CERTIFICATIONS
CAL Wrought CNC versus NAB and cast CNC
Overview of benefits of CAL wrought CNC-1 and CNC-2 compared with Nickel Aluminium Bronze (NAB) and cast CNC
Microstructure
Forging |
Casting & Forging |
Casting |
|---|---|---|
|
Fine, homogeneous, equi-axed grain structure* free from phases that can be preferentially attacked in sea water. Hot forging densifies the structure, eliminating micro cavities.
*ASTM E112 grain size 5-6 typically observed |
Complex multi-phase microstructure with risk of semi-continuous anodic phases. | Grain structure free from phases that can be preferentially attacked in sea water. Coarse cast structure with coring (alloying element segregation across grains), with inter-granular and inter-dendritic micro cavities and non uniform grain size between sections of differing thickness. |
Volumetric Inspection
Forging |
Casting & Forging |
Casting |
|---|---|---|
| Ability to be easily penetrated using conventional ultrasonic pulse-echo techniques, permitting detailed volumetric inspection to (for example) Def-stan 02-729 Part 5, rather than expensive radiography. | Wrought version (Def Stan 02-833) can be ultrasonically inspected whereas cast version (Def Stan 02-747) in practice, needs to be radiographed which is more expensive. | Coarse cast grain structure scatters and absorbs ultrasound resulting in very high attenuation. Can only be inspected volumetrically using radiography, which is relatively expensive compared with ultrasonic inspection and does not detect metal oxide films. |
In-Service Monitoring
Forging |
Casting & Forging |
Casting |
|---|---|---|
| In-service wall thickness measurements using ultrasonic thickness gauge can be carried out to check corrosion rate in-situ, without the need to remove to check corrosion damage (does not suffer SPC). | Wrought version (Def Stan 02-833) can be checked using ultrasonic thickness gauge whereas cast version (Def Stan 02-747) cannot. Selective phase corrosion, in particular in hard to reach crevices, limits it's use. | Corrosion rate cannot be monitored in-situ using ultrasonic thickness gauge techniques. Component needs physically removing to inspect corrosion damage. |
Seawater Corrosion Resistance
Forging |
Casting & Forging |
Casting |
|---|---|---|
|
No selective phase corrosion (SPC)
High general corrosion resistance in seawater |
Selective phase corrosion 0.5-1.0mm / 0.002-0.04"
General corrosion resistance in seawater ≈ 0.025-0.05mm/year (0.001-0.002"/year) |
No selective phase corrosion (SPC)
High general corrosion resistance in seawater |
Destructive Testing
Forging |
Casting & Forging |
Casting |
|---|---|---|
| Homogenous refined wrought structure induces a high combination of mechanical properties IN THE ACTUAL PRODUCT, far higher than the Def-Stan 02-886 (see mechanical property section) | Wrought version (Def Stan 02-833) has integral test pieces however cast version (Def Stan 02-747) does not and actual test results obtained from castings often fall short of specification minimum values which are for separately cast test bars. | Coarse cast grain structure differing from thin to thick sections of castings may result in actual mechanical properties in the product significantly less than the specification minimum requirements, which are determined on a separately cast test bar. |
Impact Strength
Forging |
Casting & Forging |
Casting |
|---|---|---|
|
Very high Impact Strength ≈ 100J higher than NAB and over double that g cast CNC:
CAL CNC-1 Guaranteed ≥ 110J/ 81 ft lbf (typical 120-150J / 89-111 ft lbf) CAL CNC-2 Guaranteed ≥ 90J / 66 ft lbf (typical 105-125J / 77-92 ft lbf) Determined on samples taken from the actual product - highly representative. |
Low impact strength:
Castings Def Stan 02-747 Not specified, typically 17-25J / 13-18 ft lbf on separately cast test bar Wrought Def Stan 02-833 Specified as 23-27J / 17-20 ft lbf minimum (size dependant) Typically ≈ 30-40J/ 22-30 ft lbf - integral test sample for wrought grades |
Moderate impact strength:
No specified requirement for cast material Typically ≈ 45-60J / 33-44 ft lbf on a separately cast test bar NOT from cast product. |
0.2% Proof Stress
Forging |
Casting & Forging |
Casting |
|---|---|---|
|
High 0.2% proof stress ≈ 2 x that of NAB and cast CNC:
CAL CNC-1 Guaranteed ≥ 350-390MPa / 51-57Ksi (depending on section size) Typically 380-480MPa / 55-70 Ksi CAL CNC-2 Guaranteed ≥ 600 MPa / 87 Ksi Typically 650-750MPa / 94-109 Ksi Determined on samples taken from the actual product - highly representative |
Low 0.2% proof stress:
Castings Def Stan 02-747 specified as > 250MPa / 36 Ksi on separately cast test bar (castings themselves would typically be lower). Wrought Def Stan 02-833 specified as 245-325MPa / 36-47 Ksi (size dependant) Typically 280-380MPa / 41-55 Ksi - integral test sample for wrought grades |
Low 0.2% proof stress:
Specified as 300MPa / 44 Ksi minimum but is determined on a separately cast test bar unrepresentative of the actual properties in the castings. Specification guide-line is design on a minimum expected proof stress in the castings of 240MPa / 35Ksi |
Oxide Film Issue
Forging |
Casting & Forging |
Casting |
|---|---|---|
|
Issue of linear oxide films from reactive alloying elements (Cr, Ti, Zr):
Wrought CNC-1 and CNC-2 is free from detrimental linear oxide defects. The small grain size and resulting low attenuation to ultrasound permits detailed volumetric inspection and this, combined with dye penetrant inspection, can confirm material is within the defect acceptance criteria as required by Def Stan 02-729 parts 5 & 4 respectively. |
Issue of linear oxide films from reactive alloying elements (Cr, Ti, Zr):
Non-issue |
Issue of linear oxide films from reactive alloying elements (Cr, Ti, Zr):
Cannot be detected using radiography making surface inspection using eddy current techniques required, which only determines integrity of material at or near surface. |
High Strength Wrought Copper-Nickel-Chrome Alloy CuNi30Cr1MnFeSiZrTi - composition compliant with generic alloy Def Stan 02-886, with enhanced strength and toughness exceeding specification requirements.
In our copper nickel chrome alloy (CuNi30Cr1MnFeSiZrTi), high strength is combined with extremely high toughness and good ductility together with outstanding seawater corrosion resistance.
Background
This outstanding material (Copper-Nickel-Chrome alloy/CNC) was developed by the British MoD to replace nickel aluminium bronze (NAB) in seawater systems on submarines, due to corrosion issues with NAB, in particular selective phase corrosion (SPC). The depth of attack in NAB is typically 1.1mm/year (0.043"/year), but has been observed at 1.4mm/year (0.055"/year). CNC is reported to have the ability to last the lifetime of the platform and observed 10 years service performance showing excellent results with negligible corrosion and fit for a second commission.
CNC does not contain continuous/semi-continuous anodic phases and as such, is immune to SPC and has a very low general corrosion rate.
The resulting specification - Def Stan 02-824 part 1 - is for castings and due to extreme difficulties in producing sound castings - in particular avoiding metal oxide films which form during melting and casting - its cost is generally high and its usage limited. For these reasons, it has not generally replaced NAB in seawater systems in submarines.
During the development of the cast version of the alloy, a number of companies were sponsored to develop a wrought (forged) version, but this was abandoned due to reported lack of forgeability.
Our advanced melting, alloying and casting techniques, combined with a deep metallurgical understanding of hot working materials, have allowed us to develop two forged versions of the alloy, which is very exciting. There is a 'standard' version (CNC-1) and a higher strength version (CNC-2) applicable to bars to around 150mm (6") in section.
If you are using NAB in critical seawater systems where resistance to corrosion and high shock resistance is required, you need to change to this material!
Mechanical Properties
CAL CNC-1 & CNC-2
High Strength Cupper-Nickel-Chrome Alloy
CuNi30Cr1MnFeSiZrTi
Show more ›Table 2 - Guaranteed Minimum Mechanical Properties*
| Product → | Bars - Round, square, flats, hexagon, shapes | Forgings | Cast CNC Def Stan 02-824 part 1 for reference | ||
|---|---|---|---|---|---|
| Material section-size (minor dimension) | |||||
| Property ↓ | Up to and including 150mm (6") | Over 150mm (6") | All sizes | ||
| CNC-1 | CNC-2* | CNC-1 | CNC-1 | ||
| Ultimate Tensile Strength Rm MPa | 580 (84Ksi) |
680 (99Ksi) |
550 (80Ksi) |
550 (80Ksi) |
480 (70Ksi) |
| 0.2% Proof Stress Rp0.2 MPa | 390 (57Ksi) |
600 (87Ksi) |
350 (51Ksi) |
350 (51Ksi) |
300 (44Ksi) 240 (35Ksi) for design |
| % Elongation after Fracture 5.65 √ So | 20 | 14 | 20 | 20 | 18 |
| Izod Impact J | 110 (81ft lbf) |
90 (66ft lbf) |
110 (81ft lbf) |
110 (81ft lbf) |
Typical 45-60 (33-44ft lbf) |
| Hardness Brinell HB 10/3000** | 160-200 | 190-225 | 160-200 | 160-200 | Typical 170-200 |
** For reference only - does not form part of the acceptance criteria unless agreed
The main mechanical property headlines for CAL wrought CNC is the high strength and ductility combined with extremely high impact strength and shock resistance. Izod impact strength is around 3 times or 100J (74 ft lbf) higher than forged NAB to Def Stan 02-833 and around double that reported for cast CuNiCr. This important feature can be guaranteed (see table 2), measured and reported for each batch of material.
Available in two property conditions:
- CAL CNC-1: The standard material applicable to all product forms and sizes
- CAL CNC-2: High strength version applicable to bars (round/flat/square/hexagonal) up to around 150mm (6") in section.
All mechanical test specimens used for acceptance testing are integral to the forgings or bars they represent and as such, the obtained results are entirely representative of the material. The figures in table 2 can therefore be used for design.
It is worth pointing out the cast version of this alloy (Def Stan 02-886) calls for small test bars that are separate to the castings they represent, and actual properties in the castings would routinely be lower. Because of this, Def Stan 02-886 suggests, for design purposes, a 0.2% proof stress of 240MPa (35Ksi) should be used, which is significantly lower than wrought CAL CNC-1 and 40% that of CAL CNC-2.
Tensile Test Standard: BS EN 2002-1
Impact Test Standard: BS 131 Part 1
Hardness Test Standard: BS EN ISO 6506-1
Corrosion Data
Wrought CuNiCr is specifically designed for applications where a combination of high shock resistance (resistance to crack propagation under dynamic loading) combined with high resistance to sea water corrosion is required. In particular, it offers benefits for critical components in equipment used in military submarines and fighting ships, where longevity and functionality are crucial over the life of the platform.
The structure of the alloy is free from vulnerable phases and as such is immune to selective phase corrosion (SPC), unlike Nickel Aluminium Bronze. Corrosion is only slight and general (on the metal surface) with no sub-surface attack, making the material fit for wetted sealing-faces. Being a copper based alloy, the material's resistance to marine bio-fouling is high and similar to conventional copper-nickel alloys, such as 90/10 and 70/30 Cupro Nickel. Surfaces therefore remain 'clean', avoiding accelerated corrosion and reduced functionality associated with marine growth.
The electrochemical potential of wrought CuNiCr is similar and compatible with the other copper alloys used in seawater systems, for example 90/10 and 70/30 CuNi alloys and Nickel Aluminium Bronze and are interchangeable within systems.
Table 3 - Surface Corrosion Data - Seawater
| CAL Elite Marine Alloys | Other commonly used Marine-Alloys (also offered by CAL) | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| Material | Extreme Strength Cupro Nickel | High Strength Copper-Nickel-Manganese-Aluminium Alloy | Wrought Copper-Nickel-Chrome (CNC) Alloy | Wrought Nickel Aluminium Bronze (NAB) | 70/30 Cupro Nickel | 90/10 Cupro Nickel | Naval Brass | Nickel-Copper Alloy | Nickel-Copper-Aluminium-Titanium Alloy | Stainless Steel | Stainless Steel |
| Base composition | CuAl14Al2 | CuNi15Mn4 Al1Fe |
CuNi30Cr1 MnFeSiZrTi |
CuAl9Ni5 Fe4 |
CuNi30Mn1 Fe |
CuNi30Mn1 Fe |
CuZn37Sn1 | NiCu30Fe2 Mn1 |
NiCu30Al3 Fe1MnTi |
FeCr18Ni9 | FeCr18Ni12 Mo2 |
| Specification → Property ↓ |
(DIN 2.1504) |
(Def Stan 02-835) |
(Def Stan 02-886) | Def Stan (NES) 833 / CW307G | Def Stan (NES) 780 / CN107 / C71500 / CW354H | Def Stan (NES) 779 / CN102 / C70600 / CW352H | CZ112 / CW712R / C46400 | NA13 / UNS N04400 | NA18 / UNS N05500 | 304 stainless | 316 stainless |
| General corrosion rate mm/year | 0.02mm / 0.0008" | 0.025mm / 0.001" | 0.02mm / 0.0008" | 0.025-0.05mm / 0.001-0.002" | 0.03mm / 0.001" | 0.03mm / 0.001" | 0.05mm / 0.002" (4 x at 60℃) | 0.03mm / 0.001" | 0.03mm / 0.001" | 0.025mm / 0.001" | 0.025mm / 0.001" |
| Crevice corrosion rate mm/year | <0.02mm / 0.0008" | <0.025mm / 0.001" | <0.02mm / 0.0008" | 0.5-1.0mm / 0.002-0.004" |
0.025-0.13mm / 0.001-0.005" | 0.025-0.13mm / 0.001-0.005" | 0.15mm / 0.006" | 0.5mm / 0.020" | 0.05mm / 0.002" | 0.25mm / 0.010" | >0.13mm / 0.005" |
| Selective Phase Corrosion mm/year | None | None | None | 0.5-1.0mm / 0.002-0.004" |
None | None | Yes 0.15mm / 0.006" | None | None | None | None |
| Impingement resistance limit m/second | 3.7 (12ft/sec.) | 3.7 (12ft/sec.) | 6-8 (20-26ft/sec.) | 4.3 (14ft/sec.) | 4.6 (15ft/sec.) | 3.7 (12ft/sec.) | 3.05 (10ft/sec.) | >9.1 (>30ft/sec.) | >9.1 (>30ft/sec.) | >9.1 (>30ft/sec.) | >9.1 (>30ft/sec.) |
| Corrosion Potential in Seawater Vsce | -0.18 | -0.19 | -0.18 | -0.19 | -0.18 | -0.20 | -0.24 | -0.12 | -0.12 | -0.08 | -0.08 |
| Marine bio-fouling resistance | Highly resistant | Highly resistant | Highly resistant | Partially resistant | Resistant | Highly resistant | Partially resistant | Not resistant | Not resistant | Not resistant | Not resistant |
| Cast Def Stan 02-747 | |
|---|---|
| General corrosion rate | 0.07mm (0.002") / year |
| Crevice corrosion rate | 0.05mm (0.002") / year |
| Selective Phase Corrosion | 1.1mm (0.04") / year typical 1.4mm (0.055") / year observed |
Table 4 - Physical Properties
| Properties | Metric | Imperial |
|---|---|---|
| Melting point | 1,180-1,230°C | 2,156-2,246°F |
| Density | 8,800 kg/m³ | 0.318 lbs/in³ |
| Thermal Conductivity @ 20°C | 23 W/(m.°K) | 13.3 Btu/(Hour.Ft.°F) |
| Electrical Resistivity at 20°C | 0.35 μ.Ω.m | 13.8 μ.Ω.in |
| Electrical Conductivity %IACS at 20°C | 5 | 5 |
| Coefficient of linear expansion (0-250°C) | 18.0 x 10-6/°C | 10.0 x 10-6/°F |
| Specific Heat | 0.411 J/(g.°K) | 0.0982 Btu/(lb.°F) |
| Magnetic Permeability (μr) | 1.01 | |
| 0.2% Proof Stress | 300-320Mpa | |
| Tensile Strength | 480-540Mpa | |
| Elongation, % on gauge length = 5.65√S0 | 18-25 | |
| Reduction of area | 30-50% | |
| Shear Strength | 240-270 N/mm² | 34.8 ksi |
| Brinell Hardness | 170-200 | |
| Young's Modulus, Modulus of Elasticity | 143,000 N/mm² | 20,740 ksi |
| Modulus of Rigidity | 54,000 N/mm² | 7,832 ksi |
| Poisson's Ratio | 0.3 | 0.3 |
| Izod impact value | 110J | |
| Corrosion potential in seawater | -0.18Vsce | |
| General corrosion rate | 0.02mm/year | |
| Crevice corrosion rate | <0.02mm/year | |
| Selective Phase Corrosion rate | 0mm/year | |
| Impingement resistance | 6-8m/s |
Applications
This combination of properties is unique and consequently is unavailable elsewhere in a copper based alloy.
Wrought CNC is specifically designed for applications where a combination of high shock resistance (resistance to crack propagation under dynamic loading) combined with high resistance to sea-water corrosion is required. In particular, it offers benefits for critical components in equipment used in military submarines and fighting ships, where longevity and functionality are crucial over the life of the platform.
Current components being manufactured in nickel aluminium bronze can be replaced by CAL Wrought CNC-1 / CNC-2 generally without the need to change geometry, however this will lead to an increase in component weight of around 15% due to the increase in density. If however full use is made of the following benefits, a decrease in component weight can be realised with obvious benefits including reduced inertia under shock conditions:
- Increased 0.2% proof stress over NAB
- Massively increased resistance to shock of NAB
- Much higher sea-water corrosion resistance. In particular very low crevice corrosion and lack of selective phase corrosion i.e. reduction in in-service corrosion allowance
Like conventional cupro-nickel alloys, CuNiCr can suffer from galling. When excellent anti-galling characteristics are required, extreme-strength cupro-nickel CAL T-1000 CuAl14Al2 is recommended.
Typical applications include sea-water retaining covers, clamps, flanges, valve bodies and internal components, seal-rings, actuators, heat exchangers. The higher strength version CNC-2 is ideal for fasteners.
Inspection and Certification
High Strength Wrought Copper-Nickel-Chrome Alloy
CuNi30Cr1MnFeSiZrTi
Show more...Table 5 - inspection and testing grades and classes
| Product form → |
Bars | Forgings | |
|---|---|---|---|
| Grade / Class1 → |
Grade 11 | Class 11 | Class 21 |
| Chemical Analysis (melt) | Every cast | Every cast | Every cast |
| Mechanical Testing2 | Every cast for each size Integral sample2 |
Each and every forging Integral sample2 |
One forging every cast/size Integral sample2 |
| Ultrasonic Inspection | 100% Def Stan 02-729 part 5 | 100% Def Stan 02-729 part 5 | 100% Def Stan 02-729 part 5 |
| Dye Penetrant Inspection | 100% Def Stan 02-729 part 43 | 100% Def Stan 02-729 part 4 | 100% Def Stan 02-729 part 4 |
| Visual Inspection | 100% | 100% | 100% |
| Eddy Current4 | 100% Def Stan 02-729 Part 34 | 100% Def Stan 02-729 Part 34 | 100% Def Stan 02-729 Part 34 |
All material is subjected to chemical analysis and mechanical testing to ensure compliance with tables 1 and 2.
Different levels of testing and inspection are automatically triggered by ordering according to table 5, derived from the generic material specification Def Stan 02-835 Part 2. Additional testing can be agreed e.g. Dye Penetrant Inspection of Grade 1 rods and bars, or alternative NDE standards.
Certification provided as standard in both wet-signed and electronic form (soft-copy) in accordance with EN 10204 type 3.1.
3.2 Certification can also be provided upon request.
Notes:
1Material is offered to Grade 1 and Classes 1 & 2 only which is the higher level of mechanical testing and NDE compared with Grade 2 and Class 3.
2For all grades and classes, test samples are integral to the item and the property results are therefore fully representative of the certified material.
3Dye penetrant inspection is included for grade 1 bars (not normally required in generic Def Stan specifications) to ensure freedom defects associated with linear oxide films and inclusions which become revealed as voids during the forging process.
4Eddy current testing has been historically used for evaluating the presence of dangerous linear oxide defects at/near surface, which cannot be detected using radiography, and castings cannot be ultrasonically inspected due to poor grain size and grain structure. Our wrought CNC-1 and CNC-2, due to a very fine grain structure and resulting low attenuation, can be very effectively ultrasonically inspected. This, combined with Dye Penetrant Inspection, can reasonably be expected to locate such defects, due to hot working activities further worsening any such oxides in the original cast ingot. When this is fully confirmed, Eddy Current Testing may not be offered as standard, and this table will be updated accordingly.
Forms Available
We can provide the largest and heaviest-section forged products available anywhere due to industry-leading large ingot sizes that ensure a large total forging reduction and a uniform fine-grain wrought structure in the finished product.
Our capacity continues to evolve and widen as we service ever-increasing customer demands.
- Bars (square/flat/round) from 10mm to 500mm (0.375-20") in section
- Forgings (to 5 Tonnes): Blocks/Rings to 2400mm (95") outer ø / Shafts to 7M long/Discs to 1250mm (49") ø
- Note: The higher strength version CAL Wrought CNC-2 is only available as bars to around 150mm (6") in section.
- Proof-machined or fully-machined components.
Composition
Complies with Def Stan 02-886 Table 1
High Strength Cupper-Nickel-Manganese-Aluminium Alloy
CuNi15Mn4Al1Fe
Show more...Table 1 - Composition requirements weight %
Alloying Elements |
|||||||
|---|---|---|---|---|---|---|---|
| Cu | Ni | Cr | Fe | Mn | Si | Zr | Ti |
| Remainder | 29.0-32.0 | 1.6-2.0 | 0.5-1.0 | 0.5-1.0 | 0.20-0.40 | 0.05-0.15 | 0.03-0.15 |
Impurity Elements - ultra low levels (all figures are maximum) |
||||||
|---|---|---|---|---|---|---|
Permitted Total of these Impurities 0.070% maximum by weight |
||||||
| Pb | P | Bi | S | C | Co | B |
| 0.005 | 0.005 | 0.001 | 0.005 | 0.020 | 0.050 | 0.001 |
We exercise precise control over alloy composition and, using our advanced melting and casting techniques, produce high quality ingots for converting into an extensive variety of wrought products. Our highly-calibrated laboratory ensures we are consistently fully compliant with material composition requirements including the ultra-low impurity requirements for this material.
Calibration standards provided by STGMT, Abbey Wood, were used in the calibration of our analytical instruments, satisfying the requirement for this in Def Stan 02-886. Traceability from source to customer is guaranteed.
Manufacture
Our expertise allows us to cast high quality ingots suitable for forging, using advanced melting, alloying and casting techniques. Additionally, our deep metallurgical understanding of forging and other hot working activities, allows us to create a range of high quality wrought products including forgings (rings, discs, blocks, shafts, closed die forgings) and bars (round, square, hexagonal, flats).
All material (CAL CNC-1 and CNC-2) is subjected to a stress relieving heat treatment after all working operations are complete, as required by Def-Stan 02-886. This heat treatment involves raising the temperature to 475°C ± 15°C (887°F) at a maximum rate of 200°pC/hour, then holding for 1 hour per 25mm (1") of section (2 hours minimum) followed by cooling to ambient temperature in still air within the workshop environment.
Wrought CNC is available in two conditions:
- CAL CNC-1: The standard material applicable to all product forms and sizes
- CAL CNC-2: High strength version applicable to bars (round/flat/square/hexagonal) up to around 150mm (6") in section.
United Kingdom