Stainless steel grades: AISI and ГОСТ table with analogues
A stainless steel grade is not a name but a set of guarantees: how much chromium, nickel and molybdenum is in the steel, how it will behave in water, acid and when heated. If you get the grade wrong, the part will rust not in a year but in a month.
What follows is how to read designations in three systems, an AISI and ГОСТ correspondence table, a breakdown of common grades, a way to compare them with one number and substitution rules that will not lead to a claim.
Three designation systems
| System | Where it is accepted | What it looks like | What it shows |
|---|---|---|---|
| AISI | USA, international trade | AISI 304, 316L | Chemical composition, series number |
| EN | Europe | 1.4301, 1.4404 | Full composition under the European standard |
| ГОСТ | Russia, EAEU | 08Х18Н10, 12Х18Н10Т | Composition right in the name |
In a ГОСТ grade the composition is encoded: 08Х18Н10 reads as "0.08% carbon, 18% chromium, 10% nickel". The letters at the end specify the additions: Т — titanium, М — molybdenum, Н — nickel, Д — copper, Г — manganese, Б — niobium.
In an AISI number the composition is not visible — only the series number. That is why buyers look at the correspondence table when purchasing and at the certificate of the specific batch at acceptance.
AISI and ГОСТ correspondence table
| AISI | EN | ГОСТ | Key addition | Class |
|---|---|---|---|---|
| 201 | 1.4372 | 12Х15Г9НД | manganese instead of nickel | austenitic, economy |
| 304 | 1.4301 | 08Х18Н10 | — | austenitic |
| 304L | 1.4307 | 03Х18Н11 | low carbon (≤0.03%) | austenitic |
| 316 | 1.4401 | 10Х17Н13М2 | molybdenum 2–3% | austenitic, acid-resistant |
| 316L | 1.4404 | 03Х17Н14М2 | molybdenum + low carbon | austenitic, acid-resistant |
| 316Ti | 1.4571 | 10Х17Н13М2Т | molybdenum + titanium | austenitic |
| 321 | 1.4541 | 12Х18Н10Т | titanium | austenitic, heat-resistant |
| 430 | 1.4016 | 12Х17 | — | ferritic, without nickel |
| 310S | 1.4845 | 20Х23Н18 | chromium 23–25%, nickel 18–20% | heat-resistant |
| 904L | 1.4539 | 06ХН28МДТ | copper, molybdenum | super-austenitic |
| 2205 | 1.4462 | — | duplex, nitrogen | ferritic-austenitic |
Important: the table shows closeness, not full interchangeability. The exact composition, heat treatment and mechanical properties are confirmed by the batch certificate. If the part goes into a critical place, verify the analysis, not just the number.
What the alloying elements mean
| Element | What it is responsible for | Where the effect shows |
|---|---|---|
| Chromium (Cr) | creates the passive film | basic corrosion resistance; minimum 10.5% |
| Nickel (Ni) | maintains the austenitic structure | toughness, weldability, absence of magnetism |
| Molybdenum (Mo) | resistance to pitting and crevices | chlorides, sea water, acids |
| Titanium (Ti) / niobium (Nb) | binds carbon | welded structures without heat treatment, heating |
| Manganese (Mn) | partly replaces nickel | cheaper, but lower resistance |
| Nitrogen (N) | strengthens austenite | duplex, thin-wall structures |
| Carbon (C) | increases strength | but it is precisely what causes intergranular corrosion |
Hence the logic of the grades: 304 is the base, 316 the base plus molybdenum, 321 the base plus titanium, 201 the base with manganese instead of part of the nickel, 430 with no nickel at all.
How to compare grades with one number
There is a practical indicator — PREN, the pitting resistance equivalent number:
PREN = Cr + 3.3 × Mo + 16 × N
| Grade | Approximate PREN | What it means |
|---|---|---|
| 201 | ~17 | dry rooms, décor |
| 304 / 304L | ~18 | fresh water, food environments |
| 316 / 316L | ~24–25 | chlorides, sea water, chemicals |
| 2205 (duplex) | ~34 | aggressive environments + high strength |
| 904L | ~34–35 | acids, heavy chemicals |
The values are approximate: they depend on the actual composition of the batch. But for a quick comparison of "will this grade withstand my environment", PREN is more convenient than reading composition tables.
Austenitic grades: 304, 316, 321
The main working class: about 18% chromium, 8–14% nickel, austenitic structure, weak magnetism after annealing.
AISI 304 / 08Х18Н10. The all-rounder. Sheet, pipe, round bar, fasteners, tanks, food equipment. It withstands the atmosphere, fresh water and most food environments. Weak points — chlorides and weld seams without heat treatment.
AISI 316 / 10Х17Н13М2. The same plus 2–3% molybdenum. Molybdenum closes off pitting corrosion, so 316 goes into sea water, brines, chemical equipment, pulp and paper production, and medical instruments.
AISI 321 / 12Х18Н10Т. Titanium binds carbon and prevents it from precipitating along grain boundaries when heated in the range 450–850 °C. Hence the heat resistance and service in welded structures without subsequent annealing. A classic of Russian mechanical engineering and heat technology.
The letter L. 304L, 316L are low-carbon versions (≤0.03% C). The difference shows precisely in welding: the less carbon, the lower the risk of intergranular corrosion next to the seam. If the structure is welded and not annealed, the L version is preferable.
Ferritic and economy grades: 430, 201, 409
AISI 430 / 12Х17. 17% chromium, no nickel. Magnetic, cheaper than austenitic grades, lower corrosion resistance. Household appliances, interior finishing, decorative panels, economy-class sinks, interior elements.
AISI 201 / 12Х15Г9НД. Part of the nickel is replaced by manganese. Cheaper than 304, stronger in cold deformation — thin-wall pipes and bent profiles are conveniently made from it. Worse in an aggressive environment, so it is suitable for interiors, furniture, handrails and décor, but not for contact with food and not for wet chloride environments.
AISI 409. A ferritic grade for automotive exhaust systems. It is rarely found in construction and equipment.
Heat-resistant and special grades: 310S, 904L, duplex 2205
310S / 20Х23Н18. About 25% chromium and 20% nickel. It works at 1000–1100 °C and does not scale. Furnaces, burners, muffles, hot-zone fasteners, recuperators.
904L / 06ХН28МДТ. A high content of nickel, molybdenum and copper. It goes where ordinary stainless steel does not survive: sulphuric and phosphoric acid, sea water, chemical reactors, fertiliser equipment.
Duplex 2205. A mixture of austenite and ferrite, about 22% chromium, 5% nickel, 3% molybdenum and nitrogen. Strength is about twice that of 304 at the same thickness, chloride resistance is at the level of 316 and above. Pipes, tanks, heat exchangers, oil and gas, desalination.
How to choose a grade for the environment
| Service conditions | What to take | Why |
|---|---|---|
| Dry rooms, décor, furniture | 201, 430 | cheaper, resistance is sufficient |
| Outdoors, moisture, food equipment | 304 | the basic universal grade |
| Chlorides, salt, pool, sea | 316, 316L | molybdenum against pitting |
| Welded structures without annealing | 304L, 316L, 321 | low carbon or titanium |
| Heating above 500 °C | 321, 310S, 20Х23Н18 | titanium and high chromium against scaling |
| Acids, heavy chemicals | 904L, duplex | maximum alloying |
| Strength at lower thickness | duplex 2205 | higher yield strength |
Finish deserves separate mention. 2B and brushed behave the same in the same environment, whereas a rough surface with stagnant zones and welding scale corrodes earlier. Polishing and pickling are not decoration but part of the corrosion protection.
How to read a batch certificate
The certificate is the only document that confirms the grade. Look in it at:
- Heat and batch number — to link the document to the specific metal.
- Chemical analysis — the actual content of Cr, Ni, Mo, C, not "corresponds to the grade".
- Mechanical properties — tensile strength, yield strength, elongation.
- Standard — the ГОСТ or ТУ according to which it was made.
- Mass and quantity — to check against the delivery note.
If the certificate states ТУ instead of ГОСТ, that is not a defect, but the requirements in a ТУ may be softer. Check against what is written in your specification.
Common mistakes when substituting grades
- Replacing 316 with 304 "to save money" in a chloride environment. Molybdenum is not compensated for by wall thickness.
- Using 304 instead of 304L in a welded structure without heat treatment: carbon precipitates along grain boundaries and the seam corrodes.
- Treating magnetism as a sign of quality. Austenitic grades are weakly magnetic after annealing and noticeably magnetic after cold deformation; ferritic ones are always magnetic.
- Ordering "stainless steel" without a grade in the specification. You will get whatever was in the warehouse.
- Ignoring the finish and the condition of the edge. Pitting starts where there is stagnant moisture and scale.
- Forgetting about the galvanic couple. Stainless steel next to carbon steel or aluminium without insulation accelerates corrosion of the less noble metal.
How the grade relates to the type of product
The same grade behaves differently depending on what is made from it. Thin cold-rolled sheet and hot-rolled round bar in 304 differ in surface condition and in how they are further processed.
| Product type | Typical grades | What to look at when choosing |
|---|---|---|
| Cold-rolled sheet | 304, 316L, 201, 430 | finish (2B, BA, №4, mirror) and thickness |
| Hot-rolled sheet | 304, 316L | thickness from 4 mm, edge condition, scale |
| Round pipe | 201, 304, 316L | diameter and wall, finish, purpose (décor or environment) |
| Profile pipe | 201, 304 | section shape, corner radius, finish |
| Round bar | 304, 316L, 201 | calibrated or hot-rolled, diameter tolerance |
| Angle | 304 | flange thickness, hot-rolled or bent |
The logic is simple: the thinner the product and the closer it is to a food or chemical environment, the higher the requirements both for the grade and for the finish. Decorative elements indoors live happily on 201 and 430.
What to state in the order so as not to get the grade wrong
An order on the exchange fixes the parameters before matching, so the grade must be chosen in advance. The minimum set that removes most disputes at acceptance:
- The grade in the AISI system and, where applicable, the ГОСТ analogue — for example "AISI 304 / 08Х18Н10".
- The product type and section shape: sheet, round pipe, profile pipe, round bar, angle.
- The full size: for sheet — thickness × width × length, for pipe — diameter or section × wall × length, for round bar — diameter.
- The finish: 2B, BA, mirror, №4 brushed, brushed, hot-rolled, calibrated.
- The standard you expect the metal to meet: ГОСТ or ТУ.
- The shipment week and delivery basis — they carry over into the trade unchanged.
If the specification goes to procurement or a process engineer for approval, add the purpose: "for a food environment", "for a welded structure without annealing", "for outdoors". This removes the question "why this particular grade" before the metal arrives.
Frequently asked questions
How does AISI 304 differ from 316?
By molybdenum: in 316 it is 2–3%, in 304 there is none. This gives 316 resistance to chlorides and acids — sea water, brines, chemicals. In everything else the grades are close, but 316 is more expensive, so there is no point taking it "just in case".
What is the Russian analogue of AISI 304?
08Х18Н10. For welded structures without heat treatment — 03Х18Н11, which is the analogue of 304L.
What does the grade 12Х18Н10Т mean?
0.12% carbon, 18% chromium, 10% nickel, titanium. Titanium binds carbon and increases heat resistance. This is the Russian analogue of AISI 321.
Which stainless steel is not magnetic?
Austenitic grades after annealing: 304, 316, 321. Ferritic (430) and martensitic ones are always magnetic. A magnet test does not replace a composition analysis.
Can AISI 304 be replaced with AISI 201?
Only where there is no moisture, no chlorides and no food-safety requirements. 201 is cheaper, but corrosion resistance is lower, and the manganese in its composition is undesirable for contact with food.
Which stainless steel grade is better?
The one that matches the environment. For interiors 201 and 430 are enough, for water and food — 304, for chlorides and acids — 316 and above. There is no "best grade in general".
What is PREN and why is it needed?
The pitting resistance equivalent number: Cr + 3.3 × Mo + 16 × N. It allows grades to be compared by one number for resistance in a chloride environment. The values are approximate and depend on the actual composition of the batch.
How does 316L differ from 316Ti?
In 316L the carbon is reduced, in 316Ti titanium is added — both measures are needed against intergranular corrosion during welding. The choice depends on what is available and what the service temperature is.
Buy product in the grade you need
On the GCX exchange AISI 201, 304, 316L and 430 are traded: round and profile pipe, sheet, round bar, angle. The order states the grade, size, finish and shipment week — exactly the metal you chose goes into the trade, without substitution by something "similar".