Processing and Stability of Ultrafine Grained Structures in Some Microalloy Steels

Abstract:

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The dynamic strain-induced transformation (DSIT) of ferrite from austenite in intense deformation at temperatures close to Ar3 were applied to one C-Mn steel and several Nb and Nb-Ti microalloy steels to obtain an ultrafine ferrite grain size. As another route the static recrystallisation of severely cold-rolled martensite (SRM) was utilized. It was found that in the DSIT route a fine prior austenite grain size was crucial to form ferrite with the grain size of 1-3 µm with a considerable fraction of a secondary phase, carbide aggregate/pearlite or martensite. Grain sizes achieved were somewhat finer in steels with a higher microalloying content. In the SRM route, the ferrite grain size of 1-1.5 µm was obtained by using the cold rolling of 80-90% reduction. Thermal stability of the ultrafine-grained structures, especially those from the DSIT route, was found to be excellent. In electron or laser beam welding of 1-2.5 mm sheets neither any coarse-grained zone existed in the heat-affected zone, nor did form any softened zone.

Info:

Periodical:

Materials Science Forum (Volumes 500-501)

Edited by:

J.M. Rodriguez-Ibabe, I. Gutiérrez, B. López and A. Iza-Mendia

Pages:

363-370

DOI:

10.4028/www.scientific.net/MSF.500-501.363

Citation:

L.X. Pan et al., "Processing and Stability of Ultrafine Grained Structures in Some Microalloy Steels", Materials Science Forum, Vols. 500-501, pp. 363-370, 2005

Online since:

November 2005

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Price:

$35.00

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