the almost used aluminum foundry manufacturer will check and control the moisture of the mixed sand. However, many people are not clear about the importance of strict control of the water of the old sand, and many manufacturers do not pay much attention. The old sand entering the mixed sand is too low in moisture, and the effect on the quality of the sand mixture may be no less than that of the sand temperature. Experimental research and experience have proved that wetting dry bentonite with water is much more difficult than lubricating wet bentonite. The bentonite and water in the sand mold are not simply mixed together, they should be kneaded and made into a plastic state.

    after casting, due to the influence of hot metal, a lot of water and clay conjunctiva on the surface of the sand are dehydrated and dried, and it is not easy to add water to restore the plasticity of water absorption. The moisture content of old sand is low, and the longer time it takes to mix it with water and mix it up to meet the required performance. Because the time of mixing sand in production is limited, the lower the moisture content of the old sand, the worse the comprehensive quality of the mixed sand. The old sand entering the mixer is only slightly lower than that of the mixed sand.

    a better practice is that during the cooling process of old sand, the moisture contained in the old cooling water is slightly lower than two J and several mixed into sand. In this way, it is quite a long time from the sand cooling to the mixer, and the water can fully moisten the bentonite on the surface of the old sand grains. The better way is to premix the old sand in the system, and the old sand after cooling is premixed with water in the premixed sanding machine to improve the mixing state of bentonite and water in the old sand. In foreign countries, when some foundries are premixed, additional materials such as new sand, bentonite and pulverized coal to be added are added.