KR101217428B1 - Aluminum alloy sheet for battery case and battery case - Google Patents

Abstract

Mn: 0.4-1.5 mass%, Cu: 0.7-4.0 mass%, Mg: 0.2-1.5 mass%, Si: 0.05-1.0 mass%, Fe: 0.05-1.0 mass%, and remainder is Al and an unavoidable impurity. An aluminum alloy plate composed of: an Zn: 0.3% by mass or less, Ti: less than 0.02% by mass, and B: 20% by mass or less in the above unavoidable impurities, and at the center of the plate thickness direction of the cross section of the aluminum alloy plate, the maximum The area ratio of the intermetallic compound whose length is 1 micrometer or more is more than 0.3% and less than 2.1%, and the number of intermetallic compounds whose maximum length is 11 micrometers or more shall be 140 pieces / mm <^2> or less. By this structure, it is excellent in moldability, pulse laser weldability, strength, and pressure resistance (expansion resistance), and is used suitably for a battery case.

Description

Aluminum alloy plate and battery case for battery case {ALUMINUM ALLOY SHEET FOR BATTERY CASE AND BATTERY CASE}

The present invention relates to an aluminum alloy plate suitably used for a lithium ion secondary battery case and the like, a manufacturing method thereof, and a battery case using the aluminum alloy plate.

BACKGROUND ART Lithium ion secondary batteries are widely used as power sources for mobile phones and notebook personal computers. In order to satisfy the miniaturization and weight reduction of the conventional battery, and the processability (molding) for molding into a battery case, the material of the case (hereinafter, appropriately referred to as a battery case), which is an exterior of the secondary battery, is a JIS A3003 alloy or the like. Aluminum alloy is used. In such a battery, when charge and discharge are performed, the internal pressure of the battery case increases. In addition, when the electronic device equipped with a battery is left in a high-temperature environment such as in a summer car, the temperature of the battery case itself reaches about 60 ° C to 90 ° C, and the internal pressure greatly increases due to the temperature rise. Rather, the internal stress of the battery case material itself is alleviated. As a result, the battery case is expanded and deformed, making it difficult to take out during battery replacement, and furthermore, the battery case is damaged, and the performance of the electronic device is impaired, resulting in a risk of rupture.

Therefore, such a battery case has excellent pressure resistance (expansion resistance) and stress relaxation so that the desired shape of the battery case can be maintained even when the internal pressure of the battery case increases due to the charge / discharge of the battery and use under a high temperature environment. Sex is required. On the other hand, in order to further reduce the size, weight, and cost of the battery, there is a strong demand for thinning of the battery case. By the way, when the aluminum alloy plate which consists of a conventional JIS A3003 alloy etc. is thinned, a deformation | transformation tends to occur easily, the pressure resistance of a battery case falls, and a problem arises that it is easy to produce expansion, even if a relatively small internal pressure acts.

Therefore, in recent years, by adding Cu or the like to an aluminum alloy of JIS 3000 series (JIS A3000 series), the aluminum alloy sheet has been improved in strength and has a pressure resistance that can cope with the use state of the battery even if it is thinned. The plate is developed. For example, Japanese Patent No. 3867989 discloses an aluminum alloy for battery cases in which strength is improved by adding a predetermined amount of Mn, Cu, Mg, and Si to have high pressure resistance by having sufficient stress relaxation resistance even when thinned. Plates and methods of making the same are disclosed.

In addition, in recent years, in addition to being excellent in strength and pressure resistance, it is also required to be excellent in crack resistance in pulse laser welding. Therefore, in Japanese Patent Laid-Open No. 2006-104580, the strength is improved by adding a predetermined amount of Si, Fe, Cu, Mn, and Mg, and the total value of Si, Fe, Cu, and Mg is 1.5% by mass or less. Disclosed is an aluminum alloy plate capable of preventing the occurrence of cracks in pulse laser welding.

Patent Document 1: Japanese Patent No. 3867989 Patent Document 2: Japanese Patent Publication No. 2006-104580

However, in order to further improve the safety of the secondary battery, the battery case material is required to further improve strength and pressure resistance. Furthermore, in recent years, it has become necessary to meet the requirements for miniaturization, light weight, and low cost. Therefore, in addition to the demand for thinning with strength and pressure resistance, in addition, the welding speed of pulse laser welding when fabricating a battery case can be set to 20 to conventional. Speeding up from 30 mm / sec to 30-40 mm / sec is examined. As a result, the input pulse laser power is increased 1.1-1.3 times as conventionally, and therefore, a new problem has arisen. In other words, in such a case of speeding up, weld cracking does not occur, but abnormalities (irregular beads) are formed, and discontinuity of the weld portion is likely to occur. This abnormality part becomes the penetration penetration to the back surface of the to-be-welded material, and caused the problem which adversely affects performance, such as electroconductivity and an operating voltage. There is a demand for a battery case material that can solve the problem related to weldability, but there is no JIS 3000-based aluminum alloy that can solve this problem.

For example, since the aluminum alloy plate for battery cases described in Japanese Patent No. 3867989 is regulated to a predetermined amount or less such that the content of Zn is 0.10% by mass or less, a pulse when producing a battery case using the aluminum alloy having a thickness of 1 mm is used. It is described that laser weldability is also excellent, and it is described that welding crack and Zn scattering can be prevented when performing pulse laser welding used in battery case fabrication. However, when the welding speed of pulse laser welding at the time of manufacturing a battery case is made into the speedup condition of 30-40 mm / sec, although there exists a suppression effect of a welding crack to some extent, since there is no restriction | limiting of other component range, welding is made high speed. Under conditions where the pulsed laser output for the condition is high, the occurrence of the abnormality cannot be prevented.

In addition, since the aluminum alloy plate of Unexamined-Japanese-Patent No. 2006-104580 makes the total value of Si, Fe, Cu, and Mg 1.5 mass% or less, and regulates the total value of Si, Fe, Cu, and Mg, It is described that crack generation can be prevented in pulse laser welding. However, when the welding speed of pulse laser welding at the time of manufacturing a battery case is made into the speedup condition of 30-40 mm / sec, although there exists a suppression effect of a welding crack to some extent, since there is no restriction | limiting of other component range, welding is made high speed. Under conditions where the pulsed laser output for the condition is high, the occurrence of the abnormality cannot be prevented. In addition, in this patent publication, there are descriptions of Ti and B, or the positively added ones, and the effects obtained by the positively added are described only for the purpose of preventing the surface roughness during molding from grain refinement, and pulse laser welding The increase in the welding speed is not mentioned, and therefore, it is not a technique that can naturally cope with the new problem described above.

In other words, in the conventional JIS 3000-based aluminum alloy plate, the thinning and the pressure resistance of the aluminum alloy plate are doubled when the thinning is aimed at the weight reduction required for the battery case. Although the problem which has a general relationship can be eliminated, in addition to such a problem, when the welding speed becomes high so that generation | occurrence | production of the said abnormality cannot be suppressed, the thinning of an aluminum alloy plate, pressure resistance, and weldability are trirate-excited relationship The task in cannot be solved. Therefore, it is difficult to satisfy | fill and satisfy weldability also in addition to the thinning and pressure resistance of an aluminum alloy plate with respect to a battery case.

Moreover, the conventional aluminum alloy plate for battery cases has the following problems. In the aluminum alloy sheet for battery cases, workability (formability) is improved, but work cracking may occur, such as the aluminum alloy bursts during molding, depending on the component composition and manufacturing conditions.

In addition, in order to further improve the safety of the secondary battery, the battery case material is required to further improve strength and pressure resistance.

In addition, in the conventional aluminum alloy plate for battery cases, the crack resistance in pulse laser welding is improved as mentioned above. However, in recent years, since the welding speed of pulse laser welding at the time of manufacturing a battery case becomes high, there exists a problem that an abnormal part (irregular bead) is formed in a welding part, and the discontinuity of a welding part becomes easy to generate | occur | produce. Therefore, while preventing the occurrence of cracks in pulsed laser welding, the demand for aluminum alloy plates for battery cases that can suppress the occurrence of abnormal parts is also increasing.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has an excellent moldability for producing a battery case, an excellent pulse laser weldability, and an improvement in strength and pressure resistance (expansion resistance), and a manufacturing method thereof. And it aims at providing the battery case using this aluminum alloy plate.

MEANS TO SOLVE THE PROBLEM The present inventors examined the following matter about the aluminum alloy plate suitable for battery cases.

The occurrence of abnormality in the pulse laser welding, that is, the sudden change of the melted portion, is a porosity defect remaining in the beads between the time of pulse laser melting (660 to 750 ° C) and the resolidification (660 to 640 ° C). Related to the incidence of.

At the time of welding, a pulse laser irradiation part will be in a molten state, and the bubble by hydrogen, a shield gas, metal vapor, etc. exists in the molten paper. Because the bubbles are light, they immediately escape from the surface of the melt. On the other hand, when the pulse laser irradiation of 1 pulse is completed, it will transfer to a solidification process, but when a bubble is hard to come out, it will remain as a pore defect as it is. Here, in the case of pulse laser welding, the next pulsed laser light is irradiated so that the beads newly overlap the solidified beads. When the solidified beads are re-melted again by irradiation of pulsed laser light, the pulsed laser light is irradiated to the remaining pores, and the pores expand and are usually formed by a key laser light irradiation. ) Is enlarged and the laser light easily enters deeply. As a result, penetration is deeply formed and it becomes an abnormal penetration part. This abnormal penetration part solidifies and an abnormal part in a weld part arises.

Therefore, the present inventors have investigated the influence of the trace components on the occurrence of the abnormality (irregular beads) and the generation of pores inside the beads, and as a result, the Mg, B, Ti content is affected, and among them, the B, Ti content It was also found that the impact was particularly large. That is, by optimizing the range of B and Ti content, it discovered that even if the welding speed which was a problem with the conventional alloy was quickened, generation | occurrence | production of an abnormal part can be prevented.

Moreover, as a result of earnestly examining the influence of the trace component on the weld crack generation, it was also found that Mg and Cu content were affected. That is, by optimizing Mg and Cu content, it discovered that the generation of the welding crack which was a problem with the conventional alloy can be prevented.

The inventors of the present invention conducted various experimental studies to develop a material capable of eliminating the drawbacks of welding by pulse laser welding while taking advantage of the JIS 3000-based aluminum material which is excellent as a material for lithium ion battery cases. did. As a result, the content of Ti and B in the material has a great influence on the generation of abnormal parts which are irregular beads of the pulse laser, and the content of Ti and B contained in this JIS 3000-based aluminum alloy material is regulated in an appropriate range. By discovering that the pore residual in a bead can be suppressed by this, it discovered that the abnormal part which is an irregular bead can be prevented. It was also found that excessive addition of Mg, which lowers the melting point, promotes pore retention in the beads by Ti and B-containing, so that it is necessary to regulate it to a predetermined amount.

In order to solve the said subject, the aluminum alloy plate of this invention is Mn: 0.4-1.5 mass%, Cu: 0.7-4.0 mass%, Mg: 0.2-1.5 mass%, Si: 0.05-1.0 mass%, Fe: 0.05 It contains 1.0 mass%, remainder consists of Al and an unavoidable impurity, Zn: 0.3 mass% or less, Ti: less than 0.02 mass%, and B: 20 mass ppm or less in the said unavoidable impurity.

According to this structure, by containing a predetermined amount of Mn, Cu, Mg, and Si, each element is solid-dissolved in a mother phase, and the intensity | strength of an aluminum alloy plate improves.

In addition, by containing a predetermined amount of Mn, Si, Fe, the formability is improved by the formation of an intermetallic compound, and by containing a predetermined amount of Cu, Mg, Si, Mg ₂ Si or fine S '(Al ₂ CuMg) phase Precipitation improves stress relaxation resistance. In addition, by regulating the Zn concentration to a predetermined amount or less, Zn having a low vapor pressure does not scatter during laser welding of the aluminum alloy plate, and the surroundings are not contaminated. In addition, by regulating Ti and B to a predetermined amount or less, bubbles are less likely to remain in the solidification beads during melting of the material by pulse laser welding irradiation, thereby preventing the occurrence of abnormalities in the weld portion.

In the aluminum alloy plate of the above configuration, it may further contain one or more of Zr: 0.15 mass% or less and Cr: 0.40 mass% or less.

According to such a structure, by containing a predetermined amount 1 or more of Zr and Cr, a structure can be refine | miniaturized and homogenized.

Moreover, in the aluminum alloy plate of the said structure, in the plate thickness direction center part of the cross section of the said aluminum alloy plate for battery cases, the area ratio of the intermetallic compound whose maximum length is 1 micrometer or more is more than 0.3% and less than 2.1%, and the maximum length is The number of intermetallic compounds of 11 micrometers or more shall be 140 pieces / mm <^2> or less.

According to such a structure, by containing a predetermined amount of Mn, Cu, Mg, and Si, each element is solid-dissolved in a base material, and the intensity | strength (pressure-resistant strength) of an aluminum alloy plate improves. In addition, by containing a predetermined amount of Mn, Si, Fe, formability is improved by formation of an intermetallic compound, and by containing a predetermined amount of Cu, Mg, Si, the assembled battery is exposed to a high temperature environment, or When repeatedly exposed to the high temperature environment and the normal temperature environment, in the processed aluminum alloy plate for battery case, Mg ₂ Si or fine S '(Al ₂ CuMg) phases are precipitated to improve the stress relaxation resistance. In addition, by regulating the Zn concentration to be less than or equal to a predetermined amount, Zn having a low vapor pressure does not scatter during laser welding of the aluminum alloy plate, and thus does not pollute the surroundings. In addition, by regulating Ti and B to a predetermined amount or less, bubbles are less likely to remain in the solidification beads during melting of the material by pulse laser welding irradiation, thereby preventing the occurrence of abnormalities in the weld portion.

In addition, by defining a predetermined area ratio of the intermetallic compound having a maximum length of 1 µm or more, the lubricity during processing is improved, the adhesion of the aluminum alloy plate, etc. are prevented, and cracks during molding are prevented, and the maximum length is By specifying the number of intermetallic compounds of 11 micrometers or more as predetermined, the crack at the time of shaping | molding is prevented.

The manufacturing method of the aluminum alloy plate of the said structure which prescribed | regulated the area ratio and number of the intermetallic compound whose maximum length is 1 micrometer or more is the casting process which melt | dissolves and casts the aluminum alloy which has the said composition, and produces the ingot, 420 degreeC A homogenization heat treatment step of performing a homogenization heat treatment at a temperature below the melting point of the aluminum alloy, a hot rolling process of hot rolling the homogenized heat treated ingot, and a cold rolling after cold rolling after the hot rolling process to produce a rolled plate A step, an intermediate annealing step of subjecting the rolled plate to an intermediate annealing step, and a final cold rolling step of carrying out final cold rolling to the intermediate annealing rolled plate at a reduction ratio of 20 to 50%. Roll the plate to a temperature range of at least 420 ° C and below the melting point of the aluminum alloy at a heating rate of at least 100 ° C / min. Heating, and cooling in this temperature range and kept in 0 to 180 seconds, more than 300 ℃ / min cooling rate.

According to this manufacturing method, by performing a homogenization heat treatment, the intermetallic compound is diffused and dissolved, and the structure is homogenized. In addition, by performing the intermediate annealing, in the final cold rolling, the plate thickness of the aluminum alloy plate can be easily adjusted to the desired plate thickness, and work hardening occurs, thereby improving the strength of the aluminum alloy plate. In addition, Mg ₂ Si or a fine S '(Al ₂ CuMg) phase is dissolved. By this solid solution strengthening, the strength of the aluminum alloy plate is improved. In the case where the assembled battery is exposed to a high temperature environment or is repeatedly exposed to the high temperature environment and a normal temperature environment, Mg ₂ Si or S '(Al ₂ CuMg) is used in the processed aluminum alloy plate. In addition to the pinning action due to the precipitation of) phase, the stress relaxation phenomenon is suppressed, and the pressure resistance of the aluminum alloy plate is improved. In addition, by performing intermediate annealing, the strength of the aluminum alloy plate is improved by solid solution strengthening of each element. In addition, by controlling the reduction ratio in the final cold rolling to a predetermined range, the stress relaxation phenomenon is suppressed and the pressure resistance is improved.

The battery case which concerns on this invention uses the aluminum alloy plate of the said structure.

Since such a battery case uses the above-mentioned aluminum alloy plate, strength and pressure resistance (expansion resistance) are improved.

According to the aluminum alloy sheet according to the present invention, it has excellent moldability (ironing processability) when molded into a battery case, and is excellent in pulse laser weldability, and excellent weld cracking resistance in pulse laser welding, It has the weld part strength and can suppress the generation of abnormal parts. In addition, even if the thickness of the sheet is reduced, a battery case having excellent strength and pressure resistance (expansion resistance) can be obtained.

According to the manufacturing method of the aluminum alloy plate which concerns on this invention, the aluminum alloy plate which has the said effect can be manufactured efficiently.

According to the battery case according to the present invention, since the battery case has excellent strength and pressure resistance (expansion resistance), charging and discharging may be repeated in a lithium ion secondary battery or the like, or used in a high temperature environment, resulting in an increase in the temperature inside the battery case. Even when the pressure rises, the deformation amount of the expansion of this battery case is appropriately suppressed to be low. As a result, the battery case can be expanded and deformed, making it difficult to take out during battery replacement, or moreover, the battery case can be damaged to impair or destroy the performance of the electronic device.

BRIEF DESCRIPTION OF THE DRAWINGS It is a perspective view which shows the welding part by a pulse laser for demonstrating the evaluation method of pulse laser weldability in an Example.
2: is sectional drawing by the XX line of FIG. 1, (a) is sectional drawing which shows the case of a favorable welding part, (b) is sectional drawing which shows the case where an abnormal part has arisen.
It is a schematic diagram for demonstrating the measuring method of pore generation degree in an Example.

EMBODIMENT OF THE INVENTION Hereinafter, the form for implementing the aluminum alloy plate which concerns on this invention is demonstrated.

[Configuration of Aluminum Alloy Plate]

The aluminum alloy sheet according to the present invention contains a predetermined amount of Mn, Cu, Mg, Si, Fe, and the balance is Al and inevitable impurities. Among the inevitable impurities, Zn, Ti, B Is regulated below a predetermined amount. Moreover, the area ratio and number of predetermined | prescribed intermetallic compound in the plate thickness direction center part of the cross section of an aluminum alloy plate are prescribed | regulated predetermined. Hereinafter, the reason for limitation of each component and the definition reason of distribution of an intermetallic compound are demonstrated.

(Mn: 0.4-1.5 mass%)

Mn has the effect of solid-solution in a mother phase to raise the intensity | strength of an aluminum alloy plate, and the effect improves with the increase of Mn content, and can increase the pressure-resistant strength at the time of using a battery case. In addition, Mn forms an intermetallic compound (Al-Fe-Mn-based intermetallic compound, Al-Fe-Mn-Si-based intermetallic compound) with Al, Fe, and Si, thereby increasing the number of fine intermetallic compounds. Since it contributes to the lubrication effect at the time of shaping | molding with a battery case, the moldability of an aluminum alloy plate is improved. When Mn content is less than 0.4 mass%, solid solution strengthening is not exhibited and since the number of the said fine intermetallic compounds of 1 micrometer or more and less than 11 micrometers tends to run short, such an effect is inadequate. On the other hand, when Mn content exceeds 1.5 mass%, the number of coarse said intermetallic compounds of 11 micrometers or more will increase, and since it will become a starting point of the crack at the time of shaping | molding, the moldability of an aluminum alloy plate will fall. Therefore, Mn content is made into 0.4-1.5 mass%.

(Cu: 0.7-4.0 mass%)

Cu has the effect of solid-solution in a mother phase to raise the intensity | strength of an aluminum alloy plate, and the effect improves with the increase of Cu content, and can improve the pressure-resistant strength at the time of using a battery case. Moreover, Cu has the effect of improving the intensity | strength of the weld part at the time of pulse laser welding. In addition, Cu forms a fine S '(Al ₂ CuMg) phase in conjunction with Al and Mg to precipitate. This fine S '(Al ₂ CuMg) phase prevents stress relaxation by inhibiting the shift of dislocations, thereby improving stress relaxation resistance of the aluminum alloy plate. If Cu content is less than 0.7 mass%, such an effect is inadequate. On the other hand, since the Cu content exceeds 4.0 mass%, fine S '(Al ₂ CuMg) it is excessively inhibit the movement of dislocation by the precipitates on, to lower the moldability. Moreover, since melting | fusing point falls, a welding crack arises in pulse laser welding. Therefore, Cu content is made into 0.7 to 4.0 mass%.

(Mg: 0.2-1.5 mass%)

Mg has the effect of solid-solution in a mother phase to raise the intensity | strength of an aluminum alloy plate, and the effect improves with the increase of Mg content, and the pressure-resistant strength at the time of using a battery case can be raised. In addition, Mg associates with Si to precipitate Mg ₂ Si, or associates with Al and Cu to precipitate a fine S '(Al ₂ CuMg) phase. The Mg ₂ Si and S '(Al ₂ CuMg) phases suppress the shift of dislocations, thereby preventing the stress relaxation phenomenon and improving the stress relaxation resistance of the aluminum alloy plate. If the Mg content is less than 0.2% by mass, such an effect is insufficient. Moreover, intensity | strength falls that Mg content is less than 0.2 mass%. On the other hand, when Mg content exceeds 1.5 mass%, work hardening property of an aluminum alloy plate will become high and moldability will fall. Moreover, since melting | fusing point falls, a welding crack arises in pulse laser welding.

Moreover, when Mg content contains more than 1.5 mass%, melting | fusing point will fall and the ratio of Mg atom vaporization and scattering unexpectedly increases, and abnormal part generate | occur | produces in pulse laser welding. Therefore, also in order to add the characteristic which prevents generation | occurrence | production of the abnormal part in pulse laser welding, the upper limit of Mg amount shall be 1.5 mass%. Therefore, Mg content shall be 0.2-1.5 mass%.

(Si: 0.05-1.0 mass%)

Si has the effect of solid-solution in a mother phase to raise the intensity | strength of an aluminum alloy plate, and the effect improves with Si content increase, and the pressure-resistant strength at the time of using a battery case can be raised. In addition, Si forms Al, Mn, Fe and Al-Fe-Mn-Si-based intermetallic compounds and increases the number of fine intermetallic compounds, thereby contributing to the lubrication effect when forming into a battery case. Therefore, the moldability of an aluminum alloy plate is improved. In addition, since Si precipitates Mg ₂ Si in conjunction with Mg, the stress relaxation resistance of the aluminum alloy plate is improved. If the Si content is less than 0.05% by mass, such an effect is insufficient. On the other hand, when Si content exceeds 1.0 mass%, since the said intermetallic compound tends to be coarse and becomes a starting point of the crack at the time of shaping | molding, the moldability of an aluminum alloy plate tends to fall. In addition, Mg ₂ Si may be coarsened to reduce the yield strength. In addition, an Al—Cu—Fe—Si based intermetallic compound may be formed to reduce the high capacity of Cu. Moreover, since melting | fusing point falls, a welding crack arises in pulse laser welding. Therefore, Si content is made into 0.05-1.0 mass%.

(Fe: 0.05-1.0 mass%)

Fe forms Al-Fe-Mn-based and Al-Fe-Mn-Si-based intermetallic compounds, such as Mn and Si, and increases the number of fine intermetallic compounds, thereby lubricating the effect of forming the battery case. Since it contributes to this, there exists an effect of improving the moldability of an aluminum alloy plate. When Fe content is less than 0.05 mass%, since the number of the said fine intermetallic compounds of 1 micrometer or more and less than 11 micrometers runs short, the said effect is small. On the other hand, when Fe content exceeds 1.0 mass%, the number of coarse said intermetallic compounds of 11 micrometers or more will increase, and since it will become a starting point of the crack at the time of shaping | molding, the moldability of an aluminum alloy plate will fall. In addition, the Al-Fe-Mn type, getting a lot amount of Al-Fe-Mn-Si-based intermetallic compounds formed of, so reducing the precipitation of Mg ₂ Si, there is a case where the stress relaxation property is lowered. In addition, an Al—Cu—Fe—Si based intermetallic compound may be formed to reduce the high capacity of Cu. Therefore, Fe content shall be 0.05-1.0 mass%.

(Remainder: Al and inevitable impurities)

In addition to the above components, the balance of the aluminum alloy sheet is made of Al and unavoidable impurities. On the other hand, as inevitable impurities, for example, Ga, V, Ni, and the like within the generally known ranges contained in the present and intermediate alloys do not interfere with the effects of the present invention. The inclusion of is acceptable. In addition, in this invention, Zn, Ti, and B are regulated to predetermined amount or less among inevitable impurities.

(Zn: 0.3 mass% or less)

Since Zn has a low vapor pressure, it is likely to scatter during pulse laser welding and contaminate the surroundings, and also to cause bead cracking, thereby deteriorating pulse laser weldability of the aluminum alloy plate. Therefore, Zn content is regulated to 0.3 mass% or less. Moreover, preferable Zn content for making the said contamination good is 0.10 mass% or less.

(Ti: less than 0.02 mass%)

Ti has an effect of miniaturizing and homogenizing (stabilizing) an aluminum alloy casting structure, and is usually added in an amount of 0.02% by mass or more for the purpose of preventing casting cracks at the time of ingot of a rolling slab. It is an element which falls in the range of 0.15 mass% or less since it is easy to become a starting point of the crack at the time of shaping | molding and shaping | molding. However, when 0.02 mass% or more commonly used as mentioned above is added, since it will become easy to remain a bubble in solidification beads at the time of melting | fusing material (660-750 degreeC) by pulse laser welding irradiation, following pulse laser welding By irradiation, when a coagulation bead of the previous one redissolves, it becomes difficult for a bubble to fall out in a molten paper. As a result, pore defects remain in the beads, the penetration is deeply formed, and abnormal portions are generated. Therefore, Ti content is regulated to less than 0.02 mass%.

(B: 20 mass ppm or less)

As described above, B is an element that is actively added and commercialized with Ti as the Ti-B master alloy for the purpose of preventing casting cracking during slab casting of an aluminum alloy. However, when the B content is more than 20 mass ppm, similarly to the above Ti addition, bubbles are likely to remain in the coagulation beads of the pulse laser irradiation unit, and when the previous coagulation bead portions are re-dissolved in the next pulse laser irradiation, Bubbles are hard to fall off As a result, pore defects remain in the beads, the penetration is deeply formed, and abnormal portions are generated. Therefore, B content is regulated to 20 mass ppm or less.

The aluminum alloy sheet according to the present invention may further contain one or more of Zr: 0.15 mass% or less and Cr: 0.40 mass% or less.

(Zr: 0.15 mass% or less, Cr: 0.40 mass% or less)

Zr and Cr have an effect which refine | miniaturizes and homogenizes (stabilizes) an aluminum alloy structure. Moreover, recrystallized grain at the time of resolidification at the time of welding can be refined | miniaturized, and welding crack can be avoided. However, when exceeding each prescribed | regulated content, a coarse intermetallic compound will crystallize and it will become a starting point of the crack at the time of shaping | molding, and the moldability of an aluminum alloy plate falls. Therefore, when Zr and Cr are added, Zr content is 0.15 mass% or less, and Cr content shall be 0.40 mass% or less. On the other hand, although a lower limit is not specifically prescribed | regulated, In order to acquire the said effect, it is preferable to contain Zr and Cr 0.05 mass% or more, respectively. On the other hand, Zr and Cr may contain below the said prescribed content as an unavoidable impurity.

(Area ratio of intermetallic compounds having a maximum length of 1 μm or more: more than 0.3% and less than 2.1%)

The area ratio of the intermetallic compound whose maximum length in the plate | board thickness direction center part of the cross section of an aluminum alloy plate is 1 micrometer or more shall be more than 0.3% and less than 2.1%. In addition, the sheet thickness direction center part of a cross section specifically refers to the area | region in 30 to 50% of the plate thickness centering on the sheet thickness direction center.

If the area ratio is 0.3% or less, the aluminum alloy lacks a lubricating effect of removing the aluminum mortar solidified on the punch or die during ironing, and the aluminum alloy sheet is pressed, resulting in an aluminum alloy. The formability of the plate is lowered. On the other hand, when the area ratio is 2.1% or more, many coarse intermetallic compounds tend to be a starting point of forming cracks, and thus the moldability of the aluminum alloy plate is lowered.

On the other hand, even if the compound of less than 1 micrometer is contained within the said range, these intermetallic compounds may be contained in the said range because these area ratios do not affect moldability. The upper limit of the maximum length is not determined, and the intermetallic compound having a maximum length of 11 µm or more is included in the area ratio.

(Number of intermetallic compounds with a maximum length of 11 µm or more: 140 pieces / mm ² or less)

The number of intermetallic compounds whose maximum length in the plate thickness direction center part of the cross section of an aluminum alloy plate is 11 micrometers or more shall be 140 pieces / mm <^2> or less.

When the number exceeds 140 pieces / mm ² , the number of coarse intermetallic compounds is large and tends to be a starting point of cracking during molding, and thus the moldability of the aluminum alloy plate is reduced.

On the other hand, even if the compound of less than 11 micrometers is contained within the said range, these intermetallic compounds may be contained in the said range, since the number of these does not affect moldability. In addition, there is no limitation regarding the upper limit of a maximum length.

And distribution of these intermetallic compounds is controlled by said each content of Mn, Mg, Si, Fe, and late manufacturing conditions (homogenization heat processing conditions, intermediate annealing conditions).

As an example, application of a scanning electron microscope (SEM) is mentioned as a detection means of an intermetallic compound. Intermetallic compounds with a maximum length of 1 µm or more can be identified by contrast with the mother phase on the composition of the SEM (COMPO), and Al-Mn-Fe-based and Al-Mn-Fe-Si-based intermetallic compounds are whiter than the Al mother phase. The Mg-Si-based intermetallic compound is blacker than the Al matrix. In the intermetallic compound in the plate thickness direction center part of the cross section of an aluminum alloy plate, an aluminum alloy plate is cut out, the cut surface containing a rolling direction and a plate thickness direction is polished, it is finished to a mirror surface, and it is set as an observation surface, and aluminum The area | region in 30 to 50% of plate | board thickness centering on the plate | board thickness direction center of an alloy plate is observed. From this area, preferably, a plurality of visual fields are observed and photographed in total of 1 mm ² or more, and the area ratio and the number density of the intermetallic compound of the designated size are measured using an image processing apparatus or the like.

[Method of Manufacturing Aluminum Alloy Plate]

An example of the manufacturing method of the aluminum alloy plate which concerns on this invention is demonstrated.

First, an aluminum alloy having the composition described above is melted and cast to produce an ingot, and the ingot is subjected to a surface roughening, and then the homogenization heat treatment is performed at a temperature of 480 ° C. or higher and less than the melting point of the aluminum alloy. Next, the homogenized heat treated ingot is hot rolled and cold rolled to produce a rolled plate. And this rolling plate is heated in the temperature range of 420 degreeC or more and below the melting point of the said aluminum alloy at the heating rate of 100 degreeC / min or more, hold | maintaining for 0 to 180 second in this temperature range, and then, at the cooling rate of 300 degreeC / min or more Intermediate annealing is performed by cooling. Then, final cold rolling is performed to the rolling annealing intermediate | middle anneal by 20-50% of reduction ratio, and it is set as an aluminum alloy plate. Moreover, you may perform final annealing for 80 to 200 degreeC and 0.5 to 8 hours to the rolled plate which performed the final cold rolling as needed. Since the material is softened by the final annealing and the elongation is improved, the final annealing is a preferred process for improving the formability.

Next, the manufacturing method of the aluminum alloy plate which satisfy | fills the conditions regarding the area ratio and number of the said intermetallic compound especially among the aluminum alloy plates which concern on this invention is demonstrated. The manufacturing method of the aluminum alloy plate which concerns on this invention includes a casting process, a homogenization heat processing process, a hot rolling process, a cold rolling process, an intermediate annealing process, and a final cold rolling process. Hereinafter, each process will be described.

<Casting process>

A casting process is a process of manufacturing an ingot by melt | dissolving and casting the aluminum alloy which has the said composition.

The method of melting and casting the alloy is not particularly limited, and a conventionally known method may be used. For example, it can melt | dissolve using a vacuum induction furnace and can cast using the continuous casting method or the semicontinuous casting method.

<Homogenization Heat Treatment Process>

The homogenization heat treatment step is a step of performing the homogenization heat treatment at the temperature at which the ingot is at least 420 ° C. and below the melting point of the aluminum alloy. On the other hand, in the homogenization heat treatment step, the ingot is subjected to a surface roughening, and then homogenization heat treatment is performed.

(Processing temperature: 420 degreeC or more, less than the melting point of aluminum alloy)

Before rolling the ingot, it is necessary to perform homogenization heat treatment (cracking treatment) at a predetermined temperature. By performing a cracking process, the intermetallic compound determined at the time of casting is diffused and dissolved to homogenize the structure. If the cracking treatment temperature is less than 420 ° C, the homogenization of the ingot made of the aluminum alloy according to the present invention is insufficient. That is, when forming into a battery case, the effect of reducing the number of coarse Al-Fe-Mn-Si-based compounds, such as coarse cracks, is not obtained. On the other hand, when the cracking temperature reaches the melting point of the aluminum alloy, the ingot melts. Therefore, the cracking treatment temperature is at least 420 ° C and lower than the melting point of the aluminum alloy. On the other hand, melting | fusing point of the aluminum alloy which concerns on this invention changes in the range of about 500-610 degreeC according to the composition, and especially if there is much Cu content, it will become low. In addition, since the homogenization of ingot may not be completed when a cracking treatment time is less than 1 hour, it is preferable to carry out for 1 hour or more.

<Hot rolling process and cold rolling process>

The hot rolling step is a step of hot rolling the homogenized heat treated ingot.

The cold rolling step is a step of cold rolling after the hot rolling step to produce a rolled plate.

The method of hot rolling and cold rolling is not specifically limited, A conventionally well-known method may be used.

<Intermediate annealing process>

The intermediate annealing step is a step of performing an intermediate annealing on the rolled plate.

The intermediate annealing heats the rolled plate at a temperature range of 420 ° C. or higher and less than the melting point of the aluminum alloy at a heating rate of 100 ° C./min or more, and holds 0 to 180 seconds in this temperature range, and then 300 ° C./min or more. Cool at cooling rate.

(Heating rate: 100 ° C./min or more, holding: 420 ° C. or more, 0 to 180 sec. Below the melting point of the aluminum alloy, cooling rate: 300 ° C./min or more)

By performing the intermediate annealing on the rolled sheet before the final cold rolling (final cold rolling), in the final cold rolling, the sheet thickness of the aluminum alloy sheet can be easily adjusted to the desired sheet thickness, and work hardening occurs, and the Strength is improved. In addition, Mg ₂ Si or a fine S '(Al ₂ CuMg) phase is dissolved in the rolled sheet by performing an intermediate annealing. By this solid solution strengthening, the strength of the aluminum alloy plate is improved. In the case where the assembled battery is exposed to a high temperature environment or repeatedly exposed to the high temperature and room temperature environment, in the processed aluminum alloy material for a battery case, the Mg ₂ Si or S '(Al ₂ CuMg) phase is formed. The displacement of dislocations is suppressed (pinning effect) to prevent stress relaxation and to improve the pressure resistance of the aluminum alloy plate. In addition, since solute elements such as Cu are dissolved in the mother phase by the intermediate annealing, the strength of the aluminum alloy plate is improved by the solid solution strengthening of each element.

If the treatment temperature of the intermediate annealing is less than 420 ° C., the crystal grains are not recrystallized. Therefore, in the final cold rolling step, a plate in which the recrystallized structure and the processed structure are mixed in the intermediate annealing is rolled, and cracks and surfaces are formed during the forming process. Roughness arises and moldability falls. On the other hand, when the process temperature of intermediate annealing reaches melting | fusing point of an aluminum alloy, a rolled sheet will fuse | melt. Therefore, the processing temperature of intermediate annealing is made into 420 degreeC or more and less than melting | fusing point of an aluminum alloy. In addition, since melting | fusing point of the aluminum alloy which concerns on this invention is the same as that in the upper limit temperature of the said cracking process, it abbreviate | omits. In addition, even if it hold | maintains more than 180 second in this intermediate | middle annealing temperature range, since the said effect does not increase and productivity falls, holding time is made into 180 second or less.

In addition, when the heating rate for heating the rolled plate in the temperature range of the intermediate annealing is less than 100 ° C / min, the solute element becomes a coarse precipitate in the temperature range in the middle of the temperature increase, and the precipitate is dissolved in the treatment temperature range of the intermediate annealing. It doesn't work. Moreover, when the cooling rate after intermediate annealing (holding) is less than 300 degreeC / min, the solute element solid-solution precipitates in the temperature range during temperature-fall. In addition, when the heating rate or the cooling rate is low, the crystals may coarsen and the moldability may decrease. Therefore, the heating rate for heating in the treatment temperature range of intermediate annealing is 100 ° C / min or more, and from the treatment temperature range of intermediate annealing, the cooling rate is 300 ° C / min or more and 100 ° C or less in which solute elements do not precipitate. Cool until

<Final cold rolling process>

The final cold rolling process is a process of performing final cold rolling on the intermediate annealing rolled sheet at a reduction ratio of 20 to 50%.

(Depression rate: 20 to 50%)

By adjusting the reduction ratio in final cold rolling to 20 to 50%, the stress relaxation phenomenon is suppressed and the pressure resistance of the aluminum alloy plate is improved. If the reduction ratio is less than 20%, the strength may not be sufficiently obtained, and the rigidity as the battery case may be insufficient. On the other hand, when the reduction ratio exceeds 50%, the accumulation of deformation increases, so that recovery is easily progressed, and the stress relaxation resistance decreases and the pressure resistance decreases. In addition, since cracking and surface roughening occur during molding, the moldability is lowered. Therefore, the reduction ratio of final cold rolling is made into 20 to 50%.

On the other hand, in carrying out the present invention, other steps, such as a cleaning treatment step, such as a strain correction treatment step, may be included between or before and after the above steps, within a range that does not adversely affect the above steps. .

[Battery case]

Next, a battery case according to the present invention will be described. The battery case according to the present invention is produced using the aluminum alloy plate.

Hereinafter, an example of the method of manufacturing a battery case and a secondary battery from the aluminum alloy plate which concerns on this invention is demonstrated.

<Method of manufacturing a battery case and a secondary battery>

The aluminum alloy plate which concerns on this invention used as a case main body part is made into the board thickness of about 0.3-0.8 mm by final cold rolling. The aluminum alloy plate is cut into a predetermined shape and molded into a user cylinder shape by drawing or ironing. In addition, by repeating this process a plurality of times, the side wall surface is gradually raised, and processing such as trimming is carried out as necessary, whereby it is molded into a predetermined bottom shape and side wall height to form a case main body. The shape of the battery case is not particularly limited, and the case main body portion has a shape of a user cylinder having an open upper surface according to the means of a secondary battery such as a rectangular parallelepiped such as a cylindrical shape or a flat shape.

It is preferable that the plate thickness reduction rate (ironing rate) of the side wall of a case main body part by ironing etc. is 30 to 80%. When the sheet thickness reduction rate is out of this range, it becomes difficult to adjust the side wall of the molded case body portion to a desired sheet thickness.

In addition, the lid portion is made of the aluminum alloy sheet according to the present invention, which is made of the same aluminum alloy as the case body portion and has a plate thickness of about 0.7 to 1.5 mm. The aluminum alloy plate is cut into a shape corresponding to the upper surface of the case main body portion to form an injection port or the like to form a lid portion. A secondary battery material (anode material, negative electrode material, separator, etc.) is stored in the case body portion, and the lid portion is welded to the upper surface. As for welding of a case main body part and a lid part, welding with a pulse-controlled pulse laser is common. The electrolyte is injected into the battery case from the injection port, and the injection port is sealed to form a secondary battery.

As mentioned above, the aluminum alloy plate which concerns on this invention is suitable for the molded article shape | molded in a desired shape by the transfer press in which a series of shaping | molding processes are performed sequentially, especially the battery case of a lithium ion secondary battery. That is, the aluminum alloy sheet according to the present invention has excellent strength and formability (processability) for particularly severe processing such as multi-stage drawing-ironing processing included in the transfer press. Moreover, the aluminum alloy plate which concerns on this invention has pulse laser welding property which can reliably seal a case main body part and a lid part with a pulse laser, for example, when manufacturing with a battery case. In addition, by defining the content of Ti and B to be predetermined or less in inevitable impurities, occurrence of abnormality in pulse laser welding can be suppressed, and the pulse laser weldability can be further improved.

In addition, the battery case produced from the aluminum alloy plate according to the present invention, as described above, the charge and discharge is repeated in a lithium ion secondary battery or the like, or used in a high temperature environment, the temperature inside the battery case rises, and accordingly the internal pressure Even when this rises, the amount of deformation of the expansion of the battery case can be suppressed to be appropriately low. As described above, the aluminum alloy sheet according to the present invention is excellent in moldability and satisfies strength and pressure resistance (expansion resistance). Moreover, it has excellent pulse laser weldability, is excellent in weld cracking resistance and weld part strength, and can suppress abnormal part generation | occurrence | production in pulse laser welding.

[Example]

As mentioned above, although the form for implementing this invention was described, the Example which confirmed the effect of this invention is demonstrated concretely in contrast with the comparative example which does not satisfy the requirements of this invention. In addition, this invention is not limited to this Example.

[Production materials]

(Examples No. 1-17, Comparative Examples No. 18-35)

The aluminum alloy of the composition shown in Table 1 was melt | dissolved, cast, it was made into an ingot, and after this ingot was face-treated, the homogenization heat process was performed at 500 degreeC for 4 hours. Hot-rolling and cold rolling were further given to this homogenized ingot, and it was set as the rolled board of about 0.7 mm in thickness. Then, the rolled plate was heated to 500 ° C. at a heating rate of 500 ° C./min, held at this temperature for 30 seconds, and then cooled to 500 ° C./min to perform an intermediate annealing. Finally, final cold rolling was performed at a reduction ratio of 30% to obtain an aluminum alloy plate having a sheet thickness of 0.5 mm.

(Examples No. 36-44, Comparative Example Nos. 45-53)

After dissolving and casting the aluminum alloy of the composition shown in Table 2 (the same composition as Example No. 5) to make an ingot, and indenting the ingot, the ingot was subjected to cracking for 4 hours at the temperature shown in Table 2. Carried out. Hot-rolling and cold rolling were further given to this homogenized ingot, and it was set as the rolled board of predetermined plate | board thickness. The rolled plate was subjected to intermediate annealing at the heating rate, annealing temperature (30 seconds hold), and cooling rate shown in Table 2. Finally, the final cold rolling was performed at the reduction ratio shown in Table 2 to obtain an aluminum alloy plate having a sheet thickness of 0.5 mm.

The component compositions are shown in Tables 1 and 2. In addition, in a table | surface, the thing which does not satisfy the range of this invention underlines a numerical value, and the thing which does not contain a component is represented by "-". No. 34 is a JIS A3003 alloy, and No. 35 is an alloy based on Japanese Patent No. 3867989.

[Distribution of Intermetallic Compounds]

Next, the distribution of the intermetallic compound was measured by the following method.

First, the aluminum alloy plate is cut out and embedded in resin, and the surface including the rolling direction and the plate thickness direction is polished to be the observation surface, and the mirror surface is mirrored, and the mirrored surface is accelerated by a scanning electron microscope (SEM) with an acceleration voltage of 20 KV. , 20 viewing fields (total 1 mm ² ) were observed on a composition (COMPO) at a magnification of 500 times. Observation visual field was made into the range of 0.19 mm combining the both sides (upward and downward direction) of the thickness direction in the plate | board thickness direction centering on the center of the plate | board thickness direction. The part that is whiter than the mother phase is regarded as an Al-Mn-Fe-based intermetallic compound or an Al-Mn-Fe-Si-based intermetallic compound, and the part that is blacker than the mother phase is regarded as an Mg-Si-based intermetallic compound. The area ratio was computed by calculating the sum total of the area of the intermetallic compound whose largest length is 1 micrometer or more. In addition, the number of intermetallic compounds whose maximum length was 11 micrometers or more was counted, and the number (number density) per unit area was computed. Tables 3 and 4 show the area ratios and number densities of the intermetallic compounds at the center of the plate thickness of the cross section of the aluminum alloy plate.

[evaluation]

The following evaluation was performed with the obtained aluminum alloy plate, and a result is shown to Tables 4 and 5.

(burglar)

From the aluminum alloy plate, the tensile test piece according to JIS 5 was cut out so that the tensile direction might be parallel to the rolling direction. With this test piece, the tensile test according to JIS Z2241 was performed, and tensile strength, proof strength (0.2% yield strength), and elongation were measured. As for the acceptance criteria of strength, the yield strength was 220 MPa or more.

(Moldability)

From the aluminum alloy plate, the ironing process ratio of the side wall was made into 50% using the press work machine, and the rectangular battery case main body of the box body of 5 mm x bottom side 30 mm, and 50 mm of side wall height was shape | molded. At this time, it is possible to mold, and that there is no surface roughness after molding, because of excellent moldability, "◎", and moldability is possible. Or the occurrence of remarkable surface roughness was evaluated as &quot; × &quot;

(Pulse laser weldability)

As shown in FIG. 1, the aluminum alloy plate 10 of 0.5 mm of plate | board thickness was arrange | positioned facing each other, and this abutting part was welded with the pulse laser. In pulsed laser welding, a molten pool is formed by one pulse laser, and the solidified circular weld 20 is continuously formed along the welding line by the movement of the laser. The welding machine used a pulse oscillation YAG laser, the welding speed was 2 levels of 25 mm / sec and 35 mm / sec, and the shield gas supplied nitrogen at 20 liter / min. In addition, when welding the aluminum alloy plate shown in No. 5, the frequency and the pulsed laser output were selected as shown in Table 3 on the conditions which the penetration of a bead will be about 200 micrometers.

About evaluation, the presence or absence of a weld crack was observed with the naked eye and an optical microscope, and it was determined that "(circle)" and the thing which a crack generate | occur | produced "x" that the healthy bead without a crack was obtained.

In addition, when the weld bead cross section is cut out and observed with an optical microscope as a cross section by the XX line of FIG. Evaluated that "x" was not obtained because sufficient seam strength was not obtained by the insufficiency (it describes as "infiltration" in a table). In addition, as shown in FIG.2 (a), when the abnormality part 21 (refer FIG.2 (b)) does not produce | generate as a bead shape as a good thing as "(circle)" and FIG.2 (b), it is abnormal The case where the part 21 generate | occur | produced was evaluated as "x" as having a bad bead shape (it describes as "the occurrence of an abnormal part" in a table).

On the other hand, about the occurrence of the unexpected bead abnormality in pulse laser welding, the generation | occurrence | production situation of the pore defect in which the connection was anticipated was observed. The method of measuring the pore was carried out by microscopic observation in that the pore diameter was a size which cannot be determined by a radiographic test. That is, as shown in FIG. 3, the test piece of length Ls is taken from the to-be-welded materials 10 and 10 after pulse laser welding so that a welding bead 20 may be included in the welding line direction (square of the figure shown in FIG. 3 above). This test piece was embedded in resin, and the end surface of the weld part was polished to the center part of the width direction of a weld part. Then, the polished surface was observed under a microscope at a magnification of 400 to 1000 times, and the size, number, and position of the pores 22 were measured. The size of the pores 22 was visually divided into five stages of four steps of 1.25 μm pitch from minimum diameter of 2.5 μm to 7.5 μm and one step of greater than 7.5 μm, using a microscope scale. In addition, regarding the generation | occurrence | production situation of the pore 22, the area | region is computed from the diameter of the pore 22 which generate | occur | produced in the observation surface whose length of a weld line direction is Ls, and this is the pore 22 contained in the range of this area. ), Multiplied by the total number, and the total cross-sectional area was calculated for all area ranges, and the pore incidence was calculated by dividing this by the observation distance Ls. That is, porosity generation was calculated by the following equation.

As a result, when the porosity was 3.0 µm ² / mm or less, the appearance of the beads was good, and when the porosity exceeded 3.0 µm ² / mm, dizziness occurred in the appearance of the beads. Therefore, when the porosity is 3.0 µm ² / mm or less, the bead formation is good (no abnormality), and when "○" and 3.0 µm ² / mm is exceeded, the bead formation is poor (abnormal occurrence) and it is "x". Evaluated.

(Pressure resistance)

The rectangular battery case in which the lid member was sealed by pulse laser welding repeatedly using the rectangular case produced in the evaluation of the formability was heated to 100 ° C. for 2 hours while the internal pressure of 294 kPa (3 kg / cm ² ) was applied. Maintained. After returning to room temperature, the displacement amount of the expansion of the side surface (surface of width 30mm x height 50mm) of the battery case was measured. The displacement amount of 0.8 mm or less was excellent in pressure resistance, and "◎" and more than 0.8 mm and 1.0 mm or less were good in pressure resistance, and those exceeding "(circle)" and 1.0 mm were evaluated as "x" as bad.

In addition, in a table | surface, it is underlined in numerical value that a proof strength does not satisfy | fill an acceptance criterion, and the thing which an ingot and a rolled sheet melted and was unable to evaluate is represented by "-". In the pressure resistance evaluation, the evaluation was not performed because the moldability was poor, and the evaluation was not performed because pulse crack welding caused cracks or abnormalities in the beads.

(Evaluation by aluminum alloy composition)

As shown in Table 4, Nos. 1 to 17 which are the examples were excellent in all of the strength, formability, pulse laser weldability, and pressure resistance because they satisfied the scope of the present invention.

On the other hand, Nos. 18 to 35, which are comparative examples, did not satisfy the scope of the present invention, resulting in the following results.

No. 18 was inferior in pressure resistance because the Mn content was less than the lower limit. On the other hand, regarding moldability, as a result of suppressing the decrease in yield strength by the Cu content, the moldability was barely secured. On the other hand, although the number of fine intermetallic compounds decreased, the area ratio of the intermetallic compound whose maximum length is 1 micrometer or more exceeded 0.3%.

In No. 19, since the Mn content exceeded the upper limit, the intermetallic compound was bundled and coarsened, resulting in inferior moldability. In No. 20, since the Cu content was less than the lower limit, the beads were insufficient in penetration, and the pulse laser weldability was inferior. In addition, the pressure resistance was inferior. No. 21 had poor moldability because the Cu content exceeded the upper limit. In addition, cracks occurred in the beads, resulting in inferior pulse laser weldability.

No. 22 had poor strength and pressure resistance because the Mg content was less than the lower limit. No. 23 had poor moldability because the Mg content exceeded the upper limit. In addition, cracks and abnormalities occurred in the beads, and the pore generation was high, resulting in inferior pulse laser weldability.

Since No.24 had Si content less than a lower limit, pressure resistance was inferior. On the other hand, regarding moldability, as a result of suppressing the decrease in yield strength by the Cu content, the moldability was barely secured. On the other hand, although the number of fine intermetallic compounds decreased, the area ratio of the intermetallic compound whose maximum length is 1 micrometer or more exceeded 0.3%. In No. 25, since the Si content exceeded the upper limit, cracks occurred in the beads, resulting in inferior pulse laser weldability. On the other hand, regarding moldability, as a result of suppressing the decrease in yield strength by the Cu content, the moldability was barely secured. On the other hand, coarse intermetallic compounds were produced, but the number density of the intermetallic compounds having a maximum length of 11 µm or more was 140 or less.

Since No. 26 had Fe content less than a lower limit, the intermetallic compound was insufficient and the moldability was inferior. In No. 27, since the Fe content exceeded the upper limit, the intermetallic compound was bundled and coarsened, resulting in inferior moldability. In No. 28, since the Zn content exceeded the upper limit, cracks occurred in the beads, resulting in inferior pulse laser weldability.

No. 29 was inferior in moldability because the Zr content exceeded the upper limit. No. 30 was inferior in moldability because Cr content exceeded the upper limit. On the other hand, in Nos. 29 and 30, coarse intermetallic compounds were produced, but the number density of the intermetallic compounds having a maximum length of 11 µm or more was 140 or less. No. 31 and No. 35 had abnormalities in the beads because the Ti content exceeded the upper limit, resulting in high pore generation and poor pulse laser weldability.

In No. 32, since the B content exceeds the upper limit, abnormalities were formed in the beads, the porosity was high, and the pulse laser weldability was inferior. In No. 33, since the Ti content and the B content exceed the upper limit, abnormalities were formed in the beads, the porosity was high, and the pulse laser weldability was inferior. No. 34 had inferior strength and pressure resistance because Cu content and Mg content were less than the lower limit. In addition, the beads were insufficient in penetration, resulting in poor pulse laser weldability.

(Evaluation by production method)

As shown in Table 5, Nos. 36 to 44 which are the examples were excellent in all of the strength, formability, pulse laser weldability, and pressure resistance because they satisfied the scope of the present invention.

On the other hand, Nos. 45 to 53 which are comparative examples did not satisfy the scope of the present invention, resulting in the following results.

In No. 45, since the cracking temperature was less than the lower limit, the intermetallic compound was bundled, resulting in inferior moldability. In No. 46, the ingot was molten because the cracking treatment temperature exceeded the upper limit.

In No. 47, since the heating rate in the intermediate annealing was less than the lower limit, the intermetallic compound was bundled, and the moldability was inferior. No. 48 was inferior in moldability because the annealing temperature in the intermediate annealing was less than the lower limit. In No. 49, since the cracking temperature was less than the lower limit, the homogenization of the ingot was insufficient, and since the annealing temperature in the intermediate annealing exceeded the upper limit, the rolled plate was molten.

Since the cooling temperature in intermediate | middle annealing is less than a lower limit, No. 50 bundles an intermetallic compound, and was inferior to moldability. In No. 51, since the heating rate, annealing temperature, and cooling rate in the intermediate annealing were less than the lower limit, the intermetallic compound was bundled, resulting in poor moldability. In No. 52, since the final cold reduction ratio was less than the lower limit, the strength and the pressure resistance were inferior. No. 53 had poor moldability because the final cold reduction ratio exceeded the upper limit.

Claims (7)

Mn: 0.4-1.5 mass%, Cu: 0.7-4.0 mass%, Mg: 0.2-1.5 mass%, Si: 0.05-1.0 mass%, Fe: 0.05-1.0 mass%, and remainder is Al and an unavoidable impurity. Made up of
As an aluminum alloy plate regulated by Zn: 0.3 mass% or less, Ti: less than 0.02 mass%, B: 5 mass ppm or less in the said unavoidable impurity,
At the center of the thickness direction of the cross section of the aluminum alloy plate, the area ratio of the intermetallic compound having a maximum length of 1 μm or more is more than 0.3% and less than 2.1%, and the number of intermetallic compounds having a maximum length of 11 μm or more is 140 pieces / mm ² or less aluminum alloy plate. The method of claim 1,
Furthermore, an aluminum alloy plate containing Zr: 0.15 mass% or less. The method of claim 1,
Furthermore, the aluminum alloy plate containing Cr: 0.40 mass% or less. delete As a manufacturing method of the aluminum alloy plate of Claim 1,
A casting process of manufacturing an ingot by melting and casting an aluminum alloy having the composition;
A homogenization heat treatment step of performing homogenization heat treatment at a temperature at which the ingot is at least 420 ° C. and below the melting point of the aluminum alloy,
A hot rolling process for hot rolling the homogenized heat treated ingot,
A cold rolling step of cold rolling after the hot rolling step to produce a rolled plate,
An intermediate annealing step of performing an intermediate annealing on the rolled plate, and
A final cold rolling process of performing final cold rolling on the intermediate annealing rolled sheet at a reduction ratio of 20 to 50%,
In the intermediate annealing, the rolled sheet is heated to a temperature range of 420 ° C or higher and less than the melting point of the aluminum alloy at a heating rate of 100 ° C / minute or more, and maintained at this temperature range for 0 to 180 seconds, followed by 300 ° C / minute or more. Method for cooling at a cooling rate. The method according to any one of claims 1 to 3,
Aluminum alloy plate used for battery case. The battery case using the aluminum alloy plate in any one of Claims 1-3.

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