Abstract: Disclosed herein is high strength austenitic steel having excellent cold work hardenability, consisting essentially of the following elements:C . . . 0.1-0.3 wt. %;Si . . . up to 1.5 wt. %;Mn . . . 16-22 wt. %;Cr . . . 14-18 wt. %;V . . . 0.8-1.7 wt. %;N . . . 0.3-0.6 wt. %;Ni . . . below 0.8 wt. %; andFe and inevitable impurities . . . balance,with a proviso that the C-, N- and V-contents satisfy the following inequalities:C+N-(V/10).gtoreq.0.4 wt. %; andC+N+V/5.gtoreq.0.75 wt. %.The above austenitic steel may further contain at least one element selected from the group consisting of 0.05-1.0 wt. % of Ti and 0.05-1.0 wt. % of Nb. The above high strength austenitic steel has an extremely high 0.2% proof stress, exhibits excellent resistance to stress corrosion cracking and good hot workability, and maintains its non-magnetic properties.

Abstract: This invention relates to a free-cutting steel that is used as a material for mechanical construction members be manufactured by machining as well as cold working.There has been proposed resulfurized free-machining steels containing large amounts of sulfur to improve the machinability, as well as resulfurized free-machining steels containing sulfur and zirconium to improve machinability and cold workability. None of these steels, however, simultaneously satisfy the machinability cold workability and mechanical properties required of steels used for the construction of machines.The present invention provides a steel comprising 0.08 to 0.6% of carbon, 0.35% or less of silicon, 0.3 to 1.5% of manganese, 0.04 to 0.15% of sulfur, 0.010 to 0.05% of aluminum, 0.01 to 0.08% of niobium, 0.008% or less of oxygen, 0.008% or less of nitrogen, wherein the amount of zirconium being 0.2 to 1.2 in terms of (Zr% -2.9x 0% -6.