Sand casting is suitable for casting large precision castings

2021-3-29 20:41:11

Nowadays, my country's processing plants use raw sand from Inner Mongolia, Hebei Province, Liaoning Province and other places. The quality (Character) is good and there is no problem. The problem is the supervision and usage of the sand. Precision casting is also called lost wax casting. Its products are precise, complex, and close to the final shape of the part. It can be used directly without processing or with little processing. It is an advanced technology with near net shape. Precision casting refers to the general term for obtaining precision-sized castings. Compared with the traditional sand casting process, the casting size obtained by precision casting is more accurate and the surface finish is better. It includes: investment casting, ceramic mold casting, metal mold casting, pressure casting, and lost foam casting.

As soon as the molding sand and the high-temperature molten iron touch, the sand loses the crystal water contained in it, and a thoroughly burned hard sand layer is formed. Even if the sand in the hard sand layer maintains the shape of the sand, a little pressure is compared It is easily broken and converted into fine powder. Precision casting refers to the general term for obtaining precision-sized castings. Compared with the traditional sand casting process, the casting size obtained by precision casting is more accurate and the surface finish is better. It includes: investment casting, ceramic mold casting, metal mold casting, pressure casting, and lost foam casting. There are too many fine powders that have lost crystal water in the molding sand, so the air permeability of the molding sand will be reduced, so that the clay, bentonite and other molding sand binders will not work, and the fine powder is easy to absorb water, and its own temperature resistance is not too high. When it comes into contact with high-temperature molten iron, it melts into a glassy material, causing sticky sand. The sticky sand on the inner side of the castings in the precision foundry is all caused by fine powder. The amount of fine powder [ZW (〗 〖ZW above 200 mesh) in the molding sand should be less than 1%.　　

The common precision casting method for castings in large and medium-sized precision foundries is sand casting, and the other is special precision casting methods, such as: metal mold casting, investment casting (using mold casting), chemical formula: CaSO4·2H2O precision casting, etc. . And sand casting can be divided into clay sand, organic binder sand, resin self-setting sand, lost foam and so on. The precision casting methods for castings in large and medium-sized precision foundries usually use lost foam casting technology, resin sand casting, solid precision casting, high-grade precision casting, etc., such as the bed, column, beam, and slide of the large and medium-sized cast iron platform of the CNC lathe Taiwan, etc. are all designed with these types of casting processes. Material: HT200-350 for castings in large and medium precision casting plants, which can contract castings from precision casting plants of about 60 tons of loose parts. The advantages of using resin sand for casting large and medium-sized precision castings: Lost foam casting is aimed at the production of loose parts or mass-produced car covers, CNC lathe beds and other large and medium-sized precision castings have greater advantages. Good surface quality and other advantages. Principles for the determination of precision casting methods: sand casting is preferred for castings in large and medium precision foundries. The precision casting method should match the production batch, low pressure casting, die casting molds (title: mother of industry) (essence: casting liquid die forging) One method), centrifugal casting and other precision casting methods. Because the price of machinery and equipment (shèbèi) and die-casting molds are relatively expensive, they are only suitable for mass production. Large and medium-sized precision castings can be produced in bulk or mass production. . In order to make the surface of the castings in the precision foundry beautiful, the sand must be improved. Construction Equipment 　　 When casting the castings of the precision casting factory out of the sand box, shovel the burned dry sand close to the castings of the precision casting factory with a shovel and throw it out of the processing plant, and fill the factory with new sand. Mix clay, bentonite and sand with a roller type sand mixer (mixed sand) for use. At this time, with the ratio of 70% of the old sand and 30% of the new sand in the processing plant, if it lasts for three months, the molding sand of the processing plant will be improved on the whole.