Nichtmetallische Einschlüsse in Langprodukten Entstehung, Bestimmung, Auswirkungen – ein Überblick

Klösch, Gerald; Huemer, K.; Sormann, Axel; Frank, G.

doi:10.1007/s00501-008-0437-7

Cited by 6 publications

(7 citation statements)

References 1 publication

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“…The NMI of the type mullite, which is dominating in the electrode, is typical for roller bearing steels. [33] Al 2 O 3 and MA-spinel-type NMI are often found in steels after remelting with alumina-and MgO-containing slags [20,23,24,[27][28][29][30]38] but, according to previous studies, [3,11,33] Al 2 O 3 -type NMI have significant negative effects on fatigue properties. Only with the alumina-free slag, the oxygen and the aluminum contents in the liquid bath can be kept low enough to avoid Al 2 O 3 .…”

Section: Nonmetallic Inclusionsmentioning

confidence: 99%

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Effect of the Al₂O₃ Content in the Slag on the Remelting Behavior of a Bearing Steel

Schneider

Molnar

Klösch

et al. 2020

steel research int.

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The service life of roller bearings strongly depends on nonmetallic inclusions (NMIs). Therefore, these steels request highest metallurgical standards in their production. To determine the effect of the Al2O3 content and a protective atmosphere (N2) on the electroslag remelting (ESR) behavior, laboratory scale experiments are conducted. Changes in the composition of the remelted materials and in the slag are determined. In addition, the amount and composition of the NMI prior and after remelting are investigated, and thermodynamic simulations on the formation of NMI are conducted. Changes in the chemical composition can largely be explained by well‐known equilibrium reactions between the slag and the metal. Lowest Al contents in the remelted steel can only be achieved with the Al2O3‐free slag. Higher Al2O3 contents in the slag lead to higher oxygen and sulfur contents in the steel and corresponding higher amounts of NMI after remelting. The use of a protective gas mainly reduced the loss of Si and led to lower O and S contents after remelting with the Al2O3‐free slag. The composition of the NMI changed from alumina type to MgO–Al2O3 (MA)‐spinel type and finally mixed MgO–SiO2 oxides with decreasing Al2O3 contents. These results are confirmed by thermodynamic calculations.

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Section: Nonmetallic Inclusionsmentioning

confidence: 99%

“…However, modern conventional steelmaking praxis results in excellent microstructures, reduced segregations, and low amounts of NMIs. [ 33 ] Nevertheless, further improvements to remove larger NMI or to change their chemical composition seem feasible by ESR.…”

Section: Introductionmentioning

confidence: 99%

Effect of the Al₂O₃ Content in the Slag on the Remelting Behavior of a Bearing Steel

Schneider

Molnar

Klösch

et al. 2020

steel research int.

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“…The remelting of roller bearing steels was already widely investigated in the early years of ESR, [31] showing significant advantages, especially in the amount of NMIs; however, the standard steelmaking praxis has improved greatly in the meantime, leading to excellent microstructures, reduced segregations, and low amounts of inclusions. [32] Nevertheless, further improvements, especially regarding larger NMIs, seem feasible by ESR.…”

Section: Introductionmentioning

confidence: 99%

Effect of the Al2O3 Content in the Slag on the Chemical Reactions and Nonmetallic Inclusions during Electroslag Remelting

Schneider

Molnar²,

Klösch

et al. 2020

Metall Mater Trans B

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The service life of roller bearings is extremely sensitive to large and hard nonmetallic inclusions (NMIs), requesting the highest standards in their production. To determine the metallurgical possibilities, the effect of Al2O3 contents between 0 and 33 pct in the remelting slag was investigated by remelting a roller bearing steel in an experimental electroslag remelting (ESR) plant. Thereby, changes in the chemical composition of the materials (electrode vs ingots) and in the remelting slag during remelting, as well as the amount and composition of the NMIs prior to and after remelting, were investigated. Changes in the chemical composition can largely be explained by equilibrium reactions between the slag and the metal, thereby low Al contents in the remelted materials could only be achieved with the lowest Al2O3 contents in the slag. Furthermore, higher Al2O3 contents in the slag also lead to higher oxygen and sulfur contents in the steel as well as higher amounts of NMIs after remelting. The composition of the NMIs changed from alumina type for high Al2O3 contents to spinel type and other mixed MgO-SiO2 oxides for low Al2O3 contents. The results indicate solutions for the production of bearing steels with the lowest amounts of undesired large and hard NMIs.

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“…NMI cannot be entirely eliminated in the steel production, but high efforts are made to minimize the number and sizes of inclusions in high-and ultra-high-strength steels [2,3,5]. The most common NMI in aluminum-killed steels are aluminum oxides (Al 2 O 3 ), manganese sulfides (MnS) and different types of spinels [2].…”

Section: Introductionmentioning

confidence: 99%

Micromechanical Modeling of Fatigue Crack Nucleation around Non-Metallic Inclusions in Martensitic High-Strength Steels

Schäfer

Sonnweber-Ribic

Hassan

et al. 2019

Metals

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Martensitic high-strength steels are prone to exhibit premature fatigue failure due to fatigue crack nucleation at non-metallic inclusions and other microstructural defects. This study investigates the fatigue crack nucleation behavior of the martensitic steel SAE 4150 at different microstructural defects by means of micromechanical simulations. Inclusion statistics based on experimental data serve as a reference for the identification of failure-relevant inclusions and defects for the material of interest. A comprehensive numerical design of experiment was performed to systematically assess the influencing parameters of the microstructural defects with respect to their fatigue crack nucleation potential. In particular, the effects of defect type, inclusion–matrix interface configuration, defect size, defect shape and defect alignment to loading axis on fatigue damage behavior were studied and discussed in detail. To account for the evolution of residual stresses around inclusions due to previous heat treatments of the material, an elasto-plastic extension of the micromechanical model is proposed. The non-local Fatemi–Socie parameter was used in this study to quantify the fatigue crack nucleation potential. The numerical results of the study exhibit a loading level-dependent damage potential of the different inclusion–matrix configurations and a fundamental influence of the alignment of specific defect types to the loading axis. These results illustrate that the micromechanical model can quantitatively evaluate the different defects, which can make a valuable contribution to the comparison of different material grades in the future.

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Nichtmetallische Einschlüsse in Langprodukten Entstehung, Bestimmung, Auswirkungen – ein Überblick

Cited by 6 publications

References 1 publication

Effect of the Al₂O₃ Content in the Slag on the Remelting Behavior of a Bearing Steel

Effect of the Al₂O₃ Content in the Slag on the Remelting Behavior of a Bearing Steel

Effect of the Al2O3 Content in the Slag on the Chemical Reactions and Nonmetallic Inclusions during Electroslag Remelting

Micromechanical Modeling of Fatigue Crack Nucleation around Non-Metallic Inclusions in Martensitic High-Strength Steels

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Nichtmetallische Einschlüsse in Langprodukten Entstehung, Bestimmung, Auswirkungen – ein Überblick

Cited by 6 publications

References 1 publication

Effect of the Al2O3 Content in the Slag on the Remelting Behavior of a Bearing Steel

Effect of the Al2O3 Content in the Slag on the Remelting Behavior of a Bearing Steel

Effect of the Al2O3 Content in the Slag on the Chemical Reactions and Nonmetallic Inclusions during Electroslag Remelting

Micromechanical Modeling of Fatigue Crack Nucleation around Non-Metallic Inclusions in Martensitic High-Strength Steels

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Effect of the Al₂O₃ Content in the Slag on the Remelting Behavior of a Bearing Steel

Effect of the Al₂O₃ Content in the Slag on the Remelting Behavior of a Bearing Steel