The Comprehensive Guide to ASTM A193 Fasteners

ASTM A193 is a critical standard in the world of industrial fasteners. Understanding this specification is essential whether engineering a high-temperature pressure vessel or assembling components for a refinery. In this post, we'll break down what ASTM A193 covers, who it's for, and why it's a cornerstone for engineers and procurement specialists.

What is ASTM A193?

ASTM A193 is a specification developed by ASTM International that covers alloy and stainless steel bolting materials. These fasteners are primarily designed for high-temperature or high-pressure service, or other special-purpose applications.

The standard applies to bolts, studs, threaded rods, and other externally threaded components used in pressure vessels, valves, flanges, and fittings.

Key Properties of ASTM A193 Fasteners

• Material Types: Alloy and stainless steel

• Strength: High tensile and yield strength for demanding applications

• Temperature Resistance: Suitable for high-temperature service

• Corrosion Resistance: Especially in stainless variants like B8 and B8M

• Heat Treatment: Many grades require heat treatment to meet mechanical property thresholds

Grades and Classifications

ASTM A193 includes several grades, each with distinct material properties and applications:

• Grade B7

  • Material: Chromium-Molybdenum Steel

  • Use: General high-temperature and pressure service

  • Notes: The most commonly used grade in industrial settings

• Grade B8

  • Material: Stainless Steel (Class 1 & Class 2)

  • Use: Corrosive environments, including food processing and pharmaceuticals

  • Notes: Class 1 is annealed; Class 2 is strain-hardened for added strength

• Grade B8M

  • Material: Stainless Steel with Molybdenum (Class 1 & Class 2)

  • Use: Marine, chemical, and corrosive environments

  • Notes: Offers better corrosion resistance than B8

• Grade B16

  • Material: Chromium-Molybdenum-Vanadium Steel

  • Use: High-stress, high-temperature applications

  • Notes: Higher tensile strength than B7, used in power and petrochemical industries

Common Applications

• Pressure vessels

• Flanges and fittings

• Heat exchangers

• Petrochemical and power plants

• Refineries and pipeline systems

Benefits of Using ASTM A193 Fasteners

• Proven durability under extreme pressure and temperature

• Compatibility with a wide range of industrial systems

• Availability in diverse grades and classes

• Backed by strict ASTM compliance and traceability

How to Select the Right ASTM A193 Grade

Choosing the correct grade depends on:

• Environmental conditions: temperature, moisture, chemicals

• Load requirements and design specifications

• Compatibility with nuts (typically ASTM A194)

• Consultation with engineering teams and supplier recommendations

ASTM A193 Compared to Other Standards

• ASTM A320: Similar structure, but designed for low-temperature service

• ASTM A354: Another high-strength option, with different material and treatment

• ASTM A194: Commonly paired with A193 for nuts

Frequently Asked Questions

Q1: What distinguishes B7 from B16 fasteners in ASTM A193?
B7 is more commonly used, but B16 offers higher tensile strength for more demanding environments.

Q2: Can A193 bolts be hot-dip galvanized?
Yes, but galvanization may affect thread fit and must be considered carefully.

Q3: What’s the difference between Class 1 and 2 in A193 B8?
Class 1 is annealed stainless steel, while Class 2 is strain-hardened for greater strength.

Q4: Are ASTM A193 fasteners available in metric sizes?
They are primarily imperial, but metric sizes can be custom-fabricated.

Need High-Performance Fasteners? Trust ASTM A193

When strength, reliability, and high-temperature resistance matter, ASTM A193 fasteners deliver. With multiple grades tailored to specific industrial challenges, they remain a trusted choice in critical environments. Explore California Fastener’s full inventory of ASTM A193-compliant fasteners or contact our team to find the right solution for your next project.