Improved Rolled Homogeneous Armor (IRHA) Steel Through Higher Hardness.
Final rept. Oct 89-Sep 95,
ARMY RESEARCH LAB ABERDEEN PROVING GROUND MD
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An improved rolled homogeneous armor IRHA steel with enhanced ballistic performance has been developed. Increases in ballistic performance are attributed to higher hardness levels achieved by IRHA, which maintain adequate toughness and ductility. Through augmentation of a generic chemical composition for standard rolled homogeneous armor RHA material, and optimization of heat treatment, greater hardenability, and higher hardness levels were attained. The higher hardenability ensures that through-thickness hardness, with the desired martensite microstructure, is obtained for armor plates up to 3 in thick, using current steel mill facilities and practice. The optimal, relatively low-carbon, nickel-chromium-molybdenum Ni-Cr-Mo IRHA alloy was developed in-house, employing U.S. Army Research Laboratory ARL, Materials Directorate MD laboratory facilities, followed by steel mill production heats demonstrating scale-up and producibility. Ballistic testing vs. projectiles, ranging from medium caliber to tank rounds, established that the IRHA material at the HRc 40 hardness level is best suited for vehicle hull applications, while material at HRc 48 provides better protection as applique armor. The armor plate at both hardness levels HRc 40 and 48 demonstrated structural integrity upon high kinetic energy KE ballistic loading, through passing the required full-scale 105-mm armor piercing AP T182 projectile impact tests. At the HRc 40 level, the IRHA weldability and fabricability were shown to be comparable to standard RHA for tank construction.
- Fabrication Metallurgy