Duplex Stainless Steel Welding
Transcript of Duplex Stainless Steel Welding
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WHAT ARE DUPLEX STEELS
Duplex Steels are also called FERRITIC-
AUSTINITIC steels.
Duplex Steels have approx. 50% ferritic and 50%austinitic structure.
Ferrite provides Strength and Resistance to
localized Corrosion and also refines austinitic
structure.
Austinite provides Toughness and Weldability
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DUPLEX STEELS
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UNS
N
u
m
be
r
D
up
le
x
Gr
ades
Typeb C Mn P S Si Cr Ni Mo N Cu Other
S31200 ... 0.030 2.00 0.045 0.030 1.00 24.0-26.0 5.5-6.5 1.20-2.00 0.14-0.20 ... ...
S31260 ... 0.03 1.00 0.030 0.030 0.75 24.0-26.0 5.5-7.5 2.5-3.5 0.10-0.20 0.20-0.80 W0.10-0.20
S31803 ... 0.030 2.00 0.030 0.020 1.00 21.0-23.0 4.5-6.5 2.5-3.5 0.08-0.20 ...
S32001 ... 0.030 4.0-6.0 0.040 0.030 1.00 22.0-23.0 1.00-3.00 0.60 0.05-0.17 1.00
S32205 2205 0.030 2.00 0.030 0.020 1.00 19.5-21.5 4.5-6.5 3.0-3.5 0.14-0.20 ...
S32304 2304 0.030 2.50 0.040 0.030 1.00 21.5-24.5 3.0-5.5 0.05-0.60 0.05-0.20 0.05-0.60
S32520 ... 0.030 1.50 0.035 0.020 0.80 24.0-26.0 5.5-8.0 3.0-4.0 0.20-0.35 0.50-2.00
S32550 255 0.04 1.50 0.040 0.030 1.00 24.0-27.0 4.5-6.5 2.9-3.9 0.10-0.25 1.5-2.5
S32750 2507 0.030 1.20 0.035 0.020 0.80 24.0-26.0 6.0-8.0 3.0-5.0 0.24-0.32 0.50
S32760 ... 0.030 1.00 0.030 0.010 1.00 24.0-26.0 6.0-8.0 3.0-4.0 0.20-0.30 0.50-1.00 c
S32900 329d 0.06 1.00 0.040 0.030 0.75 23.0-28.0 2.5-5.0 1.0-2.0 ... ...
S32950 ... 0.03 2.00 0.035
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HEAT TREATMENT
Thermo-Mechanical treatment is carried out
by rolling at 900-950C which results in
fine dispersion of ferrite and austinite which
are called Micro-Duplex steels having grain
size upto 3-10 micro metre.These steels
exhibit super plasticity means ductilities ofabout 500% at temperatures near 950C.
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PHYSICAL PROPERTIES
Thermal conductivity is higher than
austinitic stainless steels.
Temp(F) 68 200 400 600 800
SAF 2205 9.0 9.5 11.0 11.5 12.5
AISI 316 L 8.5 9.0 10.0 11.0 11.5
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CORROSION RESISTANCE
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CORROSION RESISTANCE
Pitting Corrosion
Pitting resistance is determinedby Cr,Mo and N contents.We define Pitting
Resistance Equivalent(PRE).PRE=%Cr+3.3*%Mo+16*%N
PRE number for some steels
Alloy %Cr %Mo %N PRE
SAF 2205 22.2 3.2 0.18 35.06
AISI 316 L 17 2.1 _ 24
AISI 317 L 18 3.5 _ 30
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CORROSION RESISTANCE
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CORROSION RESISTANCE
Resistance to SCC
Austinitic steels are prone to
SCC above 60C but Duplex Steels according
to laboratory tests have good resistance to
SCC.
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CORROSION RESISTANCE
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MECHANICAL PROPERTIES
Hardness Tensile strength %Elongation
SAF 2304 230 BHN 600-820N/mm 25
SAF 2205 260 BHN 680-900N/mm 25
YIELD STRENGTH
0.2% offset 1.0% offset
SAF 2304 400N/mm 450N/mm
SAF2205 450N/mm 500N/mm
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MECHANICAL PROPERTIES
Impact Strength:
Good impact
strength both at higher
and lower temperatures.
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APPLICATIONS
Heat exchangers where chloride bearing water or
brackish water is used as cooling medium
For use in dilute sulphuric acid solutions. For handling of organic acids e.g acetic acids.
In refineries and as flow lines for extraction of oil
and gas from sour wells.
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CERTIFICATION
Approved by the American Society ofMechanical Engineers (ASME) for use in
boilers and presssure vessels. NACE MR 01759 (sulphide stress
cracking resistent material for oil fieldequipment)
ASME B31.3 Chemical plant andpetroleum refinery piping.
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WELDING OF DUPLEX STEELS
The procedure that is carried out in welding ofDuplex steels is as followed
1-Cleaning Before Welding:-
Duplex stainless steels aremore sensitive to contamination and moisture thanother steels. As impurities effect corrosion resistanceand mechanical properties of weldment.
2-Joint Preparation:-For duplex steels,a weld joint mustfacilitate full penetration.the root gap must be widerthan that of austinitic steels.
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WELDING OF DUPLEX STEELS
Filler Metals:-Filler metals must always be used in weldingof duplex steels because PWHT is not made so
ductility and corrosion resistance can decrease due
to loss of austinite content in weld metal.WeldingWelding without filler metal must be avoided for
all duplex steels in high quality demanding
applications where quench annealing cannot be
performed after welding.
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WELDING OF DUPLEX STEELS
Sandvik C
max
Si Mn Pmax
Smax
Cr Ni Mo N
22.9.3
Covered
0.03 1.0 0.8 0.025 0.020 22.5 9.5 3 0.14
22.8.3
Wire
0.020 0.5 1.6 0.020 0.020 22.5 8 3 0.14
23.12.2
Covered
0.04 0.8 1.0 0.03 0.03 23 13 2.7
_
22.15.3
Wire
0.025 0.4 1.5 0.025 0.020 21.5 15 2.7 _
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WELDING OF DUPLEX STEELS
GMAW Welding
1-Wire Electrode:-
Sandvik 22.8.3.L should be chosen as filler metal forSAF 2205 and SAF 2304.
2-Shielding Gases:-Spray arc: Argon,oxygen(1-3%)
Short arc: Argon,Carbon dioxide(1-3%)
3-Backing Gases:-
Backing gases are required regardless of jointdesign.Argon,argon-nitrogen mixtures,nitrogen or Formler gasare used.
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WELDING OF DUPLEX STEELS
Typical Parameter Settings
Wire dia Current Voltage
Spray arc transfer
0.8 170-200 26
1.2 180-260 29
1.6 230-350 30
Short arc transfer0.8 90-120 19-21
1.2 110-140 20-22
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WELDING OF DUPLEX STEELS
TIG Welding
1-TIG Rods:-
Sandvik 22.8.3L is used for SAF 2205 SAF 2304 andSandvik 25.10.4.L is used for SAF 2205 and SAF 2507.
2-Shielding Gases:-
Argon,argon+2%nitrogen or argon helium mixtures.
3-Baking Gases:-
Backing gases are required regardless of joint design.Argon,argon-nitrogen mixtures,nitrogen or Formler gas are used.
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WELDING OF DUPLEX STEELS
4-Typical Parameter Settings:-
Parameter settings in TIG welding are largelydependent upon the material thickness,type of joint etc.For
example a typical root pass may use 100amps/11 volts at atravel speed of 60mm/min giving a heat input of 1.1kj/mm .
SAW WELDING
1- Wire electrodes and flux:-
Sandvik 22.8.3L is used for SAF 2205 SAF 2304and Sandvik 25.10.4.L is used for SAF 2205 and SAF2507.The flux sandvik 15W is recommendedfor all threegrades.
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WELDING OF DUPLEX STEELS
2-Typical Parameter Settings:-
Wire dia Current Voltage
2.4 250-450 28-32
3.2 300-500 29-34
4.0 400-600 30-355.0 500-700 30-35
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WELDING OF DUPLEX STEELS
SMAW WELDING
1- Covered electrodes:-
Sandvik 22.9.3L is used for SAF 2205 SAF 2304
and Sandvik 25.10.4.LR is used for SAF 2205 and SAF 2507.2-Typical Parameter Settings:-
Wire dia Current Voltage
2.0 35-55 22-28
2.5 50-75 22-283.25 70-120 22-28
4.0 90-160 22-28