316 Stainless Steel Tubing
316 stainless steel’s elemental differences from 304 are seemingly minor but play an important role in enhancing corrosion resistant characteristics of this alloy. Also known as DIN 1.4401 or UNS S31600, this tubing alloy owes its improved corrosion resistance to the inclusion of molybdenum during the melting process, which delivers upgraded corrosion resistance when exposed to oxidizing or chlorinated environments (such as salts). Often, this alloy is selected for more critical products that require a higher level of protection against corrosion, or for products that are repeatedly exposed to environments that have greater potential for corrosion such as repeated sterilizations where tubing products undergo high temperatures and exposure to aggressive chemicals used to destroy any microbes on the product. The atomic level invisible protective layer at the surface of the tube---a hallmark of stainless steel due to chromium and nickel content---will self-heal if disrupted under normal conditions like 316’s more common peer, 304 stainless.
The appearance of 316 stainless steel relative to a comparable 304 tube in a normal environment is indiscernible. 316 stainless steel tubing is more expensive than 304, depending on sizes and tolerances from 5 to 20% higher. This difference is largely because it contains molybdenum which is challenging and expensive to extract from ore. It is also limited in supply, with only a handful of mines producing molybdenum in the United States. Generally, raw material for manufacturing tubing in either strip or forged bar form is plentiful for 316 stainless, but with slightly fewer standard starting sizes than the ubiquitous 304 alloy.
Like other 300 series alloys, 316 SS is austenitic and can only be hardened by cold work. Annealing (heat treating) this alloy at 1900ºF will result in a soft temper, non-magnetic condition. Also similar to 304, 316 stainless steel has a low carbon variant (316 L) typically employed when tubes will be welded to other components as part of an assembly. The low carbon, or “L-grade” content results in less carbide precipitation in the weld zone. This reduced carbide precipitation delivers a more uniform chemistry in the weld zone making it less prone to oxidation or corrosion when placed in service. Widely available fabrication methods such as turning/milling/grinding (traditional and CNC) work well with 316 hypodermic , fractional and metric stainless steel tubing. 316 tubing can also be fabricated using electrochemical, electrical discharge machining or laser machining.
Industries & Applications:
Products constructed from 316 stainless tubing include, but are not limited to, some of the following examples.
- Gastroenterology suture products
- Peripheral vascular and general vascular treatment devices
- Drug and pharma uses
- HPLC / Chromatography applications
- Sensing, instrumentation and robotics devices
- Surgical applications such as cardiac, neurological and orthopedic
- Laboratory testing and research & development
- Industrial and oil & gas applications in corrosive environments
- Single and reusable medical devices including hypodermic needles