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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 black oxide surface. Conforming to DIN 125A, ISO 7089, and GB/T 97.1, these hardened washers are specifically designed for use with high-tensile bolts (Grade 8.8, 10.9, and 12.9) where standard soft washers would embed into the joint surface under high clamping loads, causing loss of preload.
The 300 HV minimum hardness requirement per ISO 7089 ensures that the washer bearing face remains flat and does not deform under the high contact pressures generated by high-strength fasteners. This is critical for maintaining accurate bolt preload in structural and precision mechanical joints.
⚠️ Important: Always use hardened washers (300 HV minimum) with Grade 10.9 and Grade 12.9 bolts. Standard soft washers (200 HV) will embed 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 | Black Oxide (Blackened) |
| Size Range | M5 – M36 |
| Recommended Bolt Grade | Grade 8.8, 10.9, 12.9 high-tensile bolts |
| Corrosion Resistance | Mild — black oxide provides minimal protection; apply oil or grease for storage and service |
| 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).
| 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) |
| Structural applications | Required for high-strength structural bolting | Not suitable for high-strength bolts |
| Surface finish | Black Oxide | Various (zinc, plain, etc.) |
| Typical use | Grade 8.8/10.9/12.9 bolted joints, structural steel, machinery | General fastening with low-strength bolts |
| 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 | Black Oxide (alkaline blackening) — 1–2 μm, oil-retentive |
| Corrosion Resistance | Mild — black oxide provides minimal protection; oil or grease recommended |
| Temperature Limit | Up to +150°C (black oxide service limit) |
| Magnetic | Yes |
| Density | 7.85 g/cm³ |
| Manufacturing Process | Cold stamped then quench & temper heat treated |
Q: Why do I need hardened washers with Grade 10.9 or 12.9 bolts?
A: High-strength bolts (Grade 10.9 and 12.9) generate very high clamping forces — the contact pressure under the bolt head and nut can exceed 1000 MPa. Standard soft washers (200 HV) will plastically deform (embed) under these pressures, causing the bolt to lose preload over time. Hardened washers (300 HV minimum) resist this embedding and maintain accurate preload throughout the service life of the joint.
Q: What is the difference between 300HV and 200HV washers?
A: The hardness designation refers to the Vickers hardness of the washer. 300 HV washers are quench and temper heat treated to achieve minimum 300 HV hardness — approximately equivalent to 30 HRC or 950 MPa tensile strength. 200 HV washers are standard soft washers (as-stamped, no heat treatment). The 300 HV grade is specified by ISO 7089 for use with high-strength fasteners.
Q: Can I use these washers with Grade 8.8 bolts?
A: Yes. 300 HV hardened washers are suitable for use with Grade 8.8, 10.9, and 12.9 bolts. For Grade 8.8 bolts in non-critical applications, standard 200 HV washers may be acceptable — but hardened washers are always the safer choice for structural and high-load applications.
Q: Does black oxide provide corrosion protection?
A: Black oxide provides only minimal corrosion protection (1–2 μm conversion coating). It is primarily used for appearance and to provide an oil-retentive surface. For corrosion protection, always apply a light oil or anti-corrosion grease to black oxide washers during storage and installation. Do not use in outdoor, marine, or corrosive environments without additional protection.
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/soft) and 300 HV (hardened). FULLERKREG 300HV washers conform to the ISO 7089 hardened washer specification and DIN 125A dimensional requirements.
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