Deep-hardening boron steel with improved fracture resistance and wear properties

摘要

A deep hardening boron steel has a composition comprising, by weight, about 0.23% to 0.37% carbon, about 0.40% to 1.20% manganese, about 0.50% to 2.00% silicon, about 0.25% to 2.00% chromium, about 0.20% to 0.80% molybdenum, from 0.05% to 0.25% vanadium, from 0.03% to 0.15% titanium, from 0.015% to 0.050% aluminum, from 0.0008% to 0.009% boron, and 0.005% to 0.013% nitrogen. Also, the composition preferably contains less than about 0.025% each of phosphorus and sulfur. After quenching and tempering, articles made from this material are substantially free of aluminum nitrides, have a fine martensitic grain structure, have a distribution of nanometer size background nitride, carbonitride, and carbide precipitates, and a combination of high hardness and fracture toughness. The deep hardening steel article embodying the present invention is particularly useful for ground engaging tools that are subject breakage and wear, often at high temperature.