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High strength, high toughness, martensitic steel
[Category : - OTHER]
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A method for designing a low cost, high strength, high toughness martensitic steel in which a mathematical model is used to establish an optimum low cost alloying concentration that provides specified levels of strength toughness. The model also predicts critical temperatures and the amount of retained austenite. Laboratory scale ingots of the optimum alloying composition were produced comprising by % wt. of about: 0.37 of C; 1.22 of Ni; 0.68 of Mn; 0.86 of Si; 0.51 of Cu; 1.77 of Cr; and 0.24 of V; and the balance Fe and incidental impurities were melted in an open induction furnace. After homogenized annealing, hot rolling, recrystallization annealing, and further oil quenching, refrigerating, and low tempering, a tempered martensite microstructure was produced consisting of small packets of martensitic laths, fine vanadium carbide, as centers of growth of the martensitic lathes, and retained austenite. Mechanical tests showed the following results: HRC of 52; UTS of 282 ksi; YS of 226 ksi; Charpy V-notch impact toughness energy of 31 ft-lbs. Energy consumption vacuum arc remelting (VAR) and electroslag remelting (ESR) were not required for improving strength and toughness.