Bolt Knowledge Map: Grades, Materials, Heads & Threads

The bolt knowledge map is reproduced on the left and converted below from its original tree into the same heading order. Product families, individual fasteners and industry applications are linked where a matching page already exists.

1. General Metric Fasteners

Stainless Steel

Austenitic Stainless Steel

A2 Stainless Steel

Characteristics: good general corrosion resistance, good formability and a widely used stainless fastener grade. Browse the stainless-steel and duplex fastener category.

A2-50

Strength: minimum tensile-strength class of 500 MPa. Typical use: light-duty stainless assemblies.

Plain — Performance: natural stainless surface, basic corrosion resistance and economical supply. Environment: indoor, dry and low-corrosion areas. Applications: furniture, light assemblies and general equipment.

Pickling — Performance: removes oxide scale and improves surface cleanliness and appearance. Applications: industrial equipment and stainless fabrication.

Pickling + Passivation — Performance: supports a stable passive film, improved corrosion reliability and a clean surface condition. Applications: food equipment, clean industrial assemblies and other contamination-sensitive service.

A2-70

Strength: minimum tensile-strength class of 700 MPa. Typical products include A2-70 stainless hex head bolts, stainless hex nuts and stainless threaded rods.

Plain — Performance: standard stainless surface and good general corrosion resistance. Environment: indoor, general outdoor and mildly humid service. Applications: machinery, equipment assembly and construction.

Pickling — Performance: removes manufacturing contamination and improves surface uniformity and cleanliness. Applications: industrial equipment, welded structures and stainless fabrication.

Pickling + Passivation — Performance: enhanced passive film, improved long-term corrosion resistance and higher surface reliability. Environment: outdoor, humid and food-processing service. Applications: food machinery, architectural work and industrial equipment.

A4 Stainless Steel

Characteristics: molybdenum-bearing stainless steel with better chloride resistance than common A2 grades. See the A2 vs A4 stainless fastener guide.

A4-70

Strength: minimum tensile-strength class of 700 MPa. Typical products include A4 stainless partial-thread hex bolts and A4 stainless socket head cap screws.

Plain — Performance: natural 316-type stainless surface with good corrosion resistance and standard marine-grade capability. Environment: coastal, humid outdoor and mild chemical service. Applications: marine equipment, outdoor structures and industrial equipment.

Pickling + Passivation — Performance: maximum surface cleanliness, stable passive film and improved corrosion reliability. Environment: marine, chemical and coastal service. Applications: shipbuilding, offshore equipment and chemical equipment. See the marine fastener application page.

A4-80

Strength: minimum tensile-strength class of 800 MPa. Products include A4-80 stainless flange bolts and A4-80 countersunk socket screws.

Plain — Performance: high-strength stainless fastener, strong corrosion resistance and high load capability. Applications: heavy stainless equipment and marine structures.

Pickling + Passivation — Performance: high strength, improved chloride resistance and long-service reliability. Environment: offshore, saltwater and severe corrosion. Applications: offshore wind, marine engineering and heavy industrial equipment.

Assembly warning: stainless steel threads are prone to galling. Use controlled tightening speed, compatible bolt/nut pairing and a verified lubricant or surface treatment.

Duplex Stainless Steel Bolts

Duplex 2205

Duplex 2205 hex head bolts combine higher strength than common 316 stainless with strong chloride and stress-corrosion-cracking resistance.

D6-80/100

Property class must be confirmed against the applicable ISO 3506 part, product type, diameter and material certificate.

Pickling + Passivation — Performance: higher strength, strong chloride resistance and good stress-corrosion-cracking resistance. Environment: offshore, chemical processing, desalination and marine service. Applications: offshore wind, oil and gas, marine engineering and chemical equipment.

Super Duplex 2507

Super duplex 2507 is selected for more severe chloride exposure and higher mechanical demand.

D8-80/110

Property class and material condition must be confirmed against the applicable product standard and certificate.

Pickling + Passivation — Performance: extreme corrosion resistance, excellent chloride resistance and excellent pitting resistance. Environment: deep sea, offshore platforms and severe chloride service. Applications: offshore oil and gas, marine structures and chemical-processing equipment.

Carbon and Alloy Steel Bolts

Carbon Steel

Low Carbon Steel

Property Class 4.8

Material: low- or medium-carbon steel. Strength: minimum tensile-strength class of 400 MPa.

Zinc Plated — Performance: basic corrosion protection and economical general-purpose fastening. Environment: indoor, dry and low-corrosion areas. Applications: furniture, light equipment and general assembly.

Black Oxide — Performance: decorative black appearance with limited corrosion protection. Environment: indoor and dry machinery. Applications: machine parts, tools and general components.

Medium Carbon Steel

Property Class 8.8

Material: medium-carbon steel or carbon-alloy steel. Strength: minimum tensile-strength class of 800 MPa. Available forms include 8.8 full-thread hex bolts.

Zinc Plated — Performance: standard, economical corrosion protection for general use. Environment: indoor industrial and mildly humid service. Applications: machinery, equipment assembly and general engineering.

Geomet / Dacromet — Performance: higher corrosion resistance with no electrolytic hydrogen-introduction step in the coating process. Environment: outdoor, automotive and humid service. Applications: automotive components, construction equipment and outdoor machinery.

High-Strength Alloy Steel

Carbon Steel / Alloy Steel

Property Class 10.9

Mechanical characteristics: high tensile and yield strength, strong preload capability and good fatigue resistance. Products include 10.9 partial-thread hex bolts, hex flange bolts and heavy structural bolts.

Geomet / Dacromet — Performance: high-strength protection, strong corrosion resistance and controlled friction options. Environment: automotive, outdoor equipment, vibration and humid conditions. Applications: automotive chassis, heavy machinery, wind-turbine equipment and construction machinery.

Hot-Dip Galvanized — Performance: thick zinc protection for long outdoor service. Environment: outdoor infrastructure, coastal areas and renewable energy. Applications: steel structures, solar mounting and outdoor machinery. Thread fit and compatible nuts must be specified.

Alloy Steel

Property Class 12.9

Material: high-alloy steel such as SCM435, 42CrMo or 40CrNiMo, depending on specification. Strength: minimum tensile-strength class of 1,200 MPa. A typical product is the 12.9 socket head cap screw.

Black Oxide — Performance: standard dark appearance with a low-friction surface and limited corrosion protection. Environment: indoor and controlled low-corrosion service. Applications: mold equipment, precision machinery and machine tools.

Special Coating — Performance: enhanced corrosion or wear resistance for special working conditions. Applications: high-performance machinery, racing equipment and special engineering.

2. ASTM / ASME Fasteners

High-Temperature and Pressure Fasteners

ASTM A193 / ASME SA193

ASTM A193 B7

Material: chromium-molybdenum alloy steel such as ASTM AISI 4140 or 4142. Characteristics: high tensile strength, high-temperature strength, good toughness and pressure-load capability. See ASTM A193 B7 stud bolts and matching ASTM A194 heavy hex nuts.

Plain / Black Oxide — Performance: standard industrial finish and high-temperature compatibility in controlled service. Applications: pressure vessels, pipeline flanges, refinery equipment and petrochemical plants.

Zinc / Protective Coating — Performance: improved corrosion protection and longer outdoor service. Environment: outdoor process equipment, humid environments and marine atmosphere. Applications: offshore platforms, chemical plants and outdoor pipeline systems. Coating acceptance must follow the project specification.

ASTM A193 B16

Material: chromium-molybdenum-vanadium steel. Characteristics: higher temperature capability than B7, improved creep resistance and better strength retention.

Plain Finish / Protective Coating — Performance: extreme-temperature resistance, high-pressure capability and long-term strength stability. Environment: steam systems, power generation, high-temperature pipelines and thermal equipment. Applications: power plants, boilers, petrochemical equipment and high-temperature flange connections. See the power-generation fastener application page.

Low-Temperature Service Fasteners

ASTM A320 / ASME SA320

ASTM A320 L7

Material: chromium-molybdenum alloy steel, quenched and tempered.

Plain Finish / Protective Coating — Performance: low-temperature toughness, impact resistance and reliable strength under specified cryogenic conditions. Environment: LNG equipment, cryogenic systems and low-temperature pipelines. Applications: LNG plants, gas-storage tanks, chemical plants and energy equipment.

Structural Steel Bolts

ASTM F3125 Grade A325

Material: medium-carbon alloy steel. Strength: high-strength structural bolting.

Plain / Hot-Dip Galvanized / Mechanically Galvanized — Performance: high preload capacity, structural load bearing and slip resistance when installed as a qualified assembly. Environment: outdoor steel structures, bridges and building construction. Applications: steel buildings, bridges, towers and heavy structures.

ASTM F3125 Grade A490

Material: heat-treated alloy steel. Strength: ultra-high-strength structural bolting. See ASTM structural bolts, ASTM A563 structural nuts and ASTM F436 hardened washers.

Plain Finish / Approved Protective Coating — Performance: higher strength than A325, high clamp force and strong fatigue resistance. Environment: heavy steel structures, bridges and infrastructure. Applications: long-span bridges, heavy buildings and industrial structures. Coating must comply with ASTM F3125 requirements. See the construction and infrastructure application page.

Anchor Bolts

ASTM F1554

Standard: ASTM F1554. Application: concrete foundation anchoring. Product page: ASTM F1554 anchor rods.

Grade 36

Material: carbon steel. Performance: standard anchor strength and general foundation use. Applications: light structures, equipment bases and general construction.

Grade 55

Material: carbon steel. Performance: higher yield strength, improved structural capacity and general engineering use. Applications: steel columns, equipment foundations and industrial buildings.

Grade 105

Material: high-strength carbon steel. Performance: high tensile capacity, heavy-load anchoring and structural reliability. Applications: heavy-machinery foundations, bridge supports and infrastructure.

3. Special-Alloy Fasteners

Nickel-Alloy Bolts

Browse the titanium and nickel-alloy fastener category.

Inconel 625 Fasteners

Material: nickel-chromium-molybdenum alloy UNS N06625. Characteristics: excellent corrosion resistance, high strength, chloride resistance, weldability and high-temperature capability. Products include Inconel 625 anchor bolts and nickel-alloy stud bolts.

Natural / Solution-Treated Finish

Performance: natural nickel-alloy protection, high corrosion resistance and standard industrial condition. Environment: marine, offshore, chemical processing, sour gas and high-corrosion service. Applications: offshore equipment, chemical plants, heat exchangers, pressure equipment and marine engineering.

Special Cleaning / Passivation

Performance: removes surface contamination and improves cleanliness for critical applications.

Inconel 718 Fasteners

Material: nickel-chromium alloy UNS N07718. Characteristics: very high tensile strength, excellent fatigue resistance, high-temperature strength and creep resistance.

Heat-Treated Finish

Performance: maximum mechanical strength, high-temperature stability and aerospace performance. Environment: aerospace, gas turbines, high temperature and extreme mechanical stress. Applications: aircraft engines, gas turbines, aerospace structures and high-performance equipment.

Special Coating

Performance: improved wear resistance and surface protection for special operating conditions.

Hastelloy C276 Fasteners

Material: nickel-molybdenum-chromium alloy UNS N10276. Characteristics: outstanding chemical-corrosion resistance, pitting resistance, crevice-corrosion resistance and resistance to strong acids.

Natural Finish / Special Cleaning

Environment: chemical processing, acids, chlorides and pollution-control equipment. Applications: chemical plants, scrubber systems, pollution-control equipment and pharmaceutical equipment.

Monel 400 Fasteners

Material: nickel-copper alloy UNS N04400. Characteristics: excellent seawater resistance, useful mechanical properties and non-sparking capability.

Natural Finish

Environment: marine, seawater and chemical service. Applications: marine equipment, pump components, valve components and offshore systems.

Titanium Bolts

Assembly warning: titanium is extremely prone to thread galling. Use anti-seize lubricant, compatible mating materials or an approved surface treatment.

Titanium Grade 2 Fasteners

Material: commercially pure titanium, ASTM B348 Grade 2. Characteristics: excellent corrosion resistance, low weight, ductility, non-magnetic behavior and strong marine performance.

Natural Titanium Finish

Performance: natural oxide protection, good corrosion resistance and standard titanium condition. Environment: marine, chemical, medical and saltwater service. Applications: marine equipment, heat exchangers, medical devices and chemical equipment.

Anodizing

Performance: improved surface protection, color identification and reduced galling risk.

Titanium Grade 5 (Ti-6Al-4V)

Material: titanium alloy referenced by ASTM F467 or ASTM B348 as applicable. Characteristics: very high strength-to-weight ratio, low weight, fatigue resistance, corrosion resistance and aerospace use. Products include Titanium Grade 5 hex bolts and titanium socket head cap screws.

Natural Finish

Performance: standard titanium protection and a lightweight fastening solution.

Anodizing

Performance: improved wear resistance, reduced galling and surface identification.

Special Coating

Performance: enhanced wear resistance and controlled friction for special aerospace requirements. Environment: aerospace, racing, marine, chemical and other high-performance systems. Applications: aircraft structures, aircraft-engine components, racing vehicles, marine equipment and medical devices. See the aerospace fastener application page.

4. Physical Forms and Heads

Head Styles

Hex Head

Most versatile head style, with high torque transmission and easy use with an external socket or wrench. Products: full-thread hex head bolts and partial-thread hex head bolts.

Socket Cap

Saves assembly space and can be recessed into counterbores for a clean finish. Product: socket head cap screws.

Countersunk / Flat

Finishes flush with the workpiece surface after installation and helps prevent interference with moving parts. Product: stainless countersunk socket screws.

Pan / Button Head

Commonly used for sheet-metal fastening and smooth, low-profile assemblies. Product: pan head screws.

Fastener Features

Flange

A built-in wide base under the head increases contact area, distributes clamping stress and may eliminate a separate flat washer when the joint design permits. Product: hex flange bolts.

5. Thread Systems

Metric Threads

ISO/DIN metric threads are denoted by M, such as M8 or M10.

M-Coarse

The default general-purpose metric thread profile, offering good assembly tolerance, fast engagement and broad availability. Common products include fully threaded rods and metric hex bolts.

M-Fine

Uses a smaller pitch and lead angle for applications involving thin walls, adjustment or specified fine-thread joint geometry. Fine pitch alone is not a complete vibration-locking solution.

Imperial Threads

ASME/ANSI inch threads are written in forms such as 1/4-20 or 3/8-16.

UNC — Unified National Coarse

The most widely used general-purpose imperial coarse-thread system.

UNF — Unified National Fine

Used where the design calls for a finer pitch, higher tensile-stress area or established fine-thread practice. See the Metric, UNC and UNF thread guide.

6. Anti-Loosening and Assembly Technology

Mechanical Methods

Nylon Insert Nuts (Nyloc)

The nylon ring deforms to generate prevailing friction. It is a common, economical locking method. Products: nylon insert lock nuts and stainless nylon insert lock nuts.

Wedge-Locking Washers

The cam geometry uses a tension-based locking effect and is intended for severe vibration environments. Product: wedge-locking washers.

Spring Washers

A traditional design. Its anti-loosening effect under severe dynamic loading is limited, so it should not replace verified preload control or a vibration-tested locking system. Product: spring washers.