Development of Low Alloy Cast Armor between February and May 1942
WATERTOWN ARSENAL MA WATERTOWN United States
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Results on the experimental plates indicate that the shock resisting properties of the new low alloy compositions will be reasonably comparable to those of the old, alloy nickel-chrome-molybdenum and chrome-molybdenum steels. Vanadium requirements for cast armor have been eliminated entirely. Chromium contents have been reduced from a maximum of 3 to a maximum of .60. Nickel contents have been reduced from a maximum of 2.50 to a maximum of .60. Of the five new compositions to be produced, only one type, AC-1a, contains nickel as an alloying element. The molybdenum contents of the new analyses are in general less than in the old compositions. The average maganese content of the new compositions is higher than in the case of the old compositions. Present indications are that the margin of excess on ballistic limit will be adequate for the low alloy compositions although slightly inferior to the old analyses. This can only be substantiated by a correlation of results on acceptance test plates. For satisfactory ballistic results, the time and temperature of homogenization may be reduced for the new alloys thus easing the extreme bottleneck on heat treating facilities. The low alloy analyses are easier to handle in production from several standpoints, but he quenching operation is critical and must be carefully controlled. The repair welding of the low alloy analyses may be performed with less or no preheat, and because of the lack of air hardening tendencies less trouble with cracking after homogenization is to be expected.