CN112030030A - High-strength high-conductivity copper alloy wire and preparation method thereof - Google Patents

Abstract

The invention discloses a high-strength high-conductivity copper alloy wire, belonging to the field of electrical materials, wherein the wire comprises the following raw materials in percentage by mass: 0.1-1.5 wt% of silver, 0.1-1 wt% of cobalt, and the balance of copper and inevitable impurities, wherein the purities of the silver, the copper and the cobalt are not lower than 99.99%, and twin crystals are contained in a wire crystal grain structure; the invention also discloses a preparation method of the high-strength and high-conductivity copper alloy wire, which comprises the steps of smelting, casting and extruding copper, silver and cobalt, then drawing at-300 to-100 ℃ and in a 0.5 to 5T magnetic field, and finally annealing to obtain the copper alloy conductive wire. The invention has the advantages that the advantages of copper, silver and cobalt are fully utilized, and the aggregation and growth of a large amount of twin crystals are induced under the combined action of a magnetic field and low-temperature deformation to form twin crystal strengthening; meanwhile, the coherent twin crystal boundary has extremely low scattering capacity to electrons, so that the copper alloy wire keeps higher conductivity and has higher strength.

Description

A kind of high-strength and high-conductivity copper alloy wire and preparation method thereof

technical field

The invention belongs to the field of electrical materials, and relates to a high-strength and high-conductivity copper alloy conductive wire and a preparation method thereof.

Background technique

High-strength and high-conductivity copper alloys are functional materials with excellent physical and mechanical properties. They are widely used in switches, circuit breakers and contactors for medium and light loads. At the same time, high-strength and high-conductivity copper alloys are also used in many fields such as high-pulse magnetic field conductor materials, integrated circuit lead frames, overhead wires for trams and electric trains, and contact wires for high-speed railways. The developed high-strength and high-conductivity copper alloys include Cu-Cr, Cu-Zr, Cu-Cr-Zr, Cu-Ag, Cu-Nb and other series of materials. Due to the low melting point of Cu-Ag alloy, it is easy to melt, and the microstructure is easy to control; the conductivity of Ag is higher than that of copper, which is more conducive to obtaining high-conductivity copper alloy. Therefore, Cu-Ag alloy has become one of the preferred materials for high-strength and high-conductivity copper alloy materials.

It is a common preparation method of high-strength and high-conductivity copper-silver alloy materials to batch and smelt copper and silver, and use deformation and heat treatment. "High-conductivity CuAg alloy material and its preparation method", this application discloses a high-strength and high-conductivity Cu-Ag alloy material and its preparation method. The copper-silver alloy ingot is obtained through extrusion, drawing and other processes to obtain a continuous fibrous structure; the composition of the alloy material is that the Ag content is 5-10 wt%, and the copper balance is the balance. The preparation process steps of copper-silver alloy are the preparation of chemical composition, vacuuming of melting chamber and directional solidification chamber, alloy melting, directional solidification, hot extrusion, heat treatment, wire drawing or rolling, to obtain high-strength and high-conductivity Cu-Ag alloy Wire/sheet. The method utilizes directional solidification, deformation and heat treatment to prepare the Cu-Ag alloy, which not only retains the excellent electrical conductivity of the Cu-Ag alloy, but also improves the strength of the alloy. The disadvantage is that the interface scattering formed by the continuous fibrous structure generated by this method and the lattice distortion scattering caused by solid solution alloying can achieve high strength while sacrificing a certain degree of electrical conductivity. At the same time, directional solidification equipment, equipment and Higher cost requirements.

Nanocrystalline materials have the characteristics of high strength. In order to improve the strength of Cu-Ag alloys, some researchers try to prepare nanocrystalline Cu-Ag alloys by adding a small amount of silver to achieve the purpose of improving the strength of materials while maintaining high electrical conductivity. The invention and creation "a high-strength and high-conductivity copper-silver alloy material and its preparation method" with the publication number CN111101008A and the publication date of May 5, 2020, the application discloses a high-strength and high-conductivity copper-silver alloy material. , and its preparation steps include: ball-milling copper powder and silver powder into nano-powder in a ball-milling tank; compressing the nano-powder to obtain a green body; sintering the green body at 350-550 ℃ for 0- 3min to obtain copper-silver alloy material. The invention achieves high electrical conductivity of the formed copper-silver alloy material by adding less silver powder, and obtains a nanocrystalline structure by controlling the growth of crystal grains during the sintering process through a relatively low sintering temperature, so that the copper-silver alloy material maintains high strength, and The copper-silver alloy material has a simple preparation process, no smelting process, energy saving and environmental protection. But its shortcomings are: firstly, in order to obtain nanocrystalline structure, the mixed powder of copper and silver needs to be ball-milled for a long time (60-180h); Its density is limited to a certain extent; thirdly, the nanocrystalline structure provides high strength, but the interface scattering caused by the existence of a large number of grain boundaries limits the improvement of its electrical conductivity. Between 90% IACS.

To sum up, in the development of high-strength and high-conductivity copper-silver alloys, grain refinement strengthening, solid solution strengthening, work hardening, etc. are mostly used to improve the strength, and a large number of defects such as dislocations, grain boundaries, etc. are introduced for strengthening. Therefore, in order to maintain the high strength of copper-silver alloys and obtain good electrical conductivity, it has become a current research hotspot, which requires a new preparation method to obtain high-strength and high-conductivity copper-silver alloys.

The twin boundary is a special low-energy state coherent grain boundary. The twin boundary can effectively hinder the dislocation movement, especially when the twinned sheet layer is refined to the nanometer level, its strengthening effect begins to appear, and the coherent twinning crystal The ability of the boundary to scatter electrons is extremely small, and its resistance value is an order of magnitude lower than that of ordinary grain boundaries. In 2004, researchers from the Institute of Metal Research, Chinese Academy of Sciences used pulsed electrolytic deposition technology to prepare pure copper thin films with high-density nano-sized growth twins, and obtained pure copper samples with ultra-high strength and high electrical conductivity. The tensile strength is as high as 1068MPa, while the room temperature conductivity is comparable to that of oxygen-free high conductivity copper (Ultrahigh Strength and High Electrical Conductivity in Copper. Science, 304 (2004) 422-426.). However, due to the limitation of pulse electrodeposition technology, the thickness of the film prepared by it is only in the micrometer level, and it is difficult to prepare bulk materials with wider application.

SUMMARY OF THE INVENTION

The purpose of the present invention is to solve at least one of the technical problems existing in the prior art, and to provide a high-strength and high-conductivity copper alloy wire and a preparation method thereof, which can maintain the wire with good electrical conductivity and also have high strength.

The technical solution of the present invention is as follows:

One aspect of the present invention provides a high-strength and high-conductivity copper alloy wire. The copper alloy wire contains raw materials with the following mass fractions: silver 0.1-1.5 wt %, cobalt 0.1-1 wt %, and the balance is copper and inevitable impurities, Wherein, the purity of silver, copper and cobalt is not less than 99.99%, and the copper alloy wire contains twin crystals in the grain structure.

Further, the average width of the twins of the copper alloy wire is 20-100 nm, and the average length of the twins is 200-800 nm.

Further, the average grain size of the copper alloy wire is 1-10 μm.

Further, the tensile strength of the copper alloy wire is greater than 600 MPa, and the electrical conductivity is greater than 90% IACS.

Another aspect of the present invention provides a method for preparing a high-strength and high-conductivity copper alloy wire, comprising the following steps:

S1, smelting and casting three raw materials of copper, silver and cobalt to obtain a copper-silver-cobalt alloy ingot;

S2, extruding the copper-silver-cobalt alloy ingot to obtain a copper-silver-cobalt alloy bar;

S3. The copper-silver-cobalt alloy rod is subjected to wire drawing treatment at -300 to -100 °C, and a magnetic field is applied to the copper-silver-cobalt alloy rod at the same time, and the intensity of the magnetic field is 0.5 to 5T;

S4, annealing the copper-silver-cobalt alloy rod processed in step S3 to obtain a copper alloy conductive wire.

Further, in the step S2, the copper-silver-cobalt alloy ingot is put into a vacuum hot pressing furnace and heated to 400-600° C., and then extruded after being kept for 1-3 hours, and the extrusion ratio is 5-10:1.

Further, in the step S3, the copper-silver-cobalt alloy bar is added to the wire drawing die, and the wire-drawing die and the copper-silver-cobalt alloy bar are soaked in liquid nitrogen for wire drawing treatment.

Further, in the step S3, during the wire drawing process, the deformation amount of each pass is 10-30%, and the total deformation amount is not less than 80%.

Further, the annealing treatment in step S4 includes: treating the copper-silver-cobalt alloy bar processed in step S3 under vacuum or inert gas protection at 200-300° C. for 1-2 hours.

Further, in the step S1, the three raw materials of copper, silver and cobalt are smelted by medium frequency induction melting, and after the three raw materials are completely melted, the casting temperature is controlled to 1150-1350°C, and the casting rate is 0.3-0.6Kg/s, A copper-silver-cobalt alloy ingot is obtained; the surface-processing of the copper-silver-cobalt alloy ingot is performed to obtain a copper-silver-cobalt alloy ingot with a smooth surface.

The present invention has at least one of the following beneficial effects:

(1) The copper alloy conductive wire in the present invention combines the advantages of three metals of copper, silver and cobalt. The present invention uses copper with good electrical conductivity as the matrix, and adds low stacking fault energy metal (16mJ/m ² ) silver and medium The stacking fault energy metal (78mJ/m ² ) copper can not only enhance the electrical conductivity and oxidation resistance of the alloy, but also reduce the stacking fault energy of the alloy, which is more conducive to the occurrence of twinning; and adding a small amount of magnetic cobalt solid solution In the alloy, the aggregation and growth of a large number of twins can be induced under the combined action of the magnetic field and low-temperature deformation to form twinning strengthening, so that there are twin boundaries in the copper alloy conductive wire prepared by the invention, and the twin boundaries are a kind of The special low-energy state coherent grain boundary and the coherent twin grain boundary have very little scattering ability to electrons, so the copper alloy wire can maintain high conductivity and high strength. The tensile strength is greater than 600MPa, and the electrical conductivity is greater than 90% IACS.

(2) The preparation method of the present invention obtains an ingot by smelting copper, silver and cobalt; then obtains a copper alloy bar by means of medium temperature extrusion; Annealing treatment, deformation at low temperature is conducive to the occurrence of twinning deformation (twin formation) of low and medium stacking fault energy metals and alloys. At the same time, due to the addition of magnetic cobalt to the alloy, under the action of an external magnetic field, the alloy is in the process of drawing deformation. It is easy to induce the aggregation and growth of twins, and finally a high-strength and high-conductivity nano-twinned copper alloy wire is obtained; the equipment used in the method of the present invention is all common material processing equipment, the preparation method is simple, the cycle is short, and the scope of application is wide. , which can be widely used in the preparation of high-strength and high-conductivity alloy wires.

Description of drawings

Fig. 1 is the transmission electron microscope photograph of the longitudinal section of the copper-silver-cobalt alloy wire prepared in Example 1 of the present invention and the corresponding selected area diffraction pattern;

2 is a transmission electron microscope photograph of a longitudinal section of a copper-silver-cobalt alloy wire prepared in Comparative Example 1 of the present invention and a corresponding selected area diffraction pattern.

Detailed ways

The invention provides a high-strength and high-conductivity copper alloy wire. The copper alloy wire contains raw materials with the following mass fractions: silver 0.1-1.5 wt %, cobalt 0.1-1 wt %, and the balance is copper and inevitable impurities, wherein silver, The purity of copper and cobalt is not less than 99.99%, the copper alloy wire contains twins in the grain structure, the average grain size of the copper alloy wire is 1-10 μm, and the average width of the twins is 20-100nm. The average length is 200-800 nm, the tensile strength of the copper alloy wire can reach more than 600 MPa, and the electrical conductivity can reach more than 90% IACS.

The preparation method of the above-mentioned high-strength and high-conductivity copper alloy wire comprises the following steps:

(1) Select 4N (99.99%) and above pure copper, silver, and cobalt raw materials, and carry out batching according to 0.1-1.5wt% silver, 0.1-1wt% cobalt, and the balance of copper and inevitable impurities, and adopt medium frequency induction melting After the raw materials are completely melted, the casting temperature is controlled at 1150-1350°C, and the casting rate is 0.3-0.6Kg/s to obtain a copper-silver-cobalt alloy ingot;

(2) processing the surface of the copper-silver-cobalt alloy ingot, specifically, turning processing, etc., to remove defects such as surface looseness and holes, and obtain a copper alloy cylinder with a smooth surface;

(3) Put the copper-silver-cobalt alloy cylinder processed in step (2) into a vacuum hot-pressing furnace and heat it to 400-600° C., hold it for 1-3 hours, and extrude, and the extrusion ratio is 5:1-10: 1. Extrude it into a bar to obtain a copper alloy bar;

(4) The copper alloy bar processed in step (3) is subjected to wire drawing treatment at -300 to -100°C, specifically, the wire drawing die and the bar are immersed in liquid nitrogen, and a wire drawing die is set on the wire drawing die at the same time. Strong magnetic field, the magnetic field strength is set to 0.5 ~ 5T, in the process of wire drawing, the deformation amount of each pass is 10 ~ 30%, and the total deformation amount is not less than 80%.

(5) Final annealing is performed on the bar processed in step (4). The annealing conditions are under the protection of vacuum or inert gas, and the treatment time at 200-300° C. is 1-2 h to obtain the copper alloy wire of the present invention.

The present invention will be described in further detail below with specific examples, but the present invention is not limited to the following specific examples.

Example 1

Copper, silver and cobalt with a purity of 4N (99.99%) are used as raw materials. The ratio is: silver 0.5wt%, cobalt 1.0wt%, and the balance is copper and inevitable impurities. It is smelted by medium frequency induction melting. After complete melting, control the casting temperature to 1150°C and the casting rate to 0.3Kg/s to obtain a copper-silver-cobalt alloy ingot; turn the copper-silver-cobalt alloy ingot to remove defects such as loose surface and holes, and obtain a copper-silver-cobalt alloy with a smooth surface. Alloy cylinder; then put the copper-silver-cobalt alloy cylinder into a vacuum hot-pressing furnace and heat it to 400°C, hold it for 3 hours, and then extrude it with an extrusion ratio of 5:1, and extrude it into a bar to obtain a copper-silver-cobalt alloy. bar; then the copper-silver-cobalt alloy bar is drawn. During the drawing process, the drawing die and the bar are immersed in liquid nitrogen. At the same time, a strong magnetic field is set on the drawing die, and the magnetic field strength is set to 2T. During the drawing process , the deformation amount of each pass is 10%, and the total deformation amount is 80%; then the bar is subjected to final annealing treatment, annealing treatment conditions are vacuum, and the treatment time is 1h at 200 ℃ to obtain copper alloy conductive wires.

Example 2

The raw materials of copper, silver and cobalt with a purity of 4N5 (99.995%) are used. The ratio is: silver 0.1wt%, cobalt 0.5wt%, and the balance is copper and inevitable impurities. After that, control the casting temperature to be 1250°C and the casting rate to be 0.4Kg/s to obtain copper-silver-cobalt alloy ingots; turn the copper-silver-cobalt alloy ingots to remove defects such as loose surfaces and holes to obtain copper-silver-cobalt alloy cylinders with smooth surfaces. ; Then put the copper-silver-cobalt alloy cylinder into a vacuum hot-pressing furnace and heat it to 500 ° C, hold it for 2 hours, and then extrude it. The extrusion ratio is 7:1, and extrude it into a rod to obtain a copper-silver-cobalt alloy rod. ; Then the rod is drawn. During the drawing process, the drawing die and the copper-silver-cobalt alloy bar are immersed in liquid nitrogen. At the same time, a strong magnetic field is set on the drawing die, and the magnetic field strength is set to 0.5T. The deformation amount of each pass is 15%, and the total deformation amount is 90%; then the copper-silver-cobalt alloy bar is subjected to final annealing treatment. Alloy conductive wire.

Example 3

The raw materials of copper, silver and cobalt with a purity of 5N (99.999%) are used. The ratio is: silver 1.5wt%, cobalt 0.1wt%, and the balance is copper and inevitable impurities. After that, control the casting temperature to 1350°C and the casting rate to 0.6Kg/s to obtain copper-silver-cobalt alloy ingots; turn the copper-silver-cobalt alloy ingots to remove defects such as loose surfaces and holes to obtain copper-silver-cobalt alloy cylinders with smooth surfaces. ; Put the copper-silver-cobalt alloy cylinder into a vacuum hot-pressing furnace and heat it to 600°C, hold it for 1 hour, and then extrude it with an extrusion ratio of 10:1, and extrude it into a bar to obtain a copper-silver-cobalt alloy bar; Then, the copper-silver-cobalt alloy bar is drawn. During the drawing process, the drawing die and the bar are immersed in liquid nitrogen. At the same time, a strong magnetic field is set on the drawing die, and the magnetic field strength is set to 5T. The secondary deformation is 30%, and the total deformation is 90%; then the bar is subjected to final annealing treatment, annealing treatment conditions are argon protection, and the treatment time is 1h at 300 °C to obtain copper alloy conductive wires.

Comparative Example 1

The difference between Comparative Example 1 and Example 1 is that the wire drawing process in Comparative Example 1 is carried out at room temperature, that is, the wire drawing die and the bar are not immersed in liquid nitrogen during the wire drawing process, and the others are the same as in Example 1.

Comparative Example 2

The difference between Comparative Example 2 and Example 1 is that no strong magnetic field is set in the wire drawing process in Comparative Example 2, and the others are the same as in Example 1.

Comparative Example 3

The difference between Comparative Example 3 and Example 2 is: Comparative Example 3 does not contain cobalt raw materials, that is, copper and silver raw materials with a purity of 4N5 (99.995%) are used, and the ratio is: silver 0.1wt%, and the balance is copper and non Avoid impurities, and the others are the same as in Example 2.

test

1. Observe the microstructure of the copper alloy wire prepared in Example 1 and Comparative Example 1 under a transmission electron microscope. The transmission electron microscope photo of the longitudinal section of the copper-silver-cobalt alloy wire and the corresponding selected area diffraction pattern are shown in Figure 1 and Figure 2, respectively. Show:

It can be seen from Figure 1 that the microstructure of the copper alloy wire prepared in Example 1 is uniform, mainly composed of dense twins parallel to each other, the average grain size of the alloy is 8 μm, the average width of the twins is 90nm, and the twins are The average length is 500 nm. It can be seen from Figure 2 that the microstructure of the copper alloy wire prepared in Comparative Example 1 presents an uneven deformed grain structure, and some grains have a dense dislocation cell structure and a small amount of intersecting twins, twins. There is no obvious directionality, and some grains have relatively few dislocation cells inside, and the average grain size of the alloy is 30 μm. It can be seen that there is a significant difference in the microstructure of the copper alloy prepared in Example 1 and Comparative Example 1, and the uniformity of the microstructure of the alloy obtained in Example 1 and the orientation of twins are significantly better than those in Comparative Example 1.

2. Test the tensile strength and electrical conductivity of the copper alloy wires prepared in Examples 1 to 3 and Comparative Examples 1 to 3. For the test method of tensile strength, refer to GB/T228.1-2010 "Metal Materials Tensile Test No. 1" Part: Room temperature test method", the test method of electrical conductivity refers to GB/T3048.2-2007 "Wire and Cable Electrical Properties Test Method Part 2: Metal Material Resistivity Test", the results are shown in Table 1 below:

Table 1 Properties of copper alloy wires prepared in Examples 1-3 and Comparative Examples 1-3

It can be seen from Table 1 that the average grain size of the copper alloy wires prepared in Examples 1 to 3 is small, below 8 μm, and there are many twin crystal structures, the tensile strength is above 600 MPa, and the electrical conductivity is 91% IACS. From the above, it can be seen that the copper alloy wires prepared in Examples 1 to 3 have high strength while maintaining high conductivity, and can be used in circuit breakers, contactors, etc.; The obtained copper alloy wire has the best tensile strength and electrical conductivity. Compared with the comparative example, it can be seen that the average grain size of the comparative examples 1 to 3 is above 20 μm, and there is little twin structure, the tensile strength is below 470 MPa, and the electrical conductivity is below 85% IACS. 3 The tensile strength and electrical conductivity of the copper alloy wire obtained are significantly better than those of Comparative Example 1 (drawing at room temperature), Comparative Example 2 (drawing without adding a magnetic field) and Comparative Example 3 (without adding cobalt in the raw material), Therefore, in the present invention, a small amount of silver and cobalt are added to the raw materials, and a large number of twins are induced to aggregate and grow under the combined action of magnetic field and low-temperature deformation to the alloy to form twinning strengthening, so as to realize the wire with good electrical conductivity. At the same time, it also has high strength.

The above are only characteristic implementation examples of the present invention, and do not constitute any limitation to the protection scope of the present invention. All technical solutions formed by equivalent exchange or equivalent replacement fall within the protection scope of the present invention.

Claims (10)

1. A high-strength and high-conductivity copper alloy wire, characterized in that it comprises the raw materials of the following mass fractions: silver 0.1-1.5 wt %, cobalt 0.1-1 wt %, and the remainder is copper and inevitable impurities, wherein silver, copper and The purity of cobalt is not less than 99.99%, and the copper alloy wire contains twin crystals in the grain structure. 2 . The high-strength and high-conductivity copper alloy wire according to claim 1 , wherein the average width of the twins of the copper alloy wire is 20-100 nm, and the average length of the twins is 200-800 nm. 3 . 3 . The high-strength and high-conductivity copper alloy wire according to claim 1 , wherein the average grain size of the copper alloy wire is 1-10 μm. 4 . 4 . The high-strength and high-conductivity copper alloy wire of claim 1 , wherein the copper alloy wire has a tensile strength greater than 600 MPa and an electrical conductivity greater than 90% IACS. 5 . 5. a preparation method of high-strength and high-conductivity copper alloy wire, is characterized in that, comprises the following steps: S1, smelting and casting three raw materials of copper, silver and cobalt to obtain a copper-silver-cobalt alloy ingot; S2, extruding the copper-silver-cobalt alloy ingot to obtain a copper-silver-cobalt alloy bar; S3. The copper-silver-cobalt alloy rod is subjected to wire drawing treatment at -300 to -100 °C, and a magnetic field is applied to the copper-silver-cobalt alloy rod at the same time, and the intensity of the magnetic field is 0.5 to 5T; S4, annealing the copper-silver-cobalt alloy rod processed in step S3 to obtain a copper alloy conductive wire. 6 . The method for preparing a high-strength and high-conductivity copper alloy wire according to claim 5 , wherein in the step S2 , the copper-silver-cobalt alloy ingot is put into a vacuum hot-pressing furnace and heated to 400-600 ℃. 7 . ℃, hold for 1 to 3 hours and then extrude, and the extrusion ratio is 5 to 10:1. 7. The preparation method of a high-strength and high-conductivity copper alloy wire according to claim 5, wherein in the step S3, the copper-silver-cobalt alloy rod is added to the wire drawing die, and the wire drawing die and the copper-silver Cobalt alloy rods are immersed in liquid nitrogen for wire drawing. 8 . The method for preparing a high-strength and high-conductivity copper alloy wire according to claim 5 , wherein in the step S3 , during the wire drawing process, the deformation amount per pass is 10-30%, and the total deformation amount is 10-30%. 9 . not less than 80%. 9 . The method for preparing a high-strength and high-conductivity copper alloy wire according to claim 5 , wherein the annealing treatment in step S4 comprises: placing the copper-silver-cobalt alloy bar processed in step S3 in a vacuum Or under the protection of inert gas, the treatment time is 1 to 2 hours at 200 to 300 °C. 10. The method for preparing a high-strength and high-conductivity copper alloy wire rod according to claim 5, wherein in the step S1, three kinds of raw materials of copper, silver and cobalt are smelted by an intermediate frequency induction melting method, and three kinds of raw materials are smelted. After the raw materials are completely melted, the casting temperature is controlled at 1150-1350° C. and the casting rate is 0.3-0.6 Kg/s to obtain a copper-silver-cobalt alloy ingot.

Images