A2-70 stainless steel hex head bolts are manufactured from 304 austenitic stainless steel and rated to property class A2-70, delivering a minimum tensile strength of 700 MPa and a minimum 0.2% proof stress of 450 MPa. Unlike carbon steel fasteners, A2-70 bolts require no plating or coating — the inherent chromium oxide passive film provides excellent resistance to atmospheric corrosion, fresh water, and a wide range of chemical media, making them suitable for outdoor, humid, and mildly corrosive environments. The bolts are fully threaded to DIN 933 / ISO 4017 / GB 5783 and available in M8 and M16 as highlighted sizes, with a complete range from M4 to M36 on request. Key Specifications Parameter Specification Material 304 stainless steel (A2, equivalent to 1.4301) Property Class A2-70 Standard DIN 933 / ISO 4017 / GB 5783 Thread Metric coarse (M), full thread Surface Finish Plain / passivated (natural stainless steel finish) Thread Diameter M4 – M36 (M8, M16 in stock) Length Range 6 mm – 600 mm Head Type Hexagon head Product Grade A Mechanical Properties (ISO 3506-1 / EN ISO 3506) Property Value Minimum Tensile Strength (Rm) 700 MPa Minimum 0.2% Proof Stress (Rp0.2) 450 MPa Minimum Elongation After Fracture (A) 0.4d Material Condition Cold drawn bar The designation "A2-70" follows the ISO 3506-1 naming system: "A" denotes austenitic stainless steel, "2" indicates the corrosion resistance group (A2 corresponds to grade 304), and "70" represents one-tenth of the minimum tensile strength in MPa (700 MPa). Property class 70 fasteners are typically manufactured from cold drawn bar, which imparts the necessary strength through work hardening without the need for quenching and tempering. Material & Corrosion Resistance Type 304 (A2) stainless steel contains approximately 18% chromium and 8% nickel, forming a stable austenitic structure that resists oxidation and corrosion across a broad temperature range. Key characteristics include: Excellent atmospheric corrosion resistance — suitable for outdoor, coastal (non-splash zone), and humid environments Resistance to fresh water and mild chemicals — effective against organic acids, dyes, and many food-grade media Non-magnetic in the annealed condition — cold working may induce slight magnetism (relative permeability μr ≈ 1.8) No hydrogen embrittlement risk — no electroplating required, eliminating the dehydrogenation step necessary for coated high-strength carbon steel bolts For more aggressive environments involving chlorides, seawater immersion, or strong acids, A4 (316) stainless steel is recommended as an alternative. Standards & Compliance These bolts conform to DIN 933 (German standard for fully threaded hexagon head screws), ISO 4017 (international equivalent, product grades A and B), and GB/T 5783 (Chinese national standard for fully threaded hex head bolts). The dimensional interchangeability across these standards allows the bolts to be used in international equipment and assemblies without modification. The A2-70 marking is stamped on the bolt head for identification and traceability. Surface Finish The standard finish is plain / passivated — the natural, bright appearance of stainless steel after pickling and passivation treatment. This finish offers the maximum corrosion resistance inherent to the 304 alloy, as it preserves the chromium-rich passive layer on the surface. No additional coating is applied, meaning there is no risk of coating damage, chipping, or hydrogen embrittlement. For applications requiring specific aesthetics or additional lubricity, options such as shot blasting or PTFE coating may be available upon request. Applications A2-70 stainless steel hex bolts are specified where corrosion resistance and clean appearance are priorities: Food and beverage processing equipment Pharmaceutical and medical device manufacturing Chemical and petrochemical plant piping and vessels Water treatment and desalination systems Marine and offshore structures (above-deck and splash-zone with A4 upgrade) Architectural and building facade fastening Solar and photovoltaic mounting systems Electrical and telecommunications enclosures Available Sizes (Select Examples) Thread (M) Common Length Range Pitch (mm) Hex Across-Flats (s) M8 10 – 200 mm 1.25 13 mm M10 10 – 300 mm 1.5 16 mm M12 12 – 500 mm 1.75 18 mm M16 20 – 600 mm 2.0 24 mm M20 25 – 600 mm 2.5 30 mm Full range available from M4 through M36, with lengths up to 600 mm. M8 and M16 are held in ready stock for immediate shipment.