KR20160084862A - Manufacturing method of aluminum alloy sheet for di can body - Google Patents

Abstract

The aluminum alloy sheet of the present invention can control the cracking condition and the hot rolling condition of the ingot at the time of producing the aluminum alloy sheet for the specified 3000 series DI can body to produce a coarse Mn intermetallic compound It is possible to secure a certain amount of Mg in a specific amount and to secure a certain amount of Mg in a certain amount.

Description

TECHNICAL FIELD [0001] The present invention relates to a method of manufacturing an aluminum alloy plate for a DI can body,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a packaging container used for beverage and food applications, and more particularly to an aluminum alloy plate which is subjected to DI forming processing with the body of a beverage can.

BACKGROUND OF THE INVENTION [0002] Currently, one of packaging containers used for beverage and food uses includes a bottomed cylindrical body (can body) having a bottom and a side wall integrally formed thereon, and a disk- (Can lid) is known. As materials for such can, aluminum alloy plates such as AA to JIS3000 series are widely applied 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 such as a beverage can, in particular, can be formed by a multi-step processing of drawing-ironing process called DI (Drawing and wall Ironing) It is often molded. Then, the opening portion is reduced in diameter by coating, baking, and necking, and the rim of the opening portion is enlarged outward by flanging to form a can body. Finally, the contents (beverage, food) are filled in the body part, and the lid part is sealed by seaming in the opening part. The can made by such a manufacturing method is called a DI can (hereinafter referred to as " can " as appropriate) and widely circulated.

BACKGROUND ART Conventionally, in order to reduce the cost of beverages packed with such a can made of an aluminum alloy, the can as a packaging container has been made thin as a measure for reducing the weight and reducing the raw material (aluminum alloy). As a result, the thickness of the side wall (the thinnest part) of the current aluminum alloy can is about 0.105 to 0.110 mm except for the coating film. However, in such thinned cans, particularly when the projection is pressed against the side wall (peripheral surface) having a thin plate thickness (press-fitted), the tip thereof penetrates through the side wall and the hole (pin hole) There is a case where a problem occurs. 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 lid 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. Further, also in the flanging process, when the rim of the opening portion is enlarged, there is a case where the end portion of the opening portion is broken (flange breakage).

Therefore, in order to prevent the occurrence of pinholes on the side wall and the flange breakage of the openings of the thinned can, that is, to improve the puncture resistance and flanging workability (can expandability) of the side wall, Improvement of edition is proceeding.

For example, Patent Document 1 discloses a method of designing a can body formed by DI molding or drawing molding from a cold-rolled sheet of an aluminum alloy cold-rolled plate having an 3000 alloy composition. That is, when the thickness of the can body subjected to the heat treatment corresponding to the coating baking 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 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 of the coating film or the like is removed can be obtained in terms of the puncture strength of the can having a wall thickness of 0.105 mm to obtain the puncture strength of 35 N or more. Therefore, the thickness of the wall portion for obtaining the stuck 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 stiffing strength.

Various techniques have also been proposed to control the intermetallic compound of an aluminum alloy cold-rolled sheet having a composition of 3000 grades to improve puncture resistance. For example, Patent Document 2 discloses a technique of distributing an intermetallic compound at a specific density and a specific area ratio on the surface of an aluminum alloy cold rolled plate having a 3000 series composition. Thus, when the side wall thickness including the outer surface and the inner surface 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% Is set to more than 290 MPa and less than 330 MPa, whereby the puncture resistance is excellent.

Patent Documents 3 and 4 also disclose a technique of improving the strength (puncture resistance) and toughness by controlling the distribution density and the area ratio of an intermetallic compound of a predetermined size in an aluminum alloy cold rolled sheet having a composition of 3000 grades . Also, in Patent Document 5, an aluminum alloy cold-rolled sheet having a 3000-series composition is subjected to DI molding at a predetermined processing rate and then heat-treated at 210 to 250 캜 to control work hardening and tensile strength by DI molding, Discloses a technique for improving the performance.

Also, in the field of aluminum alloy cold-rolled steel sheets having a composition of 3000 grades for cans, techniques for improving the DI moldability and strength, etc. in the case of thinning by specifying a high amount of Si, Cu, Mn, .

Incidentally, this is not a DI can, nor an object of improvement of sticking resistance. However, in Patent Document 6, thermal deformation of the aluminum alloy cold-rolled sheet for bottle can during coating heat treatment is prevented, strength of the can after heat treatment is secured, In order to obtain a high bottle can, the amount of Cu and Mg dissolved in the solution separated from the precipitate having a particle size exceeding 0.2 탆 by 0.05% to 0.3% and 0.75 to 1.6% %, Respectively.

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 Japanese Patent No. 4019083

However, the handling and use conditions of the DI can become more stringent under such conditions that the pressure difference between the inside and the outside of the can becomes larger and the can body becomes more susceptible to deformation. Accordingly, the stiffness required for the can body Strength) is also more strict. On the other hand, the above-described prior art still has room for improvement in order to achieve this stringent puncture resistance.

For example, there is a limitation in setting the stiffing strength, which is greatly influenced by the presence of a compound in a tissue, to the required level only by controlling the Mg content as in Patent Document 1. [ Further, the technique disclosed in Patent Document 3 improves the puncture resistance by making the thickness of the sidewall of the can larger than 0.110 mm, and it can not cope with the thinning of the sidewall thickness of the can. In addition, the technique disclosed in Patent Document 5 is not suitable for the requirements of the can manufacture side in the case of performing heat treatment at a lower temperature because the baking temperature range at the time of coating the can is high.

Further, the control of the intermetallic compounds disclosed in Patent Documents 3 to 5 is effective for reliably improving the piercing resistance. However, in order to evaluate whether or not the requirements of Patent Documents 3 to 5 are satisfied, application of a scanning electron microscope (SEM) such as a magnification of 500 times is indispensable as means for detecting an intermetallic compound to be controlled. However, as is well known, a cold rolled plate having a wide and long coil state can be DI cans made of several to several tens of can bodies over the whole area in the width direction and the rolling direction.

Even if the cold rolled sheet having a wide and long coil state is optimized, even if the production conditions are optimized, the distribution of the temperature and the deformation in the plate width direction and the like are different, and the intermetallic compound A deviation occurs in the number density, the area ratio or the distribution, of course.

Therefore, in the microscopic observation by the microscope as disclosed in Patent Documents 3 to 5, even if the measurement points are increased, the cold-rolled steel sheet, which is DI can manufactured with a large number of can bodies, The number density, the area ratio, or the distribution of the intermetallic compound as the microstructure over the area of the microstructure are not macroscopically represented. In the microscopic observation, an arbitrary one point is measured in the direction of the thickness of the plate, and the deviation of the texture in the plate thickness direction can not be taken into consideration. As a result, there is a limit to improving substantially the puncture resistance of a can body manufactured from a long and wide cold rolled sheet.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and it is an object of the present invention to provide an aluminum alloy plate for a DI can body which can improve stiffness (puncture strength) of a can body manufactured from a long and wide cold- The purpose.

The aluminum alloy sheet for a DI can body according to the present invention comprises 0.3 to 1.3% of Mn, 1.0 to 3.0% of Mg, 0.1 to 0.5% of Si, 0.1 to 0.8% of Fe, And the remaining amount is composed of Al and inevitable impurities. The structure of the aluminum alloy plate is such that the particle size separated by the residue extraction method with hot phenol is larger than 0.1 mu m It is assumed that the amount of Mn contained in the compound is 1.0% or less (including 0%), and the solubility of Mg in the solution separated by the residue extraction method with hot phenol is 0.7% or more and 2.5% or less.

Here, the aluminum alloy sheet may further contain at least one of Cu: 0.05 to 0.4%, or Cr: 0.001 to 0.1% and Zn: 0.05 to 0.5%. Further, the aluminum alloy plate was subjected to DI molding with a can body having a thickness of the side wall of the thinnest part in the range of 0.085 to 0.110 mm, and a 0.2% proof stress in the can axis direction of the sidewall after the heat treatment at 200 캜 for 20 minutes And has a strength of 280 MPa or more and 350 MPa or less. Further, the aluminum alloy plate is DI-molded into a can body having a thickness of the side wall of the thinnest portion in the range of 0.085 to 0.110 mm. When the can body is heat-treated at 200 占 폚 for 20 minutes, % Strength is not less than 280 MPa and not more than 350 MPa. The puncture resistance of the aluminum alloy plate was measured by applying an internal pressure of 1.7 kgf / cm 2 (= 166.6 kPa) to the can body, and measuring the distance from the can bottom of the can body sidewall to the distance L = , The tip of the stabbing needle having a radius of 0.5 mm was stuck at a speed of 50 mm / min perpendicularly to the side wall of the can body, and the maximum value of the load measurement until the stabbing needle passed through the side wall of the can body was 35 N or more .

As described above, the conventional control of the intermetallic compound is effective for improving the puncture resistance (puncture strength) surely. If the intermetallic compound having a large size is present in the can body structure, The property is deteriorated.

However, in the conventional definition of the area ratio, the size and the number density of the micro intermetallic compound in the aluminum alloy sheet structure, as described above, the means for detecting the intermetallic compound to be controlled is a scanning electron It is impossible to represent macroscopically the microstructure of the cold rolled sheet having a wide coil state in the width direction or in the sheet thickness direction by micro observation such as a microscope (SEM) .

Therefore, the inventors of the present invention have found that, by using analytical means for obtaining macroscopic and average information by a residue extraction method using thermal phenol without using a micro observation means such as a scanning electron microscope (SEM) (Intermetallic compound) in a wide cold rolled sheet, particularly in the width direction or the thickness direction, is macroscopically controlled. Thereby, the level of piercing can be improved to a target level.

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

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

(Aluminum alloy composition)

The composition of the aluminum alloy sheet according to the present invention contains 0.3 to 1.3% of Mn, 1.0 to 3.0% of Mg, 0.1 to 0.5% of Si and 0.1 to 0.8% of Fe, And inevitable impurities. A composition containing 0.05 to 0.4% of Cu in the aluminum alloy composition may be used. The percentages of the composition (content of each element) represent% 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 molded into the can body, the strength of the side wall is increased to secure buckling strength and puncture resistance. Further, Mn forms an Al-Fe-Mn 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. When the content of Mn is less than 0.3%, these effects are insufficient. For this reason, the content of Mn is set to 0.3% or more, preferably 0.4% or more. On the other hand, if the content of Mn exceeds 1.3%, the solid solution strengthening of the aluminum alloy sheet becomes excessive, the workability is lowered, and the amount of Al-Fe-Mn intermetallic compound produced increases, and the piercing resistance is lowered. Therefore, the upper limit of Mn is set to 1.3%, preferably 1.1%, more preferably 1.0%.

(Mg: 1.0 to 3.0%)

Mg has the effect of improving the strength of the aluminum alloy. When the content of Mg is less than 1.0%, the sidewall strength becomes low when the aluminum alloy plate is molded into the can body, and the piercing property is insufficient. 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 breakage) during ironing, It gets easier. Therefore, the Mg content is in the range of 1.0 to 3.0%, and the upper limit of the Mg content is preferably 2.5%.

(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-Fe-Mn-Si intermetallic compounds and Mg-Si intermetallic compounds are formed and the piercing resistance is lowered. For this reason, 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 but forms an Al-Fe-Mn intermetallic compound in the aluminum alloy and is appropriately dispersed so that recrystallization after hot rolling is promoted to improve the workability of the aluminum alloy plate . Fe is also useful in promoting crystallization and precipitation of Mn and controlling the amount of Mn in the aluminum matrix and the dispersed state of Mn-based intermetallic compounds. Therefore, the content of Fe is 0.1% or more, preferably 0.3% or more. On the other hand, if the Fe content is excessive, large intermetallic compounds having a size exceeding 15 mu m in diameter are liable to be generated, and DI moldability and puncture resistance are also lowered. Therefore, the upper limit of the Fe content is set to 0.8%, preferably 0.7%.

(Cu: 0.05 to 0.4%)

Cu increases the strength by solid solution strengthening. Therefore, the lower limit of the content of Cu is preferably 0.05% or more, more preferably 0.1% or more. On the other hand, when Cu is excessive, high strength is easily obtained but becomes excessively hard, so that the formability is deteriorated and the corrosion resistance is also lowered. 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%)

Examples of the element for improving the strength of the effect of Cu include Cr and Zn. One or two of Cr: 0.001 to 0.1% and Zn: 0.05 to 0.5% may be added in addition to or in place of Cu. . The content of Cr when selectively contained is 0.001% or more, preferably 0.002% or more. On the other hand, if 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, there are inevitable impurities. For example, when the inevitable impurities are Zr: 0.10% or less, Ti: 0.2% or less, preferably 0.1% or less, B: 0.05% or less, preferably 0.01% , It is allowed to be contained without affecting the characteristics of the aluminum alloy sheet according to the present invention. Among them, Ti has the effect of making crystal grains finer. When the content of Ti is too small, 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)

In order to improve the puncture property (puncture strength), the present invention also uses an intermetallic compound such as an Al-Fe-Mn compound in the structure of an aluminum alloy plate for a DI can body or a DI can body formed by DI- Control of the amount of Mg and the control of the solid solution Mg.

(The amount of Mn contained in the compound)

The mechanism of pinholes generated when protrusions are press-fitted into the side wall of the can is a mechanism of protruding to the inside of the can in a caulked shape centered on the portion where the protrusions contact, as disclosed in Patent Document 4 (A sloped surface of the trigger) at the central portion, and a crack is generated from the end of the shear end (the inner surface of the can). This crack is propagated along the shear stage to break, and if the amount of the intermetallic compound, particularly, the intermetallic compound having a large size is present in the reduced thickness portion, it tends to break.

However, in micro regulations such as area ratio, size, and number density of intermetallic compounds using observation means such as a scanning electron microscope (SEM), as described above, in the plate width direction of the DI can cold- It is impossible to macroscopically represent the structure of the area over the direction. As a result, the piercing property of the can body manufactured from the cold-rolled sheet can not be substantially improved.

Therefore, in the present invention, the cold-rolled steel sheet having a wide and elongated coil state can be obtained by means of macroscopic analysis means, that is, by means of a residue extraction method using hot phenol, without using such a micro- The interstitial intermetallic compound at the site across the direction is macroscopically controlled. That is, the amount of Mn (amount of Mn in the residue of the compound) contained in the compound as the residue separated by the residue extraction method with hot phenol (the amount of Mn in the residue of the compound) And an Al-Fe-Mn-based compound, which is to be used as a raw material.

The starting point of the fracture at the time of piercing is a coarse compound such as an Al-Fe-Mn system, which contains Mn in common and has a particle size exceeding 0.1 탆. At this point, the aluminum alloy cold rolled sheet for the DI can body or the DI can body sample subjected to the DI casting by dissolving it by hot phenol was subjected to separation by a filter of 0.1 mu m mesh (Mn precipitation amount) of Mn contained in the compound as a residue as a residue is measured, Mn of an Al-Fe-Mn type or the like, which is the starting point of the fracture described above, The amount of the compound in the tissue of the plate or can body of the compound can be determined.

Incidentally, the content of Mn contained in the compound as the above-mentioned residue, which is the structure of the aluminum alloy cold rolled plate for the DI can body, or the content of Mg in the separated solution described below, (Even when the side wall portion of the DI can body is measured as a sample), the difference between the values is a difference in value depending on the area of the aluminum alloy cold rolled plate, . Therefore, an aluminum alloy cold rolled sheet for a DI can body may be measured as a sample, or a side wall of a DI can body in which an aluminum alloy cold rolled sheet for a DI can body is DI-shaped may be measured as a sample.

In the present invention, the amount of a coarse compound having a particle size exceeding 0.1 mu m containing Mn such as Al-Fe-Mn in the structure of this plate or can body is measured by a method of separating 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 the DI can body was DI-molded into a can body having a thickness of the side wall of the thinnest part in the range of 0.085 to 0.110 mm, and the can body was subjected to heat treatment (200 占 폚 for 20 minutes ) So that the puncture resistance of the DI can body is improved when the 0.2% proof stress in the can axis direction of the can body side wall is 280 MPa or more and 350 MPa or less.

In the present invention, the content of Mn contained in the compound as the residue is defined as "average" in order to macroscopically control the amount of the Mn-based intermetallic compound in the width direction of the wide cold-rolled sheet. In the plate width direction of the cold rolled sheet having a width of 1000 mm or more, deviation in the structure state is liable to occur due to the difference in the temperature and deformation distribution in the production. In order to increase the uniformity of the structure by suppressing this deviation and improve the piercing property of the DI can body manufactured from each can manufacturing site in the plate width direction of the cold-rolled sheet substantially (uniformly or uniformly) Quot; average " of each can manufacturing site.

For this purpose, as in a later-described embodiment, a can making portion in the plate width direction of the plate at three positions in the plate width direction center portion of the longitudinal direction center portion of the cold-rolled plate and two positions at both end portions in the plate width direction from the center portion Sampling is performed from a plurality of representative points to collect a sample. Then, the amounts of Mn-based intermetallic compound (the content of Mn contained in the compound as the residue) of each sample of these plates were measured, and the Mn-based intermetallic compound content was defined as an average value obtained by averaging these measured values, .

When the average content of Mn exceeds 1.0%, there are too many coarse intermetallic compounds having a particle size exceeding 0.1 탆 and containing Mn such as Al-Fe-Mn in the structure of the plate or can body Loses. As a result, when the can body is the above-mentioned thin film and the strength is high and the use environment is strict, the puncture resistance is lowered.

(Mg content in solid solution)

The increase in the amount of Mg in solid solution improves the work hardening property by strengthening the solidification of the plate or the can body and improves the deformability of the plate or the can body when the projection is pushed into the sidewall of the can (piercing) Thereby improving the stability. Therefore, in the present invention, the Mg content of the solid solution of the plate or the can body is set to 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 the hot phenol.

Mg contains almost all of Mg added or contained when the amount of other elements is small, but when the content of other elements is large, the amount of Mg depends on the content of these other elements. Therefore, when solidification of the solid solution of the plate or the can body is ensured, it is necessary to directly measure and control the high capacity, not the ordinary Mg content.

Therefore, in the present invention, the average solid content of Mg in the plate or the can body is set to 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 the hot phenol, Is DI molded into a can body having a thickness of the sidewall of the thinnest portion of 0.085 to 0.110 mm and the 0.2% proof stress in the can axis direction of the sidewall after the heat treatment corresponding to the baking of the coat is 280 MPa to 350 MPa Thereby improving the puncture resistance. The Al-Fe-Mn compound, which is the starting point of the fracture, is reduced, and the puncture resistance of the DI can body, which is thinned and made stronger, is improved to a desired level.

Specifically, an internal pressure of 1.7 kgf / cm 2 (= 166.6 kPa) was applied to the above-mentioned can body, and a tip having a radius of 0.5 mm from the can bottom of the can body side at a distance L = The stabbing needle is stuck at a speed of 50 mm / min in a direction perpendicular to the side wall of the can body, and is increased to a level of 35 N or more at the maximum value of the load measurement until the stabbing needle passes through the side wall of the can body.

In the present invention, the "average" of the amount of Mg in the plate or the can body (the content of Mg in the solution separated by the residue extraction method using the above-mentioned thermal phenol) is defined as the ratio of the content of Mn contained in the compound as the above- Similarly, to improve the puncture resistance of a can body manufactured from a cold-rolled sheet to a desired level. In other words, in order to control the Mg solubility of the cold-rolled sheet particularly in the can-making area in the plate-width direction, like the Mn described above, The solubility of each Mg in each solution separated by the residue extraction method of each sample taken from the three representative sites of the can manufacturing site was measured and the average value of the measured values was averaged to determine the Mg solubility .

When the average high-molecular weight of Mg in the plate or the can body is excessively reduced to less than 0.7% in terms of the Mg content in the solution separated by the above-mentioned hot phenol residue extraction method, the Al-Fe-Mn system Even if the amount of water is reduced, it is impossible to improve the puncture resistance of the DI can body, which has been thinned and made stronger, to a desired level or higher. On the other hand, the larger the average solid content of Mg is, the higher the piercing resistance is. However, if the solid content of Mg exceeds 2.5% and the Mg content is excessively large, the proof strength of the cold-rolled sheet becomes remarkably high due to the strengthening of Mg, The workability is lowered, and the tear-off is likely to occur. Therefore, with only the control of the amount of solid solution Mg, the stampering property and the can manufacturing processability (DI moldability) are a trade-off.

(Manufacturing method)

Next, a method for producing an aluminum alloy plate in 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 of the above-mentioned component into an ingot, a step of homogenizing the ingot by heat treatment, a step of hot rolling the homogenized ingot, Rolled steel sheet, and a cold-rolled steel sheet obtained by cold rolling without annealing the hot-rolled sheet. In this manufacturing method, the ingot is subjected to the heat treatment for two times under the conditions described below and the hot rolling is carried out under the conditions described later, and the aluminum alloy plate structure after cold rolling is subjected to the above- The average content of Mn in the separated residue compound by thermal extraction with hot phenol is 1.0% or less (including 0%), and the average amount of Mg is determined by Mg Is not less than 0.7% and not more than 2.5%.

(Melting, casting)

First, the aluminum alloy is melted and cast by a known semi-continuous casting method such as the DC casting method and cooled to a temperature lower than the solidus temperature of the aluminum alloy to obtain an ingot. If the casting speed is slower 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 ° C / second, the ingot breakage or "blowhole" easily occurs and the casting yield decreases. Therefore, in casting, the casting speed is 40 to 65 mm / min and the cooling rate 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, and the cooling rate from the liquidus temperature of the aluminum alloy to the solidus temperature.

(Cracking treatment)

It is necessary to perform a homogenization heat treatment (cracking treatment) at a predetermined temperature before rolling the ingot. By performing the heat treatment, the internal stress is removed, the solute element segregated at the time of casting is homogenized, 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 cracking is distinguished from the two-stage cracking. The two-stage cracking means that after the first cracking, cooling is carried out at a higher temperature without cooling to 200 DEG C or lower, and after the cooling is stopped at that temperature, the temperature in that state or the reheating temperature And then hot rolling is started. On the other hand, the second cracking of the present invention means that after the first cracking, the steel sheet is cooled to a temperature of 200 ° C or lower including the room temperature, reheated again, maintained at that temperature for a certain period of time, will be.

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, the coarse Al-Fe-Mn compound remains without being solved, 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. When 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 amount of Mg-Si compound increases and the amount of dissolved Mg is decreased. 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 in the plate width direction and the plate thickness direction of the cold-rolled sheet for DI can can not be made excellent in puncture property of the can body.

The second cracking temperature is 450 캜 or higher and 550 캜 or lower. The average heating rate of the ingot between the temperatures of 200 to 400 DEG C in the second crack is set to a rate exceeding 30 DEG C / hour. This is because the Mg-Si compound is generated during the temperature rise in the second crack, but when the average heating rate of the ingot between the temperatures of 200 to 400 캜 is made to exceed 30 캜 / hour, It is possible to reduce the amount of coarse Al-Fe-Mn compound produced during the second cracking or hot rolling as well as to increase the amount of solid solution Mg have. Therefore, it is possible to satisfy the Mn amount and the Mg high-molecular weight specified in the residue extraction method using the hot phenol, and to improve the puncture resistance. If the heating rate is low, the Mg-Si-based compound is not produced at a high density and is not reusable in the process of raising the temperature to 450 ° C or higher, so that the amount of Mg in solid solution can not be increased, and during the second cracking or hot rolling The amount of the crude Al-Fe-Mn compound to be produced is also increased. Therefore, it is impossible to satisfy the Mn amount and Mg solubility defined in the residue extraction method using the hot phenol, and the possibility that the piercing resistance can not be improved is high. As a result, it is impossible to make the structure of the portion extending in the plate width direction and the plate thickness direction of the cold-rolled sheet for DI can be excellent in puncture resistance of the can body.

When each of these first and second cracking treatment times is less 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, it is preferable that each of the first and second crack processing times is 2 to 8 hours, but it is not particularly limited.

[Hot rolling]

The ingot homogenized in the cracking step is subjected to hot rolling. First, the ingot is rough-rolled and further subjected to finish rolling to obtain an aluminum alloy hot-rolled plate having a predetermined thickness.

(Hot rolling)

Hot rolling is started in a temperature range of 450 ° C or higher and 550 ° C or lower. If the rough rolling starting temperature is lower than 450 占 폚, the amount of the Mg-Si compound precipitated during the rough rolling increases and the amount of dissolved Mg is reduced, and rolling itself becomes difficult. On the other hand, when the rough rolling start temperature exceeds 550 캜, the surface properties of the plate deteriorate due to seizing during rolling.

In addition, the time between passes in the rough rolling and the time required between the rolling execution (pass) and the next rolling (pass) are also made as short as possible. The time between these passes is preferably as short as possible within 100 seconds. Here, the time between passes indicates a difference in mill passage time at the center position in the longitudinal direction of the plate. The amount of Al-Fe-Mn-based compound or Mg-Si-based compound precipitated during rough rolling increases as the reduction rate in the thin plate thickness region is lower and the time between passes becomes longer. Further, in this hot rough rolling, the lowest normal speed is set to 50 m / min or more in normal speeds of all passes several tens of times from several circuits in the case of a reverse mill. The steady speed referred to here is a speed at which the rolling speed (line speed) per one pass is highest and becomes constant. The rolling time becomes longer and the amount of the Al-Fe-Mn-based compound generated during cooling increases at a speed at which the normal speed (the lowest normal speed in the pass) which is lowest in the comparison in the entire pass in hot rolling is less than 50 m / , The residual Mn amount becomes excessive. Therefore, if these conditions are exceeded, it is impossible to satisfy the Mn amount and Mg solubility defined in the residue extraction method with hot phenol, and the desired puncture property of the can body can not be obtained.

The finish temperature of this hot rough rolling is preferably 400 DEG C or higher. When the hot rolling is divided into rough rolling and finish rolling, and when the end temperature of the hot rough rolling is excessively lowered when the hot rolling is continuously performed, the rolling temperature is lowered in the hot rolling in the next step, and edge cracking is likely to occur.

(Hot finish rolling)

The hot-rolled aluminum alloy sheet is hot-finished and rolled quickly, such as continuously. It is possible to prevent the Al-Fe-Mn-based compound and the Mg-Si-based compound from being increased by rapid hot rolling. The hot-rolled aluminum alloy sheet is preferably subjected to hot finish rolling within 5 minutes, preferably within 3 minutes. The finish temperature of the hot finish rolling is preferably 300 DEG C or higher. When the temperature is less than 300 캜, the temperature is excessively low and the entire plate is not recrystallized, resulting in a partially processed structure. In particular, the deviation in the rate of the elongation in the plate width direction increases.

[Cold rolling]

The aluminum alloy hot-rolled plate is cold-rolled without annealing and finished with an aluminum alloy plate of a predetermined plate 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.

[How to make DI can]

An example of a method for manufacturing a DI can can body from an aluminum alloy plate (cold rolled plate) according to the present invention will be described below. First, an aluminum alloy sheet according to the present invention is punched (blanking) into a disk shape, drawn in a shallow cup shape (cupping), and subjected to DI molding. These drawing processing and ironing processing are repeated a plurality of times to gradually increase the sidewall so as to form a tubular shape having a predetermined bottom shape and a bottom wall height.

The plate thickness reduction ratio (ironing processing rate) of the sidewall of the can body by these processes is preferably 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 degreased cleaned, baked on the outer surface and the inner surface, respectively, and baked, and the strength in the can axis direction of the sidewall of the thinnest portion is set to a high strength of about 0.2 MPa to about 350 MPa . Incidentally, this strength is such that, even if the above-mentioned coat film is not actually baked, the formed can body is referred to as " heat treatment equivalent to baking of the coat film of the can body " The strength after heat treatment for 20 minutes can be substituted.

The can body after the baking of the coating film is reduced in diameter (necking) and expanded to the outside of the opening portion (flanging) to obtain 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 lid produced in the other step is sealed in the opening by being sealed.

Example

The present invention has been described above in detail with reference to the following examples. However, the present invention is not limited to these examples. Further, the present invention is not limited to this embodiment.

(Aluminum alloy plate for public use)

An alloy ingot having the 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 preferred numerical values in all the examples in common.

The ingot was cracked twice in the above two times, and the average cooling rate (° C / hour) at 500 to 200 ° C until the room temperature was once once cracked for the first time at a cracking temperature of 600 ° C And then cooled to various degrees. 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 variously changed as shown in Table 1. In all the examples, And a second cracking treatment at a temperature of 4 hours was performed.

Then, hot rolling was started at this temperature. At this time, among the time between passes of the number of passes 12 in the hot rough rolling (reverse mill), the longest time (second) among the passes required from the rolling execution (pass) to the next rolling execution (pass) The results are shown in Table 1. In addition, among the normal speeds of all the passes, the lowest normal speed (m / min) was varied as shown in Table 1. In all the examples, the finish temperature of hot rolling was set to 450 DEG C, and the hot finish rolling was started within 3 minutes after completion of the hot rough rolling. The finish temperature of the hot finish rolling was set to 330 DEG C, Rolled plate having a thickness of 2.5 mm. Further, the hot-rolled sheet was subjected to cold rolling without performing pre-annealing (annealing) and without intermediate annealing in the middle to obtain a coil-like elongated aluminum sheet having a sheet thickness of 0.28 mm and a sheet width of 2000 mm Alloy plate. In the chemical composition of the aluminum alloy sheet of Table 1, " - " indicates that it is below the detection limit.

(Can body)

The aluminum alloy sheet thus obtained was subjected to cupping and DI molding (ironing processing rate: 65 to 70%) and trimmed to have an outer diameter of about 66 mm, a height of 124 mm in the can axial direction, Mm < / RTI > bottomed tubular can body. After the degreasing cleaning of the can body, heat treatment was performed under the condition of 200 占 폚 for 20 minutes, in which baking at the time of coating was assumed (simulated) to obtain a can body sealant.

〔evaluation〕

The evaluation was carried out by measuring the Mn-based intermetallic compound content (Mn content in the compound residue) and the Mg content (Mg content in the separated solution) by 0.2% proof stress and hot phenol residue extraction in the aluminum alloy cold-rolled sheet . DI moldability, puncture resistance, and 0.2% proof stress were measured and evaluated in a can body (after heat treatment under the paint baking assumption). The results are also shown in Table 1.

(Tissue = thermal phenol residue extraction method)

When each sample taken from three locations in the longitudinal center portion of the aluminum alloy cold-rolled sheet coil in the plate width direction center portion and two portions at both end portions in the plate width direction from the central portion are dissolved by hot phenol, 0.1 The contents of Mn (Mn in the compound residues) in the compound as a residue separated by a mesh filter of 탆 were each measured and averaged to obtain an average Mn content of the compound in the aluminum alloy cold rolled sheet. Simultaneously, the content of Mg in each of the solutions separated from the residue in each of the samples was measured and averaged to obtain an average value of Mg solubility in the aluminum alloy cold rolled steel sheet as an analytical value.

(Moldability)

In the DI molding described above, a blank was cut out from one portion in the longitudinal direction central portion of the aluminum alloy cold-rolled sheet coil in the vicinity of the central portion in the plate width direction and 1000 pieces in total from three portions in the vicinity of each of the two end portions, (Cupping process, DI process) at 65%. When no defects (tear-off, pinholes, etc.) occurred during molding, the moldability was evaluated as "? &Quot;

(Puncture resistance)

For each example, it was verified that the puncture resistance of many can bodies manufactured from one piece of plate, in particular, the puncture resistance in the plate width direction and plate thickness direction of the cold-rolled plate in general. For this purpose, in all of the examples, a piercing test was performed on all of the molded aluminum alloy cold-rolled plate coils so as to uniformly include the can-made cans from three places of the central portion and both ends in the plate width direction of the aluminum alloy cold- The puncture property was evaluated.

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 , And a puncture needle having a hemispherical surface with a radius of 0.5 mm was stuck at a speed of 50 mm / min perpendicularly to the side wall at a site where the distance L from the can bottom portion in the can axis direction was 60 mm. Then, the load N until the stabbing needle passed through the side wall was measured, and the maximum load thus obtained was regarded as the stabbing strength.

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

In the present invention, as the handling and use conditions of the DI can, the pressure difference of 1.7 kgf / cm 2 (= 166.6 kPa), which is a condition where the pressure difference between the inside and the outside of the can is larger, the deformation of the can body becomes larger, and the puncture resistance becomes stricter, Lt; / RTI > Although the actual rupture of the can body at the time of stabbing occurs due to 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 that the internal pressure is lowered and the deformation is increased, it is difficult to increase the puncture strength.

The evaluation of sticking resistance so far is usually carried out with a higher internal pressure of 2.0 kgf / cm 2 (= 196 kPa). As a result, even in the same test material, the test method of the present invention has a strict test condition and a low puncture strength. That is, even if the value of the stuck strength (N) in the test by the internal pressure of 2.0 kgf / cm 2 is equal to or slightly lower than the value of the stuck strength (N) by the test method of the present invention , It can be said that the material of the present invention is excellent in puncture resistance. In other words, even if the puncture resistance in the withstand pressure test of 2.0 kgf / cm 2 is excellent, it can not be said that the puncture resistance at the lower internal pressure of 1.7 kgf / cm 2 of the present invention is excellent.

(0.2% proof)

The tensile test for measuring the 0.2% proof strength of the cold-rolled sheet and the can-body side wall was carried out in accordance with JIS Z 2201 on a cold-rolled sheet and test pieces respectively taken from a sidewall of a can body (after heat treatment for baking) , And the specimen 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). Further, the crosshead speed was 5 mm / minute, and the test piece was cut at a constant speed until it was broken.

As shown in Table 1, in each of Examples 1 to 11, the composition of the aluminum alloy is within the scope of the present invention and is manufactured under the preferable manufacturing conditions. That is, the average cooling rate at 500 to 200 占 폚 in cooling to the room temperature after the first cracking in the second cracking treatment of the ingot is 80 占 폚 / hour or more, and the re- The average heating rate at 200 to 400 캜 is 30 캜 / hour or more. The longest time among the passes in the hot rough rolling is within 100 seconds and the lowest normal speed is 50 m / min or more.

As a result, in each example, as shown in Table 1, the average content of Mn in the compound having a particle size separated by a residue extraction method by hot phenol in the cold rolled plate (DI molded can body side wall) exceeding 0.1 탆 Table 1 shows the amount of residual Mn, which is 1.0% or less, and Mn-based intermetallic compounds are few. Simultaneously, the average high capacity of Mg in the cold rolled plate (DI molded can body sidewall) structure was 0.7% in terms of the Mg content in the solution separated by the above hot phenol residue extraction method (Table 1 is abbreviated as the amount of dissolved Mg) Or more and 2.5% or less, respectively.

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 0.090 mm as the sidewall thickness of the thinnest portion on the premise that the DI moldability was good, Of 0.2 MPa in the can axis direction is 280 MPa or more and 350 MPa or less. This puncture resistance is excellent at 35 N or more or 40 N or more, even though it is a strict evaluation that the internal pressure of 1.7 kgf / cm 2 (= 166.6 kPa) is applied to the can body. That is, excellent moldability and excellent puncture resistance under stricter conditions were obtained in a can body having a thin can wall thickness and a high strength.

On the contrary, in Comparative Examples 12 to 15 of Table 1, the composition of the aluminum alloy is within the range of the present invention, but any of the conditions for cracking and hot rolling is deviated from the preferable conditions of the present invention. For this reason, in each comparative example, the average content of Mn in the compound having a particle size of 0.1 mu m or more separated by a hot-phenol extraction method of a cold-rolled sheet (DI molded can body side wall) (The abbreviated amount of Mg in solid solution in Table 1) is deviated from the average high capacity of Mg. As a result, in each of the comparative examples, DI moldability was good, but the thickness of the thinnest side wall was DI molded into the thin can body of the thin film, and the sidewall after the heat treatment corresponding to baking of the coat was made to have the high strength, The puncture resistance across the plate width direction is remarkably deteriorated.

In Comparative Example 12, the average cooling rate at 500 to 200 占 폚 under cooling to room temperature after the first cracking treatment was too small, less than 80 占 폚 / hour. As a result, the amount of Al-Fe-Mn compound produced during cooling increases, and the residual Mn amount becomes excessive.

In Comparative Example 13, the average heating rate at 200 to 400 占 폚 at the second cracking temperature was too small, less than 30 占 폚 / hour. As a result, the Mg-Si-based compound is not produced at a high density and is not reusable in the process of raising the temperature to 450 ° C or higher, and the amount of solid solution Mg is excessively small.

In Comparative Example 14, the time between passes in the rough rolling exceeds 100 seconds, which is too long. As a result, the amount of the Al-Fe-Mn-based compound and the Mg-Si-based compound precipitated in the rough rolling is increased, and particularly, the Mg high-content amount is excessively small.

In Comparative Example 15, the normal steepest velocity among the steady-state velocity of the pass in the rough rolling is too slow, which is less than 50 m / min. As a result, the rolling time is prolonged, and the amount of Al-Fe-Mn compound produced during cooling increases, and the residual Mn amount becomes excessive.

In Comparative Examples 16 to 20 of Table 1, any one of Mn, Mg, Si, and Fe is excessively small, and the composition of the aluminum alloy is out of the range of the present invention.

In Comparative Example 16, the amount of Mg is excessively small, and the amount of solid solution of Mg is excessively small. In Comparative Example 17, the Mn content was excessive, and the residual Mn content was excessive. As a result, in these comparative examples, the puncture resistance across the plate width direction is poor when the above-mentioned pressure-resistant condition is strict.

In Comparative Example 18, the amount of Mn is small. In Comparative Example 19, the amount of Si is excessive. In Comparative Example 20, the amount of Si is small. As a result, in these comparative examples, since defects occurred in the DI molding, they could not be put to practical use for canning, and there was no meaning to carry out the subsequent piercing test, so they were stopped.

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.

This application is based on Japanese Patent Application (Japanese Patent Application No. 2012-026511) filed on February 9, 2012, the content of which is incorporated herein by reference.

INDUSTRIAL APPLICABILITY As described above, the aluminum alloy plate (cold-rolled sheet) for a DI can body according to the present invention can improve the puncture resistance of a can body manufactured from an aluminum alloy cold-rolled sheet to a desired level, have. As a result, the can wall thickness is made thinner and stronger, and it is optimal for an aluminum alloy cold-rolled plate used for a DI can body in which stiffness is required under more severe conditions of use.

Claims (1)

A method of manufacturing an aluminum alloy plate for a DI can body,
And an aluminum alloy having a composition containing 0.3 to 1.3% of Mn, 1.0 to 3.0% of Mg, 0.1 to 0.5% of Si, and 0.1 to 0.8% of Fe and a balance of Al and inevitable impurities, A casting step of melting and casting into an ingot,
A crack treating step of homogenizing the ingot by heat treatment,
A hot rolling step of subjecting the homogenized ingot to hot rolling to obtain a hot rolled plate,
And a cold rolling step of performing cold rolling without annealing the hot rolled sheet,
The average cracking rate at 500 to 200 占 폚 during cooling to room temperature after the first cracking is not less than 80 占 폚 / hour, and the cracking process from the room temperature of the ingot of the second cracking The average heating rate at 200 to 400 ° C at the time of reheating is 30 ° C / hour or more,
Wherein the hot rolling step includes a hot rolling step in which the longest time between passes is within 100 seconds and the lowest normal speed is at least 50 m / min.

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