Duplex 2205 Seamless Pipe | SA-790 | Tailan Metal

Duplex 2205 seamless pipe is the 22 % chromium / 3 % molybdenum
nitrogen-strengthened ferritic-austenitic stainless steel supplied to
ASME SA-790 under UNS S32205. SA-790 Scope 1.1 covers
seamless and straight-seam welded ferritic/austenitic steel pipe for general
corrosive service, with particular emphasis on resistance to stress-corrosion
cracking, and warns that the steels are susceptible to embrittlement if used for
prolonged periods at elevated temperatures.

SA-790 is the correct specification for duplex pipe. The related
SA-789 is the tubing specification for the same alloys, and
SA-182 covers forged flanges and fittings. Quote the form you need.

Dual Standard Designation

Chemical Composition (ASME SA-790, Table 2)

SA-790 Table 2 note A: values are maxima unless a range or minimum is indicated.
Where an ellipsis appears there is no minimum and the analysis need not be determined
or reported. Copper and other elements are not required for these two grades.

Mechanical Properties (ASME SA-790, Table 3)

SA-790 Table 3 note A: the common name is not a trademark and is not associated
with any one producer. Yield strength is determined by the 0.2 % offset method.

Size Range

Dimensions are taken from SA-790 Appendix Table X1.1, which reproduces
the ANSI B36.19 table for welded and seamless stainless steel pipe. Outside-diameter
and wall-thickness tolerances are not in Section II; pipe dimensional tolerance
is governed by SA-999 and the applicable dimensional standard.

Standard Dimensions and Wall Thickness (ANSI B36.19 Schedule Table)

The nominal dimensions below are the published ANSI B36.19
schedule values, reproduced from ASME Section II SA-790 Appendix Table X1.1, which is
based on Table 1 of ANSI B36.19-1965. The decimal thicknesses are nominal or
average wall dimensions, which is how ASME defines them. Dimension and
thickness tolerances for the pipe itself are given by the governing product
specification and the applicable order requirements — tell us the NPS,
schedule and service condition and we will confirm the exact tolerance that
will be applied to your order.

Note A — Schedules 5S and 10S wall thicknesses do not permit threading in accordance with ANSI B1.20.1.
Note B — These do not conform to ANSI B36.10.

SA-790 Table X1.1 extends to NPS 30. ^B Note A: Schedules 5S and 10S wall
thicknesses do not permit threading in accordance with ANSI B1.20.1. ^B Note B:
the marked wall thicknesses do not conform to ANSI B36.10-1979. Note 1 of Table X1.1:
the decimal thickness listed represents the nominal or average wall dimension. Send us
your NPS and wall list and we will confirm availability against mill capability.

Manufacturing Route & Heat Treatment

SA-790 6.1.1 requires the pipe to be made by the seamless process or by an automatic
welding process with no addition of filler metal in the welding operation, 6.1.2 allows
hot-finished or cold-finished at the manufacturer’s option, and 6.1.3 requires the pipe
to be pickled free of scale (where bright annealing is used, descaling is not
necessary).

SA-790 6.3 requires the pipe to be furnished in the heat-treated condition shown in
Table 1 unless the order states otherwise. For UNS S32205 the solution annealing range
is 1870 – 2010 °F (1020 – 1100 °C) with rapid cooling
in air or water. SA-790 6.3.1 allows an alternative for seamless pipe: instead of a final
furnace heat treatment, pipe may be individually quenched in water or rapidly cooled by
other means immediately after hot forming, provided the pipe is at or above the specified
minimum solution treatment temperature. SA-999 16.2 limits the deviation of metal-arc
welded pipe from a 10 ft (3.0 m) straightedge to 1/8 in. (3.2 mm), prorated for shorter
lengths.

Inspection & Certification

• Hydrostatic or electric test: SA-790 14.1 requires each pipe to be
  subjected to either the nondestructive electric test or the hydrostatic test, at the
  manufacturer’s option unless the purchase order states otherwise. SA-790 14.2 sets the
  hydrostatic test to SA-999 22.2, except that the stress used is 50 % of the
  specified minimum yield strength of the pipe — the ferritic/austenitic
  stainless basis, with the test pressure calculated as P = 2St/D.
• Electric test: SA-790 14.3 requires nondestructive electric testing
  in accordance with Practices E213 or E309. SA-790 14.4 requires the examination for
  acceptance to be performed after all mechanical processing, heat treatments and
  straightening operations.
• Operator qualification: SA-790 14.7 requires the test unit operator
  to be certified in accordance with SNT-TC-1A or an equivalent recognised standard.
• Eddy-current coil frequency: SA-790 14.8.2 limits the maximum coil
  frequency to 100 kHz for specified walls up to 0.050 in., 50 kHz for walls up to
  0.150 in., and 10 kHz for walls over 0.150 in.
• Ultrasonic search: SA-790 14.8.3 requires a minimum nominal
  transducer frequency of 2.00 MHz and a maximum nominal transducer size of 1.5 in.
• Tension test: one tension test for lots of not more than 100 pipes,
  specimens taken from two pipes for lots of more than 100 (SA-790 13.1).
• Hardness test: Brinell or Rockwell on specimens from two pipes per
  lot (SA-790 13.4).
• Product analysis: SA-790 9.1 makes product analysis available at the
  request of the purchaser’s inspector, with the lot size defined by NPS.
• Supplementary requirements: SA-790 S1 product analysis, S2
  transverse tension tests, S3 flattening test and S4 etching tests to Method E381, each
  applying only when specified on the purchase order.
• Certification: MTC to EN 10204 3.1 standard;
  EN 10204 3.2 issued when third-party inspection is specified on the order. PMI,
  corrosion testing and impact testing are available on request as supplementary
  requirements.

Packing & Delivery

Plastic end caps on all sizes; steel frames or wooden crates for large diameters; VCI
anti-rust wrapping. Beveled ends standard for welding; plain ends available. Each length
is marked with the standard, grade, size, heat number and heat treatment condition
(SA-790 16.1).

Applications

Seawater and cooling water systems, desalination plant intake and product piping,
oil and gas production facilities, chemical and petrochemical process lines, pulp and
paper bleaching plant piping, flue-gas desulphurisation scrubbers, waste-heat boiler
transfer lines, and potable and industrial water treatment plant piping where chloride
attack or stress-corrosion cracking governs the material selection.

Technical Notes

1. “2205” is not one UNS number, and the two that exist are not
interchangeable. SA-790 Table 2 lists S32205 and S31803 side by side, and they
carry different windows: S32205 is nitrogen-tightened at 0.14–0.20 % with
chromium 22.0–23.0 % and molybdenum 3.0–3.5 %, while S31803 allows
chromium down to 21.0 %, molybdenum down to 2.5 % and nitrogen down to 0.08 %. Both
are sold as 2205. The trap is at the fitting end: ASME SA-182 grade F 51 is
S31803 and F 60 is S32205, with different chromium, molybdenum
and nitrogen limits and different mechanical requirements (F 51 requires 90 ksi / 620 MPa
tensile against F 60 at 95 ksi / 655 MPa). A duplex fitting made to F 51 is therefore
not the same chemistry as pipe made to S32205, even though both are called 2205. Always
write the UNS number on the order and check it on the mill certificate.

2. The hydrostatic test basis is what ties wall thickness to pressure here.
SA-790 14.2 sets the hydrostatic test at 50 % of the specified minimum yield strength
of the pipe — the ferritic/austenitic stainless basis in SA-999 22.2.1, which uses
P = 2St/D with t as the specified wall thickness and D as the specified outside
diameter. SA-999 22.2.2 caps the minimum test pressure that has to be reached at
2500 psi (17.0 MPa) for outside diameters of 3.5 in. (88.9 mm) or less and 2800 psi
(19.0 MPa) above that, and SA-999 22.2.1.1 requires the resulting pressure to be
rounded to the nearest 50 psi (0.5 MPa) below 1000 psi (7 MPa) and to the nearest
100 psi (1 MPa) at or above it. Working back from the certificate, the practical
constraint is SA-999 10.1: the minimum wall thickness at any point shall not be more
than 12.5 % under the nominal wall thickness specified. That is the number to watch
when a nominal wall is being confirmed on a thin-wall duplex line.

3. The quench is the metallurgical property, not an afterthought.
SA-790 Table 1 gives S32205 a solution annealing range of 1870–2010 °F
(1020–1100 °C) followed by rapid cooling in air or water, and 6.3.1 allows
the direct quench immediately after hot forming. Duplex stainless steel derives its
corrosion resistance from a balanced ferrite-austenite microstructure, and that
balance is set by the cooling rate out of the annealing range, because slow cooling
through the intermediate range lets sigma and chi phases precipitate and tie up
chromium and molybdenum in intermetallics at the grain boundaries instead of leaving
them in solid solution. Too slow a cool and the pitting resistance falls away; too
violent a water quench and residual stress rises. SA-790 6.1.3’s pickled surface
is part of the same picture, because a mill scale that has not been removed leaves the
surface chromium-depleted. This is also why the same alloy in a different product form
carries a different anneal window — an SA-182 F 60 forging and an SA-815
WPS32205 fitting do not use the same figures as SA-790 pipe.

Frequently Asked Questions

Which ASME specification covers duplex 2205 seamless pipe?

ASME SA-790, identical to ASTM A790/A790M, Seamless and Welded Ferritic/Austenitic
Stainless Steel Pipe. SA-789 is the tubing specification for the same alloys, and
SA-182 covers forged flanges, fittings and valves. Quote the form you need.

Is SA-790 the right specification, or should I ask for SA-789?

SA-790 for pipe, SA-789 for tube. They carry the same UNS numbers and largely the
same chemistry, but they are different documents with different scope, dimensional and
inspection requirements, so a certificate written to one is not automatically
compliant with the other.

What is the difference between S32205 and S31803?

S32205 is the tightened-nitrogen version: chromium 22.0–23.0 %, molybdenum
3.0–3.5 %, nitrogen 0.14–0.20 %. S31803 is the earlier, wider window at
chromium 21.0–23.0 %, molybdenum 2.5–3.5 %, nitrogen 0.08–0.20 %. S32205
also carries the higher tensile minimum of 95 ksi (655 MPa) against 90 ksi (620 MPa),
with the same 65 ksi (450 MPa) yield in both.

Is impact testing required?

Not by the base specifications for this grade. SA-182 9.7 applies the notch
toughness requirement to F 3V, F 3VCb and F 22V, and SA-790 does not impose a Charpy
requirement on S32205. If your project calls for impact testing or a corrosion test,
state it on the order as a supplementary requirement and we will run it.

What certification is supplied?

EN 10204 3.1 mill test certificate as standard, including the heat treatment
condition, product analysis, tensile and hardness results. EN 10204 3.2 is issued when
third-party inspection is specified on the purchase order.

Can this pipe be threaded?

Not on the 5S or 10S schedules. SA-790 Table X1.1 note A states that schedules 5S
and 10S wall thicknesses do not permit threading in accordance with ANSI B1.20.1.
Schedule 40S and 80S walls are the threadable schedules in the B36.19 series.

Inquire on WhatsApp