GRADE PROFILE
2304 — S32304 / X2CrNiN23-4
2304 is a duplex with no significant molybdenum: it draws its PREN of 24 to 30 from chromium raised to 21.5–24.5%. Its real strength is not pitting resistance but resistance to chloride stress corrosion cracking, where it comfortably outperforms austenitics.
- Duplex
- PREN 24–30
- Cost index 95
When to choose it
In brackish water and moderately chlorinated industrial water, water treatment, low-salinity desalination, pulp and paper. And above all as an alternative to 316L where the main risk is chloride stress corrosion cracking: the textbook case is an insulated storage tank, where residual welding stress, heat and chlorides leached from damp insulation combine and crack an austenitic.
On structures subject to fatigue, duplex yield strength also changes the picture.
When not to choose it
In seawater. Without molybdenum, 2304 is not a marine grade, and its PREN, even at 30, must not suggest otherwise: that is the role of 2205 and 2507.
By confusing it with 2205, which the similar names encourage. Molybdenum is capped at 0.60% against 3.0 to 3.5%: these are very different grades.
In prolonged service above 250 to 280 °C, where the risk of intergranular corrosion adds to that of embrittlement.
In acidic reducing media, which is the territory of heavily molybdenum-alloyed austenitics or nickel alloys.
Composition
| Element | % |
|---|---|
| C | ≤ 0.03 |
| Mn | ≤ 2.5 |
| P | ≤ 0.04 |
| S | ≤ 0.04 |
| Si | ≤ 1 |
| Ni | 3–5.5 |
| Cr | 21.5–24.5 |
| Mo | 0.05–0.6 |
| N | 0.05–0.2 |
| Cu | 0.05–0.6 |
| Element | % |
|---|---|
| C | ≤ 0.03 |
| Mn | ≤ 2 |
| P | ≤ 0.035 |
| S | ≤ 0.015 |
| Si | ≤ 1 |
| Ni | 3.5–5.5 |
| Cr | 22–24 |
| Mo | 0.1–0.6 |
| N | 0.05–0.2 |
| Cu | 0.1–0.6 |
Mechanical properties
| Temperature (°C) | Rp0.2 (MPa) |
|---|---|
| 50 | 370 |
| 100 | 330 |
| 150 | 310 |
| 200 | 290 |
| 250 | 280 |
Valeurs pour épaisseurs jusqu'à 30 mm, état hypertrempé. La colonne 250 °C est aussi la limite au-delà de laquelle la norme signale un risque de corrosion intergranulaire après 100 000 h.
Designations and standards
| Reference | Designation |
|---|---|
| EN (numeric) | 1.4362 |
| EN (symbolic) | X2CrNiN23-4 |
| ASTM / AISI | 2304 |
| UNS | S32304 |
| JIS | — |
| AFNOR | — |
Tube product standards :
- ASTM A789/A789M
- ASTM A790/A790M
- EN 10216-5
- EN 10217-7
Availability
Available in welded and seamless tube to ASTM A789/A790 and EN 10216-5/10217-7. Structured dimensional data for this grade is not yet documented in our reference set: send us your sizes. EN 10204 3.1 material certificates supplied with the goods.
Related grades
- 2101 (S32101) — the other lean duplex, equivalent PREN, very low in nickel.
- 2205 (1.4462) — the genuine saline grade, with 3% molybdenum.
- 316L (1.4404) — the austenitic to replace where stress corrosion cracking is the issue.
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Frequently asked questions
- Can 2304 replace a 316L?
- On chloride stress corrosion cracking, it does markedly better. On pitting, the PREN figures are close, so the gain is small. On mechanical strength, it allows lighter design. It is a sensible replacement where cracking is the risk, not where pitting is.
- Why two different compositions depending on the standard?
- ASTM A789 and EN 10088 do not set the same ranges: sulphur is nearly three times tighter on the EN side, and the chromium and nickel ranges differ. One commercial designation can therefore cover two sets of requirements. State which standard applies at enquiry stage.
- Does it need a particular filler metal?
- Yes, as with any duplex: a nickel-enriched filler to restore phase balance in the weld. Its low molybdenum content waives none of the family's welding precautions.