The basic characteristics of high-density shaped sand are: high clay content, low water, and low addition amount of powdered coal. Therefore, the following points should be grasped in the sand distribution.
Clay content and mud content. Type sand with high clay content, also enhanced with specific pressure, usually effective bentonite is controlled at 7%~10%. The sum of the effective clay and dead clay in the type sand is equivalent to the mud content, which is generally controlled at 12% ~ and 16%. Too high or too low mud content will affect the performance indexes of the type sand.
Moisture water. The moisture in the manufacturing sand is the main factor that determines the plasticity and adhesion of the clay. When the water is too high, it is easy to deteriorate the clay adhesion, the fluidity of the shaped sand decreases, and no uniform density of the casting type is obtained. When the water is too low, the type sand is not easy to mix, low strength, brittle, poor mold, easy to produce the cast sticky sand defects. General moisture shall be controlled 10%~20% higher than the peak wet pressure strength.
Original sand particle size. When the high density modeling is high, the sand density is high, and the expansion is large when pouring, so the original sand grain size should not be too concentrated, the original sand particles are circular or polyangular, and three sieve sand or four sieve sand are generally selected.