The raw materials of fused AZS bricks are melted in an electric arc furnace, so that alumina is melted and recrystallized into corundum, and zircon is melted and recrystallized into baddeleyite after the decomposition of zircon. After adding soda ash and borax as flux to promote the formation of the required glass phase, the molten raw materials are poured into the pre-prepared sand mold for casting. This process is called the fusion and casting process of AZS production.
Different casting methods of fused AZS bricks will obtain different product characteristics. At present, there are four main casting methods, PT, QX, WS, ZWS.
1. PT (regular casting)
Process characteristics: molten AZS material is directly poured into the mold and naturally cooled and formed.
Advantages: simple process and low production cost.
Disadvantages: easy to produce shrinkage holes, pores and cracks; low brick density and strength, poor uniformity.
Application scenarios: ordinary occasions with low performance requirements, such as non-critical parts of glass kilns.
2. QX (tilted casting)
Process characteristics: The mold is tilted at a certain angle (usually 10°~30°), and the molten material flows slowly from one end of the mold.
Advantages: Reduce shrinkage holes and pores, improve the density of the brick body; improve the uniformity and strength of the brick body.
Disadvantages: The process is more complicated and the production cost is higher.
Application scenarios: Occasions with high density and strength requirements, such as medium erosion parts of glass kilns.
3. WS (void-free casting)
Process characteristics: Vertical casting, concentrate shrinkage holes in a certain area, and remove all shrinkage hole areas after annealing to minimize shrinkage holes.
Advantages: Very few shrinkage holes, extremely high density and uniformity of the brick body; excellent corrosion resistance and thermal shock resistance.
Disadvantages: Complex process, high equipment requirements, and the highest production cost.
Application scenarios: Occasions with high performance and high corrosion resistance requirements, such as high corrosion parts of glass kilns (pool walls, flow holes, etc.).
4. ZWS (Quasi-void-free)
Process characteristics: Similar to WS, except that a small amount of shrinkage pores remain on the upper part of the brick body, and the shrinkage pores of the cast brick are basically cut off.
Advantages: Further reduce shrinkage pores and pores, improve density and uniformity.
Disadvantages: Higher process control requirements and higher costs.
Application scenarios: Occasions with high performance requirements, such as key erosion parts of glass kilns.
Effects of different casting methods on the properties of fused AZS bricks
◐ Location of shrinkage holes: The location of shrinkage holes affects the strength and thermal shock resistance of bricks.
◑ Density: Different casting methods affect the density of refractory bricks, which in turn affects their wear resistance and corrosion resistance.
◐ Porosity: The porosity of bricks affects its thermal conductivity and thermal shock resistance.
Choice of casting method
Choosing a suitable casting method requires comprehensive consideration of the following factors:
◐ Application location: Different locations have different requirements for bricks, such as the top of the melting tank, the tank wall and the throat.
◑ Working conditions: Conditions such as temperature, atmosphere, corrosiveness, etc. will also affect the choice of bricks.
◐ Performance requirements: Consider performance requirements, including strength, density and thermal shock resistance.
How to choose a suitable casting method for AZS bricks?
☑ Select according to the application location;
☑ Select according to the operating conditions: Consider factors such as temperature, atmosphere and corrosiveness;
☑ Select according to performance requirements;
☑ Consider economic factors: Consider the overall cost-effectiveness.
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