Keywords: centrifugal casting centrifugal casting machine centrifugal casting centrifugal casting machine centrifugal casting process centrifugal casting defects centrifuge horizontal centrifuge vertical centrifuge centrifugal casting plant centrifugal casting equipment centrifugal casting machinery centrifugal casting equipment  1、 Overview of Centrifugal Casting  The first patent for centrifugal casting was proposed by the Englishman Erchardt in 1809, and it was not until the early 20th century that this method was gradually adopted in production. In the 1930s, China also began to use centrifugal pipes and cylindrical castings such as iron pipes, copper sleeves, cylinder sleeves, and bimetallic steel back copper sleeves, with centrifugal casting being almost the main method; In addition, centrifugal casting method has also been used effectively in the production of heat-resistant steel roller tables, blanks of some special steel seamless steel pipes, and drying drums of paper machines. At present, highly mechanized and automated centrifugal casting machines have been produced, and large-scale mechanized centrifugal casting pipe workshops have been established for production& nbsp; Almost all casting alloys can be used for centrifugal casting production. The minimum inner diameter of centrifugal castings can reach 8 millimeters, the maximum diameter can reach 3 meters, the maximum length of castings can reach 8 meters, and the weight range of centrifugal castings is from a few cows to tens of thousands of cows (a few kilograms to more than ten tons)& nbsp;2、 The working principle of centrifugal casting   Centrifugal casting is a casting method that involves pouring liquid metal into a rotating mold, causing the liquid metal to fill the mold and solidify under the action of centrifugal force& nbsp;& nbsp; To achieve the above process, it is necessary to use a centrifugal casting machine to create conditions for the casting to rotate. According to the different spatial positions of the mold rotation axis, there are two commonly used types: vertical centrifugal casting machines and horizontal centrifugal casting machines& nbsp; The mold on a vertical centrifugal casting machine rotates around a vertical axis and is mainly used to produce circular ring castings with a height smaller than the diameter. Sometimes, this centrifugal casting machine can also be used to pour special-shaped castings& nbsp;  & nbsp;& nbsp;& nbsp;& nbsp;& nbsp;& nbsp;& nbsp;& nbsp;& nbsp;& nbsp;& nbsp;& nbsp;& nbsp;& nbsp;& nbsp;& nbsp;& nbsp;& nbsp;& nbsp;& nbsp;& nbsp;& nbsp;& nbsp;& nbsp; Animation demonstration of centrifugal casting process& nbsp;& nbsp;& nbsp;& nbsp;& nbsp;& nbsp;& nbsp;& nbsp;& nbsp;& nbsp;& nbsp;& nbsp;& nbsp;& nbsp;& nbsp;& nbsp;& nbsp;& nbsp;& nbsp;& nbsp;& nbsp;& nbsp;& nbsp;& nbsp;& nbsp;& nbsp;& nbsp;& nbsp;  The mold of a horizontal centrifugal casting machine rotates around a horizontal axis and is mainly used to produce sleeve and tube castings with a length greater than the diameter.  Horizontal centrifugal casting machines are also divided into cantilever centrifugal casting machines and supporting wheel centrifugal casting machines. Cantilever centrifugal casting is generally used for the production of sleeve and barrel castings with shorter lengths. The supporting wheel centrifugal casting machine is used for the production of long pipe castings.  Due to the fact that liquid metal fills the mold and solidifies during centrifugal casting, centrifugal casting has the following characteristics:; 1) Liquid metal can form a hollow cylindrical free surface in the mold, so that hollow castings can be cast without core, greatly simplifying the production process of sleeve and pipe castings, greatly simplifying the casting process, high productivity and low cost& nbsp; 2) Due to the centrifugal force generated by liquid metal during rotation, centrifugal casting technology can improve the ability of metal to fill and hold the mold. Therefore, some alloys and thin-walled castings with poor fluidity can be produced using centrifugal casting method& nbsp; 3) Due to the effect of centrifugal force, the feeding conditions are improved, and gas and non-metallic inclusions are easily discharged from the liquid metal. Therefore, the microstructure of centrifugal castings is relatively dense, with fewer defects such as shrinkage cavities (porosity), pores, and inclusions, and good mechanical properties& nbsp; 4) Eliminating or greatly saving metal consumption in the pouring system and riser, resulting in high metal utilization rate& nbsp; 5) Centrifugally cast castings are prone to segregation and are not suitable for casting alloys with a high tendency for density segregation; Moreover, the size of the inner hole is not accurate, the inner surface is rough, and the machining allowance is large; It is not suitable for single piece and small batch production. At present, centrifugal casting has been widely used to manufacture Cast iron pipe, cylinder sleeve copper sleeve, bimetal bearing, special seamless tube blank, paper machine drum, etc& nbsp; 6) Convenient for producing bimetallic castings, such as steel sleeve copper bearings, etc., with a solid bonding surface, saving copper material, and reducing costs. 3、 Centrifugal casting process; 1) Selection of centrifugal casting speed& nbsp; When selecting the rotational speed of centrifugal casting, two main issues should be considered: (1) The rotational speed of centrifugal casting should at least ensure that the liquid metal can form a cylindrical color immediately after entering the mold and rotate around the axis; (2) Make full use of the centrifugal force to ensure good internal quality of the casting and avoid the occurrence of shrinkage, porosity, inclusions, and air holes in the casting& nbsp;& nbsp; When using sand mold centrifugal casting, it is also important to pay attention to defects such as sand sticking and expansion caused by the sudden centrifugal pressure of liquid metal on the mold wall. 2) Mold for centrifugal casting& nbsp; There are two main types of molds used in centrifugal casting, namely metallic and non-metallic molds. The non-metallic mold can be sand mold, shell mold, investment mold shell mold, etc. Due to the series of advantages of metal molds in mass production and batch production, metal molds are widely used in centrifugal casting& nbsp; The metal mold on a horizontal cantilever centrifugal casting machine can be divided into two types according to the structural characteristics of its main body: single-layer metal mold and double-layer metal mold. In a single-layer metal mold, the mold wall is composed of one layer. The single-layer metal mold has a simple structure and is easy to operate, but after it is damaged, a new mold needs to be made before production can begin. In this mold, only castings with a single outer diameter size can be poured. In a double-layer metal mold, the mold wall is composed of two layers, and the casting is formed on the inner surface of the mold. Although the double-layer metal mold structure is complex, centrifugal castings of various outer diameter sizes can be poured by changing the working surface size of the inner mold. After long-term work, the old mold can be used as a new mold by simply replacing the inner mold with a simpler structure& nbsp; 3) Coatings& nbsp; When centrifugal casting in metal mold, it is often necessary to spray paint on the working surface of the metal mold. The requirements for coatings used in centrifugal casting metal molds are the same as for general metal mold casting. To prevent the adhesion between castings and metal molds and the formation of white spots on cast iron parts, the coating layer on centrifugal metal molds is sometimes thicker. Most coatings used in centrifugal casting use water as a carrier. Sometimes also used for surface coatings, such as graphite powder, to make castings easier to remove from the mold& nbsp;& nbsp; When spraying paint, attention should be paid to controlling the temperature of the metal mold. When producing large castings, if the heat of the mold itself is not enough to dry the coating, the mold can be heated in a heating furnace and the working temperature of the mold can be maintained, waiting for pouring. When producing small castings, especially when using a cantilever centrifugal casting machine, it is hoped to use the heat of the mold itself as much as possible to dry the coating and wait for pouring& nbsp; 4) Pouring& nbsp; In centrifugal casting, the pouring process has its own characteristics. First of all, because the inner surface of the casting is a free surface, and the control of the casting thickness is all determined by the amount of liquid metal poured, the quantitative requirements for the poured metal are high in centrifugal casting pouring. In addition, as pouring is carried out while the mold is rotating, in order to eliminate the phenomenon of metal splashing as much as possible, it is necessary to control the direction of metal entering the mold well& nbsp;& nbsp; The quantitative methods of liquid metal include gravimetric method, volumetric method and free surface height (liquid metal thickness) method. The volumetric method uses a certain volume of ladle to control the amount of liquid metal poured. This method is relatively simple, but it is not accurate due to the influence of metal temperature, slag, and other factors, and is often used in production& nbsp;& nbsp; To minimize metal splashing during pouring, it is necessary to control the flow direction of liquid metal when entering the mold.