Common Pouring Methods for Investment Casting

As everybody knows, investment casting has the advantages of high dimensional accuracy, good surface quality, and the investment casting is a widely used advanced technology with less or no cutting. It's a simple process to make a melt-melting model with a simple melting material, using a molten mold to make a lot of money and machine tools and working hours, and to be able to significantly reduce metal and raw materials.

Therefore, investment casting is a widely used casting method in the field of casting, which effectively reduces the cost and improves the competitiveness of casting enterprises.

1. Directional crystallization.

For some investment casting parts such as turbine blades, magnetic steel and etc., if their crystal structure is arranged in a certain direction columnar crystals, their performance can be improved a lot, so investment casting oriented crystallization technology is rapidly developing.

2. Crystallization under pressure

The mold shell is placed in the pressure tank for pouring, and the pressure tank is closed immediately after completion. High-pressure air or inert gas is injected into the tank to make the casting solidify under pressure to increase the casting density.

3. Hot gravity casting

This is the most widely used form of pouring, that is, after the shell is removed from the roaster it is casted at high temperature. At this time, the metal is cooled slowly in the shell and can fill the casting mold with high fluidity. Therefore, the casting can reproduce the shape of the cavity and improve the precision of the casting parts. However, the slow cooling of the casting in the hot mold will make the grains coarse which will reduce the mechanical properties of the casting parts. During pouring process the surface of the castings with slow cooling is easy to oxidize and decarburize thus reducing the surface hardness, smoothness and dimensional accuracy of the castings.

4. Vacuum suction pouring.

The mold shell is placed in a vacuum pouring box, and the gas in the mold cavity is sucked away 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 casting precision, and prevent the defects of porosity and insufficient pouring. This method is more common in foreign countries.

The casting process of investment casting is a strict step. Different pouring methods have different characteristics, so in the process of investment casting we have to choose the right pouring method in order to get high-quality casting parts. If you don’t know how to choose please contact Sieg-Huao who will give you professional advise because we have 50-year casting experience.