Patent ID: 8071017
Filing Date: 2011-12-06
Classification: C22C

Abstract:
1. A martensitic steel comprising by weight: about 0.3% to 0.65% of C; about 7.5% to 12.5.0% of Cr; about 0.1% to 1.0% of Mo; about 0.1% to 3.0% of Ni; about 0.3% to 1.5% of Mn; at least one element selected from the group consisting of Si, Sn, and Ge wherein (Si+Sn+Ge) is about 0.1% to 1.5% and Ge is at most 0.1%; about 0.3% to 1.3% of Cu wherein Cu is less than (Si+Sn+Ge); V and Ti, wherein (V+Ti) is about 0.15 to 1.25%; at most 0.25% of Al; and a balance of Fe and incidental impurities, the sum of said alloying elements of said steel, except for Cr, being less than 9.0% of the weight, whereby said steel has a Rockwell hardness of about C 51 to 55, an ultimate tensile strength of about 250 to 310 ksi, a yield strength of about 200 to 240 ksi, a Charpy V-notch impact toughness energy of about 12 to 22 ft-lb, and a fracture toughness K1c of more than 40 ksi√in.