304 - Stainless steel – Hexagon bolt

Why Choose 304 Stainless Steel Hex Bolts?

The hexagon bolt is a fundamental component in structural assembly, requiring a material that can sustain load while resisting the elements. Grade 304 (A2) is the most widely used stainless steel alloy in the world. For hex bolts, this material offers excellent formability and durability. It relies on a chromium-rich oxide film to protect the fastener from oxidation, making it the ideal choice for environments exposed to dampness, freshwater, or normal atmospheric conditions.

Material Specifications: A2-70 Explained

Composition and Durability: Grade 304 is an austenitic stainless steel containing approximately 18% chromium and 8% nickel. This chemistry provides significant resistance to corrosion from rain, humidity, and oxidizing acids. However, it is important to note that while 304 is highly durable, it is not recommended for salt-water marine environments (where 316/A4 is preferred). Mechanical Strength (Class 70): Our 304 hex bolts are typically supplied as "A2-70". The "70" denotes the tensile strength class. These cold-worked bolts deliver a minimum tensile strength of 700 N/mm² and a yield strength of 450 N/mm². This makes them significantly stronger than unhardened mild steel bolts, allowing them to bear substantial structural loads in non-critical engineering applications.

Quality Assurance and MTC

To ensure the integrity of your assemblies, Fastener Core offers full traceability. We provide EN 10204 3.1 Material Test Certificates (MTC) free of charge upon request. This document verifies that the specific batch of 304 stainless steel bolts meets the required chemical and physical standards. Please indicate your need for these documents when placing your order. Third-party inspections can also be arranged for an additional fee.

Common Applications for 304 Hex Bolts

Due to their versatility and cost-effectiveness, 304 stainless hex bolts are the go-to solution for:

• General Construction: Fastening cladding, timber framing, and steel structures in non-coastal areas.
• Automotive: Mounting brackets, bumpers, and panels where road salt exposure is minimal.
• Food Processing: Equipment assembly in environments where sanitation is important (excluding high-chloride zones).
• Interior Fitting: Heavy-duty furniture assembly and warehouse racking systems.

Frequently Asked Questions

What does "A2-70" marked on the bolt head mean?

"A2" identifies the material group as austenitic 304 stainless steel. "70" identifies the strength class, indicating that the bolt has a minimum tensile strength of 700 N/mm². This is the standard marking for cold-forged 304 hex bolts.

Is 304 stainless steel magnetic?

In its raw, annealed state, 304 stainless steel is non-magnetic. However, the manufacturing process of hex bolts involves cold forging (heading) and thread rolling. This physical deformation slightly alters the microstructure, causing the bolts to become slightly magnetic. This is normal and does not affect the corrosion resistance.

Can I use 304 hex bolts outdoors?

Yes, 304 (A2) bolts are excellent for outdoor use in rural or urban environments. They will resist rain and humidity without rusting. However, if the project is located within 5km of the ocean or in a highly polluted industrial zone, we recommend upgrading to 316 (A4) grade to prevent surface staining or pitting.