Investment casting has the advantages of high dimensional accuracy and good surface quality. It is a widely used advanced technology with little and no cutting. In short, it is made of fusible models with fusible materials. Thrift saves machine tool equipment and processing hours, but also saves a lot of metal raw materials. Therefore, investment casting is a widely used casting method in the casting field. This casting method effectively reduces costs and improves the competitiveness of casting companies. One of the most important steps in investment casting is casting, so what are the common casting methods for investment casting?
1. Crystallize under pressure
Place the mold shell in the pressure tank for pouring. After the end, immediately close the pressure tank and pass high-pressure air or inert gas into the tank to solidify the casting under pressure to increase the density of the casting.
2. Vacuum suction pouring
Place the mold shell in the vacuum casting box, and suck the gas in the mold cavity through the tiny pores in the mold shell, so that the liquid metal can better fill the mold cavity, copy the shape of the mold cavity, improve the accuracy of the casting, prevent blowholes, pouring Insufficient defects. This method is more common abroad.
3. Directional crystallization
Some investment castings such as turbine blades, magnetic steel, etc., if their crystalline structure is columnar crystals arranged in a certain direction, their working performance can be greatly improved, so the directional crystallization technology of investment casting is rapidly developing.
4. Hot gravity casting
This is the most widely used casting form, that is, after the shell is taken out from the roaster, it is casted at a high temperature. At this time, the metal cools slowly in the mold shell and can fill the mold with high fluidity. Therefore, the casting can replicate the shape of the cavity and improve the accuracy of the casting. However, the slow cooling of the casting in the hot mold will make the grain coarse, which reduces the mechanical properties of the casting. When casting carbon steel castings, the surface of the casting that cools slowly is also susceptible to oxidation and decarburization, thereby reducing the surface hardness, smoothness and dimensional accuracy of the casting.
The casting of investment casting is a strict step. Different casting methods have different characteristics. Therefore, in the investment casting process, a suitable casting method should be selected to cast a good melting tool.