304 Stainless Steel for medical parts
304 Stainless Steel is the general purpose austenitic stainless steel, with chromium and nickel. It is used for general corrosion resistant parts where the chloride resistance of 316L is not needed. 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, medical is used as the example: validation evidence that matches the drawing exactly.
What the application demands
In medical work the requirement is validation evidence that matches the drawing exactly. The design is frozen early, and changes are expensive, which is why the specification is written the way it is.
Typical parts
- Instrument housings, where tensile strength matters.
- Surgical guide bodies, where yield strength matters.
- Implant trial components, where hardness matters.
How 304 Stainless Steel fits
304 Stainless Steel is the general purpose austenitic stainless steel, with chromium and nickel, and in this application that is used for general corrosion resistant parts where the chloride resistance of 316L is not needed. The tolerance held is ±0.005 mm, and the documentation that goes with it is ISO 13485 with device history records.
Practical notes
Choose 316L where chlorides are present. Where the drawing and the standard disagree, the conflict is raised at quotation rather than resolved silently on the machine.
| Specification | Typical value |
|---|---|
| Tensile strength | 515 MPa |
| Yield strength | 205 MPa |
| Hardness | 170 HB |
| Density | 8.00 g/cm³ |
| Machinability | moderate, with a tendency to work harden |
| Corrosion resistance | good in most atmospheres, poor in salt water |
Applications
304 Stainless Steel is used for general corrosion resistant parts where the chloride resistance of 316L is not needed, and in practice it appears most often in fasteners, food preparation surfaces, architectural hardware, general brackets.
How it fits into a machining route
304 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: material cost is lower than 316L. 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 available. 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.
Standard dimensional inspection 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 304 Stainless Steel?
±0.02 mm is realistic in production. Tightening it beyond the functional requirement increases cost without improving the part.
Which material is usually used?
304 stainless steel is the usual choice, supplied against EN 10204 3.1 available.
How is the result verified?
Standard dimensional inspection, with the results recorded so a repeat order can be compared with the first.
What is the most common mistake?
Welding a thick section without considering carbide precipitation.
How long does it take and what does it cost?
A realistic cycle is moderate cutting speed, and the cost driver is material cost is lower than 316L.
Related capability
If you are specifying 304 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 304 Stainless Steel in the encyclopedia: Duplex 2205 Stainless Steel, 4140 Alloy Steel, Hydraulic Manifolds. Reading them together gives a fuller picture of how the process, the material and the measurement affect each other.
