Expansion Nut Black Oxide ASTM A325

Quenched & tempered high-strength material, excellent tensile and shear resistance;
Black oxide treatment avoids hydrogen embrittlement, protects mechanical performance;
Uniform force distribution by expansion design, easy installation, no pre-embedding required;
Precise thread, good fit with ASTM A325 bolts, stable locking against loosening;
Neat appearance, cost-effective compared with galvanized fasteners;
Manufactured in accordance with American fastener standards, MTR certificates available.

Integrated expansion sleeve structure, strong anchoring friction
Compact Fe₃O₄ protective film formed by black oxide for short-term rust prevention
Heat treatment optimizes microstructure, balanced strength and toughness
Standard UNC coarse thread with great interchangeability
Hexagonal structure, compatible with standard torque tools
Custom dimension & material support for project demands

Anchor for steel structure accessories, factory equipment fixing, pipe support installation, curtain wall fitting, bridge attachments and machine base anchoring. Suitable for dense base materials such as concrete, solid brick wall and granite. Mainly used for indoor dry environment, temporary steel structure and North American infrastructure projects.
Note: Hot-dip galvanized items are recommended for long-term outdoor corrosive conditions instead of black oxide finish.

Raw Material Inspection: Medium carbon alloy steel wire inspection & material analysis
Wire Pre-treatment: Pickling → Phosphating → Wire drawing to target diameter
Cold Heading: Cutting blanks, forming nut body and expansion sleeve
Tapping: Precision internal thread processing, 100% thread gauge inspection
Heat Treatment: Quenching + Tempering to stabilize mechanical properties
Surface Black Oxide: Degreasing → Rinsing → Alkaline Oxidation → Saponification → Anti-rust oil dipping
Finished Test: Dimension check, thread inspection, hardness test, expansion tension sampling test
Anti-rust packing & warehouse storage

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