Method for increasing ballistic resistant performance of ultra high hard steel alloys

#The present invention relates generally to metal treatment. More particularly the present invention relates to a process of treating ultra high hard steel to have properties better suited for armor applications.

#One drawback caused by the formulation of ultra high harness (UHH) steel (Steel alloy having a Rockwell Hardness C (HRC) value of >55) is that it is quite brittle. UHH steel is substantially harder than other hardened steels such as “High Hard” steel (Mil-DTL-46100), which exhibits an HRC of approximately 51-53, but the high hard steel is not nearly as brittle.

#UHH steel having HRC values of approximately 55-70 has been heretofore dismissed as being useful for armor applications because of its brittleness (See Army Research Laboratory, Ballistic Testing of SSAB Ultra-High-Hardness Steel for Armor Applications, Showalter, Dwight D., et al. October 2008, ARL-TR-4632, pages 11-18). UHH steel, despite having a desirable hardness, is considered to be too brittle for armor applications. The brittleness is generally so substantial that a UHH steel plate may work once to defeat a projectile, but will be nearly useless after an initial impact because the plate is so heavily cracked or shattered. As such, the prior art teaches away from the use of UHH steel in armor applications.

#FIG. 1 provides a flow chart of an embodiment of the present invention.

#FIG. 2 provides a schematic view of an embodiment of the present invention.

#FIG. 3 provides an embodiment of the UHH steel composite armor.

#The present invention comprises a metal treatment method that achieves a superior steel alloy for use in armor applications by utilizing the hardness of the ultra-high hard (UHH) steel to shatter and destroy incoming projectiles. At the same time, the present invention overcomes the problem of brittleness and cracking of the steel alloy. The result is a highly effective, low cost armor system that does not add any measurable weight to the steel alloy.

#The UHH steel used herein may be of varying size and shape, and is not limited by varied configurations. In one embodiment, the UHH steel layer may be approximately 0.100 inch in thickness. In another embodiment, the UHH steel layer may be approximately 0.500 inch in thickness. In still another embodiment, the UHH steel layer may be approximately 0.250 inch thick. In yet another embodiment, the UHH steel layer may vary between 0.100 inch and 0.500 inch in thickness, depending on the projectiles it is intended to defeat.

#The UHH steel contemplated herein may be any steel based alloy having a HRC hardness of greater than 55. In one embodiment, the hardness of the UHH steel may be between approximately 55 and 70. To achieve hardness in this range, the steel may consist of approximately the following elements by weight percentage: 0.43-0.47% carbon, 0.377-1.000% molybdenum, 0.70-1.00% manganese, 0.48-1.5% chromium, and 3% nickel, the balance being iron, and other trace alloying elements which are not critical to the hardness of the UHH steel.