Influence of Sulphur Content and Molten Steel Flow on Entrapment of Bubbles to Solid/Liquid Interface

Miyake, Takashi; Morishita, Masafumi; Nakata, Hitoshi; Kokita, Masahiko

doi:10.2355/isijinternational.46.1817

Cited by 36 publications

(24 citation statements)

References 6 publications

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“…high γ m − s ) would decrease heat transfer due to the longer distance between shell-tip and mould; thus decreasing the hook risks. Some industrial evidence has been found to support this speculation, based on the effect of sulphur content on the formation of hooks by Miyake et al 61) Yet, an increased radius might also favour solidification along the curved meniscus into the melt, increasing hook formation frequency. Observations in the plant show a high variability and the results are often contradictory.…”

Section: Interfacial Tensionmentioning

confidence: 80%

Key Lubrication Concepts to Understand the Role of Flow, Heat Transfer and Solidification for Modelling Defect Formation during Continuous Casting

López¹,

Jalali

Sjöström³

et al. 2018

ISIJ Int.

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Surface defects are recurrent problems during Continuous Casting of steel due to the introduction of new grades that are often difficult to cast, as well as the everlasting pursuit for higher quality and improved yield. Accordingly, numerical modelling has become a ubiquitous tool to analyse the formation mechanisms of such defects. However, industrial application of simulations is often hampered by oversimplifications and omissions of important process details such as variations in material properties, specific casting practices or shortcomings regarding fundamental metallurgical concepts. The present manuscript seeks to create awareness on these issues by visiting key notions such as slag infiltration, interfacial resistance and Lubrication Index. This is done from a conceptual point of view based on industrial observations and numerical modelling experiences. The latter allows a re-formulation of outdated concepts and misconceptions regarding the influence of fluid flow, heat transfer and solidification on lubrication and defect formation. Additionally, the manuscript addresses common challenges and constraints that occur during industrial implementation of numerical models such as the lack of high-temperature material data for slags. Finally, the manuscript provides examples of improvements on product quality and process stability that can be achieved through a holistic approach which combines modelling with laboratory tests, experiences from operators and direct plant measurements.KEY WORDS: numerical modelling; Continuous Casting; defects; lubrication; powder consumption.introduced as an alternative to study such issues in a more cost-efficient way than using traditional trial-error tests in the plant. Starting in the late 70's and 80's with the advent of personal computers, the first generation of models managed to predict the overall behaviour of the caster based on empirical data. 5-7) Subsequently, models in the 90's added Computational Fluid Dynamics (CFD) and solidification to casting simulations. [8][9][10] Faster computers and improved codes allowed huge progress regarding multi-phase applications (e.g. bubbles and inclusions) combined with calculations of flow and solidification in the past decade. 11-14)Currently, a wide variety of commercial and in-house codes are available for CC modelling such as PROCAST, COMSOL, TEMPSIMU, CON1D/2D, etc. [15][16][17] Moreover, a recent trend is the development of thermo-mechanical models coupled to flow dynamics for solving the combined problem of flow, solidification and stress-strain during casting. 18,19) Of all these, PHYSICA and THERCAST are two of the most promising approaches; which allow: a) 3D unstructured -mesh, multi-physics model using a combina-

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Section: Interfacial Tensionmentioning

confidence: 80%

Key Lubrication Concepts to Understand the Role of Flow, Heat Transfer and Solidification for Modelling Defect Formation during Continuous Casting

López¹,

Jalali

Sjöström³

et al. 2018

ISIJ Int.

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“…The Rolling Contact Fatigue (RCF) is an important issue in the exploitation of a rail steel. Nonmetallic Al 2 O 3 , SiO 2 and MnS inclusions which frequently appear in the material have a negative impact on the durability of rail and lower RCF. Big and brittle inclusions containing Ca, Al, O and Si may initiate critical cracking under the surface of the rail head.…”

Section: Introductionmentioning

confidence: 99%

“…In the case of complex inclusions containing manganese sulphur the deformation considerably differs from that of pure MnS. The manganese sulphide may be surrounded by brittle oxidic phases, it may constitute a plastic cover on oxidic phase in the course of heterogeneous nucleation [2,3]. In this case their deformation may result in flattening and elongation of inclusions, and in the presence of brittle phases -cracks may appear.…”

Section: Introductionmentioning

confidence: 99%

“…For this reason steel should not contain more than 0.005% of sulphur, which is an insurmountable value for materials from which are made constructions, vehicles and pipelines operating in low temperature conditions, as well as materials for transport [1]. Chemically, manganese is closer to sulphur than iron; the MnS precipitations not only lower the mechanical properties of steel but also cause hydrogen accumulation on the grain interface during welding jobs, bringing about microckacks [2]. It was experimentally concluded that this shortcoming is closely connected with sulphur content in steel [3].…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Computer Simulation of Microsegregation of Sulphur and Manganese and Formation of MnS Inclusions while Casting Rail Steel

Kalisz

Gerasin

Bobrowski

et al. 2016

Archives of Metallurgy and Materials

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The quality of rail steel is conditioned by its high mechanic qualities, which greatly depend on the presence of undesired nonmetallic inclusions. The paper is devoted to the segregation of components, mainly sulphur, and the formation of manganese sulphide in the process of steel solidification, at the casting rate of 100 and 500 K/min. Sulphur is a steel component which disadvantageously influences its numerous parameters. The oxide-sulphide and sulphide precipitations cause cracks and lower the strength of the material. This phenomenon was modeled with the use of author’s computer program based on Matsumiya interdendritic microsegregation model. The main assumptions of this model and thermodynamic conditions of inclusion formation during casting of steel are discussed in this paper. Two cases were analyzed: in the first one the MnS was assumed to form a pure and constant compound, whereas in the other one the manganese sulfide was precipitated as a component of a liquid oxide solution, and its activity was lower than unity. The final conclusion is that chemical composition of steel is the major parameter deciding about the formation of MnS inclusions.

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“…6) Miyake et al believed that the distribution of bubbles in slab depends on the steel grade, especially on the sulfur content based on study on Kakogawa Work; and the authors pointed that electromagnetic stirring in the mold (M-EMS) was effective for removing bubbles and reduce sliver defect. 7) In cold rolled IF steel, slivers and blow-holes were two main types of visual surface defects; generally, the defects were caused by argon bubbles or argon bubbles in combination with entrapped mould powder; the sliver defects had relationship with the argon bubbles containing the alumina clusters or mould slag. 8) So it is important to evaluate the detriment and evolution of bubbles' distribution in steel slab.…”

Section: Introductionmentioning

confidence: 99%

Distribution and Detriment of Bubbles in Continuous Casting Interstitial Free Steel Slab

et al. 2015

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The distribution and detriment of bubbles in ultra low carbon interstitial free steel were studied by X-ray radiographic and cold-rolled experiment; a total of 24 pieces samples with size 230 mm × 65 mm × 2 mm were detection and 150 bubbles were counted; the results showed that: (1) Two bubbles bands formed in continuous casing slab; bubbles distributed asymmetrically in thickness direction of the slab; small bubbles mainly concentrated in inner art side 1/8 to 1/4 in thickness direction; large bubbles were main in center of the slab in thickness direction; (2) Hundreds of inclusions with sizes 2 μm to 10 μm accumulated in cone-shape region after bubbles. Inclusions or Fe and FeO particles often attached or mixed with the bubbles. (3) Small bubbles entered into down-flow easily and rushed out the mould, bubbles and inclusions accumulative band formed in inner art side of the slab. (4) The bubbles, inclusions around the bubbles or large Fe and FeO particles mixing with bubbles became source of the sliver defect.

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Influence of Sulphur Content and Molten Steel Flow on Entrapment of Bubbles to Solid/Liquid Interface

Cited by 36 publications

References 6 publications

Key Lubrication Concepts to Understand the Role of Flow, Heat Transfer and Solidification for Modelling Defect Formation during Continuous Casting

Key Lubrication Concepts to Understand the Role of Flow, Heat Transfer and Solidification for Modelling Defect Formation during Continuous Casting

Computer Simulation of Microsegregation of Sulphur and Manganese and Formation of MnS Inclusions while Casting Rail Steel

Distribution and Detriment of Bubbles in Continuous Casting Interstitial Free Steel Slab

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