Critical whisker bond of a profound chromium-free refractory for RH degassers

Guo, Zongqi; Ma, Ying; Dang, Xiaomei; Ding, Feng

doi:10.1007/s12046-022-01836-z

Cited by 4 publications

(3 citation statements)

References 4 publications

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“…Various conventional refractories failed to be accepted by RH degassers in the long-term attempts of chromium-free campaigns. While a kind of unburnt periclase-spinel-Al bricks made a miraculous replacement of magnesia-chrome bricks with the comparable service lifetimes of RH degassers [10], a brand-new whisker bond was discovered, playing a significant role in upgrading the eco-friendly industrial operation. In order to stimulate a fundamental development in refractories, a new concept of whisker bond is suggested, with its characterizations, forming mechanism, and differences from the whisker enhancement in refractories.…”

Section: Introductionmentioning

confidence: 99%

Whisker Bond: From Findings to Concept in Refractories

Guo,

Wei

2024

Recent Prog Mater

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Ceramic bonds are conventionally formed during the burning of refractory bricks and by using pre-fabricated blocks or monolithic lining, which is characterized as the coalescence of the particles by liquid sintering. However, the whisker bond was discovered with the outstanding performance of unburnt periclase–spinel–Al bricks while substituting magnesia–chrome bricks in the chromium-free campaign of refractory lining of RH degassers. Thanks to the prominent effect of the whisker bond, such a refractory material demonstrates ultrahigh hot strength, high resistance to slag penetration, and thermomechanical stress. Investigations reveal the initial melting of metal Al at the melting point of 660°C, aluminum liquid rims around the cavities formed before ~800°C, gaseous AlN yielded and distributed throughout the matrix with increasing temperature, gaseous Mg reduced from ~1000°C, and MgAlON whiskers eventually formed in the matrix. Microstructure observations show a dense interwoven whiskers bonded matrix in most residual parts of the used periclase–spinel–Al bricks. The whisker network in the matrix is made up of straight columns of 1–5 µm in diameter and 20–40 µm in length, which is different from birdnesting, nano-size curly whiskers observed in the past. The findings suggest a whisker-bond concept in terms of the bond mode of the whisker network and the process of the vapor-solid forming mechanism.

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Section: Introductionmentioning

confidence: 99%

Whisker Bond: From Findings to Concept in Refractories

Guo,

Wei

2024

Recent Prog Mater

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“…Additions of 0, 1, 3, and 5 wt% titania were studied in burnt magnesia–spinel brick, for possibly superior properties over magnesia–chrome brick 14 . Surprisedly, an unburnt periclase–spinel–Al brick appeared for years, achieving optimistic performance in various RH degassers and demonstrating outstanding properties 15,16 . Both studies on periclase–spinel–Al bricks heated in labs and used in RH degassers had the findings of a whisker interwoven network all over the matrix 17,18 …”

Section: Introductionmentioning

confidence: 99%

“…14 Surprisedly, an unburnt periclase-spinel-Al brick appeared for years, achieving optimistic performance in various RH degassers and demonstrating outstanding properties. 15,16 Both studies on periclase-spinel-Al bricks heated in labs and used in RH degassers had the findings of a whisker interwoven network all over the matrix. 17,18 Magnesia-chrome brick, magnesia-spinel brick and unburnt periclase-spinel-Al brick are all being used in RH degassers.…”

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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