CN116130167A

CN116130167A - Preparation method of high-strength high-conductivity impact-resistant copper-chromium-zirconium alloy contact wire

Info

Publication number: CN116130167A
Application number: CN202211632475.3A
Authority: CN
Inventors: 赵永好; 董洪振; 周凯旋; 刘亿; 李顺强; 刘吉梓
Original assignee: Nanjing University of Science and Technology
Current assignee: Nanjing University of Science and Technology
Priority date: 2022-12-19
Filing date: 2022-12-19
Publication date: 2023-05-16

Abstract

The invention belongs to the technical field of high-performance copper alloy materials, and particularly relates to a preparation method of a high-strength high-conductivity impact-resistant copper-chromium-zirconium alloy contact wire. The method comprises the following steps: (1) alloy preparation: preparing rectangular block-shaped copper-chromium-zirconium alloy, wherein the alloy comprises the following components: 0.4 to 0.8 weight percent of Cr, 0.15 to 0.3 weight percent of Zr, less than or equal to 0.006 weight percent of Sb, less than or equal to 0.072 weight percent of Si, less than or equal to 0.006 weight percent of Fe, less than or equal to 0.005 weight percent of Zn, and the balance of Cu and unavoidable impurities; (2) solution treatment: homogenizing copper-chromium-zirconium alloy, and obtaining supersaturated solid solution through water quenching; (3) machining: processing the rectangular block-shaped copper-chromium-zirconium alloy after solid solution into bars; (4) rotary forging: carrying out rotary forging on the copper-chromium-zirconium alloy rod for multiple times at room temperature until the equivalent strain amount is 2-3; and (5) aging treatment: and annealing the bar after the rotary forging, and air-cooling to room temperature. The method of the invention improves the contact line strength, impact resistance and electrical conductivity, and can reduce the production cost.

Description

Preparation method of high-strength high-conductivity impact-resistant copper-chromium-zirconium alloy contact wire

Technical Field

The invention belongs to the technical field of high-performance copper alloy materials, and particularly relates to a preparation method of a high-strength high-conductivity impact-resistant copper-chromium-zirconium alloy contact wire.

Background

With the rapid development of the modern industry in the 21 st century, the travel demands of people are expanding. The high-speed railways in China are rapidly developed, and due to the accelerated flow of all social personnel and materials, the high-speed railways have stricter requirements in the future. Among common materials for high-speed railways, the development trend of copper alloy materials widely applied to the fields of lead frames, overhead conductors, high-speed contact wires and the like determines whether more current and traction can be provided. Unfortunately, the contradiction that the conductivity of the material is improved as much as possible, and the high strength is necessarily sacrificed is still not solved, and the contact line is always exposed to the atmospheric environment, so that the contact line is inevitably collided and even impacted in the use process. Therefore, how to combine the high strength, impact resistance and high conductivity of copper alloy is a scientific and application problem to be solved in the current preparation of high-performance copper alloy.

According to the document search of the prior art, raw materials such as copper, silver and the like which are beneficial to conductivity are proportioned and smelted, and the mutual balance of the strength and the conductivity of the contact line material is obtained by adopting a deformation and heat treatment process. The Chinese patent name of the invention is a high-strength high-conductivity copper-silver alloy material and a preparation method thereof (patent grant number CN 201911368587.0) discloses a preparation method of the high-strength high-conductivity copper-silver alloy material: the copper powder and the silver powder are ball-milled into nano powder in a ball milling tank, and the nano powder is formed into a high-density blank through pressure molding. And then, the pressure-assisted low-temperature rapid activation solid-phase sintering technology is utilized, and the performance of the copper-silver alloy material is improved through the combined action of the nano structure enhancement of the copper-silver matrix and nano-scale micro-alloying. However, the above preparation method still has corresponding problems: (1) In order to obtain copper silver powder with uniform mixing and proper size, long-time ball milling is needed, impurities and oxides are easy to introduce in the ball milling process, and a certain time cost and production risk are increased; (2) The nanocrystalline structure produced by sintering is beneficial to improving the strength, but also reduces the impact toughness of the material, meanwhile, the method does not have excellent compactness like the traditional casting, the sintered material still needs subsequent processing to form a wire, and the performance indexes of the material in all aspects are further influenced. (3) Noble metal silver also increases the production cost of the material, which is unfavorable for industrialization and socioeconomic development.

Further searching the literature, chinese patent name of the invention is "a high-strength high-conductivity copper alloy wire material and a preparation method thereof" (patent grant CN 202010719297.2) discloses a preparation method of the high-strength high-conductivity copper alloy wire material: vacuum melting of copper-based alloys is performed using a plurality of microalloying elements (Ni, fe, mg, ca, ag, la, P, sn, ti). And then, by utilizing various processes such as hot extrusion, aging treatment, unidirectional drawing and the like, the high-strength Cu-Ni alloy wire with excellent comprehensive performance is obtained through solid solution strengthening, microalloying refined structure and second phase strengthening of Ni. But it also has the following disadvantages: (1) The complex microalloying process is not beneficial to the large-scale production of factories, and the time and the production cost are increased; (2) The drawing process has high demands on the plasticity of the material, which can be subject to stress concentration and fracture when the material is not plastic enough to continue supporting the drawing deformation. In order to avoid the above, it is generally necessary to perform annealing several times during the drawing process to eliminate the deformation defect and recover the plastic deformation thereof, but this also adversely affects the work hardening effect of the material and softens the material. Therefore, the conventional process thought is still adopted by the current technology and method, and the contradiction between cost and quality cannot be solved temporarily.

Disclosure of Invention

The invention aims to provide a preparation method of a high-strength high-conductivity impact-resistant copper-chromium-zirconium contact wire, which can improve the strength, impact resistance and conductivity of the contact wire and reduce the production cost by utilizing a commercialized mature and reliable rotary forging process.

The technical solution for realizing the purpose of the invention is as follows: a preparation method of a high-strength high-conductivity impact-resistant copper-chromium-zirconium alloy contact wire comprises the following steps:

step (1): alloy preparation: preparing rectangular block-shaped copper-chromium-zirconium alloy, wherein the alloy comprises the following components: 0.4 to 0.8 weight percent of Cr, 0.15 to 0.3 weight percent of Zr, less than or equal to 0.006 weight percent of Sb, less than or equal to 0.072 weight percent of Si, less than or equal to 0.006 weight percent of Fe, less than or equal to 0.005 weight percent of Zn, and the balance of Cu and unavoidable impurities;

step (2): solution treatment: homogenizing copper-chromium-zirconium alloy, and obtaining supersaturated solid solution through water quenching;

step (3): machining: processing the rectangular block-shaped copper-chromium-zirconium alloy after solid solution into bars;

step (4): rotary forging: carrying out rotary forging on the copper-chromium-zirconium alloy rod for multiple times at room temperature until the equivalent strain amount is 2-3;

step (5): aging treatment: and annealing the bar after the rotary forging, and air-cooling to room temperature.

Further, in the step (1), rectangular block-shaped copper-chromium-zirconium alloy is prepared by vacuum melting and hot forging cogging.

Further, the solution treatment in the step (2) specifically includes: the heating is carried out in an air circulation furnace, the heating temperature is 900-1000 ℃, and the heat preservation time is 1-2 h.

Further, the average grain size after the solution treatment in the step (2) is 176.+ -.10. Mu.m, the crystal orientation is relatively random, and no specific orientation texture is provided.

Further, in the step (4), rotary forging specifically includes: the diameter of the bar is reduced by 0.3-0.8 mm in each pass, the rotating speed is 100-200 r/min, and the feeding speed is 15-30 mm/s.

Further, rotary forging is carried out by replacing rotary forging dies with different radiuses and repeating the rotary satin process, so that copper-chromium-zirconium contact wires with different diameters are obtained.

Further, the aging treatment in the step (5) specifically comprises: and carrying out isothermal aging heat treatment at 200-600 ℃ for 20-120 min, and then cooling to room temperature to obtain the copper-chromium-zirconium contact wire.

Further, the copper-chromium-zirconium contact line comprises the following raw material components: 0.41wt% of Cr, 0.15wt% of Zr, less than or equal to 0.006wt% of Sb, less than or equal to 0.072wt% of Si, less than or equal to 0.006wt% of Fe, less than or equal to 0.005wt% of Zn, and the balance of Cu and unavoidable impurities.

Compared with the prior art, the invention has the remarkable advantages that:

the fractal structure and the nano precipitation design concept are introduced into alloy preparation, and nano Cr precipitation phases with the size of about 3.4nm are obtained through a rotary swaging and aging process within the given alloy composition range, as shown in figure 2, the Cr precipitation phases are in a FCC structure and are in a coherent relation with a Cu matrix, and a cutting mechanism of dislocation and the precipitation phases has a very good strengthening effect on the alloy, so that the material has excellent comprehensive performance.

The copper-chromium-zirconium alloy belongs to a commercially mature material, has low raw material cost and easy preparation, is convenient for batch production in factories and reduces the use cost.

The rotary forging lead has excellent toughness and conductivity, the tensile strength is more than or equal to 620MPa, the uniform elongation is more than or equal to 8 percent, the conductivity is more than or equal to 78 percent, and meanwhile, the rotary forging lead has higher impact resistance, thereby completely meeting the use requirement of a high-speed rail contact line.

The rotary forging introduces ultra-long ultra-fine grains along the copper spool, so that electrons pass through fewer grain boundaries, the nano precipitated phase generated by subsequent annealing improves the strength, and meanwhile, the electron scattering effect is further reduced, and the effect of improving the conductivity is achieved.

Compared with drawing, the rotary forging does not need to be annealed for many times, and a plurality of rotary forging devices can be used in combination at the same time, so that the required deformation is obtained after one rotary forging, the performance is improved, the production cost is saved, and the rotary forging device is more suitable for being put into large-scale production and application.

Drawings

FIG. 1 is an optical microscope structure of a copper chromium zirconium alloy wire showing the microscopic morphology of a side view of a sample; (a) is the strain amount 2.5, (b) is example 1, (c) is example 2, (d) and (e) are grain width and length distributions after different heat treatment temperatures based on optical microscope image statistics.

FIG. 2 is a microstructure of example 1; (a) A high resolution image of the precipitated structure, the inset being a fourier transform image of the in-frame region; (b) An inverse fourier transform image corresponding to the pattern of Cr precipitate phases in the (a) inset; (c) A transmission electron microscopy bright field image based on <001> oriented grains in the side view of the sample.

FIG. 3 is a microstructure of example 2; (a) <001> bright field image of oriented grains, the illustration being a diffraction pattern; (b) Cr precipitates (arrows); (c) A high resolution image of Cr precipitates, the inset being an inverse fourier transform image of the (200) plane corresponding to the Cr phase; and (d) a fourier transform image of the (200) plane of the Cr phase.

FIG. 4 is a photograph of impact properties and fracture morphology of copper chromium zirconium alloy wire; (a) fracture RS-RD scanning electron micrographs of example 1; (b) scanning electron micrographs of fracture RS-TD of example 1; (c) Charpy impact performance schematic of samples of each state.

Detailed Description

The invention is described in further detail below with reference to the accompanying drawings.

Aiming at the defects existing in the prior art, the invention provides a preparation method of a high-strength high-conductivity impact-resistant copper-chromium-zirconium alloy contact wire, and the batch preparation of the high-strength high-conductivity impact-resistant copper-chromium-zirconium alloy contact wire is realized through a simple industrial rotary forging technology. The objects, technical solutions and advantages of the present invention will become more apparent by describing embodiments of the present invention in detail with reference to the accompanying drawings. It will be apparent that the described embodiments are only some, but not all, embodiments of the invention. All other embodiments, which can be made by one of ordinary skill in the art without undue burden from the invention, are within the scope of the invention.

Example 1:

the preparation method of the high-strength high-conductivity impact-resistant copper-chromium-zirconium contact wire comprises the following steps:

step one, smelting and hot forging: the copper-chromium-zirconium alloy with 50 multiplied by 300mm rectangular blocks is prepared and obtained, and the alloy comprises the following components: 0.41wt% of Cr, 0.15wt% of Zr, less than or equal to 0.006wt% of Sb, less than or equal to 0.072wt% of Si, less than or equal to 0.006wt% of Fe, less than or equal to 0.005wt% of Zn, and the balance of Cu and unavoidable impurities;

step two, solution treatment: homogenizing copper-chromium-zirconium alloy in an air circulation furnace at 1000 ℃ for 2 hours, and then carrying out water quenching to obtain supersaturated solid solution;

step three, machining: machining rectangular copper-chromium-zirconium alloy into

Is a bar of (2);

step four, forging the copper-chromium-zirconium bar material at room temperature through multiple times of rotary forging

Corresponding to an equivalent strain of 2.5. Each pass reduced the diameter of the bar by about 0.3mm at a speed of 110r/min.

Step five, aging treatment: annealing the swaged bar at 450 ℃, keeping the temperature for 1h, and then air-cooling to room temperature.

Finally obtaining the copper-chromium-zirconium alloy wire with the equivalent deformation of 2.5 and the heat treatment state of 450 ℃/1 h.

Example 2:

Is a bar of (2);

Step five, aging treatment: and (3) annealing the swaged bar at 600 ℃ for 1h. And then air-cooled to room temperature.

Finally, the copper-chromium-zirconium alloy wire with the equivalent deformation of 2.5 and the heat treatment state of 600 ℃/1h is obtained.

After deformation of epsilon=2.5, the grain non-uniformity in solid solution persists in the form of thicker (100 μm) and thinner (less than 1 μm) elongated grains. As can be seen from FIG. 1, the rotary swaging incorporates ultra-long ultra-fine grains along the copper wire axis, with the average grain length of about 100um and width of about 10um as a result of the statistics of FIGS. 1 (d), 1 (e). Although ultra-long grains increase conductivity by reducing the scattering effect of high angle grain boundaries on copper, there are a large number of high density dislocations inside the grains, so high density dislocations on the electron channels will still decrease conductivity.

In the transmission electron microscope image of fig. 2, there are a large number of small angle grain boundaries parallel to the swaging direction between grains, and the inset shows that the orientation difference between two adjacent substructures is about 3 °. In the high-resolution image, when Cr phase is precipitated after the sample is annealed at 450 ℃/1h, the precipitated phase and the copper matrix are coherent, and the sample has a face-centered cubic structure. As shown in fig. 3 (c) and 3 (d), the dislocation density after 600 ℃/1h annealing was further reduced, but the precipitation phase continued to grow, and Cr precipitated as a body centered cubic structure was semi-coherent with the copper matrix.

The above heat treatment temperature is lower than the recrystallization temperature of the alloy, so that most of the dislocations on the electron channel are removed, thereby improving work hardening ability. And a large number of small-angle grain boundaries in the grains and precipitated phases generated by annealing are also helpful for improving the strength of the alloy, but the electron scattering effect is small. Meanwhile, the nano precipitated phase with dispersed distribution and proper size can be used as a potential dislocation source and can also play a role in pinning dislocation, and larger shearing stress is activated to promote dislocation movement, so that the size and the interval of the precipitate become variables with high strength and high elongation. In summary, during deformation, the evenly distributed precipitated phases with sub-micron spacing of small angle grain boundaries increase yield strength, impact resistance by effectively preventing dislocation slip and crack propagation in the radial direction, and the data for Charpy impact energy are shown in FIG. 4.

From the above analysis in combination with table 1, we use the deformation method of rotary forging (low cost, easy industrialization) to remodel grains of copper-chromium-zirconium alloy after solid solution, and introduce a large amount of dislocation and small angle grain boundaries parallel to macroscopic elongation direction, when the strain amount is 2.5, the strength is greatly improved while sacrificing the elongation and conductivity. And after further aging treatment, introducing high-density nano Cr precipitate, wherein when the time efficiency parameter is 450 ℃/1h, the copper-chromium-zirconium alloy has the comprehensive properties of high UTS (626 MPa), high uniform elongation (8.7%) and high conductivity (78.5%).

Table 1 shows the temperature performance parameters of each heat treatment

Heat treatment temperature	Tensile strength MPa	Uniform elongation%	Conductivity IACS (%)
				ε＝0	215	31	56.9
ε＝2.5	488	1.4	31.3
				200℃/1h	461	3	31.9
300℃/1h	493	5.6	37.9
				400℃/1h	609	8.3	66.7
400℃/2h	604	8	68.6
				450℃/1h	626	8.7	78.5
500℃/20min	608	7.9	83.4
				500℃/1h	599	8.1	87.3
600℃/1h	443	7.5	94.1

Claims

1. The preparation method of the high-strength high-conductivity impact-resistant copper-chromium-zirconium alloy contact wire is characterized by comprising the following steps of:

2. The method of claim 1, wherein in step (1) the rectangular-shaped copper-chromium-zirconium alloy is prepared by vacuum melting, hot forging, and cogging.

3. The method according to claim 2, wherein the solution treatment in step (2) is specifically: the heating is carried out in an air circulation furnace, the heating temperature is 900-1000 ℃, and the heat preservation time is 1-2 h.

4. A method according to claim 3, wherein the average grain size after solution treatment in step (2) is 176±10 μm, the crystal orientation is relatively random, and no specific orientation texture is present.

5. The method according to claim 4, wherein the rotary forging in step (4) is specifically: the diameter of the bar is reduced by 0.3-0.8 mm in each pass, the rotating speed is 100-200 r/min, and the feeding speed is 15-30 mm/s.

6. The method of claim 5, wherein the rotary forging is performed by replacing a rotary forging die with a different radius, and repeating the rotary satin process, thereby obtaining copper-chromium-zirconium contact wires with different diameters.

7. The method according to claim 6, wherein the aging treatment of step (5) is specifically: and carrying out isothermal aging heat treatment at 200-600 ℃ for 20-120 min, and then cooling to room temperature to obtain the copper-chromium-zirconium contact wire.

8. The method of claim 7, wherein the copper chromium zirconium contact wire comprises the following raw material components: 0.41wt% of Cr, 0.15wt% of Zr, less than or equal to 0.006wt% of Sb, less than or equal to 0.072wt% of Si, less than or equal to 0.006wt% of Fe, less than or equal to 0.005wt% of Zn, and the balance of Cu and unavoidable impurities.