Toughness Data for Monolithic High-Hardness Armor Steel

The purpose of this program was to generate meaningful toughness parameter data that could be incorporated into existing high-hardness steel armor specifications. Various toughness parameters, including Charpy V-notch impact, precracked Charpy toughness (W/A) and fracture toughness (K I c ), were explored for defining the toughness characteristics of monolithic high-hardness armor steels. Materials from three producers were investigated in thicknesses ranging from 0.125 to 0.750 in. The equivalent energy-area criterion was utilized to relate the toughness data obtained from subsize and standard size Charpy V-notch impact specimens. Results of this investigation show that the energy requirements, as set forth in the military specification for high-hardness armor steels, are met by each producer's material when the plate thickness is sufficient to use the standard size Charpy V-notch impact specimen. The equivalent energy-area criterion represents a usable approach for the interpretation of data obtained from subsize impact specimens and should now suffice to define an interim specification for the subsize Charpy test. The other toughness parameter results, plus hardness and tensile properties, are presented and discussed.