Copper Nickel 70-30 Seamless Pipe | ASME SB-466 | Tailan Metal

Copper-nickel 70/30 seamless pipe is supplied to
ASME SB-466 under UNS C71500, the
highest-nickel grade in the specification. SB-466 Scope covers C71500
alongside C70400, C70600, C70620, C71000, C71520 and C72200, and 6.1
requires the material of manufacture to be cast billets of those alloys of
such purity and soundness as to be suitable for processing into the
products prescribed by the specification.

Where 90/10 is the general-purpose seawater grade, 70/30 is the grade
chosen when the service is more aggressive than the film alone can handle:
higher flow velocity, higher temperature, sulphide-bearing or polluted
seawater, or a longer design life than the lower-nickel alloy can deliver.
This page covers C71500; the 90/10 grade is covered separately.

Grade Map

Chemical Composition (ASME SB-466, Table 1)

SB-466 7.2.1 explains that for alloys in which copper is listed as
remainder, copper is the difference between the sum of the results of all
elements determined and 100 %. Section 7.2.2 requires a minimum of 99.5 %
for the copper-plus-named-elements sum for both C71500 and C71520. The
difference between C71500 and C71520 is therefore not the nickel level but
the lead, zinc, manganese and carbon limits: C71520 carries a specified
65.0 % minimum copper instead of a remainder calculation, lead at 0.02 %
max instead of 0.05 %, zinc at 0.50 % max instead of 1.0 %, manganese at
0.50 % max instead of 1.0 %, and a carbon limit of 0.05 % max, which is
the grade to specify when the pipe will be welded into an assembly.

Mechanical Requirements (ASME SB-466, Table 2)

SB-466 8.1 gives the standard tempers as O60 (soft anneal) for pipe, with
H55 (light drawn), H80 (hard drawn) and HE80 (hard drawn and end annealed) as
the drawn tempers for tube. Table 2 note A states that the yield strength is
measured at 0.5 % extension under load, and note C that although no minimum
grain size is specified, the product must nevertheless have a fully
recrystallized grain structure. Note B restricts the Rockwell hardness values
to tube or pipe of 0.020 in. (0.5 mm) wall thickness and over and 5/16 in.
(8 mm) outside diameter and over, requires the test to be made on the inside
surface of the tube, and permits other Rockwell scales to be specified by
agreement where suitable equipment is not available. A point worth noting
for procurement is that C71500 appears in the O60 and H80 rows of Table 2
but not in the H55 row, so the light-drawn temper is not a defined condition
for this grade.

Size Range

The preferred sizes and wall thicknesses for this specification are given
in SB-466 Table X1.1, the appendix of preferred sizes, with the columns for
Regular and Extra Strong wall thickness and a set of Specials columns. The
dimension basis is the standard pipe size outside diameter rather than a
nominal bore. The wall thickness tolerances are in Table 3, the average
diameter tolerances in Table 4, and the length, roundness, squareness of cut
and straightness tolerances are referred by 12.4 to Specification
B251/B251M. Section 12.3 requires the tolerance on distances between
parallel surfaces for tubes other than round to be agreed between the
manufacturer or supplier and the purchaser. If a specific size and wall
combination is required, send it in and we will confirm availability and
the applicable dimensional tolerance.

Manufacturing Route and Heat Treatment

SB-466 6.2 requires the product to be manufactured by such hot extrusion
or piercing and subsequent cold working and annealing as to produce a
uniform, seamless wrought structure in the finished product. Section 8.1.1
identifies the O60 condition as a soft anneal, and Table 2 note C requires a
fully recrystallized grain structure in the finished product even though no
minimum grain size is specified. For a 70/30 line that will be formed on
site, the O60 soft anneal is the condition to order, because the H80
hard-drawn condition is excluded from the expansion test by 10.1.1.2 and
will not tolerate that level of deformation.

Inspection, Testing and Certification

• Expansion test: SB-466 10.1.1 requires tube in the O60
  and HE80 tempers to withstand an expansion to 30 % of the outside diameter
  when tested in accordance with Test Method B153, with no cracking or other
  defect visible to the unaided eye; 10.1.1.2 excludes other tempers from
  this requirement.
• Flattening test alternative: SB-466 10.2 permits
  B968/B968M flattening as an alternative to the expansion test for product
  over 4 in. (100 mm) in diameter, with 10.2.1 requiring the flattened areas
  to be free of defects, although blemishes that do not interfere with the
  intended application are acceptable.
• Eddy current test: SB-466 11.2.1 requires each tube up
  to and including 3.125 in. (80 mm) nominal outside diameter to be subjected
  to an eddy current test following Practice E243, with 11.2.1.4 requiring
  notch depth standards of 22 % of the wall thickness, and 11.2.1.3 requiring
  either notch depth or drilled hole standards to be used.
• Hydrostatic test: SB-466 11.2.2 requires an internal
  hydrostatic pressure sufficient to produce a fibre stress of 7000 psi
  [48 MPa], calculated as P = 2St/D, and 11.2.1.6 allows the hydrostatic test
  to be used in place of the eddy current test for tubes above 1.25 in.
  (32 mm) in diameter. Section 11.2.3 covers the pneumatic test at 60 psig
  [415 kPa] for 5 s.
• Certification: SB-466 15.1 makes the test report and
  certification requirements of Specification B251/B251M mandatory.

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 temper condition.

Applications

High-velocity seawater systems, offshore platform and subsea production
piping, tanker and shipboard seawater systems, firewater systems, power
station condensers and heat exchangers, oil and gas production facilities,
sour water and brine handling, chemical process lines carrying aggressive
chloride-bearing streams, and desalination plant piping. In these
applications 70/30 is specified where the flow velocity, the temperature or
the aggressiveness of the water is beyond what the lower-nickel grade
reliably withstands.

Technical Notes

1. The jump from 10 % to 30 % nickel is not a linear increase in
corrosion resistance; it changes the mechanism. The protective
behaviour of copper-nickel in seawater comes from the surface film, and
nickel is the element that promotes it. Moving from 90/10 to 70/30
therefore improves film formation and film stability, and at the same time
it improves the resistance of the alloy to the conditions in which the film
fails to form or fails to repair itself: de-aerated water, stagnant
water, and sulphide-polluted or anaerobic seawater. The 29.0–33.0 %
nickel window of C71500 against the 9.0–11.0 % of C70600 is the
mechanical reason behind the usual selection rule that 70/30 is specified
for high-velocity or long-design-life seawater duty and 90/10 for general
service. The trade is real and should be stated: the 70/30 grade carries a
higher strength level, in the O60 condition 52 ksi (360 MPa) tensile against
38 ksi (260 MPa) for 90/10, so a designer moving up the nickel range also
gets a different allowable working stress basis and a different set of
forming and welding parameters to qualify.

2. The welding grade is a different material with a different
set of limits, and it is the correct answer more often than it is used.
C71520 is the 70/30 grade with lead reduced to 0.02 % max, zinc to 0.50 %
max, manganese to 0.50 % max, carbon limited to 0.05 % max, and a specified
copper minimum of 65.0 % instead of the remainder calculation of C71500.
Lead and zinc are the elements associated with hot cracking in copper
alloys, and the same pattern appears at the 90/10 end of the family, where
C70620 carries lead at 0.02 % max and zinc at 0.50 % max against 0.05 % and
1.0 % for C70600, together with explicit sulfur and phosphorus limits of
0.02 % max that SB-466 Table 1 leaves as “…” for C70600 and
C71500. A pipe that is bought in the C71500 condition and then
welded into a larger assembly is being welded with a lead and zinc content
that the welding-grade grade was created to reduce. Where the pipe is
subsequently welded, C71520 is the grade to specify.

3. Hard-drawn 70/30 has the highest strength in the specification
and the least tolerance for field work. In the H80 temper Table 2
requires 70 ksi (485 MPa) tensile, 45 ksi (310 MPa) yield and a Rockwell
30 T of 70 min for C71500 and C71520, against 52 ksi (360 MPa) and 51 max
in the O60 soft anneal condition. That strength is only available in the
drawn condition, and 10.1.1.2 excludes the drawn tempers other than O60 and
HE80 from the 30 % expansion test requirement of 10.1.1. The practical
consequence is that a hard-drawn 70/30 line has to be fully formed before
delivery; it cannot be bent, re-cut or expanded on site. Note also that
9.3 restricts the H80 requirements to defined size and wall-thickness
ranges and requires the requirements for other sizes to be established by
agreement between the manufacturer and the purchaser, so a hard-drawn
enquiry has to be settled on those points at the order stage. A further
practical point for any copper-nickel grade: the surface condition of the
pipe is part of its corrosion performance, which is why packing protects
the machined surface during handling and transit.

Frequently Asked Questions

When should 70/30 be specified instead of 90/10 copper-nickel?

70/30 (C71500) is specified when the service is more aggressive than the
film alone can handle: high flow velocity, elevated temperature,
sulphide-bearing or anaerobic seawater, or a design life longer than the
lower-nickel grade can deliver. 90/10 (C70600) is the general-purpose
seawater grade. Both are covered by ASME SB-466.

What is the difference between C71500 and C71520?

C71520 is the welding-grade variant of 70/30. It carries a specified
65.0 % minimum copper instead of the remainder calculation, lead at 0.02 %
max instead of 0.05 %, zinc at 0.50 % max instead of 1.0 %, manganese at
0.50 % max instead of 1.0 %, and a carbon limit of 0.05 % max. The nickel
range is the same at 29.0–33.0 %.

Is the H55 light-drawn temper available in 70/30?

No. In SB-466 Table 2 the H55 row covers C70400, C70600 with C70620, and
C72200; C71500 and C71520 appear in the O60 and H80 rows only. If a
light-drawn condition is needed for this grade, that has to be established
by agreement rather than taken from the table.

What strength does 70/30 pipe have in the annealed condition?

In the O60 soft anneal temper, SB-466 Table 2 requires a minimum tensile
strength of 52 ksi (360 MPa), a minimum yield strength of 18 ksi (125 MPa)
and a Rockwell 30 T hardness of 51 max, with a fully recrystallized grain
structure required by Table 2 note C.

What is the test pressure for copper-nickel pipe?

SB-466 11.2.2 requires each tube to stand an internal hydrostatic
pressure sufficient to produce a fibre stress of 7000 psi [48 MPa],
calculated as P = 2St/D. Section 11.2.2.1 states that the tube need not be
subjected to a pressure gauge reading over 1000 psi [7 MPa] unless
specifically stipulated in the contract or purchase order.

How is the pipe certified?

SB-466 15.1 makes the test report and certification requirements of
Specification B251/B251M mandatory, so a full mill test report is issued
with the material, and EN 10204 3.1 or 3.2 certification can be provided
against it.

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