Recrystallization Behavior of IF Steel Sheets Immediately after Hot-rolling in Ferrite Region

Abstract

It is known that high r-value hot-rolled steel sheets can be produced by hot rolling in the ferrite region with lubrication, whereas dynamic recovery easily occurs during ferritic rolling, in which texture formation is quite different from that in cold rolling, when the quantity of recovery increases. In this study, one pass hot rolling in the ferrite region was conducted at higher temperatures, using various rolling temperatures and rolling reductions, with two types of ULC steels, 0.016% Nb and 0.023% Ti, and their recrystallization behaviors immediately after hot rolling were investigated. The Ti-bearing steel easily recrystallized; recrystallization occurred even at 1 323 K with a low rolling reduction of 30%. The γ-fiber strength reached its maximum at around 50% rolling reduction at 1 273 K with the Nb-bearing steel and 1 323 K with the Tibearing steel. On the other hand, in high temperature rolling of the Ti-bearing steel, the γ-fiber did not develop, independent of rolling reduction. These changes corresponded to the recrystallized fraction, in that the strength of the γ-fiber decreased when recrystallization occurred immediately after rolling. The deformation microstructures were different in each grain and even in each part of the same grain. New recrystallized-like grains were produced in the domain where distortions were particularly concentrated. Recrystallization seemed to be the result of various mechanisms, as some recrystallized grains were formed by a bulging mechanism, whilst others were surrounded by high angle grain boundaries.

Effect of Isothermal Treatment on Microstructure and Mechanical Properties of Cold-Deformed IF Steel

“…Urabe et al performed cold-rolling reductions of 0.080/ 0Ti-0.01%Nb IF steel until reductions of 70% and 85% were achieved, following which the deformed samples were annealed at 720°C for various durations [37]. e authors reported a trend similar to that observed in the present work, i.e., the hardness diminished as recrystallisation progressed; despite this, the deformation percent was higher in the Okuda et al carried out hot-rolling in the ferrite region at various rolling temperatures and to achieve di erent rolling reductions [38]. is process was applied to IF steel with a composition of 0.016% Nb and 0.023% Ti.…”

“…In the present work, the values of hardness measured at 0 s, 60 s, and 120 s of annealing were superior, in the range 152-186 HV. is behaviour is certainly because the present work entailed static recovery, whereas the cited work entailed a process of dynamic recovery; the former proceeds at a lower rate than the latter [38].…”

Microstructures and Mechanical Properties of Low Carbon Steel Hot Rolled in Ferrite Region Based on CSP Line

“…The finishing rolling temperature range of ferrite rolled sheet was ferrite single phase region, and the deformation rate was high in CSP process. It was difficult for ferrite to recrystallize when the low carbon steel was deformed under these conditions . As shown in Figure , The grain will be elongated along the direction of deformation, which leads to a significant increase of the ferrite grain size.…”

Microstructure and Mechanical Properties of Ferritic Rolling Low Carbon Steel

“…Kiet Tieu researched the lubrication technology of ferritic rolling process [11,12]. Kaneharu OKUDA investigated the recrystallization behavior of Nb-IF and Ti-IF steel sheets immediately after hot-rolling in ferrite region [13]. Humphreys investigated the ferritic rolling behavior of low carbon steel [14].…”