Comparison of Ballistic Performance of a Split Heat of ESR and VAR 4340 Steel

A split argon-oxygen decarburized AOD heat of 4340 steel was used to compare the relative effectiveness of the VAR Vacuum Arc Remelting and ESR Electroslag Remelting processes on ballistic performance. Forgings of VAR and ESR 4340 steel were rolled into plates with thicknesses of 0.64, 0.81, 0.96, 1. 12, and 1.27 cm 0.25, 0.32, 0.38, 0.44, and 0.50 inch. Plates were heat treated to a tempered martensite microstructure by oil quenching and then tempering at 163, 171, 191, or 204 C 325, 340, 375, or 400 F. The protection limit V sub 50 for a .50 caliber AP M2 threat was determined for ESR and VAR 4340 steel plates of several thickness-tempering temperature combinations. Results indicate that over the thickness range studied the protection limit for ESR 4340 steel tempered at 171 C 340 F is equal to or greater than that of the VAR 4340 steel. Also, within the tempering temperature range studied the 171 C 340 C temper provides the greatest protection against the .50 caliber threat for 0.64-cm 0.25 inch thick ESR 4340 steel plates. There is a greater tendency for VAR processed 0.64-cm 0.25 inch thick plates tempered at 163 and 171 C 325 and 340 F to crack when impacted by this treat then comparable ESR processed plates. Further, for both ESR and VAR 4340 steel plates tempered at 171 C 340 F it is found that the penetration mechanism gradually changes from petalling to plugging as plate thickness increases. Keywords Armor plate Low alloy steels Ballistic tests Ballistic damage Steel armor Mechanical properties Toughness and Heat treatment.