ALUMINUM SHEET WITH ENHANCED FORMABILITY AND AN ALUMINUM CONTAINER MADE FROM ALUMINUM SHEET

Abstract

In some embodiments of present disclosure, a method includes: obtaining an aluminum sheet comprising a 3xxx or a 5xxx alloy having a tensile yield strength as measured in the longitudinal direction of 27-33 ksi and an ultimate tensile strength; wherein the ultimate tensile strength minus the tensile yield strength is less than 3.30 ksi (UTS-TYS<3.30 ksi); and forming a container having a dome from the aluminum sheet.

Claims

1. A method comprising: obtaining an aluminum sheet comprising a 3xxx or a 5xxx alloy having a tensile yield strength as measured in the longitudinal direction of 27-33 ksi and an ultimate tensile strength; wherein the ultimate tensile strength minus the tensile yield strength is less than 3.30 ksi (UTS-TYS<3.30 ksi); and forming a container having a dome from the aluminum sheet.

2. The method of claim 1, wherein the tensile yield strength as measured in the longitudinal direction is 28-32 ksi.

3. The method of claim 1, wherein the tensile yield strength as measured in the longitudinal direction is 28.53-31.14 ksi.

4. The method of claim 1, wherein the ultimate tensile strength minus the tensile yield strength is 2.90-3.30 ksi.

5. The method of claim 1, wherein the ultimate tensile strength minus the tensile yield strength is 2.99-3.30 ksi.

6. The method of claim 1, wherein the aluminum sheet comprises one of AA: 3x03, 3x04 or 3x05.

7. The method of claim 1, wherein the aluminum sheet comprises AA 3104.

8. The method of claim 1, wherein the container is a bottle.

9. The method of claim 1, further comprising expanding a section of the portion of the container having a reduced diameter.

10. The method of claim 9, wherein the section has a length and the length is at least 0.3 inches.

11. The method of claim 10, wherein the length is at least 0.4 inches.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0016] FIG. 1 is a partial enlarged perspective view of an aluminum sheet;

[0017] FIG. 2 is a side view of an aluminum bottle having a dome;

[0018] FIG. 3 depicts process steps according to one embodiment;

[0019] FIG. 4 depicts process steps according to another embodiment;

[0020] FIG. 5 depicts process steps according to a further embodiment;

[0021] FIG. 6 is a graph illustrating the UTS of groups of coils 1-4;

[0022] FIG. 7 is a graph illustrating the TYS of groups of coils 1-4;

[0023] FIG. 8 is a graph illustrating the UTS-TYS of groups of coils 1-4; and

[0024] FIG. 9 plots low and high reject rate coils verses UTS-TYS.

DESCRIPTION

[0025] The formability of can bottle stock (as measured by reject rate after finishing the opening of the container) has been empirically demonstrated to increase with reduced (<3.30 ksi) UTS-TYS difference. UTS-TYS differences of <3.30 ksi have resulted in less product rejects. Specimens measured were made from finished gauge sheet with a nominal width of ˜0.50″. The samples were oriented such that the rolling direction is parallel to the applied load.

[0026] In some embodiments, finishing comprises one or a combination of the following: forming threads, expanding, narrowing, curling, flanging, or forming the opening of the container to accept a closure. Bottles made from coils of aluminum sheet with UTS-TYS<3.30 ksi have lower reject rates after finishing. Rejection can be caused by container failures, such as one or more of the following: curl splits, container fracture, container collapse. Other types of container failures may cause rejection.

[0027] One method to produce reduced UTS-TYS difference bottle stock sheet is a reduction in Ti level and an increase in preheat soak time from standard production targets. In some embodiments, the Ti levels in the aluminum sheet are in the range of 0.0030-0.008 wt %. In some embodiments, the aluminum sheet experiences presoak times in the range of 3 hours at 1080° F. plus 30-40 hours at 1060° F. In some embodiments, the aluminum sheet experiences presoak times in the range of 3 hours at 1080° F. plus 35-40 hours at 1060° F. In some embodiments, the aluminum sheet experiences presoak times in the range of 3 hours at 1080° F. plus 37-40 hours at 1060° F.

[0028] Aluminum sheet (10 coils) having an average TYS of ˜35.35 ksi (range 34.38-36.18 ksi) with UTS-TYS average of 3.47 ksi (range 3.30-3.80 ksi) are in group 1. The average UTS of group 1 was 38.89 ksi (range 38.09-39.49 ksi). The material in group 1 lacked sufficient formability to be used in the manufacture of bottles.

[0029] Coils of aluminum sheets having an average TYS of 32.15 ksi (range 31.00-34.16 ksi) with an average UTS-TYS of 3.42 ksi (range 3.08-3.72 ksi) are in group 2. The average UTS of group 2 was 35.57 ksi (range 34.34-37.49 ksi). The material in group 2 lacked sufficient formability to be used in the manufacture of bottles.

[0030] Group 3 coils of aluminum sheet had an average TYS of 30.06 ksi (range 28.97-31.23 ksi) and an average UTS-TYS of 3.36 ksi (range 3.02-3.64 ksi). The average UTS of group 3 was 33.41 ksi (range 31.65-34.81 ksi). Of the group 3 coils some were identified as performing with low bottle reject rates after finishing. Some has sufficient formability to be used in the manufacture of bottles.

[0031] Coils of aluminum sheet having an average TYS of 29.83 ksi (28.53-31.14 ksi) and an average UTS-TYS of 3.20 ksi (2.99-3.43 ksi) fall in group 4. The average UTS of group 4 was 33.03 ksi (range 31.54-34.51 ksi). Bottles made from coils of aluminum sheet in group 4 with UTS-TYS<3.30 ksi have low reject rates after finishing.

[0032] The UTS of groups 1-4 is shown in the graph in FIG. 6. The TYS of groups 1-4 is shown in the graph in FIG. 7. The UTS-TYI of groups 1-4 is shown in the graph in FIG. 8.

[0033] The UTS-TYS of a subset of coils from group 3 is plotted against reject rates in FIG. 9. As can be seen in FIG. 9, there is a statistically significant difference in the UTS-TYS for known high reject rate coils and low reject rate coils.

[0034] A partition analysis on the reject rate can split the lots into two groups that have the minimal misclassification error at a UTS-TYS value of 3.3. The table below shows the results of the partition analysis of the same data set included in FIG. 9.

TABLE-US-00001 UTS-TYS < 3.3 UTS-TYS >= 3.3 low reject rate lots 16 2 high reject rate lots 4 21

[0035] The rate at which the material work hardens is also critical to form a bottle with lower reject rates. Flow stress for aluminum is often defined by a Voce Equation (σ=A-Bexp(-Cε)) in which the strain hardening rate is defined by the coefficient “C”. Investigation of C values between 5 and 25 resulted in significant bottle forming differences. In some embodiments, a C value in the range of 12-18 can be used to minimize reject rates. In other embodiments a C value in the range of 15-25 can be used. In other embodiments a C value in the range of 20-35 can be used. In other embodiments a C value in the range of 25-50 can be used. In other embodiments a C value in the range of 5-12 can be used.

[0036] While various embodiments of the present disclosure have been described in detail, it is apparent that modifications and adaptations of those embodiments will occur to those skilled in the art. However, it is to be expressly understood that such modifications and adaptations are within the spirit and scope of the present disclosure.