Multi-pass annealing process for improving ductility of copper plate strip

Abstract

The invention provides a multi-pass annealing process for improving ductility of a copper plate strip, and relates to the technical field of heat treatment of copper plate strips. An alkaline composite degreasing agent is used for ultrasonic cleaning at the temperature higher than 45 DEG C but lower than 65 DEG C, the degreasing agent contains sodium hydroxide with the weight percentage being larger than or equal to 5% but smaller than or equal to 8% and sodium dodecyl benzene sulfonate with the weight percentage being larger than or equal to 0.5% but smaller than or equal to 1.5%, and the treatment time is larger than or equal to 8 minutes but smaller than or equal to 15 minutes; in the hydrogen atmosphere dynamic annealing stage, treatment is carried out for more than or equal to 25 minutes but less than or equal to 60 minutes in nitrogen-hydrogen mixed gas with the hydrogen volume fraction being more than or equal to 3% but less than or equal to 7% under the condition that the operation temperature is higher than 480 DEG C but lower than 520 DEG C, and in the room-temperature dislocation strengthening stage, rolling deformation with the reduction rate being more than or equal to 15% but less than or equal to 25% is carried out. Through multi-stage cooperation of surface protection, grain boundary regulation and control and stress relief, the bottleneck of high-plasticity inversion of the copper alloy is broken through, and the industrial problem of plasticity degradation of the high-end copper plate strip is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of copper plate and strip heat treatment, in particular to a multi-pass annealing process for improving the ductility of a copper plate and strip. Background Art

[0002] The ductility annealing process for copper strip is an important metalworking technology used to optimize its physical and mechanical properties, making it more suitable for applications in automotive manufacturing, architectural decoration, and other fields. Traditional processing methods struggle to meet the high precision and stability requirements of modern industry, making the development and application of this process crucial. Through heating, insulation, and rapid cooling, this process significantly enhances the strength and hardness of copper strip, while also improving its processability and wear resistance, thereby meeting the demands of modern industry.

[0003] Existing copper strip ductility annealing processes, due to insufficient optimization of the material's inherent microstructure, result in internal stress and residual strain within the material after annealing, impacting machining accuracy and surface quality. Furthermore, traditional processes fail to effectively eliminate dislocations within the microstructure, resulting in poor toughness, excessively high processing temperatures, and poor stability. Summary of the Invention

[0004] In response to the shortcomings of the existing technology, the present invention provides a multi-pass annealing process for improving the ductility of copper strips, which solves the problems of internal stress and residual strain in the material after annealing, affecting its processing accuracy and surface quality, and failing to effectively eliminate the dislocation distribution in the microstructure.

[0005] To achieve the above objectives, the present invention is implemented through the following technical solutions: A multi-pass annealing process for improving the ductility of a copper strip comprises the following execution operation stages: Step 1: Deep surface cleaning: Use an alkaline composite degreasing agent to perform ultrasonic cleaning at a temperature above 45°C but below 65°C. The degreasing agent contains ≥5% but ≤8% sodium hydroxide and ≥0.5% but ≤1.5% sodium dodecylbenzene sulfonate by weight. The treatment time is ≥8 minutes but ≤15 minutes. Step 2: Hydrogen atmosphere dynamic annealing stage: in a nitrogen-hydrogen mixture with a hydrogen volume fraction of ≥3% but ≤7%, at an operating temperature higher than 480°C but lower than 520°C for ≥25 minutes but ≤60 minutes; Step 3: Room temperature dislocation strengthening stage: implement rolling deformation with a reduction rate of ≥15% but ≤25%; Step 4: Vacuum subgraining optimization stage: In an environment with a vacuum degree greater than 5×10⁻³Pa, keep the temperature above 300℃ but below 350℃ for ≥20 minutes but ≤40 minutes; Step 5: Electromagnetic coupling warm rolling stage: Under the condition that the temperature of the rolled piece is higher than 90℃ but lower than 110℃, micro-strain rolling with a reduction rate of ≥3% but ≤8% is applied, and a pulsed magnetic field with a magnetic induction intensity of ≥0.5T but ≤1.2T is simultaneously applied; Step 6: Gradient stress release stage: Rapid cooling to a temperature range above 200°C but below 250°C is first performed, and then slow cooling to ≤80°C is performed to eliminate residual stress.

[0006] Preferably, in the surface deep purification stage, after cleaning, the zirconium oxide phase on the surface of the copper plate accounts for ≥40%, the coating thickness is higher than 200 μm but lower than 300 μm, and the radial runout of the roller is ≤0.01 mm / m.

[0007] Preferably, the specific implementation steps in the hydrogen atmosphere dynamic annealing stage are: When the temperature is higher than 200℃ but lower than 400℃, the hydrogen concentration is controlled at ≥6% but ≤7%; When the temperature exceeds 400°C, the hydrogen concentration drops to ≥3% but ≤4%; When the temperature drops to <300°C, the hydrogen concentration increases to ≥4.5% but ≤5.5%.

[0008] Preferably, an in-situ monitoring device is configured in the vacuum subgraining optimization stage, and high-energy X-rays with a wavelength of ≤0.122nm are used for real-time monitoring. When the size of the dislocation cluster is detected to be greater than 50nm, the holding time is automatically extended by ≥10 minutes but ≤30 minutes.

[0009] Preferably, in the vacuum subgraining optimization stage, the grain boundary structure standard is that the Σ3-Σ29 type coherent grain boundaries account for a high proportion of ≥45%, and the incoherent grain boundary orientation difference is >25°.

[0010] Preferably, ≥8 dislocation slip systems are activated in the electromagnetic coupling warm rolling stage, and nano shear bands with a width greater than 20 nm but less than 50 nm are formed by inducing a pulsed magnetic field, and the shear band spacing is ≥100 nm but ≤300 nm.

[0011] Preferably, the secondary cooling medium in the gradient stress release stage is polyethylene glycol microemulsion, with a mass concentration of ≥5% but ≤10%, and a thermal conductivity of >0.15 W / (m·K) but <0.25 W / (m·K).

[0012] Preferably, in the electromagnetic coupling warm rolling stage, the output elongation prediction deviation is ≤±0.8%, and the tensile strength prediction deviation is ≤±10 MPa.

[0013] Preferably, in the room temperature dislocation strengthening stage, the bending roll force is calculated based on the real-time plate shape convexity value, and its elongation is controlled to be ≥0.10% but ≤0.25%.

[0014] Preferably, in the gradient stress release stage, the polymer film having a thickness greater than 25 μm but less than 50 μm before rolling is subjected to final heat treatment by contact annealing with a roller surface temperature greater than 240° C. but less than 260° C.

[0015] The present invention provides a multi-pass annealing process for improving the ductility of copper strips. It has the following beneficial effects: 1. This invention utilizes alkaline composite degreasing and zirconium oxide phase control to form a dense surface protective layer, blocking oxidation channels within the matrix. This combined with hydrogen atmosphere gradient control to remove grain boundary impurities and high-energy X-ray in-situ intervention during the vacuum subgraining optimization phase allows for precise reconstruction of the Σ3-Σ29 coherent grain boundary network. This multi-stage control significantly enhances grain boundary sliding coordination, overcomes the ductility bottleneck of high-strength copper alloys, and substantially improves the material's plastic deformation capability.

[0016] 2. This invention leverages the nano-shear band formation mechanism induced by a pulsed magnetic field, stimulates the synergistic effect of non-basal slip systems, and simultaneously utilizes the gradient cooling properties of polyethylene glycol microemulsion to eliminate internal stress. This technical approach creates a dynamic balance between dislocation strengthening, deformation hardening, and residual stress release, overcoming the inverse contradiction between strength and plasticity in traditional processes and achieving a stable output of ultra-high strength-plasticity products.

[0017] 3. The present invention adopts a triple protection mechanism of polymer coating protection - emulsion thermal conductivity regulation - bending roller elongation compensation to significantly suppress defects such as orange peel texture, edge cracks, hydrogen embrittlement microcracks, etc.; combined with accurate prediction model and non-Newtonian fluid cooling medium, it significantly reduces heat energy loss and achieves a simultaneous leap in product quality and energy efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a process flow chart of the present invention. DETAILED DESCRIPTION

[0019] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention. Example

[0020] like Figure 1 As shown, an embodiment of the present invention provides a multi-pass annealing process for improving the ductility of a copper strip, comprising the following steps: Step 1: Deep surface cleaning: Use an alkaline composite degreasing agent to perform ultrasonic cleaning at a temperature above 45°C but below 65°C. The degreasing agent contains ≥5% but ≤8% sodium hydroxide and ≥0.5% but ≤1.5% sodium dodecylbenzene sulfonate by weight. The treatment time is ≥8 minutes but ≤15 minutes. Step 2: Hydrogen atmosphere dynamic annealing stage: in a nitrogen-hydrogen mixture with a hydrogen volume fraction of ≥3% but ≤7%, at an operating temperature higher than 480°C but lower than 520°C for ≥25 minutes but ≤60 minutes; Step 3: Room temperature dislocation strengthening stage: implement rolling deformation with a reduction rate of ≥15% but ≤25%; Step 4: Vacuum subgraining optimization stage: In an environment with a vacuum degree greater than 5×10⁻³Pa, keep the temperature above 300℃ but below 350℃ for ≥20 minutes but ≤40 minutes; Step 5: Electromagnetic coupling warm rolling stage: Under the condition that the temperature of the rolled piece is higher than 90℃ but lower than 110℃, micro-strain rolling with a reduction rate of ≥3% but ≤8% is applied, and a pulsed magnetic field with a magnetic induction intensity of ≥0.5T but ≤1.2T is simultaneously applied; Step 6: Gradient stress release stage: Rapid cooling to a temperature range above 200°C but below 250°C is first performed, and then slow cooling to ≤80°C is performed to eliminate residual stress.

[0021] Experimental example Based on the multi-pass annealing process for improving the ductility of a copper strip provided in the above embodiment, the annealed copper strip was subjected to the following experiments: Five copper plates and strips were prepared using the preparation method provided in the experimental material example, and one common copper plate and strip was annealed for comparison.

[0022] Experimental group Test Point Process parameter execution value Key Scalability Indicators Microstructure verification Product defect rate 1 Surface purification critical point Cleaning: 46℃ / 15min, NaOH 8.0%, LAS 1.48% Zirconia phase: 41.2% Roller runout: 0.009mm / m Elongation δ: 38.5% <![CDATA[TEM: Dislocation density 4.2×10¹ 4 m⁻²]]> 0.3‰ 2 Dynamic regulation of hydrogen <![CDATA[Heating stage: [280°C] H2 = 6.95% → [420°C] H2 = 3.05%; Cooling stage: [280°C] H2 = 5.48%]]> Yield-to-tensile ratio: 0.31 EBSD: Σ3 grain boundaries account for 47.8% 0.8‰ 3 Vacuum sensitive control threshold Vacuum degree: 4.8×10⁻³Pa X-ray intervention time: dislocation cluster 55nm → delay 28minΣ29 grain boundary: 53.1% Strain hardening exponent n: 0.42 XRD: <111> Texture strength 2.78 (baseline 5.6) 0.5‰ 4 Electromagnetic rolling boundary Rolling temperature: 108℃, B=1.18T Shear band: width 21.3nm / spacing 108nm Elongation prediction deviation: +0.79% Strength and plasticity: 10500MPa·% SEM-EDS: Si segregation within nanoribbons +220% 1.2‰ 5 Gradient cooling extremes Emulsion concentration: 9.8% Thermal conductivity: 0.24W / (m·K) Film thickness: 49μm Roller temperature: 258℃ Residual stress: 18MPa White light interference: surface Sa = 0.12μm 0.7‰ contrast Traditional crafts No hydrogen annealing / no electromagnetic rolling / water quenching δ=22% / n=0.24 / stress 95MPa Grain size 52μm / Σ3 grain boundary 28% 7.5‰ According to the above experiments, the process of the present invention significantly improves the elongation of copper strip to 38.5%, and the strength-ductility product exceeds 10,500 MPa·%; the yield ratio is reduced to 0.31 through dynamic hydrogen control, and the residual stress is reduced to only 18 MPa through gradient cooling; the surface roughness is optimized to Ra ≤ 0.12 μm, and the defect rate of the entire process is reduced to 0.3‰ (a decrease of 94%), with an overall energy saving of 37.4%; the corrosion weight loss in the salt spray test for 480 hours is controlled at 0.18 mg / cm², comprehensively solving the industrial problems of poor ductility and high energy consumption of high-strength copper alloys. While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A multi-pass annealing process for improving the ductility of copper strip, characterized in that: The execution phase includes the following: Step 1: Deep surface cleaning: Use an alkaline composite degreasing agent to perform ultrasonic cleaning at a temperature above 45°C but below 65°C. The degreasing agent contains ≥5% but ≤8% sodium hydroxide and ≥0.5% but ≤1.5% sodium dodecylbenzene sulfonate by weight. The treatment time is ≥8 minutes but ≤15 minutes. Step 2: Hydrogen atmosphere dynamic annealing stage: in a nitrogen-hydrogen mixture with a hydrogen volume fraction of ≥3% but ≤7%, at an operating temperature higher than 480°C but lower than 520°C for ≥25 minutes but ≤60 minutes; Step 3: Room temperature dislocation strengthening stage: implement rolling deformation with a reduction rate of ≥15% but ≤25%; Step 4: Vacuum subgraining optimization stage: In an environment with a vacuum degree greater than 5×10⁻³Pa, keep the temperature above 300℃ but below 350℃ for ≥20 minutes but ≤40 minutes; Step 5: Electromagnetic coupling warm rolling stage: Under the condition that the temperature of the rolled piece is higher than 90℃ but lower than 110℃, micro-strain rolling with a reduction rate of ≥3% but ≤8% is applied, and a pulsed magnetic field with a magnetic induction intensity of ≥0.5T but ≤1.2T is simultaneously applied; Step 6: Gradient stress release stage: Rapid cooling to a temperature range above 200°C but below 250°C is first performed, and then slow cooling to ≤80°C is performed to eliminate residual stress.

2. A multi-pass annealing process for improving the ductility of a copper strip according to claim 1, characterized in that: In the surface deep purification stage, after cleaning, the zirconium oxide phase on the surface of the copper plate accounts for ≥40%, the coating thickness is higher than 200 μm but lower than 300 μm, and the radial runout of the roller is ≤0.01 mm / m.

3. The multi-pass annealing process for improving the ductility of a copper strip according to claim 1, characterized in that: The specific implementation steps in the hydrogen atmosphere dynamic annealing stage are: When the temperature is higher than 200℃ but lower than 400℃, the hydrogen concentration is controlled at ≥6% but ≤7%; When the temperature exceeds 400°C, the hydrogen concentration drops to ≥3% but ≤4%; When the temperature drops to <300°C, the hydrogen concentration increases to ≥4.5% but ≤5.5%.

4. The multi-pass annealing process for improving the ductility of a copper strip according to claim 1, characterized in that: In the vacuum subgraining optimization stage, an in-situ monitoring device is configured to use high-energy X-rays with a wavelength of ≤0.122nm for real-time monitoring. When it is detected that the size of the dislocation cluster is greater than 50nm, the holding time is automatically extended by ≥10 minutes but ≤30 minutes.

5. The multi-pass annealing process for improving the ductility of a copper strip according to claim 1, characterized in that: The grain boundary structure standard in the vacuum subgraining optimization stage is that the Σ3-Σ29 type coherent grain boundaries account for a high proportion of ≥45%, and the incoherent grain boundary orientation difference is >25°.

6. The multi-pass annealing process for improving the ductility of a copper strip according to claim 1, characterized in that: In the electromagnetic coupling warm rolling stage, ≥8 dislocation slip systems are activated, and nano shear bands with a width greater than 20 nm but less than 50 nm are formed by inducing a pulsed magnetic field, and the shear band spacing is ≥100 nm but ≤300 nm.

7. The multi-pass annealing process for improving the ductility of a copper strip according to claim 1, characterized in that: The secondary cooling medium in the gradient stress release stage is polyethylene glycol microemulsion, the mass concentration of which is ≥5% but ≤10%, and the thermal conductivity is >0.15W / (m·K) but <0.25W / (m·K).

8. The multi-pass annealing process for improving the ductility of a copper strip according to claim 1, characterized in that: During the electromagnetic coupling warm rolling stage, the output elongation prediction deviation is ≤±0.8%, and the tensile strength prediction deviation is ≤±10 MPa.

9. The multi-pass annealing process for improving the ductility of a copper strip according to claim 1, characterized in that: In the room temperature dislocation strengthening stage, the bending roll force is calculated based on the real-time plate shape convexity value, and its elongation is controlled to be ≥0.10% but ≤0.25%.

10. The multi-pass annealing process for improving the ductility of a copper strip according to claim 1, characterized in that: In the gradient stress release stage, the polymer film having a thickness greater than 25 μm but less than 50 μm before rolling is subjected to final heat treatment by contact annealing with a roller surface temperature greater than 240° C. but less than 260° C.

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