AGE HARDENABLE ALLOY WITH A UNIQUE COMBINATION OF VERY HIGH STRENGTH AND GOOD TOUGHNESS

摘要

An age hardenable martensitic steel alloy having a unique combination of ver y high strength and good toughness consists essentially of, in weight percent, about C: 0.21-0.34; Mn: 0.20 max.; Si: 0.10 max.; P: 0.008 max.; S: 0.003 max.; Cr: 1.5-2.80; Mo: 0.90-1.80; Ni: 10-13; Co: 14.0-22.0; Al: 0.1 max.; Ti: 0.05 max.; Ce: 0.030 max.; La: 0.010 max.; the balance essentially iron. In addition, cerium and sulfur are balanced so that the ratio Ce/S is at least about 2 and not more than about 15. A small but effective amount of calcium can be present in place of some or all of the cerium and lanthanum.