Title

Mircostructure and texture of warm rolled extra-low carbon steel alloyed with chromium

RIS ID

24968

Publication Details

Stohr, R., Gazder, A. A., Davies, C. HJ. & Pereloma, E. (2008). Mircostructure and texture of warm rolled extra-low carbon steel alloyed with chromium. Materials Forum, 32 39-43.

Abstract

Contrary to interstitial free (IF) steel grades, low carbon steels exhibit dynamic strain ageing during warm rolling due to the presence of solute carbon. This leads to the reduced formation of grains containing in-grain shear bands and a weak but desirable {111} recrystallisation texture on annealing, when compared to IF steels. Addition of Cr leads to carbon depletion in the ferrite matrix as a result of Cr carbide formation. The warm rolling schedule could also have an effect on the amount of carbides and grains containing in-grain shear bands formed. In this work extra low carbon steel alloyed with 0.78wt%Cr was subjected to two different warm rolling schedules: (i) rolling to 65% reduction at 913K and (ii) rolling to 80% reduction at 853K. The microstructure was characterised using optical metallography, transmission electron microscopy, energy dispersive X-ray spectroscopy and bulk texture analysis. The results have shown that increase in the severity of deformation resulted in a very slight increase in the number of grains containing in-grain shear bands. The intensity of ND-fibre, which comprises of grains withaxes parallel to the normal direction (ND), was slightly higher in the steel warm rolled at 853K than at 913K. In both steels several types of carbides were formed, such as Cr3C2, Cr23C6 and Cr19Fe4C6. The density of fine strain-induced carbides in the steel after 80% reduction was by order of magnitude higher than after warm rolling to 65% reduction. Based on their size, the carbides could be divided in two distinctive groups: (i) coarse carbides, predominantly located at ferrite grain boundaries and microband boundaries; and (ii) fine carbides, relatively uniformly distributed within the microbands.