KR20160053858A - Alluminum alloy plate for large-sized rectangular battery case - Google Patents

Abstract

The purpose of the present invention is to provide an aluminum-manganese based aluminum alloy plate capable of manufacturing a large-sized rectangular battery case with excellent formability for a press process, excellent continuous-wave laser weldability, and high rigidity. The aluminum alloy plate comprises 0.5-1.5 wt% of Mn, 0.4-1.2 wt% of Cu, less than 0.2 wt% of Mg, less than 0.6 wt% of Si, and less than 0.8 wt% of Fe, and the remainder consisting of Al and inevitable impurities. A mass ratio of Si with respect to the Fe is less than 3.0. An O material and an H material can achieve the purpose. 0.02 wt% or less of T, less than 20 mass ppm of B, 0.15 wt% or less of Zr, 0.40 wt% or less of Cr, and 0.3 wt% or less of Zn are included as the inevitable impurities or added elements. black box in the first storage section; a step of extracting the representative frames from the videos of the black box; a step of transmitting the extracted representative frames to the second storage section and storing the representative frames in the second storage section.

Description

{ALLUMINUM ALLOY PLATE FOR LARGE-SIZED RECTANGULAR BATTERY CASE}

The present invention relates to an aluminum alloy plate for a large square battery case used for a lithium ion secondary battery case or the like.

BACKGROUND ART [0002] Lithium ion secondary batteries are widely used as power sources for portable telephones, notebook computers, and the like. However, due to their excellent characteristics, they have recently been adopted as power sources for electric vehicles and hybrid cars. As a material for the case (hereinafter, referred to as battery case), which is an exterior of the secondary battery, conventionally, an aluminum alloy plate is used in order to satisfy the miniaturization and weight reduction of the battery and the moldability for forming the battery case .

The battery case is manufactured by subjecting an aluminum alloy plate to press working (deep drawing-ironing), and after the electrode material (electrode and electrolytic solution) is put in, it is laser-welded to the cap member. For this reason, an aluminum alloy sheet for a battery case requires excellent formability. Further, in the case of a lithium ion secondary battery for a cellular phone or a notebook computer, the battery case needs strength against the swelling of the battery, and in the case of a lithium ion secondary battery for a vehicle, Strength to protect is needed. For this reason, the aluminum alloy plate for a battery case needs high strength as a material and excellent laser weldability.

Al-Mn-based aluminum alloy plates based on JIS3003 have been developed as aluminum alloy plates having such formability, material strength and laser weldability (see Patent Documents 1 to 9).

Japanese Patent Application Laid-Open No. 2000-129384 Japanese Patent Laid-Open No. 2002-134069 Japanese Patent Application Laid-Open No. 2002-339049 Japanese Patent Application Laid-Open No. 2004-2985 Japanese Patent Application Laid-Open No. 2005-336540 Japanese Patent Application Laid-Open No. 2006-188744 Japanese Patent Application Laid-Open No. 2011-38122 Japanese Patent Application Laid-Open No. 121-177186 Japanese Patent Application Laid-Open No. 121-197489

The vehicle battery case is large in size compared to a battery case for a mobile phone or a notebook computer. For example, as described in Patent Document 9, a battery case having a bottom width of 10 mm or more, a width of 70 mm or more, . Such a battery case is formed by sequentially performing a transfer press working (multi-step drawing-ironing) on an aluminum alloy sheet to be a material by using a large-sized sequential transfer press machine, but is subjected to a severe deep drawing process, ) Is apt to occur.

In addition, the vehicle-use battery case has a large outer shape and a large thickness of material, so that it is necessary to deepen the penetration depth in laser welding in order to obtain a predetermined welding strength. In a battery case for a cellular phone or a notebook computer, the penetration depth is 0.2 to 0.3 mm, while for a vehicle battery case, 0.5 to 1.0 mm is desired. In laser welding of the on-vehicle battery case, since it is necessary to obtain a deep penetration depth, continuous oscillation type laser welding is mainly used. However, there is a problem that as the depth of penetration becomes deeper, welding defects such as welding cracks, irregular beads, undercuts, adhesion of weld spatter and the like tend to occur.

The present invention has been made in order to solve the above-mentioned problems associated with the manufacture of a large square battery case such as an automotive vehicle. It is an object of the present invention to provide a battery case having excellent weldability, weldability, -Mn-based aluminum alloy plate.

The aluminum alloy sheet for a large square battery case according to the present invention comprises 0.5 to 1.5 mass% of Mn, 0.4 to 1.2 mass% of Cu, less than 0.2 mass% of Mg, less than 0.6 mass% of Si and less than 0.8 mass% of Fe, , A Si / Fe mass ratio of less than 3.0, and the balance being Al and inevitable impurities. The aluminum alloy sheet may further contain one or more of Ti: less than 0.02 mass%, B: less than 20 mass ppm, Zr: 0.15 mass% or less, Cr: 0.40 mass% or less, and Zn: 0.3 mass% May be contained as an additive element or as an inevitable impurity.

The aluminum alloy sheet according to the present invention is molded into a large square battery case with the quality (quality) of O or H. In the above composition, the proof value of the O material is 50 to 110 MPa. H, it is desirable to adjust the internal force value in the range of 160 to 260 MPa.

The aluminum alloy sheet according to the present invention is excellent in moldability and does not cause cracking or baking during press working, and is excellent in manufacturing a large square battery case. Since the aluminum alloy plate is work-hardened during its molding process, it is possible to manufacture a high-strength large square battery case.

In addition, this aluminum alloy plate is free from welding defects even when the penetration depth is deepened in laser welding, and is excellent in laser weldability. Therefore, it is possible to deepen the welding depth in the laser welding with the cap material, and to increase the welding strength, and is suitable for a large square battery case such as a lithium ion secondary battery for a vehicle.

Hereinafter, an aluminum alloy plate for a large square battery case according to the present invention will be described in more detail.

(Composition of aluminum alloy plate)

Mn: 0.5 to 1.5 mass%

Mn is solid-solved in the parent phase to enhance the strength of the aluminum alloy sheet and to improve the strength of the pressure resistance. However, when the content of Mn is less than 0.5% by mass, the effect of this action is small. On the other hand, when the Mn content exceeds 1.5% by mass, a coarse intermetallic compound (Al-Fe-Mn, Al-Fe-Mn-Si intermetallic compound) is generated, The moldability of the aluminum alloy sheet is lowered. Therefore, the Mn content is set in a range of 0.5 to 1.5 mass%, preferably 0.7 to 1.2 mass%.

Mg: less than 0.2 mass%

Mg has an effect of increasing the strength of the aluminum alloy plate by solid solution strengthening and improving the withstand pressure strength. However, when the content of Mg is 0.2 mass% or more, when the H material is molded into a large square cell case by press working, the strength is excessively increased due to work hardening, and cracks are generated. If the content of Mg is 0.2 mass% or more, cracks in the shape of the weld bead due to welding cracks or irregular beads are generated by CW (continuous oscillation type) laser welding, or defects are formed inside the weld beads It becomes easy to occur. Therefore, the Mg content is less than 0.2 mass% (does not include 0%), preferably 0.03 to 0.15 mass%.

Cu: 0.4 to 1.2 mass%

Cu has an effect of increasing the strength of the aluminum alloy plate by solid solution strengthening and improving the withstand pressure strength. However, when the content of Cu is less than 0.4 mass%, the action effect is small. On the other hand, if the content of Cu exceeds 1.2 mass%, the work hardening property becomes excessively large and cracks occur in the press working. When the content of Cu exceeds 1.2 mass%, welding crack occurs in CW (continuous oscillation type) laser welding. Therefore, the Cu content is set to 0.4 to 1.2% by mass, preferably more than 0.6 to 1.2% by mass, and more preferably 0.7 to 1.0% by mass.

Si: less than 0.6% by mass

Si is an inevitable impurity present in the aluminum alloy. Further, Si has an effect of increasing the strength of the aluminum alloy sheet by solid solution strengthening, improving the strength of pressure resistance, and further improving the formability of the aluminum alloy sheet, and is added to the aluminum alloy as needed. However, when the Si content is 0.6% by mass or more, the Al-Fe-Mn-Si intermetallic compound is coarsened, which tends to become a starting point of cracking during molding processing and the moldability of the aluminum alloy plate is lowered. If the Si content exceeds 0.6% by mass, welding cracks tend to occur. Therefore, the content of Si contained in the aluminum alloy as an unavoidable impurity or added to the aluminum alloy as necessary is less than 0.6% by mass. Preferably, the Si content is 0.05 to 0.5% by mass.

Fe: less than 0.8% by mass

Fe is present as an inevitable impurity in the aluminum alloy. Fe also has an effect of increasing the strength of the aluminum alloy sheet and is added to the aluminum alloy as needed. However, when the content of Fe exceeds 0.8 mass%, the Al-Fe-Mn and Al-Fe-Mn-Si intermetallic compounds are coarsened and this tends to be a starting point of cracking at the time of molding, The moldability is deteriorated. Therefore, the content of Fe contained in the aluminum alloy as an unavoidable impurity or added to the aluminum alloy as necessary is less than 0.8% by mass. Preferably, the Fe content is 0.1 to 0.6 mass%.

Si / Fe mass ratio < 3

When the mass ratio of Si / Fe is 3 or more, a large amount of Al-Fe-Si and Al-Fe-Mn-Si intermetallic compounds is formed and cracks and cracks are likely to occur in press molding of the aluminum alloy plate. Therefore, the Si / Fe mass ratio is preferably less than 3.

Ti: less than 0.02% by mass

Ti has an effect of refining and homogenizing (stabilizing) an aluminum alloy cast structure and is usually added in an amount of 0.02% by mass or more to an aluminum alloy for the purpose of preventing casting cracks at the time of ingot ing rolling slabs. On the other hand, when Ti is excessively added, a coarse intermetallic compound is crystallized and tends to be a starting point of cracking at the time of forming, so Ti is added in a range of 0.15 mass% or less.

However, when CW (continuous oscillation type) laser welding is performed on an aluminum alloy plate containing Ti, porosity defects remain in the coagulation beads at the time of melting (660 to 750 캜) and penetration is deeply formed, The welded bead shape is liable to be solidified and an abnormal portion (disorder of the weld bead shape due to the occurrence of irregular beads) is liable to occur.

Ti may be added as an inevitable impurity in the ground metal (including scrap) and, if necessary, added to the aluminum alloy. In either case, the aluminum alloy sheet according to the present invention preferably has a Ti content of less than 0.02 mass% 0%). The smaller the Ti content, the better the weldability, preferably 0.01 mass% or less, more preferably 0.006 mass% or less.

B: 20 mass ppm or less

B is a Ti-B parent alloy generally added together with Ti for the purpose of preventing casting cracks during the slab-barging of an aluminum alloy.

However, when the B content of the aluminum alloy sheet exceeds 20 mass ppm, pore defects remain in the solidification beads in the CW (continuous oscillation type) laser welding and penetration deeply occurs, similarly to the Ti, Occurs.

B is contained as an inevitable impurity at present (including scrap), and may be added if necessary. In either case, the aluminum alloy sheet according to the present invention is regulated to less than 20 mass ppm (including 0%) of B Needs to be. The smaller the B content, the better the weldability, preferably 10 mass ppm or less, and more preferably 8 mass ppm or less.

Zr: 0.15 mass% or less

Cr: not more than 0.40 mass%

Zr and Cr have the effect of making the aluminum alloy structure finer and homogenizing (stabilizing). However, when the content of Zr exceeds 0.15 mass% or the content of Cr exceeds 0.40 mass%, the coarse intermetallic compound is easily crystallized and easily forms a starting point of cracking at the time of molding, and the formability of the aluminum alloy plate . On the other hand, Zr and Cr are preferably contained in an amount of 0.05 mass% or more, respectively, since the recrystallized grains can be refined when welded at the time of welding, and welding cracks can be avoided.

Zr and Cr are contained as an inevitable impurity in the aluminum alloy and can be added if necessary. In either case, the content of Zr in the aluminum alloy sheet according to the present invention is 0.15 mass% or less (including 0%), Cr Is limited to 0.40 mass% or less (including 0%).

Zn: 0.3 mass% or less

Since the vapor pressure of Zn is low, it is scattered at the time of laser welding to easily contaminate the periphery, which deteriorates the laser weldability of the aluminum alloy plate. Therefore, the content of Zn is regulated to 0.3 mass% or less (including 0%).

(Production of aluminum alloy plate)

The aluminum alloy sheet according to the present invention can be produced, for example, by the following process.

An ingot is produced by dissolving and casting an aluminum alloy of a predetermined component and subjected to homogenizing heat treatment at a temperature of 480 DEG C or higher and lower than the melting point of the aluminum alloy after the ingot is subjected to surface cutting. Next, the homogeneous heat treated ingot is hot rolled and cold rolled to produce a rolled plate. Then, in the case of manufacturing the O material of the aluminum alloy sheet, the rolled sheet is annealed in a temperature range of 300 to 450 캜 and maintained for 0.5 hours or more. In the case of manufacturing H material, the O material is further cold-rolled at a rolling rate of about 20 to 50%.

(Strength of aluminum alloy plate)

The aluminum alloy sheet according to the present invention is formed into a large square cell case by the quality of O or H. In the above composition, the proof value of the O material is approximately 50 to 110 MPa. O material is easy to process because it is soft, and it is easy to form into a large square cell case by drawing and ironing. In addition, although the proof strength of the O material is slightly low, the strength of the battery case after molding can be sufficiently improved by the work hardening accompanying the molding process.

In order to increase the strength of the battery case even slightly, it is effective to set the quality of the aluminum alloy plate to H. On the other hand, the H content can not deny the lowering of the moldability as compared with the O material, and cracks are likely to occur at the time of molding. The strength of the battery case is adjusted to be within the range of 160 to 260 MPa to improve the strength of the battery case and to prevent cracking at the time of molding.

(Laser welding)

A large square battery case suitable for lithium ion secondary batteries such as automobiles has a bottom width of 10 mm or more, a width of 70 mm or more, and a height of 60 mm or more. The large square battery case to which the present invention is applied is also assumed to have this size. This large square battery case has a thickness of about 0.5 to 2.0 mm at the welding site, and a penetration depth of about 0.5 to 1.0 mm is desired in laser welding. In order to obtain this penetration depth, a continuous-oscillation (CW) type laser welding is suitably used, and a large-sized square battery case in which an aluminum alloy plate according to the present invention is molded has good weldability . A keyhole type having a keyhole type and a thermally conductive type and capable of obtaining a deep penetration depth is preferable for continuous wave (CW) laser welding.

On the other hand, in the laser welding of the aluminum alloy plate according to the present invention, a pulsed laser or a combination of a pulse laser and a continuous oscillation (CW) laser can be used.

Example

An aluminum alloy having the composition shown in Table 1 was melted and cast to obtain an ingot, and the ingot was subjected to a homogenizing heat treatment at 550 DEG C for 4 hours. This homogenized ingot was subjected to hot rolling and further cold rolling to obtain an aluminum alloy sheet having a thickness of 1.0 mm. The rolled sheet after cold rolling was heated to 370 占 폚 and held at this temperature for 4 hours to perform batch annealing to obtain a sheet material (O material) for evaluation of characteristics. The H material was hot rolled and further subjected to cold rolling to obtain a sheet having a thickness of 1.4 mm and subjected to intermediate annealing under the same conditions as the batch annealing of the O material and further subjected to cold rolling to obtain aluminum Alloy plate, and was used as a plate for evaluation of properties.

A tensile test, a formability evaluation test, and a weldability evaluation test were conducted using the aluminum alloy plate (O material, H material) produced in the following manner. The results are shown in Tables 1 and 2.

(Tensile test)

JIS No. 5 tensile test specimens were cut out from each of the evaluation plates so that their rolling directions were in the longitudinal direction and were subjected to tensile test with AG-I, The test was carried out to obtain the history. The crosshead speed was 5 mm / min, and the test specimens were cut at a constant speed until they were broken, and each was measured five times and calculated as an average value.

(Moldability Evaluation Test)

The elliptical blank plate was cut out from each evaluation plate so that the major axis thereof was in parallel with the rolling direction. Drawing and ironing were performed in a total of eleven processes using a progressive-transfer type press machine, and the ironing rate of the side walls was set at 30% To form a rectangular cell case (case body) having a rectangular shape with a bottom width of 20 mm, a bottom width of 200 mm and a height of 150 mm.

In this case, it is possible to mold without cracking, and that there is no discoloration or vertical stripe pattern on the surface caused by the firing after molding, and it is evaluated as &quot; , And it was evaluated as &quot; Good &quot; because of the good moldability, and it was judged that a crack occurred in the molding or a remarkable discoloration or vertical stripe occurred. I appreciated.

(Weldability Evaluation Test)

Test specimens having a size of 30 mm x 100 mm were cut out from each of the evaluation plates, and the specimens were cut into bead-on-plates (lengths of 90 mm) by using a welding machine using a continuous oscillation type fiber laser (IPG Photonics Japan KK, model: YLR- bead-on-plate). The laser output was adjusted so that the laser output was 1.5 to 2.0 kW, the welding speed was 10.0 m / min, the forward angle was 5 deg., And the penetration depth of the welded portion was 0.7 to 0.8 mm.

The weld bead portion of each test piece was evaluated for weld appearance and subjected to a radiation transmittance test in the following manner.

&Lt; Evaluation of welding appearance >

The presence of welding cracks, the uniformity of the weld bead width, the presence of undercuts, and the presence of welding spatter were observed with respect to the weld bead portion. As a result, it was found that the weld bead width was uniform without causing cracks in the weld bead portion, and the undercut, bumping portion, and spatter attachment with a diameter of 1 mm or more were not found in the weld bead portion. The welding spots having a diameter of 1 mm or more were observed at only one position with respect to the welding length of 90 mm. However, no cracks were observed, the weld bead width was uniform, and no undercut or bump was found at the bead portion. The results were evaluated as "⊚" and "◯", and all other welds were judged as "x" because the welding appearance was poor.

<Radiation Permeation Test>

This test was conducted in accordance with JIS Z 3105 to check for scratches (pores, etc.) in the weld bead. The number of scratches was judged as "OK" because the weld beads classified as Classes 1 and 2 of the 4-step evaluation specified in the annex to JIS Z 3105 were evaluated as satisfactory, and those classified as Classes 3 and 4 were evaluated as " Respectively.

As shown in Tables 1 and 2, in Examples 1 to 21, the alloy composition satisfies the requirements of the present invention, the strength values of O material and H material are within the range of the present invention, , H are all excellent. Examples 2, 5, 8, 11, 17, 18, and 20 in which either or both of Ti and B contents are slightly different from each other are particularly excellent in laser weldability.

On the other hand, in Comparative Example 1, since the Mn content is excessively low, the proof value is low in both the O and H materials. For this reason, the strength of the battery case as a product is insufficient.

In Comparative Example 2, since the Mn content was excessive, cracks occurred in all of the pressed material and the pressed material. This is probably due to the formation of a coarse intermetallic compound containing Mn.

In Comparative Example 3, since the Mg content was excessive, cracks were generated in the pressing process. This is presumably because the strength was excessively increased due to work hardening. Further, cracks occurred in the weld bead portions of both the O and H welds, irregular beads were generated, and the bead widths became uneven, and many scratches such as pores were detected in the weld beads.

In Comparative Example 4, since the Cu content was excessive, cracks occurred in the press working of both of the O and H materials. This is presumably because the strength was excessively increased due to work hardening. Further, cracks occurred in the weld bead portions of both the O material and the H material, irregular beads were generated, and the bead width became uneven, and many scratches such as pores were detected in the beads.

In Comparative Example 5, since the Si content was excessive, cracks occurred in the press working of both of the O material and the H material. This is probably due to the formation of a coarse intermetallic compound containing Si. Further, cracks were generated in the weld bead portions of both the O material and the H material, and many scratches such as pores were detected in the beads.

In Comparative Example 6, since the content of Ti and B is excessive, in Comparative Examples 7 and 8, since the B content is excessive, irregular beads are generated in all of the O material and the H material and the bead width becomes uneven, A lot of scratches were detected.

In Comparative Example 9, since the Zr content is excessive, in Comparative Examples 10 and 11, since the Cr content is excessive, in Comparative Example 12, since the Fe content is excessive, cracks are generated in all of the O material and the H material during press working did. This is probably because coarse intermetallic compounds were produced.

In Comparative Example 13, since a Zn content was excessive, a weld spatter adhered, and a lot of scratches such as pores were detected in the bead.

In Comparative Examples 14 and 15, since the Si / Fe content ratio was excessive, cracks occurred in all of the O material and the H material during press working. This is thought to be due to the formation of many intermetallic compounds including Si.

Claims (7)

Wherein the content of Mn is 0.5 to 1.5 mass%, the content of Cu is 0.7 to 1.2 mass%, the content of Mg is less than 0.2 mass% (excluding 0 mass%), the content of Si is 0.05 to 0.3 mass%, the content of Fe is 0.1 mass% An aluminum alloy plate for a large square battery case having a Si / Fe mass ratio of less than 3.0, the remaining Al and inevitable impurities having excellent laser weldability. The method according to claim 1,
Ti: less than 0.02 mass%, and B: less than 20 mass ppm. The method according to claim 1,
0.15 mass% or less of Zr and 0.40 mass% or less of Cr, based on the total mass of the aluminum alloy plate. The method according to claim 1,
And Zn: 0.3 mass% or less. The method according to claim 1,
And an aluminum alloy plate for a large-angle-sided battery case, which is excellent in weldability by continuous oscillation type laser welding. The method according to claim 1,
And an O-value of from 50 to 110 MPa. The method according to claim 1,
And a strength value of 160 to 260 MPa.