What types of drainage sand are common in the market?

What types of drainage sand are common in the market?
During use, the drainage sand bears a large hydrostatic pressure. In order to prevent stretching, the drainage sand is required to have very good fluidity.
The friction between them should be as small as possible; when the drainage sand is in a high temperature state, prevent the drainage sand from falling automatically or cannot effectively support the upper material during use. based on
There are four types of common drainage sand in practical applications that meet the above requirements: forsterite, silicon, zirconium and chrome drainage sand.
1. Forsterite drainage sand. The basic properties of forsterite drainage sand can meet the basic requirements of drainage sand, and it is a cheap drainage sand. But really
In actual application, the automatic casting rate of die casting can reach 95%, but in continuous casting, the automatic casting rate is low. In the current steel mills, the usage ratio of this type of drainage sand
About 15-20%.
2. Silica sand drainage sand. The melting point of silica sand is about 1680-1700℃, and it is widely used, but if the quartz sand is above 1200 cores, it will cause a large
The volume expansion of the sand filling increases the adhesion between the sand filling and the inner wall of the nozzle, which does not affect the free fall of the filling sand during pouring, and even “bridging” phenomenon occurs. Other
In addition, the artificially processed quartz sand has many edges and corners and irregularities, so the natural fluidity is poor and it is easy to cause “stretching”; and the irregularities are easy to affect the natural
opening rate. However, siliceous drainage sand is currently the most widely used drainage sand, accounting for about 50%-60%.
3. Zircon sand – general w (ZrSi04) ≥ 97%, free w (Si02) ≤ 2%, w (impurity) ≤ 1%, melting point higher than 1800C. Zircon due to thermal expansion
Low expansion rate, good thermal conductivity, high bulk density, good stability, not easy to be wetted by molten steel and other excellent properties, and at the same time in the shape of round particles, has been used as a casting
Manufacturing sand and continuous casting drainage sand materials. Zirconium sand is not easy to sinter than silica sand, but its price is too high, so it is mostly used for drainage of tundish.
4. Chromite composition w(Cr203), 32-35%; w(Fe0), 14-17%; w(Mg0), 12-18%; w(A1203), 16-25%; w(Si02) ,
2-12%. The melting point is about 1730-1750C. Chromium drainage sand is made of chromite and additives, with large specificity, good fluidity, high melting point, not excessive
Sintering and other advantages. In chrome drainage sand, when the amount of chromite added is greater than 60%, the chromite is distributed continuously, and this distribution helps to form a continuous
the sintered layer. At high temperature, Fe0 in chromite reacts and desolventizes to form secondary spinel, which changes the volume of the sintered layer and produces cracks.
When the plate is opened, the unsintered drainage sand at the lower part of the nozzle flows out rapidly, the cracks in the sintered layer expand rapidly, and the sintered layer is completely broken under the static pressure of molten steel
Bad, so as to achieve the purpose of automatic pouring. Chromium drainage sand is used by most large steel mills, accounting for about 30% of the drainage sand used in the entire ladle, especially
Refined ladle.