Martensitic stainless steel for disk brake with excellent non-rusting property

A martensitic stainless steel for disk brakes with excellent non-rusting properties, characterized by containing, in terms of mass%, 0.01-0.10% carbon, up to 2% silicon, 0.2-2.0% manganese, up to 0.010% sulfur, less than 0.05% phosphorus, 0.005-0.050% nitrogen, 10-14% chromium, up to 2% nickel, up to 0.1% aluminum, up to 1% vanadium, 0.06-0.1% carbon and nitrogen, and 0.005%-1% tin, with the remainder being iron and incidental impurities. The steel is further characterized in that γP defined by the following equation is 80 or more. γP = 420[%C] + 470[%N] + 23[%Ni] + 9[%Cu] + 7[%Mn] - 11.5[%Cr] - 11.5[%Si] - 52[%Al] - 12[%Mo] - 23[%V] - 47[%Nb] - 49[%Ti] + 189