ALUMINUM ALLOY SHEET FOR BATTERY LID USE FOR FORMING INTEGRATED EXPLOSION-PROOF VALVE AND METHOD OF PRODUCTION OF SAME

Abstract

Aluminum alloy sheet for battery lid use having suitable strength and excellent in heat radiating ability, formability, and work softenability, which aluminum alloy sheet for battery lid use enabling formation of an integrated explosion-proof valve with little variation in operating pressure and excellent in cyclic fatigue resistance, and a method of production of the same are provided, the aluminum alloy sheet for battery lid use for forming an integrated explosion-proof valve having a component composition containing Fe: 1.05 to 1.50 mass %, Mn: 0.15 to 0.70 mass %, Ti: 0.002 to 0.15 mass %, and B: less than 0.05 mass %, having a balance of Al and impurities, having an Fe/Mn ratio restricted to 1.8 to 7.0, restricting, as impurities, Si to less than 0.40 mass %, Cu to less than 0.03 mass %, Mg to less than 0.05 mass %, and V to less than 0.03 mass %, having a tensile strength of 95 MPa or more, having a value of elongation of 40% or more, having a recrystallized structure, having a value of (TS95-TS90) of less than −4 MPa when defining a tensile strength after cold rolling by a rolling reduction of 90% as TS90 and defining a tensile strength after cold rolling by a rolling reduction of 95% as TS95, and having a value of elongation after cold rolling by a rolling reduction of 90% of 5.0% or more. Furthermore, an average grain size of the recrystallized grains of the recrystallized structure is preferably 15 to 30

Claims

1. Aluminum alloy sheet for battery lid use for forming an integrated explosion-proof valve having a component composition containing Fe: 1.05 to 1.50 mass %, Mn: 0.15 to 0.70 mass %, Ti: 0.002 to 0.15 mass %, and B: less than 0.05 mass %, having a balance of Al and impurities, having an Fe/Mn ratio restricted to 1.8 to 7.0, restricting, as impurities, Si to less than 0.40 mass %, Cu to less than 0.03 mass %, Mg to less than 0.05 mass %, and V to less than 0.03 mass %, having a tensile strength of 95 MPa or more, having a value of elongation of 40% or more, having a recrystallized structure, having a value of (TS95-TS90) of less than −4 MPa when defining a tensile strength after cold rolling by a rolling reduction of 90% as TS90 and defining a tensile strength after cold rolling by a rolling reduction of 95% as TS95, and having a value of elongation after cold rolling by a rolling reduction of 90% of 5.0% or more.

2. Aluminum alloy sheet for battery lid use for forming an integrated explosion-proof valve having a component composition containing Fe: 1.05 to 1.50 mass %, Mn: 0.15 to 0.70 mass %, Ti: 0.002 to 0.15 0.08mass %, and B: less than 0.05 mass %, having a balance of Al and impurities, having an Fe/Mn ratio restricted to 1.8 to 7.0, restricting, as impurities, Si to less than 0.40 mass %, Cu to less than 0.03 mass %, Mg to less than 0.05 mass %, and V to less than 0.03 mass %, having a conductivity of 53.0% IACS or more, having a value of elongation of 40% or more, having a recrystallized structure, having a value of (TS95-TS90) of less than −4 MPa when defining a tensile strength after cold rolling by a rolling reduction of 90% as TS90 and defining a tensile strength after cold rolling by a rolling reduction of 95% as TS95, and having a value of elongation after cold rolling by a rolling reduction of 90% of 5.0% or more.

3. The aluminum alloy sheet for battery lid use for forming an integrated explosion-proof valve according to claim 1, wherein an average grain size of the recrystallized grains of the recrystallized structure is 15 to 30 μm.

4.-5. (canceled)

6. The aluminum alloy sheet for battery lid use for forming an integrated explosion-proof valve according to claim 2, wherein an average grain size of the recrystallized grains of the recrystallized structure is 15 to 30 μm.

7. A method of production of the aluminum alloy sheet for battery lid use for forming an integrated explosion-proof valve according to claim 1, comprising: a slab casting process of casting an aluminum alloy melt having a component composition according to claim 1 into a cast ingot by a semicontinuous casting method, a homogenization treatment process of homogenizing the cast ingot at a 520 to 620° C. holding temperature for a 1 hour or more holding time, a hot rolling process of setting a start temperature to 420 to less than 520° C. after said homogenization treatment process so as to hot roll the cast ingot to obtain hot rolled sheet, a cold rolling process of cold rolling said hot rolled sheet to obtain a cold rolled sheet, and a final annealing process of annealing said cold rolled sheet in a batch furnace for final annealing, wherein: in said cold rolling process, the final cold rolling is performed with a final cold rolling rate of 50% to 95% in range and, in said final annealing process, the final annealing is performed with a holding temperature of 300 to 450° C. for 1 hour or more.

8. A method of production of the aluminum alloy sheet for battery lid use for forming an integrated explosion-proof valve according to claim 2, comprising: a slab casting process of casting an aluminum alloy melt having a component composition according to claim 2 into a cast ingot by a semicontinuous casting method, a homogenization treatment process of homogenizing the cast ingot at a 520 to 620° C. holding temperature for a 1 hour or more holding time, a hot rolling process of setting a start temperature to 420 to less than 520° C. after said homogenization treatment process so as to hot roll the cast ingot to obtain hot rolled sheet, a cold rolling process of cold rolling said hot rolled sheet to obtain a cold rolled sheet, and a final annealing process of annealing said cold rolled sheet in a batch furnace for final annealing, wherein: in said cold rolling process, the final cold rolling is performed with a final cold rolling rate of 50% to 95% in range and, in said final annealing process, the final annealing is performed with a holding temperature of 300 to 450° C. for 1 hour or more.

9. A method of production of the aluminum alloy sheet for battery lid use for forming an integrated explosion-proof valve according to claim 3, comprising: a slab casting process of casting an aluminum alloy melt having a component composition according to claim 1 into a cast ingot by a semicontinuous casting method, a homogenization treatment process of homogenizing the cast ingot at a 520 to 620° C. holding temperature for a 1 hour or more holding time, a hot rolling process of setting a start temperature to 420 to less than 520° C. after said homogenization treatment process so as to hot roll the cast ingot to obtain hot rolled sheet, a cold rolling process of cold rolling said hot rolled sheet to obtain a cold rolled sheet, and a final annealing process of annealing said cold rolled sheet in a batch furnace for final annealing, wherein: in said cold rolling process, the final cold rolling is performed with a final cold rolling rate of 50% to 95% in range and, in said final annealing process, the final annealing is performed with a holding temperature of 300 to 450° C. for 1 hour or more.

10. A method of production of the aluminum alloy sheet for battery lid use for forming an integrated explosion-proof valve according to claim 6, comprising: a slab casting process of casting an aluminum alloy melt having the component composition into a cast ingot by a semicontinuous casting method, a homogenization treatment process of homogenizing the cast ingot at a 520 to 620° C. holding temperature for a 1 hour or more holding time, a hot rolling process of setting a start temperature to 420 to less than 520° C. after said homogenization treatment process so as to hot roll the cast ingot to obtain hot rolled sheet, a cold rolling process of cold rolling said hot rolled sheet to obtain a cold rolled sheet, and a final annealing process of annealing said cold rolled sheet in a batch furnace for final annealing, wherein: in said cold rolling process, the final cold rolling is performed with a final cold rolling rate of 50% to 95% in range and, in said final annealing process, the final annealing is performed with a holding temperature of 300 to 450° C. for 1 hour or more.

Description

EXAMPLES

Examples by Laboratory Test Samples

Preparation of Test Samples

[0079] Ingots of 16 levels (Examples 1 to 6 and Comparative Examples 1 to 10) of component compositions and of 5 kg weights were respectively placed in #20 crucibles. The crucibles were heated in a small electric furnace to melt the ingots. Next, lances were inserted into the melts and N.sub.2 gas was blown in by a flow rate of 1.0 L/min for 5 minutes for degassing. After that, the melts were allowed to settle for 30 minutes and the slag floating up on the surfaces was removed by stirring rods. Next, the crucibles were taken out from the small size electric furnace and the melts were cast into inside dimension 250×200×30 mm molds to prepare cast ingots. Test samples of Examples 1 to 6 and Comparative Examples 1 to 10 were obtained from the melts in the crucibles. The disk samples of these test samples were analyzed for composition by emission spectroscopy. The results are shown in Table 1.

TABLE-US-00001 TABLE 1 Results of Analysis of Component Compositions of Test Samples Component composition (mass %) Si Fe Cu Mn Mg Ti B V Fe/Mn Al Ex. 1 0.07 1.22 <0.01 0.50 0.01 0.019 0.0028 0.01 2.44 bal. Ex. 2 0.07 1.30 <0.01 0.50 0.01 0.005 <0.0005 0.01 2.60 bal. Ex. 3 0.07 1.31 <0.01 0.44 0.01 0.021 <0.0005 0.01 2.98 bal. Ex. 4 0.07 1.24 <0.01 0.50 0.02 0.018 0.003 0.02 2.48 bal. Ex. 5 0.25 1.25 <0.01 0.51 0.02 0.016 0.003 0.01 2.45 bal. Ex. 6 0.07 1.21 <0.01 0.20 0.02 0.019 0.002 0.01 6.05 bal. Comp. Ex. 1 0.07 1.58 <0.01 0.51 0.01 0.014 0.0028 0.01 3.10 bal. Comp. Ex. 2 0.07 0.97 <0.01 0.51 0.01 0.014 0.0028 0.01 1.90 bal. Comp. Ex. 3 0.07 1.24  0.04 0.50 0.02 0.018 0.002 0.01 2.48 bal. Comp. Ex. 4 0.07 1.23 <0.01 0.80 0.02 0.020 0.003 0.01 1.54 bal. Comp. Ex. 5 0.03 1.23 <0.01 0.51 0.21 0.019 0.002 0.01 2.41 bal. Comp. Ex. 6 0.07 1.24 <0.01 0.51 0.02 0.018 0.003 0.04 2.43 bal. Comp. Ex. 7 0.07 1.22 <0.01 0.51 0.02 0.019 0.002 0.11 2.39 bal. Comp. Ex. 8 0.07 1.22 <0.01 0.50 0.02 0.019 0.002 0.01 2.44 bal. Comp. Ex. 9 0.14 0.19  0.02 0.02 0.02 0.020 0.0027 0.01 9.50 bal. Comp. Ex. 10 0.18 0.20  0.14 1.29 0.02 0.019 0.0024 0.01 0.16 bal. *) In the Table, underlined values show values outside prescribed range of present invention.

[0080] These cast ingots were cut at their two surfaces by 5 mm each to make them thicknesses of 20 mm, then were consecutively homogenized at 590° C.×1 hour and 480° C.×1 hour and hot rolled to obtain thickness 6.0 mm hot rolled sheets. After this, the hot rolled sheets were cold rolled to obtain sheet thickness 1.0 mm cold rolled sheets. During the cold rolling process, no interannealing was performed. The final cold rolling reduction in this case was 83%.

[0081] Next, these cold rolled sheets (Examples 1 to 6 and Comparative Examples 1 to 7, 9, and 10) were inserted into an annealer and annealed for 340° C.×1 hour simulating batch annealing to obtain final sheets (O materials). The other cold rolled sheet (Comparative Example 8) was heated by a salt bath at 425° C.×15 seconds simulating continuous annealing at 425° C.×10 seconds, then water cooled to obtain the final sheet (O material).

[0082] Furthermore, these final sheets were cold rolled down to 0.1 mm and 0.05 mm simulating formation of integrated explosion-proof valves for the purpose of investigating the work hardening characteristic etc. Cold rolled materials were sampled at respective rolling reductions of 90% and 95%.

[0083] Next, the thus obtained test samples (final sheets: 16 levels, cold rolled materials: 16 levels×2 levels each) were measured and evaluated for various properties. Measurement of properties by tensile tests

[0084] The strengths of the obtained final sheets were evaluated by the tensile strengths (MPa) of the final sheets (O materials). The formabilities of the final sheets were evaluated by the values of elongation of the final sheets (O materials) (%). The work softenabilities of the final sheets were evaluated by the values (TS95-TS90) (MPa) of the tensile strengths TS95 (MPa) after cold rolling the final sheets (O materials) by a rolling reduction of 95% minus the tensile strengths TS90 (MPa) after cold rolling the final sheets (O materials) by a rolling reduction of 90%. The operating stabilities of the integrated explosion-proof valves were evaluated by the values of elongation (%) after cold rolling the final sheets (O materials) by a rolling reduction of 90%. Specifically, from the obtained test samples, JIS No. 5 test pieces were taken so that the tensile directions became parallel directions to the rolling direction. Tensile tests were conducted in accordance with JIS Z2241 to find the tensile strengths, 0.2% yield strengths, and elongations (elongations at break). Note that, these tensile tests were performed three times for each test sample (n=3) and the average values were calculated. The results of measurement of the tensile strengths and elongations (elongations at break) of the final sheets, the results of measurement of the tensile strengths and elongations (elongations at break) after cold rolling the final sheets by a rolling reduction of 90%, the results of measurement of the tensile strengths after cold rolling the final sheets by a rolling reduction of 95% are shown in Table 2.

Measurement of Conductivity by Conductivity Meter

[0085] The heat conductivities of the obtained final sheets were evaluated by the conductivity (IACS %) of the final sheets (O materials). Specifically, the obtained final sheets were measured for conductivity (IACS %) by a conductivity meter (AUTOSIGMA 2000, made by Nippon Hocking KK). The results of measurement of the conductivities of the final sheets are shown in Table 2.

[0086] Final sheets with tensile strengths of 100 MPa or more were evaluated as good in strength (Good), while final sheets with tensile strengths of less than 100 MPa were evaluated as poor in strength (Poor).

[0087] Final sheets with conductivities of 50.0% IACS or more were evaluated as good in heat radiating ability (Good), while final sheets with conductivities of less than 50.0% IACS were evaluated as poor in heat radiating ability (Poor).

[0088] Final sheets with values of elongation of 35.0% or more were evaluated as good in formability (Good), while final sheets with values of elongation of less than 35.0% were evaluated as poor in formability (Poor).

[0089] Final sheets with values of (TS95-TS90) of less than 3 MPa were evaluated as good in work softenability (Good), while final sheets with values of (TS95-TS90) of 3 MPa or more were evaluated as poor in work softenability (Poor).

[0090] Final sheets with values of elongation after cold rolling by a rolling reduction of 90% of 4.0% or more were evaluated as good in operating stability (Good), while final sheets with values of elongation after cold rolling by a rolling reduction of 90% of less than 4.0% were evaluated as poor in operating stability (Poor). The results of evaluation are shown in Table 2.

TABLE-US-00002 TABLE 2 Results of Evaluation of Properties of Test Samples Rolling reduction 0% 90% 95% 90% Final Cold Cold Final sheet Final rolled rolled sheet conduc- sheet material material Evaluation tensile tivity elonga- tensile TS95- elonga- Heat strength (IACS tion strength TS90 tion radiating Work Operating (MPa) %) (%) (MPa) (MPa) (%) Strength ability Formability softenability stability Ex. 1 111 50.4 38.7 201 201 0 4.8 Good Good Good Good Good Ex. 2 126 52.2 36.7 201 202 1 4.6 Good Good Good Good Good Ex. 3 122 51.8 39.0 197 198 1 5.0 Good Good Good Good Good Ex. 4 126 51.3 37.0 203 204 1 4.8 Good Good Good Good Good Ex. 5 111 52.1 41.4 195 196 1 6.0 Good Good Good Good Good Ex. 6 105 54.7 39.9 196 196 0 5.5 Good Good Good Good Good Comp. Ex. 1 127 52.1 32.6 197 202 5 3.2 Good Good Poor Poor Poor Comp. Ex. 2 114 50.9 40.4 197 202 5 4.0 Good Good Good Poor Good Comp. Ex. 3 112 50.6 38.9 209 209 0 3.6 Good Good Good Good Poor Comp. Ex. 4 115 49.1 35.8 206 207 1 3.3 Good Poor Good Good Poor Comp. Ex. 5 121 48.5 33.3 239 252 13  2.2 Good Poor Poor Poor Poor Comp. Ex. 6 126 50.3 36.4 203 205 2 3.3 Good Good Good Good Poor Comp. Ex. 7 113 46.5 39.6 202 203 1 3.4 Good Poor Good Good Poor Comp. Ex. 8 104 48.2 40.2 217 222 5 3.5 Good Poor Good Poor Poor Comp. Ex. 9  89 61.1 41.5 179 184 5 2.8 Poor Good Good Poor Poor Comp. Ex. 10 129 42.3 35.9 248 259 11  3.0 Good Poor Good Poor Poor *) In the Table, underlined values show values outside prescribed range of present invention.

[0091] Examples 1 to 6 in Table 2 showing the results of evaluation of the properties of the test samples were within the scope of composition of the present invention. Also, the final annealing was batch annealing and the tensile strengths of the final sheets, the conductivities of the final sheets, the values of elongation of the final sheets, the values of (TS95-TS90), and the values of elongation after cold rolling the final sheets by a rolling reduction of 90% all satisfied the reference values. Specifically, Examples 1 to 6 had tensile strengths of the final sheets of 100 MPa or more, conductivities of the final sheets of 50.0% IACS or more, values of elongation of the final sheets of 35.0% or more, values of (TS95-TS90) of less than 3 MPa, and values of elongation after cold rolling the final sheets by a rolling reduction of 90% of 4.0% or more. Therefore, Examples 1 to 6 were evaluated as good in strength (Good), were evaluated as good in heat radiating ability (Good), were evaluated as good in formability (Good), were evaluated as good in work softenability (Good), and were evaluated as good in operating stability (Good).

[0092] Comparative Examples 1 to 7, 9, and 10 in Table 2 were outside the scope of composition of the present invention although the final annealing was batch annealing. At least one of the tensile strengths of the final sheets, the conductivities of the final sheets, the values of elongation of the final sheets, the values of (TS95-TS90), and the values of elongation after cold rolling the final sheets by a rolling reduction of 90% failed to satisfy the reference values.

[0093] Comparative Example 1 had an Fe content of 1.58 mass % or too high, so the value of elongation of the final sheet, the value of (TS95-TS90), and the value of elongation after cold rolling the final sheet by a rolling reduction of 90% all failed to satisfy the reference values, the sheet was evaluated as poor in formability (Poor), the sheet was evaluated as poor in work softenability (Poor), and the sheet was evaluated as poor in operating stability (Poor).

[0094] Comparative Example 2 had an Fe content of 0.97 mass % or too low, so the value of (TS95-TS90) failed to satisfy the reference value and the sheet was evaluated as poor in work softenability (Poor).

[0095] Comparative Example 3 had a Cu content of 0.04 mass % or too high, so the value of elongation after cold rolling the final sheet by a rolling reduction of 90% failed to satisfy the reference value and the sheet was evaluated as poor in operating stability (Poor).

[0096] Comparative Example 4 had an Mn content of 0.80 mass % or too high, so the conductivity of the final sheet and the value of elongation after cold rolling the final sheet by a rolling reduction of 90% failed to satisfy the reference values, the sheet was evaluated as poor in heat radiating ability (Poor), and the sheet was evaluated as poor in operating stability (Poor).

[0097] Comparative Example 5 had an Mg content of 0.21 mass % or too high, so the conductivity of the final sheet, the value of elongation of the final sheet, the value of (TS95-TS90), and the value of elongation after cold rolling the final sheet by a rolling reduction of 90% all failed to satisfy the reference values, the sheet was evaluated as poor in heat radiating ability (Poor), the sheet was evaluated as poor in formability (Poor), the sheet was evaluated as poor in work softenability (Poor), and the sheet was evaluated as poor in operating stability (Poor).

[0098] Comparative Example 6 had a V content of 0.04 mass % or too high, so the value of elongation after cold rolling the final sheet by a rolling reduction of 90% failed to satisfy the reference value and the sheet was evaluated as poor in operating stability (Poor).

[0099] Comparative Example 7 had a V content of 0.11 mass % or too high, so the conductivity of the final sheet and the value of elongation after cold rolling the final sheet by a rolling reduction of 90% failed to satisfy the reference value, the sheet was evaluated as poor in heat radiating ability (Poor), and the sheet was evaluated as poor in operating stability (Poor).

[0100] Comparative Example 8 was inside the scope of composition of the present invention, but the final annealing was annealing in a salt bath simulating continuous annealing, so the conductivity of the final sheet, the value of (TS95-TS80), and the value of elongation after cold rolling the final sheet by a rolling reduction of 90% all failed to satisfy the reference values, the sheet was evaluated as poor in heat radiating ability (Poor), the sheet was evaluated as poor in work softenability (Poor), and the sheet was evaluated as poor in operating stability (Poor).

[0101] Comparative Example 9 is an AA1050 alloy composition. Its Fe content and Mn content are respectively 0.19 mass % and 0.02 mass % or too low, so the tensile strength, the value of (TS95-TS90), and the value of elongation after cold rolling the final sheet by a rolling reduction of 90% all failed to satisfy the reference values, the sheet was evaluated as poor in strength (Poor), the sheet was evaluated as poor in work softenability (Poor), and the sheet was evaluated as poor in operating stability (Poor).

[0102] Comparative Example 10 is an AA3003 alloy composition. Its Fe content is 0.20 mass % or too low, while its Cu content and Mn content are respectively 0.14 mass % and 1.29 mass % or too high, so the conductivity of the final sheet, the value of (TS95-TS90), and the value of elongation after cold rolling the final sheet by a rolling reduction of 90% all failed to satisfy the reference values, the sheet was evaluated as poor in heat radiating ability (Poor), the sheet was evaluated as poor in work softenability (Poor), and the sheet was evaluated as poor in operating stability (Poor).

Examples by Actual Machinery and Materials

Preparation of Test Sample

[0103] A melt of the composition shown in Table 3 was refined in a melting furnace and cast by a DC casting machine into a width 1200 mm×thickness 560 mm×length 3800 mm cast ingot. This cast ingot was cut at its two surfaces and inserted into a soaking furnace for heating. It was successively homogenized at 590° C.×1 hour and 480° C.×1 hour, then was hot rolled to obtain a thickness 7.0 mm hot rolled sheet which was then taken up in a coil. After this, the hot rolled sheet was cold rolled to obtain a thickness 1.0 mm cold rolled sheet which was then taken up in a coil. The final cold rolling rate in this case was 86%. From this cold rolled sheet, a cut sheet of suitable dimensions was obtained.

TABLE-US-00003 TABLE 3 Results of Analysis of Component Compositions of Test Samples Component composition (mass %) Si Fe Cu Mn Mg Ti B V Fe/Mn Al Ex. 50 0.07 1.20 <0.01 0.48 <0.01 0.011 0.004 0.01 2.50 bal.

[0104] Next, the cold rolled sheet from which this cut sheet was taken was inserted into an annealer where it was annealed at 240° C., 340° C., and 440° C.×1 hour each simulating batch annealing to obtain a final sheet (O material). Other cold rolled sheets were heated in a salt bath at 425° C.×15 seconds simulating continuous annealing at 425° C.×10 seconds respectively, then water cooled to obtain the final sheets (O materials).

[0105] Furthermore, these final sheets were cold rolled to 0.1 mm and 0.05 mm simulating formation of an integrated explosion-proof valve for the purpose of investigating the work hardening characteristic etc. Cold rolled materials having rolling reductions of 90% and 95% were taken.

[0106] Next, these obtained test samples (final sheets: 4 levels, cold rolled materials: 4 levels×2 levels each) were measured and evaluated for properties.

Measurement of Properties by Tensile Test

[0107] The strengths of the obtained final sheets were evaluated by the tensile strengths (MPa) of the final sheets (O materials). The formabilities of the final sheets were evaluated by the values of elongation of the final sheets (O materials) (%). The work softenabilities of the final sheets were evaluated by the values (TS95-TS90) (MPa) of the tensile strengths TS95 (MPa) after cold rolling the final sheets (O materials) by a rolling reduction of 95% minus the tensile strengths TS90 (MPa) after cold rolling the final sheets (O materials) by a rolling reduction of 90%. The operating stabilities of the integrated explosion-proof valves were evaluated by the values of elongation (%) in the tensile tests after cold rolling the final sheets (O materials) by a rolling reduction of 90%. Specifically, from the obtained test samples, JIS No. 5 test pieces were taken so that the tensile directions became parallel directions to the rolling direction. Tensile tests were conducted in accordance with JIS Z2241 to find the tensile strengths, 0.2% yield strengths, and elongations (elongations at break). Note that, these tensile tests were performed three times for each test sample (n=3) and the average values were calculated. The results of measurement of the tensile strengths and elongations (elongations at break) of the final sheets, the results of measurement of the tensile strengths and elongations (elongations at break) after cold rolling the final sheets by a rolling reduction of 90%, and the results of measurement of the tensile strengths after cold rolling the final sheets by a rolling reduction of 95% are shown in Table 4.

Measurement of Conductivity by Conductivity Meter

[0108] The heat conductivities of the obtained final sheets were evaluated by the conductivity (IACS %) of the final sheets (O materials). Specifically, the obtained final sheets were measured for conductivity (IACS %) by a conductivity meter (AUTOSIGMA 2000 made by Nippon Hocking KK). The results of measurement of the conductivities of the final sheets are shown in Table 4.

Measurement of Average Grain Size of Recrystallized Grains

[0109] Pieces of the obtained final sheets were cut out, were buried in a thermoplastic resin to enable the rolling surfaces of the sheets (L-LT surfaces) to be polished, and were polished to mirror finishes. The sheets were anodized in a borohydrofluoric acid aqueous solution and examined for metal structures by a polarized light microscope (magnification 50×). The obtained final sheets were measured for average grain size of the recrystallized grains by the slice method (cutting method). The gradations of the field of the polarized light microscope were successively shifted while drawing a virtual line of a length of 12.1 mm in the field. At that time, the number (n) of grain boundaries which the virtual line cut across was measured and formula (1) was used to calculate the average grain size (μm).

{12.1×10.sup.3/(n−1)}  (1)

[0110] This measurement was performed two times for each final sheet. The average value of the two measured values was employed. The results of measurement of the average grain sizes of the recrystallized grains of the final sheets are shown in Table 4.

[0111] A final sheet with a tensile strength of 95 MPa or more was evaluated as good in strength (Good), while a final sheet with a tensile strength of less than 95 MPa was evaluated as poor in strength (Poor).

[0112] A final sheet with a conductivity of 53.0% IACS or more were evaluated as good in heat radiating ability (Good), while a final sheet with a conductivity of less than 53.0% IACS was evaluated as poor in heat radiating ability (Poor).

[0113] A final sheet with a value of elongation of 40.0% or more was evaluated as good in formability (Good), while a final sheet with a value of elongation of less than 40.0% was evaluated as poor in formability (Poor).

[0114] A final sheet with a value of (TS95-TS90) of less than −4 MPa was evaluated as good in work softenability (Good), while a final sheet with a value of (TS95-TS90) of −4 MPa or more was evaluated as poor in work softenability (Poor).

[0115] A final sheet with a value of elongation after cold rolling by a rolling reduction of 90% of 5.0% or more was evaluated as good in operating stability (Good), while a final sheet with a value of elongation after cold rolling by a rolling reduction of 90% of less than 5.0% was evaluated as poor in operating stability (Poor). The results of evaluation of these are shown in Table 4.

TABLE-US-00004 TABLE 4 Results of Evaluation of Properties of Test Samples Rolling reduction 0% 90% 95% 90% Final Cold Cold Final sheet Final rolled rolled sheet conduc- sheet material material tensile tivity elonga- tensile TS95- elonga- Annealing strength (IACS tion strength TS90 tion conditions (MPa) %) (%) (MPa) (MPa) (%) Ex. 51 Annealer 114 54.4 44.0 189 183 −6 6.1 340° C.-1 hr Ex. 52 Annealer 110 54.5 45.4 187 180 −7 6.4 440° C.-1 hr Comp. Ex. 53 Annealer 135 53.3 26.5 187 185 −2 6.6 240° C.-1 hr Comp. Ex. 54 Salt bath 111 52.5 44.3 199 197 −2 4.8 425° C.-15 sec Average Evaluation grain Heat size radiating Work Operating (μm) Strength ability Formability softenability stability Ex. 51 16.0 Good Good Good Good Good Ex. 52 29.1 Good Good Good Good Good Comp. Ex. 53 — Good Good Poor Poor Good Comp. Ex. 54 13.6 Good Poor Good Poor Poor *) In the table, Comparative Example 53 was a nonrecrystallized structure, so the average grain size could not be measured.

[0116] Example 51 in Table 4 showing the results of evaluation of the properties of the test sample was within the scope of composition of the present invention. Also, the final annealing was annealer annealing simulating batch annealing at a holding temperature of 340° C. and holding time of 1 hour. Each of the tensile strength of the final sheet, the conductivity of the final sheet, the value of elongation of the final sheet, the value of (TS95-TS90), and the value of elongation after cold rolling the final sheet by a rolling reduction of 90% all satisfied the reference values. Specifically, Example 51 had a tensile strength of the final sheet of 95 MPa or more, a conductivity of the final sheet of 53.0% IACS or more, a value of elongation of the final sheet of 40.0% or more, a value of (TS95-TS90) of less than −4 MPa, and a value of elongation after cold rolling the final sheet by a rolling reduction of 90% of 5.0% or more. Therefore, Example 51 was evaluated as good in strength (Good), was evaluated as good in heat radiating ability (Good), was evaluated as good in formability (Good), was evaluated as good in work softenability (Good), and was evaluated as good in operating stability (Good). Further, the final sheet of Example 51 exhibited a recrystallized structure and had an average grain size of the recrystallized grains of 16.0 μm.

[0117] Example 52 in Table 4 showing the results of evaluation of the properties of the test sample was within the scope of composition of the present invention. Also, the final annealing was annealer annealing simulating batch annealing at a holding temperature of 440° C. and holding time of 1 hour. Each of the tensile strength of the final sheet, the conductivity of the final sheet, the value of elongation of the final sheet, the value of (TS95-TS90), and the value of elongation after cold rolling the final sheet by a rolling reduction of 90% satisfied the reference values. Specifically, Example 52 had a tensile strength of the final sheet of 95 MPa or more, a conductivity of the final sheet of 53.0% IACS or more, a value of elongation of the final sheet of 40.0% or more, a value of (TS95-TS90) of less than −4 MPa, and a value of elongation after cold rolling the final sheet by a rolling reduction of 90% of 5.0% or more. Therefore, Example 52 was evaluated as good in strength (Good), was evaluated as good in heat radiating ability (Good), was evaluated as good in formability (Good), was evaluated as good in work softenability (Good), and was evaluated as good in operating stability (Good). Further, the final sheet of Example 52 exhibited a recrystallized structure and had an average grain size of the recrystallized grains of 29.1 μm. [0077]

[0118] Comparative Example 53 in Table 4 showing the result of evaluation of the properties of the test sample was within the scope of composition of the present invention. Also, the final annealing was annealer annealing simulating batch annealing at a holding temperature of 240° C. and holding time of 1 hour. The tensile strength of the final sheet, the conductivity of the final sheet, and the value of elongation after cold rolling the final sheet by a rolling reduction of 90% satisfied the reference values, but the value of elongation of the final sheet and the value of (TS95-TS90) failed to satisfy the reference values. Specifically, Comparative Example 53 had a tensile strength of the final sheet of 95 MP or more, a conductivity of the final sheet of 53.0% IACS or more, and a value of elongation after cold rolling the final sheet by a rolling reduction of 90% of 5.0% or more, but a value of elongation of the final sheet of less than 40.0% and a value of (TS95-TS90) of −4 MPa or more. Therefore, Comparative Example 53 was evaluated as good in strength (Good), was evaluated as good in heat radiating ability (Good), was evaluated as poor in formability (Poor), was evaluated as poor in work softenability (Poor), and was evaluated as good in operating stability (Good). Further, the final sheet of Comparative Example 53 exhibited a nonrecrystallized structure. There were no recrystallized grains present so measurement of their average grain size was not possible.

[0119] Comparative Example 54 in Table 4 showing the result of evaluation of the properties of the test sample was within the scope of composition of the present invention. Also, the final annealing was salt bath annealing simulating continuous annealing at a holding temperature of 425° C. and holding time of 10 seconds. The tensile strength of the final sheet and the value of elongation of the final sheet satisfied the reference values, but the conductivity of the final sheet, the value of (TS95-TS90), and the value of elongation after cold rolling the final sheet by a rolling reduction of 90% failed to satisfy the reference values. Specifically, Comparative Example 54 had a tensile strength of the final sheet of 95 MPa or more and a value of elongation of the final sheet of 40.0% or more, but the conductivity of the final sheet was less than 53.0% IACS, the value of (TS95-TS90) was −4 MPa or more, and the value of elongation after cold rolling the final sheet by a rolling reduction of 90% was less than 5.0%. Therefore, Comparative Example 54 was evaluated as good in strength (Good), was evaluated as poor in heat radiating ability (Poor), was evaluated as good in formability (Good), was evaluated as poor in work softenability (Poor), and was evaluated as poor in operating stability (Poor). Further, the final sheet of Comparative Example 54 exhibited a recrystallized structure and had an average grain size of the recrystallized grains of 13.6 μm.

[0120] From the above, it is learned that aluminum alloy sheet for battery lid use having the above specific component composition and having a tensile strength of the final sheet of 95 MPa or more, a conductivity of 53.0% IACS or more, a value of elongation of 40% or more, and a recrystallized structure, having a value of (TS95-TS90) of less than −4 MPa when defining a tensile strength after cold rolling by a rolling reduction of 90% as TS90 and defining a tensile strength after cold rolling by a rolling reduction of 95% as TS95, and exhibiting values of elongation after cold rolling by a rolling reduction of 90% of 5.0% or more has suitable strength, is excellent in heat radiating ability, formability, and work softenability, and can form an integrated explosion-proof valve with little variation in operating pressure.