JP2014031531A - Aluminum alloy plate for battery case and manufacturing method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an aluminum alloy plate for a battery case, excellent in laser weldability, moldability and blister resistance, and to provide a manufacturing method therefor.SOLUTION: An aluminum alloy plate for a battery case contains Fe:0.8 to 2.0 mass%, Si:0.03 to 0.20 mass%, Ti:0.004 to 0.050 mass% and the balance Al with inevitable impurities, and the quantity of the Fe solid solution is 10 to 70 ppm, intermetallic compounds are dispersed in the aluminum alloy plate, an average wall distance between the intermetallic compounds having a circle-equivalent diameter of 1 to 15 μm on the surface of the aluminum alloy plate is 20 μm or less, as well as the maximum diameter of the circle which can be drawn in a region free from the intermetallic compounds is 100 μm or less. A manufacturing method therefor is also provided.

Description

  The present invention relates to an aluminum alloy plate excellent in laser weldability, formability and anti-swelling resistance suitable for a battery case such as a lithium ion battery used in an automobile, a mobile phone, a digital camera, a notebook personal computer, and the like. Further, the present invention relates to a method capable of producing a high yield aluminum alloy.

  Many of the lithium ion secondary batteries use an aluminum material for both a can body and a case material made of a lid. Generally, a can body is manufactured by deep drawing and ironing an aluminum plate or an aluminum alloy plate by pressing. The lid is formed by punching or machining an aluminum plate or an aluminum alloy plate into a predetermined shape, and is provided with holes and depressions for attaching terminals, a liquid inlet, and the like. The can body has a deep cylindrical shape, but the lid has a shape close to a flat plate. The can and the lid are sealed by laser welding after enclosing an internal structure such as an electrode.

  Thus, the battery case material is required to have excellent laser weldability as well as excellent formability. In particular, in batteries for automobiles and the like, there are increasing cases where long-term durability is required for laser junctions. In recent years, the laser welding speed has been increased for efficient battery production, and the difficulty of laser welding has increased. Even in high-speed laser welding, there is a demand for an aluminum alloy plate for a battery case that has a small variation in penetration depth and weld trace (bead) width and that can provide a stable joint.

  In the Al-Mn-based A3003 aluminum alloy sheet, weld cracks (solidification cracks, hot cracks) are easily generated due to the stress of solidification shrinkage applied to the liquid phase remaining portion, and the strength of the welded portion is reduced accordingly. It becomes a problem. As an aluminum alloy plate excellent in laser weldability, an Al—Fe-based aluminum alloy plate represented by JIS 8079 and JIS 8021 has been proposed (Patent Documents 1 to 3).

  In order to obtain laser weldability, Patent Documents 1 and 2 specify the content of Fe and the like, and Patent Document 3 defines the content of Fe and the like and the number of dispersed intermetallic compounds of 2 to 5 μm. It is known that the effect of the Fe content on laser weldability is large, and in particular, the presence of intermetallic compounds increases the laser absorption rate, so that deep penetration is likely to be obtained.

  However, in these techniques, the impediment to stability in laser welding is not accurately grasped, and no solution is presented. In these conventional techniques, stable laser weldability cannot be obtained under welding conditions that have become unstable due to an increase in welding speed or the like. Specifically, when the intermetallic compound is locally dispersed or when a coarse intermetallic compound is present, the penetration depth and the bead are non-uniform, and the slag and metal scattered during welding It causes welding defects such as bead defects due to grains (sputtering). These non-uniformities and weld defects reduce the durability of the welded part, thus shortening the battery life. In the techniques of Patent Documents 1 to 3, the dispersion state of the intermetallic compound is not strictly controlled, and there is a possibility that non-uniformity of the welded portion and welding defects may occur.

  On the other hand, a lithium ion battery that repeatedly charges and discharges has a problem in resistance to swelling due to an increase in internal pressure during battery reaction and expansion of the battery case due to creep deformation. JIS8079 and JIS8021 aluminum alloy plates have inferior resistance to blistering because the strength after molding is inferior to that of JIS3003 aluminum alloy plates. The battery case is formed by combining a plurality of processes consisting of drawing and ironing. If the difference in strength of the base plate before and after molding is large, the battery case has a bottom that is not processed and a side wall that is processed. A large strength difference occurs between the two and cracks occur. Therefore, an aluminum alloy plate is desired which has a high strength after forming and a small difference in strength before and after processing (work hardening). Thus, work hardening property suitable for an aluminum alloy plate for battery cases is required. In Patent Document 1, an aluminum alloy plate that is difficult to work by actively precipitating Fe or Si dissolved in a matrix (matrix) is used, but the strength and blistering resistance after molding are low. not enough.

  Also, for example, a rolled material obtained by subjecting an ingot made of JIS8079 or JIS8021 alloy to hot rolling, cold rolling, and annealing and punched into a circular or elliptical shape according to the shape of the battery case is formed as a battery case. It is used as an aluminum alloy plate. When such an aluminum alloy plate is formed by a combination of drawing and ironing, an aluminum alloy plate having a high ear rate increases the amount of case edge cut and deteriorates the yield. Although a certain effect of preventing the deterioration of yield can be obtained by optimizing the plate shape, it is not sufficient. Therefore, an aluminum alloy plate for a battery case having a low ear rate that can improve the yield without depending on the optimization of the plate shape is desired.

JP 2011-140708 A JP 2007-262559 A JP 2009-52126 A

  The present invention was made against the background described above. By reliably and sufficiently controlling the distribution state of intermetallic compounds, excellent laser weldability can be stably obtained, and by optimizing the amount of Fe solid solution An object of the present invention is to provide an aluminum alloy sheet for battery cases having excellent formability.

  As a result of intensive studies to solve the problems as described above, the present inventors have rigorously adjusted the contents of Fe, Si, and Ti in the aluminum alloy plate, and at the same time, the manufacturing process, particularly the amount of face cutting, The present invention has been completed by finding that the above-mentioned problems can be solved by strictly regulating the homogenization treatment conditions, the hot rolling conditions, and the cold rolling conditions in the pre-annealing process.

  Specifically, the present invention contains Fe: 0.8 to 2.0 mass%, Si: 0.03 to 0.20 mass%, Ti: 0.004 to 0.050 mass% in claim 1, and the balance An aluminum alloy plate made of Al and unavoidable impurities, the Fe solid solution amount is 10 to 70 ppm, intermetallic compounds are dispersed in the aluminum alloy plate, An aluminum alloy plate for a battery case, wherein an average inter-wall distance between intermetallic compounds having 15 μm is 20 μm or less, and a maximum diameter of a circle drawn in a region where the intermetallic compound is not present is 100 μm or less It was.

  In the present invention, the absolute value of the ear ratio of the aluminum alloy plate is 10% or less.

  This invention is the manufacturing method of the aluminum alloy plate for battery cases of Claim 1 or 2 in Claim 3, Comprising: Fe: 0.8-2.0mass%, Si: 0.03-0.20mass% , Ti: Casting step of casting an aluminum alloy containing 0.004 to 0.050 mass%, the balance being Al and inevitable impurities; and homogenizing the ingot at a temperature of 450 to 620 ° C. for a holding time of 1 to 20 hours The minimum distance from the ingot surface to the interface between the chill layer and the coarse cell layer is tmin (mm), and the maximum distance from the ingot surface to the interface between the coarse cell layer and the fine cell layer is tmax. (Mm), a chamfering process for chamfering the ingot so that a chamfering amount T (mm) satisfies 3 ≦ T <tmin or tmax <T; a hot rough rolling process and an end temperature of 250 to 370 ° C. Hot pressure on ingot A battery case comprising: a hot rolling process including a hot finish rolling process; a cold rolling process for cold rolling the hot rolled material; and an annealing process for annealing the cold rolled material. It was set as the manufacturing method of the aluminum alloy plate for an automobile.

  This invention is the manufacturing method of the aluminum alloy plate for battery cases of Claim 1 or 2 in Claim 4, Comprising: Fe: 0.8-2.0mass%, Si: 0.03-0.20mass% A casting step of casting an aluminum alloy containing Ti: 0.004 to 0.050 mass%, the balance being Al and inevitable impurities; and a minimum distance from the ingot surface to the boundary surface between the chill layer and the coarse cell layer tmin (mm), where the maximum distance from the ingot surface to the boundary surface of the coarse cell layer and the fine cell layer is tmax (mm), so that the amount of chamfering T (mm) satisfies 3 ≦ T <tmin or tmax <T A chamfering process for chamfering the ingot; and a homogenization treatment process for homogenizing the ingot after the chamfering at a temperature of 450 to 620 ° C. for a holding time of 1 to 20 hours; Room temperature maintenance work held under A hot rolling process including a hot rough rolling process and a hot finish rolling process for hot rolling the ingot at an end temperature of 250 to 370 ° C; a cold rolling process for cold rolling the hot rolled material; An annealing step of annealing the cold-rolled material; and a method for producing an aluminum alloy plate for a battery case.

  The present invention provides a method for producing an aluminum alloy plate for a battery case according to claim 1 or 2, wherein Fe: 0.8 to 2.0 mass%, Si: 0.03 to 0.20 mass%. A casting process for casting an aluminum alloy containing 0.004 to 0.050 mass% of Ti, the balance Al and inevitable impurities; a chill layer and a coarse cell layer from the ingot surface without performing a homogenization treatment The minimum distance to the boundary surface is tmin (mm), the maximum distance from the ingot surface to the boundary surface of the coarse cell layer and the fine cell layer is tmax (mm), and the chamfering amount T (mm) is 3 ≦ T < a chamfering process for chamfering the ingot so as to satisfy tmin or tmax <T; and a heating and holding process before hot rough rolling in which the ingot after chamfering is held at a temperature of 450 to 620 ° C. for 1 to 20 hours. Is what you hold in A subsequent hot rough rolling step and a hot finish rolling step for hot rolling the ingot at an end temperature of 250 to 370 ° C .; a cold rolling step for cold rolling the hot rolled material And an annealing step of annealing the cold-rolled material. A method for producing an aluminum alloy plate for a battery case.

  According to a sixth aspect of the present invention, in the sixth aspect, the hot rough rolling step hot-rolls the ingot at a start temperature of 380 to 550 ° C and an end temperature of 330 to 480 ° C. It was supposed to be.

  In the seventh aspect of the present invention, according to any one of the third to sixth aspects, the rolling reduction in the cold rolling step is set to 50 to 85%. Furthermore, the present invention according to claim 8 is the method according to any one of claims 3 to 7, further comprising a cold rolling step after the annealing step.

  ADVANTAGE OF THE INVENTION According to this invention, the method which can manufacture the aluminum alloy plate for battery cases provided with the outstanding laser-weldability, a moldability, and a swelling resistance, and this outstanding aluminum alloy with a sufficient yield can be provided.

It is a conceptual diagram which shows the distance between walls between intermetallic compounds. It is a conceptual diagram which shows the circle which can be drawn in the area | region where an intermetallic compound does not exist. It is a conceptual diagram which shows the peak height and valley depth for ear rate measurement. It is a graph which shows the conceptual diagram of DC casting method, and the change of a cooling rate. It is a conceptual diagram which shows the minimum distance tmin from the ingot surface to the boundary surface of a chill layer and a coarse cell layer, and the maximum distance tmax from the ingot surface to the boundary surface of a coarse cell layer and a fine cell layer. It is sectional drawing of the square case which performed multistage press molding. It is a front view of a swelling tester.

The present invention is described in detail below.
1. First, the component composition of the aluminum alloy plate for battery case according to the present invention and the reason for limitation will be described. The aluminum alloy plate according to the present invention contains Fe: 0.8 to 2.0 mass%, Si: 0.03 to 0.20 mass%, Ti: 0.004 to 0.050 mass%, the balance being Al and inevitable. Consists of impurities.

1-1. Fe: 0.8-2.0 mass%
Fe is an important component element that greatly affects laser weldability, strength, and metal structure. Most of the matrix phase exists as Al—Fe intermetallic compounds. The presence of the Al—Fe-based intermetallic compound increases the laser absorptance and exhibits the effect of deepening the penetration during laser welding. In addition, since the recrystallization behavior during hot rolling and subsequent annealing changes depending on the dispersion state of the Al—Fe intermetallic compound, the amount of Fe is increased due to the occurrence of rough skin after forming due to coarse crystal grains. Greatly affects rate.

  If the Fe content is less than 0.8 mass% (hereinafter, simply referred to as “%”), the strength of the final plate is insufficient, the resistance to blistering decreases, the ear rate increases due to the coarsening of the crystal grains, and the skin becomes rough after molding. Cause. Furthermore, since the average inter-wall distance of the intermetallic compound having an equivalent circle diameter of 1 to 15 μm is increased and the region where no intermetallic compound exists is increased, stable laser weldability cannot be obtained.

On the other hand, when the content exceeds 2.0%, a coarse intermetallic compound having an equivalent circle diameter exceeding 15 μm is generated, and an intermetallic compound having an equivalent circle diameter of 1 to 15 μm is locally increased. As a result, the laser absorptance locally increases, the penetration depth and the bead width become nonuniform, and the stability of laser welding deteriorates. Furthermore, it not only causes welding defects due to spattering, but also causes cracking at the time of molding, so that the moldability is remarkably deteriorated.
Thus, the Fe content is set to 0.8 to 2.0%. A preferable Fe content is 1.0 to 1.6%.

1-2. Si: 0.03-0.20%
Si is an element that greatly affects laser weldability and work hardening. When the Si content is less than 0.03%, it is necessary to use a high purity aluminum ingot, which increases raw material costs. On the other hand, if it exceeds 0.20%, the temperature difference between the liquidus and the solidus becomes large. By increasing this temperature difference, the amount of liquid phase remaining at the time of solidification immediately after laser welding is increased, and stress of solidification shrinkage is applied to the remaining portion of the liquid phase, so that welding cracks are likely to occur. Further, by adding Si, Fe that is dissolved in the matrix phase is precipitated and it is difficult to work harden, which causes a decrease in strength after molding and a decrease in swelling resistance. Accordingly, the Si content is set to 0.03 to 0.20%. In addition, preferable Si content is 0.04 to 0.15%.

1-3. Ti: 0.004 to 0.050%
Ti is an element that greatly affects the solidification structure of the aluminum alloy. If the Ti content is less than 0.004%, the ingot crystal grains are not refined and become a coarse crystal grain structure, which not only causes streak-like defects in the aluminum alloy plate, but also increases the ear rate and rough skin. Cause. Moreover, since the effect of refining the solidified structure of the laser welded portion is reduced, it causes weld cracking. On the other hand, if the Ti content exceeds 0.050%, the effect of refining the solidified structure of the laser weld is saturated. Furthermore, a coarse Al—Ti intermetallic compound is formed, and this intermetallic compound is distributed in a streak pattern on the rolled sheet, causing surface defects. Accordingly, the Ti content is set to 0.004 to 0.050%. In addition, preferable Ti content is 0.007 to 0.030%.

1-4. Other Components In order to refine the crystal grain structure, a trace amount of at least one of B and C may be added in combination with Ti. When both B and C are added, the total amount of both is preferably 0.0001 to 0.0020% when either one is added instead. In addition, a more preferable addition amount is 0.0005 to 0.0015%. When the addition amount is less than 0.0001%, the effect of crystal grain refinement is small. On the other hand, when the addition amount exceeds 0.0020%, not only the crystal grain refining effect is saturated, but also surface defects due to coarse aggregates of Ti-B compounds and Ti-C compounds are likely to occur.

1-5. Inevitable impurities Cu: 0.02% or less, Mn: 0.02% or less, Mg: 0.02% or less, Cr: 0.02% or less, Zn: 0.02% or less, Zr: About 0.02% or less, and about 0.05% or less in total as other components, you may contain these 1 type (s) or 2 or more types. If it is such component content, the characteristic as an aluminum alloy plate for battery cases will not be impaired.

  In the aluminum alloy sheet for battery cases according to the present invention, not only the component composition of the aluminum alloy is specified as described above, but also the final amount of the Fe solid solution and the size and dispersion of the intermetallic compound. It is necessary to specify the state. This will be described in detail below.

2. Fe solid solution amount The amount of Fe solid solution in the aluminum alloy plate greatly affects the strength and work hardenability after forming. The amount of Fe solid solution in the aluminum alloy plate according to the present invention is 10 to 70 ppm. When the amount of Fe solid solution is less than 10 ppm, it is difficult to work and harden, so that the strength after molding is insufficient and the resistance to swelling is poor. If the amount of Fe solid solution exceeds 70 ppm, the difference in strength before and after molding increases, and cracks occur during molding. As described above, the Fe solid solution amount is set to 10 to 70 ppm. A preferable Fe solid solution amount is 15 to 70 ppm.

3. Size and dispersion state of intermetallic compound The size and dispersion state of the intermetallic compound greatly affect laser weldability. An intermetallic compound is dispersed in the aluminum alloy plate. Therefore, the average inter-wall distance between the intermetallic compounds having an equivalent circle diameter of 1 to 15 μm on the surface of the aluminum alloy plate can be set to 20 μm or less, and the intermetallic compound having an equivalent circle diameter of 1 to 15 μm can be drawn in the region. The maximum diameter of the circle is 100 μm or less. As a result, a stable weld with uniform penetration depth and bead width can be obtained, and a sound weld with no welding defects can be obtained. Such an effect can be obtained by increasing the laser absorption rate by the intermetallic compound and by uniformly dispersing the intermetallic compound.

  A fine intermetallic compound having an equivalent circle diameter of less than 1 μm has little effect on laser weldability. In addition, when there is a coarse intermetallic compound having an equivalent circle diameter exceeding 15 μm, an increase in the laser absorption rate occurs locally. If it does so, not only the penetration will become deep especially in the local part but it will also be a cause of a welding defect etc. by non-uniform bead and spatter generating. Therefore, the superiority or inferiority of laser weldability can be determined by examining the dispersion state of the intermetallic compound for an intermetallic compound having an equivalent circle diameter of 1 to 15 μm.

  When the average inter-wall distance between intermetallic compounds having an equivalent circle diameter of 1 to 15 μm exceeds 20 μm, the distribution of intermetallic compounds becomes sparse, and laser weldability with a stable beat width and penetration depth can be obtained. Can not. Therefore, the average inter-wall distance between the intermetallic compounds having an equivalent circle diameter of 1 to 15 μm is set to 20 μm or less. A preferable average wall distance is 10 μm or less. The lower limit value of the average wall distance is not particularly specified. However, this lower limit is naturally determined by the component composition of the aluminum alloy plate and the manufacturing process, and is about 2 μm in the manufacturing process according to the present invention described later.

FIG. 1 is a conceptual diagram of the inter-wall distance between intermetallic compounds. The average inter-wall distance is an intermetallic compound having an equivalent circle diameter of 1 to 15 μm existing within an area of 250,000 μm ^{2 on} the surface of the aluminum alloy plate, and between the intermetallic compounds between adjacent intermetallic compounds in each intermetallic compound. This is the arithmetic average of the distance measurements. The definition of the distance between walls is expressed by the following formula.
(Distance between walls) = (Distance between centroids of adjacent particles)-(Sum of circle equivalent radii of two particles)
In order to measure the distance between the walls by observing the surface of the aluminum alloy plate, for example, a scanning electron microscope is used. In the measurement, it is necessary to observe an intermetallic compound having an equivalent circle diameter of 1 μm or more at a magnification allowing visual recognition.

  When the maximum diameter of a circle that can be drawn in a region where an intermetallic compound having a circle-equivalent diameter of 1 to 15 μm does not exist exceeds 100 μm, a region having a low laser absorption rate exists. When such a low laser absorption region is laser-welded, the penetration becomes shallow and the stability of the welded portion decreases. For example, when used in a case of a lithium ion battery that repeatedly charges and discharges, internal pressure rises during battery reaction, and the battery case expands due to creep deformation, so that destruction proceeds from a portion where the penetration is shallow. As described above, the maximum diameter of a circle that can be drawn in a region where an intermetallic compound having an equivalent circle diameter of 1 to 15 μm does not exist is set to 100 μm or less. The maximum diameter is preferably 50 μm or less. However, this lower limit is naturally determined by the composition of the aluminum alloy plate and the manufacturing process, and is about 19 μm in the manufacturing process according to the present invention described later.

  FIG. 2 is a conceptual diagram of a circle that can be drawn in a region where there is no intermetallic compound having an equivalent circle diameter of 1 to 15 μm. As shown in the figure, when granular intermetallic compounds having an equivalent diameter of 1 to 15 μm are distributed, a circle C indicated by a dotted line in the figure is a circle drawn in a region A where these intermetallic compounds do not exist. It will have the largest diameter (D).

Such a circle is measured by measuring the maximum diameter of a circle that can be drawn in each region where an intermetallic compound having a circle equivalent diameter of 1 to 15 μm does not exist within an area of 250,000 μm ^{2 on} the surface of the aluminum alloy plate. In order to measure such a circular diameter by observing the surface of the aluminum alloy plate, for example, a scanning electron microscope is used. In the measurement, it is necessary to observe an intermetallic compound having an equivalent circle diameter of 1 μm or more at a magnification allowing visual recognition.

  As described above, a metal whose average inter-wall distance between intermetallic compounds having an equivalent circle diameter of 1 to 15 μm is 20 μm or less and whose maximum diameter of a circle drawn in a region where the intermetallic compound does not exist is 100 μm or less An aluminum alloy plate having an intermetallic compound distribution exhibits good laser weldability because the intermetallic compound is uniformly dispersed.

4). Ear rate The absolute value of the ear rate has a great effect on the margin cut-off amount and yield when an aluminum alloy sheet is formed. When the absolute value of the ear ratio exceeds 10%, the edge cut-off amount after molding increases and the yield may deteriorate. For this reason, the absolute value of the ear rate is preferably 10% or less. The ear rate is desirably as small as possible, and the more preferable absolute value of the ear rate is 8% or less, and the more preferable absolute value of the ear rate is 5% or less. In addition, a deep drawing test is performed using a base of 62 mmφ with a universal drawing tester, and the ear rate m (%) is calculated from the measured values of the following ear height, average peak height, and average valley depth. FIG. 3 (a) shows a conceptual diagram when there are four peaks, and FIG. 3 (b) shows a conceptual diagram when there are eight peaks. In either case, the ear rate m (%) is calculated from the following equation.

Ear height e = Hh-HL (mm)
Average mountain height Hh = (Hh1 + Hh2 + Hh3 + Hh4) / 4
Average valley depth HL = (HL1 + HL2 + HL3 + HL4) / 4
Ear rate m = (e / HL) × 100 (%)
In addition, as shown in FIG. 3B, when there are a total of eight mountains and a lower mountain exists between the two mountains, the two valleys existing between these two mountains The lower one is designated as HL. Moreover, since e may be a negative numerical value depending on the magnitude relationship between Hh and HL, the absolute value is used as the ear rate.

5. Next, the manufacturing method of the aluminum alloy plate for battery cases which concerns on this invention is demonstrated in detail. The manufacturing method of the aluminum alloy plate for battery cases which concerns on this invention is a manufacturing method of the aluminum alloy plate for battery cases of Claim 1 or 2 in 1st Embodiment, Comprising: Fe: 0.8-2. A casting process for casting an aluminum alloy containing 0 mass%, Si: 0.03 to 0.20 mass%, Ti: 0.004 to 0.050 mass%, and the balance Al and inevitable impurities; A homogenization treatment step of homogenizing at ˜620 ° C. with a holding time of 1 to 20 hours; tmin (mm) as the minimum distance from the ingot surface to the boundary surface between the chill layer and the coarse cell layer, and the coarse cell layer And a chamfering step of chamfering the ingot such that the chamfering amount T (mm) satisfies 3 ≦ T <tmin or tmax <T, where tmax (mm) is the maximum distance to the boundary surface of the fine cell layer; heat A hot rolling process including a rough rolling process and a hot finish rolling process for hot rolling the ingot at an end temperature of 250 to 370 ° C; a cold rolling process for cold rolling a hot rolled material; And an annealing step for annealing the material.

  In the second embodiment, the method for producing an aluminum alloy plate for a battery case according to the present invention is provided with the homogenization treatment step provided before the chamfering step in the first embodiment after the chamfering step. Furthermore, in the third embodiment, the heating and holding process conditions of the ingot before hot rough rolling are set to a temperature of 450 to 620 ° C. without specially providing a homogenization treatment process as in the first and second embodiments. In this heating and holding step, the homogenization effect was obtained by setting the holding time to 1 to 20 hours.

  Here, the hot rough rolling step may hot-roll the ingot at a start temperature of 380 to 550 ° C. and an end temperature of 330 to 480 ° C. Furthermore, the rolling reduction in the cold rolling step is preferably 50 to 85%. Further, a further cold rolling step (final cold rolling step) may be provided after the annealing step.

5-1. Casting process First, an aluminum alloy melt adjusted within the above component composition range is appropriately subjected to a melt treatment such as a degassing treatment and a filtration treatment, and then cast according to a conventional method such as a DC casting method.

5-2. Homogenization treatment step A homogenization treatment step of homogenizing the ingot at a temperature of 450 to 620 ° C for a holding time of 1 to 20 hours is provided at least before or after the chamfering step. In this invention, the case where a homogenization process is provided before the chamfering process is defined in the first embodiment, and the case where the homogenization process is provided after the chamfering process is defined in the second embodiment. The homogenization treatment has a great influence on the metal structure and intermetallic compound size and dispersion state in the final plate. If the temperature of the homogenization treatment is less than 450 ° C. or the holding time of the homogenization treatment is less than 1 hour, the homogenization effect is small, and in the hot rough rolling process and hot finish rolling process, as well as in the intermediate annealing process and final annealing process The recrystallized grains become coarse. Due to such coarse recrystallized grains, the ear rate increases, and rough skin after molding occurs. When the temperature of the homogenization treatment exceeds 620 ° C., the fine intermetallic compound is dissolved, and the coarse intermetallic compound is further coarsened, so that a region where no intermetallic compound exists is widened. Thereby, stable laser weldability cannot be obtained. Moreover, even if the holding time of the homogenization treatment exceeds 20 hours, the homogenization effect is not improved, which is uneconomical from the viewpoint of manufacturing cost. As described above, the homogenization treatment conditions are a temperature of 450 to 620 ° C. and a holding time of 1 to 20 hours. In addition, preferable homogenization treatment conditions are a temperature of 480 to 600 ° C. and a holding time of 3 to 15 hours. Since the ingot that has been homogenized is sufficiently homogenized, the holding time and holding temperature in the subsequent heating and holding step before hot rough rolling are not particularly limited, and normal conditions are adopted. May be.

5-3. Chamfering process The ingot after the casting process is once held at room temperature and then chamfered (second and third embodiments), and the ingot after the homogenization process is once held at room temperature and then chamfered. (First embodiment). The amount of chamfering greatly affects the size and dispersion state of the intermetallic compound on the aluminum alloy plate surface. FIG. 4 shows a conceptual diagram of the DC casting method and a graph showing changes in the cooling rate. The molten metal injected into the DC mold comes into contact with the water-cooled mold wall and is rapidly cooled. The ingot surface layer produced by solidification shrinks, and a gap is formed between the ingot surface and the mold. Since the heat transfer resistance of the gap is much larger than that of the mold or spray water, the amount of heat diffused from the ingot to the outside decreases, and the cooling rate also decreases accordingly. When the ingot descends and the ingot surface comes into contact with the spray water, the cooling rate increases rapidly. In the region where it is rapidly cooled by contact with the water-cooled mold wall, a fine micro-solidified structure called a chill layer is formed, and in the region where the cooling rate decreases due to the formation of voids between the ingot surface and the mold, the coarse cell When the ingot surface falls into contact with the spray water when the ingot descends and the ingot surface comes into contact with the spray water, a fine micro solidified structure called a fine cell layer is generated. The In the coarse cell layer, a coarse intermetallic compound exceeding 15 μm is easily crystallized, whereby a region where no intermetallic compound having an equivalent circle diameter of 1 to 15 μm does not exist is easily formed. If the coarse cell layer remains exposed on the aluminum alloy plate surface, stable laser weldability cannot be obtained. Therefore, it is necessary to adjust the chamfering amount so that the coarse cell layer is not exposed and remains on the aluminum alloy plate surface. In addition, since the location and thickness of the coarse cell layer change depending on casting conditions such as casting speed, cooling conditions, and molten metal temperature, it is not possible to simply determine the amount of chamfering.

  Specifically, the minimum distance from the ingot surface to the boundary surface between the chill layer and the coarse cell layer is tmin (mm), and the maximum distance from the ingot surface to the boundary surface between the coarse cell layer and the fine cell layer is tmax ( mm), and the chamfering length from the ingot surface in the direction from the ingot surface to the coarse cell layer is the chamfering amount T (mm), 3 ≦ T <tmin (1) or tmax <T ( It is necessary to adjust the chamfering amount T so that 2). Here, the ingot surface serving as a reference for tmin and tmax is the ingot surface at the thickest part of the ingot.

  FIG. 5 shows a conceptual diagram of tmin and tmax. In the case where the above formula (1) is satisfied, the chamfering amount T is less than tmin. In this method, the coarse cell layer is left inside the ingot, and the coarse cell layer is chamfered without exposing and remaining on the ingot surface. Here, since the ingot surface is not flat, when the chamfering amount T is less than 3 mm, a part of the ingot surface may remain without being chamfered. Due to the lump surface, surface defects occur in the aluminum alloy plate. Therefore, in Equation (1), the lower limit value of T needs to be 3 (mm). When the chamfering amount T is tmin ≦ T ≦ tmax, that is, when the rough cell layer is exposed and remains on the ingot surface, the coarse cell layer is exposed and remains on the aluminum alloy surface. And stable laser weldability cannot be obtained. In the case where the above formula (2) is satisfied, the chamfering amount T exceeds tmax. This is to chamfer without leaving the coarse cell layer inside the ingot and without exposing and leaving the coarse cell layer on the ingot surface. Note that the upper limit of the chamfering amount T is not particularly specified in the formula (2), but when the chamfering amount T exceeds 40 mm, the yield deteriorates, which is not preferable from the viewpoint of manufacturing cost. Thus, the chamfering amount T is in the range of 3 ≦ T <tmin or tmax <T, and the preferable chamfering amount T is in the range of 5 ≦ T <(tmin−2) or (tmax + 2) <T.

By observing the ingot slice plate subjected to the surface treatment, tmin and tmax can be measured. Specifically, after a slice plate having a cross section perpendicular to the casting direction is collected, the cross section is ground, and the slice plate is immersed in a 5% NaOH aqueous solution at 50 to 60 ° C. for about 2 to 10 minutes. The temperature and time of the immersion treatment may be appropriately adjusted depending on the state of the metal structure appearing on the surface of the slice plate after the treatment. After the dipping treatment, the smut adhering to the slice plate surface in the first dipping treatment is removed by further dipping treatment in a 30% HNO ₃ aqueous solution at room temperature. From the metal structure that appears on the surface of the slice plate after smut removal, the location of the coarse cell layer can be specified. Therefore, tmin and tmax are obtained by measuring the minimum distance from the ingot surface to the boundary surface between the chill layer and the coarse cell layer and the maximum distance from the ingot surface to the boundary surface between the coarse cell layer and the fine cell layer. .

5-4. Hot rolling process 5-4-1. Heating and holding step The chamfered ingot is subjected to a hot rolling step. The hot rolling step includes a heating and holding step of heating the faced ingot at a predetermined temperature for a predetermined time before rolling. The ingot thus heated is then hot rolled. Hot rolling includes a hot rough rolling process after the heating and holding process and a hot finish rolling process that follows the hot rolling process. Here, without performing the above-mentioned homogenization treatment before and after the chamfering process, by setting the heating and holding process in the hot rolling process to appropriate conditions (holding temperature and holding time), You may make it provide the homogenization process effect with the heating effect before a rough rough rolling (3rd embodiment). By adopting such a heating and holding step, not only the effects similar to the homogenization treatment can be obtained, but also the number of production steps and production costs can be reduced compared to the case where the homogenization treatment step is provided before and after the chamfering step. This is advantageous in terms of reduction. On the other hand, in the case where the heating and holding step is performed under the condition that the homogenization treatment is not performed and the homogenization treatment effect is not obtained, the hot rough rolling step and the hot finish rolling step, and the intermediate annealing step and In the final annealing step, the recrystallized grains become coarse. Furthermore, due to such coarse recrystallized grains, the ear rate is increased, and rough skin after molding occurs.

  In order to obtain a homogenizing effect by the heating and holding step without providing a homogenizing step, the holding time is 450 to 620 ° C. and the holding time is 1 to 20 hours. When the holding temperature is less than 450 ° C. or the holding time is less than 1 hour, the homogenization effect is small, and the recrystallized grains become coarse in the hot rough rolling process and the hot finish rolling process, as well as in the intermediate annealing process and the final annealing process. . Due to such coarse recrystallized grains, the ear rate increases, and rough skin after molding occurs. When the holding temperature exceeds 620 ° C., the fine intermetallic compound is dissolved, and the coarse intermetallic compound is further coarsened, so that a region where no intermetallic compound exists is widened. Thereby, stable laser weldability cannot be obtained. Further, even if the holding time exceeds 20 hours, the homogenizing effect is not improved, which is uneconomical from the viewpoint of manufacturing cost. Moreover, since the manufacturing efficiency of the subsequent hot rough rolling process and hot finish rolling process falls, preferable homogenization processing conditions are the temperature of 480-600 degreeC, and holding time 3-15 hours.

5-4-2. Hot rough rolling process The starting temperature of the hot rough rolling process greatly affects the recrystallization behavior after the hot rough rolling process. If the hot rough rolling start temperature is less than 380 ° C., a uniform recrystallized structure after the hot rough rolling is not obtained, which may cause an increase in ear rate and rough skin after forming. On the other hand, if the hot rough rolling start temperature exceeds 550 ° C., the recrystallized grains after the hot rough rolling are coarsened, which may cause an increase in the ear rate that leads to deterioration of formability. Moreover, since the oxide (roll coating) produced | generated on the roll surface at the time of rolling is transcribe | transferred to the aluminum alloy plate surface, it may become a cause of a stripe-like defect. As described above, the hot rough rolling start temperature is preferably 380 to 550 ° C. A more preferable hot rough rolling start temperature is 400 to 520 ° C.

  The end temperature of the hot rough rolling process has a great influence on the recrystallization behavior after the end of hot rough rolling. If the hot rough rolling end temperature is less than 330 ° C., a uniform recrystallized structure after the hot rough rolling is not obtained, which may cause an increase in ear rate and rough skin after forming. On the other hand, if the hot rough rolling finish temperature exceeds 480 ° C., the recrystallized grains after the hot rough rolling finish may become coarse, which may cause an increase in the ear rate that leads to a deterioration in formability. As described above, the hot rough rolling finish temperature is preferably 330 to 480 ° C. A more preferable hot rough rolling end temperature is 360 to 450 ° C.

5-4-3. Hot finish rolling process The hot finish rolling method includes a tandem method in which a plurality of rolling mills are combined and a reverse method in which hot rolling is performed with a single rolling mill. Hot finish rolling refers to rolling in which a plurality of rolling mills are combined in the case of the tandem method, and from rolling immediately before winding to the final rolling in the case of the reverse method. The plate thickness at which hot finish rolling is started is about 15 to 40 mm. In the present invention, the hot finish rolling start temperature is not particularly specified, but since hot finish rolling is performed immediately after the hot rough rolling is completed, the hot rough rolling finish temperature and the hot finish rolling are performed. The temperature difference between the starting temperatures is within 20 ° C. If the temperature difference is within 20 ° C., the moldability is not impaired.

  The end temperature of the hot finish rolling step has a great influence on work hardening and recrystallization behavior after the end of hot finish rolling. When the finish temperature of hot finish rolling is less than 250 ° C., the amount of Fe solid solution decreases, and work hardening becomes difficult. As a result, the strength after molding decreases and the swelling resistance is poor. On the other hand, when the finish temperature of hot finish rolling exceeds 370 ° C., the amount of Fe solid solution increases and it becomes easy to work harden. As a result, cracks occur during molding. Furthermore, since the rolled material is in a high temperature state after the hot rolling finishing process is completed, not only self-recrystallization proceeds in the hot rolling finished state, but also the recrystallized grains become coarse. As a result, the ear rate increases, which causes rough skin after molding. Thus, the hot finish rolling end temperature is set to 250 to 370 ° C. In addition, preferable hot finish rolling completion | finish temperature is 300-360 degreeC.

5-5. Cold rolling process after hot finish rolling The rolled material subjected to the hot finish rolling process is subjected to the cold rolling process. The reduction ratio in this cold rolling step has a great influence on the recrystallization behavior in the subsequent annealing step (intermediate annealing or final annealing). When the rolling reduction is less than 50%, the amount of accumulated strain is small, and the recrystallized grains may become coarse. As a result, the ear rate increases and causes rough skin. On the other hand, when the rolling reduction exceeds 85%, the number of cold rolling increases, which is not preferable from the viewpoint of manufacturing cost. Therefore, it is preferable that the rolling reduction in the cold rolling process after the hot finish rolling process is 50 to 85%. A more preferable rolling reduction is 55 to 80%.

5-6. Annealing process and further cold rolling process (final cold rolling process)
Depending on the tempering of the final aluminum alloy sheet, it may be subjected to the final annealing process after the cold rolling process described above, or after being subjected to the intermediate annealing process after the cold rolling process, the final cold rolling process may be performed as a final cold rolling process. Hot rolling may be performed. It does not specifically limit as conditions of a final annealing process and an intermediate annealing process, What is necessary is just to carry out according to a conventional method. As preferable annealing conditions, when using a batch annealing furnace, the holding time is 1 to 8 hours at a temperature of 350 to 450 ° C., and when using a continuous annealing furnace, the holding time is 0 to 30 seconds at a temperature of 400 to 550 ° C. (Here, the holding time of 0 second means that the cooling is performed immediately after reaching the predetermined temperature). Moreover, what is necessary is just to carry out in accordance with a conventional method also about the final cold rolling process conditions after an intermediate annealing process, but 20-60% of a reduction rate is preferable normally. In addition, you may perform leveler correction after the last cold rolling process.

As mentioned above, although the manufacturing method of the aluminum alloy plate for battery cases which concerns on this invention was demonstrated, in this manufacturing method, there exists the following 1st-3rd embodiment.
The first embodiment includes a homogenization process before the chamfering process, and the second embodiment includes a homogenization process after the chamfering process. As described above, since the first and second embodiments include a homogenization treatment step, a favorable size and dispersion state in the metal structure and the intermetallic compound are obtained as a remarkable homogenization effect as compared with the third embodiment described later. It is done. In the second embodiment, the ingot is kept at room temperature from the homogenization temperature and then heated until the heating and holding step in hot rolling. Then, hot rough rolling is performed immediately after the heating and holding step, or hot rough rolling is performed after cooling to the start temperature of hot rough rolling.

  Next, in the third embodiment, the casting process, the chamfering process, and the hot rolling process are performed in this order. In this third embodiment, the homogenization process is not adopted, but after the casting process, the ingot is subjected to the chamfering process and then the heating and holding process in the hot rolling process has the same role as the homogenization process. It is subjected to hot rolling. This third aspect is advantageous in terms of manufacturing cost because the homogenization process can be omitted.

  In this third embodiment, when the difference between the temperature of the heating and holding step and the starting temperature of hot rolling is large, the ingot is heated and held to a predetermined temperature through the heating and holding step, and then the starting temperature of hot rolling. It is preferable to cool to a low temperature and then subject to hot rolling. In this case, by controlling the cooling of the heated and held ingot, the start temperature and end temperature of hot rough rolling and hot finish rolling can be adjusted to appropriate temperatures. On the other hand, when the temperature difference is small, the ingot is hot-rolled immediately from the heating and holding step without passing through the cooling step. In this case, since it does not go through the cooling stage, it can be quickly transferred to the hot rolling process, but the start and end temperatures of hot rough rolling and hot finish rolling tend to be high, and coarse recrystallized grains are generated. Or high Fe solid solution amount.

  Below, this invention is demonstrated in detail based on this invention example and a comparative example. The conditions other than those described in the claims are within the range of ordinary conditions. These examples of the present invention and comparative examples do not limit the technical scope of the present invention.

Invention Examples 1-27 and Comparative Examples 28-46
Aluminum alloys having the compositions shown in Table 1 were cast by a semi-continuous casting method. In addition, about the component of less than 0.01%, it was set as 0.00%. The obtained ingot was subjected to the production conditions shown in Tables 2 and 3 to obtain an aluminum alloy plate having a final thickness of 0.8 mm. In the first embodiment, the homogenization treatment was performed, the ingot was held at room temperature and then chamfered, and then the chamfered ingot was heated in the heating and holding step in the hot rolling step. Furthermore, by subjecting the heated ingot to the steps of hot rough rolling, hot finish rolling, cold rolling, intermediate (final) annealing, and if necessary, final cold rolling in this order, the final An aluminum alloy plate having a thickness of 0.8 mm was obtained. In the second embodiment, the ingot was chamfered and then homogenized, and then the ingot was heated in the heating and holding step in the hot rolling step. Furthermore, by subjecting the heated ingot to the steps of hot rough rolling, hot finish rolling, cold rolling, intermediate (final) annealing, and if necessary, final cold rolling in this order, the final An aluminum alloy plate having a thickness of 0.8 mm was obtained. In the third aspect, the ingot cast by the semi-continuous casting method is chamfered, and the chamfered ingot is heated in the heating and holding step in the hot rolling step as a step for homogenization. In the case where the temperature difference between the heating temperature of the heating and holding step and the hot rough rolling start temperature in the hot rolling step is 30 ° C. or less, hot rough rolling, hot finish rolling without passing through the cooling step from the heating and holding step, By subjecting each step of cold rolling, intermediate (final) annealing, and if necessary, final cold rolling in this order, an aluminum alloy plate having a final thickness of 0.8 mm was obtained. In addition, when the temperature difference between the heating temperature in the heating and holding step and the hot rough rolling start temperature in the hot rolling step exceeds 30 ° C, after cooling to the starting temperature of the hot rough rolling after completion of the heating and holding step By subjecting each process of hot rough rolling, hot finish rolling, cold rolling, intermediate (final) annealing, and final cold rolling in this order, aluminum having a final thickness of 0.8 mm An alloy plate was obtained (the third embodiment). However, in Comparative Example 26, the final thickness was 1.5 mm, and in Comparative Examples 31 and 33, the final thickness was 1.0 mm. In Tables 2 and 3, "-" in the steps of homogenization treatment and final cold rolling means that these steps were not performed. Further, as described above, the chamfering amount T was determined by measuring tmin and tmax from the obtained ingot slice. Tables 2 and 3 also show chamfering amounts T, tmin, and tmax.

  Evaluation was performed by the following method using the aluminum alloy sheet material sample prepared as described above.

(Fe solid solution amount)
The amount of Fe solid solution was measured as follows. After 50 mL of phenol was weighed in a preheated round bottom flask and water in the phenol was removed, 0.5 g of an aluminum alloy plate sample was placed in the round bottom flask, a reflux condenser was attached, and the mixture was heated and dissolved at 180 ° C. with a heater. After completion of dissolution, the mixture was kept heated at 180 ° C. for 15 minutes, and then 25 mL of benzyl alcohol was added and the whole was shaken. After maintaining this at room temperature, the entire contents of the round bottom flask were transferred to a 100 mL volumetric flask and benzyl alcohol was added to make a total of 100 mL solution. Next, 20 mL of this was weighed into a separatory funnel and 20.0 mL of a 5% aqueous citric acid solution was added. This was shaken for 10 minutes with a shaker, 10 mL of butyl acetate was added, and the mixture was allowed to stand for about 1 hour to perform liquid / liquid phase separation. The lower layer citric acid solution was collected while filtering with dry filter paper, and the amount of Fe was quantified with an ICP (Inductively Coupled Plasma) emission spectrometer. The results are shown in Tables 4 and 5.

(Dispersion state of intermetallic compound)
The dispersion state of the intermetallic compound having an equivalent circle diameter of 1 to 15 μm dispersed on the surface of the aluminum alloy plate was observed and measured using a scanning electron microscope (JSM-6460LA, manufactured by JEOL Ltd.) as described above. It was. Tables 4 and 5 show the average distance between the walls of the intermetallic compound having an equivalent circle diameter of 1 to 15 μm and the maximum diameter of the circle that can be drawn in the region where the intermetallic compound does not exist.

(Ear rate)
The absolute value of the ear ratio was obtained from the average crest height and the average trough depth of the edge of the molded sample as described above by performing a molding test using a universal drawing tester. The results are shown in Tables 4 and 5.

(Laser weldability)
The aluminum alloy sheet sample was subjected to final cold rolling that further reduced the thickness to 0.6 mm. The two rolled materials (short side: 60 mm, long side: 100 mm, thickness: 0.6 mm) prepared in this way were butted together at the long sides, and a laser welding test was performed over a total length of 100 mm. Here, the reason why the rolling is performed from 0.8 mm to 0.6 mm by the final cold rolling is because the plate thickness in the molded part of the battery case after molding is assumed. In addition, the butt | matching surface was planarized using the milling machine. Tests were conducted at welding speeds of 1 m / min, 5 m / min, and 20 m / min. The condensing diameter was 0.1 mmφ, the output was adjusted so that the average penetration depth was 70% with respect to the thickness of 0.6 mm of the rolled material, and laser welding was performed under continuous wave (CW, Continuous Wave) conditions. No termination processing was performed to reduce the output stepwise at the termination section.

<Soundness of laser welds>
About the sample after the said laser welding, the external appearance was observed visually over the full length (100 mm) of a welding part. Furthermore, 10 visual field observations of the weld cross section (cross section perpendicular to the welding direction) were made. In addition, the space | interval of each visual field in the welding part cross section was provided 10 mm or more.
In both appearance observation and cross-sectional observation, those with no weld cracks or bead defects are good (marked with ○), and those with at least one of weld cracks and bead defects are defective (marked with ×) It was determined. The results are shown in Tables 4 and 5.

<Stability of laser welds>
In the same manner as in the soundness evaluation, appearance observation and cross-sectional observation were performed on the sample after laser welding. With respect to the bead width, 10 bead widths at arbitrary positions were measured over the entire length of the welded portion of 100 mm, and the average bead width wave was calculated. Further, regarding the penetration depth, the penetration depth in 10 fields of the weld cross section (cross section perpendicular to the welding direction) was measured, and dave was calculated by the average penetration depth.

  The maximum bead width wmax, the minimum bead width wmin, the maximum penetration depth dmax and the minimum penetration depth dmin are measured, and wmax / wave, wmin / wave, dmax / dave, dmin / dave are all 0.9 to 1.1. Excellent in the range of (◎), better than 0.8 and less than 0.9 or more than 1.1 and less than 1.2 (○), less than 0.8 or more than 1.2 The thing of the range was determined to be bad (x mark). The results are shown in Tables 4 and 5.

(Formability and resistance to blisters)
The aluminum alloy plate was subjected to multi-stage molding, specifically, three-stage drawing test and ten-stage iron molding to form a square battery case 1 shown in FIG. This battery case 1 has a width of 30 mm, a height of 8 mm, a depth of 45 mm (not shown), an average plate thickness of 0.62 mm on the side surface, an average plate thickness of 0.51 mm on the top and bottom surfaces, and an angle R of 1.5 mm. It has a cross section.

<Appearance evaluation of the case>
The appearance of case 1 was evaluated. Surface defects such as cracks that occur during molding, and those that do not cause rough skin are excellent (marked with）), those that are free of surface defects and that have rough skin are good (marked with ○), and surface defects In the case where there was no surface roughness and the skin was rough, there was no problem in practical use, and the case where the skin was rough or a surface defect was judged as bad (×).

<Flip resistance of the case>
The case 1 was subjected to a heating internal pressure swelling test using a swelling tester 2 as shown in FIG. In the swelling tester 2 of FIG. 7, the case 1 is placed between the lower fixing jig 3 and the upper holding jig 4 via the upper surface sealing member 6 made of silicon rubber as well as the receiving member 5 made of silicon rubber. Clamped and pressurized with air pressure into the case 1 through the pressure supply pipe 7 from above. Further, the whole blister tester 2 holding the case 1 was heated and held at 70 ° C. in a thermostatic bath. The inside of case 1 was continuously pressurized with an air pressure of 1.5 kgf / cm ² for 24 hours, and the maximum amount of swelling of the case was measured. This heating internal pressure swelling test assumes a case where an internal pressure is generated by the expansion of the battery contents when the lithium ion battery is heated.

  Excellent blister resistance when the maximum blister amount is less than 1.0 mm (marked with ◎); The blister property was determined to be poor (x mark). The results are shown in Tables 4 and 5.

(Blank weight ratio required for ironing molding test)
The blank weight ratio required for the iron molding test represents the yield in case molding, and was determined by measuring the initial blank weight and the ear cutoff amount before ear cutting in the case molding test. Specifically, the obtained aluminum alloy plate was punched out into a circular shape and an elliptical shape in which the ratio of the major axis L to the minor axis S and L / S was 2, and a blank for molding was produced. Thereafter, using the obtained blank for molding, three-stage drawing was performed to obtain a drawn case with a width of 30 mm and a height of 8 mm. The ears generated in the drawing process cause cracks during the ironing process in a later process, and thus the ears need to be cut off. Cut off at the position of 1.5mm in the depth direction from the maximum valley depth of the ear. After the ears were cut off, the size of the initial blank, that is, the diameter in the case of a circle and the major axis and the minor axis in the case of an ellipse were determined so that the depth of the ironing case was 22 mm. Then, the initial weight W0 before cutting and the ear cutting amount WC were measured, and the ratio between the initial weight and the iron molding case weight, that is, the blank weight ratio necessary for the ironing test, W0 / (W0-WC) was obtained. The closer the blank weight ratio necessary for the ironing molding test is to 1, the smaller the edge cut-off amount after drawing and the better the yield. Therefore, the blank weight ratio necessary for the ironing molding test is 1.05 to 1.07, the blank weight ratio necessary for the ironing molding test is 1.08, and the blank weight ratio necessary for the ironing molding test is 1. The symbol “09” was Δ, and the blank weight ratio required for the molding test was 1.10 or more. ◎ and ○ were good, Δ was good, and x was bad. Here, since the maximum trough depth of the ear is cut off at a position of 1.5 mm in the depth direction, the minimum value of the blank weight ratio necessary for the ironing molding test is 1.05.

  In Invention Examples 1 to 27, the maximum amount of circle that can be drawn in a region where the solid solution amount of Fe is 10 to 70 ppm, the average inter-wall distance of an intermetallic compound having an equivalent circle diameter of 1 to 15 μm is 20 μm or less, and no intermetallic compound exists. The diameter was 100 μm or less, laser weldability, formability and blister resistance, and blank weight ratio required for the ironing molding test were excellent or good.

  In Comparative Example 28, since the chamfering position of the ingot is located inside the coarse cell layer, the average inter-wall distance of the intermetallic compound having a circle-equivalent diameter of 1 to 15 μm is large, and the intermetallic compound does not exist. Since the maximum diameter of the circle that can be drawn is large, variations in bead width and penetration depth were large, and bead defects were generated by sputtering, resulting in poor laser weldability.

  In Comparative Example 29, since the chamfering position of the ingot is located in the coarse cell layer, the average inter-wall distance of the intermetallic compound having an equivalent circle diameter of 1 to 15 μm is large and the intermetallic compound does not exist. Since the maximum diameter of the circle that can be drawn is large, variations in bead width and penetration depth were large, and bead defects were generated by sputtering, resulting in poor laser weldability.

  In Comparative Example 30, since the heat holding temperature was low and the hot finish rolling end temperature was low, it caused a decrease in the amount of Fe solid solution and an increase in the ear rate. For these reasons, moldability and blistering resistance are poor, and the weight ratio of the circle blank is increased to deteriorate the yield.

  In Comparative Example 31, since the homogenization temperature was high, the fine intermetallic compound was dissolved, the coarse intermetallic compound was coarsened, and the region where no intermetallic compound was present increased. As a result, the variation in the bead width and the penetration depth increased, and the stability of the laser welded portion was poor.

  In Comparative Example 32, since the finish temperature of hot finish rolling was high, the recrystallized grains during hot rolling were coarsened, resulting in rough skin after molding and an increase in ear rate. , And the weight ratio of the circle blank increased and yield deteriorated. Moreover, since the finish temperature of hot finish rolling was high, the amount of solid solution of Fe became high, and it was easy to work harden and cracks occurred during molding, so the appearance evaluation in formability was poor.

  In Comparative Example 33, since the aluminum alloy plate had a small amount of Fe, the strength of the base plate was low and the resistance to blistering was poor. In addition, the recrystallized grains became coarse, which caused rough skin after molding and increased ear rate. As a result, formability and blister resistance were poor, and the weight ratio of the circle blank was increased, resulting in a deterioration in yield. Furthermore, since the average inter-wall distance of the intermetallic compound having an equivalent circle diameter of 1 to 15 μm is increased and the region where the intermetallic compound is not present is increased, the stability of the laser welded portion is poor.

  In Comparative Example 34, since the amount of Fe is large, a coarse intermetallic compound having an equivalent circle diameter exceeding 15 μm is generated, and the intermetallic compound having an equivalent circle diameter of 1 to 15 μm is locally increased to locally increase the laser absorption rate. Therefore, the penetration depth and bead width became non-uniform, and this caused welding defects caused by sputtering. Further, since the amount of Mn is large, the penetration depth during laser welding locally increased. As a result, the laser weldability (soundness and stability of the laser welded portion) was poor. Moreover, moldability and swelling resistance were poor.

  In Comparative Example 35, since the amount of Si was large, the temperature difference between the liquidus and solidus became large and weld cracking was likely to occur. Specifically, no weld cracking occurred in low speed welding at 1 m / min, but welding cracking occurred in high speed welding at 5 m / min or more, and the soundness of the laser welded portion was poor. Furthermore, the swelling resistance was poor.

  In Comparative Example 36, since the Ti amount was small, the crystal grains of the ingot were coarsened. As a result, a streak-like defect occurred, which further caused rough skin after molding and an increase in the ear rate, resulting in poor appearance evaluation in formability, and increased the weight ratio of the circle blank and deteriorated yield. Moreover, since the effect of refining the solidified structure of the laser welded portion is small, weld cracks are likely to occur. Specifically, no weld cracking occurred in low speed welding at 1 m / min, but welding cracking occurred in high speed welding at 5 m / min or more, and the soundness of the laser welded portion was poor.

  In Comparative Example 37, since the amount of Ti was large, a coarse Al—Ti intermetallic compound was formed and surface defects were generated. Further, since the total amount of B and C is large, coarse agglomerates of Ti—B compounds and Ti—C compounds are formed, and surface defects are generated. Due to the occurrence of these surface defects, the appearance evaluation in formability was poor.

  In Comparative Example 38, it was a JIS3003 aluminum alloy, and since the amount of Si was large, weld cracking was likely to occur. Specifically, no weld cracking occurred in low speed welding at 1 m / min, but welding cracking occurred in high speed welding at 5 m / min or more, and the soundness of the laser welded portion was poor.

  In Comparative Example 39, the heat holding temperature was low and the hot finish rolling end temperature was low, which caused a decrease in the amount of Fe solid solution and an increase in the ear rate. For these reasons, moldability and blistering resistance are poor, and the weight ratio of the circle blank is increased to deteriorate the yield.

  In Comparative Example 40, since the heating and holding temperature was high and the finish temperature of hot finish rolling was also high, the recrystallized grains during hot rolling were coarsened, causing rough skin after molding and an increase in the ear rate. Therefore, the appearance evaluation in the formability was poor, the weight ratio of the circle blank was increased, and the yield was deteriorated. Moreover, since the finish temperature of hot finish rolling was high, the amount of solid solution of Fe became high, and it was easy to work harden and cracks occurred during molding, so the appearance evaluation in formability was poor.

  In Comparative Example 41, the heat holding temperature was low and the hot finish rolling end temperature was low, which caused a decrease in the amount of Fe solid solution and an increase in the ear rate. For these reasons, moldability and blistering resistance are poor, and the weight ratio of the circle blank is increased to deteriorate the yield.

  In Comparative Example 42, since the finish temperature of hot finish rolling was high, the recrystallized grains during hot rolling became coarse, causing rough skin after molding and an increase in the ear rate. , And the weight ratio of the circle blank increased and yield deteriorated. Moreover, since the finish temperature of hot finish rolling was high, the amount of solid solution of Fe became high, and it was easy to work harden and cracks occurred during molding, so the appearance evaluation in formability was poor.

  In Comparative Example 43, the heating retention time was short, which caused an increase in the ear rate. For these reasons, moldability and blistering resistance are poor, and the weight ratio of the circle blank is increased to deteriorate the yield.

  In Comparative Example 44, the homogenization temperature was low and the homogenization time was short, which caused an increase in the ear rate. For these reasons, moldability and blistering resistance are poor, and the weight ratio of the circle blank is increased to deteriorate the yield.

  In Comparative Example 45, since the homogenization temperature was high, the fine intermetallic compound was dissolved, the coarse intermetallic compound was coarsened, and the region where no intermetallic compound was present increased. As a result, the variation in the bead width and the penetration depth increased, and the stability of the laser welded portion was poor.

  In Comparative Example 46, the homogenization temperature was low and the homogenization time was short, which caused an increase in the ear rate. For these reasons, moldability and blistering resistance are poor, and the weight ratio of the circle blank is increased to deteriorate the yield.

  According to the present invention, it is possible to provide an aluminum alloy plate for a battery case that is compatible with laser weldability, formability, and blister resistance. Moreover, according to the manufacturing method of the aluminum alloy plate for battery cases which concerns on this invention, the said aluminum alloy plate for battery cases can be obtained reliably and stably with a sufficient yield.

DESCRIPTION OF SYMBOLS 1 ... Battery case 2 ... Swelling tester 3 ... Fixing jig 4 ... Holding jig 5 ... Receiving member 6 ... Seal member 7 ... Pressure supply pipe A ... Region where no intermetallic compound having an equivalent circle diameter of 1 to 15 μm exists C... Maximum diameter circle drawn on A D. Diameter of C Hh1, Hh2, Hh3, Hh4 ... Mountain height HL1 + HL2 + HL3 + HL4 ... Valley depth Tmin: Minimum distance (mm) from the ingot surface to the boundary surface between the chill layer and the coarse cell layer
tmax: Maximum distance (mm) from the ingot surface to the interface between the coarse cell layer and the fine cell layer

Specifically, the present invention contains Fe: 0.8 to 2.0 mass%, Si: 0.03 to 0.20 mass%, Ti: 0.004 to 0.050 mass% in claim 1, and the balance An aluminum alloy plate made of Al and unavoidable impurities, the Fe solid solution amount is 10 to 70 ppm, intermetallic compounds are dispersed in the aluminum alloy plate, An aluminum alloy for battery cases, wherein an average inter-wall distance between intermetallic compounds having 15 μm is 20 μm or less, and a maximum diameter of a circle drawn in a region where the intermetallic compounds are not present is 25 to 100 μm A board was used.

Invention Examples 1-4, 6-19, 21-27 and Comparative Examples 28-46
Aluminum alloys having the compositions shown in Table 1 were cast by a semi-continuous casting method. In addition, about the component of less than 0.01%, it was set as 0.00%. The obtained ingot was subjected to the production conditions shown in Tables 2 and 3 to obtain an aluminum alloy plate having a final thickness of 0.8 mm. In the first embodiment, the homogenization treatment was performed, the ingot was held at room temperature and then chamfered, and then the chamfered ingot was heated in the heating and holding step in the hot rolling step. Furthermore, by subjecting the heated ingot to the steps of hot rough rolling, hot finish rolling, cold rolling, intermediate (final) annealing, and if necessary, final cold rolling in this order, the final An aluminum alloy plate having a thickness of 0.8 mm was obtained. In the second embodiment, the ingot was chamfered and then homogenized, and then the ingot was heated in the heating and holding step in the hot rolling step. Furthermore, by subjecting the heated ingot to the steps of hot rough rolling, hot finish rolling, cold rolling, intermediate (final) annealing, and if necessary, final cold rolling in this order, the final An aluminum alloy plate having a thickness of 0.8 mm was obtained. In the third aspect, the ingot cast by the semi-continuous casting method is chamfered, and the chamfered ingot is heated in the heating and holding step in the hot rolling step as a step for homogenization. In the case where the temperature difference between the heating temperature of the heating and holding step and the hot rough rolling start temperature in the hot rolling step is 30 ° C. or less, hot rough rolling, hot finish rolling without passing through the cooling step from the heating and holding step, By subjecting each step of cold rolling, intermediate (final) annealing, and if necessary, final cold rolling in this order, an aluminum alloy plate having a final thickness of 0.8 mm was obtained. In addition, when the temperature difference between the heating temperature in the heating and holding step and the hot rough rolling start temperature in the hot rolling step exceeds 30 ° C, after cooling to the starting temperature of the hot rough rolling after completion of the heating and holding step By subjecting each process of hot rough rolling, hot finish rolling, cold rolling, intermediate (final) annealing, and final cold rolling in this order, aluminum having a final thickness of 0.8 mm An alloy plate was obtained (the third embodiment). However, in Comparative Example 26, the final thickness was 1.5 mm, and in Comparative Examples 31 and 33, the final thickness was 1.0 mm. In Tables 2 and 3, "-" in the steps of homogenization treatment and final cold rolling means that these steps were not performed. Further, as described above, the chamfering amount T was determined by measuring tmin and tmax from the obtained ingot slice. Tables 2 and 3 also show chamfering amounts T, tmin, and tmax.

In Invention Examples 1 to 4 , 6 to 19 , and 21 to 27, the amount of solid solution of Fe is 10 to 70 ppm, the average inter-wall distance of an intermetallic compound having an equivalent circle diameter of 1 to 15 μm, and the intermetallic compound is The maximum diameter of a circle that can be drawn in a non-existing region was 25 to 100 μm, and the laser weldability, formability and swell resistance, and the blank weight ratio required for the ironing test were excellent or good.

Claims (8)

  An aluminum alloy plate containing Fe: 0.8 to 2.0 mass%, Si: 0.03 to 0.20 mass%, Ti: 0.004 to 0.050 mass%, the balance being Al and inevitable impurities, The solid solution amount of Fe is 10 to 70 ppm, the intermetallic compound is dispersed in the aluminum alloy plate, and the average inter-wall distance between the intermetallic compounds having an equivalent circle diameter of 1 to 15 μm on the surface of the aluminum alloy plate is An aluminum alloy plate for a battery case, wherein the maximum diameter of a circle that is 20 μm or less and that can be drawn in a region where the intermetallic compound is not present is 100 μm or less.   The aluminum alloy plate for battery cases according to claim 1, wherein the absolute value of the ear ratio is 10% or less.   It is a manufacturing method of the aluminum alloy plate for battery cases of Claim 1 or 2, Comprising: Fe: 0.8-2.0mass%, Si: 0.03-0.20mass%, Ti: 0.004-0 A casting process for casting an aluminum alloy containing 0.05% by mass and the balance Al and inevitable impurities; a homogenization treatment process for homogenizing the ingot at a temperature of 450 to 620 ° C. for a holding time of 1 to 20 hours; The minimum distance from the lump surface to the boundary surface between the chill layer and the coarse cell layer is tmin (mm), and the maximum distance from the ingot surface to the boundary surface between the coarse cell layer and the fine cell layer is tmax (mm). A chamfering step for chamfering the ingot so that T (mm) satisfies 3 ≦ T <tmin or tmax <T; a hot rough rolling step and heat for hot rolling the ingot at an end temperature of 250 to 370 ° C. Inter-finish rolling process Method for producing an aluminum alloy plate for a battery case, characterized in that it comprises; No hot rolling step and, cold and hot-rolled cold-rolling rolling process and; cold annealing the rolled material annealing process and.   It is a manufacturing method of the aluminum alloy plate for battery cases of Claim 1 or 2, Comprising: Fe: 0.8-2.0mass%, Si: 0.03-0.20mass%, Ti: 0.004-0 A casting process for casting an aluminum alloy containing 0.05% by mass and the balance Al and inevitable impurities; and the minimum distance from the ingot surface to the boundary surface between the chill layer and the coarse cell layer is tmin (mm), the ingot surface The surface from which the ingot is chamfered so that the chamfering amount T (mm) satisfies 3 ≦ T <tmin or tmax <T, where tmax (mm) is the maximum distance from the boundary surface of the coarse cell layer and the fine cell layer to tmax (mm). A homogenization treatment step for homogenizing the ingot after chamfering at a temperature of 450 to 620 ° C. for a holding time of 1 to 20 hours; a room temperature holding step for holding the ingot after the homogenization treatment at room temperature; , Hot rough rolling process and finish A hot rolling step including a hot finish rolling step for hot rolling the ingot at a temperature of 250 to 370 ° C; a cold rolling step for cold rolling the hot rolled material; and an annealing for annealing the cold rolled material And a process for producing an aluminum alloy plate for battery cases.   It is a manufacturing method of the aluminum alloy plate for battery cases of Claim 1 or 2, Comprising: Fe: 0.8-2.0mass%, Si: 0.03-0.20mass%, Ti: 0.004-0 A casting process for casting an aluminum alloy containing 0.05% by mass and the balance Al and inevitable impurities; and a minimum distance from the ingot surface to the interface between the chill layer and the coarse cell layer without performing a homogenization treatment; tmin (mm), where the maximum distance from the ingot surface to the boundary surface of the coarse cell layer and the fine cell layer is tmax (mm), so that the amount of chamfering T (mm) satisfies 3 ≦ T <tmin or tmax <T A chamfering step for chamfering the ingot, and a heating and holding step before hot rough rolling hold the ingot after chamfering at a temperature of 450 to 620 ° C. for a holding time of 1 to 20 hours. Hot rough rolling process following A hot rolling process including a hot finish rolling process for hot rolling the ingot at an end temperature of 250 to 370 ° C; a cold rolling process for cold rolling the hot rolled material; and annealing the cold rolled material And an annealing step. A method for producing an aluminum alloy plate for a battery case.   The manufacturing method of the aluminum alloy plate for battery cases of Claim 3-5 in which the said hot rough rolling process hot-rolls an ingot at the starting temperature of 380-550 degreeC and end temperature 330-480 degreeC.   The manufacturing method of the aluminum alloy plate for battery cases as described in any one of Claims 3-6 whose rolling reduction in the said cold rolling process is 50 to 85%.   The manufacturing method of the aluminum alloy plate for battery cases as described in any one of Claims 3-7 provided with the further cold rolling process after the said annealing process.

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