Production of aluminum impact extrusions

The present invention relates to a method of producing an aluminum impact extrusion by preparing a slug of an aluminum based alloy made of aluminum and at least one element selected from cobalt and nickel, whereas the amounts of the cobalt and nickel are each present in amounts of 3% by weight or less and wherein the total amount of cobalt and nickel is 0.15% by weight or more; impact extruding the slug by using an impact extrusion press, and then annealing the extruded product. The present invention also involves an aluminum base alloy consisting of the ingredients mentioned above useful for impact extrusion and an aluminum collapsible tube prepared by impact extruding a slug stud of an aluminum base alloy of the type described above.

BACKGROUND OF THE INVENTION 
A. Field of the Invention 
The present invention relates to a method of producing aluminum impact 
extrusions having high ductility, and more particularly to a method of 
producing highly ductile impact extrusions having outstanding subsequent 
fabrication characteristics from slugs of aluminum base alloy containing 
cobalt and/or nickel by impact extruding the slug by an impact press and 
annealing the extruded product. 
B. Description of the Prior Art 
Impact extrusions can be produced from any commercial aluminum alloy, but 
the stock most extensively used for impact extrusion is a commercial pure 
aluminum having a purity of 99.5 to 99.8% by weight because of its impact 
extrusion characteristics and its properties in the finished product. 
Collapsible tubes, for example, are produced by impact extruding a slug of 
commercial pure aluminum having a purity of 99.7% by weight or more and 
annealing the resulting extrusion to the state of soft temper. The tubes 
are used as containers for toothpastes, foods, drugs, etc. 
However, such collapsible tubes, when filled with contents, are liable to 
break where they are frequently flexed during repeated use, possibly 
permitting leakage of the contents. It is therefore desired to provide 
collapsible aluminum tubes which are not easily breakable. To assure 
economy of transport, there is also a great demand for collapsible taper 
tubes which are prepared from impact extrusions by subsequent fabrication. 
Various other impact extrusion products are similarly produced by 
subjecting impact extrusions to necking, drawing or the like. Conventional 
impact extrusion products nevertheless are not always satisfactory in 
subsequent fabrication characteristics but are likely to break or become 
otherwise defective in the course of subsequent fabrication. Thus it is 
also desired to develop aluminum impact extrusions having outstanding 
subsequent fabrication characteristics. 
SUMMARY OF THE INVENTION 
An object of the present invention is to provide aluminum base alloys 
suitable for producing impact extrusions having excellent ductility. 
Another object of the invention is to provide a method of producing impact 
extrusions having excellent ductility. 
Another object of the invention is to provide a method of producing 
collapsible tubes by an impact extrusion process which tubes are not 
easily breakable. 
Still another object of the invention is to provide a method of producing 
impact extrusions having improved subsequent fabrication characteristics. 
To fulfil these objects, we have conducted extensive research and 
accomplished the present invention based on the finding that the foregoing 
drawbacks and problems can be overcome by impact extruding a slug stock of 
an aluminum base alloy consisting essentially of aluminium and containing 
cobalt and/or nickel. 
The slug stocks useful in this invention for the production of impact 
extrusions are made of an aluminum base alloy consisting essentially of 
aluminum and at least one element selected from the group consisting of up 
to 3% by weight of cobalt and up to 3% by weight of nickel, the total 
amount of the cobalt and the nickel being at least 0.15% by weight. Stated 
more specifically, the present invention provides a method of producing an 
impact extrusion having high ductility and outstanding subsequent 
fabrication characteristics by impact extruding a slug of an aluminum base 
alloy by an impact extrusion press and annealing the extruded product, the 
aluminum base alloy consisting essentially of aluminum and at least one 
element selected from the group consisting of cobalt and nickel, the 
content of each of said cobalt and nickel being 3% by weight or less and 
the total amount of said cobalt and nickel being at least 0.15% by weight. 
DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The present invention will be described below in greater detail. 
The aluminum base alloys to be subjected to impact extrusion as slug stocks 
according to this invention must consist essentially of cobalt and/or 
nickel each in an amount of up to 3% by weight, the total amount of the 
cobalt and the nickel being at least 0.15% by weight. If the total amount 
of the cobalt and the nickel is less than 0.15% by weight, a satisfactory 
improvement will not be achieved in ductility nor in subsequent 
fabrication characteristics, whereas with more than 3% by weight of cobalt 
or nickel present, the alloy will not have improved properties 
corresponding to the increased amount but becomes unjustifiably costly. 
Aluminum alloys containing cobalt alone, if selected for use, preferably 
contain 0.2 to 2.0% by weight of cobalt, more preferably 0.2 to 1.2% by 
weight of cobalt. 
Alloys incorporating nickel only, if useful, preferably contain 0.2 to 2% 
by weight of nickel, more preferably 0.3 to 1.5% by weight of nickel. 
With alloys containing both cobalt and nickel, it is desirable that these 
elements be present each in an amount of at least 0.05% by weight and in a 
total amount of at least 0.15% by weight so that each element will impart 
the desired effect to the alloys. Especially preferable to use are 
aluminum alloys comprising 0.2 to 2% by weight of cobalt and 0.2 to 2% by 
weight of nickel in a total amount of 3% by weight or less since these 
alloys have remarkably improved ductility. 
When annealed, such alloys containing both cobalt and nickel exhibit 
improved ductility over Al-Co alloys or Al-Ni alloys as well as over pure 
alluminum. Moreover the alloys have a reduced recrystallizing temperature 
and can therefore be annealed under moderate conditions. Thus they are 
useful when it is desired to produce articles of especially high ductility 
or to conduct the annealing treatment at a lower temperature within a 
shorter period of time for the reduction of energy cost. 
Although the aluminum serving as the base of useful alloys is not 
particularly limited in purity, it is preferable to use commercial pure 
aluminum having a purity of 99.5% by weight or higher, more advantageously 
99.7% or higher. The objects of this invention can then be fulfilled with 
the desired result without being influenced by the contents of, and the 
ratio between, Fe and Si which are the main impurities involved. 
The impact extrusions of this invention can be produced in the same manner 
as the conventional impact extrusion process under the same conditions as 
usually used for impact extruding slugs of commercial pure aluminum. The 
impact extrusion press to be used may be of any type, such as a reverse 
impact press, forward impact press, lateral impact press, combination 
forward and reverse impact press or the like. The most suitable press may 
be used in accordance with the shape of the impact extrusion product as 
finished. The shape of the slug stock is also dependent on that of the 
finished extrusion product. Useful slugs are prepared from impact 
extrusion stocks, such as rolled plates, extruded plates, extruded rods or 
the like, made of the aforementioned aluminum base alloy by machining the 
stock to a shape in conformity with the shape of the finished product as 
by blanking, sawing or trimming. Generally the slug is subjected to 
annealing heat treatment to the state of soft temper by being heated to a 
temperature, for example, of about 300.degree. to about 600.degree. C. for 
a period of time suited to the desired degree of impact extrusion 
processing, then coated with a lubricant as by tumbling, dipping or 
centrifuging, and thereafter impact extruded at or near room temperature. 
Examples of suitable lubricants are various metal soaps such as zinc 
stearate, sodium stearate, aluminum stearate or the like. The slug may be 
slightly heated and then impact extruded depending on the shape and 
extrusion degree of the product contemplated. 
According to the method of this invention, the extruded product thus 
obtained is annealed and thereby softened, giving an impact extrusion with 
much higher ductility than is afforded by the use of commercial pure 
aluminum as a slug stock. Although the annealing conditions are dependent 
on the size and design of the extruded product, the product is usually 
heated at a temperature of about 150.degree. C. to about 600.degree. C. 
for about 1 to about 30 minutes. 
When aluminum alloys containing cobalt or nickel only are used, the 
preferred annealing temperature is not lower than 300.degree. C., whereas 
those containing both cobalt and nickel can be fully softened even at 
about 150.degree. C. since such alloys have a lower recrystallizing 
temperature as already described. 
The collapsible tubes and various other impact extrusion products obtained 
by the foregoing method of the invention from aluminum base alloys 
containing cobalt and/or nickel by impact extruding the alloys and 
annealing the resulting extrusions afford finished products having higher 
ductility and less breakable than conventional like products. The annealed 
collapsible tubes and various other impact extrusion products can be 
subjected to subsequent fabrication such as trimming, curling, expanding, 
sizing, tapering, necking or bending with a reduced occurrence of faults 
or imperfections.

The present invention will be described below with reference to examples, 
to which the invention is not limited. 
EXAMPLE 1 
Commercial pure aluminum and Al-5% Co mother alloy were used to prepare 
sheet ingots of the Al-Co alloys listed in Table 1. Each of the ingots was 
hot rolled and then cold rolled into a plate 5 mm in thickness. Slug 
stocks, 38 mm in diameter, where blanked out from the plate and suitably 
trimmed for use as slug stocks for collapsible tubes. The slugs obtained 
were annealed at 600.degree. C. for 4 minutes and then impact extruded at 
room temperature into collapsible tubes, 150.mu. in wall thickness. Table 
2 shows the mechanical properties of the extruded products. 
TABLE 1 
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Composition (wt. %) 
Alloy No. Fe Si Cu Co Al 
______________________________________ 
1. This invention 
0.15 0.07 0.00 0.43 Balance 
2. This invention 
0.15 0.07 0.00 1.04 Balance 
3. Base pure Al 
0.16 0.07 0.00 0.00 Balance -4. This 
invention 0.05 0.05 0.00 0.43 Balan 
ce -5. Base pure 
Al 0.05 0.05 0.00 0.00 Balance 
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TABLE 2 
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Tensile strength 
Yield strength 
Elongation 
Alloy No. 
(kg/mm.sup.2) 
(kg/mm.sup.2) 
(%) 
______________________________________ 
1 15.2 8.9 0.5 
2 15.0 8.7 0.6 
3 14.4 7.3 0.2 
4 13.2 7.0 0.6 
5 13.7 9.2 0.6 
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The extruded products thus prepared were annealed at 500.degree. C. for 6 
minutes to obtain collapsible tubes of soft temper. Table 3 shows the 
mechanical properties of the annealed collapsible tubes in comparison with 
those of collapsible tubes prepared in the same manner as the treatment of 
the commercial pure aluminum slugs. 
TABLE 3 
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Tensile Yield Breaking 
Alloy strength strength Elongation 
test 
No. (kg/mm.sup.2) 
(kg/mm.sup.2) 
(%) (times)* 
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1 6.3 2.8 32.8 33 
2 6.7 3.2 34.7 40 
3 6.5 3.7 13.0 19 
4 5.7 3.0 38.0 48 
5 4.6 2.8 11.6 22 
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*The number of times the tube, as supported at one end, was repeatedly 
flexed through 180 degrees before breaking. 
EXAMPLE 2 
Commercial pure aluminum and Al-10% Ni mother alloy were used to prepare 
the Al-Ni alloys shown in Table 4. 
TABLE 4 
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Composition (wt. %) 
Alloy No. Fe Si Cu Ni Al 
______________________________________ 
6. This invention 
0.15 0.07 0.00 0.60 Balance 
7. This invention 
0.15 0.07 0.00 0.99 Balance 
8. Base pure Al 
0.16 0.07 0.00 0.00 Balance 
______________________________________ 
Each of the alloys was cast and rolled into a plate of 6 mm in thickness, 
which was blanked to obtain slugs 19 mm in outside diameter. The slugs 
were annealed at 380.degree. C. for 12 hours and then impact extruded into 
tubes having a wall thickness of 120.mu.. 
Table 5 shows the mechanical properties of the tubes as impact extruded and 
also as further annealed at 450.degree. C. for 10 minutes, in comparison 
with those of usual tubes prepared by the conventional method. 
TABLE 5 
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After impact extrusion 
After annealing 
Tensile Tensile 
Alloy strength Elongation 
strength 
Elongation 
No. (kg/mm.sup.2) 
(%) (kg/mm.sup.2) 
(%) 
______________________________________ 
6 10.9 0.4 6.6 24 
7 11.5 0.2 7.0 23 
8 12.0 0.2 6.8 13 
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EXAMPLE 3 
Commercial pure aluminum, Al-5% Co mother alloy and Al-10% Ni mother alloy 
were used to prepare the Al-Co, Al-Ni and Al-Ni-Co alloys listed in Table 
6. 
TABLE 6 
______________________________________ 
Composition (wt. %) 
Alloy No. Fe Si Cu Co Ni Al 
______________________________________ 
9. This invention 
0.12 0.04 0.00 0.59 0.00 Balance 
10. This invention 
0.12 0.04 0.00 0.00 0.58 Balance 
11. This invention 
0.11 0.04 0.00 0.40 1.00 Balance 
12. This invention 
0.09 0.04 0.00 0.41 0.52 Balance 
13. This invention 
0.07 0.04 0.00 1.09 0.40 Balance 
14. Base pure Al 
0.12 0.04 0.00 0.00 0.00 Balance 
______________________________________ 
Each of the alloys was cast in a mold to obtain a 20-mm-thick sheet, the 
surfaces of which are grounded. The sheet was preheated at 530.degree. C. 
and hot rolled to a thickness of 6 mm. Slugs, 38 mm in outside diameter, 
were blanked out from the plate, annealed at 380.degree. C. for 12 hours 
and thereafter impact extruded into tubes 130.mu. in wall thickness. 
For annealing, some of the tubes were held immersed in a hot bath at 
200.degree. C. or 400.degree. C. for 10 or 30 minutes. The tubes as impact 
extruded and those further annealed were tested for tensile strength with 
the results given in Table 7 and also for elongation with the results 
listed in Table 8. 
TABLE 7 
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Tensile Strength 
(kg/mm.sup.2) 
200.degree. C. 
400.degree. C. 
Alloy No. 
As impact extruded 
30 min 10 min 
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9 18.0 15.0 7.8 
10 16.8 14.5 7.7 
11 20.5 13.4 9.7 
12 20.3 14.5 8.3 
13 20.7 13.4 9.5 
14 17.0 15.5 6.8 
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TABLE 8 
______________________________________ 
Elongation 
(%) 
200.degree. C. 
400.degree. C. 
Alloy No. 
As impact extruded 
30 min 10 min 
______________________________________ 
9 0.4 2.7 27 
10 0.4 2.5 24 
11 0.5 14 33 
12 0.4 10 30 
13 0.5 12 31 
14 0.3 3.5 12 
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