Metallurgical Examination of Two Disston 1-1/2 Inches Rolled Homogeneous Armor Plates
WATERTOWN ARSENAL MA WATERTOWN United States
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The object was to determine the metallurgical characteristics of good and poor quality Disston 1-12 rolled homogeneous armor plates, including chemical analyses, macroscopic and microscopic examination, physical tests, and hardness surveys. The conclusions were 1 The defective plate from Heat 1843 D3 was heat treated to a too high hardness 311 Brinell 2 The macrostructure of the poor heat 1843 D3 as revealed by the Oberhoffer reagent indicated that the dendritic structure was improperly refined during the hot rolling operation 3 The satisfactory plate from Heat 1830 D4 which was correctly heat treated to a hardness of 293 Brinell showed the presence of some center line banding of a relative high carbon content although it was not associated with a marked aggregation of nonmetallic inclusions. This condition, noted previously in other samples of armor, is not related to spalling when the plate is heat treated to the correct hardness 4 Heats 1830 D4 and 1843 D3 are free from pronounced segregated nonmetallic inclusions and 5 For the purpose of revealing grain boundary carbides it has been determined that a 10 chromic acid electrolytic etch has been found superior to the Murakamis reagent or the alkaline sodium picrate.