Quick Answer
Quick Answer
EN 10028-7 specifies requirements for stainless steel flat products (plate, sheet, strip) intended for pressure purposes under the European Pressure Equipment Directive. It defines grade designations, chemical composition limits, mechanical properties at room and elevated temperature, and inspection requirements aligned with EN 10204.
EN 10028-7 is Part 7 of the EN 10028 series, which collectively covers flat products for pressure purposes. While other parts address carbon and alloy steels, Part 7 is dedicated entirely to stainless steels — austenitic, ferritic, martensitic, and duplex grades intended for use in pressure vessels, heat exchangers, and process equipment subject to the EU Pressure Equipment Directive (PED 2014/68/EU).
Relationship to the EN 10028 Series
The EN 10028 series is structured as follows:
| Part | Scope |
|---|---|
| EN 10028-1 | General requirements (applies to all parts) |
| EN 10028-2 | Non-alloy and alloy steels with elevated temperature properties |
| EN 10028-3 | Weldable fine grain steels, normalized |
| EN 10028-4 | Nickel alloy steels with low temperature properties |
| EN 10028-5 | Weldable fine grain steels, thermomechanically rolled |
| EN 10028-6 | High yield strength steel, quenched and tempered |
| EN 10028-7 | Stainless steels |
EN 10028-1 is always invoked alongside Part 7 — it defines general technical delivery conditions (dimensional tolerances, surface condition, marking requirements) that apply across the series.
Grade Coverage
EN 10028-7 covers stainless steel grades designated by both the EN steel name system (e.g., X5CrNi18-10) and the steel number system (e.g., 1.4301). Key grades include:
| Steel Number | Steel Name | ASTM Approximate Equivalent |
|---|---|---|
| 1.4301 | X5CrNi18-10 | 304 |
| 1.4307 | X2CrNi18-9 | 304L |
| 1.4401 | X5CrNiMo17-12-2 | 316 |
| 1.4404 | X2CrNiMo17-12-2 | 316L |
| 1.4571 | X6CrNiMoTi17-12-2 | 316Ti |
| 1.4541 | X6CrNiTi18-10 | 321 |
| 1.4550 | X6CrNiNb18-10 | 347 |
| 1.4462 | X2CrNiMoN22-5-3 | 2205 (duplex) |
Chemical Composition Requirements
EN 10028-7 sets composition limits that are broadly similar to ASTM A240 but with some differences in element windows. Key comparison for 316L:
| Element | EN 10028-7 (1.4404) | ASTM A240 (316L) |
|---|---|---|
| C max | 0.030% | 0.030% |
| Mn max | 2.00% | 2.00% |
| Si max | 1.00% | 0.75% |
| P max | 0.045% | 0.045% |
| S max | 0.015% | 0.030% |
| Cr | 16.5–18.5% | 16.0–18.0% |
| Ni | 10.0–13.0% | 10.0–14.0% |
| Mo | 2.00–2.50% | 2.00–3.00% |
Note the tighter sulfur limit in EN 10028-7 (0.015% vs 0.030%) — important for buyers sourcing material to both standards simultaneously. Material certified to EN 10028-7 will generally meet ASTM A240 chemistry limits, but the reverse is not always true.
Mechanical Properties
Mechanical property requirements under EN 10028-7 are specified at room temperature (RT) and — for austenitic grades — at elevated temperatures up to 400°C. This elevated-temperature data is essential for pressure equipment design calculations.
Room temperature requirements for selected grades:
| Grade | Rp0.2 min (MPa) | Rm (MPa) | A80 min % |
|---|---|---|---|
| 1.4301 (304) | 210 | 520–720 | 45 |
| 1.4307 (304L) | 200 | 500–700 | 45 |
| 1.4401 (316) | 220 | 530–730 | 40 |
| 1.4404 (316L) | 220 | 520–670 | 40 |
| 1.4462 (duplex) | 460 | 640–840 | 25 |
A80 = elongation measured on 80 mm gauge length.
Elevated Temperature Properties
A major differentiator between EN 10028-7 and purely commercial specifications is the inclusion of minimum 0.2% proof strength (Rp0.2) values at elevated temperatures. These values feed directly into pressure vessel wall thickness calculations per EN 13445 (unfired pressure vessels) and EN 13480 (metallic industrial piping).
For example, Grade 1.4404 (316L) has a minimum Rp0.2 of:
- 20°C: 220 MPa
- 100°C: 185 MPa
- 200°C: 160 MPa
- 300°C: 143 MPa
- 400°C: 130 MPa
This declining strength profile at elevated temperature must be accounted for in the design allowable stress. If the MTC does not report high-temperature properties where required, the designer must rely on standard tabulated values.
Inspection Requirements
EN 10028-7 references EN 10204 for inspection document requirements. For pressure equipment governed by PED:
- Category I vessels (lower risk): EN 10204 3.1 inspection certificate typically required.
- Category II and III vessels: EN 10204 3.1 minimum; 3.2 may be required for specific applications.
- Category IV vessels: EN 10204 3.2 (independent third-party countersignature) typically required.
The PED category is determined by the design pressure, volume, and fluid category — not by the material grade alone.
Ordering and Procurement Considerations
When placing a purchase order for EN 10028-7 material:
- Reference:
EN 10028-7+EN 10028-1(general requirements) - Specify steel number (e.g., 1.4404) AND steel name (X2CrNiMo17-12-2) for clarity
- State the product form: plate, sheet, or strip
- State dimensions (thickness × width × length)
- Surface condition (hot-rolled/annealed/pickled, cold-rolled)
- Required inspection document type (EN 10204 3.1 or 3.2)
- Any supplementary tests (IGC testing per EN ISO 3651, ferrite content for duplex)
Frequently Asked Questions
Is EN 10028-7 material interchangeable with ASTM A240 for pressure vessel fabrication?
Not automatically. While many grades are chemically similar, EN 10028-7 and ASTM A240 have different composition windows, and design codes (EN 13445 vs ASME BPVC) reference only their respective material standards. Using EN 10028-7 material in an ASME code vessel requires a code case or engineering alternative. Consult the relevant Authorized Inspector.
What is the difference between EN 10028-7 plate and EN 10028-7 sheet?
EN 10028-1 defines the product form boundaries: plate is generally ≥ 3 mm thick with width ≥ 600 mm; sheet is < 3 mm thick. Strip is < 600 mm wide. Some thickness/width combinations near the boundary may be offered as either plate or sheet depending on the mill's rolling practice.
Does EN 10028-7 cover super duplex grades like 2507?
EN 10028-7 covers the most common duplex grades (1.4462 / 2205). Super duplex grades such as UNS S32750 (1.4410) and super austenitic grades are covered under EN 10028-7 in later editions. Check the specific edition of the standard to confirm grade coverage.
Why does EN 10028-7 have a lower sulfur limit than ASTM A240?
EN 10028-7 imposes a tighter sulfur limit (0.015% max for most grades vs 0.030% in A240) because sulfur in stainless steel forms manganese sulfide inclusions that initiate pitting corrosion and reduce toughness. The European pressure equipment sector adopted the tighter limit as standard practice for critical applications.
Is EN 10028-7 recognition required for CE marking of pressure equipment?
Yes. Under PED 2014/68/EU, pressure equipment must use materials that either have a European Approval for Materials (EAM) or are covered by harmonized European standards. EN 10028-7 is a harmonized standard under PED, so materials certified to it are directly eligible for CE marking without additional approval.
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