Innovation and Development of Refractories for Ironmaking Industry in Sinosteel Luonai

doi:10.19691/j.cnki.1004-4493.2022.01.001

China's Refractories ›› 2022, Vol. 31 ›› Issue (1): 1-7.DOI: 10.19691/j.cnki.1004-4493.2022.01.001

Innovation and Development of Refractories for Ironmaking Industry in Sinosteel Luonai

BO Jun, ZHANG Lixin, ZHENG Desheng, FU Qiqi, LIU Ping^*()

Sinosteel Luonai Materials Technology Corporation, Luoyang 471039, China

Online:2022-03-15 Published:2022-04-02
Contact: LIU Ping
About author:Bo Jun, professorship senior engineer, is the general manager of Sinosteel Luonai Materials Technology Corporation, who receives the special government subsidy of the State Council of China. He is the vice president of the Association of China Refractories Industry and a tutor for master students. He engages in the research, development and application of new high-temperature refractories, has published more than 20 papers, and has more than 10 authorized patents and more than 10 provincial and ministerial scientific and technological progress awards.

Since China’s Reform and Opening-up, the innovation and development of refractories for ironmaking industry in Sinosteel Luonai were narrated, including silica materials, Al₂O₃-SiO₂ refractories and non-oxide composites; and the development direction of refractories for ironmaking industry was prospected.

Key words: ironmaking, silica materials, alumina-silica refractories, non-oxide composites, innovation and development, prospect

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BO Jun, ZHANG Lixin, ZHENG Desheng, FU Qiqi, LIU Ping. Innovation and Development of Refractories for Ironmaking Industry in Sinosteel Luonai[J]. China's Refractories, 2022, 31(1): 1-7.

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URL: http://www.cnref.cn/EN/10.19691/j.cnki.1004-4493.2022.01.001

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Figures/Tables 15

Table 1 Technical data of silica bricks with different residual quartz contents

Items	Index
Items	Before year 1985	Year 1988	Year 1996	Year 2002	Year 2008
Residual quartz /mass%	5-10	≤5	≤3	≤1.5	≤1.0
SiO₂ /mass%	93-94	94-95	≥94.5	≥94.5	≥95.0
Fe₂O₃ /mass%	1.1-1.3	1.0-1.2	<1	<0.8	<0.8
Al₂O₃ /mass%	1.1-1.3	1.0-1.2	<1	<1.0	<1.0
Refractoriness /℃	1 710	1 710	1 710	1 710	1 710
Refractoriness under load (0.2 MPa) /℃	1 630-1 650	1 650	1 650	1 660	1 660
Cold compressive strength /MPa	30-42	30-45	30-50	35-50	35-50
Thermal expansion rate (1 000 ℃) /%	1.32	1.30	1.28	1.26	1.26
True density /(g · cm^-3)	2.37	2.35	2.34	2.33	2.33
Apparent porosity /%	23-26	23-24	21-23	20-22	20-22

Table 1 Technical data of silica bricks with different residual quartz contents

Items	Index
Items	Before year 1985	Year 1988	Year 1996	Year 2002	Year 2008
Residual quartz /mass%	5-10	≤5	≤3	≤1.5	≤1.0
SiO₂ /mass%	93-94	94-95	≥94.5	≥94.5	≥95.0
Fe₂O₃ /mass%	1.1-1.3	1.0-1.2	<1	<0.8	<0.8
Al₂O₃ /mass%	1.1-1.3	1.0-1.2	<1	<1.0	<1.0
Refractoriness /℃	1 710	1 710	1 710	1 710	1 710
Refractoriness under load (0.2 MPa) /℃	1 630-1 650	1 650	1 650	1 660	1 660
Cold compressive strength /MPa	30-42	30-45	30-50	35-50	35-50
Thermal expansion rate (1 000 ℃) /%	1.32	1.30	1.28	1.26	1.26
True density /(g · cm^-3)	2.37	2.35	2.34	2.33	2.33
Apparent porosity /%	23-26	23-24	21-23	20-22	20-22

Fig. 1 Microstructure of high thermal conductivity silica brick and ordinary coke oven silica brick

Table 2 Technical data of high thermal conductivity silica brick and ordinary coke oven silica brick

Item	High thermal conductivity silica brick	Ordinary silica brick
Apparent porosity /%	16.8	22
True density /(g · cm^-3)	2.323	2.330
Cold compressive strength /MPa	75.5	40
Refractoriness under load (0.2 MPa, 0.6%) /℃	1 664	1 650
Thermal conductivity rate (1 100 ℃) /(W · m^-1 · K^-1)	2.65	1.90
Thermal expansion rate (1 000 ℃) /%	1.22	1.25
Residual quartz /mass%	0.41	0.55
SiO₂ /mass%	95.48	95.15
Al₂O₃ /mass%	0.79	0.81
Fe₂O₃ /mass%	0.65	0.68
CaO /mass%	2.38	2.4

Table 2 Technical data of high thermal conductivity silica brick and ordinary coke oven silica brick

Item	High thermal conductivity silica brick	Ordinary silica brick
Apparent porosity /%	16.8	22
True density /(g · cm^-3)	2.323	2.330
Cold compressive strength /MPa	75.5	40
Refractoriness under load (0.2 MPa, 0.6%) /℃	1 664	1 650
Thermal conductivity rate (1 100 ℃) /(W · m^-1 · K^-1)	2.65	1.90
Thermal expansion rate (1 000 ℃) /%	1.22	1.25
Residual quartz /mass%	0.41	0.55
SiO₂ /mass%	95.48	95.15
Al₂O₃ /mass%	0.79	0.81
Fe₂O₃ /mass%	0.65	0.68
CaO /mass%	2.38	2.4

Fig. 2 Microstructure of high thermal shock micro-expansion silica brick

Fig. 3 Expansion curves of high thermal shock micro-expansion silica brick and ordinary silica brick

Table 3 Technical data of high thermal shock micro-expansion silica brick

Item	High thermal shock micro-expansion silica brick	Ordinary silica brick
SiO₂ /mass%	99.63	94-96
Al₂O₃ /mass%	0.16	0.8-1.0
Fe₂O₃ /mass%	0.04	0.5-1.0
CaO /mass%	-	2.5
Bulk density /(g · cm^-3)	1.83	1.78-1.84
Apparent porosity /%	17.2	22-24
Cold compressive strength /MPa	43	30-50
Refractoriness under load /℃	1 670	1 640-1 660
Linear change rate (800 ℃) /%	0.10	1.25
Thermal shock resistance (1 100 ℃, water quenching) /cycles	35	0-1

Table 3 Technical data of high thermal shock micro-expansion silica brick

Item	High thermal shock micro-expansion silica brick	Ordinary silica brick
SiO₂ /mass%	99.63	94-96
Al₂O₃ /mass%	0.16	0.8-1.0
Fe₂O₃ /mass%	0.04	0.5-1.0
CaO /mass%	-	2.5
Bulk density /(g · cm^-3)	1.83	1.78-1.84
Apparent porosity /%	17.2	22-24
Cold compressive strength /MPa	43	30-50
Refractoriness under load /℃	1 670	1 640-1 660
Linear change rate (800 ℃) /%	0.10	1.25
Thermal shock resistance (1 100 ℃, water quenching) /cycles	35	0-1

Fig. 4 Creep curves of low creep Al2O3-SiO2 products at different temperatures

Table 4 Technical data of surface composited ceramic prefabricated materials for coke ovens

Item	Index
Al₂O₃/mass%	62.49
SiO₂ /mass%	32.66
MgO /mass%	3.84
Apparent porosity (110 ℃×24 h) /%	21.9
Bulk density (110 ℃×24 h) /(g · cm^-3)	2.33
Cold compressive strength (110 ℃×24 h) /MPa	99.5
Wear resistance (ASTM C704) /cm³	6 (body) 4.5 (glaze)
Thermal conductivity (1 000 ℃) /(W · m^-1 · K^-1)	1.067
Linear expansion rate (1 000 ℃) /%	0.29
Thermal shock resistance (1 100 ℃, water quenching) /cycles	>50

Table 4 Technical data of surface composited ceramic prefabricated materials for coke ovens

Item	Index
Al₂O₃/mass%	62.49
SiO₂ /mass%	32.66
MgO /mass%	3.84
Apparent porosity (110 ℃×24 h) /%	21.9
Bulk density (110 ℃×24 h) /(g · cm^-3)	2.33
Cold compressive strength (110 ℃×24 h) /MPa	99.5
Wear resistance (ASTM C704) /cm³	6 (body) 4.5 (glaze)
Thermal conductivity (1 000 ℃) /(W · m^-1 · K^-1)	1.067
Linear expansion rate (1 000 ℃) /%	0.29
Thermal shock resistance (1 100 ℃, water quenching) /cycles	>50

Fig. 5 Local structure of nitridation kilns

Table 5 Structure parameters of nitridation kilns

Item	Electric kiln (controlled N₂ atmosphere)	Shuttle kiln (high-purity N₂ atmosphere)
Heating mode	Silit bars (φ15×760 mm)	Municipal gas (burner flame)
Maximum service temperature /℃	1 500	1 650
Effective kiln dimension /mm	1 840×1 420×1 660	11 500×4 190×1 684
Effective sagger dimension /mm	—	2 260×1 210×770
Kiln car number	—	6

Table 5 Structure parameters of nitridation kilns

Item	Electric kiln (controlled N₂ atmosphere)	Shuttle kiln (high-purity N₂ atmosphere)
Heating mode	Silit bars (φ15×760 mm)	Municipal gas (burner flame)
Maximum service temperature /℃	1 500	1 650
Effective kiln dimension /mm	1 840×1 420×1 660	11 500×4 190×1 684
Effective sagger dimension /mm	—	2 260×1 210×770
Kiln car number	—	6

Fig. 6 Nitridation kilns and equipment

Fig. 7 Nitridation firing schedule

Table 6 Comparison of shuttle kiln and electric kiln

Item	Shuttle kiln	Electric kiln
Heating time /h	53	38
Maximum brick surface temperature difference during heating /℃	163	252
Minimum brick surface temperature difference during heating /℃	11	92
Reaction time /h	71 (67)	86 (79)
Maximum brick surface temperature difference during reaction /℃	29	100
Minimum brick surface temperature difference during reaction /℃	5	46
Whole firing cycle (excluding cooling time) /h	124 (35)	124 (84)
Specific volume productivity in kiln /(t · m^-3 · d^-1)	0.131 52	0.097 3
Specific energy consumption /(kJ · t^-1)	1.851×10⁷	7.44×10⁶

Table 6 Comparison of shuttle kiln and electric kiln

Item	Shuttle kiln	Electric kiln
Heating time /h	53	38
Maximum brick surface temperature difference during heating /℃	163	252
Minimum brick surface temperature difference during heating /℃	11	92
Reaction time /h	71 (67)	86 (79)
Maximum brick surface temperature difference during reaction /℃	29	100
Minimum brick surface temperature difference during reaction /℃	5	46
Whole firing cycle (excluding cooling time) /h	124 (35)	124 (84)
Specific volume productivity in kiln /(t · m^-3 · d^-1)	0.131 52	0.097 3
Specific energy consumption /(kJ · t^-1)	1.851×10⁷	7.44×10⁶

Table 7 Properties of non-oxide composite materials

Properties	Si₃N₄-SiC	SiAlON-Al₂O₃	SiAlON-SiC
SiC /mass%	73.04	79.14 (Al₂O₃)	74.86
Si₃N₄ /mass%	23.82	5.39 (N)	5.95 (N)
Free Si /mass%	0.3	≤0.3	0.32
Fe₂O₃ /mass%	0.25	0.48	0.32
Apparent porosity /%	14	9.0	8.6
Bulk density /(g · cm^-3)	2.74	3.30	2.86
Cold compressive strength /MPa	205	198	211
Cold modulus of rupture /MPa	56.4	33	59
Hot modulus of rupture (1 400 ℃×0.5 h) /MPa	69	27.3	63
Thermal shock resistance (1 100 ℃, water quenching) /cycles	>30	≥15	>30
Thermal expansion coefficient (20-1 000 ℃) /(10^-6 · K^-1)	4.5	5.8	5.1
Thermal conductivity (1 000 ℃) /(W · m^-1 · K^-1)	17.84	4.08	16.5

Table 7 Properties of non-oxide composite materials

Properties	Si₃N₄-SiC	SiAlON-Al₂O₃	SiAlON-SiC
SiC /mass%	73.04	79.14 (Al₂O₃)	74.86
Si₃N₄ /mass%	23.82	5.39 (N)	5.95 (N)
Free Si /mass%	0.3	≤0.3	0.32
Fe₂O₃ /mass%	0.25	0.48	0.32
Apparent porosity /%	14	9.0	8.6
Bulk density /(g · cm^-3)	2.74	3.30	2.86
Cold compressive strength /MPa	205	198	211
Cold modulus of rupture /MPa	56.4	33	59
Hot modulus of rupture (1 400 ℃×0.5 h) /MPa	69	27.3	63
Thermal shock resistance (1 100 ℃, water quenching) /cycles	>30	≥15	>30
Thermal expansion coefficient (20-1 000 ℃) /(10^-6 · K^-1)	4.5	5.8	5.1
Thermal conductivity (1 000 ℃) /(W · m^-1 · K^-1)	17.84	4.08	16.5

Fig. 8 Matrix microstructure images of Si3N4-SiC and β-SiAlON-Al2O3 composites

References 1

[1]	Li Yong, Bo Jun, Liu Xiongzhang. Investigation on long campaign of hot blast stove and low creep Al₂O₃-SiO₂ refractories. Naihuo Cailiao (Refractories, in Chinese), 2008, 42(3):215-218.

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