Carburized ballistic alloy

Abstract

A method for making armor plate that is resistant to armor piercing small arms ammunition is provided. The armor plate includes a steel plate having a nominal chemical composition in weight percent of 0.4C-1.8Ni-0.8Cr-0.25Mo. The steel plate is carburized on one side and produces a carburized side and a non-carburized side. The carburized side of the steel plate has a carbon concentration of at least 0.9% by weight and the non-carburized side has a carbon concentration of between 0.38 and 0.45% by weight. After the steel plate has been carburized, it is subsequently thermally processed such that the carburized side has a hardness of at least 58 Rockwell Hardness C (HRC), and the non-carburized side has a hardness of between >=50 and <=55 HRC.

I claim: 
     
         1 - 2 . (canceled) 
     
     
         3 . A method for dissipating an impact force of a 30 caliber armor piercing projectile, the method comprising:
 impacting the projectile on a high C surface of a steel armor plate having a composite thickness of 6.35 millimeters at a first impact point; wherein said steel armor plate comprises   said composite thickness with two surfaces, one surface being said high C surface and the other surface being a low C surface;   said high C surface having a composition in weight percent within the range of C>0.8, 0.3-2.0 Mn, 0.40-9.0 Cr, 0.1-10.0 Ni, 0.01-2.0 Mo, balance Fe and other incidental impurities and having a hardness of greater than 58 Rockwell hardness C;   said low C surface having a composition in weight percent within the range of C<0.5, 0.3-2.0 Mn, 0.1-0.5 Si, 0.40-9.0 Cr, 0.1-10.0 Ni, 0.01-2.0 Mo, balance Fe and other incidental impurities and having a hardness of between ≧53 and ≦55 Rockwell hardness C; and   a C concentration gradient from said high C surface to said low C surface;   said high C surface having a hardness of at least 58 HRC and said low C surface having a hardness of >=52 and <=55 HRC.   
     
     
         4 . The method of  claim 3  further comprising preventing the projectile from penetrating the steel armor plate. 
     
     
         5 . The method of  claim 4  further comprising impacting a second 30 caliber armor piercing projectile on said high C surface within a proximity of 3 centimeters of the first impact point and preventing the second projectile from penetrating the steel armor plate. 
     
     
         6 . The method of  claim 3  wherein the steel armor plate is monolithic. 
     
     
         7 . The method of  claim 3  wherein the steel armor plate is composed of at least two laminates. 
     
     
         8 . The method of  claim 7  wherein the at least two laminates are oriented in an offset sheet roll direction.