ASTM A194 Grade 4 Heavy Hex Nuts Chemical Composition

While the ASTM A193 B16 specification covers bolts and stud material, the correct companion Fasteners used with B16 bolting are typically ASTM A194 Grade 4 Heavy Hex Nuts. Grade 4 is a high-strength, chromium-molybdenum alloy steel specifically heat-treated to maintain its mechanical properties under the same extremely high-temperature and high-pressure conditions as B16. These Heavy Hex Nuts are thicker and wider than standard nuts, providing a larger bearing surface and superior strength, which is essential for resisting loosening and stress relaxation (creep) in critical flange connections in power plants, refineries, and steam lines. Zeron Fasteners manufactures these Grade 4 nuts, ensuring their dimensions, threading, and chemical composition are perfectly matched for use with B16 stud bolts to form a stable, high-integrity, creep-resistant bolted joint assembly.

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ASTM A194 Grade 4 Heavy Hex Nuts Chemical Composition

Element Composition (% by Mass)
Carbon (C) 0.40 - 0.50
Manganese (Mn) 0.50 - 1.00
Phosphorus (P) ≤ 0.035
Sulfur (S) ≤ 0.040
Silicon (Si) 0.15 - 0.35
Chromium (Cr) 0.80 - 1.10
Molybdenum (Mo) 0.15 - 0.25

ASTM A194 Grade 4 Heavy Hex Nuts Mechanical Properties

Property Minimum Requirement (Grade 4)
Proof Load Stress (up to 1-1/2") 175 ksi (1205 MPa)
Hardness, min (Brinell) 248 HBW
Hardness, max (Brinell) 327 HBW
Hardness, min (Rockwell) 24 HRC
Hardness, max (Rockwell) 35 HRC

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