SYMPOSIA PAPER Published: 01 January 1997

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


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.

Author Information

Leap, MJ
The Timken Company, Canton, OH
Wingert, JC
The Timken Company, Canton, OH
Mozden, CA
The Timken Company, Canton, OH
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Developed by Committee: A01
Pages: 160–195
DOI: 10.1520/STP16600S
ISBN-EB: 978-0-8031-5349-3
ISBN-13: 978-0-8031-2423-3