Vanadium in Interstitial Free Steels
Abstract:
Interstitial free steels containing vanadium have been studied. Hot rolled steels showing discontinuous yielding can be processed to give a range of strengths from 220 MPa to 250 MPa (depending on the vanadium addition) in the cold rolled and continuously annealed condition. Batch annealing of the hot band gives an interstitial free condition and allows the development of high levels of plastic anisotropy after cold rolling and continuous annealing. High levels of plastic anisotropy can also be obtained by controlling the hot rolling schedules, particularly the cooling rate after hot rolling. Cooling rates less than 30°C/hr give an interstitial free condition which allows texture development and attendant high levels of plastic anisotropy in cold rolled and continuously annealed materials. Vanadium retards strain ageing, but selection of a suitable annealing temperature can induce a bake hardening response of some 50-60 MPa.
Vanadium can be added to these ultra-low carbon steels either with or without titanium. Cold worked vanadium steels recrystallise at lower temperatures than do titanium steels, and titanium vanadium steels recrystallise at lower temperatures than do titanium-niobium steels.
These results are discussed in terms of the solubility of vanadium carbide or other carbo-nitrides in ferrite. Vanadium additions were made to steels containing sub-stoichiometric titanium levels in order to maintain a low titanium content thereby avoiding the white powder defects seen in galvannealed steels.
Keywords:
vanadium, IF steel.
Author:
T. Gladman (1) and P. S. Mitchell (2)
Affiiation
(1) University of Leeds
(2) Vanitec
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Source:
39th Mechanical Working and Steel Processing Conference; Indianapolis, IN; USA; 19-22 Oct. 1997, 37-48 (Vanitec Publication - V0497)
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