Actual review on secondary metallurgy

Fandrich, Rolf; Lüngen, Hans Bodo; Wuppermann, C.-D

doi:10.1051/metal:2008053

Cited by 14 publications

(7 citation statements)

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Section: Resultsmentioning

confidence: 99%

“…From all the tasks performed during secondary metallurgy, VD is critical to remove undesired dissolved gases (i.e., hydrogen and/or nitrogen), and, in some cases, also to reduce steel C content. [50][51][52][53][54][55][56] Furthermore, with an operation tightly controlled and metallurgical practices properly defined, it is also possible to improve steel cleanliness by reducing the amount of harmful inclusions during the vacuum treatment process. [51,[56][57][58][59][60][61][62][63][64] To assess the effect of VD over inclusions panorama, tundish samples from 139 heats (90 with and 49 without VD treatment) with similar processing conditions were assessed.…”

Section: Effect Of Vd On Inclusion Panoramamentioning

confidence: 99%

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Characterization of Nonmetallic Inclusions of Al‐Killed Ca‐Treated Steels by Automated SEM/EDS and Its Application to Industrial Case Studies

Capurro

Boeri

Cicutti

2022

steel research int.

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Given their potential to significantly affect steel shops, production capacity and also to impair the properties of steel in service, nonmetallic inclusions are highly undesired. In this context, the availability of accurate methods to assess the steel cleanliness at different stages of the refining process is of paramount importance for the development of sound and consistent metallurgical practices. In the current contribution, a measurement tool based on scanning electron microscopy/energy‐dispersive X‐ray spectrometry analysis is applied to characterize the nonmetallic inclusions population (e.g., density, size distribution solid fraction, and chemical composition) present in lollipop steel samples withdrawn at different stages of the fabrication process. Data collected from a large number of samples are used to verify the reproducibility of the results and to improve the accuracy of the methodology developed. Subsequently, the characterization procedure is applied to assess the effect of different industrial aspects, such as the influence of vacuum degassing on the inclusionary panorama and the role of inclusions chemical composition on steel castability.

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Section: Resultsmentioning

confidence: 99%

Section: Effect Of Vd On Inclusion Panoramamentioning

confidence: 99%

Characterization of Nonmetallic Inclusions of Al‐Killed Ca‐Treated Steels by Automated SEM/EDS and Its Application to Industrial Case Studies

Capurro

Boeri

Cicutti

2022

steel research int.

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“…10 Process Metallurgy Table 1. Progress of achievable contents of impurities in steel, in ppm [1][2][3][4].…”

Section: Factors Influencing Oxide Cleanlinessmentioning

confidence: 99%

On Physico‐Chemical and Technical Limits in Clean Steel Production

Holappa¹

2010

steel research int.

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Great progresses in steel cleanliness have been attained during the last decades. In the measures of oxygen the lowest levels are approaching 5 ppm in O tot i.e. close to the thermodynamic limit of Al deoxidation. As the thermodynamics of the reaction system is firmly anchored to the steel chemistry and thus to the properties of steel and the final product, it is useful to examine the thermodynamic constraints for selected steels in the refining and casting processes. In most steels Al-O equilibrium determines the limit of deoxidation. Calculations by applying thermodynamic software showed that in selected ''common'' steels the equilibrium oxygen content varied from below 5 ppm up to 30 ppm or higher depending on the aluminium content, interaction effect of other alloying elements and temperature.For lower oxygen content there are several possibilities. The first one is to use stronger deoxidizing additions like Ca, Zr, Ce etc. However, they can be problematic as substitutes as they produce inclusions which influence steel properties. The second way is to intensify the deoxidizing power of certain elements e.g. Si by bringing the steel in intimate contact with a proper slag with low SiO 2 activity in ladle treatment with violent stirring. In the calculation example it was possible to decrease oxygen content from 30 ppm to the level below 10 ppm in C/Mn/Si steel at very low Al level. The third potential but unused process is vacuum deoxidation especially for medium and high carbon steels. Equilibrium oxygen contents below 1 ppm are thermodynamically easily attainable. But in practice the vacuum treatment should be designed to intensify the carbon-oxygen reaction on the top surface of the stirred steel liquid. Also the eventual reactions with refractory materials should be suppressed.

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“…Ruhrstahl Heraeus (RH) degasser, widely used in secondary steel‐making process, is a vacuum molten‐steel circulating aggregate, which consists of upper and lower vessels, throat and snorkels, and is integrated with a melt‐full ladle during steel‐refining treatment 1,2 . The main purposes of RH process designed to treat molten steel concentrate on decarburization to low C content (<10 ppm), deoxidation and desulfurization in vacuum, H 2 and N 2 removal, inclusion removal, efficient alloying, and rapid homogenization of the melt in ladle.…”

Section: Introductionmentioning

confidence: 99%

Three bond modes of basic refractories used for Ruhrstahl Heraeus degassing process

et al. 2023

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Magnesia-spinel brick and unburnt periclase-spinel-Al brick are being employed as a substitution of traditional magnesia-chrome brick in the chromium-free campaign of lining materials in Ruhrstahl Heraeus (RH) degasser. These three materials are investigated, in terms of physical properties, corrosion resistance and flexibility by wedge splitting test. Tracking their physical alterations and chemical reactions through burning or heating, three bond modes are discovered. Magnesia-chrome brick is subject to a series of phase transformation with rising temperature to yield a liquid envelop around chromite-ore particles, to further form porous rim while liquid is gradually absorbed by surrounding magnesia and eventually to precipitate secondary chromite spinel lied between magnesia particles by thoroughly dissociating chrome ore. The precipitated chromite spinel functions as the featured bond that enhances hot strength and corrosion resistance to slag, and additionally liquid coexistence improves the flexibility. The direct bond mode of magnesia particles in magnesia-spinel brick endures slag penetration by immanent character of MgO. Spinel incorporation in magnesia effectively improves thermal shock resistance. Due to minor negative value of permanent linear change after reheating, further sintering (densifying) in using at high temperature would bring a risk of loosening and open joints of magnesia-spinel lining. While used in RH degasser, unburnt periclase-spinel-Al bricks undergo a miraculous process of metallic Al melting, gaseous AlN and AlON formation, MgAlON whiskers germination combined with gaseous Mg reduced, and micron-size whisker network bond domination in their matrix. Such a whisker-network bond renders the material a successful eco-friendly alternative to magnesia-chrome refractory.

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Actual review on secondary metallurgy

Cited by 14 publications

References 0 publications

Characterization of Nonmetallic Inclusions of Al‐Killed Ca‐Treated Steels by Automated SEM/EDS and Its Application to Industrial Case Studies

Characterization of Nonmetallic Inclusions of Al‐Killed Ca‐Treated Steels by Automated SEM/EDS and Its Application to Industrial Case Studies

On Physico‐Chemical and Technical Limits in Clean Steel Production

Three bond modes of basic refractories used for Ruhrstahl Heraeus degassing process

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