A high-strength aluminum alloy foil for heating element and preparation method thereof

Abstract

A high-strength aluminum alloy foil for heating elements and a preparation method thereof, the purpose of which is to solve the problems of insufficient resistivity and strength of existing aluminum alloy foils. The high-strength aluminum alloy foil for heating elements has the following components by mass percentage: Mn: 2‑2.2%, Ti: 0.5‑1%, V: 0.3‑0.5%, Fe: 0.1‑0.2%, Si: 2‑3%, Li: 0.7‑1.0%, Sr: 0.02‑0.6%, Zr≤0.2%, other impurity elements≤0.2%, and the remaining elements are Al. Mn, Ti, V, and Li have a great influence on the resistivity of aluminum alloys, and can make the resistivity of aluminum alloy foil reach 10‑15μΩ.cm, which meets the use requirements of metal wires for resistance heating elements for resistivity. Due to the addition of elements such as Mn, Ti, V, Li, and Fe, the yield strength of the aluminum alloy foil is improved, which meets the use requirements of metal wires for resistance heating elements for yield strength. The preparation method includes casting, cold rolling, annealing and foil rolling, which can effectively reduce the precipitation of solid solution elements, eliminate defects such as inclusions and pores in the melt, and reduce the pinhole rate.

Description

Technical Field

[0001] The invention relates to the technical field of aluminum alloy foils, and in particular to a high-strength aluminum alloy foil for a heating element and a preparation method thereof. Background Art

[0002] Power batteries are the core components of new energy vehicles and directly affect the performance of vehicles. Temperature is an important factor affecting the working ability of lithium batteries. The most suitable working temperature of batteries is between 15-40℃. The working principle of lithium batteries is essentially the process of Li+ ions moving back and forth between liquid electrolytes and deintercalating and intercalating inside positive and negative electrode materials. At low temperatures, the rate of lithium intercalation reaction of active substances on the electrode surface slows down and the concentration of lithium ions inside the active substances decreases, which will cause the battery equilibrium potential to decrease, the internal resistance to increase, and the discharge capacity to decrease. In extremely low temperature conditions, the electrolyte may even freeze and the battery may not be able to discharge. This greatly affects the low temperature performance of the battery system, causing the power output performance of electric vehicles to decay and the range to decrease. In extremely cold conditions, it may even threaten the safety of battery use. To solve this problem, existing new energy vehicles use battery temperature control technology to maintain the battery temperature within the optimal operating temperature range. The commonly used technical means at present is to install a temperature control device in the battery pack. The temperature control device is mainly composed of a heating element and a circuit, among which the heating element is the most important part. Common heating elements include variable resistance heating elements and constant resistance heating elements, the latter of which is usually a heating film made of metal heating wire.

[0003] Currently, the commonly used metal heating wire is steel foil, but steel foil needs to be processed into a heating element by chemical etching, which has a long processing flow and is highly polluting. In addition, due to its high hardness, it is not suitable for mechanical processing. If aluminum foil is used instead of steel foil, physical cutting can be used, which has high production efficiency and is pollution-free. However, the electrical conductivity of conventional aluminum alloy foil is currently 25-35MS / m, which is far from the electrical conductivity of the foil required for metal wires used in resistance heating elements. Moreover, the strength of aluminum alloy foil is low and it is easy to tear, which cannot meet the use requirements of metal wires used in resistance heating elements. Therefore, it is necessary to invent an aluminum alloy foil that is easy to process, has high strength, and has high resistivity to replace steel foil. Summary of the invention

[0004] In order to overcome the deficiencies in the background technology, the present invention discloses a high-strength aluminum alloy foil for a heating element and a preparation method thereof, the purpose of which is to solve the problems of insufficient resistivity and strength of the existing aluminum alloy foil.

[0005] In order to achieve the above-mentioned invention object, the present invention adopts the following technical scheme:

[0006] A high-strength aluminum alloy foil for a heating element, wherein the components of the aluminum alloy foil are, by mass percentage, respectively: Mn: 2-2.2%, Ti: 0.5-1%, V: 0.3-0.5%, Fe: 0.1-0.2%, Si: 2-3%, Li: 0.7-1.0%, Sr: 0.02-0.6%, Zr≤0.2%, other impurity elements≤0.2%, and the remaining element is Al.

[0007] To further improve the technical solution, the resistivity of the aluminum alloy foil is 10-15 μΩ.cm at 20°C.

[0008] To further improve the technical solution, the aluminum alloy foil has a yield strength of 150-200 MPa and an elongation of 14-18%.

[0009] After implementing the above technical solution, the beneficial effects are:

[0010] 1. The four elements of Mn, Ti, V and Li have a great influence on the resistivity of aluminum alloy. Adding these four elements to aluminum alloy can significantly improve the resistivity of aluminum alloy. Moreover, the higher the solid solubility of these four elements in the matrix, the greater the effect on improving the resistivity of aluminum alloy.

[0011] 2. Due to the addition of four elements, Mn, Ti, V and Li, the resistivity of aluminum alloy foil reaches 10-15μΩ.cm, which meets the resistivity requirements of metal wires used in resistance heating elements.

[0012] 3. Due to the addition of elements such as Mn, Ti, V, Li, and Fe, the yield strength of the aluminum alloy foil is improved, meeting the yield strength requirements of the metal wire used in resistance heating elements.

[0013] A method for preparing a high-strength aluminum alloy foil for a heating element comprises the following steps:

[0014] S1: Casting

[0015] S1.1: Put more than 99.5% industrial pure aluminum, Al-Mn master alloy, Al-Ti master alloy, Al-V master alloy, Al-Li master alloy, Al-Si master alloy, Al-Sr master alloy, pure Zr and iron agent into a melting furnace crucible for heating and melting, and then degas and refine in the melting furnace;

[0016] S1.2: After the ingredients are qualified, pour them into the holding furnace and keep warm and refine and degas at a temperature of 730-740℃;

[0017] S1.3: Casting and rolling, the casting and rolling temperature is 750-790℃, the casting and rolling speed is 600-750mm / h, the cooling water temperature is 30-40℃, and the thickness of the cast and rolled plate is 7-9mm;

[0018] S2: Cold rolled

[0019] After multiple rolling passes, the cast plate is rolled into a plate with a thickness of 0.1-0.3 mm;

[0020] S3: Annealing

[0021] Annealing temperature is 120-240℃, heating rate is 50-100℃ / h, and heat preservation is 10-20h;

[0022] S4: Foil rolling

[0023] After multiple rolling passes, the plate is rolled into 0.04-0.06mm aluminum alloy foil.

[0024] To further improve the technical solution, in S1.1, degassing and refining are performed twice in the smelting furnace, and the degassing and refining temperature is 740-750°C.

[0025] To further improve the technical solution, in S1.2, refining and degassing are performed every 4 hours.

[0026] To further improve the technical solution, in S2, the cast-rolled plate is rolled 3-4 times, and the deformation of a single time does not exceed 30% of the total deformation.

[0027] To further improve the technical solution, in S4, the plate is rolled 3-5 times, and the reduction rate of a single time is not less than 40%.

[0028] To further improve the technical solution, during the foil rolling process, the front tension is 30-65MPa, the rear tension is 50-75MPa, and the rolling speed is 300-500m / min.

[0029] After implementing the above preparation method, the beneficial effects produced are:

[0030] 1. During the casting process, the main purpose of adding Si is to improve the fluidity of the alloy and reduce casting defects; Ti is not added as a refiner, but as an alloying element in the melting process. Its main purpose is to reduce the precipitation of Ti to form Al3Ti second phase. On the one hand, it can reduce the refinement effect of Ti, and on the other hand, it can increase the solid solubility of Ti, thereby increasing the resistivity of the alloy; the main purpose of adding Sr is to metamorphose the precipitated Al-Si phase, thereby achieving a refinement effect and reducing the influence of Al-Si phase on the uniformity of foil structure.

[0031] 2. Perform refining and degassing twice in the melting furnace, and degassing again after transferring to the holding furnace. If the holding time is too long, refining is required every 4 hours. This can pre-eliminate defects such as inclusions and pores in the melt and reduce the pinhole degree of the aluminum foil product.

[0032] 3. If the deformation of a single cold rolling pass is too large, it will lead to aggravated work hardening, and the solid solution elements will easily precipitate, resulting in a decrease in the resistivity of the finished foil. If the deformation of a single pass does not exceed 30% of the total deformation, the precipitation of solid solution elements can be effectively reduced.

[0033] 4. If the annealing time is too long and the temperature is too high, the effective elements will precipitate, reducing the solid solubility of the effective elements, and ultimately leading to a decrease in the resistivity of the finished foil. Therefore, it is necessary to control the annealing temperature and total duration. If the annealing temperature is controlled at 120-240℃, the product can only soften and reduce the precipitation of the second phase. DETAILED DESCRIPTION

[0034] Those skilled in the art should understand that these embodiments are only used to explain the technical principles of the present invention and are not intended to limit the protection scope of the present invention. Embodiment 1:

[0035] A high-strength aluminum alloy foil for a heating element, wherein the components of the aluminum alloy foil are, by mass percentage, 2.1% Mn, 0.7% Ti, 0.3% V, 0.1% Fe, 2.5% Si, 0.9% Li, 0.02% Sr, 0.1% Zr, and other impurity elements ≤ 0.2%, and the remaining element is Al.

[0036] A method for preparing a high-strength aluminum alloy foil for a heating element is used to prepare the above-mentioned aluminum alloy foil. The preparation method comprises the following steps:

[0037] S1: Casting

[0038] S1.1: 99.5% industrial pure aluminum, Al-Mn master alloy, Al-Ti master alloy, Al-V master alloy, Al-Li master alloy, Al-Si master alloy, Al-Sr master alloy, pure Zr, and iron agent are placed in a melting furnace crucible for heating and melting, and then degassing and refining are performed in the melting furnace. Degassing and refining are performed twice in the melting furnace, and the degassing and refining temperature is 740°C.

[0039] S1.2: After the ingredients are qualified, pour them into the heat preservation furnace and carry out heat preservation and refining and degassing at a temperature of 730℃. The heat preservation is carried out for 30 hours, and refining and degassing are carried out every 4 hours.

[0040] S1.3: Casting and rolling, the casting and rolling temperature is 750℃, the casting and rolling speed is 600mm / h, the cooling water temperature is 30℃, and the thickness of the cast and rolled plate is 7mm.

[0041] S2: Cold rolled

[0042] After three rolling passes, the deformation of a single pass is 30% of the total deformation, and the cast plate is rolled into a 0.3mm plate.

[0043] S3: Annealing

[0044] The annealing temperature is 120°C, the heating rate is 50°C / h, and the temperature is kept for 10 hours.

[0045] S4: Foil rolling

[0046] After three rolling passes with a single-pass reduction rate of 50%, the plate is rolled into 0.06mm aluminum alloy foil.

[0047] During the foil rolling process, the front tension is 50MPa, the rear tension is 60MPa, and the rolling speed is 400m / min.

[0048] After testing, the prepared aluminum alloy foil has a resistivity of 12μΩ.cm, a yield strength of 180MPa, and an elongation of 16% at 20°C. Embodiment 2:

[0049] A high-strength aluminum alloy foil for a heating element, wherein the components of the aluminum alloy foil are, by mass percentage, respectively: Mn: 2.0%, Ti: 0.5%, V: 0.5%, Fe: 0.15%, Si: 3%, Li: 1.0%, Sr: 0.22%, Zr: 0.15%, other impurity elements ≤ 0.2%, and the remaining element is Al.

[0050] A method for preparing a high-strength aluminum alloy foil for a heating element is used to prepare the above-mentioned aluminum alloy foil. The preparation method comprises the following steps:

[0051] S1: Casting

[0052] S1.1: 99.7% industrial pure aluminum, Al-Mn master alloy, Al-Ti master alloy, Al-V master alloy, Al-Li master alloy, Al-Si master alloy, Al-Sr master alloy, pure Zr, and iron agent are placed in a melting furnace crucible for heating and melting, and then degassing and refining are performed in the melting furnace. Degassing and refining are performed twice in the melting furnace, and the degassing and refining temperature is 750°C.

[0053] S1.2: After the ingredients are qualified, pour them into the insulation furnace and carry out insulation and refining and degassing at a temperature of 740℃. The insulation time is 25 hours, and refining and degassing are carried out every 4 hours.

[0054] S1.3: Casting and rolling, the casting and rolling temperature is 780℃, the casting and rolling speed is 650mm / h, the cooling water temperature is 40℃, and the thickness of the cast and rolled plate is 8mm.

[0055] S2: Cold rolled

[0056] After 4 rolling passes, the deformation of a single pass is 25% of the total deformation, and the cast plate is rolled into a 0.1 mm plate.

[0057] S3: Annealing

[0058] The annealing temperature is 200°C, the heating rate is 80°C / h, and the heat preservation time is 15h.

[0059] S4: Foil rolling

[0060] After 4 rolling passes with a single-pass reduction rate of 40%, the plate is rolled into 0.04mm aluminum alloy foil.

[0061] During the foil rolling process, the front tension is 30MPa, the rear tension is 50MPa, and the rolling speed is 300m / min.

[0062] After testing, the prepared aluminum alloy foil has a resistivity of 15μΩ.cm, a yield strength of 150MPa, and an elongation of 18% at 20°C. Embodiment 3:

[0063] A high-strength aluminum alloy foil for a heating element, wherein the components of the aluminum alloy foil are, by mass percentage, respectively: Mn: 2.2%, Ti: 1%, V: 0.4%, Fe: 0.2%, Si: 2%, Li: 0.7%, Sr: 0.6%, Zr: 0.17%, other impurity elements ≤ 0.2%, and the remaining element is Al.

[0064] A method for preparing a high-strength aluminum alloy foil for a heating element is used to prepare the above-mentioned aluminum alloy foil. The preparation method comprises the following steps:

[0065] S1: Casting

[0066] S1.1: 99.7% industrial pure aluminum, Al-Mn master alloy, Al-Ti master alloy, Al-V master alloy, Al-Li master alloy, Al-Si master alloy, Al-Sr master alloy, pure Zr, and iron agent are placed in a melting furnace crucible for heating and melting, and then degassing and refining are performed in the melting furnace. Degassing and refining are performed twice in the melting furnace, and the degassing and refining temperature is 745°C.

[0067] S1.2: After the ingredients are qualified, pour them into the heat preservation furnace and carry out heat preservation and refining and degassing at a temperature of 735℃. The heat preservation is carried out for 26 hours, and refining and degassing are carried out every 4 hours.

[0068] S1.3: Casting and rolling, the casting and rolling temperature is 790℃, the casting and rolling speed is 750mm / h, the cooling water temperature is 35℃, and the thickness of the cast and rolled plate is 9mm.

[0069] S2: Cold rolled

[0070] After 4 rolling passes, the deformation of a single pass is 27% of the total deformation, and the cast plate is rolled into a 0.3 mm plate.

[0071] S3: Annealing

[0072] The annealing temperature is 240°C, the heating rate is 100°C / h, and the heat preservation time is 20h.

[0073] S4: Foil rolling

[0074] After 4 rolling passes with a single-pass reduction rate of 42%, the plate is rolled into 0.06mm aluminum alloy foil.

[0075] During the foil rolling process, the front tension is 65MPa, the rear tension is 75MPa, and the rolling speed is 500m / min.

[0076] After testing, the prepared aluminum alloy foil has a resistivity of 13μΩ.cm, a yield strength of 200MPa, and an elongation of 14% at 20°C. Embodiment 4:

[0077] A high-strength aluminum alloy foil for a heating element, wherein the components of the aluminum alloy foil are, by mass percentage, 2.1% Mn, 0.6% Ti, 0.4% V, 0.12% Fe, 2.2% Si, 0.8% Li, 0.26% Sr, 0.16% Zr, and other impurity elements ≤ 0.2%, and the remaining element is Al.

[0078] A method for preparing a high-strength aluminum alloy foil for a heating element is used to prepare the above-mentioned aluminum alloy foil. The preparation method comprises the following steps:

[0079] S1: Casting

[0080] S1.1: 99.7% industrial pure aluminum, Al-Mn master alloy, Al-Ti master alloy, Al-V master alloy, Al-Li master alloy, Al-Si master alloy, Al-Sr master alloy, pure Zr, and iron agent are placed in a melting furnace crucible for heating and melting, and then degassing and refining are performed in the melting furnace. Degassing and refining are performed twice in the melting furnace, and the degassing and refining temperature is 740°C.

[0081] S1.2: After the ingredients are qualified, pour them into the insulation furnace and carry out insulation and refining and degassing at a temperature of 740℃. The insulation is carried out for 28 hours, and refining and degassing are carried out every 4 hours.

[0082] S1.3: Casting and rolling, the casting and rolling temperature is 770℃, the casting and rolling speed is 620mm / h, the cooling water temperature is 36℃, and the thickness of the cast and rolled plate is 8mm.

[0083] S2: Cold rolled

[0084] After three rolling passes, the deformation of a single pass is 28% of the total deformation, and the cast plate is rolled into a 0.2 mm plate.

[0085] S3: Annealing

[0086] The annealing temperature is 220°C, the heating rate is 60°C / h, and the temperature is kept for 12h.

[0087] S4: Foil rolling

[0088] After 4 rolling passes with a single-pass reduction rate of 45%, the plate is rolled into 0.05mm aluminum alloy foil.

[0089] During the foil rolling process, the front tension is 45MPa, the rear tension is 60MPa, and the rolling speed is 350m / min.

[0090] After testing, the prepared aluminum alloy foil has a resistivity of 14μΩ.cm, a yield strength of 170MPa, and an elongation of 16% at 20°C. Embodiment 5:

[0091] A high-strength aluminum alloy foil for a heating element, wherein the components of the aluminum alloy foil are, by mass percentage, respectively: Mn: 2.07%, Ti: 0.65%, V: 0.42%, Fe: 0.14%, Si: 2.5%, Li: 0.85%, Sr: 0.46%, Zr: 0.2%, other impurity elements ≤ 0.2%, and the remaining element is Al.

[0092] A method for preparing a high-strength aluminum alloy foil for a heating element is used to prepare the above-mentioned aluminum alloy foil. The preparation method comprises the following steps:

[0093] S1: Casting

[0094] S1.1: 99.8% industrial pure aluminum, Al-Mn master alloy, Al-Ti master alloy, Al-V master alloy, Al-Li master alloy, Al-Si master alloy, Al-Sr master alloy, pure Zr, and iron agent are placed in a melting furnace crucible for heating and melting, and then degassing and refining are performed in the melting furnace. Degassing and refining are performed twice in the melting furnace, and the degassing and refining temperature is 745°C.

[0095] S1.2: After the ingredients are qualified, pour them into the insulation furnace and carry out insulation and refining and degassing at a temperature of 745℃. The insulation time is 30 hours, and refining and degassing are carried out every 4 hours.

[0096] S1.3: Casting and rolling, the casting and rolling temperature is 780℃, the casting and rolling speed is 650mm / h, the cooling water temperature is 40℃, and the thickness of the cast and rolled plate is 8.5mm.

[0097] S2: Cold rolled

[0098] After three rolling passes, the deformation of a single pass is 30% of the total deformation, and the cast plate is rolled into a 0.2 mm plate.

[0099] S3: Annealing

[0100] The annealing temperature is 240°C, the heating rate is 60°C / h, and the heat preservation time is 15h.

[0101] S4: Foil rolling

[0102] After 4 rolling passes with a single-pass reduction rate of 45%, the plate is rolled into 0.05mm aluminum alloy foil.

[0103] During the foil rolling process, the front tension is 45MPa, the rear tension is 60MPa, and the rolling speed is 380m / min.

[0104] After testing, the prepared aluminum alloy foil has a resistivity of 14μΩ.cm, a yield strength of 175MPa, and an elongation of 15% at 20°C.

[0105] Although the embodiments of the present invention have been shown and described, it is understood 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 present invention, and the protection scope of the present invention is defined by the attached claims and their equivalents.

Claims

1. A high-strength aluminum alloy foil for a heating element, characterized in that: The aluminum alloy foil has the following components, by mass percentage: Mn: 2-2.2%, Ti: 0.5-1%, V: 0.3-0.5%, Fe: 0.1-0.2%, Si: 2-3%, Li: 0.7-1.0%, Sr: 0.02-0.6%, Zr≤0.2%, other impurity elements≤0.2%, and the remaining elements are Al; the yield strength of the aluminum alloy foil is 150-200MPa, and the elongation is 14-18%; the resistivity of the aluminum alloy foil is 10-15μΩ•cm at 20°C.

2. A method for preparing the aluminum alloy foil as claimed in claim 1, characterized in that: The following steps are involved: S1: Casting S1.1: Put more than 99.5% industrial pure aluminum, Al-Mn master alloy, Al-Ti master alloy, Al-V master alloy, Al-Li master alloy, Al-Si master alloy, Al-Sr master alloy, pure Zr and iron agent into a melting furnace crucible for heating and melting, and then degas and refine in the melting furnace; S1.2: After the ingredients are qualified, pour them into the holding furnace and keep warm and refine and degas at a temperature of 730-740℃; S1.3: Casting and rolling, the casting and rolling temperature is 750-790℃, the casting and rolling speed is 600-750mm / h, the cooling water temperature is 30-40℃, and the thickness of the cast and rolled plate is 7-9mm; S2: Cold rolled After multiple rolling passes, the cast plate is rolled into a plate with a thickness of 0.1-0.3 mm; S3: Annealing Annealing temperature is 120-240℃, heating rate is 50-100℃ / h, and heat preservation is 10-20h; S4: Foil rolling After multiple rolling passes, the plate is rolled into 0.04-0.06mm aluminum alloy foil.

3. A preparation method as claimed in claim 2, characterized in that: In S1.1, degassing and refining are performed twice in the smelting furnace, and the degassing and refining temperature is 740-750°C.

4. A preparation method as claimed in claim 2, characterized in that: In S1.2, refining and degassing are performed every 4 hours.

5. A preparation method as described in claim 2, characterized in that: in S2, the cast-rolled plate is rolled for 3-4 times, and the deformation of a single time does not exceed 30% of the total deformation.

6. A preparation method as described in claim 2, characterized in that: in S4, the plate is rolled 3-5 times, and the reduction rate of a single pass is not less than 40%.

7. A preparation method as claimed in claim 2 or 6, characterized in that: During the foil rolling process, the front tension is 30-65MPa, the rear tension is 50-75MPa, and the rolling speed is 300-500m / min.