Casting powders: Influence of the humidity on the flowability

In this study, the possible reason for conveying problems sometimes observed in the pneumatic transport of casting powders from the storage containers to the mould was studied. Since some correlation in the occurrence of the said conveying problems to days with high humidity has been observed, the influence of the relative humidity of the air on the flowability of casting powders was investigated. The results showed that below a relative humidity of approximately 75%, all three casting powders investigated were free-flowing but with increasing humidity, the flowability decreased. At a relative humidity of 90%, only one casting powder was cohesive but not very cohesive. To avoid problems in pneumatic conveying, therefore, the relative humidity of the atmosphere in the pneumatic conveying system and the storage bins has to be limited.