STP1259

    Development of a Process for Toughening Grain-Refined, High-Strength Steels

    Published: Jan 1997


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    Abstract

    There is a gradually increasing awareness of the deleterious effects of grain-refining precipitates on the Charpy V-notch impact toughness of high-strength steels, and recognition of these effects resulted in the development of a general process that provides substantial improvements in the ductile fracture resistance of tempered mar-tensite. The results of this investigation indicate that the processing-induced refinement of grain-refining precipitates also provides significant improvements in the lower-shelf and transition toughness of 3310, 8219 and 4340 steels tempered at 180‡C and 4340 steel tempered at 593‡C. In contrast to the upper-shelf regime, where the application of the process produces a change in either the mode or character of unstable fracture at constant strength and austenite grain size, the refinement of grain-refining precipitates is associated with an increased amount of ductile fracture and an increased resistance to the initiation of unstable crack propagation at any given temperature in the lower-shelf regime.

    Keywords:

    High-strength steels, grain-refining precipitates, ductile fracture, brittle fracture, impact toughness, instrumented impact testing


    Author Information:

    Leap, MJ
    Principal Research Engineer and Research Analysts, The Timken Company, Canton, OH

    Wingert, JC
    Principal Research Engineer and Research Analysts, The Timken Company, Canton, OH

    Mozden, CA
    Principal Research Engineer and Research Analysts, The Timken Company, Canton, OH


    Paper ID: STP16600S

    Committee/Subcommittee: A01.02

    DOI: 10.1520/STP16600S


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