Grain Refinement by Rapid Transformation Annealing of Cold Rolled Low Carbon Steels

P. Álvarez; C. Lesch; Wolfgang Bleck; Hélène Petitgand; Joachim Schöttler; J. Gil Sevillano

doi:10.4028/www.scientific.net/MSF.500-501.771

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HomeMaterials Science ForumMaterials Science Forum Vols. 500-501Grain Refinement by Rapid Transformation Annealing...

Grain Refinement by Rapid Transformation Annealing of Cold Rolled Low Carbon Steels

Abstract:

A novel thermal treatment, rapid transformation annealing (RTA), has been applied to six different cold rolled low-carbon (LC) steel sheets with the aim of refining their microstructure. The process involves rapid heating to just above the austenite (g) to ferrite (a) transformation temperature and subsequent rapid cooling to room temperature. Grain sizes around 2 µm in two different Nb-Ti HSLA steels, 5 µm in a Ti-LC steel and 6 µm in a plain LC (0.037%C) steel have been produced using fast cooling rates (200°C/s). Non-equiaxed structures are obtained in a Nb-Ti HSIF steel and in a plain LC (0.135%C) (CM) steel due to their higher Mn content. However, very fine equiaxed grains (2 µm) are obtained by rapid intercritical annealing (RIA) in the CM steel. Irrespective of the microalloying concept, the grain growth of recrystallized a grains before their transformation was inhibited in CM and in both HSLA steels. This inhibition is connected with the overlapping of a recrystallization and a-g transformation processes which is essential in order to achieve extreme grain refinement either by RTA or RIA.

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Periodical:

Materials Science Forum (Volumes 500-501)

Pages:

771-778

DOI:

https://doi.org/10.4028/www.scientific.net/MSF.500-501.771

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Online since:

November 2005

Authors:

P. Álvarez, C. Lesch, Wolfgang Bleck, Hélène Petitgand, Joachim Schöttler, J. Gil Sevillano

Keywords:

Grain Refinement, Microalloyed Steel, Rapid Annealing, α Recrystallization, α-γ-α Phase Transformation

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