not conducive to high processing rate cold deformation processing. The lower limit of P element is controlled at 0.05%, which ensures the formation of a certain amount of NiP compound. At the same time, it is also beneficial to improve the alloy casting performance and reduce the formation of pores in the casting process. At the same time, an appropriate amount of P element is also beneficial to improve the material cutting performance. The upper limit of P element is controlled at 0.2%. If the P element is too high, the material's electrical conductivity will drop significantly, and it will not meet the high conductivity requirements of the connector.

[0012] The Te element, as provided in the specific embodiments of the present invention, is added primarily to form a Cu2Te free-cutting phase with Cu, further improving the material's machinability. The Cu2Te phase is dispersed within the grain boundaries, resulting in a low stress field intensity and, therefore, minimal negative impact on the material's electrical conductivity. The Te element is capped at 0.5%. Due to the high cost of Te raw materials, adding too much would make it unsuitable for industrial production. Furthermore, excessive Te addition can reduce the material's mechanical properties and plasticity. To achieve a comprehensive balance of these performance characteristics, the Te content in the present invention is controlled within a range of 0.05-0.5%.

[0013] The addition of Zn, as provided in specific embodiments of the present invention, improves casting properties. During the smelting process, Zn volatilizes and removes gases, enhancing ingot quality and the material's electrical conductivity. Furthermore, trace Zn addition can improve the material's hot working properties, while also increasing its strength and improving its machinability. The upper limit for Zn addition is 0.5%. Excessive Zn additions can reduce the material's electrical conductivity and cold deformation plasticity.

[0014] Furthermore, the impurity elements include Sn and Fe, wherein Sn: ≤0.05%, Fe: ≤0.05%.

[0015] Furthermore, the microstructure of the copper alloy contains α phase, NiP compound, CoP compound and Cu2Te phase, and the average grain size of the α phase is 1-10 μm.

[0016] The smaller average grain size of the α-phase provided by the specific embodiments of the present invention results in a greater number of grain boundaries within the copper alloy microstructure. Since Pb is distributed at the grain boundaries, it is evenly distributed throughout the matrix phase, thus preventing Pb aggregation. NiP compounds, CoP compounds, and Cu2Te phases are all distributed within the grain boundaries. The greater number of grain boundaries allows these compounds and phases to be evenly dispersed throughout the microstructure, thereby improving machinability and mechanical properties.

[0017] Furthermore, the average size of the CoP compound is 0.05-1 μm.

[0018] The CoP compound formed in the present invention has a size of 0.05-1 μm. If the size is too large, multiple softening annealing processes are required to refine the grains. However, multiple softening annealing processes can cause Pb aggregation, reducing the machinability of the resulting copper alloy, which is contrary to the purpose of the present invention. Furthermore, excessively large sizes can reduce the material's strength-enhancing effect.

[0019] Furthermore, the copper alloy further comprises 0.001-0.1% by mass of RE elements, wherein RE is one or more of Ca, S, In, Mg, and Ag.

[0020] The addition of Ca, S, and Mg elements in the RE elements provided in the specific embodiment of the present invention mainly improves the cutting performance by forming a brittle phase; the addition of In and Ag elements mainly improves the electrical conductivity.

[0021] A specific embodiment of the present invention further provides a method for preparing a free-cutting, highly conductive copper alloy, comprising:

[0022] (1) preparing, smelting, and casting the free-cutting, highly conductive copper alloy in accordance with the mass percentage of each component to obtain a master alloy ingot;

[0023] (2) extruding the master alloy ingot and then quenching it to obtain an extruded billet, wherein the extrusion process is as follows: the extrusion heating temperature is 750-850° C., the extrusion ratio is 80-200:1, and the quenching process is as follows: the quenching temperature is 700-800° C., and the cooling water temperature is 10-50° C.;

[0024] (3) performing a first coil drawing on the extruded billet and then performing an online solid solution process to obtain a first coil drawing billet, wherein the process parameters of the online solid solution process are: a solid solution temperature of 720-800° C. and a solid solution holding time of 2-10 min;

[0025] (4) performing a second post-coil aging heat treatment on the first coil-drawn blank to obtain a second coil-drawn blank, wherein the process parameters of the aging heat treatment are: an aging temperature of 360-420° C., and an aging holding time of 2-6 hours;

[0026] (5) The second disc drawn blank is subjected to finished product drawing to obtain an easy-to-cut and highly conductive copper alloy.

[0027] The extrusion heating temperature provided by the specific embodiment of the present invention is 750-850°C. If the extrusion temperature is too low, the ingot's resistance to deformation increases, and it is impossible to extrude the desired product specifications. If the extrusion temperature is too high, the alloy's hot brittleness tends to increase, and transverse periodic cracks are likely to occur during the extrusion process.

[0028] The extrusion ratio provided in the specific embodiment of the present invention is 80-200:1. A lower extrusion ratio, on the one hand, results in an increase in the extrusion gauge, which increases the number of intermediate processes and softening annealing steps, causing Pb particle aggregation and reducing the material's cutting performance. On the other hand, a lower extrusion ratio results in insufficient grain refinement, reducing the fine grain strengthening effect and resulting in poor structural uniformity. A higher extrusion ratio increases the difference in tensile and compressive stresses between the billet's outer surface and inner core, increasing the risk of periodic transverse cracks.

[0029] The quenching temperature of the extruded billet provided in the specific embodiment of the present invention is: 700-800℃, and the cooling water temperature is: 10-50℃. Direct quenching after extrusion is adopted to effectively avoid the precipitation and growth of NiP and CoP compounds during the cooling process after extrusion, which causes the material processing plasticity to decrease and the mechanical properties of the finished product to decrease; at the same time, it effectively reduces the heat treatment process, so that the Pb particles and Cu2Te are dispersed and finely distributed, ensuring good cutting performance. The upper limit of the quenching temperature is mainly determined by the extrusion temperature, and the lower limit is controlled at 700℃. If the temperature is too low and the cooling water temperature is too high, the quenching effect is not significant. The final extruded billet performance: elongation A100%: 35-60%, 1mm 2 Number of lead particles inside: 3000-10000.

[0030] The purpose of the online solution process provided by the specific embodiment of the present invention is to ensure that the matrix α grains and Cu2Te phases do not grow, the Pb particles do not aggregate, and the NiP and CoP compounds do not precipitate and grow, so as to achieve material softening and facilitate subsequent disc drawing processing. The solution temperature is controlled at 720-800°C. If the temperature is too high, the α grains have grown, the uniformity of the structure is reduced, and the fine grain strengthening effect is not significant. If the temperature is too low, the softening effect is not significant, the plasticity of the material cannot meet the requirements of subsequent processing, and the NiP and CoP compounds will also be partially precipitated. The holding time in the furnace is controlled at 2-10min. If the time is too low, the solution softening effect is not significant. If the time is too long, the Pb particles aggregate, the material cutting performance is reduced, and the α grains grow at the same time. Therefore, the temperature and time of this process need to be strictly controlled to ensure that the processing performance and comprehensive performance of the material provided by the embodiment of the present invention meet the requirements. After online solution treatment: average size of α grains: 5-20μm; 1mm 2 Number of internal lead particles: 2000-10000; elongation A100%: 30-60%.

[0031] The aging process provided in the specific embodiment of the present invention has an aging temperature of 360-420°C. Under this temperature condition, NiP and CoP compounds precipitate from the matrix, and the mechanical properties and electrical conductivity of the material are greatly improved. If the aging temperature is too low, the above-mentioned improvement effect is not obvious; if the aging temperature is too high, over-aging occurs, the material softens, and the mechanical properties are reduced, and the cutting performance is also reduced. Since the specific embodiment of the present invention proposes CoP compounds for the first time, in order to enable the CoP compounds to precipitate from the matrix, the present invention provides this suitable aging temperature.

[0032] Furthermore, in step (2), the extrusion speed includes an extrusion breakthrough speed, an extrusion stabilization speed, and an extrusion terminal speed, wherein the extrusion breakthrough speed is 5-10 mm / s, the extrusion stabilization speed is 2-5 mm / s, and the extrusion terminal speed is 3-10 mm / s.

[0033] In order to enable the copper alloy provided by the present invention to be extruded without periodic cracks, a specific embodiment of the present invention provides a suitable extrusion speed, wherein the extrusion breakthrough speed ensures that the ingot flows out of the die hole after being upset in the extrusion barrel. If the extrusion breakthrough speed is too low, the ingot is easily blocked and cannot be extruded normally; if the extrusion breakthrough speed is too high, cracks or even breaks will occur in the head end billet. The extrusion stability speed ensures that the billet can flow out normally and has good surface quality during the extrusion process. If the extrusion stability speed is too low, the billet cannot flow out of the die mouth stably. If the extrusion stability speed is too high, periodic cracks are easily formed on the billet surface. The extrusion terminal speed is to ensure that the tail end of the ingot can be extruded stably and normally when the extrusion deformation resistance increases due to temperature reduction. If the extrusion terminal speed is too low, the deformation resistance of the tail end of the ingot is large and cannot be extruded normally. If the extrusion terminal speed is too high, periodic cracks are easily formed on the surface of the tail end billet.

[0034] Furthermore, in step (2), the master alloy ingot passes through an extrusion barrel during the extrusion process, and the temperature of the extrusion barrel is 350-500° C. This reduces the temperature loss of the ingot during the extrusion process, thereby significantly increasing the resistance to extrusion deformation.

[0035] Furthermore, in step (1), the smelting temperature is 1000-1200°C, which ensures that the raw materials can be fully melted and effectively controls the burnout of elements such as Zn, Mg, P, Ca, and S. To further control the burnout of the above elements, the thickness of the covering charcoal is controlled to be in the range of 10-30 cm.

[0036] Furthermore, in step (1), the casting process is as follows: the casting temperature is 1250-1300° C., the vibration frequency is 30-100 Hz, and the casting speed is 50-100 mm / min.

[0037] The specific embodiment of the present invention controls the lower limit of the casting temperature to ensure that the melt has good fluidity and avoid defects such as cold shuts; the upper limit of the temperature is controlled to avoid the burnout of Zn, Mg, P, Ca, and S elements on the one hand, and on the other hand, when it exceeds 1300°C, the Ni element is easy to react with charcoal, affecting the stability of the alloy composition. The appropriate vibration frequency provided by the specific embodiment of the present invention effectively improves the surface finish of the ingot. The casting speed provided by the specific embodiment of the present invention is too low, the cooling effect is sufficient, the solidification liquid hole rises, the contact area between the solid billet and the crystallizer increases, the friction force increases, the surface quality of the ingot is reduced, and the life of the crystallizer is reduced. If the casting speed is too fast, the cooling effect is insufficient, and the copper liquid is prone to flow out of the crystallizer before it is completely solidified.

[0038] Furthermore, the extruded billet is subjected to a first coiling process, which includes: performing multiple coiling processes on the extruded billet, with a processing rate of 10-25% for each coiling process and a total processing rate of 40-60%.

[0039] If the processing rate of each coiling pass provided in the specific embodiment of the present invention is too small, plastic deformation will occur at the edge of the rod, while no plastic deformation will occur in the center, resulting in inconsistent performance between the center and the edge of the material; if the processing rate is too large, a large amount of heat will be generated during the material deformation process, which may easily cause local aging and softening.

[0040] If the total processing rate provided in the specific embodiment of the present invention is too small, cracking may easily occur during the subsequent online solution treatment due to uneven stress distribution of the material; if the total processing rate is too large, the plastic deformation of the material may be exceeded, and the rod may easily break and be unable to be effectively stretched.

[0041] Furthermore, the first-drawn blank is subjected to a second-drawing process, including: the first-drawn blank is subjected to multiple-pass drawing, the processing rate of each drawing process is 10-30%, and the total processing rate is 35-50%.

[0042] If the processing rate of each pass provided in the specific embodiment of the present invention is too small, plastic deformation will occur at the edge of the bar, while no plastic deformation will occur in the center, resulting in inconsistent performance between the center and the edge of the material; if the processing rate is too large, a large amount of heat will be generated during the material deformation process, which may easily cause local aging and softening.

[0043] If the total processing rate provided in the specific embodiment of the present invention is too small, cracking may easily occur during the subsequent aging heat treatment due to uneven stress distribution of the material; if the total processing rate is too large, the plastic deformation of the material may be exceeded, and the rod may easily break and be unable to be effectively stretched.

[0044] Furthermore, the second plate-drawn blank is subjected to finished product drawing, and the processing rate of the finished product drawing is 15-30%.

[0045] If the machining rate provided in the specific embodiments of the present invention is too low, the strengthening effect will be insignificant. If the machining rate is too high, the material's elongation and plasticity will decrease, affecting subsequent straightening performance. Simultaneously, the material's cutting resistance will increase, making it difficult to machine and reducing its stress corrosion resistance.

[0046] The free-cutting, highly conductive copper alloy provided by the present invention has the following properties: tensile strength of 600-800 MPa, yield strength of 500-750 MPa, elongation (A100%) of 3-15%, conductivity of 55-70% IACS, elastic modulus of 115-130 GPa, and a cutting index of at least 80% of C36000. This material possesses excellent mechanical properties, electrical conductivity, elasticity, and cutting performance.

[0047] To achieve the above performance, the present invention controls the microstructural properties of the finished product as follows: average size of α grains: 1-10 μm, average size of NiP compounds: 0.1-3 μm, average size of CoP compounds: 0.05-1 μm, average size of Cu2Te phase: 1-10 μm, 1mm2 Number of lead particles inside: 4000-11000.

[0048] Compared with the prior art, the present invention has the following beneficial effects:

[0049] Since the copper alloy provided by the present invention has a low Pb content and a high number of Pb particles per unit area, thereby avoiding Pb aggregation, and is combined with the free-cutting phase Cu2Te formed by adding an appropriate amount of Te element, the copper alloy provided by the present invention has good free-cutting performance; the present invention provides a CoP compound with appropriate amounts of Co and P to improve both mechanical properties and electrical conductivity, thereby greatly improving the comprehensive mechanical properties and electrical conductivity of the copper alloy provided by the present invention.

[0050] The present invention reduces the number of intermediate processing times and softening annealing times by controlling the extrusion ratio and extrusion temperature, thereby avoiding the aggregation of Pb particles. Quenching at a suitable quenching temperature is directly performed after extrusion, avoiding the precipitation and growth of strengthening phases and conductive phases, namely NiP and CoP compounds. The online solid solution provided by the present invention achieves the softening of the first disc-drawn blank while ensuring that the matrix α grains and Cu2Te phases do not grow, Pb particles do not aggregate, and NiP and CoP compounds precipitate and grow. The aging treatment provided by the present invention allows the precipitation of NiP and CoP compounds, significantly improving the mechanical properties of the second disc-drawn blank and greatly improving the conductive properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 This is a metallographic photograph of the free-cutting and highly conductive copper alloy prepared in Example 1 of the present invention.

[0052] Figure 2 This is a metallographic photograph of the free-cutting and highly conductive copper alloy prepared in Comparative Example 1 of the present invention. DETAILED DESCRIPTION

[0053] The present invention will be described in further detail below with reference to the accompanying drawings and embodiments.

[0054] The present invention provides 4 embodiments and 1 comparative example, and the specific components are shown in Table 1.

[0055] Example 1

[0056] (1) Melting: The proportions are determined according to the required ingredients. The melting temperature is 1180°C and the charcoal covering thickness is 30 cm.

[0057] (2) Casting: Prepared using semi-continuous casting method Ingot casting, casting temperature during drawing: 1270°C, vibration frequency: 50HZ, drawing speed: 75mm / min, primary cooling water temperature: 10-30°C, secondary cooling water temperature: 10-40°C, charcoal covering thickness: 30cm.

[0058] (3) Extrusion: adopt the quenching method after extrusion. Extrusion heating temperature: 780℃, extrusion ratio: 180:1, extrusion breakthrough speed: 6mm / s, extrusion stable speed: 3mm / s, extrusion end speed: 4-5mm / s, extrusion barrel temperature: 450℃, extrusion billet quenching temperature: 720℃, cooling water temperature: 10-40℃, obtain Extruded billet.

[0059] (4) First coiling: The extruded billet is subjected to three coiling processes, with a processing rate of 15-22% for each process and a total processing rate of 48%. Stretching the blank.

[0060] (5) Online solution treatment: The billet after coil pulling is subjected to online solution treatment, the solution temperature is 750℃, and the holding time in the furnace is 5min.

[0061] (6) Second coiling: The blank after online solid solution is subjected to two coiling processes, with a processing rate of 15-30% for each process and a total processing rate of 40% to obtain Stretching the blank.

[0062] (7) Aging: The billet after coiling is subjected to aging treatment. The aging heat treatment process uses ammonia decomposition atmosphere protection, the aging temperature is 385℃, and the aging holding time is 4h.

[0063] (8) Finished product drawing: The aged blank is drawn, and the drawing rate is 20%. Finished bars.

[0064] (9) Straightening and sizing: After straightening the wire, saw cut it into a flat head to obtain an easy-to-cut and highly conductive copper alloy. Figure 1 As shown, the finished product of Example 1 has fine grains and good uniformity, the cutting phase is dispersed at the grain boundaries, and the material has excellent mechanical properties and cutting performance.

[0065] Example 2

[0066] (1) Melting: The proportions are determined according to the required ingredients. The melting temperature is 1200°C and the charcoal covering thickness is 30 cm.

[0067] (2) Casting: Prepared using semi-continuous casting method Ingot casting, casting temperature during drawing: 1290°C, vibration frequency: 60HZ, drawing speed: 65mm / min, primary cooling water temperature: 10-30°C, secondary cooling water temperature: 10-40°C, charcoal covering thickness: 30cm.

[0068] (3) Extrusion: adopt the quenching method after extrusion. Extrusion heating temperature: 800℃, extrusion ratio: 180:1, extrusion breakthrough speed: 5mm / s, extrusion stable speed: 2.5mm / s, extrusion end speed: 3-5mm / s, extrusion barrel temperature: 450℃, extrusion billet quenching temperature: 720℃, cooling water temperature: 10-40℃, obtain Extruded billet.

[0069] (4) First coiling: The extruded billet is subjected to three coiling processes, with a processing rate of 15-22% for each process and a total processing rate of 48%. Stretching the blank.

[0070] (5) Online solution treatment: The billet after coil pulling is subjected to online solution treatment, the solution temperature is 760℃, and the holding time in the furnace is 5.5min.

[0071] (6) Second coiling: The blank after online solid solution is subjected to two coiling processes, with a processing rate of 15-30% for each process and a total processing rate of 40% to obtain Stretching the blank.

[0072] (7) Aging: The billet after coiling is subjected to aging treatment. The aging heat treatment process uses ammonia decomposition atmosphere protection, the aging temperature is 390℃, and the aging holding time is 4h.

[0073] (8) Finished product drawing: The aged blank is drawn, and the drawing rate is 20%. Finished bars.

[0074] (9) Straightening and cutting to length: The wire is straightened and then sawed to a fixed length.

[0075] Example 3

[0076] (1) Melting: The proportions are determined according to the required ingredients. The melting temperature is 1150°C and the charcoal covering thickness is 30 cm.

[0077] (2) Casting: Prepared using semi-continuous casting method Ingot casting, casting temperature during drawing: 1250°C, vibration frequency: 40HZ, drawing speed: 80mm / min, primary cooling water temperature: 10-30°C, secondary cooling water temperature: 10-40°C, charcoal covering thickness: 30cm.

[0078] (3) Extrusion: adopt the quenching method after extrusion. Extrusion heating temperature: 760℃, extrusion ratio: 133:1, extrusion breakthrough speed: 8mm / s, extrusion stable speed: 4mm / s, extrusion end speed: 5-7mm / s, extrusion barrel temperature: 420℃, extrusion billet quenching temperature: 700℃, cooling water temperature: 10-50℃, obtain Extruded billet.

[0079] (4) First coiling: The extruded billet is subjected to three coiling processes, with a processing rate of 15-25% for each process and a total processing rate of 52%. Stretching the blank.

[0080] (5) Online solution treatment: The billet after coil pulling is subjected to online solution treatment, the solution temperature is 720℃, and the holding time in the furnace is 8min.

[0081] (6) Second coiling: The blank after online solid solution is subjected to two coiling processes, with a processing rate of 15-30% for each process and a total processing rate of 41%. Stretching the blank.

[0082] (7) Aging: The billet after coiling is subjected to aging treatment. The aging heat treatment process uses ammonia decomposition atmosphere protection, the aging temperature is 375℃, and the aging holding time is 5h.

[0083] (8) Finished product drawing: The aged blank is drawn, and the drawing processing rate is 23%. Finished bars.

[0084] (9) Straightening and cutting to length: The wire is straightened and then sawed to a fixed length.

[0085] Example 4

[0086] (1) Melting: The proportions are determined according to the required ingredients. The melting temperature is 1190°C and the charcoal covering thickness is 30 cm.

[0087] (2) Casting: Prepared using semi-continuous casting method Ingot casting, casting temperature during drawing: 1270°C, vibration frequency: 80HZ, drawing speed: 65mm / min, primary cooling water temperature: 10-30°C, secondary cooling water temperature: 10-40°C, charcoal covering thickness: 30cm.

[0088] (3) Extrusion: adopt the quenching method after extrusion. Extrusion heating temperature: 750℃, extrusion ratio: 133:1, extrusion breakthrough speed: 5mm / s, extrusion stable speed: 3.5mm / s, extrusion end speed: 4-5mm / s, extrusion barrel temperature: 400℃, extrusion billet quenching temperature: 700℃, cooling water temperature: 10-50℃, obtain Extruded billet.

[0089] (4) First coiling: The extruded billet is subjected to three coiling processes, with a processing rate of 15-25% for each process and a total processing rate of 52%. Stretching the blank.

[0090] (5) Online solution treatment: The billet after coil pulling is subjected to online solution treatment, the solution temperature is 730℃, and the holding time in the furnace is 5min.

[0091] (6) Second coiling: The blank after online solid solution is subjected to two coiling processes, with a processing rate of 15-30% for each process and a total processing rate of 41%. Stretching the blank.

[0092] (7) Aging: The billet after coiling is subjected to aging treatment. The aging heat treatment process uses ammonia decomposition atmosphere protection, the aging temperature is 390℃, and the aging holding time is 3.5h.

[0093] (8) Finished product drawing: The aged blank is drawn, and the drawing processing rate is 23%. Finished bars.

[0094] (9) Straightening and cutting to length: The wire is straightened and then sawed to a fixed length.

[0095] Comparative Example 1

[0096] Comparative Example 1 uses a Cu-Ni-P-Pb alloy, such as Figure 2 As shown, the grain size of the finished product of Comparative Example 1 is relatively large, and the grains grow significantly after multiple annealing heat treatment processes in the process, and the uniformity of the structure is also average. At the same time, some easy-to-cut phases gather and grow at the grain boundaries, and the material cutting performance is average.

[0097] The obtained examples and comparative examples were tested for mechanical properties, electrical conductivity and / or microstructure. The specific test indicators and test standards are as follows:

[0098] 1) Tensile strength, yield strength, and elongation test: GB / T 228.1-2010 Tensile tests on metallic materials—Part 1: Room temperature tensile test method.

[0099] 2) Metallographic microscopy: YS / T 449-2002 Microstructure examination method of copper and copper alloy castings and processed products.

[0100] 3) Elastic modulus test: GB / T 22315-2008 Test method for elastic modulus and Poisson's ratio of metallic materials.

[0101] 4) Cutting index: Evaluate according to the cutting performance test method in Appendix B of YS-T 647-2007 "Copper-Zinc-Bismuth-Tellurium Alloy Rod", assuming that the cutting index of C36000 (HPb63-3) is 100%.

[0102] 5) Conductivity: GB / T 351-2019 Metal materials - Measurement method for resistivity.

[0103] Performance Analysis:

[0104] In Table 1, comparative example 1 does not have Te, Co and other elements added, and the material conductivity is lower than that of the embodiment. At the same time, due to the high Pb content, the material of the comparative example is relatively brittle during extrusion, so the extrusion ratio needs to be reduced and multiple intermediate softening heat treatment processes need to be performed. At the same time, the embodiment adds Te element to further improve the cutting performance of the material. Therefore, the cutting performance of the comparative example has no obvious advantage over that of the embodiment.

[0105] The average sizes of the α grains and NiP compounds in Examples 1 and 2 in Table 2 are superior to those in Comparative Example 1, resulting in higher material strength. Furthermore, the formation of CoP compounds and Cu2Te phases in Examples 1-4 further enhances the material's electrical conductivity, cutting, and mechanical properties. Through process optimization, Examples 1-4 achieve a higher number of Pb particles per unit area than the Comparative Example, resulting in even better cutting performance.

[0106] The tensile strength, yield strength and elastic modulus of Examples 1-4 in Table 3 are higher than those of the comparative example, and the cutting index and conductivity are higher, and the cutting performance and conductivity are more excellent than those of the comparative example.

[0107] Table 1 Composition of components in Examples 1-4 and Comparative Example 1 (wt%)

[0108]

[0109] Table 2 Microstructure and properties of finished rods of Examples 1-4 and Comparative Example 1

[0110]

[0111] Table 3 Properties of finished bars of Examples 1-4 and Comparative Example 1

[0112]

Claims

1. A free-cutting, highly conductive copper alloy, characterized in that: The mass percentages of the components of the copper alloy are: Ni: 0.5-1.5%, P: 0.05-0.2%, Pb: 0.1-0.3%, Te: 0.05-0.5%, Co: 0.01-0.3%, Zn: 0.01-0.5%, and the balance is Cu and impurity elements; The number of Pb particles in the copper alloy is 4000-11000 / mm 2 .

2. The free-cutting, highly conductive copper alloy according to claim 1, wherein: The copper alloy further contains an α phase, a NiP compound, a CoP compound and a Cu2Te phase. The average grain size of the α phase is 1-10 μm.

3. The free-cutting, highly conductive copper alloy according to claim 2, wherein: The average size of the CoP compound is 0.05-1 μm.

4. The free-cutting, highly conductive copper alloy according to claim 1, wherein: The copper alloy further comprises 0.001-0.1% by mass of RE elements, wherein RE is one or more of Ca, S, In, Mg, and Ag.

5. A method for preparing a free-cutting, highly conductive copper alloy according to any one of claims 1 to 4, characterized in that: include: (1) preparing, smelting, and casting the free-cutting, highly conductive copper alloy according to the mass percentage of each component as described in claims 1 to 4 to obtain a master alloy ingot; (2) extruding the master alloy ingot and then quenching it to obtain an extruded billet, wherein the extrusion process is as follows: the extrusion heating temperature is 750-850° C., the extrusion ratio is 80-200:1, and the quenching process is as follows: the quenching temperature is 700-800° C., and the cooling water temperature is 10-50° C.; (3) performing a first coil drawing on the extruded billet and then performing an online solid solution process to obtain a first coil drawing billet, wherein the process parameters of the online solid solution process are: a solid solution temperature of 720-800° C. and a solid solution holding time of 2-10 min; (4) performing a second post-coil aging heat treatment on the first coil-drawn blank to obtain a second coil-drawn blank, wherein the process parameters of the aging heat treatment are: an aging temperature of 360-420° C., and an aging holding time of 2-6 hours; (5) The second disc drawn blank is subjected to finished product drawing to obtain an easy-to-cut and highly conductive copper alloy.

6. The method for preparing a free-cutting and highly conductive copper alloy according to claim 5, wherein: In step (2), the extrusion speed includes extrusion breakthrough speed, extrusion stabilization speed and extrusion terminal speed, wherein the extrusion breakthrough speed is 5-10 mm / s, the extrusion stabilization speed is 2-5 mm / s, and the extrusion terminal speed is 3-10 mm / s.

7. The method for preparing a free-cutting and highly conductive copper alloy according to claim 5, wherein: In step (2), the master alloy ingot passes through an extrusion barrel during the extrusion process, and the temperature of the extrusion barrel is 350-500°C.

8. The method for preparing a free-cutting and highly conductive copper alloy according to claim 5, wherein: In step (1), the casting process is as follows: the casting temperature is 1250-1300° C., the vibration frequency is 30-100 Hz, and the casting speed is 50-100 mm / min.

9. The method for preparing a free-cutting and highly conductive copper alloy according to claim 5, wherein: The extruded billet is subjected to the first coiling, which includes: performing multiple coilings on the extruded billet, with the processing rate of each coiling being 10-25% and the total processing rate being 40-60%.

10. The method for preparing a free-cutting and highly conductive copper alloy according to claim 5, wherein: The second plate of blank is subjected to finished product drawing, and the processing rate of the finished product drawing is 15-30%.

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