JP6227691B2 - Manufacturing method of aluminum alloy plate for DI can body - Google Patents

Description

  The present invention relates to a packaging container used for beverages and foods, and more particularly to a method for producing an aluminum alloy plate that is DI-formed on the body of a beverage can.

  Currently, as one of packaging containers used for beverages and foods, a bottomed cylindrical body (can body) whose bottom and side walls are integrated, and an upper surface sealed by an opening of the body A two-piece can comprising a disc-shaped lid (can lid) is known. As a material for such cans, aluminum alloy plates such as AA to JIS3000 are widely used in terms of formability, corrosion resistance, strength, and the like. Among the two-piece cans manufactured with this aluminum alloy plate, the cylindrical portion of the cylindrical can having a height particularly like a beverage can has a lot of drawing and ironing called DI (Drawing and wall Ironing) molding. Often formed by step processing. And it is painted and baked, the diameter of the opening is reduced by necking, and the edge of the opening is expanded outward by flanging to form a can body. Finally, the contents (beverage, food) are filled in the body, and the lid is wound around the opening and sealed. A can made by such a manufacturing method is called a DI can (hereinafter referred to as “can” as appropriate) and is widely distributed.

  Conventionally, in order to reduce the cost of beverages packaged with such aluminum alloy cans, cans that are packaging containers have been reduced in thickness as measures for reducing weight and reducing raw materials (aluminum alloys). As a result, the thickness of the side wall (thinnest part) of the current aluminum alloy can is about 0.105 to 0.110 mm excluding the coating film. However, in such a thinned can, when a protrusion is brought into contact with and pressed against a thin side wall (circumferential surface), the tip penetrates the side wall and a hole (pin (Hall) may open and the contents may leak. Protrusion contact may include contact of hard foreign matter from the outside during manufacturing (filling contents, tightening the lid, passing through the transport system in the manufacturing process), distribution, and even when handled by consumers. Can be mentioned. Also, in the flanging process, when the edge of the opening is expanded, a crack (flange crack) may occur at the end of the opening.

  Therefore, the material of the thinned can can prevent the occurrence of pinholes on the side walls and cracks in the flanges of the openings, that is, improve the piercing resistance and flanging workability (can expandability) of the side walls. Improvement of the aluminum alloy plate on the side is underway.

  For example, Patent Document 1 discloses a method for designing a can body formed by DI molding or drawing from an aluminum alloy cold-rolled sheet having an aluminum alloy cold-rolled sheet composition having a 3000 series composition. That is, the thickness of the can body subjected to heat treatment equivalent to paint baking is in the range of 0.07 mm to 0.14 mm, the tensile strength in the can axis direction of this wall portion is 300 MPa to 500 MPa, and the elongation is 3% to 8%. In this case, the puncture strength with respect to the wall thickness (t) after removing the surface film such as a coating film can be converted to the puncture strength of a can having a wall thickness of 0.105 mm to obtain a puncture resistance of 35 N or more. I am doing so. For this reason, the thickness of the wall portion for obtaining the piercing strength is determined from the Mg content, or the Mg content with respect to the predetermined wall portion thickness is determined from the desired piercing strength.

  Various techniques for improving the puncture resistance by controlling the intermetallic compound of the aluminum alloy cold rolled sheet having a 3000 series composition have also been proposed. For example, Patent Document 2 discloses a technique for distributing an intermetallic compound at a specific density and a specific area ratio on the surface of an aluminum alloy cold rolled sheet having a 3000 series composition. Then, when the side wall thickness including the outer surface and inner surface coating of the DI molded can body is 0.110 to 0.130 mm, the elongation of the side wall in the can axis direction is 3% or more and less than 6%. The strength exceeds 290 MPa and is equal to or less than 330 MPa to improve puncture resistance.

  In Patent Documents 3 and 4, a technique for improving strength (piercing resistance) and toughness by controlling the distribution density and area ratio of an intermetallic compound of a predetermined size in an aluminum alloy cold-rolled sheet having the same 3000 series composition. Is disclosed. Furthermore, in Patent Document 5, an aluminum alloy cold-rolled plate having the same 3000 series composition is DI molded at a predetermined processing rate and heat-treated at 210 to 250 ° C., thereby controlling work hardening and tensile strength by DI molding. And the technique which improves puncture resistance is disclosed.

In addition, the technology for improving the properties such as DI formability and strength when thinned by specifying the solid solution amount of Si, Cu, Mn, Fe, etc. is also an aluminum alloy having a 3000 series composition for cans. Various proposals have been made in the field of sheeting.
By the way, it is not a DI can, it is not the purpose of improving puncture resistance, but in Patent Document 6, while preventing thermal deformation during coating heat treatment of the aluminum alloy cold-rolled sheet for bottle cans, ensuring the strength of the can after heat treatment, In order to obtain a bottle can with high roundness, the solid solution amount of Cu and Mg is defined as the amount of Cu in the solution separated from the precipitate having a particle size exceeding 0.2 μm by the residual extraction method using hot phenol. It is specified as 0.05 to 0.3% and Mg content as 0.75 to 1.6%, respectively.

Japanese Patent No. 4667722 JP 2004-68061 A JP 2007-197815 A JP 2009-270192 A JP 2007-169767 A Japanese Patent No. 4019083

However, the handling and use conditions of DI cans are more severe, such as the pressure difference between the inside and outside of the can becoming larger and the can body being easily deformed. The puncture resistance (puncture resistance) is also stricter. On the other hand, the above-described prior art still has room for improvement in order to obtain this strict puncture resistance.
For example, only by controlling the Mg content as in Patent Document 1, there is a limit to setting the puncture strength that is greatly influenced by the presence of a compound in the tissue to the required level. Moreover, the technique disclosed in Patent Document 3 improves the puncture resistance by increasing the thickness of the side wall of the can to more than 0.110 mm, and cannot cope with the tendency of the can to reduce the thickness of the side wall of the can. . Furthermore, since the technique disclosed in Patent Document 5 is limited to a high baking temperature range when painting cans, it is unsuitable for requirements on the can-making side when heat treatment is desired at lower temperatures.

Moreover, the control of the intermetallic compound disclosed in Patent Documents 3 to 5 is certainly effective for improving the puncture resistance. However, in order to evaluate whether or not the provisions of Patent Documents 3 to 5 are satisfied, it is necessary to apply a scanning electron microscope (SEM) such as a magnification of 500 times as a means for detecting an intermetallic compound to be controlled. I wo n’t. However, as is well known, a wide and long cold-rolled sheet in a coiled state can be made into DI in a large number of thousands to tens of thousands of can bodies over the entire part in the width direction and the longitudinal direction of rolling. .
And even if the manufacturing conditions are optimized for a coiled wide and long cold-rolled sheet, the distribution of temperature and strain is inevitably different in the sheet width direction, etc., and it does not affect the macroscopic mechanical properties. In both cases, the number density, area ratio or distribution of the intermetallic compound as a microstructure naturally varies.

  Therefore, in micro observation with a microscope as disclosed in Patent Documents 3 to 5, even if the number of measurement points is increased, DI cans are formed in a large number of can bodies, and a coiled long and wide cold-rolled plate The number density, area ratio, or distribution of intermetallic compounds as a microstructure across the widthwise direction are not necessarily all representative of the macro. Further, the microscopic observation is to measure an arbitrary one place in the plate thickness direction, and the variation in the structure in the plate thickness direction cannot be taken into consideration. For this reason, there is a limit to improving the overall puncture resistance of a can body made from a long and wide cold-rolled sheet.

  The present invention has been made in view of the above-mentioned problems, and a DI can body that can improve stricter puncture resistance (puncture strength) of a can body made from a long and wide cold-rolled plate. An object of the present invention is to provide a method for producing an aluminum alloy plate for use.

  The gist of the manufacturing method of the aluminum alloy plate for DI can barrel of the present invention for solving the above problems is mass%, Mn: 0.3 to 1.3%, Mg: 1.0 to 3.0%, Si When the aluminum alloy ingot containing 0.1: 0.5% and Fe: 0.1-0.8% respectively and the balance is composed of Al and inevitable impurities is subjected to soaking treatment twice, The average cooling rate of 500 to 200 ° C. during cooling to room temperature after the second soaking is 80 ° C./hour or more, and the average heating of 200 to 400 ° C. during reheating from the second soaking room temperature. The speed is set to 30 ° C./hour or more, the soaked ingot is hot-rolled by hot rough rolling and hot finish rolling, and the hot-rolled plate is cold-rolled to obtain an aluminum alloy plate. As a structure of aluminum alloy sheet, by residue extraction method with hot phenol The amount of Mn contained in the residual compound having a separated particle size exceeding 0.1 μm is set to 1.0% or less (including 0%), and Mg contained in the solution separated by the hot phenol residual extraction method is used. The amount of solid solution is 0.7% or more and 2.5% or less.

  Here, the aluminum alloy ingot further contains one or two of Cu: 0.05 to 0.4%, or Cr: 0.001 to 0.1%, and Zn: 0.05 to 0.5%. You may do it. The aluminum alloy plate is DI-molded into a can body having a thinnest side wall thickness of 0.085 to 0.110 mm, and the can body is heat-treated at 200 ° C. for 20 minutes. It is preferable that the 0.2% yield strength of the side wall in the can axis direction has a strength characteristic of 280 MPa or more and 350 MPa or less. Further, the puncture resistance of the aluminum alloy plate is obtained when DI molding is performed on a can body having a thinnest side wall thickness of 0.085 to 0.110 mm, and the can body is heat-treated at 200 ° C. for 20 minutes. An inner pressure of 1.7 kgf / cm @ 2 (= 166.6 kPa) is applied to the can body, and a hemisphere having a radius of 0.5 mm at the tip at a distance L = 60 mm in the can axis direction from the bottom of the can body side wall. It is preferable that the surface piercing needle is pierced perpendicularly to the can barrel side wall at a speed of 50 mm / min, and the maximum value of the load measurement values until the piercing needle penetrates the can barrel side wall is 35 N or more.

  As described above, the conventional control of intermetallic compounds is certainly effective for improving the puncture resistance (puncture strength), and it tends to break if there are many large intermetallic compounds in the can body structure. , Puncture resistance decreases.

  However, in the conventional definition of the area ratio, size, and number density of the micro intermetallic compound in the aluminum alloy plate structure, as described above, the detection means of the intermetallic compound to be controlled is a scanning electron microscope (SEM). ), Etc., and the microstructure of the portion of the coiled wide cold-rolled sheet that is made of DI in a large number of can bodies in the width direction and the thickness direction cannot be represented macroscopically.

  For this reason, the present inventors do not use a micro observation means such as a scanning electron microscope (SEM), but instead use a so-called macroscopic and average information obtained by a residue extraction method using hot phenol to analyze the coil state. Macroscopically control the structure (intermetallic compound) of the structure of the wide cold-rolled sheet, particularly in the width direction and the thickness direction. Thereby, the puncture resistance can be improved to a target level.

It is sectional drawing which illustrates typically the measuring method of the piercing strength of a can body.

  Hereinafter, the form for implement | achieving the aluminum alloy plate for can bodies which concerns on this invention (henceforth an aluminum alloy plate) is demonstrated.

(Aluminum alloy composition)
The composition of the aluminum alloy plate according to the present invention is mass%, Mn: 0.3 to 1.3%, Mg: 1.0 to 3.0%, Si: 0.1 to 0.5%, Fe: It shall contain 0.1-0.8% respectively, and the remainder shall consist of Al and an unavoidable impurity. It is good also as a composition which contains Cu: 0.05-0.4% further to this aluminum alloy composition. In addition, all the% display regarding a composition (each element content) means the mass%.

(Mn: 0.3 to 1.3%)
Mn has an effect of improving the strength of the aluminum alloy, and when the aluminum alloy plate is formed on the can body, the side wall strength is increased to ensure buckling strength and puncture resistance. Further, Mn forms an Al—Mn—Fe-based intermetallic compound in the aluminum alloy and is appropriately dispersed, whereby recrystallization after hot rolling is promoted and the workability of the aluminum alloy sheet is improved. If the Mn content is less than 0.3%, these effects are insufficient. Therefore, the Mn content is 0.3% or more, preferably 0.4% or more. On the other hand, if the content of Mn exceeds 1.2%, the solid solution strengthening of the aluminum alloy plate becomes excessive, the workability decreases, and the amount of Al-Mn-Fe intermetallic compound produced increases. As a result, the puncture resistance is reduced. Therefore, the upper limit of Mn is 1.3%, preferably 1.1%, and more preferably 1.0%.

(Mg: 1.0-3.0%)
Mg has the effect of improving the strength of the aluminum alloy. When the Mg content is less than 1.0%, when the aluminum alloy plate is formed on the can body, the side wall strength is lowered and the puncture resistance is insufficient. On the other hand, if the Mg content exceeds 3.0%, the work hardening of the aluminum alloy plate becomes excessive, and cracks such as tear-off (fuselage cracks) during ironing, wrinkles and streaks during necking, etc. Is likely to occur. Therefore, the Mg content is in the range of 1.0 to 3.0%, and the upper limit of Mg content is preferably 2.5%.

(Si: 0.1-0.5%)
Si forms an Al—Fe—Mn—Si intermetallic compound, and the more appropriately it is distributed, the better the moldability. Therefore, the Si content is 0.1% or more, preferably 0.2% or more. On the other hand, when Si becomes excessive, a large number of Al—Mn—Fe—Si intermetallic compounds and Mg—Si intermetallic compounds are formed, and the puncture resistance is lowered. For this reason, the upper limit of Si content is 0.5%, preferably 0.4%.

(Fe: 0.1-0.8%)
Fe is mixed into the aluminum alloy as a metal alloy impurity, but forms an Al-Mn-Fe intermetallic compound in the aluminum alloy and is appropriately dispersed to promote recrystallization after hot rolling. As a result, the workability of the aluminum alloy plate is improved. Fe is also useful in that it promotes crystallization and precipitation of Mn, and controls the Mn average solid solution amount in the aluminum matrix and the dispersion state of the Mn-based intermetallic compound. Therefore, the Fe content is 0.1% or more, preferably 0.3% or more. On the other hand, when the Fe content is excessive, a huge primary intermetallic compound having a diameter exceeding 15 μm is likely to be generated, and the DI moldability and puncture resistance are also lowered. Therefore, the upper limit of the Fe content is 0.8%, preferably 0.7%.

(Cu: 0.05-0.4%)
Cu increases the strength by solid solution strengthening. For this reason, the lower limit when Cu is selectively contained is 0.05% or more, preferably 0.1% or more. On the other hand, if Cu is excessive, high strength can be easily obtained, but it becomes too hard, so that formability is lowered and corrosion resistance is also deteriorated. For this reason, the upper limit of Cu content is 0.4%, preferably 0.3%.

(Cr: 0.001 to 0.1%, Zn: 0.05 to 0.5%)
Cr and Zn are listed as elements for improving the strength of the same effect of Cu. One or two of Cr: 0.001 to 0.1% and Zn: 0.05 to 0.5% are added to Cu. Alternatively, it can be selectively contained instead of Cu. When selectively contained, the Cr content 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, when Zn is selectively contained, the Zn content is 0.05% or more, preferably 0.06% or more. On the other hand, since corrosion resistance falls when Zn becomes excessive, the upper limit of Zn content is made into 0.5%, Preferably it is about 0.45%.

  In addition to these elements, there are inevitable impurities. Examples of the inevitable impurities include Zr: 0.10% or less, Ti: 0.2% or less, preferably 0.1% or less, and B: 0.05%. Hereinafter, if it is preferably 0.01%, the content of the aluminum alloy plate according to the present invention is not affected and the inclusion is allowed. Among these, Ti also has an effect of refining crystal grains, and when it is contained together with a small amount of B, the effect of refining the crystal grains is further improved. However, if these contents are excessive, a huge Al—Ti system Intermetallic compounds and Ti-B-based coarse particles crystallize and hinder formability.

(Structure of aluminum can plate for DI can body)
In order to improve the puncture resistance (puncture resistance), in the present invention, a metal such as an Al-Fe-Mn compound in an aluminum alloy plate for a DI can body or a DI can body formed by DI molding is used. Control of intermetallic compounds and solid solution Mg amount are performed.

(Mn content in the compound)
The piercing mechanism in which a pinhole is generated when a protrusion is pushed into the side wall of the can is, as disclosed in Patent Document 4, a mortar-like shape toward the inside of the can centering on the portion where the protrusion is in contact This is due to local thinning and shear bands occurring at the periphery of the central part (inclined surface of the mortar) and cracking from the end of the shear band (inner surface of the can) is there. When this crack propagates along the shear band, it breaks, and if the amount of intermetallic compound, particularly a large intermetallic compound, is large in the thinned portion, the crack is easily broken.

  However, according to the microscopic regulations such as the area ratio, size and number density of intermetallic compounds using an observation means such as a scanning electron microscope (SEM), as described above, the plate width direction of the cold rolled sheet for DI cans In addition, the tissue of the part extending in the plate thickness direction cannot be represented macroscopically. For this reason, the puncture resistance of the can body made from cold-rolled sheets cannot be improved as a whole.

  Therefore, in the present invention, without using such a micro observation means, a so-called macro analysis means based on a residue extraction method using hot phenol is used, so that a wide and long cold-rolled plate in a coil state can be Macroscopically control the intermetallic compound in the structure in the region extending in the plate thickness direction. That is, the starting point of destruction when a protrusion is pushed into the side wall of the can (when piercing) due to the amount of Mn contained in the compound as a residue separated by the residue extraction method using hot phenol (the amount of Mn in the compound residue) The amount of the compound containing Mn such as Al—Fe—Mn system is defined.

  The starting point of destruction at the time of piercing is a coarse compound having a particle size exceeding 0.1 μm, which commonly contains Mn, such as an Al—Fe—Mn system. In this regard, the aluminum alloy cold-rolled sheet for DI can barrels or DI can body samples formed from DI can be separated by a 0.1 μm mesh filter when dissolved in hot phenol by a hot phenol residue extraction method. If the content (Mn precipitation amount) of Mn contained in the compound as the residue is measured (Mn precipitation amount), Mn such as Al-Fe-Mn system that contains Mn and serves as a starting point of the above-described destruction The amount of the compound containing can be found in the structure of the plate or can body.

  Incidentally, the content of Mn contained in the compound as the residue, which is the structure of the aluminum alloy cold-rolled sheet for DI can barrels, or the content of Mg in the separated solution described later is for this DI can barrel. Even if the aluminum alloy cold-rolled sheet is DI-molded to form a DI can body (even if the side wall of the DI can body is measured as a sample), the difference between the values depends on the portion of the aluminum alloy cold-rolled sheet. However, it does not change to such an extent that it affects each content specification of the present invention. Accordingly, the aluminum alloy cold-rolled sheet for DI can barrel may be measured as a sample, or the side wall of the DI can cylinder obtained by DI molding of the aluminum alloy cold-rolled sheet for DI can barrel may be measured as a sample.

  In the present invention, the amount of a coarse compound having a particle size exceeding 0.1 μm containing Mn such as Al—Fe—Mn in the structure of the plate or can body was separated by a residue extraction method using hot phenol. The average content of Mn in the compound is regulated to 1.0% or less. As a result, the aluminum alloy cold-rolled sheet for DI can body is DI-molded into a can body having a thinnest side wall thickness in the range of 0.085 to 0.110 mm, and the can body is heat treatment equivalent to baking of the coating film. When the 0.2% proof stress in the can axis direction of the side wall of the can body is 280 MPa or more and 350 MPa or less, the piercing resistance of the DI can body is improved.

In the present invention, the reason why the content of Mn contained in the compound as the residue is “average” is to control macroscopically the amount of Mn-based intermetallic compound in the sheet width direction of the wide cold-rolled sheet. . In the plate width direction of a wide cold-rolled plate having a width of 1000 mm or more, the structure state tends to vary due to the difference in temperature and strain distribution during production. In order to suppress this variation and increase the uniformity of the structure and improve the overall puncture resistance (uniformly or uniformly) of the DI can body produced from each can in the width direction of the cold-rolled sheet In addition, the content of Mn is defined as the “average” of the respective can making parts.
For this purpose, as in the examples described later, the plate width of the plate in three places, one in the center in the plate width direction at the center in the longitudinal direction of the cold-rolled plate and two at both ends in the plate width direction from this center. Samples are taken by sampling from a plurality of locations representing the direction of the can making part, and the amount of each Mn-based intermetallic compound in each part sample of these plates (content of Mn contained in the compound as the residue) Are measured, and the amount of Mn-based intermetallic compound is defined and evaluated as an average value obtained by averaging these measured values.
When the average content of Mn exceeds 1.0%, a coarse intermetallic material containing Mn such as Al—Fe—Mn in the structure of a plate or can body and having a particle size exceeding 0.1 μm Too much compound. As a result, the piercing resistance is deteriorated when the can body is thin and has high strength and the use environment becomes severe.

(Solution Mg amount)
When the amount of solid solution Mg increases, the work hardening characteristics by the solid solution strengthening of the plate and the can body improve, and the deformability of the plate and the can body when the projection is pushed into the side wall of the can (when piercing). Improves puncture resistance. For this reason, in the present invention, the solid solution Mg content of the plate or the can body is 0.7% or more and 2.5% or less in terms of the average content of Mg in the solution separated by the residue extraction method using hot phenol. To do.

  When Mg is small in the amount of other elements, almost all of the added or contained Mg is in solid solution. However, when the content of other elements is large, the solid solution amount is related to the content of these other elements. It depends. Therefore, in order to ensure solid solution strengthening of the plate and the can body, it is necessary to directly measure and control the solid solution amount, not the normal Mg content.

  Therefore, in the present invention, the average solid solution amount of Mg in the plate or can body is 0.7% or more and 2.5% in terms of the average content of Mg in the solution separated by the residue extraction method using hot phenol. In the following, this aluminum alloy plate is DI-molded into a can body having a thinnest side wall thickness in the range of 0.085 to 0.110 mm, and the side wall in the direction of the can axis of the side wall after heat treatment equivalent to the baking of the coating film The puncture resistance is improved when the 0.2% proof stress is 280 MPa or more and 350 MPa or less. And together with the reduction of the amount of the Al—Fe—Mn compound that becomes the starting point of destruction, the stab resistance of the thinned and strengthened DI can body is improved to a target level.

Specifically, an internal pressure of 1.7 kgf / cm ² (= 166.6 kPa) is applied to the can body, and the tip has a radius of 0 at a position L = 60 mm in the can axis direction from the bottom of the can body side wall. A piercing needle having a hemispherical surface of 5 mm is pierced perpendicularly to the side wall of the can body at a speed of 50 mm / min, and the maximum value of the measured load until the piercing needle penetrates the side wall of the can body is 35 N or more. Improve to level.

  In the present invention, the “solid” of the solid solution amount of Mg in the plate or can body (the content of Mg in the solution separated by the residue extraction method using hot phenol) is defined as “in average” in the compound as the residue. This is to improve the puncture resistance of the can body manufactured from the cold-rolled sheet to the target level, as in the case of the Mn content contained in the steel sheet. That is, in order to control the amount of Mg solid solution in the canned portion of the cold-rolled sheet, particularly in the sheet width direction, as in the example described later, as in the case of the Mn, the center part in the sheet width direction of the cold-rolled sheet, both ends The solid solution amount of each Mg in each solution separated by the residue extraction method with the hot phenol of each sample collected from a total of three locations representing the can manufacturing site in the plate width direction of the plate, The Mg solid solution amount is defined and evaluated as an average value obtained by averaging the measured values.

  If the average solid solution amount of Mg in the plate or can body is too small, less than 0.7% in terms of the Mg content in the solution separated by the hot phenol residue extraction method, it will be the starting point of the destruction described above. Even if the amount of the Al-Fe-Mn compound is reduced, the stab resistance of the thinned and high-strength DI can body cannot be improved beyond the intended level. On the other hand, the greater the average solid solution amount of Mg, the higher the puncture resistance. However, if the solid solution Mg amount exceeds 2.5%, the proof strength of the cold-rolled sheet is remarkably increased due to the solid solution strengthening of Mg. It becomes too high and is not necessary for can manufacturing, and the ironing processability is lowered, and tear-off is likely to occur. Therefore, stab resistance and can manufacturing processability (DI moldability) are traded off only by controlling the solid solution Mg amount.

(Production method)
Next, the manufacturing method of the aluminum alloy plate in this invention is demonstrated. The aluminum alloy sheet of the present invention includes a casting process for melting and casting the aluminum alloy having the above components to form an ingot, a soaking process for homogenizing the ingot by heat treatment, and hot rolling the homogenized ingot. And a hot rolling process for producing a hot rolled sheet and a cold rolling process for performing cold rolling without annealing the hot rolled sheet. And in this manufacturing method, while performing soaking heat treatment of the ingot twice under the conditions described later, hot rough rolling is also performed under the conditions described later, and the aluminum alloy sheet structure after cold rolling is defined in the present invention, Separation solution by residue extraction method by hot phenol The average content of Mn in the residue compound separated by the residue extraction method with hot phenol is 1.0% or less (including 0%), and the average solid solution amount of Mg is the separation solution by the residue extraction method with hot phenol The average content of Mg is 0.7% or more and 2.5% or less.

(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 casting rate is less than 40 mm / min or the cooling rate is less than 0.5 ° C./sec, a large amount of coarse intermetallic compounds are crystallized in the ingot. On the other hand, if the casting speed is 65 mm / min or the cooling speed is faster than 1.5 ° C./second, ingot cracking or “soot” is likely to occur and the casting yield is lowered. Accordingly, in casting, the casting speed is 40 to 65 mm / min, and the cooling speed is 0.5 to 1.5 ° C./second. 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

(Soaking)
Before rolling the ingot, it is necessary to perform a homogenization heat treatment (soaking) at a predetermined temperature. By applying heat treatment, internal stress is removed, solute elements segregated during casting are homogenized, and intermetallic compounds crystallized during casting are diffused and dissolved to homogenize the structure.

  However, in the present invention, the soaking process is soaking twice. This two-time soaking is distinguished from two-stage soaking. Two-stage soaking means cooling after the first soaking, but it is not cooled to 200 ° C. or lower, and after stopping the cooling at a higher temperature, after maintaining at that temperature, Hot rolling is started after reheating to a high temperature. In contrast, the second soaking of the present invention means that after the first soaking, once cooled to a temperature of 200 ° C. or less including room temperature, reheated, and maintained at that temperature for a certain period of time, Hot rolling is started.

  Specifically, first, the first soaking temperature is set to 580 ° C. or higher and lower than the melting point temperature. The reason for setting the soaking temperature to 580 ° C. or higher is to dissolve the coarse Al—Fe—Mn compound produced during casting. When the soaking temperature is less than 580 ° C., the coarse Al—Fe—Mn compound remains without being dissolved, and the formability of the cold-rolled sheet to the can body decreases.

  After the first soaking process, the temperature is once cooled to 200 ° C. or less including room temperature. Under the present circumstances, the average cooling rate of the ingot between 500-200 degreeC shall be 80 degreeC / hour or more. When the average cooling rate between these temperatures is less than 80 ° C./hour, not only the amount of Al—Fe—Mn compound generated during cooling increases but also the amount of Mg—Si compound increases, and the amount of solid solution Mg increases. descend. Further, as in the case of the two-stage soaking, when the cooling is stopped in the middle high temperature state (above 200 ° C.) and the second soaking is performed continuously, the Al—Fe—Mn system already dispersed is obtained. Since the amount of the compound increases as a nucleus, it is necessary to cool it to 200 ° C. or lower once. If this condition is not satisfied, the structure of the portion extending in the plate width direction and plate thickness direction of the cold rolled sheet for DI can cannot be made excellent in the piercing resistance of the can body.

  The second soaking temperature is 450 ° C. or higher and 550 ° C. or lower. And the average heating rate of the ingot between 200-400 degreeC in this soaking | uniform-heating is made into the speed | rate which exceeds 30 degreeC / hour. This is because the Mg-Si-based compound is generated during the temperature increase in the second soaking, but by setting the average heating rate of the ingot between the temperatures of 200 to 400 ° C to more than 30 ° C / hour, Mg-Si compound is finely and densely formed, and is not only re-dissolved in the process of raising the temperature to 450 ° C or higher to increase the amount of dissolved Mg, but also during the second soaking or hot rolling. The amount of coarse Al—Fe—Mn compound to be reduced can be reduced. Therefore, the amount of Mn and the amount of Mg solid solution defined by the residue extraction method using hot phenol can be satisfied, and the puncture resistance can be improved. If this heating rate is small, the Mg-Si-based compound is not finely and densely formed, and the amount of solid solution Mg cannot be increased without re-dissolution in the process of raising the temperature to 450 ° C. or higher. The amount of the coarse Al—Fe—Mn compound generated during the second soaking or hot rolling also increases. Therefore, there is a high possibility that the amount of Mn or the amount of Mg solid solution defined by the residue extraction method using hot phenol cannot be satisfied and the puncture resistance cannot be improved. For this reason, the structure of the site | part over the board width direction and plate | board thickness direction of the cold rolled sheet for DI can cannot be made into the thing which was excellent in the puncture resistance of a can body.

  If each of the first and second soaking times is less than 2 hours, homogenization of the ingot may not be completed. On the other hand, even if soaking for more than 8 hours is performed, the effect is not improved and productivity is lowered. Therefore, the first and second soaking times are preferably 2 to 8 hours, but are not particularly limited.

(Hot rolling)
Hot rolling is performed on the ingot homogenized in the soaking process. First, the ingot is roughly rolled, and further is subjected to finish rolling to obtain an aluminum alloy hot rolled plate having a predetermined thickness.

(Hot rough rolling)
Hot rough rolling is started in a temperature range of 450 ° C. or higher and 550 ° C. or lower. If the rough rolling start temperature is lower than 450 ° C., the amount of Mg—Si compound precipitated during the rough rolling increases, so that not only does the solid solution Mg amount decrease, but also the rolling itself becomes difficult. On the other hand, when the rough rolling start temperature exceeds 550 ° C., the surface properties of the plate deteriorate due to seizure during rolling.

  Further, the time between passes in rough rolling and the time required from the rolling execution (pass) to the next rolling execution (pass) (time between passes) are made as short as possible. The time between the passes is preferably as short as possible within 100 seconds. The time between passes here shows the difference in the mill passage time at the center position in the length direction of the plate. The amount of Al—Fe—Mn compound and Mg—Si compound precipitated during rough rolling increases as the rolling reduction in the region where the plate thickness is thin and as the time between passes increases. Further, in this hot rough rolling, the lowest steady speed is set to 50 m / min or more among the steady speeds of all passes of several to several tens of times in the case of a reverse rolling mill. The steady speed here is a speed at which the rolling speed (line speed) is maximum and constant per pass. When the steady speed (the lowest steady speed during the pass) is less than 50 m / min in comparison with all passes in the hot rough rolling, the rolling time becomes long, and the Al—Fe—Mn system generated during cooling. The amount of the compound increases, and the amount of the residual Mn becomes excessive. For this reason, if these conditions are not met, the amount of Mn and the amount of Mg solid solution defined by the residue extraction method using hot phenol cannot be satisfied, and the target piercing resistance of the can body may not be obtained.

  The end temperature of the hot rough rolling is preferably 400 ° C. or higher. When the hot rolling is divided into rough rolling and finish rolling and continuously performed, if the end temperature of the hot rough rolling is too low, the rolling temperature is lowered in the next hot finishing rolling, Edge cracks are likely to occur.

(Hot finish rolling)
The aluminum alloy sheet that has been subjected to the hot rough rolling is hot-finished quickly, such as continuously. By rapidly performing hot finish rolling, an increase in Al-Fe-Mn compounds and Mg-Si compounds can be prevented. The aluminum alloy sheet that has been subjected to the hot rough rolling is preferably hot finish rolled, for example, within 5 minutes, preferably within 3 minutes. The finishing temperature of hot finish rolling is preferably 300 ° C. or higher. If the temperature is less than 300 ° C., the temperature is too low and the entire plate does not recrystallize and partially becomes a processed structure, and thus the ear rate variation in the plate width direction increases in particular.

(Cold rolling)
The aluminum alloy hot-rolled sheet is cold-rolled without being annealed to finish an aluminum alloy sheet having a predetermined thickness. The total rolling rate (cold working rate) in cold rolling is preferably 77 to 90%, and the thickness of the cold rolled sheet after cold rolling is preferably 0.25 to 0.33 mm.

[DI can manufacturing method]
An example of a method for producing a can body of a DI can from an aluminum alloy plate (cold rolled plate) according to the present invention will be described below. First, an aluminum alloy plate according to the present invention is punched into a disc shape (blanking process), drawn into a shallow cup shape (capping process), and subjected to DI molding. These drawing and 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.

  It is preferable that the plate | board thickness reduction | decrease rate (ironing process rate) of the side wall of a can body by these processes shall be 60 to 70%. Then, the edge of the side wall (opening) is trimmed and trimmed (trimming process). In this state, DI molding is performed on a thin can body in which the side wall thickness of the thinnest part is in the range 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), and the 0.2% proof stress is 280 MPa to 350 MPa as the strength of the thinnest side wall in the can axis direction. The strength is high. By the way, this strength is equivalent to the baking of the coating film as the “can heat treatment equivalent to the baking of the coating film of the can body” as used in the present invention, without actually baking (baking) the coating film. The strength after heat treatment at 200 ° C. for 20 minutes at a temperature and time can be substituted.

  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)
An aluminum alloy having the composition shown in Table 1 was melted, and an ingot was produced using a semi-continuous casting method at a casting rate and a cooling rate within the preferable numerical ranges described above in common with each example.

  This ingot is soaked twice, and in each case, after the first soaking for 4 hours at a soaking temperature of 600 ° C., an average cooling rate (° C./hour) of 500 to 200 ° C. is once brought to room temperature. Various changes were made as shown in Table 1 for cooling. After that, as the second soaking, the ingot was heated again from room temperature, and the average heating rate (° C./hour) of 200 to 400 ° C. was variously changed as shown in Table 1. A second soaking process was performed for 4 hours at a hot temperature.

  And hot rough rolling was started at this temperature. At this time, of the time between passes of the pass number of passes 12 in this hot rough rolling (reverse rolling mill), of the time of the pass required from the rolling execution (pass) to the next rolling execution (pass) The maximum time (seconds) was variously changed as shown in Table 1. In addition, among the steady speeds of all these paths, the lowest steady speed (m / min) was variously changed as shown in Table 1. In common with each example, the end temperature of the hot rough rolling is 450 ° C., the hot finish rolling is started within 3 minutes after the end of the hot rough rolling, and the end temperature of the hot finish rolling is 330 ° C. As a hot rolled plate having a thickness of 2.5 mm. Further, this hot rolled sheet is cold rolled without being roughed (annealed) and without being subjected to intermediate annealing in the middle, and is a coil-like length having a sheet thickness of 0.28 mm and a sheet width of 2000 mm. A length aluminum alloy plate was used. In Table 1, “−” in the chemical composition of the aluminum alloy plate indicates that it is below the detection limit.

(Can body)
The coiled aluminum alloy plate thus obtained was cupped, DI-molded (ironing rate 65-70%), the opening was trimmed, the outer diameter was about 66 mm, and the height (length in the can axis direction) 124 mm, A bottomed cylindrical can body having a side wall thickness of 0.090 mm was used. Furthermore, after the can body was degreased and washed, heat treatment was performed under the conditions of the above-mentioned 200 ° C. for 20 minutes assuming (simulating) baking during coating, thereby obtaining a can body test material.

[Evaluation]
Evaluation is 0.2% proof stress with the aluminum alloy cold-rolled sheet and the amount of Mn-based intermetallic compound (Mn content in the compound residue) and Mg solid solution amount (Mg content in the separated solution) Amount) was measured. In addition, DI moldability, puncture resistance, and 0.2% proof stress were measured and evaluated on the can body (after heat treatment assumed for the above-mentioned paint baking). These results are also shown in Table 1.

(Tissue = hot phenol residue extraction method)
Each sample collected from a total of three locations, one central portion in the plate width direction of the center portion in the longitudinal direction of the aluminum alloy cold rolled plate coil, and two end portions in the plate width direction from this central portion was dissolved with hot phenol. The Mn content (Mn in the compound residue) in the compound as a residue separated by a 0.1 μm mesh filter was measured and averaged, and the average Mn of the compound in the aluminum alloy cold-rolled sheet structure was measured. The content was determined as an analytical value. At the same time, the Mg content in each solution separated from this residue in each sample was measured and averaged, and the average Mg solid solution content in the aluminum alloy cold-rolled sheet structure was determined as an analytical value.

(Formability)
In the DI molding described above, 1000 blanks were cut out from a total of three locations in the vicinity of the central portion in the plate width direction of the center portion in the longitudinal direction of the aluminum alloy cold rolled plate coil and in the vicinity of each of the two ends. Cans were made by continuous molding (cupping, DI molding) at an ironing rate of 65%. When no defects (tear-off, pinholes, etc.) occurred during molding, the moldability was evaluated as “◯”, and when defects occurred, the moldability was evaluated as “x”.

(Puncture resistance)
For each example, it was verified whether the piercing resistance of a large number of cans made from a single plate, in particular, the piercing resistance in the plate width direction and the plate thickness direction of the cold-rolled plate was improved as a whole. For this reason, in each example, all the ten pieces that can be formed so that the can bodies made from three places of the center portion in the plate width direction and both end portions of the aluminum alloy cold-rolled plate coil are evenly included. A piercing test was performed to evaluate piercing resistance.

As shown in FIG. 1, this puncture resistance test is performed by fixing the can body, applying an internal pressure of 1.7 kgf / cm ² (= 166.6 kPa), and rolling the aluminum alloy plate on the side wall of the can body. Is aligned with the can axis direction, and at the site where the distance L in the can axis direction from the can bottom is 60 mm, a piercing needle whose tip is a hemisphere with a radius of 0.5 mm is perpendicular to the side wall at a speed of 50 mm / Stabbed in minutes. And the load (N) until a piercing needle penetrates a side wall was measured, and the obtained maximum load was made into the piercing strength.

  In the puncture resistance test results, the average maximum load of all can bodies was 40 N or more. If the overall width direction of the aluminum alloy cold-rolled sheet is excellent in puncture resistance, In addition, it was also evaluated as “◯” that was 35 N or more. On the other hand, if the average maximum load of all can bodies was less than 35N, the puncture resistance of the aluminum alloy cold-rolled sheet was poor in the sheet width direction and the entire sheet thickness direction. evaluated.

In the present invention, as the handling or use conditions of the DI can, the pressure difference between the inside and outside of the can is larger, the deformation of the can body becomes larger, and the puncture resistance is more severe. 1.7 kgf / cm ² ( = 166.6 kPa). The actual rupture at the time of piercing of the can body is caused by collisions of various shapes, but it is not possible to evaluate all of them, and there is a demand for evaluation by a stricter evaluation method. Therefore, it was made difficult to increase the puncture strength by adopting the conditions where the internal pressure was lowered and the deformation was increased.

The evaluation of puncture resistance so far is usually performed by applying a higher internal pressure of 2.0 kgf / cm ² (= 196 kPa). For this reason, even with the same test material, the test method of the present invention has stricter test conditions and lower puncture strength. That is, the value of the piercing strength (N) in the test with the internal pressure of 2.0 kgf / cm ² and the value of the piercing strength (N) by the test method of the present invention are the same, for example, slightly lower values. Even so, it can be said that the material of the present invention is superior in puncture resistance. In other words, even if the penetration resistance of the internal pressure test of 2.0 kgf / cm ² was excellent, quite be said penetration resistance at lower internal pressure of 1.7 kgf / cm ² of the present invention is excellent Absent.

(0.2% yield strength)
Tensile tests for measuring 0.2% proof stress of the cold-rolled plate and the side wall of the can body were conducted by using test pieces taken from the cold-rolled plate and the side wall of the can body (after the heat treatment assumed for paint baking), respectively. While performing according to 2201, the shape of the test piece was a JIS No. 5 test piece, and the test piece was prepared so that the longitudinal direction of the test piece coincided with the rolling direction (can axis direction). The crosshead speed was 5 mm / min, and the test piece was run at a constant speed until the test piece broke.

  As shown in Table 1, each of the inventive examples 1 to 11 has a composition of an aluminum alloy within the scope of the present invention, and is manufactured under preferable manufacturing conditions. That is, in the second soaking process of the ingot, the average cooling rate of 500 to 200 ° C. at the time of cooling to room temperature after the first soaking is 80 ° C./hour or more, and the second soaking ingot The average heating rate of 200 to 400 ° C. during reheating from room temperature is 30 ° C./hour or more. And the longest time of the time between passes in hot rough rolling is less than 100 seconds, and the lowest steady speed is 50 m / min or more.

  For this reason, as shown in Table 1, each example of the invention shows the Mn content in the compound having a particle size of more than 0.1 μm separated by a hot phenol residue extraction method on a cold-rolled plate (DI-shaped can barrel side wall). The average content (Table 1 is abbreviated as amount of residual Mn) is 1.0% or less, and the amount of Mn-based intermetallic compound is small. At the same time, the average solid solution amount of Mg in the cold-rolled sheet (DI-molded can body side wall) structure is the Mg content in the solution separated by the residue extraction method using hot phenol (Table 1 shows solid solution Mg The amount is abbreviated to 0.7% or more and 2.5% or less.

As a result, each of the inventive examples is based on the premise that the DI moldability is good, and the aluminum alloy plate is DI molded into a thin can body having a side wall thickness of 0.090 mm at the thinnest portion, and the coating film is baked. The puncture resistance is excellent when the 0.2% proof stress in the can axis direction of the side wall after considerable heat treatment is high strength of 280 MPa to 350 MPa. In addition, this puncture resistance is excellent at 35N or more or 40N or more despite a strict evaluation in which an internal pressure of 1.7 kgf / cm ² (= 166.6 kPa) is applied to the can body. That is, in a can body having a thin can wall thickness and high strength, good moldability and excellent puncture resistance under more severe conditions were obtained.

  On the other hand, in Comparative Examples 12 to 15 in Table 1, although the composition of the aluminum alloy is within the scope of the present invention, any of the conditions in the soaking or hot rough rolling is from the preferable conditions of the present invention. It is off. For this reason, each comparative example shows the average content of Mn in a compound having a particle size of more than 0.1 μm separated by a hot phenol residue extraction method on a cold-rolled sheet (DI-shaped can barrel side wall) (Table No. 1 is abbreviated as the amount of residual Mn), or the average solid solution amount of Mg (Table 1 is abbreviated as the solid solution Mg amount) is out of the structure. As a result, although each comparative example has a good DI moldability, the thinnest side wall thickness is DI molded into the thin can body and the side wall after heat treatment corresponding to the baking of the coating film. Is high in strength, and the puncture resistance in the plate width direction when the internal pressure condition is severe is remarkably inferior.

  In Comparative Example 12, the average cooling rate of 500 to 200 ° C. at the time of cooling to room temperature after the first soaking process is too small as less than 80 ° C./hour. As a result, the amount of Al—Fe—Mn compound generated during cooling increases, and the amount of residual Mn is excessive.

  In Comparative Example 13, the average heating rate of 200 to 400 ° C. at the second soaking temperature is too small as less than 30 ° C./hour. As a result, the Mg—Si-based compound is not formed finely and at a high density, and is not re-dissolved in the process of raising the temperature to 450 ° C. or higher, and the amount of the solid solution Mg is too small.

  In Comparative Example 14, the time between passes in rough rolling exceeds 100 seconds and is too long. As a result, the amount of Al—Fe—Mn compound or Mg—Si compound precipitated during rough rolling increases, and the Mg solid solution amount is particularly small.

  The comparative example 15 is too slow with the lowest steady speed of less than 50 m / min among the steady speeds of the path | pass in rough rolling. As a result, the rolling time is lengthened, the amount of Al—Fe—Mn compound generated during cooling is increased, and the amount of residual Mn is excessive.

  In Comparative Examples 16 to 20 in Table 1, any of Mn, Mg, Si, and Fe is too small, and the composition of the aluminum alloy is outside the scope of the present invention.

  In Comparative Example 16, the amount of Mg is too small, and the amount of solid solution Mg is too small. In Comparative Example 17, the amount of Mn is excessive, and the amount of residual Mn is excessive. As a result, these comparative examples are inferior in puncture resistance in the plate width direction when the internal pressure conditions are severe.

  In Comparative Example 18, the amount of Mn is too small. In Comparative Example 19, the amount of Si is excessive. As a result, since these defectives occurred during DI molding, they could not be put into practical use for cans and were stopped because there was no point in carrying out a subsequent piercing test.

  As described above, the aluminum alloy plate (cold rolled plate) for DI can barrel manufactured according to the present invention improves the piercing resistance of the can barrel made from the aluminum alloy cold rolled plate to a target level. It can ensure puncture resistance. For this reason, the can wall thickness is reduced in thickness and strength, and it is optimal for an aluminum alloy cold-rolled sheet used for a DI can body that requires puncture resistance under more severe use conditions.

Claims (5)

In mass%, Mn: 0.3 to 1.3%, Mg: 1.0 to 3.0%, Si: 0.1 to 0.5%, Fe: 0.1 to 0.8%, respectively Then, after the first soaking , the aluminum alloy ingot having the composition consisting of Al and inevitable impurities is once cooled to a temperature of 200 ° C. or less including room temperature, and then reheated to be constant at that temperature. After the time is maintained, when the soaking process is started twice , the first soaking temperature is set to 580 ° C. or higher and less than the melting point temperature, the first soaking time is set to 2 hours or more, and the first soaking is performed. The average cooling rate of 500 to 200 ° C. when cooling to room temperature is 80 ° C./hour or more, the second soaking temperature is 450 ° C. or more and 550 ° C. or less, and the second soaking time is 2 hours or more. , the average pressure of 200 to 400 ° C. during reheating from the second soaking at room temperature The speed is set to 30 ° C./hour or more, the soaked ingot is hot-rolled by hot rough rolling and hot finish rolling, and the hot-rolled plate is cold-rolled to obtain an aluminum alloy plate. As the structure of the aluminum alloy plate, the amount of Mn contained in the residue compound having a particle size exceeding 0.1 μm separated by the residue extraction method using hot phenol is 1.0% or less (including 0%), and the heat A method for producing an aluminum alloy plate for a DI can body, wherein the solid solution amount of Mg in the solution separated by the phenol residue extraction method is 0.7% or more and 2.5% or less.   The manufacturing method of the aluminum alloy plate for DI can bodies of Claim 1 in which the said aluminum alloy ingot contains Cu: 0.05-0.4% further.   The aluminum alloy for a DI can body according to claim 1 or 2, wherein the aluminum alloy ingot further contains one or two of Cr: 0.001 to 0.1% and Zn: 0.05 to 0.5%. A manufacturing method of a board.   The aluminum alloy plate is DI-molded into a can body having a thinnest side wall thickness of 0.085 to 0.110 mm, and when the can body is heat-treated at 200 ° C. for 20 minutes, The manufacturing method of the aluminum alloy plate for DI can bodies of any one of Claims 1 thru | or 3 which has the intensity | strength characteristic whose 0.2% yield strength of a can axis direction is 280 Mpa or more and 350 Mpa or less. The piercing resistance of the aluminum alloy plate is DI molded into a can body having a thinnest side wall thickness of 0.085 to 0.110 mm, and the can body is heat-treated at 200 ° C. for 20 minutes. An internal pressure of 1.7 kgf / cm @ 2 (= 166.6 kPa) is applied to the can body, and the tip is a hemispherical surface with a radius of 0.5 mm at a position L = 60 mm in the can axis direction from the bottom of the can body side wall. The piercing needle is pierced perpendicularly to the can barrel side wall at a speed of 50 mm / min, and the maximum value among the load measurement values until the piercing needle penetrates the can barrel side wall is 35 N or more. The manufacturing method of the aluminum alloy plate for DI can bodies of any one of Claims 1.