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Datasheet updated 2012-12-11 10:41:14 (supersedes all previous
editions)
Sandvik SAF 2304(Plate and sheet)
Sandvik SAF 2304 is a duplex (austenitic-ferritic) stainless
steel with a low carboncontent. The material is characterized by
the following properties:
Very good resistance to stress corrosion cracking (SCC)Good
resistance to general corrosion an pittingHigh strength -
approximately twice as high proof strength as austenitic stainless
steelsPhysical properties that offer design advantagesEase of
fabrication and good toughnessGood weldability
STANDARDS
UNS S32304EN number 1.4362*W.Nr. 1.4362DIN X 2 CrNiN 23 4SS
2327AFNOR Z 2 CN 23.04AZ
Products standardsPlate, sheet and coil: ASTM A240; A480
ApprovalsApproved by the American Society of Mechanical
Engineers (ASME) Boiler andPressure Vessel Code, Section VIII, div.
1 construction.ASME B31.3 Chemical and Refinery Piping
CodeVdTÜV-Werkstoffblatt 496NGS 1607 (Nordic rules for
applications) valid for SAF 2304 made by Sandvik.Approved by DNV
for general use on shipsApproved by RINA, registration No
MAC/112/90
* Valid for sheet/plate, strip, semifinished products, bars,
rods and sections for generalpurposes (not for pressure
purposes).
CHEMICAL COMPOSITION (NOMINAL) %
C Si Mn P S C r Ni Mo N Cu
0.030 1 . 0 2 .5 0 .0 4 0 .0 3 21 .5-24.5 3 .0 -5 .50 0 .05-0.60
0 .05-0 .20 0 .05-0.60
FORMS OF SUPPLY FINISHES AND DIMENSIONS
Plate and sheet are delivered in the solution annealed and
pickled condition.
The size ranges available are given below
Plate sheet and coilSandvik SAF 2304 Plate, sheet are stocked in
a wide range of sizes according to ASTM.
Details of our stock programme are given below:
Sandvik Australia's Stock Program Plate (HR-No1 Finish)
Thickness Range - 5mm - 40mm
Widths - 2000mm
Sheet (CR-2 Finish)
Thickness Range - 2mm
Widths - 1500mm,Lengths - 3000mm
MECHANICAL PROPERTIES
The following figures apply to the material in the solution
annealed condition. Tube and
••••••
••••••
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pipe with wall thickness above 20 mm (0.787 in.) may have
slightly lower values. Forseamless tubes with a wall thickness
below 4 mm we guarantee proof strength (R )values that are 50 MPa
higher than those listed below at 20°C (68°F) as well as
thoselisted at higher temperatures. More detailed information can
be supplied on request.
Proof s treng th Tensile strength Elong. Hard ness
R R R A A Brinell
MPa k s i MPa k s i MPa ks i % %
min min min min min min min max
AT 20°C (68°F)
4 0 0 5 8 4 5 0 6 5 6 0 0 8 7 2 5 2 5 2 9 0
1 MPa = 1 N/mma) R and R correspond to 0.2% offset and 1.0%
offset yield strength, respectively.b) Based on L = 5.65√ S where L
is the original gauge length and S the original cross-section
area.
Impact strengthSAF 2304 has good impact strength both at room
temperature and at lowtemperatures, as shown by figure 2.
Figure 2. Impact strength of SAF 2304 compaed with carbon
steel.Lowest value for a TIG-joint is also repoted for SAF 2304.
Charpy testspecimens (10 x 10 mm, 0.394 x 0.0394 in.) taken from
tube 260 x 20mm (10.2 x 0.29 in.) in size.
At high temperaturesIf SAF 2304 is exposed for prolonged periods
to temperatures exceeding 280 C(540 F), the microstructure changes
which results in a reduction in impact strength.This effect does
not necessarily affect the behaviour of the material at the
operatingtemperature. For example, heat exchanger tubes may be used
at higher temperatureswithout any problems. Contact Sandvik for
advice.
For pressure vessel applications, 280 °C (540 °F) is required as
maximum according toVdTÜV-Wb 496.
p0.2
p 0 . 2a )
p 1 . 0 mb )
2 "
c )
2
p0.2 p1.00 0 0 0
oo
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Temperature Proof s treng th Tensile strength
R R R
°C MPa MPa MPa
min min min
1 0 0 3 3 0 3 8 0 5 7 0
1 5 0 3 1 0 3 5 0 5 4 0
2 0 0 2 9 0 3 2 0 5 2 0
2 5 0 2 8 0 3 1 0 5 1 0
3 0 0 2 7 0 3 0 0 5 0 0
For constructions according to RN78 (NGS 1607) 5-15% lower
design valuesareapproved.
Temperature Proof s treng th Tensile strength
R R R
°F k s i k s i k s i
min min min
2 0 0 4 8 .5 5 6 .0 8 4 .5
3 0 0 4 4 .5 5 0 .0 7 7 .5
4 0 0 4 2 .0 4 6 .5 7 5 .5
5 0 0 4 0 .0 4 4 .5 7 3 .5
6 0 0 3 9 .0 4 3 .0 7 2 .0
PHYSICAL PROPERTIES
Density: 7.8 g/cm , 0.28 lb/in
Temperature °C J/(kg °C) Temperature °F Btu/(lb °F)
SPECIFIC HEAT CAPACITY
2 0 4 9 0 6 8 0 .12
1 0 0 5 0 5 2 0 0 0 .12
2 0 0 5 3 0 4 0 0 0 .13
3 0 0 5 5 0 6 0 0 0 .13
4 0 0 5 9 0 8 0 0 0 .14
Thermal conductivity
Temperature °C 2 0 1 0 0 2 0 0 3 0 0 4 0 0
W/(m °C)
METRIC UNITS
SAF 2304 1 6 1 7 1 8 1 9 2 1
AI SI 31 6L 1 4 1 5 1 7 1 8 2 0
Temperature °F 6 8 2 0 0 4 0 0 6 0 0 8 0 0
Btu/(f t h °F)
IMPERIAL UNITS
SAF 2304 9 9 . 5 1 0 .5 11.5 1 2 .5
AI SI 31 6L 8 8 . 5 9 .5 1 0 .5 11 .5
p 0 . 2a )
p 1 . 0a )
m
p 0 . 2a )
p 1 . 0a )
m
3 3
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Thermal expansionMean values in temperature ranges (x10 ) SAF
2304 has a far lower coefficient of thermal expansion than
austenitic stainless steels and therefore possesses certain
designadvantages.
Temperature °C 30 -1 00 30 -2 00 30 -3 00 3 0-400
Per °C
METRIC UNITS
SAF 2304 1 3 .5 1 4 .0 1 4 .5 1 4 .5
Carbon steel 1 2 .5 1 3 .0 1 3 .5 1 4 .0
AI SI 30 4L /3 16 L 1 6 .5 1 7 .0 1 7 .5 1 8 .0
Temperature °F 86 -2 00 86 -4 00 86 -6 00 8 6-800
Per °F
IMPERIAL UNITS
SAF 2304 7 . 5 8 . 0 8 .0 8 .0
Carbon steel 7 . 0 7 . 0 7 .5 8 .0
AI SI 30 4L /3 16 L 9 . 5 9 . 5 1 0 1 0
Figure 3. Thermal expansion, per °C(30-100°C, 86-210°F).
Temperature °C MPa Temperature °F k s i
MODULUS OF ELASTICITY
2 0 2 0 0 6 8 2 9 .0
1 0 0 1 9 4 2 0 0 2 8 .2
2 0 0 1 8 6 4 0 0 2 7 .0
3 0 0 1 8 0 6 0 0 2 6 .2
CORROSION RESISTANCE
General corrosionDue to the high chromium content and its
well-balanced composition SAF 2304possesses excellent corrosion
resistance in acidic environments. The table below showsthe
corrosion rate in different acids and figures 4-6 show isocorrosion
diagrams.
Corrosion rates in acid-water mixtures, mm/year (mpy). Activated
specimens, 1+3+3days, average of the last two periods for two
specimens.
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Conc . Weight-% Temp °C (°F) SAF 2304 AISI 304L AISI 316L
Ac et id ac id CH COOH
2 0 B 0 .01 (0 .4 ) - 0 .01 (0 .4 )
5 0 B 0 0 .04 (1 .6 ) 0
7 0 B 0 - -
9 0 B 0 .01 (0 .4 ) - -
Formic acid, HCOOH
5 6 0 (14 0) 0 - -
1 0 B 0 .04 (1 .6 ) 0 .80 (32) 0 .19 (7 .6 )
3 0 6 0 (14 0) 0 - -
3 0 9 0 (19 4) 0 - -
8 0 9 0 (19 4) 0 - 0 .50 (20)
9 0 6 0 (14 0) 0 - -
Hydrochloric acid, HCI
0 . 5 4 0 (10 4) 0 - 0
1 4 0 (10 4) 0 .3 0 (12) - 0 .70 (28)
Nitr ic acid, HNO (5x2 d ays)
6 5 B 0 .16 (6 .4 ) 0 .16 (6 .4 ) 0 .30 (12)
Phosphoric acid, H PO
3 0 B 0 .10 (4) 0 .20 (8 ) 0 .07 (2 .8 )
5 0 1 00 (212) 0 .04 (1 .6 ) 0 .09 (3 .6 ) 0 .21 (8 .4 )
6 0 9 0 (19 4) 0 .01 (0 .4 ) 0 .2 (0 .8 ) 0 .02 (0 .8 )
8 0 8 0 (17 6) 0 .01 (0 .4 ) 0 .01(0 .4) 0 .06 (2 .4 )
Sulphuric acid, H SO
5 6 0 (14 0) 0 - -
5 9 0 (19 4) 0 .06 (2 .4 ) 3 .6 (144) -
1 0 6 0 (14 0) 0 .10 (4) - 0 .66 (26 .4)
1 0 7 0 (15 8) 0 .14 (5 .6 ) - 1 .7 (68)
1 0 8 0 (17 6) 0 .20 (8) - 7 .9 (316)
1 5 5 0 (12 2) 0 .17 (6 .8 ) - 0 .47 (18 .8)
2 0 3 0 (8 6) 0 .20 (8) - 0 .02 (0 .8 )
B = Boiling
3
3
3 4
2 4
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Figure 4. Isocorrosion diagram for SAF 2304, AISI 403L and AISI
316Lin stagnant sulphuric acid. The curves represent a corrosion
rate of 0.1mm/year (4 mpy).
Figure 5. Isocorrosion diagram for SAF 2304. AISI 304L and AISI
316L informic acid. The curves represent a corrosion rate of 0.1
mm/year (4 mpy).
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Figure 6. Isocorrosion diagram for SAF 2304 and AISI 304L in
nitricacid. The curves represent a corrosion rate of 0.1 mm/year (4
mpy)
PittingThe pitting resistance of a steel is determined primarily
by its chromium andmolybdenum contents, but the nitrogen content
also has an effect. A parameter forcomparing the pitting resistance
of different steels is the PRE-number (Pitting
ResistanceEquivalent).The PRE is defined as, in weight-%
PRE = % Cr + 3.3 % Mo + 16 x % N
The minimum PRE-number for SAF 2304 and the austenitic standard
stainless steels
AISI 316L and AISI 304L are given in the following table.
Al l o y % Cr 3 % Mo % N PRE
SAF 2304 2 3 2 . 2 0 . 1 2 4
AI SI 31 6L 1 7 - - 2 4
AI SI 30 4L 1 8 .4 - - 1 8
As the table shows, the PRE-number for SAF 2304 is considerably
higher than thenumber for AISI 304L and comparable to the I number
for AISI 316L. Potentiostatictests in solutions with different
chloride contents (pH = 6) are reported in figure 7. Eachcurve is
based on at least 4 measuring points, each of which is derived from
a minimumof three separate measurements, and the variation in the
measurement results lies within
the range +/-5°C (+/-9°F). The test results for AISI 316L have
been compared withresults obtained under practical conditions of
service, and the correlation is good. As isevident from figure 7,
the critical temperature for pitting for SAF 2304 is higher
thanthat for AISI 304L and comparable to that for AISI 316L. The
experimental resultsthereby agree with the PRE ranking.
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Figure 7. Critical pitting temperature (CPT) for SAF 2304, AISI
304L andAISI 316L in neutral chloride solutions (potentiostatic
determination at+300 mV/SCE).
Stress corrosion and crackingBecause of its two-phase structure
and its well-balanced composition, SAF 2304possesses very good
resistance to stress corrosion cracking (SCC).
This is evident from the results of tests in both concentrated
chloride solutions andoxygen-containing dilute chloride
environments.
Figure 8 shows the results of tests carried out in 40% CaCl
solution at 100°C (210°F).In this environment, the stress that is
required to cause fracture due to SCC (known asthe threshold
stress) is much higher for SAF 2304 than for AISI 304/304L and
AISI316/316L. This indicates the superior resistance of SAF
2304.
Welding of SAF 2304 does not appreciably reduce the resistance
to SCC, provided thatthe welding recommendations are followed
(seeWelding).
The threshold stress of material that has been TIG-welded with
Sandvik 22.8.3.L orMMA-welded with Sandvik 22.9.3.LR is on a level
with that of the parent metal.
The results of SCC testing of SAF 2304 in chloride solutions at
high temperatures andpressures are presented in figure 9. The curve
for SAF 2304 is based on tests performedat various chloride
contents and different temperatures. Usually six
separatemeasurements were performed at each measuring point. The
testing method involvedspring-loaded specimens stressed to the
proof strength (R ) at the testingtemperature, or U-bends in which
the stress at the apex is at least equal to the proof
strength of the solution annealed material. The oxygen content
of the inlet water(refreshed autoclaves were used) was 4.6 to 10
ppm and the pH 4.5 to 7. I. The curvefor AISI 304/304L and AISI
316/316L is based on published test results and on
practicalexperience.
2
p0.2
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Figure 8. Results of SCC tests with constant load on SAF 2304,
AISI 304Land AISI 316L in 40% CaCl2, pH = 6.5, at 100°C (210°F)
withaerated test solution.
The results in figure 9 indicate that SAF 2304 can be used in
oxygen-bearing chloridesolutions up to about 125°C (260°F) without
any risk of SCC.
This is much higher than for AISI 304/ 304L and AISI 316/316L,
which should not beused above 60°C (140°F) in such environments. At
temperatures above 125°C (260°F),SAF 2304 should not be used in
oxygen-bearing solutions in environments with morethan about 10 ppm
Cl . For such conditions, we recommend Sandvik SAF 2205, SAF2507 or
Sanicro 28. At low oxygen contents, which are common in the process
andpower industries, considerably higher chloride contents and
temperatures can betolerated by SAF 2304 without any risk of
SCC.
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Figure 9. SCC resistance in oxygen-bearing (»8 ppm) neutral
chloridesolutions. Testing time 1000 hours. Load > yield
strength at testingtemperature.
Intergranular corrosionSAF 2304 is a member of the family of
modern duplex stainless steels whose chemicalmanner that the
reformation of austenite in the heat-affected zone adjacent to the
weldtakes place quickly. This results in a microstructure that
gives corrosion properties andtoughness similar to that of the
parent metal. Welded joints in SAF 2304 easily pass
Strauss' intergranular corrosion testing according to DIN 50914
and SS 117105.Crevice corrosionIn the same way as the resistance to
pitting can be related to the chromium,molybdenum and nitrogen
contents of the steel so can the resistance to crevicecorrosion.
SAF 2304 has better resistance to crevice corrosion than steels of
the AISI304/304L type and is comparable with AISI 316/316L.
Erosion corrosionSteels of the AISI 304/304L and AISI 316/316L
type can be attacked by erosioncorrosion if exposed to flowing
media containing highly abrasive solid particles, e.g.sand, or
media with very high flow rates. Due to its combination of high
hardness andgood corrosion resistance, SAF 2304 displays very good
resistance under suchconditions.
Corrosion fatigue
SAF 2304 possesses higher strength and better corrosion
resistance than ordinaryaustenitic stainless steels. Consequently,
SAF 2304 has considerably better fatiguestrength under corrosive
conditions than such steels.
HEAT TREATMENT
Plate,sheet and coil are normally delivered in heat treated
condition. If additional heattreatment is needed after further
processing the following is recommended.
Solution annealing
930 -1050°C (1710 -1920°F), rapid cooling in air or water.
WELDING
The weldability of SAF 2304 is good. Suitable welding methods
are manual metal-arcwelding with covered electrodes or gasshielded
arc welding.
Welding should be undertaken within the heat input range 0.5-2.5
kJ/mm. Preheating orpost-weld heat treatment is not normally
necessary.
Filler metals that give an austenitic-ferritic weld metal should
be used in order to obtaina weld metal with corrosion resistance
and mechanical properties close to the parent
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metal. For gas-shielded arc welding, we recommend Sandvik
22.8.3.L, and for manualmetal-arc welding the covered electrode
Sandvik 22.9.3.LR. These filler metals can alsobe used for welding
SAF 2304 to carbon steels, stainless steels and nickel alloys.
Thecovered electrode Sandvik 23.12.2.LR and the wire electrode
Sandvik 24.13.L can also beused for this purpose. When welding
components for use in high concentrated nitricacid the choice of
filler metal should be discussed with Sandvik.
FABRICATION
ending
The starting force needed for bending is slightly higher for SAF
2304 than for AISI304/316. SAF 2304 can be cold-bent to 25%
deformation without requiring subsequentheat treatment. Under
service conditions where the risk of stress corrosion
crackingstarts to increase, for example where the material
temperature is nearly 125°C (255°F)in a neutral oxygen-bearing
environment with around 100 ppm Cl , heat treatment isrecommended
even after moderate cold bending. For pressure vessel applications
inGermany and the Nordic countries heat treatment may be required
after colddeformation in accordance with VdTÜV-Wb 496 and NGS 1607.
Heat treatment iscarried out in the form of solution annealing (see
under this heading) or resistanceannealing. Hot bending is carried
out at 1100-950°C (2010-1740°F) and should befollowed by solution
annealing.
Expanding
In comparison with austenitic stainless steels, SAF 2304 has a
higher proof strength.
This must be borne in mind when expanding tubes into
tube-sheets. Normal expandingmethods can be used, but the expansion
requires higher initial force and should beundertaken in one
operation. Detailed recommendations on expanding duplex
stainlesssteels will be supplied on request.
Machining
Being a two-phase material (austenitic-ferritic) SAF 2304 will
present a different wearpicture from that of single-phase steels of
type AISI 304L. The cutting speed musttherefore be slightly lower
than that recommended for AISI 304L. It is recommendedthat a
tougher insert grade is used than when machining austenitic
stainless steels, e.g.AISI 304L.
APPLICATIONS
SAF 2304 possesses good mechanical and physical properties,
excellent resistance to
stress corrosion cracking and other forms of corrosion as well
as good weldability.These properties make it both a technically and
economically superior alternative tostainless steels such as the
austenitic steels AISI 304, 304L, 316, 316L, 321 and 347,
theferritic chromium steels AISI 430 and 444 and the martensitic
chromium steels of theAISI 410 and 420 type. SAF 2304 also has
advantages in many cases over low-alloysteels. Examples of areas
where SAF 2304 offers advantages over other materials aregiven in
the following table.
The good mechanical and corrosion properties make SAF 2304 an
economical choice inmany applications by reducing the life cycle
cost of the equipment.
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Indus try Applica t ions Usedt o d a y
Adv anta ges nof SA F 23 04
P r o c e s sI n d u s t r y
Heat exchangers and piping where chloridesare p resen t
AI SI304/304L
AI SI316/316L
Higher resistance to SCC
I ns tr um en ta ti on t ub in g, s te am t ra ci ng A IS
I304/304L
AI SI316/316L
Higher resistance to SCC
P e t r o c h e m i c a li n d u s t r y
Tubular reactors for high temperatureswhere ca rbon s tee l i s
used for the she l l
AI SI304/304L
AI SI316/316L
Coefficient of thermal expansion comparable to thatof ca rbon s
tee l
P u l p & p a p e r Digester preheater Evapora tors
AI SI304/304L
AI SI316/316L
Higher resistance to SCCHigher resistance to SCC
N u c l e a r p o w e r
Reheate rs C s tee ls AI SI 43 0 AI SI304/304L
Ease of fabricat ion, good corrosion resistance
P o w e r Feed wate r he a te rs AISI 430 AI SI304/304L
High resistance to SCC, high strength and ease of fabr ica t
ion
E n g i n e e r i n g B ea ms a nd t or qu e t ra ns mi tt in g
s ha ft s C s te el s AI SI304/304L
AI SI316/316L
High strength combined with excellent corrosionres i s tance ,
ease o f fabr ica t ion and low cos t
Hydrau l ics y s t e m
Hydrau lic tub ing C s tee ls Exce llent resistance to corros
ionReduced instal lat ion cost owing to easy cleaning
Oi l and gas Coolers on- and offshore. Piping systemsand f low l
ines on- and off shore
C steels AI SI
304/304L AI SI316/316L
AI SI 42 0
Optimal combination of strength weldabil i ty,cor ros ion res i
s tance and cos t
Tensioning systems on offshore r igs.instrumental tubing
AI SI304/304L
AI SI316/316LC steels
High strength combined with high corrosionres i s tance
DISCLAIMER:
Recommendations are for guidance only, and the suitability of a
material for a specific application can be confirmed only when
we know the actual service conditions. Continuous development
may necessitate changes in technical data without notice. This
datasheet is only valid for Sandvik materials.
www.smt.sandvik.com/contact-us
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