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.

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.

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.

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.

Effect of Dynamic Transformation on the Mean Flow Stress

2012 ◽  
Vol 84 (3) ◽  
pp. 253-258 ◽  
Author(s):  
John J. Jonas ◽  
Chiradeep Ghosh ◽  
Vladimir V. Basabe
Keyword(s):  
Flow Stress ◽  
Mean Flow ◽  
Dynamic Transformation ◽  
Mean Flow Stress ◽  
The Mean

Nonlinear vorticity-banding instability in granular plane Couette flow: higher-order Landau coefficients, bistability and the bifurcation scenario

2013 ◽  
Vol 718 ◽  
pp. 131-180 ◽  
Author(s):  
Priyanka Shukla ◽  
Meheboob Alam
Keyword(s):  
Couette Flow ◽  
Volume Fraction ◽  
Critical Density ◽  
Higher Order ◽  
Jump Discontinuity ◽  
Linear Growth Rate ◽  
Plane Couette Flow ◽  
Mean Flow ◽  
Dense Flows ◽  
The Mean

AbstractThe rapid granular plane Couette flow is known to be unstable to pure spanwise perturbations (i.e. perturbations having variations only along the mean vorticity direction) below some critical density (volume fraction of particles), resulting in the banding of particles along the mean vorticity direction: this is dubbed ‘vorticity banding’ instability. The nonlinear state of this instability is analysed using quintic-order Landau equation that has been derived from the pertinent hydrodynamic equations of rapid granular fluid. We have found analytical solutions for related modal/harmonic equations of finite-size perturbations up to quintic order in perturbation amplitude, leading to an exact calculation of both first and second Landau coefficients. This helped to identify the bistable nature of nonlinear vorticity-banding instability for a range of densities spanning from moderately dense to dense flows. For perturbations with small spanwise wavenumbers, the bifurcation scenario for vorticity banding unfolds, with increasing density from the dilute limit, as supercritical pitchfork $\rightarrow $ subcritical pitchfork $\rightarrow $ subcritical Hopf bifurcations. The transition from supercritical to subcritical pitchfork bifurcations is found to occur via the appearance of a degenerate/bicritical point (at which both the linear growth rate and the first Landau coefficient are simultaneously zero) that divides the critical line into two parts: one representing the first-order and the other the second-order phase transitions. Both subcritical oscillatory and stationary solutions have also been uncovered for dilute and dense flows, respectively, when the spanwise wavenumber is large. In all cases, the nonlinear solutions correspond to inhomogeneous states of shear stress and pressure along the vorticity direction, and hence are analogues of vorticity banding in other complex fluids. The quartic-order mean-flow resonance is evidenced in the parameter space for which the second Landau coefficient undergoes a jump discontinuity of infinite order. The importance of retaining higher-order terms to calculate the second Landau coefficient and their possible effects on the nature of bifurcations are elucidated.

scholarly journals TECHNIQUE FOR VERY HIGH ORDER NONLINEAR SIMULATION AND VALIDATION

2002 ◽  
Vol 10 (02) ◽  
pp. 211-229 ◽  
Author(s):  
RODGER W. DYSON
Keyword(s):  
Euler Equations ◽  
Harmonic Wave ◽  
Computational Cost ◽  
High Order ◽  
Mean Flow ◽  
Order Accuracy ◽  
Nonlinear Simulation ◽  
Fixed Design ◽  
The Mean ◽  
Very High

Finding the sources of sound in large nonlinear fields via direct simulation currently requires excessive computational cost. This paper describes a simple technique for efficiently solving the multidimensional nonlinear Euler equations that significantly reduces this cost and demonstrates a useful approach for validating high order nonlinear methods. Up to 15th order accuracy in space and time methods were compared and it is shown that an algorithm with a fixed design accuracy approaches its maximal utility and then its usefulness exponentially decays unless higher accuracy is used. It is concluded that at least a 7th order method is required to efficiently propagate a harmonic wave using the nonlinear Euler equations to a distance of five wavelengths while maintaining an overall error tolerance that is low enough to capture both the mean flow and the acoustics.

Mass Loading Effects on Turbulence Modulation by Particle Clustering in Dilute and Moderately Dilute Channel Flows

2015 ◽  
Vol 137 (11) ◽  
Author(s):  
Jesse Capecelatro ◽  
Olivier Desjardins
Keyword(s):  
Carrier Phase ◽  
Volume Fraction ◽  
Flow Direction ◽  
Channel Flows ◽  
Wall Region ◽  
Mass Loading ◽  
Mean Flow ◽  
Particle Clustering ◽  
Significant Volume ◽  
The Mean

Wall-bounded particle-laden flows exhibit a variety of interesting phenomena that can greatly impact the underlying carrier-phase turbulence in practical systems. This work aims at investigating the effects of particle clustering on the carrier-phase turbulence in both dilute and moderately dilute channel flows via highly resolved Euler–Lagrange simulations. It is shown that the fluid turbulence departs significantly from the initially fully developed turbulent flow at moderate concentrations. In particular, the gas velocity retains a viscous sublayer at higher values of mass loading, but displays a strongly reduced boundary layer thickness and a flatter velocity profile compared to the dilute case. Furthermore, the flow orientation with respect to gravity is found to significantly impact the multiphase dynamics. Particles showed a preference to be in the near-wall region with significant volume fraction fluctuations when gravity opposed the mean flow direction, while particles accumulated at the channel center with less significant volume fraction fluctuations for flows with gravity aligned with the mean flow direction.

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