Sand foundry is a production method in which molten metal is poured into the cavity of a mold and cooled and solidified to obtain a product. In the automobile manufacturing process, there are many parts made of cast iron blanks, which account for about 60% of the total vehicle weight, such as cylinder block, transmission case, steering gear housing, rear axle housing, brake drum, various brackets Wait.
Sand molds are usually used to manufacture iron castings. The raw material of the sand mold is mainly sand, mixed with binder, water, etc. The sand material must have a certain adhesive strength so that it can be molded into the required shape and can withstand the erosion of high temperature molten iron without collapsing. In order to mold the sand mold into a cavity that matches the shape of the casting, wood must be used to make a model, which is called a wooden mold.
The volume of the hot molten iron will shrink after cooling. Therefore, the size of the wooden mold needs to be increased according to the shrinkage rate on the basis of the original size of the casting, and the surface that needs to be cut is thickened accordingly. Hollow castings need to be made into sand cores and corresponding core wooden molds (core boxes). With the wooden mold, the cavity sand mold can be turned over.
When making sand molds, it is necessary to consider how to separate the upper and lower flasks to take out the wooden mold, and also consider where the molten iron flows from and how to fill the cavity in order to obtain high-quality castings. After the sand mold is made, it can be poured, that is, the molten iron is poured into the cavity of the sand mold.
When pouring, the temperature of molten iron is 1250~1350 degrees, and the temperature is higher during smelting. Then it has to go through the process of de-sanding, repairing, polishing, etc. before it can become a qualified casting.