The strength of resin bonded sand will be significantly improved by using four-sieve and above raw sand?
The raw sand in foundry production is composed of raw sand with different particle sizes, so there is a problem of particle size distribution in the selection process. Practice has proved that the influence of original sand particle size distribution on the strength of resin bonded sand is much greater than that of particle size.
Firstly, due to the relatively small amount of resin added, the resin film on the surface of sand particles is very thin, and the size of bonding bridge between sand particles is also very small. Secondly, there is no powder or paste filling between sand particles, and the gap is large.
In order to improve the strength of resin sand, increasing the amount of resin is the easiest but most undesirable method. It will not only increase the cost, but also increase the volatilization of harmful gases during pouring. At the same time, it will also increase the difficulty of old sand regeneration.
At this time, if a fine sand is introduced into the sand gap, although the thickness of the resin film will not be significantly increased, the number of bonding bridges is significantly increased and the gap between sand particles is reduced, which becomes the best way to improve the strength of self-hardening sand. If the strength of resin sand increases and is higher than the process requirements, the amount of resin can be reduced in turn.
In short, in the selection of raw sand, the general principle of "three sieve sand" should be followed, the particle size distribution should be appropriately relaxed, and the use of four sieve and above raw sand can significantly increase the strength of resin sand without significantly reducing the permeability. It has more obvious significance for Fused Ceramic Sand with spherical particles.
The resin content in Fused Ceramic Sand is very low. Why does it have high strength?
1. Micro pores on the surface of Fused Ceramic Sand can enhance the adhesion of resin film.
2. Fused Ceramic Sand has high roundness and smooth surface, and the whole spherical surface can be evenly coated with a small amount of resin.
The two major factors, the bonding bridge and the complete bonding film on the surface of Fused Ceramic Sand, constitute the theoretical support for the high strength of Fused Ceramic Sand. From this, it can be concluded that the specific strength of Fused Ceramic Sand is much higher than that of other raw sand, which means that the addition of resin can be reduced by using Fused Ceramic Sand, which means that it is easier to remove the film attached to the sand surface during regeneration.