Methods, compositions and structures for advanced design low alloy nitrogen steels

A method of making a low alloy high nitrogen steel structure, the method comprising:

• providing a steel composition comprising iron and, by weight:
• 0.14-0.60% nitrogen (N),
• 0.08-0.28% carbon (C),
• 0.10-2.20% nickel (Ni),
• 0.25-2.00% manganese (Mn),
• 1.20-2.70% chromium (Cr),
• 0.45-1.50% tungsten (W),
• not more than 0.05% molybdenum (Mo),
• not more than 0.02% vanadium (V),
• not more than 0.60% silicon (Si),
• not more than 0.10% copper (Cu),
• not more than 0.02% titanium (Ti),
• not more than 0.02% niobium (Nb),
• not more than 0.008% aluminum (Al), and
• not more than 0.02% of any other element with not more than 0.10% total other elements, wherein cobalt (Co) is substitutable for any part of the nickel;
• casting liquid to solid, or solid state processing under a first atmosphere to said alloy composition, then hot working or forming said steel composition to form to a shape;
• heating said steel composition to normalize or austenitize;
• quenching said steel composition at a rate to produce a substantially martensitic, bainitic, or mixed martensitic bainitic microstructure;
• and
• heating tempering said steel composition under a second gas atmosphere, wherein said second gas atmosphere comprises air, controlled atmosphere, or inert nitrogen or nitrogen and argon, or heating tempering in liquid environment.