A4-50 Hex Head Bolt

A4-50 Hex Head Bolt About

An A4-50 hex head bolt is a marine-grade metric fastener manufactured from 316-grade austenitic stainless steel that is in a soft, annealed state, providing an ultimate tensile strength of 500 MPa (N/mm). The "A4" designation signifies its premium chemical compositionalloyed with molybdenum to resist severe chloride, acid, and pitting corrosionwhile the "50" indicates its low-to-medium strength class. This bolt features a classic six-sided hexagonal head engineered for stable, high-slippage-resistant wrenching in environments where survival against aggressive elements is prioritized over high structural loading.

Technical Specifications

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

• Mechanical Strength Class: Class 50 (soft/annealed state).

• Minimum Tensile Strength: 500 MPa / 500 N/mm.

• 0.2% Proof Stress: 210 N/mm.

• Magnetic Signature: Fully non-magnetic under standard and heavily cold-worked conditions due to stable austenite structure.

• Standard Conformity: Produced under ISO 3506-1 standards, usually adapting to DIN 933 (fully threaded) or DIN 931 (partially threaded) sizing.

• Thread Type: Standard metric coarse or optional fine threads.

Key Features & Product Benefits

• Premium Chloride Resistance: Molybdenum content prevents pitting and crevice corrosion caused by saltwater, brine, spray, and industrial chemicals.

• Excellent Ductility: Because it is annealed, the bolt possesses high elongation properties, allowing it to bend slightly under extreme shock loads rather than snapping cleanly.

• Anti-Galling Properties: The lower hardness of Class 50 helps mitigate the thread-locking "galling" common with higher-torque stainless alloys.

• Cryogenic & High Heat Stability: Retains physical integrity and impact toughness in freezing environments as well as elevated operational temperatures.

Primary Applications

• Marine Infrastructure: Ideal for dock hardware, boat deck fittings, coastal architectural projects, and submarine housings where salt spray is constant.

• Chemical & Pharmaceutical Plants: Used to secure valves, stirrers, pumps, and pipe flanges handling harsh organic acids, chlorides, and solvents.

• Water Treatment Facilities: Assembly of underwater pumps, filtration tanks, and sluice gates exposed to chlorinated water.

• Food Processing & Beverage: Highly sanitary installations where aggressive sanitizing agents or acidic food products (like citrus juices or dairy) break down lesser steels.