FERRINOX® 255 Super Duplex Stainless Steel (UNS S532550)>
FERRINOX® 255 (UNS S32550) is a stainless steel containing
25.5% chromium, 6% nickel with significant additions of
molybdenum, copper and nitrogen and a PREn (pitting
resistance equivalent) of ≥40.0. The copper content of 1.6%
is particularly beneficial in promoting optimum resistance
to corrosion in acidic environments. The chemical
composition and mechanical properties conform to the
requirements of UNS S32550, 1.4507 and several oil & gas
industry specifications. The microstructure is
carefully controlled with a phase balance close to 50:50
austenite and ferrite with complete freedom from grain
boundary carbides, sigma phase and other deleterious
precipitates. Hardness is kept to a level which satisfies
the requirements of NACE MR01-75 for sour service.
It should be stressed that, although the
above standards form the basis for FERRINOX® 255 supply, a
consistent, optimised property combination is only achieved
by the targeting of a much tighter composition window and
detailed knowledge, gained from long term, volume supply, of
metal processing techniques and heat treatment regimes.
Rigorous testing carried out on all production batches, such
as ASTM G-48A at 500C to demonstrate very high
pitting resistance and notch ductility testing at minus 460C
to confirm sub-zero suitability, also guarantees the absence
of phases potentially deleterious to ductility, corrosion
resistance and weldability.
FERRINOX® 255 (UNS S32550) is categorised as a super
duplex (austenitic/ferritic) stainless steel. This high
performance alloy combines high mechanical strength
(typically up to over 600 MPa yield strength) and good
ductility with outstanding corrosion resistance to marine
environments and a wide, diverse range of industrial media.
These attributes result in the widespread specification of
FERRINOX® 255 as an alternative to 300 series stainless steel
(such as type 316), standard 22% Cr duplex steel,
precipitation hardening stainless steels (typical 17/4PH)
and the alloy can in some instances obviate the need to
choose a much higher cost nickel based alloy
The highly attractive combination of
attributes provided by FERRINOX® 255 has led to many years of
successful application in Defence, Oil & Gas production,
Chemicals processing, Pollution Control (FGD), Pulp & Paper
Production, Architecture and Nuclear Engineering.
(click here for FERRINOX® 255
data sheet) |
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