What Is Centrifugal Casting?

Centrifugal casting is a technique and method for injecting liquid metal into a mold that rotates at a high speed to make the metal liquid perform centrifugal motion to fill the mold and form a casting. Due to the centrifugal movement, the liquid metal can fill the mold well and form the free surface of the casting in the radial direction; the cylindrical inner hole can be obtained without the core; it is helpful to the exclusion of gases and inclusions in the liquid metal; Crystallization process, thereby improving the mechanical and physical properties of the casting.

Significant production benefits

advantage:

Almost non-existent

Metal filtration, pouring temperature, mold speed, solidification under slag, coating use, casting release, pouring system, pouring quantification, etc. are the process issues that must be determined or resolved in the production of centrifugal casting, because they directly affect the quality and Productivity.

Centrifugal Cast Metal Filter

Some alloy liquids have more slags that are difficult to remove. Various filters can be placed in the pouring system to remove slags, such as foam ceramic filters, glass wire filters, etc.

Centrifugal casting pouring temperature

Centrifugal castings are mostly tubular, sleeve-like, ring-shaped pieces. The resistance encountered when filling the metal liquid is small, and the centrifugal pressure or centrifugal force enhances the filling capacity of the metal liquid, so the pouring temperature during centrifugal casting can be higher than gravity casting. Low 5 ~ 10 ° C.

Centrifugal casting mold speed

It is an important process factor in centrifugal casting. Different castings and different casting processes have different mold speeds during casting.
Too low mold speed will cause poor filling of the metal liquid during vertical centrifugal casting, and the phenomenon of metal liquid rain during horizontal centrifugal casting will also cause defects such as looseness, slag inclusion, and uneven unevenness on the inner surface of the casting;
The mold rotation speed is too high, and defects such as cracks and segregation are easy to appear on the casting. Defects such as expansion boxes will be formed on the outer surface of the sand centrifugal casting. It will also cause large vibrations, increased wear and excessive power consumption. Therefore, the selection principle of the mold speed should be the minimum value under the premise of ensuring the quality of the casting.

Centrifugal casting slag utilization

In order to overcome the subcutaneous shrinkage defect caused by the two-way solidification of thick-walled centrifugal castings, the slagging agent and the molten metal can be poured into the mold during casting, and the slag covers the inner surface of the casting to prevent the heat dissipation of the inner surface. Sequential coagulation conditions outward and inward to eliminate subcutaneous shrinkage. At the same time, the slag-forming agent can also play the role of refining molten metal.
The method of pouring the slag-forming agent is: sprinkle powdery slag-forming agent in the pouring tank during pouring; and pour the molten slag into the mold together with the metal liquid.

Use of centrifugal casting coating

The composition of the coating for centrifugal metal mold is similar to that of gravity metal mold casting. When casting slender centrifugal castings, it is difficult to remove the residual paint on the mold working surface, so the residual strength of the adhesive in the coating composition after high temperature work should be as low as possible to facilitate removal.

Centrifugal casting casting release

In order to improve the production efficiency, the casting should be demoulded as soon as possible under the premise of ensuring the quality. Sometimes in order to prevent cracking of the casting, the casting after demoulding should be immediately placed in a holding furnace or buried in a sand pile to cool down. For some castings that are not easy to release and require slow cooling and crack prevention, the casting molds can be removed from the centrifugal casting machine immediately after the mold stops rotating, buried in a sand pile and slowly cooled, and then removed at room temperature type.

Centrifugal casting pouring system

The gating system during centrifugal casting mainly refers to a metal receiving cup and a pouring groove connected to it, and sometimes includes a runner in a mold. When designing the gating system, you should pay attention to the following principles:
When pouring castings with long lengths and large diameters, the pouring system should enable the metal liquid to be spread evenly on the inner surface of the mold quickly;
When pouring easily oxidizable metal liquid or using centrifugal sand mold, the pouring tank should allow the metal liquid to fill the mold in a balanced manner, minimize the splash of metal liquid and reduce the erosion of the sand mold;
When casting the formed casting, the runner in the mold should allow the molten metal to flow into the cavity smoothly;
After the pouring is finished, there should be no metal and slag in the pouring cup and pouring tank. Residual metals and slag should also be easily removed.

Centrifugal casting

The inner diameter of centrifugal castings is often determined by the amount of molten metal poured. Therefore, during centrifugal casting, the amount of molten metal in the mold must be controlled to ensure the inner diameter. Installing pressure sensors on the pouring bag rack for automatic quantitative centrifugal casting and electromagnetic pump quantitative casting of thermal insulation induction furnace has also been applied in production.