An ultra-micro-alloyed high-elongation ultra-thin oxygen-free copper strip and a preparation method thereof

Abstract

The application relates to the technical field of metal material precision machining, and discloses a super-micro-alloyed high-elongation super-thin oxygen-free copper strip and a preparation method thereof, which comprises the following steps: S1, super-micro-alloyed smelting and purification; S2, hot rolling and normalizing; S3, grain boundary engineering regulation; S4, precise super-thin rolling; and S5, deformation heat treatment and surface control. The super-micro-alloyed high-elongation super-thin oxygen-free copper strip and the preparation method thereof are characterized in that: TU00 / TU0 / TU1 high-purity oxygen-free copper is selected as a matrix, super-micro-amounts of Ag, Mg, Cr, Zr, Ti, B, P and rare earth grain boundary active elements are added, the total amount of the elements and the amount of a single element are strictly controlled, the complete preparation process of super-micro-alloyed smelting and purification, hot rolling and normalizing, multi-pass decreasing deformation cold rolling + near recrystallization temperature annealing grain boundary engineering regulation, precise super-thin rolling and deformation heat treatment and surface control are combined, and therefore, the super-thin oxygen-free copper strip with the thickness of 0.18-0.22 mm, low oxygen content, high conductivity and high elongation can be stably prepared.

Description

Technical Field

[0001] This invention relates to the field of precision machining technology for metal materials, specifically to an ultra-micro alloyed high-elongation ultrathin oxygen-free copper strip and its preparation method. Background Technology

[0002] my country is a major copper processing country, but it still faces many technological bottlenecks in the field of high-elongation ultrathin oxygen-free copper strip. Currently, domestically produced oxygen-free copper strip products have significant shortcomings in achieving a synergistic balance between ultrathinness and high elongation. Products manufactured using traditional processes often struggle to simultaneously achieve ultra-thin dimensions, high conductivity, and high elongation, and are prone to breakage and deformation under complex working conditions. Furthermore, the high-end market has long been monopolized by foreign companies, resulting in high product prices and long delivery cycles, severely hindering the independent and controllable development of my country's related industrial chains.

[0003] Existing technologies mostly focus on single-component optimization or rolling process improvement, making it difficult to simultaneously achieve ≥100% IACS conductivity and ≥25% elongation at an ultrathin thickness of 0.2mm. Therefore, developing an oxygen-free copper strip that can simultaneously meet the requirements of ultrathin size, high conductivity, high elongation, high dimensional accuracy, and high surface quality, as well as a stable and industrially feasible preparation method, has become a key technical problem that urgently needs to be solved in this field. Summary of the Invention

[0004] (a) Technical problems to be solved To address the shortcomings of existing technologies, this invention provides an ultra-thin oxygen-free copper strip with high elongation and its preparation method, which has the advantages of high conductivity, high elongation, and high surface quality, and solves the problems of conductivity and ductility of existing ultra-thin oxygen-free copper strips at a thickness of 0.2 mm.

[0005] (II) Technical Solution To achieve the aforementioned objectives of high conductivity, high elongation, and high surface quality, this invention provides the following technical solution: an ultra-thin oxygen-free copper strip with high elongation achieved by micro-alloying and its preparation method, wherein the copper strip uses TU00, TU0, or TU1 high-purity oxygen-free copper as the matrix, and its chemical composition contains one or more grain boundary active elements, wherein the grain boundary active elements are selected from one or more of Ag, Mg, Cr, Zr, Ti, B, P, and rare earth elements; The total amount of the grain boundary active elements added is 5-40 ppm, and the amount of a single element added is ≤20 ppm. The copper strip has a thickness of 0.18-0.22 mm, an oxygen content of ≤3 ppm, a conductivity of ≥100% IACS at 20℃, and an elongation of ≥25%. In microstructure, Σ3 n The proportion of key lattice grain boundaries is ≥70%, and the average grain size is ≤20μm; The surface roughness Ra is 0.15-0.40μm, and the tensile strength is 270-360MPa.

[0006] Preferably, the grain boundary active element includes at least two of Ag, Zr, Ti and B.

[0007] Preferably, the compositional fluctuation of the copper strip is ≤±5%, the oxygen content is ≤2.5ppm, and Σ3 n The proportion of heavy lattice grain boundaries is ≥75%.

[0008] Preferably, the copper strip has an elongation of ≥28%, a conductivity of ≥102% IACS, and a hardness of 90-100HV.

[0009] A method for preparing ultrathin oxygen-free copper strip with high elongation through micro-alloying. S1: Ultra-micro alloying melting and purification Using TU00, TU0, or TU1 cathode copper as raw material, grain boundary active elements are added by means of intermediate alloy or high-purity metal ingots. Melting is carried out by bottom blowing technology with high-purity covering agent combined with N2+CO reducing mixed gas. The melting temperature is controlled at 1150-1250℃ and the refining time is ≥30min. The oxygen content of the melt is ≤3ppm and the hydrogen content is ≤0.5ppm. Electromagnetic stirring and gradient cooling technology are used to prepare large-size uniform ingots with composition fluctuation ≤±5%. S2: Hot-rolled and normalized The ingot is hot rolled at an initial rolling temperature of ≥850℃ and a final rolling temperature of ≥650℃, with a total hot rolling deformation of ≥80%; then it is normalized at a temperature of 550-650℃ for 10-20 minutes. S3: Grain boundary engineering control The process employs a multi-pass cold rolling process with decreasing deformation followed by a near-recrystallization temperature annealing cycle. Perform 3-5 cycles, each cycle containing a single pass of cold rolling, with the deformation amount of a single pass controlled at 20%-30%, and the deformation amount of the subsequent pass being less than that of the previous pass; After each cold rolling pass, continuous annealing is performed, with the annealing temperature controlled at 400-600℃ and the holding time at 5-15 minutes, to induce the formation of a high proportion of Σ3. n Multiple lattice grain boundaries; S4: Precision ultra-thin rolling The strip treated with grain boundary engineering is precision rolled using a high-rigidity rolling mill, with a final rolling thickness of 0.18-0.22 mm and a thickness tolerance controlled within ±0.003 mm. S5: Deformation Heat Treatment and Surface Control After rolling, the strip undergoes a coupled treatment of tension straightening and continuous tension annealing. The tension coefficient is 30%-50% of the yield strength, and the annealing temperature is 300-400℃ to eliminate residual stress. Finally, the strip is cleaned, dried, and subjected to anti-oxidation treatment to obtain the finished product.

[0010] Preferably, in step S3, the number of cycles of multi-pass decreasing deformation cold rolling + near recrystallization temperature annealing is 3 to 4 times. The deformation amount of the first cold rolling is 26% to 30%, and the annealing temperature is 480 to 520°C. The deformation amount of the second cold rolling is 23% to 26%, and the annealing temperature is 500 to 540°C. The deformation amount of the third cold rolling is 20% to 23%, and the annealing temperature is 520 to 560°C.

[0011] Preferably, the master alloy used in step S1 is an Al-B, Cu-Mg, Cu-Zr, or Cu-Ti master alloy, and a gradient addition process is adopted, with the addition rate matching the melting temperature.

[0012] (III) Beneficial Effects Compared with the prior art, the present invention provides an ultra-micro alloyed high-elongation ultrathin oxygen-free copper strip and its preparation method, which has the following beneficial effects: 1. This ultra-micro alloyed high-elongation ultrathin oxygen-free copper strip and its preparation method achieve a conductivity ≥100% IACS and an elongation ≥25% at an ultrathin thickness of 0.2mm, breaking through the performance limits of traditional processes. Through a specific decreasing cold rolling + near-recrystallization annealing cycle, high-density Σ3 is induced to form... n Coherent twin boundaries effectively hinder crack propagation and have minimal impact on electron scattering. With oxygen content controlled below 3 ppm, the precipitation of brittle phases such as Cu2O is significantly reduced, improving the uniformity and deep-drawing performance of the material. Combined with tension straightening and precision rolling, the surface roughness Ra≤0.4μm is achieved without warping, meeting the requirements of precision etching and microelectronic packaging. Detailed Implementation

[0014] Example 1 This embodiment provides an ultra-micro alloyed, high-elongation, ultrathin oxygen-free copper strip, and also provides its preparation method, as follows: In this embodiment, the oxygen-free copper strip uses TU00 high-purity oxygen-free copper as the matrix, and adds three grain boundary active elements: Ag, Zr, and B to the chemical composition. The amount of Ag added is 10 ppm, the amount of Zr added is 8 ppm, and the amount of B added is 3 ppm. The total amount of the three elements is 21 ppm, and the amount of each individual element added is ≤20 ppm.

[0015] The final oxygen-free copper strip was 0.20 mm thick, with an oxygen content of 2.8 ppm, a conductivity of 101.2% IACS at 20℃, and an elongation of 26%. The microstructure contained Σ3... n The proportion of lattice grain boundaries is 72%, the average grain size is 18μm, the surface roughness Ra is 0.30μm, the tensile strength is 300MPa, and the compositional fluctuation is ≤±5%.

[0016] The method for preparing ultra-thin oxygen-free copper strip with high elongation by micro-alloying in this embodiment includes the following steps: (1) Ultra-micro alloying smelting and purification TU00 cathode copper was selected as the raw material, and Cu-B, Cu-Zr master alloys, and high-purity Ag metal ingots were used as additives. A gradient addition process was employed, with the addition rate matched to the melting temperature. During melting, a high-purity covering agent combined with N2+CO reducing mixed gas bottom blowing technology was used to control the melting temperature at 1200℃ and the refining time at 35 minutes, reducing the oxygen content of the melt to 2.8 ppm and the hydrogen content to 0.4 ppm. Subsequently, electromagnetic stirring and gradient cooling technology were used to prepare large-sized uniform ingots with compositional fluctuations ≤ ±5%.

[0017] (2) Hot rolling and normalizing The above-mentioned ingots were hot rolled at an initial rolling temperature of 880℃ and a final rolling temperature of 680℃, with a total hot rolling deformation of 85%. After hot rolling, normalizing treatment was carried out at a temperature of 600℃ and a holding time of 15 minutes.

[0018] (3) Grain boundary engineering control The process employs a multi-pass, decreasing deformation cold rolling cycle followed by near-recrystallization temperature annealing, involving three cycles: ① First cold rolling: The deformation amount of single-pass cold rolling is 28%. After cold rolling, continuous annealing is carried out at a temperature of 500℃ and a holding time of 10min. ② Second cold rolling: The deformation amount of cold rolling in a single pass is 25%. After cold rolling, continuous annealing is carried out at a temperature of 520℃ and a holding time of 8min. ③ Third cold rolling: The deformation amount of cold rolling in a single pass is 22%. After cold rolling, continuous annealing is carried out at a temperature of 540℃ and a holding time of 6min. The above-mentioned recycling process induces the formation of a high proportion of Σ3 n Heavy point lattice grain boundaries.

[0019] (4) Precision ultra-thin rolling The strip treated with grain boundary engineering was precision rolled using a high-rigidity rolling mill, with a final rolling thickness of 0.20 mm and a thickness tolerance controlled within ±0.003 mm.

[0020] (5) Deformation heat treatment and surface control The rolled strip undergoes tension straightening and continuous tension annealing coupled treatment, with a tension coefficient of 40% of the yield strength and an annealing temperature of 350℃ to eliminate residual stress. Finally, it is subjected to cleaning, drying, and anti-oxidation treatment in sequence to obtain the finished product of ultra-micro alloyed high elongation ultra-thin oxygen-free copper strip.

[0021] Example 2 The difference between this embodiment and Embodiment 1 is that: Using TU1 high-purity oxygen-free copper as the matrix, Ag and Ti, two grain boundary active elements, were added. The Ag addition amount was 15 ppm, the Ti addition amount was 15 ppm, and the total addition amount was 30 ppm. The final prepared oxygen-free copper ribbon had a thickness of 0.18 mm, an oxygen content of 2.5 ppm, a conductivity of 102% IACS at 20℃, an elongation of 28%, and a microstructure of Σ3 n The grain boundary ratio of the lattice is 75%, the average grain size is 16μm, the surface roughness Ra is 0.25μm, the tensile strength is 320MPa, the hardness is 95HV, the flatness of the plate is 5I-unit, and there are no scratches, oil stains and oxide layers.

[0022] In step (1), the melting temperature is 1180℃, the refining time is 40min, the oxygen content of the melt is reduced to 2.5ppm, and the hydrogen content is reduced to 0.3ppm. In step (3), the cycle process is carried out 4 times. The first cold rolling deformation is 30% and the annealing temperature is 520℃. The second cold rolling deformation is 26% and the annealing temperature is 540℃. The third cold rolling deformation is 23% and the annealing temperature is 560℃. The fourth cold rolling deformation is 20% and the annealing temperature is 580℃. In step (5), the tensile coefficient is 35% of the yield strength and the annealing temperature is 380℃. The remaining steps are the same as in Example 1.

[0023] Example 3 The difference between this embodiment and Embodiment 1 is that: Using TU0 high-purity oxygen-free copper as the matrix, three grain boundary active elements—Mg, Cr, and rare earth element (La)—were added. The addition amounts of Mg were 8 ppm, Cr 12 ppm, and La 5 ppm, for a total addition of 25 ppm. The resulting oxygen-free copper ribbon had a thickness of 0.22 mm, an oxygen content of 3 ppm, a conductivity of 100.5% IACS at 20 °C, and an elongation of 25%. The microstructure contained Σ3... n The ratio of lattice grain boundaries is 70%, the average grain size is 20 μm, the surface roughness Ra is 0.40 μm, and the tensile strength is 270 MPa.

[0024] In step (1), the melting temperature is 1150℃, the refining time is 30min, the oxygen content of the melt is 3ppm, and the hydrogen content is 0.5ppm. In step (2), the hot rolling start temperature is 850℃, the final rolling temperature is 650℃, the total hot rolling deformation is 80%, the normalizing temperature is 550℃, and the holding time is 20min. In step (3), the cycle process is carried out 3 times. The first cold rolling deformation is 26%, and the annealing temperature is 480℃. The second cold rolling deformation is 23%, and the annealing temperature is 500℃. The third cold rolling deformation is 20%, and the annealing temperature is 520℃. In step (5), the tensile coefficient is 30% of the yield strength, and the annealing temperature is 300℃. The remaining steps are the same as in Example 1.

[0025] Example 4 The difference between this embodiment and Embodiment 1 is that: Using TU00 high-purity oxygen-free copper as the matrix, only Zr grain boundary active elements were added at a concentration of 20 ppm, with a total addition of 20 ppm. The resulting oxygen-free copper ribbon had a thickness of 0.19 mm, an oxygen content of 2.6 ppm, a conductivity of 101% IACS at 20℃, and an elongation of 27%. The microstructure contained Σ3... n The ratio of lattice grain boundaries is 73%, the average grain size is 17μm, the surface roughness Ra is 0.28μm, the tensile strength is 310MPa, and the hardness is 90HV.

[0026] In step (1), the melting temperature is 1250℃, the refining time is 38min, the oxygen content of the melt is 2.6ppm, and the hydrogen content is 0.35ppm. In step (2), the hot rolling start temperature is 900℃, the final rolling temperature is 670℃, the total hot rolling deformation is 82%, the normalizing temperature is 650℃, and the holding time is 10min. In step (3), the cycle process is carried out 3 times. The first cold rolling deformation is 29%, and the annealing temperature is 510℃. The second cold rolling deformation is 24%, and the annealing temperature is 530℃. The third cold rolling deformation is 21%, and the annealing temperature is 550℃. In step (5), the tensile coefficient is 50% of the yield strength, and the annealing temperature is 400℃. The remaining steps are the same as in Example 1.

[0027] In summary, this invention utilizes high-purity oxygen-free copper (TU00 / TU0 / TU1) as the matrix, with trace amounts of grain boundary active elements such as Ag, Mg, Cr, Zr, Ti, B, P, and rare earth elements added. It also strictly controls the total amount and individual element additions. Combined with a complete preparation process including ultra-micro alloying smelting purification, hot rolling normalization, multi-pass decreasing deformation cold rolling + near-recrystallization temperature annealing for grain boundary engineering control, precision ultra-thin rolling, deformation heat treatment, and surface control, this invention can stably produce ultra-thin oxygen-free copper strips with a thickness of 0.18–0.22 mm, low oxygen content, high conductivity, and high elongation.

[0028] The copper strip produced has low oxygen content, excellent conductivity and elongation, moderate tensile strength, and a microstructure exhibiting a high proportion of Σ3 n With its key lattice grain boundaries and fine, uniform grains, it boasts high surface quality and dimensional accuracy. Its comprehensive performance meets the stringent requirements for ultra-thin copper strips in high-end precision electronics, new energy devices, and other fields. The process is stable and controllable, enabling large-scale and stable production.

[0029] It should be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0030] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A micro-alloyed, high-elongation, ultrathin oxygen-free copper strip, characterized in that: The copper strip uses TU00, TU0 or TU1 high-purity oxygen-free copper as the matrix, and its chemical composition contains one or more grain boundary active elements. The grain boundary active elements are selected from one or more of Ag, Mg, Cr, Zr, Ti, B, P and rare earth elements. The total amount of the grain boundary active elements added is 5-40 ppm, and the amount of a single element added is ≤20 ppm. The copper strip has a thickness of 0.18-0.22 mm, an oxygen content of ≤3 ppm, a conductivity of ≥100% IACS at 20℃, and an elongation of ≥25%. In microstructure, Σ3 n The proportion of key lattice grain boundaries is ≥70%, and the average grain size is ≤20μm; The surface roughness Ra is 0.15-0.40μm, and the tensile strength is 270-360MPa.

2. The ultra-thin oxygen-free copper strip with high elongation and micro-alloying according to claim 1, characterized in that: The grain boundary active elements include at least two of Ag, Zr, Ti, and B.

3. The ultra-thin oxygen-free copper strip with high elongation and micro-alloying according to claim 1, characterized in that: The compositional fluctuation of the copper strip is ≤±5%, and the oxygen content is ≤2.5ppm. n The proportion of grain boundaries in the lattice is ≥75%.

4. The ultra-thin oxygen-free copper strip with high elongation and micro-alloying according to claim 1, characterized in that: The copper strip has an elongation of ≥28%, a conductivity of ≥102% IACS, and a hardness of 90-100HV.

5. The method for preparing an ultra-thin oxygen-free copper strip with high elongation by micro-alloying according to claim 1, characterized in that: S1: Ultra-micro alloying melting and purification Using TU00, TU0, or TU1 cathode copper as raw material, grain boundary active elements are added by means of intermediate alloy or high-purity metal ingots. Melting is carried out by bottom blowing technology with high-purity covering agent combined with N2+CO reducing mixed gas. The melting temperature is controlled at 1150-1250℃ and the refining time is ≥30min. The oxygen content of the melt is ≤3ppm and the hydrogen content is ≤0.5ppm. Electromagnetic stirring and gradient cooling technology are used to prepare large-size uniform ingots with composition fluctuation ≤±5%. S2: Hot-rolled and normalized The ingot is hot rolled at an initial rolling temperature of ≥850℃ and a final rolling temperature of ≥650℃, with a total hot rolling deformation of ≥80%; then it is normalized at a temperature of 550-650℃ for 10-20 minutes. S3: Grain boundary engineering control The process employs a multi-pass cold rolling process with decreasing deformation followed by a near-recrystallization temperature annealing cycle. Perform 3-5 cycles, each cycle containing a single pass of cold rolling, with the deformation amount of a single pass controlled at 20%-30%, and the deformation amount of the subsequent pass being less than that of the previous pass; After each cold rolling pass, continuous annealing is performed, with the annealing temperature controlled at 400-600℃ and the holding time at 5-15 minutes, to induce the formation of a high proportion of Σ3. n Multiple lattice grain boundaries; S4: Precision ultra-thin rolling The strip treated with grain boundary engineering is precision rolled using a high-rigidity rolling mill, with a final rolling thickness of 0.18-0.22 mm and a thickness tolerance controlled within ±0.003 mm. S5: Deformation Heat Treatment and Surface Control After rolling, the strip undergoes a coupled treatment of tension straightening and continuous tension annealing. The tension coefficient is 30%-50% of the yield strength, and the annealing temperature is 300-400℃ to eliminate residual stress. Finally, the strip is cleaned, dried, and subjected to anti-oxidation treatment to obtain the finished product.

6. The ultra-micro alloyed high-elongation ultrathin oxygen-free copper strip and its preparation method according to claim 5, characterized in that: In step S3, the multi-pass decreasing deformation cold rolling + near recrystallization temperature annealing cycle is performed 3 to 4 times. The first cold rolling deformation is 26% to 30%, and the annealing temperature is 480 to 520°C. The second cold rolling deformation is 23% to 26%, and the annealing temperature is 500 to 540°C. The third cold rolling deformation is 20% to 23%, and the annealing temperature is 520 to 560°C.

7. The ultra-micro alloyed high-elongation ultrathin oxygen-free copper strip and its preparation method according to claim 1, characterized in that: The master alloy used in step S1 is an Al-B, Cu-Mg, Cu-Zr, or Cu-Ti master alloy, and a gradient addition process is adopted, with the addition rate matched with the melting temperature.