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Structural optimization and design of purging plug for improving its service performance

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Journal of Iron and Steel Research(International) 2022年第4期29卷 628-635页

作者： Fang-guan Tan Sheng-li Jin Zhu He Ya-wei Li The State Key Laboratory of Refractories and Metallurgy Wuhan University of Science and TechnologyWuhan 430081HubeiChina National-Provincial Joint Engineering Research Center of High Temperature Materials and Lining Technology Wuhan University of Science and TechnologyWuhan 430081HubeiChina chair of ceramics Montanuniversitaet LeobenLeoben 8700Austria

Purging plug with slits is widely used in the secondary refining process,and its service life determines the downtime and production efficiency.To achieve a good performance in service life,optimizing the geometric structure of the slit,which can alleviate the stress concentration around the slit,was employed using the finite plate model.Furthermore,the performance of the purging plugs with different shapes of slits in the refining effect was investigated by conducting the water model experiments.The numerical simulation results showed that the appropriate shapes of slits could alleviate the stress concentration phenomena.In the water model experiment,the mixing time of the purging plug with circular slits is lesser than that of the purging plug with rectangular slits when the gas flow is less than 6.02 L/min.Compared with the rectangular slits,the circular slits are detrimental to smaller and well-distributed bubbles.Thus,the inclusion removal rate of the purging plug with circular slits is approximately 10%larger than that of the purging plug with the rectangular slits.

关键词： Purging plug Stress concentration Water model experiment Mixing time Inclusion removal Ladle metallurgy

Main Wear Mechanisms of SEN Slag Band Materials

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China's Refractories 2017年第1期26卷 1-7页

作者： Harald HARMUTH Volkmar KIRCHER Nathalie KOLBL chair of ceramics Montanuniversitaet Leoben 8700 Austria

This paper summarizes experimental approaches and simulation results in order to establish a general proposition regarding SEN wear mechanisms.Marangoni convection is considered to be a major contribution to continuous SEN wear,usually causing characteristic corrosion grooves.It is governed by the interface tension gradient in the vicinity of the three phase boundary slag/refractory/steel.This interface tension gradient is caused by a lower activity of the oxygen dissolved in the steel close to the refractory/steel interface.This is due to the reducing action of the solid carbon,which is a component of the refractory.By a simulation model using the Effective Equilibrium Reaction Zone technique a calculation of the interface tension differenceΔσwas performed.While for an LC steel and the related slag a valueΔσ=150mN/m was received,this quantity is negligible in the case of a TRIP steel.Accordingly,also the wear is much less for the TRIP steel.Marangoni convection is decisive for the mass transfer at the refractory/slag interface.Here dissolution of zirconia,but also oxidation of carbon takes place.For the latter one,the above mentioned simulation showed that reduction of silica in the mold slag takes place at the three phase boundary slag/refractory/steel by solid carbon,as the activity of silicon is reduced by dissolution in the liquid steel.This is the main source of oxygen for carbon oxidation at the three phase boundary.Therefore the three phase boundary is the focus of SEN wear：It unites intense bath movement due to Marangoni convection,oxidation of carbon by SiO_2reduction and zirconia erosion and dissolution into the melt.Within the refractory itself,a thin layer of several millimetres shows reactions with slag components.This causes especially destabilisation of stabilised zirconia and prepares later erosive wear.Steel does not penetrate into the SEN microstructure,carbon dissolution is only possible at the steel/refractory interface.The results quoted here enable justified expectations about the SEN wear

关键词： SEN wear zirconia dissolution Marango-ni convection

Identification of secondary raw materials in mold powders and their melting behavior

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Journal of Iron and Steel Research(International) 2019年第4期26卷 403-411页

作者： Irmtraud Marschall Nathalie Kolbl Harald Harmuth Christina Atzenhofer KI-MET GmbH 8700 LeobenAustria Department Mineral Resources Engineering Chair of CeramicsMontanuniversitaet Leoben8700 LeobenAustria

Commercial mold powders use a limited number of main mineral constituents,but may differ significantly in chemical composition.The main mineral raw materials of specimens investigated here are quartz,fluorite and free carbon,as well as wollastonite and carbonates.The investigations revealed the use of secondary raw materials like blast furnace slag,fly ash,glass scrap and phosphorous slag as further components.Since the formation of cuspidine was one major point of interest,the influence of the silica source on its formation was identified.A replacement of wollastonite by blast furnace slag reduced the temperature of the first precipitation of cuspidine by about 100℃;the dissociation of sodium carbonate was lowered by-40℃.The lowest temperature of the first Na2CO3 dissociation could be achieved by using fluorine in combination with blast furnace slag.Cuspidine formation from the melt is further decreased if sodium and fluorine are both present.The use of glass scrap and phosphorous slag strongly reduced the temperature of first melt formation and enhanced cuspidine formation.

关键词： Mold powder Cuspidine Melting Crystallization behavior

Creep Modeling of Magnesia-chromite Bricks in a RH Snorkel During a Process Cycle

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China's Refractories 2015年第1期24卷 22-25页

作者： JIN Shengli Harald HARMUTH Dietmar GRUBER Roman RSSLER chair of ceramics Montanuniversitat LeobenA-8700Austria Voestalpine Stahl GmbH

In this paper both experimental and analytical approaches to provide the inputs for creep modeling of refractories including a newly developed high temperature compressive creep machine and an inverse estimation procedure of creep law parameters are briefly introduced.Besides,a modified shear test is applied to determine the cohesion and friction angle of refractories under shear state. A RH snorkel equipped with magnesia- chromite bricks is chosen for a case study of thermomechanical simulation applying the classical creep model and Drucker-Prager creep model available in the finite element code ABAQUS,respectively. Afterwards,thermal stresses and joint opening of magnesia- chromite bricks during a process cycle are compared to distinguish the impact of these two creep models.

关键词： creep shear failure thermomechanical modeling RH snorkel

Numerical study of creep effect on purging plug performance under cyclic service

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Journal of Iron and Steel Research(International) 2022年第7期29卷 1119-1128页

作者： Fang-guan Tan Sheng-li Jin Zhu He Xiong Liang Ya-wei Li Jing Li The State Key Laboratory of Refractories and Metallurgy Wuhan University of Science and TechnologyWuhan 430081HubeiChina National-Provincial Joint Engineering Research Center of High Temperature Materials and Lining Technology Wuhan University of Science and TechnologyWuhan 430081HubeiChina chair of ceramics Montanuniversitaet Leoben8700 LeobenAustria The Key Laboratory of Chemical Metallurgy Engineering of Liaoning Province and School of Materials and Metallurgy University of Science and Technology LiaoningAnshan 114051LiaoningChina

The service life of the purging plug is one of the fundamental factors that determine the downtime and usage efficiency of the whole ladle.The creep behaviour of the purging plug was thus investigated to identify the possible failure mechanism.At first,the creep parameters of the Norton–Bailey strain hardening rule were inversely identified via the results of the creep test.Then,the thermal-solid coupling model approach was employed to predict the creep behaviour of the purging plug,in which the Norton–Bailey strain hardening rule was applied.The numerical results show that the temperature of the purging plug presents a cyclic trend after the first service period since the preheating temperature is lower than the temperature of molten steel.Furthermore,the distribution of the creep strain intensity in a layered form could also contribute to a gradual spalling of the purging plug end in service.Besides,the creep strain concentration around the slit can be responsible for the clogging of the purging plug.

关键词： Strain hardening Creep test Creep deformation Purging plug Castable corundum

Investigation of Compressive Refractory Creep

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China's Refractories 2018年第3期27卷 21-27页

作者： JIN Shengli Harald HARMUTH chair of ceramics Montanuniversit?t

Creep of refractories at high temperatures may have significant influences on the thermomechanical behavior of refractory linings in industrial vessels,and thus the consideration of creep in finite element modeling of industrial vessels is necessary. The present paper introduces an advanced high temperature compressive creep device and a proper inverse procedure using Levenberg-Marquardt algorithm to identify Norton-Bailey creep parameters. In addition,finite element thermomechanical modeling results of a RH-snorkel are presented to illustrate the impact of creep,creep formulations and creep models on the circumferential stress and joint opening of the working lining.

关键词： creep uniaxial compression Norton-Bailey thermomechanical modeling RH snorkel joint opening

Corrosion Mechanisms of SEN Slagband Materials

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China's Refractories 2013年第2期22卷 6-10页

作者： Harald HARMUTH Nathalie KBL Barbara ROLLINGER Guangmin XIA chair of ceramics Montanuniversitaet Leoben RHI AG Voestalpine Stahl GmbH

Wear of a zirconia graphite slagband material by mold slag during casting of a TRIP steel grade was investigated on worn specimens with respect to corrosion and erosion. Corrosion dissolution of both the stabilizer oxide and the zirconia is decisive. Oxidation is dominating graphite wear whereas a possible dissolution in the liquid steel was not observed to play an important role here. The ratio of oxide corrosion to graphite oxidation decreases with decreasing vertical distance of the hot face to the steel bath. Unfortunately and contrary to other applications of carbon bonded refractories in steel industry graphite exhibits to be wetted by mold slag in the special case investigated here： it still acts as a refractive component but only partly as an infiltration inhibitor. Infiltration is followed by zirconia corrosion thus reducing erosion resistance, but nevertheless also gas phase transport of slag components may cause exsolution of the stabilizer oxide in un-infiltrated regions.

关键词： zirconia, graphite corrosion mechanism slagband

Fractographic and Fracture Mechanical Investigations of Refractories under Different Loading Conditions

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China's Refractories 2014年第1期23卷 19-23页

作者： Harald HARMUTH Elmar Karl TSCHEGG chair of ceramics Montanuniversitaet LeobenA-8700 Leoben Institute of Building Construction and Technology Vienna University of TechnologyA-1040 Wien

Crack initiation and propagation have been investigated under tensile and shear loading in ceramically and carbon bonded refractories.A wedge splitting test procedure and a modified shear test have been applied.Test results have been used for material characterization especially with respect to brittleness.Furthermore a microscopic fractographic test procedure was developed and applied on fractured test specimens.In order to explain brittleness dependence on structure properties correlation of fractographic and fracture mechanical results has been evaluated.Frequently brittleness reduction is achieved by a lower amount of transgranular crack propagation associated with a strength decrease while maintaining specific fracture energy unchanged.Deviations from pure linear fracture mechanics increase with decreasing brittleness and contribute to specific fracture energy.Shear specimens may show two generations of cracks,a first one initiated by tensile loads （stable propagation） and a second one by shear loads （unstable propagation）.

关键词： Fractographic and fracture investigation brittleness refractories wedge splitting test modified shear test

Nanodispersed Oxides-Plasma-Chemical Synthesis and Properties

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Plasma Science and Technology 2007年第5期9卷 603-610页

作者： Gheorghi VISSOKOV Katerina ZAHARIEVA Institute of Catalysis Bulgarian Academy of SciencesSofia 1113Bulgaria Chemistry chair St.Ivan Rilski University of Mining and GeologySofia 1700Bulgaria

We discuss the plasma-chemical synthesis and the properties of transition metals oxides, Al2O3, SiO2, rare-earth oxides, oxides for ceramics and metal-ceramics, and oxides used as catalysts. Bearing in mind the indisputable advantages of using plasma-chemically synthesized nanodispersed oxides for the needs of various industrial fields, we set out to review the articles published in the past few years devoted to the problems of plasma-chemical synthesis and characterization of nanodispersed oxides.

关键词： plasma synthesis nanodispersed oxides properties