JP4121932B2 - Aluminum alloy plate for cap and method for producing the same - Google Patents

Description

  The present invention relates to an aluminum alloy plate for a container cap that requires low anisotropy and a method for producing the same, and more particularly to an aluminum alloy plate for a cap of a bottle can and a method for producing the same.

  In recent years, a beverage container comprising an aluminum bottle can having a body part and a mouth part and a screw cap attached to the mouth part has been developed. With the aluminumization of bottle cans, screw cap materials suitable for bottle cans are desired.

  In general, when the anisotropy of an aluminum alloy is not strictly controlled, the ear portion becomes large during screw cap molding. Trimming is necessary to remove the ears, and the occurrence of the ears directly leads to material loss. Therefore, in order to achieve cost reduction of the screw cap, it is an important issue to reduce the anisotropy of the aluminum alloy.

  In recent screw cap manufacturing processes, there is an increasing number of cases where a printing process is performed on an aluminum alloy plate before cap forming. If a cap is formed after printing on an aluminum alloy plate having high anisotropy, the printed pattern may be distorted. From these points, an aluminum alloy with low anisotropy is desired.

As an aluminum alloy having low anisotropy, Al-Mg alloys described in the following documents are conventionally known.
JP-A-4-68054

  However, the Al—Mg alloy described in Patent Document 1 has difficulty in balancing strength and formability, and is not sufficient as a material for the screw cap.

  The present invention has been made in view of the above circumstances, and by controlling the crystal orientation of an aluminum alloy plate strictly, the aluminum alloy for caps has good strength and formability and low anisotropy. It aims at providing a board and its manufacturing method.

In order to achieve the above object, the present invention employs the following configuration.
The aluminum alloy plate for a cap of the present invention contains Mg, Fe, Mn and Cr, the balance is made of Al and inevitable impurities, the cube orientation density of the texture is 7 or less, and each orientation belonging to the β fiber and the maximum orientation density is 15 or less, a tensile strength Ri 290MPa the range der least 190 MPa, Mg, Fe, each content of Mn and Cr, Mg: 1.5 mass% or more 2.1 wt% or less Fe: 0.4% by mass or less, Mn: 0.2% by mass or less, Cr: 0.2% by mass or less .

By molding the above-described aluminum alloy plate for cap, a cap having a bottomed cylindrical shape and having a screw portion on the circumferential portion is obtained.
By manufacturing the cap using the aluminum alloy plate for a cap having the above-described configuration, ears are not generated from the edge of the circumferential portion, and a trimming step is not necessary. That is, by setting the cube orientation density to 7 or less, ears are not generated in the directions of 0 ° and 90 ° with respect to the rolling direction of the aluminum alloy. Further, by setting the maximum orientation density of each orientation belonging to the β fiber to 15 or less, no ears are generated in the direction of ± 45 ° with respect to the rolling direction of the aluminum alloy.
Further, since the tensile strength is in the above range, the cap has sufficient strength, and there is no possibility that the screw portion of the cap is cracked.

Moreover, with the above configuration, the moldability and strength are excellent, and the ear rate can be reduced to approximately 0%.

  Further, the aluminum alloy plate for a cap according to the present invention includes, as impurities, Si of 0.3 mass% or less, Cu of 0.3 mass% or less, Zn of 0.2 mass% or less, Ti of 0.1 mass% or less. It may contain.

  Moreover, the aluminum alloy plate for caps of the present invention is the aluminum alloy plate for caps described above, and has an elongation of 2.0% or more. With this configuration, the cap can be easily molded. In particular, there is no risk of cracking or the like when the screw portion of the cap is molded.

Next, a method for producing an aluminum alloy plate for a cap according to the present invention is a method for producing an aluminum alloy plate for a cap according to any one of the above, and contains Mg, Fe, Mn, and Cr, with the balance being Al and An alloy composed of inevitable impurities, Mg having a composition of 1.5% by mass or more and 2.1% by mass or less, Fe of 0.4% by mass or less, and Mn and Cr each having a composition of 0.2% by mass or less. , After casting after casting, homogenization treatment is performed at a homogenization temperature of 450 ° C. or more and 590 ° C. or less, followed by hot rolling, cold rolling, and final reduction of 68.8% or more and 80% or less. After performing cold rolling sequentially, final temper annealing is performed at an annealing temperature of 150 ° C. or higher and 300 ° C. or lower.

According to the above configuration, an aluminum alloy plate having a cube orientation density of 7 or less, a maximum orientation density of each orientation belonging to the β fiber of 15 or less, and a tensile strength of 190 MPa or more and 290 MPa or less can be obtained.
In particular, by setting the rolling reduction in the above range, the tensile strength and the maximum azimuth density in each direction belonging to the β fiber can be set in the above range. Moreover, the time aging deterioration of the intensity | strength of an aluminum alloy plate can be prevented by performing final temper annealing.

  In particular, in the present invention, Mg, Fe, Mn and Cr are contained, the balance is made of Al and inevitable impurities, Mg is 1.9% by mass to 2.1% by mass, and Fe is 0.4%. In the case of an alloy having a composition of Mn and Cr of 0.15% by mass or more and 0.2% by mass or less, respectively, after melting and casting, a homogenization temperature of 520 ° C. or more and 590 ° C. or less Followed by hot rolling, cold rolling, and final cold rolling at a rolling reduction of about 66.5% to 73.3%, followed by annealing at 200 ° C. to 260 ° C. When the final temper annealing is performed at a temperature, an excellent aluminum alloy plate for a cap can be obtained.

  Furthermore, in the present invention, Mg, Fe, Mn and Cr are contained, the balance is made of Al and inevitable impurities, Mg is 1.5% by mass to 1.7% by mass, and Fe is 0.4%. In the case of an alloy having a composition of not more than% by mass and Mn and Cr of not more than 0.2% by mass, the alloy is homogenized at a temperature of 520 ° C. or more and 590 ° C. or less after casting after casting. Subsequently, hot rolling, cold rolling, and final cold rolling at a rolling reduction of about 66.5% to 73.3% are sequentially performed, followed by final temper annealing at an annealing temperature of 160 ° C. to 220 ° C. When performing this, an excellent aluminum alloy plate for a cap can be obtained.

  As described above, according to the aluminum alloy plate for a cap of the present invention, the strength and formability are good, the anisotropy is low, and a cap for a bottle can having a screw part can be easily formed. Can do.

Embodiments of the present invention will be described below.
The aluminum alloy plate for a cap of the present embodiment contains Mg, Fe, Mn and Cr, and the balance is made of Al and unavoidable impurities. After casting the alloy after casting, hot rolling, cold rolling In addition, it is obtained by final cold rolling at a predetermined rolling reduction, further homogenization treatment and final temper annealing, and each crystal orientation exhibits anisotropy, but the degree of anisotropy is small. It has a texture.

That is, the aluminum alloy plate for caps of this embodiment has a cube orientation density of 7 or less and the maximum of each orientation belonging to the β fiber when the crystal orientation anisotropy of the texture is evaluated by an orientation density distribution function. The orientation density is 15 or less.

  Moreover, this aluminum alloy plate for caps has a tensile strength in the range of 190 MPa or more and 290 MPa or less and an elongation of 2.0% or more.

  In this aluminum alloy plate for cap, the contents of Mg, Fe, Mn, and Cr are Mg: 1.5 mass% or more and 2.1 mass% or less, Fe: 0.4 mass% or less, Mn: 0.2 It is the range of mass% or less and Cr: 0.2 mass% or less, and the remainder consists of Al and inevitable impurities. Moreover, you may contain 0.3 mass% or less Si, 0.3 mass% or less Cu, 0.2 mass% or less Zn, and 0.1 mass% or less Ti as an impurity.

  Next, the reasons for limiting each parameter specifying the aluminum alloy plate for cap will be described.

Cube orientation density: 7 or less The cube orientation is an abbreviation for an orientation in which the <100> direction of the crystal is parallel to the rolling direction and the {001} plane is parallel to the rolling surface. In the structure of aluminum alloy sheet, the number of crystals having this orientation component increases and the orientation density exceeds 7 corresponds to the rolling direction of the alloy and the direction orthogonal to the rolling direction during cap forming by deep drawing. Ears will be generated at the position to be. In the present invention, the cube orientation density is set to 7 or less in order to prevent the generation of ears. Thereby, ears hardly occur in directions of 0 °, 180 °, and ± 90 ° with respect to the rolling direction.

Maximum orientation density of each orientation belonging to β-fiber: 15 or less β-fiber is an abbreviation for an orientation group in which the <110> direction of a crystal is parallel to a direction inclined by 60 ° from the plate normal direction to the rolling direction. In the structure of the aluminum alloy plate, there are many crystals having this orientation group component, and those whose maximum orientation density in each orientation exceeds 15 is the ± 45 ° direction of the rolling direction during cap forming by deep drawing. And an ear | edge will generate | occur | produce in the position corresponding to a +/- 135 degree direction. In the present invention, in order to prevent the occurrence of this ear, the maximum orientation density of each orientation of the β fiber is set to 15 or less. Thereby, ears hardly occur in the ± 45 ° direction and the ± 135 ° direction of the rolling direction.

Tensile strength: 190 MPa or more and 290 MPa or less When the tensile strength is less than 190 MPa, the strength of the cap obtained by molding is not preferable. On the other hand, if the tensile strength exceeds 290 MPa, the moldability deteriorates and it becomes difficult to mold the screw part of the cap, which is not preferable.

Elongation: When the elongation is 2.0% or more and less than 2.0%, the moldability deteriorates and it becomes difficult to mold the cap, which is not preferable.

Mg: 1.5 mass% or more and 2.1 mass% or less Mg improves the strength of the aluminum alloy plate. If Mg is less than 1.5%, the tensile strength decreases. Moreover, when Mg exceeds 2.1 mass%, plastic workability will fall.
In particular, it is preferable to adjust the Mg amount in relation to the rolling reduction, the homogenization temperature, and the final tempering annealing temperature during the production of the cap aluminum alloy plate. For example, when Mg is in the range of 1.9 mass% to 2.1 mass%, the homogenization temperature is in the range of 520 ° C. to 590 ° C., and the rolling reduction is 66.5% to 73.3%. When the final temper annealing temperature is in the range of 200 ° C. or higher and 260 ° C. or lower, the cube orientation density and the maximum orientation density of each orientation belonging to the β fiber can be further reduced, and the anisotropy of the alloy Can be further reduced.

  Further, when Mg is in the range of 1.5 mass% to 1.7 mass%, the homogenization temperature is in the range of 520 ° C. to 590 ° C., and the rolling reduction is 66.5% to 73.3%. When the final tempering annealing temperature is in the range of 160 ° C. or higher and 220 ° C. or lower, the cube orientation density and the maximum orientation density of each orientation belonging to the β fiber can be further reduced, and the alloy is anisotropic. Can be further reduced.

Fe: 0.4% by mass or less Fe improves the strength of the aluminum alloy sheet. However, if the Fe content exceeds 0.4% by mass, coarse compound particles are crystallized during casting and the plastic workability and formability deteriorate, which is not preferable.

Mn: 0.2% by mass or less, Cr: 0.2% by mass or less Both Mn and Cr have the effect of refining the recrystallized grains and improving the mechanical properties and formability of the aluminum alloy sheet. However, if Mn exceeds 0.2% by mass, the maximum orientation density of each orientation belonging to the β fiber increases, and the anisotropy of the alloy increases. On the other hand, if Cr exceeds 0.2% by mass, coarse compound particles are crystallized during casting, and the plastic workability and formability deteriorate, which is not preferable.

  As other impurities, Si: 0.3% or less, Cu: 0.3% or less, Zn: 0.2% or less, Ti: 0.1% or less are allowed in mass%.

By forming the above-described aluminum alloy plate for cap, a cap for a bottle can having a bottomed cylindrical shape and having a screw portion at the circumferential portion is obtained.
By manufacturing the cap using the aluminum alloy plate for a cap having the above-described configuration, ears are not generated from the edge of the circumferential portion, and a trimming step is not necessary. That is, by setting the cube orientation density to 7 or less, ears are not generated in directions of 0 °, 180 °, and ± 90 ° with respect to the rolling direction of the aluminum alloy. Further, by setting the maximum orientation density of each orientation belonging to the β fiber to 15 or less, no ears are generated in the directions of ± 45 ° and ± 135 ° with respect to the rolling direction of the aluminum alloy.
For this reason, the loss of material is reduced by eliminating the occurrence of ears, and the trimming process is not required, thereby saving labor.

Next, the manufacturing method of the aluminum alloy plate for caps of this embodiment is demonstrated.
The manufacturing method of the aluminum alloy plate for caps is 450 ° C. or more and 590 ° C. after casting an alloy containing a predetermined amount of Mg, Fe, Mn and Cr and the balance being Al and inevitable impurities, and then casting. Homogenization treatment is performed at the following homogenization temperature, followed by hot rolling, cold rolling, and final cold rolling at a reduction rate of 68.8% to 80%, and then 150 ° C to 300 ° C. The final tempering annealing is performed at the annealing temperature.

  In this manufacturing method, by performing final temper annealing after hot rolling, cold rolling and final cold rolling, the recrystallization is promoted and the anisotropy of the crystal orientation of the recrystallized grains is reduced. As a result, the mechanical anisotropy of the alloy itself can be reduced. Specifically, the anisotropy of the crystal orientation is reduced by using the alloy having the composition described above and controlling the homogenization temperature, the rolling reduction, and the final temper annealing temperature. Hereinafter, manufacturing conditions will be described in detail.

Homogenization treatment temperature: 450 ° C. or more and 590 ° C. or less The homogenization treatment has the effect of eliminating the microsegregation of the alloy elements generated during casting. Specifically, the aluminum alloy sheet that has been subjected to the homogenization treatment has less variation in various characteristics. When the homogenization treatment temperature is less than 450 ° C., microsegregation remains, and variations in various characteristics become large, and the quality of the aluminum alloy plate for caps is lowered. Further, if the homogenization temperature exceeds 590 ° C., there is a risk of local melting. Therefore, in this invention, the homogenization process temperature was 450 degreeC or more and 590 degrees C or less.
The holding time for holding the homogenization temperature is preferably in the range of 3 to 10 hours.

Final cold rolling reduction: 68.8% or more and 80% or less Cold rolling has the effect of increasing the strength, but the orientation density of the β fiber increases and the anisotropy of the crystal structure increases as the rolling rate increases. . If the rolling reduction is less than 68.8% , the strength of the alloy is insufficient, and if the rolling reduction exceeds 80%, the anisotropy increases. Therefore, in the present invention, the rolling reduction is set to 68.8% or more and 80% or less.

Final tempering annealing temperature: 150 ° C. or higher and 300 ° C. or lower Final tempering annealing plays a role of obtaining target mechanical properties in accordance with the final cold rolling reduction. The strength of the aluminum alloy sheet after the final cold rolling slightly decreases when left at room temperature for a long time. Also, softening occurs when paint baking is performed. Final temper annealing has the effect of preventing such a decrease in strength. If the final tempering annealing temperature is less than 150 ° C., the effect of preventing the decrease in strength is insufficient, and if it exceeds 300 ° C., the decrease in strength increases. Accordingly, in the present invention, the final temper annealing temperature is set to 150 ° C. or more and 300 ° C. or less.
The heating method for the final temper annealing may be a batch method or a rapid heating method. The heating time is preferably in the range of 1 to 15 hours in the batch method, and in the range of 10 to 120 seconds in the rapid heating method.

  The production method of the present invention provides an aluminum alloy plate for a cap having low anisotropy and having mechanical properties suitable for the purpose. To achieve this goal, the alloy components and production conditions are not controlled separately, but the homogenization, final cold rolling, and final temper annealing processes are appropriately controlled according to the alloy components. It is desirable.

For example, when Mg is in the range of 1.9 mass% to 2.1 mass%, the homogenization temperature is in the range of 520 ° C. to 590 ° C., and the rolling reduction is 66.5% to 73.3%. The final temper annealing temperature is preferably in the range of 200 ° C. or higher and 260 ° C. or lower.
Further, when Mg is in the range of 1.5 mass% to 1.7 mass%, the homogenization temperature is in the range of 520 ° C. to 590 ° C., and the rolling reduction is 66.5% to 73.3%. It is preferable that the final temper annealing temperature be in the range of 160 ° C. or higher and 220 ° C. or lower.

  Further, an intermediate annealing step may be provided before the final tempering annealing step. The intermediate annealing temperature is preferably at least the recrystallization temperature in consideration of the alloy components.

An alloy containing a predetermined amount of Si, Fe, Cu, Mn, Mg, Cr, Zn, and Ti and the balance being Al and inevitable impurities was melted and cast into a slab. Next, the homogenization process was performed over 4 hours at the homogenization temperature of 400 degreeC-580 degreeC. Subsequently, the plate thickness was adjusted to 6 mm by hot rolling. Subsequently, cold rolling was performed, and further intermediate annealing was performed by introducing into a continuous annealing furnace at 450 ° C. And after performing the last cold rolling by the reduction rate of 47.8%-82.5%, the final temper annealing for 4 hours was performed at the annealing temperature of 130 to 330 degreeC. Thus, the aluminum alloy plate for caps of Examples 1-9 , Reference Examples 1-2, and Comparative Examples 1-9 was manufactured. Table 1 shows the composition, homogenization temperature, final cold reduction rate, and final temper annealing temperature of the aluminum alloy.

  The cube orientation density of the aluminum alloy plate thus produced, the maximum orientation density in each orientation of the β fiber, the tensile strength, the yield strength, the elongation rate, and the mechanical strength were measured over time. The results are shown in Table 2. Cube orientation density and β fiber orientation density were measured by measuring the incomplete pole figures (up to 70 ° from the center) of <111>, <200>, and <220> with an X-ray diffractometer. Asked. Also, the presence or absence of a change in mechanical strength with time was determined by the width of change in yield strength when the produced aluminum alloy plate was left in a thermostatic chamber at 25 ° C. for one year. The case where the proof stress was reduced by 5% or more was judged as “bad”, and the case where it was less than 5% was judged as “good”.

As shown in Table 1 and Table 2, the aluminum alloys of Examples 1 to Example 9 shows good properties, in particular smaller cube orientation density and β fiber orientation density, subjected to deep draw molding It can be seen that ears do not occur even if

On the other hand, in Comparative Example 1, since the Mg content was excessive, both the tensile strength and the cube orientation density increased.
In Comparative Example 2, since the Mg content was too low, the tensile strength decreased and the β fiber orientation density increased.

  Next, in Comparative Example 3, the β fiber orientation density increased because the rolling reduction was too high. Moreover, since the reduction rate was too low about the comparative example 4, the cube orientation density increased.

  Next, since the Mn content was excessive for Comparative Example 5 and the Cr content was excessive for Comparative Example 6, both the β-fiber orientation densities increased.

  Next, in Comparative Example 7, since both the homogenization temperature and the final temper annealing temperature were too low, both the β fiber orientation density and the tensile strength increased, and the change with time exceeded 5% and became “bad”. It was.

  Next, in Comparative Example 8, since the Cu content was excessive, the tensile strength increased. Furthermore, since the final temper annealing temperature was too high for Comparative Example 9, the tensile strength was significantly reduced.

Claims (3)

It contains Mg, Fe, Mn and Cr and the balance is made of Al and inevitable impurities, the cube orientation density of the texture is 7 or less, and the maximum orientation density of each orientation belonging to the β fiber is 15 or less, tensile strength Ri 290MPa following range der more than 190MPa,
The content ratios of Mg, Fe, Mn and Cr are respectively Mg: 1.5% by mass to 2.1% by mass, Fe: 0.4% by mass or less, Mn: 0.2% by mass or less, Cr: 0.00%. An aluminum alloy plate for a cap, which is in a range of 2% by mass or less . 2. The aluminum alloy plate for a cap according to claim 1 , wherein the elongation percentage is 2.0% or more. A method for producing an aluminum alloy plate for a cap according to any one of claims 1 to 2 ,
Mg, Fe, Mn and Cr are contained, the balance is made of Al and inevitable impurities, Mg is 1.5 mass% to 2.1 mass%, Fe is 0.4 mass% or less, Mn And after melting and casting an alloy having a composition of 0.2% by mass or less, Cr is homogenized at a homogenization temperature of 450 ° C. or higher and 590 ° C. or lower, followed by hot rolling and cold An aluminum alloy plate for a cap, which is subjected to final temper annealing at an annealing temperature of 150 ° C. or higher and 300 ° C. or lower after sequentially performing rolling and final cold rolling at a reduction ratio of 68.8% or higher and 80% or lower. Manufacturing method.