316L Stainless Steel specifications: what the numbers mean
316L Stainless Steel is a low carbon austenitic stainless steel with molybdenum, for corrosion resistance. It is used for medical, food and marine parts, and anything that has to be cleaned aggressively. This entry explains what it is, what the numbers on a data sheet mean, and what to put on a drawing.
It is written from the point of view of the buyer and the drawing office: the values that are realistic in production, the ones that cost money, and the way the result is verified. Where an industry sets the requirement, semiconductor is used as the example: cleanliness and surface condition that matter more than the nominal size.
What the numbers mean
A data sheet for 316L Stainless Steel is only useful if the numbers are read against the job. The usual entries, and what they tell you, are these.
- Tensile strength – 485 MPa.
- Yield strength – 170 MPa.
- Hardness – 170 HB.
- Density – 8.00 g/cm³.
- Machinability – poor: it work hardens and cuts stringy chips.
- Corrosion resistance – excellent, including in chloride environments.
Comparing offers
Two suppliers can quote the same tensile strength and mean different things, because the figures are often quoted under the most favourable conditions. Ask what the value is measured over, what the material was, and whether it is a typical or a guaranteed figure.
| Specification | Typical value |
|---|---|
| Tensile strength | 485 MPa |
| Yield strength | 170 MPa |
| Hardness | 170 HB |
| Density | 8.00 g/cm³ |
| Machinability | poor: it work hardens and cuts stringy chips |
| Corrosion resistance | excellent, including in chloride environments |
What to check before specifying
Make sure the value you need is the value you have called up. Keep the tool moving and the cut positive, and the difference between a typical and a worst case figure is where most disputes start.
Applications
316L Stainless Steel is used for medical, food and marine parts, and anything that has to be cleaned aggressively, and in practice it appears most often in medical instruments, food equipment, marine hardware, chemical plant parts.
How it fits into a machining route
316L Stainless Steel is chosen at the drawing stage, and everything downstream follows from it: the tool geometry, the cutting data, the heat treatment and the certificate. Changing the grade later is a different part, not a different quote.The route is fixed before the first part is cut, and it is the route rather than the individual setting that holds the result: cutting time, because the feed and speed are limited. Where a drawing calls for something the route cannot hold economically, that is raised at quotation rather than after the parts are made.
Standards, documentation and what is issued
The documentation requirement is EN 10204 3.1 with ISO 13485 where applicable. Material is supplied against a certificate where the application calls for it, inspection results are recorded with the job, and the records are kept so that a repeat order can be compared with the first instead of being measured from scratch.
Dimensional inspection plus a material certificate is the verification step. Where a customer format or a standard report is required, it is agreed before the batch starts, because a report written after the event is a report nobody can use.
Frequently asked questions
What tolerance should be specified for 316L Stainless Steel?
±0.01 mm is realistic in production. Tightening it beyond the functional requirement increases cost without improving the part.
Which material is usually used?
316L stainless steel is the usual choice, supplied against EN 10204 3.1 with ISO 13485 where applicable.
How is the result verified?
Dimensional inspection plus a material certificate, with the results recorded so a repeat order can be compared with the first.
What is the most common mistake?
Assuming it is magnetic like a ferritic stainless, so a magnetic chuck will not hold it.
How long does it take and what does it cost?
A realistic cycle is slow cutting, high tool wear, and the cost driver is cutting time, because the feed and speed are limited.
Related capability
If you are specifying 316L Stainless Steel on a drawing and want a second opinion on the route, send the model and the quantity. The first response is a manufacturability review with the likely risk points and a quotation, so the decision can be made on facts rather than on a price alone.
Machining, inspection and documentation are handled in one place, which is why the dimensional report and the material certificate arrive with the parts rather than after them.
Related entries
These entries sit next to 316L Stainless Steel in the encyclopedia: 4140 Alloy Steel, PEEK, Splined Shafts. Reading them together gives a fuller picture of how the process, the material and the measurement affect each other.
