What is a sand casting? How dose it comes out? The following passages would give you some answers.
Have you seen a large metal made of iron, bronze, brass of aluminum with some featured patterns in the middle? Have you noticed a cavity of wood or metal? If you say yes, I think you have already got the idea of casting. The sand is a cast part produced by forming a mold from a sand mixture and pouring molten liquid metal into the cavity in the mold. After the process of cooling, the melted metal has been solidified. At the last, a sand casting would be gotten just separated from the mold. Generally speaking, it is produced as follows.
The basic step is to place a pattern in sand to create a mold. It should be mentioned that the mould has two parts divided by the parting line. The cope is the upper half and the drag is the lower half.
And as you know, there are 2 main types of sand. One is called the “green sand”, and the other is the “air set”. The previous one is a mixture of silica sand, and the latter one is dry sand with other material through curing adhesive.
Then, remove the pattern and pour the melted metal to the mold. You can use the vibration and mechanical method to remove the pattern. And the cope is separated from drag. Within the mechanical methods, the sand mixture is assembled to for a mold cavity. According to the different types of sand, the change happened during this process is different. Whatever, a riser is needed to hold excess molten material to avoid the holes in the main casting.
Next, allow the metal to cool. At this moment, the liquids are solidified. It is time for you to break away the mold and remove the casting. It is true that the mold is destroyed in the removal process. However, the pattern itself can be reused to produce new sand molds. And if you want a more elaborate casting, surfaces should be polished.
The producing process appears to be simple. But it is definitely not. It is certain that each one hopes to produce a casting with high accuracy. It is a work which needs enough practice. During the process of casting, it is advisable to reuse some of the components of the sand mixture lost in the thermal casting process. Whatever, the material determines a lot. Generally speaking, sand castings made from coarse green sand impart a rough texture on the surface of the casting which makes them easy to identify. However, air-set molds can produce castings with much smoother surfaces.