What is 1.4305 (303)?

1.4305, steel name X8CrNiS18-9, is an austenitic chromium-nickel steel like 1.4301 with sulphur added. The sulphur forms manganese sulphide inclusions on which the chip breaks short instead of wrapping round the tool. That makes it the stainless grade for volume turning: shafts, bushes, fittings, fasteners and other small turned parts. It is supplied mainly as drawn round and hexagon bar. The sulphides lower corrosion resistance and weldability compared with 1.4301. Its US counterpart is 303.

What does the standard say about 1.4305 (303)?

The composition is in EN 10088-1, the delivery conditions for bars and sections in EN 10088-3. The US grade 303 (UNS S30300) is covered by ASTM standards; the limits correspond broadly, not in every detail.

How does 1.4305 (303) behave in the shop?

In batch turning every second of cycle time counts many times over. With 1.4305, higher cutting data than with 1.4301 are usually possible, the chip breaks short and a bird's nest is less likely, which makes unattended running with a bar feeder more feasible. Whether the part allows it depends on the application: if it is welded, sits in damp or chloride-bearing conditions or has to meet hygiene requirements, 1.4305 is often not a good choice. If the drawing says 1.4301, 1.4305 is a proposal to the customer, with the reason stated. Pickling or passivating sulphur-bearing grades needs a treatment suited to them, because the sulphides at the surface can be attacked, so tell the finisher which grade it is.

What is 1.4305 (303) often confused with?

1.4305 is not 1.4301: the same chromium-nickel base, but with sulphur, so it machines better and resists corrosion less. Nor is it ordinary free-cutting steel: 11SMnPb30 is non-alloy and rusts.