What are the differences between silica bricks and semi-silica bricks?
are refractory products with a SiO2 content of more than 92%. The product's refractoriness and resistance to acid erosion increase with the amount of SiO2 present in the silica raw material.
Semi-silica bricks are produced with pyrophyllite as the main raw material, and their refractoriness is greater than 1700 degree . It has good thermal shock resistance, can withstand the impact of steel slag and metal, and has strong creep resistance.
Silica bricks are a type of acidic refractory material. They have strong resistance to erosion by acidic slag or acidic melt, but poor resistance to erosion by alkaline substances. Moreover, the expansion coefficient of it is very large. The volume of silica fire bricks is stable from above 300 degree to close to the melting point. When heated to 1450 degree , a volume expansion of 1.5% to 2.2% will occur. The biggest disadvantages of silica bricks are poor thermal shock resistance and low refractoriness (generally 1690~1730 degree ), which limits its application range.
Semi-silica bricks made of waxstone will exhibit micro-expansion. Since the mineral composition of waxstone, pyrophyllite, changes little in the size of its crystal structure when heated, it shrinks little during baking and sometimes expands slightly. During the high-temperature use of semi silicone bricks, pyrophyllite reacts with acidic slag, forming a layer of glaze-like substance with high viscosity on the surface of semi-siliceous bricks, which prevents acidic slag from penetrating into the brick and resists acidic slag. The erosion ability is also quite good.
Silica bricks are used in large quantities and in many varieties. They are mainly used in the carbonization chamber, combustion chamber and partition walls of coke ovens, as well as the kiln roof and kiln pool of glass tank kilns. The high-temperature load-bearing parts of hot blast furnaces, carbon roasting furnaces and other kilns are also lined with silica bricks. There are many varieties of silica refractory bricks, including silica firebricks for coke ovens, silica fire bricks for hot blast furnaces, silica refractory bricks for electric furnaces, silicone bricks for glass kilns, etc.
The use range and dosage of semi-silica bricks are not as large as those of silica bricks, and are extremely limited. Although it can be used in ladle bottom linings, hot metal ladle linings and flues, due to the improvement in steel quality requirements, the amount of semi-siliceous bricks is very small.
In general, silica firebricks are suitable for special industrial environments with high requirements for high temperature resistance and corrosion resistance, while semi-siliceous bricks are suitable for some medium-temperature working environments and are used in some occasions with relatively low special requirements. Material selection should be considered based on specific working conditions and requirements.
