UNS S15500 (XM-12) Stainless steel 15 - 5 PH, also
known as UNS S15500 or XM-12, is a modification of 17-4 PH developed in
the 60's. UNS S15500 stainless steel has a more refined microstructure
as a result of the remelting process in which it was developed. This
refined structure enhances toughness, especially in the transverse
direction of the material. UNS S15500 also has excellent corrosion
resistance, good fabricating characteristics and low temperature
hardening which makes Stainless Steel 15 - 5 PH® the preferred alloy for
many industries. The composition of UNS S15500 includes
small amounts of carbon, manganese, phosphorus, columbium (or niobium),
tantalum, silicon and sulfur. 15500 can be forged, welded and formed.
Machining may be performed in the solution-annealed state or in the
final heat treat condition. Desired mechanical properties such as
ductility and strength can be achieved through heating the material at
various temperatures. UNS S15500 is a martensitic
precipitation hardening grade. Martensitic stainless steels were
designed as a type of alloy which is corrosion resistant and could also
be hardened through heat treatment.