PURPOSE: To obtain precipitation hardening type stainless steel having excellent seawater corrosion resistance as well as having good cold workability and machinability in a solid-solution heat treated state and also excellent in toughness while it has high strength after precipitation hardening.
CONSTITUTION: This stainless steel is a one contg., by weight, ≤0.020% C, ≤0.50% Si, ≤1.00% Mn, ≤0.005% S, 5.00 to 7.50% Ni, 14.5 to 17.0% Cr, 1.00 to 2.50% Mo, 0.50 to 0.100% N, 0.50 to 4.00% Cu and one or two kinds of 0.05 to 0.40% Nb and 0.05 to 0.20% Ti, and in which 6.8≤Ni+27(C+N)-3.5(Nb+2Ti)≤8.0 and 2.0≤(Nb+2Ti)/(C+N)<5.5 are satisfied and its structure after precipitation hardening is formed into a two phase structure of martensite and austenite as well as the amt. of the austenitic phase is regulated to 10 to 30%. If required, one or two kinds among B, Ca, Mg and rare earth metals are added to improve its workability.
OSHITA MASAMITSU
SHINKAWA KENZO
SAWADA TADASHI
