Casting Temperature And Casting Speed Of Fused Cast Azs Brick
2015-10-23
Casting technology is a method to manufacture fused cast azs brick, and there are several steps of casting, however, it has a close relationship with the casting temperature and casting speed which can determine the quality of fused cast azs brick.
Casting temperature is the stream temperature which is near the furnace at the mouth and is measured by optical pyrometer. When fused cast azs brick is melting, the casting temperature can reach to 1820-1840℃. The viscosity of molten liquid depends on the chemical composition and temperature of the molten liquid, however, the composition of molten liquid is determined by the formula, so temperature plays an important role. Generally speaking, the higher the temperature of the molten liquid is, the lower the viscosity is, the better the liquidity is, the better the filling ability is.
However, it is not better if the casting temperature is higher, if the casting temperature is too high, the temperature difference between the casting and the model is reduced. Accordingly, the solidification zone from the surface to inner is increased; the rate of solidification shrinkage is speeded. Meanwhile, initial grain is coarsened, component is segregated, and the core part of the casting is easy to produce hot cracking in the final solidification. Therefore, casting temperature should have a certain upper limit according to the size and shape which can prevent cracking, at the same time, lower limit is also needed which can prevent insufficient capacity.
Casting speed directly determines the casting time, and every fused cast azs brick has its own best casting time. Unreasonable casting time can cause many defects in the casting.
High casting speed
If the casting speed of fused cast azs brick is too fast, the liquid flows become wide which bring a great impact on the casting mold of fused cast azs brick, then part of casting mold is broken through or melted which can make the this part of mold risen up. In addition, when the wide liquid flow is casted into mold, some air is may brought into casting mold and rising to the top cover of the mold rapidly. Meanwhile, liquid touched top cover has already formed thin shell, so when air rises to the top cover that so-called shell is formed. What is more, it is easy to form air bubbles inside the mold when air is brought in mold. Except for the air, wide liquid flows caused by high casting speed may also brings the raw material which is in furnace mouth into molten liquid of fused cast azs brick.
Low casting speed
If the casting speed of fused cast azs brick is too slow, defects such as corner loose, knot, sand inclusion and Insufficient casting will be produced. Low casting speed leads to thin liquid flows, when the thin liquid flow is casted into the mold of fused cast azs brick, solidified to a small ball and move to the side corner which will result in loose of edge angle. If the first poured liquid flow has solidified into a thin shell which will inward contraction, then poured liquid flows will get into the gaps between the thin shell and the mold which form scar on the surface of fused cast azs brick. Meanwhile, if the liquid flows are too thin, before reaching the side corner the liquid flow will be solidify which will lead to Insufficient casting. In addition, low casting speed will also lead to long time casting which means that mold baking time will be increased, that the mold cover is easy peeling off into the molten liquid and cause sand inclusion.
