
Corundum bricks have a true specific gravity of 3.5 g/cm3 or more up to 3.9 g/cm3, a refractoriness of up to 2000℃, and a load softening point of about 1800℃. They are representative of neutral refractory materials. Due to different production methods of corundum bricks, their performance varies greatly. Its electro-fused casting products will be introduced later, and here we will only talk about sintered products. There are two main categories of sintered products. One is products with electro-fused corundum sand as aggregate, and its binder is alumina powder and a very small amount of clay. This product has good thermal shock resistance when its porosity is large and there are many large particles.
For the casting molding of corundum products, in order to meet the needs of the casting process, silicon-aluminum composite binders A and B are prepared. It is a glue-suspension mixture, in which Al2O3:SiO2 (molar ratio) = 3:2, and a promoter for the formation of mullite is added. The differential thermal curves of the two binders are shown in Figure 3-3. The difference between the two binders is that binder A can form gibbsite (331°C peak) and boehmite sol (523°C peak) in water, and has better room temperature curing performance than binder B. Since Al2O3 and SiO2 in the two composite binders are highly active, we believe that the temperature at which the temperature of non-stoichiometric mullite formation starts to drop from 743°C and 704°C for binders B and A in the differential thermal curves of Figure 3-3, which can also be confirmed by thermodynamic calculations.
The corundum particles are closely connected by well-developed mullite. Since Al2O3 and SiO2 in the composite binder are extremely active, mullite can be quickly formed and well developed under the action of the promoter.
When the amount of silica fume added to corundum exceeds 2%, its high temperature resistance will be significantly reduced. For this reason, we selected a relatively pure ultrafine quartz powder with an average particle size of less than 18Hm and high purity, and added some promoters to promote the formation of mullite. The method of forming a mullite binding phase by reaction combustion has achieved obvious results.
There are several methods to combine mullite with corundum products and reduce the firing temperature of the products: one is to add kaolin (or combined with clay); after the kaolin decomposes, the more active Al2O3 and SiO2 can form a mullite binding phase at a lower temperature; the second is to add a substance that can form a certain liquid phase to promote the sintering of the product, and the last is to add SiO2 to form a mullite binding phase with Al2O3 in the product.

|
Brand/Item |
HX98 |
HX9O |
HX80 |
HX75 |
HX75 |
HX65 |
HX90CS |
HX90C |
HX9OT |
HX85T |
HX70T |
HX28 |
|
Al2O3 % |
≥98 |
≥90 |
≥80 |
≥75 |
≥75 |
≥65 |
≥90 |
≥90 |
≥90 |
≥85 |
≥70 |
≥50 |
|
Fe2O3 % |
≤0.3 |
≤0.5 |
≤0.5 |
≤0.6 |
≤1.8 |
≤2.0 |
≤0.3 |
≤0.3 |
≤0.3 |
≤0.4 |
≤0.5 |
≤0.5 |
|
ZrO2 % |
≥28 |
|||||||||||
|
Apparent porosity % |
≤22 |
≤20 |
≤18 |
≤20 |
≤19 |
≤21 |
≤18 |
≤20 |
≤16 |
≤16 |
≤17 |
≤20 |
|
Bulk density g/cm3 |
≥3.0 |
≥2.85 |
≥2.70 |
≥2.55 |
≥2.65 |
≥2.5 |
≥2.90 |
≥2.85 |
≥2.95 |
≥2.60 |
≥2.50 |
≥3.15 |
|
Normal temperature compressive strength Mpa |
≥80 |
≥80 |
≥60 |
≥60 |
≥60 |
≥55 |
≥80 |
|||||
|
High temperature resistance Mpa |
1500℃×0.5h ≥10 |
1450℃×0.5h ≥10 |
1500℃×0.5h ≥10 |
1450℃×0.5h ≥10 |
1400℃×0.5h ≥10 |
T2≥1620 |
||||||
|
Softening temperature under load KD ℃ |
≥1700 |
≥1650 |
≥1650 |
≥1700 |
≥1520 |
≥1500 |
≥1700 |
≥1700 |
≥1700 |
≥1700 |
≥1650 |
|
|
Reburning rate of change % |
1600℃×2h 土0.1 |
1600℃×2h -0.1~+0.3 |
1500℃×2h -0.1~+0.1 |
1500℃×2h ±0.1 |
1500℃×2h 0~+0.3 |
1500℃×2h 0~+0.3 |
||||||
|
Thermal shock stability, times (1100℃ water cooling) |
≥10 |
≥10 |
≥10 |
excellent |
excellent |
excellent |
excellent |
excellent |
excellent |
|||
|
Application area |
Furnace bottom |
Slide rails |
roof |
Sidewall |
Low-slip zone Side walls, furnace top |
Low-slip zone Side walls, furnace top |
High temperature Connector plate |
Low-medium temperature Connector plate |
High temperature push plate |
Medium temperature push plate |
Low temperature push plate |
Supporting the vault |
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