Duplex stainless steels are known to have a good resistance to localised corrosion,
especially thanks to their quiet high level of chromium (and for some of them molybdenum),
but also because of their very low level of sulphur. These very low levels of sulphur are
also useful to guaranty a good toughness and a good hot workability for these grades.
Concerning long products like bars made in Duplex Stainless steels, one of their most
important property, after corrosion resistance, is their machinability. Unfortunately, one
of the most known way to improve the machinability of stainless steels is to increase
their sulphur level, thus forming manganese sulphides in the stainless steels which induce
better chip breaking and lubrication at the chip – cutting tool interface. So the question
is: can the sulphur well-known way to improve machinability of stainless steels be used on
Duplex Stainless Steels, without inducing hot rolling difficulties and too important a
decrease of their other main properties, i.e. localised corrosion resistance and
toughness? If not, are other ways possible?