A4-80 Hex Head Bolt

A4-80 Hex Head Bolt About

An A4-80 hex head bolt is an ultra-high-strength, marine-grade metric fastener manufactured from 316-grade (18/10/2) austenitic stainless steel that has undergone heavy cold-working to achieve a minimum tensile strength of 800 MPa (N/mm). The "A4" designation signifies its premium, acid-proof chemical compositionalloyed with molybdenum to withstand highly corrosive chloride, salt, and chemical environmentswhile the "80" denotes its highest standard mechanical strength tier. Featuring a six-sided external drive head designed for maximum torque transmission, this heavy-duty fastener matches the tensile strength of Grade 8.8 high-tensile carbon steel bolts while offering elite protection against environmental degradation.

Technical Specifications

• Material Composition: Grade 316 Stainless Steel (typically 16-18% Chromium, 10-14% Nickel, and 2-3% Molybdenum).

• Mechanical Strength Class: Class 80 (heavily cold-worked).

• Minimum Tensile Strength: 800 MPa / 800 N/mm (equivalent to high-tensile Class 8.8 carbon steel).

• 0.2% Proof Stress: 600 N/mm.

• Magnetic Profile: Faintly magnetic under strict testing due to intense cold-work grain transformation, but retains standard austenite characteristics.

• Standard Conformity: Fully certified to ISO 3506-1 guidelines, conforming to dimensional standards like DIN 933 (full thread) or DIN 931 (partial thread).

• Thread Options: Available in standard coarse metric profiles and specialized fine thread pitches.

Key Features & Product Benefits

• Maximum Structural Strength: Delivers up to 60% higher load-bearing capacity than A4-50 bolts and 14% higher than A4-70 bolts, accommodating high-tension engineering designs.

• Elite Corrosion & Pitting Defence: Molybdenum stops pitting, crevice erosion, and stress corrosion cracking triggered by constant exposure to saltwater, marine mist, and industrial acids.

• No Cam-Out Slippage: Robust hexagonal design pairs perfectly with impact sockets or spanners, preventing head stripping during heavy wrenching.

• Temperature Versatility: Maintains exceptional mechanical stability in deep sub-zero cryogenic setups and resists thermal oxidation up to 800C.

Primary Applications

• Subsea & Offshore Engineering: Critical load-bearing structures on deep-sea drilling platforms, underwater pipelines, boat hulls, and wave energy converters.

• Heavy Chemical & Petrochemical Refining: Assembled inside high-pressure reactors, acid storage vessels, and chemical process piping where failure is not an option.

• Desalination & Marine Infrastructure: Securing tidal gates, harbour structural beams, high-capacity water pumps, and chlorine processing machinery.

• Specialized Aerospace & Defence: Utilized in harsh outdoor military equipment, marine electronics enclosures, and structural cleanroom frames demanding both high strength and clean sanitization.