Hastelloy Grades C-276 / C-22 / B-2

1. Introduction to Hastelloy Fasteners

Hastelloy is a family of high-performance nickel-molybdenum and nickel-chromium-molybdenum alloys developed for severe corrosion environments where conventional stainless steels, duplex grades, and many nickel alloys experience rapid degradation.

For critical bolted joints operating in:

• Sulfuric acid systems
• Hydrochloric acid processing
• Chlorine handling plants
• Offshore platforms
• Sour gas facilities
• Petrochemical reactors
• Flue gas desulfurization units
• Pharmaceutical processing equipment
• LNG terminals

Hastelloy fasteners provide superior corrosion resistance, metallurgical stability, and mechanical reliability.

SM Fasteners manufactures precision-engineered Hastelloy fasteners under ISO 9001 quality systems, supported by MSME and UKAF-certified processes, supplying EPC contractors, OEMs, and industrial maintenance projects worldwide.

2. Major Hastelloy Grades Used for Fasteners

Grade	UNS Number	Principal Alloy System	Primary Strength
Hastelloy C-276	N10276	Ni-Cr-Mo-W	Universal corrosion resistance
Hastelloy C-22	N06022	Ni-Cr-Mo-W	Superior oxidizing resistance
Hastelloy B-2	N10665	Ni-Mo	Hydrochloric acid resistance
Hastelloy B-3	N10675	Ni-Mo	Improved thermal stability

These alloys are selected primarily based on corrosion performance rather than strength alone.

3. Industrial Importance of Hastelloy Fasteners

Fasteners often become the weakest component in highly corrosive assemblies.

Failure modes include:

• Thread pitting
• Crevice corrosion
• Chloride attack
• Stress corrosion cracking
• Galvanic corrosion
• Acid-induced metal loss

Hastelloy fasteners eliminate these risks in applications where equipment life can exceed 20–30 years.

Typical industries include:

Industry	Requirement
Offshore Oil & Gas	Chloride resistance
Chemical Processing	Acid resistance
LNG	Cryogenic reliability
Power Generation	Corrosion protection
Pharmaceutical	Contamination resistance
Marine	Saltwater durability
Desalination	Chloride attack prevention
Fertilizer Plants	Acid service capability

4. Technical Definition of Hastelloy Fasteners

A Hastelloy fastener is a threaded mechanical component manufactured from nickel-based corrosion-resistant alloys and used to create detachable mechanical joints while maintaining structural integrity under:

• High loads
• Elevated temperatures
• Corrosive chemicals
• Seawater exposure
• Sour gas environments

Products include:

• Hex bolts
• Heavy hex bolts
• Socket screws
• Stud bolts
• Threaded rods
• Hex nuts
• Heavy hex nuts
• Lock nuts
• Flat washers
• Spring washers
• Structural fasteners
• Custom-machined fasteners

5. Functional Role in Mechanical Assemblies

A bolted joint converts tightening torque into clamping force.

The fastener functions as a tension member.

The joint members function as compressed elements.

When preload exceeds service loads:

• Joint separation is prevented
• Leakage is minimized
• Vibration loosening is reduced
• Fatigue life increases

6. Load Mechanics of Hastelloy Fasteners

Tensile Loading

Occurs when forces attempt to pull the joint apart.

Examples:

• Pressure vessel flanges
• Heat exchangers
• Reactor closures

Formula:$$\sigma=\frac{F}{A}$$

Where:

Symbol	Definition
σ	Tensile stress
F	Applied load
A	Tensile stress area

Shear Loading

Occurs when forces act perpendicular to bolt axis.

Examples:

• Structural supports
• Pipe clamps
• Equipment frames

Formula:$$\tau=\frac{F}{A}$$

Where:

τ = Shear stress

Combined Loading

Industrial joints commonly experience:

• Tensile load
• Shear load
• Thermal load
• Vibration load

Design must account for simultaneous stress conditions.

7. Clamping Force Principles

The most important function of a fastener is preload generation.

Relationship:$$F_{clamp}= \frac{T}{K \times D}$$

Where:

Parameter	Meaning
Fclamp	Clamping force
T	Tightening torque
K	Nut factor
D	Nominal diameter

Typical Nut Factor Values

Condition	K Value
Dry Threads	0.20–0.25
Lubricated Threads	0.15–0.18
PTFE Coated	0.10–0.14
Moly Lubricated	0.08–0.12

Because Hastelloy is prone to galling, lubrication is strongly recommended.

8. Torque-Tension Relationship

Only a small percentage of tightening torque becomes useful preload.

Torque Consumption	Percentage
Under-head friction	50%
Thread friction	40%
Useful preload	10%

This is why controlled lubrication is essential.

9. Thread Engagement Principles

Minimum thread engagement depends upon:

• Material strength
• Load direction
• Corrosion allowance

General recommendation:

Material Combination	Engagement
Same Alloy	1 × Diameter
Dissimilar Metals	1.25 × Diameter
Soft Materials	1.5 × Diameter

10. Joint Stiffness Considerations

Joint performance depends on:

Bolt Stiffness

$$K_b=\frac{AE}{L}$$

Joint Stiffness

$$K_j=\frac{AE_j}{L_j}$$

Where:

• A = Area
• E = Modulus
• L = Length

A properly designed joint transfers external load through elastic deformation.

11. Load Distribution Along Threads

Thread loading is not uniform.

Approximate distribution:

Thread	Load Share
1st Thread	34%
2nd Thread	23%
3rd Thread	16%
4th Thread	11%
Remaining Threads	16%

Therefore thread quality and tolerances are critical.

12. Fatigue Behavior of Hastelloy Fasteners

Fatigue occurs under cyclic loading.

Common sources:

• Rotating equipment
• Pumps
• Compressors
• Offshore structures
• Wind loading

Factors improving fatigue life:

• High preload
• Rolled threads
• Smooth surface finish
• Proper alignment
• Corrosion protection

13. Failure Mechanisms

Fatigue Failure

Characteristics:

• Progressive crack growth
• Sudden fracture

Causes:

• Under-tightening
• Vibration
• Stress concentration

Thread Stripping

Caused by:

• Insufficient engagement
• Excess torque
• Material mismatch

Galling

Especially important for nickel alloys.

Occurs due to:

• Metal transfer
• Adhesive wear
• High friction

Mitigation:

• Silver plating
• PTFE coating
• Moly lubricant
• Controlled installation speed

Stress Corrosion Cracking

A significant concern for stainless steels.

Hastelloy C-276 and C-22 exhibit exceptional SCC resistance.

Pitting Corrosion

Localized attack causing deep penetration.

Excellent resistance:

• C-22
• C-276

Moderate resistance:

• B-2
• B-3

Crevice Corrosion

Develops beneath:

• Washers
• Gaskets
• Deposits

C-22 offers industry-leading resistance.

14. Thermal Expansion Considerations

Nickel alloys expand more than carbon steel.

Approximate coefficient:

Material	µm/m°C
Carbon Steel	12
Stainless Steel	17
Hastelloy C-276	12.4
Hastelloy C-22	13.1

Designers must account for differential expansion.

15. High-Temperature Performance

Grade	Maximum Continuous Service
C-276	1040°C
C-22	1250°C
B-2	900°C
B-3	925°C

Actual fastener design temperature depends upon stress level and environment.

16. Cryogenic Performance

Hastelloy alloys maintain toughness at:

• LNG temperatures
• Liquid nitrogen temperatures
• Cryogenic process systems

No ductile-to-brittle transition occurs as in carbon steel.

17. Joint Design Principles for EPC Projects

Engineers should evaluate:

Mechanical Requirements

• Tensile load
• Shear load
• Fatigue load

Environmental Requirements

• Acid exposure
• Chlorides
• Sour gas
• Elevated temperature

Inspection Requirements

• PMI verification
• NDT acceptance
• Traceability

Lifecycle Cost

Although Hastelloy has a higher acquisition cost, lifecycle cost is often lower due to:

• Reduced maintenance
• Longer service life
• Fewer shutdowns

18. Fastener Selection Methodology

Step-by-step approach:

Step	Evaluation Criteria
1	Service environment
2	Corrosion mechanism
3	Design load
4	Temperature
5	Applicable code
6	Inspection requirements
7	Certification requirements
8	Traceability requirements

19. Typical EPC Procurement Requirements

Procurement specifications commonly require:

• ASTM-compliant materials
• EN 10204 3.1 certification
• Heat number traceability
• PMI testing
• Mechanical test reports
• Dimensional inspection reports

SM Fasteners manufactures Hastelloy fasteners with full material traceability and inspection documentation suitable for global EPC and industrial projects.

20. Engineering Summary

Hastelloy C-276, C-22, B-2, and B-3 fasteners are critical components for severe corrosion service where stainless steel, duplex, and conventional alloys cannot provide adequate reliability.

Their engineering value derives from:

• Exceptional corrosion resistance
• Strong preload retention
• Excellent fatigue performance
• Resistance to stress corrosion cracking
• High-temperature capability
• Long-term lifecycle reliability

In complex industrial assemblies, proper preload management, thread engagement, material compatibility, and corrosion-resistant design principles are essential for achieving safe, leak-free, and maintenance-efficient bolted joints.

21. Product Types and Variants of Hastelloy Fasteners

Hastelloy fasteners are manufactured in a wide range of configurations to satisfy structural, pressure-containing, corrosive-process, offshore, power generation, and heavy engineering applications.

Selection depends upon:

• Applied load direction
• Joint accessibility
• Assembly method
• Corrosion environment
• Inspection requirements
• Maintenance frequency
• Applicable design code

SM Fasteners manufactures standard and custom Hastelloy fasteners in accordance with international standards and project-specific EPC requirements.

22. Hex Head Bolts

Hex head bolts are the most widely used Hastelloy fasteners.

Characteristics

• Six-sided external drive
• Full-thread or partial-thread construction
• Suitable for high preload applications
• Easy field installation

Typical Applications

• Pressure vessels
• Heat exchangers
• Offshore skids
• Chemical reactors
• Structural supports

Standard References

Standard	Description
ISO 4014	Hex bolts partially threaded
ISO 4017	Hex bolts fully threaded
DIN 931	Partially threaded hex bolts
DIN 933	Fully threaded hex bolts
ASTM F468	Non-ferrous bolts
ASME B18.2.1	Inch series hex bolts

23. Heavy Hex Bolt

Heavy hex bolts possess larger head dimensions than standard hex bolts.

Advantages

• Higher wrenching strength
• Improved load distribution
• Better gasket compression
• Preferred for pressure-containing joints

Typical Industries

• Oil & Gas
• LNG
• Refineries
• Petrochemical plants

Governing Standards

Standard	Description
ASME B18.2.1	Heavy hex bolts
ASTM A193	High-performance stud and bolt materials
ASTM F468	Nickel alloy bolts

24. Stud Bolt

Stud bolts are threaded on both ends or fully threaded throughout.

Benefits

• Uniform preload distribution
• Easier maintenance
• Reduced flange damage
• Preferred for critical pressure joints

Applications

• ASME B16.5 flanges
• B16.47 flanges
• Heat exchangers
• Pressure vessels

Applicable Standards

Standard	Description
ASTM A193	Alloy stud bolts
ASME B16.5	Flanged joints
ASME PCC-1	Bolted flange assembly

25. Threaded Rods

Threaded rods provide continuous threading along the entire length.

Typical Uses

• Pipe supports
• Structural anchoring
• Hangers
• Equipment mounting

Available Thread Forms

• Metric Coarse
• Metric Fine
• UNC
• UNF
• BSW
• BSF

26. Socket Head Cap Screws

Used where space limitations prevent hex head installation.

Characteristics

• Cylindrical head
• Internal hex drive
• High preload capability
• Precision assembly applications

Standards

Standard	Description
ISO 4762	Metric socket screws
DIN 912	Socket head cap screws
ASME B18.3	Inch socket screws

27. Set Screws

Used primarily for positioning and locking functions.

Common Drive Types

• Hex socket
• Slotted
• Torx

Point Styles

• Cone point
• Flat point
• Dog point
• Cup point

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28. Hex Nuts

Hex nuts provide mating threads for bolt assemblies.

Types

• Standard Hex Nut
• Heavy Hex Nut
• Jam Nut
• Lock Nut

Standards

Standard	Description
ISO 4032	Standard hex nuts
DIN 934	Hex nuts
ASTM F467	Non-ferrous nuts
ASME B18.2.2	Inch series nuts

29. Heavy Hex Nuts

Heavy hex nuts are preferred in:

• Pressure vessels
• Flanges
• Structural joints
• High-load assemblies

Advantages include:

• Greater bearing area
• Improved thread engagement
• Higher preload capability

30. Lock Nuts

Designed to resist vibration-induced loosening.

Types

Type	Function
Prevailing Torque	Friction locking
Nylon Insert	Mechanical retention
All-Metal Lock Nut	High temperature locking
Serrated Flange Nut	Surface grip

For severe temperatures, all-metal lock nuts are preferred.

31. Flat Washers

Flat washers distribute compressive loads.

Functions

• Prevent surface damage
• Reduce embedment
• Improve preload consistency

Standards

Standard	Description
ISO 7089	Plain washers
DIN 125	Flat washers
ASTM F436	Hardened washers

32. Spring Lock Washers

Provide resistance against loosening caused by vibration.

Common Types

• Helical spring washer
• Split lock washer

Used where dynamic loads are present.

33. Belleville Washers

Disc spring washers capable of generating high spring force.

Applications include:

• Thermal expansion compensation
• Vibration resistance
• High-temperature equipment

34. Structural Fasteners

Designed for structural steel connections.

Requirements

• Controlled preload
• Dimensional accuracy
• Traceability

Industries:

• Bridges
• Industrial structures
• Offshore platforms

35. Custom Machined Hastelloy Fasteners

SM Fasteners manufactures engineered specials including:

• Collar bolts
• Shoulder bolts
• Special studs
• Flange bolts
• Eye bolts
• Foundation bolts
• Anchor bolts
• Reactor fasteners

Custom designs are produced from approved engineering drawings and project specifications.

36. Dimensional Logic of Fasteners

Fastener geometry directly affects:

• Load capacity
• Fatigue resistance
• Joint reliability
• Installation torque

Key dimensions include:

Parameter	Symbol
Diameter	d
Pitch	P
Head Width	s
Head Height	k
Thread Length	b
Overall Length	L

37. Metric Thread Geometry

Metric threads follow ISO profile standards.

Thread Angle

$$60^\circ$$

Designation Example

M20 × 2.5 × 100

Where:

Parameter	Meaning
M	Metric thread
20	Nominal diameter
2.5	Pitch
100	Length

38. Unified Thread Geometry

Used extensively in North America.

UNC

Unified National Coarse

UNF

Unified National Fine

Thread angle:$$60^\circ$$

39. Whitworth Thread Geometry

Widely encountered in legacy British installations.

Thread Angle

$$55^\circ$$

Standards:

• BSW
• BSF

40. Standard Metric Hex Bolt Dimensions

ISO 4014 / ISO 4017

Size	Pitch (mm)	Head Width (mm)	Head Height (mm)
M6	1.0	10	4
M8	1.25	13	5.3
M10	1.5	16	6.4
M12	1.75	18	7.5
M16	2.0	24	10
M20	2.5	30	12.5
M24	3.0	36	15
M30	3.5	46	18.7
M36	4.0	55	22.5

41. Standard Length Ranges

Diameter	Typical Length Range
M6	10–150 mm
M8	12–200 mm
M10	16–300 mm
M12	20–400 mm
M16	25–500 mm
M20	30–600 mm
M24	40–800 mm
M30	50–1000 mm
M36	60–1200 mm

42. Thread Standards and Tolerances

Metric Threads

Standard	Tolerance Class
ISO 965	6g / 6H
ISO 261	Metric series
ISO 262	Preferred pitches

Unified Threads

Standard	Tolerance
ASME B1.1	2A / 2B
ASME B1.1	3A / 3B

British Threads

Standard	Thread Type
BS 84	BSW
BS 84	BSF

43. Thread Standards Comparison Table

Standard	Thread Angle	Application
Metric ISO	60°	Global industrial use
UNC	60°	North America
UNF	60°	High preload joints
BSW	55°	Legacy equipment
BSF	55°	Fine thread systems

44. Coarse vs Fine Thread Selection

Feature	Coarse Thread	Fine Thread
Assembly Speed	Faster	Slower
Damage Resistance	Better	Moderate
Tensile Stress Area	Lower	Higher
Vibration Resistance	Moderate	Better
Adjustment Accuracy	Lower	Higher

Fine threads are commonly selected for:

• Pressure-containing equipment
• High vibration systems
• Precision assemblies

45. Thread Engagement Chart

Diameter	Recommended Minimum Engagement
M6	6 mm
M8	8 mm
M10	10 mm
M12	12 mm
M16	16 mm
M20	20 mm
M24	24 mm
M30	30 mm

46. International Standards Governing Hastelloy Fasteners

Material Standards

Standard	Scope
ASTM B574	Hastelloy fasteners
ASTM B335	Hastelloy bars
ASTM B574 UNS N10276	C-276 fasteners
ASTM B574 UNS N06022	C-22 fasteners
ASTM B574 UNS N10665	B-2 fasteners
ASTM B574 UNS N10675	B-3 fasteners

47. Fastener Manufacturing Standards

Standard	Scope
ASTM F468	Non-ferrous bolts
ASTM F467	Non-ferrous nuts
ISO 898 (Reference)	Mechanical property framework
ASME B18 Series	Dimensional requirements

48. Pressure Equipment Standards

Standard	Application
ASME BPVC Section VIII	Pressure vessels
ASME PCC-1	Flange assembly
API 6A	Wellhead equipment
API 17D	Offshore systems
API 20E	Alloy bolting
API 20F	Nickel alloy bolting

49. NACE Compliance Considerations

For sour service:

Applicable standards:

• NACE MR0175
• ISO 15156

Evaluation includes:

• Hardness control
• Environmental compatibility
• Sulfide stress cracking resistance

Material acceptance depends on project requirements.

50. Dimensional and Standards Summary

Proper fastener selection requires evaluation of:

• Diameter
• Thread form
• Pitch
• Length
• Head geometry
• Applicable ASTM standards
• ISO dimensional requirements
• API compliance requirements
• NACE requirements
• Installation accessibility

For EPC, offshore, LNG, petrochemical, and process-industry projects, dimensional compliance and standards conformance are equally important as corrosion resistance.

SM Fasteners manufactures Hastelloy C-276, C-22, B-2, and B-3 fasteners in metric and imperial dimensions, including custom-engineered configurations, with full traceability and inspection documentation aligned with international project specifications.

51. Materials Engineering of Hastelloy Fasteners

Hastelloy alloys belong to the family of nickel-based corrosion-resistant alloys (CRAs) specifically engineered for aggressive chemical environments where stainless steel, duplex stainless steel, and many conventional nickel alloys experience rapid deterioration.

The selection of Hastelloy fasteners should be based on:

• Corrosion mechanism
• Process chemistry
• Operating temperature
• Pressure conditions
• Mechanical load requirements
• Maintenance intervals
• Regulatory compliance requirements

For critical EPC projects, material selection must consider total lifecycle performance rather than initial acquisition cost.

52. Chemical Composition of Hastelloy Grades

Hastelloy C-276 (UNS N10276)

Element	Typical %
Nickel	Balance
Chromium	14.5–16.5
Molybdenum	15.0–17.0
Iron	4.0–7.0
Tungsten	3.0–4.5
Cobalt	≤2.5
Carbon	≤0.01

Key Characteristics

• Excellent overall corrosion resistance
• Outstanding pitting resistance
• Superior crevice corrosion resistance
• Excellent chloride resistance
• Broadest industrial applicability

Hastelloy C-22 (UNS N06022)

Element	Typical %
Nickel	Balance
Chromium	20–22.5
Molybdenum	12.5–14.5
Iron	2–6
Tungsten	2.5–3.5
Carbon	≤0.015

Key Characteristics

• Highest resistance to oxidizing environments
• Superior wet chlorine resistance
• Excellent mixed acid resistance
• Exceptional crevice corrosion resistance

Hastelloy B-2 (UNS N10665)

Element	Typical %
Nickel	Balance
Molybdenum	26–30
Iron	≤2
Chromium	≤1
Carbon	≤0.02

Key Characteristics

• Outstanding hydrochloric acid resistance
• Excellent reducing acid performance
• Poor oxidizing acid resistance

Hastelloy B-3 (UNS N10675)

Element	Typical %
Nickel	Balance
Molybdenum	27–32
Iron	1–3
Chromium	1–3
Carbon	≤0.01

Key Characteristics

• Improved thermal stability
• Better fabrication characteristics
• Improved resistance to stress corrosion cracking
• Enhanced weld heat affected zone stability

53. Material Selection Criteria

Selection should be based on service environment.

Decision Matrix

Environment	Recommended Grade
Hydrochloric Acid	B-2, B-3
Sulfuric Acid	C-276
Nitric Acid	C-22
Chlorine Gas	C-22
Seawater	C-276
Sour Gas Service	C-276
Flue Gas Desulfurization	C-276
Mixed Acid Processing	C-22
Pharmaceutical Processing	C-22
Offshore Equipment	C-276

54. Material Comparison Table

Hastelloy Grade Comparison

Property	C-276	C-22	B-2	B-3
UTS (MPa)	690	690	760	760
Yield Strength (MPa)	283	310	350	350
Elongation (%)	40	45	40	45
Pitting Resistance	Excellent	Excellent+	Moderate	Moderate
Chloride Resistance	Excellent	Excellent	Good	Good
Hydrochloric Acid Resistance	Very Good	Good	Excellent	Excellent
Oxidizing Acids	Excellent	Outstanding	Poor	Poor
Fabrication Ease	Good	Good	Moderate	Better
Relative Cost	High	High	High	High

55. Corrosion Resistance Comparison

Corrosion Resistance vs Environment

Environment	C-276	C-22	B-2	B-3
Seawater	Excellent	Excellent	Good	Good
Chlorides	Excellent	Excellent	Moderate	Moderate
Hydrochloric Acid	Very Good	Good	Excellent	Excellent
Sulfuric Acid	Excellent	Excellent	Good	Good
Nitric Acid	Good	Excellent	Poor	Poor
Wet Chlorine	Excellent	Outstanding	Poor	Poor
H₂S	Excellent	Excellent	Good	Good
Acetic Acid	Excellent	Excellent	Very Good	Very Good
Phosphoric Acid	Excellent	Excellent	Good	Good

56. Mechanical Properties Table

Room Temperature Mechanical Properties

Grade	Tensile Strength MPa	Yield Strength MPa	Hardness HRB
C-276	690	283	100 Max
C-22	690	310	100 Max
B-2	760	350	100 Max
B-3	760	350	100 Max

57. Temperature Capability Table

Grade	Continuous Service Temperature
C-276	1040°C
C-22	1250°C
B-2	900°C
B-3	925°C

Actual fastener design limits must consider creep, stress relaxation, and joint preload retention.

58. NACE MR0175 / ISO 15156 Considerations

For sour service applications:

Engineers must evaluate:

• Sulfide stress cracking resistance
• Hardness limits
• Process chemistry
• Partial pressure of H₂S

Typical requirements include:

• Controlled hardness
• Material traceability
• Chemical verification
• Mechanical testing

SM Fasteners can provide material traceability documentation supporting project-specific NACE requirements.

59. Heat Treatment Objectives

Heat treatment is performed to:

• Restore corrosion resistance
• Remove residual stresses
• Dissolve harmful precipitates
• Improve metallurgical uniformity

Unlike carbon steel fasteners, Hastelloy grades are not strengthened primarily through quench and temper processes.

Strength is mainly derived from alloy chemistry and controlled processing.

60. Solution Annealing Process

The most important heat treatment for Hastelloy alloys.

Objectives

• Dissolve secondary phases
• Restore corrosion resistance
• Improve ductility
• Improve microstructural uniformity

Typical Process

Grade	Temperature Range
C-276	1120–1175°C
C-22	1120–1175°C
B-2	1065–1095°C
B-3	1065–1100°C

Followed by:

• Rapid water quenching
• Accelerated cooling

61. Stress Relief Treatment

Applied when required after machining or fabrication.

Purpose

• Reduce residual stresses
• Improve dimensional stability

Improper stress relief may reduce corrosion resistance and should only be performed under controlled procedures.

62. Metallurgical Risks During Heat Treatment

Improper thermal exposure may result in:

Sigma Phase Formation

Effects:

• Reduced ductility
• Reduced corrosion resistance

Carbide Precipitation

Effects:

• Localized corrosion susceptibility
• Intergranular attack

Grain Growth

Effects:

• Reduced mechanical properties

Proper furnace control is essential.

63. Raw Material Verification

Manufacturing begins with certified raw material.

Verification includes:

• Heat number confirmation
• Chemical analysis
• Material grade validation
• Dimensional inspection

Required documentation:

• Mill Test Certificate (MTC)
• EN 10204 3.1 certification

64. End-to-End Manufacturing Workflow

Manufacturing Flow

Raw Material Receipt

↓

Material Verification

↓

Cutting

↓

Hot Forging / Machining

↓

Heat Treatment

↓

Descaling

↓

Thread Manufacturing

↓

Dimensional Inspection

↓

PMI Verification

↓

Mechanical Testing

↓

Surface Finishing

↓

Final Inspection

↓

Packaging

↓

Dispatch

65. Hot Forging Process

Hot forging is preferred for larger fasteners.

Advantages

• Refined grain structure
• Improved fatigue performance
• Higher mechanical integrity
• Reduced internal discontinuities

Typical products:

• Hex bolts
• Heavy hex bolts
• Stud bolts
• Nuts

66. Precision Machining Operations

CNC machining is utilized for:

• Custom fasteners
• Special geometry components
• Tight tolerance products

Operations include:

• Turning
• Milling
• Drilling
• Boring
• Slotting
• Thread generation

67. Thread Rolling vs Thread Cutting

Thread Rolling

Advantages:

• Improved fatigue strength
• Compressive surface stresses
• Superior surface finish

Recommended for standard production.

Thread Cutting

Advantages:

• Suitable for large diameters
• Suitable for special threads
• Useful for low production quantities

Comparison Table

Feature	Rolled Threads	Cut Threads
Fatigue Resistance	Higher	Lower
Surface Finish	Better	Moderate
Production Speed	Faster	Slower
Tooling Cost	Higher	Lower
Thread Strength	Higher	Lower

68. Manufacturing Traceability

Each batch should maintain traceability through:

• Heat numbers
• Production lot numbers
• Inspection records
• Material certificates

Traceability is essential for:

• Oil & Gas projects
• LNG facilities
• Offshore platforms
• Nuclear-adjacent applications

69. Surface Finishing Requirements

Nickel alloys typically do not require protective coatings for corrosion resistance.

However surface finishing improves:

• Appearance
• Cleanliness
• Installation performance
• Galling resistance

70. Common Surface Finishes

Finish Type	Purpose
As Manufactured	Standard industrial use
Pickled	Oxide removal
Passivated	Surface cleaning
Electropolished	Reduced contamination
Mechanical Polished	Improved appearance

71. Pickling Process

Purpose:

• Oxide removal
• Heat tint removal
• Surface cleaning

Benefits:

• Improved corrosion resistance
• Better inspection visibility

72. Electropolishing

Used in:

• Pharmaceutical plants
• Food processing
• Semiconductor facilities

Advantages:

• Smooth surface finish
• Reduced bacterial retention
• Enhanced cleanability

73. Anti-Galling Coatings

Nickel alloys are susceptible to galling during assembly.

Recommended solutions include:

PTFE Coating

Advantages:

• Lower friction
• Improved installation

Silver Plating

Advantages:

• Excellent anti-seize properties
• High-temperature capability

Molybdenum Disulfide

Advantages:

• Reduced friction coefficient
• Improved preload consistency

74. Surface Finish Comparison Table

Surface Finish	Corrosion Resistance	Galling Resistance	Cost
As Manufactured	Good	Moderate	Low
Pickled	Better	Moderate	Low
Passivated	Better	Moderate	Low
Electropolished	Excellent	Good	High
PTFE Coated	Excellent	Excellent	Medium
Silver Plated	Excellent	Outstanding	High

75. Coating Performance Comparison

Coating	Friction Reduction	Temperature Capability	Typical Application
PTFE	Excellent	Moderate	Chemical plants
Silver Plating	Excellent	High	High-temperature bolting
MoS₂	Excellent	High	Pressure vessels
Dry Film Lubricant	Good	Moderate	Offshore systems

76. Galvanic Compatibility Considerations

When Hastelloy fasteners are installed with:

• Carbon steel
• Stainless steel
• Aluminum
• Copper alloys

Engineers must evaluate galvanic potential.

Mitigation methods:

• Isolation washers
• Non-metallic sleeves
• PEEK washers
• Insulating bushings

77. PEEK Fasteners and Isolation Components

SM Fasteners also manufactures PEEK fasteners and engineered polymer isolation components.

Applications include:

• Electrical isolation
• Galvanic corrosion prevention
• Semiconductor systems
• Chemical processing equipment

PEEK components are often combined with Hastelloy assemblies to improve long-term reliability.

78. Manufacturing and Material Selection Summary

The performance of Hastelloy C-276, C-22, B-2, and B-3 fasteners depends on:

• Correct alloy selection
• Controlled heat treatment
• Certified raw material sourcing
• Precision manufacturing
• Proper thread generation
• Traceable quality systems
• Appropriate surface finish selection

Through ISO 9001-certified manufacturing processes, material traceability controls, precision forging, machining, inspection, and custom engineering capabilities, SM Fasteners supports EPC contractors, OEMs, offshore operators, petrochemical facilities, and industrial maintenance organizations requiring high-performance Hastelloy fastening solutions for severe service environments.