+86 (0) 159 5016 9967
sales@fullerkr.com
FULLERKREG DIN 931 Duplex 2205 partially threaded hexagon bolts are manufactured from UNS S31803 / S32205 duplex stainless steel, with a whitened and passivated surface finish. Duplex 2205 is a two-phase (austenite + ferrite) stainless steel that delivers approximately twice the yield strength of standard austenitic grades (A2/A4) while simultaneously providing superior resistance to chloride stress corrosion cracking (SCC), pitting, and crevice corrosion — making these bolts the premier choice for the most demanding offshore, marine, chemical, and subsea structural applications.
The partially threaded shank — with a smooth unthreaded grip length beneath the head — provides precise shear load transfer through the bolt body, making DIN 931 the preferred choice for structural connections, flanged joints, and machinery where the bolt passes through clearance holes and the thread engages only in the nut or tapped hole.
| Standard | DIN 931 ≡ ISO 4014 (Partially Threaded Hexagon Head Bolts) |
| Thread | Metric coarse per ISO 261 / DIN 13 |
| Thread Coverage | Partial thread — unthreaded grip length beneath head |
| Head Type | Hexagon head — driven by open-end wrench, ring spanner, or socket |
| Material | Duplex 2205 Stainless Steel / UNS S31803 / S32205 / 1.4462 |
| Microstructure | Duplex (austenite + ferrite, ~50/50) — combines strength of ferritic with corrosion resistance of austenitic |
| Surface Finish | Whitened & Passivated |
| Size Range | M6 – M36 (standard); larger sizes on request |
| Length Range | 25 mm – 300 mm (size-dependent) |
| PREN | ≥ 34 (typically ~38–40) — significantly higher than A4 SUS316 (~24–26) |
| Key Advantage | ~2× yield strength of A4-70 + superior SCC & pitting resistance — the premium choice for aggressive environments |
| Related Standard | ASTM A193 B7M | NACE MR0175 / ISO 15156 | ISO 4014 | EN 10088 |
| [Product Photo 1] | [Product Photo 2] | [Product Photo 3] | [Product Photo 4] |
All dimensions in millimeters (mm). Data per DIN 931 / ISO 4014 standard.
| Thread (d) | Pitch (mm) | s — A/F (mm) | e — A/C (mm) | k — Head Height (mm) | ds — Shank Ø (mm) |
|---|---|---|---|---|---|
| M6 | 1.0 | 10 | 11.05 | 4.0 | 5.7 |
| M8 | 1.25 | 13 | 14.38 | 5.3 | 7.64 |
| M10 | 1.5 | 17 | 18.90 | 6.4 | 9.64 |
| M12 | 1.75 | 19 | 21.10 | 7.5 | 11.57 |
| M14 | 2.0 | 22 | 24.49 | 8.8 | 13.57 |
| M16 | 2.0 | 24 | 26.75 | 10.0 | 15.57 |
| M20 | 2.5 | 30 | 33.53 | 12.5 | 19.48 |
| M24 | 3.0 | 36 | 39.98 | 15.0 | 23.48 |
| M27 | 3.0 | 41 | 45.20 | 17.0 | 26.48 |
| M30 | 3.5 | 46 | 50.85 | 18.7 | 29.48 |
| M36 | 4.0 | 55 | 60.79 | 22.5 | 35.38 |
* s = across flats (A/F); e = across corners (A/C); k = head height; ds = unthreaded shank diameter (max). All dimensions per DIN 931 / ISO 4014.
| Thread (d) | b — L ≤ 125 mm | b — 125 < L ≤ 200 mm | b — L > 200 mm |
|---|---|---|---|
| M6 | 18 | 24 | — |
| M8 | 22 | 28 | — |
| M10 | 26 | 32 | 45 |
| M12 | 30 | 36 | 49 |
| M14 | 34 | 40 | 53 |
| M16 | 38 | 44 | 57 |
| M20 | 46 | 52 | 65 |
| M24 | 54 | 60 | 73 |
| M27 | 60 | 66 | 79 |
| M30 | 66 | 72 | 85 |
| M36 | 78 | 84 | 97 |
* b = threaded length. Grip length = L − b − k (approximate). Per DIN 931 / ISO 4014.
| Property | Value |
|---|---|
| Material Designation | Duplex 2205 / UNS S31803 / S32205 / 1.4462 |
| Microstructure | Duplex — ~50% austenite + ~50% ferrite |
| Nominal Composition | 22% Cr — 5% Ni — 3% Mo — 0.17% N |
| Tensile Strength (Rm) | ≥ 620 MPa (min.) — typically 750–900 MPa |
| 0.2% Proof Stress (Rp0.2) | ≥ 450 MPa (min.) — typically 550–700 MPa |
| Yield Strength advantage | ~2× that of A2-70 / A4-70 austenitic grades |
| Hardness | ≤ 310 HB / ≤ 32 HRC |
| Elongation at Break | ≥ 25% |
| Impact Toughness (Charpy) | Good — suitable down to −50°C |
| PREN (Pitting Resistance) | ≥ 34 (typically ~38–40) — vs ~24–26 for A4 SUS316 |
| Chloride SCC resistance | Excellent — far superior to austenitic grades (A2/A4) |
| Density | 7.80 g/cm³ |
| Magnetic | Yes — ferrite phase makes duplex magnetic |
| Surface Finish | Whitened & Passivated |
| Temperature Range | −50°C to +250°C (continuous service; avoid prolonged use above 300°C) |
| Property | Duplex 2205 (This Product) | A4-80 — SUS316 | A4-70 — SUS316 | A2-70 — SUS304 |
|---|---|---|---|---|
| Microstructure | Duplex (austenite + ferrite) | Austenitic | Austenitic | Austenitic |
| Tensile Strength (Rm) | ≥ 620 MPa (typ. 750–900) | ≥ 800 MPa | ≥ 700 MPa | ≥ 700 MPa |
| Proof Stress (Rp0.2) | ≥ 450 MPa (typ. 550–700) | ≥ 600 MPa | ≥ 450 MPa | ≥ 450 MPa |
| Yield strength vs A4-70 | ~1.5× to 2× higher | ~1.3× higher | Baseline | Baseline |
| PREN | ~38–40 | ~24–26 | ~24–26 | ~18–20 |
| Chloride pitting resistance | Excellent | Good | Good | Moderate |
| Chloride SCC resistance | Excellent — key advantage over austenitic | Susceptible at elevated temp. | Susceptible at elevated temp. | Susceptible |
| Crevice corrosion | Very good | Good | Good | Moderate |
| Magnetic | Yes (ferrite phase) | Slightly (cold worked) | Slightly | Slightly |
| Max service temp. | +250°C (avoid >300°C) | +300°C | +300°C | +300°C |
| Cost | Premium | High | Medium-high | Medium |
| Best for | Offshore, subsea, chemical, high-chloride structural | High-load marine & chemical | Standard marine & corrosive | General outdoor & mild corrosive |
| Element | C | Cr | Ni | Mo | N | Mn | Si | P | S |
|---|---|---|---|---|---|---|---|---|---|
| % (max/range) | ≤0.030 | 21.0–23.0 | 4.5–6.5 | 2.5–3.5 | 0.08–0.20 | ≤2.00 | ≤1.00 | ≤0.030 | ≤0.020 |
* Per ASTM A276 / EN 10088-3 for UNS S32205 / 1.4462. The nitrogen (N) content is a key strengthening and pitting resistance element in Duplex 2205.
Q: What makes Duplex 2205 superior to A4 (SUS316) for structural bolts?
A: Duplex 2205 offers three key advantages over A4 SUS316: (1) approximately 1.5–2× higher yield strength, allowing smaller or fewer bolts for the same load; (2) a PREN of ~38–40 vs ~24–26 for A4, providing dramatically better pitting and crevice corrosion resistance; and (3) far superior resistance to chloride stress corrosion cracking (SCC) — a failure mode that can affect austenitic grades (A2/A4) at elevated temperatures in chloride environments.
Q: What is chloride stress corrosion cracking (SCC) and why does it matter?
A: Chloride SCC is a failure mechanism where austenitic stainless steels (A2/A4) can crack under tensile stress in the presence of chlorides and elevated temperatures (typically above 60°C). Duplex 2205 is highly resistant to chloride SCC due to its ferrite phase, making it the preferred material for offshore, chemical, and high-temperature marine applications where SCC is a design concern.
Q: Is Duplex 2205 magnetic?
A: Yes. The ferrite phase in Duplex 2205 makes it magnetic — unlike fully austenitic grades (A2/A4) which are only slightly magnetic after cold working. This is a normal characteristic of duplex stainless steel and does not affect corrosion resistance or mechanical performance.
Q: What is the temperature limitation of Duplex 2205?
A: Duplex 2205 should not be used in continuous service above +250°C to +300°C. Prolonged exposure above 300°C can cause sigma phase embrittlement, reducing toughness. For high-temperature applications above 300°C, specify austenitic grades (A2/A4) or high-temperature alloys instead.
Q: Can Duplex 2205 bolts gall during installation?
A: Duplex 2205 has lower galling tendency than austenitic stainless steels due to its higher hardness and ferrite content. However, anti-seize compound (nickel-based recommended) should still be applied to threads before installation, especially for larger sizes (M20 and above) and stainless-to-stainless connections.
Q: What nut and washer should I use with Duplex 2205 bolts?
A: Use Duplex 2205 hexagon nuts and washers to maintain material compatibility and avoid galvanic corrosion. If Duplex nuts are unavailable, A4 stainless nuts (DIN 934) are acceptable for non-critical applications. Always use stainless washers (DIN 125) to protect the joint surface. For NACE MR0175 / ISO 15156 compliance, verify that all fastener components meet the applicable hardness and material requirements.
20% off all Cordless tool kits.
Fresh picks for your outdoor space, just in.