COPPER C110 C122

1. Industry Context

Copper fasteners manufactured from Copper C110 (Electrolytic Tough Pitch – ETP) and Copper C122 (Phosphorus Deoxidized High Residual Phosphorus – DHP) are widely specified where excellent electrical conductivity, thermal conductivity, corrosion resistance, and long-term service reliability are required. Unlike conventional carbon steel fasteners, copper fasteners provide unique functional benefits in electrical systems, grounding networks, power transmission equipment, marine installations, HVAC systems, petrochemical plants, renewable energy infrastructure, and architectural applications.

Global industrial sectors increasingly specify copper fasteners because they combine mechanical joining capability with electrical continuity and resistance to atmospheric corrosion. Engineering specifications frequently reference C110 for high-conductivity electrical applications and C122 for environments involving welding, brazing, or hydrogen exposure.

Within EPC projects, copper fasteners are commonly incorporated into:

• Electrical substations
• Busbar assemblies
• Transformer connections
• Switchgear
• Earthing systems
• Marine electrical equipment
• Heat exchangers
• HVAC equipment
• Renewable energy installations
• Lightning protection systems
• Chemical processing equipment
• Architectural copper cladding

As international infrastructure expands toward electrification and renewable energy, demand for engineered copper fastening systems continues to increase due to their durability, conductivity, recyclability, and compatibility with non-ferrous assemblies.

2. Technical Definition of Copper C110 (ETP) & Copper C122 (DHP)

Copper C110 and Copper C122 are commercially pure wrought copper alloys defined under ASTM, UNS, EN, and ISO material specifications. Although both materials contain more than 99.9% copper, they differ significantly in oxygen and phosphorus content, influencing conductivity, weldability, and resistance to hydrogen embrittlement.

2.1 Copper C110 (ETP)

Copper C110, designated as UNS C11000, is an electrolytic tough pitch copper containing approximately 99.90% copper with controlled oxygen content. It offers electrical conductivity approaching 100% IACS and is the preferred material for electrical fasteners, connectors, grounding hardware, and conductive assemblies.

Typical characteristics include:

• Excellent electrical conductivity
• Outstanding thermal conductivity
• High ductility
• Excellent cold workability
• Good corrosion resistance
• Superior electrical contact performance

2.2 Copper C122 (DHP)

Copper C122, designated as UNS C12200, is phosphorus-deoxidized copper containing residual phosphorus that eliminates oxygen from the material during manufacture.

Compared with C110, C122 provides:

• Excellent weldability
• Better brazing characteristics
• Resistance to hydrogen embrittlement
• Improved fabrication reliability
• Excellent corrosion resistance
• Slightly reduced electrical conductivity

C122 is widely selected for piping systems, heat exchangers, pressure vessels, marine components, and fabricated assemblies requiring extensive welding.

3. Chemical Composition Comparison

Element	Copper C110 (ETP)	Copper C122 (DHP)
Copper (Cu)	≥99.90%	≥99.90%
Oxygen	0.02–0.04%	Very Low
Phosphorus	Trace	0.015–0.040%
Electrical Conductivity	~100% IACS	~85% IACS
Hydrogen Resistance	Moderate	Excellent
Weldability	Fair	Excellent

4. Functional Role of Copper Fasteners

Copper fasteners are not selected solely for mechanical strength. Their engineering value lies in combining structural fastening with electrical and thermal performance.

Key functional roles include:

• Maintaining structural joints
• Providing electrical continuity
• Reducing electrical resistance
• Preventing galvanic incompatibility in copper assemblies
• Maintaining thermal conductivity across joints
• Supporting grounding systems
• Providing corrosion-resistant fastening
• Eliminating sparking risks in specific industrial environments

Copper fasteners are commonly manufactured as:

• Hex bolts
• Hex nuts
• Heavy hex bolts
• Socket screws
• Machine screws
• Set screws
• Washers
• Spring washers
• Threaded rods
• Eye bolts
• Stud bolts
• Custom-machined fasteners

At SM Fasteners, these products are manufactured under an ISO 9001-certified quality management system, with support for custom dimensions, engineered geometries, and advanced materials—including PEEK fasteners for electrically insulating applications—serving global EPC, power, marine, and industrial projects.

5. Engineering Principles of Fastened Copper Joints

Copper fasteners function by generating clamping force rather than relying solely on the shear strength of the fastener. Proper joint integrity depends on achieving and maintaining preload throughout the service life.

The tightening process converts installation torque into bolt tension, creating compressive force between assembled components. This preload generates friction at the interface, allowing external loads to be transferred through friction rather than direct bearing.

Critical design considerations include:

• Required clamp load
• Joint stiffness
• Material elasticity
• Thermal expansion compatibility
• Surface condition
• Friction coefficient
• Thread engagement
• Relaxation characteristics

Because copper has a lower modulus of elasticity than steel, copper fasteners exhibit greater elastic elongation under equivalent loads. Designers must account for this behavior to maintain preload and prevent joint loosening.

6. Load Mechanics and Force Behavior

Copper fasteners experience several loading modes during service. Understanding these forces is essential for reliable joint design.

6.1 Tensile Load

Tensile loading occurs when forces act along the fastener axis, stretching the bolt. The bolt must withstand this force without yielding or fracture.

Applications include:

• Busbar joints
• Transformer terminals
• Electrical cabinets
• Structural brackets

6.2 Shear Load

Shear loading acts perpendicular to the bolt axis. Copper fasteners generally possess lower shear strength than alloy steel fasteners; therefore, designers should minimize reliance on shear capacity by incorporating proper joint friction or locating features.

Typical applications include:

• Electrical support brackets
• Cable trays
• Copper bus supports

6.3 Compression

The clamped components experience compressive stress generated by bolt preload. Uniform compression ensures stable electrical contact and minimizes contact resistance.

6.4 Combined Loading

Many industrial joints experience combinations of:

• Tension
• Shear
• Vibration
• Thermal cycling
• Dynamic loading

Joint design should consider the interaction of these forces to ensure long-term reliability.

7. Preload and Clamping Force Principles

Preload is the tensile force induced in the fastener during tightening. It is the primary factor governing joint performance.

The relationship between tightening torque and preload is commonly expressed as:

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

Where:

• T = Tightening torque
• K = Nut factor (friction coefficient)
• F = Desired preload
• D = Nominal fastener diameter

Proper preload:

• Prevents joint separation
• Improves fatigue resistance
• Reduces vibration loosening
• Maintains electrical conductivity
• Minimizes contact resistance

Excessive preload can cause:

• Plastic deformation
• Thread stripping
• Excessive relaxation
• Reduced service life

Insufficient preload may lead to:

• Joint slippage
• Fretting corrosion
• Increased electrical resistance
• Fatigue failure
• Loosening under vibration

8. Torque–Tension Relationship

Only a small portion of applied tightening torque generates useful bolt tension. The majority is consumed by friction.

Typical distribution:

• Approximately 50% under-head friction
• Approximately 40% thread friction
• Approximately 10% produces preload

Consequently, lubrication, surface finish, and thread quality significantly influence preload accuracy.

For critical assemblies, torque control may be supplemented by:

• Turn-of-nut methods
• Direct tension indicators
• Ultrasonic elongation measurement
• Hydraulic tensioning
• Load-indicating washers

9. Thread Engagement Principles

Adequate thread engagement is essential to prevent stripping, especially because copper is softer than steel.

Recommended minimum engagement:

Material Combination	Recommended Engagement
Copper into Copper	1.5 × Diameter
Copper into Bronze	1.5 × Diameter
Copper into Brass	1.25–1.5 × Diameter
Copper into Steel	≥1 × Diameter
Copper with Inserted Nuts	As per design calculations

Proper engagement ensures that thread stripping does not occur before the bolt reaches its design preload.

10. Joint Design Principles

Reliable copper joints require careful consideration of both mechanical and electrical performance.

Key design principles include:

• Ensure uniform clamp load distribution.
• Use flat washers to reduce localized bearing stress.
• Avoid dissimilar metals where galvanic corrosion may occur.
• Design for thermal expansion compatibility.
• Minimize stress concentrations.
• Maintain adequate edge distances and spacing.
• Select appropriate thread class and tolerance.
• Prevent over-tightening of soft copper components.
• Protect joints from moisture ingress in outdoor service.
• Specify compatible coatings or insulating barriers where required.

11. Thermal Expansion Considerations

Copper exhibits a higher coefficient of thermal expansion than steel. In assemblies subjected to temperature fluctuations, differential expansion can alter preload.

Design recommendations:

• Account for operating temperature range.
• Consider relaxation during thermal cycling.
• Use spring washers or Belleville washers where preload retention is critical.
• Re-evaluate torque values for elevated-temperature service.

12. Failure Mechanisms in Copper Fasteners

Although copper fasteners provide excellent corrosion resistance and conductivity, improper selection or installation can lead to failure.

Common failure modes include:

• Tensile overload
• Shear fracture
• Thread stripping
• Bearing failure
• Fatigue cracking
• Fretting corrosion
• Galvanic corrosion
• Stress relaxation
• Creep under sustained elevated temperatures
• Wear due to repeated assembly and disassembly

Understanding these mechanisms enables engineers to implement preventive design measures and extend service life.

13. Galvanic Corrosion Considerations

When copper fasteners are used with dissimilar metals in the presence of an electrolyte, galvanic corrosion may occur.

Typical compatibility:

Base Material	Compatibility with Copper Fasteners
Copper	Excellent
Brass	Excellent
Bronze	Excellent
Stainless Steel	Good (consider environment)
Carbon Steel	Fair (insulation recommended)
Aluminum	Poor (electrical isolation recommended)
Zinc-Coated Steel	Limited (risk of galvanic attack)

Mitigation strategies include:

• Insulating washers or sleeves
• Non-conductive gaskets
• Protective coatings
• Environmental sealing
• Careful material pairing based on the galvanic series

14. Engineering Design Considerations for EPC Projects

For EPC, power generation, marine, petrochemical, and infrastructure applications, engineers should evaluate:

• Mechanical loading conditions
• Electrical conductivity requirements
• Corrosion environment
• Service temperature
• Hydrogen exposure
• Thermal cycling
• Vibration levels
• Maintenance accessibility
• Applicable international standards
• Inspection and certification requirements

Material selection between Copper C110 (ETP) and Copper C122 (DHP) should balance conductivity, fabrication needs, environmental conditions, and lifecycle performance.

15. Product Types and Variants

Copper fasteners manufactured from Copper C110 (ETP) and Copper C122 (DHP) are available in a broad range of standardized and custom-engineered configurations. Selection depends on mechanical loading, electrical conductivity requirements, installation constraints, corrosion exposure, and applicable international standards.

For EPC projects, power transmission systems, petrochemical plants, marine installations, and industrial equipment, fasteners must satisfy both structural and functional requirements while maintaining dimensional interchangeability with ISO, ASTM, DIN, and BS specifications.

Under its ISO 9001-certified quality management system, SM Fasteners manufactures standard and custom copper fasteners with full dimensional traceability, material certification, and project-specific engineering support. In addition to copper alloys, SM Fasteners also manufactures stainless steel, duplex, nickel alloys, titanium, and PEEK fasteners for electrically insulating and chemically aggressive service environments.

16. Hex Head Bolts

Hex head bolts are the most commonly specified copper fasteners for structural and electrical assemblies.

Engineering Characteristics

• Six-sided external drive
• Full or partial thread
• High clamping capability
• Suitable for repeated maintenance
• Compatible with standard spanners and sockets

Typical Applications

• Busbar assemblies
• Transformer terminals
• Switchgear
• Earthing systems
• Marine electrical equipment
• Copper structural connections
• Heat exchangers

Applicable Standards

• ISO 4014 – Hex Bolts, Partially Threaded
• ISO 4017 – Hex Bolts, Fully Threaded
• DIN 931
• DIN 933
• BS EN ISO 4014
• BS EN ISO 4017

17. Heavy Hex Bolts

Heavy hex bolts feature larger head dimensions, providing increased bearing surface and improved wrench engagement.

Advantages

• Higher clamp force distribution
• Reduced localized bearing stress
• Preferred for heavy equipment
• Better resistance to installation damage

Applications

• Petrochemical equipment
• Structural supports
• Offshore platforms
• Power generation equipment
• Heavy electrical bus systems

18. HEX NUT

Copper hex nuts provide mating threads for bolts and studs while maintaining electrical continuity throughout the joint.

Common Variants

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

Applicable Standards

• ISO 4032
• ISO 4033
• DIN 934
• BS EN ISO 4032

19. Stud Bolts

Stud bolts are threaded at both ends or fully threaded throughout their length.

Advantages

• Improved gasket loading
• Easier maintenance
• Reduced flange damage
• Uniform load distribution

Common Uses

• Heat exchangers
• Pressure vessels
• Flanged piping
• Copper process equipment
• Marine pumps

Applicable Standards

• ASTM A193 (geometry reference where applicable)
• DIN 976
• BS 4882

20. Threaded Rods

Copper threaded rods provide continuous threading over the entire length.

Engineering Applications

• Suspension systems
• Cable supports
• Electrical supports
• Busbar supports
• HVAC installations
• Architectural assemblies

Available in:

• 1 meter
• 2 meter
• 3 meter
• Custom lengths

21. Machine Screws

Machine screws are precision-threaded fasteners used in tapped holes or with nuts.

Drive Types

• Slotted
• Phillips
• Pozidriv
• Hex Socket
• Torx
• Combination Drive

Applications

• Electrical enclosures
• Instrumentation
• Electronic assemblies
• Terminal blocks
• Switchgear

22. Socket Head Cap Screws

Socket head screws provide high installation accuracy in confined spaces.

Advantages

• High tightening precision
• Compact head profile
• Controlled torque application
• Reduced installation space

Applicable Standards:

• ISO 4762
• DIN 912

23. Set Screws

Set screws secure rotating components without requiring nuts.

Applications include:

• Couplings
• Shaft collars
• Electrical connectors
• Precision equipment

24. Washers

Washers distribute bolt preload and protect softer copper components from localized deformation.

Flat Washers

Functions:

• Increase bearing area
• Reduce surface damage
• Improve preload distribution

Standards:

• ISO 7089
• ISO 7090
• DIN 125
• BS 4320

Spring Washers

Provide preload retention under vibration.

Standards:

• DIN 127
• BS 4464

Belleville Washers

Used where thermal cycling or vibration may reduce preload.

Advantages:

• Compensate for joint relaxation
• Maintain clamping force
• Suitable for electrical equipment

25. Copper Rings and Special Fasteners

Custom copper components include:

• Retaining Rings
• Earthing Connectors
• Contact Plates
• Terminal Blocks
• Custom Machined Components
• Special Electrical Connectors

These are commonly manufactured according to customer drawings and EPC project specifications.

26. Custom Fastener Engineering

Many industrial projects require non-standard geometries beyond catalogue dimensions.

SM Fasteners supports custom manufacturing including:

• Special head designs
• Reduced shank bolts
• Extra-long bolts
• Fine pitch threads
• Left-hand threads
• Combination thread forms
• Special washers
• CNC-machined parts
• Cold-forged components
• Prototype development
• Drawing-based production

Manufacturing is supported by material traceability, inspection records, and dimensional verification in accordance with ISO 9001 procedures.

27. Fastener Geometry Fundamentals

The geometry of a fastener directly influences its load-carrying capability, installation characteristics, and service performance.

Critical geometric parameters include:

• Nominal diameter
• Thread pitch
• Head height
• Across flats dimension
• Bearing surface diameter
• Fillet radius
• Thread length
• Grip length
• Overall length
• Under-head radius

Proper geometry minimizes stress concentration and promotes uniform preload distribution.

28. Metric Thread Dimensions

The ISO Metric thread system is the preferred standard for most international industrial projects.

Standard Metric Sizes

Thread Size	Coarse Pitch (mm)	Fine Pitch (Typical)
M4	0.70	0.50
M5	0.80	0.50
M6	1.00	0.75
M8	1.25	1.00
M10	1.50	1.25
M12	1.75	1.50
M16	2.00	1.50
M20	2.50	2.00
M24	3.00	2.00
M30	3.50	3.00

29. Standard Bolt Lengths

Copper bolts are generally supplied in standardized increments.

Diameter	Standard Length Range
M4	8–50 mm
M5	10–80 mm
M6	10–100 mm
M8	16–150 mm
M10	20–200 mm
M12	25–250 mm
M16	30–300 mm
M20	40–300 mm
M24	50–400 mm
M30	60–500 mm

Longer lengths are manufactured to customer specifications.

30. Hex Bolt Head Dimensions (ISO 4014 / ISO 4017)

Bolt Size	Across Flats (mm)	Head Height (mm)
M6	10	4
M8	13	5.3
M10	17	6.4
M12	19	7.5
M16	24	10
M20	30	12.5
M24	36	15
M30	46	18.7

These dimensions ensure interchangeability across internationally standardized fastening systems.

31. Thread Engagement Recommendations

Proper engagement is particularly important because copper possesses lower hardness than alloy steels.

Fastener Size	Minimum Thread Engagement
M6	9 mm
M8	12 mm
M10	15 mm
M12	18 mm
M16	24 mm
M20	30 mm
M24	36 mm

For joints subjected to dynamic loading or repeated assembly, increased engagement lengths or threaded inserts may be recommended.

32. Thread Standards and Tolerances

International projects often involve multiple thread systems. Proper specification ensures interchangeability and reliable assembly.

Thread Standard	Thread Angle	Typical Application
ISO Metric	60°	Global industrial projects
UNC	60°	North American heavy engineering
UNF	60°	Precision and vibration-resistant assemblies
BSW	55°	Legacy British equipment
BSF	55°	Fine-thread British machinery
NPT (where applicable)	60°	Tapered threaded fittings (not general fasteners)

33. Thread Tolerance Classes

Standard	External Thread	Internal Thread
ISO Metric	6g	6H
Precision Metric	4g6g	4H
UNC/UNF	Class 2A	Class 2B
High Precision UNC/UNF	Class 3A	Class 3B

Selection of tighter tolerance classes improves positioning accuracy but may require greater manufacturing precision and assembly control.

34. Applicable International Standards

Copper fasteners are manufactured in accordance with recognized international standards to ensure dimensional accuracy, interchangeability, and quality assurance.

Standard	Description
ISO 4014	Hex bolts, partially threaded
ISO 4017	Hex bolts, fully threaded
ISO 4032	Hex nuts
ISO 4762	Socket head cap screws
ISO 7089	Plain washers
ISO 7090	Chamfered washers
DIN 931	Hex bolts, partially threaded
DIN 933	Hex bolts, fully threaded
DIN 934	Hex nuts
DIN 125	Plain washers
DIN 127	Spring washers
DIN 912	Socket head cap screws
ASTM F468/F468M	Non-ferrous bolts, screws, studs, and nuts
ASTM B152/B152M	Copper sheet, strip, plate, and rolled bar (material reference)
ASTM B187/B187M	Copper bus bars, rods, and shapes
ASTM B152	Copper alloy plate and sheet
BS EN ISO 4014	British adoption of ISO hex bolt standard
BS EN ISO 4017	British adoption of ISO fully threaded bolt standard
BS EN ISO 4032	British adoption of ISO hex nut standard

35. Dimensional Inspection Requirements

Dimensional verification shall include:

• Nominal diameter
• Major diameter
• Minor diameter
• Pitch diameter
• Thread pitch
• Head dimensions
• Overall length
• Straightness
• Concentricity
• Bearing surface flatness
• Thread quality using calibrated GO/NO-GO gauges

Inspection methods typically include calibrated micrometers, vernier calipers, optical comparators, thread gauges, and coordinate measuring machines (CMM) for critical custom components.

36. Engineering Selection Considerations

Selection of the appropriate copper fastener type should consider:

• Required mechanical load
• Electrical conductivity requirements
• Service environment
• Corrosion exposure
• Thermal expansion characteristics
• Joint accessibility
• Maintenance frequency
• Applicable international standards
• Compatibility with mating materials
• Project documentation and certification requirements

For applications requiring electrical insulation rather than conductivity, PEEK fasteners manufactured by SM Fasteners provide an alternative solution, offering excellent chemical resistance, high-temperature stability, and non-conductive performance for specialized industrial assemblies.

37. Material Grades and Engineering Classification

Copper fasteners are manufactured from high-purity wrought copper alloys that comply with internationally recognized material specifications. The two primary grades used for industrial fasteners are Copper C110 (Electrolytic Tough Pitch – ETP) and Copper C122 (Phosphorus Deoxidized High Residual Phosphorus – DHP). Material selection depends on conductivity requirements, fabrication methods, mechanical loading, corrosion exposure, and service environment.

37.1 Copper C110 (UNS C11000 – ETP)

Copper C110 is produced by electrolytic refining and contains approximately 99.90% copper, offering electrical conductivity close to 100% IACS (International Annealed Copper Standard).

Engineering Characteristics

• Excellent electrical conductivity
• Excellent thermal conductivity
• High ductility
• Good corrosion resistance
• Excellent cold forming characteristics
• Suitable for precision machining
• Excellent solderability
• Moderate weldability

Typical Industrial Applications

• Busbar assemblies
• Earthing systems
• Electrical switchgear
• Transformer terminals
• Power distribution equipment
• Renewable energy installations
• Lightning protection systems

37.2 Copper C122 (UNS C12200 – DHP)

Copper C122 is phosphorus-deoxidized copper containing residual phosphorus, which minimizes oxygen content and eliminates susceptibility to hydrogen embrittlement during welding or brazing.

Engineering Characteristics

• Excellent weldability
• Excellent brazing performance
• Very good corrosion resistance
• Excellent formability
• High thermal conductivity
• Reduced hydrogen embrittlement risk
• Good fatigue resistance
• Electrical conductivity approximately 85% IACS

Typical Industrial Applications

• Heat exchangers
• Pressure vessels
• Marine piping systems
• Condensers
• HVAC systems
• Chemical process equipment
• Offshore installations

38. Material Comparison Table

Property	Copper C110 (ETP)	Copper C122 (DHP)
UNS Number	C11000	C12200
Copper Content	≥99.90%	≥99.90%
Electrical Conductivity	~100% IACS	~85% IACS
Thermal Conductivity	Excellent	Excellent
Weldability	Fair to Good	Excellent
Hydrogen Embrittlement Resistance	Moderate	Excellent
Corrosion Resistance	Excellent	Excellent
Machinability	Moderate	Moderate
Relative Cost	Moderate	Moderate to Slightly Higher
Typical Applications	Electrical Components	Fabricated & Welded Equipment

39. Mechanical Properties

Mechanical properties vary depending on temper (annealed, half-hard, hard, or cold-worked). Typical values for annealed material are shown below.

Property	Copper C110	Copper C122
Ultimate Tensile Strength	220–250 MPa	220–250 MPa
Yield Strength (0.2%)	70–100 MPa	70–100 MPa
Elongation	40–50%	40–50%
Hardness	45–65 HV	45–65 HV
Density	8.89 g/cm³	8.94 g/cm³
Elastic Modulus	117 GPa	117 GPa
Poisson’s Ratio	0.34	0.34
Melting Range	1083–1085°C	1083–1085°C

Note: Values vary according to product form and temper.

40. Material Selection Criteria

Selection of the appropriate copper alloy should be based on engineering analysis rather than cost alone.

Selection Factors

• Required electrical conductivity
• Mechanical loading
• Thermal cycling
• Operating temperature
• Exposure to corrosive media
• Fabrication process (welding, brazing, machining)
• Galvanic compatibility
• Inspection requirements
• Project specifications
• Life-cycle maintenance

Selection Guide

Requirement	Recommended Material
Maximum electrical conductivity	Copper C110
Welding-intensive fabrication	Copper C122
Busbars and switchgear	Copper C110
Heat exchangers	Copper C122
Marine piping	Copper C122
Grounding systems	Copper C110
Electrical terminals	Copper C110
Chemical processing equipment	Copper C122

41. Service Temperature Capability

Copper alloys maintain useful mechanical properties over a broad operating temperature range.

Temperature Range	Engineering Assessment
-196°C to -50°C	Excellent toughness retained
-50°C to 150°C	Excellent mechanical stability
150°C to 250°C	Suitable for continuous service
250°C to 400°C	Strength reduction should be evaluated
Above 400°C	Significant reduction in mechanical properties; engineering review required

42. Corrosion Resistance by Environment

Copper develops a stable oxide or patina layer that protects the underlying metal in many atmospheric environments.

Service Environment	Copper C110	Copper C122
Indoor Atmosphere	Excellent	Excellent
Outdoor Atmosphere	Excellent	Excellent
Fresh Water	Excellent	Excellent
Seawater	Good	Very Good
Marine Atmosphere	Excellent	Excellent
Humid Environment	Excellent	Excellent
Dilute Alkalis	Excellent	Excellent
Dilute Organic Acids	Good	Good
Oxidizing Acids	Fair	Fair
Reducing Acids	Limited	Limited
Hydrogen Sulfide (H₂S)	Fair (evaluate for service)	Good (evaluate for service)

For severe sour service, material selection should be verified against applicable project specifications and NACE requirements.

43. Heat Treatment Processes

Unlike alloy steel fasteners, copper fasteners are generally not hardened by conventional quench-and-temper heat treatment. Their properties are primarily controlled through cold working and annealing.

43.1 Annealing

Annealing restores ductility by relieving internal stresses after cold forming.

Objectives

• Improve ductility
• Reduce hardness
• Enhance formability
• Remove residual stresses
• Improve dimensional stability

Typical annealing temperature:

400–650°C, depending on alloy, section thickness, and required temper.

43.2 Stress Relieving

Stress relieving may be performed after machining or cold working to reduce residual stresses without significantly affecting mechanical properties.

Benefits include:

• Reduced distortion
• Improved dimensional stability
• Lower residual stress
• Enhanced fatigue performance

43.3 Cold Working

Cold drawing, rolling, or heading increases strength through strain hardening.

Advantages:

• Higher tensile strength
• Improved yield strength
• Better thread wear resistance
• Enhanced dimensional accuracy

Trade-offs:

• Reduced ductility
• Increased forming forces
• Potential need for intermediate annealing

44. End-to-End Manufacturing Workflow

At SM Fasteners, copper fasteners are produced through a controlled manufacturing process integrated with an ISO 9001-certified quality management system, ensuring full traceability, dimensional accuracy, and compliance with customer specifications.

Manufacturing Sequence

1. Customer specification review
2. Engineering drawing verification
3. Raw material procurement
4. Material Test Certificate (MTC) verification
5. Positive Material Identification (PMI), where required
6. Incoming dimensional inspection
7. Cutting of raw material
8. Cold heading or hot forging (depending on size)
9. Trimming and piercing
10. CNC machining (if applicable)
11. Thread rolling or thread cutting
12. Deburring
13. Intermediate dimensional inspection
14. Cleaning
15. Heat treatment/annealing (if specified)
16. Surface finishing
17. Final dimensional inspection
18. Mechanical testing
19. Packaging
20. Documentation and dispatch

45. Forging vs. Machining

Cold Forging

Advantages

• Improved grain flow
• Higher production efficiency
• Better fatigue strength
• Reduced material waste
• Excellent dimensional repeatability

Preferred for:

• Standard bolts
• Hex head bolts
• Nuts
• Screws

CNC Machining

Preferred where:

• Complex geometries are required
• Small production quantities
• Tight tolerances
• Prototype development
• Custom fasteners

46. Thread Manufacturing

Thread Rolling

Thread rolling forms threads by plastic deformation without removing material.

Benefits

• Increased fatigue strength
• Improved surface finish
• Better grain continuity
• Higher productivity
• Greater thread strength

Thread Cutting

Threads are generated by machining.

Preferred for:

• Large diameters
• Short production runs
• Special thread forms
• Repair work
• Custom components

47. Quality Assurance During Manufacturing

Quality control is integrated throughout production rather than limited to final inspection.

Typical in-process inspections include:

• Raw material verification
• Forging inspection
• Head dimension checks
• Thread profile verification
• Length inspection
• Surface defect inspection
• Hardness verification (where applicable)
• Visual examination
• Final dimensional inspection

48. Surface Finishing

Copper fasteners may be supplied with different surface conditions depending on the application.

Surface Finish	Characteristics	Typical Applications
Mill Finish	Natural copper surface	Electrical assemblies
Bright Finish	Improved appearance and conductivity	Architectural, switchgear
Polished	Low surface roughness	Decorative and precision components
Pickled & Cleaned	Removes oxide scale	Process equipment
Passivated (where specified for assemblies)	Improved cleanliness	Specialized industrial use

49. Protective Coatings

Although copper has inherent corrosion resistance, certain applications require additional protective treatments.

Coating / Treatment	Benefits	Typical Service
Clear Lacquer	Prevents tarnishing	Architectural components
Wax Coating	Temporary storage protection	Export packaging
Oil Film	Corrosion protection during transport	Industrial supply
Anti-Seize Compound	Prevents galling and facilitates maintenance	High-temperature joints
Conductive Grease	Reduces contact resistance	Electrical busbar assemblies

50. Surface Finish Comparison

Finish	Corrosion Resistance	Electrical Conductivity	Appearance	Maintenance
Mill Finish	Excellent	Excellent	Natural	Low
Bright Finish	Excellent	Excellent	High gloss	Moderate
Polished	Excellent	Excellent	Decorative	Moderate
Lacquered	Very Good	Reduced at coated interface	Excellent	Low
Wax Protected	Good (storage)	Unaffected after removal	Industrial	Temporary

51. Special Engineering Considerations

For specialized applications, additional design measures may include:

• Use of anti-seize lubricants to prevent thread galling.
• Insulating washers or sleeves to minimize galvanic corrosion with dissimilar metals.
• Controlled torque application to prevent over-compression of soft copper joints.
• Selection of fine-pitch threads where higher preload accuracy is required.
• Integration of Belleville washers in joints subjected to vibration or thermal cycling.

For assemblies requiring electrical insulation instead of conductivity, SM Fasteners also manufactures PEEK fasteners, offering excellent chemical resistance, high-temperature capability, and dielectric properties for instrumentation, semiconductor equipment, and corrosive process industries.

52. Inspection and Quality Control

Copper fasteners intended for industrial applications require systematic inspection throughout the manufacturing process to ensure dimensional accuracy, mechanical integrity, material conformity, and complete traceability. Inspection activities should comply with documented quality procedures integrated within an ISO 9001-certified Quality Management System, as implemented by SM Fasteners.

Inspection is generally divided into:

• Incoming raw material inspection
• In-process manufacturing inspection
• Final dimensional verification
• Mechanical and material testing
• Documentation review
• Packaging and dispatch inspection

Each stage contributes to product conformity and supports reliable performance in EPC, oil & gas, power generation, marine, and infrastructure projects.

53. Incoming Material Verification

Before production begins, each raw material batch is verified against purchase specifications and applicable standards.

Typical verification includes:

• Material Test Certificate (MTC) review
• Heat number verification
• Chemical composition confirmation
• Visual inspection
• Dimensional inspection of bars or wire
• Positive Material Identification (PMI), when specified
• Traceability marking

Acceptance criteria are established before releasing material for production.

54. In-Process Quality Control

Quality checks are performed throughout manufacturing to detect deviations before final inspection.

Typical checkpoints include:

• Forging dimensions
• Head geometry
• Thread rolling quality
• CNC machining accuracy
• Thread pitch verification
• Surface finish inspection
• Burr removal
• Straightness
• Concentricity
• Identification marking

Inspection frequency depends on production volume, customer specifications, and criticality of the application.

55. Final Dimensional Inspection

Each production lot is inspected using calibrated measuring instruments.

Typical inspection parameters:

• Nominal diameter
• Major diameter
• Minor diameter
• Pitch diameter
• Thread pitch
• Thread length
• Overall length
• Across flats
• Head height
• Bearing surface
• Surface finish
• Straightness
• Chamfer dimensions

Common measuring equipment includes:

• Digital vernier calipers
• Micrometers
• Height gauges
• Thread plug gauges
• Thread ring gauges
• GO/NO-GO gauges
• Optical comparators
• Coordinate Measuring Machine (CMM) for critical components

56. Mechanical Testing

Mechanical testing verifies that fasteners meet specified performance requirements.

Typical Tests

• Tensile strength
• Yield strength
• Elongation
• Hardness
• Proof load (where applicable)
• Thread stripping resistance
• Load testing for custom components

Testing is generally performed in accordance with relevant ASTM or ISO test methods, depending on project requirements.

57. Positive Material Identification (PMI)

PMI confirms alloy identity without damaging the component.

Common methods include:

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

PMI is frequently required for:

• Oil & Gas
• LNG
• Offshore platforms
• Petrochemical plants
• Nuclear projects
• Export EPC contracts

58. Non-Destructive Testing (NDT)

Where specified by the purchaser, NDT techniques may be applied to finished fasteners or forged blanks.

Typical methods include:

NDT Method	Purpose
Visual Inspection (VT)	Surface defects and workmanship
Dye Penetrant Testing (PT)	Surface-breaking cracks
Ultrasonic Testing (UT)*	Internal discontinuities in large sections
Eddy Current Testing (ECT)	Surface and near-surface defects in conductive materials

*UT is generally used for larger custom-forged components rather than small standard fasteners.

59. Documentation and Traceability

Complete documentation supports procurement audits and ensures full traceability from raw material to finished product.

Typical documentation supplied by SM Fasteners includes:

• Material Test Certificate (MTC)
• Heat Number Traceability
• Dimensional Inspection Report
• Mechanical Test Report
• Chemical Analysis Report
• PMI Report (if specified)
• Surface Finish Report (if applicable)
• Certificate of Conformity (CoC)
• Packing List
• Commercial Invoice
• Country of Origin Certificate (when required)
• EN 10204 Type 3.1 Certification
• EN 10204 Type 3.2 Certification (on request with third-party witnessing)

60. Proof Load & Tensile Strength Table (Typical Reference Values)

Copper fasteners do not use ISO property classes such as 8.8 or 10.9. Values below are indicative and depend on temper, product form, and manufacturing process.

Size	Approx. Proof Load (kN)	Approx. Ultimate Tensile Load (kN)
M6	3.5	5.0
M8	6.5	9.5
M10	10.5	15.5
M12	15.5	23.0
M16	28.0	42.0
M20	44.0	66.0
M24	63.0	95.0

Engineering calculations should always be verified against the certified mechanical properties of the supplied material.

61. Tightening Torque Chart (Typical Guidance)

Torque values are approximate for clean threads and should be validated for the specific joint design, lubrication condition, and required preload.

Thread Size	Dry Threads (Nm)	Lubricated Threads (Nm)
M6	5	4
M8	12	10
M10	24	20
M12	42	35
M16	105	88
M20	205	170
M24	355	295

62. Preload Calculation

The preload generated during tightening can be estimated using the torque–tension relationship:$$F=\frac{T}{K\times D}$$

Where:

• F = Preload (N)
• T = Tightening torque (Nm)
• K = Nut factor (typically 0.18–0.22)
• D = Nominal bolt diameter (m)

Worked Example

For an M12 Copper C110 bolt:

• Torque = 42 Nm
• Nut Factor = 0.20
• Diameter = 0.012 m

$$F=\frac{42}{0.20\times0.012}=17,500\text{ N}$$F=0.20×0.01242​=17,500 N

Estimated preload = 17.5 kN

Actual preload depends on thread condition, lubrication, washer type, and tightening method.

63. Weight Chart (Approximate)

Typical values for standard hex bolts manufactured by SM Fasteners. Actual weights vary with thread length, tolerances, and head geometry.

Bolt Size × Length	Approx. Weight / Piece (g)	Approx. Weight / 100 Pieces (kg)
M6 × 25	10	1.0
M8 × 30	22	2.2
M10 × 40	44	4.4
M12 × 50	76	7.6
M16 × 60	160	16.0
M20 × 80	310	31.0
M24 × 100	560	56.0

For commercial supply, SM Fasteners can provide project-specific weight schedules aligned with customer drawings and packing requirements.

64. Failure Analysis and Preventive Measures

Failure Mode	Primary Cause	Recommended Preventive Measure
Thread Stripping	Excessive tightening	Controlled torque and adequate engagement
Tensile Failure	Overloading	Correct bolt sizing and load analysis
Shear Failure	Improper joint design	Use locating features and increase frictional clamp load
Fatigue Cracking	Cyclic loading	Maintain correct preload and avoid stress concentrations
Fretting Corrosion	Joint movement	Increase clamp force and improve surface condition
Galvanic Corrosion	Dissimilar metals	Use insulating washers or compatible materials
Stress Relaxation	Elevated temperature	Re-evaluate preload and use spring washers where appropriate

65. Industrial Applications

Construction & Structural Steel

Copper fasteners are specified where corrosion resistance and electrical continuity are required.

Typical uses include:

• Architectural copper cladding
• Lightning protection systems
• Structural grounding
• Expansion joints

Oil & Gas

Applications include:

• Electrical earthing systems
• Instrumentation grounding
• Cable tray supports
• Control panels
• Hazardous area electrical equipment

Material compatibility should be evaluated against project specifications and applicable NACE requirements for sour service.

Petrochemical & Chemical Processing

Typical applications:

• Heat exchangers
• Process equipment
• Copper piping systems
• Electrical distribution
• Instrumentation

Power Generation

Copper fasteners are widely used in:

• Transformers
• Switchgear
• Busbar assemblies
• Generator terminals
• Renewable energy systems
• Substations

LNG & Offshore

Applications include:

• Marine electrical systems
• Offshore platforms
• Grounding networks
• Corrosion-resistant electrical connections

Automotive & Heavy Equipment

Typical uses:

• Battery terminals
• Electrical harnesses
• High-current connectors
• Specialized conductive assemblies

Railways & Infrastructure

Copper fasteners support:

• Signaling systems
• Traction power equipment
• Earthing installations
• Electrical cabinets

Shipbuilding

Marine applications include:

• Navigation equipment
• Electrical switchboards
• Communication systems
• Copper piping supports
• Grounding assemblies

PEEK Fastener Applications

Where electrical insulation, chemical resistance, or weight reduction is required, SM Fasteners also manufactures PEEK fasteners for:

• Semiconductor equipment
• Chemical processing plants
• Medical devices
• Laboratory systems
• Aerospace interiors
• High-purity instrumentation
• Electrically isolated assemblies

66. Export Packaging

Industrial packaging is designed to preserve product quality throughout transportation and storage.

Typical packaging methods include:

• VCI (Volatile Corrosion Inhibitor) bags
• Heat-sealed polyethylene packaging
• Moisture-barrier bags
• Thread protection caps
• Bubble wrapping for machined components
• Heavy-duty corrugated cartons
• Palletized shipments
• Wooden export crates compliant with ISPM-15
• Container moisture protection using desiccants where required

Each package is identified with:

• Product description
• Material grade
• Heat number
• Quantity
• Purchase Order reference
• Batch number
• Manufacturing date (where specified)

67. Export Documentation

For international EPC and industrial projects, SM Fasteners can provide documentation including:

• Commercial Invoice
• Packing List
• Bill of Lading / Air Waybill
• Material Test Certificate (MTC)
• EN 10204 Type 3.1 or 3.2 Certification
• Chemical Analysis Report
• Mechanical Test Report
• Dimensional Inspection Report
• PMI Report (when specified)
• Certificate of Conformity (CoC)
• Country of Origin Certificate
• Fumigation Certificate for wooden packaging (ISPM-15)
• Third-Party Inspection Reports (TÜV, SGS, BV, DNV or customer-approved agencies, where contractually required)

68. Engineering Summary

Copper C110 (ETP) and C122 (DHP) fasteners provide an optimal combination of corrosion resistance, thermal conductivity, and electrical performance for demanding industrial applications.

• Copper C110 (ETP) is preferred where maximum electrical conductivity is essential, including busbars, grounding systems, switchgear, and power distribution equipment.
• Copper C122 (DHP) is selected for welded or brazed assemblies, heat exchangers, marine systems, and process equipment where resistance to hydrogen embrittlement and superior fabrication characteristics are required.