Effect of Double-Doping Al and Si on Phase Reconstruction and Slag Erosion Resistance of Magnesia-Carbon Bottom-Blowing Elements

doi:10.16552/j.cnki.issn1001-1625.2025.1035

Abstract

Abstract:

Magnesia-carbon bottom-blowing element for metallurgical furnace is typically enhanced by adding Al or Si to improve its performance. To investigate the effect of double-doping Al and Si on phase reconstruction and slag erosion resistance at high-temperature nitrogen environment， the magnesia-carbon bottom-blowing element specimens were prepared using fused magnesia， flake graphite， Al powder， and Si powder. The specimens were heat-treated in a 1 600 ℃ nitrogen atmosphere， and XRD， SEM， and EDS were employed to analyze the phase reconstruction and microstructure of the matrix of the Al single-doped and Al-Si double-doped specimens before and after erosion by slag. Results indicate that different from the Al single-doped specimen， the Al-Si double-doped specimen induces distinct phase transformations in the matrix， and double-doping Al and Si has an important effect on the slag erosion resistance. After the slag erosion experiment at 1 600 ℃ for 20 min， the Al single-doped specimen shows no significant slag adhesion on its contact surface with converter slag， with oxidation erosion layer less than 1 000 μm. In contrast， the Al-Si double-doped specimen develops a 300 μm oxidation erosion layer composed of spinel， Ca₃（Al_1-_x Fe _x ）₂Si₃O₁₂， and 12CaO·7Al₂O₃， demonstrating that Si significantly influences phase reconstruction and slag erosion resistance of magnesia-carbon bottom-blowing elements and its excessive addition should be avoided.

Key words: magnesia-carbon bottom-blowing element, bottom blowing, double-doping Al and Si, phase reconstruction, slag erosion resistance

CLC Number:

TQ175

YAN Mingwei, ZHANG Lunliang, SUN Guangchao, YE Shufeng, LIU Kaiqi. Effect of Double-Doping Al and Si on Phase Reconstruction and Slag Erosion Resistance of Magnesia-Carbon Bottom-Blowing Elements[J]. BULLETIN OF THE CHINESE CERAMIC SOCIETY, 2026, 45(5): 1749-1756.

Figures/Tables 9

Table 1 Raw material mix ratio of samples

Raw material	Particle size/mm	w/%
Raw material	Particle size/mm	S0	S1	S2
Fused magnesia	0~5	77	85	79
Al powder	<0.044	5	5	10
Si powder	<0.074	0	1	2
Flake graphite	<0.149	15	6	6
Thermosetting phenolic resin	—	3	3	3

Table 2 Main chemical composition of converter smelting slag［13］

Composition	CaO	Al₂O₃	SiO₂	MgO	TFe	P₂O₅	MnO
w/%	46.65	1.54	15.27	9.01	16.16	1.68	3.65

Fig.1 XRD patterns of heat-treated samples

Fig.2 SEM image and EDS spectra of heat-treated sample S2

Fig.3 XRD patterns of slag contact zones for samples after converter smelting slag erosion at 1 600 ℃ for 20 min

Fig.4 SEM images of slag contact zones for sample S0

Fig.5 EDS spectra of selected area in Fig.4（d） and （f）

Fig.6 SEM images of slag contact area for sample S2

Table 3 Chemical composition of selected areas in Fig.6

Selected area	Chemical element （atomic fraction）/%
Selected area	Mg	Al	Ca	Mn	Fe	Si	O	C	N
1	0.42	13.28	21.43	0.32	1.02	12.55	50.98	—	—
2	21.20	20.39	—	0.12	0.16	—	58.13	—	—
3	2.64	18.88	15.55	—	—	3.99	58.94	—	—
4	0.43	1.66	1.23	—	—	0.41	26.47	69.80	—
5	1.67	9.05	4.20	—	—	2.39	35.43	40.98	6.28

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