Technical requirements and production process of sand mold for ASZ brick casting

Since the casting temperature of AZS brick is about 1800 degrees, sand casting can be used for its casting. The raw materials of sand casting are natural sand and quartz sand. Different particle size grading enhances the strength of the sand moulding plate. The quartz sand is made of fine sand and surface. There are two kinds of sand, and the silicon content is above 99%. The casting surface of each sand mold plate should have a certain thickness of surface sand to prevent impurities from contaminating the mold. There are many kinds of binders for sand molds. Generally, water glass is used because the source of water glass is stable in quality, cheap, easy to wash, and has no peculiar smell, and the sand mold made of water glass high-purity silica sand can meet the following technical requirements:

1) have good air permeability

The gas precipitated from the melt of the zirconium corundum brick can penetrate out from the gaps of the silica sand particles in the moulding wall.

2) Good thermal shock strength

The thermal shock generated by the zirconium corundum brick during casting can make the temperature of the inner wall and the outer wall of the sand mold very different, but the sand mold is relatively stable under heating conditions, because its refractoriness is not lower than 1690 degrees, and its temperature is between 20-450 degrees. The coefficient of linear expansion is about 0.03mm/degree, so it can withstand the static pressure of high temperature melt flow without breaking.

3) Good thermomechanical properties

The strength of the sand mold decreases after heating, and the load-softening test shows that it begins to soften at about 320 degrees and begins to break at 400 degrees.

4) The surface of zirconium corundum brick does not produce chemical sticky sand

After the AZS melt and the sand mold are contacted, they are rapidly cooled and hardened, and the surface of the sand mold is fused into a thin layer of sodium silicate or silica sand, which does not react with AZS. The amount of water glass added is proved to be the most suitable 5.7% by experiments, which will reduce the refractoriness of the sand mold at least, and it will not be able to form.

Sand making process

The relatively large wet sand mold that has been made often has cracks during the transportation process into the furnace. In order to make it have a certain strength, several holes are often inserted in the sand mold, and then carbon dioxide is filled into it.

The solubility of silicic acid is small and precipitates are formed, so the wet sand mold can have a certain strength in a short time. The prepared sand mold should be dried in a resistance furnace to make it have a certain strength for casting. The upper limit of the drying temperature is about 400 degrees.