ASTM A606‑2 is a high‑strength, low‑alloy (HSLA) weathering steel defined by Type 2 in the ASTM A606/A606M standard. Below is its exact chemical composition (cast/heat analysis, the primary standard; product check analysis has slightly tighter/lower limits):
| Element | Min (%) | Max (%) | Key Role |
|---|---|---|---|
| Carbon (C) | - | 0.22 | Controls strength/hardenability; limited for weldability |
| Manganese (Mn) | - | 1.25 | Strengthens steel; improves toughness |
| Silicon (Si) | 0.30 | 0.65 | Aids deoxidation; supports patina formation |
| Phosphorus (P) | - | 0.04 | Enhances atmospheric corrosion resistance |
| Sulfur (S) | - | 0.04 | Controlled low level for ductility/weldability |
| Copper (Cu) | 0.20 | - | Critical for patina; core weathering element |
| Chromium (Cr) | 0.40 | 0.65 | Stabilizes protective oxide layer |
| Nickel (Ni) | - | 0.40 | Improves corrosion resistance & toughness |
| Vanadium (V) | 0.02 | 0.10 | Precipitation strengthening; refines grain |
| Iron (Fe) | Balance | - | Base matrix |
Notes
Type 2 is the basic weathering grade; Type 4/5 add more Cr/Ni/Cu for higher corrosion resistance.
The minimum 0.20% Cu is mandatory for A606‑2 to form a stable, protective patina outdoors.
All other elements are tightly controlled to balance strength, weldability, and weathering performance.
