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High alumina refractory products are aluminum silicate refractory materials with an Al2O3 content of more than 48%. High alumina bricks are usually divided into three categories: Class I: Al2O3 content greater than 75%; Class II: Al2O3 content 60% ~75%; Class III: Al2O3 content 48%~ 60%. High alumina bricks can also be classified according to their mineral composition. Generally divided into five categories: low mullite, mullite, mullite-corundum, corundum-mullite, and corundum. Its mineral composition is mainly corundum, mullite, and glass phase. The proportion of each mineral phase depends on the Al2O3/SiO2 of the product and the type and quantity of impurities contained, as well as its production process conditions.

 

Characteristics of High Alumina Refractory Bricks

The characteristics of high alumina bricks are as follows:

1.  Load softening temperature. The load softening temperature of ordinary high alumina bricks is generally above 1420~1550℃. It is higher than that of clay refractory bricks and increases with the increase of Al2O3 content. When Al2O3<70%, its load softening temperature increases with the increase in the ratio of the mullite phase to the glass phase. The quantity and nature of the liquid phase have a significant influence on the load-softening temperature. Therefore, reducing the impurity content in raw materials is beneficial to improving the load-softening temperature and high-temperature creep properties. When Al2O3 > 70%, as the Al2O3 content increases, the load softening temperature does not increase significantly.
2.  Thermal shock resistance. The thermal shock resistance of ordinary high-alumina bricks mainly depends on the chemical mineral composition and microstructure. It is generally worse than clay bricks.
3.  Chemical erosion resistance. Ordinary high-alumina bricks have good resistance to erosion, oxidation, and reduction reactions by acidic or alkaline slag and molten metal. And it increases with the increase of Al2O3 content and the decrease of harmful impurity content.

Application of High Alumina Bricks

High alumina bricks are generally used in blast furnaces, hot blast furnaces, electric furnaces, and other industrial furnaces.

 

Technical Indicators of High Alumina Bricks

 

High alumina bricks are divided into four grades according to physical and chemical indicators: LZ-75, LZ-65, LZ-55, and LZ-48. According to the national standard GB/T2988-1987, the physical and chemical indicators of high alumina bricks are as follows.

 

Physical and Chemical Indicators of High Alumina Bricks
Items		LZ-75	LZ-65	LZ-55	LZ-48
Al2O3 %, ≥		75	65	55	48
Refractoriness ℃, ≥		1790	1790	1770	1750
0.2MPa Load Softening Start Temperature ℃, ≥		1520	1500	1470	1420
Re-burning Linear Change Rate %	1500℃, 2h	+0.1 ~ -0.4			–
	1450℃, 2h	–			+0.1 ~ -0.4
Apparent Porosity %, ≤		23		22
Compressive Strength at Normal Temperature MPa, ≥		53.9	49.0	44.1	39.2

 

High Alumina Bricks for Various Industrial Kilns

 

High Alumina Bricks for Blast Furnaces

China Metallurgical Standard YB/T5015-1993 divides high alumina bricks for blast furnaces into three grades: GL-65, GL-55, and GL-48 according to physical and chemical indicators. The physical and chemical indicators of high alumina bricks for blast furnaces are shown in the following table.

 

Physical and Chemical Indicators of High Alumina Bricks for Blast Furnaces
Items		GL-65	GL-55	GL-48
Al2O3 %, ≥		65	55	48
Al2O3 %, ≤		2.0
Refractoriness ℃, ≥		1790	1770	1750
0.2MPa Load Softening Start Temperature ℃, ≥		1500	1480	1450
Re-burning Linear Change Rate %	1500℃, 2h	0 ~ -0.2		–
	1450℃, 2h	–		0 ~ -0.2
Apparent Porosity %, ≤		19		18
Compressive Strength at Normal Temperature MPa, ≥		58.8		49

 

High Alumina Bricks for Hot Blast Furnaces

China Metallurgical Standard YB/T5016-2000 divides high alumina bricks for hot blast furnaces into two categories according to their uses: ordinary high alumina bricks and low creep high alumina bricks. According to physical and chemical indicators, ordinary high alumina bricks for hot blast furnaces are divided into three grades: RL-65, RL-55, and RL-48. Low creep high alumina bricks for hot blast furnaces are divided into seven grades: DRL-155, DRL-150, DRL-145, DRL-140, DRL-135, DRL-130, and DRL-127. The physical and chemical indicators of high alumina bricks for hot blast furnaces are as follows.

 

Physical and Chemical Indicators of Ordinary High Alumina Bricks for Hot Blast Furnaces
Items		DL-65		DL-55		DL-48
Al2O3 %, ≥		65		55		48
Refractoriness ℃, ≥		1780		1760		1740
0.2MPa Load Softening Start Temperature ℃, ≥		1500		1470		1420
Re-burning Linear Change Rate %	1500℃, 2h	0.1 ~ -0.4				–
	1450℃, 2h	–				0.1 ~ -0.4
Apparent Porosity %, ≤		22
Compressive Strength at Normal Temperature MPa, ≥		50	45		40

 

Physical and Chemical Indicators of Low Creep High Alumina Bricks for Hot Blast Furnaces
Items		DRL-155	DRL-150	DRL-145	DRL-140	DRL-135	DRL-130	DRL-127
Al2O3 %, ≥		75	75	65	65	65	60	50
Apparent Porosity %, ≤		30	21	21	22	22	22	23
Bulk Density g/cm3		2.65 ~ 2.85	2.65 ~ 2.85	2.50 ~ 2.70	2.40 ~ 2.60	2.35 ~ 2.55	2.30 ~ 2.50	2.30 ~ 2.50
Compressive Strength at Normal Temperature MPa, ≥		60	60	60	55	55	55	50
Creep Rate (0.2MPa, 50h) %, ≤		1550℃, 0.8	1500℃, 0.8	1450℃, 0.8	1400℃, 0.8	1350℃, 0.8	1300℃, 0.8	1270℃, 0.8
Re-burning Linear Change Rate %	1500℃, 2h	0.1 ~ -0.2			–
	1450℃, 2h	–			0.1 ~ -0.2	0.1 ~ -0.4

 

High Alumina Bricks for Steelmaking Electric Furnace Tops

China Metallurgical Standard YB/T5017-2000 divides high alumina bricks for steelmaking electric furnace tops into four grades: DL-75, DL-80, DBL-75, and DBL-80 according to physical and chemical indicators. The physical and chemical indicators of high alumina bricks for steelmaking electric furnace tops are as follows.

 

Physical and Chemical Indicators of High Alumina Bricks for Steelmaking Electric Furnace Tops
Items		DL-80	DL-75	DBL-80	DBL-75
Al2O3 %, ≥		80	75	80	75
Refractoriness ℃, ≥		–	–	1780	1780
0.2MPa Load Softening Start Temperature ℃, ≥		1530	1520	1530	1520
Re-burning Linear Change Rate (1500℃, 2h) %		0.2 ~ -0.4		–	–
Apparent Porosity %, ≤	Roof Bricks	19		18
	Arch Corner Bricks	21		20
Compressive Strength at Normal Temperature MPa, ≥		75	65	60	55
Thermal Shock Resistance /times, 1100℃, Water Cooling, ≥		–		8

 

High Alumina Bricks for Steel Drums

China Metallurgical Standard YB/T5020-2002 divides high alumina bricks for steel drums into five grades: CL-55, CL-65, CL-75, CL80, and PZCL-78 according to physical and chemical indicators. The physical and chemical indicators of high alumina bricks for steel drums are as follows.

 

Physical and Chemical Indicators of High Alumina Bricks for Steel Drums
Items		CL-55	CL-65	CL-75	CL-80	PZCL-78
Al2O3 %, ≥		55.0	65.0	75.0	80.0	78.0
Fe2O3 %, ≤		–	–	–	2.0	2.0
0.2MPa Load Softening Start Temperature ℃, ≥		1470	1490	1510	1530	1550
Re-burning Linear Change Rate %	1450℃, 2h	0.1 ~ 0.5	–	–	–	–
	1500℃, 2h	–	0.1 ~ 0.5	0.1 ~ 0.5	–	–
	1550℃, 2h	–	–	–	0.1 ~ 0.5	0.4 ~ 0.3
Apparent Porosity %, ≤		22.0	28.0	28.0	24.0	21.0
Compressive Strength at Normal Temperature MPa, ≥		45	35	40	50	70

 

High Alumina Bricks for Steel-casting in Ladle

China Metallurgical Standard YB/T5021-1993 divides high alumina bricks for steel casting in ladle into four grades: high alumina plug brick SL-48, high alumina casting mouth brick KL-48, high alumina sleeve brick XL-48, and high alumina seat brick ZL-48. The physical and chemical indicators of high alumina bricks for steel casting in the ladle are as follows.

 

Physical and Chemical Indicators of High Alumina Bricks for Steel-Casting in Ladle
Items	SL-48	KL-48	XL-48	ZL-48
Al2O3 %, ≥	48 ~ 55
Refractoriness ℃, ≥	1760
0.2MPa Load Softening Start Temperature ℃, ≥	1450	1450	–	1400
Re-burning Linear Change Rate (1450℃, 2h) %	–		-0.4 ~ +0.1
Apparent Porosity %	18 ~ 24	≤24	18 ~ 24	≤25
Compressive Strength at Normal Temperature MPa, ≥	–	–	–	19.6

 

Rongsheng Refractory Bricks Manufacturer

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