Caterpillar Inc.

Joseph E McVicker

Kenneth W Burris

A steel article has a composition, by weight percent, including from 0.20 to 0.45 carbon, from 0.4 to 1.5 manganese, from 0.5 to 2.0 silicon, from 0.01 to 2.0 chromium, from 0.15 to 1.2 molybdenum, from 0.01 to 0.40 vanadium, from 0.01 to 0.25 titanium, from 0.005 to 0.05 aluminum, from 0.0001 to 0.010 boron, less than 0.002 oxygen, from 0.005 to about 0.017 nitrogen, and the balance essentially iron. The steel article is free of any detrimental aluminum nitride and has, after quenching and tempering, a fully martensitic microstructure and a controlled distribution of spaced apart micrometer size titanium nitride cuboids and nanometer size background carbonitride precipitates.

Hardness, strength, and fracture toughness steel

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.

Deep hardening boron steel article having improved fracture toughness

A high toughness steel has a composition comprising, by weight, about 0.10% to 1.05% carbon, about 0.00% to 0.05% aluminum, about 0.01% to 0.20% titanium, about 0.0005% to 0.02% boron, about 0.01% to 0.20% niobium and about 0.015% to 0.04% nitrogen and the balance essentially iron. Also, the composition contains sufficient amount of manganese, silicon, nickel, chromium, vanadium, and molybdenum such that said high toughness steel article, after quenching and tempering, has a R.sub.c hardness measured in the middle of a section having a thickness of no more than 25.4 mm, of at least 50% of the hardness measured at the surface of said section. After quenching and tempering, steel articles made of this composition have a plane strain fracture toughness more than 25% higher than that for steel having the same base chemistry and heat treatment, and being free from titanium, niobium, and boron and elevated nitrogen. Also, the composition preferably contains about 0.001% to 0.004% oxygen and less than about 0.04% each of phosphorous and sulfur. A high toughness steel embodying the present invention is particularly useful for making ground engaging tools that are constantly subjected to severe impact and vibration and are susceptible to breakage.

Elevated nitrogen high toughness steel article

A deep hardening steel has a composition comprising, by weight, about 0.26% to 0.37% carbon, about 0.5% to 1.0% manganese, about 1.0% to 3.0% silicon, about 1.5% to 2.5% chromium, about 0.3% to 1.0% molybdenum, from 0.05% to 0.2% vanadium, from 0.03% to 0.1% titanium, from 0.01% to 0.03% aluminum and at least 0.005% nitrogen. Also, the composition preferably contains less than about 0.025% each of phosphorus and sulfur. After quenching and tempering, articles made of this material are substantially free of aluminum nitrides, have a fine grained microstructure, 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 to breakage and abrasive wear at high temperature.

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Chillicothe, IL, United States of America

Joseph E McVicker