2304 Stainless Steel (UNS S32304)
Duplex (lean) · ASTM A240/A240M · Density 7.75 g/cm³
2304 (UNS S32304) is a lean duplex stainless steel with roughly twice the yield strength of 304/316 but little or no molybdenum, so it prices close to 304. It matches or beats 316L in chloride stress-corrosion cracking resistance, making it an economical upgrade for tanks, structures and water heaters where strength sets the plate thickness.
Chemical Composition (wt%)
| C | Mn | Si | Cr | Ni | Mo | N | Cu | P | S |
|---|---|---|---|---|---|---|---|---|---|
| ≤0.030 | ≤2.50 | ≤1.00 | 21.5–24.5 | 3.0–5.5 | 0.05–0.60 | 0.05–0.20 | 0.05–0.60 | ≤0.040 | ≤0.030 |
Single values are maximums unless a range is shown. Balance: Fe. Per ASTM A240/A240M.
Mechanical Properties
| Tensile strength | ≥600 MPa (87 ksi) |
|---|---|
| Yield strength (0.2%) | ≥400 MPa (58 ksi) |
| Elongation (50 mm) | ≥25% |
| Hardness | ≤290 HBW |
Room-temperature minimum values are summarized for annealed flat product under ASTM A240/A240M unless a condition is named in the property label; product form and thickness can change the requirement.
Physical Properties & Structure
| Density | 7.75 g/cm³ |
|---|---|
| Magnetic response | Magnetic because the microstructure contains a substantial ferrite fraction. |
| Microstructure | Duplex (lean) |
Corrosion Resistance & Limits
- The mixed austenitic-ferritic structure provides high strength and improved resistance to chloride pitting and stress-corrosion cracking relative to 304/316-type grades.
- PREN is only a screening index. Temperature, crevices, weld phase balance, heat tint, deposits and actual solution chemistry still govern suitability.
Fabrication & Heat Treatment
| Welding | Use a qualified duplex procedure with controlled heat input, interpass temperature and filler to maintain phase balance, toughness and corrosion resistance. |
|---|---|
| Forming | Higher yield strength increases forming load and springback. Severe cold work may require solution annealing under a qualified route. |
| Machining | Use rigid equipment, positive feeds and lower cutting speed than common austenitic grades because high strength and work hardening raise cutting load. |
| Heat treatment | Solution anneal and rapid cooling are used to restore the specified duplex structure. Local stress relief can form harmful intermetallic phases and is not a generic remedy. |
Equivalent Grades
The closest international equivalents of 2304 Stainless Steel are 1.4362 (X2CrNiN23-4) in the EN system, 022Cr23Ni4MoCuN in the GB system.
These are common corresponding designations, not unconditional substitutes. Verify chemistry, mechanical properties, product standard, delivery condition, dimensions and project approval before changing designation.
| System | Designation |
|---|---|
| UNS | S32304 |
| EN | 1.4362 (X2CrNiN23-4) |
| GB | 022Cr23Ni4MoCuN |
Reference Product Forms & Dimensional Ranges
Common reference product forms for 2304 stainless steel: Sheet / Plate, Coil / Strip, Bar.
| Finishes | No.1, 2B |
|---|---|
| Sheet / coil thickness | 0.5–6.0 mm |
| Plate thickness | 6–60 mm |
Common surface and delivery options: No.1, 2B, BA or mechanically polished finish when supported by the product route; Hot rolled, peeled, bright drawn, ground or polished bar condition according to tolerance.
These published ranges are engineering references, not a live-stock or production-capability promise. Confirm the required product form, dimensions, condition, finish and supply route in the quotation.
Typical Applications
- Storage tanks and pressure vessels
- Domestic and industrial water heaters
- Structural members and bridge components
- Food and beverage process equipment
- Reinforcing bar in chloride-exposed concrete
Frequently Asked Questions
What is the difference between 2304 and 2205?
2205 carries ~3% molybdenum and more nitrogen, giving a PREN around 35 versus roughly 26 for 2304 — clearly better pitting resistance in aggressive chloride service. 2304 skips most of that molybdenum cost while keeping duplex strength, so it wins where corrosion demands are moderate but strength savings matter.
Why choose 2304 over 304 or 316L?
Its 400 MPa minimum yield is about double that of austenitics, which often allows one gauge thinner plate — direct weight and cost savings on tanks and structures. It also resists chloride stress-corrosion cracking, the classic failure mode of 304/316 hot-water equipment.
Is 2304 weldable?
Yes, with duplex practice: matching 2307 or over-alloyed 2209 filler, controlled heat input and interpass temperature below ~150 °C to keep the austenite-ferrite balance. Post-weld annealing is not required for normal sections.
2304 Compared With Other Grades
Organizational author: Tsingshan (Shandong) Iron & Steel Co., Ltd..Review method, status and limitations.
Other stainless steel grades:
304304L316316L201321310S4104302205202301309S316Ti347904L409L4204394414442507303317L254 SMO440C17-4 PH
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