Launder online degassing method for battery aluminum foil blank preparation

Abstract

The invention provides a launder online degassing method for battery aluminum foil blank preparation, which comprises the following steps: S1, melting an aluminum ingot at 650-700 DEG C, adding a Y2O3, Er2O3 and Sc2O3 composite alterant, and controlling the Fe / Si ratio in the aluminum ingot to be 1.0-1.05; s2, refining is conducted, and meanwhile electromagnetic stirring is applied; s3, the refined molten aluminum is guided into a launder and flows at the flow speed of 0.3-0.5 m / s, vacuum air exhaust is conducted in the launder, the air exhaust frequency is 1-3 times / s, and the temperature gradient delta T between an inlet and an outlet of the launder is controlled to range from 20 DEG C to 30 DEG C; s4, cast rolling is conducted on the degassed molten aluminum, and the cooling strength is larger than or equal to 1500 L / min; s5, the cast-rolled blank is subjected to cold rolling with the total reduction rate being 75-85%, the single-pass reduction rate is smaller than or equal to 6%, and intermediate annealing is conducted; and S6, the cold-rolled aluminum foil blank is subjected to segmented annealing, the annealing temperature is 450 + / -3 DEG C, the heat preservation time is 2.5 h, the mechanical property of the aluminum foil is remarkably improved, the surface quality is improved, and the production energy consumption is reduced.

Description

Technical Field

[0001] This invention relates to an online degassing method for preparing aluminum foil blanks for batteries. Background Technology

[0002] With the rapid development of new energy vehicles and smart devices, lithium-ion batteries, as core energy storage components, face increasingly stringent requirements for energy density and safety. Aluminum foil, as a key current collector material in lithium-ion batteries, directly impacts the overall performance of the battery. Currently, power battery aluminum foil primarily uses 1060 alloy as raw material and is manufactured through complex processes such as casting and rolling, multi-pass cold rolling, homogenization annealing, and foil rolling. This technological field faces the dual challenges of improving aluminum foil performance and reducing production energy consumption.

[0003] Existing aluminum foil manufacturing processes suffer from the following main problems: First, traditional processes are energy-intensive and inefficient, with multi-pass cold rolling and annealing leading to high production costs. Second, when the aluminum foil thickness is reduced to below 15μm, mechanical properties tend to degrade, manifesting as a significant decrease in tensile strength and elongation. This is primarily due to internal porosity defects and uneven grain size caused by incomplete aluminum molten metal purification. Third, current technologies often employ in-furnace refining for aluminum molten metal degassing, which has limited degassing effectiveness and makes it difficult to precisely control the melt temperature gradient, resulting in poor microstructure uniformity during subsequent casting and rolling. Furthermore, traditional processes lack precise control over the aluminum molten metal composition; in particular, an imbalance in the Fe / Si ratio severely affects the mechanical properties and surface quality of the aluminum foil. Although the industry has attempted improvements by optimizing rolling process parameters or adding alloying elements, none of these methods have fundamentally solved the performance degradation problem of aluminum foil under ultra-thin conditions.

[0004] Therefore, there is a need for an online degassing method for preparing aluminum foil blanks for batteries to improve the mechanical properties of aluminum foil, enhance surface quality, and reduce production energy consumption. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide an online degassing method for preparing battery aluminum foil blanks that can significantly improve the mechanical properties of aluminum foil, improve surface quality, and reduce production energy consumption. This purpose is achieved as follows:

[0006] This invention proposes an online degassing method for preparing battery aluminum foil blanks using a flow channel, characterized by comprising:

[0007] S1. Melt the aluminum ingot at 650-700℃, add 0.02~0.05wt% of a composite modifier of Y2O3, Er2O3, and Sc2O3, wherein the mass ratio of Er2O3 to Sc2O3 is 1:0.5, and control the Fe / Si ratio in the aluminum ingot to be 1.0~1.05. This stage is the foundation of the entire preparation process, and its purpose is to ensure precise control of the aluminum melt composition and optimization of the microstructure. By adding a specific proportion of composite modifier, the grains can be effectively refined and modified. Improving the mechanical properties of aluminum foil; and precisely controlling the Fe / Si ratio helps to improve the surface quality and processing performance of aluminum foil; the principle of this process is that the rare earth oxides in the composite modifier, Y2O3, Er2O3, and Sc2O3, form heterogeneous nucleation cores in the aluminum melt, promoting grain refinement; at the same time, these elements can also form stable compounds with impurity elements in the aluminum melt, purifying the melt, and precisely controlling the Fe / Si ratio can avoid the adverse effects of Fe and Si elements existing alone on the performance of aluminum foil.

[0008] S2. Refining is carried out at 730~750℃ by introducing argon gas with a purity ≥99.999%, while applying electromagnetic stirring at an intensity of 60~80% and a frequency of 2.5~3.0Hz for 4~5 hours. This stage aims to further purify the molten aluminum, removing gaseous and non-metallic inclusions. Electromagnetic stirring promotes homogenization of the melt composition and avoids local segregation. The principle is that high-purity argon gas forms bubbles in the molten aluminum, which carry away hydrogen and inclusions in the melt through physical adsorption. The Lorentz force generated by electromagnetic stirring drives the melt flow, promoting homogenization of composition and temperature.

[0009] S3. The refined molten aluminum is introduced into a flow channel with a length of 8-12m and a width of 35-45mm, flowing at a velocity of 0.3-0.5m / s. Vacuum evacuation is performed in the flow channel at a frequency of 1-3 times / second, and the temperature gradient ΔT between the inlet and outlet of the flow channel is controlled to be 20-30℃. The purpose is to achieve efficient purification of molten aluminum through online degassing technology in the flow channel. Controlling the temperature gradient helps to optimize the solidification behavior of molten aluminum and improve the subsequent casting and rolling quality. The principle is that when molten aluminum flows in the flow channel, vacuum evacuation creates a low-pressure zone on the surface of the molten aluminum, promoting the precipitation of dissolved gases. The control of the temperature gradient can adjust the supercooling of the molten aluminum, affecting the formation and growth of crystal nuclei.

[0010] S4. The degassed aluminum liquid is cast and rolled at a rolling speed of 0.4~0.6m / min, with a cooling intensity ≥1500L / min. In this stage, the liquid aluminum is directly converted into a solid strip, the purpose of which is to obtain a cast and rolled billet with uniform structure and good surface quality. Rapid solidification can refine the grains and improve the mechanical properties of the material. Controlling the cooling intensity can adjust the solidification rate and affect the microstructure.

[0011] S5. The cast-rolled billet is cold-rolled with a total reduction of 75-85%, and the single-pass reduction is ≤6%. Intermediate annealing is carried out at 440-460℃. Intermediate annealing can eliminate work hardening and restore the plasticity of the material. Cold rolling improves the strength of the material through dislocation multiplication and grain deformation. Intermediate annealing forms new strain-free grains through recrystallization and restores the plastic deformation capacity of the material.

[0012] S6. The cold-rolled aluminum foil blank is subjected to segmented annealing at a temperature of 450℃±3℃ and a holding time of 2.5h. This stage aims to achieve the required thickness and properties of the material through plastic deformation. This stage aims to obtain a stable microstructure and optimized mechanical properties. Segmented annealing can precisely control the recrystallization process and grain growth behavior. During annealing, processes such as recovery, recrystallization, and grain growth occur, which are affected by temperature and time and ultimately determine the properties of the material.

[0013] Furthermore, the amount of the composite modifier added in S1 is 0.03wt%Y2O3, 0.01wt%Er2O3 and 0.005wt%Sc2O3.

[0014] Furthermore, the electromagnetic stirring intensity in S2 is 70%, the frequency is 2.8 Hz, and the refining time is 4.5 h.

[0015] Furthermore, the length of the flow channel described in S3 is 10m, the width is 40mm, the vacuum pumping frequency is 2 times / second, the inlet temperature of the flow channel is 710℃, the outlet temperature is 685℃, and the temperature gradient ΔT is 25℃.

[0016] Furthermore, the absolute pressure of the vacuum pumping described in S3 is 50 Pa.

[0017] Furthermore, the rolling speed of the casting and rolling process described in S4 is 0.5 m / min, and the roll pressure is 120 MPa.

[0018] Furthermore, the total reduction rate of cold rolling described in S5 is 80%, and it is divided into 3 rolling passes, with a reduction rate of 6% per pass.

[0019] Furthermore, the segmented annealing described in S6 specifically includes: a first stage of holding at 250°C for 0.5 hours, a second stage of holding at 450°C for 1.5 hours, and a third stage of holding at 250°C for 0.5 hours.

[0020] Furthermore, it also includes S7: electrolytically cleaning the annealed aluminum foil blank with a 50 g / L NaOH solution at a temperature of 40 °C; then coating the aluminum foil surface with a 0.5 μm thick polyethylene glycol film.

[0021] Furthermore, the aluminum foil blank has a hydrogen content ≤0.08mL / 100gAl, a tensile strength ≥150MPa at a thickness of 12μm, an elongation ≥4.0%, and a grain size deviation <5μm.

[0022] Compared with existing technologies, the beneficial effects of this invention are as follows: Through optimized composite modifier formulation, online degassing technology in the flow channel, and precise temperature gradient control, the mechanical properties of aluminum foil are significantly improved, especially the tensile strength and elongation of ultra-thin aluminum foil; through precise control of melt composition and degassing process, porosity defects in aluminum foil are greatly reduced, improving the surface quality and consistency of the product; through optimized process flow, the number of cold rolling passes and annealing times is reduced, significantly lowering production energy consumption; the application of online degassing technology in the flow channel shortens the production cycle and improves production efficiency; the optimized use of composite modifiers, while ensuring performance, reduces the amount of rare earth elements added, saving production costs. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of an online degassing method for preparing aluminum foil blanks for batteries. Detailed Implementation

[0024] To enhance understanding of the present invention, the present invention will be further described in detail below with reference to embodiments and accompanying drawings. These embodiments are only used to explain the present invention and do not constitute a limitation on the scope of protection of the present invention.

[0025] Please refer to Figure 1 The present invention provides an online degassing method for preparing battery aluminum foil blanks using a flow channel, characterized by comprising:

[0026] S1. Melt aluminum ingots at 650-700℃, add 0.02~0.05wt% of Y2O3, Er2O3 and Sc2O3 composite modifier, wherein the mass ratio of Er2O3 to Sc2O3 is 1:0.5, and control the Fe / Si ratio in the aluminum ingots to be 1.0~1.05.

[0027] As an example, 99.99% pure aluminum ingots were added to a resistance melting furnace and melted at 650°C for 1.5 hours, then the temperature was raised to 700°C. A composite modifier consisting of 0.03 wt% Y₂O₃, 0.01 wt% Er₂O₃, and 0.005 wt% Sc₂O₃ was added, with the mass ratio of Er₂O₃ to Sc₂O₃ controlled at 1:0.5. The melt composition was monitored in real time using an ICP-OES spectrometer, and the Fe / Si ratio was precisely adjusted to 1.03 ± 0.01.

[0028] Understandably, the addition of the composite modifier is accomplished through an automatic feeding system, with feeding accuracy controlled within ±0.001wt%. During the smelting process, K-type thermocouples are used to monitor the melt temperature at multiple points to ensure that the temperature uniformity deviation within the furnace does not exceed ±5℃.

[0029] S2. Refine the product by introducing argon gas with a purity of ≥99.999% at 730~750℃, while applying electromagnetic stirring at an intensity of 60~80% and a frequency of 2.5~3.0Hz for 4~5 hours.

[0030] As an example, the refining stage is carried out at 730℃, specifically including the following operations: argon gas with a purity ≥99.999% is introduced into the melt at a flow rate of 25L / min for 30 minutes; simultaneously, an electromagnetic stirring device is started with a stirring intensity of 70% and a frequency of 2.8Hz for 4.5 hours; the melt temperature is monitored in real time by eight thermocouples installed on the four walls of the furnace to ensure that the temperature difference does not exceed 3℃, and the electromagnetic stirring device is controlled by frequency conversion.

[0031] Understandably, refining can be achieved through various methods such as rotary jetting and fixed jetting, while electromagnetic stirring can be achieved through a frequency-controlled electromagnetic stirring device, whose stirring intensity and frequency can be precisely adjusted as needed.

[0032] S3. The refined aluminum liquid is introduced into a flow channel with a length of 8~12m and a width of 35~45mm, and flows at a flow rate of 0.3~0.5m / s. Vacuum is pumped in the flow channel at a frequency of 1~3 times / second, and the temperature gradient ΔT between the inlet and outlet of the flow channel is controlled to be 20~30℃.

[0033] The exemplary flow channel is 10m long, 40mm wide, and 150mm deep, with a graphite lining and an external ceramic fiber insulation layer. Twelve vacuum vents and 15 temperature sensors are evenly arranged along its length. During degassing, the flow rate of the molten aluminum is controlled at 0.4m / s, which is precisely adjusted by a frequency converter pump. The vacuum venting frequency is 2 times / second, and the absolute pressure is maintained at 50Pa. The inlet temperature is 710℃, the outlet temperature is 685℃, and the temperature gradient ΔT = 25℃.

[0034] Understandably, vacuum pumping can be achieved through a multi-stage vacuum pump system, with precise control over pumping frequency and pressure, and temperature gradients can be achieved through multiple heating or cooling zones arranged along the flow channel.

[0035] S4. Cast the degassed aluminum liquid at a rolling speed of 0.4~0.6m / min, with a cooling intensity ≥1500L / min;

[0036] As an example, the rolling speed of this casting and rolling process is 0.5 m / min, precisely controlled by a servo motor; the pressure is 120 MPa, with closed-loop regulation using a hydraulic system; the cooling intensity is 1500 L / min, and the cooling water temperature is maintained at 20 ± 1℃; the length of the casting and rolling zone is 60 mm, and the casting and rolling angle is 3°; the cooling system adopts a multi-channel design, and the flow rate of each channel can be independently adjusted to ensure that the transverse temperature uniformity deviation of the cast and rolled strip does not exceed 2℃.

[0037] Understandably, casting and rolling can be achieved using equipment such as twin-roll casting mills and single-roll casting mills. The cooling system can employ a multi-channel design to ensure uniform cooling.

[0038] S5. The cast-rolled billet is cold-rolled with a total reduction of 75-85%, with a single-pass reduction of ≤6%, and then annealed at 440-460℃.

[0039] As an example, the rolling process consists of 3 passes, with a single pass reduction of 6% and a total reduction of 80%. During intermediate annealing, the plate is held at 450°C for 30 minutes. After each pass, the plate thickness is monitored online using a laser thickness gauge with a measurement accuracy of ±0.1μm. The rolling force is controlled within the range of 800-1000kN and is automatically adjusted by the mill's AGC system.

[0040] Understandably, cold rolling can be achieved using a multi-roll mill, allowing for precise control of the reduction rate per pass. Intermediate annealing can be performed in a continuous annealing furnace or a box annealing furnace.

[0041] S6. Perform segmented annealing on the cold-rolled aluminum foil blank. The annealing temperature is 450℃±3℃ and the holding time is 2.5h.

[0042] As an example, a three-stage annealing process is adopted. The first stage is held at 250℃ for 0.5 hours, the second stage is held at 450℃ for 1.5 hours with a temperature control accuracy of ±3℃, and the third stage is held at 250℃ for 0.5 hours. The annealing furnace adopts a forced convection heating method, the atmosphere inside the furnace is protected by nitrogen, the oxygen content is controlled below 50ppm, and thermocouples are evenly arranged in 9 positions in the furnace to ensure temperature uniformity.

[0043] Understandably, annealing can be carried out in a protective atmosphere annealing furnace, where temperature and time can be precisely controlled, and segmented annealing can be achieved through a multi-temperature zone continuous annealing furnace.

[0044] In another embodiment, the amount of composite modifier added in S1 is 0.03wt% Y2O3, 0.01wt% Er2O3, and 0.005wt% Sc2O3; the intensity of electromagnetic stirring in S2 is 70%, the frequency is 2.8Hz, and the refining time is 4.5h; the length of the flow channel in S3 is 10m, the width is 40mm, the vacuum pumping frequency is 2 times / second, the inlet temperature of the flow channel is 710℃, the outlet temperature is 685℃, and the temperature gradient ΔT is 25℃; the absolute pressure of vacuum pumping in S3 is 50Pa; the rolling speed of casting and rolling in S4 is 0.5m / min, and the roll pressure is 120MPa; the total reduction rate of cold rolling in S5 is 8... The aluminum foil is rolled in three passes, with a reduction rate of 6% per pass. The segmented annealing in S6 includes: the first stage is held at 250℃ for 0.5h, the second stage is held at 450℃ for 1.5h, and the third stage is held at 250℃ for 0.5h. It also includes the S7 surface treatment stage, which involves electrolytic cleaning of the annealed aluminum foil blank with a 50g / L NaOH solution at 40℃. Then, a 0.5μm thick polyethylene glycol film is coated on the aluminum foil surface. The hydrogen content of the aluminum foil blank is ≤0.08mL / 100gAl, the tensile strength is ≥150MPa when the thickness is 12μm, the elongation is ≥4.0%, and the grain size deviation is <5μm.

[0045] The following describes the overall workflow of this embodiment, taking the preparation of a 12μm thick battery aluminum foil blank as an example: 1000kg of 99.99% pure aluminum ingot is added to a melting furnace and heated to 650℃ to begin melting; 300g of Y2O3, 100g of Er2O3 and 50g of Sc2O3 are added to adjust the Fe / Si ratio to 1.03; argon gas is introduced at 730℃ for 30 minutes for refining, while electromagnetic stirring is performed for 4.5 hours; the aluminum liquid flows through a 10m long flow channel at a flow rate of 0.4m / s and is degassed under a vacuum of 50Pa; it is cast and rolled into a 6mm thick strip at a speed of 0.5m / min; after three passes of cold rolling with a total reduction of 80%, a 1.2mm thick intermediate blank is obtained; a three-stage annealing process is performed for a total time of 2.5 hours; after electrolytic cleaning, a 0.5μm polyethylene glycol protective film is coated.

[0046] The 12μm thick battery aluminum foil blank prepared in this embodiment has the following properties after testing: hydrogen content 0.048mL / 100gAl, a decrease of 6.7%; tensile strength 155MPa, an increase of 2.4%; elongation 4.2%, an increase of 5.0%; grain size uniformity deviation <3μm; surface roughness Ra0.12μm.

[0047] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for online degassing in a flow channel for preparing battery aluminum foil blanks, characterized in that, include: S1. Melt aluminum ingots at 650-700℃, add 0.02~0.05wt% of Y2O3, Er2O3 and Sc2O3 composite modifier, wherein the mass ratio of Er2O3 to Sc2O3 is 1:0.5, and control the Fe / Si ratio in the aluminum ingots to be 1.0~1.05; S2. Refine the product by introducing argon gas with a purity of ≥99.999% at 730~750℃, while applying electromagnetic stirring at an intensity of 60~80% and a frequency of 2.5~3.0Hz for 4~5 hours. S3. The refined aluminum liquid is introduced into a flow channel with a length of 8~12m and a width of 35~45mm, and flows at a flow rate of 0.3~0.5m / s. Vacuum is pumped in the flow channel at a frequency of 1~3 times / second, and the temperature gradient ΔT between the inlet and outlet of the flow channel is controlled to be 20~30℃. S4. The degassed aluminum liquid is cast and rolled at a rolling speed of 0.4~0.6m / min, with a cooling intensity ≥1500L / min; S5. The cast-rolled billet is cold-rolled with a total reduction of 75-85%, with a single-pass reduction of ≤6%, and then annealed at 440-460℃. S6. Perform segmented annealing on the cold-rolled aluminum foil blank. The annealing temperature is 450℃±3℃ and the holding time is 2.5h.

2. The online degassing method for preparing battery aluminum foil blanks according to claim 1, characterized in that, The amount of the composite modifier added in S1 is 0.03wt%Y2O3, 0.01wt%Er2O3 and 0.005wt%Sc2O3.

3. The online degassing method for preparing battery aluminum foil blanks according to claim 2, characterized in that, The electromagnetic stirring intensity described in S2 is 70%, the frequency is 2.8Hz, and the refining time is 4.5h.

4. The online degassing method for preparing battery aluminum foil blanks according to claim 3, characterized in that, The flow channel described in S3 has a length of 10m, a width of 40mm, a vacuum pumping frequency of 2 times / second, an inlet temperature of 710℃, an outlet temperature of 685℃, and a temperature gradient ΔT of 25℃.

5. The online degassing method for preparing battery aluminum foil blanks according to claim 4, characterized in that, The absolute pressure of the vacuum pumping described in S3 is 50 Pa.

6. The online degassing method for preparing battery aluminum foil blanks according to claim 5, characterized in that, The rolling speed of the casting and rolling process described in S4 is 0.5 m / min, and the roll pressure is 120 MPa.

7. The online degassing method for preparing battery aluminum foil blanks according to claim 6, characterized in that, The total reduction rate of cold rolling described in S5 is 80%, and it is divided into 3 rolling passes, with a reduction rate of 6% per pass.

8. The online degassing method for preparing battery aluminum foil blanks according to claim 7, characterized in that, The segmented annealing described in S6 specifically includes: a first stage of holding at 250℃ for 0.5h, a second stage of holding at 450℃ for 1.5h, and a third stage of holding at 250℃ for 0.5h.

9. The online degassing method for preparing battery aluminum foil blanks according to claim 1, characterized in that, It also includes S7: electrolytically cleaning the annealed aluminum foil blank with a 50g / L NaOH solution at a temperature of 40℃; then coating the aluminum foil surface with a 0.5μm thick polyethylene glycol film.

10. The online degassing method for preparing battery aluminum foil blanks according to claim 1, characterized in that, The aluminum foil blank has a hydrogen content ≤0.08mL / 100gAl, a tensile strength ≥150MPa at a thickness of 12μm, an elongation ≥4.0%, and a grain size deviation <5μm.

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