CN112646990A

CN112646990A - Rolled aluminum material for anode of low-voltage electrolytic capacitor and method for producing same

Info

Publication number: CN112646990A
Application number: CN201910952501.2A
Authority: CN
Inventors: 宗宫和久; 山之井智明
Original assignee: Showa Denko KK
Current assignee: Aluminum Co ltd; Showa Aluminum Fou International Co ltd; Showa Electric Co Ltd
Priority date: 2019-10-09
Filing date: 2019-10-09
Publication date: 2021-04-13

Abstract

The invention aims to provide an aluminum rolled material for anodes of low-voltage electrolytic capacitors, which can increase the electrostatic capacity. Low pressure electrolysisAn aluminum rolled material for capacitor anodes, which has an aluminum purity of 99.9% or more, and contains Fe: 5-50 ppm, Si: 5-50 ppm, Cu: 11 to 19ppm, satisfies 11 ≤ C_Cu+5C_AgLess than or equal to 19ppm (wherein C)_CuIs the Cu content, C_AgIs Ag content), and contains Mn: 0.5-20 ppm, Cr: 0.5-20 ppm, Mg: 0.2-10 ppm, Zn: 0.5 to 20ppm, Ga: 0.5-40 ppm, Ti: 0.2 to 5 ppm.

Description

Rolled aluminum material for anode of low-voltage electrolytic capacitor and method for producing same

Technical Field

The present invention relates to an aluminum rolled material for anodes of low-voltage electrolytic capacitors and a method for producing the same.

Background

In general, an aluminum rolled material used as an anode material for an aluminum electrolytic capacitor is generally subjected to electrochemical or chemical etching treatment in order to increase the effective area and increase the capacitance per unit area.

However, sufficient capacitance cannot be obtained only by etching the foil. Particularly in the application to low-voltage capacitors, a fine etching pit is required, and a sponge-like etching pit is formed mainly by ac etching. If excessive dissolution of the aluminum rolled material occurs during the etching treatment, the formed fine etching pits are destroyed, and effective surface area enlargement cannot be achieved, so that control from the viewpoint of the aluminum material is very important.

For such applications, for example, patent document 1 discloses a continuous casting and rolling production method in which the purity of aluminum is 99.99% or more, the content of Si, Fe, Cu, Mg, Ga, Mn, Ce is contained, and the content of B, Ti, Zr, V is limited, and patent document 2 discloses an alloy foil in which the purity of aluminum is 99.98% or more, the content of Si, Fe, Cu, Mn, Cr, Mg, Zn, Ga, Ti is contained, the content of one or more of V, Zr, and B is contained, and the content of one or more of Pb, Bi, and Sn is contained.

Prior art documents

Patent document 1: CN 101789314B

Patent document 2: CN 104616897B

Disclosure of Invention

Problems to be solved by the invention

However, the aluminum rolled material containing the trace elements does not sufficiently satisfy the demand for high capacitance of electrolytic capacitors in the present day.

In view of the background, an object of the present invention is to provide an aluminum rolled material for an electrolytic capacitor anode, which can increase the capacitance, and a method for producing the same.

Means for solving the problems

As a result of earnest study to solve the above problems, the present inventors have found that Ag coexists in an alloy containing Fe, Si, Cu, Mn, Mg, Cr, Zn, Ga, and Ti in a certain relationship with Cu in the composition of an aluminum rolled material, and thereby the area enlargement rate by etching can be increased, and further, addition of various trace elements can synergistically act to obtain an aluminum rolled material having a high electrostatic capacity. That is, the invention of the present application is as follows.

(1) An aluminum rolled material for anodes of low-voltage electrolytic capacitors, characterized in that the aluminum has a purity of 99.9% or more, and contains Fe: 5-50 ppm, Si: 5-50 ppm, Cu: 11 to 19ppm, satisfies 11 ≤ C_Cu+5C_AgLess than or equal to 19ppm (wherein C)_CuRepresents the Cu content, C_AgRepresenting Ag content), and contains Mn: 0.5-10 ppm, Cr: 0.5-20 ppm, Mg: 0.2-10 ppm, Zn: 0.5 to 20ppm, Ga: 0.5-40 ppm, Ti: 0.2 to 5 ppm.

(2) The rolled aluminum material for anodes of low-voltage electrolytic capacitors according to the above (1), which comprises a metal selected from the group consisting of V: 0.2 to 5ppm, Zr: 0.2-5 ppm, B: 0.5 to 20 ppm.

(3) The rolled aluminum material for low-voltage electrolytic capacitor anodes according to the above (2), which contains a compound selected from the group consisting of Pb: 0.2 to 3ppm, Bi: 0.2 to 3ppm, Sn: 0.2 to 10 ppm.

(4) The rolled aluminum material for anodes of low-voltage electrolytic capacitors according to the above (3), which comprises Ag: more than 0.2-5 ppm and P: at least one of 0.2 to 10 ppm.

(5) A method for producing an aluminum rolled material for anodes of low-voltage electrolytic capacitors, comprising the steps of: an aluminum alloy ingot having a composition as set forth in any one of (1) to (4) above, wherein before or after the subsequent surface cutting, homogenization treatment is performed at a temperature of 500 ℃ to 620 ℃ inclusive for a time of 1 hour to 40 hours inclusive, after cooling in this state, or after reheating for holding at a temperature of 450 ℃ to 560 ℃ inclusive for 5 minutes to 20 hours inclusive, hot rolling is started, hot rolling is performed in a plurality of passes with a reduction ratio of 95% to 99.5% inclusive, and then cold rolling is continued.

(6) The method for producing an aluminum rolled material for a low-voltage electrolytic capacitor anode according to the above (5), comprising the steps of: after cold rolling, final annealing is performed at 120 ℃ or higher and 200 ℃ or lower, or 300 ℃ or higher and 450 ℃ or lower for 1 hour or longer and 30 hours or shorter.

(7) The method for producing an aluminum rolled material for a low-voltage electrolytic capacitor anode according to the above (5) or (6), comprising the steps of: at least one time of intermediate annealing at a temperature of 120 ℃ to 200 ℃ and 1 hour to 20 hours is performed in the cold rolling process.

ADVANTAGEOUS EFFECTS OF INVENTION

The aluminum alloy foil for electrolytic capacitor anodes according to the present invention can increase the density of etching pits by forming fine etching pits, and can obtain a very large area enlargement ratio by etching treatment by uniformly dispersing the fine etching pits. Therefore, an aluminum rolled material for an electrolytic capacitor anode having a large capacitance and excellent electrical characteristics can be provided.

Detailed Description

The aluminum rolled material for electrolytic capacitor anodes of the present invention is characterized in that the aluminum has a purity of 99.9% or more, and contains Fe: 5-50 ppm, Si: 5-50 ppm, Cu: 11 to 19ppm, satisfies 11 ≤ C_Cu+5C_AgLess than or equal to 19ppm (wherein C)_CuRepresents the Cu content, C_AgRepresenting Ag content), and contains Mn: 0.5-10 ppm, Cr: 0.5-20 ppm, Mg: 0.2-10 ppm, Zn: 0.5 to 20ppm, Ga: 0.5-40 ppm, Ti: 0.2 to 5 ppm.

Hereinafter, the present invention will be described in detail.

The aluminum alloy foil according to the present invention is used for forming an aluminum rolled material for an electrolytic capacitor anode, which can increase the electrostatic capacity.

(purity of aluminum)

The reason why the aluminum purity of the rolled aluminum material for electrolytic capacitor anodes according to the present invention needs to be 99.9% or more is that if the purity is less than 99.9%, the aluminum is excessively dissolved due to the presence of many impurities during etching, and the formed fine pits are destroyed, and uniform sponge-like pits cannot be formed due to the presence of trace elements within the scope of the present invention, and therefore, an aluminum rolled material having a high electrostatic capacity cannot be obtained. The aluminum purity is preferably 99.98% or more.

The trace elements Fe, Si, Cu, Mn, Mg, Cr, Zn, Ga, Ti, and Ag contained in the foil composition contribute to the improvement of the etching characteristics of the foil, respectively, as described below, and further contain a metal element selected from the group consisting of V: 0.2 to 10ppm, Zr: 0.2-10 ppm, B: 0.5 to 20ppm of at least one compound selected from the group consisting of Pb: 0.2 to 5ppm, Bi: 0.2 to 5ppm, Sn: 0.2 to 10ppm, respectively, can obtain synergistic effects corresponding to their respective effects.

(Fe, Si content)

Fe. Si easily forms a compound with Al in the Al matrix, and the pits can be uniformly distributed by controlling the dispersion state of these elements. However, if the content is too large, it becomes a cause of excessive dissolution during etching, resulting in a decrease in electrostatic capacity. Therefore, the Fe content needs to be 5 to 50ppm, preferably 20ppm at the lower limit, and 40ppm at the upper limit. The Si content is required to be 5 to 50ppm, preferably 30ppm at the lower limit and 45ppm at the upper limit.

(Cu content)

Cu is dissolved in an Al matrix, and thereby increases the solubility of the foil, promotes the growth of pits, forms fine pits, and increases the capacitance. If the Cu content is less than 11ppm, the above effect is poor, and the strength is lowered due to abnormal grain growth in the intermediate annealing or the final annealing described later. If it exceeds 19ppm, the solubility is increased, and the uniform distribution of etching pits is hindered. Therefore, the Cu content needs to be 11 to 19ppm, preferably 12ppm at the lower limit and 18ppm at the upper limit.

(Ag content)

There is a correlation between Cu and Ag that shows an interaction for controlling the solubility of the foil, forming fine etching pits, and obtaining a high capacitance. Therefore, the range is limited to the following range.

11≤C_Cu+5C_Ag≤19ppm

Wherein, C_CuRepresents the Cu content, C_AgRepresents the Ag content.

However, if the Ag content is increased, the pits become excessively fine, and the pits are detached due to the combination thereof, thereby decreasing the electrostatic capacity. Therefore, the Ag content should be 0.2 to 5ppm, and the preferable lower limit and upper limit of the Ag content are 0.3ppm and 3ppm, respectively.

(Mn content)

Mn easily forms a compound with Al in an Al matrix, and by controlling the dispersion state of this element, the solubility of the foil can be increased, the growth of pits can be promoted, deep pits can be formed, and the electrostatic capacity can be increased. If the Mn content is less than 0.5ppm, the above effect is poor, and if it exceeds 10ppm, the local solubility is increased, which may prevent uniform distribution of the etch pits. Therefore, the Mn content should be 0.5 to 10ppm, preferably 1ppm at the lower limit and 8ppm at the upper limit.

(Cr content)

Cr is likely to form a compound with Al in an Al matrix, and by controlling the dispersion state of this element, the solubility of the foil can be increased, the growth of pits can be promoted, deep pits can be formed, and the electrostatic capacity can be increased. If the Cr content is less than 0.5ppm, the above effect is poor, and if it exceeds 20ppm, the local solubility is increased, which may prevent uniform distribution of pits. Therefore, the Cr content should be 0.5 to 20ppm, preferably 1ppm at the lower limit and 12ppm at the upper limit.

(Mg content)

Mg is an element necessary for highly dense and uniform distribution of etching pits during etching. That is, the unevenness usually present on the surface of the foil at the initial stage of etching and the uneven local dissolution pits due to the deposits such as oil and roll coating material or the deterioration products thereof cause uneven density (density) of the pits, and in a serious case, the surface dissolves like craters. This unevenness also remains after the etching is completed, and causes a decrease in capacitance. Therefore, in order to prevent such a problem, the inventors of the present invention have made extensive studies to control the cause of the unevenness of the etching pits present on the surface, and as a result, have found that Mg has an effect of removing the local portions of the etching pits and forming the etching pits at a high density. On the other hand, if it exceeds 10ppm, the local solubility is increased, which hinders the uniform distribution of the etching pits. Therefore, the Mg content is required to be 0.2 to 10 ppm. The lower limit of the Mg content is preferably 1ppm, and the upper limit thereof is preferably 8 ppm.

(Zn content)

Zn is an element that slightly lowers the substrate potential by being dissolved in an Al substrate, and the presence of a trace amount can increase the solubility of the foil, promote the growth and expansion of pits, and increase the electrostatic capacity. If the Zn content is less than 0.5ppm, the above effect is poor, and if it exceeds 20ppm, the local solubility becomes strong, which may prevent uniform distribution of pits. Therefore, the Zn content should be 0.5 to 20ppm, preferably 1ppm at the lower limit and 12ppm at the upper limit.

(Ga content)

While Ga, if present in excess, is likely to segregate at grain boundaries or subgrain boundaries, and is an element that, when present alone, causes uneven distribution of pits, Ge has the effect of improving the uniform dispersibility of pits in the presence of Mg, because Mg reduces the size of subgrain boundaries. If the Ga content is less than 0.5ppm, the above effect is poor, and if it exceeds 40ppm, the local solubility becomes strong, which may prevent uniform distribution of pits. Therefore, the Ga content needs to be 0.5 to 40ppm, preferably 1ppm at the lower limit and 25ppm at the upper limit.

(Ti content)

The small amount of Ti dissolved in the Al matrix increases the solubility of the foil, promotes the growth and enlargement of the etching pits, and increases the electrostatic capacity. However, if the content is too large, segregation tends to occur in the grain boundary, which causes uneven etching pits, and therefore, it is necessary to control the ratio of Ti: 0.2 to 5ppm, preferably 0.5ppm at the lower limit and 8ppm at the upper limit.

(V, Zr, B content)

B. V, Zr the generation of etching pits is promoted and the capacitance is increased. However, since segregation is likely to occur if the content is increased, which causes unevenness of etching pits, it is necessary to control the ratio of V: 0.2 to 5ppm, Zr: 0.2-5 ppm, B: 0.5 to 20 ppm.

(Pb, Bi, Sn content)

Pb, Bi, and Sn suppress local solubility at the initial stage of etching, and contribute to uniform distribution of etching pits. If the Pb or Bi content is less than 0.2ppm, the above effect is poor, and if it exceeds 3ppm, surface dissolution may occur. Therefore, the Pb and Bi contents should be 0.2 to 3 ppm. Sn has the same effect, but has a low influence on surface dissolution, so the upper limit is 10 ppm. Therefore, the Sn content needs to be 0.2 to 10 ppm. The preferable lower limit to the preferable upper limit are Pb: 0.2 to 2ppm, Bi: 0.2 to 2ppm, Sn: 0.5 to 8 ppm.

(P content)

P suppresses local solubility at the initial stage of etching and contributes to uniform distribution of etching pits. If the P content is less than 0.2ppm, the above effect is poor, and if it exceeds 10ppm, surface dissolution may occur. Therefore, the P content is required to be 0.2 to 10 ppm.

Next, the following method is more preferable for the production method of the present invention. For example, there is a method in which an aluminum alloy ingot produced by a semi-continuous casting method is subjected to a homogenization treatment at a temperature of 500 ℃ to 620 ℃ inclusive and a time of 1 hour to 40 hours inclusive before or after surface cutting to be performed subsequently, and after cooling in this state or after reheating at a temperature of 450 ℃ to 560 ℃ inclusive and holding for 5 minutes to 20 hours inclusive, hot rolling is started, hot rolling is performed in a plurality of rolling passes at a reduction ratio of 95% to 99.5% inclusive, and then cold rolling is continued. More preferable ranges of the homogenization treatment are a temperature of 520 ℃ to 600 ℃ inclusive, and 3 hours to 30 hours inclusive. More preferable ranges of the hot rolling start temperature and the holding time are a temperature of 480 ℃ to 540 ℃ and a temperature of 5 minutes to 15 hours.

In addition, annealing may be performed on the final cold-rolled material. The annealing conditions include 120 ℃ to 200 ℃ or 300 ℃ to 450 ℃ inclusive, and the time includes 1 hour to 30 hours inclusive. If the temperature is more than 200 ℃ and less than 300 ℃, the release of the processing strain and recrystallization do not proceed uniformly, and the unrecrystallized region and the recrystallized region coexist, so that the etching pits are not uniform, and the electrostatic capacity is lowered. In addition, in the temperature region of more than 450 ℃, the strength of the material is remarkably reduced, and in order to suppress the breakage at the time of coil etching, the etching rate has to be reduced, resulting in a reduction in electrostatic capacity. The more preferable range of the final annealing temperature may be 150 ℃ or more and 190 ℃ or less or 290 ℃ or more and 390 ℃ or less, and the time may be 2 hours or more and 20 hours or less.

In addition, at least one intermediate annealing may be performed during the cold rolling. The temperature of the intermediate annealing in this case may be 120 ℃ to 200 ℃ inclusive, and the time may be 1 hour to 20 hours inclusive. When the intermediate annealing is performed, the cold rolling reduction until the final cold rolling may be 35% or more and 70% or less. The cold rolling reduction after the intermediate annealing is more preferably in a range of 40% to 55%, and the time may be 2 hours to 15 hours.

Examples

The present invention will be described below with reference to examples. The scope of the present invention is not limited to the embodiments described herein, and can be implemented with appropriate modifications within the spirit of the present invention, and all of them are included in the technical scope of the present invention.

First, aluminum ingots having various compositions shown in Table 1 were produced by a semi-continuous casting method, and ingots having a thickness of 400mm were subjected to homogenization treatment and hot rolling under the conditions shown in Table 2. Subsequently, cold rolling (including intermediate annealing) was continued to obtain a rolled material having a thickness shown in table 1.

Next, the obtained rolled aluminum materials were subjected to etching and chemical conversion treatment under the following conditions, and then the electrostatic capacities were measured. The results are shown in Table 3 (comparative No.7) and Table 4 (comparative No.17) as relative comparisons in which the electrostatic capacity of the comparative foil is 100% and the dissolution loss is 100% for each of the comparative foils under different etching conditions.

[ etching Condition A ]

The etching solution uses 5% hydrochloric acid, 0.3% phosphoric acid and 0.1% nitric acid aqueous solution, and the etching solution has a temperature of 50 ℃, a sine wave alternating current of 60Hz and a current density of 30A/dm²And etching was performed for 5 minutes.

[ etching Condition B ]

The etching solution is 20% hydrochloric acid, 0.3% phosphoric acid and 1% sulfuric acid aqueous solution, and the etching solution has a temperature of 25 deg.C, a sine wave AC of 15Hz, and a current density AC of 15A/dm²And etching was performed for 10 minutes.

[ formation conditions ]

The chemical conversion treatment was carried out in a 15% ammonium adipate aqueous solution at a temperature of 55 ℃ and a chemical conversion voltage of 20V.

[ conditions for measuring Electrostatic capacity ]

Using an LCR tester at room temperature in 8% ammonium borate solution, the frequency: the electrostatic capacity was measured at 120 Hz.

[ measurement conditions for weight loss by etching ]

The weight of the aluminum rolled material before and after the etching was measured, and the amount of weight reduction per unit etching area was defined as the etching weight reduction.

The higher the value of the electrostatic capacity, the better. In the present invention, an improvement of 2% or more can be judged as the observation of the effectiveness. On the other hand, in the case of performing effective etching, the amount of etching reduction increases with the capacitance, but in the case of insufficient etching, the surface area is not sufficiently enlarged, and therefore the amount of etching reduction exhibits a small value, and the capacitance decreases. In addition, when the etching is excessively performed, ineffective dissolution is performed, so that the amount of etching loss increases and the capacitance decreases.

Therefore, the etching decrement has an appropriate value.

The results of the case of performing the etching a are shown in table 3, and the results of the case of performing the etching B are shown in table 4. From the results shown in tables 3 and 4, it was confirmed that the present invention examples containing Fe, Si, Cu, Mn, Cr, Mg, Zn, Ga, and Ti in the ranges of the present invention, and further containing one or more of V, Zr, and B, and one or more of Pb, Bi, and Sn, while satisfying a predetermined relationship between Cu and Ag, can increase the electrostatic capacity as compared with comparative examples outside the ranges of the present invention. Further, a synergistic effect was observed also in the material containing P as a trace element, and it was confirmed that the etching characteristics were improved and the capacitance was increased.

Industrial applicability

The aluminum alloy foil for electrolytic capacitor anodes according to the present invention can increase the density of etching pits, increase the depth thereof, uniformly disperse the pits, and obtain a very large area enlargement ratio by etching treatment. Therefore, the rolled aluminum material can be used for forming an electrolytic capacitor anode aluminum rolled material having a large capacitance and excellent electrical characteristics.

TABLE 1 compositions

TABLE 2 procedure

TABLE 3 evaluation results (etching conditions A)

TABLE 4 evaluation results (etching conditions B)

Claims

1. An aluminum rolled material for anodes of low-voltage electrolytic capacitors, characterized in that the aluminum has a purity of 99.9% or more, and contains Fe: 5-50 ppm, Si: 5-50 ppm, Cu: 11 to 19ppm, satisfies 11 ≤ C_Cu+5C_AgA relation of 19ppm or less, wherein C_CuRepresents the Cu content, C_AgRepresents an Ag content, and contains Mn: 0.5-10 ppm, Cr: 0.5-20 ppm, Mg: 0.2-10 ppm, Zn: 0.5 to 20ppm, Ga: 0.5-40 ppm, Ti: 0.2 to 5 ppm.

2. The rolled aluminum material for anodes of low-voltage electrolytic capacitors as claimed in claim 1, which comprises a metal selected from the group consisting of V: 0.2 to 5ppm, Zr: 0.2-5 ppm, B: 0.5 to 20 ppm.

3. The rolled aluminum material for anodes of low-voltage electrolytic capacitors as claimed in claim 2, which contains a compound selected from the group consisting of Pb: 0.2 to 3ppm, Bi: 0.2 to 3ppm, Sn: 0.2 to 10 ppm.

4. The rolled aluminum material for anodes of low-voltage electrolytic capacitors as claimed in claim 3, which contains Ag: more than 0.2-5 ppm and P: at least one of 0.2 to 10 ppm.

5. A method for producing an aluminum rolled material for anodes of low-voltage electrolytic capacitors, comprising the steps of: an aluminum alloy ingot having the composition according to any one of claims 1 to 4, wherein before or after the subsequent surface cutting, homogenization treatment is performed at a temperature of 500 ℃ to 620 ℃ inclusive for a time of 1 hour to 40 hours inclusive, after cooling in this state, or after reheating at a temperature of 450 ℃ to 560 ℃ inclusive for 5 minutes to 20 hours inclusive, hot rolling is started, hot rolling is performed in a plurality of rolling passes with a reduction of 95% to 99.5% inclusive, and then cold rolling is continued.

6. The method for producing an aluminum rolled material for a low-voltage electrolytic capacitor anode according to claim 5, comprising the steps of: after cold rolling, final annealing is performed at 120 ℃ or higher and 200 ℃ or lower, or 300 ℃ or higher and 450 ℃ or lower for 1 hour or longer and 30 hours or shorter.

7. The method for producing an aluminum rolled material for a low-voltage electrolytic capacitor anode according to claim 5 or 6, comprising the steps of: at least one time of intermediate annealing at a temperature of 120 ℃ to 200 ℃ and 1 hour to 20 hours is performed in the cold rolling process.