Reasons for the occurrence of air holes during the pouring process of fused zirconia corundum bricks
2023年04月24日
The relationship between the casting of fused zirconia corundum bricks and the porosity during casting
It is normal for ordinary AZS castings to have shrinkage and porosity, but it is often found that there are many pores. Obviously, the presence of any pore will directly reduce the quality of the casting.
There are two types of pores in castings, one is microscopic pores, which can only be seen under a microscope when made into thin slices; The other type is macroscopic pores, which are visible to the naked eye, also known as pores. They come from four aspects: furnace material, melting process, casting material, and casting process.
This will discuss the impact of mold and casting on porosity.
Porosity caused by mold material
There are two common types of porosity at the edges of castings that come into contact with the mold:
1) The dense subcutaneous honeycomb like pores perpendicular to the mold wall are caused by the dampness of the sand mold working surface. Water is a gas generating substance, and a unit volume of water is heated to 1000 degrees Celsius to become water vapor. When the pressure remains constant, the volume increases by 1700 times. If heated to the casting temperature, it may reach nearly ten thousand times. So the sudden generation of so much gas on the surface of the sand mold will form a high pressure, causing the gas to invade the solidifying edge melt and extend in the direction of low resistance, thus becoming a long strip shape. Therefore, it is prohibited to use damp molds during casting operations.
2) Subcutaneous circular pores are mostly single circular bubbles within 10 millimeters of the edge. This is because the sand mold adhesive decomposes and produces a large amount of gas when it comes into contact with the melt. Part of the gas escapes from the sand mold gap, while the other part invades the melt due to the instantaneous poor exhaust of the mold cavity and pressure. Therefore, it is important to pay attention to the exhaust of the mold cavity during casting, Of course, improving the permeability of the sand mold (such as using circular sand particles to clean the dust in the sand, the permeability of the back side should be greater than that of the working surface, etc.) refers to the continuous expansion from the inside out, which is more important.
Blowholes caused by casting operations
There are three kinds of pores: empty shell on the casting surface, pinholes in the foam layer, etc.
Introduction to fused zirconia corundum bricks:
Electric fused zirconia corundum brick, also known as AZS electric fused zirconia corundum brick, AZS brick, fused cast AZS brick, etc., abbreviated as AZS, is arranged according to the three chemical components of the Al2O3-Zr02-SiO2 ternary system phase diagram, in order of their content. Al2O3 takes A, Zr02 takes Z, SiO2 takes S, and national standards use this abbreviation. For example, No. 33 fused zirconia corundum brick is abbreviated as AZS33 #, No. 36 fused zirconia corundum brick is abbreviated as AZS36 #, and No. 41 fused zirconia corundum brick is abbreviated as AZS41 #. Among them, 33, 36, and 41 are named based on the content of alumina (Al2O3). For example, the fused zirconia corundum brick AZS41 # refers to the fused zirconia corundum brick with an alumina content of 41%, the fused zirconia corundum brick AZS36 # refers to the fused zirconia corundum brick with an alumina content of 36%, and the fused zirconia corundum brick AZS33 # refers to the fused zirconia corundum brick with an alumina content of 33%.
Featured News
Electric fusion bricks and clay bricks are both refractory materials and have a wide range of uses in building materials. Today, Yuhua Electric Fusion Technology will introduce their differences to everyone:
Refractory bricks are abbreviated as firebricks. Refractory materials made by firing refractory clay or other refractory materials. Light yellow or brownish in color. Mainly used for building smelting furnaces, capable of withstanding high temperatures ranging from 1580 ℃ to 1770 ℃. Also known as firebricks. Refractory materials with a certain shape and size. According to the preparation process, it can be divided into fired bricks, unburned bricks, electric fused bricks (fused cast bricks), and fire-resistant and insulated bricks; According to shape and size, it can be divided into standard bricks, ordinary bricks, special bricks, etc. It can be used as high-temperature building materials and structural materials for building kilns and various thermal equipment, and can withstand various physical and chemical changes and mechanical effects at high temperatures. For example, refractory clay bricks, high alumina bricks, silica bricks, magnesium bricks, etc.
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