Development of Armor High Strength Steel (HSS) Martensitic Plates for Troops Carriers

Abstract

The present article is dealing with the conditioning of martensitic steel plates for armoring troops carriers. The steel alloy was processed into ingots. The ingots were hot flat rolled to 80 mm, followed by rolling to 6 mm. Specimens for detection of the critical transformation temperatures were taken. The Ac1, Ac3, Ms and Mf temperatures were detected as 716, 835, 356 and 218 °C respectively. The 80mm microstructure contains plate martensite colonies, while the 6mm plates reveal complete plate martensitic structure. Both cases contain embedded carbides. Heat treatment cycles were proposed for enhancing the ballistic resistance. A treatment was consisting of austentizing at 910 °C for 20 min., followed by water quenching. This process revealed fully fine lath martensitic packets. Tempering was done on the quenched as well as on rolled plates. Tempering at 350°C, causes dissociation of some martensite, and encourages migration of the entrapped carbon atoms forming carbide aggregates embedded between martensite plates packets. Tempering at 250°C for 20 min., relieves quenching induced stresses and reveals a lath martensitic structure with a small fraction of rosette like carbides. The process enhances elongation from 3% to 11.35%. The microstructure of as-rolled tempered plates at 300 oC for 20-30 minutes contains a thin ferrite layer on the boundaries surrounding the martensite packets, and few fractions of cotton wool shape carbides between the martensite packets. The treatment cycle improves the mechanical properties. Both treatments, at 250 and 300 oC, show successful ballistic resistance plates against shooting by 3 bullets.