Stainless steel grades: 201, 304, 304L, 316, 316L and 321 explained
A buyer-friendly guide to the austenitic grades ZAIHUI supplies — what each one is made of, how it resists corrosion, how it welds, what it costs and where it belongs. Composition figures are the nominal ranges published in ASTM A240; always confirm exact chemistry against the mill test certificate.
How to read a stainless steel grade
Most architectural, food, fluid and structural work uses austenitic stainless — the 200 and 300 series — and that is exactly the family ZAIHUI rolls into pipe, tube, sheet and plate. The grade number is shorthand for an alloy recipe: roughly how much chromium gives corrosion resistance, how much nickel keeps the steel tough and formable, and whether molybdenum is added to fight chlorides. A trailing "L" means low carbon (better for welding), and a number like 321 signals a stabilising element (titanium) for high-temperature service.
Chromium is the element that makes steel "stainless": at roughly 10.5% or more it forms a thin, self-healing passive oxide film. Nickel stabilises the austenitic structure, improving ductility, toughness and weldability. Molybdenum (in 316/316L) dramatically improves resistance to pitting and crevice corrosion from chlorides — seawater, de-icing salt, swimming pools and many process chemicals. The grades below are the practical menu most projects choose from.
Grade comparison chart
A qualitative side-by-side of the six grades ZAIHUI supplies. Use it to shortlist, then confirm the exact specification and standard in your RFQ.
| Grade | Character | Corrosion resistance | Typical use | Relative cost |
|---|---|---|---|---|
| 201 | Low-nickel, high-manganese, work-hardening; economical austenitic | Mild; suits dry indoor environments | Decorative trim, furniture, signage, indoor fittings | Lowest |
| 304 | Classic 18/8 chromium-nickel "workhorse" | Good in most atmospheric and many mild chemical settings | General fabrication, architecture, kitchen and food equipment | Moderate |
| 304L | Low-carbon 304 for welded assemblies | Same as 304, with better resistance to weld sensitisation | Welded tanks, frames and pipework without post-weld anneal | Moderate |
| 316 | 304 plus 2–3% molybdenum | Strong against chlorides, marine air and many chemicals | Marine, coastal, chemical and water-treatment service | Higher |
| 316L | Low-carbon 316 for welded chloride service | 316 corrosion performance, better welded integrity | Welded process piping, sanitary and chemical fabrications | Higher |
| 321 | 304-type stabilised with titanium | Good general resistance; excels against weld decay at heat | Exhaust, expansion joints, high-temperature service | Higher |
Nominal composition by grade
The figures below are the nominal element ranges published in ASTM A240/A240M for plate, sheet and strip (the same chemistries carry across to pipe and tube specifications such as ASTM A312). They define the alloy — they are not a ZAIHUI guarantee of a specific number.
| Grade (UNS) | Cr % | Ni % | Mo % | C max % |
|---|---|---|---|---|
| 201 (S20100) | 16.0–18.0 | 3.5–5.5 | — | 0.15 |
| 304 (S30400) | 18.0–20.0 | 8.0–10.5 | — | 0.08 |
| 304L (S30403) | 18.0–20.0 | 8.0–12.0 | — | 0.03 |
| 316 (S31600) | 16.0–18.0 | 10.0–14.0 | 2.0–3.0 | 0.08 |
| 316L (S31603) | 16.0–18.0 | 10.0–14.0 | 2.0–3.0 | 0.03 |
| 321 (S32100) | 17.0–19.0 | 9.0–12.0 | — | 0.08 |
What each grade is really for
The same six grades, in plain language — alloy character, corrosion behaviour, weldability, cost and where they earn their place.
Grade equivalents (UNS / EN / JIS / GB)
The same alloy is named differently around the world. Use this to translate a drawing or an inquiry between standards. Equivalents are functional, not always identical — composition limits, product form and heat treatment can differ, so always verify against the target specification and the MTC.
| Common name | UNS | EN / DIN | JIS | GB/T |
|---|---|---|---|---|
| 201 | S20100 | 1.4372 (X12CrMnNiN17-7-5) | SUS201 | 1Cr17Mn6Ni5N |
| 304 | S30400 | 1.4301 (X5CrNi18-10) | SUS304 | 06Cr19Ni10 |
| 304L | S30403 | 1.4307 (X2CrNi18-9) | SUS304L | 022Cr19Ni10 |
| 316 | S31600 | 1.4401 (X5CrNiMo17-12-2) | SUS316 | 06Cr17Ni12Mo2 |
| 316L | S31603 | 1.4404 (X2CrNiMo17-12-2) | SUS316L | 022Cr17Ni12Mo2 |
| 321 | S32100 | 1.4541 (X6CrNiTi18-10) | SUS321 | 06Cr18Ni11Ti |
Selecting the right grade
Grade choice is a balance of corrosion environment, fabrication method and budget. Here is the shortcut ZAIHUI uses as a starting point — your RFQ confirms the final call.
Start with the environment. For dry, indoor, decorative work where price leads, 201 is the economical pick. For general-purpose architecture, equipment and food contact away from chlorides, 304 is the dependable default — choose 304L when the part is welded and will not be solution-annealed afterwards. Step up to 316 for chloride exposure: marine and coastal air, salt, pools, water treatment and many process chemicals — and to 316L when that chloride-service part is welded, as with our 316 industrial pipe for chloride service. Reserve 321 for sustained high temperature and thermal cycling, where its titanium stabilisation prevents weld decay. When unsure, describe the medium, temperature and exposure and let our team recommend rather than over- or under-specifying.
The grades we supply, your way
As a manufacturer-direct mill in Foshan since 2006, ZAIHUI produces these grades to your chosen standard, size and finish.
Other reference hubs
FAQ
Is 201 real stainless steel?
Yes. 201 is a genuine austenitic stainless steel with 16–18% chromium, but it replaces much of the nickel with manganese and nitrogen to cut cost. That makes it the most economical austenitic grade, well suited to dry indoor and decorative work, but with weaker corrosion resistance than 304 — avoid it in chloride, marine, acidic or food-acid service.
304 vs 316 in one line?
304 is the general-purpose default; 316 adds 2–3% molybdenum for far better resistance to chlorides, salt and many chemicals, so choose it for marine, coastal, pool and chemical service.
What does the "L" in 304L and 316L mean?
"L" means low carbon — capped at 0.03% versus 0.08% for the standard grade. Lower carbon limits chromium-carbide precipitation ("sensitisation") in the weld heat-affected zone, so 304L and 316L are preferred for welded assemblies that will not be solution-annealed after welding. Corrosion performance otherwise matches the parent grade.
What is grade 321 used for?
321 is a 304-type stainless stabilised with titanium, which ties up carbon and prevents weld decay after exposure to high temperatures. It is the grade for sustained heat and thermal cycling — exhaust systems, expansion joints, heat exchangers and similar high-temperature service.
Shop these grades
Not sure which grade your project needs?
Tell us the environment, temperature and what the part has to do. We will recommend the right grade — 201, 304/304L, 316/316L or 321 — and quote it manufacturer-direct.