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J J Jonas - One of the best experts on this subject based on the ideXlab platform.
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dynamic transformation and retransformation during the simulated Plate Rolling of an x70 pipeline steel
2017Co-Authors: Samuel F. Rodrigues, Fulvio Siciliano, Clodualdo Aranas, J J JonasAbstract:The controlled Rolling of pipeline steels involves pancaking the austenite and then subjecting it to accelerated cooling. However, the formation of ferrite during Rolling decreases the amount of austenite available for microstructure control. Here the formation of ferrite during Rolling is simulated using a five-pass Rolling schedule applied by means of torsion testing. The first and last pass temperatures were 920 and 860 °C with 15° of cooling between passes. All of the Rolling was carried out above the Ae3 temperature of 845 °C that applies to this steel. Interpass times of 10 and 30 s were employed, which corresponded to cooling rates of 1.5 and 0.5 °C/s, respectively. Samples were quenched before and after the first, third, and fifth passes in order to determine the amount of dynamic ferrite produced in a given pass. The amounts of dynamic ferrite formed and retained increased with pass number. The amounts of ferrite that retransformed increased with pass number. The simulations indicate that ferrite is unavoidably produced during Plate Rolling and that the microstructures present at the initiation of accelerated cooling do not consist solely of austenite.
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dynamic transformation of deformed austenite at temperatures above the ae3
Progress in Materials Science, 2016Co-Authors: Chiradeep Ghosh, Clodualdo Aranas, J J JonasAbstract:Abstract The dynamic transformation of austenite to ferrite at temperatures above the Ae 3 temperature was first investigated by Yada and co-workers in the late 1980s. This phenomenon has now been observed right up to the delta ferrite formation temperature. The basic principles of dynamic transformation are reviewed, together with recent advances in the understanding of this mechanism. The transformation product that forms has been identified as Widmanstatten ferrite, which nucleates displacively and whose growth is accompanied by carbon diffusion. It forms in pairs of self-accommodating Plates of near-identical orientation. The similar orientations of the Plates allow them to coalesce on continued straining or holding at temperature, leading to the presence of polygonal grains as well as Plates. The critical strain for the initiation of dynamic transformation is usually detected using double differentiation; results obtained by researchers on different steels are reviewed, together with observations obtained during the torsion simulation of strip and Plate Rolling. The thermodynamics of dynamic transformation are examined in detail, with attention paid to three recent approaches, the: (i) stored energy, (ii) stress activation, and (iii) phase softening models. It is concluded that the phase softening model provides the most accurate description of the transformation of the models proposed recently.
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softening and flow stress behaviour of nb microalloyed steels during hot Rolling simulation
Isij International, 1995Co-Authors: Pentti L Karjalainen, T M Maccagno, J J JonasAbstract:The roles of softening and precipitation were investigated by means of hot torsion experiments under conditions simulating either Plate or sheet Rolling. Six microalloyed steels containing Nb were studied. During the first few finishing passes in the sheet Rolling simulations, the mean flow stress (MFS) increased as the interpass time was decreased. Due to strain accumulation, the rate of static recrystallization (SRX) increased significantly after each pass. By taking both strain accumulation and grain refinement into account, it is shown that SRX plays a marked role under sheet Rolling conditions, even at temperatures below the no-recrystallization temperature for Plate Rolling conditions. The accumulated or retained strain reaches the critical value required to initiate dynamic recrystallization only at the lowest entry and Rolling temperatures and shortest interpass times. The kinetics of the strain-induced precipitation of NbCN under continuous cooling conditions, taking partial SRX into account, indicate that precipitation begins after 2 to 5 passes when 3 s interpass times are employed, thus reducing further softening. But when 1 s interpass times are used, most of the passes take place before copious precipitation, so that static and post-dynamic (i.e. metadynamic) softening may continue to take place. As a result, the MFS level decreases as the interpass time is shortened during the final passes. The extent of grain refinement was similar in both the sheet Rolling and Plate Rolling simulations. The ferrite grain size is shown to depend on MFS of the final pass, and is independent of the chemical composition of the microalloyed steel.
Cai Qingwu - One of the best experts on this subject based on the ideXlab platform.
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effect of a novel gradient temperature Rolling process on deformation microstructure and mechanical properties of ultra heavy Plate
Journal of Materials Processing Technology, 2015Co-Authors: Li Gaosheng, Cai QingwuAbstract:Abstract To improve the mechanical properties of heavy or ultra-heavy Plate, continuous casting slabs have to be thick enough to ensure that the required total Rolling reduction ratio can be achieved. A novel called gradient temperature Rolling (GTR) process, in which the slab is maintained at 800 °C at its surface and 1100 °C at its core, is suggested to improve the quality of ultra-heavy Plate which is limited by a reduction ratio. The phenomenon is studied by means of both modeling and experimentation. Finite element modeling (FEM) of ultra-heavy Plate Rolling was established with MSC Marc software. The temperature field, strain, and stress of the Rolling piece were calculated. Under a temperature gradient of about 300 °C, the effect of GTR on the strain distribution, austenite recrystallization, the microstructure in the direction of thickness, and the mechanical properties of an ultra-heavy Plate were investigated in the laboratory. The results indicate that the strain and accumulative deformation in the central area of the Rolling piece increases significantly. Due to the gradient temperature, the austenite grains are small, complying with ASTM grades 6.1–7.5 and fine and uniform ferrite is formed in the core area of the Plate, which is better than that achieved by traditional uniform temperature Rolling (UTR). The Plate rolled under gradient temperature conditions had excellent mechanical properties, which increased the impact energy by 98.2% and 174.9% in the Rolling and cross directions, respectively, and the enlarge area reduction in thickness direction ( Z -direction) by 24% compared with UTR processing.
C Fischer - One of the best experts on this subject based on the ideXlab platform.
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front end bending in Plate Rolling influenced by circumferential speed mismatch and geometry
Journal of Materials Processing Technology, 2007Co-Authors: M Philipp, Werner Schwenzfeier, F D Fischer, R Wodlinger, C FischerAbstract:Abstract Front end bending in Plate Rolling creates enormous forces impacting on the roller tables, which reduce productivity eventually entailing expensive downtimes. Furthermore, front end bending reduces the quality of the Plates considerably. Many investigations on that topic have been published in the past and are summarized in this work. Some basic relations explaining the causes and consequences of front end bending are already known. However, operators are still struggling with the problem. An implicit two-dimensional finite element model has been employed to simulate the front end bending based on fundamental geometric relations. This paper focuses on the well known bending due to the related mismatch of circumferential speed between the work rolls. The shift of the neutral point, i.e. where no curvature occurs, from thin to thick Rolling stock is reported for the first time and shows interesting results. The mismatch of bending intensity between thin and thick Rolling stock is also reported. The absence of the neutral point for very thick Rolling stock is explained. A comparison between previously published results and the current investigations provides a broad overview on the front end bending in Plate Rolling.
Clodualdo Aranas - One of the best experts on this subject based on the ideXlab platform.
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Physical Simulation Based on Dynamic Transformation Under Hot Plate Rolling of a Nb-Microalloyed Steel
'Frontiers Media SA', 2021Co-Authors: João Carlos Ferreira, Fulvio Siciliano, Clodualdo Aranas, Francisco Romario De Sousa Machado, Jubert Pasco, Gedeon Silva Reis, Edson Jansen Pedrosa De Miranda, Antônio Ernandes Macêdo Paiva, Samuel Filgueiras RodriguesAbstract:In this work, the presence of dynamically formed ferrite above the Ae3 temperature during the physical simulation of hot Rolling was presented. This unusual metallurgical process is known as dynamic transformation (DT). The metastable ferrite phase undergoes a reverse transformation when the temperature is held above the Ae3 by means of a diffusion process. These phenomena affect the Rolling load during high-temperature Plate Rolling. Therefore, a linepipe X70 steel was studied under Plate Rolling with two-pass roughing and seven-pass finishing strains of 0.4 and 0.2, respectively, applied at strain rate of 1 s−1 and interpasses of 10, 20, and 30 s. The samples were cooling down during deformation, which mimics the actual industrial hot Rolling. It was observed that the alloy softens as the hot Rolling progresses, as depicted by flow curves and mean flow stress plots, which are linked to the combined effects of dynamic transformation and recrystallization. The former initially occurs at lower strains, followed by the latter at higher strains. The critical strain to DT was affected by the number of passes and temperature of deformation. Shorter interpass time allows higher amounts of ferrite to form due to higher retained work hardening. Similarly, the closer the deformation temperature to the Ae3 permits a higher DT ferrite fraction. The information from this work can be used to predict the formation of phases immediately after hot Rolling and optimize models applied to the accelerated cooling
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Dynamic Phase Transformation Behavior of a Nb-microalloyed Steel during Roughing Passes at Temperatures above the Ae3
MDPI AG, 2019Co-Authors: Samuel F. Rodrigues, Fulvio Siciliano, Clodualdo Aranas, Eden S. Silva, Gedeon S. Reis, Mohammad Jahazi, John J. JonasAbstract:A five-pass torsion simulation of the roughing passes applied during hot Plate Rolling was performed in the single-phase austenite region of a Nb-microalloyed steel under continuous cooling conditions. The deformation temperatures were approximately half-way between the Ae3 and the delta ferrite formation temperature (i.e., 250 °C above the Ae3) in which the free energy difference of austenite and ferrite is at maximum. The microstructures in-between passes were analyzed to characterize and quantify the occurrence of deformation-induced dynamic phase transformation. It was observed that about 7% of austenite transforms into ferrite right after the final pass. The results are consistent with the calculated critical strains and driving forces which indicate that dynamic transformation (DT) can take place at any temperature above the Ae3. This mechanism occurs even with the presence of high Nb in the material, which is known to retard and hinder the occurrence of DT by means of pinning and solute drag effects. The calculated cooling rate during quenching and the time–temperature–transformation curves of the present material further verified the existence of dynamically transformed ferrite
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dynamic transformation and retransformation during the simulated Plate Rolling of an x70 pipeline steel
2017Co-Authors: Samuel F. Rodrigues, Fulvio Siciliano, Clodualdo Aranas, J J JonasAbstract:The controlled Rolling of pipeline steels involves pancaking the austenite and then subjecting it to accelerated cooling. However, the formation of ferrite during Rolling decreases the amount of austenite available for microstructure control. Here the formation of ferrite during Rolling is simulated using a five-pass Rolling schedule applied by means of torsion testing. The first and last pass temperatures were 920 and 860 °C with 15° of cooling between passes. All of the Rolling was carried out above the Ae3 temperature of 845 °C that applies to this steel. Interpass times of 10 and 30 s were employed, which corresponded to cooling rates of 1.5 and 0.5 °C/s, respectively. Samples were quenched before and after the first, third, and fifth passes in order to determine the amount of dynamic ferrite produced in a given pass. The amounts of dynamic ferrite formed and retained increased with pass number. The amounts of ferrite that retransformed increased with pass number. The simulations indicate that ferrite is unavoidably produced during Plate Rolling and that the microstructures present at the initiation of accelerated cooling do not consist solely of austenite.
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dynamic transformation of deformed austenite at temperatures above the ae3
Progress in Materials Science, 2016Co-Authors: Chiradeep Ghosh, Clodualdo Aranas, J J JonasAbstract:Abstract The dynamic transformation of austenite to ferrite at temperatures above the Ae 3 temperature was first investigated by Yada and co-workers in the late 1980s. This phenomenon has now been observed right up to the delta ferrite formation temperature. The basic principles of dynamic transformation are reviewed, together with recent advances in the understanding of this mechanism. The transformation product that forms has been identified as Widmanstatten ferrite, which nucleates displacively and whose growth is accompanied by carbon diffusion. It forms in pairs of self-accommodating Plates of near-identical orientation. The similar orientations of the Plates allow them to coalesce on continued straining or holding at temperature, leading to the presence of polygonal grains as well as Plates. The critical strain for the initiation of dynamic transformation is usually detected using double differentiation; results obtained by researchers on different steels are reviewed, together with observations obtained during the torsion simulation of strip and Plate Rolling. The thermodynamics of dynamic transformation are examined in detail, with attention paid to three recent approaches, the: (i) stored energy, (ii) stress activation, and (iii) phase softening models. It is concluded that the phase softening model provides the most accurate description of the transformation of the models proposed recently.
G D Wang - One of the best experts on this subject based on the ideXlab platform.
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evolution of microstructure and crystallographic texture of microalloyed steel during warm Rolling in dual phase region and their influence on mechanical properties
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2017Co-Authors: Xinjun Shen, Y J Wu, Shuai Tang, R D K Misra, Xiaolong Yang, Jun Chen, G D WangAbstract:Abstract High strength and high toughness steels can be developed by warm caliber Rolling in ferrite region. However, high deformation resistance limits its application. In the present study, warm Rolling was applied to Plate Rolling which is more suitable for industrial production to develop high strength and high toughness steels. To reduce deformation resistance, warm Rolling was carried out in dual phase region. We elucidate here the evolution of microstructure and crystallographic texture and their influence on mechanical properties of microalloyed steel subjected to warm Rolling. The study suggests that high strength and high toughness can also be obtained by warm Rolling in the dual phase region. Elongated ultrafine microstructure and intense α-fiber texture component and γ-fiber texture component can be obtained through warm Rolling. The main mechanism of microstructure evolution during warm Rolling was dynamic recovery. Reducing warm Rolling temperature can refine grain size, enhance α-fiber texture component and weaken γ-fiber texture component. Warm Rolling can greatly enhance strength by ~64–158 MPa compared to the conventional controlled Rolling (CR) process, and the warm-rolled Plates had high elongation in spite of high strength. The toughness was improved because of grain refinement and delamination. Delamination can induce ductile fracture at low temperature, and delay the occurrence of brittle fracture such that high toughness is obtained in steel Plates. The effect of warm Rolling temperature and impact test temperature on delamination and impact property was elucidated.