METHODS FOR MAKING HIGH HARDNESS, HIGH TOUGHNESS IRON-BASE ALLOYS

摘要

One aspect of the present disclosure is directed to low-alloy steels exhibiting high hardness and an advantageous level of multi-hit ballistic resistance with minimal crack propagation imparting a level of ballistic performance suitable for military armor applications. Certain embodiments of the steels according to the present disclosure have hardness in excess of 550 HBN and demonstrate a high level of ballistic penetration resistance relative to conventional military specifications.

主权项

1. A method of making a mill product having hardness greater than 550 HBN, the method comprising:
providing a mill product including an alloy comprising, in weight percentages based on total alloy weight, 0.48 to 0.52 carbon, 0.15 to 1.00 manganese, 0.15 to 0.45 silicon, 0.95 to 1.70 chromium, 3.30 to 4.30 nickel, 0.35 to 0.65 molybdenum, 0.0008 to 0.0030 boron, 0.001 to 0.015 cerium, 0.001 to 0.015 lanthanum, no greater than 0.002 sulfur, no greater than 0.015 phosphorus, iron, and impurities; austenitizing the alloy by heating the alloy at a temperature of at least 1500° F. (815° C.) for at least 30 minutes time-at-temperature; and cooling the alloy from the austenitizing temperature in a manner so that the alloy has a V50 ballistic limit that is at least as great as the required V50 under specification MIL-DTL-46100E.