Copper-chromium-zirconium-scandium alloy plate strip and preparation method thereof

Abstract

The invention belongs to the field of copper-chromium alloys, and particularly relates to a copper-chromium-zirconium-scandium alloy plate strip and a preparation method thereof. The copper-chromium-zirconium-scandium alloy plate strip consists of the following components in percentage by mass: 0.7-0.8% of Cr, 0.03-0.1% of Zr, 0.03-0.1% of Sc, less than or equal to 0.05% of impurity components such as Al, Si, Fe and Sn, and the balance of Cu. According to the method, through the cooperation of the Sc element and the grain boundary pinning effect of Zr and the combination of an appropriate heat treatment process, good regulation and control over the alloy structure are achieved, the inversion relation between the strength and the electric conductivity of a traditional copper alloy is broken through, and the copper alloy plate strip with the excellent mechanical property, the electric conduction and heat conduction performance and the high-temperature softening resistance is obtained; and the requirements of IC lead frames and nuclear energy heat sink materials on high-performance copper alloy can be met.

Description

Technical Field

[0001] The present invention belongs to the field of copper-chromium alloys, and in particular relates to a copper-chromium-zirconium-scandium alloy plate and strip and a preparation method thereof. Background Art

[0002] Copper-chromium-zirconium alloy is a microalloyed copper-chromium alloy with the addition of zirconium. This alloy exhibits excellent electrical conductivity and strength. The addition of zirconium also enhances the alloy's heat resistance. It is used in the power industry to manufacture high-strength electrodes, electrical contacts, and resistance welding electrodes; in the aerospace industry to manufacture wear-resistant components and heat dissipation elements for high-temperature and high-pressure environments; and in the electronics industry to manufacture integrated circuit lead frames and other conductive and thermally conductive components. It is also a promising candidate material for heat sinks in nuclear fusion reactors.

[0003] Currently, the development of copper-chromium-zirconium alloys focuses primarily on process optimization. While these changes have improved the alloy's mechanical properties, maintaining its high-temperature stability remains a major technical challenge. The increasing intelligence, diversification, and miniaturization of terminal devices such as mobile phones and new energy vehicles are driving the development of packaging materials, including lead frames, towards higher density, higher reliability, higher heat dissipation, lower power consumption, and lower costs. This requires lead frame materials to possess improved electrical and thermal conductivity, as well as high strength and stiffness to meet the multifunctional demands of integrated circuits.

[0004] The strengthening of Cu-Cr-Zr alloys primarily stems from the formation of dispersed nanoscale Cr-rich precipitates during the aging process. Preventing the coarsening of Cr at high temperatures is one approach to improving Cu-Cr alloys, and research has been conducted on the addition of other elements to Cu-Cr alloys and Cu-Cr-Zr. A Chinese invention patent application, filed on July 14, 2023, and publication number CN116426789A, discloses a copper-chromium-scandium alloy and its preparation method. The alloy consists of 0.16-0.2% Cr, 0.08-0.15% Sc, and the balance copper and unavoidable impurities. This solution uses a relatively high amount of Sc, which increases costs. Furthermore, the process is primarily designed for producing wire rods, which differ from sheet and strip in terms of preparation process and application scenarios, leading to different performance tests.

[0005] In the fields of IC lead frames and nuclear heat sink materials, it is necessary to directly use plate and strip materials. However, when processing existing plate and strip materials, the strength and conductivity of copper alloys have an inverted relationship, making it difficult to obtain copper alloy plate and strip materials with excellent strength, conductivity, and high-temperature softening resistance. Summary of the Invention

[0006] The purpose of the present invention is to provide a copper-chromium-zirconium alloy plate and strip to solve the problem that existing copper alloys are difficult to achieve a balance between strength, electrical conductivity and high-temperature softening resistance.

[0007] The second object of the present invention is to provide a method for preparing the above-mentioned copper-chromium-zirconium alloy plate and strip.

[0008] In order to achieve the above object, the technical solution adopted by the present invention is:

[0009] A copper-chromium-zirconium-scandium alloy plate and strip is composed of the following components by mass fraction: 0.7-0.8% Cr, 0.03-0.1% Zr, 0.03-0.1% Sc, the total content of impurity components Al, Si, Fe, and Sn is ≤0.05%, and the balance is Cu.

[0010] The present invention is an improved invention. Through the grain boundary pinning effect of the Sc element and Zr, combined with a suitable heat treatment process, good regulation of the alloy structure is achieved, breaking through the inverted relationship between the strength and conductivity of traditional copper alloys, and obtaining copper alloy plates and strips with excellent mechanical properties, electrical and thermal conductivity and high-temperature softening resistance. While the conductivity can reach 79.1% IACS, the room temperature tensile strength reaches 624 MPa, the elongation reaches 7%, and the high-temperature softening temperature reaches 562°C, which can meet the needs of IC lead frames and nuclear heat sink materials for high-performance copper alloys.

[0011] Preferably, the copper-chromium-zirconium-scandium alloy plate and strip is composed of the following components in mass fraction: Cr 0.8%, Zr 0.04-0.06%, Sc 0.04-0.06%, the total content of impurity components Al, Si, Fe, Sn ≤ 0.05%, and the balance is Cu.

[0012] The preparation method of the above-mentioned copper-chromium-zirconium alloy plate and strip includes the following steps: melting and pouring raw materials according to a proportion to obtain a copper-chromium-zirconium-scandium alloy ingot; homogenizing and hot extruding the copper-chromium-zirconium-scandium alloy ingot, and then sequentially performing a solid solution treatment, a first-stage cold rolling, a first-stage aging treatment, a second-stage cold rolling, a second-stage aging treatment, a third-stage cold rolling, and a stress relief annealing treatment; the temperature of the solid solution treatment is 960±10°C, and the temperature of the first-stage aging treatment and the second-stage aging treatment is 450±10°C.

[0013] The preparation method of the copper-chromium-zirconium-scandium alloy plate and strip of the present invention, after melting and casting, uses homogenization, hot extrusion, solid solution and multi-stage cold rolling and aging treatment processes to obtain a high-strength, high-conductivity and high-temperature softening alloy. The method controls the composition fluctuation within ±0.02%, has better comprehensive properties of tensile strength and conductivity and higher resistance to high-temperature softening, and can exert better performance in the field of IC lead frames or nuclear energy heat sink materials that require plate and strip manufacturing.

[0014] Preferably, the solution treatment time is 1.5 to 2 hours, the steel is put into the furnace when it reaches the temperature, and water-cooled; the primary aging treatment and the secondary aging treatment time are both 2 to 3 hours, the steel is put into the furnace when it reaches the temperature, and air-cooled.

[0015] Preferably, the total deformation of the first stage cold rolling is 80±5%, the total deformation of the second stage cold rolling is 50±5%, and the total deformation of the third stage cold rolling is 50±5%. Further preferably, during the first stage cold rolling, rough rolling is performed with a pressing depth of 0.2±0.02mm per step until the deformation reaches 60±5%, and then rolling is performed with a pressing depth of 0.05-0.1mm per step until the deformation reaches 80±5%; during the second stage cold rolling, the pressing depth is 0.1mm-0.2mm per step; and during the third stage cold rolling, the pressing depth is 0.1mm-0.2mm per step.

[0016] Preferably, the stress relief annealing temperature is 350±10° C., and the holding time is 15 to 20 minutes.

[0017] Preferably, the temperature of the homogenization treatment is 950±10° C., and the holding time is 6 to 8 hours.

[0018] Preferably, the raw materials are electrolytic copper plates, Cu-Cr master alloys, Cu-Zr master alloys, and pure scandium; and the smelting is vacuum induction smelting at a smelting temperature of 1150-1250°C.

[0019] More preferably, the temperature during pouring is 1200-1300°C. DETAILED DESCRIPTION

[0020] (1) Description of preferred embodiments of copper-chromium-zirconium alloy sheet and strip and its preparation method.

[0021] While existing research has explored the use of copper-chromium-zirconium alloys in the production of wire, wire cannot replace sheet and strip applications. Furthermore, the conductivity and tensile testing methods for wire differ from those for sheet and strip. Conductivity testing for wire uses the DC resistance-weight method, while tensile testing differs from the national standard sample preparation used for sheet and strip testing, with varying sample sizes and shapes. Therefore, the development of copper-chromium-zirconium-scandium alloys suitable for sheet and strip is needed to better meet the increasing demands of current applications such as IC lead frames and nuclear heat sinks.

[0022] The present invention is mainly based on the component screening of C18150 and C18160. The addition of chromium and zirconium elements is between the two, while the content of scandium and zirconium elements is basically consistent. In this way, through the grain boundary pinning effect of scandium and zirconium, combined with multi-stage cold rolling and aging process, the tensile strength and electrical conductivity of the copper alloy are synergistically improved, and the high-temperature softening resistance is excellent.

[0023] The copper-chromium-zirconium-scandium alloy sheet and strip is composed of the following components by mass: Cr 0.7-0.8%, Zr 0.03-0.1%, Sc 0.03-0.1%, with the combined impurity content of Al, Si, Fe, and Sn being ≤0.05%, and the balance being Cu. The Sc content can be as low as 0.04-0.06%, further reducing raw material costs.

[0024] The preparation method of the above-mentioned copper-chromium-zirconium alloy plate and strip includes: melting and pouring raw materials according to a ratio to obtain a copper-chromium-zirconium-scandium alloy ingot; homogenizing and hot extruding the copper-chromium-zirconium-scandium alloy ingot, and then sequentially performing solid solution treatment, primary cold rolling, primary aging treatment, secondary cold rolling, secondary aging treatment, tertiary cold rolling, and stress relief annealing treatment; the temperature of the solid solution treatment is 960±10°C, and the temperature of the primary aging treatment and the secondary aging treatment is 450±10°C.

[0025] The process of melting and pouring raw materials according to the proportion belongs to the casting process.

[0026] Raw materials can be selected from electrolytic copper plates (Cu≥99.95%), CuCr master alloys, CuZr master alloys, and pure scandium blocks (Sc≥99.8%). The Cr content of the CuCr master alloy can be 5-10% by weight. The Zr content of the CuZr master alloy can be 30-40% by weight. The raw materials can be cut, dried, and surface degreased before use.

[0027] Medium-frequency vacuum induction melting is preferred for melting. After adding the raw materials, vacuum is drawn until the vacuum reaches below 5.0 Pa. The vacuum pump is then turned off, the inflation valve is opened, and some pure argon gas is introduced before heating begins. The melting temperature is 1150-1250°C for 30-50 minutes. Once the melt surface reaches a mirror-like finish and is held at this temperature for 10-15 minutes, the melt is poured directly into a graphite mold at a pouring temperature of 1200-1300°C. The mold is then cooled to produce a copper-chromium-zirconium-scandium alloy ingot.

[0028] The copper-chromium-zirconium-scandium alloy ingot is machined to prepare for subsequent heat treatment after the trimming and bottom end faces are machined and the top riser is removed.

[0029] The temperature of the homogenization treatment is 950±10℃, and the holding time is 6 to 8 hours.

[0030] The temperature of the solution treatment is 960±10℃, and the heating method is to enter the furnace when the temperature reaches the temperature, and the holding time is 1.5-2 hours. After that, it is cooled by running tap water, and the transfer time is controlled within 3-5 seconds.

[0031] The total deformation of the first-stage cold rolling is 80±5%. Preferably, the steel is firstly rough-rolled with a pressing amount of 0.2±0.02 mm each time until the deformation reaches 60±5%, and then rolled with a pressing amount of 0.05-0.1 mm each time until the deformation reaches 80±5%.

[0032] The temperature of the first-stage aging heat treatment is 450±10℃. The heating method is to enter the furnace when the temperature reaches the required level, heat and hold for 2 to 3 hours, and then air cool to room temperature.

[0033] The total deformation of the secondary cold rolling is 50±5%, and the pressing amount each time is 0.1mm-0.2mm.

[0034] The temperature of the secondary aging heat treatment is 450±10℃. The heating method is to enter the furnace when the temperature reaches the required value, and the heating and holding time is 2-3 hours, and then air-cool to room temperature.

[0035] The total deformation of the three-stage cold rolling is 50±5%, and the pressing amount each time is 0.1mm-0.2mm.

[0036] The stress relief annealing temperature is 350±10℃, the heating method is to enter the furnace when the temperature reaches the required value, and the heating and holding time is 15 to 20 minutes.

[0037] The preferred embodiments of the copper-chromium-zirconium alloy plate and strip and the preparation method thereof are described below by way of example.

[0038] Example 1

[0039] The copper-chromium-zirconium-scandium alloy plate and strip of this embodiment is composed of the following components by mass fraction: Cr 0.8%, Zr 0.052%, Sc 0.046%, the total content of impurity components Al, Si, Fe, and Sn is ≤0.05%, and the balance is Cu.

[0040] The method for preparing the copper-chromium-zirconium-scandium alloy plate and strip of this embodiment includes the following steps:

[0041] (1) Melting and Casting Process: Electrolytic copper plate (Cu≥99.95%), Cu-10Cr master alloy, Cu-40Zr master alloy, pure scandium block (Sc≥99.8%) and other raw materials are selected, cut, dried and surface degreased, and then the ingredients are prepared according to the composition; in the order of adding electrolytic copper plate, Cu-10Cr master alloy, Cu-40Zr master alloy and pure scandium block, vacuum is drawn in a medium frequency vacuum induction melting furnace. When the vacuum reaches 5.0 Pa, the vacuum pump is turned off, the gas filling valve is opened, and part of the pure argon gas is filled in and then heating is started. The melting temperature is 1250°C and the duration is 30 minutes. After the melt surface becomes mirror-like and is kept warm for 15 minutes, the melt is directly poured into a graphite mold at a pouring temperature of 1200°C, then cooled and taken out to obtain a multi-element high-conductivity copper-chromium-zirconium-scandium alloy ingot.

[0042] (2) Machining process: The prepared alloy ingot is machined on a conventional lathe or CNC lathe on the circumference and bottom end face, with the circumference machining amount being 2 mm per side and the end face machining amount being 2 mm; subsequently, the machined sample is placed on a sawing machine to saw off the top riser of the ingot, with the sawed length being 1 / 5 of the total height of the ingot.

[0043] (3) Homogenization and hot extrusion process: The machined ingot is placed in a box furnace for heating and homogenization treatment at a holding temperature of 950°C for 6 hours. After 6 hours, the ingot is taken out of the furnace and plastically deformed through a horizontal hot extruder. The cylindrical ingot with a diameter and thickness of 70-75 mm is extruded (sample temperature 950°C, extrusion along the thickness direction) into a copper plate with a thickness of 10 mm, a width of 60 mm, and a length of about 400 mm.

[0044] (4) Solution treatment process: The plastically deformed alloy is heated in a gas-shielded tubular furnace (nitrogen atmosphere) at a temperature of 960°C. The heating method is to enter the furnace upon reaching the required temperature. The heating and holding time is 2 hours. The sample is then quickly removed from the heating furnace and quickly placed in running tap water (room temperature 25±5°C) for cooling. The transfer time is controlled within 3-5 seconds to complete the solution treatment.

[0045] (5) Primary cold rolling process: The solution treated ingot is cold rolled through a twin-roll mill. The initial thickness is 10 mm. Rough rolling is first performed with a downward pressure of 0.2 mm each time. When the thickness reaches 4 mm, the downward pressure is changed to 0.05-0.1 mm each time and the rolling is continued until the thickness becomes 2 mm. The total deformation of the cold rolling is 80%.

[0046] (6) Primary aging heat treatment process: The cold-rolled alloy is heated in a gas-shielded tubular furnace (nitrogen atmosphere) at a temperature of 450°C. The heating method is to enter the furnace at the desired temperature. The heating and holding time is 2 hours. The sample is then removed from the heating furnace and allowed to cool to room temperature in air.

[0047] (7) Secondary cold rolling process: The sample after primary aging treatment is subjected to a second cold rolling process, with each pressing amount being 0.1 mm to 0.2 mm, until the alloy is cold rolled from 2 mm to 1 mm, with a deformation of 50%.

[0048] (8) Secondary aging heat treatment process: The alloy after secondary cold rolling treatment is heated in a gas-shielded tubular furnace (nitrogen atmosphere) at a heating temperature of 450°C. The heating method is to enter the furnace when the temperature reaches the required level. The heating and holding time is 2 hours. The sample is then taken out of the heating furnace and allowed to cool to room temperature in air.

[0049] (9) Three-stage cold rolling process: The sample after the secondary aging treatment is subjected to a third cold rolling process, with each pressing amount being 0.1 mm to 0.2 mm, until the alloy is cold rolled from 1 mm to 0.5 mm, with a deformation of 50%.

[0050] (10) Stress relief annealing process: The sample after the third cold rolling is subjected to the final stress relief annealing treatment. The alloy after the three-stage cold rolling treatment is heated in a gas-shielded tubular furnace (nitrogen atmosphere) at a heating temperature of 350°C. The heating method is to enter the furnace at the temperature, and the heating and holding time is 15 minutes.

[0051] Comparative Examples 1 to 3: No stress relief annealing after three-stage cold rolling

[0052] The copper-chromium alloy of Comparative Example 1 has a composition of Cu-0.82Cr-0.052Zr, i.e., 0.82% Cr, 0.052% Zr, and a total impurity content of ≤0.05% for Al, Si, Fe, and Sn, with the balance being Cu. The preparation process is the same as that of Example 1, except that the stress relief annealing step is omitted after the three-stage cold rolling.

[0053] The copper-chromium alloy of Comparative Example 2 has the composition of Cu-0.8Cr-0.062Sc. The preparation process is the same as that of Example 1, except that no stress relief annealing step is performed after the three-stage cold rolling.

[0054] The copper-chromium alloy of Comparative Example 3 has the composition of Cu-0.8Cr-0.052Zr-0.046Sc. The preparation process is the same as that of Example 1, except that no stress relief annealing step is performed after the three-stage cold rolling.

[0055] Comparative Examples 4 and 5: Stress relief annealing temperature 350°C

[0056] The copper-chromium alloy of Comparative Example 4 has the composition of Cu-0.82Cr-0.052Zr, and the stress relief annealing temperature is 350° C. and the time is 15 minutes. Other conditions are the same as those of Example 1.

[0057] The copper-chromium alloy of Comparative Example 5 has the composition of Cu-0.8Cr-0.062Sc, and the stress relief annealing temperature is 350° C. and the time is 30 minutes. Other conditions are the same as those of Example 1.

[0058] Comparative Examples 6 to 8: Stress relief annealing temperature 400°C

[0059] The copper-chromium alloy of Comparative Example 6 has the composition of Cu-0.82Cr-0.052Zr, and the stress relief annealing temperature is 400° C. and the time is 15 minutes. Other conditions are the same as those of Example 1.

[0060] The copper-chromium alloy of Comparative Example 7 has the composition of Cu-0.8Cr-0.062Sc, and the stress relief annealing temperature is 400° C. and the time is 15 minutes. Other conditions are the same as those of Example 1.

[0061] The copper-chromium alloy of Comparative Example 8 has the following composition: Cu-0.8Cr-0.052Zr-0.046Sc. The stress relief annealing temperature is 400° C. and the time is 15 minutes. Other conditions are the same as those of Example 1.

[0062] (2) Experimental examples

[0063] This experiment tests the electrical conductivity, room temperature tensile strength, Test of high temperature softening temperature:

[0064] The conductivity in this experiment was measured using a Sigma 2008B1 digital eddy current conductivity meter. The sample size was 15×15 mm. Each sample was measured 10 times, and the measurement error was controlled within 0.3% IACS. The average value was then taken.

[0065] The room temperature tensile strength was tested on a SHIMADZU AG-I250KV precision universal testing machine. The tensile rate was set to 0.5 mm / min. The tensile specimen was dog-bone shaped and its size was made according to the "Room Temperature Tensile Test Method for Copper and Copper Alloy Materials" (GB / T 34505-2017).

[0066] The elongation is calculated by subtracting the original gauge length l0 from the length l1 after the tensile specimen is broken and dividing it by l0:

[0067]

[0068] According to GB / T 33370-2016, the high-temperature softening temperature refers to the annealing temperature at which the annealing temperature drops to 80% of the initial hardness. The alloy is first treated to its peak state and then held at 500°C-660°C for 1 hour at intervals of 20°C. The hardness is then measured. The electrical conductivity, room-temperature tensile strength, elongation, and high-temperature softening temperature of the copper-chromium-zirconium-scandium alloy sheet and strip of the present invention after various aging treatments are as follows:

[0069] After primary aging treatment, the electrical conductivity is ≥75% IACS, the room temperature tensile strength is ≥470MPa, the elongation is ≥19%, and the high temperature softening temperature is ≥600℃;

[0070] After secondary aging treatment, the electrical conductivity is ≥80% IACS, the room temperature tensile strength is ≥500MPa, the elongation is ≥16%, and the high temperature softening temperature is ≥520℃;

[0071] After the three-stage aging treatment, the electrical conductivity is ≥79% IACS, the room temperature tensile strength is ≥620MPa, the elongation is ≥7%, and the high temperature softening temperature is ≥560℃.

[0072] The electrical conductivity, room temperature tensile strength, elongation, and high temperature softening temperature of the final product (after the stress relief annealing step) are summarized in Table 1.

[0073] Table 1 Performance indicators of copper-chromium-zirconium-scandium alloy plates and strips

[0074] Instance number Electrical conductivity Room temperature tensile strength Elongation High temperature softening temperature Example 1 79.1% IACS 624MPa 7％ 562℃ Comparative Example 1 78.5% IACS 588MPa 2.5％ 525℃ Comparative Example 2 75.6% IACS 619MPa 3％ 528℃ Comparative Example 3 76.7% IACS 620MPa 4％ 535℃ Comparative Example 4 80.3% IACS 592MPa 4％ 543℃ Comparative Example 5 78.8% IACS 608MPa 9％ 548℃ Comparative Example 6 80.7% IACS 570MPa 6.5％ 536℃ Comparative Example 7 78.6% IACS 566MPa 9％ 540℃ Comparative Example 8 79.4% IACS 601MPa 9.8％ 542℃

[0075] The results in Table 1 demonstrate that the copper-chromium-zirconium-scandium alloy sheet and strip of the present invention exhibits excellent electrical conductivity, room-temperature tensile strength, and resistance to high-temperature softening, demonstrating its superior performance in applications such as IC lead frames and nuclear heat sinks. Furthermore, the compositional fluctuation of the copper-chromium-zirconium-scandium alloy sheet and strip produced by the present invention is controlled within ±0.02%, demonstrating the method's exceptionally high process stability, making it suitable for large-scale industrial production and ensuring consistent product quality.

[0076] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A copper-chromium-zirconium-scandium alloy plate and strip, characterized in that: It is composed of the following components in mass fraction: Cr 0.7-0.8%, Zr 0.03-0.1%, Sc 0.03-0.1%, the total content of impurity components Al, Si, Fe, Sn is ≤0.05%, and the balance is Cu.

2. The copper-chromium-zirconium-scandium alloy sheet and strip according to claim 1, wherein: It is composed of the following components by mass fraction: Cr 0.8%, Zr 0.04-0.06%, Sc 0.04-0.06%, the total content of impurity components Al, Si, Fe, Sn is ≤0.05%, and the balance is Cu.

3. A method for preparing the copper-chromium-zirconium alloy plate and strip according to claim 1, characterized in that: The method comprises the following steps: melting and pouring raw materials according to a proportion to obtain a copper-chromium-zirconium-scandium alloy ingot; subjecting the copper-chromium-zirconium-scandium alloy ingot to homogenization and hot extrusion treatment, and then sequentially performing a solid solution treatment, a first-stage cold rolling, a first-stage aging treatment, a second-stage cold rolling, a second-stage aging treatment, a third-stage cold rolling, and a stress relief annealing treatment; the temperature of the solid solution treatment is 960±10°C, and the temperatures of the first-stage aging treatment and the second-stage aging treatment are 450±10°C.

4. The method for preparing the copper-chromium-zirconium alloy plate and strip according to claim 3, wherein: The time of the solution treatment is 1.5 to 2 hours, the furnace is put into the furnace when it reaches the temperature, and water cooling is carried out; the time of the primary aging treatment and the secondary aging treatment are both 2 to 3 hours, the furnace is put into the furnace when it reaches the temperature, and air cooling is carried out.

5. The method for preparing the copper-chromium-zirconium alloy plate and strip according to claim 3, wherein: The total deformation of the first-stage cold rolling is 80±5%, the total deformation of the second-stage cold rolling is 50±5%, and the total deformation of the third-stage cold rolling is 50±5%.

6. The method for preparing the copper-chromium-zirconium alloy plate and strip according to claim 5, wherein: During the first-stage cold rolling, the steel is firstly roughly rolled with a pressing amount of 0.2±0.02mm each time until the deformation reaches 60±5%, and then rolled with a pressing amount of 0.05-0.1mm each time until the deformation reaches 80±5%; during the second-stage cold rolling, the pressing amount is 0.1mm-0.2mm each time; during the third-stage cold rolling, the pressing amount is 0.1mm-0.2mm each time.

7. The method for preparing the copper-chromium-zirconium alloy plate and strip according to claim 3 or 4, characterized in that: The stress relief annealing temperature is 350±10° C., and the holding time is 15 to 20 minutes.

8. The method for preparing the copper-chromium-zirconium alloy plate and strip according to claim 3 or 4, characterized in that: The temperature of the homogenization treatment is 950±10° C., and the holding time is 6 to 8 hours.

9. The method for preparing the copper-chromium-zirconium alloy plate and strip according to claim 3, wherein: The raw materials are electrolytic copper plate, Cu-Cr master alloy, Cu-Zr master alloy and pure scandium; the smelting is vacuum induction smelting at a smelting temperature of 1150-1250°C.

10. The method for preparing the copper-chromium-zirconium alloy plate and strip according to claim 9, wherein: The temperature during the pouring is 1200-1300°C.

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