The study of improving the strip flatness in run-out-table during laminar cooling

Wu, Wei Lin; Wang, Wei Cheng; Lo, Wei Chung

doi:10.1007/s00170-017-1558-5

Cited by 14 publications

(10 citation statements)

References 11 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The austenite decomposition kinetics depends on both steel chemistry and cooling scenario and, is thus, inherently linked to the temperature models itself, as schematically illustrated in Figure 4. [21,22,27,29,32,[35][36][37][38][39][40][41] Due to the complexity of the coupling with a phase transformation model, many ROT cooling simulation studies have neglected the heat of phase transformation. Nevertheless, these simulations showed acceptable prediction of mill data because the simplification to not account for transformation heat is, at least effectively, corrected by tuning the empirical correlations for heat transfer coefficients.…”

Section: Temperature Modelsmentioning

confidence: 99%

“…where L is the latent heat of phase transformation at temperature T i , dX i is the change of the volume fraction transformed in time increment dt. The kinetics of the isothermal austenite decomposition is frequently described by the Johnson-Mehl-Avrami-Kolmogorov(JMAK) approach, [27,38,42,43] that is,…”

Section: Temperature Modelsmentioning

confidence: 99%

“…In general, this heat source is described using

\dot{q} = L \frac{{d X}_{i}}{d t}

where

L

is the latent heat of phase transformation at temperature

T_{i}

d X_{i}

is the change of the volume fraction transformed in time increment dt . The kinetics of the isothermal austenite decomposition is frequently described by the Johnson‐Mehl‐Avrami‐Kolmogorov(JMAK) approach, that is,

\frac{X}{X^{e}} = 1 - exp true(- r t^{n} true)

here, X e is the equilibrium or maximum fraction transformed for the considered transformation product and temperature, is a rate constant which depends on steel chemistry and temperature, and

n

is the JMAK exponent. This equation can typically be extended to non‐isothermal transformation that occurs on the ROT by using the additivity rule .…”

Section: Temperature Modelsmentioning

confidence: 99%

See 2 more Smart Citations

Simulation of Runout Table Cooling

Guemo

Prodanovic

Militzer

2018

steel research int.

View full text Add to dashboard Cite

Accelerated cooling on the runout table of hot mills has become a key technology to produce thermo‐mechanically controlled processed (TMCP) steel plates and strips. During runout table cooling austenite decomposition takes place and determines the final microstructure and, hence, the properties of the hot‐rolled steel. There is an increased tendency to produce higher strength TMCP steels with complex microstructures including bainite and martensite. To tailor these microstructures, it is required to carefully design runout table cooling paths and lower the cooling stop and coiling temperature, respectively, for producing flat products with homogeneous mechanical properties. Thus, simulation of runout table cooling is a crucial aspect of process modeling. In the present paper, the status of runout table simulation approaches is reviewed. In particular, the three boiling mechanisms of water cooling, that is, nucleate, transition, and film boiling are discussed. The development of appropriate heat transfer coefficients is rather mature for nucleate and film boiling, respectively. Modeling and controlling the transition boiling regime below the Leidenfrost temperature remains a challenge as heat extraction rates increase with decreasing steel temperature. The status of heat transfer simulations for transition boiling is thus discussed in detail. Currently, the proposed heat transfer correlations, while increasingly based on the underlying physics, still contain a number of empirical parameters that require tuning with experimental and/or mill data. The review is limited to information in the open literature while recognizing that a number of proprietary in‐house runout table cooling models exist that are developed either by equipment makers or steel companies to control accelerated cooling to lower cooling stop or coiling temperatures.

show abstract

Section: Temperature Modelsmentioning

confidence: 99%

Section: Temperature Modelsmentioning

confidence: 99%

“…In general, this heat source is described using

\dot{q} = L \frac{{d X}_{i}}{d t}

where

L

is the latent heat of phase transformation at temperature

T_{i}

d X_{i}

\frac{X}{X^{e}} = 1 - exp true(- r t^{n} true)

here, X e is the equilibrium or maximum fraction transformed for the considered transformation product and temperature, is a rate constant which depends on steel chemistry and temperature, and

n

is the JMAK exponent. This equation can typically be extended to non‐isothermal transformation that occurs on the ROT by using the additivity rule .…”

Section: Temperature Modelsmentioning

confidence: 99%

See 1 more Smart Citation

Simulation of Runout Table Cooling

Guemo

Prodanovic

Militzer

2018

steel research int.

View full text Add to dashboard Cite

show abstract

“…Results show that cooling one surface faster than the other creates an asymmetry that is responsible for a bending moment which results in flatness defects such as a bow in the length or width direction. Wu et al [23] designed a 2D model to analyse the temperature history, deformation, and phase transformation during a first laminar cooling and a second alternative water or air cooling. The model was able to predict different curvatures during the individual cooling steps.…”

Section: Modelling Of Flatness Defects Via Finite Element Methodsmentioning

confidence: 99%

Towards hot levelling strategies for steel heavy plates: analysis of flatness evolution in accelerated cooling, hot levelling, and final air cooling via thermo-mechanical FE modelling

Laugwitz

Jochum

Scheffer

et al. 2022

Int J Adv Manuf Technol

View full text Add to dashboard Cite

In the production of heavy plates, the flatness of the products is an essential feature that must be set within narrow tolerances. Thus, the understanding of the flatness evolution throughout all relevant production steps in the rolling mill is paramount for high-quality products. It is known that most flatness defects arise either due to roll gap deviations in rolling or because of changing thermal conditions in the subsequent cooling processes. Severe defects induced during rolling are treated by a pre-leveller while the final heavy plate flatness after cooling is set in a dedicated hot leveller. Consequently, thermally induced defects need to be removed in this dedicated hot leveller as well. However, it is not yet feasible to model the flatness evolution throughout the relevant processing sequence consisting of accelerated cooling after hot rolling, hot levelling, and final air cooling. In order to close this gap and to analyse the process sequence with regard to flatness evolution, within this study, two cooling and a levelling model were developed and coupled with respect to thermal history, deformation, and residual stresses. These coupled thermo-mechanical finite element (FE) models were successfully applied to predict the flatness evolution in heavy plate production. Firstly, the formation of centre waves caused by inhomogeneous cooling conditions was captured. Secondly, the change in flatness during hot levelling was predicted. Thirdly, a transition from centre to edge waves was observed during final air cooling after levelling. This phenomenon (sometimes observed in industrial heavy plate production) was successfully reproduced in a sequence of coupled simulations for the first time. Finally, the hot levelling process was analysed via a parameter study to understand the root cause of this transition and to propose alternative hot levelling strategies that avoid it.

show abstract

“…This leads to the accumulation of water on the upper surface of the steel strip in the cooling section. The accumulated water stops jets having a direct impact on the steel surface, and also causes overcooling of edges and influences the cooling intensity [11]. The situation where the single circular water jet does not impinge on the steel surface directly but instead impinges on a surface covered with water was investigated by Fujimoto et al [12].…”

Section: Introductionmentioning

confidence: 99%