Dynamic Transformation during Plate and Strip Rolling

2016 ◽  
Vol 879 ◽  
pp. 29-35 ◽  
Author(s):  
John J. Jonas ◽  
Clodualdo Aranas Jr. ◽  
Samuel F. Rodrigues ◽  
In Ho Jung
Keyword(s):  
Alpha Phase ◽  
Austenite Phase ◽  
Mean Flow ◽  
Volume Percent ◽  
Strip Rolling ◽  
Dynamic Transformation ◽  
Cooling Conditions ◽  
Mean Flow Stress ◽  
Austenite Grains ◽  
Rolling Load

Torsion simulations were carried out of both plate (long interpass times) and strip (short interpass times) rolling. Both isothermal and continuous cooling conditions were employed. The dynamic transformation of austenite to ferrite was observed under all conditions and at all temperatures within the austenite phase field. About 8 to 10 volume percent ferrite was formed in a given pass, leading to about 50 - 70 % ferrite at the end of selected simulations. During the interpass intervals, some retransformation to austenite took place, the amount of which increased with holding time and temperature and decreased with the addition of alloying elements. It is shown that the driving force for the transformation is the softening associated with the replacement of work-hardened austenite grains by the softer alpha phase. The implications with respect to rolling load (i.e. mean flow stress) are also discussed.

scholarly journals Physical Simulation Based on Dynamic Transformation Under Hot Plate Rolling of a Nb-Microalloyed Steel

2021 ◽  
Vol 8 ◽  
Author(s):  
João Carlos Ferreira ◽  
Francisco Romario de Sousa Machado ◽  
Clodualdo Aranas ◽  
Fulvio Siciliano ◽  
Jubert Pasco ◽  
...  
Keyword(s):  
Hot Rolling ◽  
Physical Simulation ◽  
Accelerated Cooling ◽  
Mean Flow ◽  
Dynamic Transformation ◽  
Plate Rolling ◽  
Ferrite Fraction ◽  
Mean Flow Stress ◽  
Nb Microalloyed Steel ◽  
Rolling Load

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.

Application of Deformation to Improve Hot Ductility in the Peritectic Steel

2005 ◽  
Vol 500-501 ◽  
pp. 203-210 ◽  
Author(s):  
Ahmad Rezaeian ◽  
Faramarz Zarandi ◽  
D.Q. Bai ◽  
Steve Yue
Keyword(s):  
Flow Stress ◽  
High Strength ◽  
Microalloyed Steels ◽  
Hot Strip Mill ◽  
Mean Flow ◽  
Hot Strip Rolling ◽  
Strip Rolling ◽  
Slip Ratio ◽  
Hot Strip ◽  
Mean Flow Stress

The hot strip rolling of advanced microalloyed high strength steels still represents a new task to many mills due to the lack of data on the hot deformation resistance. With the aid of processing data from the Ispat-Inland hot strip mill, the “measured mean flow stresses” are calculated from the mill force using the Sims analysis and taking into account roll flattening, slip ratio and the redundant strain. A modification of the Misaka mean flow stress equation is proposed for C – Mn – Si – Al steels microalloyed with up to 0.02 % Nb. The effects of alloying and microalloying are then estimated. A new fitting parameter shows excellent agreement with the mean flow stress data from industrial processing of advanced high strength microalloyed steels. However, during the second half of the rolling schedule (lower temperature region), indications of austeniteto- ferrite transformation were found.

Effect of Number of Roughing Passes on the Dynamic Transformation of Austenite during Simulated Plate Rolling

2018 ◽  
Vol 941 ◽  
pp. 717-722
Author(s):  
Samuel F. Rodrigues ◽  
Fulvio Siciliano ◽  
Clodualdo Aranas Jr. ◽  
Gedeon S. Reis ◽  
Brian J. Allen ◽  
...  
Keyword(s):  
Grain Size ◽  
Volume Fraction ◽  
Austenite Phase ◽  
Mean Flow ◽  
Grain Sizes ◽  
Dynamic Transformation ◽  
Plate Rolling ◽  
Forward Transformation ◽  
The Mean ◽  
Rough Rolling

When austenite is deformed within the austenite phase field, it partially transforms dynamically into ferrite. Here, plate rolling simulations were carried out on an X70 steel using rough rolling passes of 0.4 strain each. The influence of the number of roughing passes on the grain size and volume fraction of induced ferrite was determined. Up to three roughing passes applied at 1100 °C followed by 5 finishing passes at 900 °C were employed. The sample microstructures were analysed by means of metallographic techniques. Both the critical strain to the onset of dynamic transformation as well as the grain size decreased with pass number during the roughing simulations. For the finishing passes, the mean flow stresses (MFS`s) applicable to each schedule decreased when a higher number of roughing passes was applied. The volume fraction of dynamically formed ferrite retained after simulated rolling increased with the roughing pass number. This is ascribed to the increased amount of ferrite retransformed into austenite and the finer grain sizes produced during roughing. The forward transformation is considered to occur displacively while the retransformation into austenite during holding takes place by a diffusional mechanism. This indicates that both dynamic transformation (DT) and dynamic recrystallization were taking place during straining.

scholarly journals Strain-Induced Ferrite Formation During Steckel Mill Simulations with Varying Roughing Pass Schedules

Metals ◽  
2019 ◽  
Vol 9 (8) ◽  
pp. 814 ◽  
Author(s):  
Henry B. Palhano ◽  
Clodualdo Aranas ◽  
Samuel F. Rodrigues ◽  
Eden S. Silva ◽  
Gedeon S. Reis ◽  
...  
Keyword(s):  
Volume Fraction ◽  
Rolling Process ◽  
Mean Flow ◽  
Dynamic Transformation ◽  
Plate Rolling ◽  
Mean Flow Stress ◽  
The Mean ◽  
Critical Strains ◽  
Microstructure Of The Material ◽  
Very High

It has been previously demonstrated that austenite may undergo partial dynamic transformation (DT) during the plate rolling process. Austenite dynamically transforms into unstable ferrite during hot deformation even at very high temperatures. In this work, the plate rolling simulations, with emphasis on Steckel mill operations, through torsion testing under isothermal conditions were performed on an X70 steel. Four different roughing schedules were tested followed by five finishing passes with pass strains of 0.3 applied at 900 °C. The roughing schedules had zero, one, two and three roughing passes at a temperature of 1100 °C, strain of 0.4 and strain rate of 1 s−1. The stress–strain curves as well as the mean flow stress (MFS) behaviors indicated that both dynamic transformation (DT) and dynamic recrystallization (DRX) occurred during straining. The critical strains for the onset of DT and DRX were determined by means of the double differentiation method and the critical strain values decreased with the number of roughing and finishing strains from the first going to the last pass. It was observed that the volume fraction of the dynamically formed ferrite increased sharply during the finishing stage as the number of previous roughing passes increased, which can be attributed to higher strain accumulation. The results presented here indicate that improved models are needed to control the microstructure of the material during subsequent cooling.

scholarly journals Prediction of Mean Flow Stress during Hot Strip Rolling Using Genetic Algorithms

2014 ◽  
Vol 54 (1) ◽  
pp. 171-178 ◽  
Author(s):  
Antonella Dimatteo ◽  
Marco Vannucci ◽  
Valentina Colla
Keyword(s):  
Genetic Algorithms ◽  
Flow Stress ◽  
Mean Flow ◽  
Hot Strip Rolling ◽  
Strip Rolling ◽  
Hot Strip ◽  
Mean Flow Stress

Modeling of the Resistance to Hot Deformation and the Effects of Microalloying in High-Al Steels under Industrial Conditions

2005 ◽  
Vol 500-501 ◽  
pp. 195-202 ◽  
Author(s):  
Fulvio Siciliano ◽  
Evgueni I. Poliak
Keyword(s):  
Flow Stress ◽  
Hot Deformation ◽  
High Strength ◽  
Microalloyed Steels ◽  
Hot Strip Mill ◽  
Mean Flow ◽  
Hot Strip Rolling ◽  
Strip Rolling ◽  
Hot Strip ◽  
Mean Flow Stress

The hot strip rolling of advanced microalloyed high strength steels still represents a new task to many mills due to the lack of data on the hot deformation resistance. With the aid of processing data from the Ispat-Inland hot strip mill, the “measured mean flow stresses” are calculated from the mill force using the Sims analysis and taking into account roll flattening, slip ratio and the redundant strain. A modification of the Misaka mean flow stress equation is proposed for C – Mn – Si – Al steels microalloyed with up to 0.02 % Nb. The effects of alloying and microalloying are then estimated. A new fitting parameter shows excellent agreement with the mean flow stress data from industrial processing of advanced high strength microalloyed steels. However, during the second half of the rolling schedule (lower temperature region), indications of austeniteto- ferrite transformation were found.

Induced ferrite formation above the Ae3 during plate rolling simulation of a X70 steel

MRS Advances ◽  
2019 ◽  
Vol 4 (57-58) ◽  
pp. 3077-3085
Author(s):  
Samuel F. Rodrigues ◽  
Thiago B. Carneiro ◽  
Clodualdo Aranas ◽  
Eden S. Silva ◽  
Fulvio Siciliano ◽  
...  
Keyword(s):  
Volume Fraction ◽  
Accelerated Cooling ◽  
Strain Accumulation ◽  
Mean Flow ◽  
Ferrite Formation ◽  
Dynamic Transformation ◽  
Cooling Conditions ◽  
Plate Rolling ◽  
Stable Austenite ◽  
The Mean

ABSTRACTPartial amount of austenite can be dynamically transformed into ferrite above the Ae3 temperature when it is being deformed. This happens by a displacive mechanism. On removal of the load, it retransforms back into the stable austenite by diffusional processes. Plate rolling simulation under continuous cooling conditions was carried out on a high Nb X70 steel. Pass strains of 0.2 together with interpass times of 10, 20 and 30 s were employed. The initial and final temperatures for the finishing simulation were 920 and 830 °C, respectively. The mean flow stresses (MFS`s) behaviour indicates that dynamic transformation (DT) and recrystallization (DRX) were taking place during straining. It is shown that ferrite is formed during the roughing passes and increases its volume fraction throughout the finishing rolling steps. The ferrite formation is favoured by strain accumulation, shorter time between passes and also when the temperature reaches the Ae3 line. The results obtained here can be used to design improved models for transformation on accelerated cooling.

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