ASTM A453 Grade 660 Stud Bolts Hex nuts Specification

ASTM A453 Grade 660 Stud Bolts & Hex Nuts Specification

ASTM A453 Grade 660 stud bolts and hex nuts are high-strength, precipitation-hardened alloy steel fasteners specifically designed for high-temperature and high-pressure applications. Grade 660 fasteners offer excellent creep resistance, stress rupture strength, and oxidation resistance, making them ideal for critical bolting connections in severe service environments.

Manufactured in accordance with ASTM A453 / ASME SA453, Grade 660 stud bolts and nuts are widely used in power generation, petrochemical plants, refineries, pressure vessels, turbines, and heat exchangers.

What Is ASTM A453 Grade 660?

ASTM A453 Grade 660 is a nickel-chromium-iron based alloy steel, equivalent to UNS S66286 (A-286 type alloy).
It is engineered to maintain stable mechanical properties under prolonged exposure to elevated temperatures.

Key advantages:

  • High tensile and yield strength at elevated temperatures

  • Excellent creep and stress-rupture resistance

  • Good corrosion and oxidation resistance

  • Reliable performance in cyclic thermal conditions

ASTM A453 Grade 660 Chemical Composition

Element Content (%)
Nickel (Ni) 24.0 – 27.0
Chromium (Cr) 13.5 – 16.0
Molybdenum (Mo) 1.0 – 1.75
Titanium (Ti) 1.90 – 2.35
Aluminum (Al) ≤ 0.35
Carbon (C) ≤ 0.08
Manganese (Mn) ≤ 2.00
Silicon (Si) ≤ 1.00
Phosphorus (P) ≤ 0.025
Sulfur (S) ≤ 0.025
Iron (Fe) Balance

Mechanical Properties – Grade A / B / C / D Comparison

Grade Tensile Strength Yield Strength (0.2%) Elongation
Grade A ≥ 130 ksi (895 MPa) ≥ 85 ksi (585 MPa) ≥ 15%
Grade B ≥ 140 ksi (965 MPa) ≥ 95 ksi (655 MPa) ≥ 12%
Grade C ≥ 150 ksi (1035 MPa) ≥ 105 ksi (725 MPa) ≥ 10%
Grade D ≥ 160 ksi (1105 MPa) ≥ 115 ksi (795 MPa) ≥ 8%

Higher grades provide increased strength for more demanding high-temperature applications.

Heat Treatment Requirements

All ASTM A453 Grade 660 stud bolts and hex nuts are:

  • Solution heat treated

  • Precipitation hardened (aged)

  • Heat treated strictly in accordance with ASTM A453 requirements

This ensures consistent mechanical performance and long-term service reliability.

Testing & Inspection Requirements

Mandatory Tests

  • Tensile test

  • Yield strength test

  • Elongation & reduction of area

  • Hardness test

  • Chemical composition analysis

  • Dimensional inspection

Optional Tests (Upon Request)

  • PMI (Positive Material Identification)

  • Stress rupture test

  • Creep test

  • Ultrasonic testing (UT)

Certification

  • EN 10204 3.1 Mill Test Certificate

  • Full heat number traceability

Product Range

  • Stud Bolts: 1/4″ – 4″ diameter

  • Hex Nuts: Heavy hex nuts compatible with Grade 660

  • Thread Type: UNC / UNF / Metric

  • Surface Finish: Plain,PTEF coated

  • Customization: Length, threading, packaging available

Typical Applications

ASTM A453 Grade 660 stud bolts and hex nuts are commonly used in:

  • Power generation plants

  • Oil & gas refineries

  • Petrochemical equipment

  • Boilers and pressure vessels

  • Gas and steam turbines

  • High-temperature flanged joints

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