Physical simulation of finish rolling of microalloyed steels in isothermal conditions

Abstract

The aim of this work was to establish a temperature of finish rolling stage of Nb/Ti microalloyed steel containing 0.06 wt.% C, 0.77 wt.% Mn, 0.039 wt.% Nb and 0.015 wt.% Ti, using physical simulation. Samples were subjected to laboratory simulation at a twist plastometer at high temperatures, i.e. between 825 and 950?C. Five pass deformation and interpass times were selected in accordance with a processing parameters at five stand finishing hot strip mill. Restoration (recovery and/or recrystallization) behavior was evaluated by calculation of Fraction Softening (FS) and Area Softening Parameter (ASP) values. At 950?C all individual pass stress-strain curves, FS and ASP show full recrystallization in all interpass intervals. On the other hand, with a decrease in temperature to the interval of 875-825?C, the extent of restoration is decreasing, leading to recovery as a sole softening mechanism at 825?C, which was confirmed by the stress-strain curve shape, and values of FS and ASP. It is assumed that, due to high supersaturation, strain-induced precipitation promoted pinning of grain and subgrain boundaries and suppressed recrystallization. Therefore, the critical temperature for finish rolling was estimated to be 825?C.

Determining the Role of Acicular Ferrite Carbides in Cleavage Fracture Crack Initiation for Two Medium Carbon Microalloyed Steels

“…The values of effective surface energy for the V steel ranges from 40 Jm −2 to 86 Jm −2 , while in the case of TiV steel it is noticeably similar, ranging from 55 Jm −2 to 82 Jm −2 . These values are comparable to those found in the literature for medium carbon microalloyed steels with ferrite-pearlite or bainite structures [27,41,44,53]. The observed difference in effective surface energy can be related to the effect of AF in the structure of the steels.…”

“…It can be assumed that second-phase particles, primarily individual cementite plates separated by interlocked ferrite plates, are less favorably oriented toward acting tensile stress. Moreover, it should also be kept in mind that specific deformation behavior is due to the higher dislocation density inherent in AF and B structures [28,53]. Namely, it is characterized by relatively low yield stress due to the effect of gradual yielding, leading to plastic yielding at the notch, thus lowering the overall stress level in the 4PB specimen.…”

Evaluation and Performance Analysis of Liquefied Petroleum Gas Cylinders

“…As in medium carbon steels. In this case, and to overcome the problem, the appropriate microalloying with elements such as niobium, titanium, vanadium, and boron was added and coupled with isothermal treatment processing can provide an excellent combination of high strength and ductility [21][22][23][24][25][26][27][28]38,39]. In this context, steel with low carbon content (typically < 0.3%) is known for its exceptional ductility and malleability.…”