Modification of Non-Metallic Inclusions by Rare-Earth Elements in Microalloyed Steels

Opiela, M.; Grajcar, A.

doi:10.2478/v10266-012-0050-9

Cited by 24 publications

(15 citation statements)

References 11 publications

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“…Rare earth (RE) elements are broadly utilized in functional materials, RE permanent magnetic materials, luminescent materials, and hydrogen storage materials . For structural materials, RE elements play an important role in purification, heterogeneous nucleating agents, and modifiers of nonmetallic inclusions . Moreover, they have been found to strengthen the grain boundary and suppress the crack propagation with more impact energy absorption .…”

Section: Introductionmentioning

confidence: 99%

“…4,5 For structural materials, RE elements play an important role in purification, 6 heterogeneous nucleating agents, [7][8][9] and modifiers of nonmetallic inclusions. [10][11][12][13][14][15][16] Moreover, they have been found to strengthen the grain boundary and suppress the crack propagation with more impact energy absorption. 17 Many studies have confirmed that an extremely small amount of RE addition can change the phase transformation temperature points during heating or cooling without an obvious modification of the composition.…”

Section: Introductionmentioning

confidence: 99%

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Chemical states of ppm cerium in steel by ToF‐SIMS analysis

Dai

Guo

Wang

et al. 2019

Surface & Interface Analysis

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Time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS) was employed for an analysis of the rare earth element Ce in pure iron and steel. Secondary ion images showed that the amount of the segregation of Ce and its oxides was much less as the concentration of Ce decreased to about 11 ppm in the pure iron. In terms of depth profiling from the surface to the matrix, variation of the CeO+/Ce+ ratio in a Ce oxides sample and a pure Ce sample exhibited difference between oxidized state and metallic state. It was demonstrated that metallic Ce was presented when the ratio of CeO+/Ce+ decreased to approximately 2 and even smaller. Oxygen content with concentration of tens of ppm may influence the ratio obviously. Such ToF‐SIMS analysis was also feasible to discern the states of cerium in a Q345E steel with concentration in ppm level.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Chemical states of ppm cerium in steel by ToF‐SIMS analysis

Dai

Guo

Wang

et al. 2019

Surface & Interface Analysis

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“…In fact, despite various roles of RE in steels, the main use of RE in steels concerns the shape control of inclusions, especially MnS particles during the hot deformation processes [5][6][7][8][9]. It has been suggested that the addition of these elements results in a considerable change in inclusion composition and generally leads to the formation of several constituents such as oxysulphides (Ce 2 O 2 S, La 2 O 2 S), oxides (Ce 2 O 3 , La 2 O 3 ) and sulfides (Ce 2 S 3 , La 2 S 3 ) [10,11].…”

Section: Introductionmentioning

confidence: 99%

The Influence of La and Ce Addition on Inclusion Modification in Cast Niobium Microalloyed Steels

Torkamani

Raygan

García‐Mateo

et al. 2017

Metals

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The main role of Rare Earth (RE) elements in the steelmaking industry is to affect the nature of inclusions (composition, geometry, size and volume fraction), which can potentially lead to the improvement of some mechanical properties such as the toughness in steels. In this study, different amounts of RE were added to a niobium microalloyed steel in as-cast condition to investigate its influence on: (i) type of inclusions and (ii) precipitation of niobium carbides. The characterization of the microstructure by optical, scanning and transmission electron microscopy shows that: (1) the addition of RE elements change the inclusion formation route during solidification; RE > 200 ppm promote formation of complex inclusions with a (La,Ce)(S,O) matrix instead of Al 2 O 3-MnS inclusions; (2) the roundness of inclusions increases with RE, whereas more than 200 ppm addition would increase the area fraction and size of the inclusions; (3) it was found that the presence of MnS in the base and low RE-added steel provide nucleation sites for the precipitation of coarse niobium carbides and/or carbonitrides at the matrix-MnS interface. Thermodynamic calculations show that temperatures of the order of 1200 • C would be necessary to dissolve these coarse Nb-rich carbides so as to reprecipitate them as nanoparticles in the matrix.

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“…В настоящее время в лабораторных и промышленных исследованиях [6] установлено, что применение РЗМ на заключительных этапах рафинирования позволяет существенным образом снизить содержание кислорода и серы в стали [7,8], модифицировать неметаллические включения и структуру литой стали [9]. После введения РЗМ в стали остаются незна-чительные количества в основном комплексных глобулярных оксисульфидов [10,11]. Вводятся редкоземельные элементы в металл в ограниченном (до 0,1 - 0,2 % (по массе)) количестве в составе комплексных сплавов с ферросилицием или щелочноземельными металлами [12].…”

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“…Поэтому даже незначительных добавок РЗМ в присутствии остаточного алюминия бывает достаточно для восстановления магния в жидкий металл из огнеупоров ковшей и жидкометальной проводки. В последующем этот магний может входить в состав вновь образующихся неметаллических включений [13], содержащих Al 2 O 3 и оксиды РЗМ [11,12]. После введения РЗМ максимальные размеры неметаллических включений находятся в пределах до 3 - 4 мкм, имеют в подавляющем большинстве глобулярную форму и достаточно равномерно распределены по объему слитка.…”

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THERMODYNAMICS OF THE PROCESSES OF INTERACTION OF LIQUID METAL COMPONENTS IN Fe – Mg – Al – La – O SYSTEM

Михайлов¹,

Makrovets²,

Смирнов³

2018

Izv. vysš. učebn. zaved., Čern. metall.

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At the present time, rare-earth elements in metallurgy are used in the form of mischmetal – a rare-earth elements natural mixture (with atomic numbers from 57 to 71). It contains about 50 wt. % of cerium. The remaining elements are mainly lanthanum and niobium. The specific composition is determined by the ore deposit. Inconstant composition of the modifier containing rare-earth metals (REM) can significantly reduce its efficiency. Experimentally, for every branded steels composition the ratio of various REMs can’t be selected because of the high costs of obtaining technically pure rare-earth metals. The task of determining the each rare earth element optimum concentrations and complex ligature composition can be solved by thermodynamic modeling. In the framework of thermodynamic modeling, the interaction between magnesium, aluminum and lanthanum with oxygen in liquid iron is presented. And the thermodynamic model of steel deoxidation by these active metals composition is considered. On the basis of available literature data on the phase diagrams of the systems MgO – Al2O3 , MgO – La2O3 and La2O3 – Al2O3 , the coordinates of the invariant equilibria points in the system MgO – La2O3 – Al2O3 were determined. The phase diagram of the system MgO – La2O3 – Al2O3 was constructed. It made possible to establish all phase equilibria realized in the process of deoxidation of steel with magnesium, lanthanum and aluminum and to describe these phase equilibria by chemical reactions equations. The activity of the components in liquid oxide melts was determined using the theory of subregular ionic solutions, which takes into account the dependence of the coordination number of cations on the composition of the oxide melt. The activity of components in metal melts conjugated with oxide systems were determined by Wagner’s theory using the parameters of the first order interaction. Equilibrium constants values for the steel deoxidation reactions are installed indirectly by thermodynamic calculations. On the basis of the obtained data the components solubility surface in the metal melts of Fe – Mg – Al – La – O system was constructed, which allowed to determine the liquid metal composition regions associated with the corresponding oxide phase.

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Modification of Non-Metallic Inclusions by Rare-Earth Elements in Microalloyed Steels

Cited by 24 publications

References 11 publications

Chemical states of ppm cerium in steel by ToF‐SIMS analysis

Chemical states of ppm cerium in steel by ToF‐SIMS analysis

The Influence of La and Ce Addition on Inclusion Modification in Cast Niobium Microalloyed Steels

THERMODYNAMICS OF THE PROCESSES OF INTERACTION OF LIQUID METAL COMPONENTS IN Fe – Mg – Al – La – O SYSTEM

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