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Nibron Special® Guide for Material Specifiers and Component Designers

Columbia Metals | Nibron Special® Design Guide 2

Contents

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Summary highlights. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Chemical properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Mechanical properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Physical properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Manufacturing routes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Dimensional tolerances . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Non-destructive testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Microstructure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Corrosion resistance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Galvanic compatibility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Biofouling resistance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Design considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Machining guidelines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Welding guidelines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Workability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Lubricant compatibility and anti-galling behaviour. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Literature and further reading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Appendix . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Contact us . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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INTRODUCTION

Nibron Special® is a precipitation hardened copper-nickel-

aluminium alloy suitable for a wide range of applications including

marine and subsea use. It is one of the highest strength copper

alloys available.

Columbia Metals has been selling Nibron Special® for over 30

years and has built up a wealth of experience with this versatile and

highly capable material. This design guide is written to assist

component designers and material specifiers to select Nibron with

confidence as their material of choice for demanding applications

and environments.

SUMMARY HIGHLIGHTS

Extra high strength nickel bronze

High wear resistance

Anti-galling

Outstanding resistance to corrosion and erosion

Good pitting resistance

Resistant to stress corrosion cracking

Resistant to hydrogen embrittlement

Excellent properties at sub-zero and cryogenic

temperatures

Exceptionally low magnetic permeability

Spark resistant

Weldable and brazeable

Good machinability

Inherent resistance to biofouling


Available forms and sizes

Round Bar 1/2” – 9” dia

Hexagon Up to 41mm A/F

Forgings also available

4444 4

CHEMICAL PROPERTIES

The Nibron chemistry approximates to both the German DIN 2.1504

and French NFL14-702 specifications, whilst including a range of

additional restrictions designed to both improve the mechanical

properties and improve the batch to batch consistency of material

supplied from different sources.

The nominal Nibron composition is 14.5% nickel, 3% aluminium,

1.5% iron, 0.3% manganese, remainder copper.


Specifications

Nibron Special® is closely related to

the German Werkstoff number DIN

2.1504, originally from 1956, but

updated to take account of modern

developments.

Nibron is compliant with the

requirements of API6A and NACE

MR 01-75 but does not currently

have a UNS number.

For further information see the

section below on Design

Considerations.

% Nibron DIN 2.1504

Al 2.00 - 4.00 2.0 - 3.0

Fe 0.50 - 2.50 1.5 max

Ni 13.00 - 16.00 13.0 - 16.0

Mn 0.10 - 0.50 1.0 max

Zn 0.30 max 0.3 max

Cr 0.30 max -

Si 0.25 max 0.1 max

Sn 0.02 max -

Pb 0.05 max -

Mg 0.10 max -

Cu Remainder Remainder

Impurities

(excl. Zn) 0.30 max 0.5 max

Impurities

(incl. Zn) 0.50 max -

5555 5

MECHANICAL PROPERTIES

Nibron Special®

Nibron Special® is supplied with the following guaranteed

mechanical properties at room temperature.

DIN 2.1504

The mechanical properties of DIN 2.1504 are shown below, for

reference only.


Other properties

From 2016, Nibron Special® is

available with a guaranteed IZOD

impact strength of 14J minimum.

Reduction of area values are not

guaranteed but are typically around

25% (1-2” diameter range).

≤65mm dia >65mm dia

0.2% yield strength 630 MPa 555 MPa

Tensile strength 850 MPa 770 MPa

Elongation in 5.65√So 12% 12%

Reduction of area For info For info

Hardness 240 HB 229 HB

Hot extruded

Hot rolled, forged/

machined

10 - 25mm 15 - 50mm 50 - 80mm

0.2% yield strength 690 MPa 640 MPa 590 MPa

Tensile strength 830 MPa 780 MPa 780 MPa

Elongation in 5.65√So 10% 10% 10%

Reduction of area - - -

Hardness 240 HB 230 HB 225 HB

6666 6

Elevated Temperature Properties

Like all copper alloys, the mechanical properties of Nibron fall away

at high temperature. Nibron can be safely used up to 300°C but due

to the reduction in ductility with temperature Columbia Metals

recommends the maximum continuous operating temperature of

Nibron be limited to 250°C. At 200°C, typical elongation values of 8-

10% have been recorded.

Cryogenic Properties

Because the microstructure of Nibron is 100% face centred cubic,

the material is largely impervious to cryogenic conditions. Unlike

carbon and low alloy steels, the impact behaviour of copper alloys

does not display ductile-brittle transition at temperatures above

cryogenic (-196°C) and indeed the impact performance of Nibron

improves as the temperature decreases.


Charpy impact toughness

The graph shows Charpy impact

toughness v temperature for 1”

diameter Nibron Special®. This was

based on the use of full size 10x10

Charpy test pieces taken

longitudinally from the 1/4T position,

tested at four temperatures ranging

from +23 to -196oC.

The source of this data is MIS test

certificate MAN 88741. For a copy of

the report, please contact:

[email protected]

mailto:[email protected]

7777 7

TYPICAL PHYSICAL PROPERTIES


* Fatigue Limit

There is no lower fatigue limit due to

Nibron Special®’s face centred cubic

microstructure. The figure shown

assumes a frequency of 0.5Hz and

an allowable fatigue life of 4 million

cycles.

Melting Range 1080 - 1100oC

Material Density 8.5g/cm3

Coefficient of Thermal Expansion (0-400oC) 16.4 x 10-6

Electrical Conductivity 10 - 12% IACS

Resistivity 0.17µΩm

Thermal Conductivity (20oC) 44 - 46W/Mk

Thermal Conductivity (400K) 54W/Mk

Specific Heat Capacity 435J/kgoC

Magnetic Permeability <1.001

Electrode Potential in Seawater -0.18V v SCE

Coefficient of Friction v Mild Steel 0.23

Machinability Rating (v Free Machining Brass) 30%

Hot Formability Fair

Hot Working Range 700 - 900oC

Cold Formability Fair

Young’s Modulus 141KPa

Torsional Modulus 53KPa

Poisson’s Ratio 0.33

0.1% Proof Stress in Torsion 360MPa

Ultimate Shear Stress in Torsion 670MPa

Maximum Angle of Twist in Torsion 530o

Maximum Shear Stress 60% of UTS

Brinell Hardness Range 240 - 270

Wohler Fatigue Strength* 270MPa

Fatigue Strength 1x105 cycles 400MPa



8888 8

MANUFACTURING ROUTES

Nibron Special® develops its strength through the formation of

finely dispersed nickel aluminide precipitates within a copper-nickel

matrix, with small additions of iron and manganese to improve the

mechanical properties and corrosion resistance.

Nibron is manufactured by electric arc melting in air followed by

semi-continuous or gravity casting. Billets are reheated to a

temperature in the hot working range 980 - 1050°C before being

forged, rolled or extruded. For all bars >2” diameter there is

normally sufficient residual heat in the bar to precipitate harden the

material as it cools. For smaller bars, dependent on the hot working

method, it may be necessary to add a precipitation hardening heat

treatment to allow the strength to fully develop.

A minimum 4:1 hot working reduction can be guaranteed for all

sizes <5” diameter and is possible by agreement for larger sizes.


Ageing

The graph shows the effect of

temperature on isothermal ageing of

1.1/2” diameter Nibron Special®

bars. Hardness tests were performed

after five separate heat treatments

(including baseline annealing) over a

four hour period using a

HBW10/3000 standard load.

The source of this data is MIS test

certificate MAN 88745. For a copy of

the report, please contact:

[email protected]


9999 9

DIMENSIONAL TOLERANCES AND SURFACE

FINISH

Nibron Special® is supplied with dimensional tolerances in

accordance with BS2874:1986 up to 80mm diameter and with a

diameter tolerance of +/- 1% of the diameter for sizes >80mm. All

material is supplied with a smooth surface that is either ground or

proof machined. No weld repairs are present on Nibron.

Bars have a straightness tolerance of a maximum 3mm deviation

from straight in any 1m length and come in 3m nominal lengths with

a maximum length of 3.66m.

MICROSTRUCTURE

The manufacturing process is designed to balance the heat input

into the material against the mechanical work done to produce a

microstructure that has a uniform and fine grain size (aiming for

ASTM grade 5 or finer, 6-7 being typical). This gives the correct

microstructure to allow for precipitation hardening of the material

with a fine (less than 1µm) particle size that does not embrittle grain

boundaries and reduce toughness. The precipitates that form have

been identified as Ni3Al (γ’) by transmission electron microscopy

(see appendix C). This is the same precipitate phase that gives

strength to the nickel-based superalloys.


Non-Destructive Testing

All Nibron Special® above 1”

diameter is subject to ultrasonic

testing and must meet the

acceptance criteria of API 6A PSL3.

Other ultrasonic testing standards

may be applied by agreement.

Should you have alternate NDT

requirements, please contact

[email protected]

Under the microscope

A typical Nibron Special®

microstructure (right). The

precipitates are invisible to optical

microscopy, giving Nibron the simple

appearance of a single phase

cupronickel alloy.


10101010 10

CORROSION RESISTANCE

Seawater exposure

Nibron Special® is an excellent seawater material. Small additions

of iron to cupronickels are known to improve the erosion corrosion

resistance in seawater and raise the maximum permitted persistent

flow rate for long term exposure.

The graph below compares the corrosion rate of Nibron in seawater

over time with other copper nickel materials such as Copper Nickel

90/10 and 70/30 (DefStan 02-879 annexe B) and DefStan 02-835.

This work was undertaken in the Physical Sciences department of

University College London and demonstrated Nibron to have the

lowest long term corrosion rate of the candidate materials, settling

at 0.091 mm/yr after one month of exposure.

Cupronickel alloys are resistant to seawater corrosion following the

formation of a passive copper oxide layer on the surface of the

material. Initially there is a high corrosion current which quickly

reduces to a very low level as the oxide layer is formed.

The experimental observations were then compared against the

results obtained using electrochemical techniques in which the

materials were made the working electrode in a three-electrode cell

using the same electrolyte as in the exposure tests. Polarization

sweeps at 10mV/s with one minute of holding time at the initial

potential were performed and the results measured after 10 and 30

minutes. The resulting corrosion rates, shown graphically overleaf,

were calculated by modelling software and were found to be in

close agreement with the physical exposure tests.


Corrosion rate

The graph shows the rate of

corrosion in 3.5% NaCl at 20oC. The

experiment was carried out by the

C20 Advanced Chemical Project

“Corrosion of High Strength Copper-

Nickel Alloys in Artificial Seawater”,

University College London

Department of Physical Sciences,

Wai Nga Yau, supervised by Prof. D.

Williams.

11111111 11

Stress Corrosion and Environmental Testing

Nibron Special® has been subjected to a wide range of

environmental tests and has consistently met the requirements of

the standards required. The following test reports and results are

available to provide confidence when specifying Nibron in

demanding environments.

Static Loading Tensile Test in Sour Conditions

Cortest Laboratories report T 63002-S1

NACE MR 01-77 solution A, acidified sulphide medium, initial pH

2.58, final pH 2.67. No evidence of sulphide corrosion cracking after

720 hours at 24°C with the specimen stressed to 100% of the

certified 0.2% proof stress (in this instance, 718MPa).

Stress Corrosion Test for Copper Base Alloys

Special Testing Works report C1282 (test 121592)

BS2874:1986 Appendix F mercurious nitrate test. No visible cracks

after 30 minutes’ immersion in standard acidified mercurious nitrate

solution.

Slow Strain Rate Test for Hydrogen Embrittlement in

Accordance with ASTM G129


Polarised to -1V vs SCE in 3.5% NaCl. No embrittlement and no

loss (relative to an air test) of proof stress, elongation or reduction

of area when pulled at a constant rate of 4x10-6s-1.


Linear polarization

Corrosion rates after 30 minutes’

exposure using electrochemical

techniques.

Test reports and results

Contact Columbia Metals to obtain

any of these test reports:

[email protected]


12121212 12

Slow Strain Rate Test for Stress Corrosion Cracking in

Synthetic Seawater

Cortest Laboratories reports T 64603-S, T 64703-S2, T 71203-S1

and T 71203-S2

No loss of mechanical properties (relative to an air test) at 20°C and

50°C when pulled at a constant rate of 4x10-6s-1. Time to failure:

11.9hrs in air; 13.6hrs in SSW@20°C; 13.4hrs in SSW@50°C.


10% Ammonium Chloride

Cortest Laboratories reports T 63002-S2 and T 64703-S

Nibron is not susceptible to cracking in ammonium chloride at 20°C

and 80°C. There was no deterioration of mechanical properties

(relative to an air test) at either temperature when pulled at a

constant rate of 4x10-6s-1.

C-Ring Stress Corrosion Tests

Columbia Metals report “Resistance to Environmentally Assist-

ed Cracking” and MTS Daventry report D063044

Following extended duration testing, no cracking was observed in

Nibron after 12 months’ exposure to saturated sodium chloride at

45°C or 30 days’ exposure to 3% ammonium chloride at 20°C with

the specimen stressed to 120% of the proof stress.


13131313 13

GALVANIC COMPATIBILITY

The electrode potential of Nibron in seawater is -0.18V vs a

Standard Copper Electrode. This makes the material compatible to

other copper alloys, aluminium bronzes etc. However the material

will become anodic compared to stainless steels (potential -0.350 -

0.35V) if Nibron is in direct contact. This means that the Nibron

would galvanically corrode.

It is recommended whenever possible to insulate all coppers and

brasses from stainless steel components. If this is not possible, to

minimise the current density and therefore the rate of attack on the

Nibron the ratio of the free surface area of Nibron to the free sur-

face area of stainless steel should be as large as possible.

BIOFOULING RESISTANCE

Like all copper alloys, Nibron Special® resists biofouling. Copper

nickel alloys, provided they are not part of a cathodic protection

system, resist the accumulation of biomatter in subsea

environments. Hard matter such as barnacles, grasses and shellfish

do not adhere to a copper nickel surface. Over long periods of time

some organic slime can form that can be easily sloshed away. The

anti-biofouling effect is reduced if the copper is joined with less

noble metal or cathodic protection as these slow or prevent the

release of copper ions which are the cause of the biofouling

resistance.


14141414 14

DESIGN CONSIDERATIONS

Nibron Special® and API6A

A common question asked about Nibron is its suitability for use

under API 6A. This is a very large specification (>400 pages), only

parts of which will be applicable in any given situation or for any

given part, making it difficult to give a comprehensive answer. The

key clauses to consider would appear to be:

Clause 1 – Scope

Clause 4 – Design and performance, general requirements

Clause 5 – Materials, general requirements

Clause 10 – Equipment specific requirements

Clause 1 – Does API6A apply? This is the first question and the

answer depends upon the specific end use for the component being

manufactured. API6A applies if the material is to be used in a well-

head or Christmas tree, with a specific end use in a connector or

fitting, a casing or tubing hangar, a valve or choke or a specified

application from the “other equipment” list which includes actuators,

hubs, gaskets and bushings.

On the assumption that API6A applies, clause 4 needs to be

considered in terms of the service conditions applicable to the

individual design. The designer needs to consider the service

conditions to select the correct material class. They need to be

aware that for the higher temperature service (class Y, 345°C max),

Nibron is unlikely to be acceptable and it should be restricted to

class X (180°C) on account of the loss of elongation capability with

increased temperature (>200°C). Nibron is suitable for all lower

temperature classes (K thru V).

It should also be noted that API6A does not directly address the use

of copper-based alloys. The table 3 material requirements and

clause 4.2.3.1 provide a material hierarchy which reads [Carbon

Steel – Stainless Steel – CRA], however, a CRA is defined as an

alloy of titanium, nickel, cobalt, chromium or molybdenum. Nibron

can only, therefore, be considered as a “non-standard material”.

Design in non-standard materials which do not meet the ductility

requirements of Table 5 for 75k materials (and Nibron fits in here) is

covered by clause 4.3.3.6 which utilizes the ASME viii Div2 App4

methodology for calculating acceptable stresses – this uses the ma-

terial yield and ultimate tensile strength but imposes no

restrictions based around elongation.


Clauses

These clauses refer to the 19th

Edition, Addendum 4, Errata 5

(current as of May 2009)

15151515 15

The key clause is almost certainly clause 5, covering material

requirements. The actual requirements demanded by API6A are

totally dependent on the identified end use. Unless Nibron is being

specified for an end use identified in clause 5.4 or 5.5, 5.10, 5.11,

5.12, 5.13 or 5.14 (assuming it is not being used for mandrel tubing

or casing hangers, under clause 5.3, which seems very unlikely, or

for an application listed in section 10 (see below)) then the only

material requirements in API6A which apply are those of clauses

5.1-5.2 (including sub clauses) for specification, 5.6 for testing, 5.7,

5.8 and 5.9 for qualification.

Nibron manufacture is compliant with the requirements of 5.1,

5.2.1 and 5.2.2.

5.2.3 is for non-metallics and is therefore not relevant.

5.3 (mandrel tubing and casing hangers) is an unlikely end use,

however the requirements of this clause are invoked by other end

applications (see below) so must be considered. Section 5.3 does

not require a minimum elongation value and standard Nibron is

compliant for PSL3 application with additional impact testing.

Section 5.4 applies to “bodies, bonnets, end and outlet

connections” and for a non-standard material imposes additional

requirements of a minimum elongation of 15% and a minimum

reduction of area of 20%. It also requires, in most instances, that

impact test results be provided.

If section 5.4 is active (i.e. Nibron is being used for one of these

applications) then care must be taken. Nibron CANNOT be

guaranteed with a 15% minimum elongation and a 20% RoA.

Individual batches may meet these requirements, but analysis of

the available data means Columbia Metals is unable to commit to

supplying all Nibron in accordance with this clause.

Section 5.5 (for ring gaskets) does not require a minimum

elongation and is achievable.

Sections 5.7-5.9 impose no additional requirements on Nibron.

For Section 5.10 (bullplugs and valve removal plugs), Section

5.4 requirements apply which is potentially problematic.

5.11 (back pressure valves) is subject to 5.3 requirements but

impact test results are required in addition.

Section 5.12 (pressure boundary penetrations) is not applicable.

5.13 (wear bushings) requires a hardness range only, which is

compliant with standard Nibron.


Specific requirements

Individual batches often exceed the

minimum specification requirements.

Please check with us if your

requirement demands more than the

typical properties of Nibron Special®.

16161616 16

For Section 5.14 (hub end connectors), Section 5.4 comments

apply.

Section 10 (Equipment specific requirements) lists a wide range of

end uses, some of which refer the designer back to Clause 5 for

material requirements. Only those applications that specifically

invoke section 5.4 are a problem.

To summarise:

Nibron is considered as a “non-standard” material under API6A.

It can be used without restriction for many applications but can

only be used for some applications if the elongation exceeds

15% and the RoA exceeds 20%.

A brief examination of Columbia Metals’ Nibron stocks shows

approximately only 30% compliance with the elongation

requirement and 100% compliance with the RoA where this

figure is provided. Not all Nibron, however, is certified with an

RoA.

Nibron Special® and NACE qualification

Although not specifically mentioned in NACE MR01-75 or

ISO15156, Nibron Special® can be considered under this

specification as a copper alloy.

There are no specific limits on hardness, chloride, sulphide or pH

under section A12.1 dealing with copper alloys as these alloys are

not considered susceptible to sulphide stress cracking. For a

particular down-hole environment the material may be susceptible

to corrosion.

To clarify any testing that may be required to ascertain suitability in

any high concentration environment, please contact Columbia

Metals at [email protected].


RoHS Compliance

All Nibron Special® from Columbia

Metals is supplied with a certificate

of conformity and can state

compliance with RoHS legislation,

freedom from mercury and freedom

from radiation.


17171717 17

MACHINING GUIDELINES

Nibron Special® is readily machinable, with a machinability rating

30% of free machining brass (CZ121) or 10% higher than carbon

steel. Carbide-tipped tools should be used along with water based

lubrication. Dimensional stability is excellent and no stress relief is

normally required. Where dimensional tolerances are critical it may

be desirable to heat treat for 1-2 hours in an air circulating furnace

at 300°C followed by an air cool.


Turning - Roughing

Speed 120 - 180m/min

Feed rate 0.40 - 0.75mm/rev

Depth of cut 3mm

Turning - Finishing

Speed 150 - 300m/min


Depth of cut 0.5mm

Tapping

Speed 20 - 45m/min

Milling

Speed 45 - 60m/min

Feed rate 0.15 - 0.13mm/tooth

Depth of cut 0.5 - 6.0mm

Drilling

Speed 25 - 75m/min


Reaming

Speed 22 - 45m/min


18181818 18

WELDING GUIDELINES

Welding trials have demonstrated that Nibron Special® is weldable

both to itself and to other materials such as type 316 stainless steel.

The welds produced exhibit high metallurgical integrity, good

mechanical strength and excellent ductility. The TIG welding

process was used for the trials with argon and argon/helium mixture

as the shielding gases.

As Nibron filler metal is not available, a variety of fillers were

trialled, the best results being obtained with nickel aluminium

bronze (though it should be noted that, in this case, the strength of

the weld region will be lower than in the parent metals).

WORKABILITY

Nibron components are normally machined from solid bar and both

the hot and cold workability of the alloy is limited. Cold working is

not recommended and care should be taken with hot working – hot

forming, heading or forging is possible but good control is required

over the temperature and time. Forging should be performed in the

range 980 -1050°C and the temperature should not be allowed to

fall below 850°C at any time during hot working. The cooling rate

after forging should not exceed 200°C per minute (slow air cooling

and dependent on the ruling section) to allow the material to

precipitation harden. Faster cooling rates will necessitate an

additional ageing heat treatment (see section on manufacturing

routes above).


Welding reports

A full welding report (Bodycote

Materials Testing report D804028)

and a weld hardness survey

(Bodycote Materials Testing report

D805603) are available on request

from Columbia Metals.

19191919 19

LUBRICANT COMPATIBILITY AND ANTI-GALLING

PROPERTIES

Nibron Special®, while being used for fasteners or actuators, has

consistently demonstrated a high resistance to galling or sticking.

This applies both when the material is being run against itself and

when it is used against other materials such as nickel aluminium

bronze and duplex stainless steels. Being a high strength copper

alloy which resists surface oxidation, Nibron is a logical

replacement for beryllium copper where there are health and safety

concerns over the effects of beryllium dust from machining

operations. Nibron can be used without lubrication in many cases

and is hard enough to resist wearing.

Nibron does not need lubrication or grease in threaded assemblies.

Slow strain rate tests have, however, indicated that the application

of molybdenum sulphide greases have no effect on the stress

corrosion behaviour of Nibron even though they have been known

to affect other copper nickel materials. Independent tests have

demonstrated the compatibility of Nibron with the offshore fluids

Oceanic HW443 and Oceanic HW740R (both made by MacDermid

Offshore Solutions).

Mercury-containing compounds can cause cracking in copper

alloys. Some polymers contain a mercury catalyst and, although it is

very unlikely to be exposed in most working environments, mercury

and its salts should be avoided.


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APPLICATIONS


An enviable track record

Nibron Special® has an enviable

track record of success stretching

back over 30 years. Nibron is a

highly versatile alloy and has been

specified and used in a wide range

of applications.

Application area Primary reasons for choice

Aircraft landing and steering gear bearing bushes, control surface

Strength, corrosion resistance, anti-galling, seizure and spark

Marine shafts and bearing bushes Strength, corrosion and wear

Plastic injection mould tooling Hot strength, thermal

Offshore bolting Strength, corrosion resistance, anti-galling, stress cracking and

hydrogen embrittlement

Subsea fasteners and couplings Galling resistance, long term corrosion resistance, strength,

Valve and pump trim Galling resistance, corrosion resistance, strength, biofouling

Non-magnetic components / Low magnetic permeability,

Spark resistant safety tools Strength, spark resistance

Gears and pinions Strength, galling resistance,

High performance engine shafts, gears, bearing bushes and valve

Hot strength, thermal conductivity, wear resistance and

Cryogenic fasteners and equipment No ductile-brittle transition, good

Electrical engineering components Non-magnetic properties, strength, corrosion resistance,

21212121 21

LITERATURE AND FURTHER READING

Nibron is referenced in a number of papers and publications.

Further information can be found in:

“Corrosion behaviour of copper alloys in natural sea water and pol-luted sea water”, H. Le Guyader, A. M. Grolleau, V. Debout, J. L. Heuzé and J. P. Pautasso “The development of very high strength copper alloys with re-

sistance to hydrogen embrittlement and stress corrosion cracking”,

C. D. S. Tuck

APPENDIX

This design guide contains references to several testing reports,

each of which are listed below for the reader’s convenience.

All reports are available on request from Columbia Metals.

Charpy Impact Toughness

MIS Mechanical test certificate MAN 88741

Full size 10x10 Charpy test pieces taken longitudinally from the

1/4T position, tested at four temperatures ranging from +23 to

-196oC.

Effect of Temperature on Isothermal Ageing

MIS Mechanical test certificate MAN 88745

Hardness test performed on 1.1/2” diameter Nibron Special® bars

after five separate heat treatments (including baseline annealing)

over a four hour period using a HBW10/3000 standard load.

Static Loading Tensile Test in Sour Conditions

Cortest Laboratories report T 63002-S1

NACE MR 01-77 solution A, acidified sulphide medium, initial pH

2.58, final pH 2.67. No evidence of sulphide corrosion cracking after

720 hours at 24°C with the specimen stressed to 100% of the

certified 0.2% proof stress (in this instance, 718MPa).

Stress Corrosion Test for Copper Base Alloys


BS2874:1986 Appendix F mercurious nitrate test. No visible cracks

after 30 minutes’ immersion in standard acidified mercurious nitrate

solution.


Available on demand

For a copy of any of these reports, or

to discuss the test results in more

detail, please contact Columbia

Metals at:

[email protected]


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Slow Strain Rate Test for Hydrogen Embrittlement in

Accordance with ASTM G129


Polarised to -1V vs SCE in 3.5% NaCl. No embrittlement and no

loss (relative to an air test) of proof stress, elongation or reduction

of area when pulled at a constant rate of 4x10-6s-1.


Synthetic Seawater

Cortest Laboratories reports T 64603-S, T 64703-S2, T 71203-S1

and T 71203-S2

No loss of mechanical properties (relative to an air test) at 20°C and

50°C when pulled at a constant rate of 4x10-6s-1. Time to failure:

11.9hrs in air; 13.6hrs in SSW@20°C; 13.4hrs in SSW@50°C.


10% Ammonium Chloride

Cortest Laboratories reports T 63002-S2 and T 64703-S

Nibron is not susceptible to cracking in ammonium chloride at 20°C

and 80°C. There was no deterioration of mechanical properties

(relative to an air test) at either temperature when pulled at a

constant rate of 4x10-6s-1.

C-Ring Stress Corrosion Tests

Columbia Metals report “Resistance to Environmentally

Assisted Cracking” and MTS Daventry report D063044

Following extended duration testing, no cracking was observed in

Nibron after 12 months’ exposure to saturated sodium chloride at

45°C or 30 days’ exposure to 3% ammonium chloride at 20°C with

the specimen stressed to 120% of the proof stress.

Welding Report

Bodycote Materials Testing report D804028

Metallurgical tests on 12 variously welded high strength copper

alloy to high strength copper alloy and high strength copper alloy to

stainless steel samples.

Weld Hardness Survey

Bodycote Materials Testing report D805603

REV2/12/17


Contact us

Columbia Metals operates from a

nationwide network of branches. Get

in touch for sales enquiries or for

technical support:

_________

North, Scotland and International

[email protected]

[email protected]

tel: 01422 343026

__________

Midlands & Wales

[email protected] tel: 01234 608888

__________

London & South

[email protected] tel: 020 7732 1022

__________

Technical Support

[email protected] tel: 01234 608888






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