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FULLERKREG DIN 912 / ISO 4762 / GB70.1 A4 Marine Stainless Steel Socket Cap Screws are premium corrosion-resistant, full-thread hexagon socket head cap screws manufactured from A4 (SUS316) austenitic stainless steel with a passivated natural finish. The addition of 2–3% molybdenum (Mo) in SUS316 provides dramatically superior resistance to chlorides, saltwater, and acids compared to A2 (SUS304), making these screws the definitive choice for marine, offshore, chemical, and other harsh corrosive environments.
FULLERKREG DIN 912 A4 socket cap screws are manufactured from SUS316 austenitic stainless steel. The key differentiator from A2 (SUS304) is the addition of 2–3% molybdenum (Mo), which dramatically improves resistance to pitting and crevice corrosion in chloride-rich environments. All values are maximum unless a range is indicated.
| Grade | C (max) | Si (max) | Mn (max) | P (max) | S (max) | Cr | Ni | Mo |
|---|---|---|---|---|---|---|---|---|
| SUS316 (A4) | ≤0.08 | ≤1.00 | ≤2.00 | ≤0.045 | ≤0.030 | 16.00–18.00 | 10.00–14.00 | 2.00–3.00 |
The following mechanical properties apply per ISO 3506-1 requirements for A4-70 stainless steel fasteners.
| Property | Requirement | Unit |
|---|---|---|
| Tensile Strength (Rm) | Min. 700 | MPa |
| Proof Load Stress (Rp0.2) | Min. 450 | MPa |
| Hardness (max) | ≤95 HRB / ≤210 HV | HRB / HV |
| Elongation after fracture (A) | Min. 25 | % |
| Thread Tolerance Class | 6g | — |
| Surface Treatment | Passivation (natural finish) | — |
The molybdenum content in A4 is the critical differentiator. Here is a direct comparison to help you choose the right grade:
| Property | A2 (SUS304) | A4 (SUS316) — This Page |
|---|---|---|
| Chromium (Cr) | 18–20% | 16–18% |
| Nickel (Ni) | 8–10.5% | 10–14% |
| Molybdenum (Mo) | None | 2–3% (key advantage) |
| Chloride resistance | Good | Excellent |
| Saltwater / marine | Limited | Superior |
| Acid resistance | Moderate | Superior |
| Pitting corrosion resistance | Standard | Significantly better |
| Price point | Standard | Premium |
| Environment | A4 (SUS316) Performance | Recommendation |
|---|---|---|
| Indoor / dry environments | Excellent | ✅ Ideal |
| Outdoor / atmospheric exposure | Excellent | ✅ Ideal |
| Marine / saltwater (direct) | Very good | ✅ Recommended grade |
| Offshore / coastal structures | Very good | ✅ Recommended grade |
| Food & pharmaceutical processing | Excellent | ✅ Ideal |
| Chemical processing (mild acids) | Very good | ✅ Suitable |
| Chloride-rich environments | Very good | ✅ Recommended grade |
| Swimming pools / aquatic facilities | Very good | ✅ Recommended grade |
| Strong oxidizing acids (e.g. HNO3) | Moderate | ⚠️ Consult technical team |
FULLERKREG DIN 912 A4 marine stainless steel socket cap screws are widely used in demanding corrosive environments:
Full thread socket cap screws per DIN 912 / ISO 4762 / GB70.1 standard.
| Thread (d) | Pitch (p) | Head Dia. dk Max. | Head Dia. dk Min. | Head Height k Max. | Head Height k Min. | Key Size s | Key Depth t Min. | Body Dia. ds Max. | Body Dia. ds Min. |
|---|---|---|---|---|---|---|---|---|---|
| M1.6 | 0.35 | 3.00 | 2.86 | 1.60 | 1.46 | 1.5 | 0.7 | 1.60 | 1.46 |
| M2 | 0.4 | 3.80 | 3.62 | 2.00 | 1.86 | 1.5 | 1.0 | 2.00 | 1.86 |
| M2.5 | 0.45 | 4.50 | 4.32 | 2.50 | 2.36 | 2.0 | 1.1 | 2.50 | 2.36 |
| M3 | 0.5 | 5.50 | 5.32 | 3.00 | 2.86 | 2.5 | 1.3 | 3.00 | 2.86 |
| M4 | 0.7 | 7.00 | 6.78 | 4.00 | 3.82 | 3.0 | 2.0 | 4.00 | 3.82 |
| M5 | 0.8 | 8.50 | 8.28 | 5.00 | 4.82 | 4.0 | 2.5 | 5.00 | 4.82 |
| M6 | 1.0 | 10.00 | 9.78 | 6.00 | 5.70 | 5.0 | 3.0 | 6.00 | 5.82 |
| M8 | 1.25 | 13.00 | 12.73 | 8.00 | 7.64 | 6.0 | 4.0 | 8.00 | 7.78 |
| M10 | 1.5 | 16.00 | 15.73 | 10.00 | 9.64 | 8.0 | 5.0 | 10.00 | 9.78 |
| M12 | 1.75 | 18.00 | 17.73 | 12.00 | 11.57 | 10.0 | 6.0 | 12.00 | 11.73 |
| M14 | 2.0 | 21.00 | 20.67 | 14.00 | 13.57 | 12.0 | 7.0 | 14.00 | 13.73 |
| M16 | 2.0 | 24.00 | 23.67 | 16.00 | 15.57 | 14.0 | 8.0 | 16.00 | 15.73 |
| M20 | 2.5 | 30.00 | 29.67 | 20.00 | 19.48 | 17.0 | 10.0 | 20.00 | 19.67 |
| M24 | 3.0 | 36.00 | 35.61 | 24.00 | 23.48 | 19.0 | 12.0 | 24.00 | 23.67 |
Q: Why choose A4 (SUS316) over A2 (SUS304)?
A4 contains 2–3% molybdenum which significantly improves resistance to pitting corrosion caused by chlorides (salt, seawater, bleach). If your application involves marine, coastal, chemical, or food processing environments with chloride exposure, A4 is the correct choice.
Q: Are A4 socket cap screws magnetic?
A4 stainless steel is generally non-magnetic in the annealed state. Cold working during manufacturing may induce slight magnetism. For strictly non-magnetic applications, please confirm with our technical team.
Q: What is the difference between A4-70 and A4-80?
A4-70 has a minimum tensile strength of 700 MPa. A4-80 has a minimum tensile strength of 800 MPa. This page covers A4-70. Please contact us if you require A4-80.
Q: Can I get material certificates and test reports?
Yes. PPAP reports, material certificates (mill certificates), hardness test reports, and tensile test reports are available upon request for all FULLERKREG products.
Q: What is the minimum order quantity?
We supply both small quantities and large bulk orders. Please contact our sales team for pricing and MOQ details.
All FULLERKREG DIN 912 A4 marine stainless steel socket cap screws are manufactured under strict quality control procedures including:
For wholesale pricing, bulk orders, material certificates, or technical inquiries, please contact our sales team.
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