Patent Document ID: 8137483
Application ID: 12387893
Patent Flag: 1

Claim One:
1. A method of making a low cost, high strength, high toughness martensitic steel comprising the steps of applying a mathematical model to define an optimum low cost chemical composition of said steel having specified levels of strength and toughness; predicting the content of retained austenite and critical temperatures with said mathematical model; melting said optimum chemical composition; processing ingots of said optimum chemical composition; producing articles from said ingots; heat treating said articles using said critical temperatures and said content of retained austenite; and verifying the properties of said articles by mechanical testing, said steel comprising by weight of about: C: 0.3 to 0.45%; Cr: at most 2.5%: Mo: at most 1.0; Ni: at most 3.5%; Mn: 0.3 to 1.5%; Si: 0.1 to 1.3%; Cu: about 0.1 to 1.0%, where Cu is less than Si; (V+Ti+Nb): about 0.1 to L0%; Al: at most 0.25%; a sum of alloying elements being less than about 11.5%; the balance being essentially Fe and incidental impurities, said processing ingots comprising homogeneous annealing at about 2100 to 2150° F., hot rolling/forging with start temperature at about 2150 to 2170° F. and finish temperature at about 1800 to 1850° F., air cooling, subjecting to recrystallization annealing at about 1100 to 1150° F., and air cooling.