KR20150087419A - Aluminum alloy sheet for di can body - Google Patents

Abstract

The aluminum alloy sheet of the present invention has a density of a specific atomic aggregate in a cold rolled steel sheet produced by controlling cracking conditions and cold rolling conditions of an ingot when producing an aluminum alloy sheet for a 3000 series DI can body having a specific composition To facilitate the sub-grain formation of the can body when it is subjected to a paint baking process (heat treatment) after the can body is manufactured, and even if the internal pressure of the thinned can body is high, Excellent in sex.

Description

DIAL CAN ALUMINUM ALLOY SHEET FOR DI CAN BODY}

The present invention relates to an aluminum alloy plate for a DI can body, which is used as a packaging container for beverage and food use, and is particularly DI-formed into a body portion of a beverage can.

BACKGROUND ART [0002] Currently, packaging containers used for beverage and food applications include a bottomed cylindrical body portion (can body) having a bottom and a side wall integrated with each other, and a disk- And a cap portion (can cap) of the two-piece can is known. Aluminum alloy plates such as AA to JIS 3000 series are widely used as the material for such can in terms of moldability, corrosion resistance, strength and the like. Among the two-piece cans made of this aluminum alloy plate, the body portion of the cylindrical can having a height equal to that of the beverage can is formed by multi-step processing of drawing-ironing process called DI (Drawing and wall Ironing) It is often molded. The opening portion is reduced in diameter by coating, baking, necking, and the edges of the opening portion are widened outward by flanging to form a can body. Finally, the contents (beverage, food) are filled in the body part, and the cap part is sealed in the opening part by being sealed. A can according to such a production method is called a DI can (hereinafter referred to as " can " as appropriate) and widely circulated.

Conventionally, in order to reduce the cost of beverages packed with such a can made of an aluminum alloy, a can as a packaging container has been made thinner as a measure for reducing the weight and reducing the raw material (aluminum alloy). 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 except for the coating film. However, in the thinned can such a thinned can, when the projection is contacted and pressed (press-fitted) on the side wall (circumferential surface) having a thin plate thickness, the tip end thereof penetrates the side wall, There may be a problem such as leakage of the contents through the hole. Examples of the contact of the protrusions include contact of foreign matter from the outside at the time of manufacturing (when the contents are filled, when the cap is wound, when the transfer system in the manufacturing process passes), when the product is distributed, or when the product is handled by a consumer. Also in the flanging process, cracks (flange cracks) may be generated at the ends of the openings when the edges of the openings are widened.

Therefore, in order to prevent occurrence of pinholes in side walls and flange cracks in the openings of such thinned cans, that is, to improve piercing resistance and flanging workability (can spreadability) of side walls, Aluminum alloy plates that are the material side are being improved.

For example, Patent Document 1 discloses a method of designing a can body to be formed by DI molding or drawing molding from an aluminum alloy cold-rolled sheet having a 3000-series composition. That is, when the thickness of the can body subjected to the heat treatment corresponding to the coating portion is in the range of 0.07 mm to 0.14 mm, the tensile strength in the can axis direction of the wall portion is 300 MPa to 500 MPa, and the elongation is 3 to 8% The puncture strength with respect to the wall thickness t after the surface coating film is removed can be equal to or higher than 35 N in terms of the puncture strength of the can having a wall thickness of 0.105 mm. Therefore, the thickness of the wall portion for obtaining the stamper strength is determined from the Mg content, or the Mg content with respect to the thickness of the predetermined wall portion is determined from the desired stamper strength.

There have also been proposed various techniques for controlling the intermetallic compound of an aluminum alloy cold-rolled sheet having a 3000-series composition to improve the resistance to piercing. For example, Patent Document 2 discloses a technique of distributing an intermetallic compound with a specific density and a specific area ratio on the surface of an aluminum alloy cold rolled plate having a 3000-series composition. In this case, when the side wall thickness including the outer surface and the inner surface coating of the DI-formed 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% It is said to be more than 290 MPa and not more than 330 MPa, so that the piercing resistance is excellent.

Patent Literatures 3 and 4 also disclose a technique of improving the strength (resistance to crease) 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 a composition of 3000 series Lt; / RTI > In Patent Document 5, an aluminum alloy cold-rolled sheet having a 3000-series composition is DI-molded at a predetermined processing rate and heat-treated at 210 to 250 캜 to control work hardening and tensile strength by DI molding , And a technique for improving piercing resistance is disclosed.

Further, in the field of aluminum alloy cold-rolled steel sheets having a composition of 3000 grades for cans, a technique of improving the properties such as DI formability and strength in the case of thinning by specifying a high amount of Si, Cu, Mn, Fe, There are suggestions.

Japanese Patent No. 4667722 Japanese Patent Application Laid-Open No. 2004-68061 Japanese Patent Application Laid-Open No. 2007-197815 Japanese Patent Application Laid-Open No. 2009-270192 Japanese Patent Application Laid-Open No. 2007-169767

In recent years, the handling and use conditions of the DI can become more stringent under such conditions that the pressure difference between the inside and outside of the can becomes larger and the can body becomes more susceptible to deformation. Accordingly, the piercing resistance (piercing strength) required for the thinned can body is also more severe. On the other hand, the above-mentioned prior art has still room for improvement in order to obtain this stringent puncture resistance.

For example, only the control of the Mg content as in Patent Document 1 has a limitation in setting the stamper strength, which is greatly affected by the presence of the compound in the structure, to the required level. Further, the technique disclosed in Patent Document 2 improves resistance to piercing by making the thickness of the sidewall of the can larger than 0.110 mm, and can not cope with the thinning of the sidewall thickness of the can. In addition, the technique disclosed in Patent Document 5 is limited to a high temperature range of the baking portion at the time of coating of the can, and therefore is not suitable for the requirements of the can manufacture side when it is desired to perform heat treatment at a lower temperature. Further, the control of the intermetallic compound disclosed in Patent Documents 3 to 5 is certainly effective in improving the resistance to bite, but there is still room for improvement in order to obtain the above-mentioned stiffness.

It is an object of the present invention to provide an aluminum alloy plate for a DI can body which can satisfy the stiffer piercing resistance (piercing strength) required for a thinned can body.

The aluminum alloy plate for a DI can body according to the present invention comprises 0.3 to 1.3% of Mn, 0.7 to 3.0% of Mg, 0.1 to 0.5% of Si, 0.1 to 0.8% of Fe, , And Cu: 0.01 to 0.4%, the balance being Al and inevitable impurities, and is an aggregate of atoms measured by a three-dimensional atom probe electric field ion microscope, One or both of the Mg atom and the Cu atom are included in total in addition to any one of the Mg atom and the Cu atom included in the atom, It is supposed that the distance between the atoms is 0.80 nm or less and the average density of the aggregate of atoms satisfying these conditions is regulated to 1 x 10 ²⁴ atoms / m ³ or less.

Here, the aluminum alloy sheet may further contain one or two of Cr: 0.001 to 0.1% and Zn: 0.05 to 0.5%. Further, the aluminum alloy plate is DI-shaped into a can body having a thickness of the side wall of the thinnest portion ranging from 0.085 to 0.110 mm, and when the can body is heat-treated at 200 ° C for 20 minutes, And a 0.2% proof stress of 280 MPa or more and 350 MPa or less. The internal resistance of the aluminum alloy plate was set such that the internal pressure of 1.7 kgf / cm ² (= 166.6 kPa) was applied to the can body, and the distance L = 60 mm in the can axis direction from the can bottom of the can side wall , A needle having a hemispherical surface with a radius of 0.5 mm was stuck at a speed of 50 mm / min perpendicular to the side wall of the can body, and the maximum value of the load measurement values until the needle passed through the sidewall of the can body was 35 N Or more.

When the aluminum alloy sheet of the 3000 series composition as the material for the DI can body is subjected to the coating baking treatment (heat treatment) after the can body is made into a can (DI molding) and the sub body of the can body structure is promoted, The piercing property is improved. However, it is difficult to quantitatively define the degree of sub-grain formation in the can body structure by a systematic factor such as dislocation density or grain shape.

On the other hand, according to the present invention, it is understood that the superiority of the resistance to impaction of 3000 series aluminum alloy plates containing Cu differs significantly depending on the existence state of a specific atomic group which can be analyzed by a three-dimensional atom probe electric field ion microscope did. That is, the smaller the specific atomic groups defined in the present invention, the more progressive the subgraining of the above-described structure and the better the piercing resistance. Conversely, the larger the aggregation of these specific atoms, I did not get angry, and I knew that my stabbing was lagging behind.

Therefore, the existence state (average density) of the aggregate of atoms specified in the present invention can be an index indicating the relationship between the punching performance when the 3000-series aluminum alloy plate containing Cu is made into a can body. By using this, in the present invention, it is possible to control the existence state (average density) of the specific cluster of atoms (cluster) of a 3000-series aluminum alloy plate containing Cu to improve the stiffness The penetration resistance can be improved to a level that can satisfy the penetration strength.

Fig. 1 is a cross-sectional view schematically illustrating a method of measuring a stamper strength of a can body.

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

(Aluminum alloy composition)

The composition of the aluminum alloy plate for the DI can body according to the present invention is 0.3 to 1.3% of Mn, 0.7 to 3.0% of Mg, 0.1 to 0.5% of Si, 0.1 to 0.8% of Fe, 0.01 to 0.8% of Cu, To 0.4%, and the balance of Al and inevitable impurities. The composition of the aluminum alloy may further contain one or two of Cr: 0.001 to 0.1% and Zn: 0.05 to 0.5%. On the other hand, the percentages of the composition (content of each element) are all expressed in% by 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 into the can body, the strength of the side wall is increased to secure buckling strength and resistance to impact. Further, Mn forms an Al-Mn-Fe intermetallic compound in the aluminum alloy and is appropriately dispersed, whereby recrystallization after hot rolling is promoted, and the workability of the aluminum alloy plate is improved. If the content of Mn is less than 0.3%, these effects are insufficient. Therefore, the content of Mn is set to 0.3% or more, preferably 0.4% or more. On the other hand, when the content of Mn exceeds 1.3%, the amount of coarse Al-Mn-Fe intermetallic compound produced increases, and the resistance to piercing is reduced. Therefore, the upper limit of Mn is set to 1.3%, preferably 1.1%, more preferably 1.0%.

(Mg: 0.7 to 3.0%)

Mg has the effect of improving the strength of the aluminum alloy. When the content of Mg is less than 0.7%, the strength of the side wall is lowered and the piercing property is insufficient when the aluminum alloy plate is formed into the can body. On the other hand, if the content of Mg exceeds 3.0%, the work hardening of the aluminum alloy sheet becomes excessive, and cracks such as tear-off (body crack) during ironing, wrinkles and stripes Defects are likely to occur. Therefore, the content of Mg is set in the range of 0.7 to 3.0%, preferably 1.0 to 2.6%, more preferably 1.2 to 2.2%.

(Si: 0.1 to 0.5%)

Si forms an Al-Fe-Mn-Si intermetallic compound, and the more uniformly the Al-Fe-Mn-Si intermetallic compound is formed, the better the formability. Therefore, the content of Si is set to 0.1% or more, preferably 0.2% or more. On the other hand, when Si is excessively large, a large number of Al-Mn-Fe-Si intermetallic compounds and MgSi intermetallic compounds are formed and the piercing resistance is lowered. Therefore, the upper limit of the Si content is 0.5%, preferably 0.4%.

(Fe: 0.1 to 0.8%)

Fe is incorporated as an impurity in the aluminum alloy as an impurity at present. It forms an Al-Mn-Fe intermetallic compound in the aluminum alloy and appropriately disperses it, thereby accelerating recrystallization after hot rolling, thereby improving the workability of the aluminum alloy plate . Fe is also useful in promoting crystallization and precipitation of Mn to control the average amount of Mn in the aluminum matrix and the dispersion state of the Mn intermetallic compound. Therefore, the content of Fe is 0.1% or more, preferably 0.3% or more. On the other hand, when the Fe content is excessive, a large initial intermetallic compound is likely to be generated, and the DI moldability and punch resistance are also lowered. Therefore, the upper limit of the Fe content is set to 0.8%, preferably 0.7%.

(Cu: 0.01 to 0.4%)

Cu increases strength by solid solution strengthening. For this reason, Cu is essentially contained. The lower limit of the Cu content is 0.01% or more, preferably 0.05% or more. On the other hand, when Cu is excessive, high strength is easily obtained, but since it becomes excessively hard, moldability is deteriorated and corrosion resistance is also deteriorated. For this reason, the upper limit amount of Cu content is set to 0.4%, preferably 0.3%.

(Cr: 0.001 to 0.1%, Zn: 0.05 to 0.5%)

Cr and Zn can be given as an element for improving the strength of the same effect as that of Cu. One or two of Cr: 0.001 to 0.1% and Zn: 0.05 to 0.5% can be selectively added in addition to Cu. The content of Cr when selectively contained is 0.001% or more, preferably 0.002% or more. On the other hand, when Cr is excessive, a large amount of crystallized product is formed and the moldability is deteriorated. Therefore, the upper limit of the amount of Cr is set to about 0.1%, preferably about 0.05%. The content of Zn when it is selectively contained is 0.05% or more, preferably 0.06% or more. On the other hand, when Zn is excessive, the corrosion resistance is lowered. Therefore, the upper limit of the Zn content is set to 0.5%, preferably about 0.45%.

In addition to these elements, inevitable impurities exist. For example, when Zr is 0.10% or less, Ti is 0.2% or less, preferably 0.1% or less, and B is 0.05% or less, preferably 0.01% It does not affect the characteristics of the aluminum alloy plate according to the present invention, and is allowed to be contained. Among them, Ti has the effect of making crystal grains finer. When the content of Ti is too large, the effect of refining the crystal grains is further improved. However, when the content of Ti is excessively large, a large amount of Al- B coarse particles are crystallized to deteriorate moldability.

(Structure of aluminum alloy plate for DI can body)

Aggregation of atoms and penetration resistance:

On the premise of the above-described aluminum alloy composition, in order to improve the resistance to piercing (piercing strength), the present invention controls the aggregation of extremely fine atoms present in the structure of the aluminum alloy sheet for the DI can body.

The resistance to canning of a can body made of an aluminum alloy sheet having a composition of 3000 grades is improved by the sub-grain formation of the can body structure when the material plate is subjected to the paint baking treatment after the can body is manufactured (DI molding) do. This subgrain, also called sub-structure or sub-crystallization, is a small structure that occurs during crystal grains. The inside of the sub-grain becomes a partial dislocation-free region, so that the sliding surface can be activated when the deformation is applied. Therefore, even when a so-called stain occurs in which an external force at the pin point is applied to the can body at the time of use as a can or during handling, work hardening due to deposition of a new dislocation is developed at the stuck portion, do.

In the comparison between the can bodies having a large difference in the effect of the puncture property (TEM) of the can bodies, the qualitative discrimination of the can body structure of the can bodies with respect to each other is relatively easy because the dislocations thereof are large . The structure of the can body in which the piercing resistance is poor is a large number of stripe-shaped or linear-shaped dislocations, and it is easily distinguishable from the structure of the can body having excellent resistance to pitting with a small potential. However, it is difficult at present to quantitatively distinguish the structures of these mutually by a tissue element that can be observed by SEM or TEM such as the degree of their dislocation or the degree of sub-grain formation.

On the other hand, by analyzing the existence state of the atom aggregate by the three-dimensional atom probe electric field ion microscope, the degree of the sub-grain formation of the can body structure is different, and the aggregation (density of the aggregate) The smaller the number, the more progression of the subgraining of the tissue proceeds and the piercing property is improved.

On the other hand, on the contrary, it has been found that the larger the number of the aggregates of the specific atoms, the less the sub-grain formation of the can body structure proceeds, and the piercing resistance is lowered.

In the 3000-series aluminum alloy plate containing Cu, by controlling the average density in the presence of aggregates of at least one of Mg atoms and Cu atoms measured by a three-dimensional atom probe electric field ion microscope, It is possible to control the degree of sub-grain formation of the can body and the piercing resistance of the plate. This makes it possible to improve the seizure resistance of a 3000-series aluminum alloy plate containing Cu to a stricter level required for a thinned can body.

Definition of the aggregate of atoms:

In the present invention, among the aggregates of the atoms measured by the three-dimensional atom probe electric field ion microscope, the texture of the 3000 body aluminum alloy plate containing Cu for the DI can body is changed into the sub- And a specific set of atoms capable of controlling the atom.

The aggregate of these specific atoms means either one or both of a Mg atom and a Cu atom in total in addition to 5 or more atoms in total, and even if any of the contained Mg atom or Cu atom is used as a reference, Is a group of atoms satisfying the condition that the distance between any one atom of the neighboring atoms is 0.80 nm or less.

The cluster of atoms (clusters) defined in the present invention is not limited to only two atoms of a Mg atom and a Cu atom. In many cases, the atomic cluster includes Al atoms. It may also contain atoms such as Mn, Si, and Fe, which are other alloying elements. Depending on the composition of the 3000-series aluminum alloy, atoms such as Cr, Zn, V, and Ti contained as an optional element or an impurity are contained in an aggregate of atoms, and these other atoms are necessarily counted by 3DAP analysis.

However, even if these other atoms (derived from alloy elements or impurities) are included in the cluster of atoms (clusters) defined in the present invention, they are at a lower level than the total number of Mg atoms and Cu atoms. Therefore, even when such other atoms are contained in the aggregate, it is the aggregate of atoms of the present invention that satisfies the condition of the specified distance between the Mg atom and the Cu atom and the specified total number, It functions like an aggregate of atoms. Therefore, when the number of atoms in the neighboring distance is satisfied, even if other atoms are included in the aggregate, the number of atoms in the present invention is counted as an aggregate of the present invention. When the number of atoms in the neighboring distance is not satisfied, It is not counted as the aggregate of atoms of the present invention.

In this regard, in the cluster of atoms of the present invention, atoms adjacent to each other may be not only different atoms of Mg atoms and Cu atoms but also Mg atoms and Cu atoms. For example, in an aggregate of atoms, either Mg atom or Cu atom is not detected and even if it is zero (either Mg atom or Cu atom), either Mg atoms or Cu atoms are mutually separated at a neighboring distance (Not more than 0.80 nm) and the number (not less than 5) are satisfied, the aggregates of atoms defined in the present invention are counted as the average number density as the aggregates of atoms defined in the present invention. Therefore, even when the number of atoms in a neighboring distance satisfies a prescribed number when measured by 3DAP analysis, if the aggregate of these atoms does not contain any Mg atom or Cu atom, Is not an aggregate of the defining atoms, and does not count. That is, the aggregate of atoms defined in the present invention necessarily includes either an Mg atom or a Cu atom, or an Mg atom or a Cu atom.

Here, the definition of the distance of an atom in a cluster of atoms is such that any atom of the Mg atom or the Cu atom contained in the aggregate of the atom is different from the atom (the Mg atom or the Cu atom as a reference) The distance between atoms of any one of atoms (Mg atoms, Cu atoms, or other atoms) may be 0.80 nm or less. That is, the distance between all the other atoms adjacent to the reference Mg atom or Cu atom and the reference atom may be all 0.80 nm or less. It may also be within a neighboring valence at a distance deviating from it, and at least one other atom that satisfies this distance may be present. The Mg atoms and the Cu atoms included in the aggregate of the atoms in total of five or more are all satisfying the relationship of the distances to such neighboring atoms.

Average density of aggregates of atoms:

In the present invention, an aggregate of atoms in a material aluminum alloy plate structure for a DI can body specified above and measured by 3DAP analysis is referred to as an average density of aggregates of these atoms of 1 x 10 ²⁴ pieces / m ³ or less. This promotes the sub-grain formation of the can body structure when the material aluminum alloy plate is manufactured into a can body and then subjected to a paint baking treatment, thereby improving the resistance to canning of the can body.

By regulating the aggregation of these specific atoms, a 3000-series aluminum alloy plate containing Cu can be manufactured as a can body, and when subjected to a coating baking treatment, the subgrainization is promoted, and a slip in the partially non- The activity of the face becomes possible. Therefore, even when a so-called stain occurs in which an external force at the pin point is applied to the can body at the time of use as a can or during handling, work hardening due to deposition of a new dislocation is developed at the stuck portion, do.

On the other hand, when the average density of the specific aggregate of atoms exceeds 1 x 10 ²⁴ atoms / m ³ of the upper limit value, the aggregate of atoms is excessively large, so that the material aluminum alloy plate is canned, , The sub-grain formation of the can body structure does not proceed. For this reason, when an external force is applied to a can in use or during handling, a work hardening due to the deposition of a new dislocation is difficult to occur in the stuck portion, and the resistance to piercing is not improved.

The definition of the upper limit of the average density of this specific group of atoms in the present invention includes zero that can not be detected or measured because of the aggregation of these atoms and is considered to be absent. However, the number of the aggregates of these atoms does not need to be zero, and the average density should be regulated to 1 x 10 ²⁴ / m ³ or less. Therefore, a preferable lower limit As for the public, the existence of 1 x 10 < ²² > / m < ³ >

3D Atom probe Electro ion microscope:

A method of measuring the average density of the aggregates of atoms by means of a three-dimensional atom probe electric field ion microscope is exemplified in, for example, Japanese Patent Laid-Open Publication No. 2011-184795 in the field of an aluminum alloy material. In this publication, an atomic aggregate of a 5000-series aluminum alloy plate containing Zn contributing to improvement in press formability is measured by a three-dimensional atom probe ion microscope. As a cluster of these atoms, a total of 20 or more of the Mg atoms and / or Cu atoms are included, and in addition to any of the contained Mg atoms and Cu atoms, And one atom of another atom adjacent thereto is defined as 0.80 nm or less. An aluminum alloy plate in which generation of a stretcher strain mark is suppressed by incorporating an aggregate of atoms satisfying such conditions at an average density of 1 x 10 ⁴ / μm ³ or more has been proposed .

The analysis by the three-dimensional atom probe field ion microscope is widely used for analysis of tissues and atomic assemblies in the fields of high-density magnetic recording films and electronic devices, aluminum alloys, steels and copper alloys.

A 3D Atom Probe Field Ion Microscope (hereinafter also referred to as 3DAP) is a field ion microscope (FIM) equipped with a time-of-flight mass spectrometer. With such a constitution, it is a local analyzer capable of observing individual atoms of a metal surface with an electric field ion microscope and identifying these atoms by flight time mass spectrometry. Also, since 3DAP can analyze the type and position of atoms emitted from a sample at the same time, it is a very effective means in structure analysis of an aggregate of atoms.

In this 3DAP, the ionization phenomenon of the sample atoms themselves under a high electric field called electric field evaporation is utilized. When a high voltage is applied to the sample required for the sample atomic field to evaporate, the atoms are ionized from the surface of the sample, which exits the probe hole and reaches the detector.

This detector is a position sensitive detector that measures the time of flight to the detector of individual ions along with the mass analysis of individual ions (identification of the atomic species) ) Can be determined at the same time. Therefore, the 3DAP has the advantage that the atomic structure at the tip of the sample can be reconfigured and observed three-dimensionally because the position and atomic species of the atom at the tip of the sample can be measured at the same time. Further, since the electric field evaporation occurs sequentially from the front end face of the sample, the depth direction distribution of atoms from the tip of the sample can be irradiated at the resolution of the atomic level.

Since this 3DAP uses a high electric field, it is necessary that the sample to be analyzed should have high conductivity such as metal, and furthermore, the shape of the sample is generally required to be a fine needle shape having a tip diameter of about 100 nm or less have. Therefore, a sample is taken from the central portion of the plate thickness of the aluminum alloy plate, and the sample is cut and electrolytically polished by a precision cutting device to prepare a sample having an ultrathin needle tip for analysis. As a measuring method, for example, "LEAP3000" manufactured by Imago Scientific Instruments was used, and a high pulse voltage of 1 kV order was applied to an aluminum alloy plate sample whose tip was formed into a needle shape, and millions of atoms were continuously . Ions are detected by a position sensitive detector and the ion mass analysis (identification of atomic species elements) is performed from the flight time from when the pulse voltage is applied to the individual ions released from the tip of the sample to reach the detector I do.

By using the property that the electric field evaporation occurs regularly from the front end face of the specimen in order, coordinates in the depth direction are appropriately given to the two-dimensional map indicating the arrival position of the ions, and analysis software "IVAS" And performs three-dimensional mapping (atomic structure in three dimensions: construction of atom map). Thereby, a three-dimensional atom map at the tip of the sample is obtained.

Then, the atomic cluster (cluster) is analyzed by using the Maximum Separation Method, which is a method of defining atoms belonging to the precipitate or cluster, in addition to the three-dimensional atom map. This method is a method in which the maximum spacing d _max between designated solute atoms and the minimum number of atoms N _min constituting the cluster are given as parameters. In this analysis, clusters are defined by defining the maximum spacing d _max between Mg and Cu atoms to be 0.80 nm and the total number of atomic atoms N _min of Mg and Cu atoms to be five. From this result, the dispersion state of the cluster is evaluated, and the number density of clusters (the specified average density at three or more measurement samples) is quantified.

Detection efficiency of atoms by 3DAP:

However, the detection efficiency of atoms by these 3DAPs is about 50% of the atomized atoms at the present time point, and the remaining atoms can not be detected. If the variation of the detection efficiency of the atoms by the 3DAP is greatly changed in the future, there is a possibility that the measurement result of the average number density (number / m ³ ) of the aggregate of atoms defined by the present invention have. Therefore, in order to obtain reproducibility in the measurement of the average number density of the aggregates of these atoms, it is preferable that the detection efficiency of the atoms by 3DAP is approximately constant at approximately 50%.

(Manufacturing method)

Next, a method of manufacturing an aluminum alloy plate for a DI can body according to the present invention will be described. The aluminum alloy sheet of the present invention is characterized in that it comprises a casting step of melting and casting an aluminum alloy having the above composition into an ingot, a step of homogenizing the ingot by heat treatment, a step of hot rolling the homogeneous ingot, And a cold rolling step in which the hot-rolled sheet is cold-rolled without being annealed. In this manufacturing method, the ingot is subjected to the second heat treatment under the conditions described below and the cold rolling is carried out under specific conditions to be described later, so that the aluminum alloy sheet after cold rolling is subjected to the structure specified in the present invention do.

(Melting, casting)

First, an aluminum alloy is melted and cast by a known semi-continuous casting method such as a DC casting method, and cooled to a temperature below the solidus temperature of the aluminum alloy to obtain an ingot. If the casting speed is less than 40 mm / min or the cooling rate is slower than 0.5 캜 / sec, a large amount of coarse intermetallic compound is extracted in the ingot. On the other hand, if the casting speed exceeds 65 mm / minute or the cooling rate exceeds 1.5 deg. C / second, the ingot breakage, the "cavity" or the "shrinkage cavity" tends to occur easily, and the casting yield decreases. Therefore, in casting, the casting speed is 40 to 65 mm / min and the cooling speed is 0.5 to 1.5 ° C / sec. This cooling rate refers to the temperature at the center of the ingot, that is, the temperature at the center of the plane perpendicular to the casting direction. The cooling rate is set to the cooling rate from the liquidus temperature of the aluminum alloy to the solidus temperature.

(Cracking treatment)

It is necessary to homogenize heat treatment (crack treatment) at a predetermined temperature before rolling the ingot. By performing the heat treatment, the internal stress is removed, the segregated solute element is homogenized at the time of casting, and the intermetallic compound crystallized at the time of casting is diffused and solidified to homogenize the structure.

However, in the present invention, the crack treatment is performed twice. This two-time crack is distinguished from the two-stage crack. The two-stage cracking means that after the first cracking, after cooling at 200 ° C or lower, the cooling is stopped at a higher temperature and then the temperature is maintained at the same temperature or after reheating to a higher temperature, Lt; / RTI > On the other hand, in the case of the second crack of the present invention, after the first crack, it is once cooled to a temperature of 200 ° C or lower including room temperature, further reheated, maintained at that temperature for a certain period of time, .

Concretely, first, the first cracking temperature is set at 580 DEG C or higher and lower than the melting point temperature. This cracking temperature is set to 580 DEG C or higher in order to solidify the coarse Al-Fe-Mn compound produced during casting. When the cracking temperature is lower than 580 占 폚, coarse Al-Fe-Mn-based compound remains unhardened, so that the moldability of the cold-rolled sheet to the can body deteriorates.

After this first cracking treatment, it is once cooled to 200 DEG C or lower including the room temperature. At this time, the average cooling rate of the ingot between 500 and 200 占 폚 is set to 80 占 폚 / hour or more. If the average cooling rate between these temperatures is less than 80 캜 / hour, not only the amount of Al-Fe-Mn compound generated during cooling increases but also the aggregate of Mg and Cu atoms regulated by the present invention increases. When this cooling is stopped at a high temperature state (exceeding 200 deg. C) during the second-stage cracking and the second cracking process is continuously performed as in the case of the two-stage cracking, the already dispersed Al-Fe- Therefore, it is necessary to once cool to 200 DEG C or less. If this condition is exceeded, the structure of the portion extending from the cold-rolled sheet for the DI can in the plate-width direction and the plate thickness direction can not be excellent in resistance to canning of the can body.

The second cracking temperature is 450 캜 to 550 캜. The average heating rate of the ingot between the temperatures of 200 to 400 占 폚 in this second crack is set to a rate of 30 占 폚 / hour or more, preferably 30 占 폚 / hour or more. This is because the Mg-Si based compound is produced during the temperature rise in the second crack, and in particular, by setting the average heating rate of the ingot between the temperatures of 200 to 400 캜 to exceed 30 캜 / hour, The generation amount of the Mg and Cu atoms to be regulated is suppressed. If the heating rate is low, the amount of the Mg and Cu atoms to be formed in the aggregate regulated by the present invention can not be suppressed, which may exceed the upper limit.

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

(Hot rolling)

The ingot which has been homogenized in the above-mentioned cracking step is subjected to hot rolling. The hot rolling is carried out under ordinary conditions or under ordinary conditions. First, the ingot is roughly rolled and further subjected to finish rolling to a predetermined thickness Aluminum alloy hot rolled plate is used.

(Cold rolling)

The hot-rolled sheet is cold-rolled without pre-annealing and intermediate annealing between passes and finished with an aluminum alloy sheet having a predetermined sheet thickness. The total rolling ratio (cold working ratio) in the 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. The total rolling ratio in the cold rolling is, of course, determined by the relationship with the desired sheet thickness of the cold-rolled sheet. However, in order to control the average density of aggregates of Mg and Cu atoms within the range of the present invention, , It is preferable to set the above range.

Here, the coiling temperature after cold-rolling needs to be in the range of 120 to 160 캜. If the temperature is not rolled up in such a temperature range, there is a high possibility that the cold rolled steel sheet does not fall within the range of the Mg and Cu atoms defined in the present invention. When the coiling temperature exceeds 160 캜, the average density of the aggregate of Mg and Cu atoms defined in the present invention increases to more than 1 x 10 ²⁴ pieces / m ³ , Subgrain formation when the heat treatment is performed for a minute is suppressed, and the piercing resistance is lowered. On the other hand, when the coiling temperature is in a state such as room temperature of less than 120 deg. C, as in ordinary cold rolling, the strength immediately after this winding becomes high and the elongation is low, so that the cup formability before DI molding is lowered.

Under normal cold rolling conditions, the rolling (rolling) coil and the amount of the lubricating oil or coolant to be used are controlled so as to be sufficient to cool the plate, from the viewpoint of controlling lubrication as well as processing heat generation The temperature becomes about the room temperature. On the other hand, in the present invention, on the contrary, the process heat generation is rather promoted, and the coiling temperature on the coil after cold rolling is set to the high temperature side, and the hot zone is set to 120 to 160 deg. C, preferably 120 to 145 deg.

(DI can making method)

An example of a method of manufacturing a DI can can body from a material aluminum alloy sheet (cold-rolled sheet) according to the present invention will be described below. First, an aluminum alloy sheet according to the present invention is punched out into a disk shape (blanking process), drawn in a shallow cup shape (cupping process), and subjected to DI molding. The drawing and the ironing are repeated a plurality of times to gradually raise the side wall so as to form a user tubular shape having a predetermined bottom surface shape and a height of the side wall. It is preferable that the reduction rate (ironing processing rate) of the side wall of the can body by these processes is 60 to 70%. Then, the edges of the side walls (openings) are cut out and trimmed (trimming). In this state, DI is molded into a thin can body having a thickness of the sidewall of the thinnest portion ranging from 0.085 to 0.110 mm.

Subsequently, the can body is subjected to degreasing and cleaning, and baking is applied to the outer and inner surfaces, respectively, so that the strength in the can axis direction of the sidewall of the thinnest portion is 0.2 MPa or more, . Incidentally, this strength is such that the formed can body is the "heat treatment corresponding to the small portion of the coating film of the can body" according to the present invention, without actually baking (baking) the coating film, It can be substituted for the strength after heat treatment at 200 占 폚 for 20 minutes. When this can body structure is promoted to sub-grain when subjected to this baking treatment (heat treatment), the piercing resistance is improved.

The can body after baking the coating film scales down the opening (necking) and widens the edge of the opening outward (flanging) to become the final can body. When used in beverage or food applications, the contents (beverage, food) are filled into the can body from the opening, and the can cap produced in a separate step is sealed in the opening by being sealed.

Example

Although the embodiments for carrying out the present invention have been described above, the embodiments in which the effects of the present invention are confirmed will be specifically described below in comparison with the comparative examples which do not satisfy the requirements of the present invention. On the other hand, the present invention is not limited to this embodiment.

(Aluminum alloy plate for public use)

An alloy ingot having a composition shown in Table 1 was melted and semi-continuous casting was used to produce an ingot at a casting speed and a cooling rate in the above-described preferable numerical values in all the examples in common.

The ingot was cracked twice in the above two times. In each of the examples, the average cooling rate (° C / hour) at 500 to 200 ° C until the room temperature was once commonly cracked at the cracking temperature of 600 ° C for 4 hours was measured as shown in Table 2 I changed it several times and cooled it. Thereafter, as the second crack, the ingot was heated again from room temperature, and the average heating rate (° C / hour) at 200 to 400 ° C was changed to various values as shown in Table 2. In all the examples, And a second cracking treatment at a cracking temperature of 4 hours was carried out.

In all of the examples, hot rolling was started at a temperature of 500 캜, and a hot rolled plate having a plate thickness of 2.0 to 3.0 mm was formed at an end temperature of 330 캜.

In all of the examples, cold rolling was carried out without performing intermediate annealing during roughing (annealing) of the hot-rolled sheet, and the cold-rolling was carried out to obtain a sheet having a thickness of 0.28 mm and a sheet width of 2000 mm Shaped long aluminum alloy plate. At this time, the total (total) rolling rate (%) and the coiling temperature (占 폚) of the cold rolling were changed variously as shown in Table 2.

On the other hand, the symbol "-" in the chemical composition of the aluminum alloy sheet of Table 1 indicates that the content is 0%, which is below the detection limit and does not substantially contain this element.

(Can body)

The aluminum alloy sheet thus obtained was subjected to a capping process and a DI process (ironing process rate: 65 to 70%) and trimmed to have an outer diameter of about 66 mm, a height (length in the can axis direction) of 124 mm, A can body of a user tubular shape was used. After the can body was degreased and cleaned, a heat treatment was performed under the conditions of 200 占 폚 for 20 minutes in which a bake portion at the time of coating was assumed (simulated) to obtain a can body seal material.

〔evaluation〕

The average density of the aggregates of the atoms defined in the present invention was measured by the above-described measurement method using the three-dimensional atom probe ion microscope and analysis analysis software for the structure of the aluminum alloy cold-rolled sheet. DI moldability and 0.2% proof stress on the can body were also measured. Then, the resistance to penetration and the 0.2% proof stress in the can body (after the heat treatment under the above-mentioned paint baking conditions) were also measured and evaluated, respectively. The results are shown in Table 2 which follows Table 1. (The numbers in Tables 1 and 2 are common to each other).

(Tissue measurement by 3DAP)

In the measurement by the 3DAP method, three pieces of test pieces each having a length of 30 mm and a width of 1 mm were cut out from the cold-rolled sheet by a cutting device at intervals of 1 mm in the width direction, and then the test pieces were finely processed by electrolytic polishing, A needle-shaped sample having a radius of the tip of about 50 nm was prepared. Therefore, the measurement point is measured near the central portion of the plate thickness. Performing a 3DAP measured in a sample forming the distal end to the needle using the "LEAP3000", by measuring the density (pieces / m ³⁾ of an aggregate of atoms defined in the present invention of the three test specimens, respectively, averaged ( Average density). Incidentally, the measurement volume by the 3DAP method is approximately 1.0 × 10 ^-24 to 10 ^-21 m ³ .

(Moldability)

In the DI molding described above, a blank was cut out from one portion in the longitudinal direction center portion of the aluminum alloy cold-rolled sheet coil in the vicinity of the central portion in the plate width direction, and 1,000 sheets in total from three portions in the vicinity of each of the two end portions, (65%) by continuous molding (cupping, DI molding). In the case where defects (tear-off, pinholes, etc.) did not occur at the time of molding, the results were evaluated as "? &Quot;

(Stabbing property)

For each of the examples, it was verified that the resistance to canning of the can made can body, in particular, the plate-width direction of the cold-rolled sheet and the resistance to bending in the plate thickness direction, are generally improved. For this purpose, in all of the examples, a piercing test was carried out on all of the molded aluminum alloy cold-rolled plate coils so as to uniformly include the can made of cans from the three positions of the center and both ends in the plate width direction of the aluminum alloy cold- And evaluated the piercing resistance.

1, the can body was fixed and an internal pressure of 1.7 kgf / cm ² (= 166.6 kPa) was applied so that the rolling direction of the aluminum alloy plate on the sidewall of the can body was the can axis Direction and a hemispherical surface having a radius of 0.5 mm was stuck to a portion having a distance L in the can axis direction of 60 mm from the bottom of the can at a speed of 50 mm / min perpendicularly to the side wall. Then, the load (N) until the stamper passes through the side wall was measured, and the maximum load thus obtained was regarded as the stamper strength.

The results of the piercing resistance test showed that the maximum load of the entire can body was 40 N or more on average and that the entire aluminum alloy cold rolled plate in the plate width direction was excellent in resistance to piercing, Was evaluated as "? &Quot;. On the other hand, the maximum load of the entire can body was less than 35N on the average because it was evaluated as " x " because the resistance to piercing was poor in the plate width direction and the entire plate thickness direction of the aluminum alloy cold rolled plate.

In the present invention, there is provided a handle to use conditions of the DI can, is greater than the pressure in the can inside and outside the car, large deformation of the can body, within a sting St. stricter the condition, the 1.7kgf / cm ² (= 166.6kPa ). ≪ / RTI > Although the actual can body rupture is caused by collision of various shapes, it is impossible to evaluate all of them, and it is required to evaluate by a stricter evaluation method. Therefore, by adopting the condition of lowering the internal pressure and increasing the deformation, it is difficult to increase the stamper strength.

The evaluation of the piercing resistance so far is usually carried out by applying a higher internal pressure of 2.0 kgf / cm ² (= 196 kPa). For this reason, even in the case of the same test material, the test method of the present invention has a strict test condition and a low sticking strength. That is, even if the value of the striking intensity (N) in the test with the internal pressure of 2.0 kgf / cm ² and the value of the striking intensity (N) according to the test method of the present invention are the same or slightly lower , It can be said that the material of the present invention is superior in puncture resistance. In other words, 2.0kgf / my sting even when is excellent in the withstand voltage test in cm ^2, can not be said at all that it is within the sting of the low withstand voltage than that of 1.7kgf / cm ² of the present invention it is excellent.

(0.2% proof)

The tensile test for measuring the 0.2% proof strength of the cold-rolled sheet and the can side of the can body was carried out in accordance with JIS Z 2201 on a cold-rolled sheet and test pieces respectively taken from the side walls of the can body , And the test piece shape was made with JIS No. 5 test piece so that the longitudinal direction of the test piece coincided with the rolling direction (can axis direction). In addition, the crosshead speed was 5 mm / min, and the test piece was cut at a constant speed until it was broken.

As shown in Tables 1 and 2, in each of Examples 1 to 10, the composition of the aluminum alloy is within the range of the present invention and is manufactured under preferable manufacturing conditions. For this reason, in each example of the invention, as shown in Table 2, the cold-rolled sheet is within the range of the average density of the aggregates of atoms defined in the present invention.

As a result, in each of the examples, the aluminum alloy plate was subjected to DI molding with a thin can body having a thickness of the side wall of the thinnest portion of 0.090 mm on the premise that the DI moldability was satisfactory, Of 0.2% in the can axis direction is 280 MPa or more and 350 MPa or less. Furthermore, the resistance to puncture is superior to 35 N or 40 N or more, even though the internal pressure of 1.7 kgf / cm ² (= 166.6 kPa) is strictly evaluated on the can body. That is, in the case of a can body having a thin can wall thickness and a high strength, excellent moldability and excellent piercing resistance under more severe conditions were obtained.

On the other hand, Comparative Examples 11 to 20 in Tables 1 and 2 are outside the composition range of the aluminum alloy, or the conditions for the above cracking and cold rolling are deviated from the preferable conditions of the present invention. For this reason, in each of the comparative examples, the cold rolled sheet deviates from the average density of the aggregates of the atoms specified in the present invention, the 0.2% proof stress is inferior, the DI formability is inferior, and further, all of the stamper is inferior.

In Comparative Example 11, the average cooling rate at 500 to 200 캜 at the time of cooling to room temperature after the first cracking treatment was too small, less than 70 캜 / hour. As a result, the aggregate of atoms defined in the present invention produced during cooling increases, the average density exceeds the upper limit, and the piercing resistance is inferior.

In Comparative Example 12, the average heating rate at 200 占 폚 to 400 占 폚 at the second cracking temperature was too small, less than 30 占 폚 / hour. As a result, the aggregate of atoms defined in the present invention produced during heating increases, the average density exceeds the upper limit, and the piercing resistance is inferior.

In Comparative Example 13, the total rolling ratio in cold rolling was too low, the strength of the can body after the cold-rolled sheet or BH was too low, and the piercing resistance was also inferior.

In Comparative Example 14, the coiling temperature in cold rolling was too high, and the aggregate of atoms defined in the present invention of the cold-rolled sheet increased, resulting in an average density exceeding the upper limit, and the piercing resistance was inferior.

In Comparative Examples 15 to 20 of Tables 1 and 2, the content of any one of Cu, Mn, Mg, Si, and Fe is deviated from the scope of the present invention.

In Comparative Example 15, the amount of Mg is excessively small, and the amount of solid solution Mg is excessively small. In Comparative Example 16, the amount of Mn is excessive. As a result, these comparative examples are inferior in resistance to piercing in the plate width direction when the above-mentioned pressure-resistant condition is strict.

In Comparative Example 17, the amount of Mn is low. In Comparative Example 18, the amount of Si is excessive. In Comparative Example 19, the amount of Fe is excessive. As a result, in these comparative examples, since a defect occurred in the DI molding, it was impossible to put it into practical use for canning, and there was no meaning to carry out the subsequent piercing test.

Comparative Example 20 does not contain Cu. As a result, the strength of the can body is low, and the resistance to penetration in the plate width direction is also inferior when the above-described internal pressure condition is strict.

While the invention has been described in detail and with reference to specific embodiments thereof, it is evident to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention.

The present application is based on Japanese Patent Application (Japanese Patent Application No. 2012-285870) filed on December 27, 2012, the contents of which are incorporated herein by reference.

INDUSTRIAL APPLICABILITY As described above, the aluminum alloy plate (cold-rolled sheet) for DI can bodies according to the present invention can improve the resistance to canning of a can made from an aluminum alloy cold-rolled sheet to a desired level, have. Therefore, it is optimal for an aluminum alloy cold-rolled sheet used for a DI can body in which the thickness of the can wall is thinned and the strength thereof is increased and resistance to piercing under more severe use conditions is required.

Claims (4)

And the balance of Al and inevitable impurities, in terms of mass%, Mn: 0.3 to 1.3%, Mg: 0.7 to 3.0%, Si: 0.1 to 0.5%, Fe: 0.1 to 0.8% And is an aggregate of atoms measured by a three-dimensional atom probe electric field ion microscope, wherein the aggregate of the atoms contains at least 5 or more of Mg atoms and / or Cu atoms in total In addition, even when any one of the Mg atom and the Cu atom contained in these atoms is used as a reference, the distance between any one atom of the reference atom and another atom adjacent thereto is 0.80 nm or less, Is regulated to be 1 x 10 < ²⁴ > pieces / m < ³ > or less. The method according to claim 1,
Wherein the aluminum alloy plate further contains one or two of Cr: 0.001 to 0.1% and Zn: 0.05 to 0.5%. 3. The method according to claim 1 or 2,
Wherein the aluminum alloy plate is DI-shaped into a can body having a thickness of the side wall of the thinnest portion ranging from 0.085 to 0.110 mm, and 0.2% of the can side wall of the can body side wall when the can body is heat- Is an aluminum alloy plate for a DI can body having a strength characteristic of not less than 280 MPa and not more than 350 MPa. The method according to claim 1,
The internal diameter of the can body was set to 1.7 kgf / cm ² (= 166.6 kPa) by applying an internal pressure to the can body at a distance L = 60 mm in the can axis direction from the can bottom of the can body side wall, Which is a hemispherical surface having a radius of 0.5 mm is pushed perpendicularly to the side wall of the can body at a speed of 50 mm / min, and the maximum value of the load measurement values until the needle passes through the sidewall of the can body is 35 N or more, Aluminum alloy plate for.

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