Knowledge

Under a certain quality condition of the raw sand and resin, the key factor that affecting the precoated sand strength mainly depend on the content of phenolic resin. The sand strength will increase by adding more phenolic resin, but gas evolution volume will be bigger and the collapsibility will degrade accordingly.

Therefore, in order to control the sand strength, reduce the gas evolution volume and improve the collapsibility, foundries must find a balance when setting strength standards for a specific product, to ensure the sand core surface quality, avoid the deformation and cracks.

In this way, the surface quality and dimensional accuracy can be guaranteed, gas evolution volume and casting porosity defects can be reduced, and the sand production performance can be improved. And using the special tools and transfer boxes in the process of sand core storage, handling process, laying 10-15mm thick of sponge on the boxes bottom to reduce the sand core loss rate.