TWI730717B - Method of manufacturing aluminum foil, and aluminum foil manufactured thereby - Google Patents

Abstract

A method of manufacturing an aluminum foil, and an aluminum foil manufactured by the method are provided. The method comprises steps of: a slab casting molding step, casting molten aluminum into an aluminum slab, wherein the molten aluminum comprises 0.15 wt% to 1.6 wt% of iron, 0.015 wt% to 0.03 wt% of copper, 0.01wt% to 0.2 wt% of silicon, and 0.02 wt% to 0.04 wt% of titanium, and the rest is aluminum, by weight of the molten aluminum; a hot rolling step, hot rolling the aluminum slab into a hot aluminum rolled coil having a first thickness; a first cold rolling step, cold rolling the hot aluminum rolled coil into a cold aluminum rolled coil having a second thickness smaller than the first thickness; an annealing step, partially annealing the cold aluminum rolled coil at a temperature of 200 to 250 °C, and retaining the heat; and a second cold rolling step, cold rolling the cold aluminum rolled coil to obtain the aluminum foil.

Description

Method for manufacturing aluminum foil and aluminum foil manufactured therefrom

The present invention relates to a method of manufacturing aluminum foil, in particular to a method of manufacturing aluminum foil applied to the aluminum foil of the positive electrode current collector and the aluminum foil manufactured therefrom.

Lithium-ion batteries have the advantages of higher energy density and relatively higher voltages, and are mainly used in electronic products such as notebook computers, camcorders, digital cameras, and mobile phones. In recent years, the volume of lithium-ion batteries has been gradually shrinking. Therefore, the thickness of the aluminum foil used in the positive electrode current collector has also become thinner, making the improvement of the strength and ductility after thinning become a major issue.

In order to achieve thinning of the aluminum foil and to have both high strength and ductility, several methods have been developed accordingly. For example, continuous intermediate annealing is used to control the number of secondary grains in the thickness direction to more than 30, so that the tensile strength is maintained between 220 MPa and 270 Mpa, and the elongation is more than 4%. However, in this method, a large amount of manganese, copper, and magnesium are added to reduce the conductivity of the current collector. Furthermore, the use of an expensive continuous annealing furnace for intermediate annealing results in higher production costs. In addition, for the rollability of aluminum foil, its strength is too high, which will make the last roll of the foil easy to break.

Another method is mainly through the control of the iron, silicon, copper and aluminum components and their proportions in the aluminum foil. However, in this method, the content of copper is less than 0.1%, resulting in too low strength of the aluminum foil. When the thickness of the aluminum foil is thin, it is easy to break during rolling processing. In addition, in this method, a more expensive continuous annealing furnace is also used for intermediate annealing, which makes the production cost higher.

In summary, the conventional manufacturing method of aluminum foil needs to be improved.

The main purpose of the present invention is to provide a method for manufacturing aluminum foil that can simultaneously improve strength and ductility at low cost.

In order to achieve the above objective, in an embodiment of the present invention, a method for manufacturing aluminum foil is provided, which includes the following steps: a casting molding step: casting aluminum broth into an aluminum blank, wherein the aluminum broth contains by weight: 0.15 wt % To 1.6 wt% iron, 0.015 wt% to 0.03 wt% copper, 0.01 wt% to 0.2 wt% silicon, 0.02 wt% to 0.04 wt% titanium, and the rest is aluminum; a hot rolling step, the The aluminum billet is hot-rolled into a hot-rolled aluminum coil, the hot-rolled aluminum coil has a first thickness; a first cold-rolling step, the hot-rolled aluminum coil is cold-rolled into a cold-rolled aluminum coil, the cold-rolled aluminum coil has a first Two thicknesses, where the second thickness is smaller than the first thickness; an annealing step, in which the cold-rolled aluminum coil is partially annealed and kept warm after the partial annealing, wherein the partial annealing temperature is 200 to 250°C; and In a second cold rolling step, the cold-rolled aluminum coil after the annealing step is cold-rolled to a third thickness, wherein the third thickness is smaller than the second thickness to obtain the aluminum foil.

In an embodiment of the present invention, the copper accounts for 0.015 wt% to 0.025 wt% of the total weight of the aluminum soup.

In an embodiment of the present invention, the first thickness is 2.5 to 4.5 mm.

In an embodiment of the present invention, the second thickness is 0.6 to 1.5 mm.

In an embodiment of the present invention, the third thickness is 0.012 to 0.02 mm.

In an embodiment of the present invention, in the annealing step, the holding time is 2 to 6 hours.

In an embodiment of the present invention, in the hot rolling step, the aluminum billet is preheated to 480 to 530°C and kept at a temperature for 1 to 3 hours before being hot rolled into the hot rolled aluminum coil.

In an embodiment of the present invention, the finishing temperature of the hot-rolled aluminum coil is less than 340°C.

In order to achieve the above objective, in another embodiment of the present invention, there is provided an aluminum foil made by using the method for manufacturing aluminum foil as described in claim 1, which contains by weight: 0.15 wt% to 1.6 wt% Iron, 0.015 wt% to 0.03 wt% copper, 0.01 wt% to 0.2 wt% silicon, 0.02 wt% to 0.04 wt% titanium, and the remainder is aluminum.

In an embodiment of the present invention, the copper accounts for 0.015 wt% to 0.025 wt% of the total weight of the aluminum foil.

The beneficial effects of the present invention are: through the addition of copper and its specific content, no addition of manganese, annealing treatment and annealing temperature control, the aluminum foil produced by the method of manufacturing aluminum foil of the present invention has better strength and The ductility further meets the requirements of the processing and application of the positive current collector of the lithium ion battery, and it also has good cold-rolling performance to avoid strip breakage during foil rolling.

In order to make the above and other objects, features, and advantages of the present invention more obvious and understandable, the following will specifically cite the preferred embodiments of the present invention, which will be described in detail as follows. Furthermore, the "%" mentioned in the present invention refers to "weight percentage (wt%)" unless otherwise specified; the numerical range (such as 10% to 15% of A) includes upper and lower limits unless specified (Ie 10%≦A≦15%) and all numerical points in the range (such as 11, 12, 13, 14...); if the numerical range does not define a lower limit (such as less than 0.2% of B, or 0.2%) The following B) means that its lower limit is close to 0 but does not include 0 (ie 0%>B≦0.2%); the proportional relationship of the "weight percentage" of each component can also be replaced by "weight parts" The proportional relationship. The above terms are used to describe and understand the present invention, but not to limit the present invention.

The method of manufacturing aluminum foil according to an embodiment of the present invention includes the following steps: a casting molding step, casting aluminum broth into an aluminum blank, wherein the aluminum broth contains by weight: 0.15 wt% to 1.6 wt% iron, 0.015 wt% % To 0.03 wt% of copper, 0.01 to 0.2 wt% of silicon, 0.02 to 0.04 wt% of titanium, and the rest is aluminum; a hot-rolling step, hot-rolling the aluminum billet into a hot-rolled aluminum coil, the hot-rolled aluminum The coil has a first thickness; in a first cold rolling step, the hot-rolled aluminum coil is cold-rolled into a cold-rolled aluminum coil, the cold-rolled aluminum coil has a second thickness, wherein the second thickness is smaller than the first thickness An annealing step, the cold-rolled aluminum coil is partially annealed and kept warm after the partial annealing, wherein the partial annealing temperature is 200 to 250 ° C; and a second cold rolling step, the annealing step The cold-rolled aluminum coil is cold-rolled to a third thickness, wherein the third thickness is smaller than the second thickness, so as to obtain the aluminum foil.

In detail, in the casting and molding step, a material is first added to the smelting furnace for smelting. The material includes 0.15 wt% to 1.6 wt% iron, 0.015 wt% to 0.03 wt% copper, and 0.01 to 0.2 wt%. wt% silicon, 0.02 to 0.04 wt% titanium, and the remainder is aluminum. Then, it is refined in a static furnace to obtain the aluminum soup. Then, the aluminum broth is introduced into the flow channel, degassing is performed in the flow channel, and aluminum-titanium-boron fine crystal wires are added at the same time. Finally, the aluminum broth is introduced into the semi-continuous casting machine through the runner to obtain the aluminum blank. Preferably, in other embodiments, the copper accounts for the material, that is, the total weight of the aluminum soup may be 0.015 wt% to 0.025 wt%. More preferably, the copper accounts for 0.02 wt% of the total weight of the aluminum soup.

In detail, in this hot rolling step, homogenizing the aluminum blank is omitted. Before the aluminum billet is hot-rolled, the aluminum billet is placed in a hot-rolling preheating furnace for preheating. The preheating temperature is 480 to 530°C. In order to homogenize the aluminum billet, the aluminum billet is The embryo is kept for 1 to 3 hours, and then hot-rolled. The finishing temperature is less than 340°C. In this embodiment, the first thickness is 2.5 to 4.5 mm. Of course, the present invention is not limited to this. In other embodiments, the first thickness may be 3 to 4 mm. Optionally, the first thickness may be 2.5, 2.7, 2.9, 3.1, 3.3, 3.5, 3.7, 3.9, 4.1, 4.3, or 4.5 mm.

In detail, in the first cold-rolling step, if the second thickness of the cold-rolled aluminum coil is too thin, it will lead to poor strength and elongation, and if it is too thick, it will easily break. Preferably, the second thickness is 0.6 to 1.5 mm. Of course, the present invention is not limited to this. In other embodiments, the second thickness may be 1 to 1.5 mm. Optionally, the second thickness may be 0.6, 0.7, 0.8, 0.9, 1, 1.1, 1.2, 1.3, 1.4, or 1.5 mm.

In detail, in the annealing step, the annealing temperature is controlled below the recrystallization temperature, that is, 200 to 250°C, so as to achieve the effect of generating secondary crystal grains instead of recrystallization, so that the finally obtained aluminum foil has a relatively high Good strain energy, strength and ductility. Of course, the present invention is not limited to this. In other embodiments, the annealing temperature may be 210 to 250°C, 220 to 250°C, 230 to 250°C, or 240 to 250°C. Further, the annealing temperature may be 200°C, 210°C, 220°C, 230°C, 240°C, or 250°C. In addition, in this embodiment, the heat preservation time is 2 to 6 hours. Preferably, the aluminum foil is annealed using a traditional batch type annealing furnace with lower production cost.

In detail, in the second cold rolling step, the third thickness is 0.012 to 0.02 mm. Of course, the present invention is not limited to this. In other embodiments, the third thickness may be 0.012, 0.013, 0.014, 0.015, 0.016, 0.017, 0.018, 0.019, or 0.02 mm.

The aluminum foil produced by the foregoing method of manufacturing aluminum foil of the present invention contains by weight: 0.15 wt% to 1.6 wt% iron, 0.015 wt% to 0.03 wt% copper, 0.01 to 0.2 wt% silicon, 0.02 to 0.04 wt% of titanium, and the rest is aluminum. Preferably, the copper accounts for 0.015 wt% to 0.025 wt% of the total weight of the aluminum foil.

Table 1 shows the comparison results of the yield strength, tensile strength, and elongation of the examples and the comparative examples. The examples are aluminum foils prepared by the method of manufacturing aluminum foil of the present invention, and the comparative examples are aluminum foils manufactured based on the method of manufacturing aluminum foil of the present invention, omitting the addition of copper, annealing process, or raising the annealing temperature.

Table 1 Numbering Fe (wt%) Cu (wt%) Thickness after hot rolling (mm) Intermediate annealing thickness (mm)/temperature (°C) Yield strength (MPa) Tensile strength (MPa) Extension rate (%) Example 1 0.21 0.02 4.5 1.5/250 184 212 4.2 2 0.40 0.02 4.5 1.5/200 188 226 3.9 3 0.40 0.02 4.5 1.5/220 187 223 3.7 4 0.40 0.02 4.5 1.5/250 186 221 3.7 5 0.40 0.02 4.5 1.0/250 180 211 3.0 6 1.51 0.19 2.5 1.5/250 191 235 3.0 Comparative example 1 0.21 0.02 4.5 no 181 204 3.5 2 0.41 no 4.5 no 132 149 5.9 3 0.41 no 4.5 0.6/390 132 153 3.1 4 0.40 0.02 4.5 0.6/390 165 190 1.9 5 0.40 0.02 4.5 1.5/450 183 211 3.0 6 1.53 no 4.5 no 148 184 4.5 7 1.53 no 4.5 1.2/250 145 181 3.9 8 1.51 0.19 2.5 no 182 211 3.0 9 1.51 0.19 2.5 1.5/390 187 227 2.2

The following results can be obtained from Table 1:

With or without annealing process: the yield strength, tensile strength and elongation of Example 1 with the intermediate annealing process are better than those of Comparative Example 1 without the intermediate annealing process; and the yield strength of Example 6 with the intermediate annealing process And the tensile strength is better than Comparative Example 8 without intermediate annealing process.

Annealing temperature increase: the yield strength, tensile strength and elongation of Example 4 with an annealing temperature of 200 to 250°C are better than those of Comparative Example 5 with an annealing temperature of 300°C; and the annealing temperature is 200 to 250° The yield strength, tensile strength, and elongation of Example 6 of C are better than those of Comparative Example 9 where the annealing temperature is increased to 300°C.

In addition, it can also be observed that in the comparative example, the aluminum foil produced by omitting the addition of copper and omitting the intermediate annealing process or the increase of the annealing temperature has obvious yield strength, tensile strength, and elongation. Below the examples. In other words, in the method of manufacturing aluminum foil of the present invention, it is obtained by controlling the addition of copper, the annealing process and the annealing temperature to have better yield strength, tensile strength (greater than 210 MPa), and ductility ( More than 3%) aluminum foil.

To sum up, the method for manufacturing aluminum foil of the present invention can control the addition of copper and its specific content, no addition of manganese, annealing treatment and annealing temperature, so that the aluminum foil produced has better strength and ductility at the same time. Furthermore, it meets the requirements of the processing and application of the positive current collector of the lithium ion battery, and at the same time has good cold rolling performance to avoid strip breakage during foil rolling.

Although the present invention has been disclosed in preferred embodiments, it is not intended to limit the present invention. Anyone familiar with the art can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the present invention The scope of protection shall be subject to the scope of the attached patent application.

Claims (7)

A method of manufacturing aluminum foil, comprising the following steps: a casting molding step, casting aluminum broth into an aluminum blank, wherein the aluminum broth contains by weight: 0.15wt% to 1.6wt% iron, 0.02wt% copper, 0.01wt% % To 0.2wt% of silicon, 0.02wt% to 0.04wt% of titanium, and the rest is aluminum; a hot rolling step, hot-rolling the aluminum billet into a hot-rolled aluminum coil, the hot-rolled aluminum coil has a first thickness ; A first cold rolling step, cold-rolling the hot-rolled aluminum coil into a cold-rolled aluminum coil, the cold-rolled aluminum coil has a second thickness, wherein the second thickness is smaller than the first thickness; an annealing step, the The cold-rolled aluminum coil is partially annealed and kept warm after the partial annealing, wherein the partial annealing temperature is 200 to 250°C; and a second cold-rolling step, cold-rolling the cold-rolled aluminum coil after the annealing step to A third thickness, wherein the third thickness is smaller than the second thickness to make the aluminum foil. The method according to claim 1, wherein the first thickness is 2.5 to 4.5 mm. The method according to claim 1, wherein the second thickness is 0.6 to 1.5 mm. The method according to claim 1, wherein the third thickness is 0.012 to 0.02 mm. The method according to claim 1, wherein in the annealing step, the holding time is 2 to 6 hours. The method according to claim 1, wherein in the hot rolling step, the aluminum billet is preheated to 480 to 530° C. and kept at a temperature for 1 to 3 hours before being hot rolled into the hot rolled aluminum coil. The method according to claim 6, wherein the finishing temperature of the hot-rolled aluminum coil is less than 340°C.