316 - Stainless steel - Hexagon bolt

The Superiority of 316 Stainless Steel Hex Bolts

While standard stainless steel is rust-resistant, 316 stainless steel hexagon bolts take protection to the next level. The hexagonal head allows for heavy-duty tightening, making these bolts suitable for securing heavy machinery and infrastructure. When this mechanical utility is combined with the chemical properties of 316 steel, the result is a fastener capable of surviving in the harshest conditions without seizing or corroding, ensuring the longevity of the entire assembly.

Material Profile: Grade A4 (AISI 316)

Understanding the specific properties of A4 stainless steel helps in justifying its selection for critical projects. Our inventory primarily consists of cold-worked A4-70 bolts.

The Molybdenum Advantage

The defining characteristic of 316 stainless steel is the addition of 2-3% molybdenum. This element drastically improves the steel's resistance to "pitting"—a localized form of corrosion that creates small holes in the metal. This makes 316 hex bolts essential for applications involving salt water, de-icing salts, or brine solutions.

Mechanical Performance (Class 70)

Despite its enhanced corrosion resistance, our A4 hex bolts maintain robust mechanical strength. Rated as "A4-70", they offer a minimum tensile strength of 700 N/mm² and a yield strength of 450 N/mm². This ensures they provide the same load-bearing capacity as standard A2 bolts but with extended service life in aggressive environments.

Temperature Stability

316 stainless steel exhibits better strength at elevated temperatures compared to 304. This makes these hex bolts suitable for industrial applications where fluctuating heat and chemical exposure occur simultaneously.

Quality Certification and MTC

We guarantee the chemical composition of our premium fasteners. For customers requiring validation, Fastener Core provides EN 10204 3.1 Material Test Certificates (MTC) free of charge upon request. These documents confirm that the molybdenum content and mechanical values meet strict A4 standards. While we cover the cost of standard MTCs, please note that third-party independent inspections are available as a paid service.

Critical Applications for A4 Hex Bolts

316 stainless steel hex bolts are the industry standard for sectors requiring maximum durability:

• Marine Engineering: Securing deck hardware, engine mounts, and docks exposed to sea spray.
• Chemical Processing: Flange connections in pipelines carrying corrosive substances or chlorides.
• Pharmaceuticals: Clean-room machinery assembly where aggressive sterilization chemicals are used.
• Coastal Infrastructure: Handrails, lighting, and structural beams located within 5km of the coastline.

Frequently Asked Questions

Why are 316 hex bolts more expensive than 304?

The cost difference is primarily due to the chemical composition. 316 stainless steel contains molybdenum and a higher percentage of nickel, both of which are expensive raw materials. However, the initial higher cost is often offset by the reduced maintenance and replacement costs over the lifespan of the project in corrosive environments.

What does "A4-70" stamped on the head mean?

This is the ISO standard marking for the bolt. "A4" designates the material group (AISI 316 stainless steel), and "70" designates the strength class (700 N/mm² tensile strength). This marking assures you that the bolt is not a lower-grade generic stainless steel.

Do I need special tools to install 316 hex bolts?

Standard wrenches and sockets work perfectly. However, because 316 stainless steel is slightly softer and more ductile than carbon steel, it is more prone to thread galling (cold welding). It is highly recommended to ensure the threads are clean and to use a high-quality anti-seize lubricant during installation to prevent the nut and bolt from locking together permanently.