Heavy Refractory Bricks

Heavy bricks have high mechanical strength, long service life, good chemical stability, no chemical reaction with materials and good high temperature resistance, the highest heat resistance temperature can reach 1900℃.
Heavy bricks have the advantages of high density, high strength, good wear resistance, corrosion resistance, small thermal expansion coefficient, high grinding efficiency, low noise, long service life, and no contamination of materials.

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Description

Heavy refractory bricks refer to sintered products of aluminosilicate or pure alumina containing more than 46% Al2O3 and a bulk density of more than 2.0.

1. Raw materials

The raw materials of heavy refractory bricks are mainly natural raw materials and artificial synthetic raw materials.

Natural raw materials mainly include diaspore (Al2O3·H2O), gibbsite (Al2O3·3H2O), sillimanite (Al2O3·SiO2 containing Al2O362.9%, SiO237.1%),

and isomers of kyanite and sillimanite.

Artificial synthetic raw materials are synthetic minerals, which are generally made by chemical methods, using aluminum hydroxide, aluminum hydride, selected kyanite and clay minerals for synthesis. These synthetic minerals mainly include mullite 3Al2O3·2SiO2 synthesized by sintering and fusion, a mixture of α-corundum (Al2O3) and mullite synthesized by fusion, and α-corundum manufactured by sintering.

2. Chemical composition

Heavy refractory bricks made of different raw materials have different compositions. The Al2O3 content can range from 46% to nearly 95%. The SiO2 content can range from 0.5% to 47%.

3. Crystalline phase composition

The crystal phase composition of heavy refractory bricks varies with the Al2O3 content. There are mainly sillimanite, mullite, corundum, and also contain a part of quartz and cristobalite. Bricks generally have a glass phase composed of Al2O3, SiO2 and other oxides.

When the Al2O3 content of heavy refractory bricks is 50-65%, the main crystal phases are mullite and sillimanite. When the Al2O3 content is 65-80%, mullite is the main crystal phase. When the Al2O3 content is above 80%, the α corundum content gradually increases. Except for special types, heavy refractory bricks generally contain less than 80% Al2O3. Heavy refractory bricks containing more than 80% Al2O3 are usually called corundum bricks.

Clay heavy refractory brick

project	N-1	N-2a	N-2b	N-3a	N-3b	N-4	N-5	N-6
Fire resistance/℃ ≥	1750	1730	1730	1710	1710	1690	1670	1580
Starting temperature of 0.2MPa load softening/℃≥	1400	1350	-	1320	-	1300	1300	1300
Reburning line changes(1400℃×2h)/%	+0.1～-0.4	+0.1～-0.5	+0.2～-0.5	-	-	-	-	-
Apparent porosity/% ≤	22	24	26	24	26	24	26	28
Room temperature compressive strength/MPa ≥	30	25	20	20	15	20	15	15

High alumina heavy refractory brick

project		LZ-80	LZ-75	LZ-65	LZ-55	LZ-48
Al₂O₃/% ≥		80	75	65	55	48
Apparent porosity/% ≤		22	23	23	22	22
Room temperature compressive strength/MPa ≥		55	50	45	40	35
0.2MPa Starting temperature of load softening/℃ ≥		1530	1520	1500	1450	1420
Heating permanent line change/%	1500℃×2h	+0.1～-0.4				-
Heating permanent line change/%	1450℃×2h					+0.1～-0.4

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