304 vs 18/8 Stainless Steel Guide
304 vs 18/8 stainless steel is a frequent RFQ topic.
Buyers often use both names for the same stainless family.
Yet the two terms do not work the same on a PO.
This guide shows how to specify with less risk.
304 vs 18/8 stainless steel: quick answer
In most markets, 18/8 points to Type 304 stainless.
18/8 is a shorthand chemistry nickname.
304 is a controlled grade name in standards.
Standards make acceptance criteria auditable.
That matters for QA and repeat orders.
18/8 stainless steel meaning vs 304 grade control
“18/8” describes intent, not enforceable limits.
Different suppliers may interpret it differently.
A PO written as “18/8” can invite disputes.
A PO written as “304 to ASTM or EN” reduces disputes.
It also shortens the approval cycle.
18-8 vs 304: what to write on your PO
Avoid buying only “18/8 stainless steel.”
Use a grade plus a governing specification.
Add product form, finish, and inspection scope.
Then request certification in the RFQ.
Example for sheet and plate
ASTM A240 Type 304, UNS S30400.
State thickness, width, and length.
State tolerance class when needed.
State finish, such as 2B or No.4.
Request MTC or EN 10204 3.1 if required.
For finish definitions, use this internal reference.
https://lyhsteel.com/surface-finish-chart/
Type 304 stainless steel composition: what “18/8” implies
304 vs 18/8 stainless steel is mainly a naming issue.
18/8 suggests a Cr-Ni austenitic stainless family.
Type 304 composition is defined by standards.
Limits vary by standard and product form.
So always cite the governing standard on the PO.
If you manage multi-standard projects, align equivalents early.
Use this internal equivalents chart for internal review.
https://lyhsteel.com/steel-grade-equivalent-chart/
304 vs 18/8 stainless steel: why mechanical limits matter
Many projects need minimum mechanical properties.
Standards define test methods and sampling.
They also define acceptance and rejection criteria.
That reduces subjective arguments after delivery.
It also supports traceability in audits.
If you only write “18/8,” requirements can drift.
Two mills can meet “18/8” with different results.
That creates inconsistent forming and welding behavior.
It can also create inconsistent surface performance.
304 vs 316 (18/10): when to upgrade
Some markets call 316 “18/10.”
That label is not a controlled grade name.
The real upgrade is molybdenum in 316.
Molybdenum improves chloride resistance in many cases.
Choose 304 when chlorides are controlled.
Choose 316 when chlorides are frequent.
Choose 316 for coastal air and salty wash-down.
Also review cleaners used in service.
To support corrosion selection, use this internal tool.
https://lyhsteel.com/pren-calculator/
304 vs 304L: welding and sensitization risk
304L is a low-carbon variant of Type 304.
It is often preferred for heavy welded fabrications.
Lower carbon can reduce sensitization risk near welds.
That can improve post-weld corrosion behavior.
Specify 304L when heat input is high.
Also specify weld cleanup requirements.
Include pickling or passivation when required.
Do not decide this only by price.
Is 18/8 stainless steel the same as 304 in magnetism
304 is usually low-magnetic when annealed.
Cold work can increase magnetic response.
Forming can create partial martensite.
So mild attraction can be normal.
Do not reject parts using only a magnet test.
If magnetism is functional, specify permeability.
Align forming steps to that target.
SUS304 vs 304 and 1.4301 vs 304
Global projects use different naming systems.
SUS304 is a common JIS designation.
1.4301 is a common EN designation.
304 is common in ASTM and AISI usage.
Equivalents help communication across regions.
They are not always contractual substitutes.
Call the governing standard on the PO.
Request certificates to that standard.
Use this internal chart for procurement alignment.
https://lyhsteel.com/steel-grade-equivalent-chart/
A short buyer table for 304 vs 18/8 stainless steel
| Term on RFQ | What it usually means | Better wording |
|---|---|---|
| 18/8 stainless steel | Informal chemistry label | ASTM A240 Type 304 |
| 18-8 stainless | Informal shorthand | Type 304, UNS S30400 |
| 304 stainless | Grade name, still vague | 304 to named standard |
| 304, 2B finish | Missing inspection scope | Add tolerances and MTC |
| 304L for welding | Often appropriate | Add cleanup and cert scope |
RFQ checklist for 304 vs 18/8 stainless steel
Use this checklist to speed quotations.
It also improves quote comparability.
It reduces rework after technical review.
1) Grade and standard
Write 304 vs 18/8 stainless steel clearly as a grade.
Use ASTM, EN, or JIS standard names.
Add UNS when your QA system prefers it.
2) Product form
State coil, strip, sheet, or plate.
State pipe, tube, or bar when applicable.
3) Dimensions and tolerances
State thickness, width, and length.
State tolerance class if critical.
Use this internal tool for tolerance planning.
https://lyhsteel.com/dimensional-tolerance-calculator/
4) Surface finish and appearance
State 2B, BA, No.4, HL, or mirror.
State one-side or two-side finish.
Use this internal reference for finish terms.
https://lyhsteel.com/surface-finish-chart/
5) Protection and packing
State PVC or PE film requirements.
State seaworthy packing and marking rules.
6) Processing requirements
State slitting, CTL, leveling, or edging.
For coil estimation, use this internal calculator.
https://lyhsteel.com/steel-coil-calculate/
7) Service environment
State chlorides, temperature, and cleaners.
State indoor, outdoor, or coastal exposure.
This often decides 304 versus 316.
8) Documentation and inspection
State MTC or EN 10204 3.1 requirements.
State PMI or third-party inspection when needed.
For a full tool hub, use this internal page.
https://lyhsteel.com/steel-calculators/
For shipment weight planning, use this tool.
https://lyhsteel.com/calculate-metal-weight/
FAQ
Q1: Is 18/8 stainless steel the same as 304
Usually yes in trade usage.
But 18/8 is not a controlled grade name.
304 can be purchased to a named standard.
Q2: Can 304 stainless steel rust
304 resists many environments well.
Chlorides can still cause staining or pitting.
316 may be better for chloride service.
Q3: Should I specify 304L instead of 304
304L is common for heavy welded parts.
It can reduce sensitization risk near welds.
Confirm with your service environment and QA plan.