ASTM A240 303 Stainless Steel Composition & Free‑Machining Properties

ASTM A240 303 (UNS S30300) is the free‑machining austenitic stainless steel grade under ASTM standards. With 17–19% chromium, 8–10% nickel, and elevated sulfur content, it provides excellent machinability for turning, drilling, and threading operations.
Although its corrosion resistance is slightly lower than 304, 303 delivers superior performance in automatic machining, high‑speed cutting, and precision component manufacturing. It is widely used for bolts, nuts, fittings, valve components, shafts, and electronic hardware parts.
303 is supplied mainly as bars, wires, and selected plate and profile forms. As the free‑machining variant of the 304 family, it offers improved processing efficiency and surface finish quality for machining‑intensive applications.