Super Duplex 2507 Welded Pipe | SA-790 | Tailan Metal

Super duplex 2507 welded pipe is the 25 % chromium super duplex
stainless steel supplied to ASME SA-790 in straight-seam welded form.
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 Table 2 lists two super duplex grades, S32750 and
S32760. They are covered by the same specification and the same
welding route, but they differ in chemistry, in PREN expression, in annealing window
and in the filler metal that SA-790 Table 4 associates with repair welding.

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.
Note D, applying to S32750: % Cr + 3.3 × % Mo + 16 × % N
≥ 41. Note E, applying to S32760: % Cr + 3.3 × (% Mo + 0.5 × % W)
+ 16 × % N ≥ 41.

Mechanical Properties (ASME SA-790, Table 3)

SA-790 Table 3 note B: prior to A790/A790M-04, the tensile strength value for UNS
32760 was 109–130 ksi [750–895 MPa].

Size Range

Dimensions are taken from SA-790 Appendix Table X1.1, the ANSI B36.19
table for welded and seamless stainless steel pipe. 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. 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 an automatic welding process with no addition of filler metal
in the welding operation, so the weld metal chemistry is the base metal chemistry.
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, with descaling not necessary where bright
annealing is used.

SA-790 6.3 requires the pipe to be furnished in the heat-treated condition shown in
Table 1 unless the order states otherwise. The two super duplex grades have different
solution annealing windows: 1880 – 2060 °F (1025 – 1125 °C)
for S32750 and 1960 – 2085 °F (1070 – 1140 °C) for
S32760, both with rapid cooling in air or water. SA-790 6.3.1 allows the direct quench
immediately after hot forming as an alternative to a final furnace heat treatment,
provided the pipe is at or above the specified minimum solution treatment temperature.

Inspection & Certification

• Hydrostatic or electric test: SA-790 14.1, at the manufacturer’s
  option unless the purchase order states otherwise. SA-790 14.2 sets the hydrostatic
  stress at 50 % of the specified minimum yield strength of the pipe,
  with P = 2St/D per SA-999 22.2.1. SA-999 22.2.2 caps the required test pressure at
  2500 psi (17.0 MPa) for OD of 3.5 in. (88.9 mm) or less and 2800 psi (19.0 MPa) above
  it, and SA-999 22.2.4 requires the pressure to be held for at least 5 s, and for welded
  pipe for a time sufficient to permit the entire length of the welded seam to be
  inspected.
• Electric test: SA-790 14.3, to Practices E213 or E309, performed
  after all mechanical processing, heat treatments and straightening (SA-790 14.4). SA-790
  14.3.1.3 notes that ultrasonic testing may not detect short, deep defects, which is
  why the two electric methods are normally used to complement each other.
• Flattening or guided bend: SA-790 13.3 requires the flattening test
  on 5 % of the pipe from each heat-treated lot where the pipe is heat treated in a
  batch-type furnace, and SA-790 13.3.1 allows a transverse guided face bend test in
  place of the flattening test for welded pipe of NPS 10 and larger, with specimens from
  5 % of the lot taken from pipes or test plates of the same material, the test plates
  being attached to the end of the cylinder and welded as a prolongation of the pipe
  longitudinal seam.
• Repair welding: SA-790 15.1 permits repairs with compatible
  filler metal on welded pipe of NPS 6 and larger with a specified wall of 0.188 in.
  (4.8 mm) or more, following the SA-999 plate defect repair procedures; 15.2 limits the
  repair to 20 % of the seam length; 15.3 requires gas tungsten-arc welding with bare
  filter rod qualified to AWS A5.9 as the grade of pipe being repaired, as given in
  SA-790 Table 4; 15.3.1 permits a more highly alloyed filler with purchaser approval;
  15.4 requires the “WR” symbol and identification of the filler metal on the
  certificate of tests; and 15.5 requires the repair before any heat treatment.
• Certification: MTC to EN 10204 3.1 standard;
  EN 10204 3.2 issued when third-party inspection is specified on the order. A923,
  intergranular corrosion, PMI 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 lift and discharge piping, reverse osmosis desalination plants, offshore
platform and subsea topsides piping, oil and gas sour service lines, chemical and
petrochemical process piping, pulp and paper bleach plant piping, flue-gas
desulphurisation scrubber lines, and chlorinated water distribution systems.

Technical Notes

1. SA-790 Table 4 does not list a filler metal for either super duplex
grade, and that changes how the repair clause is applied. SA-790 Table 4
associates filler metal with four pipe UNS numbers only: S31803 and S32205 with
ER2209, UNS S39209, S31200 with ER2553, UNS S39553,
and S82441 with ER2209, UNS S39209. Neither S32750 nor S32760 appears. SA-790 15.3
requires a repair to be made by gas tungsten-arc welding using the same classification
of bare filter rod qualified to the most current AWS A5.9 as the grade of pipe being
repaired, as given in Table 4, and 15.3.1 then allows a more highly alloyed filler
where the purchaser approves it, with 15.4 requiring the filler metal actually used to
be identified on the certificate of tests. In practice this means a super duplex
repair is made with a super duplex filler agreed for the job and documented on the
certificate, rather than with a classification that the pipe specification itself
names. If your project has a repair or field-weld procedure, have the filler
classification agreed in writing before fabrication, not after.

2. The autogenous seam is what makes the post-weld heat affected zone the
governing metallurgical location, and A923 is the test that governs it.
SA-790 6.1.1 requires the automatic welding process with no addition of filler metal,
so the seam and the base metal share the same chemistry and the corrosion margin of
the weld is not reduced by dilution. The cost of that is that the weld heat affected
zone passes through the sigma and chi precipitation range on its way out of the
annealing temperature, and the cooling rate through the seam region is the variable
that decides whether intermetallics form. This is why SA-790 6.3.2 exists at all: the
HT-O route requires a sample of the heat to pass Test Methods A923 Method B or C,
covering base metal, weld metal and heat affected zone, before the pipe may be
supplied without a further heat treatment, and each such pipe is stenciled
“HT-O” so the status travels with the material. SA-790 6.3.2.2 excludes
materials not listed in Table 3 of A923 from the provision. For super duplex this
is the single most important clause on the page, because super duplex is the grade
where the precipitation range matters most.

3. Two different super duplex grades mean two different certificates, and
the document to read is the one for the form you bought. SA-790 Table 3 gives
S32750 a tensile minimum of 116 ksi (800 MPa) and S32760 a minimum of 109 ksi
(750 MPa), with footnote B recording that the S32760 value was previously
109–130 ksi (750–895 MPa) prior to A790/A790M-04. SA-182 F 55 and SA-815
S32760 still carry the 109–130 ksi (750–895 MPa) range, because the change
was made in the pipe specification alone. The annealing windows differ in the same way:
SA-790 Table 1 gives S32750 1880–2060 °F (1025–1125 °C) and S32760
1960–2085 °F (1070–1140 °C), while SA-815 Table 2 gives S32750
1920–2060 °F (1025–1125 °C) and S32760 2010–2085 °F
(1100–1140 °C), and SA-182 Table 1 gives F 53 a solution treatment at
1880 °F (1025 °C) minimum and F 55 a range of 2010–2085 °F
(1100–1140 °C). The same UNS number therefore carries different figures in
the pipe, the wrought fitting and the forging specifications, and a project that
mixes pipe and fittings should confirm the requirements against the specification for
each form rather than assuming one set of numbers across the line.

Frequently Asked Questions

Which ASME specification covers super duplex 2507 welded pipe?

ASME SA-790, identical to ASTM A790/A790M, which covers seamless and straight-seam
welded ferritic/austenitic steel pipe. SA-789 is the tubing specification, SA-815
covers wrought super duplex fittings, and SA-182 covers forged flanges and fittings.

Is the welded form made with filler metal?

No. SA-790 6.1.1 requires an automatic welding process with no addition of filler
metal in the welding operation, so the weld metal chemistry is the base metal
chemistry. The separate filler metal requirements in SA-790 15.3 and Table 4 apply to
repair welding, not to the original longitudinal seam.

What filler metal is used for repairs on super duplex pipe?

SA-790 Table 4 does not list a filler metal for S32750 or S32760. SA-790 15.3
requires gas tungsten-arc welding with AWS A5.9 filler matching the grade, 15.3.1
permits a more highly alloyed filler with purchaser approval, and 15.4 requires the
filler metal actually used to be identified on the certificate of tests. Agree the
filler classification before fabrication.

When is the HT-O option available?

SA-790 6.3.2 allows pipe that has not been heat treated after welding where the
pipe is fabricated from plate already heat treated to Table 1 and a sample of that
heat passes Test Methods A923 Method B or C covering base metal, weld metal and heat
affected zone. Each such pipe is stenciled “HT-O”, and SA-790 6.3.2.2
excludes materials not listed in Table 3 of A923.

Which nondestructive test is applied?

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, so state your requirement on the order. Electric testing is
to Practices E213 or E309 and is performed after all mechanical processing, heat
treatments and straightening.

What certification is supplied?

EN 10204 3.1 mill test certificate as standard, with 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, and A923, intergranular
corrosion, PMI and impact testing are available on request.

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