SPA‑H and SPA‑C are both JIS G 3125 weathering steels, but they differ in strength, production process, thickness range, ductility, and typical applications.
1. Core Designation & Production Process
SPA‑H: "H" = High‑strength; hot‑rolled (HR).
SPA‑C: "C" = Cold‑rolled (CR).
2. Chemical Composition (JIS G 3125)
Both share nearly identical alloying (Cu, Cr, Ni, P) for patina formation; only minor process‑related variations exist.
| Element | SPA‑H | SPA‑C |
|---|---|---|
| C | ≤ 0.12% | ≤ 0.12% |
| Si | 0.25–0.75% | 0.25–0.75% |
| Mn | 0.20–0.50% | 0.20–0.50% |
| P | 0.07–0.15% | 0.07–0.15% |
| S | ≤ 0.035% | ≤ 0.035% |
| Cu | 0.25–0.55% | 0.25–0.55% |
| Cr | 0.30–1.25% | 0.30–1.25% |
| Ni | ≤ 0.65% | ≤ 0.65% |
3. Mechanical Properties (Typical)
SPA‑H is stronger; SPA‑C is more ductile.
| Property | SPA‑H (t ≤ 16 mm) | SPA‑C (t ≤ 16 mm) |
|---|---|---|
| Yield strength | ≥ 345 MPa | ≥ 315 MPa |
| Tensile strength | ≥ 490 MPa | ≥ 450 MPa |
| Elongation | ≥ 15% | ≥ 26% |
4. Thickness & Form
SPA‑H: Hot‑rolled plate; thicker: ~1.5–40 mm; used for heavy structural sections.
SPA‑C: Cold‑rolled sheet/strip; thinner: ~0.6–2.3 mm; used for thin‑gauge components.
5. Weathering & Patina Behavior
Patina formation: Both form a stable, protective rust layer in normal outdoor atmospheres; kinetics and final appearance are nearly identical.
Corrosion resistance: Comparable in rural/urban/mild industrial environments; both degrade in severe coastal/polluted conditions.
6. Typical Applications
SPA‑H: Bridges, railway cars, heavy machinery, containers, structural steel, architectural facades.
SPA‑C: Thin‑gauge parts, vehicle panels, light towers, small equipment casings, appliances requiring good formability.
