316L - Stainless steel - Hexagon bolt

Technical Advantages of 316L Hex Bolts

Hexagon bolts made from 316L stainless steel are often specified in the most rigorous engineering standards. While they share the same physical dimensions and drive style as standard bolts, their metallurgical structure provides an extra layer of insurance against failure. They are particularly favored in industries where maintenance access is difficult or costly, necessitating a "fit and forget" solution.

316 vs. 316L: Material Comparison

The primary difference lies in the carbon content. While both grades contain molybdenum for pitting resistance, 316L is engineered to prevent carbide precipitation, which can occur during manufacturing or if the bolt is used in high-temperature zones.

Feature	Standard 316 (A4)	Low Carbon 316L
Carbon Content	Max 0.08%	Max 0.03%
Corrosion Risk	Excellent, but susceptible to grain boundary decay if heated/welded.	Superior. Immune to sensitization (carbide precipitation).
Primary Use	General Marine & Chemical	Welded structures, Pharmaceutical, Nuclear

Quality Assurance and MTC

Verification is key for high-spec materials like 316L. Fastener Core provides EN 10204 3.1 Material Test Certificates (MTC) free of charge upon request. This document is essential for confirming that the carbon content is indeed below the 0.03% threshold required for the "L" designation. Please verify your requirement for third-party inspection services, as these incur additional costs.

Industrial Applications

316L hex bolts are critical in sectors with zero tolerance for corrosion:

• Pharmaceutical Manufacturing: Equipment assembly where product purity and cleanability are paramount.
• Petrochemical Plants: Flanges and valves exposed to sour gas or chlorides.
• Pulp and Paper: Machinery exposed to bleaching chemicals.
• Medical Implants/Devices: External fixation devices requiring biocompatibility (due to low carbon).

Frequently Asked Questions

Is 316L weaker than standard 316?

In its raw annealed state, 316L has a slightly lower yield strength than 316 due to the reduced carbon. However, for hexagon bolts, the cold-forging process used to form the head and threads significantly strengthens the material. Therefore, our 316L bolts typically meet the same ISO mechanical class standards as standard A4 bolts.  

Why use 316L if I am not welding the bolts?

Even without welding, 316L is often chosen for its superior consistency. It eliminates the possibility of intergranular corrosion completely, providing a safer margin in environments with high acidity or chloride concentration. It is the preferred choice for long-term subsea installations.  

Can 316L bolts be used with standard 316 nuts?

Yes, they are fully compatible. Using a 316L bolt with a standard 316 nut is a common practice. The superior corrosion resistance of the bolt (which is often under higher stress) ensures the integrity of the joint.