ASTM F436 / F436M HARDENED STEEL WASHERS — TECHNICAL DATASHEET
ASTM F436 and F436M establish the chemical, mechanical, and dimensional benchmarks for high-strength hardened steel washers. Unlike general-purpose low-carbon washers, these components are through-hardened or carburized to provide a consistent bearing surface capable of withstanding the high preloads of structural bolted joints (ASTM F3125, A325, A490, etc.) without dishing or surface embedment.
■ Material Classifications
- Type 1 (Carbon Steel): Standard grade for general-purpose structural applications. Through-hardened or carburized.
- Type 3 (Weathering Steel): Alloyed with Cu, Ni, Cr, and Si. Develops a protective oxide patina in cyclic wet-dry environments, eliminating the need for zinc coatings or paint in exposed frameworks.
■ Chemical Composition Requirements
| Element | Type 1 (Heat Analysis %) | Type 3 (Heat Analysis %) |
|---|---|---|
| Phosphorus (P) max | 0.040 | 0.040 |
| Sulfur (S) max | 0.050 | 0.050 |
| Silicon (Si) | — | 0.15 – 0.35 |
| Chromium (Cr) | — | 0.45 – 0.65 |
| Nickel (Ni) | — | 0.25 – 0.45 |
| Copper (Cu) | — | 0.25 – 0.45 |
Weathering Performance: Type 3 washers must achieve a minimum Corrosion Index (I) of 6.0 per the Legault-Leckie formula to be considered compliant.
■ Mechanical Hardness Limits
Hardness is tested per ASTM F606. Galvanized washers feature a lower minimum hardness to prevent hydrogen-induced brittle failure.
| Hardening Process | Finish State | Surface Hardness | Core Hardness |
|---|---|---|---|
| Through-Hardened | Plain / Coated | 38 – 45 HRC | 38 – 45 HRC |
| Through-Hardened | Hot-Dip Galvanized | 26 – 45 HRC | 26 – 45 HRC |
| Carburized | Plain / Coated | 69 – 73 HRA | ≥ 30 HRC |
■ Proprietary Datasheet Download
📄
ASTM F436 — Complete Technical Yield & Tolerance Datasheet
Contains empirical data for structural load capacities, full dimensional tolerance charts for all styles, and hydrogen embrittlement mitigation protocols.
⬇ DOWNLOAD DATASHEET■ Dimensional Parameters (Representative)
Standardized sizes for circular washers.
| Size (in) | OD (in) | ID (in) | Thickness (in) |
|---|---|---|---|
| 1/2" | 1.063 | 0.531 | 0.097 – 0.177 |
| 5/8" | 1.313 | 0.688 | 0.122 – 0.177 |
| 3/4" | 1.468 | 0.813 | 0.122 – 0.177 |
| 7/8" | 1.750 | 0.938 | 0.136 – 0.177 |
| 1" | 2.000 | 1.063 | 0.136 – 0.177 |
| 1-1/4" | 2.500 | 1.375 | 0.136 – 0.177 |
| 1-1/2" | 3.000 | 1.625 | 0.136 – 0.177 |
■ Hydrogen Embrittlement & Coating Protocols
- Critical Restriction: Grade A490 bolts (and washers used with them) must never be hot-dip galvanized or electroplated via standard acid pickling. Hydrogen absorption from pickling causes delayed, brittle catastrophic fracture.
- Allowed Coatings: Non-electrolytic, zinc-aluminum dispersion coatings (ASTM F1136, ASTM F3393) are preferred.
- Baking Schedule: If electrodeposition occurs, immediate post-plating "relief-baking" is mandatory: 190°C – 220°C for ≥4 hours, initiated within 4 hours of plating.
■ Product Identification
- Marking: All washers ≥ 1/4" must have a depressed (not raised) manufacturer's identifier.
- Grade: Type 1 washers may be marked "F436"; Type 3 washers must be marked "F436 3" or "3".
- Metric: ASTM F436M washers must feature a depressed "M" stamp.