NIOBIUM OR TITANIUM-CONTAINING LOW INVASION TYPE 29 CHROMIUM-4 MOLYBDENUM-WELDABLE FERRITE STAINLESS STEEL AND MANUFACTURE

摘要

A low interstitial, corrosion resistant, weldable ferritic stainless steel has an addition of between 0.05 and 0.50% by weight columbium and/or titanium to give the steel improved toughness when the maximum achievable cooling rate is limited. The steel consists of the following composition by weight percent: between 25.0 and 35% chromium, between 3.6 and 5.6% molybdenum, between 0.05 and 0.50% of columbium and/or titanium, less than 3.0% nickel, less than 2.0% manganese, less than 2.0% silicon, less than 0.5% aluminium, less than 0.5% copper, less than 0.050% phosphorous, less than 0.050% sulfur, less than 0.01% carbon, less than 0.02% nitrogen, the carbon plus nitrogen content being less than 0.025%, and the balance iron. A process is also disclosed which comprises air-cooling a steel having the above composition from the annealing temperature before cold rolling.