CUPRO NICKEL 90/10, 70/30

1. Introduction to Cupro Nickel Fasteners

Cupro Nickel (Copper-Nickel) fasteners are high-performance corrosion-resistant fastening components manufactured primarily from copper-nickel alloys containing either 90% copper and 10% nickel (C70600) or 70% copper and 30% nickel (C71500), with controlled additions of iron and manganese to enhance corrosion resistance and mechanical performance. These alloys are extensively used in marine engineering, offshore structures, desalination plants, naval applications, heat exchangers, shipbuilding, LNG facilities, offshore oil platforms, petrochemical installations, and seawater handling systems where conventional stainless steels may experience localized corrosion.

Unlike carbon steel fasteners that rely on protective coatings, Cupro Nickel develops a stable, adherent oxide film that continuously protects the metal from seawater corrosion, biofouling, and erosion. This self-protecting surface significantly extends service life in aggressive chloride-rich environments.

SM Fasteners manufactures precision-engineered Cupro Nickel fasteners in compliance with international standards for EPC contractors, OEMs, offshore projects, marine infrastructure, and industrial process plants. Manufactured under an ISO 9001 quality management system and supported by MSME and UKAF certifications, these fasteners are supplied with complete material traceability, inspection records, and global export documentation.

2. Understanding Cupro Nickel Alloys

Cupro Nickel is a non-ferrous alloy family consisting primarily of copper and nickel, with carefully controlled additions of iron and manganese.

The most commonly specified engineering grades include:

Compared with stainless steels, Cupro Nickel provides:

• Outstanding seawater corrosion resistance
• High resistance to marine biofouling
• Excellent resistance to erosion corrosion
• Good thermal conductivity
• Low magnetic permeability
• Stable long-term corrosion behavior
• Excellent weldability
• Long service life in marine environments

3. Industrial Importance of Cupro Nickel Fasteners

Fasteners are often the weakest link in corrosion-resistant piping and equipment systems if an incompatible material is selected.

Cupro Nickel fasteners provide:

• Reliable structural integrity
• Long-term preload retention
• Reduced maintenance requirements
• Minimal galvanic corrosion with CuNi piping
• Excellent durability in submerged applications

These properties make them preferred fastening materials wherever seawater is continuously present.

4. Major Industries Using Cupro Nickel Fasteners

4.1 Marine Engineering

Applications include:

• Hull equipment
• Deck machinery
• Propulsion support systems
• Sea chest assemblies
• Pump installations
• Anchor equipment

4.2 Offshore Oil & Gas

Typical uses:

• Offshore platforms
• FPSO facilities
• Produced water systems
• Seawater lift pumps
• Firewater piping
• Splash zone structures

4.3 Desalination Plants

Critical applications:

• Reverse osmosis systems
• Intake piping
• Brine discharge
• Heat exchangers
• Condenser assemblies

4.4 Shipbuilding

Used for:

• Condenser systems
• Cooling water systems
• Ballast systems
• Engine room piping
• Seawater pumps

4.5 Petrochemical Industry

Suitable for:

• Chloride-containing process units
• Cooling water circuits
• Coastal chemical facilities
• Heat recovery systems

4.6 LNG Industry

Common applications include:

• Seawater cooling
• Cryogenic auxiliary equipment
• Offshore LNG terminals
• Cooling systems

4.7 Power Generation

Used in:

• Coastal thermal power plants
• Nuclear cooling circuits
• Condensers
• Heat exchangers
• Cooling towers

4.8 Naval Defense

Applications include:

• Warships
• Submarines
• Naval cooling systems
• Weapons support systems
• Deck equipment

5. Why Engineers Select Cupro Nickel Fasteners

Engineering selection is generally based on:

• Corrosion resistance
• Chloride concentration
• Service temperature
• Galvanic compatibility
• Mechanical loading
• Design life
• Maintenance interval
• Inspection accessibility

Cupro Nickel is particularly advantageous where seawater exposure is continuous and corrosion prevention is critical.

6. Functional Role of Cupro Nickel Fasteners

Fasteners perform significantly more than simple joining functions. In engineered assemblies they are responsible for maintaining structural integrity by generating and sustaining clamping force throughout the service life.

Primary functions include:

• Clamping structural members
• Maintaining gasket compression
• Transferring tensile loads
• Resisting shear forces
• Accommodating thermal expansion
• Preventing leakage
• Supporting fatigue resistance
• Ensuring equipment alignment

7. Engineering Definition of Fastener Preload

Preload is the tensile force intentionally induced in a fastener during tightening. This force compresses the joint members together, creating friction that resists separation under external loading.

Proper preload is essential because:

• It prevents joint loosening.
• It minimizes cyclic stress in the fastener.
• It improves fatigue life.
• It maintains sealing performance.
• It distributes loads evenly across the joint interface.

8. Load Mechanics of Cupro Nickel Fasteners

When a bolt is tightened, torque is converted into tensile force within the fastener. This tensile force creates a corresponding compressive force in the clamped components.

The basic relationship is:

Applied Torque → Bolt Tension → Clamp Load → Joint Integrity

This sequence ensures that operational loads are primarily absorbed by the clamped joint rather than the fastener itself.

9. Types of Loads Acting on Fasteners

9.1 Tensile Load

Acts along the longitudinal axis of the fastener.

Examples:

• Pipe flange connections
• Pressure vessel covers
• Structural supports

9.2 Shear Load

Acts perpendicular to the fastener axis.

Common in:

• Structural frames
• Marine brackets
• Equipment bases

9.3 Combined Loading

Many offshore joints experience simultaneous:

• Tension
• Shear
• Bending
• Thermal stresses
• Dynamic loading

Joint design must account for the combined effects to ensure reliability.

9.4 Dynamic Loading

Includes:

• Wave action
• Pump vibration
• Compressor vibration
• Rotating machinery
• Ship motion
• Wind loading

These cyclic loads can significantly reduce fatigue life if preload is inadequate.

10. Force Distribution in Bolted Joints

A properly designed bolted joint distributes operational forces between:

• Bolt elasticity
• Joint stiffness
• Clamped members
• Gasket compression (if applicable)

The stiffness ratio between the bolt and the joint influences how external loads are shared, affecting preload retention and fatigue performance.

11. Elastic Behavior of Fasteners

A bolt behaves like an elastic spring.

During tightening:

• Bolt elongates elastically.
• Joint members compress.
• Stored elastic energy maintains clamping force.
• External loads are absorbed while preload remains effective.

Loss of elasticity results in preload reduction and potential joint failure.

12. Friction in Bolted Assemblies

Only a small portion of tightening torque produces useful bolt tension.

Typical torque distribution:

Therefore, lubrication, surface finish, and coating selection have a significant impact on preload accuracy.

13. Joint Design Principles

Effective bolted joint design requires consideration of:

• Fastener material compatibility
• Joint stiffness
• Bolt diameter
• Thread engagement length
• Clamp length
• Gasket characteristics
• Environmental exposure
• Service temperature
• Corrosion allowance
• Accessibility for maintenance

Proper joint design ensures sustained preload, minimizes stress concentrations, and extends service life.

14. Thread Engagement Requirements

Adequate thread engagement is necessary to prevent thread stripping and ensure full load transfer.

General engineering guidelines:

• Steel-to-steel joints: engagement approximately equal to one bolt diameter.
• Softer materials such as copper alloys or aluminum: greater engagement length may be required.
• High-vibration applications: increased engagement or locking features are recommended.

Thread engagement should be verified according to applicable design codes and material strengths.

15. Importance of Material Compatibility

Using Cupro Nickel fasteners with dissimilar materials requires evaluation of galvanic compatibility.

Preferred combinations include:

• Cupro Nickel to Cupro Nickel
• Cupro Nickel to bronze
• Cupro Nickel to copper alloys

When joining stainless steel, carbon steel, or aluminum components, insulating washers, sleeves, or protective coatings may be required to minimize galvanic corrosion, particularly in seawater service.

16. Galvanic Corrosion Considerations

In marine environments, the electrochemical potential difference between dissimilar metals can accelerate corrosion.

Engineering practices to reduce galvanic corrosion include:

• Selecting compatible materials
• Electrically isolating dissimilar metals
• Applying protective coatings where appropriate
• Avoiding unfavorable anode-to-cathode area ratios
• Ensuring proper drainage to prevent stagnant seawater accumulation

17. Temperature Performance

Cupro Nickel alloys maintain stable mechanical properties across a broad temperature range.

Typical service capabilities include:

• Excellent performance in sub-zero marine environments
• Reliable operation in hot seawater systems
• Good thermal conductivity for heat-transfer equipment
• Resistance to thermal cycling encountered in condensers and heat exchangers

18. Design Considerations for Marine Fasteners

When specifying Cupro Nickel fasteners for marine service, engineers should evaluate:

• Continuous or intermittent seawater exposure
• Chloride concentration
• Flow velocity
• Risk of erosion-corrosion
• Crevice geometry
• Oxygen availability
• Biofouling potential
• Cathodic protection systems
• Maintenance accessibility
• Expected service life

19. Advantages of Cupro Nickel Fasteners

Key engineering advantages include:

• Exceptional seawater corrosion resistance
• Excellent resistance to marine biofouling
• Superior erosion-corrosion resistance
• Good mechanical strength for marine service
• High thermal conductivity
• Low magnetic permeability
• Good weldability and fabrication characteristics
• Long operational service life
• Reduced maintenance frequency
• Excellent compatibility with Cupro Nickel piping systems

20. SM Fasteners Engineering Capability

SM Fasteners manufactures precision Cupro Nickel 90/10 (UNS C70600) and Cupro Nickel 70/30 (UNS C71500) fasteners for demanding industrial applications, including bolts, nuts, screws, washers, threaded rods, rings, custom-engineered components, and complementary PEEK fasteners for electrically insulating or non-metallic fastening requirements. Production is carried out under an ISO 9001 quality management system with MSME and UKAF certifications, emphasizing dimensional accuracy, material traceability, international standards compliance, and complete inspection documentation for EPC, offshore, marine, power generation, and global industrial projects.

21. Product Range of Cupro Nickel Fasteners

Cupro Nickel fasteners are manufactured in numerous configurations to satisfy structural, mechanical, marine, offshore, petrochemical, and heavy engineering requirements. Selection depends on joint geometry, applied loading, maintenance accessibility, corrosion environment, and international project specifications.

SM Fasteners manufactures Cupro Nickel fasteners in standard and custom dimensions suitable for EPC projects, OEM equipment, offshore platforms, naval applications, desalination plants, and process industries.

Typical product range includes:

• Hex Head Bolts
• Heavy Hex Bolts
• Hex Cap Screws
• Stud Bolts
• Fully Threaded Studs
• Threaded Rods
• Hex Nuts
• Heavy Hex Nuts
• Jam Nuts
• Lock Nuts
• Square nut
• Flat Washers
• Spring Washers
• Belleville Washers
• Fender Washers
• Socket Head Cap Screws
• Socket Set Screws
• Button Head Screws
• Countersunk Screws
• Eye Bolt
• Eye Nuts
• U-Bolts
• Foundation Bolts
• Anchor Bolts
• Machine Screws
• Custom Machined Fasteners
• Precision CNC Components

22. Hex Head Bolts

Hex head bolts are the most widely specified fastening components for industrial piping, steel structures, machinery, pressure equipment, and offshore facilities.

Engineering Characteristics

• Six-sided wrenching head
• High torque transmission capability
• Suitable for heavy preload
• Easy maintenance access
• Excellent for flange assemblies

Typical applications include:

• Pressure vessels
• Marine piping
• Offshore platforms
• Heat exchangers
• Pump assemblies
• Structural supports

23. Heavy Hex Bolts

Heavy hex bolts possess a larger head diameter and greater bearing surface than standard hex bolts.

Advantages include:

• Higher preload capability
• Improved load distribution
• Reduced bearing stress
• Better fatigue resistance
• Preferred for structural steel applications

Used extensively in:

• Offshore structures
• Oil & gas plants
• Petrochemical equipment
• Heavy fabrication
• Marine construction

24. Stud Bolts

Stud bolts consist of fully threaded rods used with two heavy hex nuts.

Advantages:

• Uniform load distribution
• Easy gasket replacement
• Suitable for high-temperature joints
• Preferred for pressure-containing flanges

Industries include:

• Refineries
• LNG terminals
• Offshore platforms
• Chemical plants
• Heat exchanger construction

25. Threaded Rods

Threaded rods provide continuous threading over the full length.

Applications:

• Pipe supports
• Equipment mounting
• Structural bracing
• HVAC systems
• Marine supports

Available in:

• Metric
• UNC
• UNF
• BSW
• BSF

26. Hex Nuts

Hex nuts provide mating threads for bolts and studs.

Common variants:

• Standard Hex Nut
• Heavy Hex Nut
• Thin Nut
• Jam Nut
• Slotted Nut
• Lock Nut

Engineering considerations:

• Thread accuracy
• Bearing surface finish
• Material compatibility
• Proof load
• Thread tolerance

27. Washers

Washers increase bearing area and improve load distribution.

Common types include:

Flat Washers

Functions:

• Load distribution
• Surface protection
• Improved joint stability

Spring Washers

Functions:

• Resistance to vibration
• Preload retention
• Dynamic load resistance

Belleville Washers

Suitable for:

• Thermal expansion
• Dynamic loading
• High vibration
• Offshore equipment

Fender Washers

Large outside diameter provides:

• Increased bearing area
• Thin plate reinforcement
• Soft material protection

28. Socket Head Cap Screws

These precision fasteners provide:

• High strength
• Compact installation
• Excellent alignment
• Reduced installation space

Widely used in:

• Pumps
• Compressors
• Precision machinery
• Marine equipment

29. Countersunk Screws

Used where flush mounting is required.

Applications:

• Marine panels
• Deck equipment
• Precision assemblies
• Instrumentation

Benefits:

• Smooth surface
• Reduced snagging
• Improved appearance

30. U-Bolts

Designed for pipe and tube support.

Applications:

• Marine piping
• Heat exchangers
• Structural supports
• Offshore process piping

31. Foundation Bolts

Foundation bolts secure heavy equipment to concrete foundations.

Common installations:

• Pumps
• Compressors
• Turbines
• Marine engines
• Offshore skids

32. Anchor Bolts

Anchor bolts connect structural members to foundations.

Common designs:

• L-Type
• J-Type
• Straight Anchor
• Sleeve Anchor
• Plate Anchor

33. Eye Bolts & Eye Nuts

Designed for lifting applications.

Used for:

• Heat exchangers
• Pumps
• Valves
• Marine equipment
• Heavy machinery

Design considerations:

• Working Load Limit
• Direction of loading
• Safety factor
• Thread engagement

34. Custom Engineered Fasteners

Many EPC projects require non-standard fasteners.

SM Fasteners manufactures:

• Special diameters
• Long-length studs
• Large forged bolts
• CNC-machined fasteners
• Non-standard thread forms
• Special washers
• Custom lifting hardware
• PEEK fasteners for electrical insulation and chemically aggressive environments

35. Fastener Geometry Fundamentals

Proper geometry ensures:

• Accurate preload
• Uniform stress distribution
• Reduced stress concentration
• Improved fatigue life
• Reliable installation

Important geometric parameters include:

• Nominal diameter
• Head height
• Across flats
• Across corners
• Thread length
• Grip length
• Radius
• Chamfer
• Under-head fillet

36. Dimensional Logic

Every fastener dimension directly influences joint performance.

Key dimensions include:

Nominal Diameter

Determines:

• Tensile capacity
• Shear capacity
• Torque requirement

Grip Length

Represents the total thickness of clamped materials.

Incorrect grip length may result in:

• Thread loading inside joint
• Reduced preload
• Fatigue cracking

Thread Length

Proper thread length ensures:

• Full nut engagement
• Uniform stress transfer
• Improved fatigue performance

Head Dimensions

Head diameter affects:

• Bearing stress
• Clamp force distribution
• Installation clearance

37. Standard Metric Bolt Dimensions

(Representative dimensions based on ISO 4014/4017 standards.)

38. Standard Length Availability

Typical production lengths:

Custom lengths are manufactured to project specifications.

39. Thread Forms

Cupro Nickel fasteners are produced in multiple thread systems.

Metric Threads

Common in:

• Europe
• Asia
• Middle East
• EPC projects

Standard:

ISO Metric Thread

UNC Threads

Preferred in:

• North America
• Offshore industry
• Oil & gas

UNF Threads

Advantages:

• Better preload
• Higher tensile area
• Improved fatigue resistance

BSW Threads

Still encountered in:

• Legacy power plants
• Marine vessels
• Railway equipment

BSF Threads

Used for:

• Maintenance
• Heritage equipment
• Existing British-standard machinery

40. Thread Standards & Tolerances

41. International Manufacturing Standards

Cupro Nickel fasteners are manufactured according to globally recognized standards to ensure dimensional interchangeability, mechanical consistency, and procurement compliance.

42. ASTM Standards

Relevant ASTM specifications include:

43. DIN Standards

Frequently referenced DIN standards include:

44. British Standards (BS)

Common BS standards include:

45. Dimensional Inspection Requirements

Each manufactured fastener undergoes dimensional verification for:

• Major diameter
• Minor diameter
• Pitch diameter
• Head dimensions
• Thread pitch
• Thread angle
• Straightness
• Overall length
• Radius
• Chamfer
• Concentricity

Inspection is performed using calibrated gauges, micrometers, vernier calipers, optical comparators, profile projectors, and thread gauges in accordance with ISO 9001 quality procedures.

46. Engineering Design Considerations

When specifying Cupro Nickel fasteners, engineers should verify:

• Applicable design code
• Operating temperature
• Pressure class
• Corrosion environment
• Thread compatibility
• Required preload
• Joint stiffness
• Inspection accessibility
• Galvanic compatibility
• Maintenance interval

These factors ensure long-term joint reliability in seawater, offshore, and process industry applications.

47. SM Fasteners Manufacturing Capability

SM Fasteners manufactures Cupro Nickel 90/10 (UNS C70600) and 70/30 (UNS C71500) fasteners in metric, UNC, UNF, BSW, and BSF thread forms, covering standard and custom dimensions for global EPC, marine, offshore, and industrial projects. Product offerings include bolts, heavy hex bolts, studs, threaded rods, nuts, washers, socket screws, anchor bolts, U-bolts, lifting hardware, and precision CNC-machined components. Production is supported by ISO 9001, MSME, and UKAF certified quality systems, ensuring dimensional accuracy, traceability, and compliance with international ISO, ASTM, DIN, and BS standards.

48. Material Engineering of Cupro Nickel Fasteners

Material selection is one of the most critical engineering decisions affecting the long-term reliability of industrial fasteners. Cupro Nickel alloys are selected where resistance to seawater corrosion, biofouling, erosion-corrosion, and chloride attack is more important than achieving the highest mechanical strength.

Unlike carbon steel and alloy steel fasteners, Cupro Nickel derives its durability from its naturally protective oxide layer rather than from external coatings. This passive film continually reforms when damaged, providing long-term protection in aggressive marine environments.

Primary engineering advantages include:

• Excellent seawater corrosion resistance
• High resistance to biofouling
• Superior erosion-corrosion resistance
• Good ductility
• Stable mechanical properties
• Excellent thermal conductivity
• Good electrical conductivity
• Low magnetic permeability
• Good weldability
• Long operational service life

49. Chemical Composition of Cupro Nickel Alloys

CuNi 90/10 – UNS C70600

CuNi 70/30 – UNS C71500

50. Comparison of Cupro Nickel Grades

51. Material Selection Criteria

Selection depends on several engineering parameters.

Operating Environment

Consider:

• Continuous seawater immersion
• Splash zone exposure
• Atmospheric marine conditions
• High-velocity seawater
• Brine service
• Chloride concentration

Mechanical Loading

Evaluate:

• Tensile load
• Shear load
• Cyclic loading
• Shock loading
• Fatigue loading
• Thermal expansion

Corrosion Requirements

Assessment should include:

• General corrosion
• Crevice corrosion
• Galvanic corrosion
• Erosion-corrosion
• Stress corrosion cracking
• Marine biofouling

Service Life

Engineering designs commonly target:

• 20 years
• 25 years
• 30 years
• 40 years or more in properly maintained marine systems

52. Material Comparison with Other Fastener Alloys

53. Corrosion Resistance by Environment

54. Mechanical Properties

Typical room-temperature properties.

55. Temperature Capability

Cupro Nickel alloys retain stable properties over a wide operating range.

56. Heat Treatment of Cupro Nickel Fasteners

Unlike alloy steel fasteners, Cupro Nickel alloys are not strengthened through quenching and tempering. Their mechanical properties are primarily obtained through alloy composition and cold working.

Typical heat treatment objectives include:

• Stress relief
• Annealing
• Recrystallization
• Improved ductility
• Removal of residual forming stresses

57. Annealing Process

Annealing is performed after extensive cold working to restore ductility and improve machinability.

Benefits include:

• Reduced residual stresses
• Increased ductility
• Improved dimensional stability
• Better forming characteristics
• Uniform grain structure

58. Stress Relieving

Stress relieving minimizes residual stresses introduced during machining, threading, or forming.

Advantages:

• Improved dimensional stability
• Reduced distortion
• Enhanced fatigue performance
• Better service reliability

59. Cold Working

Cold working increases mechanical strength without altering alloy chemistry.

Processes include:

• Cold drawing
• Thread rolling
• Cold heading
• Cold forging

Benefits:

• Increased tensile strength
• Improved yield strength
• Better fatigue resistance
• Enhanced thread quality

60. Manufacturing Workflow

Production follows a controlled manufacturing sequence to ensure dimensional accuracy, traceability, and consistent quality.

Step 1 – Raw Material Procurement

Certified CuNi bars, rods, or forgings are sourced with complete material certification.

Verification includes:

• Heat number
• Chemical composition
• Mechanical properties
• Material Test Certificate (MTC)

Step 2 – Incoming Material Inspection

Inspection activities include:

• Visual examination
• Dimensional verification
• Positive Material Identification (PMI)
• Heat number verification
• Certification review

Step 3 – Cutting

Raw stock is cut to precise lengths using:

• Band saws
• Circular saws
• CNC cutting equipment

Step 4 – Forging

Depending on size and design:

• Hot forging
• Cold heading
• Precision forging

Forging refines grain flow and enhances mechanical integrity.

Step 5 – CNC Machining

Critical dimensions are machined using CNC equipment.

Operations include:

• Turning
• Facing
• Drilling
• Slotting
• Milling
• Chamfering
• Radius generation

Step 6 – Thread Manufacturing

Threads are produced by:

Thread Rolling

Advantages:

• Superior surface finish
• Compressive residual stresses
• Improved fatigue resistance
• Better thread accuracy
• Higher strength

Thread Cutting

Used when:

• Large diameters are involved
• Custom thread forms are required
• Low production quantities
• Repair applications

61. Thread Rolling vs Thread Cutting

Thread rolling is generally preferred for critical industrial fasteners.

62. Deburring & Cleaning

After machining:

• Burr removal
• Edge conditioning
• Surface cleaning
• Degreasing
• Drying

These operations ensure safe handling and proper coating or passivation where specified.

63. Surface Engineering

Although Cupro Nickel naturally resists corrosion, surface preparation improves cleanliness, appearance, and service performance.

Typical treatments include:

• Mechanical polishing
• Glass bead blasting
• Pickling (where appropriate)
• Degreasing
• Protective oiling for storage

64. Surface Finish Comparison

65. Protective Coatings

Cupro Nickel fasteners generally do not require sacrificial coatings such as zinc or hot-dip galvanizing because these coatings can compromise galvanic compatibility and are unnecessary for marine corrosion protection.

Where project specifications require temporary storage protection, the following may be applied:

• Water-displacing protective oils
• Dry-film rust inhibitors
• Volatile Corrosion Inhibitor (VCI) packaging
• Wax-based storage coatings

66. Failure Mechanisms

Despite their excellent corrosion resistance, improper design or installation can result in failure.

Common mechanisms include:

Fatigue Failure

Caused by:

• Cyclic loading
• Inadequate preload
• Vibration
• Stress concentrations

Shear Failure

Occurs when applied shear exceeds the fastener’s shear capacity.

Common causes:

• Undersized fasteners
• Misalignment
• Poor joint design

Thread Stripping

Results from:

• Insufficient thread engagement
• Improper tightening
• Material mismatch
• Damaged threads

Galvanic Corrosion

Occurs when Cupro Nickel is coupled with dissimilar metals in an electrolyte.

Preventive measures:

• Material compatibility
• Insulating washers
• Isolation sleeves
• Appropriate joint design

Stress Corrosion Cracking (SCC)

Cupro Nickel alloys exhibit excellent resistance to chloride-induced SCC compared with many stainless steels, making them suitable for long-term marine service.

67. NACE and Sour Service Considerations

For oil and gas applications containing hydrogen sulfide (H₂S), fastener selection should be verified against:

• NACE MR0175
• ISO 15156

Material hardness, environmental severity, and service conditions should be evaluated to ensure suitability and minimize the risk of sulfide stress cracking.

68. Traceability Throughout Manufacturing

Every production lot should maintain complete traceability from raw material to finished product, including:

• Heat number identification
• Manufacturing batch records
• Process route documentation
• Inspection records
• Dimensional reports
• Material certifications
• Final release documentation

69. Stress Corrosion Cracking (SCC)

Cupro Nickel alloys exhibit excellent resistance to chloride-induced SCC compared with many stainless steels, making them suitable for long-term marine service.

70. Marine & Shipbuilding

All incoming Cupro Nickel bars, rods, forgings, or billets should be verified before production.

Inspection activities include:

71. Incoming Material Inspection

• Material Test Certificate (MTC) review
• Heat number verification
• Chemical composition confirmation
• Surface defect inspection
• Visual inspection
• Dimensional verification
• Positive Material Identification (PMI)
• Traceability marking

72. In-Process Inspection

During manufacturing, critical characteristics are continuously monitored to prevent non-conforming products.

Typical checkpoints include:

• Forging dimensions
• CNC machining accuracy
• Thread profile
• Thread pitch
• Thread concentricity
• Head dimensions
• Under-head radius
• Chamfer quality
• Surface finish
• Burr removal
• Identification marking

73. Final Dimensional Inspection

Finished fasteners undergo dimensional verification using calibrated instruments.

Measured characteristics include:

• Major diameter
• Minor diameter
• Pitch diameter
• Thread pitch
• Overall length
• Grip length
• Across flats
• Across corners
• Head height
• Straightness
• Perpendicularity
• Concentricity

Inspection equipment commonly includes:

• Digital Vernier Calipers
• Outside Micrometers
• Thread Plug Gauges
• Thread Ring Gauges
• Height Gauges
• Coordinate Measuring Machine (CMM)
• Optical Comparator
• Profile Projector

74. Mechanical Testing

Mechanical testing confirms that the fasteners meet specified strength and ductility requirements.

Typical tests include:

• Tensile Strength Test
• Yield Strength Test
• Elongation Test
• Hardness Test
• Proof Load Test
• Bend Test (where applicable)
• Shear Strength Evaluation

75. Positive Material Identification (PMI)

PMI confirms alloy chemistry and prevents material mix-ups, particularly on critical projects.

Common PMI methods:

• X-Ray Fluorescence (XRF)
• Optical Emission Spectroscopy (OES)

PMI verifies:

• Copper content
• Nickel content
• Iron
• Manganese
• Alloy grade (C70600 or C71500)

76. Non-Destructive Testing (NDT)

Where specified by project requirements, NDT methods are applied without damaging the component.

Typical methods include:

*Applied where geometry and project specifications permit.

77. Proof Load and Tensile Strength Table

Typical Engineering Reference Values

*Indicative values based on representative Cupro Nickel mechanical properties. Project-specific calculations should use certified material test data.

78. Tightening Torque Chart (Typical Guidance)

Note: Actual tightening torque depends on thread condition, lubrication, nut factor (K), joint design, and desired preload. Always follow the project specification or engineering calculation.

79. Torque–Tension Relationship

The relationship between tightening torque and clamp load is commonly estimated using:

$$\boxed{T = K \times F \times D}$$

Where:

• T = Tightening Torque (N·m)
• K = Nut Factor (Coefficient of Friction)
• F = Desired Clamp Load (N)
• D = Nominal Bolt Diameter (m)

80. Preload Calculation (Worked Example)

Given:

• Bolt Size = M16
• Desired Clamp Load = 60,000 N
• Nut Factor (Lubricated) = 0.18
• Diameter = 16 mm = 0.016 m

Formula:

$$T = K \times F \times D$$

Calculation:

$$T = 0.18 \times 60,000 \times 0.016$$

$$T = 172.8\ \text{N·m}$$

Required Tightening Torque ≈ 173 N·m

81. Recommended Thread Engagement

For softer mating materials or highly loaded joints, greater engagement may be necessary.

82. Thread Standards & Tolerances

83. Weight Chart (Approximate)

*Weights are approximate and may vary with thread length, head style, and manufacturing tolerances. SM Fasteners provides project-specific weight charts upon request.

84. Common Failure Mechanisms

Proper engineering design and installation are essential to avoid premature failures.

85. Industry Applications

85.1 Marine & Shipbuilding

Typical applications include:

• Seawater piping systems
• Deck equipment
• Condensers
• Cooling water systems
• Ballast systems
• Pump assemblies
• Heat exchangers

85.2 Offshore Oil & Gas

Cupro Nickel fasteners are widely used in:

• Offshore platforms
• FPSOs
• Firewater systems
• Seawater lift pumps
• Produced water treatment
• Splash zone equipment
• Offshore piping supports

85.3 Petrochemical & Chemical Processing

Applications include:

• Cooling water systems
• Heat exchangers
• Coastal process plants
• Chloride-containing service
• Chemical storage facilities

85.4 Power Generation

Common installations:

• Surface condensers
• Cooling towers
• Heat exchangers
• Seawater intake structures
• Coastal thermal power stations

85.5 LNG Industry

Typical uses:

• Seawater cooling circuits
• LNG terminals
• Offshore loading facilities
• Utility piping
• Auxiliary equipment

85.6 Construction & Infrastructure

Applications include:

• Coastal bridges
• Marine jetties
• Port facilities
• Harbour structures
• Structural steel exposed to marine environments

85.7 Railways

Cupro Nickel fasteners are used in:

• Coastal railway infrastructure
• Signalling equipment near marine environments
• Bridge components
• Electrical earthing assemblies

85.8 Automotive & Heavy Equipment

Typical applications:

• Marine vehicles
• Heavy-duty cooling systems
• Coastal equipment
• Specialized OEM assemblies

85.9 PEEK Fastener Applications

Where electrical insulation, low weight, or complete non-metallic fastening is required, PEEK fasteners complement Cupro Nickel assemblies.

Typical applications:

• Electrical insulation systems
• Instrumentation
• Chemical processing equipment
• Semiconductor manufacturing
• Lightweight assemblies
• High-purity process equipment

86. Packaging and Export Preparation

To maintain product quality during storage and international transportation, fasteners should be packaged using industrial export practices.

Typical packaging includes:

• Moisture-resistant poly bags
• Heat-sealed packaging
• VCI (Volatile Corrosion Inhibitor) protection
• Thread protectors
• Individual labeling
• Batch identification
• Heavy-duty corrugated cartons
• Wooden export crates
• ISPM-15 compliant fumigated pallets and crates
• Containerized shipment for international logistics

87. Export Documentation

International EPC and industrial projects commonly require the following documentation:

• Material Test Certificate (MTC)
• EN 10204 Type 3.1 Certificate
• EN 10204 Type 3.2 Certificate (when specified)
• Positive Material Identification (PMI) Report
• Chemical Analysis Report
• Mechanical Test Report
• Dimensional Inspection Report
• Heat Number Traceability Record
• Certificate of Conformance (CoC)
• Packing List
• Commercial Invoice
• Certificate of Origin
• Third-Party Inspection Report (TPI), where applicable

88. Quality Management and Traceability

A robust quality management system ensures that every fastener is fully traceable throughout its lifecycle.

Key quality elements include:

• Heat number traceability
• Batch identification
• Calibration of measuring instruments
• Documented inspection plans
• Manufacturing process control
• Corrective and preventive action (CAPA)
• Controlled documentation
• Final release authorization

These practices support project compliance, third-party inspections, and long-term asset integrity.

89. SM Fasteners Engineering & Manufacturing Capability

SM Fasteners manufactures precision Cupro Nickel 90/10 (UNS C70600) and Cupro Nickel 70/30 (UNS C71500) fasteners for demanding marine, offshore, petrochemical, LNG, power generation, and heavy engineering applications. The product portfolio includes bolts, heavy hex bolts, studs, threaded rods, nuts, washers, anchor bolts, U-bolts, custom CNC-machined fasteners, forged components, and complementary PEEK fasteners for specialized applications.

Operating under an ISO 9001 certified quality management system with MSME and UKAF certifications, SM Fasteners provides complete manufacturing traceability, precision machining, PMI verification, dimensional inspection, mechanical testing, and export-ready documentation. Global supply capability includes custom dimensions, international thread standards (Metric, UNC, UNF, BSW, BSF), project-specific packaging, and comprehensive certification to support EPC contractors, OEMs, shipyards, offshore platforms, power plants, and industrial infrastructure projects worldwide.

90. Engineering Summary

Cupro Nickel 90/10 (UNS C70600) and 70/30 (UNS C71500) fasteners are engineered for service in aggressive marine and chloride-rich environments where long-term corrosion resistance, erosion-corrosion performance, and reliability are critical. Their natural resistance to seawater, compatibility with copper-nickel piping systems, and stable mechanical properties make them preferred materials for offshore platforms, naval vessels, desalination plants, condensers, heat exchangers, LNG terminals, and coastal infrastructure.