Alloy steels include varying shares of one or more elements (most commonly manganese, nickel, silicon, and chromium, but also aluminum, molybdenum, titanium, and vanadium), added in order to improve their physical properties (hardness, strength, ductility). Stainless steel (10–20 percent chromium) was made for the first time only in 1912 for kitchenware, and is now widely used for surgical instruments, engines, machine parts, and in construction.[52]
