Metallurgical Examination of Sections from the Cast Armor Turret made by Continental Foundry and Machine Company and two Trunnion Pins from a Heavy Tank M6A2E1
WATERTOWN ARSENAL LABS MA
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A metallurgical examination consisting of fracture, hardness, notched bar impact and microscopic tests has been conducted on two sections of cast armor of variable thickness 2 to 3-12 in. and 4-12 to 9 in. and a trunnion pin from the gun mount of the Heavy Tank M6A2E1. The 2 to 3-12 in. thick section, because of its high hardness 300 BHN and temper embrittlement, possessed poor shock resistance. The 4-12 to 9 in. thick section, heat treated to a hardness of 248-269 BHN, possessed acceptable toughness. The trunnion pins were heat treated to 300 BHN, a hardness which is considered too low for the application. An increase in hardness to 340 BHN can probably be attained with out excessively impairing the toughness and this increase in strength would, no doubt, be sufficient to prevent the distortion which occurred in the subject pins during ballistic tests upon the tank.