How Dongguan Foundry controls the moisture content of old sand

Almost all foundries check and control the moisture content of the mixed sand, but many foundry leaders and technicians lack sufficient understanding of the importance of strictly controlling the moisture content of the old sand. The moisture content of the old sand entering the mixed sand is too low, which is detrimental to the mixing process. The impact of sand quality may be no less than if the sand temperature is too high. Experimental studies and experience have proven that moistening dry bentonite is much more difficult than lubricating wet soil. The bentonite and water in the molding sand cannot simply mix together but rub it, making it Become a plastic state. This is like making pottery with clay and water. The water and soil are loose and have no adhesion ability; after friction and beating, each piece of soil completely absorbs water and becomes a plastic state, which can be formed and made into ceramics. Blank.

After casting, due to the influence of hot metal, the soil-water adhesive film on the surface of many sands is dehydrated and dried. Adding water makes it absorb water, and it is not easy to restore plasticity. The water content of old sand is low, and water is added in the sand mixing machine to achieve the required The longer the time required for the performance of the mixed sand. Due to the limited mixing time in production, the lower the moisture content of the old sand, the worse the overall quality of the mixed sand. The consensus among foundry workers in various countries is that the content of the old sand entering the mixed sand machine The water content can only be slightly lower than the mixed sand. A better method is to add water during the cooling process of the old sand, and the water content after cooling will be slightly lower than the mixed sand.

In this way, there is still a long time between the sand cooling and entering the sand machine, and the water can completely wet the bentonite on the surface of the old sand particles. A better method is to set up a sand mixer in the system to premix the old sand, and the cooled old sand is Add water to the premixed sand machine to improve the mixing state of bentonite and water in the old sand.