Flange Nuts ASTM A194 2H

Flange Nuts ASTM A194 2H — Heavy Hex Nuts for High-Temperature Service | M12–M72

ASTM A194 2H heavy hex nuts are quenched and tempered carbon steel nuts designed for use with ASTM A193 B7 stud bolts in high-temperature flange applications. These heavy hex nuts exceed standard hex nut dimensions, providing greater wrenching surface and higher load capacity. Compliant with ASME B18.2.2 heavy hex nut dimensional specifications.

Material & Specifications

Size Range	M12 to M72 / 1/2″ to 4″
Standard	ASTM A194 Grade 2H, ASME SA194 2H, ASME B18.2.2 (heavy hex)
Material	Carbon Steel — Quenched & Tempered
Surface / Coating	Plain/Black (standard), Hot-Dip Galvanized, Dacromet
Hardness	159-302 HBW (35 HRC max)
Style	Heavy hex (oversized hex flats for high-torque applications)

Surface Treatment & Zinc Coating Quality

At BoltNutsPlus, we understand that surface treatment is critical to fastener longevity and performance. Our products undergo rigorous coating processes to ensure maximum corrosion resistance and durability. We offer five premium coating options, each tested to international standards:

• Hot-Dip Galvanizing (HDG) — Thick zinc layer (50-120μm) providing superior long-term corrosion protection for outdoor, marine, and industrial environments. Compliant with ISO 1461 / ASTM A153 standards. Salt spray resistance: 500-1,000+ hours. Ideal for structural steel assemblies exposed to harsh weather.
• Electroplated Zinc Blue-White (Zn Blue/White) — Bright, clean silver-blue appearance with 5-15μm zinc layer. Cr3+ passivation technology, fully RoHS compliant. Ideal for indoor machinery, electronics, and general-purpose applications requiring aesthetic appeal and moderate corrosion resistance.
• Color Zinc / Yellow Zinc (Iridescent Passivation) — Multi-colored iridescent passivation film offering enhanced corrosion resistance (100-200 hours salt spray) with a distinctive golden finish. Widely preferred in automotive, agricultural equipment, and construction machinery sectors for its balanced protection and visual appeal.
• Dacromet Coating — Advanced water-based zinc-chromium coating technology with NO hydrogen embrittlement risk. Provides 1,000+ hours salt spray resistance, making it the preferred choice for high-strength fasteners in extreme environments. Environmentally friendly (no heavy metal discharge), RoHS/ELV compliant, ideal for automotive and wind energy applications.
• Multi-Element Alloy Co-Permeation — Zinc-aluminum-rare earth alloy layer offering 2-3x the corrosion resistance of traditional galvanizing. Features self-healing properties at scratch points, ensuring long-term protection even in damaged areas. Ideal for critical infrastructure, power transmission towers, coastal projects, and marine installations.

Key Features

• Quenched and tempered carbon steel for high-temperature service
• Heavy hex pattern provides 1.5x standard hex nut wrenching surface
• Designed for pairing with ASTM A193 B7 stud bolts
• Full thread engagement with chamfered top face for easy nut starting
• Galvanized option available for atmospheric corrosion protection
• Full material certification per ASTM A194 requirements

Applications

• Matching nuts for ASTM A193 B7 flange stud bolt assemblies
• High-temperature pressure vessel and piping flange connections
• Oil & gas refinery flange bolting
• Power plant boiler and steam system connections
• Petrochemical plant process piping
• Any high-temperature flange application requiring heavy hex nuts

Why Choose BoltNutsPlus?

• ISO 9001:2015 Certified Manufacturing — consistent quality you can trust on every batch
• 15+ Years of Export Experience — serving 40+ countries across 6 continents
• Full Traceability — material certificates (EN 10204 3.1) and comprehensive test reports included
• Custom Packaging & OEM/ODM — your brand identity, your specifications, our precision manufacturing
• Third-Party SGS / Bureau Veritas Inspection Available upon request
• 24-Hour Quote Response — same-day reply for urgent requirements; standard 24-hour turnaround