Low phosphorus, zirconium micro-alloyed, fracture resistant steel alloys

An article having a cross-sectional thickness of 20 inches or more, fabricated from a steel alloy composition comprising:

• 0.36% to 0.46% by weight carbon;
• 0.30% to 0.50% by weight manganese;
• 0.001% to 0.012% by weight phosphorus;
• 0.15% to 0.30% by weight silicon;
• 1.75% to 2.25% by weight nickel;
• 1.40% to 1.60% by weight chromium;
• 0.90% to 1.10% by weight molybdenum;
• 0.015% to 0.025% by weight aluminum;
• 0.001% to 0.050% by weight zirconium;
• a balance of iron;
• further comprising
• a maximum of 0.003% by weight sulfur;
• and
• the article having a surface hardness range of 363-413 HBW and a transverse impact strength of 24 ft-lb.

An article having a cross-sectional thickness of 20 inches or less, comprising:

• 0.50% to 0.60% by weight carbon;
• 0.50% to 0.70% by weight manganese;
• 0.001% to 0.017% by weight phosphorus;
• 0.40% to 0.60% by weight silicon;
• 1.40% to 1.75% by weight nickel;
• 0.85% to 1.15% by weight chromium;
• 0.70% to 0.90% by weight molybdenum;
• 0.010% to 0.030% by weight aluminum;
• 0.001% to 0.050% by weight zirconium;
• a balance of iron;
• and
• the article having a surface hardness range of 363-413 HBW and a transverse impact strength of 24 ft-lb.