The Mechanism of Unsteady Bulging and Its Analysis with the Finite Element Method for Continuously Cast Steel.

Lee, Joo Dong; Yim, Chang Hee

doi:10.2355/isijinternational.40.765

Cited by 30 publications

(10 citation statements)

References 6 publications

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“…[11][12][13][14][15][16][17][18][19][20][21] However, their origin and detailed mechanisms have not been known clearly until now. The numerical analysis of strand bulging considering movement of strand and unsteady behavior through the full range of a continuous caster has not been reported.…”

Section: Introductionmentioning

confidence: 99%

Analysis of Mold Level Hunching by Unsteady Bulging during Thin Slab Casting.

et al. 2002

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In order to analyze the phenomenon of mold level hunching (MLH) during thin slab casting process, the variation of the mold level and the bulging of strand were measured and analyzed using Fast Fourier Transform (FFT) spectrum analysis. Both of mold level hunching and bulging had the same frequency and the specific frequency corresponded to the main roll pitch of the thin slab caster. The unsteady bulging was found to be a main reason of mold level hunching. The unsteady bulging profile through the full range of the caster and the height of mold level hunching were calculated using a heat transfer model and a continuous beam model. The effects of process variables on mold level hunching and the process condition of reducing mold level hunching were studied. The amount of mold level hunching increased as unsteady bulging increased due to the hunching of casting speed. An aperiodic roll pitch between segments could be effective in reducing mold level hunching.KEY WORDS: mold level hunching (MLH); unsteady bulging; FFT analysis; continuous beam model; thin slab casting; aperiodic roll pitch.

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Section: Introductionmentioning

confidence: 99%

Analysis of Mold Level Hunching by Unsteady Bulging during Thin Slab Casting.

et al. 2002

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“…The unstable mould level is a consequence of an agglomeration of deoxidation products, solidified steel in the submerged entry nozzle/ shroud (clogging) or rapid drop oxide from the nozzle (unclogging). The further problems with mould level stability are caused by the molten steel discharge through the submerge entry shroud (SES) into the mould (waving), changes in the strand temperature and lower shell stiffness (unstable bulging) [1][2][3]. In some cases, waving can be also linked to the mould level reading noise, which moves the stopper without having a real meniscus variation [1].…”

Section: Introductionmentioning

confidence: 99%

Challenges to State-of-the-Art Mould Level Control Systems and Innovative Solutions

Cecchini¹,

Krajewski²,

Michelic³

et al. 2017

Anais Do Seminário De Aciaria, Fundição E Metalurgia De Não-Ferrosos

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State-of-the Art Mould Level Control Solutions for continuous casting applications face different challenges. On the one hand, technological phenomena such as clogging and unclogging, unsteady bulging or waving can create unpredicted meniscus disturbances by completely changing the casting channel geometry and the flow behaviour of liquid steel to the mould. On the other hand, from the viewpoint of caster operations, long lifetime, quick interchange-ability and integration capability into existing systems must be achieved. In the present contribution, the overall development of INTECO TBR's mould level master -a comprehensive mould level control solution for all continuous casting applications -will be introduced. The basis for the presented system is a development over several years which includes investigations of all critical components such as shroud, stopper, stopper mechanism, servo actuator and mould level control program. These investigations finally resulted in a new-ly developed control algorithm for a highly dynamic servo actuator. The control algorithm with its basic functionality such as the prevention, identification and removal of clogging impacts with the associated automation functions to reduce their influence onto the overall mould level control performance will be presented. The scientific basis, the resulting control functions and their related automation implementation will also be illustrated. Finally, a patented control algorithm and control functionality for unsteady bulging and waving effects with the associated automation functions to reduce their influence onto the overall mould level control performance.

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“…The problem is common enough that thermal models have been used to redefine cooling practices in order to avoid or reduce the incidence of this operational problem. [3] Furthermore, a great deal of work has been done in an attempt to understand the mechanism of bulging, because it affects a large number of quality and operational problems such as centerline segregation and internal crack formation, [4][5][6][7] breakouts when acting in combination with corner defects, [8] depressions, [9] nonuniformity of the shell thickness, [10] and roll failure. [11] Bulging deformation is a strong function of temperature and is also time dependent.…”

Section: Introductionmentioning

confidence: 99%

Analysis of thin-slab casting by the compact-strip process: Part II. Effect of operating and design parameters on solidification and bulging

et al. 2004

Metall Mater Trans B

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The mathematical model to compute the thermal evolution and solidification of thin slabs, previously presented in Part I of this article, was used in combination with a three-dimensional (3-D) finiteelement thermomechanical model to analyze how actual operation conditions can lead to excessive deflection and jamming of the slab shell at the pinch rolls. The models suggest that these phenomena arise from a sudden loss of control of the metallurgical length stemming from the coupling of inappropriate steel superheats and casting velocities to deficient heat-extraction conditions at the mold or secondary cooling system. The bulging deformation was calculated with an elastic and creep model that takes into account the temperature distribution across the shell thickness and the different times that shell elements have to creep exposure, i.e., according to the time that rows of elements require to reach their current position in the casting direction at a given casting speed. The last point was simulated by varying the duration of application of the ferrostatic load to the inside surface of each row of elements. The conditions forecast by the models as being responsible for excessive bulging agree very well with those present during the occurrence of these events in the plant. Since bulging after the last containment roll is a major limitation to productivity, this article also presents a parametric evaluation of the casting-speed limits that two compact-strip process (CSP) casters with different supported lengths may have as a function of steel superheat, mold heat-extraction level, water flow rate of the spray and air-mist nozzles, and slab thickness.

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The Mechanism of Unsteady Bulging and Its Analysis with the Finite Element Method for Continuously Cast Steel.

Cited by 30 publications

References 6 publications

Analysis of Mold Level Hunching by Unsteady Bulging during Thin Slab Casting.

Analysis of Mold Level Hunching by Unsteady Bulging during Thin Slab Casting.

Challenges to State-of-the-Art Mould Level Control Systems and Innovative Solutions

Analysis of thin-slab casting by the compact-strip process: Part II. Effect of operating and design parameters on solidification and bulging

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