The austenitic steel with designation 1.4404 contains molybdenum in addition to chromium and nickel. The difference against 1.4301/1.4307 apart from the presence of molybdenum is that the nickel content is greater. This type of stainless steel is often referred to as acid resistant which is to some degree a misnomer since the material resists attack only by weak acids. 1.4404 has low carbon content which means that it can be welded without risking impairment of corrosion resistance in the vicinity of the weld. In terms of strength, 1.4404 is more or less equivalent to the lower alloyed grades 1.4301/1.4307.
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.
The presence of molybdenum along with chromium renders 1.4404 resistant to corrosion in weak acids and water containing chlorides so long as the chloride concentration is not too high; an example of an environment where the steel works well is salt-laden coastal atmosphere.
Cold-drawn hexagons of 1.4404 exhibit quite good cold formability even though ductility is decreased as a result of cold working. In addition, the steel is characterised by excellent weldability. Austenitic stainless grades like 1.4404 are generally troublesome to machine but working is facilitated through bespoke tooling.
The surface finish of hexagons in 1.4404 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.