The Watch Case
It has always been one of our major goals to design a
watch case with superior resistance against scratches, knocks, and general
wear, but the materials commonly available, including the rather soft
titanium definitively do not feature the necessary characteristics. The
term 316L describes the kind of steel which is predominantly used in the
watch industry. It features good corrosion resistance but is also relatively
soft. Occasional knocks with a watch made from this material will often
lead to serious scratches or dents.
Although there is the possibility to harden the surface of 316L (1.4435)
or 1.4301 up to 1200 Vickers by diffusing carbon into the top layers of
the steel, there is no way to temper the material. Due to the austenitic
structure of the alloy it is impossible to make sure that that steel remains
its hardness throughout the body.
Various tests have proved that this kind of surface treatment is not suitable
for our purposes because it only hardens the top layer of the metal. This
leads to the so-called egg-shell effect. We were able to dent and scratch
the “hardened” surface with an ordinary pair of tweezers (which
are normally made from spring steel) because the material underneath the
hard layer was not able to withstand the pressure.
Due to the reasons described above we searched extensively
for better alternatives. In 1994 after five years of research we took
out patents for 20 closely related martensitic sorts of stainless steel
which highly exceeded our expectations. They are absolutely nickel-free,
offer a good corrosion resistance, and can be tempered up to 64 HRC/800Vickers
which is four times the hardness of every other steel currently used in
the watch industry.
What makes this material so special is the fact that the molten steel
is enriched with 0.35% nitrogen under high pressure. Nitrogen and carbon
are responsible for the hardness of the alloy. Under normal circumstances
it takes about 1% of carbon to temper a martensitic steel up to 60 Rockwell
but the low nitrogen content of our steel only requires 0.35% of carbon
to achieve this superior hardness and in addition to that leads to an
excellent corrosion resistance which is many times higher compared to
other temperable martensitic steels. Due to the special process of hardening
we call this steel “ice-hardened, nickel-free stainless steel”.
This material is patented for our applications and Damasko makes exclusive
use of this pioneering material.
The entire watch case, including hardened crown and pushers
is designed, engineered, and machined at our factory near Regensburg.
Until the end of 2002 we supplied our cases to a well known German watch
brand but from now on these cases will only be available through Damasko.
After the special heat treatment mentioned above our steel reaches a maximum
hardness of 62 Rockwell which makes it superbly scratch-resistant. You
have to search hard to find a common household item ( apart from a sapphire
nail-file or a brick) that is able to scratch the case.
Due to its superior performances this steel was mainly created for aeronautical
use in:
- ball bearings for jet-engines
- rotor bearings for helicopters
- fuel pumps of the “Space Shuttle”
- high-speed bearings in CNC lathes
- dental and surgical instruments
The use of this steel in watch cases is patented for our company.
EU - Geschmacksmuster
Nr. 000004296-0002
Inhaber: Petra Damasko
