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Sintered AZS refractory brick blocks/zircon corundum refractory brick for glass furnace
The sintered zirconium corundum brick takes zirconium and alumina as raw materials, and the ZrO2 content is generally less than 20%.The following solid phase reactions occur between zirconite and alumina at 1400 ~ 1450℃ :
3 al2o3 + 2 zrsio4 - > 3 2 sio2, al2o3 + 2 zro2
The microstructures of mullite and plagioclase zircon (containing part of T -ZrO2) were uniformly distributed.This irreversible reaction is also called in situ reaction.The measured initial reaction temperature is 1397℃.1400 ~ 1425℃ and 1500℃.According to the research results of Sheng Xumin et al., the initial temperature of the reaction was 1380℃, and mullite was formed.When the temperature reaches 1400-1420 ℃, the volume effect of V+16.4% is:
1)The result-mullite + T-ZrO2 volume expands to V+13.87%;
2)The final volume effect is V+16.4% when T-ZrO2 → M-ZrO2 phase change.
The sintered zirconium corundum brick takes zirconium and alumina as raw materials, and the ZrO2 content is generally less than 20%.The following solid phase reactions occur between zirconite and alumina at 1400 ~ 1450℃ :
3 al2o3 + 2 zrsio4 - > 3 2 sio2, al2o3 + 2 zro2
In the 1960s, the prototype sintering of AZS products produced in the United States was based on the reaction sintering principle of ZrSiO4-Al2O3 system.The raw materials used are zirconite fine powder, T-alumina particles and calcined alumina fine powder.By means of the reaction between zirconite and calcined alumina, the matrix of ZrO2- mullite is formed, and the 3-phase material is formed.The contents of ZrO2, Al2O3 and SiO2 are 19.5%, 70.0% and 10.2%, indicating that the raw material is pure and has no other additives.According to the calculation of chemical composition, zirconite accounts for about 30%, and the theoretical value of volume effect of the reaction with Al2O3 to form mullite should be V+9.3%.According to Claussen's experiment, it is estimated to be +3.4%.This is the main reason for the low strength (14 ~ 16MPa) and high apparent porosity (15 ~ 23%) of the product.
Due to the large shrinkage and expansion effect in the process of reactive sintering, the sintered material can only be used as semi-finished product and pre-synthesized zirconium mullite aggregate.By crushing, forming, and firing, a sintered AZS product with mullite and plagic zircon as the main crystalline phase (with a small amount of glass phase) was obtained.If combined with sintered (or fused) corundum, three - phase products can be obtained.
In order to make the reaction complete and the content of glass phase less than 5%, the molar ratio of Al2O3 to ZrSiO4 should not be less than 1.5.Sometimes a certain amount of kaolin is added, in amounts corresponding to the composition of mullite.
| Item | Sintered AZS | |
| Trademark | AZS-30 | AZS-33 |
| ZrO2 % | ≥30 | ≥33 |
| Al2O3 % | 48 | 48 |
| Fe2O3 % | ≤0.3 | ≤0.3 |
| SiO2 % | ≤22 | ≤19 |
| Bulk density g/cm3 | ≥3.0 | ≥3.2 |
| Apparent Porosity % | ≤18 | ≤17 |
| Cold crushing strength MPa | ≥100 | ≥100 |
| Refractoriness under load °C | ≥1680 | ≥1700 |
The microstructure of sintered AZS bricks is characterized by fine (less than 10μm) diagralic zircon particles evenly dispersed between the main crystalline phases of mullite and corundum, forming a dense crystalline network with little glassy phase.It has a certain amount of pores (porosity less than 20%), but no liquid exudation.Compared with the electric fused AZS brick, the corrosion resistance of glass liquid is poor, but the thermal shock resistance is good.
Classification, preparation and properties of sintered zirconium corundum bricks for glass furnaces
Knot zirconium corundum brick (hereinafter referred to as the AZS brick) materials for alumina and zircon, general ZrO2 content is controlled at 15% ~ 30%, the main crystal each other into mullite and corundum and baddeleyite, under the condition of raw material is very pure, glass phase content can be less than 5%, so the production of such products of physical - chemical based mainly between Al2O3 and ZrSiO4 solid phase reaction.
There are three main kinds of products in this series:
(1) Reaction-sintered AZS products are two-phase and uniformly distributed microstructure composed of mullite and plagiozircon (including part of T-ZR02).This irreversible reaction is also called in situ reaction.The initial reaction temperature ranges from 1370 ℃ to 1420℃.
(2) Recombination type AZS products, with electric fusion AZS as raw material through crushing, forming and sintering.
(3) containing zirconium series products.This series of products belong to the simplest process type of generalized sintering AZS -- sintering or electric fusion of mullite or corundum or calcined coarse bauxite particles in any proportion to zirconite, adding a small amount of bound clay or other binder.The sintering temperature determines the total decomposition of the zirconite particles, slight surface decomposition or no decomposition at all.Zirconite is sintered at 1650℃ without any decomposition, but the surface in contact with Al2O3 will decompose at less than 1500℃.
Preparation of sintered zirconium corundum bricks
The key problems in the preparation process of sintered AZS products are as follows:
(1) Ensure the complete reaction of ZrSiO4 with Al2O3 and the dense sintering to form a uniform mullite -(corundum)- clinker with a glass phase content of less than 5%.
(2) Al2O3 + kaolin should conform to mullite composition.
(3) The particle size grading of the products is reasonable to ensure the maximum bulk density.
(4) The products are fully fired and the ideal microstructure is obtained.
It is very difficult to produce high quality sintered AZS products. In a sense, the strict requirements of controlling the process flow are no less than that of casting products.
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Henan hongtai kiln refractory co., LTD. Main products are high alumina brick, clay brick, fused zirconium corundum brick, fireproof ball lightweight insulation brick, wear-resistant pouring material, corundum pouring material, low cement high strength pouring material, impermeable material, self-flowing material, plastic material, and various types of refractory materials.For different industries, the cement industry with anti-flaking high-alumina bricks, alkali resistant bricks, phosphate bricks;Boiler industry USES all kinds of brand wear-resisting brick, corundum brick, mullite brick and other finalizing materials.The company insists on "product quality is the life, enterprise integrity is the foundation", in the fierce market competition, won many users' trust and praise.The products are sold all over the country, as far as Vietnam, India, Korea, Pakistan, kazakhstan, other southeast Asian countries and regions.
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