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Strength Enhancement of Nitrocarburized Crankshaft Material

Journal Article
ISSN: 1946-3979, e-ISSN: 1946-3987
Published April 14, 2008 by SAE International in United States
Strength Enhancement of Nitrocarburized Crankshaft Material
Citation: Asai, T., Takitani, Y., Sano, N., and Matsumoto, H., "Strength Enhancement of Nitrocarburized Crankshaft Material," SAE Int. J. Mater. Manf. 1(1):204-210, 2009,
Language: English


When improving the mechanical properties of a crankshaft by nitrocarburizing, it is important to achieve both strength as well as toughness (straightenability). By designing a material composition to provide maximum strengthening, a nitrocarburized crankshaft material has been developed without the use of a normalizing thermal treatment that has about 16% higher fatigue strength than previous crankshafts with the same material hardness, similar machinability and straightenability. The achievement of both high fatigue strength and straightenability of the developed material was made by adjusting the basic material composition for optimum microstructural control and by adding a small quantity of Mo to attain suitable ferrite strengthening. Furthermore, by omitting the normalizing treatment, the CO2 emitted during the post-hot forging processes could be reduced by up to 22%, and cost savings of up to 8% could be achieved in comparison with previous high strength crankshafts.