Sand casting, the method has been around for a long time but is still widely used by suppliers today.
Sand casting is a popular form of casting. Sand molds are one-time molds (pouring only once and then breaking molds). Shaping castings in sand molds have low precision, poor surface gloss, large excess machining, but sand molds have the advantage of creating castings with complex texture, large volume and low mold cost.
The manufacturing process of casting in sand molds
- The technical department shall base itself on the detailed drawings to make drawings of the casting, samples and core boxes.
- Based on drawings to manufacture a set of samples, including: a casting sample to create a mold cavity bearing the appearance of the casting; core box for core fabrication creates the inner shape of the casting, pattern of filling system for steaming, sprue used to conduct liquid metal and vent to the mold.
- Assembling mold.
- The liquid metal melting part must coordinate smoothly with the mold making and assembly process to promptly pour liquid metal into the mold.
- After the metal solidifies, the casting is formed in the mold, break the mold, core, clean the casting, inspect the casting by hand or by machine.
- Check casting about shape, size, quality of inside.
Ingredients of the molding mixture
The mixture of molding and sports (core) includes: sand, clay, binder and auxiliary substance.
- Sand: sand is the main ingredient of the mixture for making molds and sports. The main chemical composition of sand is SiO2 (quartz), in addition there is a little clay and other impurities.
- Clay: The main component is kaolin with the formula mAl2O3.n SiO2.qH2O. There are also some other impurities such as CaCO3, Fe2O3, Na2CO3. When the amount of water is suitable, the clay is flexible and sticky. When dried, the strength increases but is brittle and fragile.
- Adhesives: are the substances that are put into the mixture to increase its ductility and durability.
- Adhesives: commonly used as vegetable oils (linseed oil...), water-soluble substances (sugar, molasses, sizing powder, hardening binders (turpentine, cement, etc.) tar residue) and glass water (Na2O.nSiO2.mH2O or K2O.nSiO2.mH2O silicate solution).
- Auxiliary substances: are substances added to increase the settlement, aeration, increase the gloss of the mold surface, and increase the heat resistance of the mixture. Auxiliary substances include the following two forms:
- The auxiliary substances mixed into the mixture such as sawdust, straw, coal powder, thanks to the temperature of the liquid metal when poured into the mold, they burn to create gaps in the mixture to increase porosity, settlement and escape ability. gas of the mixture.
- Mold painters can use graphite powder, coal powder, glass water, quartz powder or their solution with clad paint on the surface of the mold, to increase their gloss, heat resistance.
Mixing the above materials in a certain ratio depends on the material, the mass of the casting is mixed and molded.
Mold mixes are divided into two types:
- Sand coat is used to cover the sample when making molds, so it must have high strength, ductility and heat resistance, because this sand layer is in direct contact with liquid metal. Sand coat is usually made of new material and accounts for about 10-15% of the sand for making molds.
- The cushion sand is used to cushion the rest of the mold to increase the durability of the mold. The cushion sand does not require as high as the coat sand but must have strong ventilation. Usually old sand is used for buffering sand and accounts for about 55 - 90% of the total amount of mold sand.
The proportion of materials in the molding mixture depends on the material and weight of the casting, but generally sand accounts for about 70-80%, clay about 8-20%. Compared to the mold making mixture, the manipulation mixture requires higher, because the manipulation works under more extreme conditions, so it often increases the amount of quartz (SiO2) sometimes up to 100%, reducing the ratio of clay, adhesive, additive and must be dried sports.
Sand molding is a long-standing method, but because of its advantages, in the mechanical industry, it is still widely used and developed by the mechanical industry. the most optimal.
Currently, VIC is always proud to be the leader in that field, always bringing real value to customers, which is assessed by the quality of the products that VIC produces.
Website: vietnamcastiron.com
