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FULLERKREG DIN 125A 300HV hardened flat washers are manufactured from carbon steel 45# (C45 / S45C) with quench and temper heat treatment to achieve a minimum hardness of 300 HV, finished with a Zinc CR3 (trivalent chromium passivation, RoHS compliant) electroplated surface. Conforming to DIN 125A, ISO 7089, and GB/T 97.1, these hardened washers combine the high bearing-face hardness required for Grade 8.8, 10.9, and 12.9 high-tensile bolts with the corrosion protection of a zinc electroplated coating — making them the preferred choice for structural, automotive, and outdoor industrial applications.
The Zinc CR3 surface finish provides a bright silver appearance with a thin trivalent chromium passivation layer (CR3, RoHS compliant — no hexavalent chromium Cr6+), offering salt spray resistance of ≥ 240 hours to red rust and significantly better corrosion protection than black oxide alone. The 300 HV minimum hardness per ISO 7089 ensures the washer bearing face resists embedding under high clamping loads, maintaining accurate bolt preload throughout the service life of the joint.
⚠️ Important: Always use hardened washers (300 HV minimum) with Grade 10.9 and Grade 12.9 bolts. Standard soft washers (≤ 200 HV) will embed under high clamping loads and cause preload loss in high-strength bolted joints.
| Standard | DIN 125A ≡ ISO 7089 ≡ GB/T 97.1 |
| Type | Hardened flat washer — normal series (Form A), chamfer on one side of inner hole |
| Material | Carbon Steel 45# (C45 / S45C / 1.0503) |
| Heat Treatment | Quenched & Tempered (Q&T) |
| Hardness | 300 – 370 HV (min. 300 HV per ISO 7089 hardened washer specification) |
| Surface Finish | Zinc CR3 — electroplated zinc with trivalent chromium passivation (RoHS compliant) |
| Zinc Coating Thickness | 5 – 8 μm (electroplated) |
| Salt Spray Resistance | ≥ 240 hours to red rust (per ISO 9227) |
| RoHS Compliance | Yes — CR3 trivalent chromium, no Cr6+ hexavalent chromium |
| Size Range | M5 – M36 |
| Recommended Bolt Grade | Grade 8.8, 10.9, 12.9 high-tensile bolts |
| Corrosion Resistance | Good — suitable for general industrial and mild outdoor environments |
| Magnetic | Yes |
| Related Standard | ISO 7089 (hardened washer grade) | GB/T 97.1 | DIN 125B (ISO 7090, double chamfer) |
| [Product Photo 1] | [Product Photo 2] | [Product Photo 3] | [Product Photo 4] |
All dimensions in millimeters (mm). Data per DIN 125A / ISO 7089 standard.
| Nominal Size (Bolt d) | d1 — Inner Ø (mm) | d2 — Outer Ø (mm) | h — Thickness (mm) | Weight (kg / 1000 pcs) |
|---|---|---|---|---|
| M5 | 5.3 | 10 | 1.0 | 0.27 |
| M6 | 6.4 | 12 | 1.6 | 0.68 |
| M8 | 8.4 | 16 | 1.6 | 1.21 |
| M10 | 10.5 | 20 | 2.0 | 2.37 |
| M12 | 13.0 | 24 | 2.5 | 4.73 |
| M14 | 15.0 | 28 | 2.5 | 6.43 |
| M16 | 17.0 | 30 | 3.0 | 8.98 |
| M18 | 19.0 | 34 | 3.0 | 11.8 |
| M20 | 21.0 | 37 | 3.0 | 14.2 |
| M22 | 23.0 | 39 | 3.0 | 15.6 |
| M24 | 25.0 | 44 | 4.0 | 27.4 |
| M27 | 28.0 | 50 | 4.0 | 35.9 |
| M30 | 31.0 | 56 | 4.0 | 45.4 |
| M33 | 34.0 | 60 | 5.0 | 64.3 |
| M36 | 37.0 | 66 | 5.0 | 83.2 |
* d1 = inner diameter (clearance hole); d2 = outer diameter; h = nominal thickness. All dimensions per DIN 125A / ISO 7089. Weights are approximate based on carbon steel density (7.85 g/cm³). Zinc CR3 coating (5–8μm) adds negligible weight.
| Property | Zinc CR3 (This Product) | Black Oxide |
|---|---|---|
| Process | Electroplated zinc + trivalent chromium passivation | Alkaline blackening (conversion coating) |
| Coating thickness | 5 – 8 μm | 1 – 2 μm |
| Salt spray resistance | ≥ 240 hours to red rust | ≤ 24 hours (oil-wetted) |
| Corrosion protection | Good — cathodic zinc protection | Minimal — oil-dependent |
| RoHS compliance | Yes (CR3 trivalent) | Yes |
| Appearance | Bright silver / light blue iridescent | Matte black |
| Outdoor suitability | Good — general industrial & mild outdoor | Poor — indoor / oil-wetted only |
| Best for | Structural, automotive, outdoor industrial | Indoor machinery, precision equipment |
| Property | 300HV Hardened (This Product) | Standard 200HV (Soft) |
|---|---|---|
| Hardness | 300 – 370 HV | ≤ 200 HV |
| Heat treatment | Quenched & Tempered | None (as-stamped) |
| Embedding under load | Minimal — maintains preload | Significant — causes preload loss |
| Suitable bolt grades | 8.8, 10.9, 12.9 | 4.6, 4.8, 5.6, 6.8 (low-strength only) |
| ISO 7089 grade | Hardened washer (300 HV) | Normal washer (200 HV) |
| Property | Value |
|---|---|
| Base Material | Carbon Steel 45# (C45 / S45C / 1.0503) |
| Carbon Content | 0.42 – 0.50% |
| Heat Treatment | Quenched & Tempered (Q&T) |
| Hardness | 300 – 370 HV (min. 300 HV per ISO 7089) |
| Tensile Strength (approx.) | ≥ 950 MPa (corresponding to 300 HV) |
| Surface Finish | Zinc CR3 — electroplated zinc + trivalent chromium passivation |
| Zinc Coating Thickness | 5 – 8 μm |
| Salt Spray Resistance | ≥ 240 hours to red rust (ISO 9227) |
| RoHS Compliance | Yes — CR3 trivalent chromium, no Cr6+ |
| Temperature Limit | Up to +120°C (zinc coating service limit) |
| Magnetic | Yes |
| Density | 7.85 g/cm³ |
Q: What is Zinc CR3 and why is it RoHS compliant?
A: Zinc CR3 refers to electroplated zinc with a trivalent chromium (Cr3+) passivation layer. Traditional zinc plating used hexavalent chromium (Cr6+) passivation, which is toxic and restricted under the EU RoHS Directive and REACH regulations. CR3 trivalent chromium passivation provides similar corrosion protection without the environmental and health hazards of Cr6+. FULLERKREG Zinc CR3 washers are fully RoHS compliant.
Q: Why do I need hardened washers with Grade 10.9 or 12.9 bolts?
A: High-strength bolts generate very high contact pressures under the bolt head and nut — often exceeding 1000 MPa. Standard soft washers (≤ 200 HV) will plastically deform (embed) under these pressures, causing the bolt to lose preload. Hardened washers (300 HV minimum) resist embedding and maintain accurate preload throughout the service life of the joint. This is critical for structural integrity and joint reliability.
Q: Can I use Zinc CR3 hardened washers outdoors?
A: Yes. The Zinc CR3 coating provides ≥ 240 hours salt spray resistance (ISO 9227), making these washers suitable for general industrial and mild outdoor environments. For long-term outdoor structural applications or coastal environments, consider hot dip galvanised (HDG) washers for superior corrosion protection (45–85 μm zinc vs 5–8 μm for electroplated).
Q: What is the difference between DIN 125A 300HV Zinc CR3 and 300HV Black Oxide?
A: Both products use the same 300HV hardened carbon steel 45# base material with identical dimensions. The difference is the surface finish: Zinc CR3 provides ≥ 240 hours salt spray resistance and is suitable for outdoor use; Black Oxide provides minimal corrosion protection and is best for indoor, oil-wetted, or precision applications. Choose Zinc CR3 for outdoor or corrosive environments; choose Black Oxide for indoor precision machinery.
Q: What is the difference between DIN 125A and ISO 7089 for hardened washers?
A: DIN 125A and ISO 7089 specify the same washer dimensions. ISO 7089 additionally defines two hardness grades: 200 HV (normal) and 300 HV (hardened). FULLERKREG 300HV Zinc CR3 washers conform to the ISO 7089 hardened washer specification and DIN 125A dimensional requirements.
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