How to specify 304 Stainless Steel on a drawing

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, aerospace is used as the example: traceability and a first article before anything enters the batch.

What belongs on the drawing

A clear drawing for 304 Stainless Steel states the function, the tolerance and the verification, and leaves the route open where the function allows it.

• The feature and its tolerance: ±0.02 mm, applied to the features that locate the part.
• The material and its condition: 304 stainless steel, with the certificate requirement.
• The surface finish: Ra 1.6 µm as machined, called out only where it does something.
• The verification: EN 10204 3.1 available, and the standard the report is written to.

Mistakes that cost money

• Using it in a marine or chloride environment, where it pits, which makes the part more expensive without making it better.
• Welding a thick section without considering carbide precipitation, which makes the part more expensive without making it better.

A workable note

Where a general note is used, say so once in the title block and keep the feature level call outs for the dimensions that matter. Passivate after welding to restore the surface

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

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: C3604 Brass, Duplex 2205 Stainless Steel, Mould Inserts. Reading them together gives a fuller picture of how the process, the material and the measurement affect each other.