JP2016180141A - Aluminum alloy sheet for drawn ironed can excellent in glossiness after making can and resin coated aluminum alloy sheet for drawn ironed can - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an aluminum alloy sheet for a can body capable of enhancing glossiness of a drawn ironed can surface.SOLUTION: There is provided an aluminum alloy sheet for a can body having a specific composition, which is made to a drawn ironed can after being coated with a resin in advance, where average percentage of small tilt angle grain boundary with tilt of 5 to 15° which affects largely on glossiness of a drawn ironed can surface, out of a crystal grain structure on the surface part of the sheet, is controlled to make a crystal grain structure mainly containing large tilt grain boundary, and particularly, glossiness of a 0° position part of the can is excellent.SELECTED DRAWING: None

Description

  The present invention relates to an aluminum alloy plate for a squeezed iron can and a resin-coated aluminum alloy plate for a squeezed iron can, which are produced in a can body of a packaging container used for beverages and foods by squeezing and 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”. A material aluminum alloy sheet is first drawn and formed into a cup consisting of a body part without a side seam and a bottom part integrally connected to the body part without a seam. 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 preliminarily 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 Patent Document 2, in order to increase the glossiness of the drawn and ironed can, the relationship between the film thickness of the resin (outer coating film) to be coated 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 thickness of the resin is increased as the Ra is decreased. For example, the thickness of the resin is 6 μm or less.

JP 2010-236075 A JP2011-201198A

  Although not limited to Patent Document 2, the Ra of the surface of the aluminum alloy plate and the thickness of the resin layer are conventionally controlled objects for improving the glossiness, but the required glossiness of the drawn iron can is obtained. Is not enough.

  In addition, there have not been many improvement proposals from the viewpoint of improving the glossiness of the composition and structure of the plate. Therefore, it is difficult to say that the factors such as the composition and structure of the rolled aluminum alloy sheet, which have a great influence on the gloss of the squeezed iron can made from the resin-coated aluminum alloy sheet, have been sufficiently clarified.

  The present invention has been made in view of such problems, and is an aluminum alloy plate that is made into a squeezed iron can after being pre-coated with a resin, and has various characteristics required for a squeezed iron can. An object of the present invention is to provide an aluminum alloy plate and a resin-coated aluminum alloy plate that can improve the gloss of a squeezed iron can.

  The gist of the aluminum alloy sheet for a drawn and ironed can excellent in gloss after can making of the present invention for solving the above problems is mass%, Mg: 0.1 to 6.0%, Fe: 0.00. An aluminum alloy containing 01 to 0.5% and Mn: 0.01 to 0.75%, the balance being made of Al and inevitable impurities, and pre-coated with a resin and then made into a squeezed iron can The average grain size of the surface portion of the plate is 50 μm or less, and the average proportion of the small-angle grain boundaries with an inclination of 5 to 15 ° is 35% or less (excluding 0%). Suppose that there is.

  Moreover, the gist of the resin-coated aluminum alloy plate for a drawn iron can according to the present invention for solving the above-mentioned problems is that the aluminum alloy plate is pre-coated with a thermoplastic resin film before the can making. .

  In the present invention, an important control factor of the material rolled sheet structure that has not been noticed so far and greatly affects the gloss of the surface of the squeezed iron can is found and controlled. This important control factor is the average ratio of the low-angle grain boundaries with an inclination of 5 to 15 ° in the structure of the surface portion of the rolled aluminum alloy sheet.

  The higher the average ratio of the low-angle grain boundaries in the crystal grain structure on the surface of the material plate, the smaller the difference in crystal orientation, and the higher the scattered light intensity ratio on the surface of the squeezed iron can, the lower the glossiness. To do. Therefore, in the present invention, the average ratio of the small-angle grain boundaries on the surface portion of the material plate is reduced to a certain value or less.

  As a result, the present invention can achieve the required gloss of the surface of the squeezed iron can, while satisfying various properties required for the squeezed iron can, and an aluminum alloy plate or resin-coated aluminum for the squeezed iron can Alloy plate can be provided.

  Hereinafter, embodiments for carrying out an aluminum alloy plate for a drawn iron can and a resin-coated aluminum alloy plate for a drawn iron can (hereinafter also simply referred to as an aluminum alloy plate or a material plate) according to the present invention will be described.

  The aluminum alloy plate of the present invention is an aluminum alloy rolled plate (cold rolled plate) as a can body material of a drawn iron can, and is drawn and ironed after being pre-coated with a resin, and the drawn iron can (Hereinafter simply referred to as a can). In the resin-coated aluminum alloy plate of the present invention, the above-mentioned aluminum alloy plate is coated in advance with a crystalline thermoplastic resin film before making the drawn iron can.

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

  For this reason, the composition of the aluminum alloy plate is, by mass%, Mg: 0.1-6.0%, Fe: 0.01-0.5%, Mn: 0.01-0.75%, respectively. To contain.

  In addition, the composition of the aluminum alloy plate has the above-mentioned characteristics required as a drawn iron can, and the average ratio of the average crystal grain size of the surface portion of the material plate and the small-angle grain boundaries with an inclination of 5 to 15 °. And is important for obtaining the gloss of the surface of the squeezed and ironed can.

  In order to further increase the strength of this aluminum alloy composition, Si: 2.0% or less (excluding 0%), Cu: 1.0% or less (excluding 0%), Cr : 0.3% or less (excluding 0%), Zr: 0.2% or less (excluding 0%), V: 0.2% or less (excluding 0%), Ti: 0.1% or less (excluding 0%), Zn: 0.5% or less (excluding 0%), Ag: 0.2% or less (excluding 0%) It is good also as a composition containing 1 type, or 2 or more types of these.

  In these aluminum alloy compositions, the balance of the essential elements and the selectively added elements is 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 becomes low, and the pressure resistance and puncture resistance as a can are insufficient.
On the other hand, if the Mg content exceeds 6.0%, the average ratio of the low-angle grain boundaries of 5 to 15 degrees of inclination of the aluminum alloy plate on the surface of the final material plate that becomes the surface of the drawn iron can tends to increase. Cracks such as tear-off (fuselage cracks) during processing, wrinkles and streaks during necking, and other defects are likely to occur.
Therefore, the Mg content is in the range of 0.1 to 6.0%, preferably 0.2 to 5.2%, more preferably 0.3 to 3.0%.

(Fe: 0.01-0.5%)
Fe forms Al-Fe-based crystallized compounds (metal compounds) such as A1-Fe (-Mn) -based and A1-Fe (-Mn) -Si-based in the aluminum alloy plate structure. These crystallized substances also contribute to the improvement of the strength of the can, but also have a great detrimental effect on the gloss (brightness) of the squeezed and ironed can surface.
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 while being crushed, It appears on the surface of the can or distributed near the surface of the can. This causes roughening of the can surface (outer surface, outer surface), and lowers the gloss of the can.
Fe is likely to be mixed from aluminum alloy melting raw materials such as bullion and scrap, and its content tends to increase beyond 0.5%, which is an allowable amount (upper limit value) that does not reduce glossiness.
For this reason, in order to improve the strength of the can, the Fe content is set to 0.01% or more. However, if the Fe content exceeds 0.5%, the amount of Al-Fe-based crystallized substances increases. The solid solution amount of Mn and Si decreases, and the average crystal grain size of the aluminum alloy plate on the surface of the final plate increases.
From the above, the Fe content is controlled in the range of 0.01 to 0.5%.

(Mn: 0.01 to 0.75%)
Mn also forms crystallized substances (intermetallic compounds) such as A1-Fe-Mn and A1-Fe-Mn-Si in the aluminum alloy sheet structure. Although these crystallized substances contribute to the improvement of the strength of the can, they are easily formed as the above-mentioned crystallized substances around the Al-Fe-based crystallized substance that adversely affects the gloss of the squeezed and ironed can surface. Reduce sex.
Furthermore, the Al—Fe—Mn-based crystallized product also reduces draw ironing workability (DI moldability), can withstand pressure strength and puncture resistance. 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 0.75%, which is an allowable amount (upper limit value) that does not reduce glossiness.
In this respect, in order to improve the strength of the can, the Mn content is set to 0.01% or more. However, if the Mn content exceeds 0.75%, the solid solution amount of Mn increases, and the final plate The average ratio of the low-angle grain boundaries having an inclination angle of 5 to 15 ° of the aluminum alloy plate on the plate surface becomes large.
From the above, the content of Mn is controlled in the range of 0.01 to 0.75%. From the viewpoint of glossiness, the upper limit of the Mn content is preferably 0.5%.

(Other elements)
In addition to the above elements, in the present invention, in order to increase the strength of the aluminum alloy plate, Si: 2.0% or less (excluding 0%), Cu: 1.0% or less (however, 0% Cr: 0.3% or less (excluding 0%), Zr: 0.2% or less (excluding 0%), V: 0.2% or less (excluding 0%) %), Ti: 0.1% or less (excluding 0%), Zn: 0.5% or less (excluding 0%), Ag: 0.2% or less (provided that One type or two or more types may be included.

  These elements are commonly treated as synergistic elements in that they have the effect of increasing the strength of the plate and play the role of refining the crystal grains. However, if the content of each of these elements is too large, there is a high possibility that recrystallization of the hot-rolled sheet will be incomplete. As a result, both the average crystal grain size after cold rolling and the average ratio of low-angle grain boundaries become high. In addition, it becomes difficult to produce a plate by forming a coarse compound, and strength, bending workability, and corrosion resistance are also lowered. Therefore, when it contains, it shall be content below each above-mentioned upper limit.

(Aluminum alloy plate surface)
The surface portion of the material aluminum alloy plate referred to in the present invention refers to a surface layer portion from the outermost surface of the plate to a depth of 30 μm in the plate thickness direction.

  In the present invention, on the premise of the above aluminum alloy composition, in order to improve the gloss of the surface of the squeezed and ironed can, in the present invention, an important control factor of the material plate structure that greatly affects the gloss of the surface of the squeezed and ironed can. As described above, the average crystal grain size of the surface portion of the material plate and the average ratio of the low-inclination grain boundaries having an inclination angle of 5 to 15 ° in the structure of the surface portion of the material plate are controlled.

(Average crystal grain size of the plate surface)
It can be said that the average crystal grain size of the surface portion of the aluminum alloy plate is a precondition for securing the gloss of the surface of the drawn and ironed can.
The larger the average crystal grain size of the surface of the plate, the larger the average crystal grain size after ironing during can making, and it becomes easier for streaks to appear perpendicular to the can axis direction. The scattered light intensity ratio at the surface portion increases, and the glossiness decreases.
Accordingly, the average crystal grain size of the surface portion of the aluminum alloy plate is set to the smallest possible average crystal grain size of 50 μm or less (excluding 0 μm). From the production limit, the lower limit of the average crystal grain size of the plate surface portion is about 5 μm.

(Average ratio of small-angle grain boundaries with an inclination of 5 to 15 °)
The higher the average ratio of the low-angle grain boundaries with an inclination of 5 to 15 ° of the plate surface portion of the aluminum alloy plate, the smaller the difference in crystal orientation, and the higher the scattered light intensity ratio of the surface portion of the squeezed iron can, Glossiness decreases.
Therefore, in the present invention, the number of small-angle boundaries with an inclination of 5 to 15 ° of the plate surface portion of the aluminum alloy plate is reduced as much as possible, and the upper limit of the average ratio of these small-angle boundaries is 35% or less (however, 0% The value is as small as possible. From the production limit, the lower limit of the average ratio of the low-angle grain boundaries of 5 to 15 ° is about 10%.

The small-angle grain boundary referred to in the present invention is a grain boundary between crystal grains having a small crystal orientation difference (tilt angle) of 5 to 15 ° among crystal orientations measured by the SEM / EBSP method described later.
In addition, the average ratio of the low-angle grain boundaries is the same as the total crystal grain boundary measured (the total length of the crystal grain boundaries of all the small-angle grains measured) The difference in orientation is an average ratio to the total length of crystal grain boundaries of 2 to 180 ° (total length of crystal grain boundaries of all crystal grains measured).
That is, the ratio (%) of the specified low-angle grain boundaries with an inclination angle of 5 to 15 ° is [(total length of 5-15 ° crystal grain boundaries) / (total length of 2-180 ° crystal grain boundaries)] × 100. The average of this value is 35% or less.

  Therefore, the plate surface portion of the aluminum alloy plate of the present invention has a crystal grain structure in which large-angle grain boundaries mainly exist. The difference between the crystal orientations (tilt angle) exceeds 15 ° from this large-angle grain boundary. , A grain boundary between crystal grains of 180 ° or less. If there are many large tilt grain boundaries, contrary to the small tilt grain boundaries, the difference in crystal orientation becomes small, the scattered light intensity ratio on the surface portion of the squeezed iron can is suppressed, and gloss is improved. To do. As a result, the required gloss of the surface of the squeezed iron can can be obtained.

  Here, the crystal grain boundary having a misorientation of less than 5 ° has a very small effect on the glossiness, and is not considered and not defined in the present invention. For this reason, even in the measurement of the crystal grain size and the small-angle grain boundary ratio, which will be described later, those whose orientation deviation (tilt angle) is less than ± 5 ° from the crystal plane belong to the same crystal plane (orientation factor) and are adjacent to each other. A crystal grain boundary having a crystal grain orientation difference (tilt angle) of 5 ° or more is defined as a grain boundary and measured.

Measurement of grain size and small-angle grain boundary ratio:
The average crystal grain size and the average ratio of the low-angle grain boundaries defined in the present invention are all measured by the SEM / EBSP method. The measurement site | part of the structure | tissue of the board in this case is taken as the cross section of this board in the width direction similarly to the measurement part of this normal structure | tissue. And what averaged each measured value of five measurement specimens (5 measurement locations) taken from any location of the cross section in the width direction of this plate, the average crystal grain size defined in the present invention, The average ratio of the low-angle grain boundaries.

  The SEM / EBSP method is widely used as a texture measurement method, and is applied to a field emission scanning electron microscope (FESEM) in a backscattered electron diffraction image (EBSP: Electron Back Scattering (Scattered) Pattern) system. Is a crystal orientation analysis method. This measurement method has high measurement accuracy because of its high resolution as compared with other texture measurement methods. This method has an advantage that the average crystal grain size and the average ratio of crystal grain boundaries at the same measurement site of the plate can be simultaneously measured with high accuracy. The measurement of the average ratio of crystal grain boundaries and the average crystal grain size of an aluminum alloy plate by this SEM / EBSP method has been conventionally known as disclosed in, for example, Japanese Patent Application Laid-Open No. 2014-62287. In the present invention, this known method is used.

  In these disclosed SEM / EBSP methods, an EBSP is projected onto a screen by irradiating an electron beam onto a sample of an Al alloy plate set in a lens barrel of the FESEM (FE-SEM). This is taken with a high-sensitivity camera and captured as an image on a computer. In the computer, the orientation of the crystal is determined by analyzing this image and comparing it with a pattern obtained by simulation using a known crystal system. Each calculated orientation of the crystal is recorded as a three-dimensional Euler angle together with position coordinates (x, y) and the like. Since this process is automatically performed for all measurement points, tens of thousands to hundreds of thousands of crystal orientation data can be obtained at the end of measurement.

  Thus, the SEM / EBSP method has a wider field of view than the electron diffraction method using a transmission electron microscope, and has an average crystal grain size and an average crystal grain size of hundreds of crystal grains. There is an advantage that information on standard deviation or orientation analysis can be obtained within a few hours. In addition, since the measurement is performed by scanning a specified region at an arbitrary fixed interval instead of measurement for each crystal grain, there is also an advantage that each of the above-described information on the numerous measurement points covering the entire measurement region can be obtained. is there. Details of the crystal orientation analysis method in which the EBSP system is mounted on these FESEMs are described in detail in Kobe Steel Engineering Reports / Vol.52 No.2 (Sep.2002) P66-70 and the like.

  Here, the average crystal grain size is calculated by the formula: average crystal grain size = (Σx) / n (where n is the number of measured crystal grains and x is the crystal grain size).

(Glossiness evaluation method)
Here, for the objectivity and reproducibility of glossiness evaluation, it is important to measure the appearance glossiness mechanically and digitize it, and consider various methods such as reflectance using a commercially available glossometer. did. As a result, a method for evaluating scattered light by a copying machine has been found as a method that can be easily evaluated by a method that matches the apparent glossiness.

The method for evaluating the scattered light by this copying machine is to place a test piece in which a squeezed iron can is developed into a flat plate shape on the copying machine so that the rolling trace of the material plate is parallel to the scanning direction of the copying machine. Then, 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.
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 the blank paper−the aluminum vapor deposition plate Reflectance), two types of standard samples, white paper and aluminum vapor-deposited plate, were scanned by a copier, and the image density, that is, white paper image (scattered light intensity ratio: 1) and aluminum vapor-deposited plate image (scattered light intensity) The difference in density of 0.1) is based on the difference in the scattered light intensity ratio, and in the specimen having the scattered light intensity ratio that is usually between the two, the change in the density of the image is the scattered light intensity ratio. The value obtained from the image of the test piece was regarded as the scattered light intensity ratio.

  In the present invention, as the glossiness of the squeezed iron can of the material plate, the scattered light intensity ratio of the surface portion of the 0 ° position portion of the squeezed iron can is 0 in relation to the visual experience of excellent glossiness. Those less than 4 are evaluated as having excellent gloss.

The 0 ° portion of the drawn and ironed can described above is a surface portion in which the rolling marks and the ironing direction are both linear in the can axis direction and are substantially parallel to each other. Such a 0 ° position portion of the can has the highest glossiness among the can surface portions as compared with the other 90 ° and −90 ° position portions. For this reason, the glossiness of the squeezed iron can is mainly evaluated by the glossiness of the surface portion at the 0 ° position.
By the way, at the 90 ° and −90 ° positions of the can, the extending direction of the rolling trace is curved in an arc shape by drawing and ironing, and the extending direction of the linear ironing trace in the can axis direction Are very different and they do not match. Naturally, the surface portion of such a can is less glossy than the 0 ° position portion of the can.

(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 usual method, and the average grain size of the surface portion of the aluminum alloy sheet after cold rolling is 50 μm or less, and a small-angle grain boundary having an inclination angle of 5 to 15 °. The average ratio is 35% or less (excluding 0%).

(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.

(Soaking)
The soaking heat treatment (homogenization heat treatment) of the ingot is performed under a temperature range of 540 ° C. or lower where the ingot can be homogenized for 1 hour or longer and for the time required for homogenization. When held at a temperature higher than 540 ° C., coarsening of crystal grains may be promoted.

(Hot rolling)
Next, hot rolling is performed on the homogenized ingot. First, the ingot is roughly rolled, and then the aluminum alloy hot rolled plate having a predetermined thickness is obtained by finish rolling.
The hot rough rolling is preferably performed within 10 minutes. For this reason, the steady speed of all passes is at least 25 m / min. Among these passes, even at one pass, if the speed is less than 25 m / min, the rolling time may be increased and the average crystal grain size may be increased.
Following this hot rough rolling, hot finish rolling is performed at an end temperature of 330 ° C. or higher. When the finish temperature of hot finish rolling is less than 330 ° C., there is a high possibility that recrystallization of the hot-rolled sheet will be incomplete. As a result, both the average crystal grain size after cold rolling and the average ratio of low-angle grain boundaries become high.

(Cold rolling)
If necessary, 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. The total processing rate of cold rolling is 70 to 90%. If this total processing rate is too low, the average crystal grain size may increase, while if it is too high, the average ratio of low-angle grain boundaries may increase. The lower limit of the total processing rate of cold rolling is preferably 80% or more.

  The cold-rolled plate may be directly coated with a 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 coarsening of the average crystal grain size of the cold-rolled sheet, so care must be taken. In this respect, for example, heat treatment at 300 ° C. or lower (annealing at low temperature or artificial age hardening treatment) may be applied, but heat treatment exceeding 400 ° C. is to coarsen the average crystal grain size 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 an aluminum alloy plate, the film which consists of thermoplastic resins, such as a polyester resin and a polypropylene resin, is laminated on both surfaces, and it is set as the resin coating aluminum alloy plate for can bodies. 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.

  The resin-coated aluminum alloy plate for the can body is punched into a disk shape (blanking process), and is subjected to a drawing process (cupping process) into a shallow cup shape. Then, these drawing processes and further ironing processes are repeated a plurality of times to gradually increase the side wall, thereby obtaining 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 such that the thinnest side wall has a thickness of 0.085 to 0.110 mm.

  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 DC casted to produce an ingot having a thickness of 600 mm. In the chemical composition shown in Table 1, when the element content is blank, it indicates that it is below the detection limit (substantially 0%).
The ingot was subjected to soaking treatment at each soaking temperature shown in Table 1 for 5 hours in common, and then hot rolled. The hot rolling starts the hot rough rolling at each soaking temperature and is finished by changing the minimum steady speed of each pass in each example as shown in Table 1, and then immediately finishes the end temperature in Table 1. As shown in Fig. 5, hot finish rolling was performed in each example, and the plate thickness was set to 0.95 to 6.3 mmt.

  The hot-rolled sheet was subjected to cold rolling to 0.315 mmt without changing the total processing rate in each example as shown in Table 1 and performing intermediate annealing. And the structure | tissue and characteristic shown below were measured, without tempering (heat processing) these cold-rolled sheets. These results are also shown in Table 1.

(Measurement of crystal grain size and small-angle grain boundary ratio)
From the cold-rolled plate, 10 specimens including the surface portion are arbitrarily cut out and filled with resin, and mechanical polishing and electrolytic polishing are performed so that the plate surface inside 5 μm from the outermost surface of the plate becomes an observation surface, The mirror surface. Then, using the FESEM, the average crystal grain size (μm) and the average proportion (%) of the small tilt grain boundaries with the tilt angle of 5 to 15 ° in the surface portion 30 μm deep from the outermost surface of the test material are measured. And averaged with 10 specimens. As the EBSP measurement / analysis system, EBSP: manufactured by TSL (OIM) was used.

(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 2. The opening was trimmed to obtain a bottomed cylindrical can body having an outer diameter of about 66 mm and a side wall thickness not including a film of 0.15 to 0.1 mm. Furthermore, heat treatment was performed at 270 ° C. for 30 seconds assuming baking during painting.

(Glossiness = Scattered light intensity ratio)
The scattered light intensity ratio of this can body was determined by using a commercially available copying machine (manufactured by FUJIXEROX: model number) on the surface portion of the can body at the 0 ° position where the rolling mark and the ironing direction coincided with each other. Apeos Port IVC4475).

  As shown in Table 1, in each invention example, the composition of the aluminum alloy is within the range 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 example of the invention has an average crystal grain size of 50 μm or less and a small inclination angle of 5 to 15 ° on the surface portion of the cold-rolled sheet as defined in the present invention. The average proportion of the tilted grain boundaries is 35% or less (excluding 0%).

  As a result, in each of the invention examples, the scattered light intensity ratio of the surface of the squeezed iron can obtained by squeezing and squeezing the raw aluminum alloy cold-rolled sheet is less than 0.4%, and the actual visual gloss In the evaluation of properties, excellent gloss was obtained.

On the other hand, as shown in Table 1, in Comparative Examples 1 to 4, although the material cold-rolled plate and the drawn iron can are manufactured under preferable manufacturing conditions, the composition of the aluminum alloy is out of the scope of the present invention.
Comparative Example 1 has an Mg content, Comparative Example 2 has an Fe content, Comparative Example 3 has an Mn content, and Comparative Example 4 has a Cu and Zr content exceeding the respective upper limit values. Too much.
For this reason, in these comparative examples, as shown in Table 1, the average crystal grain size of the surface portion of the cold-rolled sheet is larger than 50 μm, or the average ratio of the low-angle grain boundaries with an inclination angle of 5 to 15 ° is 35. It is larger than%.
As a result, in these comparative examples, the scattered light intensity ratio of the surface of the squeezed and ironed can of the cold-rolled sheet of the material exceeds 0.4%. The gloss is remarkably inferior to that of.

In Comparative Examples 5 to 9, although the composition of the aluminum alloy is within the range of the present invention, the production conditions of the plate shown in Table 1 are manufactured outside the preferable range.
In Comparative Example 5, the soaking temperature of the ingot exceeds the preferable upper limit temperature of 540 ° C.
In Comparative Example 6, the minimum steady speed of the hot rough rolling pass is less than the preferred lower limit of 25 m / min.
In Comparative Example 7, the finish temperature of hot finish rolling is less than the preferred lower limit of 330 ° C.
In Comparative Example 8, the cold rolling rate is less than 70% of the preferable lower limit.
In Comparative Example 9, the cold rolling rate exceeds 90% of the preferable upper limit.

For this reason, in these comparative examples, as shown in Table 1, the average crystal grain size of the surface portion of the cold-rolled sheet is larger than 50 μm, or the average ratio of the low-angle grain boundaries with an inclination angle of 5 to 15 ° is 35. It is larger than%.
As a result, in these comparative examples, the scattered light intensity ratio of the surface of the squeezed and ironed can of the cold-rolled sheet of the material exceeds 0.4%. The gloss is remarkably inferior to that of.

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

  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 (4)

  In mass%, Mg: 0.1-6.0%, Fe: 0.01-0.5%, Mn: 0.01-0.75%, respectively, with the balance being Al and inevitable impurities An aluminum alloy plate that is pre-coated with resin and can be made into a squeezed iron can, the average crystal grain size of the surface portion of which is 50 μm or less, and a small tilt angle of 5 to 15 ° An aluminum alloy plate for squeezed and ironed cans having excellent gloss after canning, wherein the average proportion of grain boundaries is 35% or less (excluding 0%).   The aluminum alloy plate further comprises Si: 2.0% or less (excluding 0%), Cu: 1.0% or less (excluding 0%), Cr: 0.3% or less ( However, 0% is not included), Zr: 0.2% or less (however, 0% is not included), V: 0.2% or less (however, 0% is not included), Ti: 0.1% or less (However, 0% is not included), Zn: 0.5% or less (however, 0% is not included), Ag: 0.2% or less (however, 0% is not included) The aluminum alloy plate for a drawn and ironed can according to claim 1 including the above.   The aluminum alloy plate for a drawn iron can according to claim 1 or 2, wherein the upper limit of the Mn content is 0.5%.   A resin-coated aluminum alloy plate for a drawn iron can, wherein the aluminum alloy plate according to any one of claims 1 to 3 is coated with a thermoplastic resin film in advance before making the can.