The Stainless Steel Experts - MSTAINLESS

erably used where there is a risk of
stress corrosion cracking. However,
as regards the surface quality ferritic
steels show a greater susceptibility
to wear! Roughing up the surface,
e.g. through blasting or grinding,
leads to a significant reduction in
the corrosion resistance.
Ferritic steel has a slightly higher
yield point = Rp 0.2 than austenitic
steel, but has a reduced tensile
strength which somewhat limits its
cold forming potential. E.g. deepdrawing
and hydroforming are not
possible in the majority of cases. A
further characteristic that distinguishes
ferritic steel from austenitic
steel is the reduced strain hardening
tendency. Thus, the ferritic steel
grades prove interesting particularly
on account of their high modulus of
elasticity values (220 kN/ mm²) - see
the comparison table on page 16.
The ferritic steel grades exhibit a
better fatigue strength and significantly
lower thermal expansion than
their austenitic counterparts.
Martensitic stainless steel
Martensitic steel types boast the
highest strength but have the lowest
corrosion resistance of all the
stainless steel grades. Martensitic
steel with a high carbon content is
used for making tools and is easily
hardened. On account of their high
strength and relatively limited resistance
to corrosion, they are suited to
applications in which the material
is exposed to corrosive attack and
wear simultaneously. Knife blades
are a good example of this.
Structure of martensitic steel
Austenitic-ferritic stainless
steel (stainless duplex
structure)
In terms of structure and the alloy
content, this group of steels represents
a mixture of the ferritic and
austenitic steel grades. The main distinguishing
feature is the significantly
higher green strength (see yield
point Rp0.2 on page 16). For this
reason, these steel grades are frequently
used for producing dynamically
stressed machine parts, e.g.
draw-off rollers for paper machines.
New application areas are emerging
in the oil, gas and petrochemical
sector where steel grades suitable
for saltwater-proof plants and the
offshore industry are called for.
These steels are normally referred to
as duplex steels relating to these two
phases in their structure, whereby
the combined term “duplex stainless
steel” is more fitting since there
are also coated metal sheets and
sandwich metal sheets that go under
the same name. With the commercially
available material grades in
the duplex stainless steel sector, e.g.
1.4362 or 1.4462, the benefits of
both are unified (austenitic-ferritic).
Over the last few years, the lean duplex
stainless steel sector in particular
has undergone significant further
development. Here we are referring
to duplex stainless steel with considerably
reduced nickel and molybdenum
constituents, or lacking these
entirely (e.g. 1.4062, 1.4162 or
1.4362) in relation to the standard
duplex stainless steel 1.4462. This
makes these lean duplex stainless
steel grades relatively inexpensive
despite their high performance - see
the example on page 17, paragraph
5.But duplex stainless steel grade
which a high alloy content are also
available on the market. E.g. the superduplex
stainless steel or now just
recently also the hyperduplex stainless
steel, which in many aspects are
even technically superior to the fully
austenitic grades, e.g. 1.4529.
Structure of stainless duplex
The future looks exciting and is set
to belong to the materials made
up of several basic structural types
because already now the first
triplex-stainless steel grades are being
developed, in other words steel
combining the three structural types
(austenitic, ferritic, martensitic).
Also alloys combining Cr, Ni with
aluminium (Al) have already been
extensively tested. These alloys with
an aluminium content of approx.14
% are some 10 % lighter than the
known steel grades and capable of
being cold-formed while demonstrating
a high basic strength.
BUSINESS DIVISION
Industrial components
made of stainless steel
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