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Why choose aluminum?
Aluminum is
synonymous with lightness and lightness, combined with good
strength, is the quality most appreciated in cycling. However, if not properly
treated, aluminum may deteriorate in time and this may give rise to a
deterioration in the mechanical characteristics. Consequently, an aluminum
frame inevitably requires more rigorous production processes and frequent checks
by the user to identify any superficial defects or cracks. Undoubtedly the most
obvious advantage is that it withstands the action of the atmospheric agents:
an aluminum frame does not rust! Also, with its excellent
workability, it enables the designer to come up with the most
imaginative and creative solutions.
For the production of its tube-sets in aluminum Columbus uses light alloys like
Al-Zn-Mg (series 7000) and Al-Si-Mg (series 6000). The classification derives
from the American Aluminum Association. The alloy elements: Mg = magnesium, Zn =
zinc and Si = silicium that, properly combined between each other, form
intercrystalline compounds which give the mechanical properties to the alloy.
Both alloys acquire their maximum mechanical properties through a heat treatment
cycle.
The alloy
used for the XLR8R represents the most recent product at the
top of the Columbus range together with Starship. This is a sophisticated
development of the 7000 Al-Zn-Mg, which through the addition of
Zirconium (element used in nuclear reactors, to give an example
of just one of its uses), achieving highly superior mechanical and resistance
characteristics. The zirconium modifies the kinetics of the intermetallic
composites in the matrix during the precipitation stage, conferring a very fine
grain to the structure. In practical terms this means:
| a) |
Superior mechanical characteristics of the frame: Rm=550 Mpa,
Rs=510 Ap5>12% |
| b) |
Increase of the recrystallization temperature |
| c) |
Greater resistance to the Hot Cracking phenomenon - the
weakening of the material due to thermal alterations caused by welding
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| d) |
Near complete recovery of the mechanical characteristics
after welding through the use of a simple artificial aging thermal
treatment. |
For an idea of this alloy's degree of
sophistication, consider that it is produced in a controlled environment (i.e.
the equipment is meticulously cleaned before and after processing to avoid
contamination by other components), and that heat treatment and filler materials
were developed specifically for the welding.
It is one of the elements most found on earth, second
only to oxygen and silicon. It is always found in nature combined with other
elements, and is present in many minerals. From the industrial point of view, it
is a light metal (with a density of 2.71 g/cm), produced from bauxite. Its main
properties are: low specific weight; completely recyclable; high resistance to
corrosion; high heat conductivity; atoxicity; high plasticity; excellent
ductility and malleability; good weldability (by gas, electric arc and
resistance).
The heat treatment cycle, is composed of a
heating stage and soaking at an elevated temperature (about 470°C for the 7000
series and 530°C for the 6000 series) called solubilization, during which the
alloy elements form compounds which go in solution in the metal matrix. Fast
cooling (in forced air for the 7000 series, in water for the 6000 series)
‘freezes' this structure, called supersaturated, at ambient temperature.
Successive cooling and soaking at medium temperature (90/150°C 7000, 135/150°C
in two steps for XLR8R and 180°C for the 6000 series), called ageing, enables
the precipitation of the compounds inside the crystalline structure of the
aluminium, giving it the desired mechanical properties.
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Roselli Shimano 10 speed compatible 14/25
$98.00
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Cassette 10 Speed
$156.00
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Body Bike - Classic Supreme
Call for Pricing
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24 Tube
$10.00
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