Introduction of influence factors of cast iron castings by Guizhou foundry
The influencing factors of Guizhou iron castings are as follows:
1, phosphorus: high phosphorus content in molten iron makes the solidification range expand. Meanwhile, low melting point phosphorus eutectic can not get recharge at final solidification, and make casting shell weaken, so there is a tendency to increase shrinkage porosity and porosity. The phosphorus content of the General Factory is less than 0 08%.
2, pouring riser and chill: if the gating system, riser and chill are not set properly, the sequential solidification of metal can not be guaranteed。 Besides, the number and size of risers and the connection with the casting will affect the feeding effect of risers。
3, rare earth and magnesium: the high residual amount of rare earth will deteriorate the shape of graphite and reduce the spheroidization rate, so the content of rare earth should not be too high. Magnesium is also an element that strongly stabilizes carbides, which hinders graphitization. It can be seen that residual magnesium content and residual rare earth content will increase the chilling tendency of ductile iron and decrease the expansion of graphite, so when their content is higher, it will also increase shrinkage porosity and porosity.
4, temperature: pouring temperature is high, which is good for shrinkage, but too high will increase the volume of liquid shrinkage, which is unfavorable to eliminate shrinkage and porosity. Therefore, casting temperature should be chosen according to the specific circumstances, generally 1300~1350 degrees.
5, wall thickness: when the surface of the casting is hard shell, the higher the temperature of the molten metal is, the greater the shrinkage of the liquid will be. The volume of shrinkage and porosity will not only increase, but also increase the relative value. In addition, if the wall thickness changes too suddenly, the isolated thick section can not be made up, which makes the shrinkage and loosening tendency increase.