JP2006283112A - Aluminum alloy sheet for drink can barrel, and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an aluminum alloy sheet for a drink can barrel with excellent surface quality having excellent bottom wrinkle properties, also capable of obtaining high can barrel strength, and producible at high production accuracy and productivity, and to provide a method for producing the same. <P>SOLUTION: The aluminum alloy sheet for a drink has a composition containing, by weight, 0.8 to 1.5% Mg, 0.7 to 1.5% Mn, 0.35 to 0.5% Fe, 0.1 to 0.5% Si, 0.1 to 0.3% Cu, Ti, B, and the balance Al with inevitable impurities. By controlling the maximum n value of the variation curve in a work hardening exponent (n value) to ≥0.1 and prescribing the same as a strict index, and its working hardenability is retained to the fixed one or above, so as to realize production with high accuracy, by controlling its electric conductivity to 30.0 to 39.0% IACS, the degree of elute elements to enter into solid solution in the Al matrix is regulated, and further, the tensile strength of the sheet stock is controlled to ≤320 MPa to prevent the deformation resistance of the material from being made excessive during forming. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

    TECHNICAL FIELD The present invention relates to an aluminum alloy plate for beverage can bodies used as a can body material for various beverage cans such as carbonated beverages, beer and soft drinks, and a method for producing the same.

The can body of a beverage can made of an aluminum alloy is coated with oil on an aluminum alloy plate, cupped and DI-molded (Draw-Ironing) to form a can body, trimming, cleaning, drying, outer surface and inner surface 2. Description of the Related Art Two-piece cans are often used that are painted, baked, necked, and flanged, filled with a beverage, and then the can lid is tightened.
The aluminum alloy sheet is manufactured by subjecting an aluminum alloy ingot to homogenization, hot rolling, then annealing as necessary, and then cold rolling. Usually, in addition to this, finishing treatments such as annealing, degreasing, washing, and lubricating oil application are performed.

  In recent years, due to the need for cost reduction of beverage cans, the thickness of the can body has been reduced (gauge down) and the diameter of the can lid has been reduced. Thinning the can body weakens the forming force during drawing, which increases the amount of material flowing into the can bottom chime, making it easy to buckle and constrict, resulting in an appearance defect called can bottom wrinkle. Let In addition, reducing the diameter of the can bottom requires a reduction in the ground diameter of the bottom of the can in order to ensure stackability when the cans are stacked together. In order to easily cause a buckling phenomenon in the chime portion, the generation of bottom wrinkles is promoted.

With reference to FIG. 3, the mechanism of the occurrence of bottom wrinkles will be described.
The thinning of the beverage can body 1 increases the amount of material flowing from the can side wall 2 to the can bottom chime portion 3 to easily cause buckling and constriction. 3a ... is generated. Further, it is necessary to reduce the diameter of the bottom of the can bottom, which is the diameter of the can bottom grounding portion 4, by reducing the diameter of the can lid (not shown). The bending phenomenon is likely to occur, and this also promotes the generation of the bottom wrinkles 3a, 3a.

As an aluminum alloy plate for can barrels that can solve the above problems and can be used for thinning the can barrel and reducing the diameter of the can lid, and a manufacturing method thereof, Patent Document 1 discloses Mg, Mn, Fe. , Si, Cu, and Ti are defined, the tensile strength and elongation rate are regulated, and further, homogenization treatment, hot rolling, and cold rolling comprising three passes in which the cold-rolling outlet temperature is controlled. Improvement methods have been proposed.

Furthermore, Patent Document 2 defines the contents of Cu, Mg, Mn, Fe and Si, regulates mechanical properties that affect can bottom molding such as elongation, work hardening index and proof stress, homogenization treatment and hot work. An improved method has been proposed in which rolling is performed sequentially, and then the outlet temperature and cooling rate of cold rolling are controlled.
JP 2001-262261 A JP 2004-3000537 A

It has been clarified that the bottom wrinkle is improved by lowering the strength of the aluminum alloy sheet and increasing the elongation of the element. In order to increase this elongation, annealing after cold rolling is performed. It is effective to apply the treatment.
However, performing an annealing treatment after cold rolling has a problem of increasing the cost due to a decrease in productivity and reducing the strength of the can body. Furthermore, in order to cope with further thinning of the can body and reduction in the diameter of the can lid in the future, a material having high can body strength and excellent bottom wrinkle property is indispensable.

  Based on such a request, in the aluminum alloy plate for can bodies excellent in can bottom formability described in Patent Document 1 and the manufacturing method thereof, it is proposed to perform cold rolling consisting of three passes with controlled outlet temperature. It was. However, although this aluminum alloy plate and its manufacturing method are extremely effective means, they do not clarify the conditions directly necessary for obtaining a material having high can barrel strength and excellent bottom wrinkling properties. Further study was necessary in terms of realizing highly accurate and highly efficient productivity.

On the other hand, Patent Document 2 simply defines that the elongation is 5.5% or more, the work hardening index is 0.06 or more, and the proof stress is 290 N / mm ² or less. Consideration as a reliable means to achieve the quality required for alloy sheets is still insufficient, and it is possible to produce materials with high can barrel strength and excellent bottom wrinkle with high accuracy and high efficiency. As a result, it is not possible to substantially meet the demand to make it possible to cope with the further thinning of the can body and the diameter of the can lid in the future.

  In any of the above cases, the continuous annealing is performed to increase the thickness of the oxide film on the surface of the aluminum alloy plate, and the problem regarding the deterioration of the surface quality that black streaks are generated during DI molding has not been solved.

    In view of the above problems in the prior art, the present invention is excellent in bottom wrinkle and has high can body strength, and can be further thinned, and can be produced with high production accuracy and productivity. It is an object of the present invention to provide an aluminum alloy plate for beverage can bodies and a method for producing the same.

  In order to solve the above-mentioned problems, the present inventors have conducted intensive research. As a result, in order to achieve a high can barrel strength with excellent bottom wrinkling properties, the maximum n value and the electrical conductivity in a specific strain region are specified to provide high strength. It has been found that it is possible to effectively define work hardenability by maintaining the above, and the inventors have conceived the aluminum alloy plate for beverage can bodies of the present invention. Further, in addition to optimal control of the cold rolling process of the cold rolling pass outlet temperature and the total rolling rate for the aluminum alloy containing the predetermined amount shown in the present invention alloy, continuous annealing after hot rolling It was found that by controlling the various conditions (heat treatment temperature, heat treatment time, cooling rate), the work hardenability and electrical conductivity for constituting the aluminum alloy plate of the present invention can be appropriately set, and the beverage of the present invention It came up with the manufacturing method of the aluminum alloy plate for can bodies. In addition, by controlling the thickness of the oxide film on the surface of the plate by regulating the dew point (water vapor pressure) of the atmosphere of continuous annealing after hot rolling with an aluminum alloy containing a predetermined amount shown in the present invention alloy, the surface quality The inventors have found that the problem of lowering can be solved, and for that purpose, the optimum values related to material characteristics and production conditions for a specific aluminum alloy plate have been studied, and the present invention has been achieved.

  The aluminum alloy plate for beverage can bodies of the present invention has Mn: 0.7 to 1.5% (mass%, the same applies hereinafter), Mg: 0.8 to 1.5%, Fe: 0.35 to 0.5% Si: 0.1 to 0.5%, Cu: 0.1 to 0.3%, Ti: 0.1% or less, B: 0.1% or less, the balance being Al and inevitable impurities The maximum n value of the change curve of the work hardening index (n value) with respect to the amount of strain in the entire uniform plastic strain region is 0.1 or more and the conductivity is 30.0 to 39.39. The tensile strength in the rolling direction of the base plate is 320 MPa or less, and the strength after baking is 250 MPa or more in terms of the proof stress in the rolling direction.

  The above-mentioned coating baking applied to the aluminum alloy plate for beverage can bodies according to the present invention is held at 180 to 220 ° C. for 5 to 30 minutes or at the maximum reached temperature of 210 to 260 ° C. for 2 minutes or less. It can be.

  It is also effective to regulate the thickness of the oxide film on the plate surface to 20 nm or less.

  The manufacturing method of the aluminum alloy plate for beverage can bodies of the present invention is as follows: Mn: 0.7 to 1.5%, Mg: 0.8 to 1.5%, Fe: 0.35 to 0.5%, Si: Aluminum containing 0.1 to 0.5%, Cu: 0.1 to 0.3%, Ti: 0.1% or less, B: 0.1% or less, the balance being Al and inevitable impurities An alloy ingot is manufactured, the aluminum alloy ingot is chamfered, homogenized, then hot rolled to a thickness of 1.5 to 2.5 mm, and the alloy plate is continuously annealed. The furnace is rapidly heated to a temperature of 550 to 600 ° C. and held for 300 seconds or less. As a material property, the maximum n value of the change curve of the work hardening index (n value) with respect to the strain amount in the entire uniform plastic strain region is 0. 1 or more, the conductivity is 30.0 to 39.0% IACS, in the rolling direction of the base plate Zhang intensity is less 320 MPa, the strength after paint baking is characterized in that at least 250MPa with yield strength in the rolling direction.

  The baking finish applied to the aluminum alloy plate for beverage can barrels of the present invention produced by the method for producing an aluminum alloy plate for beverage can barrels of the present invention described above is maintained at 180 to 220 ° C. for 5 to 30 minutes, or the highest Paint baking can be performed by holding at an ultimate temperature of 210 to 260 ° C. within 2 minutes.

  In the above method for producing an aluminum alloy plate for beverage cans according to the present invention, the alloy plate is rapidly heated to a temperature of 550 to 600 ° C. by a continuous annealing furnace and held for 300 seconds or less, and then cooled to 800 ° C./second or less. It is effective to perform the process of cooling at a speed.

  Moreover, in the manufacturing method of the aluminum alloy plate for beverage can bodies according to the present invention described above, the alloy plate is rapidly heated to a temperature of 550 to 600 ° C. by a continuous annealing furnace and held for 300 seconds or less, and then cold rolling is performed by 70%. The recovery process of the material structure can be performed by applying the final rolling pass temperature at 130 ° C. or higher and the other rolling pass discharge temperatures at 130 ° C. or lower at the above total rolling rate. it can.

  Moreover, in the manufacturing method of the aluminum alloy plate for beverage can bodies of the present invention described above, the homogenization treatment is performed in a temperature range of 550 to 620 ° C., and the alloy plate is rapidly heated to a temperature of 550 to 600 ° C. in a continuous annealing furnace and annealed. The thickness of the oxide film on the surface of the plate can be controlled to 20 nm or less by keeping the atmosphere gas in the furnace in an atmosphere having a dew point of 10 ° C. or less for 300 seconds or less.

[Action]
The present inventors examined in detail the cause of the bottom wrinkle, and found that the forming force was reduced due to the small resistance to bending and unbending deformation at the blank holder and the shoulder of the redodice during the drawing process. The bottom wrinkles occur when the tensile stress in the axial direction at the portion) decreases and the compressive strain in the circumferential direction increases.
Therefore, according to the present invention, the maximum n value of the change curve of the work hardening index (n value) is set to 0.1 or more, and the work hardening index (n value) is defined as a strict index. Maintains curability at a certain level and enables high-accuracy production, and further adjusts the degree of solid solution of solute elements in the Al matrix with an electrical conductivity of 30.0 to 39.0% IACS and the tensile strength of the base plate Is set to 320 MPa or less to prevent excessive deformation resistance of the material during molding to prevent cracking during ironing, and in addition, the proof stress after paint baking is 250 MPa or more, so that it can be used as an aluminum beverage can. It was possible to guarantee the strength to withstand the change in internal pressure when the was filled.

  As described above, in the aluminum alloy plate for beverage can bodies of the present invention, the maximum n value of the change curve of the work hardening index (n value) with respect to the strain amount is 0.1 or more, and the conductivity is 30.0 to 39.39. Since the tensile strength in the rolling direction of the base plate is 320 MPa or less at 0% IACS and the proof stress after baking is 250 MPa or more, high strength and excellent bottom wrinkle property can be realized. The aluminum alloy sheet of the present invention is manufactured by regulating the homogenization conditions, the sheet thickness after hot rolling, the continuous annealing conditions, the total rolling rate of cold rolling, and the exit temperature of the cold rolling pass in each pass. It becomes possible. This makes it possible to produce an aluminum can body material having excellent bottom wrinkle and high can body strength that can cope with the thinning of the aluminum can body and the reduction of the diameter of the can lid, and a remarkable industrial effect can be obtained. .

The reasons for limiting the alloy composition will be described below with respect to the aluminum alloy plate for beverage can bodies of the present invention.
[Mn component range: 0.7 to 1.5%]
Mn is an element that contributes to improving the strength of the can body and is effective for improving the DI moldability. The component range is Mn: 0.7 to 1.5%. By containing within this range, a crystallized substance having a solid lubricating action (Al-Mn system, Al-Mn-Fe system, Al-Mn-Fe-Si system) is sufficiently formed. It is possible to suppress the occurrence of scratches and seizure defects called goling or scoring that occur due to build-up in which aluminum adheres to the molding die. If the content is less than 0.7%, the effect cannot be obtained sufficiently. Conversely, if the content is 1.5% or more, a large primary compound of Al-Mn-Fe system is generated at the time of melt casting. And pinholes are induced and formability is impaired.

[Mg component range: 0.8 to 1.5%]
Similar to Mn, Mg is an element that contributes to improving the strength of the can body, and is effective in increasing the strength of the bottom portion and improving work hardening. Its component range is set to 0.8-1.5%. If it is less than 0.8%, it is difficult to sufficiently obtain the required strength. Further, since sufficient work hardening does not occur at the time of molding, bottom wrinkles are likely to occur. Further, if the content exceeds 1.5%, the strength becomes too high, so that the frequency of occurrence of can barrel breakage and cracking increases during DI molding, thereby impairing moldability. A desirable content is 1.0 to 1.4 wt%.

[Fe component range: 0.35 to 0.5%]
Fe, like Mn and Mg, is an element that contributes to the improvement of the strength of the can body, and also produces the hard Al—Mn—Fe (—Si) -based intermetallic compound having a solid lubricating action containing Mn. While promoting, the distribution state is made uniform and the moldability is improved. The component range is 0.35 to 0.5%. If it is less than 0.35%, it is difficult to impart sufficient strength, and further, an intermetallic compound necessary for preventing adhesion to a die is not sufficiently formed. If it exceeds 0.5%, the strength becomes too high, and the moldability is lowered.

[Cu component range: 0.1 to 0.3%]
Cu is an element that contributes to improving the strength of the can body by its solid solution, and is an element that contributes to improving the strength by precipitation hardening of Al-Cu-Mg-based precipitates in the coating baking process during can making. . Thereby, the strength of the can body, particularly the strength of the bottom portion can be improved. The component range is 0.1 to 0.3%. If the content is less than 0.1%, sufficient material strength cannot be obtained. If the content exceeds 0.3%, the strength becomes too high. Is damaged.

[Component range of Si: 0.1 to 0.5%]
In the homogenization treatment, Si causes a phase transformation in the Al—Mn—Fe intermetallic compound and contributes to the formation of an Al—Mn—Fe—Si intermetallic compound having higher hardness. As a result, the above-described die screening effect can be sufficiently obtained, so that the problem of seizure to the die during molding is prevented and the moldability is improved. The component range is 0.1 to 0.5%. If it is less than 0.1%, the intermetallic compound is not sufficiently formed, and seizure defects are likely to occur. If it exceeds 0.5%, the intermetallic compound becomes enormous and the formability deteriorates.

[Inevitable impurities]
In aluminum alloy plates for beverage can bodies, a small amount of Ti and B is often added to refine crystal grains. The Ti content is limited to 0.1% or less, preferably 0.005% or more and 0.05% or less. If the Ti content is less than 0.005%, the effect of crystal grain refining cannot be sufficiently obtained. If the Ti content exceeds 0.05%, a large Al-Ti intermetallic compound tends to be produced. If it exceeds 1%, the tendency to generate a huge intermetallic compound of Al-Ti system increases, and cracks and pinholes are generated during the forming process, thereby reducing the formability.

  B has an effect of promoting crystal grain refinement. The B content is limited to 0.1% or less, preferably 0.001% or more and 0.01% or less. If the content is less than 0.001%, the effect cannot be sufficiently obtained. If the content exceeds 0.01%, a Ti-B giant intermetallic compound tends to be generated. The tendency to form a large -B-based intermetallic compound increases, and cracks and pinholes are likely to occur during molding. As other inevitable impurities, if Zn is 0.3% or less, Cr is 0.3% or less, Zr is 0.1% or less, and V is 0.1% or less, the effect of the present invention is not impaired. Is acceptable.

  Next, the manufacturing method of the aluminum alloy plate of this invention is demonstrated. First, an aluminum alloy having the alloy composition of the present invention is cast into a slab (plate ingot) by a water-cooled continuous casting method. In the present invention, the temperature and time of the homogenization treatment are not particularly restricted, but when the homogenization treatment is insufficient, the segregation of the solute distribution is not sufficiently eliminated and the moldability is lowered. In this respect, in the present invention, it is preferable to perform the homogenization treatment in a temperature range of 550 to 620 ° C. in consideration of the homogenization effect and productivity. As for the homogenization time, the effect is not sufficient unless it is maintained for 1 hour or longer, and a certain amount of time is required. In view of the homogenization effect and productivity, 3 to 12 hours is desirable, and 5 to 10 hours is appropriate. If the homogenization treatment is 550 ° C. or less or less than 1 hour, a sufficient homogenization effect cannot be obtained, and if it exceeds 620 ° C., the casting surface is swollen and the eutectic part is melted.

Hot rolling is performed after the homogenization treatment. At that time, either a process of performing hot rolling as it is without reheating after the homogenization process or a process of performing reheating and hot rolling after being cooled to room temperature may be used. The hot rolling start temperature is preferably 400 to 550 ° C, more preferably 450 to 550 ° C. If it is less than 450 ° C., sufficient rolling processability cannot be obtained, so there is a concern that cracks may occur at the edge of the sheet width, and if it is 400 ° C. or less, the hot rolling end temperature is lowered, so Since sufficient crystal grains are not generated, rolling cracks occur at the plate width edge portion. When the temperature exceeds 550 ° C., the DI formability deteriorates due to surface oxidation of the hot rolled plate or coarsening of recrystallized grains.
On the other hand, the hot rolling end temperature is preferably 280 ° C to 380 ° C. When it is less than 280 ° C., sufficient recrystallized grains having a cubic orientation are not generated, which may cause rolling cracks at the sheet width edge portion or increase the ear ratio. Furthermore, since the material strength rises excessively, the DI moldability decreases. If it exceeds 380 ° C., the roll coating becomes non-uniform and surface defects tend to occur.

  In the present invention, the thickness of the hot rolled sheet is regulated to 1.5 to 2.5 mm. If the thickness is less than 1.5 mm, the hot-rolled sheet is likely to be seized or rough, and the thickness profile is further deteriorated. On the other hand, if the plate thickness exceeds 2.5 mm, the cold rolling rate increases, the material strength increases, and the DI moldability decreases.

In the present invention, after hot rolling, it is rapidly heated to a temperature of 550 to 600 ° C. by CAL (Continuous Annealing Line), and then rapidly cooled after holding for 300 seconds or less. At that time, the cooling rate is preferably 800 ° C./second or less. For this cooling, either rapid cooling by mist cooling or air cooling by introduction of outside air can be applied.
By such a continuous annealing treatment, the solute element is sufficiently solid-solved to have the conductivity defined in the present invention, and the work curability (n value) is improved and the bottom wrinkle property is improved. Further, the solute element that has been dissolved increases the strength of the material by solid solution hardening. If it is less than 550 degreeC, the effect of a bottom wrinkle improvement and an intensity | strength improvement will not fully be acquired, but if it exceeds 600 degreeC, DI moldability will fall by excessive intensity | strength raise. A preferable holding temperature is 560 to 580 ° C.

  The holding time at a temperature of 550 to 600 ° C. in the continuous annealing treatment is set to 300 seconds or less. If it exceeds 300 seconds, the solute element is dissolved in a supersaturated state, so that the material strength is excessively improved and the DI moldability is lowered. As described above, annealing conditions are set from the viewpoints of bottom wrinkle property, DI moldability, and material strength. Furthermore, the dew point of the atmospheric gas in the annealing furnace is defined as 10 ° C. or less. When the dew point of the atmospheric gas exceeds 10 ° C., the amount of water vapor in the atmosphere is large. Therefore, when annealing at 550 to 600 ° C., the oxide film on the surface of the aluminum alloy plate reacts with water vapor to increase the film thickness, and during DI moldability Black streaks appear and the surface quality decreases. In the present invention, when continuous annealing is performed, direct annealing is performed in which the atmosphere is heated with an atmosphere gas. The atmospheric gas is at least one selected from nitrogen gas, argon gas, carbon monoxide gas, carbon dioxide gas reducing gas, or air.

Cold rolling is performed after hot rolling. The exit side temperature of the final cold rolling is 130 ° C. or more, preferably 200 ° C. or less, and the exit side temperature of the other rolling passes is 130 ° C. or less, preferably 110 ° C. or less.
As described above, in the present invention, the material temperature is controlled by controlling the base plate strength which is excessively increased by reducing the processing dislocation density generated by the cold rolling of the intermediate pass by setting the exit side temperature of the final cold rolling to 130 ° C. or more. To improve the DI moldability.

  On the other hand, the exit side temperature of the intermediate pass rolling is 130 ° C. or lower, preferably 110 ° C. or lower, so that Al—Cu—Mg-based precipitates and Al—Cu—Mg—Si generated during cold rolling are used. This contributes to reducing the amount of system precipitates produced. As a result, dislocation localization starting from precipitates is less likely to occur during molding, so that local work softening due to dynamic recovery is suppressed and bottom wrinkle properties are improved. The total rolling reduction of cold rolling is 70% or more. If it is less than 70%, sufficient can body strength cannot be maintained, and the required outlet temperature during the final cold rolling cannot be sufficiently secured. The total rolling rate of this cold rolling is preferably 90% or less. If it exceeds 90%, it is excessively work-cured and the DI moldability is lowered.

  Next, regarding the aluminum alloy plate for beverage can bodies of the present invention, the maximum n value of the change curve of the work hardening index (n value) with respect to the strain amount and the reason for limiting the conductivity will be shown.

FIG. 1 schematically shows a nominal stress-nominal strain curve obtained by conducting a tensile test to obtain a nominal stress s and a nominal strain e. Fig. 1 (a) shows a material with clear upper and lower yield points such as mild steel and Al-Mg alloy, and Fig. 1 (b) shows a material with no clear yield point such as copper and aluminum. To express. In the case of a material showing a clear yield point as shown in FIG. 1 (a), the yield point s _y1 is used. In the case of a material not showing a clear yield point as shown in FIG. The nominal stress s _0.2 that produces (usually 0.2% permanent strain) is considered the yield stress (yield strength). When this yield stress is passed, the stress necessary for further plastic deformation increases and reaches the maximum load point B of the nominal stress. Until this maximum load point B is reached, it can be considered that the material to be processed is deformed substantially uniformly.

That is, the uniform plastic strain region referred to in the present invention is a plastic strain region from the lower yield point _sy1 to the maximum load point B in the case of a material having a clear yield point as shown in FIG. In the case of a material that does not show a clear yield point, it is a plastic strain region from the nominal stress s _0.2 to the maximum load point B of the nominal stress.
Therefore, in the case of a material that does not show a clear yield point as shown in FIG. 1B, the uniform plastic strain region referred to in the present invention should be understood as a plastic strain region between the 0.2% proof stress and the maximum load point B. Can do.

    In the aluminum alloy plate for beverage can bodies of the present invention, the change curve of work hardening index (n value) with respect to the amount of strain in the plastic deformation region between the entire uniform plastic strain region or 0.2% proof stress and the maximum load point as material characteristics. It is managed so that the maximum n value of is 0.1 or more.

It is known that an aluminum alloy generally increases its strain by rolling and hardens the material. The JIS3004 alloy used for the can body material actively uses the work hardening phenomenon in cold rolling in order to increase the material strength. The work hardening property indicating the degree of the work hardening phenomenon can be expressed by a constant indicating a work hardening property called an n value (work hardening exponent). This n value is calculated by the Hollomon formula in which the relationship between the true stress σ and the true strain ε is approximated by σ = Fε ⁿ when the true stress is σ, the true strain is ε, and the work hardening index is n. This work hardening index (n value) is a characteristic value that also serves as a guide for drawing workability. The larger the n value, the larger the elongation until the occurrence of local shrinkage, and the better the drawing ability.

FIG. 1 shows the work hardening index (n value) with respect to the amount of strain in the uniform plastic strain region or the plastic deformation region between 0.2% proof stress and the maximum load point which the aluminum alloy plate for beverage can bodies of the present invention has as its material characteristics. A change curve is schematically shown.
As shown in FIG. 1, in the aluminum alloy plate for beverage can bodies of the present invention, the maximum n value in the uniform plastic strain region or the plastic deformation region between 0.2% proof stress and the maximum load point exceeds 0.1. Is done.
This increases the work curability during the can molding process, so that the molding force is improved, the strain at the bottom of the can is relaxed, and the bottom wrinkle property is improved. If it is less than 0.1, the effect is not sufficiently obtained, and wrinkles are likely to occur on the bottom of the can.

  The conductivity is 30.0 to 39.0% IACS. As a result, the solute element is appropriately solid-dissolved to improve work hardening. If it is 39.0% IACS or more, the effect is not sufficiently obtained and wrinkles are likely to occur at the bottom of the can. On the other hand, if it is 30.0% IACS or less, the solute element is solid-dissolved in a supersaturated state, so that the DI moldability decreases due to an increase in strength.

Next, the reasons for limiting the tensile strength of the base plate of the aluminum alloy plate of the present invention and the yield strength after baking are described.
The tensile strength of the base plate is set to 320 MPa or less. If it exceeds 320 MPa, the deformation resistance of the material increases during molding, so the frequency of occurrence of cracks increases during ironing. The yield strength after baking is set to 250 MPa or more. When the pressure is less than 250 MPa, the pressure resistance is insufficient, and when the contents are filled as an aluminum can, the strength that can withstand changes in internal pressure cannot be maintained.

The present invention will be specifically described below based on examples.
The aluminum alloy of the present invention having the alloy components shown in Table 1 was melt cast by a conventional method to obtain a slab (plate ingot) having a thickness of 500 mm. The slab is chamfered to a thickness of 490 mm, homogenized at 600 ° C. for 6 hours, and then cooled to room temperature. Next, hot rolling is performed at a rolling start temperature of 490 ° C. and a rolling end temperature of 320 ° C. to form a hot rolled plate having a thickness of 2.2 mm, which is wound on a coil and cooled to room temperature. For hot rolling, rough rolling was performed with a single mill reverse type rolling mill, and a four-stand tandem rolling mill was used for finish rolling. This alloy plate is rapidly heated to 560 ° C. in a continuous annealing furnace, held for 30 seconds, and then cooled at a rate of 20 ° C./second. Next, cold rolling is performed to produce an aluminum alloy plate for beverage can bodies having a thickness of 0.3 mm. In cold rolling, the total rolling rate of 3 passes is 86%.

(Comparative Example 1)
An aluminum alloy plate was produced by the same method as in Example 1 except that the alloy composition was outside the specified value of the present invention.

  Table 1 shows the alloy compositions of Example 1 and Comparative Example 1 of the present invention.

  For each aluminum alloy produced in Example 1 and Comparative Example 1, (1) mechanical properties, (2) (2) conductivity, (3) maximum n value, (4) DI formability, (5) can The bottom moldability (bottom wrinkle property) and (6) pressure strength were evaluated.

(1) The mechanical properties were measured by measuring the tensile strength of the base plate in the rolling direction of the manufactured aluminum alloy plate and the yield strength after baking.
Empty baking is the assumption of paint baking conditions at the time of can-making, and was performed at 205 ° C. for 10 minutes. With respect to the tensile strength of the base plate, 320 MPa or less was evaluated as acceptable (within the specified value of the present invention), and the yield strength after baking was determined to be acceptable at 250 MPa or more.
(2) The conductivity was measured by an eddy current method after being kept at a constant temperature in a constant temperature room at 20 ° C.
(3) The n value is determined by measuring the nominal stress at an interval of 0.05% over the uniform plastic strain region, calculating the true stress and the true strain from these measured values, and then, based on JISZ2253, the nominal strain. The n value was obtained by the method of least squares with 1% before and after the calculation range. Next, using the calculated n value, a change curve of the n value with respect to the true strain is created, and a sample having a maximum n value of 0.1 or more is judged good (◯), and a sample having a value less than 0.1 is bad (×) It was.

(4) DI moldability is DI molded into a can body for a general beverage (inner diameter 66 mmΦ, side wall plate thickness 100 μm, side wall tip plate thickness 150 μm), and is a can of 10,000 cans. What was able to be made can be judged as good (◯), and those with cracks and fractures were judged as bad (x).
(5) For bottom wrinkle, the cup is squeezed from the blank, and then the re-drawn can (blank diameter 140 mmΦ, cup diameter 87 mmΦ, redrawn diameter 66 mmΦ) Measurements were made and evaluated at the maximum amplitude. A maximum amplitude of 180 μm or less was judged as good (◯), and 180 μm or more was judged as bad (×).
(6) With regard to the pressure strength, after DI molding, baking (205 ° C. × 10 minutes) was performed, and the pressure at which the can bottom dome was reversed by applying air pressure to the inside of the can body was measured. A reversal pressure of 650 kPa or higher was judged as good (◯), and a reversal pressure of 650 kPa or lower was judged as defective (x). These survey results are shown in Table 2. Table 2 shows various characteristic evaluations of the aluminum alloys manufactured in Example 1 and Comparative Example 1.

As is clear from Table 2, the sample No. 1 of Example 1 was obtained. 1 (alloy No. A), sample NO. 2 (alloy No. B), sample NO. All the aluminum alloy plates of No. 3 (alloy No. C) showed good results excellent in bottom wrinkle property, DI formability and pressure strength.
On the other hand, the sample NO. Since the aluminum alloy plate of No. 4 (alloy No. D) has a large amount of Mg, the tensile strength of the base plate increased, the DI formability decreased, and ironing cracks occurred.
Sample No. Since the aluminum alloy plate of No. 5 (Alloy No. E) has a small amount of Mg, the yield strength after baking was outside the scope of the present invention, resulting in poor pressure strength. Furthermore, since the conductivity is high and there is no portion where the maximum n value exceeds 0.1, bottom wrinkles were observed.
Sample No. Since the aluminum alloy plate of No. 6 (Alloy No. F) has a large amount of Mn, the tensile strength of the base plate increased and a giant crystallized product was generated, which started as a starting point and cracked during DI molding.
Sample No. Since the aluminum alloy plate of No. 7 (Alloy No. G) had a small amount of Mn, the amount of crystallized material having a solid lubricating action was reduced, the ironing die was baked, the surface of the can was rough, and the molding was defective. Furthermore, the proof stress after baking was out of the scope of the present invention, and the pressure resistance decreased.
Sample No. Since the aluminum alloy plate of No. 8 (alloy No. H) has a small amount of Cu, the yield strength after baking was out of the scope of the present invention, resulting in poor pressure strength.
Sample No. Since the aluminum alloy plate of No. 9 (alloy No. I) has a large amount of Cu, the tensile strength of the base plate increased and the DI moldability decreased.

  The aluminum alloy of (alloy No. A) of the present invention composition shown in Table 1 is melt cast by a conventional method to form a plate-like ingot (slab) having a thickness of 500 mm, which is chamfered to a thickness of 490 mm, and then homogenized. Processing and hot rolling. This alloy plate is rapidly heated by a continuous annealing furnace and kept for a predetermined time, and then cooled. Next, it cold-rolled and manufactured the aluminum alloy plate for drink can bodies of thickness 0.3mm variously within the regulation value of this invention.

(Comparative Example 2) An aluminum alloy plate was produced in the same manner as in Example 2 except that the production conditions were outside the specified values of the present invention. About each aluminum alloy plate obtained in Example 2 or Comparative Example 2, various characteristics were investigated by the same method as in Example 1, and the quality was judged. The manufacturing conditions are shown in Table 3, and the survey results are shown in Table 4. Table 3 shows the aluminum alloy sheet manufacturing conditions of Example 2 and Comparative Example 2 of the present invention.

  Table 4 shows various characteristics evaluations of the aluminum alloys manufactured in Example 2 and Comparative Example 2 of the present invention.

As apparent from Table 4, the aluminum alloy of Example 2 of the present invention (Sample No. 10, Sample No. 11, Sample No. 12, Sample No. 13, Sample No. 14, Sample No. 15, Sample No. 15) In all cases 16), the bottom wrinkle was good, and the maximum n value, the electrical conductivity, the tensile strength of the base plate, and the proof stress after baking were values that satisfied the conditions of the present invention.
On the other hand, sample NO. The aluminum alloy plate No. 17 had a low homogenization temperature, and a sufficient homogenization effect was not obtained, resulting in a decrease in DI formability. Furthermore, the conductivity was outside the specified value of the present invention, and there was no portion where the maximum n value exceeded 0.1, and bottom wrinkles were generated.
Sample No. Since the 18 aluminum alloy plate had a high hot rolling start temperature, the recrystallized grains were coarsened and the DI moldability was lowered.
Sample No. No. 19 aluminum alloy sheet had a low hot rolling end temperature, so that rolling cracks occurred at the coil end, and the tensile strength of the base sheet increased, so the DI formability decreased.
Sample No. Since the aluminum alloy plate of 20 was thin after hot rolling, the cold rolling rate was reduced and the yield strength and pressure strength after baking were reduced. Furthermore, the hot rolled sheet was rough and the surface properties were deteriorated.
Sample No. In No. 21, since the plate thickness after hot rolling was thick, the cold rolling rate was increased, and the tensile strength of the base plate was increased, so that DI moldability was lowered and ironing cracks were generated.
Sample No. No. 22 had a low continuous annealing temperature after hot rolling, so that the conductivity was high, and there was no portion where the maximum n value exceeded 0.1, and bottom wrinkling was noticeably observed.
Sample No. No. 23 had a long continuous annealing time, and the solute element was dissolved in supersaturation, so that the tensile strength of the base plate increased, the DI moldability decreased, and ironing cracks occurred.
Sample No. In No. 24, the cooling rate after continuous annealing was high, and the solid solution amount of the solute element increased and the tensile strength of the base plate increased, so that the DI moldability decreased.
Sample No. 25 and sample NO. In No. 26, the exit temperature of the first pass or the second pass of cold rolling was high, the conductivity increased due to the formation of precipitates, and there was no portion where the maximum n value exceeded 0.1, and bottom wrinkles occurred.
Sample No. In No. 27, the exit side temperature of the final cold rolling was low, the tensile strength of the base plate was increased, and the DI moldability was lowered.
Sample No. Since No. 28 had a low total rolling ratio, the yield strength after baking was lowered and the pressure strength was lowered.

  In the same manner as in Example 1, the aluminum alloy shown in Table 5 was melt cast, chamfered, homogenized and cooled to room temperature, and the alloy plate obtained was rapidly heated to 580 ° C. in a continuous annealing furnace. A cooling process is performed after holding for 2 seconds. At that time, the dew point of the atmospheric gas in the annealing furnace is set to 0 ° C. Next, hot rolling is performed at a rolling start temperature of 490 ° C. and a rolling end temperature of 320 ° C. to form a hot rolled plate having a thickness of 2.2 mm, which is wound on a coil and cooled to room temperature. This alloy plate is rapidly heated to 580 ° C. by a continuous annealing furnace, held for 30 seconds, and then cooled. Next, cold rolling is performed to produce an aluminum alloy plate for beverage can bodies having a thickness of 0.3 mm. Cold rolling is 3 passes and the total rolling rate is 86%.

(Comparative Example 3)
An aluminum alloy plate was produced in the same manner as in Example 3 except that the alloy composition was outside the specified value of the present invention.
Table 5 shows alloy compositions of Example 3 and Comparative Example 3 of the present invention.

For each aluminum alloy produced in Example 3, (1) mechanical properties, (2) conductivity, (4) DI formability, and (6) pressure strength, each produced in Example 1 and Comparative Example 1 (3) Maximum n value, (5) Bottom wrinkle, (7) Oxide film thickness, (8) Surface quality during DI molding (whether black streak is generated) Was evaluated as follows.
(3) For the calculation of n value, for the plastic deformation region from 0.2% proof stress to the maximum load point, the nominal stress and the nominal strain are measured at an interval of 0.05%, and each 1% of the nominal strain is the measurement range. True stress and true strain were calculated and calculated using the method of least squares. And the thing whose maximum n value is 0.1 or more was made into favorable ((circle)), and the thing below 0.1 was made into defect (x).
(5) The bottom wrinkle was visually determined for the presence or absence of a wrinkle at the bottom after DI molding.
(7) The thickness of the oxide film was measured by an element profile in the depth direction from the plate surface with an Auger electron spectrometer.
(8) The presence or absence of black streaks was evaluated visually after DI molding.
Table 6 shows various characteristic evaluations of Example 3 and Comparative Example 3 of the present invention.

  As can be seen from Table 6, the sample NO. 1 (alloy No. A), sample NO. 2 (alloy No. B), sample NO. All the aluminum alloy sheets of No. 3 (Alloy No. C) showed good results excellent in bottom wrinkle property and DI formability.

On the other hand, the sample NO. Since the aluminum alloy plate of No. 4 (Alloy No. D) has a large amount of Mg, the strength of the base plate increased, the DI formability decreased, and ironing cracks occurred.
Sample No. 5 (Alloy No. E) had a small amount of Mg, and therefore the yield strength after baking was out of the scope of the present invention, and the pressure resistance decreased. Furthermore, there was no portion where the maximum n value exceeded 0.1, and bottom wrinkles occurred.

Sample No. The aluminum alloy plate of No. 6 (Alloy No. F) has a large amount of Mn, so that a large crystallized product is generated, and iron cracks are generated at the time of DI forming, and the maximum n value is 0.1. There was no excess part and the occurrence of bottom wrinkles was observed.
Sample No. The aluminum alloy plate of No. 7 (Alloy No. G) had a small amount of Mn, so the amount of crystallized material having a solid lubricating action was reduced, the ironing die was baked, the surface of the can was rough, and the molding was defective. Furthermore, the yield strength after baking was out of the scope of the present invention, and the pressure resistance decreased.
Sample No. Since the aluminum alloy plate of No. 8 (alloy No. H) has a large amount of Si, the solid solubility of the solute atoms decreased, and the effect of increasing the strength of the can body after baking was not sufficiently obtained, and the pressure strength was increased. Further, there was no portion where the maximum n value exceeded 0.1, and bottom wrinkles occurred.
Sample No. 9 (Alloy No. I) had a small amount of Si, so the amount of crystallized material having a solid lubricating action was reduced, the ironing die was baked, the surface of the can was roughed, and molding was poor.
Sample No. 10 (Alloy No. J) has a large amount of Cu, so that the strength of the base plate increased and the DI moldability decreased.

  Using an aluminum alloy of (alloy No. A) of the present invention composition shown in the alloy composition of Example 3 of the present invention shown in Table 5, in the same manner as in Example 2, melting casting, face-cutting, homogenizing treatment, After hot rolling, this alloy plate is rapidly heated in a continuous annealing furnace, held for a certain period of time, then cooled, and then subjected to 3 passes of cold rolling to produce a 0.3 mm thick aluminum alloy plate for beverage can bodies. Various variations were made within the specified values of the invention.

(Comparative Example 4) An aluminum alloy plate was produced by the same method as in Example 4 except that the production conditions were outside the specified values of the present invention. Table 7 shows the aluminum alloy sheet production conditions of Example 4 and Comparative Example 4 of the present invention.

  About each aluminum alloy board obtained in Example 4 and Comparative Example 4, various characteristics were investigated by the same method as the case of Example 3 and Comparative Example 3, and the quality was determined. The survey results are shown in Table 8. Table 8 shows various characteristic evaluations of the aluminum alloy plates obtained in Example 4 and Comparative Example 4.

  As is apparent from Table 8, the aluminum alloy of the present invention example (Sample No. 11, Sample No. 12, Sample No. 13, Sample No. 14, Sample No. 15, Sample No. 16, Sample No. 17) The maximum n value, the tensile strength of the base plate, the yield strength after baking, and the electrical conductivity showed values satisfying the conditions of the present invention, and all had good bottom wrinkling properties and DI moldability.

On the other hand, sample NO. In No. 18, since the homogenization temperature was low, the DI moldability was lowered, and the electrical conductivity was high, the occurrence of bottom wrinkles was noticeably observed.
Sample No. Since the aluminum alloy sheet of No. 19 has a high hot rolling start temperature, the DI formability deteriorated.
Sample No. Since the aluminum alloy plate No. 20 had a low hot rolling end temperature, the rolling processability was reduced, cracking occurred at the coil end, and the DI formability was lowered.

Sample No. Since the aluminum alloy plate No. 21 had a low continuous annealing temperature after hot rolling, the electrical conductivity was high and bottom wrinkles were generated.
Sample No. The 22 aluminum alloy sheet had a long continuous annealing time after hot rolling, and the solute atoms were dissolved in supersaturation, so that the material strength was increased, the DI formability was lowered, and ironing cracks were generated.
Sample No. Since the aluminum alloy plate No. 23 had a high dew point of the atmospheric gas in the annealing furnace, the oxide film on the plate surface reacted with water vapor and became thick and black streaks were generated during DI molding.
Sample No. Since the 24 aluminum alloy sheet had a low total rolling ratio, the yield strength and pressure strength after air baking were low.

  The present invention relates to an aluminum alloy plate used as a can body material for various beverage cans such as carbonated beverages, beer and soft drinks, and has an excellent bottom wrinkle property and can provide a high can body strength. It can be applied as a plate and its manufacturing method.

FIG. 5 is a schematic diagram showing a nominal stress-nominal strain curve obtained by conducting a tensile test and obtaining a nominal stress s and a nominal strain e, wherein (a) shows the case of a material in which clear upper and lower yield points such as mild steel appear; (B) shows the case of the material which does not show the clear yield point of the nonferrous metal in general. It is a change curve of the work hardening index (n value) with respect to the strain amount in the entire uniform plastic strain region. It is sectional drawing which shows typically the site | part (can bottom chime part) where a bottom wrinkle generate | occur | produces.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Beverage can body, 2 ... Can side wall, 3 ... Can bottom chime part, 4 ... Can bottom grounding part

Claims (8)

  Mn: 0.7 to 1.5% (mass%, the same applies hereinafter), Mg: 0.8 to 1.5%, Fe: 0.35 to 0.5%, Si: 0.1 to 0.5% Cu: 0.1 to 0.3%, Ti: 0.1% or less, B: 0.1% or less, the balance is an aluminum alloy plate made of Al and inevitable impurities, The maximum n value of the change curve of the work hardening index (n value) with respect to the strain amount in the entire uniform plastic strain region is 0.1 or more, the electrical conductivity is 30.0 to 39.0% IACS, and the rolling direction of the base plate An aluminum alloy plate for a beverage can body, wherein the tensile strength in the case is 320 MPa or less and the strength after baking is 250 MPa or more in terms of proof stress in the rolling direction.   The aluminum alloy plate for beverage can bodies according to claim 1, wherein the baking is performed by holding the coating baking at 180 to 220 ° C for 5 to 30 minutes, or holding the maximum baking temperature at 210 to 260 ° C within 2 minutes.   The aluminum alloy plate for beverage can bodies according to claim 1 or 2, wherein the thickness of the oxide film on the surface of the plate is 20 nm or less.   Mn: 0.7-1.5%, Mg: 0.8-1.5%, Fe: 0.35-0.5%, Si: 0.1-0.5%, Cu: 0.1 An aluminum alloy ingot containing 0.3%, Ti: 0.1% or less, B: 0.1% or less, the balance being Al and inevitable impurities is manufactured, and the aluminum alloy ingot is face-cut. Then, a homogenization treatment is performed, and then hot rolling is performed to obtain a plate thickness of 1.5 to 2.5 mm. Further, this alloy plate is rapidly heated to a temperature of 550 to 600 ° C. in a continuous annealing furnace for 300 seconds. The maximum n value of the change curve of the work hardening index (n value) with respect to the amount of strain in the entire uniform plastic strain region is 0.1 or more and the conductivity is 30.0 to 39.0%. It is IACS, the tensile strength in the rolling direction of the base plate is 320 MPa or less, the strength after paint baking Method for producing a beverage can body for an aluminum alloy sheet, characterized in that in the rolling direction of the yield strength is at least 250 MPa.   The production of an aluminum alloy plate for beverage can bodies according to claim 4, wherein the coating baking is performed by holding at 180 to 220 ° C for 5 to 30 minutes, or holding at a maximum achieved temperature of 210 to 260 ° C within 2 minutes. Method.   The beverage can according to claim 4 or 5, wherein the alloy plate is rapidly heated to a temperature of 550 to 600 ° C by a continuous annealing furnace and held for 300 seconds or less, and then cooled at a cooling rate of 800 ° C / second or less. Manufacturing method of aluminum alloy plate for trunk.   After rapidly heating the alloy sheet to a temperature of 550 to 600 ° C. by a continuous annealing furnace and holding it for 300 seconds or less, cold rolling is performed at a total rolling rate of 70% or more and the exit temperature of the final pass is 130 ° C. or more. The aluminum alloy plate for beverage can bodies according to any one of claims 4 to 6, wherein a recovery process of the material structure is performed by applying the other side of the rolling pass under a temperature condition of 130 ° C or lower. Production method.   The homogenization treatment is performed in a temperature range of 550 to 620 ° C., the alloy plate is rapidly heated to a temperature of 550 to 600 ° C. by a continuous annealing furnace, and the atmosphere gas in the annealing furnace has a dew point of 10 ° C. or less in an atmosphere of 300 ° C. The manufacturing method of the aluminum alloy plate for drink can bodies as described in any one of Claim 4 thru | or 7 which hold | maintains time for less than second, and manages the thickness of the oxide film on the plate surface to 20 nm or less.

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