WO2016152790A1

WO2016152790A1 - Aluminum alloy sheet for resin-coated drawn and wall-ironed cans having excellent post-manufacture gloss and resin-coated aluminum alloy sheet for drawn and wall-ironed cans

Info

Publication number: WO2016152790A1
Application number: PCT/JP2016/058748
Authority: WO
Inventors: 悟高田; 康博有賀; 良治正田; 祐志井上
Original assignee: 株式会社神戸製鋼所
Priority date: 2015-03-23
Filing date: 2016-03-18
Publication date: 2016-09-29

Abstract

This aluminum alloy sheet for can bodies has a specific composition and is preliminarily coated with a resin and formed into drawn and wall-ironed cans. The surface of the sheet which is to be the outer surfaces of drawn and wall-ironed cans has a surface roughness Rq in the direction of rolling traces of not more than 0.12 μm, and the area ratio of a Fe-based crystallized product having a maximum length of not less than 0.3 μm in a surface layer part extending to a depth of 15 μm in the sheet thickness direction from the surface which is to be the outer surface of drawn and wall-ironed cans is less than 2.4%.

Description

Resin-coated aluminum alloy plate for squeezed iron cans and resin-coated aluminum alloy plate for squeezed iron cans with excellent gloss after can making

The present invention relates to an aluminum alloy plate for a resin-coated drawn iron can and a resin-coated aluminum alloy plate for a drawn iron can.
The aluminum alloy plate for a squeezed iron can according to the present invention is made into a can body (squeezed squeezed can) of a packaging container by squeezing and squeezing after the resin is pre-coated for a resin-coated squeezed iron can. It is the raw material aluminum alloy plate before resin coating.
The resin-coated aluminum alloy plate of the present invention is a material-coated aluminum alloy plate coated with a resin, which is pre-coated with resin and can be made on the can body of the packaging container by drawing ironing.

The body (can body) of a beverage can as a packaging container is generally a squeezed iron can also called a DI can. DI is an abbreviation for “Drawing and wall Ironing”. First, the aluminum alloy sheet is drawn and formed into a cup consisting of a body part that has no side joints and a bottom part that is integrally connected to the body part. Then, the can body is made by multi-stage drawing-ironing (hereinafter also referred to as drawing ironing) in which the body of the cup is ironed.

This can makes a cylindrical body with a height in a beverage can, and this body is painted and baked, the diameter of the opening is reduced by necking, and the edge of the opening is formed by flanging. Is expanded to the final can body.

As a raw material (material) of such a squeezing and ironing can, from the viewpoint of formability, corrosion resistance, strength, etc., a rolled aluminum alloy plate such as AA to JIS3000 series is pre-coated with an aluminum alloy plate (pre-coated). It is used.

Since this resin-coated aluminum alloy plate is pre-coated with a lubricant such as wax as a resin before making cans, it can be drawn and ironed in a dry state. For this reason, there is no need to use a large amount of water or water-based lubricant for reducing friction between the aluminum alloy plate and the tool, which is necessary when drawing and ironing a material aluminum alloy plate that is not coated with resin. A can-making process with low load is possible.

Many proposals have been made to improve the resin-coated aluminum alloy plate from the viewpoint of the composition and structure of the plate in response to the demand for improving the characteristics from the side of the drawn iron can.
For example, in Patent Document 1, in order to sufficiently have the stab resistance of a squeezed iron can and the can expandability of the can body opening, an intermetallic compound existing in the center in the plate thickness direction of the plate cross section is defined, The area ratio of an intermetallic compound having a maximum length of 1 μm or more is more than 0.3% and less than 1.3%, and the number of intermetallic compounds having a maximum length of 11 μm or more is 100 / mm ² or less. Proposed.

On the other hand, in recent years, in order to further improve the design of packaging containers, there is a strong demand for a squeezed iron can having an excellent appearance (outer surface), which is also expressed as glitter or sharpness. It is like that.
In this regard, the glossiness as a squeezed iron can after making a resin-coated aluminum alloy plate is inferior to that of a squeezed iron can made of an aluminum alloy plate not provided with a resin coating.

The reason for this is that in the resin-coated aluminum alloy plate, the direct contact with the punch and die used in drawing and ironing is the coating resin on the outer surface side, and the aluminum alloy plate on the inner surface side is directly By not contacting the die.
The glossiness is increased when the aluminum alloy plate comes into direct contact with the punch or the die during the drawing and ironing process, and the surface of the aluminum alloy plate is smoothed by the pressing, friction or wear action on the plate surface. Therefore, in the resin-coated aluminum alloy plate, this effect is reduced or reduced due to the presence of the coating resin on the outer surface side, and glossiness does not increase.
For this reason, the gloss of the surface of the squeezed iron can made of a resin-coated aluminum alloy plate (hereinafter also referred to as the gloss of the squeezed iron can) is effective when changing the conditions of the can making process such as squeezing and ironing. It cannot be improved.

Therefore, improvement in the gloss (brightness and sharpness) of the drawn and ironed can made from the resin-coated aluminum alloy plate inevitably requires improvement in the aluminum alloy plate on the material side. However, there is not much known prior art for improving the glossiness of such cans, and only Patent Document 2 is occasionally seen.

In this patent document 2, in order to increase the glossiness of the drawn and ironed can, the relationship between the film thickness of the resin to be coated (outer surface coating film) and the roughness of the material aluminum alloy plate surface is defined. Specifically, the arithmetic average roughness (Ra) of the surface that becomes the outer surface of the resin-coated aluminum alloy plate for drawn iron cans is set to within 0.5 μm, and the thickness of the resin coating of this aluminum alloy plate is 0.02 μm. When the Ra is less than 0.2 μm, the resin thickness is increased as the Ra is decreased, for example, the thickness of the resin is 6 μm or more.

Japanese Unexamined Patent Publication No. 2010-236075 Japanese Unexamined Patent Publication No. 2011-201198

However, the Ra of the surface of the aluminum alloy plate and the thickness of the resin layer have been conventionally controlled objects generally for improving glossiness. It is not enough to obtain the gloss of the iron can.

In this respect, it is difficult to say that the surface factors of the aluminum alloy rolled sheet, which has a great influence on the gloss of the squeezed and ironed can made from the resin-coated aluminum alloy sheet, have been fully elucidated. .

The present invention has been made in view of such a problem, and is an aluminum alloy plate that is pre-coated with a resin and can be made into a drawn and ironed can, and improves the glossiness of the drawn and ironed can. It is an object to provide an aluminum alloy plate and a resin-coated aluminum alloy plate that can be used.

In order to solve the above problems, the gist of the aluminum alloy plate for resin-coated squeezed and ironed cans excellent in gloss after canning according to the present invention is expressed by mass%, Mg: 0.1 to 6.0%, Fe: 0.01 to 0.5%, Mn: 0.01 to 0.85%, respectively, and the total content of Fe and Mn is less than 1.3%, from the balance Al and inevitable impurities An aluminum alloy plate for a resin-coated drawn iron can, wherein the surface roughness Rq in the rolling mark direction on the surface on the outer surface side of the drawn iron can is 0.12 μm or less, and the drawn iron of the plate The area ratio of the Fe-based crystallized material having a maximum length of 0.3 μm or more in the surface layer portion from the surface on the outer side of the can to the depth of 15 μm in the plate thickness direction is less than 2.4%.

Further, the gist of the resin-coated aluminum alloy plate for squeezing and ironing cans of the present invention for solving the above-mentioned problems is to have a thermoplastic resin film coating layer on the surface of the aluminum alloy plate.

In the present invention, an important control factor on the surface of the material rolled plate, which has not been noticed so far and greatly affects the gloss of the surface of the drawn and ironed can, is found and controlled.
One of the important control factors is the surface roughness Rq in the rolling mark direction (rolling direction) on the surface on the outer surface side of the drawn iron can among the various surface roughnesses of the blank.
The gloss or appearance of the drawn iron can by actual visual evaluation is, as will be described later, in particular, on the outer surface of the drawn iron can, the direction of the rolling trace and the direction of the ironing trace are substantially parallel to each other. Since the surface portion to be polished has the highest glossiness, it is the portion that gives the impression of glossiness most.
Therefore, the control of the surface roughness Rq in the rolling mark direction (rolling direction) of the raw material plate, which is closely correlated with the evaluation method for the gloss of the squeezed iron can, is the surface roughness in the other direction of the raw material plate. It is more effective than that.

At the same time, in the present invention, as another important control factor, a relatively large Fe-based crystallized material in the surface layer portion of the material plate from the surface on the outer surface side of the drawn iron can to the depth of 15 μm in the plate thickness direction. Regulate the existence of
This is because the relatively large Fe-based crystallized material in the surface layer portion of this material plate is deformed by drawing and ironing as described later, and appears as uneven parts on the surface of the can or as a different material part with respect to the matrix. This is because it has been found that the glossiness or appearance of the film is lowered.

The present invention can obtain the required glossiness of the drawn and ironed can surface by controlling the factors of the surface of the rolled steel plate, which greatly affects the glossiness of the surface of the drawn and ironed can. A resin-coated aluminum alloy plate can be provided.

It is a schematic diagram which shows the relationship between a raw material board, the rolling trace on the surface of a drawn and ironed can, and an ironing trace. It is sectional drawing which shows partially and typically the surface layer part of a raw material board (rolled board).

Hereinafter, an embodiment for realizing an aluminum alloy plate for a can body of the present invention (hereinafter also referred to as an aluminum alloy plate) will be described.

The aluminum alloy plate for a resin-coated squeezed iron can according to the present invention is an aluminum alloy rolled plate (cold rolled plate) as a can body material, and is preliminarily coated with a resin, particularly a thermoplastic resin film. It is a material aluminum alloy plate before resin coating that is ironed and can be made into a drawn iron can (hereinafter also simply referred to as a can). Moreover, the resin-coated aluminum alloy plate for a drawn iron can according to the present invention is obtained by coating the aluminum alloy rolled plate with a thermoplastic resin film before the can is made.
In the following description of the composition and structure, the aluminum alloy plate before resin coating and the aluminum alloy plate after resin coating are collectively referred to as an aluminum alloy plate or a material aluminum alloy plate.

(Aluminum alloy composition)
The composition of the aluminum alloy plate of the present invention is not only from the viewpoint of the gloss of the squeezed iron can surface, but as a premise, the required characteristics of the can, such as squeezing iron workability, required strength as a can, corrosion resistance, etc. Defined to combine.

For this reason, the composition of the aluminum alloy sheet of the present invention is, in mass%, Mg: 0.1 to 6.0%, Fe: 0.01 to 0.5%, Mn: 0.01 to 0.85%, And the total content of Fe and Mn is less than 1.3%.
In this aluminum alloy composition, as a synergistic element for further improving the strength, by mass%, Si: 0.01 to 1.5%, Cu: 0.01 to 0.5%, one or two kinds, or the above In addition to Cu, the composition may selectively contain one or two of Cr: 0.001 to 0.1% and Zn: 0.01 to 0.5%.
In this aluminum alloy composition, the balance of the essential elements and the selectively added elements is preferably Al and inevitable impurities. In addition, all the% display regarding a composition (each element content) means the mass%.

(Mg: 0.1-6.0%)
Mg has the effect of improving the strength of the aluminum alloy by solid solution strengthening. When the Mg content is less than 0.1%, when the aluminum alloy plate is formed on the can body, the thin side wall strength is lowered, and the pressure resistance and can strength as a can are insufficient. On the other hand, if the Mg content exceeds 6.0%, the work hardening of the aluminum alloy plate becomes excessive, and cracks such as tear-off (fuselage cracks) during ironing, and defects such as wrinkles and lines during necking Is likely to occur.
Incidentally, Mg may appear as a crystallized product of Mg ₂ Si, but it is an element that is easily dissolved, and the amount of crystallized product tends to depend on the Si concentration. Therefore, it is not necessary to regulate the crystallized product as described later.
Therefore, the lower limit of the Mg content is 0.1% or more, preferably 0.2% or more, more preferably 1.2% or more, and the upper limit is 6.0%, preferably 2.6%. More preferably, it is 2.2%.

(Fe: 0.01-0.5%)
Fe forms Al—Fe-based crystallized substances (metal compounds) such as A1-Fe (—Mn) -based and A1-Fe (—Mn) -Si-based in the material aluminum alloy plate structure. These crystallized substances inhibit the gloss (brightness) of the surface of the squeezed and ironed can.
That is, when the aluminum alloy plate is stretched during the ironing process during can making, the Al-Fe-based crystallized material in the vicinity of the aluminum alloy plate surface is not ductile, so it remains as it is or is crushed, It appears on the surface of the can or distributed near the surface of the can.
In addition, if there is an Al-Fe-based crystallized product, wrinkles are promoted around the crystallized product during the drawing process, and the Al-Fe-based crystallized product is not ductile. The crystallized product does not stretch, and an aluminum crack is likely to occur in the ironing direction around the crystallized product, which also causes the surface of the can to become rough and the gloss of the can to decrease. Furthermore, the Al—Fe-based crystallized product also reduces draw ironing workability (DI moldability), can withstand pressure strength and puncture resistance.
In addition, Fe is likely to be mixed from a melting raw material of an aluminum alloy such as metal or scrap, and its content tends to increase beyond an allowable amount (upper limit value) of 0.5% that does not reduce glossiness.
From the above, the Fe content is controlled to be in the range of 0.01 to 0.5%.

(Mn: 0.01 to 0.85%)
Mn also forms crystallized substances (intermetallic compounds) such as A1-Fe—Mn and A1-Fe—Mn—Si in the aluminum alloy sheet structure. These crystallized substances are easily formed around the Al—Fe-based crystallized substances that have an adverse effect on the gloss of the squeezed and ironed can surface, thereby reducing the gloss of the can.
Since the Al-Fe-Mn-based crystallized material is not ductile, it appears on the surface of the can during ironing during can making, or is distributed in the vicinity of the can surface, and the can surface (outer surface, outer surface). This causes roughening of the can and reduces the gloss of the can. In addition, the Al-Fe-Mn-based crystallized product does not stretch during the ironing process, and an aluminum crack tends to occur around the crystallized material in the ironing process direction. This can reduce the gloss of the can.
Moreover, Mn is also likely to be mixed from the melting raw materials of aluminum alloys such as bullion and scrap, and its content tends to exceed 0.85%, which is an allowable amount (upper limit value) that does not reduce glossiness.
In view of the above, the Mn content is controlled in the range of 0.01 to 0.85%. From the viewpoint of glossiness, the upper limit of the Mn content is preferably 0.5%.

(Total content of Fe and Mn is less than 1.3%)
As described above, each of Fe and Mn is controlled within the above predetermined range, but in order to more surely regulate the crystallization product based on Fe and Mn that adversely affects the gloss of the can, the total of Fe and Mn The content (Fe + Mn) is less than 1.3%. Preferably, the content is regulated to be less than 0.9%, more preferably less than 0.7%, and still more preferably less than 0.55%. Note that the total content of Fe and Mn does not become 0% because of the respective lower limit amounts of Fe and Mn.

(Si: 0.01-1.5%)
Since Si has the effect of improving the strength of the aluminum alloy, it is selectively contained. When Si is excessive, a large number of Al-Mn-Fe-Si intermetallic compounds and Mg-Si intermetallic compounds are formed as crystallized products, and the gloss (brightness) of the squeezed iron can surface. In addition, the strength of the can and puncture resistance are reduced. In order to reduce the risk of formation of this crystallized product, even if the Si content is reduced, it is preferable to reduce the Si content because the addition of Mg, which is easy to dissolve, can be used to ensure strength. . For this reason, when Si is contained, the lower limit is 0.01%, and the upper limit is 1.5%, preferably 0.4%.

(Cu: 0.01-0.5%)
Since Cu increases strength by solid solution strengthening, Cu is selectively contained. The lower limit of the Cu content is 0.01% or more, preferably 0.05% or more. On the other hand, if Cu is excessive, high strength can be easily obtained, but it becomes too hard and formability is lowered. For this reason, the upper limit of Cu content in the case of making it contain is 0.5%, Preferably it is 0.3%.

(Cr: 0.001 to 0.1%, Zn: 0.01 to 0.5%)
Examples of strength enhancing elements that can be contained simultaneously with Cu include Cr and Zn. When Cu is selectively contained, Cr: 0.001 to 0.1%, Zn: 0.01 to 0.5% One or two kinds can be selectively contained.
When Cr is contained together with Cu, the content of Cr is 0.001% or more, preferably 0.002% or more. On the other hand, when Cr is excessive, giant crystals are generated and the formability is lowered. Therefore, the upper limit of Cr content is set to 0.1%, preferably about 0.05%.
Further, the Zn content when contained together with Cu is 0.01% or more, preferably 0.02% or more. On the other hand, if Zn becomes excessive, the moldability deteriorates, so the upper limit of the Zn content is 0.5%, preferably about 0.45%.

Other than these elements are inevitable impurities. For example, if Zr: 0.10% or less, Ti: 0.2% or less, B: 0.05% or less, the characteristics of the aluminum alloy plate according to the present invention It is allowed to be contained.

(Aluminum alloy plate surface)
Based on the above aluminum alloy composition, in the present invention, the surface roughness in a specific direction of the surface of the aluminum alloy plate is controlled in order to improve the gloss of the surface of the drawn iron can.
In addition to this, in order to improve the glossiness, as will be described later, the crystallized substance present in the structure of the surface layer portion of this aluminum alloy plate (structure of the surface layer portion within 15 μm from the plate surface). Perform control (regulation).
Furthermore, it is preferable to control the aspect ratio defined as the ratio of the major axis to the minor axis (major axis / minor axis) of the crystal grains of the surface layer structure.

(Glossiness evaluation method)
In order to objectively evaluate the glossiness, it is important to quantify the apparent glossiness, and various methods such as reflectance using a commercially available glossometer were examined. As a result, a method for evaluating scattered light by a commercially available copying machine has been found as a method that matches the apparent glossiness and can be easily evaluated.

FIG. 1 shows, from the left, a plan view of a rolled material plate (aluminum alloy plate), and a plan view of the drawn and squeezed can after the plate has been made into a flat plate shape for the scattered light intensity factor.
As shown on the right side of FIG. 1, a test piece in which a squeezed iron can has been developed into a flat plate shape is placed on the copier so that the rolling trace of the material plate is parallel to the scanning direction of the copier, As usual, the copied image is digitized, the digitized image is processed, and the scattered light is evaluated. According to this, since the part and area to be measured can be arbitrarily selected, the measurement can be performed accurately and easily. From the above, this method was adopted as a glossiness evaluation method.
Since this scattered light has a scattered light intensity factor of 1 and an aluminum vapor deposition plate has a reflectance of 0.9, the scattered light intensity factor of the aluminum vapor deposition plate is 0.1 (= the scattered light intensity factor of white paper− 2 standard samples of white paper and aluminum vapor-deposited plate are scanned by a copying machine, and the density of the image, that is, the image of white paper (scattered light intensity ratio: 1) and the image of the aluminum vapor-deposited plate The difference in light and shade of (scattered light intensity factor: 0.1) is based on the difference in light intensity ratio of scattered light. Usually, in a test piece having an intermediate light intensity ratio of both, the change in light and shade of the image is The value obtained from the image of the test piece as a proportional relationship with the scattered light intensity rate was taken as the scattered light intensity rate (meaning of scattered light intensity ratio: dimensionless).
And the glossiness of the squeezed iron can surface is better as the scattered light intensity factor is lower. In the present invention, the acceptance criterion for the scattered light intensity factor is less than 0.5.

(Surface roughness)
In addition, when the surface shape is determined by the gloss, the surface roughness of several μm measured with an atomic force microscope (AFM) does not correlate, and the number measured with a laser microscope. It was found that the corrugation correlates with the unevenness of 100 μm, and in particular, the surface roughness Rq correlates best with the gloss.
From the above, in the present invention, as an important control factor of the surface of the rolled material plate, which has not been noticed so far, greatly affects the gloss of the surface of the drawn iron can, various surface roughnesses of the material plate Among them, the surface roughness Rq in the rolling mark direction (rolling direction) is controlled.

In the present invention, the glossiness or appearance of the drawn iron can by visual evaluation is mainly evaluated by visual inspection of the 0 ° position portion of the drawn iron can shown in FIG.
As shown in FIG. 1, the 0 ° position portion of the can is a surface portion in which the direction of the rolling mark and the direction of ironing not shown are both linear in the can axis direction and are substantially parallel to each other. This is because the 0 ° portion of the can has the highest glossiness in the can surface portion as compared to the other 90 ° and −90 ° portions. For this reason, improvement of the glossiness of the surface portion of the 0 ° position portion of the can is most important in order to increase the glossiness of the can.

On the other hand, at the 90 ° and −90 ° positions of the can shown in FIG. 1, the extending direction of the rolling trace shown by the solid line is curved in an arc shape by drawing and ironing, although not shown. This is greatly different from the extending direction of the ironing trace that is linear in the axial direction, and they do not match. Such a surface portion of the can is less glossy than the 0 ° position portion of the can. *

In this way, when the material rolled plate is drawn and ironed, depending on the surface area of the can, a portion where the direction of the rolling mark and the ironing matches (parallel) and a portion which does not match (not parallel) occur. The surface roughness of the rolled material sheet also depends on the direction of the rolling marks and the direction perpendicular to the rolling direction (sheet width direction).

Therefore, as the surface roughness of the material plate, the typical glossiness of the squeezed iron can, the rolling mark direction of the material plate (rolling) is closely correlated with the direction of the rolling mark at the 0 ° position and the ironing process. (Direction) of the surface roughness Rq is more important and effective than the surface roughness in the other direction of the blank.
For this reason, in the present invention, the surface roughness Rq in the rolling direction (direction perpendicular to the plate width direction) on the surface of the raw aluminum alloy plate on the outer side of the can body is 0.12 μm or less, preferably 0.1 μm or less, More preferably, it is as small as 0.07 μm or less. In this way, in particular, the scattered light intensity ratio of the surface portion of the squeezed iron can at the 0 ° position is lowered to less than 0.5, preferably less than 0.45 as described above, to improve glossiness.
As a result, the surface roughness Rq in the rolling trace direction (rolling direction) on the surface of the drawn iron can made by drawing and ironing the raw aluminum alloy plate can also be 0.12 μm or less, and the gloss of the drawn iron can surface is effective. Can be improved.
Incidentally, the surface roughness Rq in the rolling trace direction (rolling direction) on the surface of the drawn iron can easily increases due to the drawing and ironing process, so the surface roughness in the rolling trace direction (rolling direction) at the stage of the raw aluminum alloy sheet. Lowering Rq is important for improving the glossiness of the surface of the drawn and ironed can.

The surface roughness Rq is measured by using a laser microscope (reflection confocal laser microscope), and using the measurement method of JIS2001, the surface of the sample taken from the rolled material plate is the outer surface of the can. As indicated by the arrows on the rolled sheet, the surface roughness Rq is measured when a length of 200 μm is measured in a direction parallel to the extending direction of the rolling trace. The measurement is performed at 10 points with appropriate intervals between the samples, and the measured values are averaged.

As will be described later, the control of Rq can be controlled by the surface roughness of the cold-rolled roll during cold rolling and the texture treatment by mechanical or chemical polishing of the plate surface.
Incidentally, the surface roughness Rq of the rolled aluminum alloy sheet is the coating resin that directly contacts the punch and die used in the drawing and ironing cans after the resin is coated. Since the alloy plate does not directly contact the punch or the die, it is not smoothed and generally does not change.
For this reason, by setting the surface roughness Rq in the rolling mark direction on the surface of the material aluminum alloy plate on the outer side of the can body to be 0.12 μm or less, the scattered light intensity ratio of the surface at the 0 ° position of the squeezed iron can As described above, the glossiness can be improved.

(Surface layer of aluminum alloy plate)
Furthermore, in the present invention, in order to improve the gloss, the crystallized material and the crystal grains in the surface layer portion of the material aluminum alloy plate from the surface on the outer side of the can body to the depth of 15 μm in the plate thickness direction. Control aspect ratio.

(Crystallized product)
In the present invention, an Fe-based crystallized product (intermetallic compound) having a maximum length of 0.3 μm or more in the surface layer portion of the material aluminum alloy plate from the surface on the outer side of the can body to a depth of 15 μm in the thickness direction. Is controlled to less than 2.4%, more preferably less than 2.0%. As a result, the surface roughness Rq of the rolled aluminum alloy sheet can be assured to be 0.12 μm or less. In particular, the scattered light intensity ratio of the surface of the squeezed iron can at the 0 ° position is 0. The glossiness can be improved by lowering to less than 5.

The area ratio of Fe-based crystallized material having a maximum length of 0.3 μm or more in the surface layer portion of the material aluminum alloy plate from the surface on the outer side of the can body to a depth of 15 μm in the plate thickness direction is less than 2.4%. If the surface roughness Rq of the cold-rolled roll is set to 0.12 μm or less, or the surface roughness of the cold-rolled material aluminum alloy plate is reduced by the action described later at the time of making the can with this crystallized material. Even if the thickness Rq is set to 0.12 μm or less, the glossiness cannot be improved by reducing the scattered light intensity ratio of the surface at the 0 ° position of the squeezed iron can to below the acceptance standard of 0.5.

Here, the surface layer portion means a portion within 15 μm in depth from the aluminum matrix surface excluding the outermost oxide film on the surface of the aluminum alloy plate on the outer side of the can body.

The Fe-based crystallized product is a crystallized product (metal) such as A1-Fe (-Mn) -based, A1-Fe (-Mn) -Si-based, A1-Fe-Mn-based, or A1-Fe-Mn-Si-based. Generic name). In terms of the above composition, there are two types of crystallized substances in the aluminum alloy sheet, Al-Fe and Mg-Si, but Al-Fe based crystals are overwhelmingly large. Therefore, it is important to control the Al—Fe based crystallized product. Among the Al—Fe based crystallization products, the Al—Fe—Mn system has a large number, and this control is important in controlling the crystallization products.

Incidentally, the observation and measurement of the area ratio of the Al—Fe-based crystallized material are performed with a scanning electron microscope (SEM) at a magnification of 1000 times, but the Mg—Si-based crystal is compared with the Al—Fe-based crystal. There are very few artifacts. For this reason, since there is no correlation between the Mg-Si based crystallized product and the gloss, all the crystallized products that can be identified as white portions on the aluminum matrix during SEM observation are all Al-Fe based crystallized. It is counted as a product (intermetallic compound), the area of each crystallized product is measured, and the area ratio of the crystallized product can be calculated from the measured area. Incidentally, the Mg-Si-based crystallized substance appears black on the aluminum matrix in the SEM, unlike the Al-Fe-based crystallized substance, and can be easily distinguished from the Al-Fe-based crystallized substance. .

Here, the crystallized material is controlled in the past, but since it is not the purpose of improving glossiness, it is inevitably not the surface on the outer surface side of the can body of the material aluminum alloy plate, but the center of the plate thickness, etc. The internal structure of the board is a problem. For this reason, there is little influence or no effect on the glossiness of the surface of the squeezed and ironed can.
FIG. 2 partially and schematically shows a cross section of the material rolled plate. In FIG. 2, a large number of the rolling marks are shown as grooves having a groove shape extending in parallel to each other in the rolling direction.
As shown in FIG. 2, the number of Fe-based crystallized substances is usually larger on the surface side than on the inside such as the thickness center of the material aluminum alloy plate.
Moreover, the crystallized material on the outermost surface and surface layer of the material aluminum alloy plate is poor in ductility, so it does not basically change shape (although it can be crushed). For this reason, as the plate thickness is reduced by ironing, many crystallized substances on the outermost surface and surface layer of the material aluminum alloy plate are distributed more on the outermost surface side. As a result, in the can after making the can, a large amount of crystallized material appears on the surface of the aluminum alloy, or the shape of the can surface is affected even if it does not break through.

However, even if a small Fe-based crystallized substance existing in the surface layer part is present or thinned, it does not affect the surface shape (roughness). The size of the crystallized product was set to a maximum length of 0.3 μm or more. Further, in the ordinary method, there is almost no Fe-based crystallized material having such a size as to inhibit the basic properties such as the strength and formability of the plate, so the upper limit of the maximum length of this Fe-based crystallized material is about 10 μm. It is.

Further, as described above, the required surface roughness of the material aluminum alloy plate surface is Rq of 0.12 μm or less, and the peak roughness of the surface roughness at this time (maximum height: peak value P and minimum height) : Surface roughness PV value defined by the difference from the valley value V) is about 1 μm. In view of this, the minimum crystal size that affects the glossiness is at the sub-μm level.

In addition, the size of the crystallized product is also important for the glossiness, and the number of crystallized products has a great influence on the glossiness. Therefore, as in the present invention, the crystallized product including the size factor and the number factor is used. It is appropriate to evaluate by area (area ratio).

By the way, even if the large-sized crystallized substance exists in a deep position inside the plate, if it is thinned, the surface shape (roughness) is affected. As described above, since the basic properties such as the strength and formability of the plate are hindered, the plate manufactured by a conventional method hardly exists. Further, even if a small crystallized substance existing deep inside the plate is present or thinned, the surface shape (roughness) is not affected.
Therefore, considering the size of the crystallized material on the surface layer and the total processing rate of drawing and ironing is approximately 30% to 80%, the crystallized material on the plate is drawn and ironed. By processing, the depth from the matrix surface of the plate, which appears on the surface and affects the surface roughness, is up to about 15 μm, which is the reason for defining this as the depth of the surface layer.

(Aspect ratio of crystal grains)
In addition to the above crystallized substance control, in order to improve the gloss, the major axis and the minor axis of the crystal grains of the structure of the surface layer part of the aluminum alloy plate (structure of the surface layer part within 15 μm from the plate surface) It is preferable to control the aspect ratio defined as the ratio (major axis / minor axis) and to set the aspect ratio to 3.0 or more.
By increasing the aspect ratio of the surface layer portion of the aluminum alloy plate (cold rolled plate), which is a raw material, to 3.0 or more, it is possible to obtain various crystal orientation grains in the ironing process when making this aluminum alloy plate. The shape is changed, the surface roughness Rq of the can body is suppressed from increasing, and the gloss is improved.

On the other hand, when the aspect ratio of the surface layer structure is close to 1, the shape of various crystal orientation grains is changed by ironing at the time of can making, and the surface roughness Rq of the can body is increased, resulting in glossiness. Reduce. Also, the crystal plane is displaced during can making (DI), and unevenness occurs due to the difference in crystal orientation (there are crystal planes that tend to be convex and crystal planes that are concave), and the surface of the can body Roughness Rq increases and glossiness decreases.
For this reason, in the state of the raw material aluminum alloy plate (cold rolled plate) before canning, it is necessary to make the aspect ratio sufficiently large to 3.0 or more and to randomize the structure.
The aspect ratio of the crystal grains is mainly determined by the rolling process and heat treatment.
In order to increase the aspect ratio of the surface layer portion of the cold rolled sheet to 3.0 or more, as will be described later, the cold rolling rate is increased as much as possible by using a cold rolled roll having a predetermined surface roughness. Thus, a cold-rolled sheet having a predetermined thickness is obtained.

(Production method)
Next, the manufacturing method of the aluminum alloy plate for raw material can bodies in this invention is demonstrated. The aluminum alloy sheet of the present invention includes a casting process in which an aluminum alloy having the above composition is melted and cast into an ingot, a soaking process in which the ingot is homogenized by heat treatment, and the homogenized ingot is hot-rolled. It is manufactured by a conventional method comprising a hot rolling step for forming a hot rolled plate and a cold rolling step for cold rolling without annealing the hot rolled plate. However, some steps are performed under conditions different from the conventional methods, and the surface roughness of the aluminum alloy plate after cold rolling and the Fe-based crystallized material of the surface layer portion are defined in the present invention.

(Melting, casting)
First, an aluminum alloy is melted, cast by a known semi-continuous casting method such as a DC casting method, and cooled to below the solidus temperature of the aluminum alloy to form an ingot. When the average average casting speed is in the range of 20 to 100 mm / min and the average cooling rate is as low as less than 0.5 ° C./second, a large amount of coarse intermetallic compounds may crystallize in the ingot. Therefore, the average cooling rate is preferably 0.5 ° C./second or more in the range of the normal average casting rate. This cooling rate is for the temperature of the central part of the ingot, that is, the temperature of the central part of the surface perpendicular to the casting direction, and the cooling rate from the liquidus temperature to the solidus temperature of the aluminum alloy. And

(Hot rolling)
Next, hot rolling is performed on the ingot that has been homogenized by uniform heat treatment by a conventional method, and this hot rolling condition may be in the range of a conventional method or general conditions. First, the ingot is roughly rolled, An aluminum alloy hot rolled plate having a predetermined plate thickness is obtained by finish rolling.

(Cold rolling)
The hot-rolled sheet is cold-rolled while performing intermediate annealing at 300 to 580 ° C. to finish an aluminum alloy sheet having a predetermined thickness.
Cold rolling with a cold rolling rate of 5% or more is performed at least once to obtain a cold rolled sheet having a predetermined sheet thickness. This is because the surface roughness increases due to changes in the shape of various crystal orientation grains during ironing at the time of can making, so increasing the cold rolling ratio as much as possible has an effect on the surface roughness. It is because it does not give.
From the above, the intermediate annealing performed in the middle of cold rolling is not performed, the aspect ratio is 3.0 or more only by cold rolling, or the aspect ratio is selected by selecting the cold rolling ratio before and after annealing and intermediate annealing conditions. Obtaining a ratio of 3.0 or more is desirable for gloss.

However, simply rolling or a high rolling ratio does not increase the aspect ratio, and is greatly influenced by heat treatment such as alloy composition and intermediate annealing.
For example, even if the total cold rolling reduction ratio is 60% or more, the aspect ratio may not be increased depending on intermediate annealing conditions such as high temperature and long holding time.
Therefore, as in the examples of Table 1 described later, it is necessary to select an optimal rolling rate and intermediate annealing conditions for increasing the aspect ratio in relation to the alloy composition.
In this respect, it is also possible to select to obtain a cold plate having the above thickness only by cold rolling without performing the intermediate annealing performed in the middle of cold rolling.
Also, in the case of a high alloy composition such as a large amount of Mg, care is taken not to make the rolling rate too high. This is because, when the rolling rate is too high in the case of a high alloy composition, a processed texture develops by rolling, and if this processed texture exists in the material aluminum alloy sheet (cold rolled sheet), the aspect ratio is increased. This is because it develops at the time of can-making and becomes one of the factors that reduce glossiness.

Here, it is preferable that the Rq in the rolling mark direction on the plate surface to be defined is controlled by controlling the surface roughness of the cold-rolled roll with a roll texture. The surface roughness Rq in the rolling trace direction (rolling direction) of the cold-rolled roll is, of course, 0.12 μm or less, which is the upper limit value of the surface roughness Rq in the rolling trace direction on the surface on the outer surface side of the drawn and ironed can. It is necessary to be. Incidentally, the surface roughness of the cold-rolled roll is usually controlled by the roughness Ra in the axial direction (sheet width direction) of the roll and is not managed by the surface roughness Rq in the circumferential direction of the roll, but gloss In the property, management of the surface roughness Rq in the circumferential direction of the roll is important. The surface roughness in the circumferential direction of the cold-rolled roll is preferably 0.15 μm or less.
Further, the control of Rq in the direction of the rolling marks on the surface of the plate can be controlled by a texture treatment by mechanical or chemical polishing of the surface of the plate, but it is easier to use a rolling roll including productivity.
The smaller the roll diameter is, the higher the pressure can be achieved, the crystallized material can be crushed, the size can be reduced, and the roughness (roughness) of the aluminum substrate surface due to oil pits can be reduced. There is an effect to improve. In this regard, the rolling roll diameter is cold-rolled to 600 mm or less, more preferably 400 mm or less.

The cold-rolled sheet may be directly coated with resin and used as a squeezed iron material, but may be tempered (heat treated) as necessary. However, if the heat treatment temperature is too high, recrystallization occurs, which causes the surface roughness of the cold-rolled sheet to deteriorate, so care must be taken. In this respect, for example, a heat treatment of 300 ° C. or lower (annealing at low temperature or artificial age hardening treatment) may be performed, but a solution treatment exceeding 400 ° C. may deteriorate the surface roughness of the cold rolled sheet. It is impossible.

(Method for making squeezed iron can)
An example of a can-making method for producing a can body of a drawn and ironed can (DI can) from the aluminum alloy plate (cold rolled plate) of the present invention will be described below. First, in order to form a corrosion-resistant film on the aluminum alloy plate according to the present invention, for example, phosphoric acid chromate treatment is performed. And, as a protective layer of the aluminum alloy plate, a resin, specifically, a film (not shown) made of a thermoplastic resin or a crystalline thermoplastic resin such as a polyester resin, a polypropylene resin, or a polyethylene resin is laminated on both sides, A resin-coated aluminum alloy plate for a can body. By covering such a protective layer, the surface of the aluminum alloy plate does not come into contact with tools such as ironing dies, so it is possible to prevent seizure during DI molding and the occurrence of tear-off due to seizure, thereby reducing the molding yield. Can be improved.

缶 This can-clad resin-coated aluminum alloy plate is punched into a disk shape (blanking process), and then drawn into a shallow cup shape (capping process). These drawing processes and further ironing processes are repeated a plurality of times to gradually increase the side wall to obtain a bottomed cylindrical shape having a predetermined bottom surface shape and side wall height. At this time, the plate thickness reduction rate (drawing and ironing rate) of the side wall of the can body by the drawing and ironing is preferably 40% or more, and more preferably 60% or more. Then, trimming is performed to cut off and trim the edge of the side wall (opening). In this state, the thinnest can body is formed into a thin can body having a side wall thickness of 0.085 to 0.150 mm in the thinnest part.

Next, the can body is degreased and cleaned, and the outer surface and the inner surface are respectively painted and baked (baked) to increase the strength. The can body after the coating film is baked has a diameter of the opening (necking process), and an edge of the opening is expanded outward (flanging process) to become a final can body. When used for beverages and foods, the contents (beverages and food) are filled into the can body from the opening, and a can lid produced in a separate process is wound around the opening and sealed.

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

(Sample aluminum alloy plate)
Each aluminum alloy having the chemical composition shown in Table 1 was melted and continuously cast to produce an ingot having a thickness of 600 mm. The casting speed in this casting process was controlled at a preferable 50 mm / min and the cooling rate at 1.0 ° C./min in common with each example. The ingot was subjected to homogenization heat treatment at 500 ° C. within the range of ordinary methods in common with each example, and then hot-rolled to a thickness of 2 to 3 mm. In the chemical composition shown in Table 1, when the element content is blank, it indicates an inevitable impurity level (50 ppm or less).

In Example 1, after the primary cold rolling, intermediate annealing was performed in a continuous annealing furnace under conditions of 500 ° C. × 0.1 seconds, secondary cold rolling at a rolling rate of 65% was performed again, and cold rolling of 0.32 mmt was performed. A board was used.
In Examples 2, 3, 5-8, 10, 11, and Comparative Examples 12-14, cold rolling was performed to 0.32 mmt without intermediate annealing.
In Example 4, cold rolling was performed to 0.20 mmt without performing intermediate annealing.
In Example 9, after cold rolling to 0.32 mmt without intermediate annealing, annealing was performed in a continuous annealing furnace under the condition of 500 ° C. × 0.1 seconds.

The surface roughness Rq in the rolling trace direction on the surface of the cold rolled sheet on the outer surface of the can body is controlled by changing the surface roughness Rq of the final cold rolling mill roll as shown in Table 1, The surface roughness of each cold-rolled sheet listed in Table 1 was controlled. The rolling roll diameter at this time was 350 mm. The following structures and characteristics were measured without tempering (heat treatment) these cold-rolled sheets.

(Crystallized product)
From the cold-rolled sheet, a test material is cut out in the cross-sectional direction including the surface layer portion and filled with resin, and polished so that the cross section including the surface layer portion as shown in FIG. About the removed mirror surface, a surface having a depth of 15 μm from the surface of the matrix was observed with a scanning electron microscope (SEM) at a magnification of 1000 times for about 100 fields of view. The portion that appears white is regarded as the Al-Fe-based crystallized product (intermetallic compound), and the total area of intermetallic compounds with a maximum length of 0.3 μm or more is obtained by image processing, and the area ratio (%) is calculated. did.

(Cold plate surface roughness Rq and rolling roll surface roughness Rq)
A test material is cut out from the cold-rolled plate, and the surface roughness Rq in the rolling direction on the surface of the test material on the outer surface side of the drawn iron can is reflected in the manner described above using a reflective confocal laser microscope (Keyence Corporation). Measured as an average value when 200 μm was measured in the direction of the rolling mark according to JIS2001 standard.
The surface roughness Rq of the rolling roll used for cold rolling of the plate cannot be measured directly with a laser microscope because the rolling roll cannot be sampled. Therefore, after the shape of the rolling roll is once transferred to the replica film, the surface roughness Rq in the circumferential direction (rotating direction) of the rolling roll is transferred from this replica to the laser microscope in the manner of measuring the surface roughness of the cold plate. Measured.

Table 1 shows the surface roughness Rq (μm) and the area ratio (%) of an Fe-based crystallized product having a maximum length of 0.3 μm or more in the surface layer portion up to the depth of 15 μm of each of the measured plates. Respectively.

(Preparation of squeezed iron can)
The cold-rolled plate was subjected to phosphoric acid chromate treatment, and a polyethylene terephthalate resin film having a thickness of 20 μm was laminated on both sides of the plate. The aluminum alloy plate to which this film laminate was applied was cupped and DI-molded to obtain each can manufacturing rate shown in Table 1. The opening was trimmed to form a bottomed cylindrical can body having an outer diameter of about 66 mm. Furthermore, heat treatment was performed at 270 ° C. for 30 seconds assuming baking during painting.

(Glossy)
The scattered light intensity factor indicating the glossiness of the can body is a commercially available copy of the surface portion of the can position shown in FIG. This was measured with a machine (manufactured by FUJIXEROX: model Apeos Port IVC4475). Further, the surface roughness Rq in the rolling mark direction at the 0 ° position was also measured by the method described above. Table 1 shows the scattered light intensity ratios of the squeezed iron cans of each example, together with the surface roughness Rq in the rolling trace direction.

As shown in Table 1, in each example, the composition of the aluminum alloy is within the scope of the present invention, and the material cold-rolled plate and the squeezed iron can are manufactured under preferable manufacturing conditions. For this reason, as shown in Table 1, each invention example has a surface roughness Rq of 0.12 μm in the rolling mark direction on the surface on the outer surface side of the drawn and squeezed can as defined in the present invention. The area ratio of the Fe-based crystallized material having a maximum length of 0.3 μm or more in the surface layer portion from the surface of the plate on the outer surface side of the drawn iron can to the depth of 15 μm in the thickness direction is 2 Less than 4%.

Here, in Examples 1 to 8, 10, and 11, the rolling ratio of primary and secondary total cold rolling is appropriate depending on the relationship between each alloy composition and intermediate annealing, and the aluminum alloy sheet (cold rolling) The aspect ratio defined as the ratio (major axis / minor axis) of the major axis to the minor axis of the crystal grains of the structure of the surface layer portion of the plate is 3.0 or more.
On the other hand, Example 9 has a relatively low rolling ratio of cold rolling and an aspect ratio of less than 3.0.
As a result, in Examples 1 to 8, 10, and 11, scattered light from the surface of the 0 ° position portion of the drawn iron can obtained by drawing and ironing the raw aluminum alloy cold-rolled sheet with a processing rate of preferably 40% or more. The strength ratio was less than 0.5 of the acceptance standard, and 0.45 or less, which is a better measure of glossiness, was obtained.
On the other hand, in Example 9, the scattered light intensity ratio of the surface of the 0 ° position portion of the squeezed iron can is less than the acceptance standard of 0.5, which is excellent gloss, but more excellent gloss. It did not reach 0.45 which is a standard of sex.

Comparing the surface roughness Rq between the cold-rolled sheet material and the squeezed iron can in Table 1, the surface roughness Rq of the squeezed iron can becomes significantly larger than the cold-rolled sheet material due to the squeezing and ironing process. It turns out that it is the tendency for property to fall. That is, it can be seen that the drawing and ironing process has a disadvantageous effect on the gloss of the can.
Nevertheless, in each example, the scattered light intensity ratio of the surface at the 0 ° position of the squeezed iron can is less than 0.5, and excellent gloss is obtained. Is of great significance.

On the other hand, in Comparative Examples 12 and 13, as shown in Table 1, although the material cold-rolled sheet and the drawn iron can are manufactured under preferable manufacturing conditions, the composition of the aluminum alloy such as Fe + Mn is out of the scope of the present invention. Yes. For this reason, as shown in Table 1, these comparative examples have a maximum length of 0.3 μm or more in the surface layer portion from the surface of the cold-rolled steel sheet on the outer surface side of the drawn and ironed can to the depth of 15 μm in the plate thickness direction. The area ratio of the Fe-based crystallized product is increased to 2.4% or more.
As a result, in Comparative Examples 12 and 13, the surface roughness Rq in the rolling mark direction on the surface of the raw cold-rolled sheet on the outer surface side of the drawn iron can is 0.12 μm or less, but the 0 ° position of the drawn iron can. The surface roughness Rq of the surface of the portion exceeds 0.12 μm, the scattered light intensity factor exceeds 0.5, and the glossiness is remarkably inferior compared to the inventive examples.

In Comparative Example 14, although the composition of the aluminum alloy is within the range of the present invention, the surface roughness Rq in the circumferential direction of the cold-rolled roll is deviated from the preferred range. For this reason, as shown in Table 1, in Comparative Example 14, the surface roughness Rq in the rolling trace direction on the surface of the cold-rolled sheet on the outer surface side of the drawn iron can exceeds 0.12 μm.
As a result, in Comparative Example 14, although the area ratio of the Fe-based crystallized material having the maximum length of the cold-rolled sheet of 0.3 μm or more is less than 2.4%, the portion at the 0 ° position of the squeezed iron can The surface scattered light intensity ratio exceeds 0.5, and the glossiness is significantly inferior to that of the inventive examples.

The results of these examples support the technical significance of improving the gloss of the surface at the 0 ° position of the squeezed iron can, which is a requirement of the present invention.

Although the present invention has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention.
This application is based on a Japanese patent application filed on March 23, 2015 (Japanese Patent Application No. 2015-060143) and a Japanese patent application filed on January 19, 2016 (Japanese Patent Application No. 2016-007938). Incorporated herein by reference.

As described above, the present invention provides an aluminum alloy plate for a can body that can be made into a squeezed and ironed can after being pre-coated with a resin and can improve the gloss of the surface of the squeezed and ironed can. can do. For this reason, the thickness of the can wall is reduced, the strength is increased, and it is most suitable for an aluminum alloy cold-rolled sheet used for a DI can body that requires gloss under more severe can-making conditions.

Claims

In mass%, Mg: 0.1 to 6.0%, Fe: 0.01 to 0.5%, Mn: 0.01 to 0.85%, respectively, and the total content of Fe and Mn An aluminum alloy plate for resin-coated squeezed iron cans, the amount of which is less than 1.3%, comprising the balance Al and unavoidable impurities, and the surface roughness in the rolling trace direction on the surface of the squeezed iron cans on the outer surface side Fe-based crystallization with a maximum length of 0.3 μm or more in the surface layer portion from the surface on the outer surface side of the drawn ironing can of this plate to a depth of 15 μm in the plate thickness direction, with a thickness Rq of 0.12 μm or less An aluminum alloy plate for a resin-coated squeezed ironing can with excellent gloss after canning, wherein the area ratio of the product is less than 2.4%.
The aspect ratio defined as the ratio of the major axis to the minor axis (long axis / short axis) of the crystal grains of the structure in the surface layer portion from the surface of the aluminum alloy plate to the depth of 15 μm in the thickness direction is 3.0 or more. The aluminum alloy plate for resin-coated squeezed iron cans having excellent gloss after can making according to claim 1.
The aluminum alloy plate for a resin-coated drawn iron can according to claim 1 or 2, wherein the total content of Fe and Mn in the aluminum alloy plate is less than 0.55 mass%.
The aluminum alloy plate is, by mass%, Si: 0.01 to 1.5%, Cu: 0.01 to 0.5%, one or two kinds, or in addition to Si and Cu, Cr: 0.0. The aluminum alloy sheet for a resin-coated drawn iron can according to any one of claims 1 to 3, comprising one or two of 001 to 0.1% and Zn: 0.01 to 0.5%.
A resin-coated aluminum alloy plate for a drawn and ironed can having a thermoplastic resin film coating layer on the surface of the aluminum alloy plate of any one of claims 1 to 4.