JP2553898B2 - Metal foil manufacturing method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a metal foil which is less likely to cause pinholes even when its thickness is thin and has excellent repeated bending properties.

(B) Conventional Technology Conventionally, metal foil has been used as a packaging material for foods, chemicals, etc., or as a covering material for electric wires, etc. When used for these purposes, the metal foil is required to be airtight. In order to improve the airtightness of the metal foil, it is necessary to reduce pinholes.

The main causes of pinholes in the metal foil are as follows. That is, the dust, etc. attached to the surface of the metal plate before rolling penetrates in the thickness direction of the metal foil after rolling to form a pinhole. This is the thickness and dust of the metal foil,
This is because the size of dust and the like becomes the same. Bubbles mixed in at the stage of casting when producing an ingot, or defects (cavities and microcracks) during casting grow after rolling and pinholes occur. Impurities and the like inevitably mixed in the metal material penetrate through the metal foil in the thickness direction after rolling to form pinholes.
This is also because the metal foil has the same thickness as impurities.

Therefore, to prevent the occurrence of pinholes,
It is thought that the cause of should be eliminated. However, in order to eliminate the cause of, it is necessary to remove dust from the rolling site and clean it. For example, it is conceivable to make the rolling site a clean room, but the cost of equipment installation is large, the manufacturing cost is greatly improved, and it is not practical. Elimination of the cause of is related to the improvement of the casting method, but the complete casting method has not yet been developed. In order to eliminate the cause of the, the method of solidifying the impurities in the metal material, or making the impurities finer is proposed,
Since it is an unavoidable mixture of impurities, it is difficult to completely eliminate it. Also, even if one of the causes of is removed, if there are other causes, pinholes still occur, and it is necessary to eliminate the causes of all at once.
However, the method of eliminating all at once is difficult with the current technology.

(C) Problems to be Solved by the Invention Therefore, the inventors of the present invention should not prevent the causes of (1) to (3) but prevent the occurrence of pinholes while keeping these causes. I tried. The present inventors have examined the probability that the above-mentioned causes (1) to (3) exist in a metal material, and a metal material obtained through a general casting or hot or cold rolling step has a very high probability. It did not have the above-mentioned causes. The inventors of the present invention focused on this point, and when two metal materials having the above-mentioned causes are overlapped, the points causing the above-mentioned causes are not substantially matched in the thickness direction. It was The premise of the technical idea according to the present invention is based on this finding.

By the way, if this knowledge is simply pushed forward, if two metal foils are superposed and pressure-bonded to be treated as one metal foil, a metal foil substantially free of pinholes can be obtained.

However, just by stacking two metal foils and crimping them,
A metal foil with excellent mechanical performance cannot be obtained. That is, a mere polymerized metal foil is inferior in repeated bending characteristics and the like as compared with a single metal foil having the same thickness. The reason for this is that, in a mere polymerized metal foil, the polymerized interface surely remains, and it is equivalent to two thin metal foils adhered with an adhesive or the like.

From the viewpoint as described above, the present invention has a substantially non-existent polymerized interface even though two metal materials are superposed on each other (in other words, a metal crystal is generated over the polymerized interface), Another object of the present invention is to provide a method for manufacturing a metal foil that can be handled as a single foil.

(D) Means for solving the problem That is, the present invention, a plurality of metal materials of a predetermined shape are superposed and pressure-bonded to the polymerized metal material, so that the total reduction rate is 70% or more. The present invention relates to a method for producing a metal foil, which comprises rolling to reduce the thickness of the polymerized metal material to form metal crystals at the polymerization interface to form a single metal foil.

In the present invention, first, a metal material having a predetermined shape is prepared. The metal material having a predetermined shape means an ingot after casting, a thick plate after hot rough rolling or further hot finish rolling, or a plate after further cold rolling, in short, a metal foil is manufactured. It means the metal material in the previous stage. Aluminum, lead, lead-tin alloy, tin, iron, copper or the like is used as the metal material.

Next, two or more of these metal materials are overlapped and pressure-bonded to obtain a polymerized metal material. The number of superposed metal materials is generally two, but may be three or more depending on the case. It is preferable to degrease and wash the surface of the metal material to clean it before the metal material is pressure-bonded. This is because, if the dust and the dust, and further the rolling oil and the like are removed, the pressure bonding can be easily performed and the defect due to the dust and the like does not occur. From this point, it is preferable that the thickness of the metal material is large so that the surface area of the metal material is reduced. Further, when the metal material is an ingot, it is preferable to scrape the surface. This is also because pressure bonding can be easily performed.

In order to obtain the polymerized metal material, the metal materials may be superposed and pressure-bonded under a large load. The crimping is performed by heating iron, copper, aluminum or the like, but may be performed at room temperature for a low melting point metal such as lead. When heating is performed, heating / pressing may be performed while rolling through a hot rolling process. Also, when performing at room temperature, pressure bonding may be performed while rolling through a cold rolling process.

The obtained polymerized metal material is not so thin as to be called a foil and the polymerization interface remains, so that the desired thickness (about 100 μ or less) and the polymerization interface are substantially formed. Is rolled so that it does not exist. In general, one rolling leaves a polymerization interface, so rolling is performed multiple times so that the total rolling reduction is 70% or more.
For example, the cold rolling is simply repeated, or the cold rolling is repeatedly performed while appropriately annealing, so that the total rolling reduction is 70% or more and a metal foil having a desired thickness is obtained. In the present invention, if the total reduction ratio is less than 70%, it is difficult to form a metal crystal across the polymerization interface, and therefore it cannot be adopted.

The metal foil thus obtained forms a metal crystal at the polymerization interface and is completely integrated to form a single metal foil.

(E) Example Example 1 After degreasing and cleaning the surface of an aluminum plate having a thickness of 100 mm, a width of 3300 mm, and a length of 4000 mm, two aluminum plates are superposed and heated to 450 ° C. in a preheating furnace. did.
Immediately thereafter, hot rolling was performed to obtain a polymerized aluminum plate having a thickness of 3 mm. A cold rolling process and an annealing process are repeated a plurality of times on this polymerized aluminum plate to obtain a thickness of 30 μ (7 times of rolling, reduction rate 99%), 20 μ (7 times, 99.3%), 15 μ (8 times,
99.5%), 10μ (8 times, 99.7%) aluminum foil was obtained.

Comparative Example 1 An aluminum foil having a thickness of 30 μ, 20 μ, 15 μ, and 10 μ was obtained through the cold rolling process and the annealing process in the same manner as in Example 1 without overlapping the aluminum thick plates used in Example 1.

The pinhole rate and the tensile strength of the aluminum foils obtained in Example 1 and Comparative Example 1 were measured. The results are shown in Table 1.

From this result, it can be seen that the aluminum foil obtained in Example 1 has a smaller number of pinholes than the aluminum foil obtained in Comparative Example 1. In particular, in Example 1, the pinhole rate was 0 even when the foil thickness was 10 μm. Further, from the results of the tensile strength, it is found that all the aluminum foils have the same physical properties.

Example 2 Lead (95%)-tin (5% thickness 40 mm, width 500 mm, length 1000 mm)
%) The surface of the ingot of alloy is chamfered and further removed. Degreasing and cleaning were performed using an oil-treated material. Then, two ingots of this lead-tin alloy were overlapped and cold-rolled to obtain a polymerized lead-tin alloy ingot. By repeating this cold rolling multiple times, thickness 60μ (rolling frequency 14 times, 99.850%), 50μ
(14 times, 99.875%), 40μ (15 times, 99.900%), 30μ (15
(99.925%) lead-tin alloy foil was obtained.

Comparative Example 2 Without rolling the ingots of the lead-tin alloy after degreasing and washing used in Example 2, cold rolling was repeated in the same manner as in Example 2 to obtain the thicknesses of 60 μ, 50 μ, 40 μ and 30 μ. A lead-tin alloy foil was obtained.

Comparative Example 3 Thicknesses obtained by the method of Comparative Example 2 60μ, 50μ, 40μ, 30μ
Each of the lead-tin alloy foils of No. 1 was laminated and cold-rolled once, and the thickness was 60μ, 50μ, 40μ, 3 with a reduction rate of 50%.
A 0 μm lead-tin alloy foil was obtained.

The pinhole rate, the tensile strength and the cyclic bending property of the lead-tin alloy foils obtained in Example 2 and Comparative Examples 2 and 3 were measured. Table 2 shows the results.

From this result, the lead-tin alloy obtained in Example 2 was obtained. It can be seen that the foil has a smaller number of pinholes than the lead-tin alloy foil obtained in Comparative Example 2. Further, it can be seen that the repeated bending property is superior to that of the lead-tin alloy foil obtained in Comparative Example 3. Furthermore, from the results of tensile strength, it can be seen that all the lead-tin alloy foils have the same physical properties.

Example 3 Two 100 μm thick lead (95%)-tin (5%) alloy foils were superposed, cold rolled to a thickness of 100 μm, and cold rolled again to a thickness of 40 μm (80% reduction). Got foil. The state of the polymerization interface of this foil is shown in FIG. As is clear from this figure, although some traces of the polymerization interface remain, metal crystals can be observed across the polymerization interface. Therefore, this lead-
The tin alloy foil has excellent repeated bending properties.

Example 4 Two sheets of lead (95%)-tin (5%) alloy plate having a thickness of 40 mm were superposed and pressure-bonded, and then cold rolling was repeated 14 times to obtain a foil having a thickness of 50 μ (reduction ratio 99.9%). It was The state of the polymerization interface of this foil is shown in FIG. As is clear from this figure, there are almost no traces of the polymerization interface, and the metal crystal is the same as that of the portion other than the polymerization interface. Therefore, it is completely similar to one sheet of lead-tin alloy foil and has excellent repeated bending properties.

Example 5 Two 40 mm-thick lead (95%)-tin (5%) alloy plates were superposed and pressure-bonded, and then cold rolling was repeated 13 times to form a 100 μ-thick foil, and then at 200 ° C. for 1 hour. It was annealed and then cold-rolled once to obtain a foil having a thickness of 50 μ (reduction ratio 99.9%).
The state of the polymerization interface of this foil is shown in FIG. As is clear from this figure, there are almost no traces of the polymerization interface, the metal crystal becomes the same as the portion other than the polymerization interface, and the metal crystal grows by the annealing step. Therefore, it is completely similar to one sheet of lead-tin alloy foil and has excellent repeated bending properties.

Comparative Example 4 Two 100 μm thick lead (95%)-tin (5%) alloy foils were stacked and cold rolled to obtain a 100 μm thick (50% reduction) foil. The state of the polymerization interface of this foil is shown in FIG. As is clear from this figure, the polymerization interface is clearly present, and no metal crystal is present at the polymerization interface. Therefore, this lead-tin alloy foil is inferior in repeated bending characteristics as compared with those of Examples 3 to 5.

Comparative Example 5 Two 100 μm-thick lead (95%)-tin (5%) alloy foils were superposed, cold-rolled to a thickness of 120 μm, and then cold-rolled again to a thickness of 80 μm (60% reduction). Got foil. The state of the polymerization interface of this foil is shown in FIG. As is clear from this figure, the polymerization interface is clearly present, and no metal crystal is present at the polymerization interface. Therefore, this lead-tin alloy foil is inferior in repeated bending characteristics as compared with those of Examples 3 to 5.

(H) Action and effect of the invention As described above, if two or more metal materials having the cause of the pinhole are overlapped, it is substantially the same as the cause point in the thickness direction. There is no way. Therefore,
Even if the pinholes are opened due to the one metal material that is superposed, the pinholes are not opened in the other metal material, and as a result, the pinholes are not generated as a whole.
Further, in the present invention, since specific rolling is performed, metal crystals are generated at the polymerization interface, and the metal structure becomes equivalent to that of the portion other than the polymerization interface. Therefore, the repeated bending property has the same performance as that of the metal foil obtained without overlapping the metal material or the metal foil. Therefore, if the metal foil is obtained by the method of the present invention, it is possible to obtain a metal foil having few pinholes and excellent in repeated bending characteristics. The method of the present invention is not a method of removing the cause of pinholes, but a method of carrying out the cause of the pinholes, so that it also has an effect that a metal foil with few pinholes can be easily manufactured.

Further, in the case of obtaining a metal foil having no pinhole and excellent in repeated bending characteristics, it could not be obtained by increasing the thickness in the prior art, but according to the method of the present invention, the thickness can be reduced. It can be obtained even if it is thin. Therefore,
It is possible to obtain a metal foil that has a low weight and does not have pinholes and is excellent in repeated bending properties, and it is possible to reduce the raw material price, and eventually, the metal foil as a final product is inexpensive.

The metal foil obtained by the method of the present invention can be suitably used particularly as an electric wire coating material because it has no pinholes, has a low weight, and has excellent repeated bending properties. .

[Brief description of drawings]

1 to 5 are micrographs of the metal structure, and the magnification is 500 times.

Claims (1)

(57) [Claims] 1. A polymerized metal material obtained by superposing two or more metal materials having a predetermined shape and pressure bonded to each other is rolled a plurality of times so that the total rolling reduction is 70% or more, and the polymerized metal material is made thin. A method for producing a metal foil, which comprises forming a metal crystal at a polymerization interface to form a single metal foil.