Grade 1.4305 is a free-machining stainless steel. In common with other austenitic grades like 1.4301 and 1.4307, it contains about 18% chromium and 9% nickel but the steel is also alloyed with sulphur for improved machinability. In general, stainless steels are regarded as more troublesome to machine than carbon steel but in 1.4305, the sulphur addition improves machinability to a degree that it is not so far removed from that for a free-machining carbon-manganese steel.
Cold-drawn hexagons in 1.4305 are standardised in EN 10088-3. This standard covers cold-finished bars with dimensions up to 160 mm even though it is normally only smaller sizes that are available in cold-drawn execution. Tibnor’s programme encompasses dimensions (that is the distance between opposite flats) between 10-50 mm.
In comparison with 1.4301 and 1.4307, the sulphur addition to 1.4305 results in somewhat impaired corrosion resistance. However, the steel withstands atmospheric corrosion rather well while at the same time, it is reasonably resistant to attack by rain water and less aggressive chemicals.
Cold-drawn bars of 1.4305 can be shaped by cold forming but it should be remembered that sulphur in combination with cold working reduces ductility which means poorer cold formability than for 1.4301 and 1.4307, even when the latter are cold drawn. The presence of sulphur also confers a risk for hot cracking in connection with welding which is not to be recommended for this grade.
The surface finish of hexagons in 1.4305 as stocked is 2H as defined in EN 10088-3. Cold drawing to a hexagonal shape is effected on hot-rolled rounds which have been annealed and pickled but even then, small shallow surface defects can remain. Hence, for parts or structures subjected to high loads, the cold-drawn surface should not be left unworked. The dimensional tolerance of drawn hexagons is h11 as stipulated in ISO 286 - 2 which is a zero-minus tolerance. In other words, the actual dimension is marginally less than the nominal one. The bars are very straight with maximum height of arc below 0.001 x length.