Erosion Mechanism of Al2O3-SiC Castables for Lining Maintenance in Blast Furnace Hearths

doi:10.19691/j.cnki.1004-4493.2022.02.004

China's Refractories ›› 2022, Vol. 31 ›› Issue (2): 17-23.DOI: 10.19691/j.cnki.1004-4493.2022.02.004

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Erosion Mechanism of Al₂O₃-SiC Castables for Lining Maintenance in Blast Furnace Hearths

SUN Saiyang¹^,^*(), MA Xiaoqing¹, WANG Xingwei², ZHAO Yong², ZHANG Ronghui¹, FEI Weibao³

1 Beijing Allied Rongda Engineering Material Co., Ltd., Beijing 101400, China
2 Nanjing Allied Rongda Engineering Material Co., Ltd., Nanjing 210036, China
3 Dalian Special Steel Co., Ltd., Dalian 116105, China

Online:2022-06-15 Published:2022-07-05
Contact: SUN Saiyang
About author:Sun Saiyang graduated from University of Science and Technology Beijing with a master’s degree majoring Metallurgical Engineering, and now is working in Beijing Allied Rongda Engineering Material Co., Ltd. He engaged in monolithic refractories and technical support of monolithic refractories for ironmaking. As the technical director, he presided over the maintenance projects of large blast furnaces, and served large Chinese iron and steel enterprises. Recently, he is mainly engaged in the research and development of silica sol-bonded monolithic refractories, including improving the cold strength, the hot performance and the corrosion resistance, and prolonging the service life of blast furnace lining.

Abstract

Abstract:

Al₂O₃-SiC castables, for the relining of BF hearths in mid-campaign repair, were sampled and investigated after two years’ service. The chemical and mineralogical characteristics of the residual castables were analyzed by X-ray diffraction, scanning electron microscopy, and energy dispersive X-ray spectrometry to study the erosion mechanism. The results show that as gaseous K diffuses in the castables, leucite (KAlSi₂O₈) and multiple cracks are formed. Molten iron and slag penetrate through the cracks to form anorthite ([Ca,Na][Al,Si]₄O₈) and iron, which will not form an embrittlement layer similar to carbon bricks. The entire repair of the hearth with Al₂O₃-SiC castables combined with the design of thin-wall lining hearth eliminates “elephant foot shaped” erosion, greatly prolonging the service life of the hearth lining.

Key words: alumina-silicon carbide castables, blast furnace hearth repair, erosion mechanism, thin-wall lining

SUN Saiyang, MA Xiaoqing, WANG Xingwei, ZHAO Yong, ZHANG Ronghui, FEI Weibao. Erosion Mechanism of Al₂O₃-SiC Castables for Lining Maintenance in Blast Furnace Hearths[J]. China's Refractories, 2022, 31(2): 17-23.

Figures/Tables 13

Fig. 1 Sampling location in BF hearth

Table 1 Physico-chemical properties of Al2O3-SiC castables

Items		Data
Chemical composition /mass%	Al₂O₃	73.0
	SiC	12.5
	CaO	0.20
Bulk density (110 ℃×24 h) /(g · cm^-3)		3.00
Cold modulus of rupture (1 450 ℃×3 h) /MPa		12.5
Cold compressive strength (1 450 ℃×3 h) /MPa		135.0
Permanent linear change on heating (1 450 ℃×3 h) /%		-0.25

Fig. 2 Fragments and slices of Al2O3-SiC castables

Fig. 3 XRD pattern of unreacted part of castables

Fig. 4 SEM micrographs and EDS spectrum of unreacted part of castables

Fig. 5 XRD pattern of alkali-enriched layers of castables

Fig. 6 SEM micrographs, EDS spectra and element mapping spectra of alkali-enriched layers of castables

Table 2 EDS results of dots in Fig. 6 (k) /atom%

Dot	C	O	Al	Si	Fe	Ca	Mg	K	Na	Ti	Mn
7	14.99	63.82	4.25	11.58	1.52	0.21	0.87	3.02	0.60	-	-
8	9.28	61.91	1.52	13.00	0.80	5.24	6.93	0.22	0.22	0.52	0.51
9	8.70	62.95	7.43	14.98	0.13	1.96	0.29	2.13	1.29	0.15	-

Fig. 7 SEM micrograph and EDS spectrum of a small alkali-enriched layer

Fig. 8 SEM micrograph and element mapping spectra of castables near hot face

Fig. 9 Schematic diagram of erosion mechanism of Al2O3-SiC castables

Fig. 10 Relationship between Gibbs free energy and temperature for reactions of potassium with castable minerals

Fig. 11 Traditional hearth design and thin-wall lining design

References 12

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Erosion Mechanism of Al₂O₃-SiC Castables for Lining Maintenance in Blast Furnace Hearths

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