The sand-casting method is classified into the “permanent model type disappearing mold method” in which the model is permanently used, among the “disappearing molds” in which the mold disappears every time a casting is made. These methods include the “slurry mold method” in which refractory powder is mixed with a binder (caking agent) as a vanishing mold to create a mold, and the refractory particles are solidified using a vacuum without using any binders. It includes the “vacuum mold method (V process)” to create a mold, but since the usage is limited, detailed explanation is omitted.
In the sand-casting method, first, a half-split model that matches the product shape is set in a form of a certain size, and then casting sand (mainly silica sand is used) containing various types of binders. After charging, it is compressed at a constant pressure to make a mold (the cavity becomes the product). In this work, “upper mold” and “lower mold” are created separately, and these two are combined to complete the mold. At this time, when manufacturing a “hollow product”, set the separately created “core” between the upper and lower molds to complete the mold.
Inject the melted “metal molten metal” into the finished mold, and after it solidifies, remove the casting from the mold and remove the sand by an appropriate method such as shot blasting. After that, the product part and the Oshiyu / Yuguchi are cut and removed to complete the casting.
Raw sand type method
The raw sand molding method is the oldest molding method. A mold is manufactured by mixing about 10% of clay (bentonite) with natural silica sand, mixing carbon powder and starch, and about 3% of water, and applying pressure to the mold material to give it a bond. increase.
If left at room temperature, the strength of the mold will increase due to the chemical reaction of the compounded materials, and the mold will be completed. A typical example is a method in which an organic furan resin is used as a binder and the furan resin is “dehydrated and condensed” by the organic acid of the curing agent to harden the sand.
Gas curable mold
The advantages are low equipment cost, quick molding, and the need to dry the mold. The disadvantages are that the mold disintegration after pouring is inferior and it takes time to take out the product part. there is.