On Lost Foam Casting Process
What is Lost Foam Casting? Lost Foam Casting uses a foam model instead of a metal or a wood mold. After molding, it is not removed. It is a solid cavity. That is, a foam model that is completely similar to the shape of the cast remains in the cast, forming a “real†shape. "Casting, rather than the traditional sand "cavity" mold, in the molten metal, the foam model under the action of high-temperature metal liquids continue to decompose and gasification, resulting in a metal - model replacement process, unlike the traditional "empty" Type casting is a filling process of metal liquid;
Compared with the traditional sand casting technology, the lost foam casting technology has a strong technological advantages, so it is hailed as "the casting technology of the 21st century" and the "green casting project" by the domestic and foreign foundries. China has included this technology in the machinery industry promotion project in the five-year plans of the “7th Five-Year Planâ€, “Eighth Five-Year Plan†and “Ninth Five-Year Planâ€.
There are more than 20,000 foundries (workshops) in China, most of them adopt traditional sand casting, labor intensity is large, the workers are prone to get silicosis (environmental pollution is serious), and the rate of waste crystals is high; their products are completely expanded by the production area: Quality depends heavily on the technical level of the operating workers, training a batch of three or more molding team for at least 5-10 years.
In the past, lost foam casting has been developing slowly in China. The main reason is that many external objective conditions are not mature. For example, “FAW†introduced a production line in the early years and produced 100,000 pieces of aluminum alloy car inlet pipe, from adhesive to foam mold EPS ( Polystyrene pellets for casting) Raw materials and production line equipment are all supplied by imports. The high cost, together with the lost foam casting, is new to most companies.
At present, as a result of national attention and the development of domestic chemical industry, the development of lost foam casting technology in China has led to the localization of various equipment and raw materials required for the development of lost foam casting technology, which can basically meet the requirements of lost foam casting. Therefore, in the past few years, lost foam casting technology has been used in the domestic foundry industry. fast development.
1. The foam shape with a shape and size that is completely similar to that of the casting remains in the casting mold, not the "cavity" mold of the conventional sand mold.
2, using dry sand without binder, vibration modeling.
3. When pouring, the foam plastic model is continuously gasified and decomposed under the effect of high-temperature liquid metal, resulting in a metal-like replacement process, unlike the traditional “cavity†casting process in which a liquid metal is filled. To make a casting, you must "disappear" a foam model.
4, foam plastic mold can be divided into pieces, can also be made manually, and then bond the combination. The pattern shape (ie casting shape) and structure are basically not subject to process limitations.
5. When the casting falls into the sand, just turn over the box or pour out the casting. The casting is automatically separated from the sand. The casting has no flash burrs. Basically, it does not need to be polished. Only the mine is used for simple cleaning of the pouring feeder and other parts of the casting.
Third, the lost foam casting (EPC) process advantages
Lost foam casting (also known as solid casting) combines the foam model with the shape and shape of the casting into a model cluster. After brushing the refractory coating well and drying it, it is buried in the dry quartz sand and tapped in the negative pressure. Casting under the action of a new casting process.
l, high precision castings
Casting size and shape accuracy, good repeatability, high surface finish, with precision casting characteristics
2, high product quality
Disappeared in the die casting process is a precision casting technology, casting size accuracy and surface finish is much higher than the sand casting, the model does not need to type edge, the casting does not have flash burr; due to negative pressure, strong feeding capacity, the internal structure of the casting is dense, The tumbling system can handle the casting without shrinkage and shrinkage.
3, the process is simplified and easy to operate
No matter how complex castings are, there is no need to make cores, the core can be cast φ3-5mm holes; training a high-level modelling workers for at least 5-10 years, and training an EPC process mature operators only three days; that is, technology The more developed, the more streamlined the operation.
4, stable technology, low product waste rate
Sand casting from the sand to the modeling, the next core, box and other processes, human factors caused more quality problems. The EPC process is not equipped with sand, sand mixing, molding, and modification, which reduces many human factors. The main production process is performed according to a fixed program. Therefore, the scrap rate is low. In addition, under the negative pressure pouring has a strong feeding effect. The lost foam casting process can make the model (EPC-polystyrene foam model) group buried in the box, the production efficiency is 4-5 times higher than the sand casting; sandfall, cleaning workload is greatly reduced; do not have sand, mixed sand, not only Reducing the production area of ​​the Ding (the area can be reduced by 30%-50%), but also greatly reducing the manual labor of the workers. The labor labor is reduced by 50% compared with the sand casting, and the manufacturing cost is reduced by 40%-60% compared with traditional precision casting. Sand casting is quite equivalent; using the lost foam casting process, as small as several to several dozens of tons of castings, from non-ferrous metal castings to cast steel, zinc and iron can be produced.
Fourth, lost foam casting technology is not versatile, it has a certain range of Fan Pu, for each company's own products, whether the appropriate use of EPC technology, should be carefully examined.
1. It can produce cast parts with complex shape and inner cavity structure, such as box type, shell type, automobile cylinder block, cylinder head, intake and exhaust pipe, pump body, etc.;
2, the casting is very dense, can reduce the shrinkage of the internal castings, shrink porosity and other common casting defects;
3, with a high degree of copyability, casting surface finish can be achieved by casting 12.5;
4, the castings have high dimensional accuracy, are very stable, and dimensional accuracy can reach CT7-9;
5, can be cast out of other processes can not be cast grooves, internal holes, installation and so on.
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