Metallurgical Examination of 4 inch and 5 inch Thick Cast Armor Manufactured by the Pittsburgh Steel Foundry
WATERTOWN ARSENAL LABS MA WATERTOWN ARSENAL United States
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Four 4 thick and four 5 thick cast armor plates of the 2.5 Cr, 0.5 Mo type composition were subjected to metallurgical tests including fracture tests, hardness surveys, notched bar impact tests, and microscopic examination. Good correlation was established between the ballistic and metallurgical properties of the armor. The optimum hardness of both thicknesses of armor as demonstrated by the ballistic and metallurgical tests is approximately 240 BHN. The plates possessed reduced resistance to penetration at lower hardnesses and exhibited excessive brittleness at higher hardnesses. This behavior is consistent with the bainitic microstructure characteristic of the Cr-Mo steel at thicknesses in excess of approximately 3 .