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Solute carbon and nitrogen in the ferrite after continuous annealing of low carbon low aluminium steels
Author(s) -
Messien Pierre,
Leroy Vincent
Publication year - 1985
Publication title -
steel research
Language(s) - English
Resource type - Journals
eISSN - 1869-344X
pISSN - 0177-4832
DOI - 10.1002/srin.198500652
Subject(s) - supersaturation , annealing (glass) , aluminium , metallurgy , materials science , nitrogen , carbide , ferrite (magnet) , carbon steel , chemistry , composite material , corrosion , organic chemistry
Low N sol levels not only require reduced N contents (≤ 20 ppm) in steel but also Al/N ratios higher than 5 and C contents higher than 0.025% because of the synergic effect between N and C precipitations; scavenging of Al on nitrogen is far from complete even in steels coiled at 750°C. Low C sol levels are achieved either at very lowC contents (C ≤ 0.003%) or at C contents higher than 0.025%. Due to high C sol , carbon aging is expected in steels coiled at 750°C. Softer, bake hardenable steels with good aging resistance will be obtained in the range 0.025–0.030 % C independently of the coiling temperature. C supersaturation of the ferrite is reduced at higher cooling rates after continuous annealing. Changes in C and N supersaturation according to the steel composition and the continuous annealing process are explained, taking into account the carbides morphology and the annealing conditions.