ISIJ International
Online ISSN : 1347-5460
Print ISSN : 0915-1559
ISSN-L : 0915-1559
Influence of Hot Deformation Conditions on the Annealing Behaviour of Cold Rolled Ultra Low Carbon Steel
M. FerryD. YuT. Chandra
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2001 Volume 41 Issue 8 Pages 876-882

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Abstract

An ultra low carbon (ULC) steel has been deformed in plane strain compression (PSC) using a Gleeble 3500 thermal and mechanical simulator followed by cold rolling and annealing (CRA). Multiple-pass deformation was used to simulate conditions encountered during hot rolling and to study the effect of finish deformation temperature (FDT) on microstructural development during CRA. It was found that a range of ferrite microstructures were produced when FDT decreased from 920 to 600°C, a temperature range which encompasses both austenite (γ) and ferrite (α) deformation. For FDT>870°C, fine equiaxed ferrite was produced, whereas FDT 850°C produced a coarse-grained microstructure. As FDT was decreased below 850°C, as-deformed ferrite remained with a decreasing propensity for the formation of statically recrystallized grains. At higher FDT, the γ-to-α transformation produced a hot-band texture consisting mainly of {001}<110>, and at FDT below the critical transformation temperature the typical body centred cubic rolling texture also developed. Sections of the as-hot-deformed samples were cold rolled to 80% reduction and annealed at 650°C. It was found that the hot deformation microstructure has a strong influence both on the kinetics of recrystallization and texture development during CRA. In particular, a warm-deformed ferrite microstructure (lower FDT) recrystallized most rapidly to produce a strong <111>//ND recrystallization texture (γ-fibre), whereas an initial coarse-grained ferrite microstructure recrystallized most sluggishly to produce a strong {001}<110> texture. The implications of these results in the production of formable sheet steels is outlined.

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