A high-efficiency short-process preparation method of ultra-thin aluminum foil

Abstract

The present application belongs to the technical field of nonferrous metallurgy, and in particular to a short-process high-efficiency preparation technology for ultra-thin aluminum foil. The present application uses a copper crystallization roller to cool molten aluminum, and uses a uniform flow distribution technology to realize a high-pull-speed continuous casting process for the molten aluminum. The obtained cast strip is further cooled and hot-rolled, the hot-rolled plate is cooled again and then cold-rolled, and finally the aluminum foil is obtained through foil rolling. The present application uses a uniform flow distribution device in combination with a copper crystallization roller to realize rapid and uniform flow distribution and sub-rapid solidification of the molten aluminum, thereby providing necessary conditions for short-process high-efficiency preparation of high-quality ultra-thin aluminum foil.

Description

Technical Field

[0001] This invention belongs to the field of non-ferrous metallurgical technology, and particularly relates to a high-efficiency short-process preparation technology for ultra-thin aluminum foil. Background Technology

[0002] Thin strip casting technology was first proposed by Henry Bessmer in the UK. It involves directly producing cast steel strips by pouring molten steel between two opposing rotating hardened rolls. Although it attracted the attention of researchers at the time, its industrialization was not successfully achieved for the next century due to limitations in control and manufacturing technologies (Cai Changqing. Current Status and Prospect of Twin-Roll Thin Strip Casting and Rolling Technology [J]. Fujian Metallurgy, 2022, 51(01): 50-54). With the development of industrial technology, the application of thin strip casting technology has gradually matured, and various forms of thin strip casting, such as single-roll casting machines and belt casting machines, have emerged from the initial twin-roll thin strip casting technology. Among them, twin-roll thin strip casting is considered the most revolutionary cutting-edge technology in the 21st-century iron and steel metallurgy field.

[0003] The production of aluminum alloys by thin strip casting was first achieved by Hunter Corporation in the United States. By optimizing the cooling of the crystallizing roll and changing the pouring method from top pouring to bottom pouring, they finally realized the production of aluminum alloys using vertical twin-roll thin strip casting technology. However, due to the high difficulty of operation and low product qualification rate, it was gradually replaced by horizontal twin-roll casting. At present, the more common short-process production method of aluminum alloys is the Hazelett twin-strip casting and rolling technology (Ding Peidao, Jiang Bin, Yang Chunmei, et al. Development status and thinking of thin strip casting technology [J]. Chinese Journal of Nonferrous Metals, 2004(S1):192-196.). The production efficiency of horizontal twin-roll continuous casting technology and twin-belt continuous casting and rolling technology is relatively low, with drawing speeds generally below 3m / min. Therefore, it is difficult to meet the ever-increasing demand for aluminum alloys. At the same time, it is impossible to achieve a continuous production process from molten aluminum to aluminum foil. More importantly, because gravity is perpendicular to the direction of the casting strip drawing speed, the solidification in the thickness direction of the casting strip is uneven, which easily leads to severe segregation and cracking, seriously affecting the stability of the casting strip quality.

[0004] Aluminum foil, as an ultra-thin metallic material, plays an indispensable role in the industrial field, and its versatility allows for a wide range of applications. In the electronics and electrical industries, it serves as cable insulation and a heat sink for electronic devices, effectively improving the performance and reliability of electronic components. In food processing and packaging, aluminum foil is essential for maintaining food freshness and extending shelf life, protecting food from environmental influences. Furthermore, in the chemical and pharmaceutical industries, aluminum foil is used to package chemicals and pharmaceuticals, ensuring their quality and safety. More importantly, in the aerospace and automotive industries, the lightweight and tough properties of aluminum foil make it an ideal choice for manufacturing aircraft parts and automotive components, contributing to improved fuel efficiency and performance. Therefore, the widespread application of aluminum foil in industry is an indispensable element in promoting modern industrial production and technological innovation.

[0005] However, current aluminum foil production still largely relies on traditional semi-continuous casting. This traditional method involves repeated hot rolling, billet preparation, and machining, resulting in significant resource waste. Even with thin-strip continuous casting, the low casting speed still leads to low production efficiency, hindering the further adoption of aluminum foil. Against this backdrop, achieving efficient and economical aluminum foil production has become a crucial development direction in the aluminum alloy industry. Top-cast twin-roll thin-strip continuous casting technology not only offers rapid cooling and high casting speeds but also simplifies operation compared to the earlier bottom-cast method, making it an excellent method for producing and processing aluminum alloys. Osaka University in Japan designed a simple vertical twin-roller continuous casting machine for aluminum alloy strip preparation in the laboratory. They found that the preparation of aluminum alloys by top-pour twin-roller continuous casting is highly feasible. The casting and rolling force of the crystallizing roll is low throughout the process, and there is no need for lubrication between the crystallizing roll and the casting strip, which can effectively improve the efficiency of aluminum alloy preparation. However, the aluminum alloy pouring volume of the experimental machine is only 3 kg, and the complete pouring time is very short. Whether the equipment reaches balance during the entire process needs to be explored. At the same time, it does not include subsequent rolling and heat treatment processes, so it is difficult to verify the continuity of aluminum alloy strip preparation using this technology (Haga T, Takahashi K, Ikawa M, et al. A vertical-type twin rollcaster for aluminum alloy strips[J]. Journal of Materials Processing Technology, 2003, 140(1-3):610-615.). China Baowu Steel Group attempted to produce 7XXX aluminum alloys using vertical twin-roll thin-strip casting, discovering that it could achieve high-speed production of aluminum alloys, as illustrated in patent 202010868120.9. However, the process improvement only addressed alloy strengthening, neglecting the overall flow of the vertical twin-roll thin-strip casting process for aluminum alloy production. No improvements were made to the melt distribution process in the crystallizing roll, and the technology also involved directly producing aluminum alloy foil from aluminum alloy strips. However, preliminary research revealed that when this technology was applied to aluminum alloy production, fluctuations in the melt pool within the crystallizing roll easily deteriorated the edge quality of the aluminum alloy strip, indicating a need for further optimization. Furthermore, a search revealed few existing records of optimizing the flow distributor in the vertical twin-roll thin-strip casting process for direct aluminum foil production. Summary of the Invention

[0006] To address the problems existing in the prior art, the present invention aims to provide a highly efficient, short-process method for preparing ultra-thin aluminum foil. This method involves uniformly pouring molten aluminum onto a copper, water-cooled crystallizing roller using a special flow distribution device to produce aluminum alloy casting strips. Combined with subsequent rolling and heat treatment, this achieves continuous production from molten aluminum to aluminum foil. Uniform flow distribution is primarily achieved through flow distribution pipes of equal height but different diameters below the flow distributor. Because the filter box and flow distributor are connected only by a single conduit, conventional flow distribution often results in molten aluminum entering the molten pool primarily through the central flow distribution pipe, while the flow rates on the left and right sides are lower, leading to significant fluctuations in the molten pool surface. The different diameter flow distribution pipes not only effectively achieve uniform flow distribution in the crystallizing roller's molten pool but also prevent molten pool surface fluctuations caused by an excessively large central flow stream, ultimately achieving stable production of aluminum alloy casting strips and ensuring strip quality.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] This invention discloses a highly efficient, short-process method for preparing ultrathin aluminum foil, comprising the following steps:

[0009] 1) Uniform flow distribution

[0010] The degassed and impurity-removed aluminum liquid enters the distributor above the crystallizing roller through the conduit set on the filter box. The aluminum liquid is uniformly distributed through N distribution conduits of the same height and gradually expanding diameter arranged below the distributor. The crystallizing roller is a double roller. With the center of the roller gap of the double roller as the central axis, the N distribution conduits are arranged in a state where the average diameter or equivalent diameter of the distribution conduits near the central axis is small and gradually becomes thicker towards the periphery.

[0011] That is, the N unequal-diameter gradually expanding flow distribution pipes have the same height h, but the diameter or equivalent diameter D of the bottom port of the N unequal-diameter gradually increases with the distance from the central axis, and the ratio of the bottom diameter or equivalent diameter of two adjacent flow distribution pipes is . Meanwhile, the ratio between the upper diameter or equivalent diameter d of each gradually expanding flow tube and the lower diameter or equivalent diameter D is... The temperature of the molten aluminum inside the distributor is 690–720℃;

[0012] 2) Continuous casting

[0013] A vertical twin-roll continuous casting machine is used to continuously cast molten aluminum to obtain aluminum alloy strips with a thickness of 1.0–4.0 mm; the temperature of the molten aluminum entering the crystallizing roll pool is 680–720℃; the temperature of the resulting aluminum alloy strip is 450–590℃; the crystallizing roll is made of copper and is internally cooled by cooling water; the casting speed is 15–60 m / min.

[0014] 3) Hot rolling

[0015] The resulting cast strip is guided into the cooling zone by an arc-shaped guide plate, where the temperature is reduced to 350-500℃. It is then conveyed into the hot rolling zone by conveyor rollers. The hot rolling temperature is 300-450℃ and the hot rolling reduction rate is <50%.

[0016] 4) Cold rolling

[0017] The hot-rolled strip is further cooled to room temperature, and then conveyed to a cold rolling mill via conveyor rollers. The aluminum strip is rolled to 0.3-0.5 mm through 2-3 cold rolling passes; the total reduction rate is not higher than 80%.

[0018] 5) Foil rolling

[0019] The cold-rolled strip will be transported to a foil rolling mill for further foil rolling, ultimately yielding aluminum foil with a thickness of 0.1–0.15 mm; the total foil reduction rate will not exceed 80%.

[0020] 6) Curled

[0021] The aluminum foil is de-headed by a flying shear and then conveyed to a winding machine by a clamping roller to be rolled into an aluminum foil roll.

[0022] 7) Post-processing

[0023] The resulting aluminum foil rolls undergo further annealing to obtain the final product.

[0024] Preferably, the present invention provides a highly efficient short-process method for preparing ultrathin aluminum foil, wherein the degassed and impurity-removed molten aluminum is prepared through the following steps:

[0025] Step 1: Smelting aluminum liquid:

[0026] Raw materials are melted and smelted in a smelting furnace to obtain molten aluminum;

[0027] Step 2: Let it stand still and keep it warm

[0028] The smelted aluminum liquid is piped into a holding furnace, where it is kept at a temperature of 750–770°C to obtain a partially purified aluminum liquid.

[0029] Step 3: Degassing and Impurity Removal

[0030] The preliminarily purified aluminum liquid is passed through a conduit into a degassing box. The liquid is stirred in the degassing box to remove the gas inside the aluminum liquid, thus obtaining a degassed and purified aluminum liquid.

[0031] Preferably, in the distributor used for uniform flow distribution in step 1), N gradually expanding flow distribution guides of the same height are arranged in a "I" shape and projected parallel to the roller gap; the projections of the N gradually expanding flow distribution guides of the same height overlap; that is, the bottom of the N gradually expanding flow distribution guides of the same height form an "I" shape parallel to the roller gap.

[0032] This invention discloses an efficient and short-process preparation method for ultra-thin aluminum foil. In step one, a regenerative melting furnace can be used to melt and smelt the raw materials. During the melting and smelting process, natural gas, blast furnace gas, or coke oven gas are transported to melt the aluminum liquid.

[0033] This invention discloses a highly efficient, short-process method for preparing ultrathin aluminum foil. In step two, the aluminum molten metal is kept at a constant temperature in a holding furnace to allow some impurities to float to the surface. To ensure effectiveness, the holding time in step two should be greater than or equal to 20 minutes; however, if the volume of aluminum molten metal is large, the holding time should be appropriately extended.

[0034] This invention discloses a highly efficient, short-process method for preparing ultrathin aluminum foil. In step three, the molten aluminum is stirred in a degassing chamber to remove internal gases, and then further filtered to remove fine impurities, resulting in degassed and purified aluminum. In actual operation, the degassing process utilizes an electromagnetic or high-temperature resistant stirring paddle to directly stir the aluminum, with a stirring time of no less than 10 minutes, to ensure complete removal of internal gases. Furthermore, the aluminum passes through multiple filter screens in the purification chamber to remove fine impurities.

[0035] Aluminum ingots are melted and smelted in a regenerative melting furnace. The final chemical composition of the molten aluminum is controlled according to the following requirements: Si < 0.2%, Fe: 0.35-0.39%, Mn: 0.33-0.37%, Zn < 0.2%, Ti: 0.06-0.11%, with the remainder being Al, and the total impurity content not exceeding 0.1%.

[0036] Furthermore, the flow distribution conduit is a circular tube.

[0037] In practical applications, among N gradually expanding flow distribution pipes with different diameters, the lower diameter of the pipe with the largest lower diameter is 30-50mm, and the upper diameter is 10-25mm.

[0038] In practical applications, among N gradually expanding flow distribution pipes with different diameters, the lower diameter of the pipe with the smallest lower diameter is 12-20 mm, and the upper diameter is 4-10 mm.

[0039] Furthermore, in steps 1) and 2), the gap between the crystallizing rollers is 1.0–4.0 mm; the temperature of the molten aluminum entering the crystallizing roller pool is 680–720°C; the temperature of the resulting aluminum alloy casting strip is 450–590°C, and the casting speed is 15–60 m / min. The copper material in step 2) includes pure copper or copper alloy.

[0040] Furthermore, in step 3), the obtained casting strip is guided into the cooling zone by an arc-shaped guide plate, and the temperature is reduced to 350-500°C by spraying cooling water onto the casting strip. Then, it is conveyed into the hot rolling zone by the conveyor rollers. The hot rolling temperature is 300-450°C, the hot rolling reduction rate is not higher than 50%, and the thickness of the hot-rolled strip is between 1.3 and 1.6 mm.

[0041] Furthermore, in step 4), the hot-rolled strip is further cooled to room temperature by water spraying, and then further conveyed to the cold rolling mill by conveyor rollers. After 2 to 3 cold rolling passes, the average reduction rate per pass does not exceed 40%, preferably 25 to 35%, and the total reduction rate does not exceed 80%, preferably 70 to 77%, and more preferably 76% to 77%, to roll the aluminum strip to 0.3 to 0.5 mm.

[0042] Further, in step 5), the cold-rolled strip is transported to a foil rolling mill for 2-4 passes of foil rolling, with an average reduction rate of no more than 40% per pass, preferably 25-30%, and a total reduction rate of no more than 80%, preferably 65-78%, and more preferably 73-75%, ultimately obtaining aluminum foil with a thickness of 0.1-0.15 mm. Further, in step 6), the rolled aluminum foil is de-headed by a flying shear and then conveyed by pinch rollers to a winding machine for coiling, obtaining an aluminum foil roll.

[0043] Furthermore, in step 7), the obtained aluminum foil roll is annealed at 260-290°C, preferably 278-285°C, for 2-4 hours to obtain the final product.

[0044] The technical concept of this invention is as follows:

[0045] 1) Utilizing the high speed and high production efficiency of vertical twin-roll thin strip continuous casting machine, the aluminum liquid is rapidly transformed from liquid to cast state through top pouring, solving the problems of liquid core asymmetry and uneven solidification in horizontal continuous casting of aluminum alloys. Combined with subsequent online rolling and heat treatment processes, it effectively solves the problem of low production efficiency of existing aluminum foil, realizing integrated, efficient and short-process production from aluminum ingot to aluminum foil.

[0046] 2) By utilizing the high cooling rate of the copper crystallizing roller, the molten aluminum liquid is solidified at a sub-rapid speed, ensuring that the beneficial elements inside the aluminum liquid are dissolved in the Al matrix, reducing the precipitation of large-size secondary phases, thereby improving the strengthening effect on the aluminum alloy strip; at the same time, the high cooling rate can effectively avoid the macroscopic segregation inside the aluminum alloy strip under the traditional production method, thereby further ensuring the mechanical properties of the final product.

[0047] 3) The molten aluminum in the distributor can achieve uniform distribution under the distribution pipe with a special structure. The distribution pipes on the entire distribution surface are arranged in a gradient so that the distribution pipe at the center is thinner and the diameter of the distribution pipes at both ends gradually increases, which can effectively achieve uniform distribution of the molten pool. At the same time, under the action of the diffuser, the flow velocity of the melt is slowed down by the change of pipe diameter, which makes it easier to stabilize the distribution process, reduce the disturbance to the molten pool surface, and ensure the continuity of production and the quality of the casting strip.

[0048] The beneficial effects of this invention are:

[0049] 1) This invention optimizes the existing production method of horizontal thin strip continuous casting of aluminum foil by using copper crystallizing rolls for vertical thin strip continuous casting. This solves the production problems of high rolling force and slow drawing speed in the horizontal continuous casting process. At the same time, since the direction of gravity is consistent with the direction of strip movement in the vertical twin-roll continuous casting process, the influence of gravity on the solidification process of the strip inside the crystallizing roll is avoided, which ensures uniform solidification of the strip and stabilizes the quality of the strip.

[0050] 2) By utilizing the high cooling speed of the crystallizing roller, the aluminum liquid is instantly transformed into the casting strip, which effectively solidifies the beneficial elements inside the aluminum liquid. On the one hand, it achieves grain refinement and ensures the mechanical properties of the casting strip. On the other hand, it reduces the precipitation of secondary phases and reduces the impact of brittle phases on the performance of the casting strip.

[0051] 3) The flow distributor in the aluminum molten casting process was optimized. By adopting a gradually expanding flow distributor with equal height and different diameters, and optimizing the pipe diameters of the inlet and outlet of the flow distributor and its arrangement on the flow distribution surface, uniform flow distribution to the molten pool in the crystallizing roll was achieved. Simultaneously, the stability of the flow stream during the flow distribution process was effectively ensured, reducing the disturbance of the flow stream to the molten pool surface, thereby ensuring stable production of aluminum alloy casting strip. Furthermore, with appropriate continuous casting process parameters (such as cold rolling process parameters and foil rolling process parameters), foil materials with excellent performance and good surface quality were obtained. Attached Figure Description

[0052] Figure 1 This is a schematic diagram of the process flow of the vertical twin-roll thin strip continuous casting unit of the present invention.

[0053] Figure 2 This is a schematic diagram of a uniform flow distribution system.

[0054] In the diagram, 1 is a regenerative melting furnace; 2 is an aluminum molten metal transport conduit; 3 is a holding furnace; 4 is a degassing box; 5 is a filter box; 6 is a flow distributor; 7 is an aluminum molten metal pool inside the crystallizing roller; 8 is a side sealing plate; 9 is a copper crystallizing roller; 10 is a crystallizing roller brush; 11 is an aluminum alloy cast strip; 12 is an arc-shaped guide plate; 13 is a high-pressure water cooling system; 14 is an atmosphere protection box; 15 is a transport roller; 16 is a hot rolling system; 17 is a secondary cooling system; 18 is a cold rolling system; 19 is a foil rolling system; 20 is a flying shear; 21 is a pinch roll; and 22 is a coiler. Detailed Implementation

[0055] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0056] See Figure 1 The process flow of this invention is shown below:

[0057] High-purity aluminum ingots are melted and smelted using a regenerative melting furnace 1. Different intermediate alloys, such as Al-Mn, Al-Zn, and Al-Si, are added to the furnace according to the grade to adjust the composition. Natural gas is introduced to provide a heat source for the aluminum melt smelting. The furnace temperature is 800–850℃, and the smelting time is 70 minutes. After smelting, the aluminum melt enters a holding furnace 3 through a conduit 2. The aluminum melt is held at a constant temperature in the holding furnace for 25 minutes, during which larger impurities are removed by flotation. The temperature of the aluminum melt in the holding furnace is 750–770℃. The aluminum melt in the holding furnace then enters a degassing box 4 through a conduit. Inside the degassing box, physical stirring ensures that all gases in the aluminum melt are removed by flotation. The stabilized aluminum melt then enters a filter box 5, which contains multiple layers of filter screens to filter out fine impurities and ensure the purity of the aluminum melt. The filtered molten aluminum enters the distributor 6, and is uniformly distributed through N unequal-diameter gradually expanding distribution conduits arranged below the distributor. The crystallizing roller is a double roller. With the center of the roller gap of the double roller as the central axis, the N distribution conduits are arranged in a state where the average diameter or equivalent diameter of the distribution conduits near the central axis is small and gradually becomes larger towards the periphery. In Examples 1-7 and Comparative Examples 2-3, the value of N is 5, the height h of the N unequal-diameter gradually expanding distribution conduits (circular) is the same, but the diameter D of the bottom port of the N unequal-diameter gradually expanding distribution conduits gradually increases with the distance from the central axis, and the ratio of the bottom diameter of two adjacent distribution conduits is D1 / D2 = 0.6. At the same time, the ratio between the upper diameter or equivalent diameter d of each expanding distribution conduit and the lower diameter D is 0.4. Among the N unequal-diameter gradually expanding distribution conduits, the lower diameter of the one with the largest lower diameter is 41.7 mm, and its upper diameter is 16.7 mm. Among N gradually expanding flow distribution tubes with different diameters, the lower diameter of the tube with the smallest lower diameter is 15mm, and its upper diameter is 6mm.

[0058] Five equal-height, differentially sized, gradually expanding flow distribution guides are arranged in a straight line, projected parallel to the roll gap of the twin rollers; the projections of the five identical-height, differentially sized, gradually expanding flow distribution guides overlap; that is, the bottom of the five identical-height, differentially sized, gradually expanding flow distribution guides form a straight line parallel to the roll gap of the twin rollers. The five identical-height, differentially sized, gradually expanding flow distribution guides are numbered from the inside out as No. 1, No. 2, No. 3 is located directly above the center of the roll gap, with a lower diameter of 15mm and an upper diameter of 6mm; Nos. 2 and 4 both have a lower diameter of 25.02mm and an upper diameter of 10mm; Nos. 1 and 5 both have a lower diameter of 41.7mm and an upper diameter of 16.7mm.

[0059] The temperature of the molten aluminum inside the distributor is 700℃. It enters the molten pool 7, composed of the crystallizing roll 9 and the side sealing plate 8, through a special distribution pipe. The molten aluminum is then cast into a 3.0mm thick as-cast strip 11 (at 570℃) using a twin-roll continuous casting machine. The casting speed is 50m / min. Brass roller brushes 10 are arranged on the outer side of each crystallizing roll 9 to promptly remove the oxide deposits on its surface.

[0060] After exiting the crystallizing rollers 9a and 9b (at a temperature of 570℃), the aluminum alloy cast strip 11 enters the cooling zone along the arc-shaped guide plate 12. It is cooled by high-pressure water-cooled nozzles 13 evenly arranged on both sides of the guide plate, with a cooling length of 0.3m. This high-speed water cooling rapidly cools the aluminum alloy cast strip to 470℃, with a cooling rate of no less than 40℃ / s (approximately 46℃ / s). The cooled cast strip then passes through the conveyor rollers 15 into the hot rolling mill 16 for hot rolling at a temperature of 450℃. It should be noted that from the runner to the hot rolling mill, the aluminum alloy cast strip is kept in a sealed space 14 filled with nitrogen to prevent excessive oxidation of the cast strip. The hot-rolled aluminum alloy strip has a thickness of 1.6 mm and a reduction rate of 47%. The hot-rolled strip is further cooled by high-pressure water cooling 17 at a rate of not less than 50℃ / s (approximately 53℃ / s) until the strip is cooled to room temperature. Subsequently, 2-3 passes of cold rolling 18 are performed to roll the strip to 0.4 mm. Then, 2-4 passes of foil rolling 19 are performed to roll the cold-rolled strip into 0.1 mm aluminum foil. The aluminum foil is then cut by flying shear 20 and fed by pinch rolls 21 to coiler 22 to form the final aluminum foil roll.

[0061] The molten aluminum in Examples 1-7 of this invention was obtained by smelting in a regenerative melting furnace. Table 2 shows the production speed, rolling reduction rate, aluminum foil heat treatment temperature, heat treatment time, final aluminum foil grain size, aluminum foil surface quality, final aluminum foil tensile strength, and aluminum foil elongation corresponding to each example. It can be seen that the aluminum foil produced by this invention has a tensile strength higher than 150 MPa and an elongation greater than 20%, exhibiting excellent mechanical properties. In Example 5, the tensile strength reached 160 MPa and the elongation reached 24%, indicating that this technology can fully meet the production needs of aluminum foil. In contrast, when uniform flow distribution is not used, due to fluctuations in the molten pool surface of the crystallizing roller, bright and dark stripes appear on the surface of the aluminum alloy strip, and the grain size is larger. Even with improved flow distribution devices, the reduction rate during cold rolling and foil rolling must be strictly controlled. Excessive reduction rate can lead to cracks on the surface of the aluminum alloy strip, especially in the foil rolling stage, where surface cracks are very obvious when the reduction rate is high.

[0062] Aluminum ingots are melted and smelted in a regenerative melting furnace. The final chemical composition of the molten aluminum is controlled according to the following mass percentage requirements: Si < 0.2%, Fe: 0.35–0.39%, Mn: 0.33–0.37%, Zn < 0.2%, Ti: 0.06–0.11%, with the remainder being Al, and the total impurity content not exceeding 0.1%. The composition of the molten aluminum in the examples and comparative examples is shown in Table 1.

[0063] Table 1. Chemical composition (mass percentage) of aluminum liquids in Examples 1-7 and Comparative Examples 1-3

[0064]

[0065] Table 2. Thin strip continuous casting process parameters and aluminum foil surface quality and properties of Examples 1-7 and Comparative Examples 1-3

[0066]

[0067]

[0068] In Comparative Example 1, a flow distribution conduit with a uniform diameter of 16.7 mm was used.

Claims

1. A highly efficient, short-process method for preparing ultrathin aluminum foil, characterized in that, Includes the following steps: 1) Uniform flow distribution The degassed and impurity-removed aluminum liquid enters the distributor above the crystallizing roller through the conduit set on the filter box. The aluminum liquid is uniformly distributed through N distribution conduits of the same height and gradually expanding diameter arranged below the distributor. The crystallizing roller is a double roller. With the center of the roller gap of the double roller as the central axis, the N distribution conduits are arranged in a state where the average diameter or equivalent diameter of the distribution conduits near the central axis is small and gradually becomes thicker towards the periphery. That is, the height h of the N unequal-diameter gradually expanding flow distribution pipes is the same, but the diameter or equivalent diameter D of the bottom port of the N unequal-diameter gradually increases with the distance from the central axis, and the ratio of the bottom diameter or equivalent diameter of two adjacent flow distribution pipes is . Meanwhile, the ratio between the upper diameter or equivalent diameter d of each gradually expanding flow tube and the lower diameter or equivalent diameter D is... The temperature of the molten aluminum inside the distributor is 690~720℃; 2) Continuous casting A vertical twin-roll continuous casting machine is used to continuously cast molten aluminum to obtain aluminum alloy strips with a thickness of 1.0~4.0mm; the temperature of the molten aluminum when it enters the crystallizing roll pool is 680~720℃; the temperature of the resulting aluminum alloy strip is 450~590℃; the crystallizing roll is made of copper and is internally cooled by cooling water; the casting speed is 15~60m / min. 3) Hot rolling The resulting cast strip is guided into the cooling zone by an arc-shaped guide plate, where the temperature is reduced to 350~500℃. It is then conveyed into the hot rolling zone by conveyor rollers, where the hot rolling temperature is 300~450℃ and the hot rolling reduction rate is <50%. 4) Cold rolling The hot-rolled strip is further cooled to room temperature, then conveyed to a cold rolling mill via conveyor rollers. After 2-3 passes of cold rolling, the aluminum strip is rolled to 0.3-0.5 mm; the total reduction rate is no higher than 80%. 5) Foil rolling The cold-rolled strip will be transported to a foil rolling mill for further foil rolling, ultimately yielding aluminum foil with a thickness of 0.1~0.15mm; the total foil reduction rate will not exceed 80%. 6) Curled The aluminum foil is de-headed by a flying shear and then conveyed to a winding machine by a pinch roller to be rolled into an aluminum foil roll. 7) Post-processing The resulting aluminum foil rolls undergo further annealing to obtain the final product.

2. The efficient short-process preparation method for ultrathin aluminum foil according to claim 1, characterized in that: Degassed and purified aluminum liquid is prepared through the following steps: Step 1: Smelting aluminum liquid: Raw materials are melted and smelted in a smelting furnace to obtain molten aluminum; Step 2: Let it stand still and keep it warm The smelted aluminum liquid is piped into a holding furnace, where it is kept at a constant temperature of 750~770℃ to obtain a preliminarily purified aluminum liquid. Step 3: Degassing and Impurity Removal The preliminarily purified aluminum liquid is passed through a conduit into a degassing chamber. The gas inside the aluminum liquid is removed by stirring the melt in the degassing chamber, resulting in a degassed and purified aluminum liquid.

3. The efficient short-process preparation method for ultrathin aluminum foil according to claim 1, characterized in that: The flow distribution conduit is a circular tube.

4. The efficient short-process preparation method for ultrathin aluminum foil according to claim 1, characterized in that: In the distributor used for uniform flow distribution, N gradually expanding flow distribution guides of the same height are arranged in a "I" shape and projected parallel to the roller gap of the double rollers; the projections of the N gradually expanding flow distribution guides of the same height overlap; that is, the bottom of the N gradually expanding flow distribution guides of the same height form an "I" shape parallel to the roller gap of the double rollers.

5. The efficient short-process preparation method for ultrathin aluminum foil according to claim 1, characterized in that: In steps 1) and 2), the gap between the crystallizing rolls is 1.0~4.0mm; the temperature of the molten aluminum entering the crystallizing roll pool is 680~720℃; the temperature of the resulting aluminum alloy casting strip is 450~590℃, and the casting speed is 15~60m / min. The copper material in step 2) includes pure copper or copper alloy.

6. The efficient short-process preparation method for ultrathin aluminum foil according to claim 1, characterized in that: In step 3), the obtained casting strip is guided into the cooling zone by an arc-shaped guide plate. The temperature is reduced to 350~500℃ by spraying cooling water onto the casting strip. Then, it is conveyed into the hot rolling zone by the conveyor roller. The hot rolling temperature is 300~450℃, the hot rolling reduction rate is not higher than 50%, and the thickness of the hot-rolled strip is between 1.3~1.6mm.

7. The efficient short-process preparation method for ultrathin aluminum foil according to claim 1, characterized in that: In step 4), the hot-rolled strip is further cooled to room temperature by water spraying, and then further transported to the cold rolling mill by conveyor rollers. After 2 to 3 passes of cold rolling, the average reduction rate per pass is 25 to 35%, the total reduction rate is 70 to 77%, and the aluminum strip is rolled to 0.3 to 0.5 mm.

8. The efficient short-process preparation method for ultrathin aluminum foil according to claim 1, characterized in that: In step 5), the cold-rolled strip will be transported to the foil rolling mill for 2 to 4 passes of foil rolling, with an average reduction rate of 25 to 30% per pass and a total reduction rate of 65 to 78%, finally obtaining aluminum foil with a thickness of 0.1 to 0.15 mm.

9. The efficient short-process preparation method for ultrathin aluminum foil according to claim 1, characterized in that: In step 6), the aluminum foil after foil rolling is de-headed by a flying shear and then conveyed to a winding machine by a pinch roller to be rolled into an aluminum foil roll.

10. The efficient short-process preparation method for ultrathin aluminum foil according to claim 1, characterized in that: In step 7), the obtained aluminum foil roll is annealed at 278~285℃ for 2~4 hours to obtain the final product.

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