JP2016160511A - Aluminum alloy sheet for negative pressure can-top - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an aluminum alloy sheet for negative pressure can-top reducing ear rate difference of a sheet width direction in an alloy sheet manufactured by cold rolling without intermediate annealing after hot rolling.SOLUTION: There is provided an aluminum alloy sheet for negative pressure can-top containing Si:0.05 to 0.40%mass, Fe:0.10 to 0.50 mass%, Mn:0.10 to less than 0.80 mass%, Mg:1.0 to 3.5 mass% and the balance Al with inevitable impurities and having recrystallization rate of a sheet after hot rolling of 90% or more, difference of area percentage in a cube direction at a center part and an end part of 10% when measuring an aggregate structure from a sheet surface of a cross section parallel to a rolling direction at the center part and the end part of the sheet width direction to 1/4 thickness of the sheet thickness and aspect ratio of a crystal grain of a surface of the sheet after cold rolling of 5 or more. There is further provided an aluminum alloy sheet for negative pressure can-top containing Cu of 0.40% or less.SELECTED DRAWING: None

Description

  The present invention relates to an aluminum alloy plate for a negative pressure can lid, and more particularly to an aluminum alloy plate for a negative pressure can lid with a small difference in ear rate in the plate width direction.

2. Description of the Related Art Conventionally, as a packaging container for beverages, a two-piece type aluminum can having a cylindrical body with a bottom and a lid has been widely used.
<General manufacturing process for can lids>
A can lid constituting such an aluminum can is manufactured by the following process. First, after applying chemical conversion treatment such as chromate treatment to ensure corrosion resistance to the aluminum alloy plate for negative pressure can lid as a raw material, one side of the aluminum alloy plate for negative pressure can lid subjected to the chemical conversion treatment, or Paint and bake on both sides.

  Next, the painted and baked aluminum alloy plate for negative pressure can lid is blanked into a predetermined shape, and then shell molding is performed. Subsequently, the shell-formed aluminum alloy plate for negative pressure can lid is formed with a can body and a tightening portion (curl portion) for tightening to form a can lid, and rubber is attached to the tightening portion of the can lid. Perform compound drying to inject. After that, conversion molding including rivet molding process for bubble molding and button molding, score processing for groove processing of openings, bead / emboss molding process for processing irregularities and letters, and stake molding process for tabbing I do. Finally, after filling the contents of the can body, the can body and the can lid subjected to the molding process are wound and cleaned and sterilized.

<About required characteristics of can lid>
When the can lid and the can body are tightened, if the curled portion has a variation in dimensions, winding failure may occur, and the can lid is required to have strict dimensional accuracy. Furthermore, after winding, when the inner pressure rises due to heating during the sterilization process, the pressure strength is such that it does not reverse (buckling), and after reaching the consumer's hand, the tab is raised (or pulled) to open the can , It is required that the mouth open without trouble

<Required properties of materials>
In order to obtain such a can lid, the aluminum alloy plate used as a material has a moldability to the can lid, a low deformation anisotropy (ear ratio) for suppressing winding failure, a material strength for obtaining a pressure resistance strength, Rivet moldability and tearability (can openability) are required so as not to cause open can failure.
In forming can lids, in general, the blank plate to be drawn is not a perfect circle but a non-circular shape in consideration of the material's ear rate, and the amount of material flowing into the die hole during drawing is changed in the circumferential direction. The height of the mouth edge of the lid after drawing is made uniform. However, when the material has a high ear ratio, it is difficult to equalize the height of the lip of the lid after drawing, even with this method, and thus there is an increasing demand for a material with a low ear ratio.

  On the other hand, Patent Documents 1 to 3 disclose an aluminum alloy plate for can lids having a low ear rate, and Patent Document 4 discloses an aluminum alloy for can lids having a low ear rate and a small ear rate difference in the plate width direction. A plate is disclosed. In addition, the aluminum alloy plate for can lids described in Patent Documents 1 to 4 is not subjected to intermediate annealing after hot rolling or during cold rolling, from the viewpoint of cost reduction, and after cold rolling. It is manufactured by coiling and self-annealing, and is generally called a direct process material or simply a direct material.

JP2013-023757A JP 2009-221567 A JP 2011-052290 A JP2007-131920A

  In a relatively wide aluminum alloy sheet, due to the temperature difference generated between the end part and the center part in the sheet width direction during hot rolling, the structure formation during and after hot rolling is significantly affected. A structural deviation in the sheet width direction occurs in the hot rolled material. When intermediate annealing is applied after hot rolling or in the middle of cold rolling (intermediate annealing after hot rolling (before cold rolling) is also called rough annealing), the structure deviation is eliminated by intermediate annealing, In the product plate after hot rolling, the difference in the ear rate in the plate width direction can be reduced. However, in the case of a direct process material that does not perform intermediate annealing, the structural deviation that occurs in the hot-rolled material is easily carried over to the product plate after cold rolling, which causes a large ear ratio difference in the plate width direction.

In Patent Document 4, by controlling the plate temperature after hot rough rolling (immediately before the start of hot finish rolling), the flow rate of rolling oil in hot finish rolling, and the winding conditions after hot rolling, The difference in the ear rate in the width direction of the aluminum alloy plate is reduced to within 2%. However, in order to further improve the dimensional accuracy of the can lid after drawing, there is a demand for a more severe reduction in the ear rate difference.
Accordingly, an object of the present invention is to further reduce the difference in the ear rate in the plate width direction in the direct process material of the aluminum alloy plate for negative pressure can lid having the same components as the conventional material.

In order to solve the above-mentioned problems, the present inventors set each element in the aluminum alloy within a predetermined range, and then control the rolling logarithmic distortion of each stand of hot finish rolling, so The present inventors have found that the rate difference is reduced and have reached the present invention.
The aluminum alloy plate for negative pressure can lids according to the present invention has Si: 0.05% by mass or more and 0.40% by mass or less, Fe: 0.10% by mass or more, 0.50% by mass or less, Mn: 0.00%. 10% by mass or more, less than 0.80% by mass, Mg: 1.0% by mass or more, 3.5% by mass or less, consisting of the balance Al and inevitable impurities, the recrystallization rate of the plate after hot rolling is When the texture from the plate surface of the cross section parallel to the rolling direction to 90% of the plate thickness is measured at the center and the end in the plate width direction at 90% or more, the cubes at the center and the end are measured. The difference in the area ratio of the orientation is 10% or less, and the aspect ratio of the crystal grains on the surface of the plate after cold rolling is 5 or more. The aluminum alloy contains Cu: 0.4% by mass or less as required.

  According to the present invention, in the direct process material of the aluminum alloy plate for can lids, the difference in the ear rate in the plate width direction can be further reduced, so that the lid shape after drawing is formed depending on the forming position in the plate width direction. It is possible to suppress the difference between the two. Moreover, the aluminum alloy plate for negative pressure can lids according to the present invention has a high material strength and a required pressure strength, and is excellent in rivet formability.

It is a figure explaining the position which measured texture. It is sectional drawing explaining the overhang test for evaluating rivet formability. It is a figure explaining the position which extract | collected the test piece which measures an ear rate difference.

Hereinafter, regarding the aluminum alloy plate for a negative pressure can lid according to the present invention, its component composition, texture of the plate after hot rolling (area ratio of cube orientation), crystal grain of the plate after cold rolling (product plate) The aspect ratio and manufacturing method will be described.
<Ingredient composition>
Si: 0.05% by mass or more and 0.40% by mass or less Si forms Mg-Si-based and Al-Fe-Mn-Si-based crystals in the aluminum alloy, and recrystallizes after hot rolling. There is an effect to promote. When the Si content is less than 0.05% by mass, the amount of scrap that can be used as the raw material for the aluminum alloy plate is reduced, and the required purity of the aluminum ingot is increased, which increases the cost. On the other hand, when the Si content exceeds 0.40 mass%, many fine Al—Fe—Mn—Si based precipitates are generated in the aluminum alloy in the process up to hot rolling, and recrystallization after hot rolling. Hinders the rivet formability. Therefore, the Si content is set to 0.05% by mass or more and 0.40% by mass or less.

Fe: 0.10 mass% or more and 0.50 mass% or less Fe forms Al-Fe-Mn-based and Al-Fe-Mn-Si-based crystallized products in the aluminum alloy. It has the effect of promoting crystals. When the Fe content is less than 0.10% by mass, the crystallized product is insufficient, recrystallization after hot rolling becomes insufficient, and rivet formability is deteriorated. On the other hand, when the Fe content exceeds 0.50% by mass, the crystallized material in the aluminum alloy sheet is large and excessively formed, and the rivet formability is lowered. Therefore, the Fe content is set to 0.10% by mass or more and 0.50% by mass or less.

Mn: 0.10% by mass or more and less than 0.80% by mass
Mn has the effect of improving the strength of the aluminum alloy sheet, and forms Al-Fe-Mn and Al-Fe-Mn-Si crystals in the aluminum alloy sheet, and recrystallizes after hot rolling. Has the effect of promoting When the content of Mn is less than 0.10% by mass, the strength of the aluminum alloy sheet becomes insufficient, and recrystallization after hot rolling becomes insufficient, thereby reducing the rivet formability. On the other hand, when the content of Mn is 0.80% by mass or more, the crystallized material in the aluminum alloy plate is large and excessively formed, and the rivet formability is lowered. Accordingly, the Mn content is set to 0.10% by mass or more and less than 0.80% by mass.

Mg: 1.00 mass% or more and 3.50 mass% or less Mg has the effect of improving the strength of the aluminum alloy plate. When the Mg content is less than 1.00% by mass, the strength of the aluminum alloy plate is insufficient, and the pressure strength when formed into a can lid is insufficient. On the other hand, when the Mg content exceeds 3.50% by mass, the strength of the aluminum alloy plate becomes excessive, and the rivet formability decreases. Therefore, the Mg content is set to 1.00% by mass to 3.50% by mass.

Cu: 0.40 mass% or less Cu has an effect of improving the strength of the aluminum alloy plate, and is added as necessary. When the Cu content exceeds 0.40% by mass, the strength of the aluminum alloy plate becomes excessive, and the rivet formability decreases. Therefore, the Cu content is set to 0.40 mass% or less.
Inevitable Impurities The aluminum alloy sheet according to the present invention contains inevitable impurities in addition to the above elements. As inevitable impurities, for example, Cr, Ti, Zr, and Zn are each 0.30% by mass or less, preferably 0.05% by mass or less, and V, Ni, In, Sn, Ga, and other elements are each 0.05% by mass. The content is allowed in the range of% or less.

<Cover direction area ratio>
When the texture from the plate surface having a cross section parallel to the rolling direction to a quarter thickness of the plate thickness is measured at the center and end in the plate width direction of the plate after hot rolling, the center and end The difference in the area ratio of the cube orientation in the part is 10% or less. There is a high correlation between the area ratio of the cube orientation of the plate after hot rolling and the ear ratio of the plate (product plate) after cold rolling, and the difference in the area ratio of the cube orientation of the plate after hot rolling is 10% In the case of the following, in the drawing of the plate after cold rolling, the difference in the ear ratio in the plate width direction can be reduced to 1% or less. In addition, the area where the area ratio of the cube orientation is measured is the plate thickness surface layer portion (region from the plate surface to ¼ thickness of the plate thickness) because the measurement is performed on the plate thickness surface layer portion from the plate thickness center portion. This is because a difference in the area ratio of the cube orientation tends to occur between the central portion and the end portion in the plate width direction.

<Aspect ratio of crystal grains>
The aluminum alloy sheet according to the present invention is a so-called direct process material produced by cold rolling without intermediate annealing after hot rolling. The aluminum alloy sheet after hot rolling is recrystallized to make the crystal grains equiaxed, and the crystal grains are elongated in the rolling direction by the subsequent cold rolling. In the present invention, the average crystal grain size (average crystal grain length) measured in the rolling direction by the linear crossing method is the same as the average crystal grain size (average crystal grain) measured in the direction perpendicular to the rolling direction by the linear crossing method. The value divided by (width) is called the aspect ratio of the crystal grains. By performing cold rolling at a rolling rate described later, the aspect ratio of the crystal grains on the plate surface after cold rolling becomes 5 or more. When the aspect ratio is 5 or more in the plate after cold rolling, the processed structure by cold rolling is sufficiently developed, thereby reducing the difference in structure in the plate width direction that had occurred in the plate after hot rolling, The ear rate difference in the plate width direction is reduced. On the other hand, when the aspect ratio is less than 5, the development of the processed structure is insufficient, and the difference in structure in the plate width direction that has occurred in the plate after hot rolling is not reduced, and the ear ratio in the plate width direction is reduced. The difference does not become small.
In the case of an aluminum alloy plate for negative pressure can lid that is not a direct process material that has been subjected to intermediate annealing during cold rolling, the aspect ratio of the crystal grains on the plate surface after cold rolling is usually less than 5.

<Manufacturing method>
The said aluminum alloy plate for negative pressure can lids can be manufactured in the process of casting, homogenization heat processing, hot rolling, and cold rolling.
For casting, a semi-continuous casting method (DC (direct chill) casting) is used.
Homogenization heat processing is performed on the conditions which hold | maintain the ingot obtained by DC casting at 480-620 degreeC for 2 to 10 hours. If the treatment temperature is less than 480 ° C., the solute elements are not sufficiently homogenized. If the treatment temperature exceeds 620 ° C., local melting (burning) may occur on the surface of the ingot. If the holding time is 2 hours or more, homogenization is possible, and if it exceeds 10 hours, energy costs are wasted. This homogenization heat treatment also serves as preheating for subsequent hot rolling.

  Hot rolling consists of hot rough rolling and hot finish rolling. In the aluminum alloy sheet after hot rough rolling (immediately before the start of hot finish rolling), the temperature at the center of the plate is set to 400 ° C. to 480 ° C., and the temperature difference between the temperature at the end of the plate and the center of the plate is set to 40 ° C. . The temperature at the center of the plate immediately before the start of hot finish rolling is set to 400 ° C. or higher to ensure the end temperature (winding temperature) of hot finish rolling described later, while the temperature is set to 480 ° C. or lower. This is to prevent surface defects such as pickup inclusion from occurring. In addition, the temperature difference between the plate end and the plate center is 40 ° C. or less. If the temperature difference is further increased, the structure deviation in the plate width direction is sufficiently reduced even when hot finish rolling described later is performed. This is because it cannot be done.

Hot finish rolling is performed using a finishing mill composed of 4 tandem-type stands, and the sum of the logarithmic strain (ε ₁ ) of the first stand and the logarithmic strain (ε ₂ ) of the second stand is 1. 25 or less (ε ₁ + ε ₂ ≦ 1.25). In addition, the 4 stand eyes of pressure logarithmic strain (ε ₄₎ and 3 stand of the eye of the pressure logarithmic strain (ε ₃₎ the difference between the 0.16 or more _{(ε 4 -ε 3 ≧ 0.16)} . The rolling logarithmic strain ε is expressed by the following formula 1 where the entry side plate thickness is t ₀ and the exit side plate thickness is t.
ε = ln (t ₀ / t) (1)

When the sum of the logarithmic distortions of the first and second stands exceeds 1.25 (ε ₁ + ε ₂ > 1.25), the plate widths at the first and second stands due to the temperature difference in the plate width direction. More distortion accumulates at the end in the plate width direction than at the center in the direction. On the other hand, in the present invention, the total degree of logarithmic distortion of the first stand and the second stand is suppressed to 1.25 or less (ε1 + ε2 ≦ 1.25), so that the progress of recrystallization at the center in the plate width direction is reduced to the plate. It is suppressed to the same extent as the end portion in the width direction, and distortion accumulation in the plate width direction is equalized. Thereby, the ratio of the cube orientation in the crystal grains grown after hot finish rolling is equalized in the plate width direction.

Further, in the present invention, the difference between the logarithmic distortions at the 4th and 3rd stands is set to 0.16 or more (ε ₄ −ε ₃ ≧ 0.16), and the logarithmic distortion at the 3rd stand is suppressed and the final stand is used. Concentrate the distortion. By suppressing the logarithmic distortion at the 3rd stand, as in the 1st and 2nd stands, it is possible to suppress the difference in strain accumulation due to the temperature difference in the plate width direction. Accumulation is equalized. On the other hand, by increasing the logarithmic distortion at the 4th stand, the progress of recrystallization after winding is equalized in the sheet width direction, and as a result, the recrystallized grains growing after hot finish rolling The ratio of the cube orientation can be equalized in the plate width direction.

If the difference in the logarithmic distortion between the fourth stand and the third stand is less than 0.16 (ε ₄ −ε ₃ <0.16), strong processing is applied to the first to third stands, and the plate width direction Can make a difference in the progress of recrystallization. For this reason, there is a difference in strain accumulation in the plate width direction, and the amount of cube orientation in the recrystallized grains grown after hot finish rolling is larger at the end portion in the plate width direction than in the center portion in the plate width direction. As a result, the ear rate at the end in the plate width direction becomes a negative ear (strong at 0-90 °), and the difference in the ear rate in the plate width direction becomes large.

  The finish temperature (winding temperature) of hot finish rolling is 300 to 370 ° C. By winding at this temperature, the aluminum alloy plate has a recrystallized structure. In order to obtain excellent rivet formability in an aluminum alloy sheet after cold rolling, the recrystallization rate of the hot rolled sheet needs to be 90% or more (the unrecrystallized portion is less than 10%). When the coiling temperature is less than 300 ° C., the recrystallization rate of the hot-rolled plate is lowered, and the rivet formability of the plate after cold rolling (product plate) is lowered. On the other hand, when the coiling temperature exceeds 370 ° C., the material temperature during hot finish rolling is too high, and surface defects such as pickup inclusion may occur. The winding temperature can be adjusted by the amount of rolling reduction at the third stand and the fourth stand.

Cold rolling is performed at a rolling rate of 80 to 93% in total, and intermediate annealing is not performed before or during the cold rolling. When the rolling rate of cold rolling is less than 80%, the aspect ratio of the crystal grain size of the plate (product plate) after cold rolling is small, the development of the processed structure is insufficient, and the difference in the ear rate in the plate width direction is sufficient. It will not decline. Further, the strength of the plate after cold rolling is not sufficiently improved. On the other hand, if the rolling rate of cold rolling exceeds 93%, the number of cold rolling passes (the number of rolling) increases, and the productivity decreases. On the other hand, when the rolling rate exceeds 93%, the yield strength is excessively increased and the formability is lowered, or the ear rate when drawing is increased.
By the above manufacturing method, the direct process material of the aluminum alloy plate for negative pressure can lids concerning the present invention can be obtained.

  As mentioned above, although the form for implementing this invention has been described, the Example which confirmed the effect of this invention is demonstrated concretely compared with the comparative example which does not satisfy | fill the requirements of this invention below. In addition, this invention is not limited to this Example.

(Sample material production)
An aluminum alloy having the composition shown in Table 1 was melted and cast, and the ingot surface layer was chamfered to produce a slab. The slab was subjected to homogenization heat treatment and then hot rolled (hot rough rolling and hot finish rolling). Condition of homogenization treatment, end temperature of hot finish rolling (winding temperature), sum of logarithmic strain (ε ₁ ) of the first stand and logarithmic strain (ε ₂ ) of the second stand (ε ₁ + ε ₂ ) , showing 4 difference between the stand-th pressure logarithmic strain (ε ₄₎ and 3 stand of the eye of the pressure logarithmic strain (ε ₃₎ the (ε ₄ -ε ₃₎ in Table 2. In addition, the aluminum alloy plate after hot rough rolling (immediately before the start of hot finish rolling) has a temperature at the center of the plate in the range of 400 ° C to 480 ° C, and the temperature at the end of the plate and the temperature at the center of the plate. The difference was in the range of 5-30 ° C.
After hot rolling, cold rolling (coarse rolling and finish rolling) was performed without performing intermediate annealing, and a product plate (aluminum alloy plate for can lids) having a thickness of 0.250 mm was produced. Table 2 shows the total cold rolling rate.

The following measurement tests were conducted using a plate after hot rolling (hot rolled plate) and a plate after cold rolling (product plate) as test materials. The results are shown in Table 3.
<Measurement of recrystallization rate>
A test piece is cut out from each sample material (hot rolled plate), embedded in a polishing resin so that a cross section parallel to the rolling direction can be observed, the cross section is polished to a mirror surface, and then etched, and then the magnification is 100. The crystal structure was observed with a double optical microscope, and the recrystallization rate was measured. The observed cross-section was made into three places, a plate width direction center part and both ends (position of 20 mm from the end) in each specimen. The thickness of the test specimen t, when the thickness of the recrystallized structure was measured in the thickness direction t _r, also the thickness of the non-recrystallized portion has a t _n, a t = t r ₊ t _n, recrystallization ratio Is a value calculated by (t _r / t) × 100. The recrystallized structure is composed of equiaxed grains, the non-recrystallized part is a processed structure extending in the rolling direction, and both can be distinguished by the crystal grain shape in the cross section. For each sample material, the value of the lowest recrystallization rate among the three locations is shown in Table 3 as the recrystallization rate of each sample material. The appropriate range for the recrystallization rate was 90% or more. If the recrystallization rate of the hot rolled sheet is 90% or more, there will be no problem in the rivet formability of the product sheet (aluminum alloy sheet for negative pressure can lid). In Table 3, ○ mark in the column of recrystallization rate means that the recrystallization rate is 90% or more, and X mark means less than 90%.

<Measurement of texture>
A test piece was cut out from each sample material (hot rolled plate), embedded in a polishing resin so that a cross section parallel to the rolling direction could be observed, and the cross section was polished into a mirror surface. Thereafter, the cross section was subjected to ion etching using ESCA (Electron Spectroscopy for Chemical Analysis), and the cube orientation area ratio of the cross section parallel to the rolling direction was measured using an EBSD (Electron Back Scattering Diffraction) method. Measurement by the EBSD method was carried out using an FE-SEM7000F scanning electron microscope manufactured by JEOL Ltd. and TSL Solutions, Inc., a photodetector, and an acceleration voltage of the measuring apparatus at 20 kV. The observed cross section is the center in the plate width direction and one end (position of 20 mm from the end) in each specimen, and the measurement points in the cross section are the same in the plate thickness direction as shown in FIG. It was made into either one of the plate | board thickness surface layer part (area | region from the plate | board surface to 1/4 thickness of plate | board thickness) when equally dividing | segmenting into 4 equally. Further, the difference between the cube azimuth area ratios at the center in the plate width direction and the cube azimuth area ratio at the ends in the plate width direction was calculated. When the difference in the cube azimuth area ratio is 10% or less, the difference in the ear ratio in the plate width direction of the product plate can be within 1%. Here, the cube orientation is a crystal grain in which the {100} plane is the plate surface and the <001> direction is parallel to the rolling direction, and a grain having an inclination angle of 15 ° or less from the ideal orientation of the cube orientation is defined as the cube orientation. The azimuth area ratio was calculated.

<Measurement of aspect ratio of crystal grains>
A test piece was cut out from each sample material (product plate), the surface was polished to a mirror surface, then the surface was electrolytically etched, and the crystal grain structure was observed and photographed with an optical microscope at a magnification of 100 times. Using this photograph, the average crystal grain size (average crystal grain length) in the direction perpendicular to the rolling direction was measured by a straight line cutting method. Specifically, in a direction perpendicular to the rolling direction, draw a line segment that is 0.3 mm or more in terms of the scale on the photograph, count the number of crystal grains that are completely cut by the line segment, and calculate the cutting length. The average value was obtained. The same measurement was repeated by changing the place on the photograph (total 5 times), and the average value of the cut lengths was obtained. A value obtained by further averaging the obtained average values of the five cut lengths was defined as an average crystal grain size (average crystal grain width) in a direction perpendicular to the rolling direction. Moreover, the same measurement was performed also in the rolling direction using the said photograph, and the average crystal grain size (average crystal grain length) of the rolling direction was calculated | required. The value obtained by dividing the average crystal grain size (average crystal grain length) in the rolling direction by the average crystal grain size (average crystal grain width) perpendicular to the rolling direction was taken as the aspect ratio of the crystal grains.

<Measurement of 0.2% yield strength>
Each specimen (product plate) was heat-treated at 250 ° C for 20 seconds using an oil bath simulating the painting and baking process, and then the JIS-5 tensile test piece so that the tensile direction was parallel to the rolling direction. A tensile test was performed according to the provisions of JISZ2241, and a 0.2% proof stress was obtained. The suitable range of 0.2% proof stress was 250 MPa or more. When the 0.2% proof stress is 250 MPa or more, even a thin can lid satisfies the pressure strength. From the viewpoint of rivet formability, the 0.2% proof stress is preferably 298 MPa or less.

<Measurement of rivet formability>
After each sample material (product plate) was heat-treated at 250 ° C. for 20 seconds using an oil bath simulating the painting / baking process, a 50 mm × 50 mm test piece was prepared from each sample material, and the bubble process was performed. A simulated overhang test was performed to determine the limit overhang height. In the overhang test, as shown in FIG. 2, the test piece 1 is sandwiched between upper and lower dies 2 and 3, fixed with a certain wrinkle pressing force, and the punch 4 is pushed vertically into the center of the test piece 1. The overhanging process was performed. The dies 2 and 3 have an inner diameter of 6.60 mm and a shoulder radius of 0.40 mm, the punch 4 has an outer diameter of 6.00 mm, a diameter of the central flat portion of the head of 1 mm, and a shoulder radius of the head of 2 .50 mm.
By this overhang test, the limit value (limit overhang height) of the overhang height at which the overhanging process can be performed without causing cracks and constriction on the test piece 1 was measured. The appropriate range of the limit overhang height was 1.45 mm or more. If the limit overhang height is 1.45 mm or more, a button having a sufficient height can be formed at the time of actual forming, the rivet formability is excellent, and the tab can be firmly fixed by a stake process. In addition, if the tab is not fixed enough, the tab may be removed when the can is opened, and the drinking mouth does not open.

<Measurement of ear rate difference>
Each test material (product plate) was heat-treated at 250 ° C for 20 seconds using an oil bath simulating the painting and baking process, and then tested at a width of 100 mm from the center and both ends (see Fig. 3) in the plate width direction. A total of three pieces were cut out. Next, a circular blank having a diameter of 66.7 mm was collected from the center of each test piece, and drawn into a cylindrical container with a drawing ratio of 1.67. The height of the side wall of the cylindrical container was measured at a total of 8 points at a 45 ° pitch in the circumferential direction with reference to the rolling direction of the bottom surface of the cylindrical container, and the ear rate (r _e ) was obtained from the calculation formula (2) below. However, the following formula 2 in h ₄₅ is the average height of the ear 45 ° direction 4 positions relative to the said rolling direction, h _{0, 90} ears of 0 ° and 90 ° directions four locations relative to the said rolling direction Average height of h _av. Means the average height of all measurement points. The difference between the maximum value and the minimum value (ear rate difference) was determined from the value of the ear rate (r _e ) obtained from the three test pieces. A test material having an ear ratio difference of 1% or less was judged as good, and a test material exceeding 1% was judged as bad. R _e = {(h ₄₅ −h _0,90 ) / h _av. } × 100 (%) (2)

As shown in Table 3, the composition of the aluminum alloy plate, the recrystallization rate, the difference in the area ratio of the cube orientation, and the aspect ratio of the crystal grains satisfy the provisions of the present invention. Nos. 1 to 7 have high strength of the product plate (250 MPa or more), excellent rivet formability (limit overhang height of 1.45 mm or more), and the difference in the ear rate between the center portion and the end portion in the plate width direction is 1% or less. And small.
In contrast, Comparative Example No. In No. 1, since the Si content is excessive, the recrystallization rate of the hot-rolled sheet is low, and the rivet formability of the product sheet is inferior.
Comparative Example No. No. 2 has a low Fe content, so the recrystallization rate of the hot-rolled sheet is low, and the rivet formability of the product sheet is inferior.
Comparative Example No. In No. 3, since the Cu content is excessive, the strength becomes too high, and the rivet formability of the product plate is inferior. Comparative Example No. 3 has a small difference (ε ₄ −ε ₃ ) between the roll-down logarithmic strain at the 4th stand and the roll-down logarithmic strain at the 3rd stand, so the area ratio difference in the cube orientation of the hot-rolled plate is large. The rate difference has increased.

Comparative Example No. No. 4 has a low Mn content, so the recrystallization rate of the hot rolled sheet is low, and the rivet formability of the product sheet is inferior.
Comparative Example No. No. 5 is inferior in the rivet formability of the product plate because the Mn content is excessive.
Comparative Example No. No. 6 has a low Mg content, so the strength of the product plate is low.
Comparative Example No. In No. 7, since the Mg content is excessive, the strength of the product plate becomes too high and the rivet formability is poor. Comparative Example No. 7 is that the sum of the logarithmic strains of the first and second stands (ε ₁ + ε ₂ ) is too large, and the difference between the logarithmic strains of the fourth and third stands (ε ₄ −ε). ₃ ) was too small, the area ratio difference in the cube orientation of the hot rolled sheet was large, and the ear ratio difference of the product sheet was large.

In Comparative Examples 8 to 12, the sum of the logarithmic strains of the first and second stands (ε ₁ + ε ₂ ) is too large, or / and the fourth log and the third log of the logarithmic strain are reduced. The difference (ε ₄ −ε ₃ ) was too small. For this reason, all of Comparative Examples 8-12 had a large area ratio difference in the cube orientation of the hot-rolled sheet, and a difference in the ear ratio of the product sheet.
In Comparative Example 13, since the cold rolling ratio was low, the aspect ratio of the crystal grain size was small, the development of the processed structure was insufficient, and the difference in the ear ratio of the product plate was large.

1 Specimen 2, 3 Dice 4 Punch

In order to solve the above-mentioned problems, the present inventors set each element in the aluminum alloy within a predetermined range, and then control the rolling logarithmic distortion of each stand of hot finish rolling, so The present inventors have found that the rate difference is reduced and have reached the present invention.
The aluminum alloy plate for negative pressure can lids according to the present invention has Si: 0.05% by mass or more and 0.40 % by mass or less, Fe: 0.10% by mass or more, 0.50% by mass or less, Mn: 0.00%. 10% by mass or more, less than 0.80% by mass, Mg: 1.0% by mass or more, 3.5% by mass or less, a cold-rolled plate made of the balance Al and inevitable impurities, The aspect ratio is 5 or more, the 0.2% proof stress value measured after heat treatment at 250 ° C. for 20 seconds is 250 to 298 MPa, the limit overhang height value is 1.45 mm or more, and the central part in the plate width direction And the difference between the maximum value and the minimum value of the ear ratios at both ends (hereinafter, also simply referred to as a difference in ear ratio in the plate width direction) is 1% or less . However, in the present invention, the values of the 0.2% proof stress, the limit overhang height, and the ear ratio difference in the plate width direction are measured by the measurement method described in the examples described later.

<Measurement of ear rate difference in the plate width direction >
Each test material (product plate) was heat-treated at 250 ° C for 20 seconds using an oil bath simulating the painting and baking process, and then tested at a width of 100 mm from the center and both ends (see Fig. 3) in the plate width direction. A total of three pieces were cut out. Next, a circular blank having a diameter of 66.7 mm was collected from the center of each test piece, and drawn into a cylindrical container with a drawing ratio of 1.67. The height of the side wall of the cylindrical container was measured at a total of 8 points at a 45 ° pitch in the circumferential direction with reference to the rolling direction of the bottom surface of the cylindrical container, and the ear rate (r _e ) was obtained from the calculation formula (2) below. However, the following formula 2 in h ₄₅ is the average height of the ear 45 ° direction 4 positions relative to the said rolling direction, h _{0, 90} ears of 0 ° and 90 ° directions four locations relative to the said rolling direction Average height of h _av. Means the average height of all measurement points. The difference between the maximum value and the minimum value (the difference in the ear rate in the plate width direction ) was obtained from the value of the ear rate (r _e ) obtained from the three test pieces. Ear index difference good 1% or less of test material in the plate width direction, r was determined test materials of more than 1% defective _{e = {(h 45 -h 0,90} ) / h av. } × 100 (%) (2)

As shown in Table 3, the composition of the aluminum alloy plate, the recrystallization rate, the difference in the area ratio of the cube orientation, and the aspect ratio of the crystal grains satisfy the provisions of the present invention. Nos. 1 to 7 have high strength of the product plate (250 MPa or more), excellent rivet formability (limit overhang height of 1.45 mm or more), and a small ear ratio difference in the plate width direction of 1% or less.
In contrast, Comparative Example No. In No. 1, since the Si content is excessive, the recrystallization rate of the hot-rolled sheet is low, and the rivet formability of the product sheet is inferior.
Comparative Example No. No. 2 has a low Fe content, so the recrystallization rate of the hot-rolled sheet is low, and the rivet formability of the product sheet is inferior.
Comparative Example No. In No. 3, since the Cu content is excessive, the strength becomes too high, and the rivet formability of the product plate is inferior. Comparative Example No. 3, 4 for the stand-th reduction logarithmic distortion and 3 difference pressure logarithmic distortion of the stand eye (epsilon _{4-epsilon 3)} is small, the area ratio difference cube orientation of the hot rolled sheet is large, plate products plate The difference in the ear rate in the width direction became large.

Comparative Example No. No. 4 has a low Mn content, so the recrystallization rate of the hot rolled sheet is low, and the rivet formability of the product sheet is inferior.
Comparative Example No. No. 5 is inferior in the rivet formability of the product plate because the Mn content is excessive.
Comparative Example No. No. 6 has a low Mg content, so the strength of the product plate is low.
Comparative Example No. In No. 7, since the Mg content is excessive, the strength of the product plate becomes too high and the rivet formability is poor. Comparative Example No. 7 is that the sum of the logarithmic strains of the first and second stands (ε ₁ + ε ₂ ) is too large, and the difference between the logarithmic strains of the fourth and third stands (ε ₄ −ε). ₃ ) was too small, the area ratio difference in the cube orientation of the hot rolled sheet was large, and the difference in the ear ratio in the sheet width direction of the product sheet was large.

In Comparative Examples 8 to 12, the sum of the logarithmic strains of the first and second stands (ε ₁ + ε ₂ ) is too large, or / and the fourth log and the third log of the logarithmic strain are reduced. The difference (ε ₄ −ε ₃ ) was too small. For this reason, all of Comparative Examples 8-12 had a large area ratio difference in the cube orientation of the hot-rolled sheet, and a difference in ear ratio in the sheet width direction of the product sheet.
In Comparative Example 13, since the cold rolling ratio was low, the aspect ratio of the crystal grain size was small, the development of the processed structure was insufficient, and the difference in the ear ratio in the plate width direction of the product plate was large.

Claims (2)

Si: 0.05% by mass or more, 0.40% by mass or less, Fe: 0.10% by mass or more, 0.50% by mass or less, Mn: 0.10% by mass or more, less than 0.80% by mass, Mg: 1.0% by mass or more and 3.5% by mass or less, consisting of the balance Al and inevitable impurities, the recrystallization rate of the plate after hot rolling is 90% or more, and the center and end in the plate width direction When measuring the texture from the plate surface having a cross section parallel to the rolling direction to 1/4 of the plate thickness, the difference in the area ratio of the cube orientation at the central portion and the end portion is 10% or less. An aluminum alloy plate for a negative pressure can lid, wherein the aspect ratio of crystal grains on the surface of the plate after cold rolling is 5 or more. The aluminum alloy plate for a negative pressure can lid according to claim 1, further comprising Cu: 0.40% or less as an alloy component.

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