Stainless Steel
Stainless steels are iron‑chromium alloys containing at least 10.5% chromium, which forms a passive chromium oxide film that provides corrosion resistance. Commercial grades typically contain 11–30% chromium, depending on type.
Stainless steels are classified into five groups based on their crystal structure and strengthening mechanisms: Austenitic, Ferritic, Martensitic, Duplex, and Precipitation‑hardening (PH).
Martensitic grades such as SS 410 and SS 403 contain roughly 11–18% chromium and can be hardened by heat treatment. Ferritic grades such as SS 405 contain 10.5–30% chromium, low carbon, and have a BCC structure.
Precipitation‑hardening stainless steels (e.g., 15‑5 PH, 17‑4 PH) are high‑strength alloys containing ~12–17% Cr and 3–10% Ni, strengthened by nanoscale intermetallic precipitates formed during aging.
