JP5929855B2 - Aluminum alloy sheet for battery cases with excellent formability, heat dissipation and weldability - Google Patents

Description

  The present invention relates to an aluminum alloy plate excellent in formability, heat dissipation, and weldability used for a secondary battery container such as a lithium ion battery.

  Al-Mn-based 3000 series alloys are relatively excellent in strength, formability and laser weldability, and have come to be used as raw materials when manufacturing secondary battery containers such as lithium ion batteries. Yes. After forming into a desired shape, it is hermetically sealed by laser welding and used with a secondary battery container. Development has been made on an aluminum alloy plate for a secondary battery container, which is based on an existing 3000 series alloy as well as the 3000 series alloy and has further improved strength and formability.

  For example, in Patent Document 1, the aluminum alloy plate has a composition defined by JIS A3003, the ear rate is 8% or less, the average grain size of recrystallized grains is 50 μm or less, and the conductivity is An aluminum alloy plate for a rectangular battery case characterized by being 45 IACS% or less is described.

On the other hand, as a battery case, an aluminum alloy plate for a battery case that is excellent in resistance to blistering under a high temperature internal pressure load has been developed. In Patent Document 2, Mn 0.8 to 2.0% (mass%, the same applies hereinafter) is contained, the amount of Fe as impurities is restricted to 0.6% or less, and the amount of Si is restricted to 0.3% or less, and the balance Is made of Al and inevitable impurities, the Mn solid solution amount is 0.75% or more, the ratio of the Mn solid solution amount to the Mn addition amount is 0.6 or more, and the proof stress is 185 to 260 N / mm ^2. The aluminum alloy plate for battery cases, which is excellent in high-temperature blistering resistance, is characterized by being in the range.

  Furthermore, in patent document 3, 0.5 to 1.5% of Mn, 0.1 to 0.5% of Si, and 0.3 to 1.0% of Fe are contained, and the balance is Al and inevitable impurities. The resulting aluminum alloy ingot is subjected to hot rolling and cold rolling, and after the cold rolling, it is held at a temperature of 450 ° C. or higher, and then annealed to 200 ° C. at a cooling rate of 1 ° C./sec or higher. A method for producing an aluminum alloy case material for a sealed rectangular battery having excellent formability and creep resistance is described.

However, it is known that an abnormal bead may occur in an aluminum alloy plate based on a 3000 series alloy and whose composition is improved, and there is a problem in laser weldability. Therefore, an aluminum alloy plate for a secondary battery container that is excellent in laser weldability based on 1000 series has also been developed. Patent Document 4 describes an aluminum alloy plate excellent in laser weldability that does not generate irregular beads when laser welding an A1000 series aluminum material. According to this, the aluminum alloy plate contains Si: 0.02 to 0.10 mass%, the Fe content is limited to 0.30 mass% or less, the balance is Al and inevitable impurities, and the equivalent circle diameter 1 The number of intermetallic compound particles of 0.5 to 6.5 μm may be restricted to 1000 to 2400 particles / mm ² .

Japanese Patent No. 3620955 Japanese Patent No. 3844368 Japanese Patent No. 4244252 JP 2009-256754 A

Certainly, the 1000 series has problems that the weldability is stable and the formability is excellent, but the strength is low. Therefore, as the size of the lithium ion battery is increased, it is expected that high strength characteristics are required, and there is a problem in applying the 1000 series aluminum material as it is.
As described above, although a 3000 series alloy plate provides strength and resistance to swelling when subjected to high-temperature internal pressure, it has a tendency to be inferior to a 1000 series alloy plate and have a large number of abnormal beads. In addition, as the size of lithium ion batteries increases, it is expected that the amount of heat generated from the lithium ion batteries during charging and discharging will increase, and there is also a demand for batteries with excellent heat dissipation characteristics. Moreover, the 3000 series aluminum alloy plate generally has a high Mn solid solution amount, and depending on its component composition as a large lithium ion battery container, the proof stress may be too high, and spring back is likely to occur after press molding, There is also a problem of so-called shape freezing property that does not fit into a predetermined design shape.
The present invention has been devised to solve such problems, has heat dissipation characteristics applicable to large-sized lithium ion battery containers, and is excellent in moldability and shape freezing property. An object of the present invention is to provide a 3000 series aluminum alloy plate having excellent laser weldability.

In order to achieve the object, the aluminum alloy plate for battery case having excellent formability and weldability according to the present invention has Fe: more than 0.2 to less than 1.4% by mass, Mn: 0.5 to 2.0. Ingredient composition containing: mass%, Si: more than 0.2 to 1.1 mass%, Cu: 0.05 to 1.0 mass%, consisting of the balance Al and impurities, and Mg being less than 0.05 mass% And the conductivity exceeds 45% IACS.
When a cold-rolled annealed material is used, the 0.2% yield strength is less than 30 to 85 MPa, and the number of second phase particles having a circle-equivalent diameter of 2 μm or more in the metal structure is less than 1800 / mm ² . When the material is cold-rolled, the 0.2% proof stress is less than 90 to 180 MPa, and the number of second phase particles having an equivalent circle diameter of 2 μm or more in the metal structure is less than 1800 / mm ² .
As a manufacturing method of the cold-rolled annealed material, a molten aluminum alloy having the above chemical composition is cast into a 5 to 10 mm thin slab by a twin belt type continuous casting machine, and directly applied to a roll without hot rolling. It is preferable to perform the final annealing treatment by winding and cold rolling to the final plate thickness.
Moreover, as a manufacturing method of the said cold-rolled material, the aluminum alloy molten metal which has the said chemical composition is cast to a 5-10 mm thin slab with a twin belt type continuous casting machine, and it does not perform hot rolling directly, It is preferable to wind up on a roll, cold-roll it, perform intermediate annealing at an appropriate plate thickness, and further perform final cold rolling at a final cold rolling rate of 5 to 20%.

The aluminum alloy plate of the present invention has high thermal conductivity, excellent formability, and excellent laser weldability. Therefore, the aluminum alloy plate has a low secondary battery container that has excellent sealing performance and improved heat dissipation characteristics. Can be manufactured at cost.
In particular, in the case of cold-rolled annealed material, it exhibits an elongation of 10% or more, expresses excellent weldability, and has a low yield strength of less than 30 to 85 MPa, so that springback during press molding is suppressed. Excellent shape freezing.
Moreover, in the case of a cold-rolled material, it exhibits an elongation value of 3% or more, exhibits excellent formability, and has a low yield strength of less than 90 to 180 MPa, so that springback during press molding is suppressed, and as a result It also has excellent shape freezing properties.

Conceptual diagram explaining how to measure / evaluate the number of weld defects

Secondary batteries are manufactured by putting an electrode body in a container and then sealing it with a lid by welding or the like. When such a secondary battery is used for a mobile phone or the like, the temperature inside the container may rise during charging. For this reason, if the thermal conductivity of the material forming the container is low, the heat dissipation characteristics are inferior, which leads to a problem that the life of the lithium ion battery is shortened. Therefore, a material having high thermal conductivity is required as a material to be used.
Further, since a press method is generally used as a method for forming a container, the material itself is required to have excellent press formability. Furthermore, it is expected that large-sized lithium ion battery containers will accelerate the material thinning in the future. Of course, if the material is thinned, springback is likely to occur after press molding, and the problem that the material does not fit in a predetermined design shape may become apparent. Therefore, it is required that the material to be used has an excellent shape freezing property.

  In addition, since a welding method is used as a method of sealing with a lid, it is also required to have excellent weldability. In many cases, a laser welding method is used as a welding method for manufacturing a secondary battery container or the like. The 3000 series aluminum alloy plate according to the present invention has high thermal conductivity, so when pulse laser joining a container and a lid obtained by press molding, the energy per pulse is increased, etc. It is necessary to perform bonding under severe conditions. However, when laser welding is performed under such relatively severe conditions, there is a problem in that welding defects called undercut and blowhole are generated in the weld bead.

  It is estimated that the surface temperature of the weld bead during joining locally reaches a high temperature of 2000 ° C. or higher by irradiation with such a pulse laser. Aluminum is considered to be a highly reflective material and reflects about 70% of the laser beam. On the other hand, second-phase particles that existed in the vicinity of the surface of the aluminum alloy plate, for example, intermetallic compounds such as Al- (Fe.Mn) -Si, have a specific heat and heat conduction even at room temperature, compared to the parent phase aluminum. The rate is small and the temperature rises preferentially. The thermal conductivity of these intermetallic compounds further decreases with increasing temperature, the light absorption rate thereof increases at an accelerated rate, and only the intermetallic compounds are rapidly heated and dissolved. The irradiation time of one pulse of the pulse laser is a very short time of nanoseconds or femtoseconds. Therefore, when the α-Al of the matrix dissolves and transitions to the liquid phase, the intermetallic compound such as Al— (Fe · Mn) —Si rapidly reaches the boiling point and evaporates. Inflates the volume.

Therefore, in the present invention, in the cold-rolled annealed material, a molten aluminum alloy having a specific chemical composition is cast into a thin slab of 5 to 10 mm by a twin belt type continuous casting machine, and without hot rolling. The production method of directly winding on a roll was adopted. Since the cooling rate in the vicinity of 1/4 of the ingot thickness when casting into a 5 to 10 mm thin slab by a twin belt type continuous casting machine is about 40 to 200 ° C./sec, Al— (Fe · Mn) — A thin slab having a metal structure in which an intermetallic compound such as Si is finely dispersed is obtained. As a result, the number of second phase particles having a circle-equivalent diameter of 2 μm in the metal structure of the final plate can be restricted to less than 1800 / mm ^2, and the number of welding defects generated in the laser weld can be reduced.
However, since the solid solution amount of Mn, Si, etc. in the matrix is too high as it is, the final plate is inferior in formability and thermal conductivity although sufficient anti-swelling resistance at high temperature internal pressure load can be secured. Therefore, (1) a manufacturing method in which the rolled roll is cold-rolled to the final plate thickness and subjected to a final annealing treatment, or (2) the rolled roll is cold-rolled to an appropriate plate. A production method was adopted in which intermediate annealing was performed on the thickness, and final cold rolling with a final cold rolling rate of 5 to 20% was performed. In this way, the cold-rolled coil is subjected to intermediate annealing treatment or final annealing treatment, so that Mn, Si, etc. dissolved in the matrix are actively diffused and absorbed in the intermetallic compound, and Mn, Si, etc. The amount of solid solution is reduced, the thermal conductivity of the final plate is increased, and at the same time, the elongation value is increased and the proof stress is kept low. As a result, it is possible to obtain an aluminum alloy plate having high heat dissipation characteristics and excellent in formability and shape freezing property.

In the present invention, the content of Fe, Mn, Si, Cu is regulated, the intermetallic compound in the thin slab is finely dispersed and precipitated (crystallization), and the content of Mg as an impurity is kept low, thereby reducing the laser welded portion. In addition to reducing the number of welding defects occurring in the steel, heat treatment is performed while keeping the yield strength low by reducing the amount of Mn, Si, etc. by subjecting the cold-rolled coil to intermediate annealing or final annealing. The aluminum alloy plate is excellent in formability, heat dissipation and weldability. The present inventors have intensively studied to obtain an aluminum alloy plate excellent in laser weldability through investigation of characteristics relating to thermal conductivity (conductivity) and press formability, and investigation of the number of weld defects generated in the weld. Again, the present invention has been reached.
The contents will be described below.

First, the effect | action of each element contained in the aluminum alloy plate for secondary battery containers of this invention, appropriate content, etc. are demonstrated.
Fe: More than 0.2 to less than 1.4% by mass Fe is an essential element for increasing the strength of the aluminum alloy sheet. When the Fe content is 0.2% by mass or less, the strength of the aluminum alloy plate is lowered, which is not preferable. When the Fe content exceeds 1.4% by mass, coarse intermetallic compounds such as Al— (Fe · Mn) —Si and Al ₆ (Fe · Mn) are precipitated during thin slab casting. The compound is not preferable because it is more likely to evaporate than the α-Al matrix during laser welding, and the number of welding defects increases to lower the weldability.
Therefore, the Fe content is in the range of more than 0.2 to less than 1.4% by mass. A more preferable Fe content is in the range of 0.25 to less than 1.3% by mass. A more preferable Fe content is in the range of 0.3 to less than 1.2% by mass.

Mn: 0.5 to 2.0% by mass
Mn is an essential element for increasing the strength of the aluminum alloy plate. If the Mn content is less than 0.5% by mass, the strength of the aluminum alloy plate is lowered, which is not preferable. If the Mn content exceeds 2.0% by mass, the Mn solid solution amount in the matrix becomes too high, not only the thermal conductivity of the final plate is lowered, but also the proof stress is too high and the shape freezing property is also lowered. To do. Furthermore, coarse intermetallic compounds such as Al- (Fe · Mn) -Si and Al ₆ (Fe · Mn) crystallize during thin slab casting, and these intermetallic compounds evaporate compared to α-Al matrix during laser welding. This is not preferable because the number of welding defects increases and the weldability decreases.
Therefore, the Mn content is in the range of 0.5 to 2.0 mass%. A more preferable Mn content is in the range of 0.5 to 1.9% by mass. A more preferable Mn content is in the range of 0.6 to 1.8% by mass.

Si: more than 0.2 to 1.1% by mass
Si is an essential element that increases the strength of the aluminum alloy plate and improves the flow of molten metal during casting. When the Si content is 0.2% by mass or less, the strength of the aluminum alloy plate is lowered and the hot water flowability is lowered, which is not preferable. When the Si content exceeds 1.1% by mass, a relatively coarse intermetallic compound such as Al- (Fe · Mn) -Si crystallizes in the final solidified portion during thin slab casting. It is not preferable because it is more likely to evaporate than the α-Al matrix during welding, and the number of welding defects increases to lower weldability.
Accordingly, the Si content is in the range of more than 0.2 to 1.1 mass%. A more preferable Si content is in the range of 0.25 to 1.0% by mass. A more preferable Si content is in the range of 0.3 to 1.0% by mass.

Cu: 0.05-1.0 mass%
Cu is an essential element for increasing the strength of the aluminum alloy plate. If the Cu content is less than 0.05% by mass, the strength of the aluminum alloy plate is lowered, which is not preferable. When Cu content exceeds 1.0 mass%, since heat conductivity and weldability will fall, it is unpreferable.
Therefore, the Cu content is in the range of 0.05 to 1.0 mass%. A more preferable Cu content is in the range of 0.05 to 0.9 mass%. A more preferable Cu content is in the range of 0.05 to 0.8 mass%.
Mg as an unavoidable impurity: less than 0.05 mass% Mg as an unavoidable impurity may be contained less than 0.05 mass%. In the present invention, when the Mg content is less than 0.05% by mass, characteristics such as thermal conductivity, formability, and weldability are not deteriorated.

Other inevitable impurities are inevitably mixed from raw materials, return materials, etc., and their allowable contents are, for example, less than 0.05 mass% of Zn and 0.10 mass of Ni. %, Pb, Bi, Sn, Na, Ca, and Sr are each less than 0.02 mass%, less than 0.01 mass% of Ga and Ti, less than 0.1 mass% of Nb and V, and 0 of Co. Less than 3% by mass and other than 0.05% by mass, and inclusion of an element outside the control within this range does not hinder the effects of the present invention.

Elongation value and 0.2% yield strength
Cold-rolled annealed material: elongation value of 10% or more and 0.2% proof stress of less than 30 to 85 MPa
As-cold rolled material: When the elongation value is 3% or more and the 0.2% proof stress is less than 90 to 180 MPa , when applying the 3000 series aluminum alloy plate to a large-sized lithium ion battery container, etc., it has high heat dissipation characteristics and excellent It is necessary not only to have laser weldability but also to be excellent in moldability and shape freezing property while maintaining an appropriate strength. The shape freezing property and strength of the material can be known from the 0.2% proof stress when the tensile test is conducted, and the moldability can be known from the elongation value at the tensile test.
The details will be given in the description of Examples below. As a 3000 series aluminum alloy plate of the present invention applied to a large-sized lithium ion battery container or the like, the elongation value is 10% or more in the cold-rolled annealed material, and 0 .2% proof stress is less than 30-85MPa, but if the material is cold-rolled, the elongation value is 3% or more and 0.2% proof stress is less than 90-180MPa. It is.

When the electrical conductivity exceeds 45% IACS and the characteristics as described above are produced, when the 3000 series aluminum alloy sheet having the specific component composition is manufactured, the cold-rolled coil is subjected to intermediate annealing treatment or final annealing treatment, It is expressed by reducing the solid solution amount of Mn, Si, etc. in the matrix.
Specifically, for example, it is preferable to insert a cold-rolled coil into a batch annealing furnace, and perform an intermediate annealing process or a final annealing process in which the coil is heated and held at 330 to 470 ° C. for 1 to 8 hours.

  In this way, the intermediate annealing process or the final annealing process of the cold rolled coil is performed in a batch annealing furnace, for example, at a holding temperature of 330 to 470 ° C. and a holding time of 1 to 8 hours. Mn, Si, etc. are diffused and absorbed by intermetallic compounds such as Al- (Fe · Mn) -Si that have already been finely dispersed and precipitated during the casting of thin slabs. It is possible to reduce well.

In the intermediate annealing process or the final annealing process, and in the heating / cooling process, the intermetallic compound such as Al- (Fe · Mn) -Si absorbs Mn, Si, etc., which are solid-solved in the matrix, and the size is reduced. Increasing the solid solution amount of the matrix such as Mn and Si decreases.
In the alloy composition range of the present invention, the present inventors adopt a manufacturing method in which a twin belt type continuous casting machine casts a thin slab of 5 to 10 mm and directly winds up on a roll without hot rolling. In this way, an intermetallic compound such as Al— (Fe · Mn) —Si is uniformly and finely precipitated, and in the subsequent intermediate annealing step or the final annealing step, the solid solution of Mn, Si, etc. in the matrix efficiently. It was possible to reduce the amount and increase the conductivity.

On the other hand, in a semi-continuous cast slab of 3000 series alloy (DC cast slab), particularly in a place such as the final solidified portion, although depending on the component composition, relatively coarse Al ₆ (Fe · Mn), Al— Intermetallic compounds such as (Fe · Mn) -Si are crystallized. These relatively coarse intermetallic compounds are more likely to evaporate than the α-Al matrix during laser welding of the final plate, and are considered to be a cause of increasing the number of welding defects. The inventors have prepared a manufacturing method in which a molten metal having a composition range of the present invention is cast into a thin slab of 5 to 10 mm by a twin belt type continuous casting machine and directly wound on a roll without hot rolling. By adopting it, an intermetallic compound such as Al— (Fe · Mn) —Si is uniformly and finely precipitated, and the number of second phase particles having an equivalent circle diameter of 2 μm or more in the metal structure of the final plate is 1800 / mm ^2. By making it less than, it succeeded in reducing the number of welding defects in a laser welding part remarkably.

Next, a method for producing the above-described aluminum alloy plate for a secondary battery container will be briefly introduced.
When the raw material is charged into the melting / melting melting furnace and the predetermined melting temperature is reached, the flux is appropriately charged and stirred, and further, if necessary, degassing in the furnace using a lance or the like, Hold the sedation to separate the soot from the surface of the melt.
In this melting / melting process, it is important to add raw materials such as a master alloy again because it is a predetermined alloy component, but a sufficient sedation time is allowed until the flux and soot float and separate from the molten aluminum alloy to the molten metal surface. It is extremely important to take The sedation time is usually preferably 30 minutes or longer.

In some cases, the molten aluminum alloy melted in the melting furnace may be cast after it is once transferred to the holding furnace, but may be cast directly from the melting furnace. A more desirable sedation time is 45 minutes or more.
If necessary, in-line degassing or filtering may be performed.
In-line degassing is mainly of a type in which an inert gas or the like is blown into a molten aluminum from a rotating rotor, and hydrogen gas in the molten metal is diffused and removed in bubbles of the inert gas. When nitrogen gas is used as the inert gas, it is important to control the dew point to, for example, −60 ° C. or lower. The amount of hydrogen gas in the ingot is preferably reduced to 0.20 cc / 100 g or less.
In addition, hydrogen gas that is supersaturated in the ingot may be deposited during laser welding after the final plate is formed, and a large number of blow holes may be generated in the bead. For this reason, the more preferable amount of hydrogen gas in the ingot is 0.15 cc / 100 g or less.

The cast ingot continuously casts a thin slab having a thickness of 5 to 10 mm by a twin belt type continuous casting machine. The twin belt casting machine includes an endless belt and a pair of rotating belt portions facing each other up and down, a cavity formed between the pair of rotating belt portions, and a cooling means provided inside the rotating belt portion. The molten metal is supplied into the cavity through a nozzle made of a refractory, and a thin slab is continuously cast.
Since the cooling rate in the vicinity of 1/4 of the ingot thickness when casting into a 5 to 10 mm thin slab by a twin belt type continuous casting machine is about 40 to 200 ° C./sec, Al— (Fe · Mn) — A thin slab having a metal structure in which an intermetallic compound such as Si is finely dispersed is obtained.
In the case of the alloy slab within the composition range of the present invention, when the thickness of the slab exceeds 10 mm, it is difficult to wind it on a roll. Moreover, when the slab thickness is less than 5 mm, it becomes difficult to flow the molten metal uniformly into the cavity. Therefore, the slab thickness was limited to 5 to 10 mm. Next, the thin slab is directly wound on a roll without being subjected to hot rolling and homogenization, and is subjected to cold rolling.

The coil wound in the cold rolling process is passed through a cold rolling machine, and is usually subjected to several passes of cold rolling. At this time, work hardening occurs due to plastic strain introduced by cold rolling, and therefore, an intermediate annealing process is usually performed in consideration of the tempering of the final plate as necessary.
In the present invention, when the final annealing described later is not performed, an intermediate annealing process between cold rolling processes is essential. For example, a cold rolled coil is inserted into a batch annealing furnace and heated to a temperature of 330. It is preferable to perform an intermediate annealing treatment that is held at ˜470 ° C. for 1 to 8 hours.
Thus, the intermediate annealing treatment of the cold-rolled coil is performed in a batch annealing furnace at a holding temperature of 330 to 470 ° C. and a holding time of 1 to 8 hours, so that Mn, Si, etc. dissolved in the matrix Can be diffused and absorbed in an intermetallic compound such as Al- (Fe · Mn) -Si that has already been finely dispersed and precipitated during thin slab casting, and the amount of solid solution such as Mn and Si can be reduced efficiently. Become. If the holding temperature is less than 330 ° C., Mn, Si, etc., dissolved in the matrix are not sufficiently diffused and absorbed by the intermetallic compound, so that the solid solution amount of Mn, Si, etc. cannot be reduced sufficiently. If the holding temperature exceeds 470 ° C., it takes too much time for the coil to cool, and productivity is lowered, which is not preferable.
Further, if the holding time of the coil at a predetermined holding temperature is less than 1 hour, the actual temperature of the coil may be non-uniform, which is not preferable. If the holding time of the coil at a predetermined holding temperature exceeds 8 hours, productivity is lowered, which is not preferable. Accordingly, preferable intermediate annealing conditions are a holding temperature of 330 to 470 ° C. and a holding time of 1 to 8 hours.

The coil that has been cold-rolled to the final plate thickness through the final annealing cold rolling step is preferably softened as much as possible in view of the moldability in the mold forming step, and therefore it is desirable to perform the final annealing. In the present invention, particularly when intermediate annealing is not performed during the cold rolling process, final annealing is essential, and the final plate needs to be used as an annealing material.
In the present invention, the final annealing performed after the final cold rolling is performed, for example, by inserting a coil cold-rolled to the final plate thickness into a batch annealing furnace and heating it and maintaining the temperature at 330 to 470 ° C. for 1 to 8 hours. It is preferable to perform a final annealing treatment.
In this way, the final annealing treatment of the cold-rolled coil is performed at a holding temperature of 330 to 470 ° C. and a holding time of 1 to 8 hours by a batch annealing furnace, so that Mn, Si, etc. dissolved in the matrix Can be diffused and absorbed in an intermetallic compound such as Al- (Fe · Mn) -Si that has already been finely dispersed and precipitated during thin slab casting, and the amount of solid solution such as Mn and Si can be reduced efficiently. Become. If the holding temperature is less than 330 ° C., Mn, Si, etc., dissolved in the matrix are not sufficiently diffused and absorbed by the intermetallic compound, so that the solid solution amount of Mn, Si, etc. cannot be reduced sufficiently. If the holding temperature exceeds 470 ° C., it takes too much time for the coil to cool, and productivity is lowered, which is not preferable.
Further, if the holding time of the coil at a predetermined holding temperature is less than 1 hour, the actual temperature of the coil may be non-uniform, which is not preferable. If the holding time of the coil at a predetermined holding temperature exceeds 8 hours, productivity is lowered, which is not preferable. Accordingly, preferable final annealing conditions are a holding temperature of 330 to 470 ° C. and a holding time of 1 to 8 hours.
In the present invention, the final annealing may be a batch annealing treatment in which the temperature is kept at 330 to 470 ° C. for 1 to 8 hours by the batch annealing furnace as described above, but the temperature is 400 ° C. to 550 ° C., for example, by the continuous annealing furnace. If it is kept within 15 seconds and then cooled rapidly, it can also serve as a solution treatment.
In any case, final annealing is not necessarily essential in the present invention, but it is desirable to use an annealing material in consideration of formability in the mold forming process. In the case where the mechanical strength is given priority over the formability, the intermediate annealing is performed between the cold rolling processes, and then cold rolling to the final sheet thickness is provided as a cold rolled material.

Final cold rolling rate When the final annealing is performed, the final cold rolling rate is preferably in the range of 50 to 90%. If the final cold rolling rate is within this range, the average grain size of recrystallized grains in the final plate after annealing can be about 10 to 20 μm, and the elongation value can be 10% or more. Can be finished beautifully. A more preferable final cold rolling rate is in the range of 60 to 90%.
On the other hand, the final cold rolling rate when the material is cold rolled without being subjected to final annealing is preferably in the range of 5 to 20%. If the ironing process increases during DI molding, it is necessary to provide a final plate that is slightly harder than the annealed material. If the final cold rolling rate is less than 5%, depending on the composition, it becomes difficult to make the proof stress in the final plate 90 MPa or more. If the final cold rolling rate exceeds 20%, it depends on the composition but in the final plate. It becomes difficult to make the elongation value 3% or more.
If the final cold rolling rate is within this range, the elongation value in the final plate can be 3% or more and the proof stress can be less than 90 to 180 MPa while cold rolling. A more preferable final cold rolling rate is in the range of 5 to 15%.
An aluminum alloy plate for a secondary battery container can be obtained through the normal steps as described above.

Preparation of Final Plate Various predetermined ingots were weighed and blended, and 6 kg each (total 8 test materials) of ingots were inserted and loaded into a # 20 crucible coated with a release material. These crucibles are inserted into an electric furnace and melted at 780 ° C. to remove the soot, and then the molten metal temperature is maintained at 740 ° C. Then, a small lance is inserted into the molten metal, and N ₂ gas is flowed. Degassing was performed by blowing at 1.0 L / min for 10 minutes. Thereafter, the sedation was performed for 30 minutes, and the cocoon floating on the surface of the molten metal was removed with a stirring rod, and a disk sample was collected with a spoon as a mold for component analysis.
Subsequently, the crucible was sequentially taken out from the electric furnace using a jig, and a molten aluminum was cast into a water-cooled mold having an inner size of 200 mm × 200 mm × 16 mm to produce a thin slab. The disk sample of each sample material was subjected to composition analysis by emission spectroscopic analysis. The results are shown in Tables 1 and 2.

After the hot slab of the thin slab was cut, each side was chamfered by 3 mm to obtain a thickness of 10 mm, and the thin slab was cold-rolled without being homogenized and hot-rolled.
The cold-rolled annealed material was first cold-rolled to a final thickness of 1.0 mm. The final cold rolling rate in this case was 90%. In the final annealing, this cold-rolled sheet is inserted into an annealer, heated to 430 ° C. at a heating rate of 50 ° C./hr, and subjected to an annealing treatment of 430 ° C. × 2 hours, and then a cooling rate of 50 ° C./hr. At room temperature. This was used as a cold-rolled annealed material (tempered symbol: O). In addition, about some test materials (Examples 10-12, Comparative Examples 9-10), after cold-rolling to 1.0 mm which is the final board thickness, this cold-rolled board is used as final annealing. The sample was inserted into an annealer, heated to 330 ° C. at a temperature rising rate of 50 ° C./hr, annealed at 330 ° C. for 2 hours, and then cooled to room temperature at a temperature lowering rate of 50 ° C./hr. This was used as a cold-rolled annealed material (tempered symbol: O).
In addition, the cold-rolled material was first cold-rolled to a thickness of 1.18 mm. In the intermediate annealing, this cold-rolled sheet is inserted into an annealer, heated to 430 ° C. at a heating rate of 50 ° C./hr, and subjected to an annealing treatment of 430 ° C. × 2 hours, and then a cooling rate of 50 ° C./hr. At room temperature. Next, cold rolling was performed to a final plate thickness of 1.0 mm, and this was used as a cold-rolled material (tempered symbol: H ₁₂ ). The final cold rolling rate in this case was 15%. For some of the test materials (Examples 22 to 24), first, cold rolling was performed to a plate thickness of 1.05 mm, intermediate annealing was performed under the same conditions as the above annealing conditions, and then the final plate thickness 1 Cold-rolled to 0.0 mm and used as a cold-rolled material (tempered symbol: H ₁₂ ). The final cold rolling rate in this case was 5%.

Next, the final plate (each sample material) thus obtained was evaluated for formability, shape freezing property and strength, laser weldability, and thermal conductivity.
Evaluation of formability Evaluation of formability of the obtained final plate was performed by elongation (%) of a tensile test.
Specifically, a JIS No. 5 test piece was collected so that the tensile direction was parallel to the rolling direction, and a tensile test was performed according to JISZ2241, to obtain 0.2% proof stress and elongation (breaking elongation).
In the final plate that was annealed after cold rolling, the test material having an elongation value of 10% or more was considered to have good moldability (◯), and the test material that was less than 10% was considered to have poor moldability (×). did. The evaluation results are shown in Tables 3 and 4.
In the final plate as cold-rolled, the test material having an elongation value of 3% or more was defined as good moldability (◯), and the test material that was less than 3% was defined as poor moldability (x). The evaluation results are shown in Tables 3 and 4.

Evaluation of shape freezing property and strength Evaluation of the shape freezing property and strength of the obtained final plate was performed by 0.2% proof stress (MPa) of a tensile test.
In the final plate (cold-rolled annealed material) that was annealed after cold rolling, the test material whose 0.2% proof stress was less than 30 to 85 MPa was defined as shape freezing property and good strength (◯), and was 85 MPa or more. The specimen was defined as a shape freezing defect (x). Further, the test material having a 0.2% proof stress of less than 30 MPa was regarded as insufficient in strength (x).
In the final plate (cold rolled material) as cold-rolled, the sample material whose 0.2% proof stress was less than 90 to 180 MPa was defined as shape freezing property and good strength (◯), and the sample material was 180 MPa or higher. Was defined as defective shape freezing (×). In addition, a test material having a 0.2% proof stress of less than 90 MPa was regarded as insufficient in strength (x). The evaluation results are shown in Tables 3 and 4.

Laser welding conditions The final plate obtained was subjected to pulsed laser irradiation to evaluate laser weldability. Using YAG laser welder JK701 manufactured by LUMONICS, frequency 33.0 Hz, welding speed 400 mm / min, energy per pulse 6.5 J / p, pulse width 1.5 msec., Shielding gas (nitrogen) flow rate 15 (L / L min), two plates of the same test material were brought into contact with each other without any gap between the end portions, and pulse laser welding having a total length of 100 mm was performed along the portion.

Evaluation of laser weldability
Measurement / Evaluation of Black Defects Next, as an evaluation of laser weldability, the number of weld defects generated in the welds was measured. First, of the 100 mm long weld line, the remaining 80 mm long region excluding the weld start 20 mm long weld line was determined as the measurement region. The vicinity of the welding start was removed because it was unstable.
And as shown in FIG. 1, the X-ray CT image in the plate | board thickness cross section parallel to a weld line was acquired by the X-ray CT inspection for the cross section of the weld bead formed along the 80 mm long weld line. Further, based on this X-ray CT image, a black defect portion was detected by image editing software, and the area of the black portion defect was calculated by image analysis software. The number of particles corresponding to each equivalent circle diameter was calculated from the black part defect area.
In the present specification, a test material in which the number of black part defects having an equivalent circle diameter of 0.1 mm or more was less than 5 was regarded as good (◯) in the number of weld defects, and a black part having an equivalent circle diameter of 0.1 mm or more. The test material in which the number of defects was 5 or more was defined as a defective weld defect evaluation (x). The evaluation results are also shown in Tables 3 and 4.

Evaluation of thermal conductivity
Measurement / Evaluation of Conductivity Conductivity (IACS%) was measured with a conductivity meter (AUTOSIGMA 2000, manufactured by Nippon Hocking Co., Ltd.). A test material having an electrical conductivity exceeding 45 (IACS%) was defined as good conductivity (O), and a test material having an electrical conductivity of 45 (IACS%) or less was defined as poor conductivity (x). The evaluation results are also shown in Tables 3 and 4.

For the final plates of Examples 3, 5, 15, and 17 shown in Table 3 and Comparative Examples 4, 8, 14, and 18 shown in Table 4, a longitudinal section parallel to the rolling direction (cross section perpendicular to the LT direction) was cut out. Then, it was embedded in a thermoplastic resin, mirror-polished, etched with a hydrofluoric acid aqueous solution, and the metal structure was observed. The micro metallographic structure is photographed with an optical microscope (area per field of view; 0.0334 mm ² , 15 fields of each sample are photographed), image analysis of the photograph is performed, and the equivalent circle diameter per unit area (1 mm ² ) is 2 μm. The number of the above second phase particles was measured. Table 5 shows the measurement results.

Examples 1 to 24 in Table 3 showing the evaluation results for the evaluation final plate of each test material are final plates (cold-rolled annealed material, cold-rolled material) within the composition range of the present invention, and laser weldability. The evaluation (black part defect), shape freezeability and strength evaluation (0.2% yield strength), moldability evaluation (elongation), and thermal conductivity evaluation (conductivity) were all good (◯). Therefore, comprehensive evaluation about Examples 1-24 was favorable ((circle)).
Comparative Examples 1 to 18 in Table 4 showing the evaluation results for the final plate are final plates (cold-rolled annealed material, cold-rolled material) outside the composition range of the present invention, and laser weldability evaluation (black part defects). Among the evaluations of shape freezing property and strength (0.2% yield strength), moldability evaluation (elongation), and thermal conductivity evaluation (conductivity), at least one evaluation was poor (x). Therefore, comprehensive evaluation about Comparative Examples 1-18 was a defect (x).

Since Comparative Example 1 was a cold-rolled annealed material and the Si content was too low at 0.05% by mass, the thermal conductivity evaluation was poor (x).
Comparative Example 2 was a cold-rolled annealed material, and the Si content was too high at 1.18% by mass, resulting in poor weldability evaluation (x).
Comparative Example 3 was a cold-rolled annealed material, and the Fe content was too low at 0.06% by mass, resulting in poor thermal conductivity evaluation (x).
Comparative Example 4 was a cold-rolled annealed material, and the Fe content was too high at 1.50% by mass, resulting in poor weldability evaluation (x).
Comparative Example 5 was a cold-rolled annealed material, and the Cu content was too high at 1.2% by mass, resulting in poor thermal conductivity evaluation (x) and poor weldability evaluation (x).
Comparative Example 6 was a cold-rolled annealed material, and the Cu content was too high at 1.5% by mass, and thus was poor in thermal conductivity evaluation (x) and poor in weldability evaluation (x).
Comparative Example 7 was a cold-rolled annealed material, and the Mn content was too low at 0.30% by mass, resulting in poor shape freezeability and strength evaluation (x).
Comparative Example 8 was a cold-rolled annealed material, and the Mn content was too high at 2.20% by mass, and thus was poor in thermal conductivity evaluation (x) and poor in weldability evaluation (x).

Comparative Example 9 is a cold-rolled annealed material (final annealing temperature: 330 ° C.), and the Cu content was too high at 1.2% by mass. Therefore, poor thermal conductivity evaluation (x), shape freezing property and strength evaluation They were defective (x), formability evaluation failure (x), and weldability evaluation failure (x).
Comparative Example 10 is a cold-rolled annealed material (final annealing temperature: 330 ° C.), and the Cu content was too high at 1.5% by mass. Therefore, poor thermal conductivity evaluation (x), shape freezing property and strength evaluation They were defective (x), formability evaluation failure (x), and weldability evaluation failure (x).

Since Comparative Example 11 was a cold-rolled material and the Si content was too low at 0.05 mass%, it was a poor thermal conductivity evaluation (x).
Since Comparative Example 12 was a cold-rolled material and the Si content was too high at 1.18% by mass, the weldability evaluation was poor (x).
Since Comparative Example 13 was a cold-rolled material and the Fe content was too low at 0.06% by mass, it was a poor thermal conductivity evaluation (x).
Since Comparative Example 14 was a cold-rolled material and the Fe content was too high at 1.50% by mass, the weldability evaluation was poor (x).
Comparative Example 15 is a cold-rolled material, and the Cu content was too high at 1.2% by mass. Therefore, poor thermal conductivity evaluation (x), poor formability evaluation (x), poor weldability evaluation (x). Met.
Comparative Example 16 is a cold-rolled material, and the Cu content was too high at 1.5% by mass. Therefore, thermal conductivity evaluation failure (x), shape freezeability and strength evaluation failure (x), and formability evaluation. They were defective (x) and poor weldability evaluation (x).
Since Comparative Example 17 was a cold-rolled material and the Mn content was too low at 0.30% by mass, the shape freezing property and strength were poorly evaluated (x).
Since Comparative Example 18 was a cold-rolled material and the Mn content was too high at 2.20% by mass, it was a poor thermal conductivity evaluation (x) and a poor weldability evaluation (x).

Results of image analysis Examples 3, 5, 15, and 17 in Table 5 showing the results of image analysis are the final plates (cold-rolled annealed material, cold-rolled material) within the composition range of the present invention, and in the metal structure As a result of image analysis of the second phase particles, the number of second phase particles having an equivalent circle diameter of 2 μm or more is less than 1800 / mm ² , and the presence of a relatively coarse intermetallic compound such as Al— (Fe · Mn) —Si. The density was considered low. Comparative Examples 4, 8, 14, and 18 are final plates (cold-rolled annealed material, cold-rolled material) outside the composition range of the present invention, and the number of black part defects in the evaluation of laser weldability. In many cases, the number of second phase particles having an equivalent circle diameter of 2 μm or more was 1800 particles / mm ² or more, and the presence density of relatively coarse intermetallic compounds such as Al— (Fe · Mn) —Si was considered to be high. Although the evaluation results of the image analysis of the second phase particles in these metal structures do not necessarily completely coincide with the above-mentioned evaluation results of laser weldability, at least direct generation of welding defects that occur during laser welding. The cause was an intermetallic compound present in the metal structure, and its particle size distribution and type were considered important.

  As described above, according to the present invention, a 3000 series aluminum alloy having heat dissipation characteristics applicable to a large-sized lithium ion battery container, excellent in moldability, shape freezing property, and laser weldability. A board is provided.

Claims (2)

Fe: more than 0.2 to less than 1.4% by mass, Mn: 0.5 to 2.0% by mass, Si: more than 0.2 to 1.1% by mass, Cu: 0.05 to 1.0% by mass Comprising the balance Al and impurities, Mg having a component composition of less than 0.05% by mass,
The electrical conductivity exceeds 45% IACS, the number of second phase particles having an equivalent circle diameter of 2 μm or more in the metal structure is less than 1800 particles / mm ² , the 0.2% proof stress at room temperature is 30 to 61 MPa , 10% or more An aluminum alloy plate for a battery case, which is a cold-rolled annealed material exhibiting an elongation value and excellent in formability, heat dissipation and weldability. Fe: more than 0.2 to less than 1.4% by mass, Mn: 0.5 to 2.0% by mass, Si: more than 0.2 to 1.1% by mass, Cu: 0.05 to 1.0% by mass Comprising the balance Al and impurities, Mg having a component composition of less than 0.05% by mass,
The electrical conductivity exceeds 45% IACS, the number of second phase particles having an equivalent circle diameter of 2 μm or more in the metal structure is less than 1800 / mm ² , the 0.2% proof stress is less than 90 to 180 MPa, and the elongation is 3% or more. An aluminum alloy plate for a battery case that is excellent in formability, heat dissipation and weldability, characterized by being a cold-rolled material exhibiting the following value.