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| Mailing Address |
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UKF Stainless Ltd
12 Buntsford Park Road
Bromsgrove
Worcestershire
B60 3DX
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| Telephone / Fax |
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| Tel: |
01527 578686 |
| Fax: |
01527 837792 |
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| Email |
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 info@ukfstainless.co.uk |
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S32550 / S39553
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Introduction:
This long-estabilished steel, yet to be incorporated
into Euronorm, ranks as a 'Super' duplex having a
PREN of about 40. Duplex steels combine high strength
with corrosion resistance. Their resistance to stress-corrosion
cracking in neutral chlorides is superior to that
of the 18/10 and 18/12/3 austenitics. In high chloride
acidic or moderately sour environments where hydrogen
or sulphide stress cracking is more likely higher
alloyed austenitics need also to be considered. Exposure
to moderate and higher temperatures and less rapid
cooling may cause embrittlement. Accordingly, design
stress values in ASME II do not extend above 260°C
for S32550 / S39553. Impact values are high at room
temperature with transition temperatures of base material
below -50°C. However, the proportion and orientation
of ferrite in welds and base material may affect toughness
at subzero temperatures.
Metallurgy:
When ferrite forming elements (Cr,Mo,Si,Nb)
are kept at high levels but austenite promoting elements
(Ni,Mn,N,C) are reduced, stainless steels with a mixed
or duplex microstructure are produced. Mixtures of
40-60% of either phase are near optimum.
Careful control of both the compositions and cooling
rate from high temperatures is necessary to prevent
the steel or weldment containing large amounts of
ferrite and/or traces of sigma phase that both embrittle
and impair corrosion resistance. Welding requires
control of heat-input and thermal cycles plus use
of special consumables enriched with nitrogen and/or
nickel.
Duplex stainless steels may suffer severe embrittlement
due to sigma phase formation in the 550-900°C
range and from alpha prime in the 280-550°C range.
The period for embrittlement may be short or long
depending on composition, time, temperature and amount
of cold work.
Composition:
| Element |
Minimum
(%) |
Maximum
(%) |
| Chromium |
24.00 |
27.00 |
| Nickel |
4.50 |
6.50 |
| Molybdenum |
2.90 |
3.90 |
| Nitrogen |
0.10 |
0.25 |
| Manganese |
- |
1.50 |
| Carbon |
- |
0.04 |
| Copper |
1.50 |
2.50 |
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Similiar Specifications:
EURONORM X2 CrNiMoCuN
25 6 3 (1.4507)
24-26%Cr, 5.5-7.5%Ni, 2.7-4.0%Mo, 0.15-0.30%N, <2.0%Mn,
<0.03%C, 1.0-2.0%Cu
ASTM UNS S32550
24-27%Cr, 4.5-6.5%Ni, 2.9-3.9%Mo, 0.10-0.25%N, <1.5%Mn,
<0.04%C, 1.5-2.5%Cu
Applications:
Used in wrought and cast forms for:
Shafting, propellers, rudders and fasteners for small
craft.
Marine pumps and shafts.
Water injection pumps and valves for offshore service.
Structural fabrications for seawater and brackish
water.
Components for submarines and submersibles.
Product Forms:
Plate,sheet & strip
ASTM UNS S32550 240, 480
Bar & long
products
ASTM UNS S32550 479
Tube
ASTM UNS S32550 789
Pipe
ASTM UNS S32550 790
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Page Last Modified: 7/04/06 17:57
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